Amphoteric zwitterionic environmentally friendly organic chrome-free tanning agent and method for its preparation

Abstract

The present application relates to a kind of zwitterionic environmentally friendly organic chrome-free tanning agent and its preparation method.First, the prepolymer is prepared using polyisocyanate, cationic hydrophilic monomer, organic acid compound, then the emulsified prepolymer is capped by adding a mixture of aqueous solution of bisulfite and sulfite, and finally the zwitterionic organic chrome-free tanning agent is obtained by adjusting the solid content and pH.The zwitterionic organic chrome-free tanning agent developed in the present application is safe and environmentally friendly, and the wet white leather obtained by tanning has high wet and hot stability and does not contain free formaldehyde.The zwitterionic organic chrome-free tanning agent overcomes the problems of yellowing resistance and insufficient subsequent material combination caused by insufficient positive charge in the general organic tanning system, especially the defects of poor fullness, poor elasticity and poor dyeability caused by insufficient absorption of fatliquoring agents and dyes.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of leather chemical industry, in particular to a zwitterionic environmentally friendly organic chrome-free tanning agent and a preparation method thereof. BACKGROUND

[0002] At present, chrome-free tanning agents and chrome-free tanning methods are mainly divided into four categories, namely, vegetable tanning, non-chromium metal tanning, aldehyde tanning and non-aldehyde organic tanning. The vegetable tanned leather is hard and full, and has certain application in heavy leather and the like, and the tanning agent used is also pure natural plant root stem leaf skin extract tannin, but the vegetable tanning style is not much, and the commonly used four types of tannin such as Chinese scholartree bark, ironwood, chestnut wood and tara are not produced on a large scale in China. Non-chromium metal tanning is researched more, but aluminum tanning, zirconium tanning or zirconium-aluminum multi-metal tanning has problems such as rapid combination of tanning agent with skin collagen, hard leather body, easy washing and the like. Aldehyde tanning is a typical representative of organic tanning, mainly including glutaraldehyde and organic phosphine salt and the like, but the free formaldehyde content in the leather produced by this kind of tanning agent is relatively high, which limits its use. Non-aldehyde organic tanning is a new tanning method applied to leather making in recent years, such as tricyanogen chloride tanning agent, which is a relatively meaningful new tanning agent because it does not produce formaldehyde in the tanning process. However, the water solubility of the tricyanogen chloride tanning agent is not good, the activity of each chlorine atom on the s-triazine ring in tricyanogen chloride is different at different temperatures, the reaction needs stepwise temperature rise, and the construction process is complex, which affects the penetration and combination of the tanning agent in the skin. In addition, most of the non-aldehyde tanning agents developed at present, like aldehyde tanning agents, also mainly rely on the reaction of the tanning agent with the amino group on the collagen fiber, and have the common problem that the white wet skin in the tanning process has less positive charge, and the subsequent retanning, dyeing and finishing materials are difficult to absorb, which results in unsatisfactory performance of the finished leather. SUMMARY

[0003] The existing organic chrome-free tanning agent has poor water solubility, poor penetration, insufficient positive charge of the skin blank, and the subsequent retanning, dyeing and finishing materials are difficult to absorb, which results in problems such as low shrinkage temperature of the finished leather, poor dyeing fastness, flat and thin leather body and the like. In order to solve the above problems, the present application provides a zwitterionic environmentally friendly organic chrome-free tanning agent and a preparation method thereof.

[0004] In the present application, the tertiary amine organic cation hydrophilic monomer is embedded in the molecular structure of the tanning agent, and water-soluble anion reactive groups (aminocarbonyl sulfonate) are introduced at both ends of the molecule. The former can introduce appropriate positive charge into the collagen, and the latter gives the tanning agent excellent water solubility and high reactivity with collagen amino groups. The tanning agent developed in the present application not only anchors in the collagen fibers in the form of covalent bond, so as to form effective crosslinking, but also significantly improves the shrinkage temperature of the skin blank, and effectively solves the problems that the negative charge of the leather body is increased after the general organic tanning agent is combined with the amino group of the collagen, the subsequent fatliquoring agent and dye are difficult to absorb, and the leather dyeing property and fullness are not good.

[0005] The technical scheme of the present application is as follows:

[0006] An amphoteric ionic environmentally-friendly organic chrome-free tanning agent, the structural general formula of which is shown in (1), (2), (3) or (4):

[0007] (1) ;

[0008] (2) ;

[0009] (3) ;

[0010] (4) ;

[0011] wherein RH is a carboxylic compound, and R' is Na or K. The structural general formula of the carboxylic compound can be RH, or written as R - H + Since the carboxylic acid is a weak electrolyte and cannot be completely ionized in the natural state, it is directly represented by the general formula RH.

[0012] The preparation method of the above-mentioned amphoteric ionic environmentally-friendly organic chrome-free tanning agent comprises the following steps:

[0013] (1) The cationic hydrophilic monomer and the polyisocyanate after vacuum dewatering are added to a reactor and reacted at 50-80 DEG C for 2-5 hours. After the NCO reaction reaches the theoretical value, the temperature is lowered to 45 DEG C, a small amount of diluent is added, and the organic acid compound is added and reacted for 0.5-2 hours. Then the system is cooled to 3-30 DEG C to obtain a prepolymer solution.

[0014] (2) The sulfite and bisulfite aqueous solution are added to the prepolymer solution obtained in step (1) in one portion, and the mixture is rapidly stirred and dispersed to obtain a micro-blue to white amphoteric ionic tanning agent emulsion. Deionized water is added to adjust the solid content to 35%, and the emulsion pH is further adjusted to about 4-6 by adding an acid compound to obtain an amphoteric ionic organic chrome-free tanning agent.

[0015] Further, the cationic hydrophilic monomer in step (1) is any one or more of N-methyldiethanolamine, N-(2-cyanoethyl)diethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, N,N-dimethylamino-N',N'-di(2-hydroxyethyl)-1,3-propanediamine, N,N-dimethylamino-N',N'-di(2-hydroxypropyl)-1,3-propanediamine, 3-(dimethylamine)-1,2-propanediol, N,N-dimethyl-(2-dimethylol)butylamine, N,N-diethyl-(2-dimethylol)butylamine, 1,4-butanediol di(3-diethylamino-2-hydroxypropanol) ether, 1,2-ethanediol di(3-diethylamino-2-hydroxypropanol) ether, preferably any one or more of 3-(dimethylamine)-1,2-propanediol, N,N-dimethyl-(2-dimethylol)butylamine, N,N-diethyl-(2-dimethylol)butylamine, 1,4-butanediol di(3-diethylamino-2-hydroxypropanol) ether, 1,2-ethanediol di(3-diethylamino-2-hydroxypropanol) ether.

[0016] Further, the polyisocyanate in step (1) is any one or more of dimethylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated phenylmethane diisocyanate, 1,5-pentane diisocyanate, L-lysine diisocyanate, dimer acid diisocyanate, preferably any one or more of 1,5-pentane diisocyanate, L-lysine diisocyanate, dimer acid diisocyanate.

[0017] Further, the carboxylic compound in step (1) is any one of formic acid, acetic acid, lactic acid, glycolic acid, aspartic acid, glutamic acid.

[0018] Further, the amount of the carboxylic compound in step (1) is 0.8-1.1 times the molar amount of the cationic hydrophilic monomer.

[0019] Further, the diluent in step (1) is any one of dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol methyl ether acetate, propylene carbonate.

[0020] Further, the amount of the diluent in step (1) is not more than 3% of the total mass of the polyisocyanate and the cationic hydrophilic monomer.

[0021] Further, the bisulfite in step (2) is any one of sodium bisulfite, potassium bisulfite; the sulfite is any one of sodium sulfite, potassium sulfite.

[0022] Further, the mass fraction of the mixed aqueous solution of bisulfite and sulfite in step (2) is 20%-35%.

[0023] Further, the acid compound in step (2) is any one of hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, formic acid and acetic acid.

[0024] Further, the dispersion rotation speed in step (2) is 1000r / min-2000r / min, and the dispersion time is 20min-60min.

[0025] Further, the molar ratio of the polyisocyanate, the cationic hydrophilic monomer, the bisulfite and the sulfite in steps (1) and (2) is 1-3:0.5-2:1-6:0.1-2.

[0026] The present application has the following advantages:

[0027] (1) Compared with the traditional chrome tanning, the tanning agent developed in the present application is an organic chrome-free and formaldehyde-free tanning agent, which is safe and environmentally friendly, and the tanned leather does not contain chromium and formaldehyde, thereby avoiding the pollution problems of heavy metals and free formaldehyde.

[0028] (2) The tanning agent developed in the present application contains an amidoformyl sulfonic acid group, which reacts with the amino group of collagen under weak alkaline conditions (pH≥8) to form a urea bond, so that covalent crosslinking occurs between the collagen molecular chains, and tanning effect is produced. Moreover, as the tanning process proceeds, the molecular weight of the tanning agent gradually increases, and different spacings of collagen are crosslinked, so that the tanning effect is further strengthened, and therefore the shrinkage temperature of the tanned white wet leather is high (Ts≥80℃), and the leather body appears full due to the filling of tanning agents with different molecular weights. The chrome-free tanning agent of the present application does not contain formaldehyde, is resistant to yellowing, and the tanned white wet leather is white in color, and is particularly suitable for the preparation of high-grade light-colored leather.

[0029] (3) The chrome-free tanning agent developed in the present application overcomes the problem that after the traditional organic tanning agent is combined with the amino group of collagen, the positive charge of the leather blank is reduced, resulting in excessive negative charge of the leather body, which is not conducive to the combination of synthetic tanning agents, fatliquoring agents and dyes (mainly anionic materials) in the subsequent retanning and dyeing processes, and avoids the general problems of organic tanning such as poor dyeing fastness and thin leather. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 SEM and elemental energy spectrum analysis of the cross section of the white wet leather tanned in Example 2;

[0031] Figure 2 2D and 3D images of the grain surface of the white wet leather tanned in Example 2. DETAILED DESCRIPTION

[0032] The following description is merely exemplary of the present application and is intended to provide an overview for the understanding of the present application and is not intended to limit the scope of the application in any way.

[0033] Example 1

[0034] (1) 1 mol of N,N-dimethyl-(2-dimethylol)butylamine after vacuum dehydration at 105°C and 2.5 mol of 1,5-pentane diisocyanate were added into a reactor and reacted at 50°C for 2 h. After the NCO reaction reached the theoretical value, the temperature was lowered to 45°C, a small amount of dipropylene glycol dimethyl ether was added for dilution, 1.1 mol of glacial acetic acid was added, and the reaction was continued for 0.5 h. Then the system was cooled to 5°C to obtain a prepolymer solution.

[0035] (2) A mixed aqueous solution containing 3 mol of sodium bisulfite and 0.3 mol of sodium sulfite with a mass fraction of 30% was added to the prepolymer solution obtained in step (1) at one time, and dispersed at a speed of 1000 r / min for 30 min to obtain a milky white zwitterionic tanning agent emulsion. Deionized water was added to adjust the solid content to 35%, and a dilute sulfuric acid solution was added to adjust the pH of the emulsion to 4 to obtain a zwitterionic organic chrome-free tanning agent, the structure of which is as follows:

[0036]

[0037] Example 2

[0038] (1) 1.5 mol of N,N-diethyl-(2-dimethylol)butylamine after vacuum dehydration at 105°C and 3 mol of 1,5-pentane diisocyanate were added into a reactor and reacted at 60°C for 3 h. After the NCO reaction reached the theoretical value, the temperature was lowered to 45°C, a small amount of diethylene glycol dimethyl ether was added for dilution, 1.5 mol of glacial acetic acid was added, and the reaction was continued for 1 h. Then the system was cooled to 10°C to obtain a prepolymer solution.

[0039] (2) A mixed aqueous solution containing 3.3 mol of sodium bisulfite and 0.4 mol of sodium sulfite with a mass fraction of 30% was added to the prepolymer solution obtained in step (1) at one time, and dispersed at a speed of 1500 r / min for 50 min to obtain a slightly blue zwitterionic tanning agent emulsion. Deionized water was added to adjust the solid content to 35%, and a dilute hydrochloric acid solution was added to adjust the pH of the emulsion to 5 to obtain a zwitterionic organic chrome-free tanning agent, the structure of which is as follows:

[0040]

[0041] Example 3

[0042] (1) Put 1 mol 1,4-butanediol di(3-diethylamino-2-hydroxypropanol) ether and 3 mol 1,5-pentane diisocyanate into a reactor after vacuum dehydration at 105°C, and react at 80°C for 3 h. After the NCO reaction reaches the theoretical value, cool to 45°C, add propylene glycol methyl ether acetate for dilution, then add 1.1 mol glutamic acid, continue to react for 2 h, and then cool the system to 20°C to obtain a prepolymer solution.

[0043] (2) Add a 25% mass fraction mixed aqueous solution containing 4.5 mol sodium bisulfite and 0.5 mol sodium sulfite to the prepolymer solution obtained in step (1) at one time, and disperse at a speed of 2000 r / min for 60 min to obtain a milky white zwitterionic tanning agent emulsion. Add deionized water to adjust the solid content to 35%, and then add a dilute sulfuric acid solution to adjust the emulsion pH to 5 to obtain a zwitterionic organic chrome-free tanning agent, the structure of which is as follows:

[0044]

[0045] Application of the product of the example

[0046] After the salted sheepskin is subjected to conventional pre-soaking, main soaking, degreasing, lime-soaking and hair removal, weighing, liming, fleshing, weighing, deliming, softening, and washing, it is used for tanning experiments (the dosages of the chemicals used are calculated based on the weight of the limed skin. The specific tanning process is shown in Table 1). The shrinkage temperature, tensile strength, tear strength, and sensory state of the white wet leather obtained by tanning are shown in Table 2. The dye uptake rate in the dyeing process and the observation results of the dyeing effect are shown in Table 4, according to the process method described in Table 3.

[0047] Table 1 Tanning process method

[0048]

[0049] Table 2 Shrinkage temperature and mechanical properties, appearance results of white wet skin

[0050]

[0051] Table 3 Tanning and fatliquoring process

[0052]

[0053] Table 4 Sensory evaluation of raw skin and dyeing effluent uptake effect

[0054]

[0055] As shown in Table 2, the amphoteric ion type environment-friendly organic chrome-free tanning agent developed in the application has high shrinkage temperature (≥80℃) of the sheep white wet leather, good mechanical properties, and clean and fine grain surface of the leather body; as shown in Table 4, the leather blank tanned by the tanning agent has good softness and fullness, good hand feeling, deep color, and light and transparent waste liquid after conventional fatliquoring and dyeing, which indicates that the tanning agent has good absorption performance on the subsequent fatliquoring agent and dye. Figure 1 It can be seen that the skin collagen fibers are fully dispersed after tanning by the amphoteric ion type tanning agent, and present obvious fibrous structure, which indicates that the crosslinking effect of the tanning agent is remarkable. Figure 2 It can be seen that the grain surface of the leather blank is very fine, which is clearly reflected in the 2D and 3D maps.

Claims

1. A zwitterionic organic chromium-free tanning agent, characterized in that, The general structural formulas of tanning agents are shown in (1), (2), (3) or (4): （1） ； （2） ； （3） ； （4） ； In this compound, RH is a carboxylic acid compound, and R' is Na or K.

2. A method for preparing an amphoteric organic chromium-free tanning agent as described in claim 1, characterized in that, Includes the following steps: (1) Add the vacuum-dehydrated cationic hydrophilic monomer and polyisocyanate to the reactor and react at 50-80℃ for 2-5h; after the NCO reaction reaches the theoretical value, cool down to 45℃, add diluent, add carboxylic acid compounds and continue the reaction for 0.5h-2h, then cool the system to 3℃-30℃ to obtain the prepolymer solution; (2) Add a measured amount of bisulfite and sulfite aqueous solution to the prepolymer solution obtained in step (1) at once, stir rapidly, and disperse strongly to obtain a slightly blue to white zwitterionic tanning agent emulsion. Add deionized water to adjust the solid content to 35%, add acidic compound, and further adjust the pH of the emulsion to 4-6 to obtain zwitterionic organic chromium-free tanning agent.

3. The method for preparing an amphoteric organic chromium-free tanning agent according to claim 2, characterized in that, In step (1), the cationic hydrophilic monomer is any one or more of the following: N-methyldiethanolamine, N-(2-cyanoethyl)diethanolamine, N-ethyldiethanolamine, N-propyldiethanolamine, N,N-dimethyl-N',N'-di(2-hydroxyethyl)-1,3-propanediamine, N,N-dimethyl-N',N'-di(2-hydroxypropyl)-1,3-propanediamine, 3-(dimethylamine)-1,2-propanediol, N,N-dimethyl-(2-dihydroxymethyl)butylamine, N,N-diethyl-(2-dihydroxymethyl)butylamine, 1,4-butanediol di(3-diethylamino-2-hydroxypropanol) ether, and 1,2-ethylenediol di(3-diethylamino-2-hydroxypropanol) ether. In step (1), the polyisocyanate is any one or more of the following: dimethylene diisocyanate, isoflurone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, hydrogenated toluene diisocyanate, hydrogenated phenyl dimethylene diisocyanate, hydrogenated phenylmethane diisocyanate, 1,5-pentane diisocyanate, L-lysine diisocyanate, and dimer acid diisocyanate. In step (1), the carboxylic acid compound is any one of formic acid, glacial acetic acid, lactic acid, glycolic acid, aspartic acid, and glutamic acid. In step (1), the amount of carboxylic acid compound used is 0.8-1.1 times the molar amount of the cationic hydrophilic monomer; In step (1), the diluent is any one of dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol methyl ether acetate, and propylene carbonate. In step (1), the amount of diluent used shall not exceed 3% of the total mass of the polyisocyanate and the cationic hydrophilic monomer.

4. The method for preparing an amphoteric organic chromium-free tanning agent according to claim 2, characterized in that, In step (2), the bisulfite is either sodium bisulfite or potassium bisulfite; the sulfite is either sodium sulfite or potassium sulfite. In step (2), the mass fraction of the mixed aqueous solution of bisulfite and sulfite is 20%-35%. In step (2), the acidic compound is any one of hydrochloric acid, sulfuric acid, phosphoric acid, citric acid, formic acid, and acetic acid. In step (2), the dispersion speed is 1000r / min-2000r / min and the dispersion time is 20min-60min.

5. The method for preparing an amphoteric organic chromium-free tanning agent according to claim 2, characterized in that, The cationic hydrophilic monomer mentioned in step (1) is any one or more of 3-(dimethylamine)-1,2-propanediol, N,N-dimethyl-(2-dihydroxymethyl)butylamine, N,N-diethyl-(2-dihydroxymethyl)butylamine, 1,4-butanediol di(3-diethylamino-2-hydroxypropanol) ether, and 1,2-ethylenediol di(3-diethylamino-2-hydroxypropanol) ether; The polyisocyanate mentioned in step (1) is any one or more of 1,5-pentanediisocyanate, L-lysine diisocyanate, and dimer diisocyanate.

6. The method for preparing an amphoteric organic chromium-free tanning agent according to claim 2, characterized in that, In steps (1) and (2), the molar ratio of polyisocyanate, cationic hydrophilic monomer, bisulfite, and sulfite is 1-3:0.5-2:1-6:0.1-2.

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