Extremely white high-yellowing-resistant PU synthetic leather and preparation method thereof

Abstract

This invention discloses an ultra-white, highly yellowing-resistant PU synthetic leather and its preparation method. The PU synthetic leather comprises a base fabric layer, an adhesive layer, a dense reflective foam layer, a surface layer, and a surface treatment layer, arranged sequentially. The foaming solution for preparing the dense reflective foam layer includes anionic waterborne polyurethane resin, foaming expansion powder, white waterborne coating, modified siloxane surfactant, and modified polycarbodiimide crosslinking agent. This invention incorporates a dense reflective foam layer between the surface layer and the adhesive layer. The "vacuum" created by foaming effectively prevents yellowing of other coatings from conducting to the PU surface, thus preventing the PU from yellowing. Simultaneously, this dense reflective foam layer also reflects the colored light from the surface resin, improving the reflectivity of the white PU and thus increasing its L-value.

Description

Technical Field

[0001] This invention belongs to the field of leather technology, specifically relating to an ultra-white, highly yellowing-resistant PU synthetic leather and its preparation method. Background Technology

[0002] In recent years, the domestic and international new energy vehicle markets have experienced rapid growth, giving rise to a wide variety of new models. The increasing youthfulness, comfort, and technological sophistication of these new models have brought both opportunities and challenges to automotive interior materials. Among these, ultra-white PU, due to its unique color and tendency to yellow, presents significant challenges for development in the automotive interior PU industry, and mature processes are still lacking both domestically and internationally. This invention aims to develop an ultra-white PU synthetic leather that is resistant to yellowing, to meet market demand and create economic value. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an ultra-white, high-yellowing-resistant PU synthetic leather and its preparation method. This invention incorporates a dense reflective foam layer between the surface layer and the adhesive layer. From the outside to the inside, the layers are a surface treatment layer, a surface layer, a dense reflective foam layer, an adhesive layer, and a base fabric layer.

[0004] The technical solution of this invention is as follows:

[0005] This invention relates to an ultra-white, high-yellowing-resistant PU synthetic leather, comprising a base fabric layer, an adhesive layer, a dense reflective foam layer, a surface layer, and a surface treatment layer arranged sequentially. The foaming solution for preparing the dense reflective foam layer comprises anionic waterborne polyurethane resin, foaming expansion powder, white waterborne coating, modified siloxane surfactant, and modified polycarbodiimide crosslinking agent.

[0006] Preferably, the raw material composition for preparing the foaming layer solution is as follows, by weight: 100±10 parts of anionic waterborne polyurethane resin, 10±5 parts of foaming expansion powder, 10±1 parts of white waterborne coating, 2±0.2 parts of modified siloxane surfactant, and 10±1 parts of modified polycarbodiimide crosslinking agent.

[0007] Preferably, the foaming powder is a thermoplastic polymer foaming agent, the foam film wall thickness is 2-15μm, and the foam particle size is 5-50μm.

[0008] Preferably, the drying temperature for preparing the dense reflective foam layer is 80℃±5℃.

[0009] The foaming liquid prepared by this invention will produce a large number of smooth-surfaced bubbles when dried at a temperature of 80℃±5℃, thereby improving the reflectivity of the dense foamed layer, thus increasing the white L value and the ability to resist yellowing.

[0010] Preferably, the adhesive layer solution used to prepare the adhesive layer includes isocyanate, flame retardant and solvent. The adhesive layer prepared by the present invention will also foam, in two cases: one is CO2 gas generated by the reaction of isocyanate and water, and the other is that the solvent of the adhesive layer does not evaporate and directly vaporizes, resulting in very few bubbles, which are of different sizes. The reaction principle is completely different, and the bubbles are irregular and cannot be effectively controlled. The generated bubbles also do not have a membrane wall.

[0011] Preferably, the surface layer solution used to prepare the surface layer comprises aliphatic polyurethane, a solvent, and a pigment.

[0012] Preferably, the surface treatment liquid used to prepare the surface treatment layer includes polyurethane, a hand-feeling agent, and a crosslinking agent, wherein the polyurethane is an aqueous solvent-free polyurethane; the hand-feeling agent is a modified siloxane hand-feeling agent; and the crosslinking agent is a carbodiimide crosslinking agent.

[0013] This invention also relates to a method for preparing ultra-white, highly yellowing-resistant PU synthetic leather, characterized by comprising the following steps:

[0014] Step 1, Surface layer preparation: Prepare the surface layer solution, apply the surface layer solution to the prepared release paper, and dry the surface layer to form the desired shape;

[0015] Step 2, Fabrication of dense reflective foam layer: Prepare foam layer solution, apply foam layer solution to the surface layer of Step 1, and dry the dense reflective foam layer to form the desired shape;

[0016] Step 3, Adhesive layer preparation: Prepare adhesive layer solution, apply adhesive layer solution to the dense reflective foam layer of Step 2, and dry the adhesive layer to form the desired shape;

[0017] Step 4, Base fabric layer bonding: Bond the base fabric layer to the adhesive layer on one side of the material obtained in Step 3 to form a composite leather blank with release paper;

[0018] Step 5, Peeling: Peel the composite leather blank with release paper obtained in Step 4 from the release paper mold to obtain the composite leather blank;

[0019] Step 6, Curing treatment: The composite leather blank obtained in step 5 is cured in an oven and then cooled to obtain a cured composite leather blank;

[0020] Step 7, Surface treatment: Prepare a surface treatment liquid and apply it to the surface layer of the cured composite leather blank obtained in Step 7, and then bake it to obtain the finished PU synthetic leather.

[0021] Preferably, in step 2, the stirring speed of the foaming layer solution is 600 rpm, the stirring time is 60 min to 65 min, and the viscosity of the foaming layer solution is 3000 cps to 5000 cps.

[0022] Preferably, in step 2, the speed of the foaming layer solution coating process is 9±1 m / min, and the coating amount (dry weight) is 37 g / m. 2 ~43g / m 2 .

[0023] Preferably, in step 2, the temperature for drying the dense reflective foam layer is 80±5℃ and the time is 5±0.5min.

[0024] Preferably, in step 1, the surface layer solution is coated onto the prepared release paper at a coating speed of 8±0.5 m / min and a coating amount (dry weight) of 40±3 g / m. 2 ;

[0025] In step 3, the next layer solution is coated onto the dense reflective foam layer from step 2. The coating speed is 8 ± 0.5 m / min, and the coating amount (dry weight) is 150 ± 15 g / m. 2 ;

[0026] In step 7, the surface treatment liquid is applied to the surface layer of the cured composite leather blank obtained in step 7. The coating speed is 8±0.5 m / min, and the coating amount (wet weight) is 40±3 g / m. 2 .

[0027] The beneficial effects of this invention are:

[0028] (1) The ultra-white high yellowing resistance PU synthetic leather prepared by the present invention contains a dense reflective foam layer, and the dense reflective foam layer is located between the surface layer and the adhesive layer. The dense reflective foam layer has dense foaming reflective ability. The "vacuum" formed by foaming can effectively prevent the yellowing of other coatings from being conducted to the PU surface and causing the PU to yellow. At the same time, the dense layer can also reflect the color light of the surface resin, improve the reflectivity of white PU, and achieve the purpose of improving the L value of white PU. The PU synthetic leather product prepared by the present invention has a target color L>97 and has a high yellowing resistance.

[0029] (2) The dense reflective foam layer and the surface layer of the present invention have a synergistic effect to improve the resistance to yellowing. The surface layer needs to use aliphatic polyurethane. If aromatic polyurethane is used, it is easy to cause PU yellowing. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0031] Figure 1 This is a structural diagram of the finished PU synthetic leather. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0033] The ultra-white, high-yellowing-resistant PU synthetic leather prepared in Examples 1-3 consists of a base fabric layer, an adhesive layer, a dense reflective foam layer, a surface layer, and a surface treatment layer arranged sequentially.

[0034] In the following examples and comparative examples, the coating weight mentioned only represents the wet weight in the surface treatment layer, and the coating weight for other coatings represents the dry weight.

[0035] Example 1

[0036] Step 1: Surface Layer Creation

[0037] Prepare the surface layer solution with the following formulation: 100 parts aliphatic polyurethane, 50 parts N,N-dimethylformamide, and 25 parts titanium dioxide pigment. Weigh and mix the above additives at 400 rpm for 30 minutes, achieving a viscosity of 2000-3000 cps. Then, coat the surface layer solution onto the prepared release paper with a coating weight (dry weight) of 40 g / m². 2 The surface layer is then dried and shaped.

[0038] Step 2: Fabrication of a dense reflective foam layer

[0039] (1) Prepare the raw materials according to the following weight proportions: 100 parts of anionic waterborne polyurethane resin, 10 parts of thermoplastic polymer foaming expansion powder, 10 parts of white waterborne coating, 2 parts of modified siloxane surfactant, and 10 parts of modified polycarbodiimide crosslinking agent.

[0040] (2) Mix the raw materials prepared in step (1) to prepare a dense reflective foam layer solution. The stirring speed of the dense reflective foam layer solution is 600 rpm, the stirring time is 60 min, and the solution viscosity is 4500 cps.

[0041] (3) The dense reflective foam layer solution is coated onto the surface layer prepared in step 1. The coating speed is 9.0 m / min, and the coating amount (dry weight) is 38 g / m. 2 ;

[0042] (4) Then, the surface layer is dried and shaped at a temperature of 80°C for 5.0 min.

[0043] Step 3: Continue layer creation

[0044] Prepare the adhesive layer solution with the following formula: 100 parts of two-component isocyanate, 60 parts of phosphorus-based flame retardant, and 20 parts of N,N-dimethylformamide. Mix and stir the above raw materials at 400 rpm for 30 minutes until the viscosity reaches 6000-10000 cps. Then, coat the adhesive layer solution onto the dense reflective foam layer from step 2 with a coating weight (dry weight) of 200 g / m². 2 The adhesive layer is then dried and molded.

[0045] Step 4: Bonding and bonding of the base fabric layer

[0046] The base fabric layer is bonded together with the material obtained in step 3 to form a composite leather blank with release paper. The composite leather blank includes a base fabric layer, an adhesive layer, a dense reflective foam layer and a surface layer arranged in sequence. The base fabric layer is a warp-knitted polyester lining with a thickness of 0.9±0.1mm.

[0047] Step 5: Peeling

[0048] Peel the composite leather blank with release paper obtained in step 4 off the release paper to obtain the composite leather blank.

[0049] Step 6: Aging process

[0050] The composite leather blank obtained in step 5 is baked in an oven for maturation, and then cooled to obtain a matured composite leather blank.

[0051] Step 7: Surface treatment

[0052] Prepare the surface treatment liquid with the following formula: 100 parts waterborne polyurethane resin, 10 parts modified siloxane hand feel agent, and 10 parts carbodiimide crosslinking agent. Mix the above solvents and stir at 400 rpm for 30 minutes until the viscosity reaches 500-1000 cps. Apply the surface treatment liquid to the cured composite leather blank from step 6. Coating amount (wet weight): 38 g / m³. 2 (Wet weight) is then baked to obtain the finished PU synthetic leather.

[0053] Example 2

[0054] Compared with Example 1, the only difference in this example is step 2.

[0055] Step 2: Fabrication of a dense reflective foam layer

[0056] (1) Prepare the raw materials according to the following weight proportions: 100 parts of anionic waterborne polyurethane resin, 10 parts of thermoplastic polymer foaming expansion powder, 10 parts of white waterborne coating, 2 parts of modified siloxane surfactant, and 10 parts of modified polycarbodiimide crosslinking agent.

[0057] (2) Mix the raw materials prepared in step (1) to prepare a dense reflective foam layer solution. The stirring speed of the dense reflective foam layer solution is 600 rpm, the stirring time is 60 min, and the solution viscosity is 4500 cps.

[0058] (3) The dense reflective foaming layer solution is coated onto the surface layer at a speed of 9.0 m / min and a coating amount of 42 g / m. 2 ;

[0059] (4) Then, the surface layer is dried and shaped at a temperature of 80°C for 5.0 min.

[0060] Example 3

[0061] Compared with Example 1, the only difference in this example is step 2.

[0062] Step 2: Fabrication of a dense reflective foam layer

[0063] (1) Prepare the raw materials according to the following weight proportions: 100 parts of anionic waterborne polyurethane resin, 15 parts of thermoplastic polymer foaming expansion powder, 10 parts of white waterborne coating, 2 parts of modified siloxane surfactant, and 10 parts of modified polycarbodiimide crosslinking agent.

[0064] (2) Mix the raw materials prepared in step (1) to prepare a dense reflective foam layer solution. The stirring speed of the dense reflective foam layer solution is 600 rpm, the stirring time is 60 min, and the solution viscosity is 4500 cps.

[0065] (3) The dense reflective foaming layer solution is coated onto the surface layer at a speed of 9.0 m / min and a coating amount of 38 g / m. 2 ;

[0066] (4) Then, the surface layer is dried and shaped at a temperature of 80°C for 5.0 min.

[0067] Comparative Example 1

[0068] Compared with Example 1, this comparative example does not include step 2, the fabrication of the dense reflective foam layer. First, the surface layer is prepared according to step 1 of Example 1. Then, the adhesive layer solution is prepared according to step 3 of Example 1. The adhesive layer solution is then coated onto the surface layer, and the adhesive layer is dried and shaped. The remaining preparation conditions are the same as in Example 1.

[0069] Comparative Example 2

[0070] Compared with Example 1, the only difference in this comparative example is step 2.

[0071] Step 2: Fabrication of a dense reflective foam layer

[0072] (1) Prepare the raw materials according to the following weight proportions: 100 parts of anionic waterborne polyurethane resin, 3 parts of foaming expansion powder, 10 parts of white waterborne coating, 2 parts of modified siloxane surfactant, and 1 part of modified polycarbodiimide crosslinking agent.

[0073] (2) Mix the raw materials prepared in step (1) to prepare a dense reflective foam layer solution. The stirring speed of the dense reflective foam layer solution is 600 rpm, the stirring time is 60 min, and the solution viscosity is 4500 cps.

[0074] (3) The dense reflective foaming layer solution is coated onto the surface layer at a speed of 9.0 m / min and a coating amount of 30 g / m. 2 ;

[0075] (4) Then, the surface layer is dried and shaped at a temperature of 80°C for 5.0 min.

[0076] Comparative Example 3

[0077] In Examples 1-3, the polyurethane used to prepare the surface layer solution was aliphatic polyurethane. The only difference between this comparative example and the corresponding examples is that the aliphatic polyurethane used in step 1 for surface layer preparation is replaced with aromatic polyurethane. All other conditions are the same.

[0078] The performance of Comparative Examples 1 and 2 was compared with that of the PU synthetic leather prepared in Examples 1-3 above, and the results are listed in Table 1.

[0079] Table 1. Performance comparison of the examples and comparative examples.

[0080]

[0081] Example 1 and Example 2 have the same ingredient ratio, but the amount of dense reflective foam layer coating is different. Example 2 has a thicker coating, more foam, and better effect.

[0082] The foaming agent dosage differs in the formulations of Examples 1 and 3. Example 3 uses a larger amount of foaming agent, resulting in more foam and better performance. Comparative Example 2 uses a smaller amount of foaming agent, only 3 parts by weight, and the coating is thinner, failing to meet the requirements for L value and yellowing resistance (NG).

[0083] Comparing Examples 2 and 3 with Comparative Example 3, Comparative Example 3, with a larger coating amount of dense reflective foam layer and a greater amount of foaming agent, changed the surface layer resin type from aliphatic to aromatic. The comparison shows that because aromatic resins exhibit yellowing, and the coating is above the dense reflective foam layer, it leads to severe yellowing of the PU and a low L value. Therefore, the dense reflective foam layer and the surface layer of this invention have a synergistic effect, improving yellowing resistance. The surface layer needs to use aliphatic polyurethane; if aromatic polyurethane is used, it easily leads to PU yellowing.

[0084] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A type of ultra-white, highly resistant to yellowing PU synthetic leather, characterized in that, The material comprises a base fabric layer, an adhesive layer, a dense reflective foam layer, a surface layer, and a surface treatment layer arranged sequentially. The foaming solution for preparing the dense reflective foam layer comprises anionic waterborne polyurethane resin, foaming expansion powder, white waterborne coating, modified siloxane surfactant, and modified polycarbodiimide crosslinking agent. The foaming expansion powder is a thermoplastic polymer foaming agent. The raw materials for preparing the foaming layer solution, by weight, are as follows: 100±10 parts anionic waterborne polyurethane resin, 10±5 parts foaming expansion powder, 10±1 parts white waterborne coating, 2±0.2 parts modified siloxane surfactant, and 10±1 parts modified polycarbodiimide crosslinking agent. The coating weight of the foaming layer solution is 37 g / m³ (dry weight). 2 ~43g / m 2 ; The drying temperature for preparing the dense reflective foamed layer is 80℃±5℃; The surface layer solution used to prepare the surface layer includes aliphatic polyurethane, solvent, and pigment.

2. The ultra-white, high-yellowing-resistant PU synthetic leather according to claim 1, characterized in that, The foaming film of thermoplastic polymer foaming agent has a wall thickness of 2-15μm and a foaming particle size of 5-50μm.

3. The ultra-white, high-yellowing-resistant PU synthetic leather according to claim 1, characterized in that, The adhesive layer solution used to prepare the adhesive layer includes isocyanate, flame retardant and solvent; The surface treatment liquid used to prepare the surface treatment layer includes polyurethane, a hand-feeling agent, and a crosslinking agent.

4. A method for preparing ultra-white, highly yellowing-resistant PU synthetic leather according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1, Surface layer preparation: Prepare the surface layer solution, apply the surface layer solution to the prepared release paper, and dry the surface layer to form the desired shape; Step 2, Fabrication of dense reflective foam layer: Prepare foam layer solution, apply foam layer solution to the surface layer of Step 1, and dry the dense reflective foam layer to form the desired shape; Step 3, Adhesive layer preparation: Prepare adhesive layer solution, apply adhesive layer solution to the dense reflective foam layer of Step 2, and dry the adhesive layer to form the desired shape; Step 4, Base fabric layer bonding: Bond the base fabric layer to the adhesive layer on one side of the material obtained in Step 3 to form a composite leather blank with release paper; Step 5, Peeling: Peel the composite leather blank with release paper obtained in Step 4 from the release paper mold to obtain the composite leather blank; Step 6, Curing treatment: The composite leather blank obtained in step 5 is cured in an oven and then cooled to obtain a cured composite leather blank; Step 7, Surface treatment: Prepare a surface treatment liquid and apply it to the surface layer of the cured composite leather blank obtained in step 6, and then bake it to obtain the finished PU synthetic leather.

5. The preparation method according to claim 4, characterized in that, In step 2, the stirring speed of the foaming layer solution is 600 rpm, the stirring time is 60 min to 65 min, and the viscosity of the foaming layer solution is 3000 cps to 5000 cps.

6. The preparation method according to claim 4, characterized in that, In step 2, the foaming layer solution coating speed is 9±1 m / min, and the coating dry weight is 37 g / m. 2 ~43g / m 2 .

7. The preparation method according to claim 4, characterized in that, In step 2, the temperature for drying the dense reflective foam layer is 80±5℃ and the time is 5±0.5min.

8. The preparation method according to claim 4, characterized in that, In step 1, the surface layer solution is coated onto the prepared release paper at a coating speed of 8±0.5 m / min, and the dry weight of the coating is 40±3 g / m. 2 ; In step 3, the next layer solution is coated onto the dense reflective foam layer from step 2. The coating speed is 8 ± 0.5 m / min, and the dry weight of the coating is 150 ± 15 g / m. 2 ; In step 7, the surface treatment liquid is applied to the surface layer of the cured composite leather blank obtained in step 6. The coating speed is 8±0.5 m / min, and the wet weight of the coating is 40±3 g / m. 2 .

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