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
  • C14C15/00—Apparatus for chemical treatment or washing of hides, skins, or leather
• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14B—MECHANICAL TREATMENT OR PROCESSING OF SKINS, HIDES OR LEATHER IN GENERAL; PELT-SHEARING MACHINES; INTESTINE-SPLITTING MACHINES
  • C14B1/00—Manufacture of leather; Machines or devices therefor
  • C14B1/02—Fleshing, unhairing, samming, stretching-out, setting-out, shaving, splitting, or skiving skins, hides, or leather
• • C—CHEMISTRY; METALLURGY
  • C14—SKINS; HIDES; PELTS; LEATHER
  • C14B—MECHANICAL TREATMENT OR PROCESSING OF SKINS, HIDES OR LEATHER IN GENERAL; PELT-SHEARING MACHINES; INTESTINE-SPLITTING MACHINES
  • C14B1/00—Manufacture of leather; Machines or devices therefor
  • C14B1/26—Leather tensioning or stretching frames; Stretching-machines; Setting-out boards; Pasting boards

Definitions

• the present invention generally relates to the technical field of tannery, and particularly relates to a process and plant for the continuous treatment of laminar products such as industrial hides or the like.
• Industrial processes for treatment of laminar products, particularly hides or similar products are known to include a plurality of steps, which are generally continuously carried out from a raw product ad have the purpose of stopping bacterial and enzymatic processes, or protecting the product, while imparting a given exterior appearance thereto.
• a typical method includes a first sequence of chemical and mechanical processes, known as "beamhouse processes", in which the hides are prepared for the proper tanning process, during which the hide structure is stabilized.
• these processes are carried out in wet conditions, i.e. by dipping the hides in more or less dense water- or oil-based liquids, containing organic or inorganic chemicals.
• a first hide impregnation step is followed by a liming step for relaxation of tissues and by a fleshing step for separating the hide from residual muscle and fat tissues.
• a first mechanical splitting step may be also provided to reduce and level out hide thickness.
• the hide that still has a high moisture content in certain cases above 80%, undergoes tanning with chrome (namely "wet-blue” tanning) or with vegetable or synthetic dyes or aldehyde (namely "wet-white” tanning) and then pressed to reduce the moisture content to a value in a range from 40% to 50%.
• chrome namely "wet-blue” tanning
• vegetable or synthetic dyes or aldehyde namely "wet-white” tanning
• the hides may be submitted to splitting and shaved, or only shaved, to achieve uniform thickness.
• the process ends with the retanning, dyeing and drying steps.
• a hide stretching step may be further provided, using a variety of operating techniques.
• An industrial hide treatment which includes all the above steps, although the stretching step is carried out before the splitting step, so that hides with a high residual moisture content can be processes by further maintaining such moisture content value is substantially constant to obtain a considerably increased final footage.
• a well-known drawback of the prior art solutions that provide one of the above processing schemes is the difficulty in obtaining a substantially even thickness during the final splitting and shaving steps.
• these areas will be compacted to a greater extent than the other areas, and the hides will have a smaller thickness thereat, wherefore the hides will be stretched and thinned in differentiated manner, thereby resulting in lower quality.
• a shaving step is required, which involves relatively high costs, due to the required provision of a relatively large number of skilled operators, as well as high hide damage risk.
• the object of the present invention is to overcome the above drawbacks, by providing a process for treating laminar products, particularly industrial hides or the like, that is highly efficient and relatively cost-effective.
• a particular object is to provide a process for treating laminar products, particularly industrial hides pre-treated by a chemical bath, that affords considerably increased final product footage, while reducing damaging risk.
• Yet another object is to provide a process of the above type that provides a semifinished product of uniform thickness and density, without requiring any shaving step or similar processing.
• Another important object of the present invention is to provide a plant for treating laminar products such as industrial hides or the like, that includes a relatively small number of treating stations and requires a reduced number of operators.
• a process for treating laminar products in accordance with claim 1 which comprises the successive steps of pre-treating the laminar products by soaking tanning greasing or the like, picking up the pre-treated products with a predetermined initial moisture content, partial pre-drying of the pre-treated products for reducing the moisture content from said initial value to a predetermined intermediate value, and splitting the pre-dried products, wherein before the splitting step a wet stretching step is carried out on the pre-dried products for reducing thickness and density variations throughout their surface extension.
• This will avoid the provision of a further shaving step for the split products to obtain final products of constant thickness, thereby allowing the products under treatment to avoid any further stress that might cause damages thereto.
• the wet stretching step may be carried out in view of maintaining the intermediate moisture content substantially constant, i.e. in a range from 30% to 60% and preferably from 40% to 50%.
• the process of the invention allows processing of softer products throughout the stretching step, thereby affording considerably increased footage as compared with prior art dry stretching solutions.
• the invention relates to a plant for treating laminar products, such as industrial hides and the like, in accordance with claim 12.
• FIG. 1 is a flowchart of a process for treating laminar products according to the invention
• Fig. 2 is a top view of a plant for the implementation of the process according to the invention
• FIG. 3 is a front view of the system of FIG. 2.
• the process of the invention may be used for treating and conditioning semifinished laminar products, particularly in tannery processing of industrial hides for use in the automotive and clothing industries or as linings in general.
• the process may be used for continuous and uniform stretching of hides whose initial thickness and density vary along their surface extension, which have been subjected to prior pre-treatment by treatment with or dipping in a water-, oil- or grease-based solution containing organic or inorganic chemicals.
• a process of the invention includes the following successive steps: a) pre-treating the hides with one or more processes such as soaking, tanning, greasing or the like, b) picking up the pre-treated hides P with an initial moisture content, c) partial pre-drying of the pre-treated hides P for reducing the moisture content from the initial value to a predetermined intermediate value, and splitting the pre-dried hide P.
• a wet stretching step e) is carried out on the pre — dried hides P before the splitting step d), in such a manner that the hides P subjected to this latter step have particularly smooth fibers, and can be stretched with a minimal risk of local ruptures and damages.
• the semifinished hides P to be split will have substantially constant thickness and density, with negligible variations along the surface extension thereof.
• the hides P will not exhibit portions with higher density and portions with higher weakness, that would be likely to cause local rupturing thereof P during a subsequent splitting or shaving step.
• the pre-treating step a) can include a step ao) of impregnation or soaking wherein the hide P is dipped in a treating liquid or mixture of treating liquids to obtain a pre-treated hide P with an initial moisture content above 70% and preferably in a range from 80% to 100%.
• the hides P can be limed at ai), to facilitate loosening of tissues and make them more responsive to further processing, and then subjected to a 2 ) fleshing and possibly pre-split (8 3 ) to remove residues of flesh and fat from the subcutaneous layers and reduce the thickness of the hides P overall its extension.
• the hide P may undergo the proper tanning process (step a 4 ) by application of a tanning agent selected from the group comprising inorganic tanning agents, such as chrome, aluminum, iron, titanium, zirconium ("wet-blue” tanning) or using an organic tanning agent, of the synthetic or vegetable type (“wet-white” tanning).
• a tanning agent selected from the group comprising inorganic tanning agents, such as chrome, aluminum, iron, titanium, zirconium (“wet-blue” tanning) or using an organic tanning agent, of the synthetic or vegetable type (“wet-white” tanning).
• the pre-treating step a) may be carried out in a drum bath, wherefrom the hides P may be automatically or manually picked up and carried to the pre-drying step c).
• This latter step may in turn be carried out by feeding the hides P through a pressure roller device or press, forwarding them through a tunnel or through similar techniques, to reduce the initial moisture content to an intermediate value from 30% to 60% and preferably of 40% to 50%.
• the wet stretching step e) may be adjusted to cause maintenance of a constant intermediate moisture content value of the hide P at the exit of the pre-drying step c). It has been verified that the wet stretching step carried out with these starting moisture content values will achieve a considerably higher footage increase, up to 10% or higher as compared to dry stretching, whereas values above the range would cause considerable difficulties in processing without leading to significant footage increases.
• the wet stretching step e) may be carried out by transmitting mechanical stresses to the hide P being treated in directions substantially perpendicular to its lying plane to generate substantially radial local tension on the hide.
• the mechanical stresses may be evenly distributed over one or both faces of the hide P being stretched by staking, using a pair of beating plates, located on opposite sides of the hides P under treatment, and operating with a predetermined frequency in opposite directions substantially perpendicular to the lying plane of the hides P.
• the plates may be associated with a pair of impermeable or water repellent belts in mutually facing relationship to contain the hides P to be processed and avoid moisture losses.
• the stretched hide P may be mechanically split by any operation as typically used in the technical field of tannery, for imparting even thickness throughout its surface extension.
• the pre-drying c), stretching e) and splitting d) steps may be carried out while feeding the hides P in a longitudinal direction substantially parallel to the lying plane thereof, possibly by continuous operation, to increase the speed of the whole process and require the use of a considerably smaller number of operators.
• the stretched hides P may undergo one or more conditioning steps, generally indicated f), which are designed to impart such structural and exterior appearance features to the product as required for them to be fit for marketing, without requiring a shaving step.
• the semifinished hides P may undergo a retanning step, which is designed to confer the desired degree of fullness, softness, pastiness, sweat resistance, a dying step and a greasing step using greases or oils of animal, vegetable, synthetic or mineral nature, which are useful to increase softness and hydrophobic features and improve mechanical strength.
• the hides P may be dried, e.g. by being fed through a tunnel, aerated, subjected to vacuum suction or the like to adjust its moisture content to a minimum value, generally in a range from 14% to 18%.
• the hides P may possibly undergo a further staking and/or stretching step to increase the final footage and finished with resins, waxes, pigments and dyes, to define and improve its exterior appearance.
• the drying and staking steps may be also carried out in two or more cycles to gradually reduce the moisture content increase stretching.
• Figs. 2 and 3 schematically shows a plant for carrying out the above process, overall designated by numeral 1, which comprises a station 2 for picking up and pre-drying the hides P coming from a preceding pre-treatment station, not illustrated, to adjust the moisture content from a relatively high initial value of the pretreated product to a predetermined intermediate value, a wet stretching station operating on the pre-dried hides P and a splitting station 4 operating on the pre- dried and stretched hides P downstream from the stretching station 3.
• a movable conveying surface is further provided to cause the hides P to forward in a predetermined longitudinal direction L through the pre-drying station 2, stretching station 3 and splitting station 4.
• the specific location of the stretching station 3 upstream of the splitting station 4 affords significant reduction of thickness and density variations in the hides P during post-stretching steps, to avoid a shaving step for the split hides P.
• the plant 1 will have a highly simplified and comparatively cost-effective construction, a minimum configuration being allowed with two operators located at the stations 6 and 7 for loading and unloading the hides P.
• the movable conveying surface 5 may be comprised of a plurality of sections 8, 9, 10, 11 , 12, defined by respective belt or roller conveyors, with the hides P to be treated lying thereon.
• the sections 8, 9, 10, 11 , 12 may be located in longitudinally side-by-side relationship, thereby defining a seamless surface 5 and allowing full process automation.
• the respective section 10 may comprise an annular surface with a belt conveyor having two facing lengths and made of an impermeable material to maintain the predetermined intermediate moisture content value in the hides P to be stretched.
• the staking machine 13 may include at least one pair of substantially horizontal beating plates located on opposite sides of the feeding plane ⁇ for the hides P, as defined by the movable surface 5, to operate on the wet shide P to be stretched in a transverse direction X substantially orthogonal to the feeding plane ⁇ .
• the pre-drying 2 and splitting 4 stations may be of conventional type and will not be described herein in greater detail.
• the plant 1 may be complemented by one or more product pre-treating stations, not shown because they are known per se, e.g. with one or more drums for dipping the products in soaking, tanning and greasing liquids, which are located upstream from the pre-drying station 2 to impart a predetermined initial moisture content to the hides P.
• An automatic stacking station 14 for the split hides P and one or more conditioning stations, which are known and not shown herein, may be located downstream of the splitting station 4, for carrying out one of the above steps designated T).
• the invention fulfills the intended objects and particularly meets the requirement of providing a process and a plant for treating laminar products, particularly industrial hides and the like, characterized by high throughput and cost-effectiveness.
• the particular configuration of the process and the plant for carrying it out can avoid the provision of a shaving step, thereby reducing the risks of damaging the products and achieving considerable power and labor savings.
• the subcutaneous layers at the exit of the splitting station may be resold, with an additional economic advantage.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Treatment And Processing Of Natural Fur Or Leather (AREA)

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Cited By (3)

Citations (4)

• 2008
  • 2008-02-12 IT ITVI20080034 patent/ITVI20080034A1/it unknown
  • 2008-02-15 WO PCT/IB2008/050552 patent/WO2009101480A1/en not_active Ceased

Patent Citations (4)

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