ADHESIVE TAPE

Abstract

The invention relates to an adhesive tape comprising a backing consisting of a film, to at least one side of which an adhesive mass is applied, wherein the film is a monoaxially stretched film, at least 95 wt. % of which, preferably at least 99 wt. % of which, particularly preferably 100 wt. % of which consists of a propylene polymer composition having different phases and comprising the following components: i) 80 to 99 wt. %, preferably 93 to 96 wt. %, relative to the total weight of components i) and ii), of a propylene polymer matrix which comprises a propylene homopolymer and particularly preferably a propylene copolymer, preferably a propylene random copolymer, which has a comonomer selected from ethylene or C.sub.4- to C.sub.10--olefins, the propylene polymer matrix having a comonomer content of not more than 15 wt. %, ii) 1 to 20 wt. %, preferably 4 to 7 wt. %, relative to the total weight of components i) and ii), of an elastomer in the form of an ethylene-propylene copolymer having an ethylene content of 50 to 90 wt. %.

Claims

1. An adhesive tape having a carrier comprising a film bearing on at least one side an applied adhesive, wherein: the film is a monoaxially oriented film which comprises at least 95 wt %, of a propylene polymer composition having different phases and comprising the following components: i) 80 to 99 wt %, based on the total weight of components i) and ii), of a propylene polymer matrix which comprises a propylene homopolymer and further preferably including a preferably random propylene copolymer having a comonomer which is selected from ethylene or C.sub.4 to C.sub.10 -olefins, the comonomer content of the propylene polymer matrix being not more than 15 wt %; ii) 1 to 20 wt %, based on the total weight of components i) and ii), of an elastomer in the form of an ethylene-propylene copolymer having an ethylene content of 50 to 90 wt %.

2. The adhesive tape of claim 1, wherein the propylene polymer composition consists essentially of components i) and ii).

3. The adhesive tape of claim 1, wherein the fractions of propylene homopolymer and of propylene copolymer in component i) are 70 to 99 wt % propylene homopolymer and 1 to 30 wt % propylene copolymer.

4. The adhesive tape of claim 1, wherein the propylene polymer matrix has: a melt flow index MFI of 0.5 to 10 g/10 min (measured as claimed in ISO 1133 at 230 C. and under a weight of 2.16 kg) and, an elasticity modulus of 1000 to 1300 MPa.

5. The adhesive tape of claim 1, wherein the polypropylene homopolymer comprises granules whose only polymer is polypropylene.

6. The adhesive tape of claim 1, wherein: ethylene is selected as comonomer in the propylene copolymer, with an ethylene-propylene ratio of 0.9:1 to 1.1:1.

7. The adhesive tape of claim 1, wherein: the ethylene content in the elastomer in the form of an ethylene-propylene copolymer is 55 to 80 wt %.

8. The adhesive tape of claim 1, wherein: the melting point (DSC) of the elastomer is less than 70 C.

9. The adhesive tape of claim 1, wherein: the degree of crystallinity of component ii) is 0.1.

10. The adhesive tape of claim 1, wherein: the draw ratio on orientation of the extruded primary film in longitudinal direction is 1:5 to 1:9.

11. The adhesive tape of claim 1, wherein: the film thickness after orientation is between 40 and 150 m.

12. The adhesive tape of claim 1, wherein: the adhesive is selected from natural rubbers or from a blend of natural rubbers and synthetic rubbers.

13. The adhesive tape of claim 1, wherein: the adhesive comprises at least one tackifier resin.

14. The adhesive tape of claim 1, wherein: the adhesive comprises at least one UV stabilizer and/or other blending components.

15. A method of securing movable parts on printers, copiers, or household appliances comprising the step of: applying an adhesive tape according to claim 1 between the moveable parts.

16. An adhesive strapping tape for bundling and palletizing cardboard-boxed items which adhesive strapping tape is an adhesive tape according to claim 1.

17. The adhesive tape of claim 13, wherein: the tackifier resin is selected from: resins based on hydrogenated, partly-hydrogenated or unhydrogenated hydrocarbon resins, terpene-phenols and rosin esters.

18. The adhesive tape of claim 14, wherein: the at least one UV stabilizer and/or other blending component is selected from: plasticizers, aging inhibitors, processing assistants, fillers, dyes, optical brighteners, stabilizers, and endblock reinforcer resins.

Description

EXAMPLE

[0151] All quantity data, fractions, and percent fractions are given by weight pwb denotes parts by weight.

Experimental Protocol

[0152] A dry blend is prepared of the heterophasic copolymer with the EPM (preferred concentration 4 to 7 wt %) and is melted by means of a single-screw extruder (at temperatures between from 160 to 240 C.). The melt is formed into a film through a slot die, and is laid down and cooled on a chill roll (at temperatures between 60 to 100 C.). A monoaxial drawing unit is used to orient the film in a short stretching gap process with draw rates of 1:5 to 1:9 (preferably 1:6 to 1:8).

[0153] The dry blend consists of 5 wt % of the EPM elastomer Vistalon 722 from ExxonMobil, an ethylene-propylene copolymer having an ethylene content of 72 wt % and also having an MFI (measured at 190 C. under 2.16 kg loading) of 1.0 g/10 min and an elasticity modulus of 1240 MPa, and of 95 wt % of the heterophasic PP copolymer Profax SV 258 from LyondellBasell, having an MFI (measured at 230 C. under 2.16 kg loading) of 1.2 g/10 min and an elasticity modulus of 1240 MPa. The material is melted in a single-screw extruder at temperatures from 180 to 230 C., formed into a flat film with the aid of a slot die, and laid down and cooled on a chill roll with a temperature of 95 C. The thickness of the resulting film is 325 m. After cooling, the film is again heated to temperatures of 127 C. in a monoaxial drawing unit and oriented in a short gap with a draw rate of 1:6.5, after which it is conditioned at a temperature of 127 C. and finally wound up. Therefore an ultimate film thickness of 50 m is produced.

Results

[0154] In in-transit securement, the mechanical properties of the film are of central importance. A very soft film will be likely not to exhibit any shredding, but instead will have a very high elongation with little accommodation of force. This would mean that the film would stretch if forces occurred during transit. The adhesive tape would therefore go slack instead of holding together the product being transported.

TABLE-US-00001 TABLE 1 Mechanical properties and shredding results for various MOPP films Material F5 % [N/mm.sup.2] Fmax [N/mm.sup.2] Shredding MOPP film 76 273 Fail Profax SV 258 112 328 Fail Profax SV 258 + 110 328 Fail 2.5 wt % Vistalon 722 Profax SV 258 + 108 317 Pass 5 wt % Vistalon 722 Profax SV 258 + 103 315 Pass 10 wt % Vistalon 722

[0155] As can be seen in table 1, the addition of Vistalon 722 lowers the mechanical properties only slightly as compared with the pure heterophasic copolymer. At a concentration of 5 wt %, however, the film passes the shredding test. Concentration of 10 wt % of Vistalon has no further advantage over 5 wt % of Vistalon, and so a concentration of around 5 wt % is preferred. The MOPP film investigated for comparison purposes in the Tesa 64294 adhesive tape, furnished with a natural rubber adhesive, has a significantly lower accommodation of force. Moreover, the film fails the shredding test.

Test Methods

[0156] The measurements are carried out (unless indicated otherwise) under test conditions of 231 C. and 505% relative humidity.

Shredding

[0157] The films are aged for 2 weeks and then pretreated with a corona dose of 60.7 W*min/m.sup.2 at a speed of 30 m/min in order to increase the surface energy and therefore the anchorage to a d/s adhesive tape. The film is laminated to a suitable adhesive tape, for example Tesa 61795 PV40 or Tesa 4965 PV0, and slit to form strips 20 mm wide. Tesafix 4965 is a double-sidedly adhesive, transparent polyester tape bearing an acrylate adhesive.

[0158] The properties of Tesa 4965 are as follows: [0159] carrier material: PET film [0160] thickness: 205.00 m [0161] adhesive: modified acrylate [0162] elongation at break: 50.00% [0163] tearing force: 20.00 N [0164] peel adhesion on steel (initial): 11.50 N/cm [0165] peel adhesion on ABS (initial) [0166] 10.30 N/cm peel adhesion on aluminum (initial): 9.20 N/cm [0167] peel adhesion on PC (initial): 12.60 N/cm [0168] peel adhesion on PE (initial): 5.80 N/cm [0169] peel adhesion on PET (initial): 9.20 N/cm [0170] peel adhesion on PP (initial): 6.80 N/cm [0171] peel adhesion on PS (initial): 10.60 N/cm [0172] peel adhesion on PVC (initial): 8.70 N/cm

[0173] These assemblies are subsequently adhered to an ABS test plate cleaned with ethanol, and are stored at room temperature for 24 hours. The film is subsequently removed from the double-sided adhesive tape by hand, at three different speeds and angles: at 90 slowly, at 180 slowly, and then at 180 quickly. This test is likewise carried out after storage for 24 hours at 20 C. The test is passed if, after the film has been peeled off, there are no residues of film remaining on the adhesive.

Tensile Test and Elasticity Modulus

[0174] According to DIN ISO 527: On a tensile testing machine, a film strip 15 mm wide is clamped in a clamping jaw spacing of 100 mm. The tensile test is carried out at a velocity of 300 mm/min to tearing point. The maximum tensile force Fmax and the force at 5% elongation (F5%) are ascertained from the measurement curve. The values are reported in N/mm.sup.2, meaning that the measurement value is standardized to the film thickness. The elasticity modulus is ascertained from the force-elongation curve at low elongation in accordance with DIN ISO 527.

Degree of Crystallization

[0175] The degree of crystallization is determined by the method as described in the article by Schubnell, M.: Determination of the crystallinity for polymers from DSC measurements; Mettler Toledo Deutschland; de.mt.com; USERCOM vol. 1, 2001, pages 12 to 13.

[0176] In this case the degree of crystallization is ascertained by means of a DSC measurement at a heating rate of 10 K/min explicitly from the free enthalpy of the 1st heating curve, assuming a value of 207 J/g (literature value) for the enthalpy of fusion of a 100% crystalline homo-PP.

Peel Adhesion

[0177] The determination of the peel adhesion (in accordance with AFERA 5001) is carried out as follows: the defined substrate used is galvanized steel sheet with a thickness of 2 mm (obtained from Rocholl GmbH). The bondable sheetlike element under test is cut to a width of 20 mm and a length of about 25 cm, provided with a handling section, and immediately thereafter pressed five times using a 4 kg steel roller, with a rate of advance of 10 m/min, onto the selected substrate. Immediately after that, the bondable sheetlike element is peeled from the substrate at an angle of 180 using a tensile testing instrument (from Zwick) at a velocity v=300 mm/min, and the force needed to achieve this at room temperature is recorded. The measured value (in N/cm) is obtained as the average from three individual measurements.

Melt Index (MFI)

[0178] The melt index (MFI) is measured according to ISO 1133. For polyethylenes it is determined at 190 C. and with a weight of 2.16 kg, for polypropylenes at a temperature of 230 C. and a weight of 2.16 kg.

Flexural Modulus (Flexural Elasticity Modulus)

[0179] The test takes place according to ASTM D 790 A (2% secant), in other words according to Procedure A (see also section 1 of the ASTM) with a test specimen for determining the flexural modulus, with dimensions of 0.1250.55.0 (3.2 mm12.7 mm125 mm).

Crystallite Melting Point

[0180] The crystallite melting point of copolymers, hard blocks and soft blocks, and uncured reactive resins is determined calorimetrically via differential scanning calorimetry (DSC) according to DIN 53765:1994-03. Heating curves run with a heating rate of 10 K/min. The specimens are subjected to measurement in Al crucibles with perforated lid and a nitrogen atmosphere. Evaluation takes place on the second heating curve. In the case of amorphous substances, glass transition temperatures occur; in the case of (semi)crystalline substances, melting temperatures occur. A glass transition can be recognized as a step in the thermogram. The glass transition temperature is evaluated as the center point of this step. A melting temperature can be perceived as a peak in the thermogram. The melting temperature recorded is the temperature at which the maximum heat change occurs.

Density

[0181] The density is measured according to ASTM D 792.

Molecular Weight Determination

[0182] The molecular weight determinations of the weight-average molecular weights M.sub.w were made by means of gel permeation chromatography (GPC). The eluent used was THF (tetrahydrofuran) with 0.1 vol % of trifluoroacetic acid. Measurement took place at 25 C. The pre-column used was PSS-SDV, 5, 10.sup.3 , ID 8.0 mm50 mm. Separation took place using the columns PSS-SDV, 5, 10.sup.3 and also 105 and 106 each with ID 8.0 mm300 mm. The sample concentration was 4 g/l, the flow rate 1.0 ml per minute. Measurement was made against PMMA standards.