Organic aluminum salt leather color fixing and darkening agent and preparation method thereof

Abstract

The preparation method comprises the following steps: dissolving sulfuric acid, formic acid and nitriloacetic acid in deionized water in a temperature-controlled reactor with stirring, slowly adding sodium metaaluminate at low temperature by several times, heating to react after adding the sodium metaaluminate, and after the appearance state of the system is changed from milky white to transparent, cooling to room temperature to obtain the organic aluminum salt leather color-fixing darkening agent. The organic aluminum salt leather color-fixing darkening agent product in a colorless and transparent liquid state is obtained. Compared with a common conventional aluminum salt complex product, a special nitriloacetic acid structure is introduced into a ligand of the aluminum complex, and due to the existence of a tertiary nitrogen structure in the nitriloacetic acid structure, the aluminum complex shows positive electricity after protonation under an acidic condition, so that the cationic characteristic of the aluminum complex is further enhanced, the cationic charge characteristic of the color fixation darkening agent is improved, and the color fixation darkening agent has a good color fixation effect. More combination and fixation points are provided for the anionic dye for dyeing, and the obvious dyeing assisting effect of color fixation and darkening can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of leather chemicals, and in particular relates to an organic aluminum salt leather color fixing and darkening agent and a preparation method thereof. Background Art

[0002] Leather making is the process of processing animal raw skins into leather products with usable properties through complex physical and chemical processes. The processing process involves many series of operation procedures, and each process affects the quality of leather products, among which the color and appearance of the leather surface are also very important. Dyeing is an important process in the leather making process, especially in the processing of light leather. Leather can obtain various bright colors through dyeing, and at the same time, it can increase the variety of product colors to meet various market needs.

[0003] In the dyeing process of leather production and processing, the basic requirements are that the dyed color is uniform, full, pure, the crust leather has good resistance to dry and wet rubbing, the dye absorption rate is high, and the dyeing waste liquid has low chroma. In order to achieve this dyeing effect and performance requirements, in addition to the dye having good dyeing properties, adding dyeing auxiliaries to assist dyeing in the dyeing process is also a very important key measure. Leather dyeing auxiliaries can be divided into leveling agents, fixing agents and darkening agents according to their functions. The selection and application of these auxiliaries generally depend on the leather variety and requirements. Among them, fixing agents and darkening agents are also commonly used dyeing auxiliaries in most leather dyeing processes. The market usage is gradually increasing, and the performance requirements are also constantly improving.

[0004] However, leather dyeing is usually the last step in the wet processing, so many previous processes affect the subsequent dyeing process. At present, most of the wet processing retanning and filling operations before dyeing basically use anionic synthetic resin materials, which give the leather fiber surface a large amount of negative electrical characteristics, making it difficult for anionic dyes in the subsequent dyeing process to firmly bind and absorb, resulting in a light color effect (also known as color failure phenomenon) of leather dyeing, which makes the leather dyeing have defects such as light color, not full color, low dry and wet rubbing resistance, and dark chroma of waste liquid. Therefore, materials that play a role in fixing and deepening color are a type of dyeing auxiliaries frequently used in the current leather dyeing process, and are also a type of functional auxiliaries for the innovative development of leather chemical materials.

[0005] In the early processing of leather, cationic chrome tanning agents were basically used for fixing and deepening the color of the dyeing process. Later, it was discovered that water-soluble rare earth salts also have a good effect on leather dyeing, fixing and deepening. However, due to the color of the chrome tanning agent itself, it is easy to affect the hue of the dyeing and is not suitable for dyeing light-colored leather. At the same time, due to the rarity and potential radioactivity of rare earth elements, their widespread use is limited. Some nitrogen-containing compounds such as cationic surfactants and cationic polymers are also good leather dyeing fixing agents. There are products on the market, all of which use the charge interaction between cationic properties and anionic dyes to produce a fixing and deepening effect. Some cationic polymers have gradually withdrawn from the ranks of leather dyeing auxiliaries due to the problem of free formaldehyde; however, cationic surfactant materials used as softeners are still the commonly used leather dyeing fixing agents, but due to their small molecules, the color abrasion resistance after fixing is not significantly improved.

[0006] Aluminum tanning agent is also a commonly used fixing agent used in the later stage of dyeing in leather making. There are two main types of products: basic aluminum chloride (AI(OH)Cl2) and aluminum triformate (AI(HCOO)3). The color fixing and darkening effects are average. Summary of the invention

[0007] In view of the problems existing in the background technology, the purpose of the present invention is to provide an organic aluminum salt leather color fixing and darkening agent and a preparation method thereof, provide a new organic ligand, and prepare a new type of organic aluminum salt leather color fixing and darkening agent.

[0008] In order to achieve the above object, the present invention provides an organic aluminum salt leather fixing and darkening agent, which includes an organic complex of an aluminum salt, and the structure of the organic complex of the aluminum salt is:

[0009]

[0010] The present invention also provides a method for preparing the organic aluminum salt leather color fixing and darkening agent as described above, which comprises the following steps: (1) adding deionized water and slowly adding at least one of sulfuric acid and formic acid into a constant temperature reactor equipped with a thermometer, a reflux condenser and a mechanical stirring device, stirring for 5 to 10 minutes, then adding nitroacetic acid, and stirring until the nitroacetic acid is completely dissolved; (2) controlling the temperature of the mixed system to be below 45° C., slowly adding sodium aluminate in portions under stirring, and heating the system to 70 to 80° C. after adding the sodium aluminate and keeping the temperature for reaction for 4 to 6 hours, the appearance of the system gradually changes from milky white to transparent, and cooling the system to 45 to 55° C. to obtain a colorless and transparent liquid product.

[0011] In one embodiment, the mass concentration of the sulfuric acid is 98%; the mass concentration of the formic acid is 85%.

[0012] In one embodiment, when only sulfuric acid is added, the molar ratio of nitroacetic acid, sulfuric acid, and sodium aluminate is 1:1:1;

[0013] In one embodiment, when only formic acid is added, the molar ratio of nitriloacetic acid, formic acid, and sodium aluminate is 1:2:1;

[0014] In one embodiment, when sulfuric acid and formic acid are added, the molar ratio of nitroacetic acid, sulfuric acid, formic acid and sodium aluminate is 1:m:(2-2m):1, wherein 0<m<1.

[0015] In one embodiment, the solid content of the obtained product is 45% to 55%, and the pH value is 3.0 to 4.0.

[0016] The beneficial effects of the present invention are as follows:

[0017] Compared with the two conventional aluminum complex products of basic aluminum chloride and aluminum triformate, a ligand with a nitriloacetic acid structure is introduced into the ligand of the aluminum complex. Due to the presence of the tertiary nitrogen structure in the nitriloacetic acid structure, it shows positive charge after protonation under acidic conditions, further enhancing the cationic properties of the aluminum complex, that is, improving the cationic charge characteristics of this type of color fixing and darkening agent, providing more binding and fixing points for the anionic dyes being dyed, and can play a significant role in color fixing, darkening and dyeing. DETAILED DESCRIPTION

[0018] In order to more clearly present the purpose, technical solutions and advantages of the present invention, the technical solutions in the embodiments of the present invention will be fully described below. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0019] The organic aluminum salt leather color fixing and darkening agent according to the present invention comprises an organic complex of an aluminum salt, and the structure of the organic complex of the aluminum salt is:

[0020]

[0021] The chemical reaction principle of the preparation process of the organic aluminum salt leather color fixing and darkening agent according to the present invention is:

[0022]

[0023] The preparation method of the organic aluminum salt leather color fixing and darkening agent according to the present invention comprises the following steps: (1) adding deionized water and slowly adding at least one of sulfuric acid and formic acid into a constant temperature reactor equipped with a thermometer, a reflux condenser and a mechanical stirring device, stirring for 5 to 10 minutes, then adding nitroacetic acid, and stirring until the nitroacetic acid is completely dissolved; (2) controlling the temperature of the mixed system to be within 45° C., slowly adding sodium aluminate in portions under stirring, and heating the system to 70 to 80° C. after adding the sodium aluminate, and keeping the temperature for reaction for 4 to 6 hours, until the appearance of the system gradually changes from milky white to transparent, and cooling the system to 45 to 55° C. to obtain a colorless and transparent liquid product.

[0024] In the preparation method of the organic aluminum salt leather color fixing and darkening agent according to the present invention, the mass concentration of the sulfuric acid is 98%; the mass concentration of the formic acid is 85%.

[0025] In the preparation method of the organic aluminum salt leather color fixing and darkening agent according to the present invention, when only sulfuric acid is added, the molar ratio of the nitroacetic acid, sulfuric acid and sodium aluminate is 1:1:1, the mass concentration of sulfuric acid is 98%, and the mass fractions of the nitroacetic acid, sulfuric acid and sodium aluminate are 191 parts, 100 parts and 82 parts respectively. 450-300 parts of deionized water can be added in step (1) to obtain a product with a solid content of 45% to 55%.

[0026] In the preparation method of the organic aluminum salt leather color fixing and darkening agent according to the present invention, when only formic acid is added, the molar ratio of the nitroacetic acid, formic acid and sodium aluminate is 1:2:1, the mass concentration of formic acid is 85%, and the mass fractions of the nitroacetic acid, formic acid and sodium aluminate are 191 parts, 108 parts and 82 parts respectively. 427-280 parts of deionized water can be added in step (1) to obtain a product with a solid content of 45% to 55%.

[0027] In the preparation method of the organic aluminum salt leather color fixing and darkening agent according to the present invention, when sulfuric acid and formic acid are added, the molar ratio of the nitroacetic acid, sulfuric acid, formic acid and sodium aluminate is 1:m:(2-2m):1, wherein 0<m<1, the mass concentration of sulfuric acid is 98%, and the mass concentration of formic acid is 85%. Then, the mass fractions of the nitroacetic acid, sulfuric acid, formic acid and sodium aluminate are 191 parts, 100m parts, 54*(2-2m) parts and 82 parts respectively, wherein 0<m<1.

[0028] The solid content of the product prepared according to the present invention is 45% to 55%, and the pH value is 3.0 to 4.0. According to the organic aluminum salt leather color fixing and deepening agent and its preparation method of the present invention, sulfuric acid, formic acid and nitriloacetic acid are first dissolved in deionized water in a temperature-controlled stirring reactor, sodium aluminate is slowly added in batches at low temperature, and the temperature is raised after the sodium aluminate is added, and the appearance of the system is changed from milky white to transparent, and the organic aluminum salt leather color fixing and deepening agent product in a colorless transparent liquid state is obtained. Compared with the general conventional aluminum salt complex product, a special nitriloacetic acid structure is introduced into the ligand of the aluminum complex. Due to the presence of the tertiary nitrogen structure in the nitriloacetic acid structure, it is positively charged after protonation under acidic conditions, further enhancing the cationic characteristics of the aluminum complex, improving the cationic charge characteristics of this type of color fixing and deepening agent, providing more binding and fixing points for the dyed anionic dye, and can play a significant color fixing and deepening auxiliary dyeing effect.

[0029] The organic aluminum salt leather color fixing and darkening agent and its preparation method of the present invention are described in detail below in conjunction with specific examples.

[0030] Main raw materials and equipment used: Unless otherwise specified, the raw materials and equipment of each embodiment and comparative example are the same; materials without specifying the specific model or type are from the same common model purchased on the market, without specific limitation.

[0031] Example 1

[0032] A method for preparing an organic aluminum salt leather color fixing and darkening agent comprises the following steps:

[0033] (1) In a thermostatic reactor equipped with a thermometer, a reflux condenser and a mechanical stirring device, 307 parts of deionized water and 108 parts of formic acid with a mass concentration of 85% were added, and after stirring for 5 minutes, 191 parts of nitroacetic acid was added and stirred until the nitroacetic acid was completely dissolved.

[0034] (2) The temperature of the mixed system was controlled within 45°C, and 82 parts of sodium aluminate were slowly added in portions under stirring (the system temperature did not exceed 45°C). After the addition of sodium aluminate, the temperature was raised to 75°C and kept for 5 hours. The appearance of the system gradually changed from milky white to transparent, and the temperature was lowered to 40°C for discharge. A colorless and transparent liquid product with a solid content of 53% and a pH value of 3.5 was obtained.

[0035] Example 2

[0036] A method for preparing an organic aluminum salt leather color fixing and darkening agent comprises the following steps:

[0037] (1) In a thermostatic reactor equipped with a thermometer, a reflux condenser and a mechanical stirring device, 359 parts of deionized water were added, and 50 parts of sulfuric acid with a mass concentration of 98% were slowly added, and then 54 parts of formic acid with a mass concentration of 85% were added. After stirring for 7 minutes, 191 parts of nitroacetic acid were added and stirred until the nitroacetic acid was completely dissolved.

[0038] (2) The temperature of the mixed system was controlled within 40°C, and 82 parts of sodium aluminate were slowly added in portions under stirring (the system temperature did not exceed 40°C). After the sodium aluminate was added, the temperature was raised to 70°C and kept for 6 hours. The appearance of the system gradually changed from milky white to transparent, and the temperature was lowered to 43°C for discharging. A colorless and transparent liquid product with a solid content of 50% and a pH value of 3.8 was obtained.

[0039] Example 3

[0040] A method for preparing an organic aluminum salt leather color fixing and darkening agent comprises the following steps:

[0041] (1) In a thermostatic reactor equipped with a thermometer, a reflux condenser and a mechanical stirring device, 433 parts of deionized water were added by weight, and 100 parts of sulfuric acid with a mass concentration of 98% were slowly added. After stirring for 10 minutes, 191 parts of nitroacetic acid were added and stirred until the nitroacetic acid was completely dissolved.

[0042] (2) The temperature of the mixed system was controlled within 43°C, and 82 parts of sodium aluminate were slowly added in portions under stirring (the system temperature did not exceed 43°C). After the addition of sodium aluminate, the temperature was raised to 80°C and kept for 4 hours. The appearance of the system gradually changed from milky white to transparent, and the temperature was lowered to 45°C for discharge. A colorless and transparent liquid product with a solid content of 46% and a pH value of 3.3 was obtained.

[0043] The application effect of the organic aluminum salt leather color fixing and darkening agent prepared in Example 1, Example 2 and Example 3 was tested. The specific experimental process is as follows:

[0044] Weigh the shaved sheep blue wet leather (based on the amount of chemical used)

[0045] Rewetting water washing: water 150%, 30℃

[0046] Penetrant 0.2% transfer for 30 minutes, drain

[0047] Neutralization: water 150%, 30℃

[0048] Sodium formate 2.0% for 20 min

[0049] Baking soda 0.5% transfer for 40 minutes, pH 5.5-6.0 drainage

[0050] Washing: 150% water, 30℃, 30min, drain

[0051] Dyeing oil: 150% water, 55℃

[0052] Composite black 2% transfer 30min

[0053] Synthetic fatliquor 6%

[0054] Lecithin fatliquor 2%

[0055] Sulfated neatsfoot oil 4% 60min

[0056] Fixing: Formic acid (85%) 1.0% (diluted with 10 times water, added twice, 15 minutes apart)

[0057] After adding formic acid, transfer for 30 minutes

[0058] Organic aluminum salt leather fixing and darkening agent 1.5% 45min pH at 3.0~3.6

[0059] After the drum is taken out, it is left to stand to control water, hung to dry, and the drum is softened and then stretched to finish.

[0060] At the same time, a blank group and a control group were tested, the blank group did not add leather color fixing and darkening agent, and the control group added 1.5% aluminum triformate color fixing agent. Other operations were the same.

[0061] The dyeing waste liquid and the leather blank after drying and finishing were subjected to various performance tests, and the performance test results of Examples 1-3, the blank group, and the comparison group are shown in Table 1. From the data results in Table 1, it can be seen that the use of the organic aluminum salt leather color fixing and darkening agent of the present invention can improve the color fastness of the surface of the leather in terms of dry and wet rubbing resistance by about 0.5 level compared with the comparison group, and by nearly 1 level compared with the blank group, and the dye uptake rate is also significantly improved accordingly.

[0062] Table 1 Leather color fixation effect test results

[0063] Test items Example 1 Example 2 Example 3 Blank Group Comparison group Dye uptake rate (%) 98％ 98％ 98％ 93％ 96％ Wet rubbing resistance level of leather 3.5-4.0 3.5-4.0 3.5-4.0 2.5-3.0 3.0-3.5 Leather dry rub resistance level 4.0-4.5 4.0-4.5 4.0-4.5 3.0-3.5 3.5-4.0

[0064] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. An organic aluminum salt leather color fixing and darkening agent, characterized in that: An organic complex comprising an aluminum salt, wherein the structure of the organic complex of the aluminum salt is:

2. The method for preparing the organic aluminum salt leather color fixing and darkening agent according to claim 1, characterized in that: The following steps are involved: (1) adding deionized water and slowly adding at least one of sulfuric acid and formic acid into a thermostatic reactor equipped with a thermometer, a reflux condenser and a mechanical stirring device, stirring for 5 to 10 minutes, then adding nitroacetic acid, and stirring until the nitroacetic acid is completely dissolved; (2) The temperature of the mixed system is controlled within 45°C, and sodium aluminate is slowly added in portions under stirring. After the addition of sodium aluminate, the temperature is raised to 70-80°C and kept warm for reaction for 4-6 hours. The appearance of the system gradually changes from milky white to transparent. The temperature is lowered to 45-55°C to obtain a colorless and transparent liquid product.

3. The method for preparing the organic aluminum salt leather color fixing and darkening agent according to claim 2, characterized in that: The mass concentration of the sulfuric acid is 98%; the mass concentration of the formic acid is 85%.

4. The method for preparing the organic aluminum salt leather color fixing and darkening agent according to claim 2, characterized in that: When only sulfuric acid is added, the molar ratio of nitroacetic acid, sulfuric acid and sodium aluminate is 1:1:1; When only formic acid is added, the molar ratio of nitriloacetic acid, formic acid and sodium aluminate is 1:2:1; When sulfuric acid and formic acid are added, the molar ratio of nitriloacetic acid, sulfuric acid, formic acid and sodium aluminate is 1:m:(2-2m):1, wherein 0<m<1.

5. The method for preparing the organic aluminum salt leather color fixing and darkening agent according to claim 2, characterized in that: The solid content of the prepared product is 45% to 55%, and the pH value is 3.0 to 4.0.

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