Waterborne polyurethane emulsion and synthetic leather pressure change base

Abstract

The invention discloses a waterborne polyurethane emulsion, which is prepared from the following raw materials: a closed polyurethane prepolymer, gallic acid, acetic acid and water, wherein the blocked polyurethane prepolymer is prepared by reacting a sealing agent with an-NCO group in the polyurethane prepolymer; the closed polyurethane prepolymer contains a hydrophilic chain extender, and the hydrophilic chain extender is N-methyldiethanolamine; the ratio of the total mole number of gallic acid and acetic acid to the mole number of N-methyldiethanolamine is 1: (1-1.02); the molar ratio of gallic acid to acetic acid is 1: (1-3). The invention further discloses a preparation method and application of the waterborne polyurethane emulsion. The invention further discloses the synthetic leather water-based slurry. The invention also discloses a synthetic leather pressure change base and a preparation method thereof. The synthetic leather pressure change base prepared from the synthetic leather water-based slurry has good hand feeling, air permeability and color fixing performance, and is good in adhesion performance and excellent in knurling color changing performance.

Description

Technical Field

[0001] The invention relates to the field of synthetic leather, in particular to an aqueous polyurethane emulsion and a synthetic leather compression base. Background Art

[0002] Synthetic leather compression base has air permeability, moisture permeability and excellent mechanical strength. Traditional synthetic leather compression base mainly adopts wet process, and the specific steps are: add solvent-based polyurethane resin to organic solvent (such as DMF), add other additives to make mixed emulsion, then impregnate or coat it on the base fabric, and then put it into water. Taking advantage of the fact that the organic solvent is more soluble in water than in polyurethane slurry, more organic solvent is soluble in water or more organic solvent is replaced by water, thereby achieving solvent replacement, and forming bubbles in the coating during the replacement process, and then washing and drying to obtain synthetic leather compression base.

[0003] However, the wet process requires the use of organic solvents, which not only pollutes the environment but also endangers the health of production workers. In addition, a large amount of water is required for solvent replacement during the preparation process. During the replacement process, the size of the bubbles cannot be controlled, resulting in different bubble sizes, which affects the performance of the synthetic leather base. In addition, the color of the base is easily discolored during the water replacement process, making it uncontrollable and the color of each batch cannot be kept uniform and stable.

[0004] Waterborne polyurethane resin can meet international environmental standards, but it is rarely used in the production of synthetic leather compression bass. When waterborne polyurethane resin is used in the production of synthetic leather compression bass, there are often problems such as easy discoloration of the leather and easy collapse of the bubbles during the drying process. In addition, the polyurethane will migrate to the surrounding area with the water during the drying process, making it easy for holes to appear in the middle of the leather, affecting the feel and breathability of the synthetic leather, and the waterborne polyurethane has insufficient adhesion to the base fabric. Summary of the invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes an aqueous polyurethane emulsion and a synthetic leather pressed base. The synthetic leather pressed base made from the synthetic leather aqueous slurry of the present invention has good hand feel, air permeability, color fixing performance, good adhesion performance, and excellent embossed color change performance.

[0006] The present invention provides an aqueous polyurethane emulsion, the raw materials of which include: a blocked polyurethane prepolymer, gallic acid, acetic acid and water;

[0007] Among them, the blocked polyurethane prepolymer is prepared by reacting a blocking agent with the -NCO group in the polyurethane prepolymer;

[0008] The closed polyurethane prepolymer contains a hydrophilic chain extender, which is N-methyldiethanolamine;

[0009] The ratio of the total moles of gallic acid and acetic acid to the moles of N-methyldiethanolamine is 1:1-1.02;

[0010] The molar ratio of gallic acid to acetic acid is 1:1-3.

[0011] Preferably, in the blocked polyurethane prepolymer, the weight ratio of diisocyanate to N-methyldiethanolamine is 5-7:0.6-0.8.

[0012] Preferably, the blocking agent is acetone oxime.

[0013] Preferably, the number of -NCO groups in the blocked polyurethane prepolymer is 0.

[0014] Preferably, the solid content of the waterborne polyurethane is 35-65 wt %.

[0015] The raw materials of the closed polyurethane prepolymer include: diisocyanate, polyol compound, small molecule chain extender, N-methyldiethanolamine, catalyst and blocking agent.

[0016] The amount of each raw material in the blocked polyurethane prepolymer is not limited, as long as the blocked polyurethane prepolymer can be obtained; more appropriate amounts of each raw material may also be selected.

[0017] The raw materials of the blocked polyurethane prepolymer include, by weight percentage: 5-7 parts of diisocyanate, 13-18 parts of polyol compound, 0.14-0.19 parts of small molecule chain extender, 0.6-0.8 parts of N-methyldiethanolamine, and 0.65-0.9 parts of blocking agent.

[0018] The diisocyanate may be 4,4-diphenylmethane diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, or the like.

[0019] The polyol compound may be polyether polyol, polyester polyol or the like.

[0020] The small molecule chain extender may be 1,4-butanediol, 1,2-propylene glycol, or the like.

[0021] The preparation method of the above-mentioned blocked polyurethane prepolymer comprises the following steps: in an inert gas atmosphere, diisocyanate, polyol compound, small molecule chain extender, N-methyldiethanolamine and organic solvent are mixed, and a prepolymerization reaction is carried out at 60-70°C for 2-4 hours; then a blocking agent is added, and the blocking reaction is continued at a constant temperature until the content of -NCO groups is 0, and the organic solvent is removed to obtain a blocked polyurethane prepolymer.

[0022] In the above-mentioned method for preparing the blocked polyurethane prepolymer, the organic solvent may not be removed and may be stored for later use. The amount of the blocked polyurethane prepolymer may be calculated according to the solid content of the solution.

[0023] The present invention also proposes a method for preparing the above-mentioned water-based polyurethane emulsion, comprising the following steps: in an inert gas atmosphere, mixing a blocked polyurethane prepolymer, an organic solvent, gallic acid and acetic acid, reacting, adding water for emulsification, removing the organic solvent, and obtaining a water-based polyurethane.

[0024] Preferably, the reaction is carried out at 50-60°C for 0.5-1 h.

[0025] Preferably, the organic solvent is acetone.

[0026] The invention also proposes the application of the aqueous polyurethane emulsion in synthetic leather.

[0027] The present invention also provides a synthetic leather aqueous slurry, the raw materials of which include, by weight: 70-100 parts of the above aqueous polyurethane emulsion, 0.1-1 parts of a dispersant, 3-10 parts of a foam stabilizer, 0-20 parts of heavy calcium powder, 0.5-3 parts of a thickener, 0.1-1 parts of a color paste, 8-12 parts of a modified natural leather powder and an amine curing agent;

[0028] The molar ratio of the amino group in the amine curing agent to the -NCO group in the polyurethane prepolymer before blocking is 1-1.05:1.

[0029] The above-mentioned amine curing agent can be diethylenetriamine, polycarbodiimide curing agent or the like.

[0030] The viscosity of the synthetic leather aqueous slurry at 25° C. is 18000-22000 cP.

[0031] Preferably, the modified natural leather powder is natural leather powder with a methacrylated gelatin layer coated on the surface.

[0032] The above-mentioned methacryloyl gelatin can be purchased from the market.

[0033] Preferably, the thickness of the methacrylated gelatin layer is 8-12 μm.

[0034] Preferably, the particle size of the modified natural leather powder is 0.4-0.5 mm.

[0035] Preferably, the dispersant is at least one of sodium dodecyl sulfate and polyacrylamide surfactants.

[0036] Preferably, the foam stabilizer is at least one of a fatty amide surfactant or a sulfonate surfactant.

[0037] Preferably, the particle size of the heavy calcium powder is greater than 500 meshes.

[0038] Preferably, the thickener is an associative polyurethane thickener.

[0039] Preferably, the color paste is an anionic color paste.

[0040] The present invention also provides a synthetic leather compression base, comprising: a base fabric and a synthetic leather aqueous slurry adhered to the surface of the base fabric, wherein the synthetic leather aqueous slurry is such as the synthetic leather aqueous slurry mentioned above.

[0041] The present invention also proposes a method for preparing a synthetic leather compression-transformed bass, comprising the following steps: mixing various raw materials to obtain a synthetic leather aqueous slurry, then foaming it, and then coating it on the surface of a base fabric, and drying it to obtain a synthetic leather compression-transformed bass.

[0042] The base fabric is pre-treated first, and the pre-treatment steps are: the base fabric is treated with a tartaric acid aqueous solution with a mass fraction of 0.5-3wt%, and then ironed for standby use.

[0043] Preferably, the foaming method is: introducing air for bubbling, and the bubbling rate is 0.2-0.8m 3 / h, stirring and foaming at a speed of 600-1000r / min for 5-10min.

[0044] Preferably, the drying temperature is greater than the deblocking temperature of the blocking agent.

[0045] 1. The present invention introduces a tertiary amine by using a hydrophilic chain extender N-methyldiethanolamine, and blocks the -NCO group with a blocking agent; then gallic acid and acetic acid react with the tertiary amine to form a salt, form a cationic polyurethane prepolymer and introduce gallic acid; the catechol group in the gallic acid has good adhesion performance, which can improve the adhesion performance of the polyurethane to the base fabric and the color paste, thereby improving the color fixation and adhesion, and its strong adhesion to the base fabric can avoid the problem of easy occurrence of voids in the middle of the leather during drying; the cationic polyurethane prepolymer can also be mutually adsorbed and fixed with the anionic color paste, further improving the color fixation performance.

[0046] 2. The present invention selects natural leather powder of suitable particle size and then coats it with methacrylic gelatin. On the one hand, the natural leather powder can provide support for the pores during drying to prevent the pores from collapsing during the drying process, thereby improving the air permeability and feel of the synthetic leather; on the other hand, the methacrylic gelatin can cooperate with the dispersant and the foam stabilizer to make the pores formed by foaming uniform in size and maintain stability, thereby improving the feel and air permeability of the synthetic leather, and making the natural leather powder evenly distributed around the pores, thereby further improving the air permeability of the synthetic leather.

[0047] 3. The present invention selects a suitable curing agent to cooperate with the aqueous polyurethane emulsion. During the drying process, the blocking agent is unblocked, and the curing agent and the -NCO group form a cross-linking network, which can further improve the adhesion of the polyurethane to the base fabric; and the methacrylic gelatin on the surface of the natural leather powder contains double bonds, which can be copolymerized during the drying process, further improving the density of the cross-linking network, improving the adhesion of the slurry to the base fabric and fixing the natural leather powder; and the amide group in the methacrylic gelatin can form a hydrogen bond with the amide group in the polyurethane to improve the mechanical properties of the synthetic leather.

[0048] 4. The water-based polyurethane emulsion of the present invention is used for embossed color-changing foaming materials, and the embossed color-changing microporous base is produced by dry direct coating process, which is not seen in the market and is a first. The method of the present invention solves the problems of solvent-based wet base, environmental pollution, difficulty in color adjustment, poor batch color stability, often requiring color correction treatment, and poor pressure-changing color changeability. In addition, the water-based polyurethane used in the present invention is environmentally friendly, harmless to the environment and human body, easy to adjust color, can produce bright products, good batch color stability, excellent embossed color changeability, simple processing technology, easier operation, small equipment investment, and less space occupied. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a compression deformation bess photo of synthetic leather made from the synthetic leather aqueous slurry of the present invention. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is described in detail below through specific embodiments.

[0051] Example 1

[0052] A method for preparing an aqueous polyurethane emulsion comprises the following steps:

[0053] In a nitrogen atmosphere, 5 parts of 4,4-dicyclohexylmethane diisocyanate, 13 parts of polytetrahydrofuran diol 2000, 0.14 parts of 1,4-butanediol, and 0.6 parts of N-methyldiethanolamine were added to acetone and mixed, and a prepolymerization reaction was carried out at 60° C. for 4 hours; then 0.65 parts of acetone oxime was added, and the temperature was kept to continue the blocking reaction until the content of -NCO groups was 0, to obtain a blocked polyurethane prepolymer solution;

[0054] In a nitrogen atmosphere, the blocked polyurethane prepolymer solution was mixed with gallic acid and acetic acid, reacted at 60° C. for 0.5 h, emulsified with water, and acetone was removed to obtain a waterborne polyurethane with a solid content of 65 wt %;

[0055] Among them, the molar ratio of gallic acid to acetic acid is 1:3;

[0056] The ratio of the total moles of gallic acid and acetic acid to the mole of N-methyldiethanolamine is 1:1.02.

[0057] A synthetic leather aqueous slurry, the raw materials of which include, by weight: 70 parts of the above aqueous polyurethane emulsion, 1 part of sodium lauryl sulfate, 3 parts of fatty amide surfactant, 0.5 parts of associative polyurethane thickener, 0.5 parts of anionic color paste, 8 parts of modified natural leather powder and diethylenetriamine;

[0058] The molar ratio of the amino group in the diethylenetriamine to the -NCO group in the polyurethane prepolymer before blocking is 1:1;

[0059] The modified natural leather powder is natural leather powder with a methacrylated gelatin layer coated on the surface, the thickness of the methacrylated gelatin layer is 8 μm, and the particle size of the modified natural leather powder is 0.5 mm.

[0060] Example 2

[0061] A method for preparing an aqueous polyurethane emulsion comprises the following steps:

[0062] In a nitrogen atmosphere, 7 parts of 4,4-diphenylmethane diisocyanate, 18 parts of polytetrahydrofuran diol 2000, 0.19 parts of 1,4-butanediol, and 0.8 parts of N-methyldiethanolamine were added to acetone and mixed, and a prepolymerization reaction was carried out at 70° C. for 2 hours; then 0.9 parts of acetone oxime was added, and the temperature was kept to continue the blocking reaction until the content of -NCO groups was 0, to obtain a blocked polyurethane prepolymer solution;

[0063] In a nitrogen atmosphere, the blocked polyurethane prepolymer solution was mixed with gallic acid and acetic acid, reacted at 50° C. for 1 h, emulsified with water, and acetone was removed to obtain a waterborne polyurethane with a solid content of 35 wt %;

[0064] Wherein, the molar ratio of gallic acid to acetic acid is 1:1;

[0065] The ratio of the total moles of gallic acid and acetic acid to the mole of N-methyldiethanolamine is 1:1.

[0066] A synthetic leather aqueous slurry, the raw materials of which include, by weight: 100 parts of the above aqueous polyurethane emulsion, 0.1 parts of sodium lauryl sulfate, 10 parts of fatty amide surfactant, 20 parts of heavy calcium powder with a particle size of 800, 3 parts of associative polyurethane thickener, 1 part of anionic color paste, 12 parts of modified natural leather powder and diethylenetriamine;

[0067] The molar ratio of the amino group in the diethylenetriamine to the -NCO group in the polyurethane prepolymer before blocking is 1.05:1;

[0068] The modified natural leather powder is natural leather powder with a methacrylic gelatin layer coated on the surface, the thickness of the methacrylic gelatin layer is 12 μm, and the particle size of the modified natural leather powder is 0.4 mm.

[0069] Example 3

[0070] A method for preparing an aqueous polyurethane emulsion comprises the following steps:

[0071] In a nitrogen atmosphere, 6 parts of 4,4-dicyclohexylmethane diisocyanate, 15 parts of polytetrahydrofuran diol 2000, 0.16 parts of 1,4-butanediol, and 0.7 parts of N-methyldiethanolamine were added to acetone and mixed, and a prepolymerization reaction was carried out at 65° C. for 3 hours; then 0.78 parts of acetone oxime was added, and the temperature was kept to continue the blocking reaction until the content of -NCO groups was 0, to obtain a blocked polyurethane prepolymer solution;

[0072] In a nitrogen atmosphere, the blocked polyurethane prepolymer solution was mixed with gallic acid and acetic acid, reacted at 55° C. for 1 h, emulsified with water, and acetone was removed to obtain a waterborne polyurethane with a solid content of 50 wt %;

[0073] Wherein, the molar ratio of gallic acid to acetic acid is 1:2;

[0074] The ratio of the total moles of gallic acid and acetic acid to the mole of N-methyldiethanolamine is 1:1.

[0075] A synthetic leather aqueous slurry, the raw materials of which include, by weight: 90 parts of the above aqueous polyurethane emulsion, 0.5 parts of sodium lauryl sulfate, 5 parts of fatty amide surfactant, 10 parts of heavy calcium powder with a particle size of 800, 2 parts of associative polyurethane thickener, 0.5 parts of anionic color paste, 10 parts of modified natural leather powder and diethylenetriamine;

[0076] The molar ratio of the amino group in the diethylenetriamine to the -NCO group in the polyurethane prepolymer before blocking is 1:1;

[0077] The modified natural leather powder is natural leather powder with a methacrylated gelatin layer coated on the surface, the thickness of the methacrylated gelatin layer is 10 μm, and the particle size of the modified natural leather powder is 0.45 mm.

[0078] Comparative Example 1

[0079] A method for preparing an aqueous polyurethane emulsion, wherein gallic acid is not added, the molar ratio of acetic acid to N-methyldiethanolamine is 1:1, and the other contents are the same as those in Example 3.

[0080] Take the above aqueous polyurethane emulsion and prepare a synthetic leather aqueous slurry according to Example 3.

[0081] Comparative Example 2

[0082] A synthetic leather aqueous slurry, wherein "modified natural leather powder" is replaced by "natural leather powder", and the rest is the same as Example 3.

[0083] Comparative Example 3

[0084] A synthetic leather aqueous slurry, wherein "modified natural leather powder" is replaced with "methacrylated gelatin", and the rest is the same as Example 3.

[0085] The synthetic leather aqueous slurry of Examples 1-3 and Comparative Examples 1-3 was used to prepare synthetic leather compression bessiere according to the same method. The specific steps include: bubbling the synthetic leather aqueous slurry with compressed air at a bubbling rate of 0.5 m / s; 3 / h, stirring and foaming at a speed of 800r / min for 8min, and set aside;

[0086] The base fabric was passed through a 1wt% tartaric acid aqueous solution at a uniform speed, and then ironed with an ironing roller. Then, the foamed synthetic leather aqueous slurry was coated on the surface of the base fabric at a coating amount of 500g / m 2 , dried at 120-140°C, the oven length is 60 meters, the line speed is 12m / min, and the synthetic leather compression bess is obtained.

[0087] The performance of the synthetic leather pressure-transformer bass in each group was tested respectively, and the results are shown in Table 1.

[0088] The synthetic leather compression bessie prepared in Example 3 was subjected to pattern pressing, and the photo thereof is shown in FIG. Figure 1 As shown; Figure 1 This is a compression deformation bess photo of synthetic leather made from the synthetic leather aqueous slurry of the present invention.

[0089] Depend on Figure 1 It can be seen that the synthetic leather embossed base prepared by the present invention has uniform color, bright colors and obvious contrast, and excellent embossing color changeability.

[0090] Table 1 Test results

[0091]

[0092] It can be seen from Table 1 that the synthetic leather compression base prepared by the synthetic leather aqueous slurry of the present invention has good hand feel, air permeability, color fixation performance, and good adhesion performance.

[0093] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An aqueous polyurethane emulsion, characterized in that Its raw materials include: blocked polyurethane prepolymer, gallic acid, acetic acid and water; Among them, the blocked polyurethane prepolymer is prepared by reacting a blocking agent with the -NCO group in the polyurethane prepolymer; The blocked polyurethane prepolymer contains a hydrophilic chain extender, which is N-methyldiethanolamine; The ratio of the total moles of gallic acid and acetic acid to the moles of N-methyldiethanolamine is 1:1-1.02; The molar ratio of gallic acid to acetic acid is 1:1-3.

2. The aqueous polyurethane emulsion according to claim 1, characterized in that: In the blocked polyurethane prepolymer, the weight ratio of diisocyanate to N-methyldiethanolamine is 5-7:0.6-0.8; preferably, the blocking agent is acetone oxime; preferably, the -NCO group in the blocked polyurethane prepolymer is 0; preferably, the solid content of the waterborne polyurethane is 35-65wt%.

3. A method for preparing the aqueous polyurethane emulsion according to claim 1 or 2, characterized in that: The method comprises the following steps: in an inert gas atmosphere, mixing a closed polyurethane prepolymer, an organic solvent, gallic acid and acetic acid, reacting, adding water for emulsification, removing the organic solvent, and obtaining waterborne polyurethane.

4. The method for preparing the aqueous polyurethane emulsion according to claim 3, characterized in that: The reaction is carried out at 50-60° C. for 0.5-1 h; preferably, the organic solvent is acetone.

5. Use of the aqueous polyurethane emulsion as claimed in claim 1 or 2 in synthetic leather.

6. A synthetic leather aqueous slurry, characterized in that: The raw materials include, by weight: 70-100 parts of the aqueous polyurethane emulsion as claimed in claim 1 or 2, 0.1-1 parts of a dispersant, 3-10 parts of a foam stabilizer, 0-20 parts of heavy calcium powder, 0.5-3 parts of a thickener, 0.1-1 parts of a color paste, 8-12 parts of a modified natural leather powder and an amine curing agent; The molar ratio of the amino group in the amine curing agent to the -NCO group in the polyurethane prepolymer before blocking is 1-1.05:

1.

7. The aqueous slurry for synthetic leather according to claim 6, characterized in that: The modified natural leather powder is natural leather powder with a methacrylated gelatin layer coated on the surface; preferably, the thickness of the methacrylated gelatin layer is 8-12 μm; preferably, the particle size of the modified natural leather powder is 0.4-0.5 mm.

8. The aqueous slurry for synthetic leather according to claim 6 or 7, characterized in that: The dispersant is at least one of sodium dodecyl sulfate and polyacrylamide surfactants; preferably, the foam stabilizer is at least one of fatty amide surfactants or sulfonate surfactants; preferably, the particle size of the heavy calcium powder is greater than 500; preferably, the thickener is an associative polyurethane thickener; preferably, the color paste is an anionic color paste.

9. A synthetic leather pressure-transformer bass, characterized in that: include: A base fabric and an aqueous slurry of synthetic leather adhered to the surface of the base fabric, wherein the aqueous slurry of synthetic leather is the aqueous slurry of synthetic leather as claimed in any one of claims 6 to 8.

10. A method for preparing a synthetic leather pressure-transformed bass, characterized in that: The method comprises the following steps: mixing the raw materials to obtain a synthetic leather aqueous slurry, foaming the slurry, coating the slurry on the surface of the base fabric, and drying the slurry to obtain a synthetic leather compression base; preferably, the foaming method comprises: introducing air for bubbling at a bubbling rate of 0.2-0.8 m / s. 3 / h, stirring and foaming at a speed of 600-1000r / min for 5-10min; preferably, the drying temperature is greater than the unsealing temperature of the sealing agent.

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