阅读说明：本技术 皮革染色和/或复鞣的方法 (Process for dyeing and/or retanning leather ) 是由 T·吉奥西克 I·F·M·科雷曼斯 S·派特鲁西克 于 2020-04-29 设计创作，主要内容包括：本发明涉及一种皮革制品染色和/或复鞣的方法,所述方法包括以下步骤：提供(2)皮革制品,所述皮革制品至少经过鞣制工艺的处理；将所述皮革制品引入(4)处理室；将所述处理室中的所述皮革制品经受(6)加压流体的作用；控制(10)所述加压流体的压力以达到超临界状态；将所述皮革制品经受染色剂和/或复鞣剂的作用,在所述加压流体处于超临界状态时,所述染色剂或复鞣剂至少在预定时间段内在所述加压流体中溶解和/或输送；降低(12)所述处理室中的压力；从所述处理室中移除(14)所述皮革制品；其中,降低所述处理室中的所述压力的步骤包括控制压力随时间降低。(The present invention relates to a method for dyeing and/or retanning a leather article, said method comprising the steps of: providing (2) a leather article, the leather article being subjected to at least a tanning process; introducing (4) the leather articles into a treatment chamber; subjecting (6) the leather article in the treatment chamber to a pressurized fluid; controlling (10) the pressure of the pressurized fluid to reach a supercritical state; subjecting the leather article to the action of a colouring agent and/or a retanning agent which is dissolved and/or transported in the pressurized fluid at least for a predetermined period of time while the pressurized fluid is in a supercritical state; reducing (12) the pressure in the process chamber; removing (14) the leather articles from the treatment chamber; wherein the step of reducing the pressure in the process chamber comprises controlling the pressure to decrease over time.)

1. A method of dyeing and/or retanning a leather article, the method comprising the steps of:

-providing (2) a leather article, which has been subjected at least to a tanning process,

-introducing (4) the leather articles into a treatment chamber,

-subjecting (6) the leather articles in the treatment chamber to the action of a pressurized fluid,

-controlling (10) the pressure of the pressurized fluid to reach a supercritical state,

-subjecting the leather product to the action of a colouring agent and/or a retanning agent which dissolves and/or is transported in the pressurized fluid at least for a predetermined period of time when the pressurized fluid is in a supercritical state,

-reducing (12) the pressure in the process chamber,

-removing (14) the leather articles from the treatment chamber,

wherein the step of reducing the pressure in the process chamber comprises controlling the pressure to decrease over time.

2. The method according to claim 1, wherein the step of reducing (12) the pressure in the process chamber comprises removing the pressurized fluid from the process chamber.

3. The method of claims 1 and 2, further comprising: a step of removing (16) residual stain and/or retanning agent from the pressurized fluid during or after the pressurized fluid is moved out of the treatment chamber.

4. The method of any of claims 1-3, wherein the pressurized fluid removed from the process chamber is directed to a storage vessel at a storage pressure.

5. The method of claim 4, wherein subjecting the leather articles in the treatment chamber to the pressurized fluid comprises utilizing the pressurized fluid from the storage vessel.

6. The method according to any one of claims 1-5, wherein the step of controlling the pressure in the process chamber of the pressurized fluid to reach a supercritical state comprises increasing the pressure by keeping within predetermined limits over time.

7. The method of any of claims 1-6, wherein the step of subjecting the leather product to a coloring agent comprises one of:

-introducing the staining agent directly into the treatment chamber,

-introducing the colouring agent into the pressurized fluid before the pressurized fluid is introduced into the treatment chamber,

-introducing the dyeing agent into the treatment chamber together with the leather product, and

-introducing the colorant into the pressurized fluid when the pressurized fluid is controlled to reach or has reached the supercritical state.

8. The method of any of claims 1-7, wherein the step of subjecting the leather article to the action of a retanning agent comprises one of:

-introducing the retanning agent directly into the treatment chamber,

-introducing the retanning agent into the pressurized fluid before the pressurized fluid is introduced into the treatment chamber,

-introducing the retanning agent into the treatment chamber together with the leather product, and

-introducing the retanning agent into the pressurized fluid when the pressurized fluid is controlled to reach or has reached the supercritical state.

9. The method according to any one of claims 1-7, wherein the dyeing agent is any dye associated with dyeing leather and textiles, and at least one type of dye selected from acid dyes, basic dyes, direct dyes, reactive dyes, chromium dyes, mill dyes, metal complex dyes, mordant dyes, and sulfur dyes, disperse dyes, reactive disperse dyes, and natural dyes.

10. The method of any one of claims 1-9, wherein the stain is a collagen-reactive stain.

11. Method according to any one of claims 1 to 10, wherein the amount of stain and/or retanning agent is dosed as a function of the weight, thickness and/or surface area of the leather product.

12. Method according to any of claims 1-11, wherein the amount of the stain and/or retanning agent is dosed according to the type of leather product.

13. The method of any of claims 1-12, wherein the leather article is finished with a primer prior to being subjected to the pressurized fluid.

14. The method of any of claims 1-13, wherein the pressurized fluid comprises CO₂It has a purity of at least 99.0%, preferably at least 99.9%.

15. The method according to any one of claims 1-14, further comprising: a step of adding a coloring agent in an automatic manner based on the characteristics of the leather product.

16. The method according to any one of claims 1 to 15, wherein the step of subjecting the leather product to the action of a colouring agent and/or a retanning agent, wherein the colouring agent or retanning agent is dissolved and/or transported in the pressurized fluid at least for a predetermined period of time while the pressurized fluid is in the supercritical state, further comprises mixing, stirring or circulating of the pressurized fluid in the supercritical state.

17. The method of any of claims 1-16, wherein the dyeing step comprises using a fixing agent.

18. The method of any one of claims 1-17, wherein the method comprises fatliquoring.

19. The method according to any of claims 1-18, wherein the pressure of the pressurized fluid in the supercritical state is at least 70bar, such as between 70 and 260bar, such as 90 to 150bar, such as 130 to 250bar, or such as 180 to 240 bar.

20. The method according to any of claims 1-19, wherein the temperature of the pressurized fluid in the supercritical state is between 30 and 120 degrees celsius, such as between 30 and 100 degrees celsius, such as between 30 and 60 degrees celsius, such as between 30 and 50 degrees celsius, such as between 30 and 40 degrees celsius.

21. The method according to any one of claims 1-20, wherein the predetermined time, i.e. the time the leather article is subjected to the action of the stain and/or retanning agent in the pressurized fluid in the supercritical state, is at least 1 minute, such as at least 15 minutes, such as between 15 minutes and 4 hours, such as between 25 minutes and 2 hours, such as more than 35 minutes.

22. The method according to any one of claims 1-21, further comprising: a step of providing (22) a leather material, wherein said leather material is subjected to at least a tanning process, whereby at least one leather product is cut (24) out of said leather material before being provided (2) and introduced (4) into said treatment chamber.

23. The method according to any one of claims 1-22, wherein the pressure of the pressurized fluid in the supercritical state and/or the temperature of the pressurized fluid in the supercritical state is controlled to provide a density of the pressurized fluid in the supercritical state within a predetermined range.

24. The method according to any of claims 1-23, wherein the pressure reduction is controlled over time such that the reduction period exceeds a time interval of 5 minutes, such as 5 minutes to 2 hours, such as 15 minutes to 45 minutes, such as 15 minutes to 30 minutes, such as 30 minutes to 2 hours, such as 30 minutes to 65 minutes.

25. Method according to any of claims 1-24, wherein the pressure reduction is controlled over time such that the pressure reduction does not exceed a predetermined leather pressure reduction gradient, such as 10bar/min, such as 8bar/min, such as 6bar/min or such as 4 bar/min.

26. The method according to any of claims 1-25, wherein the pressure of the pressurized fluid is controlled to reach a supercritical state such that the time period exceeds a predetermined 5 minute increase period, such as an interval between 5 minutes and 1 hour, such as between 15 minutes and 45 minutes, such as between 15 minutes and 30 minutes.

27. The method according to any of claims 1-26, wherein pressurizing the pressurized fluid in the processing chamber to reach a supercritical state comprises increasing the pressure by no more than a predetermined leather pressure increase gradient, such as 20bar/min, such as 15bar/min, such as 10bar/min, such as 8bar/min, such as 6bar/min, such as 5bar/min or such as 4 bar/min.

28. An apparatus for dyeing and/or retanning leather goods according to the method of any one of claims 1 to 27, the apparatus comprising:

-a treatment chamber for treating the substrate,

-a source of a pressurized fluid,

-a source of a coloring agent and/or a retanning agent,

-a pump for increasing the pressure of the pressurized fluid to reach a supercritical state,

-a pressure reducer for reducing the pressure in the process chamber; and

-a controller for controlling the operation of the electronic device,

wherein the controller is configured to control the depressurizer to depressurize the treatment chamber over time after the leather article has been subjected to the coloring agent dissolved in the pressurized fluid in the supercritical state for at least a predetermined time.

29. An apparatus for dyeing leather goods according to claim 28 and wherein said controller is further configured to control the pressure in said treatment chamber of said pressurized fluid to reach a supercritical state by increasing the pressure over time within predetermined limits.

Technical Field

The invention relates to a method for dyeing leather products.

Background

It is well known that in the field of leather manufacture, dyeing is one of the more important steps, since it is generally the first characteristic of leather that a consumer evaluates. The dyeing of leather is currently carried out mainly with acid, sulphur, direct, pre-metallised, reactive or basic dyes under humid conditions, but acceptably high colour depth and high moisture resistance are difficult and therefore improved solutions are needed. It is also well known that water and processing aids such as dyes, retanning agents and fatliquoring agents are used in large quantities in the leather dyeing process and can be energy intensive.

It is therefore an object of the present invention to provide an advantageous and more environmentally sustainable dyeing process with high dyeing efficiency and high moisture resistance. Another objective is to ensure that the leather quality meets all common physical and chemical test standards, including high color fastness.

Disclosure of Invention

The present invention relates to a method for dyeing and/or retanning a leather article, said method comprising the steps of:

-providing a leather product, which has been subjected at least to a tanning process,

-introducing said leather articles into a treatment chamber,

-subjecting the leather article in the treatment chamber to the action of a pressurized fluid,

-controlling the pressure of the pressurized fluid to reach a supercritical state,

-subjecting the leather product to the action of a colouring agent and/or a retanning agent which is dissolved and/or transported in the pressurized fluid at least for a predetermined period of time when the pressurized fluid is in the supercritical state,

-reducing the pressure in the process chamber,

-removing the leather article from the treatment chamber,

wherein the step of reducing the pressure in the process chamber comprises controlling the pressure to decrease over time.

The dyeing/coloring of leather articles can thus be achieved using the method according to the invention, which is distinguished in that the use of relatively large amounts of water in the dyeing process is avoided and, owing to the reduced process time, also less energy can be used, compared to conventional dyeing methods. This is achieved by using a coloring agent which is soluble in the pressurized fluid at least in the supercritical state, whereby the dissolved coloring agent, in combination with the pressurized fluid in the supercritical state, can penetrate into the leather structure comprising at least part of the internal structure, performing a coloring not only of the surface of the leather structure but also of the underlying structure, e.g. collagen fibres in the leather structure.

According to the invention, the step of reducing the pressure in the treatment chamber, for example at the end of the dyeing step in supercritical conditions, comprises controlling the pressure reduction over time in such a way that the leather article retains the desired characteristics vital to the long-term use of the leather, for example the colour and surface characteristics, so that any tendency of the leather to delaminate is minimized or even completely avoided, and so that the preventive requirements of the leather delamination are met. This may involve setting a minimum time period for reducing the pressure, setting a maximum number of pressure reduction gradients, setting a maximum number of average pressure reduction gradients, etc., which will ensure that the leather structure, particularly one that has been dyed with a dyeing agent and penetrated by the pressurized fluid in the supercritical state, is not adversely affected during the pressure reduction.

The step of reducing the pressure in the chamber comprises controlling the pressure reduction over time to meet leather delamination prevention requirements, meaning for example that the leather structure, in particular the leather structure which has been dyed by the dyeing agent and permeated by the pressurized fluid in the supercritical state, is not affected by leather delamination during or after the dyeing process.

It is worth noting that the method according to claim 1 states the treatment of "leather articles", but it is clear that two or more leather articles can be treated simultaneously.

Further, it should be noted that the coloring agent may be introduced into the treatment chamber at any convenient stage and in any convenient manner, such as before the leather article is introduced, while the leather article is introduced, before or with the pressurized fluid, when the pressurized fluid reaches a supercritical state, and the like.

According to one embodiment of the present invention, tanning is generally understood to convert compostable organic materials into stable materials that are resistant to biochemical attack.

In one embodiment of the invention, the step of reducing the pressure in the process chamber comprises removing the pressurized fluid from the process chamber.

Thus, the pressure reduction may be combined with the process of removing the pressurized fluid from the treatment chamber, for example as a related and advance measure to the removal of the leather articles from the treatment chamber, in some embodiments it may be desirable to reduce the pressure of the treatment chamber substantially to ambient pressure, for example, to enable opening of the treatment chamber and removal of the leather articles.

In one embodiment of the invention, the method further comprises: a step of removing residual stain and/or retanning agent from the pressurized fluid during or after the pressurized fluid is removed from the treatment chamber.

Thus, any staining agent that may not be absorbed or attached to the leather product may preferably be removed from the pressurized fluid, e.g. by distillation, precipitation processes, etc. (e.g. directly related to the pressure reduction). The excess stain can advantageously be reused and, more importantly, the purity of the pressurised fluid can be maintained and reused.

In one embodiment of the invention, the pressurized fluid removed from the process chamber is directed to a storage vessel at a storage pressure.

Thus, the pressurized fluid can be stored and prevented from leaking into the environment, for example.

In one embodiment of the invention, the step of subjecting the leather articles in the treatment chamber to the action of the pressurized fluid comprises utilising the pressurized fluid from the storage container.

Thus, the pressurized fluid may be stored and reused afterwards, e.g. for a later dyeing cycle, for increasing the amount of the pressurized fluid, etc.

In one embodiment of the invention, the step of controlling the pressure in the process chamber of the pressurized fluid to reach a supercritical state comprises increasing the pressure by remaining within predetermined limits over time.

Thus, the pressure increases over time in such a way that the leather article retains the desired properties that are critical to its long-term use, for example, color and surface properties, such that any tendency of the leather to delaminate is minimized or even completely avoided, and such that the preventive requirements of leather delamination are met. This may involve setting a minimum period of increasing pressure, setting a maximum value of a pressure increase gradient, setting a maximum value of an average pressure increase gradient, etc., which will ensure that the leather structure, in particular the leather structure being dyed by a dyeing agent and to be penetrated by the pressurized fluid in the supercritical state, is not adversely affected during the pressure increase.

The step of increasing the pressure of the treatment chamber comprises controlling the pressure increase over time to meet leather delamination prevention requirements, e.g. meaning that the leather structure is not affected by the leather delamination during or after the dyeing process.

In one embodiment of the invention, the step of subjecting the leather product to the action of a colouring agent comprises one of:

-introducing the staining agent directly into the treatment chamber,

-introducing the colouring agent into the pressurized fluid before the pressurized fluid is introduced into the treatment chamber,

-introducing the dyeing agent into the treatment chamber together with the leather product, and

-introducing the colorant into the pressurized fluid when the pressurized fluid is controlled to reach or has reached the supercritical state.

In one embodiment of the invention, the step of subjecting the leather article to the action of a retanning agent comprises one of:

-introducing the retanning agent directly into the treatment chamber,

-introducing the retanning agent into the pressurized fluid before the pressurized fluid is introduced into the treatment chamber,

-introducing the retanning agent into the treatment chamber together with the leather product, and

-introducing the retanning agent into the pressurized fluid when the pressurized fluid is controlled to reach or has reached the supercritical state.

In one embodiment of the invention, the dyeing agent is any dye associated with the dyeing of leather and textiles, and at least one type of dye selected from the group consisting of acid dyes, basic dyes, direct dyes, reactive dyes, chromium dyes, mill dyes, metal complex dyes, mordant dyes and sulfur dyes, disperse dyes, reactive disperse dyes and natural dyes.

An example of a natural dye may be rose extract, for example.

In one embodiment of the invention, the stain is a collagen-reactive stain.

The dyeing process can therefore be carried out in a particularly advantageous manner, since, for example, leather priming, which may be mandatory in connection with conventional leather dyeing agents, can be avoided. Thus, a simplified process can be achieved. Avoiding leather priming is achieved by using dyes that have an affinity for the non-primed collagen fibres in the leather, and a great advantage is the intense colour across the leather cross-section, as the dyes are immobilised on all available collagen active sites.

Examples of reactive dyes may be Levafix Brilliant blue E-BRA (C.I. reactive blue 114 from Dstar Japan Ltd.), Levafix Brill.Red CA (Dstan Japan Ltd.), Levafix Golden Yellow E-G (C.I. reactive Yellow 27 from Dstan Japan Ltd.), Eriofast Red B (Huntsman), Novacron Red P-GRABN N (Hunsmy), Lanasol Red 6G (C.I. reactive Red 84 from Hunsmy).

In one embodiment of the invention, the processing aid is a retanning agent.

Thus, the retanning agent can impart fullness to the leather by selectively filling the structure and providing a tight and uniform grain finish to the leather.

It should be noted that the invention can be applied with particular advantages in connection with dyes, but the apparatus and method described herein can also be applied to leather processing in general using retanning agents. Part of the retanning or retanning process may thus be performed by the application of supplementary tanning agents such as inorganic or organic substances. Inorganic retanning agents which may be used in place of the above dyes include chromium, aluminium and zirconium salts. Organic retanning agents include vegetable tanning agents, syntans, resins and aldehydes.

In one embodiment of the invention, the amount of coloring and/or retanning agent is dosed according to the weight, thickness and/or surface area of the leather product.

Thus, the amount of dye, e.g. weight, volume, etc. of dye, may be added to match the leather product, e.g. such that at least the necessary amount and possibly the exact amount is added to achieve the desired dyeing effect and, thus, a minimum amount of dye will remain in the pressurized fluid after the dyeing process.

In one embodiment of the invention, the amount of coloring and/or retanning agent is dosed according to the type of leather product.

The dosing of the dye, which can be automated, can thus take into account parameters such as, for example, the type of leather, for example full grain or top grain leather, embossed grain leather, suede leather and suede leather, and the origin of the leather. It is thus possible to reduce the amount of residual coloring agent and to optimize the coloring result in this way.

In one embodiment of the invention, the leather article is finished with a primer prior to being subjected to the action of the pressurized fluid.

The primer may consist of an acceptor polymer. The acceptor polymer then forms the intended basis for dyeing, since such leathers are not suitable for dyeing themselves. The finishing underlayer may be part of a tanning, retanning and/or finishing (finish) process. The dyeing can in principle be carried out at any time after finishing the substrate, as long as the applied dye matches the polymer of said finished substrate.

Thus, it is achieved that a wide range of staining agents can be used. In addition, additional effects can be achieved, for example, only certain parts of the leather product are dyed, which parts have already been finished with the base layer, the corresponding dyeing agents influencing the coloration. Thus, it is even possible to carry out two-tone dyeing or the like in the same dyeing process according to the invention. Even two or more types of stains may be used for staining, one requiring finishing of the substrate and one not requiring finishing of the substrate, such as collagen reactive stains. Other options are also possible.

In one embodiment of the invention, the pressurized fluid comprises CO₂It has a purity of at least 99.0%, preferably at least 99.9%.

Comprising CO₂The pressurized fluid of (a) may have a purity of up to 99.99%.

In one embodiment of the invention, the method further comprises: a step of adding a coloring agent in an automatic manner based on the characteristics of the leather product.

Since the dyeing process is associated with one or more leather articles cut specifically for a certain purpose and having a predetermined size, a substantially precise amount can be allocated for the dyeing process. Thus, a specific amount of coloring agent may be automatically introduced, for example, into the pressurized fluid, the treatment chamber, or the leather article(s) associated with the process. It is thereby achieved that waste of colorant is minimized or even completely avoided. Furthermore, the effort to remove excess stain from the pressurized fluid and/or subsequent washing of the treatment chamber after one stain cycle may be minimized.

The characteristics of the leather article may be the weight and/or surface area of the leather article, the type of leather (e.g., full grain or top grain leather, embossed grain leather, suede leather, and suede leather), and the source of the leather. Other characteristics may also be relevant, or alternative.

In one embodiment of the invention, the step of subjecting the leather article to the action of a colouring agent and/or a retanning agent, which is dissolved and/or transported in the pressurized fluid at least for a predetermined period of time when the pressurized fluid is in the supercritical state, further comprises mixing, stirring or circulating the pressurized fluid in the supercritical state.

Other retanning agents and/or colorants may also be carried or transported by the pressurized fluid. In other words, the retanning agent and/or stain does not have to be dissolved in a pressurized fluid, as long as the final dyeing and/or retanning is achieved. For example, the retanning agent and/or stain may be carried and/or transported by the pressurized fluid due to the flow rate of the pressurized fluid in the supercritical state.

In one embodiment of the present invention, the dyeing step comprises the use of a fixing agent.

In one embodiment of the invention, the method comprises fat liquoring.

The fatliquoring process may be performed simultaneously with dyeing, but may also be as a separate process. Vegetable, animal or synthetic oils, fats and waxes may be used.

Examples of fatliquoring agents may be fatliquoring agents that may be used, including anionic fatliquoring agents such as sulfonated fatliquoring agents and sulfited oils, soap fatliquoring agents, and cationic fatliquoring agents. Nonionic fatliquoring agents, including alkyl ethylene oxide condensates and protein emulsifiers, may also be used. The high-price fatliquor as a preparation of non-ionic, anionic and cationic fatliquors can also be used in the fatliquor process.

In one embodiment of the invention, the method comprises a retanning agent.

Tanning as a primary tannage may not be sufficient to maintain the desired properties and the leather may therefore be retanned.

The retanning agent can be an inorganic mineral (chromium, aluminium, zirconium, titanium, iron salts or combinations thereof) or an organic substance (aldehydes, vegetable and synthetic tanning agents, resins, oils).

The retanning process may be carried out simultaneously with dyeing and/or fatliquoring, but may also be carried out as a separate process.

In an embodiment of the invention, the pressure of the pressurized fluid in the supercritical state is at least 70bar, such as between 70 and 260bar, such as 90 to 150bar, such as 130 to 250bar, or such as 180 to 240 bar.

In an embodiment of the invention, the temperature of the pressurized fluid in the supercritical state is between 30 and 120 degrees celsius, such as between 30 and 100 degrees celsius, such as between 30 and 60 degrees celsius, such as between 30 and 50 degrees celsius, such as between 30 and 40 degrees celsius.

In one embodiment of the invention, the predetermined time, i.e. the time the leather article is subjected to the action of the stain and/or retanning agent in the pressurized fluid in the supercritical state, is at least 1 minute, such as at least 15 minutes, such as between 15 minutes and 4 hours, such as between 25 minutes and 2 hours, such as more than 35 minutes.

In one embodiment of the invention, the leather articles are subjected to the action of the stain and/or retanning agent in the pressurized fluid in the supercritical state for a predetermined time of at least 1 minute, such as at least 15 minutes, such as from 1 minute to 40 minutes, such as from 1 minute to 4 hours, such as from 5 minutes to 2 hours, such as more than 15 minutes and such as less than 1 hour.

The predetermined time for which the leather article is subjected to the action of the stain and/or retanning agent in the pressurised fluid in the supercritical state may also be between 40 minutes and 4 hours, such as between 45 minutes and 2 hours, such as between 55 minutes and 2 hours, such as between 1 hour and 2 hours, such as over 40 minutes.

In one embodiment of the invention, the method further comprises: a step of providing a leather material, wherein said leather material is subjected to at least a tanning process, whereby at least one leather article is cut out of said leather material before being provided and introduced into said treatment chamber.

The leather material, which has been treated by at least the tanning process, may for example be hides or skins from whole animals, wherein the hides or skins have been subjected to the usual initial hide or skin treatment including the tanning process and are ready for the dyeing process. According to this embodiment, one or more leather parts are now cut from the hide or skin to cut the hide or skin. These leather articles may have different uses, such as different parts of a shoe, and may for example also be desired to be differently dyed. By means of this embodiment it is now possible to introduce one or more leather articles into the treatment chamber for dyeing according to the invention. Thus, dyeing of the entire pelt or skin is avoided, for example in the case of the long-term known techniques used in the art, since this can lead to a part of the entire dyed pelt or skin being discarded according to the prior art. Thus, by means of the described embodiments, waste of leather material can be reduced, and consumption of e.g. colouring agents can be reduced leading to a higher degree of cost-effectiveness, as well as reducing the impact on the environment. Furthermore, given the specific characteristics of leather products, individual leather products may be specially processed, for example, leather products from upper rawhide parts may be dyed with precise amounts of dyeing agents in order to achieve the desired coloration in view of, for example, the characteristics of the leather and the intended use, while leather products from other parts of the raw skin (e.g., the belly) may be treated and dyed with correspondingly precise amounts of dyeing agents to match their specific origin and intended use.

In one embodiment of the invention, the pressure of the pressurized fluid in the supercritical state and/or the temperature of the pressurized fluid in the supercritical state is controlled to provide a density of the pressurized fluid in the supercritical state within a predetermined range.

In one embodiment of the invention, the pressure reduction is controlled over time such that the reduction period exceeds a time interval of 5 minutes, such as 5 minutes to 2 hours, such as 15 minutes to 45 minutes, such as 15 minutes to 30 minutes, such as 30 minutes to 2 hours, such as 30 minutes to 65 minutes.

In one embodiment of the invention, the pressure reduction is controlled over time such that the pressure reduction does not exceed a predetermined leather pressure reduction gradient, such as 10bar/min, such as 8bar/min, such as 6bar/min or such as 4 bar/min.

In one embodiment of the invention, the pressure of the pressurized fluid is controlled to reach a supercritical state such that the time period exceeds a predetermined 5 minute increase period, such as an interval between 5 minutes and 1 hour, such as between 15 minutes and 45 minutes, such as between 15 minutes and 30 minutes.

In one embodiment of the invention, pressurizing the pressurized fluid in the treatment chamber to reach a supercritical state comprises increasing the pressure by no more than a predetermined leather pressure increase gradient, such as 20bar/min, such as 15bar/min, such as 10bar/min, such as 8bar/min, such as 6bar/min, such as 5bar/min or such as 4 bar/min.

The invention also relates to an apparatus for dyeing leather articles according to the method of any one of claims 1 to 27, comprising:

-a treatment chamber for treating the substrate,

-a source of a pressurized fluid,

-a source of a coloring agent and/or a retanning agent,

a pump, for example a controllable compressor, for increasing the pressure of the pressurized fluid to reach a supercritical state,

a pressure reducer, such as a pressure reducing member for reducing the pressure in the process chamber, and

-a controller for controlling the operation of the electronic device,

wherein the controller is configured to control the depressurizer to depressurize the treatment chamber over time after the leather article has been subjected to the coloring agent dissolved in the pressurized fluid in the supercritical state for at least a predetermined time.

The dyeing of leather articles can thus be achieved using the apparatus according to the invention, which is distinguished in that the use of relatively large amounts of water is avoided in comparison with conventional dyeing methods. This is achieved by the use of a coloring agent that is soluble in the pressurized fluid at least in the supercritical state, whereby the dissolved coloring agent, in combination with the pressurized fluid in the supercritical state, can penetrate into the leather structure comprising at least part of the internal structure, staining not only the surface of the leather structure but also underlying structures, such as collagen fibers in the leather structure.

According to the invention, the controller is configured to reduce the pressure in the treatment chamber, for example at the end of the dyeing process in supercritical state, in such a way that the pressure is reduced over time in such a way that the leather article retains the desired characteristics vital to its long-term use, for example the color and surface characteristics, that any tendency of the leather to delaminate is minimized or even completely avoided, and that the preventive requirements of the leather delamination are met. This may involve setting a minimum time period for the reduced pressure, setting a maximum number of pressure reduction gradients, setting a maximum number of average pressure reduction gradients, etc., which will ensure that the leather structure, particularly one that has been dyed with a dyeing agent and penetrated by the pressurized fluid in the supercritical state, is not adversely affected during the pressure reduction.

The controller is configured to reduce the pressure of the treatment chamber by controlling the pressure reduction over time to meet the preventive requirements of leather delamination, for example meaning that the leather structure, in particular the leather structure that has been dyed by the dyeing agent and permeated by the pressurized fluid in the supercritical state, is not affected by leather delamination during or after dyeing.

In one embodiment of the invention, the controller is further configured for controlling the pressure in said process chamber of said pressurized fluid to reach a supercritical state by increasing the pressure over time within predetermined limits.

It should be noted that a controller refers to a control device of one or more interactive circuits that may be preconfigured or configured to perform some desired method, such as the methods claimed and described in the present invention, for example, in the disclosed apparatus. The controller may thus include RAM or ROM memory.

Thus, the process of dyeing and/or retanning leather may be automated to varying degrees, including in a substantially fully automated manner, e.g. including one or more steps that are partially or fully automated, i.e. in a manner that is substantially fully automated

-providing a leather product, which has been subjected at least to a tanning process,

-introducing said leather articles into a treatment chamber,

-subjecting the leather article in the treatment chamber to the action of a pressurized fluid,

-controlling the pressure of the pressurized fluid to reach a supercritical state,

-subjecting the leather product to the action of a coloring agent, which is dissolved in or carried/transported by the pressurized fluid at least for a predetermined time while the pressurized fluid is in the supercritical state,

and/or subjecting the leather article to the action of a retanning agent while the leather article is in a pressurized fluid in a supercritical state

-reducing the pressure in the process chamber,

-removing the leather article from the treatment chamber,

wherein the step of reducing the pressure in the process chamber comprises controlling the pressure to decrease over time.

According to a further embodiment, the method may be applied in an at least partially automated manner by integrating the automation of the steps and/or features as exemplified in the dependent claims.

Thus, the pressure increases over time in such a way that the leather article retains the desired properties that are crucial for its long-term use, for example, the color and surface properties, that any tendency of the leather to delaminate is minimized or even completely avoided, and that the preventive requirements for leather delamination are met. This may involve setting a minimum period of increased pressure, setting a maximum value of a gradient of increase in average pressure, etc., which will ensure that the leather structure, in particular a leather structure that has been dyed by a dyeing agent and penetrated by a pressurized fluid in a supercritical state, is not adversely affected during the increase in pressure.

The increase in pressure in the treatment chamber comprises controlling the pressure increase over time to meet the preventive requirements of leather delamination, for example meaning that the leather structure is not affected by leather delamination during or after dyeing.

Drawings

The invention will now be described with reference to the accompanying drawings, in which

Figures 1-4 show examples of processing leather articles by dyeing and/or retanning according to embodiments of the present invention,

fig. 5a and 5b show an example of an apparatus for dyeing and/or retanning according to an embodiment of the present invention,

fig. 6a and 6b show an example of an apparatus for dyeing and/or retanning according to an embodiment of the present invention,

FIG. 7 shows a phase diagram of carbon dioxide, an

Fig. 8a and 8b show graphs of pressure over time.

Detailed Description

Figure 1 shows the composition of the overall process flow.

First, a leather article is provided 2, either as a previously uncut or trimmed piece of leather, or as at least one pre-cut piece of leather. The leather articles are placed in the treatment chamber 4 and subjected to the action of the pressurized fluid 6. The dye is introduced 8 and brought to a supercritical state 10, for example by pumping, further compressing the fluid, etc. Finally, after the dyeing process has been carried out, the pressure is reduced 12 and the leather goods are removed 14.

Figure 2 also shows the composition of the overall process flow. First, the leather product 2 is provided, either as a previously uncut or trimmed piece of leather, or as at least one pre-cut piece of leather. The leather articles are placed in the treatment chamber 4 and subjected to the action of the pressurized fluid 6. The dye is introduced 8 and a supercritical state is reached 10. Finally, the pressure is reduced 12, for example by removing 16 the residues of the process stains, such as distillation, precipitation etc., for example in connection with the pressure reduction, and the leather goods are removed 14.

Figure 3 further illustrates the composition of the overall process flow. First, the leather product 2 is provided, either as a previously uncut or trimmed piece of leather, or as at least one pre-cut piece of leather. The leather articles are placed in the treatment chamber 4 and subjected to the action of the pressurized fluid 6. The dye is introduced 8 and a supercritical state is reached 10. Finally, the pressure is reduced 12, the fluid is recirculated 18, for example into a container, from which it can be supplied for subsequent use, as shown in the flow chart, and the leather goods are removed 14.

Figure 4 shows the composition of the overall process flow. First, a leather material 22 is provided and cut into articles 24. At least one leather article is placed in the treatment chamber 4 and subjected to the action of the pressurized fluid 6. The dye is introduced 8 and a supercritical state is reached 10. Finally, the pressure is reduced 12 and the leather product is removed 14.

Referring now to fig. 1-4, a process flow is shown in which a processing chamber in which one or more leather articles are placed is illustrated herein as a box, according to an embodiment of the present invention. It should be noted, however, that the process chamber may have any form associated with adjusting the optimal conditions to maintain supercritical conditions for a period of time. In one embodiment of the invention, the process chambers and equipment may appear in some relationships on a small scale and in other relationships on a large scale, depending on a given application.

The pressurized fluid may be in liquid form, but may also be in gaseous form.

It is noted that a retanning agent may be introduced in place of the stain in the example shown in fig. 1-4. .

Fig. 5a and 5b show an example of a device in an embodiment of the invention, e.g. using a method according to an embodiment of the invention.

Fig. 5a shows the processing of the leather material 30. the leather material 30 may be a single piece of leather without any pre-cutting, or may be a piece of leather, such as a leather product that has been subjected to a cutting or trimming step.

Fig. 5b shows the processing of leather material 30, wherein the leather piece has undergone at least one process of cutting the leather into at least one piece (e.g., leather goods 32) prior to entering the processing chamber.

In fig. 5a and 5b, the leather product, either as a piece of leather not subjected to pre-cutting 30 or as a piece of pre-cut leather 32, is subjected to the action of a treatment chamber 34. The process chamber may be configured in the form of a pressure chamber.

The pressure chamber may be connected to at least one controllable compressor 36 for pressurizing a fluid provided by a high pressure storage vessel 38. The pressure provided by the controllable compressor 36 is introduced into the pressure chamber 34 via an introduction member 42, such as a controllable valve or the like. At the output, the pressure may be reduced by a pressure reduction member 44 (e.g., in the form of a controllable valve or the like). According to one embodiment of the invention, the apparatus may further include a separator 46 that receives the escaping pressurized fluid and wherein, for example, residual coloring agents may be separated from the pressurized fluid. The pressurized fluid may exit the separator 46 via an outlet 48, and the separated residual stain may be collected via a residual outlet 50. The outlet 48 may lead to further processing for storage in storage containers or the like. Processing agent 56 is introduced into the chamber from a source of processing agent 52 through a controllable inlet 54 and, in a preferred embodiment of the invention, the processing agent is a dye.

The dye may be introduced into the treatment chamber at the same time as the leather product, but may also have been introduced in the treatment chamber or after the leather product has been introduced into the treatment chamber.

The pressure is introduced in such a way that supercritical conditions are reached and optimal dyeing conditions are achieved in such a way that the dye dissolves and bonds optimally to the leather. The pressure is released in such a way that the desired properties vital to the long-term use of the leather are maintained, for example the colour and surface properties are maintained, so that any tendency of the leather to delaminate is minimized or even completely avoided, and so that the preventive requirements for leather delamination are met. The introduction and release of pressure and the introduction of dye is controlled by a controller 40, wherein the controller 40 as shown may be connected to the controllable compressor 36, the introduction means 42, the controllable inlet 54 and the pressure reduction means 44 to control these according to parameters such as time, pressure, temperature, characteristics of the leather product, etc.

The pressurized fluid may be in liquid form, but may also be in gaseous form.

Fig. 6a and 6b further illustrate an example of a device in an embodiment of the invention. Features shown in fig. 6a and 6b and corresponding to features shown in fig. 5a and 5b are indicated by the same reference numerals. The leather product 30 is placed in a treatment chamber 34, which may be configured in the form of a pressure chamber. The leather product may be a single piece of leather that has not been pre-cut or trimmed prior to processing, but may also be at least one pre-cut piece of leather. The device shown in fig. 6b substantially corresponds to the example shown in fig. 6a, but the modifications to be explained below may be implemented in any other embodiment described herein. After the dyeing process, the supercritical fluid with dye is circulated via the recirculation connection 80, and the pressurized fluid can exit the process chamber via the separator 46. However, as shown in fig. 6b, the separator is omitted and the separation of the remaining dye may be performed in the process chamber 34, for example by reducing the pressure of the fluid, so that any residue or remaining dye is separated from the fluid and eventually falls to the bottom of the process chamber. After the remaining dye is separated, a fluid, such as carbon dioxide, may be pumped from the processing chamber 34, through the pressure reduction member 44, through the recirculation connection 70, and the recirculation compressor 82, whereby the fluid will be directed back into the storage vessel 38. With respect to residual dye in the process chamber 34, a rinse cycle may be performed, for example with carbon dioxide, to clean the process chamber and its connections.

Pressurized fluid may be circulated from the pressurization chamber and reused back to the pressurization chamber as shown by recirculation connection 80. The pressurized fluid may also be recycled and reused, or as a single process step, after exiting separator 46 and returning to high pressure storage vessel 38 via recycle compressor 82.

Fig. 7 shows a phase diagram of carbon dioxide in proportion (schematic and not to scale). Carbon dioxide appears as a gas G in air at standard temperature and pressure, or as a solid S when frozen. When both the temperature and the pressure increase above the critical point CP of carbon dioxide, it has properties intermediate between those of the gas and the liquid L. Here, it behaves as a supercritical fluid SCF above the critical temperature (31.1 ℃) and critical pressure (73.9 bar).

Fig. 8a illustrates an exemplary time line of the pressure P as a function of time T, for example illustrating the condition of the treatment chamber 34 during a leather product dyeing cycle. The pressure may start at ambient pressure t1 and at this point the leather articles may be introduced into the processing chamber. After a given time, the pressure is increased, for example by introducing and further pressurizing a substance such as CO₂Increases t2 and increases up to the critical point t3 of the pressure CP. The gradient of the pressure increase over time may be a sharp increase, wherein the pressure increases over a shorter period of time, or a slow increase, wherein the pressure increases slowly over a given time. Between t3 and t5, the supercritical state is maintained for a given time. In this example, the illustrated curve shows a flat top of constant pressure over time, however, the top may also have a pressure increase over time, extending directly to a decrease, without having a constant pressure over time. After a given time period t4, the pressure drops and over time until ambient conditions are reached. The gradient of the pressure drop over time may be a sharp drop, where the pressure drops over a short period of time, or may be a slow drop, where the pressure drops slowly over a given time.

The dye may be added to the process chamber at the beginning of the process, for example at t1 or t2, but may also be added later, perhaps during supercritical conditions. When the pressure is reduced or the conditions reach ambient conditions, the dye, which may be in excess, may be released and removed from the processing chamber (or separated from the pressurized fluid exiting the processing chamber).

Fig. 8b illustrates a corresponding exemplary timeline of pressure P over time T, showing substantially the same pressure curve and the same points in time as in fig. 8 a. Further, as illustrated as an example in fig. 8b, at time t7, i.e. after the liquid reaches a supercritical state, dye is added to the process chamber. Thus, as shown below the time axis (T-axis), the leather articles in the treatment chamber will be subjected to the action of the coloring agent dissolved or diluted in the supercritical liquid for a time period Td corresponding to T5-T7.

Further, illustrated in FIG. 8b, the pressure reaches a maximum at t8, after which the pressure remains substantially constant until t 4. Thus, as shown below the time axis (T-axis), the leather articles in the fluid will be subjected to a pressure increase for a time period Tinc corresponding to T8-T2. In addition, it can be seen that a pressure gradient can be determined and monitored, here expressed as the value | Pgrad-i |. The device may be configured to control the pressure increase by monitoring the period Tinc, which must exceed a predetermined increase period, such as 15 minutes, such as 25 minutes, such as 5 minutes to 1 hour, such as 15 minutes to 45 minutes, such as 15 minutes to 30 minutes, or the device may be configured to control the pressure increase by monitoring a pressure gradient, such as a value | Pgrad-i |, which must not exceed a predetermined leather pressure increase gradient, such as 20bar/min, such as 15bar/min, such as 10bar/min, such as 8bar/min, such as 6bar/min, such as 5bar/min or such as 4 bar/min.

Still further, illustrated below the time axis (T-axis) of fig. 8b, the leather articles in the fluid will be subjected to a pressure reduction over a period Tred corresponding to T6-T4. Further, it is shown that a pressure gradient can be determined and monitored, here expressed as a numerical value | Pgrad-r |. The device may be configured to control the pressure reduction by monitoring the period Tred, which must exceed a predetermined reduction period, such as 15 minutes, such as 25 minutes, such as 30 minutes, such as between 5 minutes and 2 hours, such as between 15 minutes and 45 minutes, such as between 15 minutes and 30 minutes, such as between 30 minutes and 2 hours, such as between 30 minutes and 65 minutes, or the device may be configured to control the pressure reduction by monitoring a pressure gradient, such as the value | Pgrad-r |, which must not exceed a predetermined leather pressure reduction gradient, such as 10bar/min, such as 8bar/min, such as 6bar/min or such as 4 bar/min.

The figure is schematic, the time intervals for pressurizing and lowering may be different from each other, even quite large, and pressurizing may be much faster than depressurizing, thus implying that the curve for pressurizing may be relatively steeper.

In this context, pressurized fluids and fluids refer to compounds that adopt properties intermediate between those of gases and liquids and behave as supercritical fluids.

Any substance is characterized by a critical point obtained under specific pressure and temperature conditions. When the pressure and temperature to which a compound is subjected is above its critical point, the fluid is said to be "supercritical".

Carbon dioxide is the most widely used supercritical fluid because it is a naturally occurring gas and is readily available for industrial consumption.

Carbon dioxide typically behaves as a gas in air at standard temperature and pressure, or as a solid (dry ice) when frozen. When both the temperature and pressure increase above the critical point CP of carbon dioxide, it has properties intermediate between gas and liquid. Here, it behaves as a supercritical fluid above the critical temperature (31.1 ℃) and the critical pressure (73.9 bar). In this way, the supercritical carbon dioxide has a liquid-like density, which is advantageous for dissolving the dye, and a gas-like low viscosity and diffusion characteristic, which may result in a shorter dyeing time than water and dye penetrate into the material.

The critical point of the pressurized fluid may vary depending on various conditions, such as the density and/or purity of the fluid. Therefore, the method of dyeing leather products can be not only in the supercritical state but also in the near supercritical state. Supercritical and near supercritical may be used interchangeably herein. Accordingly, it should be understood that when reference is made in the claims and specification of the present application to "pressurized fluid in a supercritical state" or similar terms, such terms are intended to include pressurized fluid in a near supercritical state.

The terms "supercritical carbon dioxide" or "SC-CO 2" are used interchangeably herein. In addition, carbon dioxide and CO₂May be used interchangeably herein.

The term "dye" or the term "dyeing" refers herein to a dyeing substance other than chromium-based compounds commonly used in the art as tanning agents, although it is noted that in conventional tanning processes, for example chromium-based substances often result in tanned leathers appearing blue. Thus, in the present context, dye or stain refers to a substance added with the purpose of obtaining a desired color. In other words, the dyeing within the scope of the invention is preferably carried out under supercritical carbon dioxide conditions.

The dyeing process of the invention may be carried out in a treatment chamber, but in general, it should be noted that the dyeing process may be applied with any suitable dyeing apparatus designed for dyeing according to the provisions of the present invention.

The term leather or leather material refers to animal skins that are prepared for use by tanning or similar processes that are intended to protect them from decay and to impart flexibility or softness when dry.

The type of leather used within the scope of the present invention may be any bovine derived type, such as cow or calf. Examples of leather types used within the scope of the present invention may be of the type such as full grain or top grain leather, embossed grain leather, suede leather and suede leather.

In principle, the leather may be from any source, including horse hide, goat hide, sheep hide, kangaroo hide, and the like. Even so, preferably the leather is mammalian or marsupial leather (i.e., hide derived from a mammal such as cattle or horses, or a marsupial such as kangaroo). Cow leather is the most commonly used.

The term "leather article" refers to any piece of leather that can be used as a one-piece leather or a pre-cut piece of leather. Leather in this context is to be understood broadly as an article comprising a leather part. In other words, the leather product must comprise portions of animal skins which have been prepared for use by tanning or similar processes aimed at protecting them from decay.

The leather article may also comprise, for example, yarns or filaments.

The leather article may be pre-cut parts, such as a shoe, wherein the parts may be, for example, an upper, a vamp (vamp), a toe cap (toe cap), a quarter (quarter), or a heel cap (heel cap).

Leather articles may of course also refer to other types of leather, including apparel, apparel parts, leather accessories such as bags, leather parts of bags, wrist bands, cell phone covers, and the like. Leather articles may also include leather components associated with automobiles, such as leather articles for seats, leather articles for steering wheel covers, shift lever grip gloves, and the like.

Leather articles may also refer to articles comprising leather parts, such as filaments or yarns reconstituted from leather, for example as disclosed in PCT/EP2018/053849, PCT/EP2018/053848, hereby incorporated by reference. Such yarns or filaments are therefore understood to be leather products within the scope of the present invention, provided that the small leather parts (also called fibers in the above-mentioned application) originate from tanned leather, even if the leather product in this case also comprises additives which promote the aggregation of such small leather parts.

It should be noted that "leather articles" processed within the scope of the present invention may mean that one, two or more leather articles may be processed simultaneously.

Preferably, the leather type is carefully selected based on the characteristics of the leather and the chemicals used to pretreat the leather, for example during the tanning process.

In principle, the process can be carried out with any type of leather. However, in general, leather has been tanned.

Tanning is used as a conventional method for treating leather and is applicable to the present invention. Depending on the compound, the fabric may vary in color and texture. Technical definitions of Tanning are well known in the art, but briefly, according to Anthony D.Covington, Chapter 10 of Tanning Chemistry, the only strict definition of Tanning is the conversion of compostable organic materials into stable materials that are resistant to biochemical attack. Tanning involves several steps and reactions, depending on the starting materials and the final product.

In the case of collagen, the side chain determines to a large extent its reactivity and the ability to be altered by the stabilizing reactions of tanning in the manufacture of leather. Furthermore, the chemical composition of the backbone defined by the peptide chain provides different reaction sites that can be utilized in some tanning processes. During the process of tanning leather, the modification of collagen by the chemical reaction of the tanning agent affects different characteristics of the material characteristics; the hydrophilic-hydrophobic balance of the leather may be significantly affected by the chemical reaction of the tanning agent by altering the relationship between the leather and the solvent, which in turn affects the balance of any agents between the solvent and the substrate. In addition, the reactive sites between the agent and the collagen may affect the isoelectric point of the collagen, and thus, there may be a different relationship between the pH and the charge on the leather. The lower the isoelectric point, the more or less anions or cations the charge on the material may be at any pH: the higher the isoelectric point, the more cationic or less anionic the charge on the hide will be at any pH. Furthermore, the relative reactions at the side chains and the backbone of the protein may determine the type of reaction and thus the degree of stability of tanning: the fastness of the reagent may be affected by the interaction between the reagent and the substrate.

Any type of tanned leather may be used, including metal tanning (e.g. using chromium, aluminium, zirconium, titanium, iron or combinations thereof), vegetable tanning (e.g. using tannins from bark or other sources), aldehyde tanning (e.g. using aldehydes) or natural tanning, e.g. oil tanning.

Typically, leather is chrome tanned or vegetable tanned, with chrome tanned leather being the most commonly used.

Tanning as a primary tannage may not be sufficient to maintain the desired properties and therefore re-tanning may be possible. The tannins used in this process may be different from those used in the primary tanning stage.

Fatliquoring refers to a process of fixing fats/oils and waxes onto leather fibers. The primary function of the fatliquoring is to prevent the fibrous structure from re-sticking during drying by providing an oil surface to the fibrous structure. Any fatliquor may be used, including anionic fatliquors such as sulfonated fatliquors and sulfitated oils, soap fatliquors, and cationic fatliquors. Nonionic fatliquoring agents, including alkyl ethylene oxide condensates and protein emulsifiers, may also be used. The high-price fatliquor as a preparation of non-ionic, anionic and cationic fatliquors can also be used in the fatliquor process.

The raw material of the fatliquor can be marine animal oil, such as fish oil; land animal oils and fats such as claw oil (claw oil), beef tallow, lard, and bone tallow; vegetable oils and fats such as palm oil, sunflower oil, rapeseed oil, soybean oil, coconut fat, palm kernel fat, and turkey red oil; waxes such as baxipalm wax, montan wax and lanolin. Grease; synthetic fats such as paraffin oil, mineral oil, fatty alcohol and fatty acid ester.

As used herein, "at least one" means one or more, i.e., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.

The term "comprising" may be used as an open term, but it also includes the closed term "consisting of … …".

It should be noted that the application of the invention in the dyeing sector has particular advantages, but the apparatus and the process described here can also be applied to leather processing in general, using retanning agents. A part of the retanning or retanning process may be performed by, for example, applying a supplementary retanning agent such as an inorganic or organic substance. Inorganic retanning agents that can be used in place of the above identified dyes thus include chromium, aluminium, zirconium salts. Organic retanning agents include vegetable tanning agents, syntans, resins and aldehydes.

Reference numerals

2. Providing leather articles

4. The leather products enter the processing chamber

6. Subjected to the action of a pressurised fluid

8. Introduction of coloring agents

10. Pressurized fluid in supercritical state

12. Reducing the pressure

14. Removing leather articles

16. Removing stain residue

18. Recirculating fluid

22. Providing a leather material

24. Cutting material into articles

30. Leather product

32. Precut leather product

34. Processing chamber

36. Controllable compressor

38. High pressure storage vessel

40. Controller

42. Lead-in part

44. Pressure relief component

46. Separator

48. An outlet

50. Residue outlet

52. Source of processing aids

54. Controllable inlet

56. Processing aid

70. Recirculating connection

80. Recirculating connection

82. Recirculation compressor

A. Environment(s)

Critical point of CP

G. Gas (es)

L. liquid

Pressure (P)

S. solid

SCF, supercritical fluid

Time T

Time of pressure increase

Time to pressure reduction tred

IPgrad-iI. pressure increase gradient

IPgrad-rI. pressure reduction gradient

Td. exposure to a coloring agent