RU2454664C1 - Method to recognise leather and leather-like materials - Google Patents

Abstract

FIELD: textile, paper.

SUBSTANCE: at the first stage the organoleptic analysis of tested samples is carried out. At the second stage the microscopic analysis of the material structure is carried out. At the third stage the chemical analysis of the tested samples is carried out by means of their treatment with an organic dissolvent selected from the group: butyl ether of acetic acid, dimethylketone, dimethylformamide, tetrahydrofuran, furfural, cyclohexanol at the ratio of sample-dissolvent equal to 1:(10-15) at the boiling temperature of the selected dissolvent for 20-30 minutes. If a sample has dissolved fully, the conclusion is made that is pertains to leather-like materials, and if a sample has not dissolved, it is identified as leather.

EFFECT: accurate and reliable recognition of leather from leather-like materials.

2 cl, 3 ex

Description

The invention relates to light industry and is intended to identify genuine leathers and to recognize them from leather-like materials.

Faux leather or artificial leather (leather-like materials), the production of which is being improved more and more every year, is very difficult to distinguish from genuine leather, especially to an unenlightened consumer in such matters. But it’s no secret that the leather substitute is less durable, less environmentally friendly and, accordingly, its cost is much lower, therefore, the task of quickly and accurately determining the naturalness of the skin is currently an urgent task for customs, certification authorities and metrology, wholesale buyers of shoes and ordinary consumers.

The urgent task of today is a quick and reliable way to recognize genuine leather from leather-like materials.

There are many types of leathers that differ: by type of raw material (skins of different animals), by methods of processing and finishing leathers (Chemistry and technology of leather and fur. / Strakhov I.P., Shestakova I.S., Kutsidi D.A. et al. M.: Light Industry, 1979, p. 504). Natural leathers have a unique, non-reproducibly artificially fibrous structure of the dermis of the animal's skin: uniqueness lies in the endless structure of mutually interlacing collagen fibers of the dermis.

In order to get genuine skin, animal skins are first preserved, then hair is removed, tanned, fattened and dyed. Now tanning is carried out by combined methods - mineral, vegetable and synthetic tannins (Chemistry and technology of leather and fur. / Strakhov I.P., Shestakova I.S., Kutsidi DA. Et al. M.: Light Industry, 1979, p. 504).

The manufacturing techniques of soft artificial leathers are quite diverse, but three main stages can be distinguished: preparing the fibrous base, applying polymer coatings, final finishing (Andrianova G.P., Polyakova K.A., Filchikov A.S. et al. - Plastic processing technology masses and elastomers in the production of polymer film materials and artificial leather, Part 1, 2, - M .: Koloss, 2008 - part 1 - 367 s., part 2 - 447 s.).

As the fibrous base used fabrics, knitwear, paper and various non-woven materials from natural, artificial or synthetic fibers. The properties of soft artificial leathers are largely determined by this important structural element: the quality of the finished leathers, such as strength, extensibility in various directions, the ability to drape, etc., depend on the base material. To give greater strength and density, the fibrous base is impregnated with polymer compositions. Then, the surface of the fibrous base is coated - from melts, solutions and dispersions of polymers, using various technological methods and equipment.

Various methods are used as finishing methods: polishing, wrinkling, embossing, applying a varnish or matting layer, applying a printed drawing, etc. The finished material can imitate the texture of fabric, genuine leather and suede, there are multi-color leather and change their color - the so-called “Chameleons”, metallic leathers, etc.

An intermediate option between natural and artificial leather is the so-called pressed (or composite) leather - a material produced under pressure from waste products from genuine leather: scraps and shreds, chrome shavings, leather dust and other waste. Pressed skin also has binders. They can be made of any synthetic material: polyester, polyamide, polyvinyl chloride, polyurethane, polyethylene and other polymers. When heated, they melt and glue all the “particles” together (Andrianova G.P., Polyakova K.A., Filchikov A.S. and others. - Technology for processing plastics and elastomers in the production of polymer film materials and artificial leather, Ch. 1, 2, - M .: Koloss, 2008 - part 1 - 367 s., Part 2 - 447 s.).

Natural leathers (tanned dermis of animal skins), which have infinitely intertwined collagen fibers, are not able to dissolve (without hydrolysis of collagen fibers) in any organic and inorganic solvents.

A known method of dissolving collagen in a 1 M solution of acetic acid with a liquid coefficient (liquid = 15-30 of the initial mass) after hours of alkaline-salt treatment (A. Golovteeva and others. Laboratory workshop on chemistry and technology of skin and fur . - M: Legprombytizdat, 1987. - p. 47-50).

The disadvantages of this method are its limited functionality, since it provides the dissolution of only undecided collagen.

A known method of dissolving tanned collagen in a 15% solution of sulfuric acid at 100 ° C for 24 hours. The disadvantage of this method is that it does not dissolve collagen to a fibrous structure, but completely hydrolyzes it to low molecular weight substances (Golovteeva A. A. et al. Laboratory workshop on chemistry and technology of leather and fur. - M: Legprombytizdat, 1987. - p.198).

There is a method of recognizing genuine leather by burning it, because genuine leather is the only material that does not burn, but smolders, but this method is characterized by low accuracy, since modern artificial leather is carbonized in the same way as genuine leather. Already invented is a composition that gives artificial skin the smell of genuine leather (http://www.obuvnoi.ru/adv/adv6.htm).

A known method for recognizing natural skin by analyzing the structure of the material using a microscope that determines the nature of the fibers. Features of the microscopic structure make it possible to establish whether the sample belongs to leather-like materials or to natural leathers (A. Golovteeva and others. Laboratory workshop on the chemistry and technology of leather and fur. - M: Legprombytizdat, 1987. - 312 p.).

The disadvantage of this method is its low accuracy.

A known method for identifying genuine leather using a non-destructive testing device is that the test sample is subjected to vibrational loads and the physical and mechanical properties of the test sample are determined from the vibration sensor (Patent RU 2138803, op. September 27, 1999).

The disadvantages of this method are its limited functionality.

The closest to the claimed method, the prototype, is a method for recognizing genuine leather and leather-like materials using organoleptic analysis of samples (www.kozhinfo.ru). Organoleptic analysis is based on the study of the external characteristic features of the skin. For example, when a test sample comes in contact with the inner surface of a person’s palm, the natural skin heats up, transfers heat to the palm and gives a pleasant warm feeling, while the artificial skin moistens the palm slightly, gives off a chill, and after removing the hand there will be a slight thaw. Upon contact with water, natural skin absorbs moisture and darkens at the point of contact with a drop of water, while artificial skin remains unchanged. The edges of genuine leather are more rounded and thicker than those of leather-like materials, and the underside is fleecy. Genuine leather has a specific smell peculiar only to it. Based on the organoleptic analysis, a conclusion is drawn on whether the sample belongs to leather-like materials or to natural skin.

The disadvantage of this method is its low accuracy, since modern technology allows to obtain a skin-like material that effectively imitates natural skin in terms of basic organoleptic characteristics.

An object of the invention is to develop an accurate and reliable method for the recognition of genuine leather and leather-like materials.

The technical task is solved by the proposed method, which consists in the following.

At the first stage of recognition of genuine leather and leather-like materials, an organoleptic analysis of the tested samples is carried out.

At the second stage of recognition, a microscopic analysis of the structure of the material is carried out, which determines the nature of the fibers.

At the third stage of recognition, a chemical analysis of the tested skin samples is carried out. To do this, the samples are cut into pieces of size (10-15) × (10-15) mm and placed in a heat-resistant flask filled with an organic solvent selected from the group: acetic acid butyl ether, dimethyl ketone, dimethylformamide, tetrahydrofuran, furfural, cyclohexanol, in the ratio sample solvent equal to 1: (10-15). Dissolution of the samples is carried out at the boiling point of the selected solvent for 20-30 minutes with stirring. Upon complete dissolution of the sample, it is identified as a skin-like material, and if the sample does not dissolve, it is identified as genuine leather.

The method is simple to implement and allows reliable and unambiguous recognition of genuine leather from leather-like materials. The method can be used in any chemical laboratory with a standard set of equipment.

The defining differences of the proposed method from the prototype are:

- conduct a comprehensive test of samples, including organoleptic, microscopic and chemical analysis of samples, which allows to increase the recognition accuracy of natural leather from leather-like materials;

- at the stage of chemical analysis, the test samples are treated with an organic solvent selected from the group: acetic acid butyl ether, dimethyl ketone, dimethylformamide, tetrahydrofuran, furfural, cyclohexanol, with a sample-solvent ratio of 1: (10-15), at the boiling point of the selected solvent for 20-30 minutes, which improves the accuracy and reliability of the method.

The invention is illustrated by the following examples of specific performance.

Example 1

At the first stage of recognition of genuine leather (skin-like material), the tested samples received from customs were examined using organoleptic analysis: the presence of a reinforcing base (fabric) made it possible to classify the material as leather-like.

At the second stage of recognition, a microscopic analysis of the structure of the material was carried out, on the basis of which the belonging of the sample to leather-like materials was established.

At the third stage of recognition, a chemical analysis of the test samples was carried out. To do this, the samples were cut into pieces 10 × 10 mm in size and placed in a reflux condenser filled with dimethylformamide, at a sample-solvent ratio of 1:10, at a temperature of 153 ° C for 20 minutes with stirring. The test sample completely dissolved, which was the basis for classifying it as leather-like materials.

Example 2

At the first stage of recognition of natural skin (skin-like material), the test samples received from the NCLM testing laboratory were examined using organoleptic analysis. Determined the type of material: genuine leather.

At the second stage of recognition, a microscopic analysis of the structure of the material was carried out, on the basis of which the belonging of the sample to natural skin was established.

At the third stage of recognition, a chemical analysis of the test samples was carried out. To do this, the samples were cut into pieces measuring 15 × 10 mm and placed in a container filled with tetrahydrofuran in a sample-solvent ratio of 1:15 at a temperature of 66 ° C for 30 minutes with stirring. The sample did not dissolve, which was the basis for referring it to natural skin.

Example 3

At the first stage of recognition of genuine leather (skin-like material), test samples from trade organizations were examined using organoleptic analysis. Determined the type of material: genuine leather.

At the second stage of recognition, a microscopic analysis of the structure of the material was carried out, on the basis of which the belonging of the sample to natural skin was established.

At the third stage of recognition, a chemical analysis of the test samples was carried out. To do this, the samples were cut into pieces with a size of 15 × 15 mm and placed in a container filled with dimethylketone in a sample-solvent ratio of 1:12 at a temperature of 56.5 ° C for 25 minutes with stirring. The sample dissolved, which was the basis for classifying it as a skin-like material.

Example 4

At the first stage of recognition of genuine leather (skin-like material), test samples from trade organizations were examined using organoleptic analysis. Determined the type of material: genuine leather.

At the second stage of recognition, a microscopic analysis of the structure of the material was carried out, on the basis of which the belonging of the sample to natural skin was established.

At the third stage of recognition, a chemical analysis of the test samples was carried out. To do this, the samples were cut into 15 × 15 mm pieces and placed in a container filled with acetic acid butyl ether in a sample-solvent ratio of 1:10 at a temperature of 118 ° C for 20 minutes with stirring. The sample dissolved, which was the basis for classifying it as a skin-like material.

Example 5

At the first stage of recognition of genuine leather (skin-like material), test samples from trade organizations were examined using organoleptic analysis. Determined the type of material: genuine leather.

At the second stage of recognition, a microscopic analysis of the structure of the material was carried out, on the basis of which the belonging of the sample to natural skin was established.

At the third stage of recognition, a chemical analysis of the test samples was carried out. To do this, the samples were cut into pieces 15 × 15 mm in size and placed in a container filled with furfural, in a sample-solvent ratio of 1:12 at a temperature of 162 ° C for 20 minutes with stirring. The sample dissolved, which was the basis for classifying it as a skin-like material.

Example 6

At the first stage of recognition of genuine leather (skin-like material), test samples from trade organizations were examined using organoleptic analysis. Determined the type of material: genuine leather.

At the second stage of recognition, a microscopic analysis of the structure of the material was carried out, on the basis of which the belonging of the sample to natural skin was established.

At the third stage of recognition, a chemical analysis of the test samples was carried out. To do this, the samples were cut into pieces with a size of 15 × 15 mm and placed in a container filled with cyclohexanol in a sample-solvent ratio of 1:15 at a temperature of 161 ° C for 30 minutes with stirring. The sample did not dissolve, which was the basis for referring it to natural skin.

Using the proposed method will accurately, reliably and quickly recognize natural leather and distinguish them from flooding the Russian market of leather-like materials. The proposed method can be in demand in the territorial regulatory organizations, testing laboratories, in customs, etc.

Claims (2)

1. A method for recognizing genuine leather and leather-like materials, including preparing samples, their organoleptic analysis and drawing a conclusion about the belonging of the sample to leather-like materials, or to natural skin, characterized in that the test samples are additionally subjected to microscopic and chemical analysis, while the latter is treated with organic a solvent selected from the group: acetic acid butyl ether, dimethyl ketone, dimethylformamide, tetrahydrofuran, furfural, cyclohexanol in the ratio and a solvent sample equal to 1: (10-15) at a boiling point of the selected solvent for 20-30 minutes and when the sample is completely dissolved, it is concluded that it belongs to leather-like materials, and if the sample does not dissolve, it is identified as genuine leather. 2. The method according to claim 1, characterized in that they prepare samples of size (10-15) × (10 × 15) mm.