HMPSA CROSSLINKABLE UNDER UV IRRADIATION

Abstract

A UV-crosslinkable HMPSA composition comprises 10-24% by weight of a block copolymer comprising a styrenic block and a polybutadiene block comprising at least 25% by weight of the 1,2-vinyl unit; 43-65% by weight of a tackifying resin obtained by polymerization, then complete or partial hydrogenation of a C9 fraction, having a softening point of 80-150° C.; 10-25% by weight of a petroleum-derived hydrocarbon oil; and an appropriate amount of a photoinitiator (D). A self-adhesive article comprises a carrier layer (b) coated with a self-adhesive layer (a) comprising the HMPSA composition in the crosslinked state.

Claims

1.-12. (canceled)

13. A UV-crosslinkable hotmelt pressure sensitive adhesive (HMPSA) composition comprising, based on the total weight of said composition: from 10% to 24% by weight of a block copolymer (A) which comprises at least: a block A1 consisting of a repeating unit of aromatic hydrocarbon substituted by a vinyl group, and a polybutadiene block A2 comprising at least 25% by weight of the 1,2-vinyl unit, based on the total weight of said polybutadiene block; from 43% to 65% by weight of a tackifying resin (B) obtained by polymerization, then complete or partial hydrogenation of a petroleum-derived C9 fraction of unsaturated or aromatic hydrocarbons, said resin (B) having a softening point of from 80 to 150° C.; from 10% to 25% by weight of a liquid plasticizer (C) comprising a petroleum-derived, completely or partially saturated hydrocarbon oil; and an appropriate amount of a photoinitiator (D).

14. The HMPSA composition as claimed in claim 13, wherein the block copolymer (A) comprises 2 styrenic blocks A1 and the weight content of the 1,2-vinyl unit in the polybutadiene block A2 is within a range of from 30% to 70% by weight.

15. The HMPSA composition as claimed in claim 13, wherein the tackifying resin (B) has a softening temperature of between 90 and 120° C.

16. The HMPSA composition as claimed in claim 13, wherein the liquid plasticizer (C) comprises an oil having an average molecular mass as measured by the ASTM D 2502 method of less than or equal to 2000 g/mol.

17. The HMPSA composition as claimed in claim 13, further comprising up to 25% by weight of a liquid polybutadiene (E) of low molecular mass.

18. The HMPSA composition as claimed in claim 13, wherein it comprises: from 12% to 19% by weight of the block copolymer (A); from 50% to 65% by weight of the tackifying resin(s) (B); and from 14% to 23% by weight of the liquid plasticizer (C).

19. A self-adhesive article comprising a carrier layer (b) coated with a self-adhesive layer (a), wherein said self-adhesive layer (a) comprises the adhesive composition as defined in claim 13, in the crosslinked state.

20. The self-adhesive article as claimed in claim 19, wherein the article is a single-sided or double-sided self-adhesive tape.

21. The self-adhesive article as claimed in claim 19, wherein the article further comprises a nonstick protective layer (c) adjacent to the adhesive layer (a).

22. The self-adhesive article as claimed in claim 19, wherein the thickness of the layer (a) is from 5 μm to 2000 μm.

23. A method for manufacturing the self-adhesive article as defined in claim 19, said process comprising the sequential steps: i. of preheating the HMPSA composition to a temperature of between 70 and 180° C.; ii. of applying said composition by coating to a bearing surface; iii. of crosslinking said composition by UV irradiation to form the layer of crosslinked adhesive composition (a); then iv. of laminating or transferring the layer (a) onto a carrier layer or onto a nonstick protective film.

24. A bonding method employing the self-adhesive article as defined in claim 19, comprising the following steps: A. removing the nonstick protective layer, when such a layer is present; B. applying the self-adhesive article to one surface of a product; and C. applying a pressure to said article.

Description

EXAMPLE 1

[0131] 1. Preparation of a UV-Crosslinkable HMPSA Composition:

[0132] The composition appearing in table 1 below is prepared by simple hot mixing at 165° C. of the ingredients indicated, with the photoinitiator (D) being added last. The Brookfield viscosity of this composition was measured at a temperature of 163° C. The result is indicated in table 2 in mPa.Math.s.

[0133] 2. Preparation of a Self-Adhesive Multilayer System Comprising a PET Carrier Layer (b) Coated with a Layer (a) Consisting of the Crosslinked HMPSA Composition and Having a Thickness of 60 μm:

[0134] A continuous laboratory coater operating at a line speed of about 15 m/minute is used, said coater being available from Acumeter Laboratory Inc. This coater is equipped in particular with a lip coating nozzle and a melting tank.

[0135] The carrier layer (b) is a PET film 50 μm thick, in the form of a strip 10 cm wide, packaged as a reel.

[0136] The nonstick protective film (c) used is a siliconized paper (obtained from Laufenberg), in the form of a strip 10 cm wide, packaged as a reel.

[0137] The HMPSA composition obtained above in 1. is heated in the melting tank to a temperature of 120° C. It is then coated in a surface weight of 60 g/m.sup.2 onto the protective film (c), to form a layer 60 μm thick and 6 cm wide, centered on the corresponding strip of said film (c). Lastly, the applied nonstick protective film thus obtained is laminated onto the PET film.

[0138] Rectangular sheets with dimensions of 10 cm×20 cm are then cut from the resulting three-layer film, for exposure to a UV source. The UV lamp used is a Delolux 03S mercury UV lamp with a power of 400 W which is placed about 20 cm from the three-layer sheets.

[0139] UV irradiation is carried out with the three-layer sheets placed at a distance of about 20 cm from the lamp (PET layer facing the lamp) and exposed for a period of 5 to 30 seconds.

[0140] The self-adhesive article (or multilayer system) thus obtained is subjected to the tests described hereinafter.

[0141] 180° Peel Test on a Stainless Steel Plate:

[0142] The adhesive strength is evaluated by the 180° peel test on a plate of stainless steel, as described in the FINAT No. 1 method, published in the FINAT Technical Handbook, 6th edition, 2001. FINAT is the International Federation of Self-Adhesive Label Manufacturers and Converters. The principle of this test is as follows:

[0143] A test specimen in the form of a rectangular strip (25 mm×175 mm) is cut from the self-adhesive multilayer system prepared in section 2. This test specimen is attached over half of its length (after removal of the corresponding portion of nonstick protective layer) to a substrate consisting of a plate of stainless steel. The assembly obtained is left at ambient temperature for 20 minutes. It is then placed in a tensile testing device capable, starting from the end of the rectangular strip which has remained free, of performing the peeling or detachment of the strip at an angle of 180° and with a separation speed of 300 mm per minute. The instrument measures the force required to detach the strip under these conditions.

[0144] The corresponding result is expressed in N/2.54 cm and indicated in table 2.

[0145] Instantaneous Adhesion Test (Also Known as the Loop Tack Test):

[0146] The tack, or immediate bonding strength, is evaluated by the “loop” test as described in the FINAT No. 9 method, the principle of which is as follows:

[0147] A test specimen in the form of a rectangular strip (25 mm×175 mm) is cut from the self-adhesive multilayer system prepared in section 2. After removal of all of the protective nonstick layer, the two ends of this strip are joined so as to form a loop with the adhesive layer facing outward. The two joined ends are placed in the movable jaw of a tensile testing device capable of imposing a displacement speed of 300 mm/minute along a vertical axis with a back-and-forth option. The lower part of the loop placed in the vertical position is first brought into contact with a horizontal stainless steel plate of 25 mm by 30 mm over a square region with a side length of approximately 25 mm Once this contact has been established, the direction of displacement of the jaw is reversed. The tack is the maximum value of the force required for the loop to become completely detached from the sheet.

[0148] The corresponding result is expressed in N/(2.54 cm).sup.2 and is indicated in table 2.

[0149] Temperature Causing Failure of the Bonded Joint with Static Shearing:

[0150] The high-temperature integrity of the adhesive strength of the self-adhesive multilayer system prepared in section 2 is evaluated by a test which determines the temperature causing failure of the bonded joint with static shearing. This test is also known under the name of Shear Adhesion Failure Temperature (SAFT) test.

[0151] For this test, reference is made to the FINAT No. 8 method. The principle is as follows:

[0152] A test specimen in the form of a rectangular strip (25 mm×75 mm) is cut from the self-adhesive multilayer system prepared in section 2. After removal of all of the protective nonstick layer, a square portion with a side length of 25 mm located at the end of the adhesive strip is attached to a plate of stainless steel.

[0153] The test plate thus obtained is introduced, by means of an appropriate support, in a substantially vertical position into an oven at a temperature of 20° C., the unbonded portion of the strip with a length of 50 mm being located below the plate. After thermal equilibration, the portion of the strip which has remained free is connected to a 500 g weight, the whole of the device always remaining in said oven throughout the duration of the test.

[0154] Under the effect of this weight, the bonded joint attaching the strip to the plate is subjected to a shearing stress. For more effective control of this stress, the test plate is in fact placed so as to form an angle of 2° relative to the vertical.

[0155] This oven is caused to undergo a programmed temperature rise at 0.4° C. per minute up to a maximum temperature of 200° C.

[0156] The temperature at which the strip falls off the plate following the failure of the bonded joint under the effect of this stress is recorded, and is reported in table 2.

[0157] No failure of the bonded joint is observed up to 200° C., which is the maximum temperature allowed by the oven's temperature rise programming, and consequently the result obtained is reported in table 2 as: “>200° C.”

EXAMPLES 2 TO 8

[0158] Example 1 is repeated with the compositions indicated in table 1.

[0159] The results of the tests on the self-adhesive multilayer systems obtained are also indicated in table 2.

TABLE-US-00001 TABLE 1 Amount in weight/weight % Ingredient Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 (A) Kraton ® D- 15 15 15 17.6 14.8 19.1 23.3 19.1 KX222 (B) Regalite ® S1100 25.7 27.75 31.90 30.6 29.4 27.8 27.75 21.6 Regalite ® S5100 25.7 27.75 31.90 30.6 29.4 27.8 27.75 21.6 (C) Primol ® 352 18.6 18.6 18.6 18.6 18.6 18.6 18.6 18.6 (D) Omnirad ® BDK 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 (E) Ricon ® 152 12.4 8.3 0 0 5.2 4.1 0 16.5 (F) Sumilizer ® GS 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Irgafos ® 168 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2

TABLE-US-00002 TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Brookfield 703 810 830 1355 847 1545 3287 1327 viscosity at 163° C. (mPa.Math.s) 180° C. peel 25.2 33.1 41.2 38.6 38.4 26.2 22.4 19.5 (N/2.54 cm) Tack 35.6 47.6 14 43.2 44.5 28.3 34.1 22.7 (in N/(2.54 cm).sup.2 SAFT >200 168 176 >200 >200 175 >200 164 (in ° C.)