ULTRAHIGH MOLECULAR WEIGHT POLYETHYLENE ADHESIVE TAPES

Abstract

The invention relates to an adhesive tape comprising an adhesive tape comprising a layer A comprising at least one anisotropic tape, wherein said tape comprises ultrahigh molecular weight polyethylene; and a layer B comprising a first adhesive being a pressure sensitive adhesive, wherein layer A covers at least 60% of the surface area of layer B. The invention also relates to the use of said adhesive tape in different applications.

Claims

1. An adhesive tape comprising: a) a layer A comprising at least one anisotropic tape, wherein said anisotropic tape comprises ultrahigh molecular weight polyethylene, and layer A covers at least 60% of the surface area of layer B; and b) a layer B comprising a first adhesive being a pressure sensitive adhesive.

2. The adhesive tape according to claim 1, wherein the ratio of tensile strength in longitudinal direction to tensile strength in transversal direction of the at least one anisotropic tape is least 10, preferably at least 20, more preferably at least 30, and most preferably at least 50.

3. The adhesive tape according to claim 1, wherein layer A comprises at least one solid state anisotropic tape comprising UHMWPE.

4. The adhesive tape according to claim 1, wherein the thickness of the layer A is between at least 0.005 mm and at most 0.3 mm and preferably, between at least 0.03 mm and at most 0.05 mm.

5. The adhesive tape according to claim 1, wherein layer B is selected from a group comprising acrylic-based adhesives, rubber-based adhesives and water-based adhesives.

6. The adhesive tape according to claim 1, further comprising a layer C comprising a carrier, said carrier comprising preferably a material selected from a group comprising a polyester, a polyamide, a polyolefin, a polycarbonate, paper, tissue, a polymeric foam, a woven material, a non-woven material.

7. The adhesive tape according to claim 1, wherein layer C is polyethylene terephthalate.

8. The adhesive tape according to claim 1, further comprising a layer D comprising a second adhesive, preferably the second adhesive being a pressure sensitive adhesive or a hot melt adhesive, the pressure sensitive adhesive being selected from a group comprising acrylic-based adhesives, rubber-based adhesives and water-based adhesives or a hot melt adhesive.

9. The adhesive tape according to claim 1, further comprising layer E comprising a material preferably selected from a group comprising paper, a polymer and a metal.

10. The adhesive tape according to claim 1, wherein the adhesive tape comprises the layer A located between layer B and the outside, with layer C being the outmost upper layer of the adhesive tape; the layer B located between layer A and layer C; the layer C located between layer B and layer D; the layer D located between layer C and layer E and the layer E located between layer D and the outside, with layer E being in this case the outmost lower layer of the adhesive tape.

11. The adhesive tape according to claim 1, wherein the adhesive tape comprises layer C located between layer B and the outside, with layer C being the outmost upper layer of the adhesive tape, layer B located between layer C and layer A; layer A located between layer D and layer B; layer D located between layer A and layer E, with layer E being the outmost lower layer of the adhesive tape.

12. The adhesive tape according to claim 1, wherein the adhesive tape comprise layer C located between layer D and the outside, with layer C being the outmost upper layer of the adhesive tape, layer D located between layer C and layer A; layer A located between layer D and layer B; layer B located between layer A the outside, layer B located between layer A and layer E, with layer E being the outmost lower layer of the adhesive tape.

13. The adhesive tape according to claim 1, further comprising a multilayered film comprising at least one film layer comprising a polyolefin and/or at least one film layer comprising a polymer, the multilayer film being the outmost upper layer of the adhesive tape.

14. An article comprising the adhesive tape according to claim 1.

15. Use of the adhesive tape according to claim 1 cut resistant applications, in heat management applications, as repair kit, as construction part and as reinforcement part, in the fields of electronics, radomes, sports, automotive, aviation, marine, renewable energy, clothing, in anti-icing applications, damaged metal, paper and printing, filtration and venting, furniture, packaging, luggage, medical, cables, sling splicing, constructions, infrastructure repairs, earthquake protection, storm and hurricane protection, snow fences and tents, car aero patch, space crafts, pipes, containers, strapping tapes, logistics, erosion protection.

Description

EXAMPLES

Methods of Measurement

[0069] Thickness of any one of the layers in the adhesive tape according to the invention was measured with a micrometer on an original location and on eight peripheral locations, said peripheral locations being within a radius of at most 0.5 cm from the original location, and averaging the values. [0070] Tensile properties, e.g. tensile strength and tensile modulus of the adhesive tape and of the tapes and of films according to this invention were defined from tensile testing. The width and thickness of the tapes were measured with a micrometer having an accuracy of 1 micron for the thickness and with a Vernier caliper with 100 microns accuracy for the width. The cross section area was obtained by multiplying width and thickness and expressed as square mm (mm.sup.2). Clamping was done in such a way that clamping damage was prevented, e.g. was done by draping the ends of the tapes around a circular bar, thus allowing load introduction by the capstan effect. The encircling around the circular bar was 180 degree and then the bar was clamped with mechanical means. A nominal gauge length of the tape of 440 mm and a crosshead speed of 50 mm/min were chosen. Tensile strength was obtained by measuring the breaking force, expressing it in newton and dividing that breaking force by the cross section area. The resulting breaking stress in N/mm.sup.2 is identical to a stress expressed in MPa (1 MPa=1 N/mm.sup.2). A modulus was obtained by adding reflective markers on the tape and measuring elongation (increase of distance between the markers) with optical means. The strain was then obtained by dividing the distance increase by the original distance. A modulus was obtained by dividing the stress difference by the according strain. Typically the modulus was obtained at a strain of about 0.15%, where initial setting of the specimens in the clamps and straightening was completed, but non-linearites occurring at higher strains were not yet present. [0071] Peeling strength was measured by measuring the adhesion force in cN/20 mm per tape width of the adhesive tape on different substrates at a peel angle of 180°, a peel speed of 300 mm/min, by using a test equipment Dynamo Tester Zwicki TRB43/009, at different conditions (temperature, time, relative humidity). The substrates to which an adhesive tape was applied on were first cleaned by using an alcohol, e.g. isopropyl alcohol and then the adhesive tape was applied on each substrate with a 2 kg hand roller. [0072] Shear tests were done by connecting two aluminum strips with adhesive tape. The adhesive tape was applied at one side of the strips only. However, for comparative experiments the strength was so low that tape was applied at both sides of the aluminium strips, thus doubling the strength. The connected strips were then loaded in tension. Thus forcing the tension load to be transferred from the strips to the tape, via the adhesive interface. The length of each strip was 150 mm. The surface of commercially available aluminum strips was cleaned with isopropyl alcohol and then dried until no wet spot was seen. On two of the aluminum strips with a gap length between the aluminum strips of 1 mm, a 25 mm wide adhesive tape (covering thus entire width of the strips) according to the invention, or as a comparative experiment was attached and consolidated with a hand-roller, the tape having different overlap lengths (25 mm; 35 mm; 45 mm and 50 mm on each aluminium strip). After 72 h the shear tests were done by measuring the tensile strength on these samples and also on the samples with commercially available adhesive tapes that were prepared in the same way. Breaking force and fracture location was observed. The strength result can be recalculated to an average shear stress in the adhesive at the moment of fracture. This was done by dividing the force at fracture by the total surface covered by adhesive tape on one strip. This average shear stress was a measure of adhesive tape performance. [0073] Intrinsic Viscosity (IV) for UHMWPE was determined according to method PTC-179 (as described in Hercules Inc. Rev. Apr. 29, 1982) at 135° C. in decaline, the dissolution time being 16 hours, with DBPC as anti-oxidant in an amount of 2 g/I solution, by extrapolating the viscosity as measured at different concentrations to zero concentration. [0074] Contact angle was determined by initially cleaning the surface of the samples (e.g. the tape as obtained as disclosed herein below in section in Production of a solid state tape comprising UHMWPE) with an alcohol. The alcohol is chosen such that it does not dissolve the samples. The alcohol used for cleaning the samples was ethanol. Then, a small droplet (preferably between 3 and 5 microliters) of water was added to the surface of the sample. The droplet size was 5 microliters. Subsequently, the contact angle between the droplet and the sample was measured using a microscope. This measurement can be repeated for at least 3 times (it was repeated 5 times herein) and the average value of the contact angle values obtained from the results was measured.

Production of a Solid State Tape Comprising UHMWPE

[0075] A powder bed of UHMWPE powder was compacted in a double belt press at a pressure of 40 bar and a temperature of 130° C. The aerial density of the powder bed was 1 kg per square meter. The resulting product was compressed between two calendar rolls at a temperature of 135° C., down to a thickness of 0.27 mm (270 microns) and subsequently was drawn with a factor 10 in an oven at 147° C. and then it was drawn again in another oven with a factor 2.5 at a temperature of 150° C. The resulting oriented tape had a thickness of 0.042 mm (42 microns), a tensile strength of 1.7 GPa, a tensile modulus of 115 GPa and a width of 35 cm. The ratio of tensile strength of the tape in longitudinal direction to tensile strength of the tape in transversal direction was 150.

Production of Woven Sheets Comprising UHMWPE

[0076] 4 monolayers of the tape as obtained as described under Production of a solid state tape comprising UHMWPE, each monolayer containing a 10 cm width and 0.042 mm thick solid-state UHMWPE tape produced as described herein above, were woven into two plain woven structures, each plain woven structure containing 2 monolayers consisting of said tapes. The two plain weave structures were stacked on top of each other under ambient condition in a 0.90° cross-plied manner to produce one fabric sheet layer having 4 monolayers, each monolayer consisting of said tape. The obtained sheet was cut in a sheet sample having a width of 40 cm, a length of 40 cm and a thickness of 0.168 mm, a tenacity of 8.5 cN/dTex in the 0.90° direction of the tape and an area density of 168 g/m.sup.2.

Example 1

[0077] An adhesive tape was obtained by applying a double sided 0.1 mm (100 microns) thick adhesive sheet (commercially available from Nitto under the trade name 5015P) made of a layer of a modified acrylic adhesive of 0.044 mm (44 microns) thick (layer B), a 0.012 mm (12 microns) thick PET carrier layer (layer C) and a modified acrylic adhesive of 0.044 mm (44 microns) thick (layer D) on a tape obtained as described herein above under Production of a solid state tape comprising UHMWPE, which was treated in advance by applying a Corona treatment at 400 Watt min/m.sup.2 to increase the surface tension of the tape (layer A), obtained as described herein above. Layer A tape covered about 100% of the surface area of first adhesive layer B. A siliconised paper (layer E) commercially available from Mondi, type S-liner that is a super-calendared kraft paper liner was then applied as a release liner on the adhesive sheet between layer D and the outside. The obtained tape had the structure of layer A located between layer B and the outside, with layer A being the outmost upper layer of the adhesive tape; layer B located between layer A and layer C; layer C located between layer B and layer D; layer D located between layer C and layer E and layer E is located between layer D and the outside, with layer E being the outmost lower layer of the adhesive tape All layers A-E overlapped substantially on their entire width. The orientation direction of the UHMWPE tape (layer A) in Example 1 was in the load direction. The ratio of tensile strength of the adhesive tape in longitudinal direction to tensile strength of the adhesive tape in transversal direction was 21. Table 1 shows the results of measuring the tensile strength of the adhesive tape obtained with Example 1. Table 2 shows the results of measuring the shear tests of the adhesive tape obtained with Example 1.

Example 2

[0078] Example 1 was repeated with the only difference that the adhesive tape was obtained in a two-step process. In the first step, a commercially available bi-laminate commercially available from EK-Pack Folien under the trade name EK Ester 12/30 comprising a LDPE hot melt adhesive with a thickness of 30 micron (0.03 mm) (layer D) and a layer comprising polyethylene terephthalate (layer C) having a thickness of 12 micron (0.012 mm), was applied on a tape obtained as described herein above under Production of a solid state tape comprising UHMWPE (layer A), which was not treated by applying the Corona treatment. In the second step, layer A (having on one side by layers C-D), was treated by applying a Corona treatment at 400 Watt min/m.sup.2 to increase the surface tension of the tape (layer A), and then a pressure sensitive adhesive layer with a thickness of 0.04 mm (40 micron) was applied (layer B), the PSA being a modified acrylate adhesive commercially available from Nitto under the trade name 5015T. A siliconised paper (layer E) having 0.1 mm thickness was then applied as a release liner on the outside of the adhesive tape, between layer B and the outside. The adhesive tape had the structure of layer C located between layer D and the outside, with layer C being the outmost upper layer of the adhesive tape, layer D located between layer C and layer A; layer A located between layer D and layer B; layer B located between layer A and layer E, with layer E being the outmost lower layer of the adhesive tape. All layers A-E substantially overlapped substantially on their entire width. The orientation direction of the UHMWPE tape (layer A) in Example 2 was in the load direction. The ratio of tensile strength of the adhesive tape in longitudinal direction to tensile strength of the adhesive tape in transversal direction was 21. The adhesive tape obtained with Example 1 showed similar tensile strength as the adhesive tape obtained with Example 1 (Table 1). Table 2 shows the results of measuring the shear tests of the adhesive tape obtained with Example 2.

Comparative Experiment 1 (CE1)

[0079] A solid state tape as obtained as described herein above under Production of a solid state tape comprising UHMWPE was analyzed and the results are shown in Table 1.

Comparative Experiment 2 (CE2)

[0080] An adhesive tape commercially available from Nitto under the name No. 443 was analysed. This is a pressure-sensitive adhesive tapes with a release liner and an ultrahigh-molecular-weight polyethylene isotropic film base and contains an acrylic adhesive layer having a thickness of 0.17 mm.

Comparative Experiment 3 (CE3)

[0081] An adhesive tape commercially available from Nitto under the name No. 4430 was analysed. This is a pressure-sensitive adhesive tape with a release liner and an ultrahigh-molecular-weight polyethylene isotropic film base and contains an acrylic adhesive layer having a thickness of 0.03 mm.

Comparative Experiments 4 (CE4)

[0082] A commercially available adhesive tape Duct tape (CE3) was analysed. The results are shown in Table 2.

Comparative Experiment 5 (CE5)

[0083] A commercially available adhesive tape Marko superkraftband tape (CE4) was analysed. The results are shown in Table 2.

Comparative Experiment 6 (CE6)

[0084] 5 layers of a commercially available adhesive tape Duct tape (CE3) were applied on top of each other, overlapping with each other. This was done as another attempt in order to reach a higher strength with commercial adhesive tapes. The obtained adhesive tape was analysed. The results are shown in Table 2.

Comparative Experiment 7 (CE7)

[0085] 7 layers of a commercially available adhesive tape Duct tape (CE3) were applied on top of each other, overlapping with each other. This was done as another attempt in order to reach a higher strength with commercial adhesive tapes. The obtained adhesive tape was analysed. The results are shown in Table 2.

Comparative Experiment 8 (CE8)

[0086] Example 1 was repeated with the same adhesive tape according to the invention, but now the orientation direction of tape layer A was perpendicular to the load direction.

TABLE-US-00001 TABLE 1 Tensile strength, Sample Fmax [N] Example 1 6128 Example 2 6097 CE 1 4883

TABLE-US-00002 TABLE 2 Shear Average test— shear tensile stress strength, at Overlap length Fmax fracture Sample on each [mm] [N] [N/mm2] Fracture type Ex 1 25 (on one side 1025 1.64 Along adhesive of the strips) interface Ex 1 35 (on one side 1078 1.23 Along adhesive of the strips) interface Ex 1 45 (on one side 1743 1.55 Along adhesive of the strips) interface Ex 1 50 (on one side 1681 1.34 Along adhesive of the strips) interface Ex 2 25 (on one side 950 1.52 Along adhesive of the strips) interface Ex 2 35 (on one side 1221 1.40 Along adhesive of the strips) interface Ex 2 45 (on one side 1341 1.19 Along adhesive of the strips) interface Ex 2 50 (on one side 1429 1.14 Along adhesive of the strips) interface CE2 50 (on both sides 123 0.05 Through tape of the strips) material CE3 50 (on both sides 100 0.04 Through tape of the strips) material CE4 50 (on both sides 218 0.09 Through tape of the strips) material CE5 50 (on one both 317 0.13 Through tape sides of the strips) material CE6 50 (on one both 337 0.27 Through tape sides of the strips) material CE7 50 (on one both 393 0.31 Along adhesive sides of the strips) interface CE7 40 (on one both 358 0.36 Along adhesive sides of the strips) interface CE8 50 81 0.065 Through tape material

[0087] The results in Table 1 clearly show that the adhesive tape according to the present invention (Example 1 and Example 2) is about 25% stronger than the tape of CE 1. In addition, the adhesive tape according to the present invention shows higher transfer capacity between adherent surfaces compared to the adhesive tapes of the prior art (Table 2). Also, the tensile strength of the adhesive tape according to the present invention is much higher than that of the commercial adhesive tapes. If judged in terms of average shear stress at fracture, about decade improvement is reached by the adhesive tape according to the present invention in comparison with the commercial adhesive tapes. Even by applying 5- or 7-fold commercial adhesive tape, the load transfer of such adhesive tapes was much lower than that of the adhesive tape according to the invention.