JP5419766B2 - Protective film against textured substrate - Google Patents

Description

  The present invention relates to a film for use in protecting a substrate surface from damage or contamination. More specifically, the present invention relates to a surface protective film that does not include an adhesive coating but provides high adhesion to a substrate, particularly a substrate having a textured surface topography.

  A surface protective film, also called a masking film, is used in various applications as a protective cover for the surface. Typically, films are used to protect smooth and relatively rigid surfaces (eg, acrylic, polycarbonate, glass, polished or painted metal, glaze ceramic) and other smooth and relatively rigid surfaces. Yes. The film is applied to the surface to be protected and acts as a physical barrier to prevent surface scratches, scratches and surface damage. The protection afforded by the masking film is particularly useful when the surface is printed, transported or otherwise handled before use.

  Conventionally, the smooth surface is protected by a corona-treated film and / or masking paper having an adhesive coating. However, these techniques have drawbacks. For example, it is difficult to control the amount of corona treatment so as to give good peelability while giving good adhesion. In addition, corona-treated masking films have a relatively high surface friction coefficient and tend to form hard wrinkles in the film. It is difficult if not impossible to remove such wrinkles, thus preventing the film from sufficiently protecting the surface to be protected and / or prematurely protecting the surface to be protected. It distorts. In addition, the corona-treated polyethylene film usually has a large amount of gel and accompanying carbon dust, which may cause dents on the surface to be protected or damage the surface to be protected.

  There are also disadvantages associated with masking films using paper with an adhesive coating. Moisture from moisture or elsewhere can penetrate the masking material, causing it to loosen or completely separate from the surface it is intended to protect. The tendency for moisture to adversely affect the performance of this type of masking film is high when heat is required to activate the adhesive coating. In addition, even if the masking material remains firmly adhered to the surface to be protected until it is desired to peel, the stripping may require the use of a solvent to remove trace amounts of the adhesive coating. is there. The adhesive residue remaining on the surface is particularly problematic when the surface to be protected is used in a situation where clean conditions are desirable, such as food industry applications.

  Recent advances in masking film technology have resulted in improved masking films formed without corona treatment or the use of adhesive coatings, such as single-side smooth / single-side smooth (OSM) masking films. OSM films are described in detail in (Patent Document 1) and (Patent Document 2), which are incorporated herein by reference. These advanced masking films take advantage of the tendency to adhere smooth surfaces together to provide a sufficient and constant level of adhesion without the need for corona treatment and without the use of an adhesive coating. In addition, the matte surface of the OSM film prevents film blocking and wrinkle formation by preventing intimate contact between the surfaces.

  While OSM films are advancing, the level of adhesion obtained with these improved masking films can vary depending on the temperature and other conditions associated with making and using the improved films. The above conditions sometimes result in masking films that exhibit an adhesion level that is too high or not sufficient for the desired application. In other applications, a heater may be required to raise the temperature of the film to reach the proper application and sufficient adhesion level. Moreover, since the level of adhesion obtained is mainly a function of the interaction between the smooth surface of the masking film and the smooth surface to be protected, the smoothness of the surface that needs to be protected is an important factor. This factor is problematic and the use of masking films of the above type is limited if the surface to be protected is not very smooth, i.e. the surface has a textured topography.

  The multilayer masking film is coextruded using a pressure sensitive adhesive as described in (Patent Document 3) and (Patent Document 4). These films use styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), styrene-butadiene (SB) and styrene-isoprene (SI) block copolymers. These block copolymers have poor thermal and aging stability due in part to the presence of double bonds. These films also contain anti-blocking agents to give good unwinding ability, to suppress the increase in stickiness, and to prevent the film from sticking to itself when stored in rolls. Yes. The anti-blocking agent may migrate (blooming) with temperature and time and eventually contaminate the substrate surface. Changing the level of anti-blocking agent also changes the level of adhesion to the substrate.

U.S. Pat. No. 4,895,760 US Pat. No. 5,100,709 US Pat. No. 5,286,781 US Pat. No. 5,427,850

  There remains a need for masking films that can provide a sufficient level of protection to the surface being textured. In addition, it can be functionally adjusted between the textured surface and the masking film to be protected under various protection and application conditions without the use of corona treatment or adhesives and without presenting the disadvantages associated with them. Need to give a controlled level of adhesion.

  According to the present invention, a masking film is provided that adheres to and protects the textured surface. This masking film does not contain an adhesive coating. The level of adhesion between the film and the textured substrate can be adjusted to match the chemistry and topology of various substrates. For example, the masking film can provide a functional level of adhesion to textured polycarbonate, acrylic, polyvinyl chloride, nylon and polyester (PET, PETG, PEN) at room or ambient temperature. Thus, in practice, the protective film can provide a sufficient level of adhesion to the surface in a given processing environment including temperature, line equipment layout and desired application. The protective film remains removably adhered to the substrate even after aging and / or heating.

1 is an embodiment of a film according to the present invention. FIG. 2 is an embodiment of a film according to the present invention showing adhesion to a textured substrate. FIG. 3 is a view similar to FIG. 2 but showing the contact area of a prior art masking film with a textured surface substrate.

  The film of the present invention provides an excellent balance of adhesion strength (measured in a peel test), film tensile strength, low elongation and good handleability. Since the surface topography of the textured substrate can vary greatly, it is advantageous that the film properties can be easily adapted to achieve a good balance of properties. Importantly, the film of the present invention satisfies important commercial and practical needs.

  The terms “substantially” and “about” mean that a given property or parameter (eg, surface roughness) may differ from a specified value by up to 20%.

  As used herein, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a compound” includes a plurality of said compounds, and reference to “component” or “additive” is a reference to one or more of said components or additives, or equivalents known to those skilled in the art. , And so on.

  Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. doing. Although methods and materials similar or equivalent to those disclosed herein can be used in the practice of the present invention, the preferred methods, devices and materials are now described. All publications mentioned in this specification are reported in the publication and are cited for purposes of describing and disclosing various films, compounds, compositions, methods, etc. used in connection with the present invention. Has been.

  The term “film” refers to a web made by extruding a molten sheet of polymeric material by a casting or inflation process and then cooling the sheet to form a solid polymer web.

  With reference to FIGS. 1 and 2, the film of the present invention, indicated generally at 10, has a surface contact layer 12, a reinforcing layer 14, and three core layers 16 located between the surface contact layer 12 and the reinforcing layer 14. Consists of layers. These layers are in intimate contact with each other as obtained by coextrusion or extrusion lamination. Any of the layers of film 10 may itself consist of one or more layers of material. For example, in some embodiments, the core layer may occupy 70% by volume of the total film thickness. It may not be possible to extrude a film layer having the desired thickness as a single layer, and the core layer of such embodiments may be extruded with two or more layers having the same (or different) composition .

  With particular reference to FIG. 2, the surface contact layer 12 is adapted to substantially contact the surface of the substrate 20. As can be seen in FIG. 2, the substrate 20 has a plurality of outliers 22 on its surface. The size and frequency of the alien locations can vary widely from substrate to substrate. In particular, the surface roughness of the substrate 20 can be 3 to 100 microns between the peaks and valleys that make up the textured surface. The surface roughness may not be uniform across the width and length of the substrate.

  The masking film of the present invention is designed to provide a surface contact layer 12 that has good conformity and thus can substantially match a surface having a substrate topography. This conformity provides better surface contact between the substrate and the surface contact layer, thus providing a higher adhesion between the two. However, high adhesion increases the likelihood that the film layer may tear when the film is peeled from the substrate. Thus, the film of the present invention provides good adhesion and the film remains intact when peeled from the substrate.

  As shown in FIG. 3, the prior art film 110 is in contact only with the peaks 122 on the surface of the substrate 120. Therefore, the adhesion capability of the prior art masking film to the textured surface was reduced due to the small contact area between the substrate surface and the film. In order to compensate, it was often necessary to increase the adhesion level of the film to a point where it would plug the residue remaining on the substrate or film. In contrast, the film 10 of the present invention (as shown in FIG. 2) can be substantially matched to the peaks and valleys that make up the surface topography of the substrate 20, so that the textured substrate 20 and film The contact surface area between the surface contact layers 12 becomes larger.

  The surface contact layer consists of a blended mixture of thermoplastic polymers. In one embodiment, the blend mixture comprises a mixture of styrene block elastomers. In another embodiment, the blend mixture comprises a styrene block elastomer mixed with low density polyethylene. The surface contact layer 12 may account for 15-30% of the total film thickness. Ideally, the thickness of the surface contact layer is 18-22% of the total film thickness.

  More specifically, the surface contact layer comprises a blend selected from Blend 1, Blend 2, Blend 3 or Blend 4 as detailed below.

  Blend 1 is composed essentially of a tackified quad block styrene block copolymer elastomer and a triblock copolymer elastomer. The quad block component usually accounts for 5-60% by weight of the blend and the triblock component accounts for 40-95% by weight.

  The tackified quad block copolymers are styrene-isoprene-styrene-isoprene (S-I-S-I ') and styrene-ethylene / propylene-styrene-ethylene / propylene (S-EP-S-EP'), As well as mixtures thereof. In either case, a tackifier is compounded with the quad block copolymer. Particularly preferred S-I-S-I 'copolymers are disclosed in detail in US Patent Application Publication No. 2006/0151901, the disclosure of which is incorporated herein by reference. Preferred S-I-S-I 'and S-EP-S-EP' quad block copolymers are available from Kraton Polymers, LLC. Fully or partially saturated versions are preferred in terms of oxidation and stability against long-term storage.

  The second essential component of Blend 1 is styrene-isoprene-styrene (S-I-S), styrene-butadiene-styrene (S-B-S), styrene-ethylene / butadiene-styrene (S-EB-S) and A triblock styrene block elastomer selected from styrene-ethylene / propylene-styrene (S-EP-S). S-EB-S and S-EP-S are fully saturated or hydrogenated versions of S-I-S and S-B-S copolymers. In any case, up to 30% by weight of the corresponding diblock styrene copolymer elastomer to triblock elastomer, such as styrene-isoprene (SI), styrene-butadiene (SB), styrene-ethylene / butadiene diblock copolymer (S -EB) or styrene-ethylene / propylene diblock copolymer (S-EP) may be compounded. The elastomers are commercially available from various suppliers including Kraton Polymers, LLC.

  Blend 2 consists essentially of a tackified quad block / triblock styrene block copolymer elastomer and a triblock copolymer elastomer. The quadblock / triblock component typically accounts for 5-60% by weight of the blend and the triblock component accounts for 40-95% by weight.

  The quad block / triblock copolymer component may be SIS-I 'or S-EP-S-EP' quad block copolymer or mixtures thereof, S-I-S, S-B-S, S-EB-S. Or S-EP-S and mixtures thereof, and a compounded mixture of tackifiers. Particularly preferred S-I-S-I 'and S-EP-S-EP copolymers are disclosed in detail in US Patent Application Publication No. 2006/0151901, the disclosure of which is incorporated herein by reference. Preferred tackified quad block copolymers and tackified triblock copolymers are available from Kraton Polymers, LLC. Fully or partially saturated versions are preferred in terms of oxidation and stability against long-term storage. Preferred triblock copolymers are S-EP-S and S-EB-S, and mixtures thereof. The elastomer is available from Kraton Polymers.

  The second essential component of Blend 2 is a triblock styrene block copolymer elastomer selected from S-I-S, S-B-S, S-EB-S and S-EP-S, or mixtures thereof, Up to 30% by weight of a diblock copolymer (eg S-EB or S-EP). This is the same as the second component of Blend 1.

  Blend 3 consists essentially of a triblock styrene block copolymer elastomer that is tackified and a triblock copolymer elastomer containing up to 30% by weight styrene diblock copolymer elastomer. The tackified triblock component usually accounts for 5-60% of the blend and the triblock component accounts for 40-95%.

  The tackified triblock copolymer component consists of S-EB-S and S-EP-S or mixtures thereof and a tackifier. Such polymers are available from Kraton Polymers. The second essential component of Blend 3 is the same as the second essential component of Blends 1 and 2.

  Blend 4 is a mixture of S-EB-S or S-EP-S triblock copolymer and low density polyethylene (LDPE) essentially compounded with 0-30 wt% S-EB or S-EP diblock copolymer. It is composed of Suitable LDPE polymers have a density in the range of 0.915 to 0.925 and a melt index of 3 to 20. The polymers are commercially available from various suppliers. The triblock / diblock component accounts for 45-90% by weight of the mixture and the LPDE component accounts for 10-55% by weight of the mixture.

  The isoprene unit in the S-I-S-I or S-I-S copolymer contains double bonds and may be sensitive to ultraviolet light. Therefore, it may be desirable to add a UV stabilizer to the blend when using a S-I-S-I copolymer.

  Tackifying resins are known to those skilled in the art, and various types of tackifying resins are commercially available. The tackifying resin used in the present invention is a hydrogenated, partially hydrogenated or non-hydrogenated hydrocarbon resin. Preferred resins are non-hydrogenated hydrocarbon resins or natural rosin resins. The tackifying resin preferably has a softening point in the range of 70 to 130 ° C, more preferably 80 to 105 ° C as measured by the ring and ball method (ASTM E28).

  The tackifying resin is present in an amount of 50 to 150 parts by weight per 100 parts by weight (pbw) of the block copolymer. Compositions containing less than 50 pbw do not have sufficient tack, compositions containing more than 150 pbw are not very tacky and are difficult to extrude with coextruded films. Preferably, the tackifying resin is present in an amount of 80 to 130 pbw, more preferably 90 to 120 pbw per 100 parts by weight of the block copolymer.

  Useful tackifying resins include hydrocarbon resins, synthetic polyterpenes, ester gums, which are semi-solid or solid at ambient temperature and usually soften or liquid at temperatures in the range of 70-135 ° C, preferably 85-120 ° C. Natural terpenes are included.

  Examples of major tackifying resins are compatible resins such as (1) natural and modified rosins such as gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin and polymerized rosin, (2) natural and Glycerol and pentaerythritol esters of modified rosin, for example, pale, glycerol ester of wood rosin, glycerol ester of hydrogenated rosin, glycerol ester of polymerized rosin, pentaerythritol ester of hydrogenated rosin and phenol modified pentaerythritol ester of rosin, (3 ) Natural terpene copolymers and terpolymers, such as styrene / terpene and α-methylstyrene / terpene, (4) polyterpene resins having a softening point of 80-150 ° C. as measured by ASTM method E28-58T; The terpene resin is usually obtained by polymerizing a terpene hydrocarbon (for example, a bicyclic monoterpene known as pinene) in the presence of a Friedel-Crafts catalyst at a moderate low temperature. (5) Phenol-modified terpene resin And a hydrogenated derivative thereof, for example, a resin product obtained by condensing a bicyclic terpene and phenol in an acidic medium, (6) an aliphatic petroleum hydrocarbon resin having a ring and ball softening point of 70 ° C to 135 ° C; the latter These resins are obtained by polymerizing monomers composed mainly of olefins and diolefins; including hydrogenated aliphatic petroleum hydrocarbon resins, (7) aromatic petroleum hydrocarbon resins and mixed aromatic-aliphatic Petroleum hydrocarbon resins and hydrogenated derivatives thereof, (8) aromatic modified alicyclic petroleum hydrocarbon resins and hydrogenated derivatives thereof, and (9) alicyclic stones Oil hydrocarbon resins and hydrogenated derivatives thereof.

  Preferred tackifying resins are those of the aforementioned subgroups (6), (7), (8) and (9), or a mixture thereof. It has been found that the most preferred tackifying resin belongs to the type of resin specified in subgroup 6. Examples of said resins are the trade names PICCOTAC, HERCULES MBG, HERCOTAC, WINGTACK and ESCOREZ, in particular the resin sold under PICCOTAC 212 or 1094, the resin sold by EXXON under the trade name ESCOREZ 2000 series, such as ESCOREZ 2203, It is a resin sold by GOODYEAR under trade names such as WINGTACK 95 and WINGTACK Extra. A preferred tackifying resin is PICCOTAC 212 or 1094 which is actually composed of a modified aliphatic hydrocarbon resin.

  The reinforcing layer 14 serves many functions. First, the reinforcing layer 14 facilitates handling of the film during manufacture and use. Second, when the film is wound on a roll during the manufacturing process, the reinforcing layer 14 is peeled away to prevent the continuous layers of film from sticking to each other (ie, preventing the film from “blocking”). Serving as a layer. Third, the reinforcing layer 14 maintains the topography of the surface contact layer 12. Fourth, the reinforcing layer provides resistance to elongation when the film is peeled off from the substrate 20. This is important for maintaining the integrity of the film.

  In many embodiments, the reinforcing layer 14 accounts for 15-20% of the total thickness of the film. Reinforcing layer 14 can be made of a polyolefin polymer, and in a preferred embodiment is made of high density polyethylene (HDPE), a blend of linear low density polyethylene (LDPE) and HDPE, or a blend of LDPE and polypropylene (PP). When using a blend of LDPE and HDPE, LDPE can comprise 5-30% by weight of the blend and HDPE can comprise 70-95% by weight. If a blend of LDPE and PP is used, LDPE may comprise 5-20% by weight of the blend and PP may comprise 80-95% by weight. Suitable LDPE polymers include those having a density of 0.915 to 0.925.

  In some embodiments, cyclic olefin polymers and copolymers (COP) may be used in the reinforcing layer. The polymers and copolymers described above have a fairly high density (ie> 1 g / cc) and tend to provide good reinforcement while still being flexible. When used in the reinforcing layer, COP is used in an amount of 60-90% and may be mixed with LDPE or linear medium density polyethylene (LMDPE).

  The core layer 16 also serves many functions. First, the core must be soft enough so that the surface contact layer can conform to the topography of the textured substrate. Second, the core must have good film tensile strength so that the film can be peeled from the substrate without leaving a residue. The core layer can also serve to impart the desired opacity and / or color, stiffness and toughness to the masking film.

  In a preferred embodiment, the core layer is composed of a polymer blend, such as a combination of HDPE and LDPE, a combination of PP and LDPE, or all LDPE. When using one of the above combinations, it is preferred that LDPE accounts for 5-40% by weight of the core layer. The core layer can account for 40-70% of the total thickness of the film. As noted above, the core layer is mixed to provide sufficient softness so that the surface contact layer can conform to the surface of the textured substrate.

  Fillers may be added to the core layer 16 and / or the reinforcing layer 14 to obtain certain desired properties including film texture, electrostatic discharge, abrasion resistance, printability, writeability, opacity and color. Fillers are well known in the art and include, for example, calcium carbonate, mica, titanium dioxide and silicon dioxide, synthetic silica, calcined clay and other synthetic fillers.

  The total thickness of the film is usually 25-100 microns. When applied to a textured substrate, the masking film is preferably 1-700 g / in, more preferably 1-150 g / in, more preferably 1-40 g / in, more preferably 1-10 g / in, most preferably It has a peel strength in the range of 1 to 5 g / in. The masking film can be made to be pulled from the textured substrate without leaving a residue, without tearing or stretching.

  In a preferred embodiment, the surface contact layer 12 includes a surface having a smoothness of 0 to 1.52 microns, more preferably 0 to 0.762 microns. The relatively rough or matte finish on the reinforcing layer 14 includes a roughness of 0.508-15.24 microns, more preferably 1.02-5.08 microns.

  It is preferred to produce the film by mixing the desired components of each layer, charging the blend into the respective extruder, and coextruding the film layers. Matte embossing (for example, one roll is a smooth roll and the other roll is extruded into a pair of textured nip rollers) provides a sufficient level of roughness to the reinforcing layer This is a preferred technique for applying. However, the reinforcement layer 14 may be textured using any suitable method, including but not limited to air impingement, air jets, water jets, and combinations thereof. The texture on the reinforcing layer is blocked by preventing the masking film surface from coming into intimate contact with another surface so that the masking film can be easily unwound and / or peeled off from another surface. To help prevent. This requirement also prevents wrinkles often associated with conventional masking films. Multilayer matte embossed film layers can also contain mechanical differential slip as opposed to chemically (anti-tack) induced differential slip.

  It is preferred to apply the masking film to a textured surface having a surface roughness “Ra” in the range of 3 to 100 microns. Throughout this specification, “smoothness” and “roughness” are defined as the arithmetic mean heights of micro-tops and micro-valleys of the surface relative to the center line of the surface as measured by a profilometer. The smoothness and roughness defined in this way are typically expressed in units of μm. All surface texture (relative smoothness and roughness) tests were performed according to ANSI / ASME test method B46.1-1985.

  The masking film disclosed herein protects textured surfaces such as polycarbonate, polyurethane, polyester, acrylic, polyvinyl chloride, nylon, PET, PETG, PEN, glass, ceramic, metal and various coatings. Especially suitable for. For example, the textured polycarbonate film can be velvet (about 3.81 micron Ra) and suede (12.7 to 17.8 micron Ra). The prismatic polyester can have a roughness in the range of 5.08 to about 50 microns. Vinyl floor tiles may have a roughness in the range of about 3.81 to about 10.16 microns.

A series of multilayer coextruded films were made using various blends according to the previous disclosure. All three-layer films were prepared such that each of layer A (surface contact layer) and layer C (reinforcing layer) accounted for 20% of the total film thickness and the core (layer B) accounted for the remaining 60%. The bilayer film contained 20% of the surface contact layer (Layer A) and the remaining 80% was the reinforcing layer (Layer C). Quad block and triblock copolymers with tackifiers were obtained from Kraton Polymers, LLC. Other ingredients were obtained from various commercial sources. The composition of the film is listed in Table 1. The density of the polymer used in the surface contact layer ranged from 0.90 for SEBS, ˜0.924 for LDPE, and ˜0.93 for the tackified block copolymer.

Several films were then tested for 180 ° peel adhesion to various substrates. The method includes placing the film against one of three polycarbonate prism substrates and laminating the film to the substrate by rolling the film using a 22 kg roller. The film was left at room temperature for 1-2 hours. The film was then peeled from the substrate by pulling the film at 180 ° (ie, the film was substantially parallel to the substrate surface) using an AR 1000 instrument at a rate of 12 ″ / min. The results are reported in Table 2.

  The masking film can provide a controlled, adjustable and sufficient level of protection to the textured surface without the use of pressure sensitive adhesives and without the disadvantages associated with pressure sensitive adhesives. The peel strength can be adjusted by adjusting the amount of quadblock, tackified triblock or non-tacked triblock copolymer component that is tackified based on the particular substrate. The unique effects of the protective film allow the film to be modified to suit the desired substrate chemistry and topography.

DESCRIPTION OF SYMBOLS 10 Film 12 Surface contact layer 14 Reinforcement layer 16 Core layer 20 Base material 22 Different place 110 Film 120 Base material 122 Summit

Claims (2)

A surface contact layer and a reinforcing layer, the surface contact layer essentially comprising
5-60 and Quad block styrenic block copolymer elastomer having a weight% tackifying, containing up to 30 wt% of diblock styrene copolymer, a mixture of 40 to 95 wt% of triblock styrene block copolymer
Film that is configured pressurized et al. a) adhering the film to a textured surface having a surface roughness of 5.08 to 50 microns of a substrate that is a prismatic polyester ;
b) the film is
5-60 and Quad block styrenic block copolymer elastomer having a weight% tackifying, containing up to 30 wt% of diblock styrene copolymer, a mixture of 40 to 95 wt% of triblock styrene block copolymer
Pressurized et essentially surface contact layer is configured, and include a reinforcing layer;
c) The method of adhering the film to the textured surface comprises positioning the surface contact layer against the textured surface such that the surface contact layer substantially matches the texture of the surface.

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