阅读说明：本技术 一种复鞣剂的制备方法、复鞣剂及其应用 (Preparation method of retanning agent, retanning agent and application of retanning agent ) 是由 张达 郭连娣 贺卫勃 沈扬 于 2020-07-23 设计创作，主要内容包括：本发明公开了一种复鞣剂的制备方法,先对二醛单体进行改性得到部分磺化二醛,然后与氨基单体进行亲核加成反应生成含磺酸基的氨基树脂预聚物,最后加入醚化剂封闭游离的醛基得到氨基树脂复鞣剂,其中,所述的氨基单体中的伯氨基与二醛单体中的醛基摩尔比为1:1.3～1:3,所述的部分磺化二醛中未反应醛基比例为40％～90％。还提供了一种复鞣剂及其应用。本发明的制备方法,提高了氨基树脂预聚物以及复鞣剂产物的水溶性与分散性,使复鞣剂的质量好,综合性能高,其复鞣性能可与传统的氨基树脂复鞣剂相媲美。(The invention discloses a preparation method of a retanning agent, which comprises the steps of modifying a dialdehyde monomer to obtain partially sulfonated dialdehyde, carrying out nucleophilic addition reaction on the partially sulfonated dialdehyde monomer and an amino monomer to generate an amino resin prepolymer containing sulfonic groups, and finally adding an etherifying agent to seal free aldehyde groups to obtain the amino resin retanning agent, wherein the molar ratio of primary amino groups in the amino monomer to aldehyde groups in the dialdehyde monomer is 1: 1.3-1: 3, and the proportion of unreacted aldehyde groups in the partially sulfonated dialdehyde is 40-90%. Also provides a retanning agent and application thereof. The preparation method of the invention improves the water solubility and the dispersibility of the amino resin prepolymer and the retanning agent product, so that the retanning agent has good quality and high comprehensive performance, and the retanning performance of the retanning agent can be comparable with that of the traditional amino resin retanning agent.)

1. The preparation method of the retanning agent is characterized in that firstly, a dialdehyde monomer is modified to obtain partially sulfonated dialdehyde, secondly, the partially sulfonated dialdehyde and an amino monomer are subjected to nucleophilic addition reaction to generate amino resin prepolymer containing sulfonic groups, and finally, an etherifying agent is added to seal excessive free aldehyde groups to obtain the retanning agent; wherein, the mole ratio of primary amino in the amino monomer to aldehyde group in the dialdehyde monomer is 1: 1.3-1: 3, and the proportion of unreacted aldehyde group in the partially sulfonated dialdehyde is 40-90%.

2. A process for the preparation of a retanning agent according to claim 1, characterized by the steps of:

(1) firstly, stirring and mixing a dialdehyde monomer and pure water at 0-40 ℃, adjusting the pH value to 7.5-9.0, adding a sulfonating agent, stirring uniformly, and then heating to 70-90 ℃ for reaction for 0.5-2.0 hours to obtain partially sulfonated dialdehyde;

(2) uniformly mixing an amino monomer and pure water at 0-40 ℃, adjusting the pH value to 7.5-9.0, then adding the partially sulfonated dialdehyde prepared in the step (1), reacting at 70-85 ℃ for 0.5-1.0 h, heating to 80-95 ℃, and continuing to react for 10-30 min to obtain an amino resin prepolymer containing sulfonic groups;

(3) and (3) adding an etherifying agent into the amino resin prepolymer containing sulfonic groups obtained in the step (2), adjusting the pH value to 3.0-6.0, then preserving the heat at the temperature of 50-70 ℃ for 1-3 hours, and finally adjusting the pH value to 6.0-8.0 to obtain the retanning agent product.

3. A method of preparing a retanning agent according to claim 1 or 2, characterised in that the dialdehyde monomer is at least one of glyoxal, glutaraldehyde or adipaldehyde.

4. A process for preparing a retanning agent according to claim 1 or 2, characterized in that the amino monomer is at least one of melamine, urea and dicyandiamide.

5. A process for preparing a retanning agent according to claim 1 or 2, characterized in that the sulfonating agent is at least one of sodium sulfite, sodium sulfamate, sodium bisulfite and sodium metabisulfite.

6. A process for the preparation of a retanning agent according to claim 1 or 2, characterised in that the etherifying agent is at least one of methanol, ethanol, isopropanol, diethylene glycol or n-butanol.

7. A retanning agent obtained by the method according to any one of claims 1 to 6.

8. Use of a retanning agent prepared by the method according to any one of claims 1 to 6 or a retanning agent according to claim 7 for retanning leather products.

Technical Field

The invention belongs to the technical field of retanning agents for tanning leather and fur, and particularly relates to a retanning agent and a preparation method thereof.

Background

Leather retanning is an essential process in leather processing, and the softness, the smoothness and the fineness of grain surfaces, the wear resistance, the embossing qualitative performance, the fullness and the like of the leather can be improved by retanning the leather; and leather with different styles can be formed by retanning the leather, so that the demand of the market on leather products is better met.

The retanning agent is widely used, such as aromatic synthetic retanning agent, resin retanning agent, aldehyde retanning agent, oil retanning agent and the like, wherein the aromatic synthetic retanning agent generally contains the following functional groups: phenolic hydroxyl group and sulfonic group (-SO)₃H) Sulfone group (-SO)₂-), sulfonimidyl (-SO)₂NH-), which can make the leather have better fullness, softness and filling property and certain light resistance; the retanning agent has auxiliary dispersion and permeation effects on tannin extract, dye and grease, and has tanning combination effect with skin collagen; in addition, the retanning agent has small astringency, so that the retanning effect is uniform, and the retanning agent can be used for the procedures of pretanning, tanning, retanning, neutralization and the like.

At present, retanning agents mainly used in China are two major types of acrylic acid and amino resin. The amino resin is used as a synthetic tanning agent, is an extremely important retanning agent, is mainly applied to pretanning, retanning and filling, has good thickening effect and filling performance, can promote the combination of subsequent chemicals (such as fatliquoring agents, dyes and the like) and leather particularly for softer parts, and effectively avoids the phenomenon of 'color losing' after the use of the acrylic acid tanning agent.

The existing amino resin retanning agent can release formaldehyde in the production or use process, and poses a threat to health. Or the softness, compactness and the like of the tanned product are not good, and the quality of the product is still to be improved.

Disclosure of Invention

The invention provides a preparation method of a retanning agent, which can solve the defects in the prior art.

The technical scheme of the invention is as follows:

firstly, modifying a dialdehyde monomer to obtain partially sulfonated dialdehyde, secondly, carrying out nucleophilic addition reaction on the partially sulfonated dialdehyde and an amino monomer to generate amino resin prepolymer containing sulfonic groups, and finally adding an etherifying agent to seal excessive free aldehyde groups to obtain the retanning agent; wherein, the mole ratio of primary amino in the amino monomer to aldehyde group in the dialdehyde monomer is 1: 1.3-1: 3, and the proportion of unreacted aldehyde group in the partially sulfonated dialdehyde is 40-90%.

Firstly, modifying a dialdehyde monomer to obtain partially sulfonated dialdehyde, and then performing nucleophilic addition, so that the water solubility, the active group dispersibility and the product quality of the amino resin prepolymer can be improved; and finally, an etherifying agent is adopted to seal the excessive free aldehyde group, and the free aldehyde group is sealed by introducing a water-soluble sulfonic acid group and an etherification reaction, so that the retanning agent product has good stability, the retanning performance of the retanning agent is improved, and the retanned finished leather has good softness, fullness, compactness and surface hand feeling.

The method comprises the following steps of (1) controlling the proportion of unreacted aldehyde groups in partially sulfonated dialdehyde by controlling the dosage of a dialdehyde monomer and a sulfonating agent, wherein when the proportion of the unreacted aldehyde groups exceeds 90%, sulfonation is less, the water solubility of the obtained amino resin prepolymer is poor, and the water solubility of the obtained retanning agent product is poor, so that the retanning quality of leather is influenced; when the proportion of unreacted aldehyde groups is less than 40%, sulfonation is excessive, the amount of reactive groups is too small, and the bonding and crosslinking density of the retanned leather is too low, so that the final retanning quality of the leather is affected. Therefore, the balance between the water solubility of the retanning agent, the distribution uniformity of active groups in the product and the leather crosslinking density during retanning needs to be found, and the proportion of unreacted aldehyde groups in the sulfonated dialdehyde is preferably controlled to be between 40 and 90 percent.

And the mole ratio of primary amino in the amino monomer to aldehyde group in the dialdehyde monomer is controlled to be 1: 1.3-1: 3, and the ratio of unreacted aldehyde group in part of sulfonated dialdehyde is controlled to be 40-90%, so that the retanning agent has good stability and retanning performance, and the quality of finished leather after retanning by the retanning agent is improved.

Preferably, the preparation method specifically comprises the following steps:

(1) firstly, stirring and mixing a dialdehyde monomer and pure water at 0-40 ℃, adjusting the pH value to 7.5-9.0, adding a sulfonating agent, stirring uniformly, and then heating to 70-90 ℃ for reaction for 0.5-2.0 hours to obtain partially sulfonated dialdehyde;

(2) uniformly mixing an amino monomer and pure water at 0-40 ℃, adjusting the pH value to 7.5-9.0, then adding the partially sulfonated dialdehyde prepared in the step (1), reacting at 70-85 ℃ for 0.5-1.0 h, heating to 80-95 ℃, and continuing to react for 10-30 min to obtain an amino resin prepolymer containing sulfonic groups;

(3) and (3) adding an etherifying agent into the amino resin prepolymer containing sulfonic groups obtained in the step (2), adjusting the pH value to 3.0-6.0, then preserving the heat at the temperature of 50-70 ℃ for 1-3 hours, and finally adjusting the pH value to 6.0-8.0 to obtain the retanning agent product.

The method comprises the steps of modifying a dialdehyde monomer to obtain partially sulfonated dialdehyde, and then reacting with an amino monomer in batches to ensure that the generated amino resin prepolymer can be well dispersed in an aqueous solution, thereby effectively overcoming the product quality problem caused by the water solubility and dispersion problems of the dialdehyde monomer in the process of reacting to generate the amino resin prepolymer, and ensuring that the reaction product is simpler and the distribution of active groups is more uniform. The prepared retanning agent has good comprehensive performance of finished leather and high product quality, can effectively improve the humidity and heat resistance stability of finished leather products, and has the shoe retanning performance comparable to that of the traditional amino resin retanning agent.

Preferably, the dialdehyde monomer is at least one of glyoxal, glutaraldehyde or adipaldehyde.

Preferably, the amino monomer is at least one of melamine, urea and dicyandiamide.

Preferably, the sulfonating agent is at least one of sodium sulfite, sodium sulfamate, sodium bisulfite and sodium metabisulfite.

Preferably, the etherifying agent is at least one of methanol, ethanol, isopropanol, diethylene glycol or n-butanol.

The invention also provides a retanning agent prepared by any one of the preparation methods.

The invention also provides the application of the retanning agent or the retanning agent prepared by any one of the preparation methods in retanning leather products.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the retanning agent provided by the invention, firstly, a dialdehyde monomer is modified to generate partial sulfonated dialdehyde, finally, an etherifying agent is adopted to seal excessive free aldehyde groups, and the free aldehyde groups are sealed by introducing water-soluble sulfonic acid groups and etherification reaction, so that the retanning agent product has good water solubility and stability, the phenomenon of precipitation and segregation cannot occur in the storage and use processes of the retanning agent product, and the leather has a better retanning effect.

2. According to the invention, the dialdehyde monomer is modified to obtain the partially sulfonated dialdehyde, and then the partially sulfonated dialdehyde is reacted with the amino monomer in batches, so that the generated amino resin prepolymer can be well dispersed in the aqueous solution, the product quality problem caused by the water solubility and dispersion problems in the process of reacting the dialdehyde monomer to generate the amino resin prepolymer is effectively solved, the active groups are more uniformly distributed in the reaction product, and the product is simpler.

3. The retanning agent has good comprehensive performance of finished leather, high product quality, and can effectively improve the humidity and heat resistance stability of finished leather products, and the retanning performance of the retanning agent can be comparable with that of the traditional amino resin retanning agent.

4. The preparation process of the retanning agent does not use formaldehyde as a condensing agent, and the possibility of generating formaldehyde in the retanning agent product and the retanning leather-forming process is avoided.

Detailed Description

In this context, a range of values from one value to another is a general expression avoiding any recitation of all values in the range in the specification. Thus, recitation of a range of values herein is intended to encompass any value within the range and any smaller range defined by any value within the range, as if the range and smaller range were explicitly recited in the specification.

As used herein, "retanning agent", "retanning agent product" and "amino resin retanning agent" have the same meaning.

It is worth noting that the dialdehyde monomers used in the following examples are all 40% aqueous solution by mass; the shrinkage temperatures of the blanks in the following examples and comparative examples were measured using a HG shrinkage temperature recorder.

The COD in the waste liquid is tested by the following steps: firstly, under an acidic condition, heating and oxidizing reductive substances in a water sample by using potassium dichromate as an oxidant and silver sulfate as a catalyst, then titrating unreduced potassium dichromate in the water sample by using ferrous sulfate, and calculating the oxygen consumption of the reductive substances in the water according to the consumption of the potassium dichromate.

The method for testing the formaldehyde content comprises the following steps: firstly, 2g of leather sample is put into 50ml of sodium dodecyl sulfate washing liquid with the concentration of 0.1 percent, the washing liquid is shaken for 1 hour at the temperature of 40 ℃, extraction is carried out, then the extraction solution is filtered and reacts with phthalein acetone, and the formaldehyde content in the leather sample is quantitatively determined.

The retanning process used in the following specific examples was:

putting the animal skin clothing raw material or the shaved blue leather of the vamp leather into a rotary drum, sequentially softening, neutralizing and washing by a conventional process, adding 8 percent of amino resin retanning agent and 200 percent of water by weight of the shaved blue leather, rotating for 1h at the temperature of 35 ℃ and the pH value of 5.0-6.0, and then completing the retanning process by conventional dyeing, fatliquoring and acid fixing processes.

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. In practice, the invention will be understood to cover all modifications and variations of this invention provided they come within the scope of the appended claims.