Water-based polyurethane emulsion and synthetic leather pressure variable bed

Abstract

The application discloses a kind of water-based polyurethane emulsion, raw material includes: blocked polyurethane prepolymer, gallic acid, acetic acid and water;Wherein, blocked polyurethane prepolymer is with blocking agent and the -NCO group in polyurethane prepolymer is reacted to obtain;Blocked polyurethane prepolymer contains hydrophilic chain extender, and hydrophilic chain extender is N-methyl diethanolamine;The ratio of the total number of moles of gallic acid and acetic acid, the number of moles of N-methyl diethanolamine is 1:1-1.02;The molar ratio of gallic acid and acetic acid is 1:1-3.The application also discloses the preparation method and application of the above-mentioned water-based polyurethane emulsion.The application also discloses a kind of synthetic leather water-based slurry.The application also discloses a kind of synthetic leather press variable bass and preparation method thereof.The synthetic leather press variable bass prepared by the synthetic leather water-based slurry disclosed by the application has good hand feeling, air permeability, color fixing performance, and good adhesion, and excellent embossing discoloration.

Description

Technical Field

[0001] This invention relates to the field of synthetic leather, and more particularly to an aqueous polyurethane emulsion and a synthetic leather compression molding compound. Background Technology

[0002] Synthetic leather embossed base coats possess breathability, moisture permeability, and excellent mechanical strength. Traditional synthetic leather embossed base coats primarily employ a wet process. The specific steps are as follows: solvent-based polyurethane resin is added to an organic solvent (such as DMF), along with other additives, to create a mixed emulsion. This emulsion is then impregnated or coated onto a base fabric, followed by immersion in water. Taking advantage of the fact that organic solvents are more soluble in water than in polyurethane slurry, more organic solvent dissolves in water, or more is displaced by the water, thus achieving solvent replacement. During this replacement process, bubbles are formed in the coating. Finally, the coating is washed and dried to obtain the synthetic leather embossed base coat.

[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. Furthermore, a large amount of water is required for solvent replacement during the preparation process, and the size of the cells cannot be controlled during the replacement process, resulting in inconsistent cell sizes that affect the performance of the synthetic leather base. In addition, the water replacement process is prone to discoloration, making the base color uncontrollable and preventing the color from being consistent and stable across different batches.

[0004] Waterborne polyurethane resin can meet international environmental standards, but it is rarely used in the production of synthetic leather pressed baseboards. When waterborne polyurethane resin is used in the production of synthetic leather pressed baseboards, problems often arise such as easy discoloration of the leather, easy collapse of the pores during the drying process, and polyurethane migrating to the periphery with water during the drying process, making it easy for voids to appear in the middle of the leather, affecting the feel and breathability of the synthetic leather. In addition, 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 a water-based polyurethane emulsion and a synthetic leather embossing base. The synthetic leather embossing base made from the synthetic leather water-based slurry of the present invention has good hand feel, breathability, color fixation performance, good adhesion performance, and excellent embossing color change performance.

[0006] This invention proposes 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 groups in the polyurethane prepolymer;

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

[0009] The ratio of the total molar amount of gallic acid and acetic acid to the molar amount 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 closed 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 -NCO groups in the closed polyurethane prepolymer are 0.

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

[0015] The raw materials for the above-mentioned blocked 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 closed polyurethane prepolymer is not limited, as long as a closed polyurethane prepolymer can be obtained; or more suitable amounts of each raw material can be selected.

[0017] The raw materials of the above-mentioned 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 mentioned above can be 4,4-diphenylmethane diisocyanate, isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, etc.

[0019] The aforementioned polyol compounds can be polyether polyols, polyester polyols, etc.

[0020] The aforementioned small molecule chain extenders can be 1,4-butanediol, 1,2-propanediol, etc.

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

[0022] In the above-mentioned preparation method of closed polyurethane prepolymer, the organic solvent may not be removed and can be stored for later use. When calculating the amount of closed polyurethane prepolymer, it can be calculated according to the solid content of the solution.

[0023] The present invention also proposes a method for preparing the above-mentioned waterborne polyurethane emulsion, comprising the following steps: in an inert gas atmosphere, a closed polyurethane prepolymer, an organic solvent, gallic acid, and acetic acid are mixed and reacted, water is added for emulsification, the organic solvent is removed, and waterborne polyurethane is obtained.

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

[0025] Preferably, the organic solvent is acetone.

[0026] The present invention also proposes the application of the above-mentioned waterborne polyurethane emulsion in synthetic leather.

[0027] The present invention also proposes a water-based slurry for synthetic leather, the raw materials of which, by weight, include: 70-100 parts of the above-mentioned water-based polyurethane emulsion, 0.1-1 parts of dispersant, 3-10 parts of foam stabilizer, 0-20 parts of heavy calcium carbonate powder, 0.5-3 parts of thickener, 0.1-1 parts of color paste, 8-12 parts of modified natural leather powder, and 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 sealing is 1-1.05:1.

[0029] The aforementioned amine curing agents can be diethylenetriamine, polycarbodiimide curing agents, etc.

[0030] The viscosity of the above-mentioned synthetic leather water-based sizing agent at 25°C is 18000-22000 cP.

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

[0032] The above-mentioned methacrylamide gelatin is available from the market.

[0033] Preferably, the thickness of the methacrylamide 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 fatty amide surfactants or sulfonate surfactants.

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

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

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

[0040] The present invention also proposes a synthetic leather pressure-modified base, comprising: a base fabric and a synthetic leather water-based sizing agent adhered to the surface of the base fabric, wherein the synthetic leather water-based sizing agent is as described above.

[0041] The present invention also proposes a method for preparing synthetic leather embossed base, comprising the following steps: taking each raw material and mixing them to obtain a synthetic leather water-based slurry, then foaming it, then coating it on the surface of a base fabric, and drying it to obtain synthetic leather embossed base.

[0042] The base fabric must be pretreated first. The pretreatment steps are as follows: the base fabric is treated with a tartaric acid aqueous solution with a mass fraction of 0.5-3wt%, ironed, and then set aside.

[0043] Preferably, the foaming method is as follows: air is introduced to induce bubbling, and the bubbling rate is 0.2-0.8 m / s. 3 Stir and foam at 600-1000 rpm for 5-10 minutes per hour.

[0044] Preferably, the drying temperature is higher than the unsealing temperature of the sealant.

[0045] 1. This invention introduces a tertiary amine using the hydrophilic chain extender N-methyldiethanolamine and capsulates the -NCO groups with a capping agent; then, gallic acid and acetic acid are reacted with the tertiary amine to form a cationic polyurethane prepolymer and gallic acid is introduced; the cationic polyurethane prepolymer contains catechol groups, which have good adhesion properties, which can improve the adhesion of polyurethane to the base fabric and color paste, thereby improving color fixation and adhesion, and its strong adhesion to the base fabric can avoid the problem of voids easily appearing in the middle of the leather during drying; the cationic polyurethane prepolymer can also be mutually adsorbed and fixed with anionic color paste, further improving the color fixation performance.

[0046] 2. This invention selects natural leather powder with a suitable particle size and then coats it with methacrylamide gelatin. On the one hand, the natural leather powder can provide support for the foam cells during drying, preventing the foam cells from collapsing during the drying process and improving the breathability and feel of the synthetic leather. On the other hand, methacrylamide gelatin can work together with dispersants and foam stabilizers to make the foamed cells uniform in size and remain stable, improving the feel and breathability of the synthetic leather. Furthermore, it allows the natural leather powder to be evenly distributed around the foam cells, further improving the breathability of the synthetic leather.

[0047] 3. This invention selects a suitable curing agent in combination with waterborne polyurethane emulsion. During the drying process, the sealing agent is unsealed, and the curing agent forms a cross-linking network with the -NCO groups, which can further improve the adhesion performance of polyurethane to the base fabric. Furthermore, the methacrylamide gelatin on the surface of the natural leather powder contains double bonds, which can copolymerize during the drying process, further increasing the density of the cross-linking network, improving the adhesion of the slurry to the base fabric, and fixing the natural leather powder. In addition, the amide groups in the methacrylamide gelatin can form hydrogen bonds with the amide groups in the polyurethane to improve the mechanical properties of synthetic leather.

[0048] 4. The waterborne polyurethane emulsion described in this invention is used in embossed color-changing foaming materials, employing a dry direct coating process to produce embossed color-changing microporous foam. This method is unprecedented in the market and represents a first. The method described in this invention solves the problems of solvent-based wet-process foams, which are not environmentally friendly, have difficulty in color matching, poor batch color stability, often require color correction, and have poor embossed color-changing properties. Furthermore, the waterborne polyurethane used in this invention is environmentally friendly, harmless to the environment and human body, easy to match colors, can produce bright products, has good batch color stability, excellent embossed color-changing properties, simple processing technology, is easier to operate, requires less equipment investment, and occupies less space. Attached Figure Description

[0049] Figure 1 This is a photograph of the synthetic leather press-molded base material obtained from the synthetic leather water-based slurry described in this invention. Detailed Implementation

[0050] The technical solution of the present invention will now be described in detail through specific embodiments.

[0051] Example 1

[0052] A method for preparing an aqueous polyurethane emulsion includes 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 well. The mixture was then subjected to a prepolymerization reaction at 60°C for 4 hours. Then, 0.65 parts of acetone oxime were added, and the mixture was kept at the same temperature to carry out a blocking reaction until the content of -NCO groups was 0, thus obtaining a blocked polyurethane prepolymer solution.

[0054] In a nitrogen atmosphere, a closed polyurethane prepolymer solution was mixed with gallic acid and acetic acid and reacted at 60°C for 0.5 h. Water was added for emulsification and acetone was removed to obtain an aqueous polyurethane with a solid content of 65 wt%.

[0055] The molar ratio of gallic acid to acetic acid is 1:3.

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

[0057] A synthetic leather water-based sizing agent comprises the following raw materials by weight: 70 parts of the above-mentioned water-based polyurethane emulsion, 1 part of sodium dodecyl sulfate, 3 parts of fatty amide surfactant, 0.5 parts of associative polyurethane thickener, 0.5 parts of anionic pigment, 8 parts of modified natural leather powder, and diethylenetriamine.

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

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

[0060] Example 2

[0061] A method for preparing an aqueous polyurethane emulsion includes 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 well. The mixture was then subjected to a prepolymerization reaction at 70°C for 2 hours. Then, 0.9 parts of acetone oxime were added, and the mixture was kept at the same temperature to carry out a blocking reaction until the content of -NCO groups was 0, thus obtaining a blocked polyurethane prepolymer solution.

[0063] In a nitrogen atmosphere, a closed polyurethane prepolymer solution was mixed with gallic acid and acetic acid and reacted at 50°C for 1 hour. Water was added for emulsification and acetone was removed to obtain an aqueous polyurethane with a solid content of 35 wt%.

[0064] The molar ratio of gallic acid to acetic acid is 1:1.

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

[0066] A synthetic leather water-based sizing agent comprises the following raw materials by weight: 100 parts of the above-mentioned water-based polyurethane emulsion, 0.1 parts of sodium dodecyl sulfate, 10 parts of fatty amide surfactant, 20 parts of heavy calcium carbonate 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 diethylenetriamine to the -NCO group in the unblocked polyurethane prepolymer is 1.05:1.

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

[0069] Example 3

[0070] A method for preparing an aqueous polyurethane emulsion includes 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 well. The mixture was then subjected to a prepolymerization reaction at 65°C for 3 hours. Subsequently, 0.78 parts of acetone oxime were added, and the mixture was kept at the same temperature to carry out a blocking reaction until the content of -NCO groups was 0, thus obtaining a blocked polyurethane prepolymer solution.

[0072] In a nitrogen atmosphere, a closed polyurethane prepolymer solution was mixed with gallic acid and acetic acid and reacted at 55°C for 1 hour. Water was added for emulsification and acetone was removed to obtain an aqueous polyurethane with a solid content of 50 wt%.

[0073] The molar ratio of gallic acid to acetic acid is 1:2.

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

[0075] A synthetic leather water-based sizing agent comprises the following raw materials by weight: 90 parts of the above-mentioned water-based polyurethane emulsion, 0.5 parts of sodium dodecyl sulfate, 5 parts of fatty amide surfactant, 10 parts of heavy calcium carbonate powder with a particle size of 800, 2 parts of associative polyurethane thickener, 0.5 parts of anionic colorant, 10 parts of modified natural leather powder, and diethylenetriamine.

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

[0077] The modified natural leather powder is a natural leather powder with a methacrylamide gelatin layer on its surface. The thickness of the methacrylamide 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 other aspects are the same as in Example 3.

[0080] Take the above-mentioned waterborne polyurethane emulsion and formulate a synthetic leather waterborne slurry according to Example 3.

[0081] Comparative Example 2

[0082] A synthetic leather water-based slurry, wherein "modified natural leather powder" is replaced with "natural leather powder", and the rest is the same as in Example 3.

[0083] Comparative Example 3

[0084] A synthetic leather water-based sizing agent, wherein "modified natural leather powder" is replaced with "methacrylamide gelatin", and the rest is the same as in Example 3.

[0085] Take the synthetic leather water-based sizing agents from Examples 1-3 and Comparative Examples 1-3, and prepare synthetic leather compression molding compound using the same method. Specific steps include: using compressed air to bubble the synthetic leather water-based sizing agent at a bubbling rate of 0.5 m / s. 3 Stir and foam at 800 rpm for 8 minutes, then set aside.

[0086] The base fabric is passed through a 1 wt% tartaric acid aqueous solution at a uniform speed, then ironed flat with an ironing roller. Finally, a foamed synthetic leather water-based slurry is coated onto the base fabric surface at a coating weight of 500 g / m². 2 The material is dried at 120-140℃ in an oven with a length of 60 meters and a linear speed of 12m / min to obtain synthetic leather pressed base.

[0087] The performance of the synthetic leather compression molding base of each group was tested, and the results are shown in Table 1.

[0088] The synthetic leather embossed base prepared in Example 3 was subjected to pattern embossing, and the photograph is shown below. Figure 1 As shown; Figure 1 This is a photograph of the synthetic leather press-molded base material obtained from the synthetic leather water-based slurry described in this invention.

[0089] Depend on Figure 1 It can be seen that the synthetic leather embossed with this invention has a uniform color, bright and obvious color contrast, and excellent embossing and color-changing properties.

[0090] Table 1 Test Results

[0091]

[0092] As can be seen from Table 1, the synthetic leather blister pack made from the synthetic leather water-based slurry of the present invention has good hand feel, breathability, color fastness, and adhesion.

[0093] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A synthetic leather aqueous slurry, characterized by, The raw materials include, by weight parts, 70-100 parts of water-based polyurethane emulsion, 0.1-1 part of dispersant, 3-10 parts of foam stabilizer, 0-20 parts of heavy calcium powder, 0.5-3 parts of thickening agent, 0.1-1 part of color paste, 8-12 parts of modified natural leather powder, and amine curing agent; The raw materials of the water-based polyurethane emulsion include blocked polyurethane prepolymer, gallic acid, acetic acid, and water; The blocked polyurethane prepolymer is prepared by reacting a blocking agent with -NCO groups in the polyurethane prepolymer; The blocked polyurethane prepolymer contains a hydrophilic chain extender, which is N-methyl diethanolamine; The ratio of the total moles of gallic acid and acetic acid to the moles of N-methyl diethanolamine is 1:1-1.02; The molar ratio of gallic acid to acetic acid is 1:1-3; The molar ratio of amino groups in the amine curing agent to -NCO groups in the polyurethane prepolymer before blocking is 1-1.05:1; The modified natural leather powder is natural leather powder coated with a layer of methacrylated gelatin.

2. The aqueous sizing composition according to claim 1, wherein In the blocked polyurethane prepolymer, the weight ratio of diisocyanate to N-methyl diethanolamine is 5-7:0.6-0.

8.

3. The aqueous sizing composition of claim 1, wherein The blocking agent is acetone oxime.

4. The aqueous sizing composition of claim 1, wherein, The blocked polyurethane prepolymer contains 0 -NCO groups.

5. The aqueous sizing composition of claim 1, wherein, The solid content of the water-based polyurethane is 35-65wt%.

6. The aqueous sizing composition of claim 1, wherein, The preparation method of the water-based polyurethane emulsion includes the following steps: mixing the blocked polyurethane prepolymer, organic solvent, gallic acid, and acetic acid uniformly in an inert gas atmosphere, reacting, adding water for emulsification, removing the organic solvent, and obtaining the water-based polyurethane.

7. The aqueous sizing composition of claim 6, wherein, The reaction is carried out at 50-60℃ for 0.5-1h.

8. The aqueous sizing composition of claim 6, wherein the polyurethane is a polyurethane dispersion. The organic solvent is acetone.

9. The aqueous sizing composition of claim 1, wherein, The thickness of the methacrylated gelatin layer is 8-12μm.

10. The aqueous sizing composition of claim 1, wherein, The particle size of the modified natural leather powder is 0.4-0.5mm.

11. The aqueous sizing composition of claim 1, wherein, The dispersant is at least one of sodium dodecyl sulfate and polyacrylamide surfactant.

12. The aqueous sizing composition of claim 1, wherein, The foam stabilizer is at least one of fatty amide surfactant or sulfonate surfactant.

13. The aqueous sizing composition of claim 1, wherein, The particle size of the heavy calcium powder is greater than 500 mesh.

14. The aqueous sizing composition of claim 1, wherein, The thickening agent is an associated polyurethane thickening agent.

15. The aqueous sizing composition of claim 1, wherein, The color paste is an anionic color paste.

16. A synthetic leather press varnishing machine characterized by, It comprises: A base cloth and a synthetic leather water-based slurry adhered to the surface of the base cloth, wherein the synthetic leather water-based slurry is as claimed in any one of claims 1-15.

17. A method of producing a synthetic leather press varnish according to claim 16, characterized by, It comprises the following steps: mixing the raw materials to obtain a synthetic leather water-based slurry, foaming, coating on the surface of the base cloth, and drying to obtain a synthetic leather press variation bass, wherein the drying temperature is greater than the deblocking temperature of the blocking agent.

18. The method for preparing synthetic leather pressure-modified base metal according to claim 17, characterized in that, The foaming method is: bubbling with air, the bubbling rate is 0.2-0.8 m 3 / h, stirring the foaming at the speed of 600-1000 r / min for 5-10 min.

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