DE2852122C2 - A film made of an olefin resin or a vinylidene chloride resin - Google Patents

Description

30th

The invention relates to a film made of olefin resin or of a vinylidene chloride shark without functional ones Groups such as acid or acid amide residues.

The treatment of plastics ien to activate their surfaces is known. It is also known that such activated films can be printed better and a higher adhesion to meat and Meat-like materials have untreated foils as corresponding. Adhesion to meat and Meat-like substances are briefly referred to below as meat adhesion

It is also known that a film made of a plastic with a high insulating or barrier effect, such as such as vinylidene chloride resin to activate the surface before can be treated, and the treated film for shrink packaging of meat and meat-like Substances can be used; because of the high shrinkage capacity of the film, the film comes in close contact with the meat or the meat gen substance, and because of the high meat adhesion, there is an intimate connection between the film and meat; because of the barrier effect of the film, the packaged goods have a remarkably high level Shelf life for the meat or meat-like substance.

However, conventional films with activated surfaces do not meet this because of various disadvantages necessary requirements; These disadvantages include, for example, insufficient activation in the course of the surface treatment, if the meat can be adequately written on, poor meat adhesion, Dependence of meat adhesion on differences in quality of the meat-like substance to be packaged, Decrease in the insulating or blocking effect due to the occurrence of pinholes or similar defects, uneven distribution of the activity of the film surface with the consequence of an uneven Writability and meat adhesion of the film, as well as very significant differences in the granted activity Foils from different parts and, in the case of different parts, from one and the same lot,

A possible cause for all of these disadvantages can be that the surface of a given It is difficult to activate the film to the desired extent of activation.

A prior art corresponding to the above statements is, for example, in the Japanese Patent Publications 35947/1975, 18770/1976 and 6157/1968 in Japanese Utility Model Laid-Open 47 578/1977 and in FR-PS 15 03 246 described.

From DE-OS 19 25 749 a method for the production of several narrow film tubes is from a wide film tube known in which the inner surfaces of the with a gaseous medium filled wide film tube are preferably pretreated by means of corona discharges. With this one The process is merely a partial internal pretreatment of the tubular film, a pair of connecting strips to accomplish.

From DE-AS 16 29 212 is a similar method and a device for treating the surfaces a tubular film made of thermoplastic material by spray discharges with an electrode and a Counter electrode, with rollers for squeezing off the tubular film at the beginning and at the end of the treatment zone and with means for introducing a pressurized gas into the interior of the tubular film between known to the rollers. The electrical pretreatment is also intended to modify the surface here in such a way that it that the later gluing can be improved.

The object of the present invention is to provide a new film made of olefin resin or from a Provide vinylidene chloride resin without functional groups, such as acid or acid amide radicals, one of which Surface has been activated to a high degree so that the film is printable and one of quality differences of meat and meat-like substances has independent meat adhesion, the original film properties such as insulating and barrier properties and other advantageous properties in the Course of activation has not been affected, and the storage of meat and meat-like Substances allowed for a remarkably long period of time with the usual activated foils so far has never been achieved

This problem is solved by the features of the characterizing part of the claim.

The film according to the invention is preferably a largely oriented tubular film. Preferably is they continue to shrink when heated.

The invention is described in detail below with reference to FIGS. 1 to 3 explained; it shows

F i g. 1 the inner surface of a tubular film treated according to the invention at 8000x magnification,

F i g. 2 the inner surface of an untreated tubular film at 8000x magnification; and

F i g. 3 in the form of a graphical representation of the in Results given in Table 2.

The surface of the film of the present invention made of a polyolefin resin or a vinylidene chloride resin without functional groups such as acid or acid amide residues must have been activated to such an extent that their Properties within the in F i g. 3 area delimited by solid lines.

FIG. 3 is a graphical representation for specifying the range limits for the activation given to the film surface in the context of the present invention. In the graphic representation, the values of films according to the invention are indicated with a double circle “®” (corresponding to the information with “@” in Table 2); the values for films that do not meet the conditions provided according to the invention are indicated with a cross “χ” (and corresponding to the information “x” in Table 2); it can be clearly seen that the respective values differ from one another. In detail, that corresponds to FIG. 3 area according to the invention, the condition that the surface of the film is activated to such an extent that when the surface is treated with an aqueous albumin solution and starch (in a certain ratio specified below) on the surface per cm ² 1.1 to 2 mg A mixture of starch and albumin adhere, and the haze of the film as a result of the adhering mixture is not less than 75%

This method of determining activation is three-dimensional in the sense that there is none for turbidity sufficiently high value is obtained even if a A sufficiently large amount of the mixture adheres to the surface of the film, but unevenly there (for example is arranged in the form of a strip); furthermore, a sufficiently high value for the haze is not obtained if Although the mixture adhering to the surface is evenly distributed, the amount of adhering However, the mixture does not exceed a certain value

The designation that the layer to be activated has no functional groups is intended to express be that there is not a sufficient number of functional groups present in the film according to the invention In short, the present invention is entirely without Realize the help of acid residues and other functional groups, which the film quality affect and make the production of the film more difficult.

If the proportion of the mixture adhering to the surface of ^{the film is less than 1.1 mg / cm 2} , the film has inadequate writability or meat adhesion. If, on the other hand, more than 2.2 mg of mixture per cm ^{2 of} surface adheres to the film surface, the film has a lower, inadequate barrier or insulating effect, and pinholes occur.

Even if, under the specified conditions, the proportion of mixture adhering to the film surface is within the required range of 1.1 to 2.2 mg / cm ² , uneven adhesion of the meat to the film in the finished packaging can occur, namely if the haze of the film, which can be attributed to the adhering mixture, is less than 75%

In the activation according to the invention, the inner surface of the tubular film is selected to be activated In contrast, the activation of the outer surface is negligibly small,

The difference between films according to the invention and known films is from various points of view been investigated. Samples of untreated tubular films treated according to the invention are each using a microscope below 8000 times Photographed magnification. The photographs obtained are shown in FIG. 1 (according to the invention treated) and 2 (untreated films) shown; the end the comparison shows that the film surface according to FIG. 1 is not coarser than that according to FIG. * 2. The comparison leads to the possible conclusion that, when viewed under a microscope, the Surface of the film according to the invention differs from the surface of the known film, from which it must be concluded that the corona discharge leads to a special surface appearance

ίο The summarized analyzes of the various benefits brought about by this invention to choose the one shown in FIG. 3 specified range, which is an effective criterion for differentiating the product according to the invention from known ones Products

A) Sample preparation

The mixture of aqueous albumin solution and starch is made by carefully mixing 100 parts by weight of aqueous 25% egg albumin solution (grade 1 according to the JI ^ K-8068 standard) with 100 parts by weight of starch (starch made from wheat flour, grade 1), prepared
From a long web of seamless tubular film, 10 tubular film samples are cut, all of which have the same width in the flat state and a length of at least 100 mm. One cut end of each tubular film is closed and the vessel formed is then completely filled with the mixture of albumin solution and starch, taking care that no air is introduced with the mixture. The other cut end of the film is then closed so that a cylindrical package is obtained. The packaging is 30 min

immersed long in 90 ⁰ C hot water. After this period of time, the sample is taken out of the hot water, ^{cooled under running water of 20 0} CIh long dried on filter paper to remove the water droplets adhering to the package surface, and then for 3 h in one Maintained room that is kept at 20 ± 1 ° C and at a humidity of 60 ± 5%.

After the storage in this room has ended, the packaging is cut open; in detail two steps are carried out parallel to the central plane in the circumferential direction at a distance of 50 mm; the ring-shaped, 50 mm wide film segment obtained from the surface of the cylinder is once in Cut lengthways so that a rectangular one

in this way a piece of film is obtained which is subsequently used as a sample (a total of 10 such samples obtain).

B) Determination of the proportion of mixture adhering to the sample (in mg / cm ² )

From the total number of 10 samples, 5 samples are selected and the weight (W {) of each sample is carefully determined. Weighing is carried out in a room kept at (20 ± 1) ° C. and (60 ± 5)% humidity within 5 minutes after separation the sample from the cylinder. After weighing, the mixture of abumin and starch adhering to the sample surface is quickly removed under running water and the film that remains is dried on filter paper in order to remove water droplets adhering to the surface of the film. The Foiw is then dried for 3 hours in a room kept at (20 + I) ⁰ C and (60 ± 5)% humidity

dry film carefully weighed, determining the weight (W ₇ ) .

The proportion of adhering mixture (mg / cm ² ) results from the formula

Area of the samples

The proportion of mixture adhering to the film is determined separately for each of the five samples and the arithmetic mean is formed from the five values obtained.

C) Determination of the turbidity (in%)

Each of the obtained five samples is spread out and at a central portion with a diameter of approximately 25 mm, which is kept correspondingly taut, the haze according to ASTM D 1003-16 certainly. This test must be carried out in a room kept at (20 ± 1) ° C and (60 ± 5)% relative humidity 30 min after sample preparation. Again, the The turbidity value is determined and the arithmetic mean is calculated from the 5 values obtained.

The activation treatment according to the invention consists in that the tubular film or the double-layer, flat film is passed between at least two electrodes, the outer surface of the Tubular film or the outer surface of each layer of the double layer flat film in contact with one Electrode is held. The inner surfaces of the film are held opposite one another at a distance, there is gas (air, N2, He, or Ar) in the space formed, and a corona discharge occurs or glow discharge carried out The inner surfaces of the not in contact with the electrode The foil is activated in the process. The distance between the inner surfaces of the foil is a maximum of 8 mm, preferably 5 mm or less. During activation, the temperature of the film surface is preferably 15 ° C up to a temperature at which no significant shrinkage of the film occurs (for example at 80 ° C as the upper limit).

Sufficient activation is expediently obtained with a voltage of 23 to 10 kV at a frequency of 30 to 120 kHz and a discharge duration in the range from 0.05 to 0.2 s. The activation is carried out so far that the proportion of mixture adhering to the film surface is not less than 1.1 mg / cm ^J , preferably more than 1.4 mg / cm ² , and the haze has a value of not less than 75%. , preferably more than 80%

Tests have shown that on an activated Insofar as the slide, no noticeable loss of activation occurs over the course of a month at 30 "C electrical discharge is carried out on a film in the oriented state is that given to the film Activation several times greater than when this treatment was carried out on the non-oriented film and the film is then oriented

The term polyolefin resins refers to materials such as polypropylene, polyethylene, Ethylene-vinyl acetate copolymers and ionomer resin Understood; The term vinylidene chloride resins also includes copolymers by copolymerization a greater proportion (not less than 65%) of vinylidene chloride with a minor proportion (less than 35%) other activatable components have been obtained; also come under the Invention such copolymers into consideration, the copolymerization of olefins and vinylidene chloride have been obtained and additionally contain a few percent other resins, as well as combinations and mixtures of these resins.

Investigation and measurement procedures and evaluation of the results

1) Assessment of meat adhesion and turbidity, such as this using a mixture of aqueous Albumin solution and strength according to the above

Executions have been determined

ι Ί 2) Determination of meat adhesion

a) Production of the meat-like substance

A sample for determining meat adhesion is Hiirrh kneading of a different composition made from the following components:

Meat-like substances for determining meat adhesion

Components substance Il III (Parts by weight) I. 40 jo shredded 40 Haddock meat 25th - tuna 25th - 50 pork meat - 10 30th jr lard 5 10 11th strength IO 0.5 0.5 spices 0.5 2.5 3 Table salt 2.5 20th 12th 40 ice water 20th b) test procedure

A total of 15 pieces approximately 200 mm long are cut out of a long strip of seamless tubular film. Each piece is closed at one end and filled with the meat-like substance.In this case, 5 pieces of tubular film are filled with the various meat-like substances (I), (II) and (III). Each bag-like piece of film is carefully sealed with the intended meat-like substance filled whereby the inclusion of air is avoided; then the open end of each film bag is closed so that a cylindrical pack is obtained. This packing 50 is inserted min hot in 90 ^0C water and then for 1 hour cooled in cold water at 20 ° C h then 5 seconds hot in 96 ° C water is immersed to eliminate the film to shrink and wrinkle, so that eline

μ packaged sausage is obtained. This will result in an arbitrarily selected area along the entire circumference of the package at a longitudinal distance made two cuts from 50 mm; then one is made between the two circumferential cuts

bi longitudinal section made so that a 50 mm wide A piece of film is obtained from the cylinder circumference. This piece of film is made into square specimens with cut out to an edge length of 50 mm.

c) Determination and evaluation of meat liability

5 (fl = 5) pieces of film are obtained from each meat-like substance (I), (II) and (III); each Foil piece is placed on a glass plate into which a checkerboard-like pattern is carved so that it is easy those fields can be determined where meat; »'(ige substance adheres to the foil. From the Area ratio of the individual fields to which meat-like substance adheres to the total area of the ι ο Glass plate a percentage value is determined: from the 5% values for each packaged meat Substance, the arithmetic mean is formed.

d) Scale for assessing meat adhesion

® more than 90, up to 100%

excellent preservation (preservation)

the fleshy substance;
O more than 80 to? » 90 ⁰ A

good preservation of the meat-like substance; Δ more than 70 up to 80%

insufficient preservation of the meat-like substance;

χ more than 5, up to 70%
- # ■ 0 up to 5% obviously unsuitable of the film for meat packaging.

3) Evaluation of the decrease in gas barrier effect

a) Preparation of the test samples and implementation
the investigation

A tubular film present as a sample is cut open to form a flat J5 Get a piece of foil. The oxygen permeability is determined on this test sample using the method according to Test standard ASTM D-1434 (with a commercially available test device at (30 ± l) ° C and 90% humidity) is determined so that a value for the transmittance is obtained.

Separately from this, a comparison sample (a piece of film that essentially corresponds to the tested film; the only difference is that the corona discharge has not been carried out) is tested in order to determine the 4-. Determine permeability. The evaluation of the decrease in the gas barrier effect corresponds to the difference between the values determined for the test sample and the comparison sample (the permeability is determined in cm ³ gas / m ² area in the course of> 24 hours at a pressure of 1 atm).

b) yardstick for the evaluation

© the difference is up to 10 cm ³ ;

O the difference is more than 10 cm ³ and up to

30 cm ³ ;
Δ the difference is more than 30 cm ³ and up to

50 cm ³ ; and
χ the difference is more than 50 cm ³ .

-

4) Evaluation of the occurrence of pinholes

a) Preparation of the test sample and
Carrying out the measurement

A total of 200 1 m long tubular films are arbitrarily selected from a predetermined supply of tubular films; each tubular film is at one end

65 closed so that a sack or bag is obtained. Each film bag is closed at one end and then filled with compressed air and then the other end is also closed, so that an air-filled film cylinder is obtained. This cylinder is submerged under water. The presence or absence of a pinhole in the cylinder is determined by the presence or absence of air bubbles emerging from the film surface. The number of pinholes per cylinder is counted.

b) Standard for evaluating the number of pinholes

(based on the number of pinholes / 200 pieces

Tubular films)

® 0 pinholes;

O Ibis 5 pinholes;

Δ 6 to 10 pinholes; and

χ 11 or more pinholes.

5) Overall rating

The overall evaluation is carried out according to the following standard, whereby the results of the Evaluation of the meat adhesion for the three meat-like substances (I), (II) and (III) as well as the acceptance Gas barrier effect and the occurrence of pinholes are taken into account.

® A combination of the following ratings for the specified properties: three times »©« or twice »®« plus once »O«;

O a combination of the following ratings for the properties given above:
no »x« and only once »Δ« plus twice »®« or twice »O« plus once »®«;

Δ a combination of the following ratings for the above properties:
never »χ« and two or more times »Δ«; and

χ a combination of the following ratings for the above properties:
one or more times "x".

Example and comparative example!

A vinylidene chloride copolymer with the various compositions given in Table 1 below (which additionally contains about 7% plasticizer and a stabilizer) becomes a common one Melt extruder fed, melted and kneaded; then the mass becomes a tubular film extruded, supercooled and peeled off with biaxial expansion, so that a seamless tubular film with a Wall thickness of 0.04 mm and a width of 55 mm (in the folded state) is obtained.

A common device for performing the corona discharge is between the stretching stage and the winding station in the film production for treatment by means of corona discharge various conditions are provided as shown in Table 1 below; the treatment the oriented, seamless tubular film is thus exposed

As indicated above, the adhesion of the albumin-starch mixture to the various tubular films obtained is determined (Adhesion and haze values of the film being obtained as a result of adhesion) for Description of meat adhesion, also the decrease in the gas barrier effect and the occurrence of needle loosening

ίο

brazen determined. The results obtained are given together in Table 2.

Experiments 1 to 6 are according to the invention

Table 1
Trial condition '.! R £'? ^r i

Trials, and Trials 7 to 12 are comparative trials. In book no. 12 there was no electrical Discharge treatment of the film carried out.

Attempt no. Plastic pigment Conditions for corona discharge distance
between
FoI ic η-
layers tension frequency together
settlement
Weight ratio
Vinylidene
chloride: vinyl Feed
the slide mm kV kHz Chloride (wt,%) m / min 4th 5 70 I. 85/15 15th 4th 5 70 2 85/15 TiO ₂ (7.0%) 15th 1 3 30th 3 85/15 15th 3 2 80 4th 70/30 15th 5 7th 40 5 85/15 15th 3 7th 50 6th 85/15 15th 5 5 60 7th 85/15 15th 5 5 60 8th 85/15 10 4th 6th 110 9 70/30 10 5 5 60 IO 85/15 TiO ₂ (7.0%) 15th 3 7th 110 Il 70/30 10 - - - 12th 85/15 15th Table 2 Test results Gas barrier needle
effect holes
(III) Total-
Werlung Determination using an albumin-starch mixture
Try turbidity adhering amount
ISIr ι
"% (mg / cm ² ) Meat adhesion
(D (H)

100

100

80

75

100

90

1.1 © ι, ι © 2.2 © 2.2 ® 1.7 © 1.9 © 1.0 O 1.6 © 2.3 © 1.0 O 2.3 © not more than 0.1

ο © © © O © ® © © © © © O © © © © © © © © © X X © © X X Δ X X χ © © X

For this purpose 2 sheets of drawings

Claims (1)

Claim: Film of Olefroharz or a Vmyljdenchloridharz oh ^"e functional groups such as acid or acid amide, characterized obtainable so passing the film through an electrode arrangement with at least two spaced oppositely disposed electrodes, that the outer surface of a tubular film and the outer surfaces two flat foils touch the electrodes and a corona or glow discharge takes place to activate the inner surface of the foil or foils, the inner surfaces of the foil or foils being at a distance of at most 5 mm and the voltage 2 $ to 10 kV, the frequency 30-12OkHz and the discharge duration 0.05-0.2s, characterized in that the process parameters mentioned are coordinated in such a way that the inner surface of the film is activated to such an extent that the surface is treated with a mixture of aqueous albumin solution and starch there per cm ² surface 1.1 to 22 mg mixture of albumin and starch a nourishing; and the haze of the film caused by the adhered mixture is not less than 75%