Solvent type polyurethane resin and application thereof on base cloth

Abstract

The invention belongs to the technical field of automotive interior material superfine fiber synthetic leather, and relates to solvent type polyurethane resin and application thereof to base cloth. According to the resin, a unique hard segment structure is designed, and organosiloxane residues and short-carbon-chain branched micromolecular diol residues are introduced, so that the wear resistance and the hand feeling are improved and balanced. The resin is prepared from the following raw materials: an oligomer dihydric alcohol monomer, diisocyanate, an unbranched micromolecular dihydric alcohol monomer, an organosiloxane monomer, a short carbon chain branched micromolecular dihydric alcohol monomer and the like. The resin is suitable for super-fiber leather veneering, and meets the requirements of the fields of automotive interior materials and the like on high-performance synthetic leather.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrafine fiber synthetic leather as an automobile interior material, and relates to a solvent-based polyurethane resin and application thereof on a base cloth. Background Art

[0002] Polyurethane material is an organic polymer copolymer, which contains carbamate (-NHCOO-) repeating units in the main chain of the molecule. This material has a unique chemical structure of soft and hard segment copolymerization and a physical structure of microphase separation, making it a unique elastic material between flexible rubber and rigid plastic. Polyurethane material has excellent wear resistance, flexible resilience, weather resistance and other advantages, so it is widely used in the field of synthetic leather.

[0003] With the continuous upgrading of the transportation industry and the accelerated construction of a three-dimensional transportation network, traveling by car has become an indispensable part of people's lives. This has promoted the technological development and process innovation of the automotive synthetic leather industry. Among them, the simulation design material microfiber bass, as an island-type microfiber, has a three-dimensional microfiber and polyurethane microporous structure. This structure is similar to the bundled collagen fibers and matrix in the animal dermis, presenting a three-dimensional structure. Combined with the dry lamination process, a microfiber polyurethane synthetic leather composite material can be made. This material is comparable to genuine leather in terms of appearance texture, microstructure and surface properties. Even in terms of mechanical strength, exudative properties, restricted substances, color and leather grain designability, and cutting and processing utilization, microfiber leather is better than genuine leather. This is in full compliance with the current policy trend of de-dermalization, low-carbon environmental protection and sustainable development, so microfiber leather can replace traditional high-end first / second layer leather, ordinary PU leather and PVC leather.

[0004] Microfiber leather usually uses solvent-based polyurethane and uses transfer coating technology to make the surface layer. Its main functions include soft touch, wear resistance, anti-fouling, easy cleaning and weather resistance. As the requirements for product differentiation and functionalization continue to increase, downstream applications expect to maintain the good touch feel of the surface material while also having high Martin wear resistance. The key to solving this problem lies in regulating the bulk structure of the surface polyurethane.

[0005] In order to improve the wear resistance of microfiber leather, the commonly used methods are as follows:

[0006] 1. Introducing a rigid benzene ring structure. Although this method can greatly improve the wear resistance of the resin, its texture is relatively hard and its weather resistance is poor.

[0007] 2. Silicone wear-resistant additives are added later. These additives exist in the polyurethane macromolecular chain segments in a free state, which will cause defects such as additive failure and overflow, poor resin matching, production complexity and uncontrollability, and timeliness of effect to a certain extent.

[0008] 3. Introduce a siloxane structure with low molecular weight linear characteristics into the main chain or side chain structure of the polyurethane molecule by chemical bonding. The silicon-oxygen bond in the siloxane molecule has a high bond energy and can effectively improve the wear resistance of the material. For example, patent application CN110951030A discloses a low-temperature resistant, wear-resistant, non-yellowing polyurethane resin and a superfine fiber synthetic leather prepared therefrom. The siloxane structure is introduced into the side chain of the polyurethane resin, which is easy to aggregate on the surface after film formation, thereby significantly improving the wear resistance. The siloxane used in this technical solution is a dihydroxy silicone oligomer, the main chain of which is a double-terminal hydroxyl group of 3-8 carbon chains, and the side chain is a prepolymer of high number average molecular weight silicone. However, with the continuous improvement of the industry's requirements for the wear resistance of superfine leather, higher requirements are placed on the wear resistance of polyurethane.

[0009] Therefore, it is necessary to develop a solvent-based polyurethane resin with good hand feel and high wear resistance. Summary of the invention

[0010] The purpose of the present invention is to solve the problems existing in the prior art and provide a solvent-based polyurethane resin and its application on a base fabric.

[0011] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] A solvent-based polyurethane resin comprises a soft segment structure and a hard segment structure, wherein the soft segment structure is formed by oligomer diol residues and diisocyanate residues connected in a urethane structure;

[0013] The hard segment structure is composed of three different structural units randomly distributed, which are denoted as hard segment unit 1, hard segment unit 2 and hard segment unit 3;

[0014] The hard segment unit 1 is formed by connecting an unbranched small molecule diol residue and a diisocyanate residue via a carbamate structure; the raw material unbranched small molecule diol monomer corresponding to the unbranched small molecule diol residue is a C2-C12 straight-chain small molecule diol, such as ethylene glycol, 1,3-propylene glycol or 1,4-butanediol;

[0015] The hard segment unit 2 is formed by connecting an organosiloxane residue and a diisocyanate residue via a carbamate structure; the number average molecular weight of the raw material organosiloxane monomer corresponding to the organosiloxane residue is 1000-5000 g / mol;

[0016] The hard segment unit 3 is formed by short carbon chain branched small molecule diol residues and diisocyanate residues connected by a carbamate structure; the main chain of the raw material short carbon chain branched small molecule diol monomer corresponding to the short carbon chain branched small molecule diol residue is a C3-C6 double-terminal hydroxyl chain, and the branch chain is a C5-C10 alkyl chain.

[0017] The prior art generally designs organic siloxane residues into the soft segment structure of polyurethane resin. The present invention unexpectedly finds that designing organic siloxane residues into the hard segment structure of polyurethane resin will increase the rigidity of the molecular chain of polyurethane resin. As the rigidity increases, the modulus of polyurethane resin increases, which is manifested as improved Martin wear resistance of polyurethane resin.

[0018] The molecular weight of the organosiloxane monomer determines the contribution of the formed hard segment unit 2 to the rigidity of the polyurethane resin. Within an appropriate range, the smaller the molecular weight of the organosiloxane monomer, the greater the rigidity of the polyurethane resin. The molecular weight of the organosiloxane monomer should not be too small, otherwise the low stress modulus of the polyurethane resin will be too large, the difference between the high and low stress moduli will be relatively small, and the hand feel of the obtained polyurethane resin will become harder; the molecular weight of the organosiloxane monomer should not be too large, otherwise the high stress modulus of the polyurethane resin will be too small, the difference between the high and low stress moduli will be relatively small, and the wear resistance of the obtained polyurethane resin will not be sufficiently improved.

[0019] However, the method of improving the Martin abrasion resistance of polyurethane resin by introducing organosiloxane residues into the hard segment structure of polyurethane resin will simultaneously lead to a serious loss of the hand feel of polyurethane resin, which is manifested as a significant decrease in softness. Therefore, balancing the abrasion resistance and hand feel of polyurethane resin is a major difficulty.

[0020] Based on this difficulty, the present invention further introduces short carbon chain branched small molecule diol residues into the hard segment structure of the polyurethane resin. The results show that this not only improves the Martin wear resistance of the polyurethane resin, but also reduces the loss of the feel of the polyurethane resin.

[0021] The present invention conducts a modulus numerical evaluation test of different stress simulations on such solvent-based polyurethane resins. The study found that such solvent-based polyurethane resins can balance Martin wear resistance and hand feel characteristics because they show different response capabilities of the molecular chain of the polyurethane resin to the force under different forces. When the Martin wear resistance changes significantly, the external force on the polyurethane resin is larger, and when the softness changes significantly, the external force on the polyurethane resin is smaller. Specifically, when a smaller external force acts on such solvent-based polyurethane resins, the short carbon chain branched small molecule diol residues can increase the flexibility of the polyurethane resin as a buffer chain, and the polyurethane resin is more flexible. Deformation, when a larger external force acts on such solvent-based polyurethane resins, the short carbon chain branched small molecule diol residues produce a specific rapid shear orientation, showing the original rigidity of the hard segment structure, and the polyurethane resin is more rigid to resist deformation. It is precisely because such solvent-based polyurethane resins have the above-mentioned modulus properties that they can take into account the Martin wear resistance and hand feel of polyurethane resins.

[0022] The length of the alkyl chain in the short carbon chain branched small molecule diol monomer determines the physical properties of the formed hard segment unit 3 for the low stress flexibility and high stress wear resistance of the polyurethane resin; when the length of the alkyl chain is too small, it is difficult to disrupt the regular arrangement of the hard segment and the flexibility is not improved; when the length of the alkyl chain is too large, it will reduce the activity of the hard segment molecular chain, which is not conducive to the crystallization of the hard segment, and reduce the modulus under high and low stress, resulting in a significant decrease in the wear resistance of the polyurethane resin.

[0023] As the preferred technical solution:

[0024] As described above, in a solvent-based polyurethane resin, the molar ratio of the total molar number of short carbon chain branched small molecule diol residues and unbranched small molecule diol residues to the organosiloxane residues is 4-4.3; if the molar ratio is too large, the proportion of organosiloxane is too small, and the wear resistance is insufficiently improved; if the molar ratio is too small, such a solution cannot be obtained through reaction at present.

[0025] In a solvent-based polyurethane resin as described above, the percentage of the molar number of short carbon chain branched small molecule diol residues to the total molar number of short carbon chain branched small molecule diol residues and unbranched small molecule diol residues is 29-34%; if the molar number of short carbon chain branched small molecule diol residues accounts for too large a proportion, the material will lack rigidity, and if the proportion is insufficient, the material will lack flexibility.

[0026] In the solvent-based polyurethane resin as described above, the total molar number of active hydrogen monomer residues in the hard segment accounts for 78-79% of the total molar number of active hydrogen monomer residues in the polyurethane; if the total molar number of active hydrogen monomer residues in the hard segment accounts for too little, the rigidity is insufficient, and if the total molar number of active hydrogen monomer residues in the hard segment accounts for too much, the flexibility is insufficient.

[0027] In the solvent-based polyurethane resin as described above, the number average molecular weight of the raw material oligomer diol monomer corresponding to the oligomer diol residue is 1000-3000 g / mol.

[0028] In the solvent-based polyurethane resin as described above, the oligomer diol monomer is polycarbonate diol and / or polycaprolactone diol.

[0029] In the solvent-based polyurethane resin as described above, the organosiloxane monomer is a dihydroxy branched organosiloxane.

[0030] In the solvent-based polyurethane resin as described above, the short carbon chain branched small molecule diol monomer is 2,2-di-n-hexylpropane-1,3-diol or 2-butyl-1,3-propanediol.

[0031] In the solvent-based polyurethane resin as described above, the raw material diisocyanate monomer corresponding to the diisocyanate residue is isophorone diisocyanate or 4,4-dicyclohexylmethane diisocyanate.

[0032] As described above, a solvent-based polyurethane resin, the difference between the high stress modulus and the low stress modulus of the solvent-based polyurethane resin is 4.8-5.1MPa. The high stress modulus and the low stress modulus determine the wear resistance and feel of the resin respectively. The larger the difference between the two, the better the resin can balance good feel and high wear resistance. The high stress modulus refers to the tensile elastic modulus measured at a tensile speed of 50mm / min in a tensile test, and the low stress modulus refers to the tensile elastic modulus measured at a tensile speed of 1mm / min in a tensile test.

[0033] The present invention also provides the use of a solvent-based polyurethane resin as described in any one of the above items on a base fabric for microfiber leather veneer.

[0034] The present invention also provides a method for preparing a solvent-based polyurethane resin as described in any one of the above items, comprising the following steps:

[0035] (a) prepolymerization;

[0036] Add oligomer diol monomer, diisocyanate monomer and solvent a (N,N-dimethylformamide or toluene) into the reaction kettle, control the molar ratio of NCO group to active hydrogen monomer (hydroxyl group) in the reaction system to be 2.0-2.3 to ensure that the active hydrogen monomer is fully reacted, react at 70-80°C for 3-4h under nitrogen or inert gas protection, and the reaction product is recorded as A;

[0037] The ratio of the mass of solvent a to the total mass of the oligomer diol monomer and the diisocyanate monomer is 1-3:1-2;

[0038] (b) preparing polyol-modified diisocyanates;

[0039] First, add diisocyanate monomer into the reaction kettle, and then add dropwise a mixed solution of short carbon chain branched small molecule diol monomer and solvent b (N,N-dimethylformamide or toluene) in a mass ratio of 1:0.4-0.8, the molar ratio of diisocyanate monomer to short carbon chain branched small molecule diol monomer is 2.1-2.3, react at 65-75°C for 3-4h under nitrogen or inert gas protection, and the reaction product is recorded as B;

[0040] (c) polymerization;

[0041] First, add organic siloxane monomer, unbranched small molecule diol monomer and solvent c (N, N-dimethylformamide or toluene) into A and stir evenly, then add B and stir evenly, add diisocyanate monomer to control the molar ratio of NCO group to active hydrogen monomer (hydroxyl group) in the reaction system to 1.02-1.04 to ensure that the active hydrogen monomer is fully reacted, and react at 70-80° C. for 3-4 hours under nitrogen or inert gas protection to obtain a solvent-based polyurethane resin;

[0042] The content of solvent c in the reaction system is 55-65wt%.

[0043] Beneficial effects:

[0044] (1) The present invention improves the Martin wear resistance of the polyurethane resin by designing the organosiloxane residue into the hard segment structure of the polyurethane resin.

[0045] (2) The present invention further introduces short carbon chain branched small molecule diol residues into the hard segment structure, so that the hand feel loss of the polyurethane resin is relatively small; when subjected to a small external force, the short carbon chain branched small molecule diol residues act as buffer chains to increase the flexibility of the polyurethane resin, which manifests as flexible deformation; when subjected to a large external force, the short carbon chain branched small molecule diol residues produce a specific rapid shear orientation, showing the original rigidity of the hard segment structure, which manifests as rigid resistance to deformation; this characteristic enables the solvent-based polyurethane resin to take into account both Martin wear resistance and hand feel.

[0046] (3) The solvent-based polyurethane resin of the present invention can be applied to microfiber leather veneer, meeting the demand for high-performance synthetic leather in the fields of automotive interior materials and the like. DETAILED DESCRIPTION

[0047] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0048] In polyurethane, the soft segment provides flexibility to polyurethane while also reducing wear resistance, and the hard segment provides wear resistance while also reducing flexibility. The innovation of the present invention lies in the special design of the hard segment, which enables the polyurethane to improve wear resistance while relatively obtaining better softness. The soft segment design of the present invention is a conventional design, and the above relative modification effects can be reproduced in polyurethanes with different soft segment designs. Exemplarily, the soft segment designed in the embodiment of the present invention is composed of polycarbonate diol residues and / or polycaprolactone diol residues, and the number average molecular weight of the raw material oligomer diol monomer corresponding to the oligomer diol residue is 1000-3000g / mol; the soft segment can freely adjust the overall high stress modulus and low stress modulus to high or low positions according to the required physical property development goals, and the above examples do not constitute a constraint on the present invention.

[0049] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0050] Viscosity: The test was conducted using a Brookfield DV2TRVTJ0 rotational viscometer in a laboratory environment (temperature 23±2°C, relative humidity 50±10%RH), with a rotor RV-06(6) and a rotation speed of 6.0RPM.

[0051] High Stress Modulus, Low Stress Modulus: Follow the steps below to perform the test:

[0052] (1) Preparation of samples: 100 g of the sample to be tested was mixed with 20 g of N,N-dimethylformamide and vacuum degassed for 10 min to obtain a slurry; the slurry was evenly coated on a horizontal release paper (manufacturer: Zhejiang Jumei Special Materials Co., Ltd., model: 7M9009) using a scraper with a scraper distance of 0.2 mm, and the slurry was allowed to stand for 2 min to defoam; the release paper coated with the slurry was placed in a 120°C constant temperature blast oven for 5 min, and the film was taken out and cut into 105 mm × 25 mm samples after cooling to room temperature;

[0053] (2) Using a universal testing machine, according to GB / T 1040.1-2018 and GB / T 1040.3-2006 standards, the specimen gauge length was 75 mm, and each group was tested in parallel 5 times. The measured values ​​were recorded and averaged to obtain the stress-strain curve. The slope of the elastic region was calculated to obtain the tensile elastic modulus. Among them, the tensile elastic modulus measured at a tensile speed of 50 mm / min is the high stress modulus, and the tensile elastic modulus measured at a tensile speed of 1 mm / min is the low stress modulus.

[0054] Abrasion times: Cut the sample to be tested into a disc specimen with a diameter of 38mm, balance it in a laboratory environment for more than 12 hours, then install the sample on the high-speed rail testing instrument GT-7012-M Martindale abrasion tester, and use a fixing ring to stabilize it. Then, place the wool felt and friction cloth on the 140mm base grinding table in turn, and fix them with a fixing ring. Insert the load shaft (12kPa) into the circular groove of the test fixture, set the test times, start the test switch, and wait until the surface of the sample is damaged. Immediately stop the machine and take samples to determine the results, and record the abrasion times. Each set of tests is carried out on 3 samples in parallel.

[0055] Deflection value: Cut the sample to be tested into 100mm×100mm square specimens, balance them in a laboratory environment for more than 12 hours, and use Tianjin Nikos ST300 leather softness tester (accuracy 0.1mm, range 0-6.6mm, common range 2-6mm) for testing. Clamp the sample in a test hole with an aperture of 25mm, apply a load of 50±5N to the sample through the small hole, read the deflection value indicated by the scale pointer and record it, and test 5 samples in parallel in each group.

[0056] In the following embodiments, the specific process of using solvent-based polyurethane resin for microfiber leather veneer is as follows:

[0057] (1) adding black paste (manufacturer: Jiangxi Mitsukoshi New Materials Co., Ltd., product name: PU-9100) to the solvent-based polyurethane resin for dyeing, and then adding N,N-dimethylformamide (DMF) to obtain a paste with a viscosity of 1500 mPa·s; wherein the mass ratio of the black paste to the solvent-based polyurethane resin is 3:100;

[0058] (2) After the resin slurry is scraped onto the release paper (manufacturer: Zhejiang Jumei Special Materials Co., Ltd., model number: 7M9009) using a scraper, three film-forming operations are performed (i.e., first scraping → first drying → second scraping → second drying → third scraping → third drying); wherein, the blade distance of the first scraping is 0.2 mm, the blade distance of the second scraping is 0.25 mm, and the blade distance of the third scraping is 0.3 mm; the drying process of each drying adopts a drying tunnel with stepped temperature zones of 70°C, 100°C, and 140°C, and the drying is performed for 1 min at each drying tunnel temperature;

[0059] (3) A 0.3 mm thick layer of polyurethane adhesive (composed of polyurethane resin, crosslinking agent and DMF in a mass ratio of 100:5:10; the polyurethane resin is manufactured by Shanghai Huide Technology Co., Ltd., with the product name HDBA-2602P; the crosslinking agent is manufactured by Shanghai Huide Technology Co., Ltd., with the product name HDN-75) was scraped onto the film, and then laminated with the base fabric (manufactured by Shanghai Huafeng Microfiber Technology Co., Ltd., with the product name EZNB0-110P91) at a laminating pressure of 5±0.5 kg. The film was transferred to a 150°C oven for aging treatment for 0.2 h, and then peeled at an angle of 45° to obtain a microfiber leather test sample.

[0060] Example 1

[0061] A method for preparing a solvent-based polyurethane resin, the specific steps are as follows:

[0062] (1) Preparation of raw materials;

[0063] Polycarbonate diol: manufacturer: Ube Industries, Ltd., brand: UH-100, number average molecular weight: 1000 g / mol;

[0064] Polycaprolactone diol: manufacturer is Daicel Industries, Ltd., brand name is PCL 220N, number average molecular weight is 2000 g / mol;

[0065] Diisocyanate monomer: isophorone diisocyanate;

[0066] Solvent a, solvent b and solvent c: all are N,N-dimethylformamide;

[0067] Organic siloxane monomer: dihydroxy branched organic siloxane, manufacturer is Silok New Materials Co., Ltd., model 8621F1, number average molecular weight is 1000 g / mol;

[0068] Unbranched small molecule diol monomer: ethylene glycol;

[0069] Short carbon chain branched small molecule diol monomer: 2,2-di-n-hexylpropane-1,3-diol;

[0070] (2) preparing a solvent-based polyurethane resin;

[0071] (a) prepolymerization;

[0072] Add polycarbonate diol, polycaprolactone diol, diisocyanate monomer and solvent a into a reactor, control the molar ratio of NCO group to active hydrogen monomer in the reaction system to be 2, react at 70°C for 4 hours under nitrogen or inert gas protection, and record the reaction product as A; wherein, the addition amount of polycarbonate diol is 0.25 mol, the addition amount of polycaprolactone diol is 0.17 mol, and the ratio of the mass of solvent a to the total mass of polycarbonate diol, polycaprolactone diol and diisocyanate monomer is 1:1;

[0073] (b) preparing polyol-modified diisocyanates;

[0074] After preparing a mixed solution of a short carbon chain branched small molecule diol monomer and a solvent b, first add a diisocyanate monomer into a reaction kettle, then add the mixed solution dropwise, and react at 65° C. for 4 hours under the protection of nitrogen or an inert gas. The reaction product is recorded as B; wherein the addition amount of the carbon chain branched small molecule diol monomer is 0.35 mol, the mass ratio of the short carbon chain branched small molecule diol monomer to the solvent b is 1:0.4, and the molar ratio of the diisocyanate monomer to the short carbon chain branched small molecule diol monomer is 2.3;

[0075] (c) polymerization;

[0076] First, add an organic siloxane monomer, an unbranched small molecule diol monomer and a solvent c into A and stir evenly, then add B and stir evenly, supplement a diisocyanate monomer to control the molar ratio of NCO groups to active hydrogen monomers in the reaction system to be 1.03, and react at 70° C. for 4 hours under the protection of nitrogen or an inert gas to obtain a solvent-based polyurethane resin; wherein the input amount of the organic siloxane monomer is 0.28 mol, the input amount of the unbranched small molecule diol monomer is 0.84 mol, and the content of the solvent c in the reaction system is 65wt%.

[0077] The solvent-based polyurethane resin finally prepared consists of a soft segment structure and a hard segment structure. The soft segment structure is formed by oligomeric diol residues and diisocyanate residues connected by a carbamate structure; the hard segment structure is composed of three different structural units randomly distributed, which are respectively recorded as hard segment unit 1, hard segment unit 2 and hard segment unit 3. Hard segment unit 1 is formed by unbranched small molecule diol residues and diisocyanate residues connected by a carbamate structure, hard segment unit 2 is formed by organic siloxane residues and diisocyanate residues connected by a carbamate structure, and hard segment unit 3 is formed by organic siloxane residues and diisocyanate residues connected by a carbamate structure. Segment unit 3 is formed by short carbon chain branched small molecule diol residues and diisocyanate residues connected by a carbamate structure; the molar ratio of the total molar number of short carbon chain branched small molecule diol residues and unbranched small molecule diol residues to the organosiloxane residue is 4.3; the percentage of the molar number of short carbon chain branched small molecule diol residues to the total molar number of short carbon chain branched small molecule diol residues and unbranched small molecule diol residues is 29%; the total molar number of active hydrogen monomer residues in the hard segment accounts for 78% of the total molar number of active hydrogen monomer residues in the polyurethane;

[0078] The high stress modulus of solvent-based polyurethane resin is 13.5MPa, and the low stress modulus is 8.4MPa. After the solvent-based polyurethane resin is used for microfiber leather veneer, the wear resistance of the microfiber leather is 240,000 times, and the deflection value is 3.6mm.

[0079] Comparative Example 1

[0080] A method for preparing a polyurethane resin, which differs from Example 1 only in that the organosiloxane monomer is not added in step (c), but is added into a reaction kettle together with polycarbonate diol, polycaprolactone diol, diisocyanate monomer, and solvent a in step (a) (i.e., the organosiloxane residue is not introduced into the hard segment unit 2, but is introduced into the soft segment structure).

[0081] The high stress modulus of the polyurethane resin finally obtained is 7.9MPa, and the low stress modulus is 6MPa; after the solvent-based polyurethane resin is used for microfiber leather veneer, the wear resistance of the microfiber leather is 100,000 times.

[0082] Compared with Example 1, the difference between the high and low stress moduli of the polyurethane resin in Comparative Example 1 is significantly reduced; after the solvent-based polyurethane resin is used for the microfiber leather veneer, the wear times of the microfiber leather are significantly reduced. This is because when the organic siloxane residues are introduced into the soft segment structure, the rigidity increase of the polyurethane resin molecular chain is insufficient. In the soft segment structure, the organic siloxane residues have limited effect on improving the overall rigidity of the molecular chain, making it difficult to effectively improve the high stress modulus of the resin, thereby relatively reducing the difference between the high and low stress moduli; due to the insufficient rigidity of the molecular chain, when subjected to friction, the molecular chain is more likely to slip and deform relatively, and cannot resist wear as effectively as when the organic siloxane residues are introduced into the hard segment, so the wear times of the microfiber leather are significantly reduced.

[0083] Comparative Example 2

[0084] A method for preparing a polyurethane resin, which differs from Example 1 only in that a short carbon chain branched small molecule diol monomer (2,2-di-n-hexylpropane-1,3-diol) is replaced by an equimolar amount of an unbranched small molecule diol monomer (ethylene glycol).

[0085] The high stress modulus of the polyurethane resin finally obtained is 13.2MPa, and the low stress modulus is 12.4MPa; after the solvent-based polyurethane resin is used for microfiber leather veneer, the deflection value of the microfiber leather is 2.8mm.

[0086] Compared with Example 1, the difference between the high-stress modulus and the low-stress modulus of the polyurethane resin in Comparative Example 2 is significantly reduced; after the solvent-based polyurethane resin is used for the microfiber leather veneer, the deflection value of the microfiber leather is significantly reduced. This is because ethylene glycol has no branched structure. In the hard segment structure of the polyurethane resin, it cannot act as a buffer chain to increase the flexibility of the resin when a small external force is applied. The overall flexibility of the material decreases, and it is not easy to produce a large bending deformation when subjected to a bending force. Therefore, the deflection value of the microfiber leather is significantly reduced; when subjected to external force, the unbranched structure makes it difficult for the polyurethane resin to exhibit more flexible deformation, so the flexibility is insufficient under low stress, resulting in a higher low stress modulus and a smaller difference between the high and low stress moduli.

[0087] Comparative Example 3

[0088] A method for preparing a polyurethane resin, which is different from Example 1 only in that the model of the organosiloxane monomer (dihydroxy branched organosiloxane) is Silok 8621F15, and the number average molecular weight is 15000 g / mol.

[0089] The high stress modulus of the polyurethane resin finally obtained is 10.6MPa, and the low stress modulus is 6.8MPa; after the solvent-based polyurethane resin is used for microfiber leather veneer, the wear resistance of the microfiber leather is 120,000 times.

[0090] Compared with Example 1, the difference between the high and low stress moduli of the polyurethane resin in Comparative Example 3 is significantly reduced; after the solvent-based polyurethane resin is used for the microfiber leather veneer, the wear times of the microfiber leather are significantly reduced. This is because when the molecular weight of the organic silicone monomer is too large, the high stress modulus of the polyurethane resin will be too small, and the difference between the high and low stress moduli will become relatively smaller; since the high stress modulus is too small, the resin cannot effectively provide rigid support when resisting wear, and the molecular chain is more easily damaged during the friction process and cannot resist friction well, resulting in a significant reduction in the wear times of the microfiber leather.

[0091] Comparative Example 4

[0092] A method for preparing a polyurethane resin, which differs from Example 1 only in that a short carbon chain branched small molecule diol monomer (2,2-di-n-hexylpropane-1,3-diol) is replaced by 2-methyl-1,3-propanediol.

[0093] The high stress modulus of the polyurethane resin finally obtained is 13.7MPa, and the low stress modulus is 11.8MPa; after the solvent-based polyurethane resin is used for microfiber leather veneer, the deflection value of the microfiber leather is 2.9mm.

[0094] Compared with Example 1, the difference between the high-stress modulus and the low-stress modulus of the polyurethane resin in Comparative Example 4 is significantly reduced; after the solvent-based polyurethane resin is used for the microfiber leather veneer, the deflection value of the microfiber leather is significantly reduced. This is because the alkyl chain of 2-methyl-1,3-propanediol is relatively short, and it is difficult to disrupt the regular arrangement of the hard segment, so that the flexibility of the polyurethane resin is not improved. When subjected to external force, the resin cannot effectively buffer the external force through flexible deformation, and cannot exhibit good flexibility under low stress, so the low stress modulus is relatively high, resulting in a significant reduction in the difference between the high-stress modulus and the low stress modulus; because the material is not flexible enough, it is difficult to produce a large bending deformation when subjected to a bending force, and it is impossible to increase the deflection through flexible deformation under a small external force, so the deflection value of the microfiber leather is significantly reduced.

[0095] Comparative Example 5

[0096] A method for preparing a polyurethane resin is different from Example 1 only in that the short carbon chain branched small molecule diol monomer (2,2-di-n-hexylpropane-1,3-diol) is replaced by 2,2-dioctyl-1,3-propanediol.

[0097] The high stress modulus of the polyurethane resin finally obtained is 11.5MPa, and the low stress modulus is 7MPa; after the solvent-based polyurethane resin is used for microfiber leather veneer, the wear resistance of the microfiber leather is 160,000 times.

[0098] Compared with Example 1, the difference between the high and low stress moduli of the polyurethane resin in Comparative Example 5 is significantly reduced; after the solvent-based polyurethane resin is used for the microfiber leather veneer, the wear times of the microfiber leather are significantly reduced. This is because the alkyl chain length of 2,2-dioctyl-1,3-propanediol is too large, which will reduce the activity of the hard segment molecular chain and is not conducive to the crystallization of the hard segment, which makes the modulus under high and low stresses decrease, and the difference between the high and low stress moduli decreases accordingly; due to the reduced activity of the hard segment molecular chain and the deterioration of the crystallization, when subjected to friction, the rigid resistance of the molecular chain becomes weak and cannot effectively resist wear. Therefore, after the solvent-based polyurethane resin is used for the microfiber leather veneer, the wear times of the microfiber leather are significantly reduced.

[0099] Example 2

[0100] A method for preparing a solvent-based polyurethane resin, the specific steps are as follows:

[0101] (1) Preparation of raw materials;

[0102] Polycarbonate diol: manufacturer: Ube Industries, Ltd., brand: UH-100, number average molecular weight: 1000 g / mol;

[0103] Polycaprolactone diol: manufacturer is Daicel Industries, Ltd., brand name is PCL 230N, number average molecular weight is 3000 g / mol;

[0104] Diisocyanate monomer: 4,4-dicyclohexylmethane diisocyanate;

[0105] Solvent a, solvent b and solvent c: all are N,N-dimethylformamide;

[0106] Organic siloxane monomer: dihydroxy branched organic siloxane, manufacturer is Silok New Materials Co., Ltd., model 8621F131, number average molecular weight 3100 g / mol;

[0107] Unbranched small molecule diol monomer: 1,3-propylene glycol;

[0108] Short carbon chain branched small molecule diol monomer: 2,2-di-n-hexylpropane-1,3-diol;

[0109] (2) preparing a solvent-based polyurethane resin;

[0110] (a) prepolymerization;

[0111] Add polycarbonate diol, polycaprolactone diol, diisocyanate monomer and solvent a into a reactor, control the molar ratio of NCO group to active hydrogen monomer in the reaction system to be 2.1, react at 75°C for 3 hours under nitrogen or inert gas protection, and record the reaction product as A; wherein, the addition amount of polycarbonate diol is 0.28 mol, the addition amount of polycaprolactone diol is 0.14 mol, and the ratio of the mass of solvent a to the total mass of polycarbonate diol, polycaprolactone diol and diisocyanate monomer is 3:1;

[0112] (b) preparing polyol-modified diisocyanates;

[0113] After preparing a mixed solution of a short carbon chain branched small molecule diol monomer and a solvent b, first add a diisocyanate monomer into a reaction kettle, then add the mixed solution dropwise, and react at 68° C. for 3 hours under the protection of nitrogen or an inert gas. The reaction product is recorded as B; wherein, the amount of the carbon chain branched small molecule diol monomer added is 0.39 mol, the mass ratio of the short carbon chain branched small molecule diol monomer to the solvent b is 1:0.5, and the molar ratio of the diisocyanate monomer to the short carbon chain branched small molecule diol monomer is 2.1;

[0114] (c) polymerization;

[0115] First, add an organic siloxane monomer, an unbranched small molecule diol monomer and a solvent c into A and stir evenly, then add B and stir evenly, supplement a diisocyanate monomer to control the molar ratio of NCO groups to active hydrogen monomers in the reaction system to be 1.02, and react at 75° C. for 3 hours under the protection of nitrogen or an inert gas to obtain a solvent-based polyurethane resin; wherein the input amount of the organic siloxane monomer is 0.29 mol, the input amount of the unbranched small molecule diol monomer is 0.82 mol, and the content of the solvent c in the reaction system is 62wt%.

[0116] The solvent-based polyurethane resin finally prepared consists of a soft segment structure and a hard segment structure. The soft segment structure is formed by oligomeric diol residues and diisocyanate residues connected by a carbamate structure; the hard segment structure is composed of three different structural units randomly distributed, which are respectively recorded as hard segment unit 1, hard segment unit 2 and hard segment unit 3. Hard segment unit 1 is formed by unbranched small molecule diol residues and diisocyanate residues connected by a carbamate structure, hard segment unit 2 is formed by organic siloxane residues and diisocyanate residues connected by a carbamate structure, and hard segment unit 3 is formed by organic siloxane residues and diisocyanate residues connected by a carbamate structure. Segment unit 3 is formed by short carbon chain branched small molecule diol residues and diisocyanate residues connected by a carbamate structure; the molar ratio of the total molar number of short carbon chain branched small molecule diol residues and unbranched small molecule diol residues to the organosiloxane residue is 4.2; the percentage of the molar number of short carbon chain branched small molecule diol residues to the total molar number of short carbon chain branched small molecule diol residues and unbranched small molecule diol residues is 32%; the total molar number of active hydrogen monomer residues in the hard segment accounts for 78% of the total molar number of active hydrogen monomer residues in the polyurethane;

[0117] The high stress modulus of solvent-based polyurethane resin is 13.1MPa, and the low stress modulus is 8.3MPa. After the solvent-based polyurethane resin is used for microfiber leather veneer, the wear resistance of the microfiber leather is 220,000 times, and the deflection value is 3.9mm.

[0118] Example 3

[0119] A method for preparing a solvent-based polyurethane resin, the specific steps are as follows:

[0120] (1) Preparation of raw materials;

[0121] Polycaprolactone diol: manufacturer is Daicel Industries, Ltd., brand name is PCL 220N, number average molecular weight is 2000 g / mol;

[0122] Diisocyanate monomer: 4,4-dicyclohexylmethane diisocyanate;

[0123] Solvent a, solvent b and solvent c: all are N,N-dimethylformamide;

[0124] Organic siloxane monomer: dihydroxy branched organic siloxane, manufacturer is Silok New Materials Co., Ltd., model 8621F5, number average molecular weight 5000 g / mol;

[0125] Unbranched small molecule diol monomer: 1,4-butanediol;

[0126] Short carbon chain branched small molecule diol monomer: 2-butyl-1,3-propanediol;

[0127] (2) preparing a solvent-based polyurethane resin;

[0128] (a) prepolymerization;

[0129] Add polycaprolactone diol, diisocyanate monomer and solvent a into a reaction kettle, control the molar ratio of NCO group to active hydrogen monomer in the reaction system to be 2.2, react at 75°C for 3 hours under nitrogen or inert gas protection, and record the reaction product as A; wherein, the addition amount of polycaprolactone diol is 0.41 mol, and the ratio of the mass of solvent a to the total mass of polycaprolactone diol and diisocyanate monomer is 1:2;

[0130] (b) preparing polyol-modified diisocyanates;

[0131] After preparing a mixed solution of a short carbon chain branched small molecule diol monomer and a solvent b, first add a diisocyanate monomer into a reaction kettle, then add the mixed solution dropwise, and react at 70° C. for 3 hours under the protection of nitrogen or an inert gas. The reaction product is recorded as B; wherein, the amount of the carbon chain branched small molecule diol monomer added is 0.42 mol, the mass ratio of the short carbon chain branched small molecule diol monomer to the solvent b is 1:0.6, and the molar ratio of the diisocyanate monomer to the short carbon chain branched small molecule diol monomer is 2.1;

[0132] (c) polymerization;

[0133] First, add an organic siloxane monomer, an unbranched small molecule diol monomer and a solvent c into A and stir evenly, then add B and stir evenly, supplement a diisocyanate monomer to control the molar ratio of NCO groups to active hydrogen monomers in the reaction system to be 1.03, and react at 80° C. for 3 hours under the protection of nitrogen or an inert gas to obtain a solvent-based polyurethane resin; wherein the input amount of the organic siloxane monomer is 0.3 mol, the input amount of the unbranched small molecule diol monomer is 0.81 mol, and the content of the solvent c in the reaction system is 58wt%.

[0134] The solvent-based polyurethane resin finally prepared consists of a soft segment structure and a hard segment structure. The soft segment structure is formed by oligomeric diol residues and diisocyanate residues connected by a carbamate structure; the hard segment structure is composed of three different structural units randomly distributed, which are respectively recorded as hard segment unit 1, hard segment unit 2 and hard segment unit 3. Hard segment unit 1 is formed by unbranched small molecule diol residues and diisocyanate residues connected by a carbamate structure, hard segment unit 2 is formed by organic siloxane residues and diisocyanate residues connected by a carbamate structure, and hard segment unit 3 is formed by organic siloxane residues and diisocyanate residues connected by a carbamate structure. Segment unit 3 is formed by short carbon chain branched small molecule diol residues and diisocyanate residues connected by a carbamate structure; the molar ratio of the total molar number of short carbon chain branched small molecule diol residues and unbranched small molecule diol residues to the organosiloxane residue is 4.1; the percentage of the molar number of short carbon chain branched small molecule diol residues to the total molar number of short carbon chain branched small molecule diol residues and unbranched small molecule diol residues is 34%; the total molar number of active hydrogen monomer residues in the hard segment accounts for 79% of the total molar number of active hydrogen monomer residues in the polyurethane;

[0135] The high stress modulus of solvent-based polyurethane resin is 12.9MPa, and the low stress modulus is 7.9MPa. After the solvent-based polyurethane resin is used for microfiber leather veneer, the wear resistance of the microfiber leather is 210,000 times, and the deflection value is 4mm.

[0136] Example 4

[0137] A method for preparing a solvent-based polyurethane resin, the specific steps are as follows:

[0138] (1) Preparation of raw materials;

[0139] Polycarbonate diol: manufacturer is Ube Industries, Ltd., brand name is UH-300, number average molecular weight is 3000 g / mol;

[0140] Diisocyanate monomer: isophorone diisocyanate;

[0141] Solvent a, solvent b and solvent c: all are N,N-dimethylformamide;

[0142] Organic siloxane monomer: dihydroxy branched organic siloxane, manufacturer is Silok New Materials Co., Ltd., model 8621F1, number average molecular weight is 1000 g / mol;

[0143] Unbranched small molecule diol monomer: 1,4-butanediol;

[0144] Short carbon chain branched small molecule diol monomer: 2-butyl-1,3-propanediol;

[0145] (2) preparing a solvent-based polyurethane resin;

[0146] (a) prepolymerization;

[0147] Add polycarbonate diol, diisocyanate monomer and solvent a into a reactor, control the molar ratio of NCO group to active hydrogen monomer in the reaction system to be 2.3, react at 80°C for 4 hours under nitrogen or inert gas protection, and record the reaction product as A; wherein, the addition amount of polycarbonate diol is 0.41 mol, and the ratio of the mass of solvent a to the total mass of polycarbonate diol and diisocyanate monomer is 3:2;

[0148] (b) preparing polyol-modified diisocyanates;

[0149] After preparing a mixed solution of a short carbon chain branched small molecule diol monomer and a solvent b, first add a diisocyanate monomer into a reaction kettle, then add the mixed solution dropwise, and react at 75° C. for 4 hours under the protection of nitrogen or an inert gas. The reaction product is recorded as B; wherein the amount of the carbon chain branched small molecule diol monomer added is 0.43 mol, the mass ratio of the short carbon chain branched small molecule diol monomer to the solvent b is 1:0.8, and the molar ratio of the diisocyanate monomer to the short carbon chain branched small molecule diol monomer is 2.2;

[0150] (c) polymerization;

[0151] First, add an organic siloxane monomer, an unbranched small molecule diol monomer and a solvent c into A and stir evenly, then add B and stir evenly, supplement a diisocyanate monomer to control the molar ratio of NCO groups to active hydrogen monomers in the reaction system to be 1.04, and react at 75° C. for 4 hours under the protection of nitrogen or an inert gas to obtain a solvent-based polyurethane resin; wherein the input amount of the organic siloxane monomer is 0.31 mol, the input amount of the unbranched small molecule diol monomer is 0.82 mol, and the content of the solvent c in the reaction system is 55wt%.

[0152] The solvent-based polyurethane resin finally prepared consists of a soft segment structure and a hard segment structure. The soft segment structure is formed by oligomer diol residues and diisocyanate residues connected by a carbamate structure; the hard segment structure is composed of three different structural units randomly distributed, which are respectively recorded as hard segment unit 1, hard segment unit 2 and hard segment unit 3. The hard segment unit 1 is formed by unbranched small molecule diol residues and diisocyanate residues connected by a carbamate structure, and the hard segment unit 2 is formed by organic siloxane residues and diisocyanate residues connected by a carbamate structure. The hard segment unit 3 is formed by connecting a short carbon chain branched small molecule diol residue and a diisocyanate residue via a carbamate structure; the molar ratio of the total molar number of the short carbon chain branched small molecule diol residue and the unbranched small molecule diol residue to the organosiloxane residue is 4; the percentage of the molar number of the short carbon chain branched small molecule diol residue to the total molar number of the short carbon chain branched small molecule diol residue and the unbranched small molecule diol residue is 34%; the total molar number of the active hydrogen monomer residues in the hard segment accounts for 79% of the total molar number of the active hydrogen monomer residues in the polyurethane;

[0153] The high stress modulus of solvent-based polyurethane resin is 13.2MPa, and the low stress modulus is 8.1MPa. After the solvent-based polyurethane resin is used for microfiber leather veneer, the wear resistance of the microfiber leather is 230,000 times, and the deflection value is 3.7mm.

Claims

1. A solvent-based polyurethane resin comprising a soft segment structure and a hard segment structure, wherein the soft segment structure is formed by oligomer diol residues and diisocyanate residues connected by a urethane structure, characterized in that: The hard segment structure is composed of three different structural units randomly distributed, which are denoted as hard segment unit 1, hard segment unit 2 and hard segment unit 3; The hard segment unit 1 is formed by connecting an unbranched small molecule diol residue and a diisocyanate residue via a carbamate structure; the raw material unbranched small molecule diol monomer corresponding to the unbranched small molecule diol residue is a C2-C12 straight-chain small molecule diol; The hard segment unit 2 is formed by connecting an organosiloxane residue and a diisocyanate residue via a carbamate structure; the number average molecular weight of the raw material organosiloxane monomer corresponding to the organosiloxane residue is 1000-5000 g / mol; The hard segment unit 3 is formed by short carbon chain branched small molecule diol residues and diisocyanate residues connected by a carbamate structure; the main chain of the raw material short carbon chain branched small molecule diol monomer corresponding to the short carbon chain branched small molecule diol residue is a C3-C6 double-terminal hydroxyl chain, and the branch chain is a C5-C10 alkyl chain.

2. A solvent-based polyurethane resin according to claim 1, characterized in that: The molar ratio of the total molar number of the short carbon chain branched small molecule diol residues and the unbranched small molecule diol residues to the organosiloxane residues is 4-4.

3.

3. A solvent-based polyurethane resin according to claim 1, characterized in that: The percentage of the molar number of the short carbon chain branched small molecule diol residues to the total molar number of the short carbon chain branched small molecule diol residues and the unbranched small molecule diol residues is 29-34%.

4. A solvent-based polyurethane resin according to claim 1, characterized in that: The total molar number of active hydrogen monomer residues in the hard segment accounts for 78-79% of the total molar number of active hydrogen monomer residues in the polyurethane.

5. The solvent-based polyurethane resin according to claim 1, characterized in that: The number average molecular weight of the raw material oligomer diol monomer corresponding to the oligomer diol residue is 1000-3000 g / mol.

6. A solvent-based polyurethane resin according to claim 5, characterized in that: The oligomer diol monomer is polycarbonate diol and / or polycaprolactone diol.

7. The solvent-based polyurethane resin according to claim 1, characterized in that: The organosiloxane monomer is a dihydroxy branched type organosiloxane.

8. The solvent-based polyurethane resin according to claim 1, characterized in that: The short carbon chain branched small molecule diol monomer is 2,2-di-n-hexylpropane-1,3-diol or 2-butyl-1,3-propanediol.

9. The solvent-based polyurethane resin according to claim 1, characterized in that: The difference between the high stress modulus and the low stress modulus of solvent-based polyurethane resin is 4.8-5.1MPa. The high stress modulus refers to the tensile elastic modulus measured at a tensile speed of 50mm / min in a tensile test, and the low stress modulus refers to the tensile elastic modulus measured at a tensile speed of 1mm / min in a tensile test.

10. Use of a solvent-based polyurethane resin on a base fabric as claimed in any one of claims 1 to 9, characterized in that: Used for microfiber leather veneer.