FR2610643A1 - BIOLOGICALLY STABILIZED AND NON-TANNED SKINS AND PROCESS FOR OBTAINING THESE SKINS - Google Patents

Abstract

These hides, completely free from chromium, have a moisture content of between 15 and 20%, a maximum inorganic matter content of 10 +/- 2%, an aluminium oxide content of 0.7 +/- 0.2% and an acrylic derivatives content of approximately 2%. Their pH is in the region of 4.0% and their dermic substance content is approximately 85 +/- 3%. They are capable of being rewetted in less than an hour. The process for obtaining them, of the type consisting in subjecting the completely delimed and bated hides to a pickling treatment in the presence of acrylic resin and then, after a rest, to a pretanning treatment with the aid of aluminium salts, is characterised in that there is introduced at any stage of the treatment a chemical agent facilitating the rewetting and enabling the hide to retain, after drying, a residual moisture close to 20% and in that the hide thus treated is subjected to drying. This chemical agent is chosen from the group consisting of polyalcohols, condensates of fatty alcohols with ethylene oxide and condensates of alkylphenols with ethylene oxide.

Description

I

  BIOLOGICALLY STABILIZED AND NON-TANNED SKINS

AND METHOD FOR OBTAINING THESE SKINS

  The present invention relates to biologically stable skins

  lized and not tanned as well as the process of obtaining these skins.

  It is known that skins, and especially skins for teasing, are currently marketed in different forms according to their state of preparation. Thus these skins can be delivered in the raw state, having undergone a simple treatment intended to prevent or stop the microbial development (salting, salting and drying, drying ...). They can be delivered in the pickled state, that is to say after having undergone a simple preparation by treatment with a strong acid solution in the presence of salt, or after having been tanned with the chrome (wet-blue treatment ) or otherwise; finally, the skins can be delivered in the semi-worked state (stain) or in the finished state. One of the important problems currently facing the leather industry is to be able to detect defects in skins as early as possible in the leather processing industry, so as to allow a better orientation of the skins, according to their quality and the needs of the market. This information is also essential for specialists in the different stages of preparation to enable them to

  possibly modify their mode of treatment.

  However, each state and each form of presentation is associated with a set of advantages and disadvantages. As a general rule, any orientation from the raw state to the finished state is accompanied by an improvement of the possibilities of assessment of the quality of the material, of an increase of its stability and of its lifetime, of an optimization of the material balance in manufacturing; in return, the field of diversification becomes more and more

narrower.

  The main advantages and disadvantages of the presentation states of the hides and skins most frequently marketed are summarized in a simplified manner in the table below.

2 6 1 0 6 4 3

  Advantages Disadvantages DRY SKINS Transport Difficulty rewetting Storage and Accident on conservation flower SALT SKIN Conservation Salt pollution Diversification Irregularity PEEL PICKLEES Diversification Hydrolysis and embrittlement Ease of Transport sorting WET BLUE Stability Chromium irreversible Report of Non remobilability pollution Color of background STAIN No products Few secondary possibilities of diversification Transport Cost Transparency of the market It is therefore after the pickling stage that we should be able to dispose of skins that we can orient according to the needs of the market, since at this stage these skins do not have undergone chemical treatments

  irreversible; however, they are relatively fragile.

  We have already developed skins called White Stabilized Wet (BSH) that meet these requirements in part; these are skins that have been pre-tanned in the presence of sulphate

  of alumina after pickling in the presence of acrylic resins.

  These light-colored wet skin contains about 60%

  of water, 7 to 10% of mineral matter, less than 1% of aluminum oxide,

  minium, the rate of dermal substance amounting to 85-90%.

  The storage behavior of these skins is satisfactory for

  durations of up to six months.

  BSH skins, however, have certain disadvantages especially because of their high water content, which makes them

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  difficult to handle and greatly increases their transport.

  One might think that the best solution would be to

  subject the BSH skins to drying, so as to remove excess water

  silent. However, experience has shown that one then obtained very stiff skin, even brittle, parchment type, so difficult to store. Else

  on the other hand, the skins thus dried were practically impossible to rewet.

  It was therefore necessary to find a way to allow the dried skin to maintain a sufficient moisture content, that the tests have shown to be between 18 and 20%, without causing it to lose the qualities communicated to the treated skins White Stabilized Wet; he

  was also suitable for allowing dried skin to integrate easily

  in the cycle of subsequent manufacture, that it is likely to re-wrap easily, within a reasonable period of time, which must be

less than one hour.

  The Applicant has therefore established criteria for selecting the many wetting chemical agents to determine which ones were able to meet these requirements. These criteria are as follows: This agent must have good stability in a pH zone

ranging from 2.5 to 4.5.

  It must be compatible both with the aluminum salts and with the acrylic derivatives, used, as will be seen hereafter, in the treatments

  special pickling and pre-tanning.

  It must be capable of exerting an action of solubilization and distribution of the mineral salts, so that during drying no crystallisation occurs under a flower which could communicate with the

skin a grainy appearance.

  It must be compatible with the products used later for tanning, be it vegetable tanning, mixed tanning

  (vegetable-synthetic) or mineral tanning (chromium, zinc, titanium).

  It must allow the skin to retain sufficient residual moisture giving it the flexibility needed for handling and storage while maintaining the structural moisture of the collagen fiber. It must allow easy drying of the skin, as well as rewetting in the heart in less than an hour, the temperature of retraction of

  the rewired form being the highest possible.

  Its presence must not be an impediment to the completion, before rewetting, of a dry degreasing treatment, and the ability to

  rewetting should not be changed by this degreasing treatment.

  Finally, its price must be low enough not to significantly change the price of the skin. A selection made among many products, according to the above criteria, allowed the inventors to determine that the best-performing products were in the group consisting of polyalcohols, ethylene oxide fatty alcohol condensates and condensate

  of alkyl phenols on ethylene oxide.

  Thus, the present invention relates to clear skins, biologically stabilized and not tanned and which will be referred to below as "Dry Stabilized White", which are characterized in that, completely free of chromium, they have a moisture content between 15 and 20%, a maximum mineral content of 10 + 2%, an aluminum oxide content of 0.7 + 0.2%, a content of acrylic derivatives of approximately 2%, that their pH is around 4.0, and that their rate of dermal substance is about 85 + 3%. and

  in that they are able to rewet in less than an hour.

  This last property, absolutely decisive for allowing the skins according to the invention to undergo, even after a long storage period, following conventional treatments, and in particular tanning, is obtained thanks to the presence, in the dry stabilized white. , a small amount of

  the specially selected chemical agent mentioned above.

  The invention makes it possible to have, after the stage of pickling where the skin is still diversifiable but relatively fragile, a skin that can be described as biologically preserved, which has the following advantages: - ease of storage and transport, especially because of its low moisture content; - inertia towards aging, - reasonable cost of production, - very broad ability to diversify (including flower and crust to different destinations) - better integration into the environment (decreased water pollution and obtaining waste non-chromed solids) - ability to subsequently undergo all subsequent tanning treatments. The subject of the invention is also a process for obtaining the

  Dry White Stabilized skins described above.

  This process is of the type consisting in

  cold-set and confited to a picklage treatment in the presence of acrylic resin and, after standing, to a pre-tanning treatment using aluminum salts and is characterized in that it is introduced, in any phase treatment, a chemical agent facilitating rewet and allowing the skin to retain, after drying, a residual moisture of 20%, and in that the skin thus treated is subjected to drying. According to one embodiment of the invention, the chemical agent

  facilitating rewetting is introduced in the pickling step.

  According to another embodiment, said chemical agent is

  introduced in the pre-tanning step.

  Alternatively, said chemical agent is introduced during a

  later step, after picklage and pretannage.

  The chemical agent facilitating rewetting is chosen, as specified above, from the group consisting of polyalcohols, condensates of fatty alcohols on ethylene oxide and condensates of alkylphenols on

ethylene oxide.

  The present invention will be better understood and its advantages will emerge from the following examples which illustrate it without in any way limiting it. Example I: Manufacture of a Stabilized White Skin Wet We start from small skins (sheep, goats) thoroughly dehydrated and

  candied (phenolphthalein colorless slice).

  They are then subjected to a treatment in the following baths (the percentages are calculated on the tripe weight). All treatments are done

in the same device.

  Picklage: we treat first in a bath containing: cold water 25%

sea salt 5% Rotation 15 minutes.

  An acrylic resin type LEUKOTANR, marketed by ROHM and HAAS, is added at a rate of 1% (diluted in 3% water) Rotation 30 minutes 1.3% sulfuric acid (diluted 1/10) Rotation 45 minutes Finally, 0.7% of sodium formate is added. Rotation 3 hours The pH of the bath is close to 3.2-3.3. Stabilization: it is left overnight and then 3.5% basic aluminum sulphate, 0.05% of a suitable fungicide, type BUSAN 30 L, marketed by BUCKMAN Rotation 3 hours Finally, the pH is adjusted bath around 4.2 using two

  times 0.5% sodium bicarbonate.

  Finally, the "moist stabilized white" skin thus obtained, which contains about 60% of water, 7 to 10% of mineral matter and less than 1% of aluminum oxide, is finally wrung, the rate of dermal substance amounting to

85-90%.

  The hides thus obtained can be easily sorted and can be

  stored approximately six months before being processed

  subsequent tanning and finishing.

  It should be noted, however, that the high amount of water they contain makes them extremely heavy and difficult to handle and transport. A skin drying test obtained in Example I leads to a rigid and brittle skin which is very difficult to store by stacking.

  and which, on the other hand, is not easily rewettable.

  The following examples illustrate different ways of manufacturing

  White Stabilized Dry (B.S.S.) skins from B.S.H.

Example 2

  Preparation of B.S.S., without prior degreasing of the skin; this process is more particularly intended for raw materials containing little natural fat and easily remouldable (crusts of

  calf or bovine, skin up to 0.8 mm thick).

  We start from completely broken skin and eventually

  confit (colorless reaction with phenolphthalein).

  They are then subjected to a treatment in the bath prepared as follows (the quantities of added products are evaluated as a percentage of the tripe weight): a) preparation of a water bath (temperature 5 to 20 C) in a fuller, an elbow or any other apparatus normally used in tannery-tanners whose volume is between 20 and 100% of the

value of the weight of skins in tripe.

  In this bath, a quantity of soluble inorganic agents is added, making it possible to obtain an ionic strength adapted to the optimal conditions of the acidification or pickling of the skins: Chloride or sodium sulphate Chloride or potassium sulphate Calcium chloride

  Mixture of acid salts, aromatic or aliphatic acids.

  Agitation of the skins in this bath during 10 to 30 minutes.

  b) progressive acidification by successive additions of previously diluted quantities of mineral or organic acids (sulfuric acid, hydrochloric acid, acetic acid, formic acid) and of soluble organic salts with a complexing nature (sodium formate, sodium acetate, sodium tartrate, citrate of sodium, sodium sulfophthalate). The amounts of acids are understood, according to their chemical nature, between 0.5 and 5% and those of agents

complexing between 0 and 10%.

  The reactions between the skins and the chemicals incorporated in the bath must allow, after contact from 1 to 6 hours, to obtain

pH between 2.0 and 4.0.

  c) incorporation of a weakly tanning stabilizing agent whose essential constituent is a more or less complex salt

  resulting from the combination of a mineral or organic acid and aluminum.

  The quantities of stabilization products used as well as

  that the physicochemical conditions of the reaction (concentration, temperature,

  ture, pH) should result in a stabilized material with a minimum shrink temperature of 65 C and a pH of 3.5

and 4.5.

  Preparation - Water 16-18 C: 40% - Sodium Chloride: 4% Fuller Rotation, 10 minutes - Dispersant: 0.8% (Acrylic preparation) Fuller Rotation, 20 minutes - Sulfuric Acid diluted 10 times: 1% Fuller Rotation, 60 minutes - Sodium formate: 0.6% Fuller Rotation, 4 hours 3.1 bath pH 3.3 - Aluminum Complex Salt: 3% (containing 10% AI2 03) Fuller Rotation, 3 hours for fixing by pH correction to have a value of 4.3-4.4 using bicarbonate

sodium.

  Storage on an easel, 24 hours Spinning under low pressure (5 X 105 Pa) At this stage, is incorporated in the white stabilized material in the wet state a preparation allowing both a drying without side effects such migration of adjuvants or recrystallizations parasites, an excellent rewetting for the skin postponed to further manufacture and a preparation for the degreasing operation essential to

  successful manufacture of quality leather from B.S.S.

  The preparation contains a mixture of: - emulsifying and wetting agents of the nonionic type (products

  oxyethylation of amines, amides, alkylphenols and alkylnaphthols,

  or fatty alcohols); hygroscopic agents of the glycerol, glycol and sorbitol type. Preparation recipe Nonylphenol with 9 or 10 moles of ethylene oxide: ......... 60 parts Glycerol: .................

  .................................................30 Isopropanol parts: ............................................... ............... 10 parts The skins brought to the state of wet stabilized white are crushed for 15 minutes with a quantity of 4% calculated by DTD: ratio to the weight of the merchandise to be treated with the above preparation.

  They are then stored for 24 hours and then dried.

  Example 3: Preparation of B.S.S., without degreasing the skin This process is more particularly intended for raw materials with a medium natural fat content (3 to 6%), (goats, calves,

bulls).

  We start from completely broken skin and eventually

  confit (colorless reaction with phenolphthalein).

  The course of steps a) and b) is identical to that of

  Example No. 2, as well as the course of step c).

  Between step b) and step c), and according to the invention, there is added a compound of the food oil or cationic food aid type (hydroxyethylated fatty amine derivative) in amounts of

between 0.2% and 1.5%.

  EXAMPLE 4 Preparation of B.S.S., without degreasing the skin, more particularly intended for raw materials with a high natural fat content (greater than 6%), (lambs, sheep, mestizos,

pigs).

  In this case, it operates in a first time similarly to that of Example No. 2, to the stages of storage and spinning. At this level, the white stabilized material is incorporated in the wet state a preparation allowing both a drying without side effects of the migration type adjuvant products or parasitic recrystallizations, an excellent re-wetting for the skin put back into further manufacture and a preparation for the degreasing operation essential to the successful manufacture of a

  quality leather from B.S.S.

  The preparation contains a mixture of: - emulsifying or wetting agents of the nonionic type (oxyethylation products of amines, amides, alkylphenols and alkynaphthols, acids or fatty alcohols); hygroscopic agents of the glycerol, glycol or sorbitol type. In the present example, this mixture is the following Nonylphenol with 9 or 10 moles of ethylene oxide: ....... 60 parts Glycerol: ................ ............

  .................................... 30 parts Isopropanol: .......... .... DTD: ............................................ .... 10 parts The skins brought to the state of wet stabilized white are crushed with a quantity of 4% of this mixture, calculated with respect to the weight of the merchandise to be treated with the preparation described above, for 15 minutes. . They are then stored for 24 hours and then dried. DTD: as in example n 2.

  EXAMPLE 5 Preparation of B.S.S., with preliminary degreasing of the skin, more particularly intended for high-grade raw materials

in natural fat.

  Stage of departure We start from completely depleted skins and eventually

  confit (colorless reaction with phenolphthalein).

  The skins are first dumped in a tempered bath containing an emulsifier and a solvent for natural fats or a commercial preparation whose composition is obtained from

these basic agents.

  For particularly oily origins, degreasing is

  kills in two or even three successive steps interspersed with rinses.

  The degreased wet skin is then drained and then

  is chained according to a procedure of the type of that of Example No. 2.

  B.S.S. skins obtained by carrying out the processes described in Examples 2 to 5 retain a moisture content of about 18 to 20% which allows them to easily integrate into the cycle of subsequent fabrications. They can be easily shaken in less than an hour. We

  therefore, after the pickling stage, has a biologically preserved skin

  with all the advantages described above.

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Claims (7)

- CLAIMS -   1- clear skin biologically stabilized and not tanned, characterized in that, completely free of chromium, they have a moisture content of between 15 and 20%, a maximum mineral content of 10 + 2%, an oxide content aluminum content of 0.7 + 0.2%, a content of acrylic derivatives of about 2%, in that their pH is around 4.0, in that their rate of dermal substance is about 85 + 3% and in that they are able to recover in less than an hour.   2-skins according to claim 1, characterized in that they contain a small amount of a product selected from the group consisting of polyalcohols, condensates of fatty alcohols on ethylene oxide and   condensates of alkyl phenols on ethylene oxide.   3- Skin production process according to claim I and claim 2 of the type consisting in subjecting the fully dehulled and confected skins to a pickling treatment in the presence of acrylic resin, then, after standing, to a pre-tanning treatment with using aluminum salts, characterized in that is introduced into any phase of the treatment a chemical agent facilitating rewet and allowing the skin to retain, after drying, a residual moisture close to   9%, and in that the skin thus treated is subjected to drying.   4- Method according to claim 3, characterized in that the agent   chemical facilitating rewetting is introduced in the pickling stage.   - Method according to claim 3, characterized in that the agent   chemical facilitating rewetting is introduced in the pre-tanning step.   6. Process according to claim 3, characterized in that the chemical agent facilitating rewetting is introduced at a later stage.   of the process, after pickling and pre-tanning.   7- Method according to any one of claims 3 to 6,   characterized in that the chemical re-wetting agent is selected from the group consisting of polyalcohols, fatty alcohol condensates   on ethylene oxide and alkyl phenol condensates on ethylene oxide.   8- Process according to any one of claims 3 to 7,   characterized in that the chemical agent facilitating rewetting is introduced   in a treatment phase at a rate of I to 10% by weight.