DE1236171B - Method of treating a film of varying thickness across its width - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

B29d

German class: 39 a3- 7/26

Number: 1236 171

File number: B 66027 X / 39 a3

Filing date: February 20, 1962

Opened on: March 9, 1967

The invention relates to a method of treating a film of varying thickness over its width, which can be wound into a smooth roll, being one consisting of solid particles Fabric is evenly applied to at least one side of the film prior to winding.

Films are commonly wound in a roll or on a core for convenient storage and can transport. The films produced in the usual way have stripes of different length in the longitudinal direction Thick, and when winding into a roll, the thicker parts come on top of each other with each turn to lie and form hard circumferential ligaments. If the film is wound under tension, so that the turns are strong enough to create a telescopic Avoid napping the roll, the layers of film that are over the tough Edges are wrapped, deformed. This deformation is increased during storage of the roll, when the film shrinks because of the stretch that occurred during wrapping under tension, subsides, and therefore the turns become tighter. It was found that when the film was unwound from such a roll the deformation caused by winding over the hard straps is, remains and difficulties in processing such a film into bags or in Bedrakken on a printing press where the film must lie flat to avoid pinches and faulty printing avoid occurring.

The invention has set itself the goal of treating a film in such a way that it does not have the disadvantages of the known films mentioned, that is to say that it can be unwound into a roll which is essentially free of hard peripheral bands. Accordingly, the method according to the invention is characterized in that the substance consisting of solid particles is applied in a total amount of 0.001 · S to 0.025 · S g / m ^{2 of} film, where S is the specific gravity of the substance and the average particle size of the substance is between 5 and 45 microns.

From British patent specification 686 492 it is known to treat the surface of a heat-sealing film in order to prevent undesired sticking. A finely divided powdery substance, which is in a non-volatile viscous liquid, ζ. B. is dispersed in an oil, applied to the film surface. In this known treatment method, the particle size can be arbitrary up to the point where the transparency is eliminated. There are also methods for treating a film with the amount to be applied
different thickness across its width

Applicant:

British Cellophane Limited,

Bridgwater, Somerset (UK)

Representative:

Dr. W. Koch and Dr. R. Glawe,

Patent Attorneys, Hamburg 52, Waitzstr. 12th

Named as inventor:

Cyril Howard Phillips,

Cedric Michael Lulham,

Brian Lyall,

Bridgwater, Somerset (UK)

Claimed priority:
Great Britain of February 24, 1961 (6917),
dated February 8, 1962

no details and the treatment of the film is for a different purpose than that Method according to the invention, which makes it possible to use simple means to differentiate one over its width handle thick film so that it can be unwound into a smooth roll.

In a preferred embodiment, the film is volatile with a coating mixture Liquid coated, and the fabric applied to the coated film before the coating dried is.

When the film treated in this way is wound into a roll, the solid particles lie uniformly have been applied to the film, between the individual turns, and it is assumed that they keep the individual turns at a distance.

In the places where thick parts of the film are superimposed, the particles become during the winding process and then shrinking either crushed or forced partially into the surfaces penetrate the adjacent film parts, while the particles essentially penetrate the thinner parts are unaffected, so that the role is essentially free of hard bands and the layers of the the roll of wound film will not be deformed.

709 518/488

It is preferred, for convenience, to have the particulate matter only on a surface of the film. However, when the material is applied to both surfaces, it is united the material applied to one surface of the film is in the space between the turns with the material applied to the other surface of the film when the Film is wound into a roll.

The method of the invention is particularly useful with cellulosic film which is either a simple one Cellulosic film or a cellulosic film coated on one or both sides with a suitable heat sealable and / or moisture-proof coating mixture is coated, can be. examples for such coating mixtures are nitrocellulose-wax mixtures or polymeric products, such as z. B. polyethylene, or copolymers of vinylidene chloride, which are based on the base cellulose film from a Solution in a volatile solvent by a melt strand skewer process or from aqueous Dispersions have been applied.

The method according to the invention can also be applied to films made of polymeric materials, such as B. polyethylene, polypropylene, polyvinyl chloride, polyvinyl acetate, polyamides or vinylidene chloride copolymers, are produced, either in the case of simple films or films coated with a suitable coating mixture, or in the case of laminates from the same or different films.

If the film is coated with a coating mixture consisting of a solution in a volatile solvent or is applied from an aqueous dispersion, it is preferable that from to apply individual particles of material to the coated surface, while the Coating mixture is still damp. Then, when the coated surface dries, the Particles held in place by the dry coating. Such coatings usually have a thickness of about 1.2 microns. In the case where the coating mixture is a polymeric substance, which in one molten state is applied to the film, or the film is made of a polymeric substance and formed by melt extrusion, the particulate material may be The surface of the polymeric material can be conveniently applied before it solidifies as it cools. The particles are partially embedded in the surface of the polymeric substance, so that the particles, when the polymeric material solidifies, become trapped on the surface.

A preferred particulate matter applied to film in accordance with the invention is strength, especially in terms of its non-toxicity when the film is used for wrapping and food packaging is to be used.

Bulk density determinations indicate that starch particles have an average specific gravity of 1.0 and, for a starch sample with an average particle size of 15 microns, are about 6.0 x 10 ⁸ particles per gram. It can be readily seen that for any single particulate matter having the same average particle size there will be the same number of particles in separate samples of the matter if each sample has a weight which is the specific gravity of the matter, expressed in grams , is equal to.

Other particulate matter used in the practice of the invention are starch extender, resin-coated starch particles, diatomaceous earths, silicon dioxide, talc or powdered polymers, such as. B. polyvinyl chloride, or copolymers, such as. B. vinylidene chloride / acrylonitrile or vinylidene chloride-methyl methacrylate copolymer.

It is found that when the particulate matter is applied to one surface or both surfaces in total of the film in an amount less than 0.001 x 5 g / m ² (where S is the specific gravity of the particulate matter) or the average particle size is less than 5 microns, the advantages of the invention are not obtained, that is, when the film is wound into a roll, it tends to form hard peripheral bands. On the other hand, if the particles applied to the film exceed 0.025 · S g / m ² or the average particle size exceeds 45 microns, then undesirable surface effects are exhibited which render the film unsightly and adversely affect its printability. Furthermore, excess particulate matter in a heat sealable film tends to decrease the strength of the heat seal bond, so that the bond temperature must be increased to undesirable levels in order to obtain a satisfactory bond. In addition, excess particulate matter tends to be rubbed off on film processing machines and build up on the working parts.

In a preferred embodiment of the invention, and particularly if the film is to be gravure printed in light tones, the total amount of particulate matter placed on one or both sides of the film is in the range between 0.002 x 5 and 0.020 · S per square meter of film, where S is the specific gravity of the particulate matter.

In a more preferred embodiment of the invention, the weight range of particulate matter applied to one or both sides of the film per square meter for particles having an average size of 5 microns, 15 microns and 45 microns is as follows:
Average particle size 5 microns:

between 0.005 · S and 0.020 · S g;
Average particle size 15 microns:

between 0.003 x S and 0.015 x S g;

Average particle size 45 microns:

between 0.002 · S and 0.010 · S g.
The invention also includes a roll of film when treated in accordance with the invention.

Specific methods for practicing the invention will now be given by way of the following examples described.

example 1

A regenerated cellulose film was produced, covered on both sides with a coating mixture of vinylidene chloride-methyl methacrylate copolymer had been coated and dried, at a chipboard

Output of 454 g per 2.54 cm width and a speed of 54.9 m per minute on one Pulled the powder dispenser past and wound it into a roll. The coated film was an average thickness of 0.00254 cm, but the thickness fluctuated over the width by ± 0.0002032 cm because Longitudinal strips of various thicknesses were present, which resulted in the manufacture of the coated film had formed.

It became starch powder with an average particle size of 15 microns and at which all Particles substantially in the range between 10 and 20 microns were uniformly distributed from a manifold applied to one side of the film at such a rate that the square meter The amount applied to the film surface was 0.008 g. The starch particles were average specific weight of 1.0, determined according to bulk weight methods.

The resulting roll of film had a smooth cylindrical appearance and was free from hard peripheral bands. The roll was stored for three months. It was found that the roll after storage her Maintained a smooth cylindrical appearance. The film was found to be unwound from the roll lay flat in the transverse section and in printing and on bag making machines could be handled without difficulty.

For comparison, the procedure described above was repeated with the difference that none Strength was brought to the film. The obtained roll of film had a number of hard circumferential tapes, which became more prominent after storage and caused the surface of the roll to be deformed became. After the film was unwound from the roll, it was found that the film was deformed in the transverse direction and could not be easily held flat on processing machines, resulting in formation led by gimmicks. It was found that the density of the roll obtained by weighing and measuring was obtained was greater than the density of the roll of film which was treated with the starch particles.

Example 2

It became a regenerated cellulose film with an average thickness of 0.002032 cm, but its Thickness due to longitudinal strips of different thicknesses across its width by ± 0.0002032 cm fluctuated, on one side with an aqueous dispersion of a vinylidene chloride-methyl methacrylate copolymer coated. The wet surface was cleaned at a speed of 30.48 m / min. pulled past a powder dispenser and starch ester powder with an average particle size of 15 microns, with the size of the particles in the range between 10 and 20 microns lay.

Density determinations from the bulk weight showed that the specific weight of the starch tars 1.20 was.

The starch ester powder was evenly spread over the wet surface at such a rate

ίο of the film distributed so that the amount of powder applied to the square meter of film surface was 0.010 g / m ² .

Then the coating was dried on the film by the application of radiant heat and the Film wound into a roll. The coating was 1.5 microns thick.

The roll of film had a smooth cylindrical appearance and was free of hard circumferential bands even after a storage period of 2 months.

It was found that when the film was unwound from the roll, it lay flat in the transverse direction and could be processed by the converting machines without difficulty.
The procedure was repeated with the difference that the powder application was omitted. It was found that the roll of film had hard, cylindrical ribbons which became more prominent after storage, and film unwound from the roll was deformed in the transverse direction and did not easily lay flat.

Claims (2)

Patent claims: 1. A method for treating a film with different thicknesses across its width, which can be wound into a smooth roll, wherein a substance consisting of solid particles is uniformly applied to at least one side of the film before winding, characterized in that the substance in a total of 0.001 x S to 0.025 x 5 g / m * of film, where S is the specific gravity of the fabric and the average particle size of the fabric is between 5 and 45 microns. 2. The method according to claim 1, characterized in that the hair dryer is coated with a coating mixture in a volatile liquid and the fabric is applied to the coated film before the coating is dried is. Considered publications:
British Patent No. 686 492. 709 518/488 2.67 © Bundesdruckerei Berlin