Extremely-white high-yellowing-resistance PU (polyurethane) synthetic leather and preparation method thereof

Abstract

The invention discloses extremely-white high-yellowing-resistance PU synthetic leather and a preparation method thereof.The PU synthetic leather comprises a base cloth layer, a bonding layer, a compact reflection foaming layer, a surface layer and a surface treatment layer which are sequentially arranged, a foaming layer solution for preparing the compact reflective foaming layer comprises anionic waterborne polyurethane resin, foaming expansion powder, white water-based paint, a modified siloxane surfactant and a modified polycarbodiimide cross-linking agent. According to the invention, the compact reflective foaming layer is arranged between the surface layer and the bonding layer, so that other coatings can be effectively prevented from yellowing to conduct the PU surface through vacuum formed by foaming, and the PU is prevented from yellowing; and meanwhile, the dense reflection foaming layer can also reflect color light rays of the surface resin, so that the reflection capability of the white PU is improved, and the purpose of improving the L value of the white PU is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of leather, and particularly relates to extremely white and highly yellowing-resistant PU synthetic leather and a preparation method thereof. Background Art

[0002] In recent years, the domestic and foreign new energy vehicle markets have developed rapidly, and many diversified new models have emerged; the new models are younger, more comfortable, and more technological, bringing more opportunities and challenges to automotive interior materials. Among them, due to its special color and easy yellowing characteristics, the ultra-white PU is extremely difficult to develop in the automotive interior PU industry. There is no mature process at home and abroad. The present invention aims to develop an ultra-white and yellowing-resistant PU synthetic leather to meet market demand and create economic value. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention provides an extremely white and highly yellowing-resistant PU synthetic leather and a preparation method thereof. The present invention adds a dense reflective foaming layer between the surface layer and the adhesive layer, which are respectively a surface treatment layer, a surface layer, a dense reflective foaming layer, an adhesive layer, and a base fabric layer from the outside to the inside.

[0004] The technical solution of the present invention is:

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

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

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

[0008] Preferably, the drying temperature for preparing the dense reflective foamed layer is 80°C±5°C.

[0009] The foaming liquid prepared by the present invention will generate a large number of bubbles with smooth surfaces under a drying environment at a temperature of 80°C±5°C, thereby improving the reflectivity of the dense foaming layer, thereby improving the white L value and increasing the yellowing resistance of the white.

[0010] Preferably, the bonding layer solution used to prepare the bonding layer includes isocyanate, a flame retardant and a solvent. The bonding layer prepared by the present invention will also foam. There are two situations: one is the CO2 gas generated by the reaction of isocyanate and water, and the other is that the solvent of the bonding layer does not volatilize but directly vaporizes, resulting in very few bubbles of different sizes. The reaction principle is completely different, and the bubbles are irregular and cannot be effectively controlled, and the generated bubbles have no membrane wall.

[0011] Preferably, the surface layer solution for preparing the surface layer comprises aliphatic polyurethane, a solvent and a pigment.

[0012] Preferably, the surface treatment layer liquid for preparing the surface treatment layer comprises polyurethane, a feel agent and a crosslinking agent, wherein the polyurethane is a water-based solvent-free polyurethane; the feel agent is a modified siloxane feel agent; and the crosslinking agent is a carbodiimide crosslinking agent.

[0013] The present invention also relates to a method for preparing extremely white and highly yellowing-resistant PU synthetic leather, which is characterized by comprising the following steps:

[0014] Step 1, surface layer preparation: prepare a surface layer solution, apply the surface layer solution on the prepared release paper, and dry the surface layer to form;

[0015] Step 2, making a dense reflective foaming layer: preparing a foaming layer solution, applying the foaming layer solution on the surface layer of step 1, and drying the dense reflective foaming layer to form;

[0016] Step 3, making an adhesive layer: preparing an adhesive layer solution, applying the adhesive layer solution on the dense reflective foaming layer of step 2, and drying the adhesive layer to form;

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

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

[0019] Step 6, aging treatment: aging the composite leather stock obtained in step 5 in an oven and cooling it to obtain an aged composite leather stock;

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

[0021] Preferably, in step 2, the stirring speed for preparing 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 foaming layer solution coating process speed is 9±1m / min, and the coating amount (dry weight) is 37g / m 2 ~43g / m 2 .

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

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

[0025] In step 3, the next layer solution is coated on the dense reflective foaming layer of step 2, and the coating process speed is 8±0.5m / min, and the coating amount (dry weight) is 150±15g / m 2 ;

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

[0027] The beneficial effects of the present invention are:

[0028] (1) The ultra-white and highly yellowing-resistant PU synthetic leather prepared by the present invention comprises a dense reflective foaming layer, and the dense reflective foaming layer is located between the surface layer and the adhesive layer. The dense reflective foaming layer has dense foaming reflective ability, and the "vacuum" formed by foaming can effectively prevent other coatings from yellowing and transmitting to the PU surface to cause the PU to turn yellow; at the same time, the dense layer can also reflect the color light of the surface resin, thereby improving the reflective ability of the white PU and achieving the purpose of improving the L value of the white PU. The color target L of the PU synthetic leather product prepared by the present invention is greater than 97, and has a high yellowing resistance.

[0029] (2) The dense reflective foam layer of the present invention has a synergistic effect with the surface layer to improve the yellowing resistance. The surface layer needs to use aliphatic polyurethane. If aromatic polyurethane is used, it is easy to cause PU yellowing. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0031] Figure 1 Schematic diagram of the structure of finished PU synthetic leather. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0033] The extremely white and highly yellowing-resistant PU synthetic leather prepared in Examples 1-3 consists of a base fabric layer, an adhesive layer, a dense reflective foaming layer, a surface layer and a surface treatment layer which are arranged in sequence.

[0034] The coating amounts mentioned in the following examples and comparative examples represent wet weight only in the preparation of the surface treatment layer, and all other coatings represent dry weight.

[0035] Example 1

[0036] Step 1: Surface layer preparation

[0037] Prepare the surface layer solution, surface formula: 100 parts of aliphatic polyurethane, 50 parts of N,N-dimethylformamide, 25 parts of titanium dioxide pigment, weigh and mix the above additives, speed 400rpm, time 30min, viscosity 2000-3000cps; then apply the surface layer solution on the prepared release paper, coating amount (dry weight) 40g / m 2 And dry the surface layer into shape.

[0038] Step 2: Preparation of dense reflective foam layer

[0039] (1) Prepare the following raw materials in parts by weight: 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) mixing the raw materials prepared in step (1) to prepare a dense reflective foaming layer solution, wherein the stirring speed for preparing the dense reflective foaming layer solution is 600 rpm, the stirring time is 60 min, and the solution viscosity is 4500 cps;

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

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

[0043] Step 3: Next layer production

[0044] Prepare the adhesive layer solution, the formula is as follows: 100 parts of two-component isocyanate, 60 parts of phosphorus flame retardant, 20 parts of N,N-dimethylformamide, mix the above raw materials, the speed is 400rpm, the time is 30min, the viscosity is 6000-10000cps; then apply the adhesive layer solution on the dense reflective foaming layer of step 2, the coating amount (dry weight) is 200g / m 2 And the next layer is dried and formed.

[0045] Step 4: Bonding the base fabric layer

[0046] The base fabric layer is bonded and laminated with the material obtained in step 3 to form a composite leather blank with release paper. The composite leather blank comprises a base fabric layer, a bonding layer, a dense reflective foaming layer and a surface layer in sequence, wherein the base fabric layer is a warp-knitted original silk polyester lining with a thickness of 0.9±0.1mm.

[0047] Step 5 Peel

[0048] The composite leather stock with the release paper obtained in step 4 is peeled off from the release paper to obtain the composite leather stock.

[0049] Step 6: Aging

[0050] The composite leather stock obtained in step 5 is baked in an oven for ripening, and then cooled after ripening to obtain a ripened composite leather stock.

[0051] Step 7: Surface treatment

[0052] Prepare the surface treatment layer liquid, the formula is as follows: 100 parts of waterborne polyurethane resin, 10 parts of modified siloxane hand feeling agent, 10 parts of carbodiimide crosslinking agent, mix the above solvents, speed 400rpm, time: 30min, viscosity 500-1000cps and apply the surface treatment layer liquid on the aged composite leather blank in step 6, coating amount (wet weight): 38g / m 2 (wet weight) and then baked to obtain finished PU synthetic leather.

[0053] Example 2

[0054] Compared with Embodiment 1, the difference of this embodiment is only in step 2.

[0055] Step 2: Preparation of dense reflective foam layer

[0056] (1) Prepare the following raw materials in parts by weight: 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) mixing the raw materials prepared in step (1) to prepare a dense reflective foaming layer solution, wherein the stirring speed for preparing the dense reflective foaming 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 on the surface layer. The surface layer solution coating process speed is 9.0 m / min and the coating amount is 42 g / m 2 ;

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

[0060] Example 3

[0061] Compared with Embodiment 1, the difference of this embodiment is only in step 2.

[0062] Step 2: Preparation of dense reflective foam layer

[0063] (1) Prepare the following raw materials in parts by weight: 100 parts of anionic waterborne polyurethane resin, 15 parts of thermoplastic polymer polymerization 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) mixing the raw materials prepared in step (1) to prepare a dense reflective foaming layer solution, wherein the stirring speed for preparing the dense reflective foaming 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 on the surface layer. The surface layer solution coating process speed is 9.0 m / min, and the coating amount is 38 g / m 2 ;

[0066] (4) Then the surface layer is dried and formed 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 of preparing the dense reflective foaming layer. The surface layer is first prepared according to step 1 of Example 1, and then the bonding layer solution is prepared according to step 3 of Example 1. The bonding layer solution is then coated on the surface layer, and the bonding layer is dried and formed. The remaining preparation conditions are the same as those in Example 1.

[0069] Comparative Example 2

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

[0071] Step 2: Preparation of dense reflective foam layer

[0072] (1) Prepare the following raw materials in parts by weight: 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) mixing the raw materials prepared in step (1) to prepare a dense reflective foaming layer solution, wherein the stirring speed for preparing the dense reflective foaming 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 on the surface layer. The surface layer solution coating process speed is 9.0 m / min and the coating amount is 30 g / m 2 ;

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

[0076] Comparative Example 3

[0077] The polyurethane used in preparing the surface layer solution in Examples 1-3 is aliphatic polyurethane, and the difference between this comparative example and the corresponding example is that the aliphatic polyurethane used in preparing the surface layer in step 1 is replaced by aromatic polyurethane. Other conditions are the same.

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

[0079] Table 1 Performance comparison between examples and comparative examples

[0080]

[0081] The proportions of ingredients in embodiments 1 and 2 are the same, except that the coating amount of the dense reflective foaming layer is different. The coating of embodiment 2 is thicker, has more foaming, and has a better effect.

[0082] The amount of foaming agent used in the formula of Examples 1 and 3 is different. The amount of foaming agent used in Example 3 is larger, the foaming is more, and the effect is good. The amount of foaming agent used in Comparative Example 2 is less, only 3 parts by weight, and the coating is also thinner, and the L value and yellowing resistance are NG and do not meet the requirements.

[0083] Comparison between Examples 2 and 3 and Comparative Example 3 shows that in Comparative Example 3, when the dense reflective foam layer is coated in a large amount and a large amount of foaming agent is used, the surface layer resin type is changed from aliphatic to aromatic. The comparison shows that, because the aromatic resin is yellowing, and the coating is above the dense reflective foam layer, the PU will be severely yellowed and the L value will be low. Therefore, the dense reflective foam layer of the present invention has a synergistic effect with the surface layer to improve the yellowing resistance. The surface layer needs to use aliphatic polyurethane. If aromatic polyurethane is used, it is easy to cause PU yellowing.

[0084] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. An extremely white and highly yellowing-resistant PU synthetic leather, characterized in that: The invention comprises a base fabric layer, an adhesive layer, a dense reflective foam layer, a surface layer and a surface treatment layer which are arranged in sequence, wherein the foam layer solution for preparing the dense reflective foam layer comprises an anionic waterborne polyurethane resin, foaming expansion powder, a white waterborne coating, a modified siloxane surfactant and a modified polycarbodiimide crosslinking agent.

2. The ultra-white high yellowing resistance PU synthetic leather according to claim 1, characterized in that: In parts by weight, the raw material composition for preparing the foaming layer solution is as follows: 100±10 parts of anionic water-based polyurethane resin, 10±5 parts of foaming expansion powder, 10±1 parts of white water-based coating, 2±0.2 parts of modified siloxane surfactant, and 10±1 parts of modified polycarbodiimide crosslinking agent.

3. The ultra-white high yellowing resistance PU synthetic leather according to claim 2, characterized in that: The foaming expansion powder is a thermoplastic polymer foaming agent, the foaming film wall thickness is 2-15 μm, and the foaming particle size is 5-50 μm.

4. The ultra-white high yellowing resistance PU synthetic leather according to claim 1 or 2, characterized in that: The drying temperature for preparing the dense reflective foam layer is 80°C ± 5°C.

5. The ultra-white high yellowing resistance PU synthetic leather according to claim 1, characterized in that: The surface layer solution for preparing the surface layer includes aliphatic polyurethane, a solvent and a pigment.

6. A method for preparing the ultra-white and highly yellowing-resistant PU synthetic leather according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1, surface layer preparation: prepare a surface layer solution, apply the surface layer solution on the prepared release paper, and dry the surface layer to form; Step 2, making a dense reflective foaming layer: preparing a foaming layer solution, applying the foaming layer solution on the surface layer of step 1, and drying the dense reflective foaming layer to form; Step 3, making an adhesive layer: preparing an adhesive layer solution, applying the adhesive layer solution on the dense reflective foaming layer of step 2, and drying the adhesive layer to form; Step 4, bonding and laminating the base fabric layer: bonding and laminating the base fabric layer and the adhesive layer on one side of the material obtained in step 3 together to form a composite leather blank with release paper; Step 5, peeling: peeling the composite leather blank with the release paper obtained in step 4 from the release paper mold to obtain the composite leather blank; Step 6, aging treatment: aging the composite leather stock obtained in step 5 in an oven and cooling it to obtain an aged composite leather stock; Step 7, surface layer treatment: prepare a surface treatment layer liquid, and apply the surface treatment layer liquid to the surface layer of the matured composite leather blank obtained in step 7, and then bake to obtain a finished PU synthetic leather.

7. The preparation method according to claim 6, characterized in that: In step 2, the stirring speed of preparing 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.

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

9. The preparation method according to claim 6, characterized in that: In step 2, the temperature for drying and molding the dense reflective foam layer is 80±5° C. and the time is 5±0.5 min.

10. The preparation method according to claim 6, characterized in that: In step 1, the surface layer solution is coated on the prepared release paper, and the coating process speed is 8±0.5m / min, and the coating amount (dry weight) is 40±3g / m 2 ; In step 3, the next layer solution is coated on the dense reflective foaming layer of step 2, and the coating process speed is 8±0.5m / min, and the coating amount (dry weight) is 150±15g / m 2 ; In step 7, the surface treatment layer liquid is coated on the surface layer of the aged composite leather blank obtained in step 7, and the coating speed is 8±0.5m / min, and the coating amount (wet weight) is 40±3g / m 2 .

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