PRESSURE-SENSITIVE ADHESIVE

Abstract

Pressure-sensitive adhesives, adhesive tapes, and methods enable high bond strengths on non-polar or rough substrates. The pressure-sensitive adhesives and methods comprise (a) at least one poly(meth)acrylate, (b) at least one resin A selected from colophony resins and terpene-phenolic resins, (c) at least one hydrocarbon resin B1 having a softening point of greater than 50 C., and (d) at least one hydrocarbon resin B2 having a softening point of less than or equal to 25 C. The adhesive tapes comprise one or more layers of the pressure-sensitive adhesives, and the methods may produce adhesive bonds on substrates with low surface energy and/or on substrates with a mean roughness of at least 5 m.

Claims

1. A pressure-sensitive adhesive comprising: a) at least one poly(meth)acrylate; b) at least one resin A selected from colophony resins and terpene-phenolic resins; c) at least one hydrocarbon resin B1 having a softening point of greater than 50 C.; and d) at least one hydrocarbon resin B2 having a softening point of less than or equal to 25 C.

2. The pressure-sensitive adhesive of claim 1, wherein the poly(meth)acrylate is a copolymer derivable from a monomer composition comprising: i) one or more alkyl acrylates having an alkyl radical comprising 1 to 4 carbons; ii) one or more alkyl acrylates having an alkyl radical comprising 5 or more carbons; and iii) acrylic acid.

3. The pressure-sensitive adhesive of claim 2, wherein the monomer composition comprises acrylic acid at 0.5 to 5 wt %, based on a total weight of the monomer composition.

4. The pressure-sensitive adhesive of claim 1, wherein the pressure-sensitive adhesive comprises one or more resins A at in total 15 to 30 wt %, based on a total weight of the pressure-sensitive adhesive.

5. The pressure-sensitive adhesive of claim 1, wherein the at least one resin A is a terpene-phenolic resin.

6. The pressure-sensitive adhesive of claim 1, wherein the pressure-sensitive adhesive comprises one or more resins B1 at in total 10 to 25 wt %, based on a total weight of the pressure-sensitive adhesive.

7. The pressure-sensitive adhesive of claim 1, wherein the pressure-sensitive adhesive comprises one or more resins B2 at in total 5 to 15 wt %, based on a total weight of the pressure-sensitive adhesive.

8. An adhesive tape comprising the pressure-sensitive adhesive of claim 1.

9. A method comprising at least one of: bonding a first substrate to a second substrate with the pressure-sensitive adhesive of claim 1; or adhesively bonding the adhesive tape of claim 8 to substrates, wherein at least one of the first substrate, the second substrate, and the substrates have at least one of low surface energy and a mean roughness of at least 5 m.

Description

EXAMPLES

[0126] Test Methods

[0127] Glass Transition Temperature (T.sub.g):

[0128] The static glass transition temperature is determined by dynamic scanning calorimetry (DSC) in accordance with DIN EN ISO 11357-2. The values stated for the glass transition temperature T.sub.g are based on the glass transition temperature value T.sub.g according to DIN 53765:1994-03, unless otherwise indicated in a particular case.

[0129] Gel Permeation Chromatography (GPC):

[0130] The values stated for number-average and weight-average molecular weights M.sub.n, M.sub.w and M.sub.z and also for the polydispersity PD in this specification are based on their determination by gel permeation chromatography.

[0131] The determination is made on 100 L of a sample having undergone clarifying filtration (sample concentration 0.5 g/L). The eluent used is tetrahydrofuran with 0.1 vol % of trifluoroacetic acid. The measurement is made at 25 C. The pre-column used is a column of type PSS-SDV, 10 m, ID 8.0 mm.Math.50 mm. Separation takes place using columns of type PSS-SDV, 5 m, 10.sup.3 (SN9090201) and also 5 m, 10.sup.2 (SN9090200) each with ID 8.0 mm.Math.300 mm (columns from Polymer Standards Service; detection by differential refractometer PSS-SECurity 1260 RID). The flow rate is 0.5 mL per minute. Calibration takes place against PMMA standards (polymethyl methacrylate calibration).

[0132] Softening Point:

[0133] The softening points were ascertained in a usual way in accordance with ASTM E28 (Ring-and-Ball).

[0134] Bonding Power:

[0135] The determination of the bonding power, as peel adhesion, took place under test conditions of 23 C.+/1 C. temperature and 50%+/5% relative humidity. The specimens of adhesive were cut to a width of 20 mm and adhered to a plate of the respective material indicated (PE, PP, steel, EPDM rough). The plates were cleaned and conditioned prior to measurement. For this the plates were first wiped down with solvent and then left to stand in the air for 10 minutes (steel/acetone) or two hours (PE, PP/ethanol; EPDM rough/isopropanol) to allow the solvent to evaporate. The side of the specimen facing away from the test substrate was then lined with an etched PET film 23 m thick so as to prevent the specimen stretching during the measurement. After that, the test specimen was rolled onto the substrate. For this, the adhesive was rolled down five times back and forth using a 4 kg roller, with a rolling speed of 10 m/min. One minute (initial) after the rolling procedure, the plate was inserted into a special mount which allowed the specimen to be peeled off at an angle of 180. Peel adhesion was measured using a Zwick tensile testing machine, at a peel velocity of 300 mm/min. The results of the measurement are reported in N/cm as the mean from three separate measurements.

[0136] Raw Materials

[0137] Commercially Available Chemicals Used

TABLE-US-00002 Chemical compound Trade name Manufacturer CAS No. Acrylic acid (AA) Sigma Aldrich 79-10-7 2-Ethylhexyl BASF 103-11-7 acrylate (2-EHA) n-Butyl acrylate BASF 141-32-2 (n-BA) 2,2-Azobis(2- Vazo 67 Akzo Nobel 13472-08-7 methylbutyronitrile) Bis(4-tert- Perkadox 16 Akzo Nobel 15520-11-3 butylcyclohexyl) peroxydicarbonate N,N,N,N- Syna Epoxy Synasia 65992-66-7 Tetrakis(2,3- S-610 epoxypropyl)cyclo- hexyl-1,3- dimethylamine Terpene-phenolic Dertophene T DRT 25359-84-6 resin Colophony resin Foral 85-E Eastman 65997-13-9 (softening point 85 C.) Hydrocarbon resin Kristalex F85 Eastman 9011-11-4 Hydrocarbon Resin (softening point 86 C.) Hydrocarbon resin Dercolyte TS 105 DRT (softening point 105 C.) Hydrocarbon resin Wingtack 10 CrayValley 26813-14-9 (softening point 10 C.)

[0138] Preparation of the Polyacrylates

[0139] A 300 L reactor conventional for radical polymerisations was filled with the amounts as specified in the examples of acrylic acid, 2-ethylhexyl acrylate (EHA) and n-butyl acrylate and also 72.4 kg of benzine/acetone (70:30). After nitrogen gas had been passed through the reactor for 45 minutes with stirring, the reactor was heated up to 58 C. and 50 g of Vazo 67 were added. The jacket temperature was then set to 75 C. and the reaction was carried out constantly at this external temperature. After a reaction time of 1 h a further 50 g of Vazo 67 were added. The reaction mixture was diluted after 3 h with 20 kg of benzine/acetone (70:30) and after 6 h with 10.0 kg of benzine/acetone (70:30). In order to reduce the residual initiators, one 0.15 kg portion of Perkadox 16 was added after 5.5 h, and one after 7 h. The reaction was terminated after a reaction time of 24 h and the product was cooled to room temperature. The polymers obtained had weight-average molar masses M.sub.w in the range from 1 100 000 to 1 300 000 g/mol.

[0140] Lastly the crosslinker solution (syna epoxy S-610, 3 wt % in acetone; 0.05 part by weight of crosslinker per 100 parts by weight of polyacrylate) and also the resins in the amounts reported in Table 1 were added to the polymer solution. The adhesive thus produced was coated onto a siliconized release paper on a laboratory coating platform using a coating knife. The coatings were subsequently dried at 120 C. for 15 min.

[0141] The specimens were conditioned for 14 days under standard conditions (23 C., 50% relative humidity).

[0142] The adhesive compositions and the test results are contained in Tables 1 and 2.

TABLE-US-00003 TABLE 1 Composition of the pressure-sensitive adhesives HC HC HC Polyacrylates (wt %) TP C resin resin resin No. n-BA 2-EHA AA resin resin 1 2 3 1 (C) 49.5 49.5 1 20 15 2 (C) 49.5 49.5 1 20 20 0 3 49.5 49.5 1 20 15 10 4 (C) 49.5 49.5 1 25 15 5 (C) 49.5 49.5 1 20 6 (C) 49.5 49.5 1 25 7 (C) 49.5 49.5 1 20 10 8 (C) 49.5 49.5 1 30 9 (C) 49.5 49.5 1 20 20 10 (C) 49.5 49.5 1 20 20 11 49.5 49.5 1 20 20 5 12 49.5 49.5 1 30 15 5 13 49.5 49.5 1 15 15 15 14 (C) 67 30 3 20 20 15 67 30 3 20 20 10 16 67 30 3 20 15 10 17 (C) 67 30 3 30 20 18 67 30 3 25 10 10 TP resinTerpene-phenolic resin (Dertophene T) C resinColophony resin (Foral 85E) HC resin 1Hydrocarbon resin 1 (Kristalex F85) HC resin 2Hydrocarbon resin 2 (Dercolyte TS 105) HC resin 3Hydrocarbon resin 3 (Wingtack 10) CComparative experiment (not inventive)

TABLE-US-00004 TABLE 2 Test results EPDM rough Peel adhesion (N/cm), measured on . . . (mean roughness No. PE PP Steel (ASTM) 7.5 m) 1 (C) 3.51 4.68 5.18 3.32 2 (C) 3.32 6.07 5.74 3.78 3 5.93 9.71 6.78 6.32 4 (C) 3.92 7.32 5.50 3.95 5 (C) 2.59 5.06 4.92 3.58 6 (C) 2.33 4.13 5.10 2.55 7 (C) 3.17 5.78 5.63 3.63 8 (C) 2.44 4.37 4.99 2.44 9 (C) 3.52 6.07 5.27 3.28 10 (C) 3.47 3.89 3.99 3.26 11 5.14 8.21 6.20 5.67 12 5.24 7.80 6.38 5.13 13 4.94 7.25 5.99 5.47 14 (C) 3.52 8.76 6.01 3.11 15 6.05 9.50 6.22 6.85 16 5.23 8.88 6.15 6.69 17 (C) 3.25 7.96 5.48 3.20 18 5.11 8.10 5.67 6.40 PEPolyethylene PPPolypropylene EPDMEthylene-Propylene-Diene copolymer