1. A preparation method of modified waterborne polyurethane is characterized by comprising the following steps:

(1) in the presence of a catalyst, carrying out a first contact reaction on dihydric alcohol I, dihydric alcohol II and diisocyanate to obtain a product I; the average molecular weight of the diol I is 500-3000; the dihydric alcohol II is at least one selected from ethylene glycol, 1, 4-butanediol, 2-methyl-1, 3-propanediol, diethylene glycol and 1, 6-hexanediol;

(2) carrying out second contact reaction on the product I, a modifier and a cross-linking agent in sequence to obtain a product II;

(3) carrying out a third contact reaction on the product II, water and a chain extender in sequence to obtain modified waterborne polyurethane;

wherein the step of preparing the modifier comprises:

(a) carrying out fourth contact reaction on the compound shown in the formula (I) and sulfuric acid, and carrying out neutralization reaction on a product obtained after the fourth contact reaction and sodium bicarbonate to obtain an intermediate I;

(b) and (2) carrying out fifth contact reaction on the intermediate I and glycerol in the presence of sodium methoxide to obtain the modifier, wherein the weight ratio of the intermediate I to the glycerol is 4.5-5: 1;

the preparation method comprises the following steps of (1) relative to each weight part of the dihydric alcohol II, using 8-15 parts of the dihydric alcohol I, 5-15 parts of the diisocyanate, 2-12 parts of the modifier, 0.5-1.5 parts of the cross-linking agent and 0.5-1.5 parts of the chain extender.

2. The preparation method according to claim 1, wherein the compound represented by formula (I) is provided from rapeseed oil.

3. The production method according to claim 1 or 2, wherein, in the step (a) of producing the modifier, the compound represented by the formula (I), the sulfuric acid, and the sodium hydrogencarbonate are used in a weight ratio of 2 to 15: 1: 1-5; and

in the step (b) of preparing the modifier, the sodium methoxide is used in an amount of 0.05 to 5g per 100g of the intermediate I.

4. The production method according to any one of claims 1 to 3, wherein, in step (1), the conditions of the first contact reaction at least satisfy: the temperature is 70-90 ℃ and the time is 2-5 h; and

in step (a), the conditions of the fourth contact reaction at least satisfy: the temperature is 15-30 ℃, and the time is 3-6 h; and

in step (b), the conditions of the fifth contact reaction at least satisfy: the temperature is 170-180 ℃, and the time is 2-6 h.

5. The production method according to any one of claims 1 to 4, wherein, in the step (2), the step of subjecting the product I to a second contact reaction sequentially with a modifier and a crosslinking agent comprises: firstly, reacting the product I with a modifier for 1-4h at 70-90 ℃, and then reacting the obtained product with a cross-linking agent for 0.5-2h at 70-90 ℃; and

in the step (3), the step of performing a third contact reaction on the product II with water and a chain extender sequentially at least comprises the following steps: under the condition of stirring, firstly reacting the product II with water at 5-10 ℃ for 3-10min, and then reacting the obtained product with a chain extender at 5-10 ℃ for 20-40 min.

6. The production method according to any one of claims 1 to 5, wherein the diisocyanate is at least one selected from the group consisting of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate; and

the catalyst is at least one of dibutyltin dilaurate, bismuth isooctanoate and bismuth laurate.

7. The production method according to any one of claims 1 to 6, wherein the method further comprises: in the step (1), before the first contact reaction, the dihydric alcohol I and the dihydric alcohol I are subjected to vacuum dehydration treatment, so that the water contents of the dihydric alcohol I and the dihydric alcohol II are respectively and independently less than 0.02 wt%.

8. The production method according to claim 7, wherein the vacuum dehydration treatment is performed under conditions at least satisfying: the temperature is 120 ℃ and 130 ℃, the time is 3-5h, and the vacuum degree is-0.08 MPa to-0.10 MPa.

9. A modified aqueous polyurethane prepared by the preparation method of any one of claims 1 to 8.

10. Use of the modified waterborne polyurethane of claim 9 in the preparation of microfiber leather.

Background

The microfiber leather uses a three-dimensional reticular structure non-woven fabric made of superfine fibers as a base material, simulates the microstructure of dermal collagen, is used as the best substitute of natural leather, and has the advantages of high production efficiency, uniform finished leather, good physical and chemical properties and the like.

The microfiber leather is prepared by impregnating, splitting and post-finishing a nonwoven fabric with a three-dimensional structure based on microfiber short fibers, wherein the performance of the microfiber leather is greatly influenced by an impregnation process.

The impregnation process is to impregnate the polyurethane solution into the non-woven fabric in a rolling mode, the non-woven fabric has a macroscopic integral structure through polyurethane bonding, and the effect of the impregnation process directly determines the hand feeling, style, elasticity and mechanical property of the microfiber leather. However, almost all the resin used in the current microfiber leather impregnation process is solvent-based polyurethane, which easily causes environmental pollution and resource waste, so that the application of the solvent-based polyurethane in the microfiber leather is gradually limited.

The waterborne polyurethane takes water as a dispersion medium, and has the advantages of no solvent discharge, environmental protection and the like, so that the preparation of the waterborne polyurethane-based microfiber leather is a trend of the microfiber leather industry.

CN106868880A discloses a waterborne polyurethane imitated microfiber and a manufacturing method thereof, and a microfiber leather with a fine and compact structure and high tearing strength is prepared.

CN111040118A discloses a waterborne polyurethane for microfiber leather, a preparation method and an application thereof, which can solve the technical problems of poor stability and general water resistance caused by the fact that the waterborne polyurethane for microfiber leather is easy to gel.

CN111909351A discloses a synthetic method and application of waterborne polyurethane for microfiber impregnation, and high-temperature-resistant and ultraviolet-resistant microfiber leather is prepared.

However, in the prior art, the preparation process of the microfiber leather does not comprise a greasing process, the manufacturing process of the genuine leather comprises the greasing process, and leather collagen fibers absorb a certain amount of grease through the greasing process to endow the genuine leather with certain physical and mechanical properties and usability, so that the microfiber leather prepared based on the waterborne polyurethane has certain differences in softness, fullness, elasticity and the like compared with genuine leather, and the greasing process in the genuine leather is directly added into the preparation process of the microfiber leather, so that the cost is increased, the compatibility of the greasing agent and the polyurethane is poor, and the usability of the microfiber leather is reduced.

Disclosure of Invention

The invention aims to solve the problem that the existing microfiber leather has certain differences in softness, fullness and elasticity compared with real leather.

In order to achieve the above object, a first aspect of the present invention provides a method for producing a modified aqueous polyurethane, comprising:

(1) in the presence of a catalyst, carrying out a first contact reaction on dihydric alcohol I, dihydric alcohol II and diisocyanate to obtain a product I; the average molecular weight of the diol I is 500-3000; the dihydric alcohol II is at least one selected from ethylene glycol, 1, 4-butanediol, 2-methyl-1, 3-propanediol, diethylene glycol and 1, 6-hexanediol;

(2) carrying out second contact reaction on the product I, a modifier and a cross-linking agent in sequence to obtain a product II;

(3) carrying out a third contact reaction on the product II, water and a chain extender in sequence to obtain modified waterborne polyurethane;

wherein the step of preparing the modifier comprises:

(a) carrying out fourth contact reaction on the compound shown in the formula (I) and sulfuric acid, and carrying out neutralization reaction on a product obtained after the fourth contact reaction and sodium bicarbonate to obtain an intermediate I;

(b) and (2) carrying out fifth contact reaction on the intermediate I and glycerol in the presence of sodium methoxide to obtain the modifier, wherein the weight ratio of the intermediate I to the glycerol is 4.5-5: 1;

the preparation method comprises the following steps of (1) relative to each weight part of the dihydric alcohol II, using 8-15 parts of the dihydric alcohol I, 5-15 parts of the diisocyanate, 2-12 parts of the modifier, 0.5-1.5 parts of the cross-linking agent and 0.5-1.5 parts of the chain extender.

The second aspect of the present invention provides a modified aqueous polyurethane obtained by the production method of the first aspect.

The third aspect of the invention provides the application of the modified waterborne polyurethane described in the second aspect in preparing microfiber leather.

According to the invention, through formula design and process optimization, the modified waterborne polyurethane with excellent performance is prepared, the modified waterborne polyurethane has lower water absorption rate, more excellent mechanical property and alkali resistance and better storage stability, and the microfiber leather prepared from the modified waterborne polyurethane has higher thickening rate and better softness and handfeel while the normal-temperature folding resistance (25 ℃), color fastness to rubbing and temperature resistance are ensured.

Meanwhile, the technical scheme of the invention under the preferable condition also has the following advantages:

(1) the rapeseed oil is used as a raw material and introduced into the synthetic process of the waterborne polyurethane for the microfiber leather, and the rapeseed oil is used as a new material and a new process for replacing petroleum base, so that the rapeseed oil is beneficial to the continuous development of the microfiber leather industry.

(2) The traditional vegetable oil is applied to the synthesis of waterborne polyurethane, generally used as a polyol component, and the main chain of grease is used as the main component of the waterborne polyurethane, and generally has a crosslinking function. The rapeseed oil is used for synthesizing the waterborne polyurethane as a fat-liquoring function, and the rapeseed oil and the glycerol are subjected to ester exchange reaction, so that two ends of the rapeseed oil are provided with hydroxyl groups, and side chains are fatty chain segments with the fat-liquoring function.

(3) Because the side chain of the synthesized waterborne polyurethane is longer, the compatibility and the stability of the traditional micromolecule hydrophilic compound are difficult to ensure, and the rapeseed oil is prepared into the hydrophilic chain segment to replace the micromolecule hydrophilic compound, so that the compatibility of the prepared waterborne polyurethane is improved when the rapeseed oil is applied to the synthesis of the waterborne polyurethane.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

As described above, the first aspect of the present invention provides a method for producing a modified aqueous polyurethane, comprising:

(1) in the presence of a catalyst, carrying out a first contact reaction on dihydric alcohol I, dihydric alcohol II and diisocyanate to obtain a product I; the average molecular weight of the diol I is 500-3000; the dihydric alcohol II is at least one selected from ethylene glycol, 1, 4-butanediol, 2-methyl-1, 3-propanediol, diethylene glycol and 1, 6-hexanediol;

(2) carrying out second contact reaction on the product I, a modifier and a cross-linking agent in sequence to obtain a product II;

(3) carrying out a third contact reaction on the product II, water and a chain extender in sequence to obtain modified waterborne polyurethane;

wherein the step of preparing the modifier comprises:

(a) carrying out fourth contact reaction on the compound shown in the formula (I) and sulfuric acid, and carrying out neutralization reaction on a product obtained after the fourth contact reaction and sodium bicarbonate to obtain an intermediate I;

(b) and (2) carrying out fifth contact reaction on the intermediate I and glycerol in the presence of sodium methoxide to obtain the modifier, wherein the weight ratio of the intermediate I to the glycerol in terms of pure substances is 4.5-5: 1;

the preparation method comprises the following steps of (1) relative to each weight part of the dihydric alcohol II, using 8-15 parts of the dihydric alcohol I, 5-15 parts of the diisocyanate, 2-12 parts of the modifier, 0.5-1.5 parts of the cross-linking agent and 0.5-1.5 parts of the chain extender.

Preferably, the compound of formula (I) is provided by rapeseed oil.

Preferably, the iodine value of the rapeseed oil is 94-106g/100g, and the saponification value is 168-178mg KOH/g.

Preferably, the catalyst is used in an amount of 0.02 to 0.15 parts by weight per one part by weight of the diol II.

In the present invention, the amount of water used in step (3) is not particularly limited, and is, for example, 40 to 100 parts by weight per part by weight of the diol II.

Preferably, the chain extender is ethylene diamine.

More preferably, the chain extender is a 5-15 wt% aqueous solution of ethylenediamine, and when the chain extender is a 5-15 wt% aqueous solution of ethylenediamine, the chain extender is used in an amount of pure substance.

Preferably, the concentration of the sulfuric acid is 95 to 99 wt%.

Preferably, the sodium bicarbonate is an aqueous solution with a concentration of 5-10 wt%.

Preferably, in the step (a) of preparing the modifier, the compound represented by the formula (I), the sulfuric acid and the sodium bicarbonate are used in a weight ratio of 2-15: 1: 1-5.

Preferably, in step (b) of preparing said modifier, said sodium methoxide is used in an amount of 0.05 to 5g per 100g of said intermediate I.

According to another particularly preferred embodiment, in step (a) of preparing the modifier, the compound of formula (I), the sulfuric acid and the sodium bicarbonate are used in a weight ratio, calculated on pure substance, of from 2 to 15: 1: 2-5; and

in the step (b) of preparing the modifier, the sodium methoxide is used in an amount of 0.05 to 5g per 100g of the intermediate I.

Preferably, in step (1), the conditions of the first contact reaction at least satisfy: the temperature is 70-90 ℃ and the time is 2-5 h.

Preferably, in step (a), the conditions of the fourth contact reaction at least satisfy: the temperature is 15-30 ℃ and the time is 3-6 h.

Preferably, in step (b), the conditions of the fifth contact reaction at least satisfy: the temperature is 170-180 ℃, and the time is 2-6 h.

According to another particularly preferred embodiment, in step (1), the conditions of the first contact reaction are at least such that: the temperature is 70-90 ℃ and the time is 2-5 h; and

in step (a), the conditions of the fourth contact reaction at least satisfy: the temperature is 15-30 ℃, and the time is 3-6 h; and

in step (b), the conditions of the fifth contact reaction at least satisfy: the temperature is 170-180 ℃, and the time is 2-6 h.

According to a preferred embodiment, in step (2), the step of subjecting the product I to a second contact reaction with a modifier and a crosslinking agent in this order at least comprises: firstly, the product I reacts with a modifier for 1 to 4 hours at the temperature of between 70 and 90 ℃, and then the obtained product reacts with a cross-linking agent for 0.5 to 2 hours at the temperature of between 70 and 90 ℃.

According to another preferred embodiment, in the step (3), the step of subjecting the product II to a third contact reaction with water and a chain extender sequentially comprises at least: under the condition of stirring, the product II reacts with water for 3-10min, and then reacts with a chain extender for 20-40 min.

Preferably, in the step (2), the step of carrying out second contact reaction on the product I with the modifier and the crosslinking agent sequentially comprises the following steps: firstly, reacting the product I with a modifier for 1-4h at 70-90 ℃, and then reacting the obtained product with a cross-linking agent for 0.5-2h at 70-90 ℃; and

in the step (3), the step of performing a third contact reaction on the product II with water and a chain extender sequentially at least comprises the following steps: under the condition of stirring, firstly reacting the product II with water at 5-10 ℃ for 3-10min, and then reacting the obtained product with a chain extender at 5-10 ℃ for 20-40 min.

Preferably, in step (2), the temperature of the second contact reaction is 70 to 90 ℃.

Preferably, in step (3), the stirring speed is 2500-.

Preferably, in step (3), the temperature of the third contact reaction is 5 to 10 ℃.

Particularly preferably, the diol I is selected from at least one of polypropylene oxide polyol (PPG), polytetrahydrofuran ether Polyol (PTMG), polyethylene glycol (PEG), polycarbonate Polyol (PCDL), Polycaprolactone (PCL).

Preferably, the diisocyanate is selected from at least one of Toluene Diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), Hexamethylene Diisocyanate (HDI), Lysine Diisocyanate (LDI).

Preferably, the crosslinking agent is at least one selected from Trimethylolpropane (TMP) and pentaerythritol.

Preferably, the catalyst is at least one selected from dibutyltin dilaurate, bismuth isooctanoate and bismuth laurate.

According to another particularly preferred embodiment, the diisocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, lysine diisocyanate; and the catalyst is at least one of dibutyltin dilaurate, bismuth isooctanoate and bismuth laurate.

According to a particularly preferred embodiment, the method further comprises: in the step (1), before the first contact reaction is carried out on the dihydric alcohol I and the dihydric alcohol I, the dihydric alcohol I and the dihydric alcohol I are subjected to vacuum dehydration treatment, so that the water content of the dihydric alcohol I and the water content of the dihydric alcohol II are respectively and independently less than 0.02 wt%.

Preferably, the vacuum dehydration treatment is performed under conditions at least satisfying: the temperature is 120 ℃ and 130 ℃, the time is 3-5h, and the vacuum degree is-0.08 MPa to-0.10 MPa.

According to a particularly preferred embodiment, in step (a), the product obtained after the fourth contact reaction is washed and then neutralized with sodium bicarbonate.

The manner of cleaning is not particularly limited by the present invention, and the specific operations exemplified in the examples of the present invention hereinafter may be performed by methods known in the art, and those skilled in the art should not be construed as limiting the present invention.

Preferably, in step (b), the fifth contact reaction is carried out in the presence of stirring under the protection of nitrogen, and the stirring speed is preferably 100-300 rpm.

According to a particularly preferred embodiment, the product after the fifth contact reaction is sequentially subjected to water removal and drying treatment to obtain the modifier.

The manner of removing water and drying is not particularly limited in the present invention, and a method known in the art may be used, and the specific operations exemplarily illustrated in the following examples of the present invention should not be construed as limiting the present invention by those skilled in the art.

As described above, the second aspect of the present invention provides a modified aqueous polyurethane produced by the production method according to the first aspect.

As mentioned above, the third aspect of the present invention provides the use of the modified waterborne polyurethane described in the second aspect in the preparation of microfiber leather.

According to a particularly preferred embodiment, the method for preparing microfiber leather comprises: and (2) uniformly permeating the modified waterborne polyurethane in the second aspect into the non-woven fabric by adopting an impregnation process, and then sequentially carrying out drying and splitting processes to obtain the microfiber leather.

Preferably, the impregnation process has at least the following conditions: the pressure of the compression roller is 2-4MPa, the dipping temperature is 40-55 ℃, and the time is 1-3 min.

Preferably, the opening process is carried out in a NaOH solution having a concentration of 15-25 wt%.

More preferably, the conditions of the opening process at least satisfy: the temperature is 90-100 deg.C, and the time is 30-60 min.

Preferably, the modified aqueous polyurethane has a solids content of 20 to 30 wt.%, more preferably 25 to 28 wt.%.

Preferably, the solid content represents the ratio of the weight of the modified waterborne polyurethane after drying to the weight of the modified waterborne polyurethane before drying.

In the present invention, the drying process conditions and the operation manner are not particularly limited, and a known method may be used.

The impregnation process is not particularly limited, and may be carried out by a known method, for example, a tank impregnation method in which the nonwoven fabric is completely immersed in the impregnation solution, the impregnation solution is uniformly introduced into the nonwoven fabric by a guide roller and a roll in the tank, and the nonwoven fabric is internally impregnated with the impregnation solution after the rolling and the repeated padding.

The fourth aspect of the invention provides microfiber leather prepared by the preparation method in the application of the third aspect.

The present invention will be described in detail below by way of examples. In the following examples, all the raw materials used are commercially available ones unless otherwise specified.

Rapeseed oil: purchased from agriculture products limited, Tongcheng, Pingxiang, food grade;

sulfuric acid: purchased from Jiading chemical technology Co., Ltd, and the concentration is 98 wt%;

sodium bicarbonate: purchased from Henan gold geodetic chemical, Inc.;

and (3) vacuum drying oven: purchased from Shanghai Yunan instruments Inc., model DZF-6020;

PPG: available from scientific polymer (china) ltd, model PPG 1000;

PCDL: purchased from kossima polymers (china) ltd, model PCDL 1000;

PCL: available from Asahi Chun chemical (Suzhou) Ltd, model PCL 1000;

PEG: purchased from kossima polymers (china) ltd, model PEG 500;

PTMG: purchased from kossima polymers (china) ltd, model PTMG 1000;

HDI was purchased from kossima polymers (china) ltd;

ethylene glycol: purchased from Nanjing Rongji chemical Co., Ltd;

butanediol: purchased from Guangdong Zhongpeng chemical Co., Ltd;

TDI: purchased from kossima polymers (china) ltd;

HMDI: purchased from kossima polymers (china) ltd;

IPDI: purchased from kossima polymers (china) ltd;

dibutyltin dilaurate: purchased from Guangdong Sanding Jia New Material science and technology Co., Ltd;

in the following examples, the diols have been subjected to a dehydration treatment, unless otherwise specified: vacuumizing and dehydrating at 120 ℃ for 5h, wherein the vacuum degree is-0.10 mPa, and the water content is less than 0.02 wt%;

in the following examples, the room temperature or the normal temperature means 25 ± 1 ℃ unless otherwise specified.

Preparation example 1

This preparation is intended to illustrate the preparation of the modifier:

(1) adding 100g of rapeseed oil into a three-neck flask, controlling the reaction temperature to be 20 ℃, then dropwise adding 20g of sulfuric acid, reacting at 20 ℃ for 5 hours after dropwise adding, then transferring the reaction liquid into a separating funnel, washing with 150mL of saturated sodium chloride solution, neutralizing with sodium bicarbonate solution (the concentration of the sodium bicarbonate solution is 5 wt%, wherein the concentration of the sodium bicarbonate is 40g), and finally removing water with anhydrous sodium sulfate to obtain an intermediate I.

(2) 100g of the intermediate I obtained by the preparation, 21g of glycerol and 0.5g of sodium methoxide are transferred into a four-mouth bottle provided with a stirrer, a condenser tube, a thermometer and a nitrogen guide tube, the four-mouth bottle is reacted at 180 ℃ for 5 hours, nitrogen is continuously introduced into the four-mouth bottle for protection during the reaction process, anhydrous sodium sulfate is used for removing water after the reaction is finished, and the four-mouth bottle is placed into a vacuum drying oven (the temperature is 110 ℃ and the time is 6 hours) for drying to obtain the modifier I.

Preparation example 2

This preparation is intended to illustrate the preparation of the modifier:

(1) 100g of rapeseed oil is added into a three-neck flask, the reaction temperature is controlled to be 20 ℃, then 30g of sulfuric acid is dripped, the reaction is carried out for 4 hours at 20 ℃ after the dripping is finished, then the reaction solution is transferred into a separating funnel, is washed by 150ml of saturated sodium chloride solution, is neutralized by sodium bicarbonate solution (the concentration of the sodium bicarbonate solution is 10 wt%, wherein the concentration of the sodium bicarbonate is 40g), and finally is dewatered by anhydrous sodium sulfate to obtain an intermediate I.

(2) 100g of the intermediate I, 21g of glycerol and 0.5g of sodium methoxide obtained by the preparation method are transferred into a four-mouth bottle provided with a stirrer, a condenser tube, a thermometer and a nitrogen guide tube, the four-mouth bottle reacts at 170 ℃ for 5 hours, nitrogen is continuously introduced into the four-mouth bottle for protection in the reaction process, anhydrous sodium sulfate is used for removing water after the reaction is finished, and the four-mouth bottle is placed into a vacuum drying oven (the temperature is 110 ℃ and the time is 6 hours) for drying to obtain a modifier II.

Preparation example 3

This preparation is intended to illustrate the preparation of the modifier:

the preparation example is the same as the process flow of preparation example 1, except that:

the dosage of the intermediate I is 100g, and the weight ratio of the intermediate I to the glycerol is 2.4: 1, obtaining the modifier III.

Example 1

This example serves to illustrate the preparation of a modified aqueous polyurethane:

10g of PPG1000 (diol I), 20g of PTMG1000 (diol I), 3g of ethylene glycol (diol II), 15g of TDI (diisocyanate), 10g of HMDI (diisocyanate), 10g of IPDI (diisocyanate), 0.2g of dibutyltin dilaurate (catalyst) were reacted at 70 ℃ for 4 h;

then 10g of modifier I is added to react for 2h at 90 ℃, and 3g of TMP (cross-linking agent) is added to react for 1h at 90 ℃;

and cooling to 10 ℃, adding 200g of deionized water, stirring at 2500rpm for 5min, slowly adding 10 wt% of ethylenediamine aqueous solution (chain extender, wherein the content of ethylenediamine is 2g), stirring at 2500rpm for 30min, and distilling out acetone to obtain the modified waterborne polyurethane S1, wherein the solid content is 30 wt%.

Example 2

This example serves to illustrate the preparation of a modified aqueous polyurethane:

10g of PCDL1000 (diol I), 5g of PCL1000 (diol I), 20g of PTMG1000 (diol I), 3g of butanediol (diol II), 10g of IPDI (diisocyanate), 10g of HMDI (diisocyanate) and 0.3g of dibutyltin dilaurate (catalyst) were reacted at 80 ℃ for 4 hours;

then 20g of modifier I is added to react for 3h at 70 ℃, 3g of pentaerythritol (cross-linking agent) is added to react for 1h at 80 ℃;

and cooling to 5 ℃, adding 200g of deionized water, stirring at 2500rpm for 5min at high speed, slowly dropwise adding 10 wt% of ethylenediamine aqueous solution (chain extender, wherein the content of ethylenediamine is 2g), stirring at 2500rpm for 30min at high speed, and distilling out acetone to obtain the modified waterborne polyurethane S2, wherein the solid content is 30 wt%.

Example 3

This example serves to illustrate the preparation of a modified aqueous polyurethane:

10g of PCDL1000 (diol I), 5g of PEG500 (diol I), 5g of PPG1000 (diol I), 10g of PTMG1000 (diol I), 3g of butanediol (diol II), 10g of IPDI (diisocyanate), 5g of HMDI (diisocyanate), 5g of HDI (diisocyanate), 0.3g of dibutyltin dilaurate (catalyst) were reacted at 70 ℃ for 3 h;

then adding 30g of modifier II to react for 2h at 90 ℃, adding 2g of pentaerythritol (crosslinking agent) to react for 1h at 80 ℃;

and cooling to 8 ℃, adding 200g of deionized water, stirring at 2500rpm for 5min, slowly adding 10 wt% of ethylenediamine aqueous solution (chain extender, wherein the content of ethylenediamine is 3g), stirring at 2500rpm for 30min, and distilling out acetone to obtain the modified waterborne polyurethane S3, wherein the solid content is 30 wt%.

Comparative example 1

This comparative example is the same process flow as example 1, except that:

the amount of modifier I was 5g, giving modified waterborne polyurethane D1 having a solids content of 30% by weight.

Comparative example 2

This comparative example is the same process flow as example 1, except that:

the amount of modifier I was 50g, giving modified waterborne polyurethane D2 with a solids content of 30 wt%.

Comparative example 3

This comparative example is the same process flow as example 1, except that:

in this comparative example, no modifier I was added, specifically:

10g of PPG1000 (diol I), 20g of PTMG1000 (diol I), 3g of ethylene glycol (diol II), 15g of TDI (diisocyanate), 10g of HMDI (diisocyanate), 10g of IPDI (diisocyanate), 0.2g of dibutyltin dilaurate (catalyst) were reacted at 70 ℃ for 4 h;

adding 3g of TMP (cross-linking agent) and reacting for 1h at 90 ℃;

and cooling to 10 ℃, adding 200g of deionized water, stirring at 2500rpm for 5min, slowly dropwise adding 10 wt% of ethylenediamine aqueous solution (chain extender, wherein the weight of ethylenediamine is 2g), stirring at 2500rpm for 30min, standing, and precipitating to obtain the waterborne polyurethane.

Comparative example 4

This comparative example is the same process flow as example 1, except that:

in the comparative example, modifier I was replaced with equal weight of modifier III, and the aqueous polyurethane could not be obtained by settling after standing.

Test example 1:

the following tests were carried out on each of the aqueous polyurethanes prepared in the preceding examples, and the test results are shown in table 1:

storage stability: standing the waterborne polyurethane, observing whether the emulsion has precipitation or not, layering, and recording the emulsion stabilization time when the stability of the emulsion is determined (the precipitation and layering do not occur along with the time extension);

tensile strength: according to the test standard GB/T1040-92: (ii) a

Elongation at break: according to the test standard of GB/T1040-92;

water absorption: curing 30g of aqueous polyurethane to form a coating film (temperature 100 ℃ C., time 5 hours), cutting into a 2cm × 2cm square, and weighing M at room temperature₀Then putting the film into deionized water to be soaked for 24 hours, taking out the film, absorbing the water on the surface of the film by using filter paper, and then weighing the film as M, wherein the water absorption rate is calculated by the following formula: (M-M)₀)÷M₀×100％。

Alkali resistance: curing 30g of waterborne polyurethane to form a coating film (the temperature is 100 ℃ and the time is 5 hours), cutting the coating film into a square shape of 2cm multiplied by 2cm, weighing the mass as M0 at room temperature, putting the square shape into a beaker of 25 wt% sodium hydroxide solution, taking the square shape out after 1 hour, drying and measuring the weight of the square shape M1, wherein the alkali resistance is calculated by the following formula: (M)₀﹣M₁)÷M₁×100％。

TABLE 1

Item	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2
						Storage stability, month	6	6	7	2	10
Tensile strength, MPa	8.4	7.9	7.3	3.34	5.43
						Elongation at break,%	110	90	85	105	75
Water absorption percentage%	1.34	2.32	2.47	0.65	27.32
						Alkali resistance,%	3.43	4.12	4.67	3.12	10.34

Test example 2:

the nonwoven fabric (300 mm) was completely impregnated with each of the aqueous polyurethane (2000ml, 25 wt%) prepared in the foregoing examples and the known aqueous polyurethane PU-1001F, respectively, by rolling with a press roll in a tank at a pressure of 3MPa and an impregnation temperature of 50 c for 3min to allow the aqueous polyurethane to uniformly penetrate into the nonwoven fabric. Drying the impregnated non-woven fabric, then performing a fiber opening process in a 15 wt% NaOH solution at a fiber opening temperature of 90 ℃ for 50min, after the fiber opening is finished, performing post-finishing (washing, drying, sanding, facing and other procedures) to prepare microfiber leather, and performing the following tests on the microfiber leather, wherein the test results are shown in Table 2:

thickening rate: the test criteria were: QB/T2709-2005;

softness: the test criteria were: QB/T4870-2015;

hand feeling: the test method comprises the following steps: the average value is obtained by scoring by 10 experts, and the hand feeling is judged by combining the softness;

normal temperature folding resistance: the test criteria were: QB/T3812.9-1999;

color fastness to rubbing: the test criteria were: GB/T14254-1993;

temperature resistance: the test method comprises the following steps: and (3) placing the microfiber leather at 120 ℃ for 168h, and determining that the mechanical property of the microfiber leather is not obviously changed.

TABLE 2

As can be seen from the results in Table 1, the modified aqueous polyurethane of the present invention has lower water absorption, more excellent alkali resistance, better mechanical properties and better storage stability.

The results in table 2 show that the microfiber leather prepared from the modified waterborne polyurethane of the present invention has high softness and good hand feeling while ensuring normal temperature folding resistance, color fastness to rubbing and temperature resistance, and can be completely used as a substitute for real leather.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.