A kind of solvent-free polyurethane synthetic leather and preparation method thereof

Abstract

The invention discloses a solvent-free polyurethane synthetic leather and a preparation method thereof, wherein the preparation method comprises the following steps: adding diisocyanate to polyol under nitrogen protection and anhydrous conditions, stirring and reacting at a first speed, adding a composite catalyst, continuing stirring, and cooling the reaction system to room temperature to obtain a first component; controlling the reaction temperature, adding polyol to diisocyanate under nitrogen protection and anhydrous conditions, stirring and reacting at a second speed to obtain a second component; uniformly mixing the first component and the second component, adding water for foaming, adding an auxiliary agent, and uniformly stirring to obtain a polyurethane slurry; coating the polyurethane slurry on a surface material, pre-curing, and then laminating the bottom material with the pre-cured polyurethane slurry, and post-curing to obtain a solvent-free polyurethane synthetic leather. The method has reasonable design, controllable reaction, high raw material conversion rate, simple process, and excellent performance of the obtained solvent-free polyurethane synthetic leather.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic leather preparation, and relates to solvent-free polyurethane synthetic leather and a preparation method thereof. Background Art

[0002] Polyurethane synthetic leather is considered to be an ideal substitute for natural leather due to its beautiful appearance, comfortable feel, excellent physical properties, moderate price, good wear resistance, excellent low-temperature flexibility, and good chemical stability. In recent years, with the increasing environmental awareness of consumers, the emphasis on environmental protection, and the continuous introduction of environmental protection policies in various countries, consumer demand has continued to increase, and solvent-free polyurethane synthetic leather has become the development trend of the industry.

[0003] Solvent-free polyurethane does not use any solvent in the raw materials and processing process, and will not be flammable and explosive. Therefore, it will not pollute the ecological environment and harm the health of workers, and greatly reduce the risk factor of enterprise production, and ensure the safety of employees' personal property. Solvent-free polyurethane not only has the excellent properties of solvent-based polyurethane such as high mechanical strength, wear resistance, aging resistance, good elasticity, and strong reprocessability, but also has the advantages of non-toxicity, pollution-free, low energy consumption, and good moisture permeability. However, the production process of solvent-free polyurethane synthetic leather belongs to online in-situ reaction, the reaction is difficult to control, the conversion rate is low, and the foaming technology is poorly controllable, and the selection and requirements of the catalyst are extremely high. In the invention patent of publication number CN114015002A, an organic tin catalyst is used as a reaction catalyst to prepare a polyurethane floor material with a fast molding speed. However, the polyurethane prepared by a general catalytic method has a low reaction degree and conversion rate, which will cause adhesion to the mold during online peeling or pressing. At the same time, the catalyst is difficult to disperse in the reaction system, resulting in uneven product structure, thereby affecting the mechanical properties of the product. Patent No. CN112175163A introduces a method of first introducing a tertiary amine group with catalytic effect into polyester polyol, so that the solvent-free polyurethane undergoes self-catalysis during the preparation process, which greatly improves the dispersibility and catalytic efficiency of the catalyst in the reaction system. However, this method is too complicated, which will increase the cost and is not convenient for operation. Therefore, it has become an urgent problem to develop a simple and feasible high-efficiency catalytic method to prepare solvent-free polyurethane with high conversion rate and strong reaction controllability for use in synthetic leather. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a solvent-free polyurethane synthetic leather and a preparation method thereof, thereby effectively solving the problems of uneven catalyst dispersion, insufficient catalytic efficiency and uncontrollable reaction in the preparation process of solvent-free polyurethane synthetic leather.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for preparing solvent-free polyurethane synthetic leather comprises the following steps:

[0007] S1: Under nitrogen protection and anhydrous conditions, after the diisocyanate and the polyol are stirred and reacted at a first speed, a composite catalyst is added to the reaction system, wherein the composite catalyst is obtained by compounding an organic zirconium catalyst and a tertiary amine catalyst, and the stirring reaction is continued at the first speed, and the reaction system is cooled down to obtain a first component; under nitrogen protection and anhydrous conditions, the polyol is added to the diisocyanate, and the stirring reaction is carried out at a second speed to obtain a second component; the first speed is greater than the second speed;

[0008] S2: Mix the first component and the second component evenly, then add water and stir to foam, then add the additive and stir to obtain polyurethane slurry;

[0009] S3: coating the polyurethane slurry on the surface material, pre-curing it, and then laminating the bottom material with the pre-cured polyurethane slurry, and post-curing it to obtain the solvent-free polyurethane synthetic leather.

[0010] Preferably, in step S1, when the diisocyanate and the polyol are stirred and reacted at the first rotation speed, the reaction temperature is 80-85° C.

[0011] Preferably, in step S1, when the diisocyanate and the polyol are stirred and reacted at the second rotation speed, the reaction temperature is 70-85°C.

[0012] Preferably, in step S1, the mass ratio of the organic zirconium catalyst to the tertiary amine catalyst when compounded is 1:(0.5-2).

[0013] Preferably, the organic zirconium catalyst is any one of zirconium acetate, zirconium propionate and diacetoxy zirconium oxide, and the tertiary amine catalyst is any one of bis(dimethylamino)ethyl ether, N-methylmorpholine and triethylenediamine.

[0014] Preferably, in step S1, the first rotation speed is 1000-1500 r / min.

[0015] Preferably, in step S1, the second rotation speed is 300-500 r / min.

[0016] Preferably, in step S3, the pre-curing temperature is 90-120° C., and the time is 60-120 seconds; the post-curing temperature is 130-160° C., and the time is 5-30 minutes.

[0017] A solvent-free polyurethane synthetic leather is prepared by the method.

[0018] Preferably, the breaking strength of the solvent-free polyurethane synthetic leather is 20.5-30.7 MPa, the breaking elongation is 487-523%, and the conversion rate of the reactants is greater than 98%.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] A method for preparing a solvent-free polyurethane synthetic leather comprises the following steps: firstly, preheating a composite catalyst and a small amount of a polyol system and dispersing them by high-speed shearing; the molten polyol after heating can encapsulate the composite catalyst sheared into small droplets at high speed therein; and then, after cooling, a microcapsule structure of the composite catalyst encapsulated by the polyol can be formed. The shell layer of the microcapsule structure is a polyol, which can make the composite catalyst uniformly dispersed in the reaction system, effectively ensure the dispersibility of the catalyst, and also improve the specific surface area of ​​the composite catalyst, increase the active sites of the reaction, and effectively improve the conversion rate of the reactants. At the same time, the core-shell microcapsule structure can make the composite catalyst slowly released from the microcapsule, which can effectively reduce the reaction rate at the initial stage of the reaction, making the reaction process efficient and controllable. In addition, an organic zirconium catalyst and a tertiary amine catalyst are used as a composite catalyst, rather than a single type of catalyst. The main gel of the organic zirconium catalyst can play a key role in the chain growth, curing and online stripping efficiency of the polyurethane, and the tertiary amine catalyst is a type of catalyst that can effectively control the balance of water foaming and polyurethane gel, can improve the efficiency of the reaction of water and polyol components with isocyanate groups, and can also prevent the hydrolysis of the product. Therefore, the compounding of the two types of catalysts can not only obtain the advantages of the two catalysts, but also achieve efficient catalysis and controllable reaction. At the same time, the metal ions in the metal organic compound can also form coordination bonds with the nitrogen in the tertiary amine catalyst, so that the composite catalyst has good stability, greatly exerts the synergistic catalytic effect of the two, and effectively improves the conversion rate of the reaction. During the reaction, the first speed is greater than the second speed, which can effectively break up the composite catalyst to form tiny droplets, effectively improving the dispersibility of the composite catalyst. The pre-curing process can further react and cure the active groups that have not reacted completely inside the polyurethane, further improving the conversion rate. The post-curing process can eliminate the internal stress of the product, further relieve the molecular chain, improve the crystallinity of the product, and further optimize the mechanical properties of the product. The method of the present invention is reasonably designed, controllable, high in raw material conversion rate, simple in process, and the solvent-free polyurethane synthetic leather obtained has excellent performance.

[0021] Furthermore, in step S1, when the diisocyanate and the polyol are stirred and reacted at the first speed, the reaction temperature is 80-85° C., and when the diisocyanate and the polyol are stirred and reacted at the second speed in step S1, the reaction temperature is 70-85° C., which can effectively accelerate the reaction rate and shorten the reaction time.

[0022] Furthermore, the mass ratio of the organic zirconium catalyst to the tertiary amine catalyst is 1: (0.5-2). The organic zirconium catalyst main gel can play a key role in the chain growth, curing and online stripping efficiency of polyurethane, while the tertiary amine catalyst is a type of catalyst that can effectively control the balance of water foaming and polyurethane gel, which can improve the efficiency of the reaction of water and polyol components with isocyanate groups and prevent the hydrolysis of the product. Therefore, by adjusting the amount of the two catalysts, effective control of the different processes of the entire reaction can be achieved.

[0023] Furthermore, the first rotation speed is 1000-1500 r / min, which can effectively achieve the coating of the composite catalyst by the polyol and form a microcapsule structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a schematic diagram of a process for preparing a solvent-free polyurethane synthetic leather in the present invention;

[0026] Figure 2 These are the test results of the breaking strength and breaking elongation of the solvent-free polyurethane synthetic leathers prepared in Examples 1 to 6 of the present invention. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0028] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0029] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0030] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0031] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0032] The present invention provides a method for preparing solvent-free polyurethane synthetic leather, such as Figure 1 As shown, the following steps are included:

[0033] S1: nitrogen is introduced into the reaction vessel to remove the moisture in the container, mainly to remove the moisture in the reactor, because the diisocyanate itself has a high reactivity and can react with water without a catalyst. The byproduct produced is polyurethane urea, which has a high hardness and will affect the performance of the final product. Therefore, it is ensured that the reaction process is carried out under anhydrous conditions to avoid the occurrence of side reactions. Then, under the protection of nitrogen, 95 to 100 parts of dried polyols are added to a reaction vessel at 80 to 85°C according to the mass fraction, and then 5 to 15 parts of diisocyanate are added. The system temperature is maintained at 80 to 85°C, and the high-speed shear reaction is carried out at a stirring speed of 1000 to 1500 r / min for 1 to 2 hours until the reaction is complete to obtain a polyurethane prepolymer. After the reaction is completed, 4 to 8 parts of a composite catalyst are added to the reaction system. The composite catalyst is obtained by compounding an organic zirconium catalyst and a tertiary amine catalyst in a mass ratio of 1: (0.5 to 2). The composite catalyst is continuously subjected to a high-speed shear reaction at a stirring speed of 1000 to 1500 r / min to form tiny droplets of the composite catalyst, and the droplets are uniformly mixed with the obtained polyurethane prepolymer. The reaction system is cooled to room temperature while stirring at high speed, and the polyurethane prepolymer undergoes a phase change, so that the composite catalyst and the polyurethane prepolymer form a stable microcapsule structure. At the same time, the cooling process enhances the stability of the microcapsule wall material. After the reaction is completed, the first component is obtained, that is, a microcapsule of a hydroxyl-terminated polyurethane prepolymer encapsulating the composite catalyst. The organic zirconium catalyst is any one of zirconium acetate, zirconium propionate, and diacetoxy zirconium oxide, and the tertiary amine catalyst is any one of bis(dimethylaminoethyl)ether, N-methylmorpholine, and triethylenediamine.

[0034] In another reaction container, nitrogen is introduced to remove the moisture in the container. Under nitrogen protection, 10 to 25 parts of diisocyanate are added by weight, the temperature of the reaction system is controlled to be 70 to 85°C, and 80 to 100 parts of polyol are added, wherein the molar ratio of the isocyanate group on the diisocyanate to the hydroxyl group on the polyol is 1:(1.5 to 2.0), the reaction temperature is maintained at 70 to 85°C, and the reaction is stirred at a speed of 300 to 500 r / min for 1 to 3 hours, so that the reactants react completely to obtain the second component, i.e., the isocyanate-terminated polyurethane prepolymer. Wherein, the polyols in step S1 and step S2 are one or two of polyester polyols and polyether polyols compounded in any proportion. The polyester polyol is one or more of polycarbonate diol 2000, polyoxypropylene diol 2000, polycaprolactone diol 1000, polycarbonate diol 1000, polyoxypropylene diol 1000 and polyoxypropylene triol 2000. The polyether polyol is polytetramethylene ether diol 2000.

[0035] The diisocyanate is any one of isophorone diisocyanate, toluene diisocyanate, diphenyl diisocyanate and hexamethylene diisocyanate.

[0036] S2: The first component and the second component are mixed evenly at a mass ratio of 1: (0.5-2), and then water is added for stirring and foaming. According to the mass fraction, the ratio of the amount of water added to the amount of polyol added in step S1 is (95-100): (4-6), the foaming time is 1-1.5h, and the stirring speed during foaming is 300-500r / min. Then, an auxiliary agent is added, and the auxiliary agent includes a flame retardant and an antioxidant. Stir evenly to form a polyurethane slurry, and then the polyurethane slurry is coated on a release paper provided with a surface material, and pre-cured. The pre-curing temperature is 90-120°C and the time is 60-120s. Then, the ultrafine fiber synthetic leather, i.e., ultra-fine fiber, is laminated with the pre-cured polyurethane slurry under a certain pressure, and then post-cured. The post-curing temperature is 130-160°C and the time is 5-30min. Finally, the release paper is separated to obtain the solvent-free polyurethane synthetic leather. The flame retardant and antioxidant added in this step can be flame retardant FR191 (flame retardant FR191 is a phosphorus and nitrogen environmentally friendly flame retardant purchased from Yucheng (Hongji) Plastic Dongguan Co., Ltd.) and ASCININ ANTI SKIN1240 (purchased from Xiamen Aikema Chemical Co., Ltd.).

[0037] The conversion rate of the raw materials in the invention is greater than 98%. The breaking strength of the solvent-free polyurethane synthetic leather prepared by the method of the invention is 20.5-30.7 MPa and the breaking elongation is 487-523%.

[0038] The preparation process of solvent-free polyurethane synthetic leather is divided into multiple processes. A single type of catalyst is not only difficult to achieve efficient catalysis of polyurethane reaction, but also difficult to achieve controllable progress of each step of the reaction. The use of a catalyst composited with a tertiary amine catalyst and an organic zirconium catalyst can greatly improve the conversion rate of the reaction. This is mainly because the main gel of the organic zirconium catalyst can play a key role in the chain growth, curing and online stripping efficiency of polyurethane, while the tertiary amine catalyst is a type of catalyst that can effectively control the balance of water foaming and polyurethane gel, which can improve the efficiency of the reaction of water and polyol components with isocyanate groups and prevent the hydrolysis of the product. Therefore, the compounding of the two types of catalysts can not only obtain the advantages of the two catalysts, but also achieve efficient catalysis and controllable reaction. At the same time, the metal ions in the metal organic compound can also form coordination bonds with the nitrogen in the tertiary amine catalyst, so that the composite catalyst has good stability and greatly exerts the synergistic catalytic effect of the two.

[0039] Since the catalyst and the reaction system are essentially two incompatible phases, the dispersibility of the catalyst in the reaction system greatly affects the efficiency of the catalysis and the uniformity of the reaction. The present invention first preheats the composite catalyst and a small amount of polyol system and disperses them by high-speed shearing. Since the polyol system is generally a waxy solid or a high-viscosity oily liquid, the catalyst sheared into small droplets at high speed can be coated therein by melting after heating, and then a microcapsule structure of the polyol-coated composite catalyst can be formed after cooling. Further heating during the reaction process, the catalyst will participate in the reaction in the form of microcapsules. On the one hand, since the shell of the microcapsule is a polyol, it can be evenly dispersed in the reaction system, so that the catalytic reaction is carried out evenly; on the other hand, the contact specific surface area between the composite catalyst of the microcapsule structure and the reactant is greatly improved, and the catalytic effect is greatly amplified, which improves the conversion rate of the reactant and avoids the problem of stickiness of the product due to low conversion rate. Furthermore, the catalyst is slowly released from the microcapsule, which can effectively reduce the reaction rate in the initial stage of the reaction, so that the viscosity of the system is not too high, thereby achieving a controllable and efficient reaction and significantly improving the physical properties of the product.

[0040] By adjusting the ratio of the two components (diisocyanate and polyol) in the resin and the reaction conditions; adjusting the molecular weight of the soft and hard segment monomers (the soft segment refers to the polyol, and the hard segment refers to the isocyanate), the degree of polymerization of the prepolymer, and the compound catalyst, the conversion degree of each reaction component and the polyurethane chain structure can be improved; by precisely controlling the temperature and reaction time and optimizing the excess ratio of isocyanate, the degree of microphase separation of the polyurethane elastomer can be adjusted, thereby adjusting the performance of the synthetic leather.

[0041] The pre-curing process can further react and cure the unreacted active groups inside the polyurethane, further improving the conversion rate. Since the catalyst is well dispersed, the curing time can be greatly reduced, saving time and energy costs. The post-curing process can eliminate the internal stress inside the product, further relax the molecular chain, improve the crystallinity of the product, and further optimize the mechanical properties of the product. This method is not only simple to operate, but also program controllable, without adding new raw materials and reaction steps, and can also control the catalytic reaction by controlling the catalyst ratio, feed rate and feed amount of the polyol microcapsules.

[0042] Therefore, the method of the present invention is used to prepare solvent-free polyurethane synthetic leather, which not only has controllable reaction, high raw material conversion efficiency, simple process, but also excellent product performance, and is therefore suitable for continuous large-scale production of high-quality solvent-free polyurethane synthetic leather.

[0043] 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.

[0044] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0045] Example 1

[0046] A method for preparing solvent-free polyurethane synthetic leather comprises the following steps:

[0047] (1) Preparation of the first component

[0048] Nitrogen is introduced into the reactor to remove the moisture in the reactor, and then 100 parts of dried polycarbonate diol 2000 are put into the reactor at 80°C under nitrogen protection, and then 8 parts of isophorone diisocyanate are put into the reactor, and stirred at a high speed of 1500r / min for 1h. After the reaction is completed, a polyurethane prepolymer is obtained. 8 parts of a composite catalyst prepared by triethylenediamine and zirconium acetate in a mass ratio of 1:1 are added to the polyurethane prepolymer, and stirred at a high speed of 1500r / min to break up the composite catalyst and form tiny droplets. While stirring, the temperature is gradually lowered so that the system forms a microcapsule structure of the composite catalyst coated with a polyol, and a microcapsule of the composite catalyst coated with a hydroxyl-terminated polyurethane prepolymer is obtained.

[0049] (2) Preparation of the second component

[0050] The moisture in another reaction kettle was evacuated by nitrogen, and then 13 parts by mass of isophorone diisocyanate were added under nitrogen protection, and 80 parts of polycarbonate diol 2000 were added at 70°C to make the ratio of isocyanate group to hydroxyl group in the system be 1:1.5. The reaction was stirred at a speed of 300 r / min for 1 hour to allow the reactants to react completely to obtain an isocyanate-terminated polyurethane prepolymer.

[0051] (3) The first component and the second component are mixed at a mass ratio of 1:1.5, and then water is added for stirring and foaming. The ratio of the amount of water added to the amount of the polyol added in step (1) is 100:4 in terms of mass fraction. The mixture is stirred and foamed at a speed of 300 r / min for 1 hour, and then 2 parts of flame retardant and 1 part of antioxidant are added. After stirring evenly, a polyurethane slurry is obtained. The polyurethane slurry is then coated on a release paper provided with a surface layer material, and pre-cured in an oven at 90°C for 60 seconds; then the required bottom surface material is laminated with the pre-cured product under a certain pressure, and fully heated and cured in an oven at 130°C for 20 minutes. Finally, the release paper is separated to obtain a solvent-free polyurethane synthetic leather.

[0052] The test results of the breaking strength and breaking elongation of the solvent-free polyurethane synthetic leather prepared in this embodiment are shown in Figure 2 ,like Figure 2 As shown, the breaking strength of the solvent-free polyurethane synthetic leather prepared in this embodiment is 25.3 MPa, the elongation at break is 487%, the conversion rate of the reactants is 98.0%, and the product is demoulded without adhesion, and the product quality is good.

[0053] Example 2

[0054] A method for preparing solvent-free polyurethane synthetic leather comprises the following steps:

[0055] (1) Preparation of the first component

[0056] Nitrogen is introduced into the reactor to remove the moisture in the reactor, and then 95 parts of dried polyoxypropylene glycol 2000 are put into the reactor with a temperature of 85°C under nitrogen protection, and then 10 parts of diphenylmethane-4,4'-diisocyanate (i.e. diphenyl diisocyanate) are put into the reactor, and stirred at a high speed of 1200r / min for 1.5h. After the reaction is completed, a polyurethane prepolymer is obtained. 5 parts of a composite catalyst prepared by N-methylmorpholine and zirconium propionate at a mass ratio of 1:0.5 are added to the polyurethane prepolymer, and stirred at a high speed of 1200r / min to break up the composite catalyst and form tiny droplets. While stirring, the temperature of the reaction system is gradually reduced, so that the system forms a microcapsule structure of a polyol-coated composite catalyst, and a hydroxyl-terminated polyurethane prepolymer-coated composite catalyst microcapsule is obtained.

[0057] (2) Preparation of the second component

[0058] The moisture in another reaction kettle was evacuated by nitrogen, and then 22 parts by mass of diphenylmethane-4,4'-diisocyanate were added under nitrogen protection, and 85 parts of polyoxypropylene glycol 2000 were added at 70°C to make the ratio of isocyanate group to hydroxyl group in the system be 1:2.0. The reaction was stirred at a speed of 500 r / min for 1 hour to allow the reactants to react completely to obtain an isocyanate-terminated polyurethane prepolymer.

[0059] (3) The first component and the second component are mixed at a mass ratio of 1:0.5, and then water is added for stirring and foaming. The ratio of the amount of water added to the amount of the polyol added in step (1) is 95:5 in terms of mass fraction. The mixture is stirred and foamed at a speed of 300 r / min for 1.5 hours, and then 2 parts of flame retardant and 1 part of antioxidant are added. After stirring evenly, a polyurethane slurry is obtained. The polyurethane slurry is then coated on a release paper provided with a surface material, and pre-cured in an oven at 100°C for 80 seconds; then the required bottom material is laminated with the pre-cured product under a certain pressure, and fully heated and cured in an oven at 150°C for 5 minutes. Finally, the release paper is separated to obtain a solvent-free polyurethane synthetic leather.

[0060] The test results of the breaking strength and breaking elongation of the solvent-free polyurethane synthetic leather prepared in this embodiment are shown in Figure 2 ,like Figure 2 As shown, the breaking strength of the solvent-free polyurethane synthetic leather prepared in this embodiment is 20.5 MPa, the breaking elongation is 523%, the conversion rate of the reactants is 99.2%, the product is demoulded without adhesion, and the product quality is good.

[0061] Example 3

[0062] A method for preparing solvent-free polyurethane synthetic leather comprises the following steps:

[0063] (1) Preparation of the first component

[0064] Nitrogen is introduced into the reactor to remove the moisture in the reactor, and then 98 parts of dried polycaprolactone diol 1000 are put into the reactor with a temperature of 82°C under nitrogen protection, and then 13 parts of toluene diisocyanate are put into the reactor, and stirred at a high speed of 1400r / min for 2h. After the reaction is completed, a polyurethane prepolymer is obtained. 7 parts of a composite catalyst prepared by dimethylaminoethyl ether and diacetoxy zirconium oxide in a mass ratio of 1:1.2 are added to the polyurethane prepolymer, and stirred at a high speed of 1400r / min to break up the composite catalyst and form tiny droplets. While stirring, the temperature of the reaction system is gradually reduced, so that the system forms a microcapsule structure of a polyol-coated composite catalyst, and a hydroxyl-terminated polyurethane prepolymer-coated composite catalyst microcapsule is obtained.

[0065] (2) Preparation of the second component

[0066] The moisture in another reaction kettle was evacuated by nitrogen, and then 25 parts by mass of toluene diisocyanate were added under nitrogen protection, and 85 parts of polycaprolactone diol 1000 were added at 70°C to make the ratio of isocyanate group to hydroxyl group in the system be 1:1.7. The reaction was stirred at a speed of 400 r / min for 2.5 hours to allow the reactants to react completely to obtain an isocyanate-terminated polyurethane prepolymer.

[0067] (3) The first component and the second component are mixed at a mass ratio of 1:0.7, and then water is added for stirring and foaming. The ratio of the amount of water added to the amount of the polyol added in step (1) is 98:4 in terms of mass fraction. The mixture is stirred and foamed at a speed of 300 r / min for 1.2 hours, and then 3 parts of flame retardant and 1 part of antioxidant are added. After stirring evenly, a polyurethane slurry is obtained. The polyurethane slurry is then coated on a release paper provided with a surface layer material, and pre-cured in an oven at 120°C for 120 seconds; then the required bottom surface material is laminated with the pre-cured product under a certain pressure, and fully heated and cured in an oven at 160°C for 10 minutes. Finally, the release paper is separated to obtain a solvent-free polyurethane synthetic leather.

[0068] The test results of the breaking strength and breaking elongation of the solvent-free polyurethane synthetic leather prepared in this embodiment are shown in Figure 2 ,like Figure 2 As shown, the breaking strength of the solvent-free polyurethane synthetic leather prepared in this embodiment is 23.1 MPa, the breaking elongation is 498%, the conversion rate of the reactants is 98.9%, the product is demoulded without adhesion, and the product quality is good.

[0069] Example 4

[0070] A method for preparing solvent-free polyurethane synthetic leather comprises the following steps:

[0071] (1) Preparation of the first component

[0072] Nitrogen is introduced into the reactor to remove the moisture in the reactor, and then 100 parts of the dried polycaprolactone diol 2000 and polyoxypropylene diol 2000 are put into the reactor at 80°C under nitrogen protection, wherein the mass ratio of polycaprolactone diol 2000 to polyoxypropylene diol 2000 is 1:1. Then 13 parts of toluene diisocyanate are put into the reactor, and stirred at a high speed of 1500r / min for 1.5h. After the reaction is completed, a polyurethane prepolymer is obtained. 6 parts of a composite catalyst prepared by dimethylaminoethyl ether and diacetoxy zirconium oxide at a mass ratio of 1:0.5 are added to the polyurethane prepolymer, and stirred at a high speed of 1500r / min to break up the composite catalyst and form tiny droplets. While stirring, the temperature of the reaction system is gradually reduced, so that the system forms a microcapsule structure of the composite catalyst coated with a polyol, and obtains a microcapsule of a hydroxyl-terminated polyurethane prepolymer coated with a composite catalyst.

[0073] (2) Preparation of the second component

[0074] The moisture in another reaction kettle was evacuated by nitrogen, and then 15 parts by mass of toluene diisocyanate were added under nitrogen protection, and 85 parts of polytetramethylene ether diol 2000 were added at 75°C to make the ratio of isocyanate group to hydroxyl group in the system be 1:1.8. The reaction was stirred at a speed of 300 r / min for 2.3 hours to allow the reactants to react completely to obtain an isocyanate-terminated polyurethane prepolymer.

[0075] (3) The first component and the second component are mixed in a mass ratio of 1:1, and then water is added for stirring and foaming. The ratio of the amount of water added to the amount of polyol added in step (1) is 100:3 in terms of mass fraction. The mixture is stirred and foamed at a speed of 300 r / min for 1.1 hours, and then 3 parts of flame retardant and 1 part of antioxidant are added. After stirring evenly, a polyurethane slurry is obtained. The polyurethane slurry is then coated on a release paper provided with a surface layer material, and pre-cured in an oven at 100°C for 90 seconds; then the required bottom surface material is laminated with the pre-cured product under a certain pressure, and fully heated and cured in an oven at 150°C for 15 minutes. Finally, the release paper is separated to obtain a solvent-free polyurethane synthetic leather.

[0076] The test results of the breaking strength and breaking elongation of the solvent-free polyurethane synthetic leather prepared in this embodiment are shown in Figure 2 ,like Figure 2 As shown, the breaking strength of the solvent-free polyurethane synthetic leather prepared in this embodiment is 26.9 MPa, the elongation at break is 503%, the conversion rate of the reactants is 99.7%, and the product is demoulded without adhesion, and the product quality is good.

[0077] Example 5

[0078] A method for preparing solvent-free polyurethane synthetic leather comprises the following steps:

[0079] (1) Preparation of the first component

[0080] Nitrogen is introduced into the reactor to remove the moisture in the reactor, and then 100 parts of the polyol composed of dried polycarbonate diol 1000 and polyoxypropylene diol 1000 are put into the reactor with a temperature of 80°C under nitrogen protection, wherein the mass ratio of polycarbonate diol 1000 to polyoxypropylene diol 1000 is 1:0.7. Then 10 parts of toluene diisocyanate are put into the reactor, and stirred at a high speed of 1200r / min for 1h. After the reaction is completed, a polyurethane prepolymer is obtained. 8 parts of a composite catalyst prepared by dimethylaminoethyl ether and diacetoxy zirconium oxide at a mass ratio of 1:0.7 are added to the polyurethane prepolymer, and stirred at a high speed of 1200r / min to break up the composite catalyst and form tiny droplets. While stirring, the temperature of the reaction system is gradually reduced, so that the system forms a microcapsule structure of the composite catalyst coated with the polyol, and obtains a microcapsule of the composite catalyst coated with the hydroxyl-terminated polyurethane prepolymer.

[0081] (2) Preparation of the second component

[0082] The moisture in another reaction kettle was evacuated by nitrogen, and then 15 parts by mass of toluene diisocyanate were added under nitrogen protection, and 85 parts of a complex polyol composed of polytetramethylene ether diol 2000 and polyoxypropylene diol 2000 were added at 75°C, wherein the mass ratio of polytetramethylene ether diol 2000 to polyoxypropylene diol 2000 was 1:1, so that the ratio of isocyanate group to hydroxyl group in the system was 1:1.8, and the reaction was stirred at a speed of 450r / min for 2.3h to allow the reactants to react completely to obtain an isocyanate-terminated polyurethane prepolymer.

[0083] (3) The first component and the second component are mixed in a mass ratio of 1:1, and then water is added for stirring and foaming. The ratio of the amount of water added to the amount of the polyol added in step (1) is 100:3 in terms of mass fraction. The mixture is stirred and foamed at a speed of 300 r / min for 1.1 hours, and then 3 parts of flame retardant and 1 part of antioxidant are added. After stirring evenly, a polyurethane slurry is obtained. The polyurethane slurry is then coated on a release paper provided with a surface layer material, and pre-cured in an oven at 100°C for 90 seconds; then the required bottom surface material is laminated with the pre-cured product under a certain pressure, and fully heated and cured in an oven at 150°C for 25 minutes. Finally, the release paper is separated to obtain a solvent-free polyurethane synthetic leather.

[0084] The test results of the breaking strength and breaking elongation of the solvent-free polyurethane synthetic leather prepared in this embodiment are shown in Figure 2 ,like Figure 2 As shown, the breaking strength of the solvent-free polyurethane synthetic leather prepared in this embodiment is 24.8 MPa, the breaking elongation is 506%, the conversion rate of the reactants is 99.1%, and the product is demoulded without adhesion, and the product quality is good.

[0085] Example 6

[0086] A method for preparing solvent-free polyurethane synthetic leather comprises the following steps:

[0087] (1) Preparation of the first component

[0088] Nitrogen is introduced into the reactor to remove the moisture in the reactor, and then 100 parts of the dried polyoxypropylene triol 2000 are put into the reactor with a temperature of 85°C under nitrogen protection, and then 10 parts of toluene diisocyanate are added to the reactor, and stirred at a high speed of 1500r / min for 1.5h. After the reaction is completed, a polyurethane prepolymer is obtained. 8 parts of a composite catalyst prepared by dimethylaminoethyl ether and diacetoxy zirconium oxide at a mass ratio of 1:0.7 are added to the polyurethane prepolymer, and stirred at a high speed of 1500r / min to break up the composite catalyst and form tiny droplets. While stirring, the temperature of the reaction system is gradually reduced, so that the system forms a microcapsule structure of the composite catalyst coated with a polyol, and obtains a microcapsule of a hydroxyl-terminated polyurethane prepolymer coated with a composite catalyst.

[0089] (2) Preparation of the second component

[0090] The moisture in another reaction kettle was evacuated by nitrogen, and then 15 parts by mass of toluene diisocyanate were added under nitrogen protection, and 85 parts of a complex polyol composed of polytetramethylene ether diol 2000 and polyoxypropylene diol 1000 were added at 75°C, wherein the mass ratio of polytetramethylene ether diol 2000 to polyoxypropylene diol 1000 was 1:1, so that the ratio of isocyanate group to hydroxyl group in the system was 1:1.8, and the reaction was stirred at a speed of 450r / min for 2.3h to allow the reactants to react completely to obtain an isocyanate-terminated polyurethane prepolymer.

[0091] (3) The first component and the second component are mixed in a mass ratio of 1:1, and then water is added for stirring and foaming. The ratio of the amount of water added to the amount of the polyol added in step (1) is 100:3 in terms of mass fraction. The mixture is stirred and foamed at a speed of 300 r / min for 1.1 hours, and then 3 parts of flame retardant and 1 part of antioxidant are added. After stirring evenly, a polyurethane slurry is obtained. The polyurethane slurry is then coated on a release paper provided with a surface layer material, and pre-cured in an oven at 100°C for 90 seconds; then the required bottom surface material is laminated with the pre-cured product under a certain pressure, and fully heated and cured in an oven at 150°C for 30 minutes. Finally, the release paper is separated to obtain a solvent-free polyurethane synthetic leather.

[0092] The test results of the breaking strength and breaking elongation of the solvent-free polyurethane synthetic leather prepared in this embodiment are shown in Figure 2 ,like Figure 2 As shown, the breaking strength of the solvent-free polyurethane synthetic leather prepared in this embodiment is 30.7 MPa, the breaking elongation is 487%, the conversion rate of the reactants is 99.1%, and the product is demoulded without adhesion, and the product quality is good.

[0093] Example 7

[0094] A method for preparing solvent-free polyurethane synthetic leather comprises the following steps:

[0095] (1) Preparation of the first component

[0096] Nitrogen is introduced into the reactor to remove the moisture in the reactor, and then 100 parts of the dried polyoxypropylene triol 2000 are put into the reactor at 85°C by weight under nitrogen protection, and then 10 parts of hexamethylene diisocyanate are added to the reactor, and stirred at a high speed of 1500r / min for 1.5h. After the reaction is completed, a polyurethane prepolymer is obtained. 8 parts of a composite catalyst prepared by dimethylaminoethyl ether and diacetoxy zirconium oxide at a mass ratio of 1:0.7 are added to the polyurethane prepolymer, and stirred at a high speed of 1500r / min to break up the composite catalyst and form tiny droplets. While stirring, the temperature of the reaction system is gradually reduced, so that the system forms a microcapsule structure of the composite catalyst coated with the polyol, and obtains a microcapsule of the composite catalyst coated with the hydroxyl-terminated polyurethane prepolymer.

[0097] (2) Preparation of the second component

[0098] The moisture in another reaction kettle was evacuated by nitrogen, and then 15 parts by mass of hexamethylene diisocyanate were added under nitrogen protection, and 85 parts of a complex polyol composed of polytetramethylene ether diol 2000 and polyoxypropylene diol 1000 were added at 75°C, wherein the mass ratio of polytetramethylene ether diol 2000 to polyoxypropylene diol 1000 was 1:1, so that the ratio of isocyanate group to hydroxyl group in the system was 1:1.8, and the reaction was stirred at a speed of 450r / min for 2.3h to allow the reactants to react completely to obtain an isocyanate-terminated polyurethane prepolymer.

[0099] (3) The first component and the second component are mixed in a mass ratio of 1:1, and then water is added for stirring and foaming. The ratio of the amount of water added to the amount of the polyol added in step (1) is 100:3 in terms of mass fraction. The mixture is stirred and foamed at a speed of 300 r / min for 1.1 hours, and then 3 parts of flame retardant and 1 part of antioxidant are added. After stirring evenly, a polyurethane slurry is obtained. The polyurethane slurry is then coated on a release paper provided with a surface layer material, and pre-cured in an oven at 100°C for 90 seconds; then the required bottom surface material is laminated with the pre-cured product under a certain pressure, and fully heated and cured in an oven at 150°C for 30 minutes. Finally, the release paper is separated to obtain a solvent-free polyurethane synthetic leather.

[0100] The present invention develops a method for preparing solvent-free polyurethane with high efficiency catalysis, wherein a catalyst compounded with a tertiary amine catalyst and an organic zirconium catalyst is used to exert the advantages of the two catalysts and the synergistic catalytic effect to improve the conversion rate of the raw materials, and at the same time, the composite catalyst is preheated and dispersed in the polyol so that it can be stably present in the reaction system in the form of microcapsules, thereby improving the dispersibility and compatibility of the catalyst and the reaction system, and also increasing the contact specific surface area with the substrate, greatly improving the reaction rate and the utilization rate of the catalyst. The method is simple to operate, does not introduce new equipment, stabilizes the cost, and is suitable for large-scale production operations in the future.

[0101] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a solvent-free polyurethane synthetic leather, characterized in that: The following steps are involved: S1: Under nitrogen protection and anhydrous conditions, after the diisocyanate and the polyol are stirred and reacted at a first speed, a composite catalyst is added to the reaction system, wherein the composite catalyst is obtained by compounding an organic zirconium catalyst and a tertiary amine catalyst, and the stirring reaction is continued at the first speed while the reaction system is cooled to obtain a first component; Under nitrogen protection and anhydrous conditions, adding polyol to diisocyanate, stirring at a second speed to react to obtain a second component; the first speed is greater than the second speed; S2: Mix the first component and the second component evenly, then add water and stir to foam, then add the additive and stir to obtain polyurethane slurry; S3: coating the polyurethane slurry on the surface material, pre-curing it, and then laminating the bottom material with the pre-cured polyurethane slurry, and post-curing it to obtain the solvent-free polyurethane synthetic leather; The mass ratio of the organic zirconium catalyst to the tertiary amine catalyst in step S1 is 1:(0.5-2); In step S1, the first rotation speed is 1000-1500 r / min; The organic zirconium catalyst is any one of zirconium acetate, zirconium propionate and diacetoxy zirconium oxide, and the tertiary amine catalyst is any one of bis(dimethylamino)ethyl ether, N-methylmorpholine and triethylenediamine.

2. The method for preparing a solvent-free polyurethane synthetic leather according to claim 1, characterized in that: In the step S1, when the diisocyanate and the polyol are stirred and reacted at the first rotation speed, the reaction temperature is 80-85° C.

3. The method for preparing a solvent-free polyurethane synthetic leather according to claim 1, characterized in that: In the step S1, when the diisocyanate and the polyol are stirred and reacted at the second rotation speed, the reaction temperature is 70-85° C.

4. The method for preparing a solvent-free polyurethane synthetic leather according to claim 1, characterized in that: In step S1, the second rotation speed is 300-500 r / min.

5. The method for preparing a solvent-free polyurethane synthetic leather according to claim 1, characterized in that: In step S3, the pre-curing temperature is 90-120° C., and the time is 60-120 seconds; the post-curing temperature is 130-160° C., and the time is 5-30 minutes.

6. A solvent-free polyurethane synthetic leather, characterized in that: Prepared by the method according to any one of claims 1 to 5.

7. The solvent-free polyurethane synthetic leather according to claim 6, characterized in that: The breaking strength of the solvent-free polyurethane synthetic leather is 20.5-30.7 MPa, the breaking elongation is 487-523%, and the conversion rate of the reactants is greater than 98%.

Images