BE1019868A3 - PRESSURE SENSITIVE ADHESIVE TAPE. - Google Patents

Description

Pressure sensitive adhesive tape.

This invention relates to a multilayer surface protective tape comprising a sheet of a backing layer containing a plastic polymer, a sheet of a protective layer containing a plastic polymer and coated on a side facing the adhesive with a release layer, a layer of a pressure-sensitive adhesive sandwiched between the support layer and the protective layer, according to the preamble of the first claim.

BACKGROUND OF THE INVENTION.

The use of the backing layer of surface protection tapes of the type described above as a protective layer for delicate surfaces when they are transported, processed, cured, checked, stored and subjected to another process is well known in the art. Typical applications include the protective layer protection of metal plates, coated plates, aluminum windows, plates made of resin, decorated steel plates, glass plates, optical films, optical parts of the surface of electrical parts. The backing layer is often made of crystal-clear plastic. Protect the surface of a highly glossy hard LCD. lenses for electronic and communication equipment, for example television screens, screens of mobile phones and GPS systems include other adaptations, in which the surface to be protected is covered with a transparent protective sheet that can remain on the screen, also during quality control.

Surface protection tapes for use in such applications usually contain a transparent backing sheet attached to a sheet of a protective layer. The side of the backing sheet facing the protective layer is usually coated with a layer of pressure-sensitive adhesive. To facilitate peeling off the backing sheet and adhesive from the protective layer, the surface of the protective layer facing the pressure-sensitive adhesive is usually coated with a layer of a release material, the release layer being disposed between the pressure-sensitive adhesive and the protective layer. A release layer may also be applied to the outer surface of the protective layer, in particular the side of the protective layer opposite that facing the pressure-sensitive adhesive, to ensure and facilitate the peeling of successive layers of surface protection tape during unwinding of the protective layer. band of a roll.

To be suitable for use as part of a surface protection tape for special applications, the backing layer usually has a multitude of properties, including transparency, protective properties, the ability to uniformly adhere to surfaces, peel properties, and so on. Commercially available surface protection tires include those produced by Nitto Denko and known as Lensguard ™. The Lensguard ™ surface protection tape contains a PET film as a transparent backing layer coated with a pressure-sensitive acrylic-based adhesive combined with a white pigmented protective layer. The use of a white pigmented protective layer offers advantages in "peak and place" operations, where a part of a multi-layered sheet is cut into a mold in a shape corresponding to the shape of the lens of the screen to be covered, over a predetermined thickness corresponding to the thickness of the transparent backing layer. The transparent PÉT film is then removed from the protective layer and applied to the surface of the screen to be protected as a protective sheet.

The multilayer surface protection tape, including the backing layer, protective layer, and pressure-sensitive adhesive layer, is usually produced using a laminating process. The result is a multi-layer sheet with a long length, which is stored in the form of rolls of piles of sheets of surface protection tape. The protective layer is usually pigmented. In a roll, the backing layer of a previous layer of sheet of surface protection tape is in contact with the protective layer of a subsequent layer of sheet of surface protection tape and dimensional deviations in the protective layer can be transferred to the backing layer. It has been established that the known protective layer materials can contain relatively high concentrations of particle material, for example pigments and anti-blocking agents. In addition, the particles can occur as single particles, but usually a considerable amount of agglomerated particles with a relatively large particle size is also present. These particles and agglomerates can give rise to peaks that protrude relative to the surface of the pigmented sheet of the protective layer. The peaks of these irregularities often have a magnitude of the order of several microns. When stacking a plurality of such layers of surface protection tape from when producing a roll of the tape, the peaks protruding relative to the protective layer of a previous layer of surface protection tape may cause local deformation of the backing layer of a subsequent layer of surface protective tape that is in direct contact with it and causes the occurrence of so-called impressions of impressions in that support layer. It. occurrence of indentations will increase in importance as the pressure to which the belt is exposed increases, i.e. the occurrence of indentations will increase from the outer to the inner part of the roller. This is shown in fig. 1.

Before being placed on the market, screens and lenses of products such as mobile phones, GPS devices, television screens etc. are subjected to an optical quality check. During this quality check, the screen to be inspected is allowed to light up and the screen covered with a transparent backing layer is subjected to a visual inspection, with the aim of detecting optical defects that would be present in the lens screen. This visual quality check not only detects production errors in the screen, but errors present in the backing layer are also detected. However, the visual quality check is unable to distinguish between defects in the screen and defects in the backing layer. Consequently, there is a serious risk that error-free lenses covered with a backing layer containing indentations will be rejected in the quality control, which is undesirable.

There is therefore a need for a surface protection tape that exhibits a lower risk of the presence of indentations in the backing layer.

BRIEF DESCRIPTION OF THE INVENTION.

It is therefore an object of the present invention to provide a multi-layered surface protection tape which exhibits a lower risk of the occurrence of undesired indentations.

This problem is solved according to the invention by means of a surface protection tape which has the technical features of the feature of the independent claims.

To this end, the surface protection tape of this invention is characterized in that the protective layer comprises a multi-layered sheet, which multi-layered sheet 1 comprises at least a first layer on a side of the protective layer directed towards the pressure-sensitive adhesive, which first layer comprises a plastic polymer, 2. at least a second layer of a plastic polymer, which second layer is on the side of the first layer opposite the side facing the adhesive, in particular the pressure-sensitive adhesive layer of the same tape. This second layer contains less than 2.50 wt. % relative to the weight of the second layer of a particulate material having an average particle size of 7.0 µm or more, preferably 5.0 µm or more, more preferably 2.5 µm or more, most preferably 1.0 µm or more.

Preferably the second layer contains less than 2.50 wt. % relative to the weight of the second layer of particulate material with an average particle size of 6 µm or greater, preferably 5 µm or greater, more preferably 2.5 µm or greater, most preferably 1 µm or greater.

Preferably the second layer contains less than 2.00 wt. %, preferably less than 100 wt. %, more preferably less than 0.50 wt. %, most preferably less than 0.25 wt. % of particulate material with an average particle size of 6 μηι or more, preferably 5 μιη or more, more preferably 2.5 μιτι or more, most preferably 1 μηη or more, relative to the weight of the second layer.

In the context of this invention, the term "particulate material" includes both individual particles and aggregates of multi-particle agglomerates. Particle material may include, for example, pigment particles, anti-blocking agent particles, particles remaining from the catalyst, etc., or mixtures of two or more of these materials.

The inventors have found that an improved dispersion of the particulate material in the second layer of the protective layer can be obtained at these concentrations. In this way, the risk of agglomerating particles in the second layer, to an extent that would give rise to peaks that would protrude relative to the second layer of the protective layer and thus form the surface of the protective layer, can lead to a minimized. In the rolled-up state of the surface protection tape or when stacking a plurality of layers of sheets of surface protection tape, the second layer of the protective layer of a previous sheet of a previous layer of surface protection tape is in contact with the backing layer of a subsequent sheet of layer surface protection band. By minimizing the risk of the formation of peaks protruding relative to the protective layer, the risk of the formation of undesired indentations caused by the protective layer of a previous layer of surface protection band in the support layer of a next layer of surface protection band can also be reduced.

In the surface protection band of this invention, within the same sheet of surface protection band, the second layer of the protective layer is capable of peaks caused by the presence of particulate material in the first layer of the protective layer on a side of the first layer which the second layer of the protective layer contacts, absorbs and averages out. The layer of adhesive material which is located on the other side of the protective layer of the surface protection tape, in particular on the side of the first layer of the protective layer opposite the side facing the second layer, is capable of peaks which to protrude that other side of the first layer of the protective layer. Since the adhesive material will usually be poor in particle material of the dimensions described above, the risk of peaks is negligibly small.

By ensuring that both opposite sides or surfaces of the first layer of the protective layer of the surface protection band are shielded by a layer of a material capable of averaging peaks or distortions occurring in the first layer, and by certainly If the shielding layer or layers exhibit a low risk of peaks, it is possible to reduce the risk of unwanted indentations in the backing layer of a subsequent sheet or layer of surface protection band, due to peaks relative to the second layer from the protective layer of a previous sheet of surface protection band.

In particular, this invention makes it possible to minimize the occurrence of peaks protruding over at least 1 µm relative to the surface of the protective layer. The inventors have determined that these peaks contribute to and play an important role in the formation of indentations in the backing layer. These indentations would be established in a visual inspection and would result in rejection based on the quality of the surface protection tape.

By using a multi-layer material for the protective layer, in which the layer which, in a rolled state, contacts the supporting layer of a subsequent surface protection band contains a minimal amount of particle material as described above, the risk of forming undesirable indentations in the supporting layer can be limited and this without increasing the thickness of the protective layer. The use of a multi-layer protective layer makes it possible to control the overall thickness of the protective layer. This is an advantage since in this way the rolling-up properties and handling of the belt are not adversely affected and there is a minimal risk of disrupting the conversion process at the end user. The solution provided by this invention further offers the advantage that it is not necessary to provide a lead band along the edges of a roll of surface protection tape for creating a distance between successive layers in a roll of the surface protection tape, to provide a distance between successive layers and to prevent the formation of indentations.

The second layer of the protective layer preferably comprises less than 0.50 wt. %, preferably less than 0.40 wt. %, more preferably less than 0.25 wt. %, most preferably less than 0.15 wt. % of particulate antiblocking agent, in particular less than 0.10 wt. %. More preferably, the second layer of the protective layer contains less than 0.20 wt. %, preferably less than 0.15 wt. % anti-blocking agent particles with an average particle size between 5.00 and 0.5 µm, in particular less than 0.10 wt. % with an average particle size between 5.00 and 0.5 µm. Most preferably, the second layer of the protective layer is substantially free of anti-blocking agent particles, which means that the anti-blocking agent is preferably present in a concentration lower than the detection limit of that material.

At the concentrations described in the previous paragraph, an optimum dispersion of the anti-blocking agent can be obtained, with a minimal risk of agglomeration of the anti-blocking agent particles. Thus, the risk of the occurrence of peaks protruding over a distance of 1 µm or more with respect to the first layer can be reduced to a minimum, while at the same time the risk of undesired indentations is minimized.

The second layer of the protective layer is preferably substantially free of pigment particles, which means that the pigment is preferably present in a concentration that is lower than the detection limit for that material. The inventors have found that the pigmentation and the uniformity of the pigmentation of a sheet of a protective layer containing at least a first and a second layer of a plastic polymer, in which the first layer directed towards the adhesive and the backing layer is pigmented while the second layer is not pigmented and contains a minimum amount of pigment particles, it is not adversely affected. Uniform pigmentation is not only important from an aesthetic point of view, but is also an important parameter in the "peak and place" process where the support layer is split and separated from the protective layer, whereby the support layer is selectively separated from the pigmented protective layer based on the detection of the pigmentation of the protective layer.

A preferred embodiment of the surface protection band of this invention is characterized by a sheet of a protective layer that further comprises a third layer of a plastic polymer, which may contain particulate material, wherein the third layer is on a side of the first layer which faces the pressure sensitive .......

adhesive of the same layer of surface protection tape. This third layer is preferably pigmented. It was found that the presence of two pigmented layers in the protective layer, in particular the first and third layers, enhances the uniformity of the pigmentation. Since the third layer of the protective layer is sandwiched between the first layer of the protective layer and the pressure-sensitive adhesive of the same layer of surface protection tape, all peaks caused by agglomeration of anti-blocking agent and / or pigment particles in the third layer can be averaged and absorbed by the pressure-sensitive adhesive layer.

The protective layer of this invention is preferably produced by means of multi-layer co-extrusion, this is a widely used process for producing (tires), liners and backing layers of this type. This offers the possibility of abandoning a coating process to apply one or more layers. Coating a transparent acrylic resin on the side of the protective layer opposite the side facing the pressure-sensitive adhesive can provide a mechanical barrier capable of averaging out deformations protruding from the protective layer. However, applying a coating can cause dust formation, and is therefore not suitable for use in clean room applications, which are typically used in the production of electronic devices, in particular when applying a protective film to a screen of an electronic device.

This invention also relates to a multi-layer surface protection tape comprising a sheet of a support layer containing a plastic polymer, a sheet of a protective layer containing a plastic polymer and which is coated on a side facing the adhesive with a release layer, a layer of a pressure-sensitive adhesive sandwiched between the support layer and the protective layer, characterized in that the protective layer comprises a multi-layered sheet, which comprises multi-layered sheet - on a side of the protective layer directed towards the pressure-sensitive adhesive, at least a first layer containing a plastic polymer, at least a second layer of a plastic polymer on the side of the first layer opposite the side facing the adhesive, which plastic contains dispersed particulate material, in which protrusions which are relative to a side of the surface of the second layer opposite to the first protrude low-facing side, protrude maximum over 1.5 µm, preferably maximum 1.25 pm, more preferably a maximum of 1.0 pm.

Such bulges will usually be caused by the presence of particulate material as described above. In particular, such protrusions will be caused by the presence of anti-blocking agent particles as described above.

DETAILED DESCRIPTION OF THE INVENTION.

Figure 1 shows a cross-section of a surface protection tape according to the prior art and the prevention of indentations in the transparent support layer.

Figure 2 shows a cross section of a surface protection tape of the present invention.

Figure 3 shows the measurement of d 50

Figure 4a shows a photograph taken with an interferometer of agglomerated particles protruding relative to the surface of the protective layer at two different positions on the protective layer. FIG. 4b shows a photograph taken with an interferometer of indentations on the support layer corresponding to the agglomerated particles of FIG. 4a protruding with respect to the surface of the protective layer.

FIG. 5 shows a SEM-EDX element analysis of an agglomerated particle.

The over-all thickness of the surface protection tape is not essential to this invention and can vary within wide limits. Usually the over-all thickness of the surface protection band will range from 25.0 to 300.0 µm, preferably from 30.0 to 200.0 µm, more preferably from 40.0 to 150.0 µm, in particular from 70.0 µm or 80.0 µm to 130.0 µm.

The protective layer.

The material used for manufacturing the protective layer 2 in the surface protection band of this invention comprises a film of a polymeric material, in particular a multi-layered sheet containing 1. at least a first layer 23 of a plastic polymer that faces the pressure-sensitive adhesive 3 and the backing layers and 2. at least one second layer 24 of a plastic polymer on one side of the first layer 23 opposite the side facing the backing layer.

The protective layer 2 may comprise a third layer 22, between the first layer 23 and the pressure-sensitive adhesive 3, and further may be present if this is indicated for the intended application.

The thickness of the protective layer 2 is not essential for this invention and it can vary within wide limits, depending, inter alia, on the dimensions of the protective tapes and the intended application.

Usually, however, the thickness of the protective layer will be at least 10.0 µm, preferably at least 20.0 µm, more preferably at least 25.0 µm. The thickness of the protective layer will preferably be less than 150.0 µm, preferably less than 100.0 µm, more preferably less than 75 µm.

The first layer 23 is usually the supporting base layer of the protective layer 2, which supports the other layers. The material of the first layer 23 may contain, in addition to the polymer, the usual additives or additives. The second layer 24 is often the outermost layer of the surface protection tape, which is in contact with the transparent backing layer 11 of a subsequent layer of surface protection tape in a stack of a plurality of surface protection tapes or in a rolled-up state of the surface protection tape. This second layer preferably contains only a minimal concentration of particulate material. This second layer preferably contains only a minimum concentration of particle material, in particular a minimum concentration of particles with an average particle diameter of 5.0 µm or more. More preferably, this second layer contains a minimum concentration of particles with an average particle diameter of less than 5.0 μηη but greater than 0.5 μηη. With a minimum concentration is meant, a concentration that is lower than 0.20 wt. %. Usually the concentration of such particles will be higher than 0.01 wt. % relative to the weight of that low, but it can also be lower than 0.01 wt. %. The inventors have found that this low concentration results in a good dispersion of the particles in the polymer, with minimal risk of agglomeration. In this way, the formation of protrusions or peaks in the second layer, which would protrude relative to the second layer of a sheet or layer of surface protection tape toward the support layer of a subsequent sheet or layer of surface protection tape, while a multi-layered film allows a uniform layer thickness, as opposed to a solution in which a lacquer layer or varnish would be applied to the side of the protective layer opposite that facing the pressure-sensitive adhesive. Although this would provide a solution for minimizing the problem of imperfections in the protective layer being transferred to the transparent backing layer, applying a substantially uniform thickness that may vary only within limited limits is difficult to accomplish.

The first layer 23 will usually serve as the base layer of the protective layer 2. The thickness of the first layer 23 of the protective layer is not essential to this invention and will usually vary between 20.0 and 80.0 µm, preferably between 25.0 and 75.0 µm.

The second layer 24 mainly serves as a layer for absorbing and averaging protrusions protruding from the contact surface between the first 23 and the second layer 24 and into the second layer 24. The thickness of the second layer 24 of the protective layer 2 is not essential for this invention. The second layer 24 may have a thickness similar to the first layer 23, but will usually have a smaller thickness between 2.0 and 20.0 µm, preferably between 2.0 and 10.0 µm, typically 4.0-6.0 µm.

In order to improve the uniformity of the pigmentation of the protective layer and to provide a stable production process for producing sheets for improved quality protective layers, the protective layer 2 preferably comprises between the first layer 23 and the adhesive layer 3, a third layer 22 comprising a polymeric material. This third layer 22 is preferably pigmented, since the presence of two pigmented layers improves the uniformity of the pigmentation of the protective layer and facilitates the separation and selection of the transparent support layer from the protective layer by peak and place equipment. Preferably, the third layer 22 also contains particles of at least one anti-blocking agent. If desired, additional layers can be added between the first and second layers and between the first and third layers. The thickness of the third layer 22 is not essential to the invention and will usually vary between 1.0 and 40.0 µm, preferably between 1.0 and 30.0 µm, more preferably between 2.0 and 20.0 µm, most preferably between 2.0 and 10.0 µm, typically 4.0-6.0 µm.

The first and second layer 23, 24 of the protective layer 2, as well as the third layer and any further layer, can all be made of the same plastic polymer, or they can be made of different plastic polymers. To simplify the production process, they are preferably all made from the same plastic polymer. Suitable plastic polymers for producing the first, second and or third layer of the protective layer include polyolefins, for example propylene polymers (e.g., homo-type, block-type, renom-type etc.); ethylene polymers (low density, high density, linear low density, etc.); polyesters, for example polyethylene terephthalate; polybutylene terephthalate; polyethylene naphthalate; polybutylene naphthalate; polyesters of polylactic acid etc .; polyamides, for example 6-nylon, 6.6-nylon, 12-nylon and blends of two or more of the aforementioned materials. Most preferably, however, a biaxially stretched multi-layer polyester film is used to produce the protective layer.

In order to obtain the desired whiteness and the desired opacity of the film, a white pigment is preferably introduced into the first layer of the protective layer 2 directed towards the pressure-sensitive adhesive, and preferably in all further layers of the multi-layer protective layer, with the exception of the second layer. The second layer preferably contains no pigment particles as described above. Suitable materials for use as a white pigment include barium sulfate, titanium dioxide, calcium carbonate, etc. The use of a white pigment is preferred since other pigments usually provide a non-uniform color. However, taking into account the nature of the application, pigment particles of a color other than white can be used.

The amount of pigment that is incorporated into the first and / or third layer of the protective layer will usually vary between 5.0 and 25.0 wt. % based on the weight of the layer in which the pigment is located, preferably 10.0 to 25.0 wt. %, and in particular 15.0 to 25.0 wt. %. The pigment particles will usually have an average particle size (d50 value) in the range of 0.1 to 5 µm, preferably 0.1 to 3.0 µm, more preferably 0.2 to 1.5 µm.

In order to achieve the intended whiteness (preferably> 70) and the desired low transparency (preferably <40%) of the film, the first layer and all other layers of the protective layer with the exception of the second layer have a high content of particles and / or pigment. In order to further control the whiteness, suitable optical brighteners may be present in the first layer of the protective layer, but also in all other layers, with the exception of the second layer.

To improve the wrapability of the surface protection tape of this invention and the presentation of a roll of the surface protection tape, the first layer may contain an anti-blocking agent, with the exception of the second layer. Examples of materials suitable for use as an anti-blocking agent in this invention include inorganic and / or organic particles, e.g. silica, talc, magnesium carbonate, barium carbonate, calcium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide, calcined clay, lithium fluoride, the calcium, barium, zinc, or manganese would be from dicarboxylic acids, kaolin, or cross-linked polystyrene particles or acrylate particles, or mixtures of two or more of the aforementioned materials. Preferred anti-blocking agents are silica particles. The anti-blocking agents can be added to the individual layers in the desired concentration, for example in the form of a dispersion in glycol during polycondensation or in a masterbatch during extrusion. The concentration of the anti-blocking agents in the first and / or third layer of the protective layer will usually vary from 0.05 to 3.5 wt. % preferably from 0.1 to 3.0 wt. %. In addition, the concentration of the antiblocking agent in the different layers of the protective layer can be the same or different. The average particle size of the anti-blocking agent particles will usually range from 1.0 to 7.0 µm, preferably from 1.0 to 6.0 µm, more preferably from 1.0 to 5.0 µm, most preferably from 1.5 to 4.0 µm. Outside of these limits, there is a risk that the winding, processability and optical properties of the film will be adversely affected.

The layers of the multi-layer protective layer may further contain the appropriate additives (e.g. antioxidants for preventing degradation, ultraviolet absorbers, light stabilizers, antistatic additives, etc.).

To impart optimum release properties to the protective layer, the surface of the protective layer facing the pressure-sensitive adhesive layer is typically coated with a release agent, for example, a silicone coating. Such coatings are commercially available from Mondi, Laufenberg GmbH, Hutamaki, etc. The release agent can be applied in an off-line or an on-line coating process.

The support layer.

The backing layer 1.11 can be transparent or not or it can be partially transparent or made of a printable material. The support layer 1, 11 can be made of any material and contains thermoplastic resin that can be formed into a sheet or film, or it can be made entirely from such a thermoplastic resin. The polymer is preferably chosen such that the support layer is sufficiently flexible to be able to roll into a roll. Preferred polymeric plastics include polyesters and polyolefin-based resins, more preferably those that have good heat resistance, are solvent resistant, and are flexible. A polyester is most preferably used.

Suitable polyesters include polyethylene terephthalate and polyethylenaphthalate. Other suitable polymers include cellulose type polymers such as diacetyl cellulose and triacetyl cellulose; acrylic type polymers such as poly methyl methacrylate; styrene type polymers such as polystyrene and acrylonitrile-styrene copolymer; polycarbonate type polymer. Examples of suitable polyolefin type polymers include polyethylene, polypropylene, polyolefins with cyclic or norbornene structures, ethylene-propylene copolymers; vinyl chloride type polymers; amide type polymers such as nylon and aromatic polyamide; imide type polymers; sulfone type polymers; polyether sulfone type polymers; polyether ether ketone type polymers; poly phenylene sulfide type polymers; vinyl alcohol type polymers; vinylidene chloride type polymers; vinyl butyral type polymers; arylate type polymers; polyoxymethylene type polymers; epoxy type polymers; or blends of two or more of these polymers.

Examples of polyolefin resins suitable for use in this invention include polyethylene-based resins, propylene-based resins composed of propylene components or propylene components and ethylene components, and copolymers of ethylene and a polar monomer. Examples of the polyolefin-based resins that are particularly suitable for use in this invention include, but are not limited to, low density polyethylene, linear low density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-pentene, ethylene-propylene copolymers, ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-4-methyl-1-pentene copolymers, ethylene-1-octene copolymers, ethylene-methyl acrylate copolymers, ethylene-methyl methacrylate copolymers, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-vinyl alcohol copolymers and blends of two or more of these materials.

The support layer 1, 11 is preferably as colorless and transparent as possible.

The support layer can be used in the form of a sheet or film composed of a single layer, a two-layer or multi-layer structure. Particularly if the backing layer is a two or multi-layer structure, abutting layers may be made of material that adheres strongly to co-extrusion.

The backing layer may contain additives that are common to the tire of this invention. Examples of such additives include fillers, pigments, ultraviolet absorbers, antioxidants, heat-resistant stabilizers, and lubricants.

The thickness of the backing layer is not essential to this invention and will usually vary between 5.0 µm and 50.0 µm, preferably between 10.0 and 40.0 µm, more preferably between 30.0 and 40.0 µm. A backing layer with a thickness less than 5.0 µm exhibits a risk of breaking or tearing during peeling.

In order to be suitable for cutting or to provide anti-slip properties, the free surface of the backing layer of the surface protection tape of this invention can be subjected to a method of applying relief, a convex / concave process or the like, depending on the intended application.

Typically, the support layer 1 and the protective layer 2 are produced by extrusion or co-extrusion. The production of, for example, commercial polyester films for use as a backing or protective layer usually comprises the following process steps: in a first step, the polyester melt is subjected to melt extrusive or co-extrusion, using a mold with a slit, after which the extruded polymer is quenched on a cold drum to an amorphous glass state 2. in a second step the quenched film is reheated and subjected to orientation (this is simultaneous stretching or sequential stretching in the longitudinal direction or machine direction (MD) and crosswise direction (TD) 3. in a third step the film thus obtained is subjected to curing under the influence of heat 4. in a fourth step the multi-layer film is wound on a roll.

A well-known production process for producing polyester films is described in detail in "Polyester films", Encyclopedia of Polymer Science and Engineering, Vol. 12, Second Edition, 1988, John Wiley & Sons, INC., S. 193 - 216 and Film processing, Edited by Kanai and Campbell, Series Editor: Warren Baker, Carl Hanser Verlag, Munich, DE, 1999.

The pressure sensitive adhesive.

A pressure-sensitive adhesive is preferably used as the adhesive 3 sandwiched between the supporting layer 1 and the protective layer 2. Any pressure-sensitive adhesive that is considered suitable by those skilled in the art can be used. Examples of adhesives suitable for use in this invention include polyurethane, polyester, acrylic polymer based pressure sensitive adhesives, rubber based pressure sensitive adhesives (e.g., natural rubber based pressure sensitive adhesives and synthetic rubber based pressure sensitive adhesives), silicone based pressure sensitive adhesives, and urethane based pressure sensitive adhesives. If desired, a single pressure-sensitive adhesive can be used or a mixture of two or more. The pressure-sensitive adhesive layer can take the form of a single layer or two or more superimposed layers.

Preferably, however, use is made of an acrylic-based pressure-sensitive adhesive composition. Suitable examples include homopolymers of (meth) acrylates and copolymers of (meth) acrylates and a copolymerizable monomer, and the like. For example acrylic polymers obtained by homopolymerizing or copolymerizing monomers such as alkyl (meth) acrylate (e.g. methyl ester, ethyl ester, propyl ester, butyl ester, 2-ethylhexyl ester, octyl ester and the like), glycidyl (meth) acrylate, (meth) acrylic acid, itaconic acid, maleic anhydride, (meth) acrylamide, (meth) acrylic N-hydroxyamide, alkylaminoalkyl (meth) acrylate (eg, dimethylaminoethyl methacrylate, t-butylaminoethyl methacrylate and the like, vinyl acetate, styrene, acrylonitrile and the like. One or more of the aforementioned monomers can be used Particularly preferred are monomers such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-propyl (meth) acrylate, n-octyl (rrieth) acrylate and the like. can be obtained by conventional polymerization, for example in solution, emulsion and the like.

In the case of the pressure-sensitive adhesive layer on both surfaces of the release layer of the surface protection tape, the same or a different pressure-sensitive adhesive can be applied. The pressure sensitive adhesive can be mixed with the usual additives such as softening agents, colorants, antistatic agents, blowing agents and surfactants, if desired. The pressure sensitive adhesive may contain a cross-linker and, if desired, a catalyst to activate the cross-linking.

The thickness of the pressure sensitive adhesive layer is not essential to this invention, but will usually range from about 1.0 to 100.0 µm, preferably 5.0 to 75.0 µm, more preferably 10.0. to 50.0 µm, most preferably 10.0 to 40.0 µm.

The pressure sensitive adhesive layer can be formed by any method suitable by those skilled in the art. Examples of suitable methods include a method in which a solution or an emulsion of a pressure-sensitive adhesive in a solvent, etc., is applied as a coating on the surface (one or both surfaces) of the protective layer of the surface protection tape; and a method in which a hot-melting pressure-sensitive adhesive is extruded as a melt and applied or laminated to the base material of the surface protection tape. Incidentally, after the base material of the surface protection tape is obtained by rolling using a calendaring machine where the rotation speed of each roll can be controlled individually, the pressure-sensitive adhesive can be coated continuously. The step of forming the protective layer for the surface protection tape and the step of coating the pressure-sensitive adhesive can be carried out separately. If desired, the surface of the pressure-sensitive adhesive layer can be subjected to a surface treatment to control adhesion, retention practicability or the like, such as, for example, a corona discharge treatment, ultraviolet irradiation, flame treatment, plasma treatment or a sputter etching treatment.

The pressure sensitive adhesive layer may contain the usual additives for controlling the adhesive properties or other properties. Examples of such additives include various known softeners, tackifiers, olefin-based resins such as those used in the backing layer, silicone-based polymers, liquid acrylic copolymers, phosphorus ester-based compounds, anti-aging agents, hindered amine light stabilizers, ultraviolet absorbents , surface lubricants, leveling agents, plasticizers, low-molecular-weight polymers, antioxidants, corrosion Inhibitors, polymerization Inhibitors, silane coupling agents, inorganic or organic fillers (such as calcium oxide, magnesium oxide, silica, zinc oxide and titanium oxide), powders, metal particles or flakes, dyes and pigments or the like, and heat-resistant stabilizers.

The surface protection tape known from the prior art, indicated in Figure 1, is a multi-layer material that can take the form of a sheet, a layer, a tape or any other shape deemed suitable by the qualified person. The multi-layer material is often stored in the form of a roll or an accumulation of stacked layers of multi-layer material, as shown in the upper and left part of Figure 1.

The surface protection tape known from the state of the art, shown in Figure 1, comprises a support layer which may not be transparent, a protective layer 2 and a pressure-sensitive adhesive layer 3. In general, a release material 7 or release layer will be present. between the protective layer and the pressure-sensitive adhesive 3. The protective layer 2 can be pigmented and contains both pigment particles 4 and anti-blocking particles 4, which must guarantee easy rolling of a roll of the tape. Pigment and anti-blocking agent particles can be incorporated in relatively high concentrations and can give rise to the formation of co-bonded particles 6 protruding from the surface of the pigmented protective layer from a previous sheet or layer of the surface protection tape to a subsequent layer of the surface protection tape , over a distance in height and width of the order of magnitude of several microns. When a cumulation of such layers of the surface protection band or when a roll of the band is produced, as shown in the left-hand part of Figure 1, the peaks protruding from the surface of the protective layer, local deformation of a backing layer of the cause subsequent layer of the surface protection band - in direct contact with it - and may cause the occurrence of the so-called indentations or impressions in that support layer, as shown in the right-hand part of Figure 1. The prevention of indentations 5 will become more important as the pressure to which the belt is subjected increases. In a roll, the pressure will increase when moving from an outer part to the inner part of the roll. On a stack, the pressure will increase in the lower layers.

The surface protection tape of the present invention is shown in Figure 2. The left-hand part of Figure 2 shows an accumulation of two layers or sheets of surface protection tape (a first sheet 15, a second sheet 25), the right-hand part of Figure 2 shows an individual sheet of the surface protection tape. The surface protection band of the present invention, shown in Figure 2, comprises a layer 1, a protective layer 2, which comprises a multi-layered sheet. The protective layer is a multilayer material which comprises - at least a first layer 23 on one side of the protective layer opposite the pressure-sensitive adhesive 3. The first layer 23 comprises a plastic polymeric material and it may comprise pigment particles, anti-blocking agent particles and optionally other particle material, suitably deemed by the qualified person - at least one second layer 24 of a plastic polymeric material on the side of the first layer 23 opposite the side opposite the support layer 1 or the pressure-sensitive adhesive. This second layer preferably comprises only a minimum concentration of particulate material as described above. FIG. 4a shows a photograph of a protective layer according to the state of the art, taken with an interferometer from Wyko® NT3300 DMEMS from Veeco instruments Ine. As can be seen from Figure 4a, co-bonded particles protrude from the surface of the protective layer, produced as described above. FIG. 4b shows an image of the indentations on the support layer corresponding to the protrusions on the protective layer of FIG. 4a for a supporting layer in contact with the protective layer of FIG. 4a. FIG. 5 shows a photograph of a particle that has been glued together and protrudes from the surface of a protective layer according to the state of the art.

The following test methods are used to characterize the raw materials for the protective layer and the supporting layer: DIN = Deutsches Institut für Normung

Standardization] ASTM = American Society for Testing and Materials

Transparency.

Transparency of the backing layer was measured using a method based on the ASTM D1003-00.

Whiteness.

The whiteness of the protective layer is determined by the Berger method, generally by mutually more than 20 superimposed layers of film. Whiteness is determined using an ELREPHO electric reflection photometer from Zeiss, Oberkochem (DE), standard light type C, 2 ° standard observer. Whiteness WG is defined as WG = RY + 3RZ-3RX, where RX, RY, RZ are congruent reflection factors using an X, Y or Z color measurement filter.

The white standard used comprises a pressure barium sulfate (DIN 5033, part 9). A detailed description is given, by way of example, in Hansl Loos, Farbmessung [color measurement], Verlag Beruf und Schule (Professional and Education Publisher), Itzehoe (1989).

SV (standard viscosity) - polyethylene terephthalate

Standard viscosity SV (DCA) is measured at 25 ° C in dichloroacetic acid (ethanoic acid) by a method based on DIN 53726. Intrinsic viscosity (IV) is calculated based on standard viscosity, as follows: IV [η] = 6,907 * 1 θ 4 SV (DCA) + 0.063096 [dl / g]

Friction coefficient.

The friction coefficient is determined up to 53 375 DIN. The sliding friction coefficient was measured 14 days after production.

Average section diameter dsn.

The average particle diameter d50 is determined by means of a laser on a Malvern Mastersizer (Malvern Instruments, Ltd., UK), using the standard method (examples of other measuring equipment, such as: Horiba LA 500 or Sympathec Helos, which use the same measuring principle. ). For the test, the sample of the particulate material is placed in a cell with water, the cell is then placed in the Mastersizer. The average particle diameter is measured in an automatic way, the measurement contains a mathematical determination of d50 (see figure 3). d50 of the "relative" cumulative particle size distribution curve is determined as follows: the desired d50 is given directly on the abscissa axis by the intersection of the ordinate value of 50% with the cumulative curve. Figure 3 illustrates in more detail what is meant.

Inspection method - Indentations

Samples of the surface protection tape for inspection for the presence of indentations were prepared as follows: - 7 pieces of 20 cm X 20 cm were cut from a surface protection tape and the entire width of the block roll taken over should be inspected.

- A randomly chosen strip of 10 cm X 10 cm is marked on each of the pieces.

Inspection of these samples is carried out as follows: - the sample of the surface protection tape (including foil) is placed on a table that is illuminated from above in such a way that no direct reflection occurs, the presence of direct sunlight is avoided - the surface of the tire is inspected with the naked eye by moving the sample up and down with respect to the table. Surface irregularities (such as indentations) are visible in a distortion of the light reflection. Surface irregularities with a surface area of 0.02 mm2, which have the dimension of typical surface roughness, will usually not be visible to the naked eye - all detected indentations within the 10 cmX10 cm strip are marked - the size of the indentations is measured with the template on transparency size, shown below, which is placed on top of the surface of the surface protection tape, comprising the protective layer. The size of the dimples is determined by covering the dimples by dots displayed on the template, and, determining the smallest dot size needed to fully cover the indentation. The number of indentations is calculated as a function of their size for a 10 cm X 10 cm area, converted into 1 m2 and compared with the product specification.

Example 1 SCREW LAYER.

A multi-layer protective layer was produced for use in a multi-layer surface protection band. The protective layer consisted of 1. a first layer 2. a second layer on one side of the first layer opposite the side opposite the pressure-sensitive adhesive or the backing layer of the same layer or sheet of the surface protection tape 3. and a third layer on a side of the first layer opposite the pressure sensitive adhesive.

For the first layer, chips composed of polyethylene terephthalate, including barium sulfate as white pigment, were dried and introduced into the extruder. The material of the first layer consisted of 100 wt. % by weight of polyethylene terephthalate (SV = 800), which is 22 wt. % of barium sulfate (Blanc fixe XR-HX, Sachtleben Chemie, d50 = 0.7 µm) contained as white pigment. For the second layer, chips composed of polyethylene terephthalate and a small amount of anti-blocking particles were dried and introduced into the extruder.

The material used to produce the second layer was composed of a mixture of 1.97 wt. % of polyethylene terephthalate (SV = 800) and 2. 3 wt. % of a masterbatch composed of 97 wt. % of polyethylene terephthalate and 3 wt. % of Sylysia 320 (synthetic SiO 2 from Fuji, Japan, d50 = 2.5 µm)

The material used for the production of the third layer consisted of a mixture of 1.89 wt. % of polyethylene terephthalate (SV = 800) contained 22% by weight of barium sulfate (Blanc fixe XR-HX, Sachtleben Chemie, d50 = 0.7 µm) as white pigment 2. 11 wt. % of a masterbatch composed of 99 wt. % of polyethylene terephthalate and 1 wt. % of Sylobloc® 44 H (synthetic SiO2 from Grâce, d50 = 2.5 µm)

A white, three-layer film was produced via co-extrusion using the blends for the first, second, and third layers described above. Co-extrusion was followed by later, stepwise, longitudinal and transverse orientation, until a multi-layer film was obtained with a first total thickness of 50 µm. The thickness of the second layer was 6 µm, the thickness of the third layer was 4 µm.

The production conditions in the individual steps of the film process were:

A co-extruded multi-layer film was obtained with very good optical properties, very good winding performance, very good winding quality and very good processing performance.

The surface of the third layer was then coated off-line with a standard, thin, silicone-based release layer.

The whiteness and transparency of the protective layer were determined as described above. The whiteness of the protective layer was 110 and the transparency was 23%.

SUPPORT LAYER.

A transparent, biaxially oriented polyester film (Hostaphan® RNK 36 Mitsubishi Polyester Film GmbH, Deutschland (Germany)) with a thickness of 36 µm was used as a backing layer.

ADHESIVE LAYER.

As a pressure sensitive adhesive, an acrylic, pressure sensitive adhesive composition was used.

Production, properties and assessment of the surface protection tape.

The surface protection tape was produced by coating the backing layer with the pressure sensitive adhesive and then laminating the protective layer against it. Visual inspection with the naked eye, as described above, revealed that the surface protection band contained 5 indentations - with an area smaller than 0.1 mm 2 on an area of 100 cm 2.

Comparative example 1 SCREW LAYER.

Example 1 was repeated, but instead of a multi-layer film, a monolayer film was used as the protective layer. The monolayer film had a thickness of 50 µm and a composition as described in Example 1 for the first layer. The whiteness of the protective layer was 112 and the transparency was 22%.

One surface of the film was coated off-line with a thin, silicone-based release layer.

SUPPORT LAYER.

A transparent, biaxially oriented polyester film (from Mitsubishi Polyester Film GmbH, Deutschland (Germany)) with a thickness of 36 µm was used as a backing layer.

ADHESIVE LAYER.

As a pressure-sensitive adhesive, an acrylic, pressure-sensitive adhesive composition used in Example 1 was used.

Production, properties and assessment of the surface protection tape.

The surface protection tape was produced by coating the backing layer with the pressure sensitive adhesive and then laminating the protective layer against it.

Visual inspection with the naked eye, as described above, using the indicated template, revealed that the surface protection band has more than 15 indentations with an area smaller than 0.1 mm 2 and 1 indentation with an area between 0.1 and 0.5 mm 2.

Claims (17)

A multi-layer surface protection tape comprising a sheet of a backing layer (1) containing a plastic polymer, a sheet of a protective layer (2) containing a plastic polymer and coated on a side facing the adhesive (3) release layer (7), a layer of pressure-sensitive adhesive sandwiched between the support layer (1) and the protective layer (2), characterized in that the protective layer (2) comprises a multi-layered sheet, which multi-layered sheet 1. comprises at least a first layer (23) on a side of the protective layer facing the pressure-sensitive adhesive (3), which first layer comprises a plastic polymer; 2. at least a second layer (24) of a plastic polymer on the side of the first layer (23) opposite the the adhesive-oriented side, which second side is less than 2.50 wt. % relative to the weight of the second layer of a particulate material with an average particle size of 7.0 µm more, preferably 5.0 µm. of more, more preferably 2.5 µm of more, most preferably 1.0 µm of more. A surface protection tape according to claim 1, characterized in that the second layer is less than 2.00% by weight, preferably less than 1.00% by weight. %, more preferably less than 0.50 wt. %, most preferably less than 0.25 wt. % particulate material relative to the weight of the second layer. A surface protection tape according to claim 1 of 2, characterized in that the second layer is less than 0.50% by weight, preferably less than 0.25% by weight. %, more preferably less than 0.20 wt. %, most preferably less than 0.15 wt. % with respect to the weight of the second layer contains anti-blocking agent particles. A surface protection band according to claim 3, characterized in that the second layer is substantially free of anti-blocking agent particles with an average particle size of 5 µm of more, preferably 4 µm of more. A surface protection tape according to any one of claims 1-4, characterized in that the second layer is less than 0.20 wt. % with respect to the weight of the second layer contains particles of an anti-blocking agent as the only particle material whose particles have an average diameter of less than 5.0 µm but greater than 0.5 µm. A surface protection tape according to any one of the preceding claims, characterized in that the second layer is substantially free of added pigment particles. A surface protection tape according to any one of the preceding claims, characterized in that the protective layer further comprises a third layer (22) containing a plastic polymer, which third layer is located between the first layer and the pressure-sensitive adhesive (3). A surface protection tape according to any one of the preceding claims, characterized in that the protective layer is made by co-extrusion. A surface protection tape according to any one of the preceding claims, characterized in that the surface protection tape has an overall thickness between 25.0 and 300.0 µm, preferably between 30.0 and 200.0 µm, more preferably between 40.0 and 150.0 µm, particularly preferably between 80.0 and 130.0 pm. A surface protection band according to any one of the preceding claims, characterized in that the second layer of the protective layer has a thickness between 2.0 and 20.0 µm, preferably between 2.0 and 10.0 µm, typically 4.0-6.0 µm. A surface protection band according to any one of the preceding claims, characterized in that the first layer of the protective layer has a thickness between 20.0 and 80.0 µm, preferably between 25.0 and 75.0 µm. A surface protection band according to any one of the preceding claims, characterized in that the third layer of the protective layer has a thickness between 1.0 and 40.0 µm, preferably between 1.0 and 30.0 µm, more preferably between 2.0 and 20.0 µm, most preferably between 2.0 and 10.0 μιτι, typically 4.0-6.0 pm. A surface protection tape according to any one of the preceding claims, characterized in that the protective layer has a minimum thickness of at least 10.0 µm, preferably at least 20.0 µm, more preferably at least 25.0 µm. A surface protection band according to any one of the preceding claims, characterized in that the protective layer has a maximum thickness of 150.0 µm, preferably 100.0 µm, more preferably 75.0 µm. A surface protection tape according to any one of the preceding claims, characterized in that the transparent backing layer has a thickness between 5.0 µm and 50.0 µm, preferably between 10.0 and 40.0 µm, more preferably between 30.0 and 40.0 µm. A surface protection tape according to any one of the preceding claims, characterized in that the pressure-sensitive adhesive layer has a thickness of about 1.0 to 100.0 µm, preferably between 5.0 and 75.0 µm, more preferably of 10.0. to 50.0 µm, most preferably from 10.0 to 40.0 µm. A multi-layered surface protection tape comprising a sheet of a backing layer (1) containing a plastic polymer, a sheet of a protective layer (2) containing a plastic polymer and coated on a side facing the adhesive (3) with a release layer (7), a layer of pressure-sensitive adhesive (3) sandwiched between the support layer (1) and the protective layer (2), characterized in that the protective layer (2) comprises a multi-layered sheet, which comprises multi-layered sheet 1. pressure sensitive adhesive (3) facing side of the protective layer, at least a first layer (23) containing a plastic polymer, 2. at least a second layer (24) of a plastic polymer on the side of the first layer (23) opposite the side facing the adhesive, which plastic contains dispersed particulate material, wherein protrusions protruding relative to a side of the surface of the second layer (24) opposite the side facing the first layer (23) protrude a maximum of 1.5 µm , Bee preferably a maximum of 1.25 pm, more preferably a maximum of 1.0 pm.