DE1546841A1 - Heat sealable, coated polyolefin film - Google Patents

Description

Heat Sealable Coated Polyolefin Film The invention has no to coated polyolefin films, particularly heat sealable coating compositions coated polyolefin films, which by conventional operations in bags, pouches, en and similar articles can be converted for use in packaging.

Though polyolefin films such as polyethylene, polypropylene, polybutylene or the like. Are self-sealable in the heat, d. H. two or more layers of film are capable of being merged with each other by the application of pressure and pressure, so it is often desirable to have a polyolefin film with a heat sealable to cover tbersugamasse. For example may be required on be that the polyolefin film is heat-sealable at a temperature which is less than the melting point of the polyolefin material, or if the film is stretched has been, at a temperature which is lower than the temperature at which Shrinkage occurs. conventional heat-sealable coating compositions which are based on Cellulose film and similar hydrophilic film bases are important Nitrocellulose compositions such as nitrocellulose softened with dibutyl phthalate. Such However, compositions have not heretofore been used to coat polyolefin films, because the anchoring of the coatings to the films was all found to be defective and consequently, heat seals of very low strength are obtained.

It has now been found that by choosing certain, more special Plasticizers for nitrocellulose coating compositions are obtained as a coating composition which, when applied to polyolefin films, have good adhesion and heat seal bond strength owns.

Accordingly, the present invention includes a heat sealable, coated polyolefin film which on at least one surface is coated with a heat-sealable nitrocellulose coating composition, which as a plasticizer trioyolohexyl citrate, dioyclohexyl atrate or di (methyloyclohexyl) tartrate or contains a mixture of one or more of these substances.

As for soft nitrocellulose overgamasBen Ublich last, ch the amount of plasticizer masso incorporated into the nitrocellulose transfer should be be sufficient to equip the nitrocellulose over @ ug with sufficient flexibility, in order to avoid it: to avoid the TpgaellanishKge and the @@@ @@@@ @@@ onge did not respond @@ @@@@ ge, at wlcher @@@@@@@@@@@@@@ kl @@ rig will be and the overdrawn Film surfaces g @@@@@@@@@ st, @@@@ ht anwinandarMhaben, ifwiebaiUmgebng3tjBpe? Gtren i.e. at around 20 ° C, come into contact with one another.

The plasticizer is preferably incorporated into the nitrocellulose coating composition in the range between about 30 and 1 ion, especially between 40 and 100% the weight of the dry nitrocellulose in the mass, incorporated.

If necessary, su der Maeee can use a Wachaßleitmittel, for example a high-melting paraffin wax (melting point 60 ° a or higher) Cereainxaoha, Beewwake, or veine wacha-like substance like pentaerythritol tetrastearate, hydrogenated risinusdl or dilauryl ketone, for example in an amount in the range between 0.2 and 0.5%, based on the dry weight of the softened nitrocellulose coating mass, may be added to facilitate the gliding of one leaf but another. Furthermore, if the wax or wax-like substance used is such, which tends to be incompatible with the nitrocellulose, a wax admixture, which is made from a resin (gum or pure) or contains such a material will. Suitable, known resins include, for example, dammar resin, rosin, Glyoeryl citrate modified with rosin, alkyd resin, cycloketone resin and Bsterhurze, which in the mass bia to an extent of between 1 and 25%, based on the Dry weight of the softened nitrocellulose coating compound can.

An anti-blocking agent to reduce the tendency to stick one surface on the other with stacked leaves, for example powdered Talc, finely divided silica or clays of the kaolin type can be added to the coating mass in the range between about 0.2 and 5%, preferably between 0.5 and 3.0% to the trooken weight of the soft-cut nitrocellulose coating mass will.

Nitrosellulose is of the same type as for use is known in coating compositions for cellulose film and preferably has a substance content in the range between 10, 8 and 12 and usually stands with a dampening agent like isopropyl alcohol in connection.

The polyolefin base film can be made of polyethylene? Polypropylene or polybutylene formed film, which also count in one or more directions can be stretched to at least partial orientation of the molecular structure effect of the film.

The softened nitrogen @@@@@ sem @ s @ e karm on the polyolefin films applied in solution in a suitable volatile organic solvent, which preferably has a boiling point below about 100 ° C and preferably is an organic ester or a peton.

Examples of suitable solvents include ethyl acetate and methyl ethyl ketone or Aoeton. You can also loung the nitrocellulose coating before application diaper on the polyolefin film in water. The coating can be used to remove excess Mass can be wiped off with conventional means and de solvent or that The solvent-water mixture is then removed by evaporation.

The adhesion of the soft nitrocellulose compound to the polyolefin film can be bidded, index the film before coating according to known methods pretreated, for example, by giving it the glow discharge, an electrostatic High voltage field, or exposed to ultraviolet radiation, or it with a liquid or gaseous oxidizing agents.

The invention now stands out through the following specific belelopes Illustrates: Example 1 15g of tricyclohexyl citrate are mixed with 47.3g of nitrocellulose (with a nitrogen content of 11.5%) which contains 30% isopropyl alcohol (i.e. Nitrocellulose with a dry weight of 33g) mixed and the mixture is then dissolved in 200g ethyl acetate. A biaxially oriented polypropylene film having a Thickness of 0.0165mm and a tensile strength tone of 1828kg / om2 in both longitudinal and also in horizontal direction, is coated on both sides by pulling the film through a bath leads which contains the above coating composition. jade coated surface the film is scraped off with a squeegee roller and the film is then dried, so that there is a coating weight of about 2g jo square meter each side results. A strip of pressure-sensitive adhesive tape, commercially available available under the designation "Sootch" marking tape, with a width won 22x and a length of about lOom, the sticky side down, is then applied by pinger pressure pressed into contact with a coated surface of the polypropylene film.

The tape is then quickly pulled away from the coated film and it is found that the tape does not remove anything from the coating. The Verauoh with the band using fresh band samples a few times with eohnellen and repeated long detachment movements, but the coating is a little removed will.

The heat-sealing compound @ strength of the coated P then becomes measured, inden one swel strips of the coated film of 16.5 cm length and 3, 8on wide, coated surface placed on coated surface on top of each other, between the strip on one end through boxes of the eighth on a chewy base Heat seal forms, and W1 12000 brings down a metal bat to under to press against the strip at a pressure of 1.4kg / cm2.

The contact time of the rod with the films is t seconds. the Frein Ehden the strips are then grasped by suitable handles and the force (known as the Heat barrier bond strength) which is required is to separate the strips at the heat seal bond is measured and one finds that ze is 125g.

The experiment is repeated with the exception that tricyclohexyl citrate is used is replaced by another plasticizer, namely tributyl citrate. In this Palle is found because the coating compound is easily removed by the "Sootoh" strip and it is found that the heat seal bond strength is less than 50g Example 2 The experiment described in Example 1 is repeated with the assumption that dame instead of 15g Tricyclohexyloitrat, 15g Dicyclohexyltartrat can be used. When using the "8cotch" tape test, as it is shown in Example 1, is the pull through the tape is not removed.

The measurement of the heat seal binding strength according to the example 1 method described above, a heat seal bond strength of 260g is achieved. The Versuoh is repeated with the exception that the dicyclohexyl tartrate is through Dibutyl tartrate is replaced. The "Scotoh" tape is found to be the coating compound easily removed and the heat seal bond strength is below about 50g.

In another repetition of the experiment, instead of dicyclohexyl tartrate, Isobutyl tartrate used. The coating is easily removed in the "scotch" tape test and a heat seal bond strength of about 48g is achieved.

Example 3 The process described in Baiapiel 1 is repeated with the exception that instead of 15g trioyolohexyl citrate, 15g di (methylcyclohexyl) tartrate used. When using the adhesive tape tests, as described in e @ i example 1 bo-3 9? ßaßr? f '' '<is removed. The heat sealing bandage @@@ rke wi @ d @@@@ the in example 1 Beschrisbe @@@ Mathode measured and one finds that aie 90g amounts to. bi8Pi 4 En is prepared in a liquid passage which the following. Components (based on weight) has: Weight in g of nitrocellulose (nitrogen content 11.5%) 47.3g with a content of 305 isopropyl alcohol, corresponding to a dry weight of 33 dicyclohexyl tartrate 25 pentaerythritol tetrastearate 0.3 powdered talc 0.3 Ethyl acetate 200 Sa finds that the pentaerythritol tetrastearate good with nitrocellulose.

A biaxially oriented polypropylene film 0.0165mm thick and a tensile strength of 1828kg / cm2 both lengthways and crossways, is covered with the Oberzugamaeee on both belon, indien the film through a man runs a bath. The film is removed from the bath to remove excess Spread the mass on both sides with an Abatretchrolls and dry it, like this that there is a coating weight of 2g per square meter on r side.

The adhesive tape is applied to the oversized fils in Example 1 and it is found that it is removed in Ubersug. Then the heat seal bond strength is as described in Example 1 Method measured and it is found that it is 215g.

Example 5 The procedure described in Example 4 is repeated with the exception that instead of the pentaerythritol tetrastearate, a hydrogenated Castor oil with the trade name "Synthawax" is used. The hydrogenated castor oil mixed with the nitrocellulose. Through the tape the coating is not removed from the film and the heat seal is found to be bid strength 300g.

The foregoing should be understood to be within the scope of the invention a method of making a heat sealable polyolefin film is, wherein The procedure is characterized by the fact that one is on at least one surface sine polyolefin film one dissolved in a volatile organic solvent Nitrocellulose coating mass applies, which ala "ichaohar <ricyclohe.xyl '" itralT hoxyl tartrate or di methyloyclohexyl) tartrate or an Oexßeeh of on or more @@@@ the plasticizer contains, after which the solvent is removed by Ver @@@ fung.

The nitrocellulose coating composition soldered prior to application to the polyolefin film preferably in aer diepergiort, causing evaporation of the solvent and water mixture follows.

The nitrocellulose coating composition of the invention can also include tri (methylcyclohexyl) citrate as plasticizers with include.

- patent claims -

Claims (1)

Claims 1.) Heat-sealable, coated polyolefin film, for example polypropylene film, characterized in that the film is on at least one surface covered with a heat-sealable nitrocellulose coating @@ asse which ale plasticizers is tricyclohexyl citrate, dicyclohexyl tartrate or di (methylcyclohexyl) tartrate or contain a mixture of two or more of the plasticizers and are preferably in an amount in the range between 30 and 150%, based on the dry weight the nitrocellulose in the coating mass. 2.) Heat-sealable, coated Polyolofinfils nsoh claim 1, characterized in that the polyolefin film to increase the adhesion between the film and the nitrocellulose coating is pretreated. 30) Modified heat sealable coated polyolefin film according to claim 1, characterized in that the Uberzueaasse as a plasticizer Tri (methylcyclohexyl) oltrate includes.