A wet-process polyurethane resin, a wet-process synthetic leather base, its preparation method and application

Abstract

This invention provides a wet-process polyurethane resin, a wet-process synthetic leather base, a preparation method thereof, and its application. The raw materials for the wet-process polyurethane resin include specific weight parts of polyester polyol, base diol, diisocyanate, chain extender, and solvent A. The raw material for the base diol includes bio-based monounsaturated fatty acid, and the base diol is defined to have the structure shown in Formula I. By using the base diol having the structure shown in Formula I to combine with the polyester polyol, the wet-process polyurethane resin is further processed into a wet-process synthetic leather base with good hydrolysis resistance, excellent resilience, and good peel strength, while also reducing dependence on petroleum resources.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane technology, specifically relating to a wet-process polyurethane resin, a wet-process synthetic leather base, its preparation method, and its application. Background Technology

[0002] Polyurethane synthetic leather, also known as PU synthetic leather, is a plastic product that mimics the composition and structure of natural leather. It is typically made with an impregnated non-woven fabric as the mesh layer and a microporous polyurethane layer as the grain layer. It boasts numerous advantages, such as high strength, abrasion resistance, cold resistance, breathability, aging resistance, solvent resistance, soft texture, and attractive appearance. Furthermore, it exhibits excellent processing performance, making it a highly ideal substitute for natural leather and even surpassing the performance of PVC leather. Currently, polyurethane synthetic leather is widely used in the clothing, footwear, bag, and furniture industries.

[0003] Diols are the main raw materials for wet-process polyurethane resins, accounting for more than 20% of the resin's solid components. The diols commonly used in wet-process polyurethane resins are derived from petroleum, but petroleum products are energy-intensive, emit large amounts of greenhouse gases, and are non-renewable resources. In contrast, vegetable oil polyols are bio-based polyols synthesized from vegetable oils through chemical modification, and are now widely used in the field of polyurethane materials.

[0004] The use of bio-based polyols can effectively increase the renewable content of polyurethane products, reduce dependence on petroleum resources, and, due to their biodegradability, have a smaller impact on the ecological environment. Production methods for vegetable oil polyols mainly include epoxidation, ozone oxidation, hydroformylation, transesterification, and ammonolysis. Among these, epoxidation is currently the most mature method for the industrial production of vegetable oil polyols. Common strategies involve epoxidation, ring-opening, alcoholysis, or combinations of reactions involving the unsaturated double bonds in vegetable oils to prepare bio-based polyols, which are frequently used in polyurethane foams. However, due to the high functionality of the polyhydroxyl groups in bio-based polyols obtained by epoxidation, they are difficult to apply in the preparation of conventional wet-process polyurethane resins. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a wet-process polyurethane resin, a wet-process synthetic leather base, a preparation method thereof, and its application. The wet-process synthetic leather base prepared using the aforementioned wet-process polyurethane resin has excellent resilience, hydrolysis resistance, and high peel strength, while reducing dependence on petroleum-based raw materials and being environmentally friendly.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a wet-process polyurethane resin, wherein the raw materials of the wet-process polyurethane resin comprise the following components in parts by weight:

[0008]

[0009] The raw materials for the base diol include bio-based monounsaturated fatty acids, and the base diol has the structure shown in Formula I:

[0010]

[0011] Wherein, R1 is selected from C3 to C15 (e.g., C3, C5, C7, C9, C11, C13 or C15, etc.) straight-chain or branched hydrocarbon groups;

[0012] R2 is selected from C1 to C4 (e.g., C1, C2, C3, or C4, etc.) straight-chain or branched hydrocarbon groups;

[0013] m is an integer from 2 to 16 (e.g., 2, 4, 6, 8, 10, 12, 14, or 16, etc.);

[0014] n is an integer from 3 to 20 (e.g., 3, 5, 7, 9, 11, 13, 15, 17, 18, or 20).

[0015] The raw materials for the wet-process polyurethane resin provided by this invention include the aforementioned basic diols with specific structures. The raw materials for the basic diols include bio-based monounsaturated fatty acids, and the two hydroxyl groups in the structure of the basic diols are located in the main chain and the side chain, respectively. By limiting different side chain lengths and adding polyester polyols, the coagulation rate of the obtained wet-process polyurethane resin in the coagulation bath can be controlled. The inventors creatively discovered through experiments that maintaining a reasonable coagulation rate can make the prepared wet-process synthetic leather bases have good resilience, peel strength and hydrolysis resistance.

[0016] The content of the basic diol can be 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, or 15 parts by weight, etc.

[0017] The content of the polyester polyol can be 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, or 15 parts by weight, etc.

[0018] The content of the diisocyanate can be 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, or 12 parts by weight, etc.

[0019] The content of the chain extender can be 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, or 3 parts by weight, etc.

[0020] The content of solvent A can be 60 parts by weight, 62 parts by weight, 64 parts by weight, 66 parts by weight, 68 parts by weight, 70 parts by weight, 72 parts by weight, 74 parts by weight, 76 parts by weight, 78 parts by weight, or 80 parts by weight, etc.

[0021] In some preferred embodiments, the molecular weight of the base diol is 300 to 1000 g / mol, such as 300 g / mol, 400 g / mol, 500 g / mol, 600 g / mol, 700 g / mol, 800 g / mol, 900 g / mol, or 1000 g / mol.

[0022] In some preferred embodiments, the hydroxyl value of the base diol is 110–380 mg KOH / g, for example, 110 mg KOH / g, 120 mg KOH / g, 140 mg KOH / g, 160 mg KOH / g, 180 mg KOH / g, 200 mg KOH / g, 240 mg KOH / g, 280 mg KOH / g, 320 mg KOH / g, 340 mg KOH / g, 360 mg KOH / g, or 380 mg KOH / g, etc.

[0023] In some preferred embodiments, the base diol is obtained by esterification and epoxidation of bio-based monounsaturated fatty acids, followed by ring-opening of the diol.

[0024] Using the aforementioned bio-based monounsaturated fatty acids as raw materials, esterification followed by epoxidation can form epoxidized fatty acid esters. These esters can then be ring-opened with a diol under acidic catalysis to obtain the basic diol. This invention does not specifically limit the preparation method; existing technologies can be referenced, such as those provided in Kou Xiuying and Yu Guoping. Research on Methyl Esterification Methods of Fat and Fatty Acids [J]. Food Research and Development, 2005, 26(2):46-47 and European Polymer Journal 48(2012)2097-2106. The present invention uses the bio-based monounsaturated fatty acid as a raw material and a diol as a ring-opening agent, which ensures a single reaction site and controllable functionality of the resulting base diol. However, if vegetable oils (such as castor oil and palm oil) are used as raw materials, the presence of saturated stearic acid makes functionalization impossible and hinders effective utilization. Furthermore, the presence of polyunsaturated fatty acids in vegetable oils leads to uncontrollable functionality of the resulting base diol, making it prone to cross-linking and thus difficult to apply in the preparation of conventional wet-process synthetic leather bases. Similarly, if glycerol, a triol, is used as a ring-opening agent, the resulting polyol will also be binary or higher, making it unsuitable for use in conventional wet-process polyurethane.

[0025] In some preferred embodiments, the bio-based monounsaturated fatty acids include any one or a combination of at least two of myristoleic acid, palmitoleic acid, oleic acid, trans oleic acid, or erucic acid.

[0026] It should be noted that since the basic diol is obtained by esterification and epoxidation of bio-based monounsaturated fatty acids, followed by ring-opening of the diol, the choice of the bio-based monounsaturated fatty acid will affect the structure of the obtained basic diol. Specifically, it will directly determine the choice of R1 and the range of values ​​of n in the basic diol with the structure shown in Formula I.

[0027] In some preferred embodiments, the diol is selected from at least one of diols having a carbon number of 2 to 16 (e.g., 2, 4, 6, 8, 10, 12, 14, or 16, etc.); for example, any one or a combination of at least two of ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, or 1,16-hexadecanediol may be selected.

[0028] Similarly, since the base diol is obtained by esterification and epoxidation of bio-based monounsaturated fatty acids, followed by ring-opening of the diol, the choice of the diol will also affect the structure of the obtained base diol. Specifically, it will directly determine the range of values ​​for m in the base diol with the structure shown in Formula I. Furthermore, the inventors of this invention creatively discovered during the research process that if the C chain of the selected diol is too short, m will be too small, which will result in a slow solidification rate of the obtained wet-process polyurethane resin, leading to poor performance of the obtained wet-process base. On the other hand, if the C chain of the selected diol is too long, m will be too large, which will result in a fast solidification rate of the obtained wet-process polyurethane resin and fast surface solidification, which will affect the internal solvent and water exchange, resulting in uneven overall solidification and thus poor performance of the obtained wet-process synthetic leather base.

[0029] In some preferred embodiments, the two hydroxyl groups of the diol are located at both ends of the C chain, and the diol is selected from at least one of diols having 3 to 12 C atoms.

[0030] In some preferred embodiments, the diol is a bio-based diol. The purpose of using bio-based is to make the wet-process polyurethane resin and wet-process synthetic cellulose obtained by the present invention more environmentally friendly. Currently commonly used bio-based diols include bio-based ethylene glycol, bio-based 1,3-propanediol or bio-based 1,4-butanediol.

[0031] In some preferred embodiments, the esterification reagent used for esterification includes methanol and / or ethanol; the type of esterification reagent directly determines the selection of R2 in the base diol having the structure shown in Formula I.

[0032] In some preferred embodiments, the molecular weight of the polyester polyol is 2000-4000 g / mol, such as 2000 g / mol, 2200 g / mol, 2400 g / mol, 2600 g / mol, 2800 g / mol, 3000 g / mol, 3200 g / mol, 3400 g / mol, 3600 g / mol, 3800 g / mol, or 4000 g / mol.

[0033] In some preferred embodiments, the hydroxyl value of the polyester polyol is 25-60 mgKOH / g, such as 25 mgKOH / g, 30 mgKOH / g, 35 mgKOH / g, 40 mgKOH / g, 45 mgKOH / g, 50 mgKOH / g, 55 mgKOH / g, or 60 mgKOH / g.

[0034] In some preferred embodiments, the polyester polyol is obtained by polymerizing at least one C2-C10 (e.g., C2, C3, C4, C5, C6, C7, C8, C9 or C10) dicarboxylic acid with at least one C2-C10 (e.g., C2, C3, C4, C5, C6, C7, C8, C9 or C10) diol.

[0035] In some preferred embodiments, the C2-C10 dicarboxylic acid includes any one or a combination of at least two of malonic acid, succinic acid, glutaric acid, adipic acid, or phthalic acid.

[0036] In some preferred embodiments, the C2-C10 diols include any one or a combination of at least two of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, or diethylene glycol.

[0037] In some preferred embodiments, the diisocyanate includes any one or a combination of at least two of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, or isophorone isocyanate.

[0038] In some preferred embodiments, the chain extender includes any one or a combination of at least two of ethylene glycol, propylene glycol, or butanediol, such as 1,3-propanediol and / or 1,4-butanediol.

[0039] In some preferred embodiments, the chain extender is of bio-based origin, including any one or a combination of at least two of bio-based ethylene glycol, bio-based 1,3-propanediol, or bio-based 1,4-butanediol; selecting the above-mentioned specific bio-based chain extender can further increase the proportion of bio-based materials in the raw materials, making the resulting wet-process polyurethane resin less dependent on petroleum resources and more environmentally friendly.

[0040] In some preferred embodiments, solvent A includes N,N-dimethylformamide and / or dimethylacetamide.

[0041] In some preferred embodiments, the coagulation rate of the wet-process polyurethane resin in the coagulation bath is 0.2 to 0.6 mm / min, for example, 0.2 mm / min, 0.21 mm / min, 0.22 mm / min, 0.25 mm / min, 0.26 mm / min, 0.3 mm / min, 0.31 mm / min, 0.35 mm / min, 0.4 mm / min, 0.41 mm / min, 0.45 mm / min, 0.5 mm / min, 0.51 mm / min, 0.52 mm / min, 0.55 mm / min, 0.59 mm / min, or 0.6 mm / min.

[0042] In some preferred embodiments, the formation time of the skin layer of the wet polyurethane resin in the coagulation bath is 0.5 to 2 minutes, for example, 0.5 minutes, 0.6 minutes, 0.7 minutes, 0.8 minutes, 0.9 minutes, 1.0 minutes, 1.1 minutes, 1.2 minutes, 1.3 minutes, 1.4 minutes, 1.5 minutes, 1.6 minutes, 1.7 minutes, 1.8 minutes, 1.9 minutes, or 2 minutes.

[0043] Preferably, the total amount of base diol and polyester polyol in the raw materials of the wet-process polyurethane resin is 11 to 25 parts by weight, for example, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, or 25 parts by weight.

[0044] In some embodiments of the present invention, the raw materials of the wet-process polyurethane resin further include a certain amount of end-capping agent by weight. The function of the end-capping agent is to react away residual isocyanate groups as needed. There is no particular limitation on the amount of end-capping agent added; it can be added according to conventional dosages in the art, generally 0.01 to 0.1 parts by weight, such as 0.01 parts by weight, 0.02 parts by weight, 0.04 parts by weight, 0.06 parts by weight, 0.08 parts by weight, or 0.1 parts by weight.

[0045] In some preferred embodiments, the capping agent includes any one or a combination of at least two of methanol, ethanol, or isopropanol.

[0046] In a second aspect, the present invention provides a method for preparing a wet-process polyurethane resin as described in the first aspect, the method comprising the following steps:

[0047] (1) Mix the base diol, polyester polyol, part of diisocyanate and part of solvent A, and after the prepolymerization reaction, when the NCO value in the system reaches the theoretical value, the polyurethane prepolymer is obtained.

[0048] (2) React the polyurethane prepolymer, chain extender and remaining solvent A obtained in step (1) and then add the remaining diisocyanate to carry out chain growth reaction. When the viscosity of the system reaches the standard, optionally add end-capping agent to end-cap the system to obtain the wet polyurethane resin.

[0049] In some preferred embodiments, the portion of diisocyanate in step (1) accounts for 5 to 12.5% ​​of the total weight of diisocyanate, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or 12.5%.

[0050] In some preferred embodiments, the solvent A in step (1) accounts for 20% to 60% of the total mass of solvent A, for example, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 36%, 40%, 45%, 50%, 55%, or 60%.

[0051] In some preferred embodiments, the isocyanate index in the mixture obtained in step (1) is 0.5 to 0.9 or 1.1 to 1.2, for example 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9 or 2, etc. There are no special requirements, as long as the NCO value of the prepolymer reaction is controlled within the above range.

[0052] In some preferred embodiments, the reaction temperature in step (1) is 70 to 80°C, for example, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C.

[0053] In some preferred embodiments, the reaction time in step (1) is 1 to 1.2 hours, for example, 1 hour, 1.02 hours, 1.04 hours, 1.06 hours, 1.08 hours, 1.1 hours, 1.12 hours, 1.14 hours, 1.16 hours, 1.18 hours, or 1.2 hours.

[0054] In some preferred embodiments, the reaction temperature in step (2) is 70 to 80°C, for example, 70°C, 72°C, 74°C, 76°C, 78°C or 80°C.

[0055] In some preferred embodiments, the reaction time in step (2) is 0.3 to 1 hour, for example, 0.3 hours, 0.4 hours, 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours or 1 hour.

[0056] In some preferred embodiments, the viscosity of the system described in step (2) is 160 to 300 Pa·s / 25℃ (e.g., 160 Pa·s / 25℃, 180 Pa·s / 25℃, 200 Pa·s / 25℃, 220 Pa·s / 25℃, 240 Pa·s / 25℃, 260 Pa·s / 25℃, 280 Pa·s / 25℃ or 300 Pa·s / 25℃, etc.) to meet the standard.

[0057] In this invention, the preparation method can be carried out in the presence of a catalyst known in the art to accelerate the reaction rate, such as an organotin catalyst. There is no special limitation on the amount added; it can be added according to the conventional dosage in the art.

[0058] Thirdly, the present invention provides a wet-process synthetic leather base material, the wet-process synthetic leather base material comprising a base fabric and a coating;

[0059] The raw materials for the coating include, by weight: 100 parts by weight of wet-process polyurethane resin as described in the first aspect, 50-80 parts by weight of solvent B, and 10-35 parts by weight of wood powder.

[0060] The amount of solvent B can be 50 parts by weight, 55 parts by weight, 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, or 80 parts by weight, etc.

[0061] The amount of wood powder used can be 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, or 35 parts by weight, etc.

[0062] In some preferred embodiments, solvent B comprises N,N-dimethylformamide and / or dimethylacetamide.

[0063] In this invention, there are no special requirements for the base fabric. Commonly used base fabrics in the art can be selected, such as single-sided napped fabric or single-sided napped knitted fabric.

[0064] Fourthly, the present invention provides a method for preparing a wet-synthetic leather base as described in the third aspect, the method comprising the following steps:

[0065] (A1) The working solution is obtained by thoroughly mixing the wet polyurethane resin, solvent B and wood powder as described in the first aspect;

[0066] (A2) The working fluid obtained in step (A1) is scraped onto the base fabric to form a coating, and the base fabric with the coating is placed in a coagulation bath for coagulation to obtain a molded base.

[0067] (A3) The molded base obtained in step (A2) is subjected to extrusion and hot water soaking treatment, and then dried to obtain the wet synthetic leather base.

[0068] In some preferred embodiments, the viscosity of the working fluid obtained in step (A1) is 5 to 10 Pa·s, for example, 5 Pa·s, 6 Pa·s, 7 Pa·s, 8 Pa·s, 9 Pa·s or 10 Pa·s.

[0069] In some preferred embodiments, the concentration of the solvent in the coagulation bath in step (A2) is 20 to 25 wt%, such as 20 wt%, 20.5 wt%, 21 wt%, 21.5 wt%, 22 wt%, 22.5 wt%, 23 wt%, 24 wt%, or 25 wt%.

[0070] In some preferred embodiments, the temperature of the coagulation bath in step (A2) is 25 to 30°C, for example, 25°C, 26°C, 27°C, 28°C, 29°C, or 30°C.

[0071] In some preferred embodiments, the temperature of the hot water immersion treatment in step (A3) is 50 to 65°C, such as 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C or 65°C.

[0072] In some preferred embodiments, the drying temperature in step (A3) is 115 to 125°C, for example, 115°C, 117°C, 119°C, 121°C, 123°C or 125°C.

[0073] Compared with the prior art, the present invention has the following beneficial effects:

[0074] (1) The raw materials of the wet polyurethane resin provided by the present invention include a specific weight part of a base diol, a polyester polyol, a diisocyanate, a chain extender and a solvent A, and the raw material of the base diol includes a bio-based monounsaturated fatty acid. The base diol has the structure shown in Formula I. By using the base diol with the structure shown in Formula I to make the wet synthetic leather base made from the wet polyurethane resin has good resilience, good hydrolysis resistance and high peel strength.

[0075] (2) By further optimizing the types of basic diols and adjusting the formulation, the coagulation rate of the prepared wet polyurethane resin in the coagulation bath is 0.2 to 0.6 mm / min, and the skin layer formation time in the coagulation bath is 0.5 to 2 min, thereby making the final wet synthetic leather base have better resilience, better hydrolysis resistance, aging resistance and peel strength.

[0076] (3) The present invention limits the raw materials of the basic diol to bio-based sources, which reduces the dependence on petroleum and has environmentally friendly characteristics. Detailed Implementation

[0077] 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.

[0078] Terminology Explanation:

[0079] "Skin layer": When wet polyurethane resin is wet-processed in a coagulation bath, after the polyurethane mixture is applied to the base fabric, the base fabric with the polyurethane coating is placed in the coagulation bath. The layer that the polyurethane coating first solidifies in contact with the liquid in the coagulation bath is called the skin layer. During the experiment, the formation time of the skin layer can be determined by observation or by temporarily removing the base fabric with the coating from the coagulation bath.

[0080] Raw material preparation or source:

[0081] (1) Basic diols

[0082] Referring to the literature by Kou Xiuying and Yu Guoping, Research on the Methyl Esterification Method of Fat and Fatty Acids [J]. Food Research and Development, 2005, 26(2):46-47, fatty acid methyl esters were prepared by methyl esterification of bio-based monounsaturated fatty acids and methanol; then, referring to European Polymer Journal 48(2012)2097-2106, the obtained fatty acid methyl esters were subjected to epoxidation under hydrogen peroxide and formic acid conditions to obtain epoxy fatty acid methyl esters, which is also applicable to ethyl esterification with ethanol first; continuing to refer to European Polymer Journal 48(2012)2097-2106, the obtained epoxy fatty acid methyl esters were ring-opened with diols and post-treated to obtain basic diols.

[0083] Following the preparation method described above, the following basic diols A to F and methyl oleate polyols were prepared, and their hydroxyl values ​​were determined according to HG / T 2709-2022:

[0084] The following basic diols A through F all have the structure shown in Formula I:

[0085]

[0086] Basic diol A: prepared from oleic acid (CAS 112-80-1), methanol, formic acid, hydrogen peroxide, and bio-based 1,3-propanediol, with a hydroxyl value of 295 mg KOH / g, wherein R1 is -C8H. 17 R2 is a methyl group, m is 3, and n is 6;

[0087] Basic diol B: Myristoleic acid (CAS 544-64-9) was prepared by ethanol, formic acid, hydrogen peroxide and bio-based 1,4-butanediol, with a hydroxyl value of 241 mgKOH / g, wherein R1 is -C4H9, R2 is ethyl, m is 4 and n is 6;

[0088] Basic diol C: oleic acid (CAS 112-80-1) was prepared from methanol, formic acid, hydrogen peroxide, and 1,6-hexanediol, with a hydroxyl value of 270 mg KOH / g, wherein R1 is -C8H. 17 R2 is a methyl group, m is 6, and n is 6;

[0089] Basic diol D: oleic acid (CAS 112-80-1) was prepared from methanol, formic acid, hydrogen peroxide, and 1,10-decanediol, with a hydroxyl value of 230 mg KOH / g, wherein R1 is -C8H. 17 R2 is a methyl group, m is 6, and n is 10;

[0090] Basic diol E: oleic acid (CAS 112-80-1) was prepared from methanol, formic acid, hydrogen peroxide, and 1,16-hexadecanediol, with a hydroxyl value of 180 mg KOH / g, wherein R1 is -C8H. 17 R2 is a methyl group, m is 6, and n is 16;

[0091] Basic diol F was prepared from oleic acid (CAS 112-80-1), methanol, formic acid, hydrogen peroxide, and ethylene glycol, with a hydroxyl value of 305 mg KOH / g, wherein R1 is -C8H. 17 R2 is a methyl group, m is 2, and n is 6.

[0092] Methyl oleate polyol: prepared from oleic acid (CAS 112-80-1), methanol, formic acid, hydrogen peroxide and glycerol, with a hydroxyl value of 421 mgKOH / g.

[0093] (2) Polyester polyols

[0094] Polybutylene adipate diol: molecular weight 2000 g / mol;

[0095] Poly(ethylene glycol-butylene glycol) polyol: functionality 2, molecular weight 2500 g / mol;

[0096] Polyglutaric acid-ethylene glycol-pentanediol polyol: functionality 2, molecular weight 4000 g / mol.

[0097] Example 1

[0098] A wet-process polyurethane resin, the raw materials of which comprise the following components by weight:

[0099]

[0100] The method for preparing wet-process polyurethane resin provided in this embodiment includes the following steps:

[0101] (1) The basic diol C, poly(butylene adipate) diol, 10% of the total mass of diphenylmethane diisocyanate and 40% of the total mass of N,N-dimethylformamide were mixed and prepolymerized at 75°C for 1.1 h. After the NCO value in the system reached the theoretical value, the polyurethane prepolymer was obtained.

[0102] (2) The polyurethane prepolymer obtained in step (1), bio-based 1,4-butanediol and the remaining N,N-dimethylformamide are reacted at 75°C for 0.5 h, and the remaining diphenylmethane diisocyanate is added to carry out chain growth reaction. When the viscosity of the system reaches 200 Pa·s / 25°C, the wet polyurethane resin is obtained.

[0103] Example 2

[0104] A wet-process polyurethane resin, the raw materials of which comprise the following components by weight:

[0105]

[0106]

[0107] The method for preparing wet-process polyurethane resin provided in this embodiment includes the following steps:

[0108] (1) The basic diol B, poly(ethylene glycol-butylene glycol) polyol, 5% diphenylmethane diisocyanate and 20% N,N-dimethylformamide were mixed and prepolymerized at 70°C for 1.2 h. After the NCO value in the system reached the theoretical value, the polyurethane prepolymer was obtained.

[0109] (2) The polyurethane prepolymer obtained in step (1), 1,4-butanediol and the remaining N,N-dimethylformamide are reacted at 70°C for 1 h, and the remaining diphenylmethane diisocyanate is added to carry out chain growth reaction. When the viscosity of the system reaches 300 Pa·s / 25°C, the wet polyurethane resin is obtained.

[0110] Example 3

[0111] A wet-process polyurethane resin, the raw materials of which comprise the following components by weight:

[0112]

[0113] The method for preparing wet-process polyurethane resin provided in this embodiment includes the following steps:

[0114] (1) Mix the basic diol C, polyglutaric acid-ethylene glycol-pentanediol polyol, diphenylmethane diisocyanate accounting for 12% of the total mass and N,N-dimethylformamide accounting for 40% of the total mass, and prepolymerize at 80°C for 1 hour. After the NCO value in the system reaches the theoretical value, the polyurethane prepolymer is obtained.

[0115] (2) The polyurethane prepolymer obtained in step (1), 1,4-butanediol and the remaining N,N-dimethylformamide are reacted at 70°C for 1 h, and the remaining diphenylmethane diisocyanate is added to carry out chain growth reaction. When the viscosity of the system reaches 180 Pa·s / 25°C, the wet polyurethane resin is obtained.

[0116] Example 4

[0117] A wet-process polyurethane resin differs from Example 1 in that an equimolar amount of base diol A is used to replace base diol C, while the other components and amounts are the same as in Example 1.

[0118] Example 5

[0119] A wet-process polyurethane resin differs from Example 1 in that an equimolar amount of base diol D is used to replace base diol C, while the other components and amounts are the same as in Example 1.

[0120] Example 6

[0121] A wet-process polyurethane resin differs from Example 1 in that an equimolar amount of base diol E is used to replace base diol C, while the other components and amounts are the same as in Example 1.

[0122] Example 7

[0123] A wet-process polyurethane resin differs from Example 1 in that an equimolar amount of base diol F is used to replace base diol C, while the other components and amounts are the same as in Example 1.

[0124] Example 8

[0125] A wet-process polyurethane resin, the raw materials of which comprise the following components by weight:

[0126]

[0127] The preparation method of the wet-process polyurethane resin provided in this embodiment is the same as that in Example 1.

[0128] Example 9

[0129] A wet-process polyurethane resin, the raw materials of which comprise the following components by weight:

[0130]

[0131] The preparation method of the wet-process polyurethane resin provided in this embodiment is the same as that in Example 1.

[0132] Comparative Example 1

[0133] A wet-process polyurethane resin differs from Example 1 in that an equimolar amount of methyl oleate polyol is used to replace the base diol C, while the other components and amounts are the same as in Example 1.

[0134] Comparative Example 2

[0135] A wet-process polyurethane resin differs from Example 1 in that the amount of poly(butylene adipate) diol is 4 parts by weight, the amount of base diol C is 16 parts by weight, and the other components, amounts, and preparation methods are the same as in Example 1.

[0136] Comparative Example 3

[0137] A wet-process polyurethane resin differs from Example 1 in that the amount of poly(butylene adipate) diol is 16 parts by weight, the amount of base diol C is 4 parts by weight, and the other components, amounts, and preparation methods are the same as in Example 1.

[0138] Application Example 1

[0139] A wet-process synthetic leather base, the preparation method of which includes the following steps:

[0140] (1) 100 parts by weight of wet polyurethane resin, 70 parts by weight of DMF and 30 parts by weight of wood powder provided in Example 1 were thoroughly mixed to obtain a working solution with a viscosity of 6 Pa·s.

[0141] (2) The working liquid obtained in step (1) is scraped onto a conventional single-sided napped cloth to form a coating with a thickness of 1.2 mm. The single-sided napped cloth with the coating is placed in a coagulation bath with a concentration of 20 wt% DMF aqueous solution and a temperature of 25 °C. After coagulation, a molded base is obtained. The time of skin formation and the coagulation time of the base are recorded during the coagulation process.

[0142] (3) The molded base obtained in step (2) is extruded, soaked in hot water at 60°C, and dried at 120°C to obtain the wet synthetic leather base.

[0143] Application Examples 2-9

[0144] A wet-process synthetic leather base differs from Application Example 1 in that the wet-process polyurethane resin provided in Examples 2-9 is used instead of the wet-process polyurethane resin provided in Example 1, while other substances, amounts, and preparation methods are the same as in Application Example 1.

[0145] Comparative Application Examples 1-3

[0146] A wet-process synthetic leather base differs from Application Example 1 in that the wet-process polyurethane resin provided in Comparative Examples 1 to 3 is used instead of the wet-process polyurethane resin provided in Example 1, while the other substances, amounts, and preparation methods are the same as in Application Example 1.

[0147] Comparative Application Example 4

[0148] A wet-process synthetic leather base differs from Application Example 1 in that the concentration of DMF in the coagulation bath is 30 wt%, while the other substances, amounts, and preparation methods are the same as in Application Example 1.

[0149] Performance testing:

[0150] (1) Curing time: The curing time is defined by the finger-pressure rebound method (the curing time is defined by the curing time of the base fabric coated with resin being placed into the curing bath and the curing time is defined by the curing time of the base fabric being placed into the curing bath and the curing time is defined by the finger-pressure rebound method (the curing time is defined by the finger or nail pressing the surface of the base fabric).

[0151] (2) Epidermal layer formation time: The time from when the surface resin is observed to have completely solidified and formed the epidermal layer, from when the resin-coated base fabric is placed in the coagulation bath to when the epidermal layer is formed, is called the epidermal layer formation time.

[0152] (3) Hydrolysis resistance: This refers to the degree of decrease in peel strength after the prepared base is immersed in 10% NaOH at room temperature, with immersion times of 24h and 72h; peel strength is measured according to GB / T 1040.3 standard.

[0153] (4) Resilience: Press the wet bass and record the recovery time. If it recovers within 3 seconds, it indicates good resilience. If it recovers within 3 to 5 seconds, it indicates relatively good resilience. If it recovers within 5 to 10 seconds, it indicates average resilience. If it does not recover after more than 10 seconds, it indicates poor resilience.

[0154] The wet-process synthetic leather bases obtained from test cases 1-9 and comparative application examples 1-4 were tested according to the above test methods. The test results are shown in Table 1.

[0155] Table 1

[0156]

[0157] According to the data in Table 1:

[0158] The wet-process synthetic leather base provided in Application Examples 1-9 has good resilience, high peel strength, and good hydrolysis resistance. Specifically, the resilience is rated as average, good, and good, the original peel strength is as high as 25-32 N / 3 cm, the peel strength after soaking in 10% NaOH for 24 h is still as high as 24-32 N / 3 cm, and the peel strength after soaking in 10% NaOH for 72 h is still as high as 21-30 N / 3 cm.

[0159] Comparing the data from Application Example 1 and Comparative Application Examples 1-2, it can be seen that replacing the base diol C with methyl oleate polyol leads to an excessively fast solidification rate and a short skin layer formation time, which in turn results in poorer resilience and peel strength of the obtained wet-process synthetic leather base.

[0160] Comparing the data from Application Example 1 and Comparative Application Examples 2-3, it can be seen that both excessively low and excessively high proportions of the base diol can lead to poorer resilience and peel strength of the resulting wet-synthesized leather base.

[0161] Further comparison of the data from Application Example 1 and Comparative Application Example 4 shows that an excessively high concentration of solvent in the coagulation bath will also lead to a decrease in the resilience and peel strength of the resulting wet-synthesized leather base.

[0162] Finally, comparing the data from Application Example 1 and Application Examples 8-9, it can be found that if the total amount of base diol and polyester polyol in the raw materials of wet-process polyurethane resin is too low or too high (i.e., the solid content is too high or too low), it will affect the solidification rate, which will also have an adverse effect on the resilience and peel strength of the final wet-process synthesized base.

[0163] The applicant declares that this invention illustrates a wet-process polyurethane resin, its preparation method, and its application 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 product, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of this invention.

Claims

1. A wet-process polyurethane resin, characterized in that, The raw materials for the wet-process polyurethane resin include the following components in parts by weight: 5-15 parts by weight of basic diol; 5-15 parts by weight of polyester diol; 5-12 parts by weight of diisocyanate; Chain extender 0.1~3 parts by weight; Solvent A: 60-80 parts by weight; The raw materials for the base diol include bio-based monounsaturated fatty acids, and the base diol has the structure shown in Formula I: Equation I; R1 is selected from C3~C15 straight-chain or branched hydrocarbon groups; R2 is selected from C1~C4 straight-chain or branched hydrocarbon groups; m is an integer from 2 to 16; n is an integer from 3 to 20; The molecular weight of the polyester diol is 2000~4000 g / mol; The chain extender includes any one or a combination of at least two of ethylene glycol, propylene glycol, or butanediol.

2. The wet-process polyurethane resin according to claim 1, characterized in that, The molecular weight of the basic diol is 300~1000 g / mol.

3. The wet-process polyurethane resin according to claim 1, characterized in that, The hydroxyl value of the base diol is 110~380 mgKOH / g.

4. The wet-process polyurethane resin according to claim 1, characterized in that, The base diol is obtained by esterification and epoxidation of bio-based monounsaturated fatty acids, followed by ring-opening of the diol.

5. The wet-process polyurethane resin according to claim 4, characterized in that, The bio-based monounsaturated fatty acids include any one or a combination of at least two of myristoleic acid, palmitoleic acid, oleic acid, trans oleic acid, or erucic acid.

6. The wet-process polyurethane resin according to claim 4, characterized in that, The diol is selected from at least one of diols having 2 to 16 carbon atoms.

7. The wet-process polyurethane resin according to claim 4, characterized in that, The two hydroxyl groups of the diol are located at both ends of the C chain.

8. The wet-process polyurethane resin according to claim 4, characterized in that, The diol is a bio-based diol.

9. The wet-process polyurethane resin according to claim 8, characterized in that, The diols include any one or a combination of at least two of the following: bio-based 1,3-propanediol, bio-based 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, or 1,16-hexadecanediol.

10. The wet-process polyurethane resin according to claim 4, characterized in that, The esterification reagents used in the esterification include methanol and / or ethanol.

11. The wet-process polyurethane resin according to claim 1, characterized in that, The polyester diol is obtained by polymerizing at least one C2-C10 dicarboxylic acid with at least one C2-C10 diol.

12. The wet-process polyurethane resin according to claim 11, characterized in that, The C2~C10 dicarboxylic acids include any one or a combination of at least two of malonic acid, succinic acid, glutaric acid, adipic acid, or phthalic acid.

13. The wet-process polyurethane resin according to claim 11, characterized in that, The C2-C10 diols include any one or a combination of at least two of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, or diethylene glycol.

14. The wet-process polyurethane resin according to claim 1, characterized in that, The diisocyanate includes any one or a combination of at least two of diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, or isophorone isocyanate.

15. The wet-process polyurethane resin according to claim 1, characterized in that, The chain extender is of bio-based origin, including any one or a combination of at least two of bio-based ethylene glycol, bio-based 1,3-propanediol, or bio-based 1,4-butanediol.

16. The wet-process polyurethane resin according to claim 1, characterized in that, Solvent A includes N,N-dimethylformamide and / or dimethylacetamide.

17. The wet-process polyurethane resin according to claim 1, characterized in that, The coagulation rate of the wet-process polyurethane resin in the coagulation bath is 0.2~0.6 mm / min.

18. The wet-process polyurethane resin according to claim 1, characterized in that, The formation time of the skin layer of the wet-process polyurethane resin in the coagulation bath is 0.5~2 minutes.

19. The wet-process polyurethane resin according to claim 1, characterized in that, The total amount of base diol and polyester diol in the raw materials of the wet-process polyurethane resin is 11-25 parts by weight.

20. The wet-process polyurethane resin according to claim 1, characterized in that, The raw materials for the wet-process polyurethane resin also include a capping agent.

21. The wet-process polyurethane resin according to claim 20, characterized in that, The content of the end-capping agent in the raw materials of the wet-process polyurethane resin is 0.01~0.1 parts by weight.

22. The wet-process polyurethane resin according to claim 20, characterized in that, The capping agent includes any one or a combination of at least two of methanol, ethanol, or isopropanol.

23. A method for preparing a wet-process polyurethane resin as described in any one of claims 1 to 22, characterized in that, The preparation method includes the following steps: (1) Mix the base diol, polyester diol, part of diisocyanate and part of solvent A, and after the prepolymerization reaction, when the NCO value in the system reaches the theoretical value, the polyurethane prepolymer is obtained. (2) React the polyurethane prepolymer, chain extender and remaining solvent A obtained in step (1) and then add the remaining diisocyanate to carry out chain growth reaction. When the viscosity of the system reaches the standard, optionally add end-capping agent to end-cap the system to obtain the wet polyurethane resin.

24. The preparation method according to claim 23, characterized in that, The diisocyanate in step (1) accounts for 5 to 12.5% ​​of the total weight of the diisocyanate.

25. The preparation method according to claim 23, characterized in that, In step (1), the solvent A accounts for 20-60% of the total mass of solvent A.

26. The preparation method according to claim 23, characterized in that, The temperature of the prepolymerization reaction in step (1) is 70~80℃ and the time is 1~1.2 h.

27. The preparation method according to claim 23, characterized in that, The reaction in step (2) is carried out at a temperature of 70-80°C for 0.3-1 h.

28. The preparation method according to claim 23, characterized in that, The viscosity of the system described in step (2) is 160~300 Pa•s / 25℃ to meet the standard.

29. A wet-process synthetic leather base, characterized in that, The wet-process synthetic leather base includes a base fabric and a coating; The raw materials for the coating include, by weight, 100 parts of wet polyurethane resin as described in any one of claims 1 to 22, 50 to 80 parts of solvent B, and 10 to 35 parts of wood powder. The method for preparing the wet-synthetic grabe includes the following steps: (A1) The working solution is obtained by thoroughly mixing the wet polyurethane resin as described in any one of claims 1 to 22, solvent B, and wood powder; (A2) The working fluid obtained in step (A1) is scraped onto the base fabric to form a coating, and the base fabric with the coating is placed in a coagulation bath for coagulation to obtain a molded base. (A3) The molded base obtained in step (A2) is subjected to extrusion and hot water soaking treatment, and then dried to obtain the wet synthetic leather base; The concentration of the solvent in the coagulation bath in step (A2) is 20~25wt%.

30. A method for preparing wet-synthesized leather base as described in claim 29, characterized in that, The preparation method includes the following steps: (A1) The working solution is obtained by thoroughly mixing the wet polyurethane resin as described in any one of claims 1 to 22, solvent B, and wood powder; (A2) The working fluid obtained in step (A1) is scraped onto the base fabric to form a coating, and the base fabric with the coating is placed in a coagulation bath for coagulation to obtain a molded base. (A3) The molded base obtained in step (A2) is subjected to extrusion and hot water soaking treatment, and then dried to obtain the wet synthetic leather base; The concentration of the solvent in the coagulation bath in step (A2) is 20~25wt%.

31. The preparation method according to claim 30, characterized in that, The viscosity of the working fluid obtained in step (A1) is 5~10 Pa•s.

32. The preparation method according to claim 30, characterized in that, The solidification temperature in step (A2) is 25~30℃.

33. The preparation method according to claim 30, characterized in that, The temperature of the hot water soaking treatment in step (A3) is 50~65℃.

34. The preparation method according to claim 30, characterized in that, The drying temperature in step (A3) is 115~125℃.

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