Patent Application
20080182050
The invention relates to a bag having walls formed at least predominantly of paper material, the paper material having been made antistatic by addition of a conductive salt.
The invention further relates to the use of a flame retardant as addition to paper material.
Bags are typically produced from paper material, craft paper for example. The walls of a bag may be composed of a plurality of paper plies, between which frequently, in addition, a polymeric ply has been inserted as a moisture barrier.
Bags of this kind serve as transit packaging for bulk goods of a very wide variety of kinds. Accordingly such bags are also used in environments where there are explosion risks. For numerous applications, therefore, it is important that the material of the bag walls is not subject to any static electrical charges which could be discharged in the form of a spark and would therefore trigger an explosion or the like.
It is therefore known to make the paper material of bag walls antistatic. They are said to have been made anti-static when the leakage resistance of the paper material is <109Ω). Making a bag material of this kind antistatic can be effected in a known way by the addition of suitable conductive salts, which should dissociate easily and be neutral, such as sodium sulfate, for example.
It is known to impart flame retardance to cellulose materials, more particularly wood and textiles, by admixing the materials with a flame retardant. The function of the flame retardants is to react chemically, when higher temperatures occur, in such a way that any flames that are formed are extinguished—for example, by the formation of CO2 in the reaction of the flame retardant. Another type of flame retardant releases water on reaction, which hinders combustion. Known flame-retardant additives are halogen, phosphorus, boron or nitrogen compounds. Suitable compounds are, for example, pyrophosphates (diphosphates).
Bag materials are not typically provided with flame-retardant additions, since in temperate climatic zones paper bags possess a sufficient residual moisture content, which naturally hinders inflammation. The intrinsic flame-retardant quality of paper materials processed to a bag is only lost when the bag is stored for a prolonged time in very dry and hot ambient conditions.
It is an object of the present invention to provide a bag which has been made antistatic with an additional benefit.
This object is achieved in accordance with the invention by a bag of the type mentioned at the outset which is characterized in that the paper material has been admixed with a flame retardant in a concentration such that the leakage resistance is <109Ω.
The bag of the invention, accordingly, comprises merely one additive with which both an antistatic quality and a flame-retardant quality are achieved. This is done by making the bag material antistatic using not a conventional salt but instead an additive possessing suitability as a flame retardant. This additive, however, must be added at a high concentration, which is generally higher than the typical concentration in which the salts typically used to form an antistatic bag are added. Accordingly, when adding the flame retardant, it is necessary to ensure that the concentration is high enough for the leakage resistance to be <109Ω. In accordance with the invention it is possible to achieve a leakage resistance of ≦108Ω.
The basis for the present invention is therefore the realization that a salt that can be used as a flame retardant is also suitable, in a high enough concentration, for making the paper bag material antistatic. Accordingly, with the addition of a single additive, the paper bag of the invention is rendered not only antistatic but also flame retardant as well. The corresponding bag is therefore suitable, for example, for export to dry and hot climatic zones, since even in those zones—in contrast to the conventional paper bags—it exhibits flame-retardant properties.
The flame retardant is preferably an inorganic halogen salt, phosphorus salt or boron salt or a salt containing nitrogen compounds. Preference is given to the use of an alkali metal pyrophosphate, alkaline earth metal pyrophosphate or ammonium pyrophosphate.
The flame retardant is added with a concentration of preferably ≧20% by weight, based on the paper material.
The core of the present invention lies, accordingly, in the use of a flame retardant as an addition to a paper material that serves at least as the predominant component for producing bag walls, the addition being made in a concentration such that the leakage resistance of the paper material is <109Ω, preferably <108Ω.
The addition of the flame retardant in the inventive concentration requires a certain degree of care, since the paper material, which is typically sized, is slow in absorbing the aqueous solution of the salt.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 005 218.0 | Jan 2007 | DE | national |
