HK1105990B - Polyvinylidene chloride coating, process for producing a coating and use thereof - Google Patents

Description

Polyvinylidene chloride-based coating, method for producing a coating and use thereof

Technical Field

The invention relates to a polyvinylidene chloride-based sheet materialCoating of materials, method for the production of coatings and use thereof.

Background

Multilayer composites, hereinafter referred to as "composites" or "composite films", are used, inter alia, for packaging food and pharmaceutical products. Often, the top film or layer of such composites is coated with a vinylidene chloride polymer or copolymer dispersion. For example, for the packaging of pharmaceutical products, PVC films or PVC-PE composite films are coated with a vinylidene chloride copolymer dispersion and then processed in a thermoforming process into blisters, which are then filled with packaging goods and closed by sealing with an aluminum foil or polymer film cover film. Vinylidene chloride monomers are typically polymerized with methacrylates, acrylates, vinyl chloride or acrylonitrile to form copolymers. The purpose of the vinylidene chloride copolymer coating is to form a sealable coating and/or to form a barrier to water vapor, oxygen and aroma.

Vinylidene chloride copolymer dispersions form plastic films which are characterized, in the freshly prepared state, in particular when they contain no waxes or other lubricant additives, on the one hand by a tendency to block, i.e. to adhere to smooth surfaces, such as the nearest winding of a film roll, and on the other hand by very high coefficients of static and sliding friction with respect to metals, plastics and natural substances. The friction coefficient may decrease after the surface of the PVDC coating has become harder due to more or less rapid initial and gradual crystallization. However, the tendency to stick to machine parts, or insufficient sliding properties when filled with packaging articles, in particular with gelatin capsules, remains unchanged. Undesirable adhesion of the PVDC layer to hot machine parts, such as in the heating zone of a thermoformer, has also been observed.

The blocking tendency results in the formation of a rubbing image (Abklatschbilder) on the soft PVDC surface after winding up of the composite film due to contact with the nearest film winding. If the PVDC surface is very smooth, as is the case with the wire-cylinder or triple-helix (hascuren) roll coating systems currently commonly used for PVDC dispersion coating, it is the case that the formation of a larger area with a glossy surface is caused by the air being wound in, if no countermeasures are taken, because contact with the adjacent winding is prevented by entrained air bubbles. Adjacent to these areas are areas with a matt surface which is in contact with the nearest adjacent winding and in which a rubbing image results. The rubbing image itself does not lead to technical defects in the PVDC coating, but such composites are often not acceptable for aesthetic reasons. However, PVDC coated films may also in many cases produce undesirable film deformation due to air bubbles being wound in, which may lead to secondary defects.

Generally, this air entrainment effect is reduced by applying a specific surface structure which allows air to escape from the side. Likewise, the rubbing images, since they substantially always appear on the peaks of the surface structure, are uniformly distributed over the entire surface of the film, and in this way the film obtains a more uniform appearance.

The specific generation of such surface structures dictates the use of additional equipment in the coating machine. The quality of the structure, i.e. the roughness depth, the appearance, the average layer thickness of the top layer of the composite, has to be controlled by the machine settings and in general the generation of the surface structure is accomplished with a loss of film layer thickness and therefore possibly with a loss of throughput, compared to a smooth film surface. The application of the surface structure on the PVDC-coated film is disadvantageous due to the unevenness of the surface or even impossible if the coated composite is subjected to an additional lamination or coating process on the PVDC side.

The newly coated and wound up composite film roll relaxes after a period of hours or days by: they collapse to some extent in those sections that are wound less tightly, or where the film is less thick, and are tensioned where there is a greater film thickness. One consequence of the blocking tendency of freshly coated PVDC is that, due to the insufficient sliding capacity between the film windings and the simultaneous relaxation, tensions occur along the film surface which, if the blocking tendency is too high, may even lead to material damage due to the unraveling of the composite film into individual films or layers.

DE 10064800A 1 describes micronized polyethylene waxes which are prepared by copolymerization of ethylene under high pressure conditions using aliphatic or cycloaliphatic ketones as molecular weight regulators and subsequent micronization. Micronization means that the material is crushed to a particle size of 1 μm to a maximum of 100 μm. The material is brought into the desired form by grinding or spraying. There are a number of known applications for micronized polyethylene waxes, for example as carriers for printing inks, coatings, abrasives for toothpastes and additives for cosmetic preparations, such as eye shadow, lipstick or rouge.

DE 4316025 a1 relates to micronized polyethylene waxes having an average particle size of 1 to 30 μm, which are suitable as release agents for the deadhesion of the surface of sticky pellets. Micronized polyethylene wax has shown its effect even at small amounts of 0.01 to 2% by weight, based on the pellets. Micronized polyethylene wax is prepared by spraying the relevant polyethylene wax melt with gas in a two-stage nozzle.

EP 0403542B 1 discloses a polymer composition comprising a vinylidene chloride copolymer formed from a monomer mixture. The monomer mixture comprises from 60 to 99% by weight of vinylidene chloride and from 40 to 1% by weight of at least one ethylenically unsaturated comonomer copolymerizable therewith. The vinylidene chloride copolymer is mixed with a formulation package comprising 0.1-95 wt.%, relative to the total weight of the formulation package, of an alkali metal salt or alkaline earth metal salt of a weak acid, an ethylene homopolymer, and at least one plasticizer and one lubricant. The vinylidene chloride copolymer can be made into articles by casting, blow molding, extrusion molding, coextrusion, lamination, or calendering the polymer composition.

EP 0736067B 1 describes a process for stabilizing a polyolefin blend comprising PVDC and describes a stabilized polyolefin blend comprising PVDC. The plastic mixture comprises a polyolefin and 0.05 to 20 wt% of PVDC and at least one organic phosphite or phosphonite and at least one metal salt of a fatty acid.

DE 19832500 a1 relates to a thermoformable composite film comprising a film comprising at least one cycloolefin copolymer and a film of a thermoplastic material laminated to at least one side thereof. The thermoformable film is joined to the cyclic olefin copolymer-containing film by means of a solvent-free one-component adhesive. The thermoplastic film comprises PVDC. The thickness of the whole film is 100-500 μm, the thickness of the PVC film is 5-150 μm, and the thickness of the COC film is 50-400 μm. The thermoformable composite film is used to prepare blister packages. The thermoplastic film may also be selected from the group consisting of polyolefins, polyamides, polyesters, polycarbonates, polystyrenes, polyvinyl chlorides, and polyurethanes.

Disclosure of Invention

The object of the invention is to provide a coating for composite bodies, in particular for composite films, which has a low coefficient of static friction and sliding friction for improving the sliding properties of the composite film and which facilitates the handling of the composite film to be coated in a machine and the further processing in a corresponding machine.

The object of the invention is achieved by a coating for sheet-like materials based on polyvinylidene chloride in the following manner: particles made of polymers, natural substances, modified natural substances, inorganic materials or mixtures thereof are contained in polyvinylidene chloride.

In this case the density of the particles is from 0.1 to 2.0g/cm³And has an average particle diameter of 1 μm to 100. mu.m.

Suitably, the maximum particle size is equal to/greater than the thickness of the PVDC layer.

The invention therefore provides a polyvinylidene chloride-based coating comprising particles made of a polymer, a natural substance, a modified natural substance, an inorganic material or a mixture thereof, characterized in that a large number of the particles protrude from the coating and form spacers and in that the particles have a density of 0.1-2.0g/cm³。

In a preferred embodiment, the particles have an average particle size of 1 μm to 100 μm.

In a preferred embodiment, the density of the particles is less than or equal to 1.30g/cm³Preferably less than or equal to 1g/cm³。

In a preferred embodiment, the maximum particle size of the particles is equal to/greater than the thickness of the coating.

In a preferred embodiment, the particles are selected from the group consisting of HDPE, LDPE, LLDPE, polypropylene, PVC, PVDC, polyamides, polyurethanes, polyacrylates, polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene polymers, polytetrafluoroethylene, hard waxes, mixtures and copolymers thereof.

In a further preferred embodiment, the particles have a surface coating made of one of the polymers selected from the group consisting of: HDPE, LDPE, LLDPE, polypropylene, PVC, PVDC, polyamide, polyurethane, polyacrylate, polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene polymer, polytetrafluoroethylene, hard wax, mixtures and copolymers thereof.

In a further preferred embodiment, the particles have a dry proportion of 0.1 to 10 wt.%, based on the dry weight of the PVDC, preferably the particles have a dry proportion of 0.3 to 8 wt.%, based on the dry weight of the PVDC, more preferably the particles have a dry proportion of 0.2 to 2 wt.%, based on the dry weight of the PVDC.

In a preferred embodiment, the particles are introduced into the PVDC in powder form.

In a preferred embodiment, the coating contains an anionic surfactant.

In a preferred embodiment, the particles consist of HDPE.

The invention also provides a process for the preparation of a polyvinylidene chloride-based coating for sheet-like materials, said coating comprising particles made of a polymer, a natural substance, a modified natural substance, an inorganic material or a mixture thereof, wherein a large number of the particles protrude from the coating and form spacers, and the density of the particles is between 0.1 and 2.0g/cm³Characterized in that a PVDC dispersion is provided, the particles are metered in directly or while stirring, the mixture consisting of the PVDC dispersion and the particle dispersion is applied as a top layer on the sheet-like material and dried, and the particles float or do not float in the coating depending on their density.

In a preferred embodiment, the particle dispersion is prepared by adding the particle powder to water with stirring without the use of an emulsifier or with the use of one or more emulsifiers.

In a preferred embodiment, a pigment dispersant or other dispersing aid is mixed into the particle dispersion.

In a preferred embodiment, a PVDC dispersion comprising 5-80 wt% PVDC and a particle dispersion comprising 10-95 wt% particles are mixed together, preferably a PVDC dispersion comprising 30-70 wt% PVDC and a particle dispersion comprising 40-70 wt% particles are mixed together.

In a preferred embodiment, 80-99 wt% of the PVDC dispersion and 1-20 wt% of the particle dispersion are mixed together.

In a further preferred embodiment the particle dispersion is a PVDC-HDPE dispersion having a dry proportion of HDPE of from 0.50 to 3.0 wt%, based on the mixture of PVDC dispersion and HDPE dispersion.

The invention also provides the use of the coating according to the invention for coating plastic films, paper webs and metal foils.

The invention also provides the use of the coating according to the invention for coating a multilayer composite made of a PVC-PE composite film and a metal foil.

The invention also provides the use of a coating according to the invention for coating a PVDC film of a multilayer composite consisting of: PVDC film, adhesion promoter, carrier film; PVDC film, adhesion promoter, polyethylene film, adhesion promoter and carrier film; PVDC film, adhesion promoter, cyclic olefin copolymer, adhesion promoter, PVC; or PVDC film, adhesion promoter, PE, adhesion promoter, PVC.

The invention also provides the use of a coating according to the invention for coating a PVDC film in a multilayer composite of the following composition: (PVC/PE/PVDC/PVDC + HDPE/PE/PVC) or (PVC/PVDC/PVDC + HDPE/PE).

In a development of the invention, the particles are selected from the group consisting of HDPE, LDPE, LLDPE, polypropylene, PVDC, PVC, polyamide, polyurethane, polyacrylate, polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene polymer (ABS), Polytetrafluoroethylene (PTFE), synthetic resins, hard waxes and mixtures and copolymers thereof.

In one embodiment of the invention, the particles have a surface coating made of one of the polymers selected from the group consisting of: HDPE, LDPE, LLDPE, polypropylene, PVDC, PVC, polyamide, polyurethane, polyacrylate, polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene polymer (ABS), Polytetrafluoroethylene (PTFE), synthetic resins, hard waxes and mixtures and copolymers thereof.

The method for producing such a polyvinylidene chloride-based coating for sheet-like materials is characterized in that a PVDC dispersion is provided, to which the particles are metered directly or while stirring. Suitably, the particle dispersion is prepared by adding the particle powder to water with stirring, without the use of an emulsifier or with the use of one or more emulsifiers. To this particle dispersion, a pigment dispersant or other dispersing aid is preferably mixed. In a further implementation of the method according to the invention, a mixture of PVDC and particle dispersion is applied as a top layer to the sheet-like material and dried.

In particular, a PVDC dispersion comprising 5-80 wt% PVDC and a particle dispersion comprising 10-95 wt% particles are mixed together.

The coating of the invention is used for coating plastic films, paper webs and metal foils. In particular, the coating can be used for coating PVC single films, multilayer composites made of PVC and PE, multilayer composites made of PVC-PE composite films and a layer of metal foil, single films made of cycloolefin copolymers, and composite films made of cycloolefin copolymers with PVC and/or other polymers. It is likewise possible to use composite films of the type listed which are further improved by lamination and/or coating after coating with PVDC. All customary polymer films, for example PET, PP, PE, acrylate, ABS, PS, cellophane, cellulose acetate, polyamide, polyacrylonitrile, PCTFE, etc., and corresponding composites made from two or more of the listed polymer films can be provided with the coating according to the invention. It is particularly preferred that the coating is used for coating the PVDC layer of a multilayer composite made of a PVDC film, an adhesion promoter and a carrier film and of a multilayer composite made of a PVDC film, an adhesion promoter, polyethylene, an adhesion promoter and a carrier film. PVDC film refers to a PVDC film to which a PVDC dispersion has been applied as a primer during previous operations. Other multilayer composites with PVDC coated films are PVC/PE/PVDC + HDPE/PE/PVC; PVC/COC/PVDC/-PVDC + HDPE; PVC/PVDC/PVDC + HDPE/PE. The coating according to the invention can also be applied to metal foils and to composites made of metal foils and polymer films coated in this way. In all these applications, it is also possible to use the coating according to the invention without pre-coating the primer with unmodified PVDC. Such films are used, for example, in the manufacture of blister packs.

By embedding polymer particles, preferably HDPE micropowder, into the top polyvinylidene chloride copolymer layer of the composite films, the above difficulties are eliminated or greatly reduced and the process of making these composite films is simplified and more efficient. These polymer particles act as spacers between the windings of the film and improve the sliding properties of the PVDC surface of the film sheet.

Polymers considered suitable for such particles in the liquid and powder form are those which are highly compatible with the particular PVDC dispersion, are non-abrasive, and in particular are not significantly harder than the bottom side of the support film or underlying film to which the PVDC coating or PVDC coating is applied. If the particles are harder than the remaining film surface of the composite, the surface of the particles should be as smooth as possible and, ideally, spherical. Ideally, the particles have as low a static and sliding friction coefficient as possible. The particles should not be film-forming at the drying temperatures conventionally used for PVDC drying up to 100 ℃, should not "fuse" with the PVDC during drying, i.e. should not form a uniform PVDC/particle polymer film. Instead, the polymer particles protrude from the PVDC layer, and thus, satisfy their function as spacers. In addition, the particle material should have a refractive index similar to PVDC, so that as low haze as possible occurs in the PVDC particle layer. The density of the particle material is 0.1-2.0g/cm³In particular less than or equal to 1.30g/cm³And preferably less than 1g/cm³So that flotation in the particle dispersion and thus protrusion from the PVDC surface is facilitated. Suitably, the largest particle size is equal to/greater than the thickness of the coating. The average particle size of the particles must also be coordinated with the application system so that irregularities in particle content due to oversize particles or non-uniform application are unlikely to occur. In order not to have an adverse effect on the barrier effect of the PVDC coating, the particles must not be porous. The barrier action must be as high as possible in the field of application of the composite film or composite.

In principle, all polymers which fully or partially satisfy the above conditions, for example: HDPE, LDPE, LLDPE, PP, PVDC, PVC, polyamide, polyurethane, polyacrylate, polystyrene, polyacrylonitrile, ABS, PTFE, hard waxes, synthetic resins, etc., and mixtures and copolymers thereof. Particles having a suitable surface coating may also be used. The core material of such coated particles is, for example, selected from the polymers listed above, as well as natural substances, such as cellulose, natural waxes, poly (hydroxyalkanoic acids), shellac, modified natural substances, such as casein derivatives and casein condensates, cellulose derivatives, such as cellulose acetate and cellulose nitrate, or inorganic substances, such as silica, silicates, alumina, titanium dioxide. As coating materials, the abovementioned polymers or other correspondingly suitable surface coatings, for example silanes, siloxanes, Ormocere (organically modified ceramics), ceramic materials, can be used.

Particles having purely inorganic properties, such as silica, silicates, alumina, titania, and having the properties listed above, may also be used.

If the particles are of polymeric origin, they may be prepared by addition polymerisation, polycondensation, polyaddition, polymer analogous reaction or mixtures of preformed polymers. Particle formation and dispersion is typically carried out directly during polymerization, e.g., suspension polymerization or emulsion polymerization, or by subsequent mechanical dispersion and/or suspension and stabilization in a carrier liquid. The inorganic particles can be prepared, for example, by grinding of natural substances or synthetically. A surface coating may be applied to such particles.

When particles are used, the percentage proportion of particles based on the dry weight of the PVDC is generally between 0.1% and 10% by weight. For particles in the form of HDPE micropowder, for example, a dry proportion of about 0.2 to 2 wt% micropowder, based on the dry weight of PVDC, has proven particularly effective.

To prepare such particle-containing PVDC coatings, a PVDC dispersion is mixed with a corresponding amount of particle suspension or dispersion, while stirring, before application to the sheet-like material, until said suspension or dispersion is homogeneously mixed with the PVDC dispersion. For this purpose, commercially available non-shearing stirrers, for example paddle stirrers, are used. Subsequently, the mixture is applied to the material to be coated using application tools customary for PVDC coatings and dried. If the particle size is chosen correctly and compatibility with the PVDC dispersion is given, it can be confirmed that there is no difference in coating and/or drying behavior from the unmodified PVDC dispersion. The finished coating material has the following main process and product advantages:

the static and sliding friction of the surface of the coating material is, especially in the freshly coated condition, significantly less than that of an unmodified PVDC coating.

The blocking tendency of the freshly coated material, although the PVDC surface is not structured, is significantly reduced. In this context, "unstructured" refers to a surface from which particles protrude, but which is not shaped or forms valleys or peaks.

The blocking marks caused by embossing on the back side of the most adjacent film roll on the film roll are greatly reduced or completely absent.

The spacer action of the particles ensures that air is expelled from the film or material roll despite the absence of surface structuring. Entrapped air can cause the film or material to deform and cause irregular surface opacity of the film due to the tendency of new PVDCs to block.

The shear forces acting parallel to the material surface, generated by the relaxation motion of the newly coated web material, can be better relaxed by the sliding of the PVDC surface on the nearest winding of film, due to the reduced static friction of the PVDC surface. This avoids material damage due to delamination between the PVDC layer and the substrate carrier resulting from shear forces for a PVDC surface that slides less well.

The reduction in the friction resistance of the PVDC-coated flat film on the machine parts of the thermoforming machine used to prepare blisters from the flat film. This reduces or completely eliminates film shrinkage caused by too high a sheet tension.

The filling of the packaged articles in the form of tablets or capsules is significantly improved, since the packaged articles can be better slid into the blister cavities by means of a significantly reduced coefficient of static and sliding friction. In particular, when unmodified PVDC is used, gelatin capsules tend not to slip into the cavity, queue into the cavity or even jump out of the cavity. In the sealing section immediately downstream of the filling section, this leads to contamination of the crushed packaged articles and, as a result, to a longer cleaning operation.

In addition, it is advantageous if further equipment and special processes for surface structuring on the machine side are not required. The surface properties are only dependent on the formulation and can therefore be safely adapted and easily repeated.

By means of coating, a smooth, flat surface is produced, which is more aesthetically appealing than a structured surface.

A flat surface allows setting a larger layer volume for the top PVDC layer than a structured surface, since in the structured layer the maximum dryable layer thickness is predetermined by the highest point of the structure, i.e. the tip of the wave peak, whereas in a flat surface the dryable layer thickness is as large as the maximum dryable layer thickness of the structurable layer, but in contrast does not have a wave trough, but rather has a consistently constant layer thickness.

It is also advantageous that the surface modified in this way proves to slide very easily along the back side of the coated film and along the cavity of the mould. This results in, on the one hand, the possibility of dispensing with significantly less resistance/power consumption the final formed, not yet filled blister film (entrapeling) with cavities stacked alternately, for example in the form of properly cut blister format sections, -or, on the other hand, the possibility of removing the newly formed blister cup from the deep-drawing tool, provided that a modified PVDC side is used on the outside of the blister cup. In the first case, this leads to faster dispensing and thus to an increase in throughput; in the second case, this leads to an uninterrupted operation of the bubble cap machine and thus to an increase in the output.

Drawings

The invention is explained in more detail with the aid of the following figures.

FIG. 1 shows in a diagrammatic cross-sectional view a conventional PVDC coating of a composite film made of a PVDC film/carrier film with a structured PVDC surface, and

figure 2 shows in a diagrammatic cross-section a coating according to the invention consisting of PVDC blended with particles on a composite film made of PVDC film/carrier film.

The composite film 6, shown in cross-section in fig. 1, comprises a carrier or base film 4, an adhesion promoter 3, and a PVDC film 2. The adhesion promoter 3 prepares a composite of the PVDC film 2 and the carrier film 4. On top of the PVDC film 2, a PVDC coating 7 is applied, which has a structured surface 5, such that the layer thickness of the PVDC coating is non-uniform over the width of the composite film 6 and comprises peaks and valleys.

The composite film 1 shown in cross-section in fig. 2 consists of a carrier or base film 11, an adhesion promoter 10, a PVDC film 9, and a coating 8 made of PVDC, which coating 8 has particles 12 made of HDPE embedded therein. The particles 12 have different particle sizes, the average particle size is 6-8 μm and is suitable for HDPE dispersions, which results in coatings with a thickness of up to 6 μm. The largest particles have a diameter of about 12 μm.

For a layer thickness of 12 μm, the average particle size is 12-13 μm. The largest particles are about 17 μm large. A large number of particles 12 protrude from the flat surface 13 of the coating 8 and act as spacers between immediately adjacent windings of the wound composite film 1.

Detailed description of the preferred embodiments

Mixture of PVDC dispersions with HDPE dispersions

The following examples serve to explain the invention in more detail, without implying any limitation to the scope of the invention as claimed in the claims of the present invention. In each case 1000 liters of a coating consisting of a PVDC dispersion was mixed with a commercially available or freshly prepared HDPE dispersion. The PVDC dispersion had a PVDC proportion of 55% by weight, relative to the total mass of the PVDC dispersion, and had a density of 1.29g/cm³. The proportion of HDPE in the HDPE dispersion is 65% by weight, relative to the total mass of the HDPE dispersion, and has a density of 0.96g/cm³。

The required amount of PVDC dispersion was charged into a 1000 liter capacity vessel and uniformly stirred. The calculated amount of HDPE dispersion was added in a thin stream while the PVDC dispersion was stirred in a non-foaming manner and the mixture was stirred for an additional 5-10 minutes. The HDPE dispersion used may be a ready commercial dispersion or a freshly prepared dispersion of HDPE powder by adding the particle powder to water with or without the aid of one or more emulsifiers, pigment dispersants or other dispersing aids, with corresponding stirring, and anionic surfactants. HDPE powder can also be added directly to the PVDC dispersion, whereby special care must be taken not to have lump formation which may lead to an inhomogeneous coating thickness.

Example 1

The proportion of HDPE dispersion is 1% by volume, based on the total volume of the coating (in liters). The relative weight ratio χ of PVDC and HDPE in the dried film was calculated as follows:

χ_PVDCPVDC ratio in wt.% of dry coating

χ_PEHDPE proportion of dry coating in wt%

V_PVDCVolume of PVDC dispersion used

V_PEVolume of HDPE Dispersion used

ρ_PVDCDensity of PVDC dispersion

ρ_PEDensity of HDPE Dispersion

FK_PVDCProportion of solids in PVDC dispersion in wt.%

FK_PEProportion of solids in HDPE Dispersion in wt%

Components	Number of dispersions (l)	Drying ratio, chi, wt%
			PVDC dispersions	990	99.12
HDPE dispersions	10	0.88

Example 2

The proportion of HDPE dispersion was 2% by volume, based on the total volume of the coating (in liters)

Components	Number of dispersions (l)	Drying ratio, chi, wt%
			PVDC dispersions	980	PVDC 98.24
HDPE dispersions	20	HDPE 1.76

The following are the measured coefficients of static and sliding friction of a conventional composite film with a pure PVDC coating, as shown by means of fig. 1, and those of the films according to examples 1 and 2 listed opposite one another. The friction force was measured using test pieces made of aluminum coated with hard gelatin.

The measurement conditions were as follows:

test piece speed:	5mm/min
		test piece quality:	200g
materials:	aluminum, anodized
		Coating on the test piece:	hard gelatin
Air humidity:	50％r.h.
		the method comprises the following steps:	according to ASTM D1894
Aging (Alter) of each of the PVDC coatings of the three films:	10 days

Material	Static friction systemNumber of	Coefficient of sliding friction
			PVDC without particles but with surface structure	1.04	Cannot be measured because a continuous movement does not occur
PVDC with 1 vol% HDPE	0.41	0.21
			PVDC with 2 vol% HDPE	0.29	0.19

It can be seen that the static friction coefficient is strongly indirectly dependent on the proportion of HDPE in the coating according to the invention. As the proportion of HDPE increases, the static coefficient of friction decreases. By the formula ((HRK)_OP-HRK_P)/HRK_OP) X 100% wherein HRK_OPIs the coefficient of static friction, HRK, of a PVDC-coated composite film without particles in the PVDC coating_PIs the static friction coefficient of a PVDC coated composite film containing particles in a PVDC coating, the static friction coefficient is HRK_PA reduction of 61% and 72% at 1% or 2% HDPE volume fraction.

Processing of composite films

During processing, the following advantages are achieved compared to PVDC coatings without particles:

better release from blister deep-drawing dies when externally processing PVDC coated composite films with PVDC coatings.

Less shrinkage of the film sheet due to lower frictional resistance to the machine parts.

Better filling performance of gelatin capsules in blister packs made from composite films (PVDC side towards the filled article).

The tendency of the composite film to adhere strongly to the thermo-mechanical component is less.

Claims (23)

1. Polyvinylidene chloride-based coating comprising particles made of a polymer, a natural substance, a modified natural substance, an inorganic material or a mixture thereof, characterized in that a large number of the particles protrude from the coating and form spacers and in that the density of the particles is between 0.1 and 2.0g/cm³。

2. The coating of claim 1, characterized in that the particles have an average particle size of 1 μm to 100 μm.

3. The coating of claim 1, characterized in that the density of the particles is less than or equal to 1.30g/cm³。

4. The coating according to claim 3, characterized in that the density of the particles is less than or equal to 1g/cm³。

5. The coating of claim 2, wherein the particles have a maximum particle size equal to or greater than the thickness of the coating.

6. The coating of claim 1, characterized in that the particles are selected from the group consisting of HDPE, LDPE, LLDPE, polypropylene, PVC, PVDC, polyamides, polyurethanes, polyacrylates, polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene polymers, polytetrafluoroethylene, hard waxes, mixtures and copolymers thereof.

7. The coating of claim 6, characterized in that the particles have a surface coating made of one of the polymers selected from the group consisting of: HDPE, LDPE, LLDPE, polypropylene, PVC, PVDC, polyamide, polyurethane, polyacrylate, polystyrene, polyacrylonitrile, acrylonitrile-butadiene-styrene polymer, polytetrafluoroethylene, hard wax, mixtures and copolymers thereof.

8. The coating according to claim 7, characterized in that the particles have a dry proportion of 0.1 to 10 wt.%, based on the dry weight of the PVDC.

9. The coating according to claim 8, characterized in that the particles have a dry proportion of 0.3 to 8 wt.%, based on the dry weight of the PVDC.

10. The coating according to claim 8, characterized in that the particles have a dry proportion of 0.2 to 2 wt.%, based on the dry weight of the PVDC.

11. The coating of claim 1, characterized in that the particles are introduced into the PVDC in powder form.

12. The coating of claim 1, characterized in that the coating contains an anionic surfactant.

13. The coating of claim 6, characterized in that the particles consist of HDPE.

14. Method for producing a coating for sheet-like materials based on polyvinylidene chloride, said coating comprising particles made of polymers, natural substances, modified natural substances, inorganic materials or mixtures thereof, wherein a large number of the particles protrude from the coating and form spacers, and the density of the particles is between 0.1 and 2.0g/cm³Characterized in that a PVDC dispersion is provided, the particles are metered in directly or while stirring, the mixture consisting of the PVDC dispersion and the particle dispersion is applied as a top layer on the sheet-like material and dried, and the particles float or do not float in the coating depending on their density.

15. The method according to claim 14, characterized in that the particle dispersion is prepared by adding the particle powder to water with stirring without the use of an emulsifier or with the use of one or more emulsifiers.

16. A method according to claim 14, characterized in that a pigment dispersant or other dispersing aid is mixed into the particle dispersion.

17. A method according to claim 14, characterized in that a PVDC dispersion comprising 5-80 wt% PVDC and a particle dispersion comprising 10-95 wt% particles are mixed together.

18. A method according to claim 17, characterized in that a PVDC dispersion comprising 30-70 wt% PVDC and a particle dispersion comprising 40-70 wt% particles are mixed together.

19. The method according to claim 14, characterized in that 80-99 wt% of the PVDC dispersion and 1-20 wt% of the particle dispersion are mixed together.

20. The method of claim 18, characterized in that the particle dispersion is a PVDC-HDPE dispersion having a dry proportion of HDPE in the range of 0.50 to 3.0 wt.%, based on the mixture of PVDC dispersion and HDPE dispersion.

21. Use of the coating according to any one of claims 1 to 13 for coating plastic films, paper webs and metal foils.

22. Use of the coating according to any one of claims 1 to 13 for coating a multilayer composite made of a PVC-PE composite film and a metal foil.

23. Use of a coating according to any one of claims 1 to 13 for coating a PVDC film of a multilayer composite consisting of: PVDC film, adhesion promoter, carrier film; PVDC film, adhesion promoter, polyethylene film, adhesion promoter and carrier film; PVDC film, adhesion promoter, cyclic olefin copolymer, adhesion promoter, PVC; or PVDC film, adhesion promoter, PE, adhesion promoter, PVC.