RU2382073C1 - Agent for separating adhesive tape from carrying surface - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: agent for separating adhesive tape from carrying surface is characterised by that, the agent used is petroleum ether which provides temporary loss of adhesion properties of the adhesive tape when deposited, while preserving initial structure of the adhesive layer after separating the tape from the surface.

EFFECT: efficient and fast separation of adhesive tape from surface, with preservation of initial structure of adhesive layer, thus providing efficient detection of traces on the adhesive tape during crime detection.

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Description

FIELD OF THE INVENTION

The invention relates to forensic science (forensic technology), and in particular to the field of trasology (fingerprinting), and can be used as a means for separating adhesive (sticky) tape from various surfaces, as well as for disconnecting or separating parts of adhesive tape glued together preservation of its technological properties (integrity and invariance of the adhesive layer) for subsequent detection and identification of handprints on the surface of the adhesive side of the tape.

State of the art

At present, adhesive (sticky) tape (“scotch tape”) is widely used not only in the economic, household, and manufacturing spheres of human activity, but also in the commission of crimes. For example, criminals wrap the damaged handles of knives, pistols, rifle butts with adhesive tape, use it to bind the hands and feet, close the eyes and mouth of the victim. All this is being done to facilitate the commission of a crime.

The adhesive tape has specific properties that make it difficult to identify the invisible traces of hands that are present on its surface. This consists, firstly, in the impossibility of treating the adhesive side of the tape with fingerprint powders (the most common way to detect invisible handprints), and secondly, in firmly bonding the layers of the tape to each other, which complicates the process of peeling the layers apart to detect them surface of handprints.

Usually an adhesive tape is wound onto an object in several layers.

In forensic practice, currently used mainly film adhesive materials - adhesive (adhesive) tapes used in everyday life, which usually contain two layers - the base and the stickiness layer. As the latter, existing films mainly use compositions based on low molecular weight and high molecular weight compounds (gum rosin, cellulose ethers, chloroprene, isoprene, isobutylene, styrene butadiene rubbers, phenol formaldehyde, acrylic and other resins).

The basis of such films consists of polyvinyl chloride, cellophane, polyethylene, paper polyethylene terephthalates, etc.

At present, adhesive tapes can be removed from the bearing surfaces or separated by any of four methods:

- heating;

- physical;

- using volatile solvents;

- cooling.

The use of heat to separate the adhesive tape entails damage to its adhesive layer with almost one hundred percent loss of handprints left by the criminal on its adhesive layer. Because of this, the specified method of separation has no real application in forensic practice.

The physical (mechanical) way of separating the adhesive tape by tearing it off the surface also leads to complete damage to the adhesive (sticky) layer with fingerprints, since the adhesion force of the adhesive layer to the surface exceeds the force of tearing it off the surface.

Known means "Label Off 50" for separating adhesive tape from various surfaces by dissolving and neutralizing the adhesive component. In this case, a rapidly evaporating solvent is used, which after a while leaves no traces on the surface.

(Label Off 50 - Means for removing self-adhesive labels and adhesive tape residue. Technological materials KONTAKT CHEMJE. Manufacturer CRC Jndustries Europe NV, Belgium).

The main purpose of the application of this tool is to maintain the cleanliness of the surface from which the adhesive layer is separated, while the adhesive layer is not preserved as a result of partial dissolution, and therefore, Label Off 50 cannot be used in forensic practice to separate the adhesive tape from the surface or separate it adhesive layers, as it does not allow you to save, detect and identify handprints on the adhesive layer.

Known means that corresponds to the task of preserving the sticky layer. It is a mixture of volatile solvents, the composition of which, according to Sirchie, includes such solvents as butylbenzyl phthalate (5-10%), chloroform 5%, toluene 30-60%, poly (butyl methacrylate - co-methyl methacrylate) (d) 30-60%.

(Means for separating the film "UN-du Adhesive Removal System" with the preservation of handprints of the company "Sirchie Finger Print labs" (USA), catalog number UN-DU 100).

Toluene is known to be among the toxic products of the third hazard class, as well as fire and explosive products, its vapors act narcotically, adversely affect the nervous system, and irritate the skin and mucous membranes of the eyes. When working with him, it is necessary to use personal protective equipment: a filtering gas mask with a box of brand A and BKF, safety glasses, rubber gloves, protective clothing, protective ointments and pastes.

Chloroform, which is part of the UN-DU product, is also dangerous, because if stored incorrectly or for too long, it can form phosgene, which causes poisoning. In addition, working with chloroform can have a harmful effect on the liver and kidneys, as well as cause a violation of cardiac activity.

In addition, the aforementioned product, according to Sirchie, cannot be used to separate adhesive tape from leather and suede products.

The most effective tool in forensic practice for separating an adhesive tape from a surface is the use of liquid nitrogen: either by means of a plate cooled by liquid nitrogen, or by means of an aerosol jet.

However, this method has a number of disadvantages and a limited scope.

So, when using liquid nitrogen, special precautions must be taken both during storage and during use: wearing a face mask, special gloves, etc. At the same time, nitrogen can only be used on a limited area because of the impossibility of cooling large volumes of physical bodies and cannot be used to separate (separate) one layer of adhesive tape from another, as well as for living persons wrapped with adhesive tape (“Home Office building a safe just and tolerant society Scientific Development Branch Investigation Enforcement and Protection Sector ”, March 2006 Publication No. 23/06“ Additional Fingerprint Development Techniques for Adhesive Tapes Abstract ”).

The technical result of the invention is the expansion of the arsenal of tools used to separate the adhesive tape from the surface, and relatively less dangerous and providing efficient and quick separation of the adhesive side of the tape from any surface while maintaining its technological properties.

SUMMARY OF THE INVENTION

The specified technical result is achieved in that as a means of separating the adhesive tape from the bearing surface, petroleum ether C ₅ -C ₆ isostructure is used.

Petroleum ether is a liquid mixture of saturated hydrocarbons (mainly C ₅ -C ₆ ) obtained by re-distillation of gasoline by isolating light fractions (Glinka NL General chemistry. 16th edition, revised L., “Chemistry”, 1974 , p. 464). Petroleum ether is used as a solvent for resins, fats, and essential oils (Papok K.K., Ragozin N.A. “Dictionary of fuels, oils, lubricants, additives and special fluids.” 4th ed., M., 1975, p. 356).

However, this liquid mixture was not used as a means for separating the adhesive tape from the surface and separating the adhesive (sticky) sides from each other.

Moreover, in the case indicated by us, petroleum ether is not used as a solvent. The action of this liquid substance is based on the effect of a temporary loss of adhesive properties of the adhesive tape as a result of the short-term saturation of its sticky (adhesive) layer with petroleum ether. Due to this, there is a separation of the sticky (adhesive) layer of the tape with the preservation of its original structure and the traces of the hands on it. As a result of the rapid evaporation of petroleum ether, a subsequent complete restoration of all the properties of the adhesive (sticky) tape is observed 30-40 seconds after the application of the specified agent. In this case, traces of hands and other external influences are also fully preserved.

The use of petroleum ether to separate the adhesive tape from the bearing surfaces is as follows.

Petroleum ether is applied between the adhesive tape and the surface by capillary and gradually, as the adhesive (sticky) layer is wetted, the tape is separated from the surface.

After separation, the tape in expanded form is dried for 2-3 minutes, after which it is completely ready for further forensic research. Moreover, this can be carried out not only in the conditions of the forensic laboratory, but also when examining the scene of the incident.

To ensure safety when working with petroleum ether, it is enough to use a “Petal” type respirator and medical or plastic gloves.

Currently, tests of the proposed tool (code name “Sticker”) have been conducted in forensic centers, including The Ministry of Internal Affairs of the Republic of Belarus and the Ministry of Internal Affairs of the Russian Federation (copies of letters are attached).

Tests have shown that our tool allows you to quickly and efficiently separate glued together adhesive (sticky) tapes and separate them from the bearing surface while preserving hand traces on the adhesive (sticky) layer for further expert research.

Claims (1)

Means for separating the adhesive tape from the bearing surface, characterized in that petroleum ether is used as the agent, providing, when applied, a temporary loss of adhesive properties of the adhesive tape while maintaining the original structure of the adhesive layer as a result of separation of the tape from the surface.