Classifications

• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C3/00—Tanning; Compositions for tanning
  • C14C3/02—Chemical tanning
  • C14C3/08—Chemical tanning by organic agents
  • C14C3/18—Chemical tanning by organic agents using polycondensation products or precursors thereof
• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C3/00—Tanning; Compositions for tanning
  • C14C3/02—Chemical tanning
  • C14C3/08—Chemical tanning by organic agents
  • C14C3/16—Chemical tanning by organic agents using aliphatic aldehydes
• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C3/00—Tanning; Compositions for tanning
  • C14C3/02—Chemical tanning
  • C14C3/08—Chemical tanning by organic agents
  • C14C3/18—Chemical tanning by organic agents using polycondensation products or precursors thereof
  • C14C3/20—Chemical tanning by organic agents using polycondensation products or precursors thereof sulfonated
• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C3/00—Tanning; Compositions for tanning
  • C14C3/02—Chemical tanning
  • C14C3/08—Chemical tanning by organic agents
  • C14C3/22—Chemical tanning by organic agents using polymerisation products
• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C3/00—Tanning; Compositions for tanning
  • C14C3/02—Chemical tanning
  • C14C3/28—Multi-step processes
• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14C—CHEMICAL TREATMENT OF HIDES, SKINS OR LEATHER, e.g. TANNING, IMPREGNATING, FINISHING; APPARATUS THEREFOR; COMPOSITIONS FOR TANNING
  • C14C9/00—Impregnating leather for preserving, waterproofing, making resistant to heat or similar purposes
  • C14C9/02—Impregnating leather for preserving, waterproofing, making resistant to heat or similar purposes using fatty or oily materials, e.g. fat liquoring

Definitions

• the present invention relates to a skins tanning process.
• a tanning process includes preliminary operations producing the so-called pelt; the actual tanning; the retanning; and dressing treatments.
• Preliminary operations are basically aimed at removing, from the skins, various impurities and the preservatives used to maintain the skins intact until the tanning process as well as at restoring the features of the skins, thus making them suitable for the following actual tanning treatments.
• tanning transforms the pelt into leather by means of proper tanning substances, which penetrate the skin and are steadily fixed to the dermal fibres.
• tanning vegetable tanning, mineral tanning, etc.
• manufacturers select the tanning process that is deemed to be the most appropriate to obtain specific features of the end product .
• the skins are then subjected to dressing operations, even based on the uses for which the skins are intended.
• Tanning processes known at the moment have proven to be not good enough, in particular from the point of view of their environmental impact.
• known processes because of the products used in the different processing steps and of the techniques involved, cause the production of waste waters and of processing waste that are highly polluting and, anyway, are very difficult to be handled from an environmental point of view; moreover, they do not lead to an end product or to a processing waste that are completely (or at least largely) biodegradable or compostable.
• the object of the present invention is to provide a tanning process that is not affected by the above-mentioned drawbacks shown by prior art processes; in particular, it is an object of the present invention to provide a tanning process that allows manufacturers to obtain a fully biodegradable product, besides being versatile and effective, which leads to the production of high-quality products .
• the present invention relates to a tanning process as defined, in its essential aspects, in appended claim 1 and, in its additional features, in the dependent claims .
• the process according to the present invention thanks to the specific products used and to the processing techniques applied, allows manufacturers to obtain a fully biodegradable product.
• the process according to the present invention allows the skins to gain (after having been dried) features that are comparable with the ones obtained with traditional techniques, in particular softness, a peasant feel, colouring and technical performances that are suitable for the use in different fields, such as shoes, leather products, furniture, car upholstery, etc.
• - figure 1 contains a table (Table I) showing examples of the ways in which a preliminary step, in particular a soaking-liming step, of the process according to the invention can be carried out;
• - figure 2 contains a table (Table II) showing examples of the ways in which further steps, defining - as a whole - a tanning macro-step, of the process according to the invention can be carried out;
• FIG. 3 contains a table (Table III) showing examples of the ways in which a retanning step of the process according to the invention can be carried out.
• the process according to the invention is advantageously carried out in drums, for example in the ways (processing recipes) shown, by way of example, in the appended tables.
• a rotary drum which is manually or semi-manually operated or is controlled by a control unit, which automatically manages, based on operating schedules corresponding to pre-set recipes, the operation of the drum and, therefore, the different steps of the process.
• the drum can be set so as to rotate for predetermined time intervals at the desired speed, if necessary alternating rest times (still drum) .
• an indication such as "automatic cycle x-y-x" indicates that the drum rotates for periods of x minutes alternated with rest periods of y minutes .
• the drum is drained, when the processing recipe requires to do so, through suitable openings.
• the process according to the present invention is used to treat raw skins, for example skins that are freshly salted immediately after having flayed the animal.
• Raw skins are firstly introduced into the drum for a preliminary soaking-liming step, during which, in substantially known ways, the first processing in preparation of the tanning is carried out, thus obtaining the so-called pelt (state of the skin at the end of the preliminary soaking-liming step) .
• the preliminary step is carried out in the ways shown in appended Table I of figure 1 (where the compositions of the products used are indicated as percentage of the weight of the raw skin treated in the preliminary step) .
• Table I of figure 1 where the compositions of the products used are indicated as percentage of the weight of the raw skin treated in the preliminary step.
• the commercial names of the products used are provided by mere way of example; each product indicated herein can be replaced with equivalent products.
• tanning macro-step (carried out, for example, in the ways shown in Table II of figure 2) , which comprises four main steps: deliming, bating, pickling, tanning .
• compositions of the products used in the tanning macro-step are indicated as percentage of the weight of the pelt of the skin (weight of the material obtained from the preliminary step and destined to the tanning macro-step) .
• the deliming step has the function of completely removing the lime absorbed by the skin during the preliminary soaking-liming step.
• a first bath which contains:
• thioglycolic acid e.g.: COSMOCAL E
• the drum is caused to rotate for 15-45 minutes, then it is drained. Subsequently, after having drained the drum, (cold) water is added, in particular 30-100%; then, in successive stages, a deliming agent is added, in particular a sulfamic acid-based deliming agent (e.g.: DECALCINANTE A-OS SPECIAL), in increasing quantities:
• a deliming agent is added, in particular a sulfamic acid-based deliming agent (e.g.: DECALCINANTE A-OS SPECIAL), in increasing quantities:
• the drum is drained and a delimed skin is obtained, which is completely free from lime.
• the skin undergoes a bating treatment, which basically consists in the removal of the so-called surface shield (residues of proteins, albumins, etc.) and of elastin.
• the bating step can be carried out in basically known ways, through suitable degreasing substances and enzymes (as indicated, for example, in Table II) .
• the skin is subjected to a pickling step, consisting in conditioning the skin at a highly acid pH below 4 and approximately ranging from 2.7 to 3.5, preferably around 3-3.2.
• the pickling step is carried out with known products (basically, sodium chloride, formic acid and sulfuric acid) , but, according to the invention, it requires specific operating techniques, which ensure a particular balance among the content of water, salts and acids in the treatment bath contained in the drum, this condition being necessary to make sure that the subsequent addition of the tanning substance and the penetration into the section of the skin produce good results.
• known products basicly, sodium chloride, formic acid and sulfuric acid
• the pickling step is carried out as follows:
• the drum After having emptied the drum from the water left by the previous step (bating) , the drum is filled with a bath containing :
• the drum is caused to rotate for 10-20 minutes and then density of the bath is controlled to make sure that it ranges from 8 to 10 degrees Baume .
• the result is a bath with a pH below 4 and approximately ranging from 2.7 to 3.5, preferably ranging from approximately 3 to 3.2.
• the total content of water at the end of the pickling step (hence, before the tanning step) , starting from 25% of initial water and after the addition of the diluted acids, is approximately 40% +/- 5%.
• the content of water at the beginning of the tanning step should range from 25% to 55%.
• experiments have shown that a total water content below 25% or exceeding 55% slows down - or even completely blocks - the penetration of the tanning product and, therefore, the stability of the tanning itself.
• a tanning product (2-10%) is added to the drum, which contains an acid naphthalene tannin, an acid phenolic tannin and sodium sulphate; and a synthetic ester (0.1-1.0%) .
• the drum is rotated for 5 hours.
• the skins are discharged from the drum without being washed (contrary to what normally happens in traditional tanning processes) .
• This type of tanning allows manufacturers to obtain a partial stabilization of the skins, which can be stored after having been subjected to pressing (or, if necessary, complete drying), split, shaved and, at the end, sent to the retanning and drying steps .
• the skins Once the skins have been split and/or shaved to obtain the desired thickness, they are reintroduced into drums, in which a retanning step is carried out so as to give to the skins (after the drying thereof) high softness, a peasant feel, colouring and technical performances that are useful in the production of articles such as shoes, leather products, furniture, car upholstery, etc.
• the retanning step is carried out, for example, in the ways shown in Table III of figure 3, where (like in the description below) the compositions of the products used are indicated as percentage of the weight of the shaved skin (material ready for the retanning step) .
• the retanning step is carried out using a retanning compound containing a C4-C6 linear di-aldehyde in an aqueous solution, wherein the di-aldehyde is available in quantity ranging from 1 to 15% of the weight of the treated skin.
• the retanning compound is prepared by mixing (for example, through rotation in the drum for approximately 20 minutes) :
• a fatliquor for example a synthetic oil mixed with deodorized sulphited fish oil (e.g.: COSMOFAT G) , rotating for 30 minutes; then a liquid tanning product (8-12%) is added, which contains sulphone-based synthetic tannins, in particular phenolsulphone-based and/or di-idroxy-diphenilsulphone- based (e.g.: COSMOWHITE SR) , rotating for 120 minutes.
• the drum is rotated for periods of 3 minutes with rest intervals of 30 minutes for a whole night (8 hours) .
• the drum is drained and two washing steps are carried out with 300% of hot water (40°C) .
• a vegetable fatliquor for example a vegetable lecithin-based one (e.g.: COSMOFAT C) , rotating for 30 minutes;
• a vegetable lecithin-based one e.g.: COSMOFAT C
• a vegetable extract-base filler e.g.: COSMOWHITE F
• COSMOWHITE F a vegetable extract-base filler
• tanning product containing sulphone- based synthetic tannins e.g.: COSMOWHITE SR
• COSMOWHITE SR sulphone- based synthetic tannins
• the drum is drained and two further washing steps are carried out .
• the skin is pressed, vacuum-dried at a temperature not exceeding 40 °C and then hung in a catenary for complete drying.
• the skin Once the skin has dried, it can be processed to manufacture any kind of article.
• the products used for the dressing of the skins must be selected so as not to jeopardize the biodegradability of the leather obtained with the process according to the invention .

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Cited By (2)

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Citations (3)

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• 2015
  • 2015-04-21 IT ITTV2015A000055A patent/ITTV20150055A1/it unknown
• 2016
  • 2016-04-21 WO PCT/IB2016/052282 patent/WO2016170503A1/en active Application Filing
  • 2016-04-21 EP EP16723529.0A patent/EP3286342B1/en active Active
  • 2016-04-21 CN CN201680023111.1A patent/CN107743525B/zh active Active
  • 2016-04-21 ES ES16723529T patent/ES2887790T3/es active Active

Patent Citations (3)

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