Process for preparing waterborne polyurethane impregnated microfiber leather

Abstract

The application specifically relates to a process method for preparing water-based polyurethane impregnated microfiber leather, and belongs to the technical field of polyurethane microfiber leather production. The method comprises the following steps: 1) performing plasma treatment on island fiber base cloth; 2) impregnating the island fiber base cloth in prepared water-based polyurethane slurry; 3) performing water-based polyurethane demulsification through a demulsifier after completing impregnation; and 4) obtaining the water-based polyurethane microfiber leather by using infrared heating for pre-drying and then high-temperature hot air drying during curing and drying. The method improves the process method for preparing water-based polyurethane impregnated microfiber leather. The method enhances the cross-linking firmness of the polyurethane / fiber composite through plasma modification, reduces the problems of uneven distribution and low retention rate caused by water migration during the polyurethane curing process through demulsification and infrared pre-drying, and the prepared polyurethane microfiber leather has good surface morphology and does not crack even after repeated stretching, and also has similar elasticity, softness and full hand feeling to real leather.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyurethane microfiber leather production, and particularly relates to a process method for preparing water-based polyurethane impregnated microfiber leather. BACKGROUND

[0002] Microfiber leather (full name: microfiber synthetic leather) is a kind of base cloth with three-dimensional network structure made of microfiber, which is used as a substrate. Polyurethane elastomer network structure, nylon bundle structure and microstructure simulating real leather collagen are formed in the substrate. The microfiber leather has similar elasticity, softness and fullness to real leather, and also has excellent mechanical properties. As the third generation of artificial leather products, the microfiber leather has many properties that have reached or even surpassed those of natural leather. In recent years, the microfiber leather has gradually expanded its market share due to its advantages such as proper use of non-natural resources, low price and high production efficiency.

[0003] In the production process of microfiber leather, the impregnation step is very important. The impregnation process is to impregnate polyurethane (PU) emulsion into the gap of microfiber base cloth by pressing, and to obtain similar texture to natural leather by using the adhesive structure of PU. The process conditions and the performance of the polyurethane used determine the style, hand feeling, elasticity and mechanical properties of the microfiber leather.

[0004] At present, the polyurethane impregnated microfiber leather produced on the market is mainly solvent type polyurethane impregnated product. This is because the solvent type polyurethane has excellent performance in all aspects and has a mature wet impregnation process. Therefore, the microfiber leather product prepared has excellent performance and unique hand feeling. However, the use of solvent type polyurethane causes serious environmental pollution and waste of resources due to the residue and volatilization of organic solvents. The recovery and utilization of organic solvents increase the production cost, so the use of solvent type polyurethane is becoming more and more inconvenient, and the market urgently needs water-based polyurethane that can replace solvent type polyurethane to enter the production link. However, due to the fact that water-based polyurethane cannot be used in wet impregnation process, the crosslinking effect of the polyurethane / microfiber composite prepared is poor, which is manifested in the presence of cracks and gullies on the surface of the microfiber leather, and the problem of poor flatness. SUMMARY

[0005] The problem to be solved by the present application is to overcome the technical defects and deficiencies of water-based polyurethane impregnated microfiber leather, and to improve the water-based polyurethane impregnation process from the aspects of base cloth modification, process optimization and improvement of traditional process, so as to obtain microfiber leather with excellent hand feeling performance and smooth surface.

[0006] The technical scheme adopted by the present application to achieve the above-mentioned purpose is as follows:

[0007] A preparation method of water-based polyurethane microfiber leather, steps are as follows:

[0008] (1) Take water-based polyurethane and water, stir, add thickening agent, crosslinking agent, wetting agent, stir, and prepare water-based polyurethane slurry;

[0009] (2) The island fiber base cloth is treated by plasma, and then immersed in the water-based polyurethane slurry prepared in step (1) to obtain an immersed base cloth;

[0010] (3) The immersed base cloth is subjected to double-dip double-rolling to obtain a double-dip double-rolled base cloth;

[0011] (4) The double-dip double-rolled base cloth is soaked in a demulsification solution, then dried by infrared pre-drying, and then dried to obtain water-based polyurethane impregnated microfiber leather.

[0012] According to some embodiments of the present application, the water-based polyurethane in step (1) is DIC WLI-630AR, and the solid content is 49%.

[0013] According to some embodiments of the present application, the thickening agent in step (1) is an associated thickening agent DH-72165.

[0014] According to some embodiments of the present application, the crosslinking agent in step (1) is an aminopropyl modified isocyanate.

[0015] According to some embodiments of the present application, the wetting agent in step (1) is a polyether modified silicone oil.

[0016] According to some embodiments of the present application, the mass ratio of water-based polyurethane and water in step (1) is 50: (50-100).

[0017] Preferably, the mass ratio of water-based polyurethane and water in step (1) is 50:72.5.

[0018] According to some embodiments of the present application, the mass ratio of water-based polyurethane and thickening agent in step (1) is 30-70:1, and specifically can be selected as 50:1.

[0019] According to some embodiments of the present application, the mass ratio of water-based polyurethane emulsion and crosslinking agent in step (1) is 30-70:0.8, and specifically can be selected as 50:0.8.

[0020] According to some embodiments of the present application, the mass ratio of water-based polyurethane emulsion and wetting agent in step (1) is 30-70:0.5, and specifically can be selected as 50:0.5.

[0021] According to some embodiments of the present application, the dynamic viscosity of the aqueous polyurethane slurry in step (1) ranges from 2000 to 4000 mpa.s.

[0022] Preferably, the dynamic viscosity of the aqueous polyurethane slurry in step (1) ranges from 2000 to 2500 mpa.s.

[0023] More specifically, the dynamic viscosity of the aqueous polyurethane slurry in step (1) is 2267 mpa.s, 2375 mpa.s or 2339 mpa.s.

[0024] According to some embodiments of the present application, the plasma treatment in step (2) is performed in a nitrogen atmosphere, with a gas flow of 50 sccm and a vacuum degree of 50 Pa, for 10 min.

[0025] According to some embodiments of the present application, the soaking time in step (2) ranges from 0.5 to 2 h, and is more specifically 1 h.

[0026] According to some embodiments of the present application, the parameters of the double-dip double-nip in step (3) are a first pressure of 20 to 40 kg / cm 2 , and a second pressure of 5 to 20 kg / cm 2 . More specifically, the first pressure is 30 kg / cm 2 , and the second pressure is 10 kg / cm 2 .

[0027] According to some embodiments of the present application, the demulsifier solution in step (4) is a 6 to 10 wt% sodium sulfate solution or anhydrous ethanol, and is more specifically an 8 wt% sodium sulfate solution.

[0028] According to some embodiments of the present application, the demulsification soaking time in step (4) ranges from 2 to 5 min, and is more specifically 3 min.

[0029] According to some embodiments of the present application, the infrared pre-drying in step (4) is performed by uniformly irradiating both sides of the base fabric with infrared light, and maintaining the surface temperature at 60°C for 10 min.

[0030] According to some embodiments of the present application, the drying temperature in step (4) is 110°C, and the drying time is 20 min.

[0031] The present application provides an aqueous polyurethane microfiber leather prepared by the method.

[0032] A method for reducing the internal cracks of an aqueous polyurethane microfiber leather, comprising the following steps:

[0033] (1) stirring an aqueous polyurethane and water, and adding a thickening agent, a crosslinking agent and a wetting agent to prepare an aqueous polyurethane slurry;

[0034] (2) treating the sea-island fiber base cloth with plasma, and then immersing the base cloth into the water-based polyurethane slurry prepared in step (1) to obtain an immersed base cloth;

[0035] (3) performing double-dip-double-nip on the immersed base cloth to obtain a double-dip-double-nip base cloth;

[0036] (4) immersing the double-dip-double-nip base cloth in a demulsification solution, and then performing infrared pre-drying and drying to obtain the water-based polyurethane impregnated microfiber leather.

[0037] According to some embodiments of the present application, the water-based polyurethane in step (1) is DIC WLI-630AR, and the solid content is 49%; the thickening agent in step (1) is an associated thickening agent DH-72165; the crosslinking agent in step (1) is an aminopropyl modified isocyanate; and the wetting agent in step (1) is a polyether modified silicone oil.

[0038] According to some embodiments of the present application, the mass ratio of the water-based polyurethane and water in step (1) is 50:72.5.

[0039] According to some embodiments of the present application, the mass ratio of the water-based polyurethane and the thickening agent in step (1) is 30-70:1, and specifically can be 50:1.

[0040] According to some embodiments of the present application, the mass ratio of the water-based polyurethane emulsion and the crosslinking agent in step (1) is 30-70:0.8, and specifically can be 50:0.8.

[0041] According to some embodiments of the present application, the mass ratio of the water-based polyurethane emulsion and the wetting agent in step (1) is 30-70:0.5, and specifically can be 50:0.5.

[0042] According to some embodiments of the present application, the viscosity of the water-based polyurethane slurry in step (1) is 2000-2500 mpa.s, and specifically can be 2267 mpa.s, 2375 mpa.s, or 2339 mpa.s.

[0043] According to some embodiments of the present application, the plasma treatment in step (2) is performed in a nitrogen atmosphere, with a gas flow of 50 sccm and a vacuum degree of 50 Pa, and the treatment time is 10 min.

[0044] According to some embodiments of the present application, the immersion time in step (2) is 0.5-2 h, and specifically can be 1 h.

[0045] According to some embodiments of the present application, the double-dip-double-nip parameters in step (3) are a first pressure of 20-40 kg / cm 2, the second pressure is 5~20kg / cm 2 , the first pressure is 30kg / cm 2 , the second pressure is 10kg / cm 2 .

[0046] According to some embodiments of the present application, the demulsifier solution in step (4) is a 6~10wt% sodium sulfate solution or anhydrous ethanol, and specifically a 8wt% sodium sulfate solution can be selected.

[0047] According to some embodiments of the present application, the demulsification soaking time in step (4) is 2~5min, and specifically 3min can be selected.

[0048] According to some embodiments of the present application, the infrared pre-drying in step (4) is to keep the two sides of the base cloth uniformly irradiated by infrared light, and the surface temperature is maintained at 60℃ for 10min.

[0049] According to some embodiments of the present application, the drying temperature in step (4) is 110℃, and the time is 20min.

[0050] The present application has the following beneficial effects:

[0051] The present application uses plasma modification to change the surface structure of the base cloth by etching, improve the bonding degree between polyurethane and fiber during curing, that is, the etching effect of nitrogen plasma is used to make the fiber surface rough, form micro-pits and micro-cracks, and make the polyurethane particles stay in these micro-cracks during immersion, prevent them from migrating outward during the heating and curing process, and improve the subsequent cross-linking and curing effect.

[0052] The present application immerses the finished microfiber leather base cloth in the demulsification solution to break the polyurethane particles in the base cloth, release the polyurethane molecules, facilitate cross-linking, and make the gel state water-based polyurethane of the sizing agent produce aggregated water, avoiding the migration of polyurethane molecules with water evaporation.

[0053] The present application also uses infrared radiation pre-drying to use infrared radiation heating to conduct heat from the surface of the base cloth to the inside of the base cloth, and slowly evaporate water from the outside to the inside, preventing the migration of polyurethane molecules with internal water evaporation.

[0054] The water-based polyurethane microfiber leather prepared by the present application has significantly reduced original texture of the island fiber base cloth after stretching, and the appearance of the microfiber leather surface is smooth and flat, and has good hand fullness. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1Digital photos of the waterborne polyurethane impregnated microfiber leather of Example 2 and Comparative Examples 1, 2, 3, 4, 5 under tension, Figure a corresponds to Example 2, Figure b corresponds to Comparative Example 1, Figure c corresponds to Comparative Example 2, Figure d corresponds to Comparative Example 3, Figure e corresponds to Comparative Example 4, and Figure f corresponds to Comparative Example 5.

[0056] Figure 2 Cross-sectional electron micrographs of microfiber leather; (a) is a cross-sectional electron micrograph of microfiber leather as received; (b) is a cross-sectional electron micrograph of microfiber leather prepared by impregnation with the waterborne polyurethane emulsion of Example 2. DETAILED DESCRIPTION

[0057] Source of raw materials

[0058] Waterborne polyurethane: DIC WLI-630AR, purchased from DIC Corporation, Japan.

[0059] Thickening agent: associative thickening agent DH-72165, purchased from Suzhou Qingtian New Material Co., Ltd.

[0060] Crosslinking agent: aminopropyl modified isocyanate, purchased from Guangzhou Wanjun Chemical Technology Co., Ltd.

[0061] Wetting agent: polyether modified silicone oil, purchased from Asahi Kasei Corporation, Japan.

[0062] Island-in-sea fiber base cloth, purchased from Jiangsu Juyi Microfiber Co., Ltd.

[0063] Cracks per unit area: five 1 cm 2 areas were taken from the surface of the microfiber leather, and the number of cracks appearing in each area after a certain tension was applied was counted, and finally the average number of cracks per unit area was calculated.

[0064] Specific compression resilience: the compression properties of the microfiber synthetic leather base cloth were measured on a YG (B) 141D digital fabric thickness meter. First, the thickness of the base cloth under light pressure (0.0196 N / cm 2 ) was measured (T0), then the thickness of the base cloth under heavy pressure (0.49 N / cm 2 ) was measured (T s ), and finally the pressure was removed and the base cloth was allowed to recover for 60 s and its thickness was measured (T r ). The specific compression resilience (R) was calculated according to the following formula:

[0065]

[0066] Softness: the softness of the impregnated microfiber leather was measured using a GT-303 leather softness tester.

[0067] Example 1

[0068] Take 50g DIC WLI-630AR (solid content 49%) in a beaker, then add 72.5g deionized water, stir for 30min, then add 1.0g associative thickener DH-72165, 0.8g aminopropyl modified isocyanate, 0.5g polyether modified silicone oil, magnetic stirring for 30min, the preparation of the required water-based polyurethane slurry. The viscosity of the slurry was measured three times by steady-state measurement using a Physica MCR301 rotary rheometer, and the average value was obtained. The viscosity of the slurry was 2267mpa.s.

[0069] The island fiber base cloth was immersed in the above-mentioned water-based polyurethane slurry after being treated with plasma in a nitrogen atmosphere at a gas flow rate of 50sccm for 10min; after immersing the base cloth for 1h, the base cloth was subjected to two-dip-two-roll, the first pressure was 30kg / cm 2 , the second pressure was 10kg / cm 2 , and the liquid rate of the base cloth was calculated to be 70% after weighing. The immersed and rolled base cloth was immersed in the prepared 8% sodium sulfate solution for 3min, and then infrared pre-drying was performed to maintain the cloth surface temperature at about 60℃, and then transferred into a 110℃ hot air oven for drying for 20min to obtain a water-based polyurethane impregnated microfiber leather.

[0070] The water-based polyurethane microfiber leather prepared had a weight gain rate of 16.7%, and the surface did not crack significantly after repeated stretching, and the number of cracks per unit area (1cm 2 ) was 1.8; the microfiber leather had excellent elasticity, and the specific compression resilience was 3.76%; the hand feeling was soft, and the softness value was 7.64.

[0071] Example 2

[0072] Take 50g DIC WLI-630AR (solid content 49%) in a beaker, then add 48g deionized water, stir for 30min, then add 0.8g associative thickener DH-72165, 0.8g aminopropyl modified isocyanate, 0.5g polyether modified silicone oil, magnetic stirring for 30min, the preparation of the required water-based polyurethane slurry. The viscosity of the slurry was measured three times by steady-state measurement using a Physica MCR301 rotary rheometer, and the average value was obtained. The viscosity of the slurry was 2375mpa.s.

[0073] The island fiber base cloth was immersed in the above-mentioned water-based polyurethane slurry after being treated with plasma in a nitrogen atmosphere at a gas flow rate of 50sccm for 10min; after immersing the base cloth for 1h, the base cloth was subjected to two-dip-two-roll, the first pressure was 30kg / cm 2 , the second pressure was 10kg / cm 2After weighing, the liquid content of the base fabric was calculated to be 70%. The impregnated base fabric was immersed in a prepared 8wt% sodium sulfate solution for 3 minutes, then infrared pre-drying was performed to maintain the fabric surface temperature at about 60°C for 10 minutes, and then transferred to a 110°C hot air oven for drying for 20 minutes to obtain waterborne polyurethane impregnated microfiber leather.

[0074] The prepared waterborne polyurethane microfiber leather had a weight gain of 18.8%, and after repeated stretching, there was no obvious surface cracking. The weight gain per unit area (1 cm²) was [not specified]. 2 The internal cracks number 1.2; the microfiber leather has excellent elasticity with a compression recovery rate of 4.10%; it has a soft feel with a softness value of 7.62.

[0075] Example 3

[0076] Take 50g of DIC WLI-630AR (49% solids content) into a beaker, add 32g of deionized water, stir for 30min, then add 0.6g of associative thickener DH-72165, 0.8g of aminopropylidin modified isocyanate, and 0.5g of polyether modified silicone oil, and stir magnetically for 30min to prepare the required waterborne polyurethane slurry. The viscosity of the slurry was measured three times under steady-state conditions using a Physica MCR301 rotational rheometer, and the average value was taken, yielding a viscosity of 2339 mPa·s.

[0077] After being plasma-treated in a nitrogen atmosphere at a gas flow rate of 50 sccm for 10 min, the island fiber base fabric was impregnated in an aqueous polyurethane slurry. After impregnation for 1 h, the base fabric underwent a second dip and treading process, with the first pressure being 30 kg / cm. 2 The second pressure was 10 kg / cm². 2 After weighing, the liquid content of the base fabric was calculated to be 70%. The impregnated base fabric was immersed in a prepared 8wt% sodium sulfate solution for 3 minutes, then infrared pre-drying was performed to maintain the fabric surface temperature at about 60°C for 10 minutes, and then transferred to a 110°C hot air oven for drying for 20 minutes to obtain waterborne polyurethane impregnated microfiber leather.

[0078] The prepared waterborne polyurethane microfiber leather had a weight gain of 19.7%, and after repeated stretching, there was no obvious surface cracking. The weight gain per unit area (1 cm²) was [not specified]. 2 The internal cracks number 1.2; the microfiber leather has excellent elasticity with a compression recovery rate of 4.22%; it has a soft feel with a softness value of 7.59.

[0079] Comparative Example 1

[0080] The preparation method is basically the same as in Example 2, except that the island fiber base fabric is not subjected to plasma treatment during preparation, but is directly subjected to subsequent operations such as water-based polyurethane impregnation.

[0081] The prepared water-based polyurethane microfiber leather has a weight gain rate of 16.2%, and after repeated stretching, cracking occurs in some areas, and a small amount of base fabric patterns appear, with 2.8 cracks per unit area (1 cm 2 ) of the microfiber leather; the specific compression resilience of the microfiber leather is 3.52%; and the softness value is 7.62.

[0082] Comparative Example 2

[0083] The preparation method is basically the same as that of Example 2, except that the impregnated base fabric is not subjected to demulsification treatment during preparation, and subsequent operations such as drying are directly performed.

[0084] The prepared water-based polyurethane microfiber leather has a weight gain rate of 17.2%, and after repeated stretching, cracking occurs in some areas, and a small amount of base fabric patterns appear, with 2.6 cracks per unit area (1 cm 2 ) of the microfiber leather; the specific compression resilience of the microfiber leather is 3.59%; and the softness value is 7.65.

[0085] Comparative Example 3

[0086] The preparation method is basically the same as that of Example 2, except that the base fabric after demulsification treatment is not subjected to infrared pre-drying during preparation, and is directly dried by high-temperature hot air until the end.

[0087] The prepared water-based polyurethane microfiber leather has a weight gain rate of 18.1%, and after repeated stretching, cracking occurs in some areas, and a small amount of base fabric patterns appear, with 2.2 cracks per unit area (1 cm 2 ) of the microfiber leather; the specific compression resilience of the microfiber leather is 3.66%; and the softness value is 7.20.

[0088] Comparative Example 4

[0089] The preparation method is basically the same as that of Example 2, except that the prepared water-based polyurethane slurry has a dynamic viscosity of ≤2000 mpa.s, and the preparation process is as follows:

[0090] Take 50g DIC WLI-630AR (solid content 49%) in a beaker, then add 48g deionized water, stir for 30min, then add 0.5g associative thickener DH-72165, 0.8g aminopropyl modified isocyanate, 0.5g polyether modified silicone oil, magnetic stirring for 30min, the preparation of the required water-based polyurethane slurry. The viscosity of the slurry was measured three times by steady-state measurement using a Physica MCR301 rotary rheometer, and the average value was obtained. The viscosity of the slurry was 1250mpa.s. The weight gain rate of the prepared water-based polyurethane microfiber leather was significantly reduced compared with Example 2, from 18.8% to 13.72%, the hand fullness of the microfiber leather was obviously not good, and due to the low content of water-based polyurethane in the microfiber leather, cracking occurred in some areas after repeated stretching of the microfiber leather, and a large number of base fabric lines per unit area (1cm 2 ) had 4 cracks; the elasticity was not good, and the specific compression resilience of the microfiber leather was 2.59%; the softness value was 7.83.

[0091] Comparative Example 5

[0092] The preparation method is basically the same as that of Example 2, except that the dynamic viscosity of the prepared water-based polyurethane slurry is >4000mpa.s, and the preparation process is as follows:

[0093] Take 50g DIC WLI-630AR (solid content 49%) in a beaker, then add 48g deionized water, stir for 30min, then add 1.4g associative thickener DH-72165, 0.8g aminopropyl modified isocyanate, 0.5g polyether modified silicone oil, magnetic stirring for 30min, the preparation of the required water-based polyurethane slurry. The viscosity of the slurry was measured three times by steady-state measurement using a Physica MCR301 rotary rheometer, and the average value was obtained. The viscosity of the slurry was 4250mpa.s. The weight gain rate of the prepared water-based polyurethane microfiber leather was significantly increased compared with Example 2, from 18.8% to 22.72%, and the high viscosity led to uneven distribution of water-based polyurethane in the microfiber leather, with more cracks in some areas per unit area (1cm 2 ) had 3.2 cracks; while some areas had fewer cracks per unit area (1cm 2 ) had 1 crack, and the softness and specific compression resilience of the microfiber leather decreased significantly, with a softness value of 6.70 and a specific compression resilience of 2.78%.

[0094] Although the present application has been disclosed with reference to the preferred embodiments above, it is not intended to limit the present application, and any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present application, therefore the protection scope of the present application should be defined by the claims.

Claims

1. A method for preparing a waterborne polyurethane microfiber leather, characterized by, The steps are as follows: (1) stirring water-based polyurethane and water, adding thickening agent, crosslinking agent and wetting agent, and stirring to prepare water-based polyurethane slurry; the mass ratio of water-based polyurethane to water is 50: (50-100); the mass ratio of water-based polyurethane to thickening agent is 30-70:1; the mass ratio of water-based polyurethane emulsion to crosslinking agent is 30-70:0.8; the mass ratio of water-based polyurethane emulsion to wetting agent is 30-70:0.5; the dynamic viscosity of the water-based polyurethane slurry is 2000-4000 mpa.s; (2) treating the island fiber base cloth with plasma, and then immersing it in the water-based polyurethane slurry prepared in step (1) to obtain an immersed base cloth; (3) double-dipping and double-rolling the immersed base cloth to obtain a double-dipping and double-rolled base cloth; (4) soaking the double-dipping and double-rolled base cloth in a demulsification solution, then pre-drying with infrared, and then drying to obtain a water-based polyurethane impregnated microfiber leather.

2. The production method according to claim 1, characterized by, The water-based polyurethane in step (1) is DICWLI-630AR with a solid content of 49%; the wetting agent in step (1) is polyether modified silicone oil.

3. The preparation method according to claim 1, characterized in that, The plasma treatment conditions in step (2) are as follows: nitrogen atmosphere, gas flow of 40-60 sccm, vacuum degree of 40-60 Pa, and treatment time of 8-12 min.

4. The preparation method according to claim 1, characterized in that, The parameters of the double-dipping and double-rolling in step (3) are 20-40 kg / cm for the first pressure and 5-20 kg / cm for the second pressure. 2 2 ​​ 5. The preparation method according to claim 1, characterized in that, The demulsification solution in step (4) is a 6-10 wt% sodium sulfate solution or anhydrous ethanol.

6. The preparation method according to claim 1, characterized in that, In step (4), the infrared pre-drying is to uniformly irradiate the base cloth on both sides with infrared light, and the surface temperature is maintained at 50-70°C for 8-12 min.

7. A water-based polyurethane microfiber leather prepared by the method of any one of claims 1-6.

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