Title of the Invention

Water-based paint and antimicrobial leather prepared thereby

[Technical Field]

The present invention relates to a water-based paint and an antimicrobial leather prepared thereby. The water-based paint and the antimicrobial leather can be used in the automotive field.

[Background art]

Leather is widely used as a surface decoration material in various fields such as automotives and home decoration. Common leathers include genuine leathers, polar artificial leathers such as a polyvinyl chloride (referred to as PVC below) artificial leather, and a nonpolar artificial leather such as a thermoplastic polyolefin elastomer (TPO) artificial leather, etc., wherein the PVC artificial leather is an artificial leather prepared by polyvinyl chloride as a resin raw material, and the TPO artificial leather is an artificial leather prepared by a thermoplastic polyolefin as a resin raw material. Taking the automotive field as an example, leathers are widely used in door panels, dashboards, armrests, headrests and seats of automobiles. However, after a long period of use, a lot of microbes will appear on leathers, especially on headrests and seats, which seriously affects the health and safety of drivers. Therefore, the development of antimicrobial leathers has been a relatively important sector in the leather field. Particularly, since the global outbreak of the coronavirus (COVID-19) pandemic in 2020, people have paid more attention to antimicrobial leathers, but the leathers on the market cannot satisfy the requirement from people in view of antimicrobial performance.

Therefore, it is desired to provide a new technical solution to solve the technical problem mentioned above.

[Content of the invention]

The technical problem to be solved by the present invention is to provide a water-based paint and an antimicrobial leather prepared thereby, wherein the antimicrobial leather has better antimicrobial performance while ensuring the abrasion resistance and noise resistance. To solve the technical problem mentioned above, the present invention can be achieved by the technical solution as follows: a water-based paint for preparing leathers, comprising an organic polymer and an antimicrobial agent loaded on the organic polymer, wherein the antimicrobial agent is a metal and/or a metal ion and/or a metal oxide.

By a lot of experiments, the applicant has unexpectedly found that by loading an antimicrobial agent of a metal and/or a metal ion and/or a metal oxide, onto an organic polymer, the organic polymer can allow the antimicrobial agent to be uniformly dispersed in the water-based paint without flocculation and sedimentation, and can also ensure the slow release of the antimicrobial agent in the paint layer prepared by the water-based paint; which effectively improves the antimicrobial performance of leathers prepared by the water-based paint and, meanwhile, can also ensure the abrasion resistance and noise resistance of the leathers. The leathers may be genuine leathers, PVC artificial leathers, TPO artificial leathers, PU artificial leathers and the like.

In the present invention, the organic polymer as an organic carrier can be one, two or three of a polyurethane resin, an acrylic resin, and an epoxy resin. The particle size of the organic polymer is preferably 50-500 nm, and more preferably 440-500 nm. If the particle size of the organic polymer is too large, the organic polymer with a larger particle size has poor dispersibility itself and the antimicrobial agent tends to be wrapped by the molecular chain of an organic polymer with a larger particle size, thus reducing the antimicrobial performance; if the particle size of the organic polymer is too small, the strength of the water-based paint after film-formation will be decreased. The organic polymer in the present invention may be Permutex EVO-WF-3649/A or Permutex WF- 43-005, both of which are available from the Stahl Coatings and Fine Chemicals (Suzhou) Co., Ltd., Suzhou, China.

In the present invention, the antimicrobial agent is one, two or more of silver, silver ions, oxides of silver, zinc, zinc ions, oxides of zinc, copper, copper ions, oxides of copper, nickel, nickel ions, oxides of nickel, cobalt, cobalt ions, oxides of cobalt, lead, lead ions and oxides of lead. The antimicrobial agent is preferably silver and ions thereof, zinc and ions thereof, and copper and ions thereof, wherein the antimicrobial effect of silver and ions thereof is the best and the safest. When the antimicrobial agent is zinc ions, the water-based paint preferably comprises 0.3-10 %oo of the antimicrobial agent, based on the total weight of the water-based paint. When the antimicrobial agent is silver ions, the water-based paint comprises, based on the total weight of the water-based paint, 0.2- 3%oo of the antimicrobial agent, for example 0.2%oo, 0.3%oo, 0.4%oo, 0.5%oo, 0.6%oo,

0.7%oo, 0.8%oo, 0.9%oo, 1 %oo, 1.2%oo, 1.4%oo, 1.6%oo, 1.8%oo, 2%oo, 2.2%oo, 2.5%oo, 2.7%oo, 2.8%oo, and 3%oo, or the antimicrobial agent in a range between any two of these numerical values, preferably 0.3-2.5%oo of the antimicrobial agent, more preferably 0.3-2%oo of the antimicrobial agent.

In the present invention, loading refers to the antimicrobial agent being fixed on the organic polymer by a certain treatment process, making the antimicrobial agent difficult to separate from the organic polymer in the water-based paint, and an ordinary person skilled in the art can select conventional treatment processes for a treatment.

In the present invention, the organic polymer and the antimicrobial agent are prepared as an aqueous antimicrobial agent solution, and then the water-based paint is prepared; when the antimicrobial agent is silver ions, the aqueous antimicrobial agent solution comprises, based on the total weight of the aqueous antimicrobial agent solution, 0.1- 3% of the antimicrobial agent, 1-30% of an organic polymer, and 69-98.5% of water. Further, the water-based paint comprises, based on the total weight of the water-based paint, 50-98% of a water-based resin, 1-20% of the aqueous antimicrobial agent solution, 1-10% of a curing agent, and 0-25% of an auxiliary agent; more preferably, the water-based paint comprises 60-95% of the water-based resin, 2-10% of the aqueous antimicrobial agent solution, 1-10% of the curing agent and 0-25% of the auxiliary agent. In the present invention, the water-based resin refers to a mixture of a resin and water, and the water-based resin can be one, two or three of a water-based polyurethane resin, a water-based acrylic resin, and a water-based epoxy resin. The particle size of the water-based resin is preferably 50-900 nm. The solid content of the water-based resin is 10-60%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, and 60% or in a range between any two of these numerical values, and more preferably 15-

30%. A person skilled in the art would have known how to select suitable water-based resins according to the actual needs and application situations to prepare the water- based paint of the invention, and for example, the water-based resins suitable for the invention can be Permutex EVO-WF -3649/A or Permutex WF -43-005, both of which are available from the Stahl Coatings and Fine Chemicals (Suzhou) Co., Ltd., Suzhou, China.

In the present invention, the curing agent can be any suitable curing agents that are suitable for preparing water-based paints, and a person skilled in the art would have known how to choose, according to specific application situations and requirements, suitable curing agents, for example, polyisocyanate curing agents, polycarbodiimide curing agents, and oxazoline curing agents, and these curing agents can be used alone or in combination. For example, the curing agents that are suitable for the invention can be an Aquolin 166 isocyanate curing agent, which is available from Wanhua Chemical Group Co., Ltd, Yantai, China.

In the present invention, the auxiliary agent may be an antifoaming agent, a leveling agent, a thickener, a hand-feel agent, a stabilizer, etc., and a person skilled in the art would have known how to select the auxiliary agent to be added according to actual needs. The antifoaming agent can be any suitable antifoaming agents that are suitable for manufacturing water-based paints. A person skilled in the art would have known how to select a suitable antifoaming agent according to specific application situations and requirements. The antifoaming agents that are suitable for the invention can be an organosilicone antifoaming agent, a polyether antifoaming agent, and a mineral oil antifoaming agent, etc. For example, the antifoaming agents that are suitable for the present invention can be BYK093 which is available from German BYK Additives & Instruments and Tego Airex 902W which is available from German Evonik Industries AG.

The leveling agent can be any suitable leveling agents that are suitable for manufacturing water-based paints. A person skilled in the art would have known how to select a suitable leveling agent according to specific application situations and requirements. The leveling agents that are suitable for the invention may be selected from acrylic leveling agents, organosilicone leveling agents and fluorocarbon leveling agents. The organosilicone leveling agents can also be selected from, for example, silicone oil, polydimethylsiloxane, polyether polyester modified organosiloxane, alkyl modified organosiloxane, end group modified organosilicone, and reactive leveling agents, etc. For example, the leveling agents that are suitable for the invention can be BYK333 and BYK306, which are available from German BYK Additives & Instruments.

The thickener can be any suitable thickeners that are applicable for preparing water- based paints. A person skilled in the art would have known how to select a suitable thickener according to specific application situations and requirements. The thickener in the present invention can be a polyurethane thickener or a copolymer of methacrylic acid and acrylate. For example, the thickener that is suitable for the invention can be PUR 48, a water-based polyurethane thickener, which is commercially available from MUNZING, Germany. The hand-feel agent can be any suitable hand-feel agents that are applicable for preparing water-based paints. A person skilled in the art would have known how to select a suitable hand-feel agent according to specific application situations and requirements. For example, polysiloxane, and for example, a wax powder, with product no. 920, which is available from BYK Additives & Instruments.

The stabilizer is used to prevent oxidation and discoloration, and increase the ageing resistance of water-based paints. A person skilled in the art would have known how to select a suitable stabilizer according to specific application situations and requirements. The stabilizer in the invention can be selected from one, two or more of hindered amine stabilizers, hindered phenolic antioxidants, thioesters, phosphites, and thioethers.

To solve the technical problem mentioned above, in the present invention, the technical solution as follows can also be used: an antimicrobial leather comprising a paint layer, wherein the paint layer is prepared by the water-based paint described above. To solve the technical problem mentioned above, in the present invention the technical solution as follows can also be used: an antimicrobial leather comprising a surface layer and a paint layer, wherein the paint layer comprises an organic polymer and an antimicrobial agent loaded on the organic polymer, wherein the antimicrobial agent is a metal and/or a metal ion and/or a metal oxide.

In the present invention, the surface layer is a genuine leather, a PVC surface layer, a TPO surface layer, or a PU surface layer. In the present invention, the organic polymer as an organic carrier can be one, two or three of a polyurethane resin, an acrylic resin, and an epoxy resin. The particle size of the organic polymer is preferably 50-500 nm, and more preferably 440-500 nm. If the particle size of the organic polymer is too large, on the one hand, the organic polymer with a larger particle size has poor dispersibility itself, and on the other hand, the antimicrobial agent tends to be wrapped by the molecular chain of an organic polymer with a larger particle size, thus reducing the antimicrobial performance; if the particle size of the organic polymer is too small, the strength of the water-based paint after forming films will be decreased. In the present invention, the antimicrobial agent is one, two or more of silver, silver ions, oxides of silver, zinc, zinc ions, oxides of zinc, copper, copper ions, oxides of copper, nickel, nickel ions, oxides of nickel, cobalt, cobalt ions, oxides of cobalt, lead, lead ions and oxides of lead. The antimicrobial agent is preferably silver and ions thereof, zinc and ions thereof, and copper and ions thereof, wherein the antimicrobial effect of silver and ions thereof is the best and the safest.

In the present invention, loading refers to the antimicrobial agent being fixed on the organic polymer by a certain treatment process, making the antimicrobial agent difficult to separate from the organic polymer in the water-based paint, and an ordinary person skilled in the art can select conventional treatment processes for a treatment.

Compared with the prior art, the present invention has the following beneficial effects: it has been unexpectedly found that the present invention, by loading an antimicrobial agent of a metal and/or metal ions and/or metal oxides, onto an organic polymer and preparing an antimicrobial leather by a water-based paint comprising the antimicrobial agent and the organic polymer, can not only improve the antimicrobial performance of the antimicrobial leather, but also ensure the abrasion resistance and noise resistance of the antimicrobial leather. [Detailed Description of Embodiments] The present invention will be further illustrated below by examples and comparative examples. Example 1

The present example involves the preparation of a PVC artificial leather, the preparation method of the PVC artificial leather used in this example is a convention method in the art, and a person skilled in the art would have clearly known how to select specific apparatuses, process steps and conditions; therefore, the following description of the preparation process only involves the critical steps and conditions for one of the preparation methods.

Step I, material mixing The preparation of PVC dense layer slurry: 50 parts of a PVC powder, 45 parts of a phthalate plasticizer, 2 parts of a calcium and zinc composite stabilizer, 1 part of an aluminum hydroxide auxiliary agent, 1 part of a hindered amine light stabilizer, 1 part of a hindered phenolic antioxidant and 3 parts of a pigment are selected as raw materials, the raw materials are put into a mixing tank, followed by mechanical mixing, and vacuumizing until achieving uniform mixing, thus to obtain the PVC dense layer slurry. The preparation of PVC foaming layer slurry: 50 parts of a PVC powder, 2 parts of a foaming agent, 45 parts of a phthalate plasticizer, 2 parts of a calcium and zinc composite stabilizer, 1 part of an aluminum hydroxide auxiliary agent, 1 part of a hindered amine light stabilizer, 1 part of a hindered phenolic antioxidant and 1 part of a pigment are selected as raw materials, the raw materials are put into a mixing tank, followed by mechanical mixing, and vacuumizing until achieving uniform mixing, thus to obtain the PVC foaming layer slurry. The preparation of PVC glue layer slurry: 50 parts of a PVC powder, 45 parts of a phthalate plasticizer, 2 parts of a calcium and zinc composite stabilizer, 1 part of an aluminum hydroxide auxiliary agent, 1 part of a hindered amine light stabilizer and 1 part of a hindered phenolic antioxidant are selected as raw materials, the raw materials are put into a mixing tank, followed by mechanical mixing, and vacuumizing until achieving uniform mixing, thus to obtain the PVC glue layer slurry.

Step II, the preparation of PVC surface layer and combination with the base fabric

By an indirect coating method, the PVC dense layer slurry is coated onto a release paper and sent to a first-stage oven for plasticization and shaping. Then the plasticized and shaped PVC dense layer is coated with the PVC foaming layer, and sent into a second-stage oven for plasticization and shaping, so as to obtain the PVC surface layer.

The plasticized and shaped PVC foaming layer is roller-coated with the PVC glue layer slurry, then a polyester warp knitted fabric is combined therewith and is sent to a third- stage oven for final shaping, so as to obtain a PVC artificial leather coating material. After taking out of the oven, the PVC artificial leather coating material is separated from the release paper, and the two are rolled up individually. The rolled-up PVC artificial leather coating material is sent to a printing stage.

Step III, the preparation of the water-based polyurethane paint

According to the formulation of the water-based polyurethane paint of example 1 in table 1-1 , the raw materials of the water-based polyurethane paint are put into a paint bucket for mechanical mixing until uniformly mixed, so as to obtain the water-based polyurethane paint.

Step IV, printing After the rolled-up PVC artificial leather coating material in step II is unrolled, the water- based polyurethane paint prepared in step III is printed onto the PVC dense layer of the PVC artificial leather coating material. After 3 layers of the water-based polyurethane paint are printed by a printing machine, the same is sent to an oven for drying, then cooled and rolled up, so as to obtain a printed semi-finished product of the rolled-up PVC artificial leather. The printed semi-finished product of the PVC artificial leather is sent to an embossing stage.

Step V, embossing The above-mentioned rolled-up printed semi-finished product of the rolled-up PVC artificial leather is unrolled. The surface of the printed semi-finished product of the PVC artificial leather is softened by means of heating, and by using an embossing roller, the pattern on the surface of the embossing roller is imparted onto the side of the PVC dense layer of the printed semi-finished product of the PVC artificial leather by pressure. After cooling same, a PVC artificial leather with patterns on the surface is obtained.

Examples 2-9

Examples 2-9 are also the preparation of PVC artificial leathers. The preparation processes of PVC artificial leathers, the components and contents of the PVC dense layer, the components and contents of the PVC foaming layer and the components and contents of the PVC glue layer, and the selection of the basic fabric layer therein are all completely the same as example 1 , and the difference only lies in the formulation of the paint layer. See table 1-1, table 1-2 and table 1-3 for more details.

Comparative examples 1-8

Comparative examples 1-8 are also the preparation of PVC artificial leathers. The preparation processes of PVC artificial leathers, the components and contents of the PVC dense layer, the components and contents of the PVC foaming layer and the components and contents of the PVC glue layer, and the selection of the basic fabric layer therein are all completely the same as example 1 , and the difference only lies in the formulation of the paint layer. See table 1-1, table 1-2 and table 1-3 for more details. Table 1-1

Table 1-2

Note: The parts in table 1-1 , table 1-2 and table 1-3 are parts by weight, and the reference parts are all the same.

Performance tests

Noise resistance test

The surface noise resistance tests of the PVC artificial leathers prepared in examples 1- 9 and comparative examples 1-8 are performed according to the industry standard VDA230-206, and the test results are shown in table 2-1 , table 2-2, table 2-3 and table

2-4.

Abrasion resistance test The surface abrasion resistance tests of the PVC artificial leathers prepared in examples 1-9 and comparative examples 1-8 are performed, with a load of 1 ,000 grams and the number of tests of 1 ,000 times selected, according to the General Motor Standard

GMW3208, and the test results are shown in table 2-1, table 2-2, table 2-3 and table 2-4. Antimicrobial performance test

The antimicrobial performance test on the initial samples: The surface antimicrobial performance tests of the initial samples of PVC artificial leathers prepared in examples 1-9 and comparative examples 1-8 are performed according to the National Standard GB/T31402-2015, and the test results are shown in table 2-1 , table 2-2, table 2-3 and table 2-4. The antimicrobial performance test after heat aging: The initial samples are placed in an oven at 120°C for 21 days, and the surface antimicrobial performance tests after ageing of the PVC artificial leathers prepared in examples 1-9 and comparative examples 1-8 are performed according to the General Motor Standard GMW14122. The test results are shown in table 2-1 , table 2-2, table 2-3 and table 2-4.

The antimicrobial performance test after the Martindale abrasion resistance: The surface antimicrobial performance tests after abrasion of the PVC artificial leathers prepared in examples 1-9 and comparative examples 1-8 are performed, with the number of abrasions of 20,000 selected, according to the National Standard GB/T19089-2003, and the test results are shown in table 2-1 , table 2-2, table 2-3 and table 2-4. Light resistance test

The initial samples are placed in a test device and exposed to light for 5 cycles, and the light resistances of the PVC artificial leathers prepared in examples 1-9 and comparative examples 1-8 are performed according to the Volkswagen Standard PV1303. The test results are shown in table 2-1 , table 2-2, table 2-3 and table 2-4.

Amine resistance test The amine resistance tests of the PVC artificial leathers prepared in examples 1-9 and comparative examples 1-8 are performed according to the Volkswagen Standard PV3944, and the test results are shown in table 2-1 , table 2-2, table 2-3 and table 2-4.

Table 2-1

Table 2-2

Table 2-3

Table 2-4

It could be seen from the test results of example 2, example 4, example 5 and comparative example 7 that adding the antimicrobial agent of silver ions, zinc ions or zinc oxide into the water-based paint and loading the antimicrobial agent on the organic polymer polyurethane resin can significantly improve the antimicrobial performance of the PVC artificial leathers prepared thereby, and the noise resistance and abrasion resistance of the PVC artificial leathers also can reach the standards. Based on this, a person skilled in the art could reasonably learn that metals, metal ions and metal oxides can all be loaded onto the organic polymers to achieve similar technical effects.

It can be seen from the test results of example 2, example 4, example 5 and comparative example 8 that, compared with the antimicrobial agent loaded onto an inorganic carrier, by loading the antimicrobial agent onto an organic polymer, the surface of the PVC artificial leathers has significantly improved antimicrobial performance, noise resistance and abrasion resistance, and unexpected technical effects are achieved.

It can be seen from the test results of examples 1-3 and comparative examples 1 and 2 that, the content of silver ions in the water-based paint will affect all of the antimicrobial performance, the noise resistance and the abrasion resistance of the antimicrobial leathers prepared by the water-based paint. If the content of the silver ions is too small, for example, in comparative example 1 with a content of 0.08%o, the critera of the antimicrobial performance therein are all relatively poor; if the content of silver ions is too large, for example, in comparative example 2 with a content of 3.5%o, although some of the antimicrobial performance reaches the standards (for initial samples, > 99.9%; for samples after heat aging, > 99.9%), the antimicrobial performance of the samples after the noise resistance, the abrasion resistance and the Martindale abrasion resistance are all relatively poor. It can be seen from the test results of examples 1 -3 that when the content of silver ions is in a certain range, the change of the content of silver ions will not have an obvious influence on the antimicrobial performance, the light resistance and the amine resistance, but will have a relatively obvious influence on the noise resistance and the abrasion resistance. Among the three examples, the overall performance of example 1 is the best.

It can be seen from the test results of example 2, examples 6 and 7 and comparative examples 3 and 4 that the solid content of the main resin, the water-based polyurethane resin, in the water-based paint has a certain influence on the antimicrobial performance of the antimicrobial leathers prepared by the water-based paint. If the solid content of the main resin, the polyurethane resin, is too small, (for example, comparative example 3), the paint layer prepared by the water-based paint is relatively thin, and although the antimicrobial performance of the initial sample and the sample after heat ageing can reach the standard, the antimicrobial performance of the sample after Martindale abrasion resistance can not reach the standard; if the solid content of the main resin, the polyurethane resin, is too large, (for example, comparative example 4), the paint layer prepared by the water-based paint is relatively thick, and the antimicrobial performance of the antimicrobial leathers in various aspects cannot reach the standards.

It can be seen from the test results of example 2, examples 8 and 9 and comparative examples 5 and 6 that the particle size of the carrier, the water-based polyurethane resin, in the water-based paint has an influence on all of the antimicrobial performance, the noise resistance, and the abrasion resistance of the antimicrobial leathers prepared by the water-based paint. If the particle size of the carrier, the water-based polyurethane resin, is too small (for example, comparative example 5), the antimicrobial performance and abrasion resistance of the antimicrobial leathers in various aspects cannot reach the standards; if the particle size of the carrier, the water-based polyurethane resin, is too large (for example, comparative example 6), the antimicrobial performance of the antimicrobial leathers in various aspects cannot reach the standards. It can also be seen from the test results of example 2 and examples 8 and 9 that when the particle size of the carrier, the water-based polyurethane resin, is in a certain range, the particle size of the carrier polyurethane resin will not have an obvious influence on the antimicrobial performance, the light resistance and the amine resistance, but will have a more obvious influence on the noise resistance and the abrasion resistance. Among the three examples, the overall performance of example 9 is the best.

Examples 1-9 are all PVC artificial leathers. On this basis, a person skilled in the art could reasonably learn that the above-mentioned water-based polyurethane paint can also be applied to genuine leathers, TPO artificial leathers, PU leathers etc., to achieve similar technical effects.

It can be understood that in the absence of conflict, the abovementioned examples of the present invention may be combined with each other to obtain further examples. The various specific technical features described in the particular examples above may, in the absence of contradiction, be combined in any suitable manner.

The above examples are only preferred examples of the present invention rather than all examples. It can be understood that those of ordinary skill in the art can make many reasonable changes to the technical solutions of the present invention without departing from the essential spirit and scope of the present invention, and these reasonable changes are all within the protection scope of the present invention.