Highly restored ancient leather smoking tanning process

Abstract

The present invention belongs to the field of leather processing technology, and discloses a highly restored ancient leather smoke tanning process. This process uses pickled bare skin as raw material, and sequentially carries out tanning, squeezing water, primary heat treatment, brush fatliquoring, secondary heat treatment, and post-treatment; wherein, based on the weight of the limed bare skin, the tanning process uses 0.5-3wt% furfural, 0.5-3wt% guaiacol and 10-20wt% pregelatinized starch for tanning; the primary heat treatment is to process 1-4h at 60-70℃ and 50-70RH%; the secondary heat treatment is to process 1-6h at 60-70℃ and 70-90RH%. In the antique smoke tanning system constructed by the present invention, furfural and guaiacol give the smoked tanned leather simulation sample a "smoke" smell, and the two heat treatment processes under the reversible support of pregelatinized starch give the smoked tanned leather simulation sample a light brown color and a slight oily smell, and finally obtain a standard smoked tanned leather simulation sample with high antique fidelity.

Description

Technical Field

[0001] The invention belongs to the technical field of leather processing, and in particular relates to a highly restored ancient leather smoking tanning process. Background Art

[0002] Leather is one of humanity's earliest artifacts and is closely intertwined with the development of human civilization. my country mastered early leathermaking techniques through long-term practice during the Zhou Dynasty over 1700 B.C., resulting in a large number of unearthed or handed-down leather artifacts. However, many of these artifacts have exhibited varying degrees of deterioration, necessitating systematic research into the deterioration mechanisms of leather artifacts to develop targeted preventative conservation strategies. Research into deterioration mechanisms requires subjecting samples to aging treatments such as light, heat, and microbial degradation, which inevitably damages the samples. However, the preciousness, scarcity, complexity, and fragility of leather artifacts make them difficult to exploit for destructive scientific research. Therefore, restoring ancient leather tanning techniques and producing antique leather products have become pressing challenges in the study of the deterioration mechanisms of leather artifacts.

[0003] Smoke tanning is a classic ancient leather tanning method that uses smoke to treat animal hides for corrosion and insect repellency. However, due to the complex composition of smoke, the tanning agent composition and tanning mechanism of traditional smoke tanning are extremely complex, making it difficult to clarify the deterioration mechanism of smoke-tanned leather. Furthermore, the smoke tanning process is a typical non-standard process, affected by many factors that are difficult to precisely control, such as wood type / batch, combustion intensity, and smoke volume. These reasons make it impossible to provide standard simulated samples with clear tanning agent composition and to study degradation mechanisms.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] In order to solve the problems in the background technology, the purpose of the present invention is to provide a highly restored ancient leather smoke tanning process to obtain a standard smoke tanned leather simulation sample with clear tanning agent composition and high antique realism.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] Highly restored ancient leather smoke tanning process, using pickled bare leather as raw material, sequentially undergoing tanning, squeezing, primary heat treatment, brush greasing, secondary heat treatment, and post-treatment;

[0008] wherein, based on the weight of the limed hide, the tanning process uses 0.5-3 wt% furfural, 0.5-3 wt% guaiacol and 10-20 wt% pregelatinized starch for tanning;

[0009] The primary heat treatment process is to treat at 60-70°C and 50-70RH% for 1-4h;

[0010] The secondary heat treatment process is to treat at 60-70° C. and 70-90 RH% for 1-6 hours.

[0011] Preferably, the pregelatinized starch comprises any one or more of pregelatinized potato starch, pregelatinized corn starch and pregelatinized wheat starch.

[0012] Preferably, the moisture content of the tanned leather after squeezing is 40-50 wt% of the weight of the tanned leather.

[0013] Preferably, the brush fatliquoring is to mix natural oil and hot water, stir to form an emulsion, and evenly apply it to the tanned leather surface.

[0014] Preferably, based on the weight of the limed hide, the amount of the natural oil is 10-25 wt%, and the amount of the hot water is 30-75 wt%.

[0015] Preferably, the post-treatment includes water washing, secondary squeezing, drying on a stretch board and oscillation softening.

[0016] Preferably, before brush fatliquoring, the moisture content in the tanned leather is 8-12 wt% of the tare weight, and after brush fatliquoring, the standing time is preferably 4-48 h.

[0017] Preferably, the natural oil comprises any one or more of rapeseed oil, castor oil, fish oil and lard.

[0018] The present invention also discloses highly restored ancient leather obtained by adopting any of the above-mentioned smoke tanning processes.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) In the "furfural + guaiacol + pregelatinized starch" ternary antique smoke tanning system constructed by the present invention, the pregelatinized starch acts as a "reversible support material" that supports the collagen fibers, preventing the fiber network of the tanned leather from collapsing under high temperature and high humidity conditions, that is, preventing thermal shrinkage. This is a technical effect that cannot be achieved using the "furfural + guaiacol" binary tanning system. Thereafter, the pregelatinized starch can be removed by washing, thus avoiding its interference with the study of the deterioration mechanism of smoke-tanned leather.

[0021] (2) In the antique smoke tanning system constructed by the present invention, furfural and guaiacol give the smoke tanned leather simulation sample a "smoke" smell, and the two high-temperature and high-humidity heat treatment processes under the reversible support of pregelatinized starch give the smoke tanned leather simulation sample a light brown color and a slight oily smell, and finally a standard smoke tanned leather simulation sample with high antique realism is produced.

[0022] (3) The present invention uses furfural and guaiacol as characteristic simulants of wood combustion smoke components, and formulates a standardized antique smoke tanning process flow to produce a standard smoke-tanned leather simulation sample with clear tanning agent components, providing a material basis for the deterioration mechanism of smoke-tanned leather, which is an effect that is difficult to achieve with existing smoke tanning methods. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments.It should be understood that these descriptions are exemplary only, and are not intended to limit the scope of the present invention.In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.Unindicated specific conditions in the embodiment are carried out according to the conditions of normal conditions or manufacturer's advice.Reagents used or instruments are not indicated by manufacturers, and are conventional products that can be obtained by commercial purchase.

[0024] The smoke-tanned leather produced by existing smoke tanning technology is difficult to use for deterioration mechanism research. The reason is that the smoke composition is complex, which makes the tanning agent composition and tanning mechanism of traditional smoke tanning method too complicated. In addition, the smoke tanning process is a typical non-standard process flow, which is affected by many factors that are difficult to accurately control, such as wood type / batch, burning fire size, smoke size, etc., resulting in the inability to obtain standard smoke-tanned leather simulation samples.

[0025] Through a large number of experiments, the applicant discovered that by using the large amount of smoke generated by igniting wet firewood and placing the rawhide above the smoke for smoking, the volatile aldehydes and phenols in the smoke generated by burning firewood combine with the skin collagen, producing a tanning effect and enhancing the stability of the rawhide. Since the main component of firewood is lignocellulose, we selected its thermal decomposition products - furfural and guaiacol as effective tanning agent components to simulate the volatile small molecules that may be present in the smoke. In addition to simulating the tanning agent components, it is also necessary to simulate the high temperature and high humidity conditions of the smoking process. The reason is that high temperature and high humidity conditions help promote the combination of tanning agents with skin collagen fibers and enhance the tanning effect; in addition, high temperature and high humidity conditions help promote the oxidation of tanning agent components and oil components in the skin, giving the smoked tanned leather the color and the smell of oxidized oil, and finally producing a standard smoked tanned leather simulation sample with high antique realism. However, the tanning properties of furfural and guaiacol are weak, the thermal stability of tanned leather is limited, and the collagen fiber network cannot withstand high temperature and high humidity conditions. Therefore, by tanning bare leather only with the binary tanning system of "furfural + guaiacol", it is impossible to obtain a standard smoked tanned leather simulation sample with high antique realism.

[0026] The applicant further discovered through a large number of experiments that by cleverly introducing pregelatinized starch into the binary tanning system of "furfural + guaiacol" to form a ternary tanning system of "furfural + guaiacol + pregelatinized starch", the collagen fiber network of the tanned leather can withstand high temperature and high humidity conditions, and a standard smoked tanned leather simulation sample with high antique realism can be produced. Afterwards, the pregelatinized starch is removed by washing with water, which can avoid its interference with the study of the deterioration mechanism of smoked tanned leather. The scientific principle that enables this process is that pregelatinized starch is a "reversible support material" that has no tanning properties itself, but can play a supporting role in the collagen fiber network of the leather, so that the tanned leather will not shrink under high temperature and high humidity conditions. At the same time, pregelatinized starch is a natural polymer material with good water solubility. After wet and heat treatment, the pregelatinized starch in the collagen fiber network can be removed by a water washing process, ensuring that there is no interference from other irrelevant components in the smoked tanned leather simulation sample. It is precisely because of the "reversible supporting effect" of the pregelatinized starch that the present invention can ultimately obtain a standard smoked tanned leather simulation sample with clear tanning agent composition and high antique fidelity.

[0027] The embodiment provided by the present invention is to highly restore the ancient leather smoking tanning process, using pickled bare leather as raw material, and sequentially carrying out tanning, squeezing, primary heat treatment, brush fatliquoring, secondary heat treatment, and post-treatment;

[0028] wherein, based on the weight of the limed hide, the tanning process uses 0.5-3 wt% furfural, 0.5-3 wt% guaiacol and 10-20 wt% pregelatinized starch for tanning;

[0029] The primary heat treatment process is to treat at 60-70°C and 50-70RH% for 1-4h;

[0030] The secondary heat treatment process is to treat at 60-70° C. and 70-90 RH% for 1-6 hours.

[0031] In an embodiment of the present invention, the amount of furfural added is 0.5-3wt%, the amount of guaiacol added is 0.5-3wt%, and the amount of pregelatinized starch added is 10-20wt%. The smoked tanned leather simulation sample prepared within this amount range has a high degree of antique fidelity. Furfural and guaiacol simulate the tanning agent components in smoke, providing a certain degree of thermal stability and "smoke" smell to the tanned leather. If the amount of both is less than 0.5wt%, the thermal stability of the tanned leather is low and the "smoke" smell is insufficient. More importantly, too low an amount is not conducive to the study of the deterioration mechanism of smoked tanned leather. If the amount of both is higher than 3wt%, the theoretical amount of the tanning agent components in smoked tanned leather is exceeded, resulting in distorted imitation results, which is also not conducive to the study of the deterioration mechanism. Pregelatinized starch plays a key "reversible supporting role" in the present invention. If its usage is less than 10wt%, the supporting effect is not strong enough to resist the thermal shrinkage of collagen fibers under high temperature and high humidity conditions; if its usage is higher than 20wt%, the pregelatinized starch is excessive and difficult to remove by water washing.

[0032] The pregelatinized starch used in the embodiment of the present invention includes but is not limited to any one or more of pregelatinized potato starch, pregelatinized corn starch and pregelatinized wheat starch.

[0033] It can be understood that the primary heat treatment and the secondary heat treatment both simulate the high temperature and high humidity conditions during the smoking process, and cooperate with the tanning process to ultimately achieve a high degree of restoration of ancient smoked tanned leather.

[0034] In the tanning process, furfural and guaiacol both have tanning properties and are used as tanning agents, while pregelatinized starch does not have tanning properties and is used as an auxiliary agent in the tanning process to complete the tanning process. The tanning method used is a tanning method commonly used in leather processing, and those skilled in the art can choose to use it.

[0035] For example, the specific process of the tanning step can be: adding pickling solution, furfural, guaiacol and pregelatinized starch to the pickled bare skin, tanning for 1-4 hours, adding alkali to pH 4.5-5.5, continuing tanning for 1-4 hours, and standing for 0-72 hours.

[0036] In some preferred embodiments, the amount of pickling solution used is 50-150 wt% of the weight of the limed pelt.

[0037] In some preferred embodiments, an alkali-raising agent is used to raise the alkali to a pH of 4.5-5.5, and the alkali-raising agent includes but is not limited to any one or more of sodium carbonate and sodium bicarbonate.

[0038] The squeezing is to appropriately reduce the moisture content in the tanned leather after tanning so as to carry out a subsequent heat treatment. The moisture content in the tanned leather after squeezing is controlled by those skilled in the art according to the adaptability of the subsequent treatment process. For example, the moisture content in the tanned leather can be controlled to 40-50wt% of the weight of the tanned leather by squeezing before the primary heat treatment.

[0039] In the embodiment of the present invention, the brush greasing process is to mix natural oil and hot water, stir them into an emulsion, and then evenly brush them on the tanned leather surface; the brush greasing method can be a greasing method that has been disclosed in the prior art using a brushing means, or any other method that can evenly apply the greasing emulsion to the tanned leather surface. The specific greasing method does not affect the tanning effect of this patent.

[0040] In some preferred embodiments, the amount of natural oil is 10-25 wt %, and the amount of hot water is 30-75 wt %, based on the weight of the limed hide. The amounts of natural oil and hot water can be determined by those skilled in the art according to actual fatliquor requirements.

[0041] In some embodiments, after the primary heat treatment and before fatliquoring, the moisture content of the tanned leather is preferably controlled within a certain range. If the moisture content of the tanned leather is high, a longer resting time is required for the grease to fully infiltrate the collagen fibers; if the moisture content of the tanned leather is low, a shorter resting time is required for the grease to infiltrate the collagen fibers. The moisture content and resting time can be selected by those skilled in the art based on the infiltration of the fatliquoring agent in the tanned leather. For example, the moisture content of the tanned leather is preferably 8-12wt% of the tare weight, and the leather can be left to stand for 4-48 hours after the fatliquoring agent is applied.

[0042] In some preferred embodiments, the natural oil includes but is not limited to any one or more of rapeseed oil, castor oil, fish oil and lard.

[0043] The post-treatment process described is commonly used in traditional tanning and includes washing, secondary squeezing, board drying, and oscillation softening. Washing is intended to remove pre-gelatinized starch from the collagen fiber network after the secondary heat treatment. Secondary squeezing, board drying, and oscillation softening are all conventional treatments for washed leather in the art and can be used selectively.

[0044] For example, the washing process may include adding 400-800 wt% deionized water to the tanned leather, rotating at 35-45° C. for 4-8 hours, controlling the water content, and then adding deionized water to repeat the second and third washings.

[0045] In order to better understand the technical solution provided by the present invention, the following uses a number of specific examples to illustrate the highly restored ancient leather smoking tanning process and performance testing provided by the above-mentioned embodiment of the present invention.

[0046] The furfural, guaiacol and pregelatinized starch used in the following examples and comparative examples are all conventional commercially available unmodified reagents, and the pickled bare hides are materials obtained by conventional leather making processes.

[0047] In the following examples and comparative examples, the shrinkage temperature of the smoked tanned leather simulation sample was determined as follows:

[0048] After the tanning process is completed, samples are taken and the shrinkage temperature of the tanned leather is measured using a shrinkage thermometer.

[0049] In the following examples and comparative examples, the method for determining the leather yield of smoked tanned leather simulation samples is as follows:

[0050] Use square area board (1cm 2 The area of the pickled bare hide and smoke-tanned leather simulation samples was measured using a grid ( / grid). The formula for calculating the leather yield of the smoke-tanned leather simulation samples is as follows. A higher leather yield indicates less area shrinkage during the high-temperature, high-humidity treatment process.

[0051]

[0052] In the following examples and comparative examples, the softness of the smoked tanned leather simulation samples was determined as follows:

[0053] The softness of smoked tanned leather simulation samples was measured using a softness tester.

[0054] In the following examples and comparative examples, the sensory evaluation method for smoked tanned leather simulation samples is as follows:

[0055] Three professionals with experience in leather sensory testing and two with experience in leather heritage conservation were invited to evaluate the color and odor of the smoked tanned leather simulation samples. The smoked tanned leather simulation samples were also scored for their authenticity. Excellent: 5 points; Good: 4 points; Fair: 3 points; Fair: 2 points; Poor: 1 point.

[0056] Example 1

[0057] Highly restored ancient leather smoking tanning process, including the following process steps:

[0058] Tanning: Based on the weight of the limed hide, add 100 wt% pickling solution, 1.5 wt% furfural, 1.5 wt% guaiacol and 15 wt% pregelatinized potato starch to a rotary drum. After rotating for 2.5 hours, add sodium carbonate to extract the alkali to pH 5.0, rotate for 2.5 hours, and then leave the drum for 36 hours.

[0059] Water squeezing: water squeezing is carried out according to conventional process;

[0060] Primary heat treatment: 2.5h at 65℃ and 60RH%;

[0061] Brush fatliquoring: Based on the weight of the limed leather, mix 18wt% rapeseed oil and 75wt% hot water, stir to form an emulsion, then evenly brush the emulsion on the flesh side of the tanned leather with a moisture content of 10wt% and let it stand for 24h;

[0062] Secondary heat treatment: 70°C, 80RH% for 3h;

[0063] Washing: Add 600 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 40°C for 6 hours, and control the water content; then add deionized water and repeat the second and third washings;

[0064] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0065] Instrumental measurement and sensory evaluation showed that the smoked tanned leather simulation sample had a shrinkage temperature of 64.6°C, a leather yield of 99.7%, a softness of 8.1 mm, and a light brown color. It had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell caused by oil oxidation. The antique realism score was 5 points. The specific results are shown in Table 1.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that in Comparative Example 1, only 1.5 wt% furfural was used in the tanning process, and 1.5 wt% guaiacol and 15 wt% pregelatinized potato starch were not used to treat the pickled skins.

[0068] Instrumental measurement and sensory evaluation showed that the smoked tanned leather simulation sample had a shrinkage temperature of 62.7°C, a leather yield of 72.4%, a softness of 4.3 mm, and a light brown color. It had the odor of aldehydes and a greasy smell caused by oil oxidation, but no phenolic odor. The leather board shrank severely, so the antique realism score was only 1 point. The specific results are shown in Table 1.

[0069] Comparative Example 2

[0070] The difference from Example 1 is that in Comparative Example 2, only 1.5 wt% guaiacol was used in the tanning process, and 1.5 wt% furfural and 15 wt% pregelatinized potato starch were not used to treat the pickled skins.

[0071] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 62.2°C, the leather yield was 71.8%, the softness was 4.1mm, and it was light brown in color. It had the odor of phenolic substances and the oily smell produced by oil oxidation, but no odor of aldehydes. The leather board shrank severely, so the antique realism was only 1 point. The specific results are shown in Table 1.

[0072] Comparative Example 3

[0073] The difference from Example 1 is that in Comparative Example 3, only 1.5 wt% guaiacol and 1.5 wt% furfural were used in the tanning process, and 15 wt% pregelatinized potato starch was not used to treat the pickled skins.

[0074] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 64.4°C, the leather yield was 73.2%, the softness was 4.4mm, and it was light brown. It had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. However, the leather board shrank severely, so the antique realism was only 1 point. The specific results are shown in Table 1.

[0075] Comparative Example 4

[0076] The difference from Example 1 is that in Comparative Example 4, only 1.5 wt% furfural and 15 wt% pregelatinized potato starch were used in the tanning process, and 1.5 wt% guaiacol was not used to treat the pickled bare skin.

[0077] Instrumental measurement and sensory evaluation showed that the smoked tanned leather simulation sample had a shrinkage temperature of 62.9°C, a leather yield of 99.5%, a softness of 8.0 mm, and a light brown color. It had an aldehyde odor and an oily smell from oil oxidation, but no phenolic odor. The antique realism score was 3 points. The specific results are shown in Table 1.

[0078] Comparative Example 5

[0079] The difference from Example 1 is that in Comparative Example 5, only 1.5 wt% guaiacol and 15 wt% pregelatinized potato starch were used in the tanning process, and 1.5 wt% furfural was not used to treat the pickled skins.

[0080] Instrumental measurement and sensory evaluation showed that the smoked tanned leather simulation sample had a shrinkage temperature of 62.5°C, a leather yield of 99.6%, a softness of 8.0 mm, and a light brown color. It had an odor of phenolic substances and an oily smell produced by oil oxidation, but no odor of aldehydes. The antique realism score was 3 points. The specific results are shown in Table 1.

[0081] Comparative Example 6

[0082] The difference from Example 1 is that, although the tanning process of Comparative Example 6 uses 1.5 wt% guaiacol, 1.5 wt% furfural and 15 wt% pregelatinized potato starch to treat the pickled skin, it does not perform two heat treatments.

[0083] Instrumental measurement and sensory evaluation showed that the smoked tanned leather simulation sample had a shrinkage temperature of 63.7°C, a leather yield of 99.5%, a softness of 8.0 mm, and was white in color. It had a "smoky smell" composed of phenolic and aldehyde substances, but no oily smell caused by oil oxidation. The antique realism score was 2 points. The specific results are shown in Table 1.

[0084] According to the instrument test and sensory evaluation results of Example 1 and Comparative Examples 1-6, it can be seen that in Comparative Example 1, 1.5wt% furfural was first used to tan the pickled bare skin, and then two heat treatments were performed. The shrinkage temperature of the obtained smoked tanned leather simulation sample was 62.7°C, the leather yield was 72.4%, the softness was 4.3mm, and it was light brown. It had the smell of aldehydes and the oily smell produced by oil oxidation, but no phenolic smell and the leather board shrank severely, so the antique realism was only 1 point; Comparative Example 2 first used 1.5wt% guaiacol to tan the pickled bare skin, and then two heat treatments were performed. The shrinkage temperature of the obtained smoked tanned leather simulation sample was 62.2°C, the leather yield was 71.8%, and the softness was 4.1m m, light brown, with the smell of phenolic substances and the oily smell produced by the oxidation of fats, but no smell of aldehydes and the leather board shrinks severely, so the antique fidelity is only 1 point; Comparative Example 3 first used 1.5wt% guaiacol and 1.5wt% furfural to tan the pickled bare skin, and then carried out two heat treatments. The shrinkage temperature of the obtained smoked tanned leather simulation sample was 64.4°C, the leather yield was 73.2%, the softness was 4.4mm, and it was light brown, with a "smoke smell" composed of phenolic substances and aldehydes and the oily smell produced by the oxidation of fats, but the leather board shrank severely, so the antique fidelity was only 1 point; Comparative Example 4 first used 1.5wt% furfural and 15wt% pregelatinized potato starch to treat the pickled bare skin, and then After two heat treatments, the shrinkage temperature of the smoked tanned leather simulation sample obtained was 62.9°C, the leather yield was 99.5%, the softness was 8.0mm, it was light brown, had the smell of aldehydes and the oily smell produced by oil oxidation, but no phenolic smell, and the antique fidelity was 3 points; Comparative Example 5 first used 1.5wt% guaiacol and 15wt% pregelatinized potato starch to treat the pickled bare skin, and then carried out two heat treatments. The shrinkage temperature of the smoked tanned leather simulation sample obtained was 62.5°C, the leather yield was 99.6%, the softness was 8.0mm, it was light brown, had the smell of phenols and the oily smell produced by oil oxidation, but no aldehyde smell, and the antique fidelity was 3 points; Comparative Example 6 used 1 .5wt% guaiacol, 1.5wt% furfural and 15wt% pregelatinized potato starch were used to treat the pickled leather, but without performing the double heat treatment. The obtained smoke tanned leather simulation sample had a shrinkage temperature of 63.7°C, a leather yield of 99.5%, a softness of 8.0mm, a white color, a "smoky smell" composed of phenolic and aldehyde substances, but no oily smell caused by oil oxidation, and an antique realism score of 2 points; Example 1 first used 1.5wt% guaiacol, 1.5wt% furfural and 15wt% pregelatinized potato starch to treat the pickled leather, and then performed the double heat treatment. The obtained smoke tanned leather simulation sample had a shrinkage temperature of 64.6°C, a leather yield of 99.7%, a softness of 8.1mm, light brown in color, with a "smoky" smell composed of phenolic and aldehyde substances and a greasy smell caused by oil oxidation, with an antique realism rating of 5 points.

[0085] The results of the above embodiments and comparative examples show that, when tanned with furfural alone (Comparative Example 1), the obtained smoked tanned leather simulation sample is severely affected by the heat shrinkage board, has low softness, and has no phenolic smell, and the antique fidelity is only 1 point; when tanned with guaiacol alone (Comparative Example 2), the obtained smoked tanned leather simulation sample is also severely affected by the heat shrinkage board, has low softness, and has no aldehyde smell, and the antique fidelity is 1 point; when tanned with the combination of "furfural + guaiacol" (Comparative Example 3), the shrinkage temperature of the tanned leather is also low, and it is still unable to resist thermal shrinkage under high temperature and high humidity conditions, resulting in the obtained smoked tanned leather simulation sample having a "smoke smell" composed of phenolic and aldehyde substances, but low softness, and the antique fidelity is also 1 point. The above results show that if furfural and guaiacol are simply combined, it is impossible to obtain a smoked tanned leather simulation sample with high antique fidelity.

[0086] Through the treatment of the combination of "furfural + pregelatinized starch" (Comparative Example 4) and the combination of "guaiacol + pregelatinized starch" (Comparative Example 5), although the shrinkage temperature of the tanned leather is low, the pregelatinized starch plays a "reversible supporting role" on the collagen fibers, so that the tanned leather will not shrink during the two heat treatments, and the final smoked tanned leather simulation sample is high in softness. However, because the leather sample prepared by the combination of "furfural + pregelatinized starch" lacks the smell of phenolic substances, and the leather sample prepared by the combination of "guaiacol + pregelatinized starch" lacks the smell of aldehyde substances, the "smoke" components of the two tanned leathers are incomplete and the taste is insufficient, and the antique realism is only 3 points. This shows that furfural and guaiacol are crucial for enriching the "smoke" components, and the supporting role of pregelatinized starch is crucial for maintaining the network structure of collagen fibers under high temperature and high humidity conditions.

[0087] By treating with the combination of "furfural + guaiacol + pregelatinized starch", since there is no double heat treatment (Comparative Example 6), furfural and guaiacol will not be oxidized, that is, the obtained smoked tanned leather simulation sample is white; in addition, the oil of the pickled bare leather itself and the oil introduced by brush greasing are not easily oxidized under conditions without heat treatment, so there is no smell produced by oil oxidation, that is, oily smell. Due to the above two problems, the antique realism is only 2 points. It can be seen that two heat treatments can give the leather sample a light brown color and an oily smell, indicating that heat treatment is an important and indispensable process for improving the antique realism of smoked tanned leather simulation samples.

[0088] It is particularly important to note that only by combining the "furfural + guaiacol + pregelatinized starch" with two heat treatments (Example 1), the obtained smoked tanned leather simulation sample will not shrink by heat, has high softness, is light brown, and has both the "smoke smell" composed of phenolic substances and aldehydes and the oily smell produced by grease oxidation, with an antique realism of 5 points. Among them, furfural and guaiacol give the smoked tanned leather simulation sample a "smoke smell", and pregelatinized starch plays a reversible supporting role, ensuring that the tanned leather does not shrink under high temperature and high humidity conditions, and ultimately gives the smoked tanned leather simulation sample a high leather yield, excellent softness, light brown color and the oily smell produced by grease oxidation. The above results prove that only by cleverly adopting the ternary tanning system of "furfural + guaiacol + pregelatinized starch" and combining it with a two-step heat treatment can the technical effects of the present invention be achieved.

[0089] Table 1 Test results

[0090]

[0091] Example 2

[0092] Highly restored ancient leather smoking tanning process, including the following process steps:

[0093] Tanning: Based on the weight of the limed hide, add 50 wt% of pickling solution, 0.5 wt% of furfural, 3.0 wt% of guaiacol and 10 wt% of pregelatinized corn starch to a rotary drum. After rotating for 1 hour, add sodium bicarbonate to extract the alkali to pH 4.5, rotate for 4 hours, and then remove from the drum.

[0094] Water squeezing: water squeezing is carried out according to conventional process;

[0095] Primary heat treatment: 4h at 60℃ and 70RH%;

[0096] Brush fatliquoring: Based on the weight of the limed leather, mix 25wt% castor oil and 50wt% hot water, stir to form an emulsion, then evenly brush the emulsion on the flesh side of the tanned leather with a moisture content of 12wt% and let it stand for 48h;

[0097] Secondary heat treatment: 65°C, 70 RH% for 1 hour;

[0098] Washing: Add 400 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 35°C for 4 hours, and control the water content; then add deionized water and repeat the second and third washings;

[0099] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0100] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 63.4°C, the leather yield was 99.8%, the softness was 8.4mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0101] Example 3

[0102] Highly restored ancient leather smoking tanning process, including the following process steps:

[0103] Tanning: Based on the weight of the limed hide, add 150wt% pickling solution, 3.0wt% furfural, 0.5wt% guaiacol and 20wt% pregelatinized wheat starch to a rotary drum. After rotating for 4 hours, extract the base with sodium carbonate and sodium bicarbonate to pH 5.5, rotate for 1 hour, and then leave the drum to stand for 72 hours.

[0104] Water squeezing: water squeezing is carried out according to conventional process;

[0105] Primary heat treatment: 70°C, 50 RH% for 1 h;

[0106] Brush fatliquoring: Based on the weight of the limed leather, mix 10wt% fish oil and 30wt% hot water, stir to form an emulsion, then brush the emulsion evenly on the tanned leather with a moisture content of 8wt% and let it stand for 4 hours;

[0107] Secondary heat treatment: 60°C, 90RH% for 6h;

[0108] Washing: Add 800 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 45°C for 8 hours, and control the water content; then add deionized water and repeat the second and third washings;

[0109] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0110] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 65.9°C, the leather yield was 99.4%, the softness was 7.8mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0111] Example 4

[0112] Highly restored ancient leather smoking tanning process, including the following process steps:

[0113] Tanning: Based on the weight of the limed hide, add 50 wt% of pickling solution, 0.5 wt% of furfural, 0.5 wt% of guaiacol, 5 wt% of pregelatinized potato starch and 5 wt% of pregelatinized corn starch into a rotary drum. After rotating for 1 hour, extract the base with sodium carbonate to pH 4.5, rotate for 1 hour, and remove from the drum.

[0114] Water squeezing: water squeezing is carried out according to conventional process;

[0115] Primary heat treatment: 2.5h at 60℃ and 50RH%;

[0116] Brush fatliquoring: Based on the weight of the limed leather, mix 10wt% lard and 30wt% hot water, stir to form an emulsion, then brush the emulsion evenly on the tanned leather with a moisture content of 8wt% and let it stand for 4 hours;

[0117] Secondary heat treatment: 1h at 60℃ and 70RH%;

[0118] Washing: Add 400 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 35°C for 4 hours, and control the water content; then add deionized water and repeat the second and third washings;

[0119] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0120] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 63.2°C, the leather yield was 99.9%, the softness was 7.9mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0121] Example 5

[0122] Highly restored ancient leather smoking tanning process, including the following process steps:

[0123] Tanning: Based on the weight of the limed hides, 100 wt% of pickling solution, 0.5 wt% of furfural, 1.5 wt% of guaiacol, 7 wt% of pregelatinized potato starch, and 7 wt% of pregelatinized wheat starch were added to a rotary drum. After rotating for 2.5 hours, the drum was alkali-treated to pH 5.0 with sodium bicarbonate, and the drum was rotated for another 2.5 hours. The drum was then left to stand for 36 hours.

[0124] Water squeezing: water squeezing is carried out according to conventional process;

[0125] Primary heat treatment: 65°C, 60 RH% for 1 h;

[0126] Brush fatliquoring: Based on the weight of the limed bare hide, mix 9wt% rapeseed oil, 9wt% castor oil and 50wt% hot water, stir to form an emulsion, then brush the emulsion evenly on the flesh side of the tanned leather with a moisture content of 10wt% and let it stand for 24h;

[0127] Secondary heat treatment: 3h at 65℃ and 80RH%;

[0128] Washing: Add 600 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 40°C for 6 hours, and control the water content; then add deionized water and repeat the second and third washings;

[0129] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0130] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 63.3°C, the leather yield was 99.8%, the softness was 8.2mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0131] Example 6

[0132] Highly restored ancient leather smoking tanning process, including the following process steps:

[0133] Tanning: Based on the weight of the limed hide, add 150wt% of pickling solution, 1.5wt% of furfural, 0.5wt% of guaiacol, 10wt% of pregelatinized corn starch and 10wt% of pregelatinized wheat starch to a rotary drum. After rotating for 4 hours, extract the base with sodium carbonate and sodium bicarbonate to pH 5.5, rotate for 4 hours, remove from the drum and let it stand for 72 hours.

[0134] Water squeezing: water squeezing is carried out according to conventional process;

[0135] Primary heat treatment: 4h at 70℃ and 70RH%;

[0136] Brush fatliquoring: Based on the weight of the limed hide, mix 12wt% of rapeseed oil, 13wt% of fish oil and 75wt% of hot water, stir to form an emulsion, then evenly brush the emulsion on the flesh side of the tanned leather with a moisture content of 12wt% and let it stand for 48h;

[0137] Secondary heat treatment: 70°C, 90 RH% for 6 hours;

[0138] Washing: Add 800 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 45°C for 8 hours, and control the water content; then add deionized water and repeat the second and third washings;

[0139] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0140] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 64.4°C, the leather yield was 99.7%, the softness was 8.5mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0141] Example 7

[0142] Highly restored ancient leather smoking tanning process, including the following process steps:

[0143] Tanning: Based on the weight of the limed hide, add 150 wt% of pickling solution, 1.5 wt% of furfural, 3.0 wt% of guaiacol, 6 wt% of pregelatinized potato starch, 7 wt% of pregelatinized corn starch and 7 wt% of pregelatinized wheat starch to a rotary drum. After rotating for 1 hour, extract the base with sodium carbonate to pH 5.5, rotate for 1 hour, and remove from the drum.

[0144] Water squeezing: water squeezing is carried out according to conventional process;

[0145] Primary heat treatment: 4h at 65℃ and 60RH%;

[0146] Brush fatliquoring: Based on the weight of the limed leather, mix 5wt% rapeseed oil, 5wt% lard and 30wt% hot water, stir to form an emulsion, then brush the emulsion evenly on the flesh side of the tanned leather with a moisture content of 10wt% and let it stand for 24h;

[0147] Secondary heat treatment: 3h at 60℃ and 80RH%;

[0148] Washing: Add 400 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 35°C for 8 hours, and control the water content; then add deionized water and repeat the second and third washings;

[0149] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0150] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 64.9°C, the leather yield was 99.6%, the softness was 7.9mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0151] Example 8

[0152] Highly restored ancient leather smoking tanning process, including the following process steps:

[0153] Tanning: Based on the weight of the limed hide, add 100 wt% of pickling solution, 3.0 wt% of furfural, 1.5 wt% of guaiacol and 10 wt% of pregelatinized potato starch to a rotary drum. After rotating for 2.5 hours, add sodium bicarbonate to extract the base to pH 4.5, rotate for 4 hours, and then leave the drum for 36 hours.

[0154] Water squeezing: water squeezing is carried out according to conventional process;

[0155] Primary heat treatment: 60°C, 50RH% for 1h;

[0156] Brush fatliquoring: Based on the weight of the limed hide, mix 6wt% castor oil, 6wt% fish oil, 6wt% lard and 75wt% hot water, stir to form an emulsion, then evenly brush the emulsion on the flesh side of the tanned leather with a moisture content of 12wt% and let it stand for 48 hours;

[0157] Secondary heat treatment: 65°C, 70 RH% for 1 hour;

[0158] Washing: Add 800 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 40°C for 6 hours, and control the water content; then add deionized water and repeat the second and third washings;

[0159] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0160] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 66.1°C, the leather yield was 99.3%, the softness was 8.2mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0161] Example 9

[0162] Highly restored ancient leather smoking tanning process, including the following process steps:

[0163] Tanning: Based on the weight of the limed hide, add 50 wt% pickling solution, 3.0 wt% furfural, 3.0 wt% guaiacol and 15 wt% pregelatinized corn starch to a rotary drum. After rotating for 4 hours, add sodium carbonate to extract the alkali to pH 5.0, rotate for 2.5 hours, and then leave the drum for 72 hours.

[0164] Water squeezing: water squeezing is carried out according to conventional process;

[0165] Primary heat treatment: 2.5h at 70℃ and 70RH%;

[0166] Brush fatliquoring: Based on the weight of the limed leather, 8wt% castor oil, 8wt% fish oil, 9wt% lard and 50wt% hot water were mixed and stirred into an emulsion. The emulsion was then evenly brushed on the flesh side of the tanned leather with a moisture content of 8wt% and allowed to stand for 4 hours.

[0167] Secondary heat treatment: 70°C, 90 RH% for 6 hours;

[0168] Washing: Add 600 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 45°C for 4 hours, and control the water; then add deionized water and repeat the second and third washings;

[0169] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0170] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 66.7°C, the leather yield was 99.1%, the softness was 8.6mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0171] Example 10

[0172] Highly restored ancient leather smoking tanning process, including the following process steps:

[0173] Tanning: Based on the weight of the limed hide, add 150wt% pickling solution, 1.5wt% furfural, 1.5wt% guaiacol and 20wt% pregelatinized wheat starch to a rotary drum. After rotating for 2.5 hours, add sodium carbonate and sodium bicarbonate to extract the alkali to pH 4.5, rotate for 1 hour, and then leave the drum to stand for 36 hours.

[0174] Water squeezing: water squeezing is carried out according to conventional process;

[0175] Primary heat treatment: 70°C, 60RH% for 4h;

[0176] Brush fatliquoring: Based on the weight of the limed hide, mix 6wt% rapeseed oil, 6wt% castor oil, 6wt% fish oil, 7wt% lard and 50wt% hot water, stir to form an emulsion, then brush the emulsion evenly on the flesh side of the tanned leather with a moisture content of 8wt% and let it stand for 4 hours;

[0177] Secondary heat treatment: 65°C, 80 RH% for 6 hours;

[0178] Washing: Add 600 wt% of deionized water to the drum based on the weight of the limed hides, rotate at 40°C for 4 hours, and control the water; then add deionized water and repeat the second and third washings;

[0179] According to conventional process, the washed leather blanks were subjected to secondary water squeezing, stretch drying and oscillation softening operations to obtain smoked tanned leather simulation samples.

[0180] After instrumental measurement and sensory evaluation, the shrinkage temperature of the smoked tanned leather simulation sample was 64.7°C, the leather yield was 99.7%, the softness was 8.2mm, it was light brown in color, and had a "smoky smell" composed of phenolic and aldehyde substances and an oily smell produced by oil oxidation. The antique realism level was 5 points.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. Highly restored ancient leather smoking tanning process, characterized by: Using pickled bare hides as raw materials, the process includes tanning, squeezing, primary heat treatment, brush fatliquoring, secondary heat treatment and post-treatment. wherein, based on the weight of the limed hide, the tanning process uses 0.5-3 wt% furfural, 0.5-3 wt% guaiacol and 10-20 wt% pregelatinized starch for tanning; The primary heat treatment is performed at 60-70°C and 50-70 RH% for 1-4 h; The secondary heat treatment is performed at 60-70° C. and 70-90 RH% for 1-6 h.

2. The highly restored ancient leather smoke tanning process according to claim 1, characterized in that: The pregelatinized starch comprises any one or more of pregelatinized potato starch, pregelatinized corn starch and pregelatinized wheat starch.

3. The highly restored ancient leather smoke tanning process according to claim 1, characterized in that: The moisture content of the tanned leather after squeezing is 40-50wt% of the weight of the tanned leather.

4. The highly restored ancient leather smoke tanning process according to claim 1, characterized in that: The brush fatliquoring is to mix natural oil and hot water, stir them into an emulsion, and evenly apply it to the tanned leather surface.

5. The highly restored ancient leather smoke tanning process according to claim 4, characterized in that: Based on the weight of the limed bare hide, the amount of the natural oil is 10-25 wt%, and the amount of the hot water is 30-75 wt%.

6. The highly restored ancient leather smoke tanning process according to claim 1, characterized in that: The post-treatment includes water washing, secondary squeezing, drying on a stretch board and oscillation softening.

7. The highly restored ancient leather smoke tanning process according to claim 1, characterized in that: Before the brush fatliquoring, the moisture content in the tanned leather is 8-12 wt% of the tare weight, and after the brush fatliquoring, the standing time is 4-48 h.

8. The highly restored ancient leather smoking tanning process according to claim 4, characterized in that: The natural oil comprises any one or more of rapeseed oil, castor oil, fish oil and lard.

9. Highly restored ancient leather obtained by the smoke tanning process according to any one of claims 1 to 8.

Images