KR20010107976A - Backing for Adhesive Tape and Such Tape - Google Patents

Abstract

The present invention relates to films useful as tape supports, and more particularly to biaxially oriented polypropylene film supports and tapes comprising such supports. A brittle biaxially oriented polypropylene film is provided by minimizing nucleation density in the extruded and quenched polypropylene polymer cast sheet, and then maximizing the spherical growth rate of the formed quenched polymer. The cast sheet so formed is drawn at a temperature higher than the standard temperature in a sequential alignment step to produce a biaxially oriented polypropylene film. This method allows to produce more brittle films. The polypropylene composition, extrusion temperature, cast roll temperature (ie, quench temperature), and stretching temperature and other parameters are selected in accordance with the teachings herein so that the forming support or tape has the following desirable properties taken individually or in any desired combination. do:

A) MD break point tensile energy of about 90 N-mm / mm or less;

B) an MD fracture elongation of at least 70%;

C) breaking energy of about 130 N-mm or less;

D) distribution energy of about 350 N-cm / cm 2 or less;

E) When dispensed on commercially serrated plastic or metal dispenser blades, the serrated edges of the tape or support follow the contour of the dispensing blade snugly;

F) ability to tear by hand.

Description

Backing for adhesive tape and such tape

Biaxially oriented polypropylene films are typically used in applications where a combination of low cost and good mechanical and optical properties is advantageous. Some uses of such films include overpacking and adhesive tape supports.

An important factor in determining the properties of semicrystalline polymers such as polypropylene is the order of filling of the polymer chains. Crystallization is a means of controlling the degree and form of filling of the polymer chains. The degree and nature of this sequence has a huge impact on the final mechanical properties of the material.

Important parameters that control crystallization in polypropylene include (1) the total crystallinity, (2) the number of crystal entities per unit dose, also known as nucleation density, and (3) the presence of microcrystalline or microcrystalline aggregates (called spheres). Average diameter or size and (4) average distance between crystal entities. When extruding and quenching the polypropylene polymer from the melt, the polymer crystallizes into a lamellar structure that will lead to a spherical macrostructure in the final cast sheet. These lamellar and spherical structures are linked through tie molecules, which are part of a polymer chain extending from one lamellar to another. These tie molecules concentrate stress and distribute throughout the final material.

The prior art has suggested that it is advantageous for spherical macrostructures formed during the quenching of the polymer as small as possible. In order to achieve this, it has been proposed that the number of crystal entities per unit dose should be high and therefore the "undercooling" of the cast polymer by quenching should be high and rapid. It has also been suggested that it is desirable to maximize the growth rate of lamellar and spherical structures [D.W. van Krevelen, Chimia, 32 (8), August, 1978]. Van Krevelen developed a universal synthesis curve for the growth rate of the spherical well as a function of the ratio of crystallization temperature to polymer melting temperature. In the case of polypropylene, van xerylene has reported that the maximum spherical growth rate occurs at a crystallization temperature of about 90 ° C.

Commercially available pressure sensitive adhesive tapes are generally provided in the form of rolls fitted in tape dispensers (see, eg, US Pat. Nos. 4,451,533 and 4,908,278). Tape dispensers typically have a sawtooth cutting blade of metal or plastic. The "cleavability" of an adhesive tape is defined as the amount of energy or work required to cut or cut a length of tape by pulling the tape over the teeth on the cutting edge of the tape dispenser. Cleavability is also called "distribution".

The cut tape is not sculpted, cut longitudinally, broken or broken in an unpredictable manner (see, for example, US Pat. Nos. 4,451,533 and 4,908,278), so that the cut edges on the clean cut tape strips are cut. It is preferably formed in. Cleanly cut edges are desirable for aesthetic reasons in applications such as gift wrapping, sewing, and the like.

Cleavability is mainly determined by the mechanical properties of the support of the adhesive tape. Whether the adhesive tape can be easily cut depends on the deformation resistance (toughness) of the tape support film, also called the support. Typically, this support is coated or laminated with a surface layer to provide an adhesive surface and a release surface. In most cases, the energy required to cut the tape is largely determined by the support, regardless of the adhesive and other layers or coatings.

Several attempts to provide preferred biaxially oriented polypropylene films are known in the art (see, eg, US Pat. Nos. 4,451,533, 5,252,389 and 5,366,796). Several attempts to provide a tape support that can be teared by hand (typically in the transverse direction of the support) are known in the art (eg, US Pat. Nos. 3,491,877, 3,853,598, 3,887,745, 4,045,515, 4,137,362). 4,139,669, 4,173,676, 4,393,115, 4,414,261, 4,447,485, 4,513,028, 4,563,441, 4,581,087, 5,374,482 and 5,795,834).

Summary of the Invention

A brittle biaxially oriented polypropylene film is provided by minimizing nucleation density in the extruded and quenched polypropylene polymer cast sheet, and then maximizing the spherical growth rate of the formed quenched polymer. It is also desirable to stretch the cast sheet so formed at a temperature higher than the standard temperature in a subsequent orientation step to produce a biaxially oriented polypropylene film. This method allows to produce more brittle films.

The polypropylene composition, extrusion temperature, cast roll temperature (ie, quench temperature), and stretching temperature and other parameters are taught herein so that the forming film, support or tape has the following desirable properties, taken individually or in any desired combination. Thus is chosen:

A) about 90 N-mm / mm or less, more preferably about 30 to 90 N-mm / mm, even more preferably about 60 N-mm / mm or less, most preferably about 30 to 60 N-mm / mm MD breakpoint tensile energy of VII;

B) an MD fracture elongation of at least 70%, preferably from about 70 to 150%;

C) a breakdown energy of about 130 N-mm or less, more preferably about 70 N-mm or less, when tested according to the Failure Test described below;

D) a distribution energy of about 350 N-cm / cm 2 or less, more preferably about 170 N-cm / cm 2 or less, when tested according to the Dispense Test described below;

E) When dispensed on commercially serrated plastic or metal dispenser blades, the serrated edges of the tape or support follow the contour of the dispensing blade;

F) The ability to tear by hand in a TD, defined as a success rate of at least 50% as described below. More preferably, the support or tape may be hand teared with a success rate of at least 90%, most preferably 100% as described below;

F) The ability to tear by hand in the MD, defined as a success rate of at least 50% as described below. More preferably, the support or tape may be hand teared with a success rate of at least 90%, most preferably 100%, as described below.

One aspect of the invention provides an adhesive tape comprising a support and an adhesive layer on the support. The support comprises polypropylene and was biaxially oriented with the MD and TD of the support. The support is tearable by hand in the TD, and when the support is cut on a sawtoothed plastic cutting blade, the support exhibits a serrated edge that fits snugly to the contour of the blade.

In one preferred embodiment of the tape, the support comprises a single layer.

In another preferred embodiment of the tape, when the support is cut according to the dispensing test, the support has an MD cutting energy of 350 N-cm / cm 2 or less. Even more preferably, the support has an MD cleavage energy of 170 N-cm / cm 2 or less.

In another preferred embodiment of the tape, when the support is tested according to the breaking test, the support has a breaking energy of 130 N-mm or less. Even more preferably, the support has a breaking energy of 70 N-mm or less.

In another preferred embodiment of the tape, the support has an MD fracture tensile energy of 90 N-mm / mm or less.

In another preferred embodiment of the tape, the support has a MD elongation at break of at least 70%.

In another preferred embodiment of the tape, the support is tearable by hand in the MD.

In another aspect, the present invention provides a replacement adhesive tape comprising a support and an adhesive layer on the support. The support comprises polypropylene and was biaxially stretched. The support has a first direction break tensile energy of 90 N-mm / mm or less and when the support is cut on a sawtoothed plastic cutting blade, the support exhibits a sawtooth edge that fits snugly to the contour of the blade.

In one preferred embodiment of the tape, the support comprises a single layer.

In another preferred embodiment of the tape, the first direction is MD.

In another preferred embodiment of the tape, the support has a MD elongation at break of at least 70%.

In another preferred embodiment of the tape, the support is tearable by hand in the TD. More preferably, the support is also tearable by hand in the MD.

In another preferred embodiment of the tape, when the support is cut according to the dispensing test, the support has an MD cutting energy of 350 N-cm / cm 2 or less. More preferably, the support has an MD cleavage energy of 170 N-cm / cm 2 or less.

In another preferred embodiment of the tape, when the support is tested according to the fracture test, the support has a breaking energy of 130 N-mm or less. More preferably, the support has a breaking energy of 70 N-mm or less.

In another aspect, the present invention provides another alternative adhesive tape comprising a support and an adhesive layer on the support. The support comprises polypropylene and was biaxially stretched with MD and TD. The support has an MD fracture tensile elongation of 70% to 150% and is tearable by hand in TD.

In one preferred embodiment of the tape, the support comprises a single layer.

In another preferred embodiment of the tape, when the support is tested according to the fracture test, the support has a breaking energy of 130 N-mm or less. More preferably, the support has a breaking energy of 70 N-mm or less.

In another preferred embodiment of the tape, when the support is cut on a serrated plastic cutting blade, the support exhibits a serrated edge that fits snugly to the contour of the blade.

In another preferred embodiment of the tape, when the support is cut according to the dispensing test, the support has an MD cutting energy of 350 N-cm / cm 2 or less. More preferably, the support has an MD cleavage energy of 170 N-cm / cm 2 or less.

In another preferred embodiment of the tape, the support has an MD fracture tensile energy of 90 N-mm / mm or less.

In another preferred embodiment of the tape, the support is tearable by hand in the MD.

In another aspect, the present invention provides another alternative adhesive tape comprising a support and an adhesive layer on the support. The support comprises polypropylene and was biaxially stretched with MD and TD. The support is tearable by hand in TD and MD.

In one preferred embodiment of the tape, the support comprises a single layer.

In another preferred embodiment of the tape, when the support is tested according to the fracture test, the support has a breaking energy of 130 N-mm or less. More preferably, the support has a breaking energy of 70 N-mm or less.

In another preferred embodiment of the tape, when the support is cut on a serrated plastic cutting blade, the support exhibits a serrated edge that fits snugly to the contour of the blade.

In another preferred embodiment of the tape, when the support is cut according to the dispensing test, the support has an MD cutting energy of 350 N-cm / cm 2 or less. More preferably, the support has an MD cleavage energy of 170 N-cm / cm 2 or less.

In another preferred embodiment of the tape, the support has an MD fracture tensile energy of 90 N-mm / mm or less.

In another preferred embodiment of the tape, the support has a MD elongation at break of at least 70%.

In any of the tapes described above, the support preferably has an MD draw ratio of at least 4: 1.

In any of the tapes described above, the support preferably has a TD draw ratio of at least 7: 1.

In any of the tapes described above, the support preferably has a MD draw ratio of at least 4: 1 and a TD draw ratio of at least 7: 1.

The present invention provides such films, tape supports made from such films, tapes comprising the supports, and methods of making the films, supports and tapes thereof.

While most are well known, certain terms are used in the description and the claims that may require some explanation. As used herein to describe a film, “biaxially stretched” refers to the film being stretched in two different directions, first direction and second direction, in the plane of the film. Typically, but not always, the two directions are substantially perpendicular and the machine direction of the film ("MD") (the direction in which the film is produced on the film maker) and the transverse direction of the film ("TD") (the direction perpendicular to the MD of the film). )to be. MD is sometimes called longitudinal ("LD"). Biaxially stretched films may be drawn sequentially, simultaneously drawn or by some combination of simultaneous and sequential stretching. “At the same time biaxially stretched” when used herein to describe a film, indicates that a significant portion of stretching in each of the two directions is performed simultaneously. Unless the context otherwise requires, the terms "orientation," "take", and "stretch" are interchangeable throughout, and the terms "orientated," "taken" and "stretched" and the term "orientated," The same is true of "and" stretching.

The term "stretch ratio", as used herein to describe the stretching method and the stretched film, refers to the ratio of the linear dimensions of the same portion of the stretched film to the linear dimension of a portion of the film before stretching. For example, in a stretched film with an MD draw ratio (“MDR”) of 5: 1, some portion of the unstretched film with a 1 cm linear measurement in the machine direction will have a 5 cm measurement in the machine direction after stretching. . In a stretched film with a TD draw ratio (“TDR”) of 9: 1, certain portions of the unstretched film having a 1 cm linear measurement in the transverse direction will have a 9 cm measurement in the transverse direction after stretching.

As used herein, "area draw ratio" refers to the ratio of the area of the same portion of a stretched film to the area of a portion of the film before stretching. For example, in a biaxially stretched film having a total area draw ratio of 50: 1, certain 1 cm 2 portions of the unstretched film will have an area of 50 cm 2 after stretching.

The mechanical draw ratio, also known as the nominal draw ratio, is determined by the undrawn and drawn dimensions of the entire film and can be measured in a film gripper at the film edge, which is typically used to stretch the film in the particular apparatus used. The total draw ratio is the total draw ratio of the next film that lies near the gripper and excludes from consideration the part affected during drawing by the gripper. The overall draw ratio may be equivalent to the mechanical draw ratio when the input unstretched film has a constant thickness over its entire width and the effect of being close to the gripper at the time of stretching is small. However, more typically the thickness of the input unstretched film is adjusted to be thicker or thinner near the gripper than at the center of the film. In that case, the overall draw ratio will be different from the mechanical or nominal draw ratio. This total or mechanical draw ratio should be distinguished from the local draw ratio. Local draw ratios are determined by measuring specific portions (eg, 1 cm portions) of the film before and after stretching. When the stretching is not substantially uniform for the film where the entire edge is cut off, the local ratio may differ from the overall ratio. When the stretching is substantially uniform over the entire film (except near the edge and the side of gripper attention along the edge), the local ratio will be substantially equal to the overall ratio. Unless the context otherwise requires, the term draw ratio is used herein to describe the overall draw ratio.

The present invention relates generally to films useful as tape supports, and more particularly to biaxially oriented polypropylene film supports and tapes comprising such supports.

The invention will be further described with reference to the accompanying drawings, wherein like structures are designated by like reference numerals in the several views,

1 is an isometric view of a length of tape according to the present invention;

2 is a side view of a roll of adhesive tape according to the present invention;

3 is an isometric view of a test fixture used to test the cutting characteristics of a film according to the present invention;

4 is an isometric view of a metal dispenser blade useful for the test fixture of FIG. 3;

5 is a side view of the metal dispenser blade of FIG. 4;

6 is a side view of a portion of the apparatus of FIG. 3 and the metal dispenser blade of FIG. 6;

7 is an illustration of a typical cut or dispense test curve for the polypropylene tape support of the present invention;

8 is an enlarged photograph of a polypropylene film according to the present invention (Example E5) cut according to the test method described herein;

9 is an enlarged photograph of a prior art polypropylene film (Example C1) cut according to the test method described herein.

Referring to FIG. 1, a length of tape 10 is shown in accordance with one preferred embodiment of the present invention. The tape 10 comprises a biaxially oriented polypropylene film support 12 comprising a first major surface 14 and a second major surface 16. Preferably, the support 12 has a thickness of about 0.002 to about 0.006 cm. The support 12 of the tape 10 is coated on the first major surface 14 with an adhesive layer 18. Adhesive 18 may be any suitable adhesive as known in the art. The support 12 can have a selective peel or low adhesive backsize layer 20 coated on the second major surface 16 as known in the art.

The support film 12 preferably comprises polypropylene. For the purposes of the present invention, the term "polypropylene" is meant to include copolymers comprising at least about 90% by weight of propylene monomer units. "Polypropylene" is also meant to include a polymer mixture comprising at least about 75 weight percent polypropylene. Polypropylene for use in the present invention is preferably predominantly isotactic. Co-array polypropylene has a chain homomorphism index of at least about 80%, n-heptane soluble content of less than about 15% by weight, and about as measured according to ASTM D1505-96 ("Density of Plastics by the Density-Gradient Technique"). And a density of 0.86 to 0.92 g / cm 3. Typical polypropylenes for use in the present invention have a melt flow index of about 0.1 to 15 g / 10 minutes according to ASTM D1238-95 (“Flow Rates of Thermoplastics by Extrusion Plastometer”) at a temperature of 230 ° C. and a force of 2160 g, It has a weight average molecular weight of about 100,000 to 400,000 and a polydispersity index of about 2 to 15. Typical polypropylenes for use in the present invention have a peak melting temperature as determined using a differential scanning calorimeter of greater than about 130 ° C., preferably greater than about 140 ° C., most preferably greater than about 150 ° C. Has In addition, the polypropylenes useful in the present invention may be copolymers, terpolymers, etc., having ethylene monomer units and / or alpha-olefin monomer units having 4 to 8 carbon atoms, wherein the comonomer (s) are described herein. It is present in an amount that does not adversely affect the desired properties and characteristics of the support and the tape, and typically its content is less than 10% by weight. One suitable polypropylene resin is Pina Oil & Chemical Co. Is a co-array polypropylene homopolymer resin having a melt flow index of 2.5 g / 10 min, available as product registration number 3374 from FINA Oil and Chemical Co., Dallas, TX.

Polypropylene for use in the present invention may optionally comprise synthetic or natural resins having a molecular weight of about 300 to 8000 and a softening point of about 60 to 180 ° C. in amounts such that they do not adversely affect the desired features and properties described herein. have. Typically such resins are selected from 1 to 4 main classes: petroleum resins, styrene resins, cyclopentadiene resins and terpene resins. Optionally, resins from any of these classes can be partially or fully hydrogenated. Petroleum resins typically have styrene, methylstyrene, vinyltoluene, indene, methylindene, butadiene, isoprene, piperylene and / or pentylene as monomer components. Styrene resins typically have styrene, methylstyrene, vinyltoluene and / or butadiene as monomer components. Cyclopentadiene resins typically have cyclopentadiene and optionally other monomers as monomer components. Terpene resins typically have pinene, alpha-pinene, dipentene, limonene, myrcene and camphor as monomeric components.

Polypropylene for use in the present invention may optionally include additives and other components as is known in the art. For example, the films of the present invention may contain fillers, pigments and other colorants, anti-sticking agents, lubricants, plasticizers, processing aids, antistatic agents, antioxidants and heat stabilizers, ultraviolet light stabilizers and other modifiers. Fillers and other additives are preferably added in selected effective amounts so as not to substantially affect the nucleation of the cast film and to adversely affect the properties obtained by the preferred embodiments described herein. Typically such materials are added to the polymer before it is made into an oriented film (eg, in the polymer melt before being extruded into the film).

The polypropylene can be cast in sheet form by devices known to those skilled in the art if it is cast according to the preferred temperatures and methods described herein. Thereafter, such cast film is stretched to reach the preferred film described herein. When producing the polypropylene film, a suitable method of casting the sheet is to feed the resin to a feed hopper of an extruder barrel temperature having an extruder barrel temperature adjusted to produce a single screw, a twin screw, a cascade or a suitable homogeneous melt. The polypropylene melt can be extruded through a sheet die onto a rotationally cooled metal casting wheel. Optionally, the casting wheel may be partially immersed in the fluid filled cooling tank, or optionally the cast sheet may be passed through the fluid filled cooling tank after removal from the casting wheel. Such operating temperatures can be selected by those skilled in the art to take advantage of the teachings herein to provide the desired nucleation density, size, and growth rate so that the stretched film formed has the desired characteristics and properties described herein. . This temperature will vary depending on the material used and the heat transfer characteristics of the particular device used. For one particular arrangement, the following temperatures are preferred. Preferably, the polypropylene composition is extruded at a temperature of about 245-250 ° C. Preferably, the cast roll is at a temperature of at least 90 ° C, more preferably of about 90-94 ° C.

Thereafter, the sheet is stretched to provide a support 12 having the desired features and properties described herein. Preferably, the support is biaxially stretched.

In one preferred sequential stretching embodiment, the MD stretching ratio is about 4: 1 to 6: 1. More preferably, the MD draw ratio is about 4.5: 1 to about 5.5: 1. In another preferred sequential stretching embodiment, the TD draw ratio is at least 7: 1. More preferably, the TD draw ratio is about 7: 1 to about 12: 1. In another preferred sequential draw aspect, the MD draw ratio is about 4: 1 to about 6: 1 and the TD draw ratio is at least 7: 1. More preferably, the MD draw ratio is about 4.5: 1 to about 5.5: 1 and the TD draw ratio is about 7: 1 to about 11: 1. One particularly preferred support is one that is biaxially drawn sequentially with an MD draw ratio of about 5: 1 and a TD draw ratio of about 8: 1 to 10: 1.

In one preferred simultaneous biaxial draw embodiment, the area draw ratio is from about 35: 1 to about 108: 1. More preferably, the area draw ratio is about 45: 1 to about 60: 1. The MD component and TD component of these embodiments are selected to provide the desired properties and characteristics described herein.

Preferred properties described herein can be obtained by any suitable device for biaxially oriented the support 12 in accordance with the preferred methods described herein. Of all stretching methods, preferred apparatus for commercial production of films for tape support are first drawn into MD and then diverted through a film on a series of rotating rollers that typically provide a discharge film line speed faster than the feed rate. Known sequential biaxial stretching apparatus for TD stretching in a tenter on a rail; Mechanical tenters for simultaneous biaxial stretching such as devices described in US Pat. Nos. 4,330,499 and 4,595,738; And tenter devices for simultaneous biaxial stretching described in US Pat. Nos. 4,675,582, 4,825,111, 4,853,602, 5,036,262, 5,051,225, and 5,072,493. Although biaxially stretched films can be produced by tubular blown films or flat film tenter stretching processes, the films of the present invention are flat to avoid processing difficulties that may arise with tubular blown film processes when used as tape supports. It is preferable to be manufactured by the film stretching apparatus.

The temperature of the stretching operation can be selected by those skilled in the art to take advantage of the teachings herein to provide films with the desired features and properties described herein. This temperature will vary depending on the material used and the heat transfer characteristics of the particular device used. In one preferred sequential stretching apparatus, the preheat rolls and stretching rolls for MD stretching are preferably maintained at about 120-135 ° C. It is also preferred that the preheat zone is maintained at about 180-190 ° C. and the draw zone is maintained at about 160-177 ° C. when TD stretching in the tenter. In the case of co-stretched supports, the preheating and stretching is preferably about 170 to 200 ° C.

The support 12 useful in the present invention, when used as a support for the tape 10, preferably has a final thickness of about 0.002-0.006 cm. The variation in film thickness is preferably less than about 5%. Thicker or thinner films can be used while understanding that the film must be unnecessarily hard or rigid and not too thick to be difficult to handle or use, but thick enough to avoid excessive flimsiness and handling difficulties.

The polypropylene composition, extrusion temperature, cast roll temperature, and stretching temperature and other parameters are selected according to the teachings herein so that the forming support or tape has the following desirable properties, taken individually or in any desired combination:

A) about 90 N-mm / mm or less, more preferably about 30 to 90 N-mm / mm, even more preferably about 60 N-mm / mm or less, most preferably about 30 to 60 N-mm / mm MD breakpoint tensile energy of VII;

B) an MD fracture elongation of at least 70%, preferably from about 70 to 150%;

C) a breaking energy of about 130 N-mm or less, more preferably about 70 N-mm or less, when tested according to the fracture test described below;

D) a distribution energy of up to about 350 N-cm / cm 2, more preferably up to about 170 N-cm / cm 2 when tested according to the dispensing test described below;

E) When dispensed on commercially serrated plastic or metal dispenser blades, the serrated edges of the tape or support follow the contour of the dispensing blade;

F) The ability to tear by hand in a TD, defined as a success rate of at least 50% as described below. More preferably, the support or tape may be hand teared with a success rate of at least 90%, most preferably 100% as described below;

F) The ability to tear by hand in the MD, defined as a success rate of at least 50% as described below. More preferably, the support or tape may be hand teared with a success rate of at least 90%, most preferably 100%, as described below.

The above properties and features are described herein in terms of preferred embodiments and reported herein for examples for films or supports 12 that do not apply adhesive 18 thereon. In most cases, the features and properties are largely determined by the support, almost without regard to the adhesive or other layer or coating. Therefore, the above preferred features and properties also apply to the adhesive tape of the present invention.

One preferred embodiment of the present invention comprises a monolayer support. As used herein, the term monolayer includes multiple layers of substantially the same material.

The adhesive 18 coated on the first major surface 14 of the tape support 12 can be any suitable adhesive as known in the art. Preferred adhesives are those which can be activated by pressure, heat or combinations thereof. Suitable adhesives include those based on acrylates, rubber resins, epoxies, urethanes or mixtures thereof. The adhesive 18 can be applied by solution, water based or hot melt coating. Adhesives may include laminating, thermally activated and water-activated adhesives as well as hot melt coated formulations, transfer coated formulations, solvent coated formulations and latex formulations. Useful adhesives according to the present invention include all pressure sensitive adhesives. Pressure sensitive adhesives are well known for having properties including dry and permanent tack, adhesion by pressure less than finger pressure, and sufficient ability to retain on adherends. Examples of adhesives useful in the present invention include polyacrylates; Polyvinyl ethers; Diene rubbers such as natural rubber, polyisoprene and polybutadiene; Polyisobutylene; Polychloroprene; Butyl rubber; Butadiene-acrylonitrile polymer; Thermoplastic elastomers; Block copolymers such as styrene-isoprene and styrene-isoprene-styrene (SIS) block copolymers, ethylene-propylene-diene polymers and styrene-butadiene polymers; Poly-alpha-olefins; Amorphous polyolefins; silicon; Ethylene containing copolymers such as ethylene vinyl acetate, ethyl acrylate and ethyl methacrylate; Polyurethane; Polyamides; Epoxy; Polyvinylpyrrolidone and vinylpyrrolidone copolymers; Polyester; And those based on the general composition of the above mixtures or blends (continuous or discontinuous phase). The adhesive may also contain additives such as tackifiers, plasticizers, fillers, antioxidants, stabilizers, pigments, diffusion materials, curing agents, fibers, filaments and solvents. In addition, the adhesive may optionally be cured by known methods.

A general description of useful pressure sensitive adhesives is described in Encyclopedia of Polymer Science and Engineering, Vol. 13, Wiley-Interscience Publishers (New York, 1988). Further description of useful pressure sensitive adhesives is described in the Encyclopedia of Polymer Science and Technology, Vol. 1, Interscience Publishers (New York, 1964).

The film support 12 of the tape 10 may optionally be treated by flame exposure or other surface treatment including corona discharge or chemical coating to improve the adhesion of subsequent coating layers. In addition, as is well known in the art of making adhesive coated tapes, the second surface 16 of the film support 12 is coated with any low-adhesive backsize material 20 to form the opposing surface adhesive layer 18 and the film 12. By limiting the adhesiveness between the sheets), it becomes possible to produce an adhesive tape roll that can be easily unwound. The tape 10 may optionally be spirally wound to produce a roll 22 on the core 24 as illustrated in FIG. 2.

The supports described herein are well suited for many adhesive tape support applications. Since the support can conform to the surface shape of the object to be attached, it is useful as a masking tape support. The support is also well suited for other applications including utility tapes and low load sealing tapes.

The operation of the present invention will be further described with reference to the following detailed examples. These examples are provided to further illustrate various specific and preferred aspects and techniques. However, it should be understood that many variations and modifications may be made within the scope of the invention.

Test Methods

Film Tensile Properties Measurement

The mechanical direction (MD) break tensile energy and break tensile elongation of the film were measured according to the procedure described in ASTM D-882 (“Tensile Properties of Thin Plastic Sheeting,” Method A). The film was conditioned for 24 hours at 22 ° C. (72 ° F.) and 50% relative humidity (RH) prior to testing. The test was performed using a tensile tester commercially available as Model No. Sintech 400 / S from MTS Systems Corporation (Eden Prairie, MN). Samples for this test were 1.25 cm wide and 15 cm long. Initial jaw separation of 5 cm and crosshead speed of 50.8 cm / min were used. Ten specimens were tested for each sample in the MD.

Fracture Energy Measurement

Fracture energy was measured using a model number Sintech 400 / S tensile tester manufactured by MTS Systems Corporation (Eden Prairie, MN). A clamp assembly consisting of two rigid plates with a 7.62 cm diameter hole in the center of each plate was used. A plunger consisting of a 0.318 cm diameter steel rod with a hemispherical tip was used. The displacement of the plunger assembly was measured during the load and complete penetration of each test piece. The test piece was cut into 1.9 cm wide strips parallel to the MD. The test piece had a length of 12.7 cm to allow proper clamping in the clamp assembly. Each test was performed at a rate of 254 cm / min. Five or more specimens were tested for each measurement.

For each test, the test piece was clamped into the assembly. Each specimen was centered across the plate opening. A piece of pressure-sensitive adhesive tape was used to allow the weight (75 g) to hang on the other side of the test specimen to keep the sample loaded under constant tension while maintaining the sample on one side of the bottom plate of the clamp assembly. Thereafter, the clamping plate was tightened using the thumbscrews to prevent the sample from slipping during the test. The clamp assembly was placed under the plunger so that the path of the plunger was through the center of the sample. The total energy needed to break the sample was measured.

As used herein, including in the claims, the term “destructive test” relates to the test just described.

TD hand tear measurement

Ten film specimens were cut out parallel to the MD with a 2.5 cm width using a razor blade. Thus, the sample had a smooth edge as it did not contain intentional irregularities, roughness, scratches or other tear initiation sites. Hand tearing along the TD was attempted 10 times at 22 ° C. The success rate of tear is considered to be indicative of TD tear characteristics.

MD hand tear measurement

Ten film specimens were cut out parallel to the TD by 2.5 cm width using a razor blade. Thus, the sample had a smooth edge as it did not contain intentional irregularities, roughness, scratches or other tear initiation sites. Hand tearing along the MD was attempted 10 times at 22 ° C. The success rate of tearing is considered to be indicative of MD tearing characteristics.

Confirmation of appearance of serrated edges on film

Films prepared according to the invention and comparative films described herein were dispensed on a sawtoothed plastic blade (3M Catalog # 105, sold as of this application date from Minnesota Mining and Manufacturing Company, St. Paul, Minnesota). Films dispensed on this day were photographed using a Model Laborlux 12 POL microscope manufactured by Leitz, Wetzler, Germany. The sample was tested at 50 times magnification between quadrature polarizers with quarter wave shift plates. Each of Examples E1 to E5 of the present invention was observed to have a sawtooth edge that closely fits the contour of the cutting blade. Each of Comparative Examples C1 to C7 had jagged edges that were irregular and did not fit snugly to the contour of the cutting edge.

8 is an enlarged photograph 10 times of the polypropylene film according to Example E5 of the present invention. The serrated edge of the cut support appears to fit snugly against the contour of the plastic cutting blade. 9 is a 10-fold magnification of a prior art polypropylene film example C1. The cut edges do not appear to fit snugly into the contour of the cutting protrusion of the plastic dispenser blade.

Cutting characteristics: dispensing test of film

Test specimens 1.91 cm wide and 15 cm long were cut lengthwise from the uncoated sample film using a razor blade equipped with a new blade. The test pieces were conditioned for 24 hours at 25 ° C. and 50% relative humidity before testing.

The test fixture used to measure cleavability is shown in FIG. 3. The test facility is a commercially available tape dispenser 100M mounted on a 15.2 cm x 15.2 cm x 1.1 cm aluminum rear mounting plate 102 (metal cutting edge device sold as of this application date from Minnesota Mining & Manufacturing Co., St. Paul, MN). Scotch (trade name) Cat.H-127 polystyrene two-component mold dispenser). The dispenser was placed between the rear mounting plate 102 and the 0.3 cm thick aluminum front mounting plate 104 milled to the contour of the test dispenser 100 M to prevent it from bending during the cutting test. The test dispenser was held firmly in the position between the front 104 and rear 102 mounting plates by screwed thumb screws 106. The rear mounting plate 102 was attached to a 2.4 cm diameter cylindrical base mounting stud 108 by a small screw 110. The base mounting stud 108 was milled to include a 90 ° angle cutout such that the rear mounting plate 102 is maintained at the vertical centerline of the tensile tester, ie the angle between the axis of the rear mounting plate 102 and the test dispenser 100M. Was 0 ° with respect to the machine center line. Base stud 108 was attached to the test machine deck by locking a pin inserted into drillout 109 in the base stud.

The test dispenser 100M was mounted on the rear mounting plate 102 by inserting the dispenser hub on an aluminum hub mounting shaft 112 screwed to the rear mounting plate 102. The bottom of the dispenser was placed on a sheet 115 that prevents the dispenser from rotating during the test. The test dispenser was mounted so that the protrusion line of the dispenser cutting blade was perpendicular to the machine centerline. In this way, the film to be tested was substantially evenly loaded throughout its width when cut.

The dispenser 100M included the steel serrated cutting blade 120 illustrated in FIGS. 4 and 5. The steel cutting blade 120 was formed of nickel surface coated steel about 0.05 cm thick, which was at least about the width of the film 12 and in a direction corresponding to the reference direction R of the film 12 extending over the blade. 0.3 cm long rectangular land portions 122 were included. Land portion 122 defines a generally planar surface at which the test sample is temporarily cut. The blade 120 also included a blade support portion 126 at the rear edge of the land portion 122 such that the land portion formed an angle β of 80 ° with the support 126. The blade support 126 is about 1.32 cm long. The blade 120 further included a generally U-shaped portion 128 at the edge of the land portion opposite the support portion with the protrusion line 130 along its distal edge. Each protrusion 130 is generally triangular, has a tip in the plane of land 122 or slightly lower and spaced about 0.12 cm from the tip of adjacent protrusion 130, about 0.06 cm in height, about 0.003 cm It is defined by the vertex 132 of the protrusion 130, which is defined by the sharpness defined by the bending radius of and the narrow angle of 60 degrees. The protrusion 130 protrudes outward from the plane of the blade support portion 126 at an angle α of about 50 °. Generally the sides of the U-shaped portion 128 are at an angle γ of 72 ° with respect to each other.

A piece of double coated adhesive tape (Scotch ™ Cat. 665) was affixed to the land face 122 and the test piece was firmly attached to the adhesive surface of the double coated tape with finger pressure to prevent forward movement during cut testing. The specimens were aligned at an angle of 0 ° to the machine centerline so that the force of the dispenser was substantially evenly distributed over the sample width. The dispenser 100M was oriented so that the tip of the cutting blade 120 was just below the jaws 162. The dispenser was oriented at an angle such that the land 122 was at an angle σ ₁ of 110 ° with respect to the vertical direction of movement A of the tester (the cutting blade for the jaws 162 with the dispenser and test fixture removed for the purpose of illustration only). 6 illustrating only 120).

Thereafter, the free end of the test piece was clamped in the upper jaw 162 of the tensile tester so that the distance between the upper jaw and the cutting blade 120 was 10.2 cm. The test piece was loaded without tension so that the cutting blade did not contact the test piece prior to the start of the test. The upper jaw was attached to the mechanical crosshead moved on the support rail 103. The specimen was then preloaded with tension to a value of 0.9 N to come into contact with the cutting edge 120. Thereafter, the support 12 was pulled in the direction A by the jaws 162 at a speed of 30 cm / min. The load and elongation of the test piece were measured and recorded, and the cut energy was calculated from the area under the load / elongation as illustrated in FIG. 7 and is shown in Table 2. In Figure 7, the load is indicated along the vertical axis and the elongation is indicated on the horizontal axis. Load and elongation increase along portion 200 of the curve until peak load 202 is reached, where elongation is indicated by 204. Thereafter, the load decreases as the elongation continues along the portion 206 of the curve. As reported herein, energy is calculated for the curved portion from zero elongation to elongation 204 at maximum load 202. The protrusion of the dispenser breaks the film near the point of maximum load 202, at which time the load is believed to be reduced when the break through the film leads to a complete cut.

As used herein, including in the claims, the term "distribution test" relates to the test just described.

Preparation of Examples

Example E1

A monolayer film with a final thickness of 0.030 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.8 g / 10 min at 230 ° C. and a 2160 g load (ASTM D1238) and a melting temperature of 157.8 ° C. The extruded film was sent onto a casting roll, cooled, stretched in the longitudinal direction, then stretched transversely and thermoset.

Example E2

A monolayer film with a final thickness of 0.033 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 1.8 g / 10 min at 230 ° C. and a 2160 g load (ASTM D1238) and a melting temperature of 164.0 ° C. The extruded film was sent onto a casting roll, cooled, stretched longitudinally, stretched transversely and thermoset.

Example E3

A monolayer film with a final thickness of 0.020 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.5 g / 10 min at 230 ° C. and a 2160 g load and a melting temperature of 161.5 ° C. The extruded film was sent on a casting roll and cooled. Thereafter, the extruded film was simultaneously drawn in both the transverse and longitudinal directions.

Example E4

Example E4 was prepared as reported in Example E3 except for a final thickness and draw ratio of 0.022 mm.

Example E5

A monolayer film with a final thickness of 0.036 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.5 g / 10 min at 230 ° C. and a 2160 g load and a melting temperature of 161.5 ° C. The extruded film was sent onto a casting roll, cooled, stretched longitudinally, stretched transversely and thermoset.

Comparative Example C1

A monolayer film with a final thickness of 0.030 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.8 g / 10 min at 230 ° C. and a 2160 g load (ASTM D1238) and a melting temperature of 157.8 ° C. The extruded film was sent onto a casting roll, cooled, stretched longitudinally, stretched transversely and thermoset.

Comparative Example C2

A monolayer film with a final thickness of 0.039 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.5 g / 10 min at 230 ° C. and a 2160 g load and a melting temperature of 161.5 ° C. The extruded film was sent onto a casting roll, cooled, stretched longitudinally, stretched transversely and thermoset.

Comparative Example C3

A monolayer film with a final thickness of 0.038 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.5 g / 10 min at 230 ° C. and a 2160 g load and a melting temperature of 161.5 ° C. The extruded film was sent onto a casting roll, cooled, stretched longitudinally, stretched transversely and thermoset.

Comparative Example C4

A monolayer film with a final thickness of 0.038 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.5 g / 10 min at 230 ° C. and a 2160 g load and a melting temperature of 161.5 ° C. The extruded film was sent onto a casting roll, cooled, stretched longitudinally, stretched transversely and thermoset.

Comparative Example C5

A monolayer film with a final thickness of 0.038 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.5 g / 10 min at 230 ° C. and a 2160 g load and a melting temperature of 161.5 ° C. The extruded film was sent onto a casting roll, cooled, stretched longitudinally, stretched transversely and thermoset.

Comparative Example C6

A monolayer film with a final thickness of 0.031 mm was prepared by extruding a polypropylene homopolymer having a melt flow index of 2.5 g / 10 min at 230 ° C. and a 2160 g load and a melting temperature of 161.5 ° C. The extruded film was sent onto a casting roll and cooled. Thereafter, the extruded film was simultaneously drawn in both the longitudinal and transverse directions.

Comparative Example C7

Comparative Example C7 was prepared as reported in C6 except for a final thickness and draw ratio of 0.028 mm.

These examples were prepared as described in Table 1 below. The draw ratios shown are the total draw ratios. Specific examples were tested by the specific method described above. The results of such tests are reported in Table 2 below.

Example Extrusion (℃) Cast roll (℃) MD draw ratio TD draw ratio Sequential stretching Simultaneous stretching MD stretching TD stretching Thermosetting (℃) Preheat Roll (℃) Stretch Roll (℃) Preheat Zone (℃) Stretch band (℃) Preheat (℃) Stretching (℃) E1 250 90 5: 1 9: 1 130 130 184 160 160 - - E2 245 90 5: 1 11: 1 135 135 180 177 146 - - E3 245 90 5: 1 9: 1 - - - - - 170 170 E4 245 90 7: 1 7: 1 - - - - - 170 170 E5 245 94 5: 1 10: 1 135 135 190 174 145 - - C1 250 34 5: 1 9: 1 125-134 136 177 159 160 - - C2 245 50 5: 1 8.7: 1 135 135 165 165 145 - - C3 245 50 5: 1 9: 1 135 135 180 165 145 - - C4 245 80 5: 1 8.3: 1 135 135 165 165 145 - - C5 245 80 5: 1 8.7: 1 135 135 180 165 145 - - C6 245 90 5: 1 9: 1 - - - - - 160 160 C7 245 90 7: 1 7: 1 - - - - - 160 160

Example MD fracture tensile energy (N-mm / ㎜) MD Elongation at Break (%) Fracture Energy (N-mm) Distribution energy (N-cm / cm 2) TD hand tear (%) MD hand tear (%) E1 32 70 69 167 100 100 E2 62 145 7 155 100 100 E3 57 74 - - 90 - E4 62 73 - - - 100 E5 89 145 127 322 100 100 C1 130 136 719 519 30 10 C2 170 141 529 455 0 0 C3 160 138 542 360 0 0 C4 150 137 565 355 0 0 C5 100 122 260 500 30 0 C6 120 104 - - - 0 C7 144 95 - - - 0

The above tests and test results are for illustration only, not for prediction, and changes in the test procedure may be expected to yield different results.

The present invention has been described with reference to some embodiments thereof. The foregoing detailed description and examples have been given for clarity of understanding only. Unnecessary limitations should not be understood therefrom. All patents and patent applications cited herein are hereby incorporated by reference. It will be apparent to those skilled in the art that many changes can be made in the described embodiments without departing from the scope of the invention. Thus, the scope of the present invention should be limited not by the exact details and structures described herein, but by the structures described by the terms of the claims and their equivalents.

Claims (49)

A support and an adhesive layer on the support, wherein the support comprises polypropylene, the support is biaxially oriented in its MD and TD, the support is tearable by hand in the TD, and the support is a sawtoothed plastic cut Adhesive tape showing a sawtooth edge that, when cut on the blade, the support fits snugly to the contour of the blade. The adhesive tape of claim 1, wherein the support comprises a single layer. The adhesive tape of claim 1, wherein when the support is cut according to a Dispense Test, the support has an MD cutting energy of 350 N-cm / cm 2 or less. The adhesive tape according to claim 3, wherein when the support is cut according to the dispensing test, the support has an MD cutting energy of 170 N-cm / cm 2 or less. The adhesive tape according to claim 1, wherein when the support is tested according to a failure test, the support has a breaking energy of 130 N-mm or less. The adhesive tape according to claim 5, wherein when the support is tested according to the breaking test, the support has a breaking energy of 70 N-mm or less. The adhesive tape of claim 1, wherein the support has an MD fracture tensile energy of 90 N-mm / mm 3 or less. The adhesive tape of claim 1, wherein the support has a MD elongation at break of at least 70%. The adhesive tape of claim 1, wherein the support has an MD draw ratio of at least 4: 1. The adhesive tape of claim 1, wherein the support has a TD draw ratio of at least 7: 1. The adhesive tape of claim 1, wherein the support has a MD draw ratio of at least 4: 1 and a TD draw ratio of at least 7: 1. The adhesive tape of claim 1 wherein said support is tearable by hand in MD. A support and an adhesive layer on the support, wherein the support comprises polypropylene, the support is biaxially stretched, the support has a first direction break tensile energy of 90 N-mm / mm or less, and the support Is a sawtooth edge when the support is cut on the sawtoothed plastic cutting blade, the support fits snugly to the contour of the blade. The adhesive tape of claim 13, wherein the support comprises a single layer. The adhesive tape according to claim 13, wherein said first direction is MD. 16. The adhesive tape of claim 15 wherein said support has a MD elongation at break of at least 70%. The adhesive tape of claim 15 wherein the support is tearable by hand in the TD. 18. The adhesive tape of claim 17 wherein the support is tearable by hand in MD. The adhesive tape according to claim 15, wherein when the support is cut according to the dispensing test, the support has an MD cutting energy of 350 N-cm / cm 2 or less. 20. The adhesive tape of claim 19, wherein when the support is cut according to a dispensing test, the support has an MD cutting energy of 170 N-cm / cm 2 or less. The adhesive tape according to claim 13, wherein when the support is tested according to the breaking test, the support has a breaking energy of 130 N-mm or less. The adhesive tape according to claim 21, wherein when the support is tested according to the breaking test, the support has a breaking energy of 70 N-mm or less. The adhesive tape of claim 15 wherein said support has an MD draw ratio of at least 4: 1. The adhesive tape of claim 15 wherein said support has a TD draw ratio of at least 7: 1. The adhesive tape of claim 15 wherein the support has a MD draw ratio of at least 4: 1 and a TD draw ratio of at least 7: 1. A support and an adhesive layer on the support, the support comprises polypropylene, the support is biaxially stretched in MD and TD, the support has an MD fracture tensile elongation of 70% to 150%, and the support Adhesive tape tearable by hand in TD. 27. The adhesive tape of claim 26, wherein said support comprises a single layer. 27. The adhesive tape of claim 26 wherein the support has a breaking energy of 130 N-mm or less when the support is tested according to the failure test. The adhesive tape according to claim 28, wherein when the support is tested according to the breaking test, the support has a breaking energy of 70 N-mm or less. 27. The adhesive tape of claim 26 wherein when the support is cut on a sawtoothed plastic cutting blade, the support exhibits a serrated edge that fits snugly to the contour of the blade. The adhesive tape according to claim 26, wherein when the support is cut according to a dispensing test, the support has an MD cutting energy of 350 N-cm / cm 2 or less. The adhesive tape of claim 31, wherein when the support is cut according to a dispensing test, the support has an MD cutting energy of 170 N-cm / cm 2 or less. 27. The adhesive tape of claim 26, wherein the support has an MD fracture tensile energy of 90 N-mm / mm or less. 27. The adhesive tape of claim 26 wherein the support is tearable by hand in MD. 27. The adhesive tape of claim 26, wherein the support has an MD draw ratio of at least 4: 1. 27. The adhesive tape of claim 26, wherein the support has a TD draw ratio of at least 7: 1. 27. The adhesive tape of claim 26, wherein the support has a MD draw ratio of at least 4: 1 and a TD draw ratio of at least 7: 1. A support and an adhesive layer on the support, wherein the support comprises polypropylene, the support is biaxially stretched in MD and TD, the support is tearable by hand in TD, and the support is hand-drawn in MD Tearable adhesive tape. The adhesive tape of claim 38, wherein the support comprises a single layer. The adhesive tape according to claim 38, wherein when the support is tested according to the failure test, the support has a breaking energy of 130 N-mm or less. 41. The adhesive tape of claim 40 wherein the support has a breaking energy of 70 N-mm or less when the support is tested according to the fracture test. The adhesive tape according to claim 38, wherein when the support is cut on a sawtoothed plastic cutting blade, the support exhibits a sawtooth edge that fits snugly to the contour of the blade. The adhesive tape of claim 38, wherein when the support is cut according to a dispensing test, the support has an MD cutting energy of 350 N-cm / cm 2 or less. The adhesive tape of claim 43, wherein when the support is cut according to a dispensing test, the support has an MD cutting energy of 170 N-cm / cm 2 or less. The adhesive tape of claim 38, wherein the support has an MD fracture tensile energy of 90 N-mm / mm 3 or less. 39. The adhesive tape of claim 38, wherein said support has a MD elongation at break of at least 70%. 39. The adhesive tape of claim 38, wherein said support has an MD draw ratio of at least 4: 1. The adhesive tape of claim 38, wherein the support has a TD draw ratio of at least 7: 1. The adhesive tape of claim 38, wherein the support has a MD draw ratio of at least 4: 1 and a TD draw ratio of at least 7: 1.