DE1228170B - Moisture-impermeable, heat-sealable packaging material, consisting of a cellulose hydrate film with a coating of vinylidene chloride copolymer - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

B44d

German class: 75 c -S / 06

Number:
File number:
Registration date:
Display day:

1228 170
B45604VIb / 75c August 7, 1957 November 3, 1966

It is known that vinylidene chloride copolymer coatings provided films are impermeable to moisture and heat-sealable and are very suitable for use as packaging films. Coatings made from a vinylidene chloride copolymer make film bases on which they are applied become impermeable to moisture in an excellent manner when the copolymers through Polymerization polymerizable mixtures have been produced that are greater than 90 percent by weight contain monomeric vinylidene chloride. Such moisture-impermeable coatings are known from vinylidene chloride copolymers, which are different in their composition by using polymerizable monomeric compounds in the production of the coating copolymers differentiate. Also copolymers of vinylidene chloride made from monomer mixtures with the addition of olefin carboxylic acids, preferably itaconic acid, are for the formation the moisture barrier coatings have been used. While you used to have the covers generated by applying the mixed polymer solution in organic solvents is maintained in more recently to apply aqueous dispersions of the copolymers to the cellulose hydrate film and dry.

Packaging material that has a film base made of regenerated cellulose and with a coating such a copolymer is coated, nevertheless sometimes shows certain inadequacies with regard to the strength of the heat-sealed connection and the slippage of such a coated one Slide over another. As a result of the high proportion of polymeric vinylidene chloride in the coating copolymers the use of relatively high temperatures becomes a durable heat seal the packaging film required, for example 170 ° C. When using such However, damage to the packaging film is to be feared at high temperatures. One diminishes the proportion of polymers! Vinylidene chloride in the coating copolymers, so must for the purpose Maintaining a sufficiently large slip of the additive that ensures machine processing to be increased in slip agents. But from this again the necessity arises, too raise the temperature for heat sealing.

One places z. B. in a known manner, a copolymer by adding an aqueous emulsion Polymerized mixture that

Moisture-impermeable, heat-sealable packaging material, consisting of a Cellulose hydrate film with a coating of vinyl chloride mixed polymer

Applicant:

British Cellophane Limited, Bridgwater, Somerset (Great Britain)

Representative:

Dr. H. Häring and H. Brinkmann, lawyers, Wiesbaden-Biebrich, Rheingaustr. 190-196

Named as inventor:

Cyril Howard Phillips,

Jerzy Konrad Moltan, Bridgwater, Somerset (Great Britain)

Claimed priority:

Great Britain August 8, 1956 (24 332) - -

94 parts by weight of monomeric vinylidene chloride, 6 parts by weight of monomeric methyl methacrylate, 1 part by weight of itaconic acid

contains. A coated with this copolymer is commercially available film of regenerated cellulose had when the film was tested by the Mischpolymerisatüberzug within a few hours after its completion, g, a strength of the heat seal 500, the seal provided at a temperature of 13O ⁰ C completed was. If, however, the film coated with the copolymer was aged for 2 or 3 days in air at 25 ° C. after its production and was tested as stated above, a decrease in the strength of the heat-seal joint to g was found. Artificial acceleration of aging by heating the freshly coated film for 1 minute at a temperature of 105 ° C. resulted in a similar drop in the strength of the heat-seal joint. This change is presumably related to the progressive crystallization of the copolymer of the coating.

609 709/275

If you add a small amount of a lubricant, e.g. B. Carnauba wax, as described in British Patent Specification 655,006, there is a tendency to increase the temperature at which sealing is best done. So had the copolymer-coated Foil which had been produced in the manner described above, but Va percent by weight of carnauba wax as a lubricant, even when tested within a few hours of its manufacture a heat seal joint strength of 0 to 50 g, provided that the seal was carried out as before at a temperature of 130 ° C had been carried out. However, when the Sealing temperature to 170 ° C a strength of the heat-seal connection of 300 g, if the coated Foil was tested within a few hours of its manufacture. The strength of the 170.degree. C., however, was found to have dropped up to 180 g after the film after its manufacture for 2 to 3 days in the air at a temperature of Aged 25 ° C. This change is probably due to the coincidence of the effects of the progressive crystallization of the copolymer of the coating, and the precipitation of the applied Carnauba wax on the surface of the coating.

The present invention relates to a moisture-impermeable packaging material, that from a cellulose hydrate film with a vinylidene chloride copolymer coating which is clear and translucent, and which is made by the application of gentle pressure and gentle heat when proportionately low sealing temperature solid connections are created by winners. The packaging material is characterized by a moisture-proof coating, which consists of a vinylidene chloride copolymer, which by joint polymerization of a Mixture of monomers is made, which is composed of

a) 91 to 94 percent by weight vinylidene chloride,

b) 3 to 7 percent by weight methyl methacrylate

and

c) 1 to 3 percent by weight vinyl acetate.

It is advantageous that the polymerizable mixture, from which the vinylidene chloride copolymer is produced, also contains itaconic acid, however not more than 2 parts by weight per 100 parts by weight of polymerizable substance. The anchorage the mixed polymer coating on the carrier film is improved by the itaconic acid.

The moisture-proofing coating preferably also contains wax as a lubricant of the type of ester waxes that are in a proportion between 0.1 and 3.0 percent by weight, always based on the weight of the solid components in the Coating, is incorporated.

Any first type of wax, natural or artificial, is suitable. Carnauba wax, whale wax, candelilla wax and palm wax are named as examples of natural ester-like waxes. Artificial ester-like waxes include hydrogenated castor oil, benzyl stearate, pentaerythritol distearate, pentaerythritol tetrastearate, and n-octadecyl stearate. The amount of wax incorporated into the coating can vary and is, to some extent, dependent on the type of specific wax used, the thickness of the coating and the degree of lubricity desired. For carnauba wax, which is the preferred ester type wax, the optimal amounts are normally between 0.1 and 1 percent by weight based on the weight of the solids in the coating.
Different coating methods are on the market

ίο area known. So z. B. the copolymer coating be applied to the carrier film from a solution in an organic solvent, z. B. tetrahydrofuran, the solvent being removed by heating. But preferably the copolymer coating is applied to the carrier film from an aqueous colloidal dispersion of the interpolymer in the manner described, for example, in British patents 655 732, 663 645, 749 276 and 756 851.

Such packaging films are clearly transparent and to a high degree impermeable to moisture. As a result the monomers added to the vinylidene chloride and the particular percentage composition of the interpolymer is the use of lower heat sealing temperatures in use of the packaging material possible.

The packaging films, which are in the coating as slip agent, carnauba wax in an amount of 1 percent by weight, based on the weight of the solid. Components contained in the coating are easy to seal with heat and, when applying gentle pressure at a temperature of 135 ° C, result in solid connections if the packaging film is tested within a few hours of its manufacture. Even if the packaging film has been air-aged for 3 months at room temperature, the optimal heat-sealing temperature does not exceed 150 ° C.
The progress attained by the inventive packaging material in the simultaneous achieve heat sealability of the film at temperatures that do not exceed 15O ⁰ C, and that the film is also suitable for high-speed packaging machines in achieving such a good lubricity.

example

An aqueous dispersion of a vinylidene chloride copolymer is prepared from the following components in the specified proportions:

92.0 parts by weight of freshly distilled vinylidene chloride,

6.0 parts by weight of freshly distilled methyl methacrylate,

2.0 parts by weight of vinyl acetate,

1.0 part by weight of itaconic acid,

0.3 part by weight of ammonium octadecyl sulfate,

1.0 part by weight of a condensation product of formaldehyde and naphthalenesulfonic acid z. B. under the trademarked name »Lissatan« AC im Traded product,

0.6 part by weight of ammonium persulfate,

0.3 part by weight of sodium metabisulphite,
150.0 parts by weight of water.

This mixture was filled with nitrogen and provided with a stirrer and a

Glass reaction vessel provided with a reflux condenser is filled and the temperature is maintained vigorously stirred from 40 ° C. When the reflux stopped after stirring for about 4 hours, the Reaction aborted. The dispersion obtained was used as a slip agent in an aqueous medium emulsified carnauba wax added. The addition was 1 percent by weight of carnauba wax, calculated on the existing solid constituents of the copolymer.

The resulting wax copolymer dispersion was according to that in the British patent 663 645 described method on the two sides of a serving as a carrier commercially available Regenerated cellulose film applied. A good-looking, coated film was produced which was the total thickness of the order on both sides 3 g per square meter. The slip and the adhesion-preventing properties were only slight in the case of the film coated with the copolymer, when measured within a few hours after the coated film was made. They were enough however, assumed that the film could be wound into a roll in a satisfactory manner. However, after the film coated with the copolymer for 3 days after its production had been in the air at 25 ° C, the same test shows that the slip and the adhesion-preventing Properties had improved to a satisfactory degree.

The film coated with the copolymer had a permeability value of 40. The strength of the connection produced by heat sealing was 350 g when the seal was completed at 135 ° C. within a few hours after production of the coated film. When the coated foil at 25 ° C was aged for 2 months at the air and was then heat sealed at 15O ⁰ C, the strength of heat seal was 300 g.

For the sake of comparison, it should be noted that a similar commercially available film made of regenerated cellulose, which was coated in the same way with an aqueous dispersion, which was also composed of 92 parts by weight of vinylidene chloride, 8 parts by weight of methyl methacrylate, 1 part by weight of itaconic acid, but without the addition of vinyl acetate, consisted of 1 percent by weight Carnauba wax had a permeability value of 50 and, provided the coated film was within A heat seal seam strength of 350 g was tested a few hours after its manufacture when the heat seal was carried out at 135 ° C. The slip and the anti-stick properties were low, nor did they increase with the aging of the film. An acceptable one was obtained Slippage if at least 4 weight percent carnauba wax was used. If, as before said that 4 percent by weight carnauba wax was used, but was after 3 days of aging in air at 25 ° C the strength of a heat seal connection, which was made at 155 ° C was less than 50 g. To obtain a strength of 300 g, the sealing temperature had to be increased to 170 ° C.

For the sake of comparison, the following is also given. A commercially available film made from regenerated cellulose, which was coated in the same way with an aqueous dispersion, which also consists of 94 parts by weight of vinylidene chloride, 6 parts by weight of methyl methacrylate, 1 part by weight of itaconic acid, but without the addition of vinyl acetate, with V2 percent by weight Carnauba wax had been produced had a permeability value of 25 and - when the coated ones were tested Foil within a few hours of its manufacture - a strength of the heat-sealed connection of 70 g, provided the film is sealed at 165 ° C, and of 300 g, provided the seal is at 180 ° C was done. After the film was aged in air at 25 ° C, the strength was less than 50 g if the film was sealed at 165 ° C and 180 g if the seal was done at 180 ° C was.

The permeability value was calculated using the Charch and Scroggie method of measuring the Permeability determined. The method is described in Paper Trade Journal TAPPI Section dated October 3, 1935, Pp. 201 to 209.

The slip value is measured by the cotangent of the angle of inclination at which a fixed Steel cube with a side length of 3.17cm slide straight in begins when both the substrate and the cube are covered with the film to be tested. Man performs the test at temperatures between

«5 15 and 20 ° C.

The anti-stick property value of the film is measured as follows. 50 sections of the Freshly made film, each 2.54 x 2.54 cm, is piled up and loaded in a press of 5 t. After 30 minutes, the pile is released and easily and without pinching folded four times so that only the opposite sides are combined in pairs and then the opposite corners. This separates the stack into individual ones that are separate from one another Leaves or in individual piles of leaves. The total number of single leaves or piles of leaves gives the value of the anti-adhesion properties of the film. If the detention value is 50 complete division before; the value 1, on the other hand, indicates complete block formation.

The strength of the heat seal connection has been measured according to the following test:
Two strips of the heat sealable sheet-like packaging material 3.81 cm wide are placed on top of one another so that opposite surfaces of the film are in contact with one another. At one end, a sealing seam is placed across the width of the material, the film being placed on a metal plate heated to the desired temperature, and a roller 1.89 cm wide and weighing 700 g being rolled over it. The roller and sheet packaging material remain in contact with each other for 3 seconds. The two strips sealed in this way are opened at the free ends. One end is held in place with a clamp and a light weighing pan is attached to the other end with a suitable clamp. Weights are then placed on the scale until the connection loosens and separates. The total weight, hi grams, required to separate the joint is referred to herein as the strength of the heat seal joint.

Claims (2)

Patent claims: 1. Moisture-impermeable, heat-sealable packaging material, consisting of a cellular loose hydrate film with a coating of vinylidene chloride copolymer, which is made from a methyl methacrylate in addition to a monomer mixture predominantly containing vinylidene chloride, characterized by vinylidene chloride copolymers obtained by joint polymerization of monomer mixtures of the percentage composition 91 to 94 percent by weight vinylidene chloride, 3 to 7 percent by weight methyl meth- acrylate,
1 to 3 percent by weight vinyl acetate and optionally not more than 2 parts by weight of itaconic acid per 100 parts by weight of polymerizable Substance are manufactured. 2. Packaging material according to claim 1, characterized in that the coatings are based on the amount of polymeric substance, contain 0.1 to 3 percent by weight of ester wax, in particular Carnauba wax. Considered publications:
British Patent Nos. 651769, 654 342,
496, 703 010. 609 709/275 10.66 © Bundesdruckerei Berlin