HU202901B - Self adhesive foil structure and process for producing same - Google Patents

Abstract

A self bonding foil assembly consists of a base foil coated on one side by a uniform layer of an aq. dispersion adhesive, the adhesive coating is covered by a backing foil. Although the adhesive layer is constituted of identical formulating agents the bond strength decreases from the base towards the cover, due to a gradual increase of the moisture content in that direction. The aq. adhesive is applied to the base foil and after a required degree of drying the cover is applied. Following this, the assembly is aminotropically heated to develop the moisture gradient.

Description

BACKGROUND OF THE INVENTION The present invention relates to a self-adhesive film structure having a base film, an adhesive layer comprising an aqueous base dispersion adhesive applied uniformly to one surface of the base film and adhering thereto, and knitting.

The present invention also relates to a process for making a self-adhesive film structure by applying an adhesive layer to one surface of the base film, drying the adhesive layer to a certain extent and covering the outer surface thereof.

Self-adhesive foil structures, self-adhesive foils, labels, adhesive tapes, wallpapers and other decorative and inscription elements are commonly used in industry, commerce, household and many other applications. In all cases, the self-adhesive film structures consist of a substrate, also known as a base film, an adhesive layer applied thereto, and a covering film covering its free surface. In use, the topsheet is removed and the backing film is secured to the desired surface using an adhesive layer. In the case of self-adhesive films (such as adhesive tapes), the top foil is formed by the non-adhesive side, also known as the color side, of the base film due to winding.

Various methods of making self-adhesive film structures are comprehensively described in the prior art part of DE 17 19 335 B1. As described herein, the known procedures can be divided into two main groups. In the first group of processes, the adhesive is diluted in a suitable solvent, the solvent or the diluted adhesive is applied to the surface of the substrate by calendering, stripping, or other means, and the solvent is evaporated.

In contrast, in the case of the second group of processes, the adhesive is melted by heating, and then the liquid adhesive is applied to the surface of the substrate by the methods used in the first group.

These known methods have several disadvantages. For example, the methods of the first group cannot be used in places where the carrier material is dissolved by the solvent of the adhesive. Evaporation of the solvent is usually a slow process, and economy also requires the solvent to be recovered again, which requires expensive equipment. The removal of various synthetic solvents requires the use of significant extraction and protection equipment in view of the flammable, toxic and environmental nature of the agents. Apart from additional equipment, the removal of such solvents is time consuming and slows down the process and reduces productivity.

The second group of processes has the disadvantage that heating can lead to the structural degradation of the adhesive itself and, in some cases, the support material. Providing proper temperature conditions and producing suitable adhesives are both costly.

In DE 17 19 335 B1, the carrier is passed through a fluid bed of powdered powdered adhesive, cooled with liquid nitrogen, while being heated to the other side, to ensure proper properties. The powder adheres to the contacting surface of the substrate and the substrate thus coated is passed through a tunnel furnace where the powder adhesive flows and the coating is formed.

This solution is economical only for the production of self-adhesive tapes for very specific purposes, and the creation of specific temperature conditions (eg use of liquid nitrogen) increases the production costs.

DE 3544790 C2 discloses a solvent-dispersed multicomponent suspension having particles of various diameters, ranging in size from a few microns to a few hundred microns. The adhesive consists of copolymers suitable for internal crosslinking. The particles have a regular spherical shape. The foil can be repeatedly applied and detached, and the spherical particles adhere like the suction cups of an octopus. This solution does not require the use of a solvent, but the adhesive layer can only be applied to the substrate using an intermediate primer.

The effect of molecular size on adhesion properties has long been recognized. See HU 166,901. For example, in the patent, several layers of adhesive are applied to the surface of the substrate, the molecular weight of the macromolecules differing from layer to layer, and the molecular weight increases from the substrate to the outside.

The multi-layer construction of the adhesive coating significantly increases the manufacturing cost, since the coating step has to be performed separately for each layer.

A multilayer structure is described in DE 22 36 575. also patent (which is a supplementary patent to patent No. 22 14 293 C2). This publication relates to a water-soluble self-adhesive adhesive in which a polyvinyl ether dispersion is used wholly or partially in place of the crosslinking and non-crosslinking acrylic acid ester copolymers.

Prior to applying the adhesive layer, a substrate layer of vinyl alcohol or ethoxyvinyl alcohol is applied to the substrate so that the aqueous solvent in the adhesive does not weaken the substrate.

An example of a multilayer adhesive coating can also be found in DE 32 35 203 A1. The adhesive tape is applied in several layers, with the top layer being the thinnest, which provides the adhesive, adhesive and cohesive properties of the tape, and the primer layer or layers are made of a relatively inexpensive material to complement the adhesive thickness, i.e. smoothing the final coating.

A solution for the second group referred to is described in DE 32 20 865 A1, which

-2EN 202901 Β refers to solvent-free or at least solvent-free self-adhesive adhesive. This material consists of a liquid resin mixture at 100 ° C, which cures at temperature. The resin is still fluid at room temperature, so its use eliminates the need for solvent. The crosslinking is carried out in a separate operation after application to the carrier foil.

This process also includes the solution described in DE 24 55 133 B2, where the special melt formed adhesive, which is a very complex composition, is cured with high doses of X-rays after being applied to the substrate.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for self-adhesive film structures which is simple to manufacture, does not require expensive extraction and protection devices or special expensive adhesives, and wherein the adhesive layer can be formed in a single coating step.

It is also an object of the present invention to provide a self-adhesive film structure having an adhesive layer produced by the process.

In order to solve this problem, we have started from a known solution containing an aqueous based dispersion adhesive. In this solution, water is removed from the adhesive layer applied to the substrate substrate by drying (e.g., by blowing hot air or in a tunnel furnace). The drying effect is, of course, exterior to inward, resulting in a thin film on the outer free surface of the adhesive layer, which prevents water from leaving the lower layers. However, aqueous-based dispersion adhesives exhibit the highest adhesion when their moisture content is minimal. Therefore, the adhesion of the substrate to the substrate is lower than that of the dried adhesive, and therefore a topcoat of a specific material (eg made of silicone paper or plastic that does not adhere to the adhesive) is used, which increases costs and reduces application possibilities. It is a fundamental discovery of the invention that the aqueous dispersion adhesive be applied to the base film so that its moisture content increases along the cross-section from the base film to the topsheet. In this case, the adhesion between the base film and the adhesive layer will be high, whereas on the outer, wetter surface, its value will be much lower and may even be covered by a cover film of the same material as the base film.

BACKGROUND OF THE INVENTION The present invention relates to a self-adhesive film structure having a base film, an adhesive layer comprising an aqueous base dispersion adhesive applied uniformly to one surface of the base film and adhering thereto, and a lower degree of bonding, characterized in that it has a single layer of adhesive of homogeneous material and has an increasing moisture content perpendicular to the surface from the base film to the topsheet.

In a preferred embodiment, the cover film is a plastic film with a reduced pattern, preferably a polyethylene film, to reduce peeling.

A preferred embodiment of the self-adhesive film structure according to the invention is formed in a rolled form and the top foil is formed by the surface of the base film opposed to the adhesive layer which is connected to the higher moisture content surface of the adhesive layer during winding. For example, such rolls can be made into an adhesive tape, an insulating tape.

The present invention also provides a process for making a self-adhesive film structure by applying an adhesive layer of an aqueous-based dispersion adhesive to one surface of a base film, drying the adhesive layer appropriately and covering the outer surface of the adhesive with moisture. increases from the base film to the topsheet.

In a preferred embodiment of the method, the base film is applied to a given web and moved along the web, the adhesive layer is uniformly distributed on the free surface of the base film at a moisture content of 40-60 V%, and then the base film is heated to 80100C. is moved along the cooled support surface and the outer surface of the adhesive layer is covered with the protective film.

Especially in the manufacture of an insulating tape or a roll of adhesive tape, where the color side of the base film is wound outside.

In another embodiment of the process, the adhesive layer is applied to a circumference of a silicone rubber or other roller with a slightly coated adhesive, drying the applied adhesive layer by blowing warm air, and upon drying the outer surface, the roller is supported by roll it over and apply the adhesive layer to the base film. By using the intermediate roller, the disadvantage of external drying is turned into an advantage because the earlier film with a lower moisture content is placed on the base film and the less dried adhesive is exited, which is further prevented by the presence of the top foil.

In one embodiment of this method, the base film is moved along the cooling surface after application of the adhesive layer.

In another embodiment, the adhesive layer is spread over a base film stretched over a given support surface at a uniform thickness of 40-60% moisture, and then dried in a microwave oven. Microwave heating is primarily internal because the outside (free) surface is cooled by air and the environment. This solution is also capable of providing inhomogeneous moisture distribution.

In certain applications, the adhesive layer was pressed to facilitate removal of the topsheet

EN 202 901 Β with a plastic cover film, preferably a polyethylene cover film.

For decorative purposes, such as in the manufacture of self-adhesive film structures for wallpaper, it is preferable to use a patterned base film on its free surface.

The process can also be performed by selecting a base film made of plastic or metal.

The process according to the invention uses a known aqueous dispersion adhesive. These adhesives are usually aqueous dispersions of polyacrylate, with various additives depending on the manufacturer. The process yielded equally favorable results with the adhesive marketed by the Palm Rubber Factory under the trade name "PALMATALP" and the Tisza Chemical Plant under the trade name "CELLÁKON". The aqueous dispersion adhesives used contained 50-55% by weight of the active ingredient and the amount of water phase to be removed was 45-50% by weight.

In a first embodiment of the process of the invention, the adhesive layer is applied to the base film using an intermediate roll. This solution is particularly advantageous in the case of water-sensitive base films, such as water-swellable or more absorbent materials, especially paper-based films. This solution is described in more detail in Examples 1 and 2.

Example 1

In order to form a self-adhesive layer structure on a paper-based base film, the base film of 1000 mm width was moved above a flat surface at a constant speed of 500 m / h. With the table an approx. An intermediate roller 800 mm in diameter wider than the base film came in contact with one tangent. The surface of the cylinder was coated with silicone rubber and its axis was perpendicular to the direction of motion of the base film. The roller was rotated, and its peripheral speed was equal to that of the base film.

On the periphery of the intermediate roll, said aqueous-based dispersion adhesive (Cells) was applied at a distance of 50-80 micrometers from said tangent. The moisture content of the adhesive was between 47 and 48% by weight. The thickness of the applied layer was adjusted with a swing blade. The peripheral surface between the application site and said contact was dried with hot air at 90 ° C. The running power was 18 kW.

Hot air causes water to evaporate from the adhesive on the silicone rubber-coated transfer roller sheath. Due to the formation of a skin layer on the surface, the moisture content of the adhesive layer on the transfer roller increased from the outside to the inside, reaching the highest value with the silicone rubber coating.

With the selected heat output, speed, and roll size, complete drying of the surface occurred just prior to contact with the base film. Upon contact between the base film and the transfer roller, the dry, highly adherent adhesive layer adheres to the surface of the base film and leaves the contacting surface completely detached from the surface of the transfer roller. The complete separation was ensured by the silicone rubber surface and the higher moisture content of the adhesive contacting the surface.

The outer, wetter surface of the adhesive layer on the coated base film, which passes through the table, has cooled down in a short free path, with a slight decrease in moisture.

Subsequently, the free surface of the moving adhesive-coated base film was coated with a polyethylene topsheet and the finished structure was wound.

Example 2

In a variant of the procedure, the procedure of Example 1 was followed, but the so-called pregel foil was used as the topsheet.

The 0.1 mm thick, 1000 mm wide polyethylene film used as the topsheet was moved at 1000 m / h. The film was passed through a half-circumferential surface of a 500 mm diameter, 1050 mm wide 80 ° C heating cylinder and then passed through a 500 mm diameter 85 SH hard rubber rolled cylinder to a 350 mm diameter copper cylinder. The copper cylinder had an embossed pattern on the surface of the cylinder having an average sample depth of 1.5 mm and a density corresponding to an average 50% raster distribution. The copper cylinder was cooled with cooling water and the feed film was heated with the radiant heat of a 6 kW electric radiator. As a result, a topsheet having a printed surface following the saggy pattern was obtained.

The topsheet was applied to the surface of the base film coated with the adhesive as in Example 1. Due to its patterned surface, the top foil was easier to remove from the base foil.

The specimens made in Examples 1 and 2 were subjected to comparative quality tests and found that the quality characteristics of the self-adhesive film structure were the same as those of the commercially available self-adhesive sandwich structures made by known methods. The difference was due to the significantly lower manufacturing costs resulting from the present invention.

The procedure was not affected if a pre-pattern was also applied on the side of the base film opposite to the adhesive layer.

Thus, the adhesive layer was located between the base film and the top film, the manufacturing process ensuring that the moisture content at the contact surface of the base film and the adhesive layer was minimal (resulting in good adhesion to the base layer) and increased outward, . This maximum is also not considered high (3-101%), which on the one hand facilitates peeling off and on the other hand is low enough to reduce its value to the degree of self-adhesion during the transition between removal of the topsheet and application.

Similar results were obtained when using PALMATALP commercially available adhesive.

HU 202 901 Β

Another embodiment of the process of the invention is illustrated in Example 3.

Example 3

In the case of a base film made of water-resistant plastic, in this case 0.15 mm thick polyethylene, 1000 mm wide, the base film was moved on a horizontal table at a uniform speed of 500 m / h. The base film was coated with a 60 micrometer layer of adhesive used in Example 1 using a swing blade.

The path of the base film was guided through a microwave oven and a microwave space of 18 kW was created in the oven. The tunnel was 1.5 m long. Under the base leaving the furnace, the table was cooled, then, as in Example 1, the free surface was covered with a top foil and the finished structure was wound.

Because the microwave energy acts uniformly in space, a layer that prevents the release of internal moisture (vapor) on the surface is not formed during drying. The temperature conditions were such that the highest temperature zone was formed inside, near the base film and the adhesive layer, as the cooling effect of the external factors was the smallest here. Thus, along the cross-section of the adhesive layer, the moisture content increased from the surface of the base film to the surface, with the advantages mentioned in Example 1.

1-3. For each of the methods of Examples 1 to 4, the advantage is obtained when starting from a base foil, the color side of which has previously been printed by a pattern to suit the application. In this case, the cost price of the final product will be lower than if printing was done on the finished film structure according to the usual technology. This can be explained by the fact that the waste that is inevitably produced during printing occurs in a product that has not yet been processed, so it is much cheaper. Prior to forming a self-adhesive structure, the process of the present invention enables the backing of the backing film to be soaked in adhesive aqueous solvent for a very short period of time (if not at all).

In a fourth embodiment of the process of the invention, the procedure described in Example 4 was followed.

Example 4

In the manufacture of soft polyvinyl chloride foil insulating tape we started with a base foil having a width of 1000 mm and a thickness of 0.15 mm. The base film was guided through a heated track having a curved lead-in section at a uniform speed of 380 m / h. The surface temperature of the web was maintained at 95-100 ° C, the color side of the base film gliding along this web. In the initial curved portion of the web, the adhesive used in Example 1 was applied in a thickness of 0.02-0.03 mm on the free upper surface (i.e., opposite to the color side) of the base film. The moisture content of the adhesive layer was 501%. As the velocity passes through the heated track, moisture is removed from the adhesive layer. After heat transfer from the bottom film through the bottom, the moisture gradient is from the bottom to the top, with the lowest moisture on the top surface of the base film and the highest on the free outer surface. By the end of the heated period, the moisture content had completely disappeared, and at the surface zone it had varied between 3 and 8%.

After the heated section, the coated base film was passed along a table with a water-cooled surface, leaving the room temperature down to room temperature. The cooled base film was then wound, and the direction of winding was such that the outer side of the roll was always the color side of the base film. Because of the winding, the color side of the base film acts as a cover film for the adhesive layer of the underlying thread.

We cut insulating tape rolls of the width of the lm width by cutting perpendicularly to the axis to meet the application requirements.

The insulating tape rolls have been subjected to the tests prescribed by the relevant standard. According to the tests, the sealing tape met the very strict standards.

In fact, both surfaces of the adhesive layer are bonded to the same polyvinyl chloride film, due to the fact that the adhesive layer has a moisture gradient and a perfect adhesion to the surface opposite to the color side, while the adhesion to the other surface is significantly reduced.

From the examples presented, it can be seen that the application and method of application of the self-adhesive sandwich structures made by the process of the present invention are substantially the same as those of conventional sandwich structures made with known solvent adhesives.

Claims (12)

PATENT CLAIMS A self-adhesive film structure having a base film, an aqueous layer dispersion adhesive layer of uniform thickness applied to one surface of the base film and adhering thereto, and an adhesive layer covering a surface opposed to the base film, said adhesive layer and characterized in that it has a single layer of adhesive of homogeneous material and has an increasing moisture content in the direction perpendicular to the surface from the base film to the topsheet. (Priority: October 22, 1987) Self-adhesive film structure according to Claim 1, characterized in that the top foil is a plastic film with a printed pattern, preferably a polyethylene film. (Priority: October 22, 1987) A self-adhesive film structure according to claim 1, characterized in that it is in rolled form. EN 202 901 Β ve, and the topsheet is formed by a surface opposed to the adhesive layer of the base film, which engages with the higher moisture content of the adhesive layer during winding. (Priority: 10.5.1989) 4. A method of producing a multilayer self-adhesive film structure comprising applying an adhesive layer of an aqueous-based dispersion adhesive to one surface of a base film, drying the adhesive layer to a certain extent, and covering the outer surface with a increases from the base film to the topsheet. (Priority: October 22, 1987) A method according to claim 4, characterized in that the base film is applied to a given web and moved along the web, the adhesive layer is distributed at a uniform thickness on the free surface of the base film at a moisture content of 40-60 V%, and then the base film is 80-100 ° C. moving along the surface of the heated jacketed body at a length and at a speed appropriate for drying, the base film thus coated is then guided along a chilled support surface and the outer surface of the adhesive layer is covered with a protective film. (Priority: 10.5.1989) 6. The method of claim 5, wherein after cooling, the base film is wound onto a roll, wherein the color side of the base film is outwardly wound. (Priority: 10.5.1989) 7. A method according to claim 4, wherein the adhesive layer is applied to a circumference of a silicone rubber or other roller coated with a layer of adhesive that is slightly adhesive to the adhesive, the applied adhesive layer is dried by blowing warm air, and after drying the outer surface. and roll it along the backing of the backing film on the other side to apply the adhesive layer to the backing film. (Priority: October 22, 1987) 8. The method of claim 7, wherein the base film is moved along the cooling surface after application of the adhesive layer. (Priority: October 22, 1987) 9. The method of claim 4, wherein the adhesive layer is spread over a base film stretched over a given support surface at a uniform thickness of 40-60 V% moisture, and the structure is dried in a microwave oven. (Priority: October 22, 1987) 10. Figures 4, 5 and 7-9. A method according to any one of claims 1 to 4, characterized in that the adhesive layer is covered with a plastic cover film, preferably a polyethylene cover film, having a reduced pattern. (Priority: October 22, 1987) 11. A method according to any one of claims 1 to 4, characterized in that a patterned base film is used on its free surface. (Priority: October 22, 1987) 12. A 4-11. A process according to any one of claims 1 to 3, characterized in that a base film made of plastic or metal is used. (Priority: 1987.