Source: https://patents.google.com/patent/US5721289?oq=6272333
Timestamp: 2018-02-24 06:47:36
Document Index: 672673863

Matched Legal Cases: ['arts 75', 'arts 75', 'arts 1', 'arts 1', 'arts 1', 'art 1995']

US5721289A - Stable, low cure-temperature semi-structural pressure sensitive adhesive - Google Patents
US5721289A
US5721289A US08531275 US53127595A US5721289A US 5721289 A US5721289 A US 5721289A US 08531275 US08531275 US 08531275 US 53127595 A US53127595 A US 53127595A US 5721289 A US5721289 A US 5721289A
US08531275
wherein there is essentially no conversion of the cationically-polymerizable monomer of the curable pressure sensitive adhesive for at least 10 days, at 20° C., -50% RH, when stored in a manner to exclude actinic radiation which is capable of activating the catalyst system.
Preferred thermal free-radical initiators are selected from the group consisting of peroxides and azo compounds that do not contain nitriles or basic groups. Most preferred initiators are V-601, Lupersol™ 11 and Perkadox™ 16S, and mixtures thereof, because of their preferred decomposition temperature is in the range of about 45° to 95° C. Additionally, they are generally inert toward cationic polymerization initiators.
Once coated, the curable adhesive composition is processed through at least one polymerization zone wherein the curable adhesive composition is thermally polymerized by heating the same within a thermal buffer having a heat transfer process characterized by a heat transfer coefficient of at least 25 W/(m2 ·K) to a temperature sufficient to initiate thermal polymerization for a period a time sufficient to effect about 5-100% conversion of the free-radically polymerizable monomeric mixture or prepolymerized syrup to polymer. When the process is carried out in one heating zone, it is preferred that the time and temperature be such that at least 90% of the free radically polymerizable monomeric mixture or prepolymerized syrup is converted to polymer. Furthermore, it is advantageous that the heat transfer coefficient for the heat transfer process within the thermal buffer be relatively high, preferably 100 W/(m2 ·K) and most preferably at least 500 W/(m2 ·K).
The heat transfer process within the thermal buffer can include but is not limited to forced or impinged air, helium, or hydrogen; heat transfer via conduction, such as a metal platen, or heated metal rolls; or via convective transfer to liquids, such as water, perfluorinated liquids, glycerin, or propylene glycol. Heat transfer processes that are characterized by having heat transfer coefficients of at least 25 W/(m2 ·K) are considered to be within the scope of the present invention. Additionally, it is also within the scope of the present invention to add salts or low molecular weight organic compounds to a fluid heat transfer medium to alter the characteristics of the thermal buffer, such as providing for reduced oxygen content, solubility of monomers and the like. It should be noted that it is not necessary within the thermal buffer to surround the coated construction with the heat transfer medium; contact on one side of the carrier web or polymerization mixture may be sufficient. Furthermore, physical properties, such as boiling point of the heat transfer fluid should be taken into consideration when designing a thermal buffer, along with initiator type and concentration, processing temperature and the like.
In practice, a monomer mixture or prepolymer as described in Method One or Method Two, above, is prepared in a premix tank or holding tank where it is degassed and covered with a blanket of inert gas such as nitrogen. From the holding tank, it may optionally be pumped to a static mixer, where it may optionally be preheated to a temperature in the range of 35° C. to 55° C., then introduced into the inlet of the wiped surface reactor at a pressure sufficient to maintain process stability. After an appropriate residence time, the resulting polymeric material is withdrawn from the reactor and directed to a coater or otherwise packaged.
In another aspect of this invention a mixture of free-radically polymerized polymer, cationically-polymerizable monomer and catalyst system may be melt blended. A melt blend is formed by heating the mixture to at least the softening point of the free-radically polymerized polymer, typically between about 100° C. and 150° C., with mechanical agitation to produce a homogeneous mixture. During the process of melt-blending, the free-radically polymerized polymer, cationically-polymerizable monomer and catalyst system are mixed, such as in the mixing barrel of a single screw or twin-screw extruding apparatus wherein the mixture is heated during mixing in the absence of actinic radiation that would activate the catalyst. See, for example, "Polymer Extrusion" by Chris Rauwendaal, ed. Hanser Publishers, 1986, pages 322-330, for a detailed description of mixing in screw extruders.
Differential Scanning Calorimetry was used to measure the exothermic heat of reaction (Joule/gram (J/g)) associated with the cure of the cationically polymerizable monomer. The exotherm profile, that is, peak temperature, onset temperature, etc., of the exotherm provided information on conditions that were needed to cure the material. DSC samples were typically 6 to 12 milligrams and were run in sealed pans on a Seiko Instruments DSC 220C at a heating rate of 10° C./min. The onset temperature (Tonset) is the point of intersection between the tangents drawn to the curve along the baseline, and after the onset of the exotherm at the point of maximum change in slope. The integrated energy under the exothermic peak is related to the extent of cure. For a stable composition, more of that exotherm should remain with time indicating the composition is not curing prematurely. For an unstable composition, the exotherm energy will decrease more rapidly with time indicating that the composition has undergone some degree of cure prematurely.
Photo Differential Scanning Calorimetry was used to measure the exothermic heat of reaction (Joule/gram (J/g)) associated with the cure of the cationically polymerizable monomer upon exposure to light. PDSC samples were typically 6-12 milligrams and were run in open pans on a Seiko Instruments PDC121 at a heating rate of 10° C./minute after a photolysis step using a 200 watt mercury-xenon lamp. The analysis of the exotherm profile was conducted in the same manner as described under the DSC description.
Samples were prepared by cutting 12.7 mm×25.4 mm specimens from the adhesive film. The silicone release liner was removed from one side of the specimen and the exposed adhesive was applied to one end of an aluminum test coupon measuring 1.7 mm×25.4 mm×50.8 mm. The silicone release liner was removed from the other side of the specimen and another identical aluminum coupon was placed over the adhesive such that there was a 12.7 mm overlap of the coupons and with the uncoated ends of the coupons aligned in opposite directions from each other. The coupons were clamped together and thermally cured. The prepared samples were cooled for at least 1 hour at about 22° C. before testing. The lap shear was determined using an Instron Model 1122 tensile tester according to ASTM Test Method D1002-72 with a crosshead speed of 5 cm/min. The lap shear strength is reported in Megapascals (MPa).
Peel adhesion samples were prepared by applying a 12.7 mm wide strip of the PSA tape to a desired panel (either 1.7 mm thick 50 mm×125 mm aluminum or standard 25 mm×75 mm glass microscope slide). The average peel adhesion value was determined by doubling one end of the adhesive strip back over itself at 180°, and measuring the force required to peel the tape from the substrate at a rate of 30.5 cm/minute using an Instron Model 1122 tensile tester. The 180° peel adhesion values were reported in Newton/centimeters (N/cm). Further details of this test are shown in "Test Methods for Pressure Sensitive Tapes", available from the Specifications and Technical Committee of the Pressure Sensitive Tape Council, 5700 Old Orchard Road, First Floor, Skokie, Ill. 60077, under the test designation PSTC-1.
A mixture of 60 parts 75:25 ratio of phenoxyethyl acrylate:isobornyl acrylate, 40 parts 75:25 ratio of EPON™ 828:EPON™ 1001F, 3.8 parts 1:1 ratio of cyclohexane dimethanol:1,6-hexanediol, 1.2 parts WAKO V-601™ (25 weight percent in propylene carbonate) and 1.6 parts CpFeXyl SbF6 (25 weight percent in propylene carbonate) was metered into the throat of an 18 mm counter-rotating twin screw extruder by means of a peristaltic pump. The mixture was conveyed down the length of the extruder, operated at a screw speed of 50 rpm, through 8 heated zones (72°, 81°, 92°, 96°, 105°, 110°, 115°, and 120° C., respectively), exiting the extruder at 120° C. as a relatively low viscosity, foamy viscoelastic mass. DSC analysis of the material, cooled to room temperature, indicated a peak exotherm temperature of 229.9° C. and a cure exotherm of 74.6 J/g. PhotoDSC analysis showed a peak exotherm temperature shift to 105.2° C. and an increase in cure exotherm to 173 J/g after a two-minute photolysis step. After 429 days of storage in the dark at room temperature, photoDSC of the sample gave a peak exotherm temperature of 110.3° C. and a cure exotherm of 171 J/g. This example shows that the PSA prepared by reactive extrusion has a very long shelf life, with essentially no advancement of the epoxy resin over a 14-month period.
Adhesive tapes were prepared by pressing this polymeric material to a thickness of 0.200 mm between a 0.036 mm poly(ethylene terephthalate) film and 0.100 mm silicone-coated poly(ethylene terephthalate) film using a heated platen press at a temperature of 170° C. After cooling to room temperature these tapes were tested for 180° peel adhesion to glass and aluminum substrates with and without curing. Curing was carried out by exposing the previously prepared panels to irradiation under Super Actinic™ bulbs for 5 minutes and then heating in an oven at 100° C. for 10 minutes. The resulting peel values are summarized below.
A mixture of 100 parts of the above syrup, 0.4 parts ground CpFeXyl SbF6, 0.8 parts methyl ethyl ketone, 0.1 parts hexanediol diacrylate, 0.1 parts V601 initiator, 0.075 parts PERKADOX™ 16 initiator and 4.0 parts 1:1 mixture of 1,4-cyclohexane dimethanol:1,6-hexane diol was degassed and knife-coated at 0.125 mm thickness between two 0.050 mm silicone-coated white poly(ethyleneterephthalate) films under subdued lighting. The sandwich construction was placed on an aluminum plate heated to 90° C. for 15 minutes, then cooled to room temperature. DSC analysis of the acrylate-cured film, in the absence of a photopolymerization step, showed an exotherm onset temperature of 210.4° C., a peak exotherm temperature of 226.8° C. and a cure exotherm of 45.2 J/g. PhotoDSC of the sample showed an exotherm onset temperature of 77.9° C., a peak exotherm at 94.6° C. and a cure exotherm of 204.7 J/g after a five-minute photolysis step.
Prior to coating, each of the formulations was de-aerated in a vacuum chamber, then knife coated at 0.75 mm thickness between two 0.100 mm transparent polyethylene terephthalate release liners. Samples C1 through C4 were irradiated for 13 minutes with 350BL fluorescent bulbs at a light dosage of 1960 mJ/cm2. These films were transparent, tacky, self-supporting pressure sensitive adhesives. Samples 3 through 5 were immersed in 83° C. water for 15 minutes followed by 10 minutes in a 100° C. oven. These films were also transparent, tacky, self-supporting pressure sensitive adhesives.
Samples of these adhesives were used to bond 50.8 mm×25.4 mm×1.7 mm aluminum panels. Prior to bonding, the panels were wiped clean with isopropanol. Samples 3 through 5 were irradiated for 5 minutes under Super Actinic™ bulbs prior to preparing the bond. An overlap joint of approximately 1.2 cm in length was formed and the bonded strips were placed in an air circulating oven at 100° C. for 30 minutes. The overlap shear bond strength was measured using an Instron Tensile Tester, model #1122. The jaw separation rate was 5 cm/min. The results are summarized in Table 3.
Samples 3 and 4 were found not to be fully cured. Additional overlap shear panels were prepared in the same manner as described above with the exception that the bonded strips were placed in an air circulating oven at 120° C. for 30 minutes. The overlap shear bond strength of these samples was measured as described above and the results are tabulated below.
A mixture of 100 parts of the above syrup, 0.4 parts ground CpFeXyl SbF6, 0.8 parts methyl ethyl ketone, 0.4 parts hexanediol diacrylate, 0.1 parts V-601 initiator, and 0.15 parts Perkadox 16 initiator was degassed and knife-coated at 0.125 mm thickness between two 0.100 mm silicone-coated PET films under subdued lighting. The sandwich construction was placed in 85° C. water for 15 minutes followed by 98° C. water for 10 minutes, then cooled to room temperature. The film was a transparent, tacky, self supporting pressure sensitive adhesive. DSC analysis of the film after 5 minutes of irradiation with Super Actinic™ bulbs showed a peak exotherm at 72.2° C. and a cure exotherm of 297.1 J/g. The rate of cure of this film at an isothermal temperature of 60° C. was determined by irradiating the film for 2 minutes with Super Actinic™ bulbs with the top liner removed, after which the liner was replaced and the sample immersed in a silicone oil bath heated to 60° C. for a predetermined length of time (see Table 5). DSC analysis was performed on the sample after removing it from the silicone oil to determine the extent of cure.
TABLE 5______________________________________Minutes at60° C.       Cure Energy (J/g)                   Residual Cure (%)______________________________________0           297.1       100.02           91.6        30.85           28.7        9.710          16.5        5.640          0.0         0.0______________________________________
The rate of cure of this film at room temperature was determined by irradiating the film for 2 minutes with Super Actinic™ bulbs with the top liner removed, after which the liner was replaced and the sample stored in the dark at room temperature (˜22° C.). DSC analysis was performed on the sample after various lengths of time to determine the extent of cure.
TABLE 6______________________________________Minutes at Room Cure Energy                     Residual CureTemperature (22° C.)           (J/g)     (%)______________________________________0               297.1     100.030              237.8     80.060              111.9     37.7180             80.9      27.2540             50.1      16.94680            36.9      12.4______________________________________
A mixture of 100 parts of the above syrup, 3.8 parts 1:1 mixture of 1,4-cyclohexane dimethanol:1,6 hexane diol, 0.3 parts V-601 initiator, 0.1 parts PERKADOX 16 initiator, and the cationic photocatalyst listed in Table 7 was degassed and knife-coated at 0.200 mm thickness between a 0.036 mm poly(ethylene terephthalate) film and 0.100 mm silicone-coated poly(ethylene terephthalate) film under subdued lighting. The sandwich construction was placed in 85° C. water for 15 minutes followed by 98° C. water for 10 minutes, then cooled to room temperature.
These tapes were tested for 180° peel adhesion to glass and aluminum substrates with and without curing. Curing of the Example 8 material was carried out by exposing the panels to irradiation under Super Actinic™ bulbs for 5 minutes and then heating in an oven at 100° C. for 10 minutes. Curing of the Example 9 material was carried out by exposing the panels to irradiation under 350BL bulbs for 5 minutes with no heating step. The resulting peel values are summarized in Table 7.
In Example 10, a molten mixture of the polyacrylate-epoxy material with cationic photocatalyst was prepared by combining 100 parts of the polymerized Mixture 2 (the liners having been previously removed before combination) with 3.0 parts UVI-6974 cationic photo-initiator with stirring in an aluminum container heated to 150° C.
Pressure sensitive adhesive tapes were prepared by pressing this polymeric material to a thickness of 0.250 mm between a 0.036 mm poly(ethylene terephthalate) film and 0.100 mm silicone-coated poly(ethylene terephthalate) film using a heated platen press at a temperature of 120° C. After cooling to room temperature these tapes were tested for 180° peel adhesion to glass substrate before and after curing the epoxy component of the pressure sensitive adhesive. Curing was carried out by exposing the previously prepared panels to irradiation under 350BL bulbs for 5 minutes without a heating step. The resulting peel values are summarized in Table 8 below.
In Example 11, a molten mixture of the polyacrylate-epoxy material with cationic photocatalyst was prepared by combining 100 parts of the polymerized Mixture 2 with 1.0 parts CpFeXylSbF6 cationic photo-initiator, predissolved at 25 wt-% in propylene carbonate, with stirring in an aluminum container heated to 150° C.
Pressure sensitive adhesive tapes were prepared by pressing this polymeric material to a thickness of 0.250 mm between a 0.036 mm poly(ethylene terephthalate) film and 0.100 mm silicone-coated poly(ethylene terephthalate) film using a heated platen press at a temperature of 120° C. After cooling to room temperature these tapes were tested for 180° peel adhesion to glass substrate before and after curing the epoxy component of the pressure sensitive adhesive. Curing was carried out by exposing the panels to irradiation under Super Actinic bulbs for 5 minutes followed by heating in a 100° C. oven for 10 minutes. The resulting peel values are summarized in Table 8 below.
1. A post curable pressure sensitive adhesive consisting essentially of:
(1) at least one free radically polymerized polymer;
wherein there is essentially no conversion of the cationically-polymerizable monomer component of the curable pressure sensitive adhesive for at least 10 days at 20° C., 50% relative humidity, when the curable pressure sensitive adhesive is stored in a manner to exclude actinic radiation.
2. A method of preparing a post curable pressure sensitive adhesive (PSA) comprising the steps of:
( 1) preparing a polymerizable composition consisting essentially of
(d) a photoactivatable catalyst system for the cationically-polymerizable monomer comprising at least one organometallic complex salt or at least one onium salt, and
(2) applying sufficient thermal energy to the mixture to effect essentially complete polymerization of the free-radically polymerizable monomer; and wherein there is essentially no conversion of the cationically-polymerizable monomer component of the curable pressure sensitive adhesive for at least 10 days at 20° C., 50% relative humidity, when the curable pressure sensitive adhesive is stored in a manner to exclude actinic radiation.
(a) applying sufficient irradiation to the curable PSA to activate the photoactivatable catalyst system, and
(b) providing sufficient time and/or thermal energy to effect essentially complete polymerization of the cationically polymerizable monomer.
4. A method for preparing a curable pressure sensitive adhesive (PSA) comprising the steps:
(1) preparing a first polymerizable composition consisting essentially of a mixture of
(c) at least one cationically-polymerizable monomer, and
(d) optionally, a monohydric or polyhydric alcohol;
(3) mixing into the polymerized composition,
(a) a photoinitiated catalyst system for the cationically-polymerizable monomer comprising at least one organometallic complex salt or at least one onium salt, and
(b) optionally, a monohydric or polyhydric alcohol; and wherein there is essentially no conversion of the cationically-polymerizable monomer component of the curable pressure sensitive adhesive for at least 10 days at 20° C., 50% relative humidity, when the curable pressure sensitive adhesive is stored in a manner to exclude actinic radiation.
6. A method for preparing a curable pressure sensitive adhesive (PSA) comprising the steps:
(b) at least one free-radical initiator; and
(b) a photoinitiated catalyst system for the cationically-polymerizable monomer comprising at least one organometallic complex salt or at least one onium salt, and
(c) optionally, a monohydric or polyhydric alcohol; and wherein there is essentially no conversion of the cationically-polymerizable monomer component of the curable pressure sensitive adhesive for at least 10 days at 20° C., 50% relative humidity, when the curable pressure sensitive adhesive is stored in a manner to exclude actinic radiation.
US08531275 1994-11-04 1995-10-05 Stable, low cure-temperature semi-structural pressure sensitive adhesive Expired - Lifetime US5721289A (en)
US33469294 true 1994-11-04 1994-11-04
US44514395 true 1995-05-19 1995-05-19
US08531275 US5721289A (en) 1994-11-04 1995-10-05 Stable, low cure-temperature semi-structural pressure sensitive adhesive
CA 2203400 CA2203400A1 (en) 1994-11-04 1995-10-13 Stable, low cure-temperature semi-structural pressure sensitive adhesive
PCT/US1995/013204 WO1996014349A1 (en) 1994-11-04 1995-10-13 Stable, low cure-temperature semi-structural pressure sensitive adhesive
EP19950936331 EP0789720B1 (en) 1994-11-04 1995-10-13 Stable, low cure-temperature semi-structural pressure sensitive adhesive
JP51531896A JPH10508636A (en) 1994-11-04 1995-10-13 -Stable low curing temperature of the semi-structural pressure sensitive adhesive
DE1995621056 DE69521056T2 (en) 1994-11-04 1995-10-13 Stable, pressure-sensitive at low temperature curing adhesive semistruktuierte
KR19970702971A KR100427195B1 (en) 1994-11-04 1995-10-13 Stable, Low Cure-Temperature Semi-Structural Pressure Sensitive Adhesive
KR20037014516A KR100433778B1 (en) 1994-11-04 1995-10-13 Stable, Low Cure-Temperature Semi-Structural Pressure Sensitive Adhesive
DE1995621056 DE69521056D1 (en) 1994-11-04 1995-10-13 Stable, pressure-sensitive at low temperature curing adhesive semistruktuierte
US44514395 Continuation-In-Part 1995-05-19 1995-05-19
US5721289A true US5721289A (en) 1998-02-24
ID=26989327
US08531275 Expired - Lifetime US5721289A (en) 1994-11-04 1995-10-05 Stable, low cure-temperature semi-structural pressure sensitive adhesive
US (1) US5721289A (en)
JP (1) JPH10508636A (en)
KR (2) KR100433778B1 (en)
DE (2) DE69521056T2 (en)
EP (1) EP0789720B1 (en)
WO (1) WO1996014349A1 (en)
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KR100966403B1 (en) * 2001-11-02 2010-06-28 쓰리엠 이노베이티브 프로퍼티즈 컴파니 Hybrid adhesives, articles, and methods
EP0789720B1 (en) 2001-05-23 grant
KR20040012803A (en) 2004-02-11 application
DE69521056T2 (en) 2002-01-24 grant
JPH10508636A (en) 1998-08-25 application
KR100427195B1 (en) 2004-08-16 grant
KR100433778B1 (en) 2004-06-09 grant
EP0789720A1 (en) 1997-08-20 application
DE69521056D1 (en) 2001-06-28 grant
WO1996014349A1 (en) 1996-05-17 application
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