阅读说明：本技术 环保植鞣弹力皮革产品复鞣片皮工艺 (Retanning splitting process for environment-friendly vegetable elastic leather product ) 是由 仲济德 冯献青 段旭阳 查姣 冯雪伟 汤海涛 王丹 于 2020-08-28 设计创作，主要内容包括：本发明属于弹力皮革产品的生产技术领域,公开了一种环保植鞣弹力皮革产品复鞣片皮工艺,包括以下步骤：1)将弹力皮革胚皮进行回水；2)复鞣；3)染色；4)加脂；5)搭马、挤水、吊晾；6)板面喷水、静置、摔软；7)片皮：将皮片至0.2mm厚度；8)背胶；9)静置、回鼓酸洗；10)搭马、挤水、吊晾；11)板面喷水、静置、摔软。本发明加工工艺处理的植鞣弹力皮革服饰产品,保持了良好的弹性、皮身强度、薄度、均匀度。(The invention belongs to the technical field of production of elastic leather products, and discloses an environment-friendly retanning splitting process for a vegetable tanning elastic leather product, which comprises the following steps: 1) returning water to the elastic leather embryonic skin; 2) retanning; 3) dyeing; 4) fat liquoring; 5) building, squeezing water, and hanging and airing; 6) spraying water on the board surface, standing and milling; 7) splitting into sheets: the leather sheet is made to be 0.2mm thick; 8) carrying out gum application; 9) standing and back-drum pickling; 10) building, squeezing water, and hanging and airing; 11) spraying water on the board surface, standing and softening. The vegetable-tanned elastic leather clothing product treated by the processing technology keeps good elasticity, skin strength, thinness and uniformity.)

1. The retanning splitting process of the environment-friendly elastic vegetable tanning leather product is characterized by comprising the following steps of:

1) elastic leather embryonic skin is backwashed, and the backwashed materials comprise the following components in parts by weight of the embryonic skin: 200 percent of water, 40 ℃, 0.2 percent of acetic acid, 1 percent of rewetting auxiliary agent BPR or rewetting auxiliary agent VLC-3 and 0.5 percent of synthetic fatting agent NP-2;

2) retanning: adding the following components in parts by weight of the embryonic skin into a rotary drum: 100% of water, 40 ℃, 1% of tearing-resistant fatting agent NZ or universal fatting agent WWL, 2% of sulfonated fatting agent TIS or sulfited fatting agent CFS, 0.2% of emulsifier SAF or emulsifier ML-N, rotating for 30 minutes, pre-fatting the embryo skin after water return, then adding 0.8% of formic acid, rotating for 20 minutes, adding 6% of environment-friendly tanning agent TWE, rotating for 60 minutes, adding 1% of sodium formate, rotating for 90 minutes, adjusting the pH value of bath liquid to 3.6-3.8, rotating the rotary drum for 5 minutes per hour overnight, draining water, and washing twice with cold water;

3) dyeing;

4) fat liquoring;

5) building, squeezing water, and hanging and airing;

6) spraying water on the board surface, standing and milling;

7) splitting into sheets: the leather sheet is made to be 0.2mm thick;

8) carrying out gum application;

9) standing and back-drum pickling: the material selected by the drum-returning pickling comprises the following components in parts by weight of the embryo skin: 500% of water, 30 ℃, 0.6% of acetic acid, 1% of synthetic fatting agent NP-2 or synthetic fatting agent GLH;

10) building, squeezing water, and hanging and airing;

11) spraying water on the board surface, standing and softening.

2. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 1, is characterized in that: the backwater in the step 1) is that materials selected for backwater are sequentially added into a rotary drum, the rotary drum is uniformly rotated and then quickly thrown into the skin, the rotary drum is rotated for 60 minutes, the rotary drum rotates for 5 minutes per hour and is kept overnight for 4 hours, and the rotary drum is drained and washed once by cold water.

3. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 1, is characterized in that: the dyeing of step 3) comprises: adding the following components in parts by weight of the embryonic skin into a rotary drum: 400% of water, 30 ℃ of temperature, 2% of a rewetting assistant PERMIT 2L or a rewetting assistant ML-N, 2% of a fatliquoring agent LIPSOL SQS, rotating for 30 minutes, then adding 2% of a leveling agent, 2% -4% of MELIODERM HF series dyeing plate dye, rotating for 60 minutes, adding 1% of acetic acid, rotating for 20 minutes, adding 0.5% of formic acid, rotating for 20 minutes, draining, and cleaning for 2 times.

4. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 3, characterized in that: IN the step 3), the leveling agent is a leveling agent NNOL, a leveling agent TF-2N or a leveling agent CORALON OT-IN POWDER;

the MELIODERM HF series dye plate dye is selected from at least one of MELIODERM HF Brown G, MELIODERM HF Brown R, MELIODERM HF Brown DGV, MELIODERM HF Pardo DGV, MELIODERM HF Havana AN, MELIODERM HF Beige D, MELIODERM HF Dark Brown MP, MELIODERM HF Grey GB, MELIODERM HF Grey N and MELIODERM HF Grey LL.

5. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 1, is characterized in that: the step 4) of fatliquoring comprises the following steps: adding the following components in parts by weight of the embryonic skin into a rotary drum: 100% water, 55 deg.C, 2% neutralized tannin PAK-N or neutralized tannin MP3, rotating for 30 min, adding 2% synthetic tanning agent BASYTAN DLE liquid, 2% filled polymer TERGOTAN PMB or filled polymer IPF, rotating for 45 min, adding 3% lecithin fatting agent DERMINOL NLM or lecithin fatting agent PROVOL BA, 3% synthetic fatting agent DX1202, 0.5% emulsifier SAF or emulsifier ML-N, rotating for 120 min, adding 1% acetic acid, rotating for 45 min, adding 0.5% formic acid, rotating for 30 min, measuring pH of bath liquid to 3.9, draining, and washing with cold water twice.

6. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 1, is characterized in that: in the step 5) and the step 10), the step of erecting comprises the following steps: leveling and setting up, and standing for 12 hours; the water squeezing comprises the following steps: adopting a reciprocating wringing machine and a 3-knife method to wring water once; and the hanging and airing process is natural airing.

7. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 1, is characterized in that: in step 6) and step 11), the standing step includes: standing the plate-to-plate, wrapping and standing for 6-8 hours by using film paper; the breaking comprises the following steps: the water content of the board surface is measured to be 22 degrees +/-1, and the board surface is rotated for 2 hours.

8. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 1, is characterized in that: in the step 7), a passing type sheet splitting machine is adopted for splitting the sheets, the thickness of the sheets is adjusted to 0.2mm, and the sheets are transversely passed once.

9. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 1, is characterized in that: in the step 8), the leather and the base cloth are bonded by a through-type back gluing machine.

10. The process for retanning split leather of environment-friendly elastic vegetable tanning leather products according to claim 1, is characterized in that: in step 9), the standing step comprises: leveling and setting up, and standing for 12 hours; the drum-returning acid washing is to add the materials selected by the drum-returning acid washing into a rotating drum in sequence, quickly throw the skin after uniform rotation, rotate for 30 minutes, drain water and wash with cold water once.

Technical Field

The invention belongs to the technical field of elastic leather product production, and particularly relates to an environment-friendly retanning splitting process for a vegetable tanning elastic leather product.

Background

Two major problems currently exist with respect to the production of vegetable-tanned resilient leather apparel products: pure vegetable tanned leather has the great defects of low physical property and poor tensile and tear resistance, elastic leather is required to keep high extensibility, and subsequent leather sheets are required to have good uniformity to an extremely thin thickness, which brings great challenge to a retanning procedure of a water field and needs to improve the uniformity and strength of a leather body through retanning; secondly, the thickness of the elastic leather is required to be uniform and consistent, and is mostly kept at 0.2mm, and on the basis of the light and thin structure, the elasticity is required to be kept, which brings great challenges to the precision of the splitting machine. These factors directly affect the quality and stability of the production and processing of the environment-friendly vegetable tanning elastic leather.

As is well known, elastic dress fabric products consistently pursue excellent high elasticity, high physical property, lightness, thinness, naturalness and comfortable wearing, and the elastic dress products made of environment-friendly plant tanned leather have the value of nature, safety and sanitation, so the elastic dress fabric products are deeply favored by consumers at home and abroad, and the plant tanned elastic leather dress products in the market are often in short supply. Therefore, on the premise of energy conservation, emission reduction and environmental protection, the technical problem of retanning the vegetable elastic leather into the piece leather is solved, and the economic benefit and the environmental benefit are achieved.

At present, the main technical means aiming at the problem of retanning split leather of environment-friendly vegetable tanning elastic leather in the industry comprises the following steps: firstly, in the retanning procedure, a proper amount of chrome-containing tanning agent is added, and other tanning assisting agents are used for combined tanning to promote adsorption and fixation of chrome, so that the aim of improving the strength and physical properties of the leather body is fulfilled; secondly, the thickness of the split leather is increased a little compared with the expected thickness of the split leather due to insufficient precision of the common splitting machine, and then the thickness of the leather is reduced by shaving and buffing, so that the finished product thinness required by the elastic leather is achieved. The physical property of the vegetable-tanned elastic leather and the operability of the splitting process are improved through the two points, and mechanical damage is reduced as much as possible.

Even if the above technical means are adopted, the prior art still has the following defects: firstly, the treatment effect is poor, the tearing strength of the leather is general, the sanitary performance of the leather body is poor, the problem of insufficient physical property of the leather is difficult to effectively solve only through the combined tanning with the chromium powder, and through multiple production verification, even if the conventional combined tanning treatment methods of chromium-aluminum, chromium-chromium, aldehyde-chromium and the like are adopted, the problem of poor strength of the leather body of the finished elastic leather product in a certain proportion still occurs, and the wearing experience of a client is influenced; the working procedure is long, the shaving procedure and the leather grinding procedure are needed to further thin the leather, the production cost is increased, and the production period is prolonged; the performance of finished products, such as the fullness, softness, waterproof performance and the like of leather boards can be improved by adding the chromium-containing chemical material in the retanning process, but the potential hazards in environmental protection and safety are also caused, and one thing is that chromium-containing waste cannot be effectively treated and is harmful to the environment; secondly, the finished product of the chrome tanned leather contains trace hexavalent chromium, and the safety of long-term wearing cannot be guaranteed.

Disclosure of Invention

In view of the above situation, the present invention aims to provide an environment-friendly retanning process for a vegetable-tanned elastic leather product, which can effectively solve the technical problem of retanning the vegetable-tanned elastic leather, and the vegetable-tanned elastic leather clothing product treated by the present invention maintains good high elasticity, skin strength, thinness and uniformity, and has extremely high customer acceptance.

The invention provides an environment-friendly retanning leather sheet process for a vegetable tanning elastic leather product, which comprises the following steps:

1) elastic leather embryonic skin is backwashed, and the backwashed materials comprise the following components in parts by weight of the embryonic skin: 200 percent of water, 40 ℃, 0.2 percent of acetic acid, 1 percent of rewetting auxiliary agent BPR or rewetting auxiliary agent VLC-3 and 0.5 percent of synthetic fatting agent NP-2;

2) retanning: adding the following components in parts by weight of the embryonic skin into a rotary drum: 100% of water, 40 ℃, 1% of tearing-resistant fatting agent NZ or universal fatting agent WWL, 2% of sulfonated fatting agent TIS or sulfited fatting agent CFS, 0.2% of emulsifier SAF or emulsifier ML-N, rotating for 30 minutes, pre-fatting the embryo skin after returning water, then adding 0.8% of formic acid, rotating for 20 minutes, adding 6% of environment-friendly tanning agent TWE, rotating for 60 minutes, adding 1% of sodium formate, rotating for 90 minutes, adjusting the pH value of bath liquid to 3.6-3.8, draining water, and washing twice with cold water;

3) dyeing;

4) fat liquoring;

5) building, squeezing water, and hanging and airing;

6) spraying water on the board surface, standing and milling;

7) splitting into sheets: the leather sheet is made to be 0.2mm thick;

8) carrying out gum application;

9) standing and back-drum pickling: the material selected by the drum-returning pickling comprises the following components in parts by weight of the embryo skin: 500% of water, 30 ℃, 0.6% of acetic acid, 1% of synthetic fatting agent NP-2 or synthetic fatting agent GLH;

10) building, squeezing water, and hanging and airing;

11) spraying water on the board surface, standing and softening.

In the invention, the backwater in the step 1) is that materials selected for backwater are sequentially added into a rotary drum, the rotary drum is uniformly rotated and then quickly thrown into the skin for 60 minutes, the rotary drum rotates for 5 minutes per hour and then goes overnight for 4 hours, and then the materials are drained and washed once by cold water.

In the invention, the drum rotates for 5 minutes per hour for overnight, which means that the drum rotates and stops rotating and combining, each rotation is 5 minutes, and the drum stops rotating for 55 minutes, and generally the overnight means 8 hours; the drum was rotated 5 minutes per hour overnight for 4 hours, meaning that the drum was stopped and combined 5 minutes per revolution for 55 minutes, and 4 hours overnight for 4 hours. Overnight and overnight for 4 hours are common statements in the art and are a clear presentation. The moisture content of the board surface is 22 +/-1 and is detected by a hand-held leather moisture detector, and the method for expressing the moisture content is a common mode in the field.

In the retanning step, the pre-fatliquoring is firstly carried out, and then the retanning is carried out, so that the advantages that firstly, the penetration and combination process of the tanning agent is more uniform and mild are achieved; ② the tanning agent is promoted to obtain higher absorption rate; and thirdly, the surface hand feeling of the leather is improved, so that the leather keeps warm and moist and is not dry in hand feeling.

Preferably, the dyeing of step 3) comprises: adding the following components in parts by weight of the embryonic skin into a rotary drum: 400% of water, 30 ℃ of temperature, 2% of a rewetting assistant PERMIT 2L or a rewetting assistant ML-N, 2% of a fatliquoring agent LIPSOL SQS, rotating for 30 minutes, then adding 2% of a leveling agent, 2% -4% of MELIODERM HF series dyeing plate dye, rotating for 60 minutes, adding 1% of acetic acid, rotating for 20 minutes, adding 0.5% of formic acid, rotating for 20 minutes, draining, and cleaning for 2 times.

The invention adopts MELIODERM HF series dyeing plate dye, combines corresponding auxiliary agents and process steps for dyeing, and has the following advantages: firstly, compatible dyeing is carried out by adopting the same series of dyes, and the compatibility of the dyes is good, so that the improvement of the level dyeing effect is facilitated; before the dye is added, the anionic fatting agent LIPSOL SQS is permeated in one step to promote the charge consistency of the surface of the leather body and have a slight dyeing slowing effect, wherein the dyeing slowing effect is to improve the softness of the leather body, and the dyeing evening effect is to improve the level dyeing effect; the leveling agent and the dyeing plate dye are added into the rotary drum together, so that the leveling agent can play a role in dissolving the dye, prevent the dye from being excessively combined on the surface of the leather body and penetrate into the leather core more deeply, and is favorable for leveling and dyeing; fourthly, acid is slowly reduced in multiple steps, instead of reducing the pH value by adding enough acid at one time, the absorption rate of the dye can be increased, and the color problem can be effectively prevented.

Further preferably, the leveling agent is a leveling agent NNOL, a leveling agent TF-2N or a leveling agent CORALON OT-INPOWDER.

Further preferably, the MELIODERM HF series stain dye is selected from at least one of MELIODERM HF Brown G, MELIODERM HF Brown R, MELIODERM HF Brown DGV, MELIODERM HF Pardo DGV, MELIODERM HF Havana AN, MELIODERM HF Beige D, MELIODERM HF darkfown MP, MELIODERM HF Grey GB, MELIODERM HF Grey N and MELIODERM HF Grey LL. The series of dye plates is available from STAHL.

Preferably, the step 4) of fatliquoring comprises: adding the following components in parts by weight of the embryonic skin into a rotary drum: 100% water, 55 deg.C, 2% neutralized tannin PAK-N or neutralized tannin MP3, rotating for 30 min, adding 2% synthetic tanning agent BASYTAN DLE liquid, 2% filled polymer TERGOTAN PMB or filled polymer IPF, rotating for 45 min, adding 3% lecithin fatliquor DERMINOL NLM or lecithin fatliquor PROVOL, 3% synthetic fatliquor DX1202, 0.5% emulsifier SAF or emulsifier ML-N, rotating for 120 min, adding 1% acetic acid, rotating for 45 min, adding 0.5% formic acid, rotating for 30 min, measuring pH of bath liquid to be 3.9, draining, and washing with cold water twice.

The use of the above-described fatliquoring procedure and formulation has the following advantages: firstly, high-temperature and low-liquid-ratio greasing is beneficial to improving the absorption rate of the greasing agent, and the purposes of energy conservation, emission reduction, cost reduction and efficiency improvement are achieved; secondly, the neutral tannin PAK-N or the neutral tannin MP3 is added in advance, so that the anionic charge property of the leather body can be effectively improved, and a good foundation is laid for uniform penetration of subsequent filling chemicals and fatting agents; and the filling chemical material BASYTAN DLE liquid, TERGOTAN PMB or IPF and the fatting agent act on the leather in one bath, so that the absorption can be mutually promoted, the elastic leather embryo skin is softer and firmer, and the water resource and the production cost are saved.

According to the invention, in step 5), the hitching comprises: and (5) flatly building and standing for 12 hours. The water squeezing comprises the following steps: the reciprocating wringing machine is adopted, the 3-knife method is adopted, wringing is carried out once, and the 3-knife method is a conventional method in the field, namely wringing is carried out once on the two transverse abdomens, and wringing is carried out once on the longitudinal back and hip. And the hanging and airing process is natural airing.

According to the invention, in the step 6), the water is sprayed on the board surface, 4 rows are adopted, wherein 4 rows in the invention refer to a conventional water sprayer for dry finishing in the field, and 4 water discharge is opened for the step. The standing step comprises the following steps: standing the plate-to-plate, and wrapping and standing for 6-8 hours by using the film paper. The breaking comprises the following steps: the water content of the board surface is measured by 22 +/-1 degrees, and the board surface is rotated for 2 hours, wherein the water content is measured by a hand-held psychrometer for leather detection commonly used in the field.

Preferably, in the step 7), a passing type splitting machine is adopted for splitting the sheet, the thickness of the sheet is adjusted to 0.2mm, and the sheet is transversely passed once. The passing type splitting machine adopts a high-precision NEWSPLIT 6007287 model of TURNER company. The splitting machine has high precision and can meet the following splitting requirements: the precision is 0.2 mm; secondly, mechanical damage is avoided, and the defects such as skip printing and the like cannot occur; the thickness of the sheet skin is uniform and consistent; and fourthly, the leather cannot be penetrated and broken, otherwise, the leather is scrapped. The splitting machine can solve the problem of splitting operation difficulty, is high in splitting precision, convenient to operate and small in mechanical damage.

In the invention, the back adhesive adopts a through type back adhesive machine to bond the leather and the base cloth. The adhesive glue and the back glue machine adopt the conventional composition and structure in the field.

According to the invention, in step 9), the resting comprises: and (5) flatly building and standing for 12 hours. The drum-returning acid washing is to add the materials selected by the drum-returning acid washing into a rotating drum in sequence, quickly throw the skin after uniform rotation, rotate for 30 minutes, drain water and wash with cold water once.

In step 10), the method comprises the following steps: and (5) flatly building and standing for 12 hours. The water squeezing comprises the following steps: the reciprocating wringing machine is adopted, and the 3-knife method is adopted for wringing once. And the hanging and airing process is natural airing.

In the step 11) of the invention, the plate surface is sprayed with water, and 4 rows are carried out. The standing step comprises the following steps: standing the plate-to-plate, and wrapping and standing for 6-8 hours by using the film paper. The breaking comprises the following steps: the water content of the board surface is measured to be 22 degrees +/-1, and the board surface is rotated for 2 hours.

The bath in the present invention refers to the liquid in the rotating drum.

The retanning technology suitable for the vegetable elastic leather comprises the following steps: in the water return stage, a moisture-returning auxiliary agent mainly comprising BPR or VLC-3 is adopted under an acidic condition, so that the moisture-returning effect is kept favorably on one hand, and the quick moisture-returning effect is achieved on the other hand. Retanning is carried out by matching sulfonated fatliquor TIS or sulfited fatliquor CFS with a chrome-free tanning agent TWE, so that the aim of retanning without chrome tanning and high absorption is fulfilled, the process is green and environment-friendly, the production period is shortened, and the uniformity and the strength of the leather body are improved.

The materials or process parameters not defined in the present invention can be selected conventionally according to the prior art.

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

1) the process has the advantages of remarkable treatment effect, good physical property, extensibility and safety of the leather, uniform and consistent integral thickness of the leather body, suitability for dyeing various light-colored products, reduction of the operation difficulty of the subsequent splitting process, simple and convenient splitting operation, maintenance of the characteristics of the vegetable tanning leather and qualification of various physicochemical indexes of the product.

2) The splitting method has the advantages that the splitting precision is high, the splitting can be carried out to 0.2mm, compared with the conventional process flow, the splitting and grinding processes are omitted, the production period is shortened, and the aims of saving energy, reducing emission, reducing cost and improving efficiency are fulfilled. In addition, the product does not contain chromium, so the pressure on environmental protection is small, the processing concept of environmental protection is highlighted from the material selection and the process setting in the production process, and the green development of the industry is led.

3) The invention solves the problems of poor quality and low physical property of elastic leather manufactured by a pure vegetable tanning environment-friendly tanning method through specific process steps and combined with specific operations of backwater, retanning, splitting and the like, has economic and environment-friendly processes, improves the strength and uniformity of a leather body, has high splitting precision, starts from the aspects of environment-friendly and green production, is outstanding to reduce harmful substance emission, improves the utilization rate of chemical materials, reduces the production energy consumption, takes the product performance as a final target, and fundamentally establishes a processing idea of producing beautiful and comfortable vegetable tanning elastic leather clothing products in an ecological environment-friendly mode.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

In the following examples and comparative examples:

the moisture regain auxiliary BPR, purchased from Deng chemical;

synthetic fatting agent NP-2, available from QUIMIPIEL corporation;

tear-resistant fatliquoring agent NZ, available from Dexin chemical;

universal fatliquoring agent WWL available from STAHL corporation;

sulfonated fatliquoring agent TIS, available from STAHL corporation;

sulfited fatliquor CFS, available from STAHL;

emulsifier SAF, available from STAHL;

the moisture-regaining assistant ML-N and the emulsifier ML-N are purchased from Kokai Fine chemical industry (Shanghai) Co., Ltd;

the environment-friendly tanning agent TWE is purchased from Tingjiang chemical industry;

a rewetting aid PERMIT 2L, available from Kekeh Fine chemical (Shanghai) Co., Ltd;

the moisture regain assistant VLC-3 is purchased from Kokai Fine chemical engineering (Shanghai) Co., Ltd;

fatliquoring agent LIPSOL SQS, available from debarket, spain;

leveling agent NNOL, available from STAHL corporation;

leveling agent TF-2N, available from LANXESS, Inc.;

leveling agent CORALON OT-IN POWDER available from STAHL;

MelioDERM HF series plate dyes, available from STAHL corporation;

the neutralized tannin PAK-N, available from LANXESS;

neutralized tannin MP3, available from keka fine chemicals (shanghai) ltd;

synthetic tanning agent BASYTAN DLE liquid, available from BASF corporation;

the filled polymer TERGOTAN PMB available from STAHL;

filled polymer IPF, available from TFL corporation;

lecithin fatliquoring agent DERMINOL NLM, available from STAHL corporation;

lecithin fatliquoring agent PROVOL BA, purchased from sima chemical;

synthetic fatliquor DX1202, available from TFL corporation;

synthetic fatting agent GLH, available from Kekei Fine chemical (Shanghai) Co., Ltd;

the rewet aid FORYL HIC is purchased from Kokai Fine chemical engineering (Shanghai) Co., Ltd;

the tanning agent Synektan AL, available from STAHL;

leveling agent INVADERM LU, purchased from TFL corporation;

dyeplate dye RED RTN, available from TFL corporation;

chromium powder B, available from LANXESS corporation;

the mass concentration of the acetic acid is 36-40%;

the mass concentration of formic acid is 85 percent;

the pass-through skin machine was a high precision NEWSPLIT 6007287 model skin machine, available from TURNER corporation.