CN109137573B

CN109137573B - Method for making sandwich style leather

Info

Publication number: CN109137573B
Application number: CN201811033290.4A
Authority: CN
Inventors: 许维奇; 雷丙南
Original assignee: Zhangzhou Xiangzhou Leather Co ltd
Current assignee: Zhangzhou Xiangzhou Leather Co ltd
Priority date: 2018-09-05
Filing date: 2018-09-05
Publication date: 2021-04-13
Anticipated expiration: 2038-09-05
Also published as: CN109137573A

Abstract

The invention relates to a method for manufacturing sandwich style leather, which is characterized in that secondary dyeing is carried out after primary dyeing, and the secondary dyeing comprises a dyeing II process and a pretreatment II, wherein the pH value of the dyeing II process is 3.5-4.0, the drum time is controlled within 5min, and the pretreatment II comprises the processes of rewetting, greasing, fixing and re-fixing the leather material which is dyed out of a drum, ground, cleaned and ash in the drum in sequence. The invention fixes the inner surface of the leather and the surface dye of the leather before the dyeing II treatment through the fixing and re-fixing procedures, enhances the color fastness and reduces the color migration, and is beneficial to finishing the surface dyeing, and the drum time of the dyeing II is controlled within 5min and the pH of the dye solution is controlled to be less than 4.0, so that the dye can be effectively controlled to be uniformly dyed on the surface of the leather without penetrating to the inner surface of the leather, the inner surface is prevented from generating variegated colors, the dyeing is uniform, the color fastness is high, and the sandwich-style leather has strong layering sense, good visual sense and soft leather body.

Description

Method for making sandwich style leather

Technical Field

The invention relates to the technical field of leather treatment, in particular to a method for manufacturing sandwich-style leather.

Background

The existing leather production is basically monochromatic, the color is not bright enough, the mode is fixed and single, and the requirements of consumers can not be met more and more. In order to realize the difference of the surface and the inner color of the leather, the prior method is to dye the surface and the inner surface of the leather simultaneously and then to coat the surface of the dyed leather by adopting a spraying mode to form the surface color which is different from the inner surface color, but the mode has poor color uniformity, low color fastness, easy fading and poor hand feeling.

Disclosure of Invention

In order to overcome the technical defects in the prior art, the invention provides the method for manufacturing the sandwich-style leather, so that the surface and the inner surface of the leather are in two different color styles, the dyeing is uniform, the color fastness is high, and the leather body is soft.

The technical solution adopted by the invention is as follows:

the manufacturing method of the sandwich style leather is characterized in that secondary dyeing is carried out after primary dyeing, the secondary dyeing comprises a dyeing II process and a pretreatment II before the dyeing II process, wherein the pH value of the dyeing II process is 3.5-4.0, the drum time is controlled within 5min, and the pretreatment II comprises the steps of putting the leather material which is dyed out of a drum, ground, cleaned and ash in a rotary drum again and sequentially carrying out rewetting, greasing, fixing and re-fixing processes.

Preferably, the rewetting process specifically includes: and adding 290-310 wt% of water into the drum for 20-25 min, draining, adding water, washing and draining.

Preferably, the re-fatliquoring process specifically comprises: 145-155 percent of water, 1.3-1.5 percent of fatting agent 707, 1.4-1.6 percent of synthetic oil and 0.1-0.2 percent of mildew preventive calculated according to the weight percent of the leather to be dyed twice are added into the rotary drum, and the rotary drum lasts for 28-35 min.

Preferably, the fixing process specifically comprises: adding 0.4 to 0.6 weight percent of formic acid into the rotary drum according to the weight percent of the leather to be dyed twice, and rotating the rotary drum for 10 to 12 min; then adding formic acid accounting for 0.7 to 0.8 percent of the weight percentage of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 14 to 16 min; then discharging liquid, adding water for washing and discharging liquid again.

Preferably, the re-fixing process specifically comprises: adding 290-310 wt% of water and 0.4-0.6 wt% of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 4.5-5.5 min; then adding 1.5 to 1.8 weight percent of aluminum tannin into the rotary drum according to the weight percent of the leather to be dyed twice, and rotating the rotary drum for 20 to 25 min; then adding a color fixing agent accounting for 2.0-2.5 percent of the weight percentage of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 40-45 min; finally discharging liquid, adding water for washing and discharging liquid.

Preferably, the dyeing II process is specifically as follows: adding 400-420 wt% of water and 0.3-0.35 wt% of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, adjusting the pH value to 3.5-4.0 after the rotary drum is used for 4.5-5.5 min, then adding the dye into the rotary drum, and rotating the rotary drum for 250-300 seconds.

Preferably, the leather after dyeing II treatment is continuously subjected to post-treatment II, the specific steps of the post-treatment II sequentially comprise the working procedures of re-fixing, washing water out of a drum, hanging and drying, and drum throwing and color repairing, wherein the re-fixing working procedure specifically comprises the following steps: adding 0.8 to 1.0 weight percent of formic acid into the rotary drum according to the weight percent of the leather to be dyed twice, rotating the drum for 7 to 9min, discharging liquid, adding water, washing and discharging the drum.

Preferably, the specific dyeing steps are a pretreatment I, a dyeing I and a post-treatment I in sequence, wherein the pretreatment I is to carry out water returning, retanning, alkali extraction and neutralization procedures on wet blue leather to be dyed in sequence, and the post-treatment I is to carry out procedures of greasing, color fixing, washing out of a drum, vacuum drying, softening, polishing and ash removal by grinding the leather after the dyeing I in sequence.

Preferably, the dyeing I process is specifically as follows: adding 1.8-2.3% of synthetic tannin, 1.4-1.6% of displaced tannin, 1.8-2.1% of dispersant, 1.0-1.2% of ammonia water and dye into the rotary drum in sequence according to the weight percentage of the wet blue, and then rotating the rotary drum for 55-65 min.

Preferably, the step of greasing specifically comprises: 3.8 to 4.5 percent of sulfited oil, 2.8 to 3.2 percent of synthetic oil, 1.3 to 1.5 percent of fatting agent 707, 0.4 to 0.6 percent of fatting agent AK and 0.1 to 0.2 percent of mildew preventive are sequentially added into the rotary drum according to the weight percentage of the wet blue, and then the rotary drum is rotated for 55 to 65 min.

The invention has the beneficial effects that: according to the invention, the leather is uniformly dyed on the surface and the inner surface of the leather by primary dyeing, and before primary dyeing, the leather is ensured to be more easily dyed and have uniform color tone in the dyeing I through the procedures of pretreatment I such as water return, retanning, alkali extraction and neutralization, and meanwhile, the dyed leather is endowed with soft hand feeling and high color fastness by combining with the post-treatment I; and then, the leather is re-fed into the drum after being dyed out of the drum and cleaned with dust, the surface of the leather material also meets the soft requirement through the procedures of rewetting and grease adding, the inner surface of the leather and the surface dye of the leather before the dyeing II treatment are fixed through the procedures of fixing and re-fixing, the color fastness is enhanced, the color migration is reduced, and the surface dyeing is favorably completed, while the drum time of the dyeing II is controlled within 5min, and the pH of the dyeing solution is controlled to be less than 4.0, so that the dye can be effectively controlled to be uniformly dyed on the surface of the leather without penetrating into the inner surface of the leather, the inner surface is prevented from generating variegated colors, the dyeing is uniform, the color fastness is high, and therefore, the sandwich-style leather disclosed by the invention has strong layering sense.

Detailed Description

The raw materials used in the invention are all commercial products, wherein:

the degreasing agent is a degreasing agent Eusanpon OC which is purchased from Pasteur (China) Co;

the rewetting agent is Youshaban W available from BASF (China) Inc.;

the softening enzyme is Baxinmei B10 available from Bassfu (China) Co.Ltd;

the aldehyde tanning agent is Litan GM from BASF (China) GmbH;

the white tannin is white tannin WT available from Schmidt (Nanjing) leather chemicals, Inc.;

the neutralizer is SYNTAN PN from Schmidt (Nanjing) leather chemicals, Inc.;

acrylic acid is SYNTAN RS3 available from Smit & Zoon;

synthetic tannins are UT from basf (china) ltd;

the displaced tannin is SYNTAN SM available from Schmidt (Nanjing) leather chemicals, Inc.;

the dispersant is Tamol M available from Pasteur (China) Co.Ltd;

the sulfated oil is SULPHIROL EG60 available from Smit & Zoon;

the synthetic oil was SYNTHOL AC available from Smit & Zoon;

the mildew preventive is a mildew preventive TJ-A2233 purchased from New materials GmbH, Sichuan province, Inc.;

the fixing agent is a fixing agent WF purchased from Taiwan Yongphotochemical Industrial Co.

Example 1:

the invention provides a method for manufacturing sandwich-style leather, which is specifically divided into a first dyeing process and a second dyeing process, wherein the first dyeing process sequentially comprises a pretreatment process I, a dyeing process I and a post-treatment process I, and the second dyeing process sequentially comprises a pretreatment process II, a dyeing process II and a post-treatment process II.

The pretreatment I is to carry out water returning, retanning, alkali extraction and neutralization processes on wet blue leather to be dyed in sequence so as to carry out level dyeing and dye through on the leather to be dyed in the dyeing I process. Wherein:

the water return process specifically comprises the following steps: putting wet blue leather into a rotary drum, sequentially adding 200 wt% of water at 40-42 ℃, 0.5 wt% of degreasing agent OC and 0.5 wt% of rewetting agent W into the rotary drum, after 60min of the rotary drum, then adding 1.0 wt% of deliming agent into the rotary drum, after 60min of the rotary drum, then adding 0.8 wt% of softening enzyme B10, 0.6 wt% of oxalic acid and 0.4 wt% of formic acid into the rotary drum, then 60min of the rotary drum, then discharging liquid, then adding water at 40-50 ℃ for washing for 5-10 min, and then discharging liquid.

The leather after backwater treatment is left in the rotary drum for retanning, and the retanning process comprises the following specific steps: and (2) sequentially adding 100% of water and 0.3% of formic acid in percentage by weight of the wet blue leather into the rotary drum, after the rotary drum is rotated for 30min, adding 1.5% of aldehyde tanning agent GX in percentage by weight of the wet blue leather into the rotary drum, after the rotary drum is rotated for 30min, adding 2% of chromium powder and 2% of white tannin WT in percentage by weight of the wet blue leather into the rotary drum, and rotating the rotary drum for 90 min.

And (3) continuously carrying out alkali extraction on the leather after the retanning treatment, wherein the alkali extraction process specifically comprises the following steps: adding 80 percent of water and 1.0 percent of sodium formate according to the weight percent of the wet blue skin into the rotary drum, after the rotary drum is rotated for 30min, then adding 0.5 percent of baking soda according to the weight percent of the wet blue skin into the rotary drum, after the rotary drum is rotated for 30min, adjusting the pH value to 4.0, then discharging the liquid, finally adding 40-50 ℃ water to wash for 5-10 min, and then discharging the liquid.

The leather after the alkali extraction treatment is left in a rotary drum for continuous neutralization, and the neutralization process specifically comprises the following steps: adding 150% of water, 2.0% of sodium formate and 2.0% of neutralizing agent PN into the rotary drum in sequence according to the weight percentage of the wet blue skin, after the rotary drum is rotated for 40min, then adding 1.0% of baking soda, 0.8% of baking soda and 0.5% of sodium sulfite into the rotary drum according to the weight percentage of the wet blue skin, after the rotary drum is rotated for 90min, then adding 1.0% of acrylic acid RS-3 into the rotary drum according to the weight percentage of the wet blue skin, after the rotary drum is rotated for 60min, adjusting the pH to 5.8-6.0, discharging liquid, then adding water at 40-50 ℃ to wash for 5-10 min, and discharging liquid again.

And (3) leaving the leather after the neutralization treatment in a rotary drum to continue dyeing I, wherein the dyeing I process specifically comprises the following steps: 2.0 percent of synthetic tannin UT, 1.5 percent of displaced tannin SM, 2.0 percent of dispersant M, 1.0 percent of ammonia water and dye are sequentially added into the rotary drum according to the weight percentage of the wet blue, and then the rotary drum is used for 60 min.

And (3) reserving the leather treated by the dyeing I in the rotary drum, and then performing aftertreatment I, wherein the aftertreatment I is to sequentially perform the procedures of greasing, color fixation, washing water out of the drum, vacuum drying, softening, buffing and ash sweeping on the leather after the dyeing I so that the leather after the dyeing I has high color fastness and soft hand feeling. Wherein:

the step of greasing specifically comprises the following steps: 4.0 percent of sulfited oil EG60, 3.0 percent of synthetic oil AC, 1.5 percent of fatting agent 707, 0.5 percent of fatting agent AK and 0.1 percent of mildew preventive TJ-A2233 are added into the rotary drum in sequence according to the weight percentage of the blue wet skin, and then the rotary drum is rotated for 60 min.

And (3) continuously fixing the color after the fatliquoring treatment, wherein the color fixing process specifically comprises the following steps: adding 150% of water in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 5 min; then adding 0.5 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 10 min; then adding 0.5 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 10 min; then adding 0.5 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 10 min; finally, adding 0.5 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 15 min; then discharging liquid, adding water for washing and discharging from the drum.

And (3) drying the leather after being discharged from the drum in a vacuum dryer at the drying temperature of 55-60 ℃ and the drying humidity of 40% for 8min, then drying the dried leather in a drying box at the drying temperature of 65-70 ℃ and the drying humidity of 12.2%, and then softening and polishing the dried leather in sequence and sweeping ash to finish primary dyeing.

And (2) performing secondary dyeing pretreatment II after the primary dyeing is finished, wherein the pretreatment II is to perform the procedures of re-returning water, re-greasing, fixing and re-fixing on the leather to be dyed two in sequence so as to uniformly dye the surface of the leather to be dyed two in the dyeing II procedure. Wherein:

putting the leather to be dyed after the leather grinding and ash sweeping treatment into a rotary drum for further rewetting, wherein the rewetting process specifically comprises the following steps: and adding 300 percent of water in percentage by weight of the leather to be dyed into the rotary drum, discharging the liquor after the rotary drum is used for 20min, then adding water, washing and discharging the liquor.

And (3) continuously re-greasing the leather subjected to the rewetting treatment, wherein the re-greasing process specifically comprises the following steps: 150 percent of water with the temperature of 40-42 ℃, 1.5 percent of fatting agent 707, 1.5 percent of synthetic oil AC and 0.1 percent of mildew preventive TJ-A2233 which are calculated according to the weight percentage of the leather to be dyed twice are added into the rotary drum, and the rotary drum is rotated for 30 min.

And (3) continuously fixing the leather after the grease adding treatment, wherein the fixing process specifically comprises the following steps: adding 0.5 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 10 min; then adding 0.7 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 15 min; then discharging liquid, adding water for washing and discharging liquid again.

The leather after the fixing treatment is left in the rotary drum to be continuously fixed, and the color fixing process comprises the following specific steps: adding 300 percent of water with the temperature of 50-52 ℃ and 0.5 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 5.0 min; then adding 1.5 percent of aluminum tannin in percentage by weight of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 20 min; then adding a color fixing agent WF accounting for 2.0 percent of the weight percentage of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 40 min; finally discharging liquid, adding water for washing and discharging liquid.

And (3) leaving the leather subjected to the re-fixation treatment in the rotary drum to continue dyeing II, wherein the dyeing II process specifically comprises the following steps: adding 400% of water and 0.3% of formic acid in percentage by weight of the leather to be dyed twice into the rotary drum, adjusting the pH value to 3.5-4.0 after the rotary drum is used for 5.0min, then adding the dye into the rotary drum, and rotating the rotary drum for 220 seconds.

And (3) leaving the leather treated by the dyeing II in the rotary drum to continue carrying out post-treatment II, wherein the post-treatment II is to sequentially carry out the working procedures of re-fixing, washing, drum discharging, hanging, drying, drum throwing and color repairing on the leather treated by the dyeing II so that the surface of the leather treated by the dyeing II is dyed uniformly and has high color fastness, cannot permeate into the inner surface and has soft hand feeling. Wherein: the re-fixing process specifically comprises the following steps: and adding 0.8 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, rotating the rotary drum for 8min, discharging liquid, adding water, washing and discharging the drum.

Example 2:

the water return process specifically comprises the following steps: putting wet blue leather into a rotary drum, adding 190 wt% of water at 40-42 ℃, 0.4 wt% of degreasing agent OC and 0.4 wt% of rewetting agent W into the rotary drum in sequence, after 65min of the rotary drum, adding 1.0 wt% of deliming agent into the rotary drum, after 65min of the rotary drum, adding 0.8 wt% of softening enzyme B10, 0.5 wt% of oxalic acid and 0.2 wt% of formic acid into the rotary drum, after 65min of the rotary drum, draining, adding 40-50 wt% of water, washing for 5-10 min, and draining.

The leather after backwater treatment is left in the rotary drum for retanning, and the retanning process comprises the following specific steps: and sequentially adding 90% of water and 0.2% of formic acid in percentage by weight of the wet blue leather into the rotary drum, after 35min of the rotary drum, adding 1.5% of aldehyde tanning agent GX in percentage by weight of the wet blue leather into the rotary drum, after 30min of the rotary drum, adding 2.3% of chromium powder and 2.3% of white tannin WT in percentage by weight of the wet blue leather into the rotary drum, and rotating the rotary drum for 92 min.

And (3) continuously carrying out alkali extraction on the leather after the retanning treatment, wherein the alkali extraction process specifically comprises the following steps: adding 75 percent of water and 1.0 percent of sodium formate according to the weight percent of the wet blue leather into the rotary drum, adding 0.4 percent of baking soda according to the weight percent of the wet blue leather into the rotary drum after 35min of the rotary drum, adjusting the pH value to 4.0 after 35min of the rotary drum, discharging the liquid, finally adding 40-50 ℃ of water, washing for 5-10 min, and discharging the liquid.

The leather after the alkali extraction treatment is left in a rotary drum for continuous neutralization, and the neutralization process specifically comprises the following steps: adding 145% of water, 1.8% of sodium formate and 1.8% of neutralizing agent PN into the rotary drum in sequence according to the weight percentage of the wet blue skin, after the rotary drum is rotated for 45min, then adding 1.0% of baking soda, 0.7% of baking soda and 0.4% of sodium sulfite into the rotary drum according to the weight percentage of the wet blue skin, after the rotary drum is rotated for 95min, then adding 1.0% of acrylic acid RS-3 into the rotary drum according to the weight percentage of the wet blue skin, after the rotary drum is rotated for 65min, adjusting the pH to 5.8-6.0, discharging liquid, then adding water at 40-50 ℃ to wash for 5-10 min, and discharging liquid again.

And (3) leaving the leather after the neutralization treatment in a rotary drum to continue dyeing I, wherein the dyeing I process specifically comprises the following steps: 1.8 percent of synthetic tannin UT, 1.4 percent of displaced tannin SM, 1.8 percent of dispersant M, 1.0 percent of ammonia water and dye are sequentially added into the rotary drum according to the weight percentage of the wet blue, and then the rotary drum is used for 65 min.

the step of greasing specifically comprises the following steps: 3.8 percent of sulfited oil EG60, 2.8 percent of synthetic oil AC, 1.3 percent of fatting agent 707, 0.4 percent of fatting agent AK and 0.1 percent of mildew preventive TJ-A2233 are sequentially added into the rotary drum according to the weight percentage of the wet blue, and then the rotary drum is rotated for 65 min.

And (3) continuously fixing the color after the fatliquoring treatment, wherein the color fixing process specifically comprises the following steps: adding 150% of water in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 6 min; then adding 0.4 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 12 min; then adding 0.4 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 12 min; then adding 0.4 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 12 min; finally, adding 0.4 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 16 min; then discharging liquid, adding water for washing and discharging from the drum.

And (3) drying the leather after being discharged from the drum in a vacuum dryer at the drying temperature of 55-60 ℃ and the drying humidity of 43-45% for 9min, then drying the dried leather in a drying box at the drying temperature of 65-70 ℃ and the drying humidity of 13.6%, and then softening, grinding and ash-sweeping the dried leather in sequence, thereby finishing primary dyeing.

putting the leather to be dyed after the leather grinding and ash sweeping treatment into a rotary drum for further rewetting, wherein the rewetting process specifically comprises the following steps: and adding 290% of water in percentage by weight of the leather to be dyed into the rotary drum, discharging the liquid after the rotary drum is rotated for 25min, then adding water, washing and discharging the liquid.

And (3) continuously re-greasing the leather subjected to the rewetting treatment, wherein the re-greasing process specifically comprises the following steps: 145 percent of water with the temperature of 40-42 ℃, 1.3 percent of fatting agent 707, 1.4 percent of synthetic oil AC and 0.1 percent of mildew preventive TJ-A2233 which are calculated according to the weight percentage of the leather to be dyed twice are added into the rotary drum, and the rotary drum lasts for 35 min.

And (3) continuously fixing the leather after the grease adding treatment, wherein the fixing process specifically comprises the following steps: adding 0.4 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 12 min; then adding 0.7 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 16 min; then discharging liquid, adding water for washing and discharging liquid again.

The leather after the fixing treatment is left in the rotary drum to be continuously fixed, and the color fixing process comprises the following specific steps: adding 290% of water with the temperature of 50-52 ℃ and 0.4% of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 5.5 min; then adding 1.5 percent of aluminum tannin in percentage by weight of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 25 min; then adding a color fixing agent WF accounting for 2.0 percent of the weight percentage of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 45 min; finally discharging liquid, adding water for washing and discharging liquid.

And (3) leaving the leather subjected to the re-fixation treatment in the rotary drum to continue dyeing II, wherein the dyeing II process specifically comprises the following steps: adding 400% of water and 0.3% of formic acid in percentage by weight of the leather to be dyed twice into the rotary drum, adjusting the pH value to 3.5-4.0 after 5.5min of the rotary drum, adding the dye into the rotary drum, and rotating the rotary drum for 280 seconds.

And (3) leaving the leather treated by the dyeing II in the rotary drum to continue carrying out post-treatment II, wherein the post-treatment II is to sequentially carry out the working procedures of re-fixing, washing, drum discharging, hanging, drying, drum throwing and color repairing on the leather treated by the dyeing II so that the surface of the leather treated by the dyeing II is dyed uniformly and has high color fastness, cannot permeate into the inner surface and has soft hand feeling. Wherein: the re-fixing process specifically comprises the following steps: and adding 0.8 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, rotating the rotary drum for 9min, discharging liquid, adding water, washing and discharging the drum.

Example 3:

the water return process specifically comprises the following steps: putting wet blue leather into a rotary drum, adding 210 wt% of water at 40-42 ℃, 0.6 wt% of degreasing agent OC and 0.6 wt% of rewetting agent W into the rotary drum in sequence, after 55min of the rotary drum, adding 1.2 wt% of deliming agent into the rotary drum, after 55min of the rotary drum, adding 1.0 wt% of softening enzyme B10, 0.7 wt% of oxalic acid and 0.4 wt% of formic acid into the rotary drum, after 55min of the rotary drum, draining, adding water at 40-50 ℃ for washing for 5-10 min, and draining.

The leather after backwater treatment is left in the rotary drum for retanning, and the retanning process comprises the following specific steps: and (2) sequentially adding 110% of water and 0.4% of formic acid in percentage by weight of the wet blue leather into the rotary drum, after the rotary drum is rotated for 25min, adding 1.8% of aldehyde tanning agent GX in percentage by weight of the wet blue leather into the rotary drum, after the rotary drum is rotated for 25min, adding 3% of chromium powder and 3% of white tannin WT in percentage by weight of the wet blue leather into the rotary drum, and rotating the rotary drum for 85 min.

And (3) continuously carrying out alkali extraction on the leather after the retanning treatment, wherein the alkali extraction process specifically comprises the following steps: adding 85 percent of water and 1.2 percent of sodium formate according to the weight percent of the wet blue leather into the rotary drum, adding 0.6 percent of baking soda according to the weight percent of the wet blue leather into the rotary drum after the rotary drum is carried out for 25min, adjusting the pH value to 4.0 after the rotary drum is carried out for 25min, discharging the liquid, finally adding water with the temperature of 40-50 ℃ for washing for 5-10 min, and discharging the liquid.

The leather after the alkali extraction treatment is left in a rotary drum for continuous neutralization, and the neutralization process specifically comprises the following steps: adding 155% of water, 2.1% of sodium formate and 2.1% of neutralizing agent PN into the rotary drum in sequence according to the weight percentage of the wet blue skin, after 35min of the rotary drum, adding 1.2% of baking soda, 0.9% of baking soda and 0.6% of sodium sulfite into the rotary drum according to the weight percentage of the wet blue skin, after 85min of the rotary drum, adding 1.2% of acrylic acid RS-3 into the rotary drum according to the weight percentage of the wet blue skin, after 55min of the rotary drum, adjusting the pH to 5.8-6.0, discharging liquid, then adding 40-50 ℃ of water, washing for 5-10 min, and discharging liquid.

And (3) leaving the leather after the neutralization treatment in a rotary drum to continue dyeing I, wherein the dyeing I process specifically comprises the following steps: 2.3 percent of synthetic tannin UT, 1.6 percent of displaced tannin SM, 2.1 percent of dispersant M, 1.2 percent of ammonia water and dye are sequentially added into the rotary drum according to the weight percentage of the wet blue, and then the rotary drum is rotated for 55 min.

the step of greasing specifically comprises the following steps: 4.5 percent of sulfited oil EG60, 3.2 percent of synthetic oil AC, 1.5 percent of fatting agent 707, 0.6 percent of fatting agent AK and 0.2 percent of mildew preventive TJ-A2233 are added into the rotary drum in sequence according to the weight percentage of the blue wet skin, and then the rotary drum is rotated for 55 min.

And (3) continuously fixing the color after the fatliquoring treatment, wherein the color fixing process specifically comprises the following steps: adding 160% of water in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 4 min; then adding 0.6 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 10 min; then adding 0.6 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 10 min; then adding 0.6 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 10 min; finally, adding 0.6 percent of formic acid in percentage by weight of the wet blue into the rotary drum, and rotating the rotary drum for 14 min; then discharging liquid, adding water for washing and discharging from the drum.

And (3) placing the leather after being discharged from the drum in a vacuum drier for drying at the drying temperature of 60-65 ℃ and the drying humidity of 40-42% for 7min, then placing the dried leather in a drying box for drying at the drying temperature of 70-75 ℃ and the drying humidity of 10.5%, and then softening, grinding and sweeping the leather of the dried leather in sequence to finish primary dyeing.

putting the leather to be dyed after the leather grinding and ash sweeping treatment into a rotary drum for further rewetting, wherein the rewetting process specifically comprises the following steps: and adding 310 percent of water by weight percentage of the leather to be dyed into the rotary drum, discharging the liquid after the rotary drum is used for 20min, then adding water, washing and discharging the liquid.

And (3) continuously re-greasing the leather subjected to the rewetting treatment, wherein the re-greasing process specifically comprises the following steps: 155 percent of water with the temperature of 40-42 ℃, 1.5 percent of fatting agent 707, 1.6 percent of synthetic oil AC and 0.2 percent of mildew preventive TJ-A2233 which are calculated according to the weight percentage of the leather to be dyed twice are added into the rotary drum, and the rotary drum is rotated for 28 min.

And (3) continuously fixing the leather after the grease adding treatment, wherein the fixing process specifically comprises the following steps: adding 0.6 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 10 min; then adding 0.8 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 14 min; then discharging liquid, adding water for washing and discharging liquid again.

The leather after the fixing treatment is left in the rotary drum to be continuously fixed, and the color fixing process comprises the following specific steps: adding 310 percent of water with the temperature of 50-52 ℃ and 0.6 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 4.5 min; then adding 1.8 percent of aluminum tannin in percentage by weight of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 20 min; then adding a color fixing agent WF accounting for 2.5 percent of the weight percentage of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 40 min; finally discharging liquid, adding water for washing and discharging liquid.

And (3) leaving the leather subjected to the re-fixation treatment in the rotary drum to continue dyeing II, wherein the dyeing II process specifically comprises the following steps: adding 420% of water and 0.35% of formic acid in percentage by weight of the leather to be dyed twice into the rotary drum, adjusting the pH value to 3.5-4.0 after the rotary drum is used for 4.5min, then adding the dye into the rotary drum, and rotating the rotary drum for 150 seconds.

And (3) leaving the leather treated by the dyeing II in the rotary drum to continue carrying out post-treatment II, wherein the post-treatment II is to sequentially carry out the working procedures of re-fixing, washing, drum discharging, hanging, drying, drum throwing and color repairing on the leather treated by the dyeing II so that the surface of the leather treated by the dyeing II is dyed uniformly and has high color fastness, cannot permeate into the inner surface and has soft hand feeling. Wherein: the re-fixing process specifically comprises the following steps: adding 1.0 percent of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, rotating the rotary drum for 7min, then discharging liquid, adding water, washing and discharging the drum.

Comparative example 1:

this comparative example also provides a leather manufacturing process which differs from the process steps and parameter settings of example 2 above only in that: the treatment solution of comparative example 1, which had a pH of greater than 4.0 and a tumbler time of 320 seconds, was used.

Comparative example 2:

this comparative example also provides a leather manufacturing process which differs from the process steps and parameter settings of example 2 above only in that: this comparative example 2 lacks the refixation procedure of example 2 and the pH of the treatment liquor of the dyeing ii procedure of this comparative example 2 is greater than 4.0.

The leather produced in the above examples 1 to 3 and comparative examples 1 to 2 were subjected to the following physical property index tests, and the test results were shown in Table I.

Table one: tables of results of leather tests obtained in examples 1 to 3 and comparative examples 1 to 2

Item	Test method	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2
							Softness (mm)	ISO17235	3.5	3.4	3.5	3.4	3.4
Bending resistance (times)	DIN EN ISO 5402	More than 10 ten thousand	More than 10 ten thousand	More than 10 ten thousand	More than 10 ten thousand	More than 10 ten thousand
							Color fastness to rubbing: dry wiping	DIN EN ISO 11640	4-5	4-5	4-5	4-5	3-4
Color fastness to rubbing: wet eraser	DIN EN ISO 11640	4-5	4-5	4-5	4-5	4
							Yellowing resistance (grade)	ASTMD1148-095	4	3.5	4	4	3
Color migration (grade)	ISO15701	4-5	4-5	4-5	3-4	3-4
							The inner surface has no mottle	Sensory testing	Qualified	Qualified	Qualified	Fail to be qualified	Fail to be qualified

While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be understood by those skilled in the art that the invention is not limited by the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Claims

1. The method for manufacturing the sandwich style leather is characterized in that secondary dyeing is carried out after primary dyeing, and the secondary dyeing comprises a dyeing II process and a pretreatment II before the dyeing II process, wherein the pretreatment II comprises the steps of putting a leather material which is dyed out of a drum, ground, cleaned and ash-swept in a rotary drum again, and carrying out rewetting, greasing, fixing and re-fixing in sequence; the dyeing II process specifically comprises the following steps: adding 400-420 wt% of water and 0.3-0.35 wt% of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, adjusting the pH value to 3.5-4.0 after the rotary drum is used for 4.5-5.5 min, then adding the dye into the rotary drum, and rotating the rotary drum for 150-300 seconds.

2. The method of making sandwich-style leather of claim 1, wherein the rewetting step is specifically: and adding 290-310 wt% of water into the drum for 20-25 min, draining, adding water, washing and draining.

3. The method of making sandwich-style leather of claim 1, wherein the re-fatliquoring process comprises: 145-155 percent of water, 1.3-1.5 percent of fatting agent 707, 1.4-1.6 percent of synthetic oil and 0.1-0.2 percent of mildew preventive calculated according to the weight percent of the leather to be dyed twice are added into the rotary drum, and the rotary drum lasts for 28-35 min.

4. The method of manufacturing sandwich-style leather of claim 1, wherein the fixing process comprises: adding 0.4 to 0.6 weight percent of formic acid into the rotary drum according to the weight percent of the leather to be dyed twice, and rotating the rotary drum for 10 to 12 min; then adding formic acid accounting for 0.7 to 0.8 percent of the weight percentage of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 14 to 16 min; then discharging liquid, adding water for washing and discharging liquid again.

5. The method for making sandwich-style leather of claim 1, wherein the re-fixing step specifically comprises: adding 290-310 wt% of water and 0.4-0.6 wt% of formic acid into the rotary drum according to the weight percentage of the leather to be dyed twice, and rotating the rotary drum for 4.5-5.5 min; then adding 1.5 to 1.8 weight percent of aluminum tannin into the rotary drum according to the weight percent of the leather to be dyed twice, and rotating the rotary drum for 20 to 25 min; then adding a color fixing agent accounting for 2.0-2.5 percent of the weight percentage of the leather to be dyed twice into the rotary drum, and rotating the rotary drum for 40-45 min; finally discharging liquid, adding water for washing and discharging liquid.

6. The method for manufacturing sandwich-style leather according to claim 1, wherein the leather material after the dyeing II treatment is subjected to a post-treatment II, and the post-treatment II comprises the following specific steps of re-fixing, washing water out of a drum, hanging and drying, and drum dropping and color repairing, wherein the re-fixing step specifically comprises the following specific steps: adding 0.8 to 1.0 weight percent of formic acid into the rotary drum according to the weight percent of the leather to be dyed twice, rotating the drum for 7 to 9min, discharging liquid, adding water, washing and discharging the drum.

7. The method for manufacturing sandwich style leather according to claim 1, wherein the dyeing step comprises a pretreatment step I, a dyeing step I and a post-treatment step I in sequence, wherein the pretreatment step I comprises the steps of carrying out water returning, retanning, alkali extraction and neutralization on wet blue leather to be dyed in sequence, and the post-treatment step I comprises the steps of carrying out fatliquoring, color fixing, washing water out of a drum, vacuum drying, softening, polishing and ash removal on leather dyed in sequence.

8. The method for manufacturing sandwich-style leather according to claim 7, wherein the dyeing step I comprises: adding 1.8-2.3% of synthetic tannin, 1.4-1.6% of displaced tannin, 1.8-2.1% of dispersant, 1.0-1.2% of ammonia water and dye into the rotary drum in sequence according to the weight percentage of the wet blue, and then rotating the rotary drum for 55-65 min.

9. The method of making sandwich-style leather of claim 7, wherein the step of fatliquoring is specifically: 3.8 to 4.5 percent of sulfited oil, 2.8 to 3.2 percent of synthetic oil, 1.3 to 1.5 percent of fatting agent 707, 0.4 to 0.6 percent of fatting agent AK and 0.1 to 0.2 percent of mildew preventive are sequentially added into the rotary drum according to the weight percentage of the wet blue, and then the rotary drum is rotated for 55 to 65 min.