CN117005213A - Preparation and application of a water-based polyurethane composite coating with high ductility - Google Patents

Abstract

The application relates to preparation and application of a high-ductility aqueous polyurethane composite coating, which comprises the following steps: firstly, coating lower-layer aqueous polyurethane slurry on the surface of a target object, drying and curing to form a lower-layer aqueous polyurethane coating, then coating middle-layer aqueous polyurethane slurry on the lower-layer aqueous polyurethane coating, drying and curing to form a middle-layer aqueous polyurethane coating, coating upper-layer aqueous polyurethane slurry on the middle-layer aqueous polyurethane coating, drying and curing to form an upper-layer aqueous polyurethane coating, and finally standing to obtain the aqueous polyurethane composite coating with high ductility; when the target object for coating is microfiber base cloth, the product is used for preparing microfiber PU synthetic leather; the tensile load of the superfine fiber PU synthetic leather is more than or equal to 540N, and the elongation at break is more than or equal to 60 percent. The preparation method of the application obtains the coating material with high strength and high ductility; the product is used for preparing superfine fiber PU synthetic leather, and has excellent strength and toughness.

Description

Preparation and application of a water-based polyurethane composite coating with high ductility

Technical field

The invention belongs to the technical field of polyurethane and relates to the preparation and application of a water-based polyurethane composite coating with high ductility.

Background technique

In the existing technology, the polyurethane usually used for the surface coating of synthetic leather is a water-based polyurethane with good strength and high hard segment content. 100% modulus is usually used to evaluate the hard segment content level of water-based polyurethane. The higher the hard segment content, the higher the hard segment content. The larger the modulus, usually 100% modulus ≥ 34MPa is selected to meet the strength requirements of the material. However, waterborne polyurethanes with high hard segment content often lack ductility.

In the field of PU elastomers, small molecule lubricants are usually added to increase the plasticity of polyurethane materials, thereby increasing the ductility, so that the polyurethane materials can have higher ductility and strength, and are less likely to cause damage during subsequent processing and use. Problems such as cracking and breakage. For example, CN201410802061. The dosage is 0.05-5% of the total mass of the formula.

It is more effective to improve ductility by adding small molecule lubricants. This additive is also suitable for the field of polyurethane coatings. However, for polyurethane matrices with different rigidities, the effects of using small molecule lubricants to improve their ductility are different. When the 100% modulus is as high as 40MPa, the material rigidity is too high, and it is difficult to obtain the desired effect through small molecule lubricants; for polyurethane with a 100% modulus of 34 to 40MPa, it is possible to improve the ductility by adding small molecule lubricants. It has a certain effect, but the limit addition level of small molecule lubricant in water-based polyurethane with high hard segment content is low. The limit addition amount is about 10%. When the addition amount exceeds the limit value, the ductility modification of the material will no longer continue. It increases with the increase of the added amount. This is because after exceeding the limit added amount, the lubricant will precipitate to the surface, so that the concentration of small molecules actually distributed in the matrix does not actually increase, but causes appearance problems. Currently, the generally applicable lubricant can be obtained The means of high ductility is to choose a polyurethane matrix with a lower 100% modulus, and further can add a lubricant within 30%, but this means that it is impossible to obtain a material with high strength and high ductility at the same time, because of the selected matrix The lower the 100% modulus, the worse the strength, and the addition of lubricant can only improve the ductility but not the strength.

Therefore, it is of great significance to study the preparation method and application of a water-based polyurethane coating with excellent strength and toughness to solve the above problems.

Contents of the invention

The purpose of the present invention is to solve the problems existing in the prior art and provide a preparation and application of a water-based polyurethane composite coating with high ductility.

In order to achieve the above objects, the technical solutions adopted by the present invention are as follows:

A method for preparing a water-based polyurethane composite coating with high ductility. First, a lower layer of water-based polyurethane slurry is coated on the surface of the target object, dried and solidified to form a lower layer of water-based polyurethane coating, and then a middle layer is coated on the lower layer of water-based polyurethane coating. The water-based polyurethane slurry is dried and solidified to form a middle layer of water-based polyurethane coating, and then the upper layer of water-based polyurethane slurry is coated on the middle layer of water-based polyurethane coating, dried and solidified to form the upper layer of water-based polyurethane coating, and finally left to obtain a highly ductile coating. Water-based polyurethane composite coating;

The middle layer water-based polyurethane slurry contains high 100% modulus water-based polyurethane resin, small molecule lubricant and water;

The upper water-based polyurethane slurry contains low 100% modulus water-based polyurethane resin, small molecule lubricant and water;

The lower layer of water-based polyurethane slurry contains low 100% modulus water-based polyurethane resin, small molecule lubricant and water;

The 100% modulus of high 100% modulus water-based polyurethane resin is 34~40MPa, and the 100% modulus of low 100% modulus water-based polyurethane resin is 1~2MPa;

The monomer units of high 100% modulus waterborne polyurethane resin are the same as those of low 100% modulus waterborne polyurethane resin;

In the middle layer water-based polyurethane slurry, 100 parts by mass of high 100% modulus water-based polyurethane resin is correspondingly added with 8 to 10 parts by mass of small molecule lubricant, and the addition amount of the small molecule lubricant is close to the precipitation limit but is still Within the precipitation limit; if the small molecule lubricant in the middle layer of water-based polyurethane exceeds the precipitation limit, precipitated oil spots will appear on the surface after film formation. These are aggregates of small molecule lubricants and are incompatible with water-based polyurethane. This makes it difficult to further apply a qualified composite coating on the surface. The mass parts of the small molecule lubricant corresponding to 100 parts by mass of the water-based polyurethane resin in the upper layer of water-based polyurethane slurry and the lower layer of water-based polyurethane slurry with a modulus of 100% lower than that of the water-based polyurethane resin in the middle layer are 100 parts by mass of a water-based polyurethane resin in the middle layer with a modulus of 100% lower The modulus of the water-based polyurethane resin corresponds to at least 1.5 times the mass fraction of the added small molecule lubricant, and if the added amount of the small molecule lubricant is within the precipitation limit, if it is less than 1.5, there will be no significant passing concentration difference. Diffusion to increase the concentration of small molecule lubricants in high 100% modulus waterborne polyurethane resins did not show a significant improvement in the ductility of the material.

As the preferred technical solution:

As described above, the preparation method of a highly ductile water-based polyurethane composite coating, the thickness ratio of the upper water-based polyurethane coating to the middle water-based polyurethane coating is 10:90 to 17:83; the thickness ratio of the lower water-based polyurethane coating is The thickness is the same as the thickness of the upper water-based polyurethane coating.

As described above, in the preparation method of a highly ductile water-based polyurethane composite coating, the thickness of the middle water-based polyurethane coating is 50-300 μm, and the thickness of the upper water-based polyurethane coating is 10-50 μm.

As described above, in terms of parts by mass, the middle layer water-based polyurethane slurry contains 100 parts of high 100% modulus water-based polyurethane resin and 8 to 10 parts of small molecule lubrication. agent and 70 to 500 parts of water; in parts by mass, the upper water-based polyurethane slurry contains 100 parts of low 100% modulus water-based polyurethane resin, 12 to 22 parts of small molecule lubricant and 70 to 500 parts of water; in parts by mass In total, the lower water-based polyurethane slurry contains 100 parts of low 100% modulus water-based polyurethane resin, 12 to 22 parts of small molecule lubricant and 70 to 500 parts of water;

Additives such as thickeners can also be added according to actual needs. For example, 0.1 to 1 part of thickener can be added to adjust the viscosity of the water-based polyurethane coating to 1000mPa·s to 6000mPa·s (tested with a rotational viscometer, the test temperature is 25°C ), which is more conducive to smooth coating. The thickener can be selected from Stahl Company. EVO RM-4417 and EVO RM-4456, these additives and their functions are state of the art. According to actual needs, colorants can also be added to the upper water-based polyurethane slurry to adjust the color. For example, 1 to 10 parts of colorants can be added, such as the QCS-840 series of Guangzhou Qicai New Materials Co., Ltd.

As described above, in the preparation method of a highly ductile water-based polyurethane composite coating, the small molecule lubricant is triethyl phosphate. The solubility of triethyl phosphate in water is large, so more small molecule lubricants can be added. .

As described above, the preparation method of a water-based polyurethane composite coating with high ductility is a roller coating process. This is a conventional coating method. Those skilled in the art can adjust it according to the target coating thickness. to obtain process parameters.

As mentioned above, the preparation method of a highly ductile water-based polyurethane composite coating requires a standing temperature of 50 to 70°C and a standing time of more than 48 hours. The setting of the standing temperature and standing time is because a certain amount of time is required. The high-concentration small-molecule lubricant diffuses into the polyurethane, and the high temperature of 50 to 70°C can accelerate the diffusion. The elongation at break of the composite coating that has not been left standing and the composite coating that has been left standing are significantly different.

As described above, a method for preparing a water-based polyurethane composite coating with high ductility, the target material is a microfiber base fabric, non-woven fabric, woven fabric or knitted fabric.

The present invention also provides the application of a water-based polyurethane composite coating with high ductility prepared by any of the above methods for preparing ultra-fine fiber PU synthetic leather, and the target object used for the coating is ultra-fiber base cloth ;

The tensile load of microfiber PU synthetic leather is ≥540N, and the elongation at break is ≥60%.

Invention mechanism:

During the polymerization of polyurethane, oligomer active hydrogen substances (such as oligomer glycols) and small molecule active hydrogen substances (such as ethylene glycol) are added at the same time, and their active hydrogen end groups react with diisocyanate to form polyurethane Molecular chain, in which oligomer active hydrogen substances constitute the soft segment of polyurethane, and small molecule active hydrogen substances constitute the hard segment of polyurethane. The soft segment provides the flexibility of the molecular chain and the hard segment provides the rigidity of the molecular chain. The hard segment content The higher the value, the stronger the rigidity of the material and the lower the flexibility. The rigidity of the material is usually evaluated at the 100% modulus level, and then the proportion of polyurethane hard segments is evaluated. The high 100% modulus water-based polyurethane resin is a polyurethane with a high hard segment content, and the low 100% modulus water-based polyurethane resin is a polyurethane with a high soft segment content.

By analyzing the precipitation behavior of small molecules in polyurethane matrices containing different soft segment proportions, it is believed that the proportion of soft segments affects the solubility of small molecule additives in the polymer matrix. Polyurethane with a larger proportion of soft segments can dissolve more small molecule lubricants. Polyurethane with a high soft segment ratio has good ductility and generally does not need to add additional small molecule lubricants for toughening modification. However, polyurethane with a high soft segment ratio is too low in strength to be used for synthetic leather. For coatings, polyurethane with a high soft segment ratio itself requires strength modification rather than toughening modification. Therefore, even if it has a higher solubility of small molecule additives, it cannot solve the problems faced by the existing technology. Water-based polyurethane with high hard segment content, which has many hard segments and few soft segments, has high strength, but its ductility is insufficient. It is generally improved by adding small molecule additives.

In the early stages of research and development, we compounded 100% waterborne polyurethane with a modulus of 44MPa and 100% of the same waterborne polyurethane with a modulus of 1.5MPa to adjust waterborne polyurethanes with different 100% modulus levels, that is, with different softness. water-based polyurethane to adjust the strength and ductility of the coating. To ensure ideal strength, the 100% modulus of the water-based polyurethane resin must be adjusted to at least exceed 30MPa. Adding a small molecule lubricant can improve the ductility, but the level of improvement is limited because when the small molecule lubricant is added to more than 12 parts (i.e. When the addition amount of small molecule lubricant is more than 12wt% of water-based polyurethane, a precipitated oil film will occur. At this time, the 100% modulus is 30MPa.

The compatibility of hard segments and small molecule lubricants is poor, and the limit precipitation concentration of small molecule lubricants in polyurethanes with different hard segment contents is different; among them, the limit precipitation concentration is to add different proportions of small molecule lubricants to water-based polyurethane, and then scrape The film is formed, dried at 100℃ and then cooled to 25℃. The proportion of small molecule lubricant added when oil spots or precipitates appear on the surface of the polyurethane film. When we set the low 100% modulus waterborne polyurethane resin containing a higher concentration of small molecule lubricant distribution above and below the high 100% modulus waterborne polyurethane resin containing a distribution of small molecule lubricant close to the limiting precipitation concentration, it was found that at low The high concentration of small molecule lubricant in the 100% modulus water-based polyurethane resin diffuses into the high 100% modulus water-based polyurethane resin, significantly improving the overall ductility of the material. When the small molecule lubricant exceeds the limit concentration, it generates a greater outward diffusion force, and the difference in lubricant concentration on both sides causes the small molecule lubricant to generate an inward diffusion force.

The conditions for forming a certain concentration difference so that small molecule lubricants have the power to diffuse inward are: the content of small molecule lubricants in the upper water-based polyurethane coating and the content of small molecule lubricants in the lower water-based polyurethane coating are respectively The content of small molecule lubricant in the coating is ≥1.5 times.

During the preparation process, the small molecule lubricant in the upper, middle and lower layers did not exceed the limit precipitation concentration. The small molecule lubricant in the water-based polyurethane coating in the middle layer was 8 to 10 parts, which was close to the limit concentration. After being treated at high temperatures of 50 to 70°C for 48 hours, the small molecule lubricant in the upper and lower layers diffused into the middle layer, and the actual small molecule lubricant concentration in the water-based polyurethane coating in the middle layer exceeded its limit concentration.

In the present invention, it is ensured that the polyurethanes in the upper, middle and lower water-based polyurethane coatings are of the same material. The monomer units of the high 100% modulus water-based polyurethane resin and the low 100% modulus water-based polyurethane resin are the same, and the only difference is the soft segment. The content is different. Replacing the upper material with a coating of another material with the same solubility, due to the poor compatibility of the two materials, the concentration difference causes small molecule lubricants to precipitate at the interface, exacerbating material delamination.

beneficial effects

(1) A method for preparing a water-based polyurethane composite coating with high ductility of the present invention, by arranging a high 100% modulus water-based polyurethane resin containing a higher concentration of small molecule lubricant distributed above and below the extreme precipitation concentration. The low 100% modulus water-based polyurethane resin with a low concentration of small molecule lubricant uses diffusion power to allow the small molecule lubricant exceeding the limit concentration to stably exist in the high 100% modulus water-based polyurethane resin, achieving high strength and Highly ductile material.

(2) The water-based polyurethane composite coating with high ductility of the present invention is used to prepare ultrafine fiber PU synthetic leather with excellent strength and toughness.

Description of the drawings

Figure 1 is a schematic diagram of the highly ductile water-based polyurethane composite coating of the present invention;

Figure 2 is a difference spectrum of Example 1 before and after heat treatment at 50°C for 48 hours;

Among them, 1-upper water-based polyurethane coating, 2-middle water-based polyurethane coating, 3-lower water-based polyurethane coating.

Detailed ways

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

The test methods involved in the present invention are as follows:

100% modulus: Use a universal testing machine to measure the tensile force when the film is stretched to 100% elongation at break, and then divide the tensile force by the cross-sectional area of the film before stretching, which is 100% of the material. modulus.

Tensile strength and elongation at break of the composite coating: replace the target object in the examples and comparative examples with flat glass, remove the composite coating from the flat glass after molding, and prepare a test sample of the composite coating; According to GB/T 1040.3-2006, a universal testing machine is used to measure the tensile strength and elongation at break of the composite coating. The distance between the sample marking lines is 100mm, and the test speed is 200mm/min±10mm/min.

Tensile load and elongation at break of synthetic leather: The prepared synthetic leather was measured according to QBT 4909-2016 water-based polyurethane microfiber synthetic leather.

The water-based polyurethane resin of the present invention is an anionic water-based polyurethane resin. The difference between the low-modulus water-based polyurethane resin and the high-modulus water-based polyurethane resin lies in the different proportions of the soft segments. The soft segments of the low-modulus water-based polyurethane resin (i.e., in the structural formula The third part) is 40 times the soft segment of the high-modulus water-based polyurethane resin; the two water-based polyurethane resins are:

The structural formula of a high 100% modulus waterborne polyurethane resin with a 100% modulus of 44MPa is:

The structural formula of a low 100% modulus water-based polyurethane resin with a 100% modulus of 1.0MPa is:

The number average molecular weight of the high-modulus water-based polyurethane resin was determined to be 156,000; the number-average molecular weight of the low-modulus water-based polyurethane resin was determined to be 168,000. Water-based polyurethane resins with different modulus can be prepared from high 100% modulus water-based polyurethane resin and low 100% modulus water-based polyurethane resin. In specific examples and comparative examples, the mixing ratio is:

100% water-based polyurethane with a modulus of 1.2MPa is obtained by dispersing and mixing evenly in water 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in a mass ratio of 99.5:0.5.

100% water-based polyurethane with a modulus of 1.3MPa is obtained by mixing evenly dispersed 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in water at a mass ratio of 99.30:0.70.

100% water-based polyurethane with a modulus of 1.5MPa is obtained by dispersing and uniformly mixing 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in water at a mass ratio of 98.84:1.16.

100% water-based polyurethane with a modulus of 1.6MPa is obtained by dispersing and uniformly mixing 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in water at a mass ratio of 98.60:1.40.

100% water-based polyurethane with a modulus of 1.8MPa is obtained by dispersing 100% water-based polyurethane resin with a modulus of 1.0MPa and 100% water-based polyurethane with a modulus of 44MPa in water and mixing them uniformly in water with a mass ratio of 98.14:1.86.

100% water-based polyurethane with a modulus of 2.0 MPa is obtained by dispersing and uniformly mixing 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in water at a mass ratio of 97.67:2.33.

100% water-based polyurethane with a modulus of 34MPa is obtained by dispersing and mixing evenly in water 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in a mass ratio of 23.26:76.74.

100% water-based polyurethane with a modulus of 35MPa is obtained by dispersing and mixing evenly in water 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in a mass ratio of 20.93:79.07.

100% water-based polyurethane with a modulus of 36 MPa is obtained by dispersing and mixing evenly in water 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in a mass ratio of 18.60:81.40.

100% water-based polyurethane with a modulus of 40 MPa is obtained by dispersing and mixing evenly in water 100% water-based polyurethane resin with a modulus of 1.0 MPa and 100% water-based polyurethane with a modulus of 44 MPa in a mass ratio of 9.30:90.70.

The microfiber base fabric used in the examples is from Toray Industries, Inc. Series 500R products;

The non-woven fabric used in the example is a non-woven fabric with a thickness of 1.2 mm from Changshu Yanrui Non-Woven Products Co., Ltd., product number: leather base fabric-07;

The woven fabric used in the examples is polyester woven fabric from Dongguan Jihui Textile Co., Ltd., product number: B103/8P4736;

The knitted fabric used in the embodiment is a polyester knitted fabric with a weight of 220g/ ^m2 from Tongxiang Jinbolai Knitting Co., Ltd., product number: XX.

Table 1 The precipitation limit addition amount of small molecule lubricants with different 100% modulus

100% modulus Small molecule lubricant precipitation limit Remark 40MPa 9 parts (relative to 100 parts polyurethane) Slight oil spots began to appear at 9 servings 35MPa 10 parts (relative to 100 parts polyurethane) Slight oil spots began to appear at 10 servings 30MPa 12 parts (relative to 100 parts polyurethane) Slight oil spots began to appear at 12 servings 2MPa More than 30 parts (relative to 100 parts of polyurethane) Added to 30 servings and still no oil spots appeared 1MPa More than 30 parts (relative to 100 parts of polyurethane) Added to 30 servings and still no oil spots appeared

The term "precipitation limit" in Table 1 refers to the small molecule lubrication when oil spots or precipitates appear on the surface of the water-based polyurethane coating after adjusting the addition ratio of small molecule lubricant in water-based polyurethane, drying at 100°C and cooling to 25°C. The minimum addition ratio of the agent.

Example 1

A method for preparing a highly ductile water-based polyurethane composite coating, as shown in Figure 1. The specific steps are as follows:

(1) The lower layer of water-based polyurethane slurry is roller-coated on the surface of the microfiber base cloth, and dried at 80°C for 60 minutes to solidify to form a lower layer of water-based polyurethane coating 3 with a thickness of 17 μm; among which, in terms of parts by mass, the lower layer of water-based polyurethane slurry The material contains 100 parts of low 100% modulus water-based polyurethane resin, 15 parts of triethyl phosphate and 500 parts of water; the 100% modulus of low 100% modulus water-based polyurethane resin is 2MPa;

(2) Roll-coat the middle layer of water-based polyurethane slurry on the lower layer of water-based polyurethane coating 3, and dry it at 80°C for 60 minutes to solidify to form a middle layer of water-based polyurethane coating 2 with a thickness of 83 μm; wherein, in terms of mass parts, the middle layer of water-based polyurethane slurry is The polyurethane slurry contains 100 parts of high 100% modulus water-based polyurethane resin, 10 parts of triethyl phosphate and 500 parts of water; the 100% modulus of high 100% modulus water-based polyurethane resin is 34MPa;

(3) Roll-coat the upper water-based polyurethane slurry on the middle water-based polyurethane coating 2, dry it at 80°C for 60 minutes and solidify to form an upper water-based polyurethane coating 1 with the same thickness as the lower water-based polyurethane coating 3, and then bake it at 70°C Let stand for 60 hours to obtain a highly ductile water-based polyurethane composite coating; wherein, in terms of parts by mass, the upper water-based polyurethane slurry contains 100 parts of low 100% modulus water-based polyurethane resin, 15 parts of triethyl phosphate and 500 parts of Water; low 100% modulus The 100% modulus of water-based polyurethane resin is 2MPa.

The tensile strength of the prepared water-based polyurethane composite coating with high ductility is 149N, and the elongation at break is 324%; the tensile load of the ultrafine fiber PU synthetic leather is 540N, and the elongation at break is 89%.

Using a water-based polyurethane composite coating with high ductility as a measurement sample, the concentration changes and ductility changes of triethyl phosphate on the upper and lower surfaces were measured. As shown in Figure 2, it was found that the characteristic peak intensity of the 1280cm ^-1 phosphate group was relatively There is an obvious change, showing a decreasing trend after heat treatment, but there is no precipitation phenomenon on the surface of the composite material. Combined with the elongation after heat treatment increasing by 1.24 times compared with before treatment (261%), it is speculated that the triethyl phosphate in the upper and lower layers has diffused into the middle layer.

Comparative example 1

A method for preparing a water-based polyurethane composite coating, which is basically the same as Example 1. The only difference is that in parts by mass, the addition amounts of triethyl phosphate in the upper, middle and lower layers are 12, 10 and 12 parts respectively ( That is, the mass fraction of triethyl phosphate in the upper and lower water-based polyurethane coatings is less than 1.5 times that of the middle water-based polyurethane coating).

The tensile strength of the prepared water-based polyurethane composite coating is 153N, and the elongation at break is 268%; the water-based polyurethane composite coating is used to prepare ultrafine fiber PU synthetic leather, and the tensile load of ultrafine fiber PU synthetic leather is 549N. The elongation at break is 58%.

Comparing Example 1 with Example 1, it can be found that the elongation at break of the water-based polyurethane composite coating and the ultrafine fiber PU synthetic leather made in Comparative Example 1 is significantly lower than that of Example 1. This is because the The interlayer concentration difference of the small molecule lubricant did not promote inward diffusion.

Example 2

A method for preparing a highly ductile water-based polyurethane composite coating. The specific steps are as follows:

(1) The lower layer of water-based polyurethane slurry is roller-coated on the surface of the microfiber base cloth, and dried at 80°C for 60 minutes to solidify to form a lower layer of water-based polyurethane coating with a thickness of 10 μm; among which, in terms of parts by mass, the lower layer of water-based polyurethane slurry Contains 100 parts of low 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high soft segment content), 14 parts of triethyl phosphate and 70 parts of water; the 100% modulus of low 100% modulus water-based polyurethane resin is 1.5MPa;

(2) Roll-coat the middle layer of water-based polyurethane slurry on the lower layer of water-based polyurethane coating, dry it at 80°C for 60 minutes and solidify to form a middle layer of water-based polyurethane coating with a thickness of 90 μm; wherein, in terms of parts by mass, the middle layer of water-based polyurethane slurry The material contains 100 parts of high 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high hard segment content), 8 parts of triethyl phosphate and 70 parts of water; the 100% modulus of high 100% modulus water-based polyurethane resin is 40MPa;

(3) Roll the upper water-based polyurethane slurry on the middle water-based polyurethane coating, dry it at 80°C for 60 minutes to solidify to form an upper water-based polyurethane coating with the same thickness as the lower water-based polyurethane coating, and then let it stand at 50°C. A water-based polyurethane composite coating with high ductility was obtained in 48 hours; in which, in terms of parts by mass, the upper water-based polyurethane slurry contained 100 parts of low 100% modulus water-based polyurethane resin, 14 parts of triethyl phosphate and 70 parts of water; low 100% modulus The 100% modulus of water-based polyurethane resin is 1MPa.

The tensile strength of the prepared water-based polyurethane composite coating with high ductility is 207N, and the elongation at break is 255%; the tensile load of the ultrafine fiber PU synthetic leather is 621N, and the elongation at break is 60%.

Example 3

A method for preparing a highly ductile water-based polyurethane composite coating. The specific steps are as follows:

(1) Roll-coat the lower layer of water-based polyurethane slurry on the surface of the microfiber base cloth, dry it at 80°C for 60 minutes and solidify to form a lower layer of water-based polyurethane coating with a thickness of 12 μm; among which, in terms of parts by mass, the lower layer of water-based polyurethane slurry Contains 100 parts of low 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high soft segment content), 15 parts of triethyl phosphate and 250 parts of water; the 100% modulus of low 100% modulus water-based polyurethane resin is 1MPa;

(2) Roll-coat the middle layer of water-based polyurethane slurry on the lower layer of water-based polyurethane coating, dry it at 80°C for 60 minutes and solidify to form a middle layer of water-based polyurethane coating with a thickness of 100 μm; wherein, in terms of parts by mass, the middle layer of water-based polyurethane slurry The material contains 100 parts of high 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high hard segment content), 9 parts of triethyl phosphate and 250 parts of water; the 100% modulus of high 100% modulus water-based polyurethane resin is 35MPa;

(3) Roll the upper water-based polyurethane slurry on the middle water-based polyurethane coating, dry it at 80°C for 60 minutes to solidify to form an upper water-based polyurethane coating with the same thickness as the lower water-based polyurethane coating, and then let it stand at 60°C. A water-based polyurethane composite coating with high ductility was obtained in 50 hours; in which, in terms of parts by mass, the upper water-based polyurethane slurry contained 100 parts of low 100% modulus water-based polyurethane resin, 15 parts of triethyl phosphate and 250 parts of water; low 100% modulus The 100% modulus of water-based polyurethane resin is 1.5MPa.

The tensile strength of the prepared water-based polyurethane composite coating with high ductility is 191N, and the elongation at break is 298%; the tensile load of the ultrafine fiber PU synthetic leather is 601N, and the elongation at break is 76%.

Example 4

A method for preparing a highly ductile water-based polyurethane composite coating. The specific steps are as follows:

(1) Roll-coat the lower layer of water-based polyurethane slurry on the surface of the non-woven fabric, dry it at 80°C for 60 minutes and solidify to form a lower layer of water-based polyurethane coating with a thickness of 20 μm; where, in parts by mass, the lower layer of water-based polyurethane slurry contains 100 parts of low 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high soft segment content), 16 parts of triethyl phosphate and 100 parts of water; the 100% modulus of low 100% modulus water-based polyurethane resin is 1.6MPa;

(2) Roll-coat the middle layer of water-based polyurethane slurry on the lower layer of water-based polyurethane coating, dry it at 80°C for 60 minutes and solidify to form a middle layer of water-based polyurethane coating with a thickness of 200 μm; wherein, in terms of parts by mass, the middle layer of water-based polyurethane slurry The material contains 100 parts of high 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high hard segment content), 8.5 parts of triethyl phosphate and 80 parts of water; the 100% modulus of high 100% modulus water-based polyurethane resin is 36MPa;

(3) Roll the upper water-based polyurethane slurry on the middle water-based polyurethane coating, dry it at 80°C for 60 minutes to solidify to form an upper water-based polyurethane coating with the same thickness as the lower water-based polyurethane coating, and then let it stand at 55°C. A water-based polyurethane composite coating with high ductility was obtained in 52 hours; in which, in terms of parts by mass, the upper water-based polyurethane slurry contained 100 parts of low 100% modulus water-based polyurethane resin, 14 parts of triethyl phosphate and 100 parts of water; low 100% modulus The 100% modulus of water-based polyurethane resin is 1.2MPa.

The tensile strength of the prepared water-based polyurethane composite coating with high ductility was 184N, and the elongation at break was 377%.

Example 5

A method for preparing a highly ductile water-based polyurethane composite coating. The specific steps are as follows:

(1) Roller-coat the lower layer of water-based polyurethane slurry on the surface of the woven fabric, dry it at 80°C for 60 minutes and solidify to form a lower layer of water-based polyurethane coating with a thickness of 25 μm; wherein, in parts by mass, the lower layer of water-based polyurethane slurry contains 100 Parts of low 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high soft segment content), 18 parts of triethyl phosphate and 200 parts of water; the 100% modulus of low 100% modulus water-based polyurethane resin is 1.3MPa;

(2) Roll-coat the middle layer of water-based polyurethane slurry on the lower layer of water-based polyurethane coating, dry it at 80°C for 60 minutes and solidify to form a middle layer of water-based polyurethane coating with a thickness of 250 μm; wherein, in terms of parts by mass, the middle layer of water-based polyurethane slurry The material contains 100 parts of high 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high hard segment content), 8.5 parts of triethyl phosphate and 180 parts of water; the 100% modulus of high 100% modulus water-based polyurethane resin is 36MPa;

(3) Roll the upper water-based polyurethane slurry on the middle water-based polyurethane coating, dry it at 80°C for 60 minutes to solidify to form an upper water-based polyurethane coating with the same thickness as the lower water-based polyurethane coating, and then let it stand at 65°C. A water-based polyurethane composite coating with high ductility was obtained in 54 hours; in which, in terms of parts by mass, the upper water-based polyurethane slurry contained 100 parts of low 100% modulus water-based polyurethane resin, 16 parts of triethyl phosphate and 200 parts of water; low 100% modulus The 100% modulus of water-based polyurethane resin is 1.6MPa.

The tensile strength of the prepared water-based polyurethane composite coating with high ductility is 201N, and the elongation at break is 398%.

Example 6

A method for preparing a highly ductile water-based polyurethane composite coating. The specific steps are as follows:

(1) Roll-coat the lower layer of water-based polyurethane slurry on the surface of the knitted fabric, dry it at 80°C for 60 minutes and solidify to form a lower layer of water-based polyurethane coating with a thickness of 50 μm; wherein, in parts by mass, the lower layer of water-based polyurethane slurry contains 100 parts of low 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high soft segment content), 20 parts of triethyl phosphate and 300 parts of water; the 100% modulus of low 100% modulus water-based polyurethane resin is 1.8MPa;

(2) Roll-coat the middle layer of water-based polyurethane slurry on the lower layer of water-based polyurethane coating, dry it at 80°C for 60 minutes and solidify to form a middle layer of water-based polyurethane coating with a thickness of 300 μm; wherein, in terms of parts by mass, the middle layer of water-based polyurethane slurry The material contains 100 parts of high 100% modulus water-based polyurethane resin (i.e. water-based polyurethane with high hard segment content), 10 parts of triethyl phosphate and 280 parts of water; the 100% modulus of high 100% modulus water-based polyurethane resin is 34MPa;

(3) Roll the upper water-based polyurethane slurry on the middle water-based polyurethane coating, dry it at 80°C for 60 minutes to solidify to form an upper water-based polyurethane coating with the same thickness as the lower water-based polyurethane coating, and then let it stand at 70°C. A water-based polyurethane composite coating with high ductility was obtained in 55 hours; in which, in terms of parts by mass, the upper water-based polyurethane slurry contained 100 parts of low 100% modulus water-based polyurethane resin, 18 parts of triethyl phosphate and 300 parts of water; low 100% modulus The 100% modulus of water-based polyurethane resin is 1.8MPa.

The tensile strength of the prepared water-based polyurethane composite coating with high ductility was 209N, and the elongation at break was 412%.

Claims (9)

1. A method for preparing a water-based polyurethane composite coating with high ductility, which is characterized by: first coating a lower layer of water-based polyurethane slurry on the surface of the target object, drying and solidifying to form a lower layer of water-based polyurethane coating, and then coating the lower layer of water-based polyurethane slurry on the surface of the target object. Apply the middle layer of water-based polyurethane slurry on the coating, dry and solidify to form the middle layer of water-based polyurethane coating, then apply the upper layer of water-based polyurethane slurry on the middle layer of water-based polyurethane coating, dry and solidify to form the upper layer of water-based polyurethane coating, and finally leave it alone Obtain a water-based polyurethane composite coating with high ductility; The middle layer water-based polyurethane slurry contains high 100% modulus water-based polyurethane resin, small molecule lubricant and water; The upper water-based polyurethane slurry contains low 100% modulus water-based polyurethane resin, small molecule lubricant and water; The lower layer of water-based polyurethane slurry contains low 100% modulus water-based polyurethane resin, small molecule lubricant and water; The 100% modulus of high 100% modulus water-based polyurethane resin is 34~40MPa, and the 100% modulus of low 100% modulus water-based polyurethane resin is 1~2MPa; The monomer units of high 100% modulus waterborne polyurethane resin are the same as those of low 100% modulus waterborne polyurethane resin; In the middle layer of water-based polyurethane slurry, 100 parts by mass of a 100% higher modulus water-based polyurethane resin should be added with 8 to 10 parts by mass of a small molecule lubricant; in the upper layer of water-based polyurethane slurry and in the lower layer of water-based polyurethane slurry, 100 parts by mass of a 100% lower modulus water-based polyurethane resin should be added. The modulus water-based polyurethane resin corresponds to the mass fraction of the small molecule lubricant added, which is at least 100 mass parts lower than the 100% modulus water-based polyurethane resin corresponding to the mass fraction of the small molecule lubricant added in the middle layer water-based polyurethane slurry. 1.5 times. 2. The preparation method of a highly ductile water-based polyurethane composite coating according to claim 1, characterized in that the thickness ratio of the upper water-based polyurethane coating to the middle water-based polyurethane coating is 10:90-17 :83; The thickness of the lower water-based polyurethane coating is the same as the thickness of the upper water-based polyurethane coating. 3. The preparation method of a highly ductile water-based polyurethane composite coating according to claim 2, characterized in that the thickness of the middle water-based polyurethane coating is 50-300 μm, and the thickness of the upper water-based polyurethane coating is 10 ~50μm. 4. The preparation method of a water-based polyurethane composite coating with high ductility according to claim 1, characterized in that, in parts by mass, the middle layer water-based polyurethane slurry contains 100 parts of high 100% modulus water-based polyurethane. resin, 8 to 10 parts of small molecule lubricant and 70 to 500 parts of water; in terms of parts by mass, the upper water-based polyurethane slurry contains 100 parts of low 100% modulus water-based polyurethane resin, 12 to 22 parts of small molecule lubricant and 70 parts of water. ~500 parts of water; in terms of parts by mass, the lower water-based polyurethane slurry contains 100 parts of low 100% modulus water-based polyurethane resin, 12-22 parts of small molecule lubricant and 70-500 parts of water. 5. The method for preparing a highly ductile water-based polyurethane composite coating according to claim 1, wherein the small molecule lubricant is triethyl phosphate. 6. The method for preparing a highly ductile water-based polyurethane composite coating according to claim 1, characterized in that the coating method is roller coating. 7. The preparation method of a highly ductile water-based polyurethane composite coating according to claim 1, characterized in that the standing temperature is 50-70°C and the standing time is more than 48 hours. 8. A method for preparing a highly ductile water-based polyurethane composite coating according to claim 1, characterized in that the target object is a microfiber base fabric, non-woven fabric, woven fabric or knitted fabric. 9. The application of a water-based polyurethane composite coating with high ductility prepared by the method of any one of claims 1 to 7, characterized in that: used to prepare ultrafine fiber PU synthetic leather, used for coating The target object is microfiber base cloth.