Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Patent
1996-11-21
1998-06-16
Buffalow, E. Rollins
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
428500, 428910, 428513, 229 8708, 2641761, 426129, B32B 2708
Patent
active
057667721
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to a film endowed with high anti-fog properties, a method for packaging products having a high moisture content and products thus packaged.
In particular, the invention relates to a thermoplastic polyolefin film with high anti-fog properties wherein said properties are obtained by incorporation of a composition comprising the following additives (i) a mono-ester of glycerol with a saturated or unsaturated fatty acid, (ii) a di-ester of glycerol with a saturated or unsaturated fatty acid, (iii) at least one ether of a polyoxyethylene with a fatty alcohol.
With the term "anticondensation" (or, to use the English term more immediately evident to the person skilled in the art, "anti-fog"), it is meant the capability of the film to prevent water vapour from condensing onto its surface in the form of small water drops redistributing them in the form of a continuous film of water in a very thin layer.
In fact, it is common practice in supermarkets to package perishable food products, such as fresh meat cuts, vegetables, cooked food, deep-frozen food and the like, in trays of different materials and shapes, wrapped in a transparent, heat-shrinking film, through which it is very important for the product to be clearly visible. With films that have no anti-fog properties, in the case for instance of easily-perishable food products, having a high moisture content, there will be a rapid condensation of water vapour and the formation of droplets on the internal surface of the film with the consequent loss of transparency of the packaging. This occurs especially when, after packaging, the product is subjected to sharp and substantial changes in temperature, such as, for example, when it is subjected to refrigeration or deep-freeze cooling.
This phenomenon occurs to a greater or to a lesser extent depending on the type of polymer or of the blend of polymers of which the film is made or, in the case of a multi-layer film, of which is made the surface layer facing the content of the tray. More particulararly, this phenomenon occurs to a greater or to a lesser extent depending on the greater or lesser hydrophobic properties of said polymer or said blend. Indeed, even if this phenomenon is common to all types of film that do not contain suitable anti-fog additives, it is especially important when said polymer or said blends are polyolefinic in nature.
Several very large families of potentially anti-fog compounds, as well as their use in film compositions used to produce film for food-wrapping uses, have been studied for a number of years.
Examples of such families comprise sorbitan esters of aliphatic carboxylic acids, glycerol esters of aliphatic carboxylic acids, esters of other polyhydric alcohols with aliphatic carboxylic acids, polyoxyethylene compounds, such as the polyoxyethylene sorbitan esters of aliphatic carboxylic acids and polyoxyethylene ethers of higher aliphatic alcohols.
The literature is rich in papers relating to investigations to find which are the specific members of the abovementioned families that, alone or in admixture among them, impart the maximum anti-fog properties to one or to the other type of film-forming composition but general criteria suitable for predicting which is the most effective anti-fog composition for each type of film-forming composition do not yet exist. In this field, experiments continue to offer new and unexpected results.
The publication--even recent--of various patent applications concerning anti-fog compositions made of members belonging to the abovementioned families is a clear indication of the fact that an optimunm solution of the problem has not yet been found and that the search for new compositions capable of improving the results attained thus far, in terms of anti-fog properties, or of guaranteeing their reproducibility under increasingly severe conditions or--again--of simplifying the process of obtaining films having the desired anti-fog properties, is still open.
In particular, the need is still very keenly felt of a comp
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Bax Serge
Buongiorno Livio
Ciocca Paolo
Buffalow E. Rollins
Quatt Mark B.
W. R. Grace & Co.,-Conn.
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