Hybrid Polymer Adhesive and Laminate Using the Adhesive

BACKGROUND OF THE INVENTION

[OOO1] Field of the Invention

The present invention relates to a hybrid polymer adhesive and laminate using the adhesive.

Description of the Related Art

[0002] Both polyurethanes and polyacrylates are useful as adhesives. Both find utility in multiple applications as laminating adhesives and Pressure Sensitive Adhesives (PSAs). Although blends of polyurethanes (PUs) and polyacrylates (PAs) are known to exist, they are characterized as 1) phase separated blends where distinct phases exist either in discreet phases or in core -shell morphologies or 2) as copolymerized grafted polymers. In both cases, these PU-PA systems are typically produced by copolymerizing the polyacrylate in the presence of the PU. [0003] It would be beneficial to provide an adhesive formed by compatible mixture of polyurethane and polyacrylate polymers, which lead to a miscible hybrid polymer system that displays a single glass transition temperature (Tg).

SUMMARY OF THE INVENTION

[0004] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0005] In one embodiment, the present invention is a polymer adhesive comprising a pre-polymerized polyacrylate and a polyurethane.

[0006] In another embodiment, the present invention is a laminate that includes a first substrate, a second substrate, and the polymer adhesive between the first substrate and the second substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. In the drawings:

[0008] FIG. 1 is a graph of a blend of polymers in the ratio from adhesive example 1, with "Parts cross-linker" being a ratio of cross-linker to 100 parts of the solid polymer blend;

[0009] FIG. 2 is a Table of Properties of 1.2 mil MTI black/grey polypropylene laminated onto Raven F450WB;

[0010] FIGS. 3 is a table of break force, elongation at maximum load, and elongation at maximum extension for 1.2 Mil (.03 mm) MTI Black/Grey Polypropylene Laminated onto Raven F450WB; and

[0011] FIG. 3A is a table of break force, elongation at maximum load, and elongation at maximum extension for.004" (0.1 mm) Black Valeron.

DETAILED DESCRIPTION

[0012] In the drawings, like numerals indicate like elements throughout. Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. The terminology includes the words specifically mentioned, derivatives thereof and words of similar import. The embodiments illustrated below are not intended to be exhaustive or to limit the invention to the precise form disclosed. These embodiments are chosen and described to best explain the principle of the invention and its application and practical use and to enable others skilled in the art to best utilize the invention.

[0013] Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term "implementation."

[0014] As used in this application, the word "exemplary" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the word exemplary is intended to present concepts in a concrete fashion.

[0015] The word "about" is used herein to include a value of +/- 10 percent of the numerical value modified by the word "about" and the word "generally" is used herein to mean "without regard to particulars or exceptions." Unless explicitly stated otherwise, each numerical value and range should be interpreted as being approximate as if the word "about" or "approximately" preceded the value of the value or range.

[0016] Additionally, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless specified otherwise, or clear from context, "X employs A or B" is intended to mean any of the natural inclusive permutations. That is, if X employs A; X employs B; or X employs both A and B, then "X employs A or B" is satisfied under any of the foregoing instances. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more" unless specified otherwise or clear from context to be directed to a singular form.

[0017] It should be understood that the steps of the exemplary methods set forth herein are not necessarily required to be performed in the order described, and the order of the steps of such methods should be understood to be merely exemplary. Likewise, additional steps may be included in such methods, and certain steps may be omitted or combined, in methods consistent with various embodiments of the present invention.

[0018] Although the elements in the following method claims, if any, are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

[0019] The present invention provides a compatible mixture of polyurethane and polyacrylate polymers, which lead to a miscible hybrid polymer system that displays a single glass transition temperature (Tg). This hybrid system can be produced by a simple blending technique and has particular utility as a laminating adhesive. Not only is the inventive system advantageous to lower the cost of the polyurethane system by blending the polyurethane with a lower cost polyacrylate, adhesion to polyolefin films is enhanced as well elongation properties of the olefin laminates produced.

[0020] The present invention is a blend of a pre-polymerized polyacrylate (PA) and polyurethane (PU) polymers. A crosslinker is added to the blend to enhance properties. The PA-PU displays adhesive properties with excellent adhesion to olefin substrates. The PA-PU is particularly useful for laminating a Polyester Film to a polyolefin film or a bonding two polyolefin films.

[0021] An exemplary PA, PU, and crosslinker, along with exemplary laminate layers, is provided below in Table 1.

[0022] Table 1

[0024] T = High density polyethylene

[0025] rr= Low density polyethylene

[0026] TTT=Linear low density polyethylene

[0027] Example 1

[0028] Adhesive Formulation 1 :

[0029] E5721- 73 pounds (33.12 Kgs) [0030] L3941-123 pounds (55.84 Kgs) [0031] XP 2547- 4 pounds (1.82 Kgs) [0032] The above formulation was mixed with mild agitation and coated with a gravure cylinder onto a moving web of a .0045" inch (.11 mm) thick olefin film (WB450) and dried in a 4-zone infrared oven with zone temperatures of 115°F (46°F), 125°F(52°C), 125°F(52°C), and 125°F (52°C) (the multiple 125°F (52°C), temperatures are used to maintain film integrity). The dried adhesive basis weight was 4.9-5.3 pounds per ream (2.22-2.41 Kgs per 279 square meters). The dried adhesive coated WB450 was laminated to the 3 Ply MTI film by passing both layers through a nip consisting of a rubber roll and a stainless steel roll. The laminating pressure was 65 PSA (448,175 Pascals) and the stainless steel roll temperature was 250°F (121°C).

[0033] Test Results.

[0034] T-peel testing was done according to ASTM D1876-08, Standard Method for Peel Resistance of Adhesives, with a Mark-10 Model M5-20 force gauge at a speed of 3 in/min (76 mm/min). Average force in pounds and kilograms is reported.

[0035] ASTM D1938-19-Standard Test Method for Tear-Propagation Resistance (Trouser Tear) of Plastic Film and Thin Sheeting by a Single-Tear Method. This test method covers the determination of the force necessary to propagate a tear in plastic film and thin sheeting (thickness of 1 mm (0.04 in.) or less) by a single-tear method. The method is not applicable for film or sheeting material where brittle failures occur during testing.

[0036] Experimental conditions:

[0037] Grip separation of 2" (50.8 mm); and

[0038] 10"/minute (254 mm/minute) test speed.

[0039] Recorded maximum tear force (Newtons) and extension at maximum force (millimeters).

[0040] ASTM 1004-13 -Standard Test Method for Tear Resistance (Graves Tear) of Plastic Film and Sheeting. This test method covers the determination of the tear resistance of flexible plastic film and sheeting at very low rates of loading, 51 mm (2 in.)/min. and is designed to measure the force to initiate tearing.

[0041] Experimental conditions:

[0042] Grip separation of 1" (25.4 mm); and

[0043] 2"/minute (50.8 mm/minute) test speed.

[0044] Recorded maximum tear force (Newtons) and extension at maximum force (millimeters).

[0045] ASTM D1000-10 section 123 - Standard Test Methods for Pressure- Sensitive Adhesive-Coated Tapes Used for Electrical and Electronic Applications. Puncture resistance is a test to measure the resistance of a tape to puncture by a rounded probe. Puncture resistance is important because of the possibility that objects with irregular surfaces or relatively sharp contours (such as wire or laminate) will be present in the application and have the potential to cause a rupture in the tape.

[0046] Experimental conditions:

[0047] 2"/minute (50.8 mm/minute) test speed; and

[0048] Maximum puncture force (IbF and Newtons) was recorded.

[0049] ASTM D638 Tensile and Elongation (modified for sample width and pull rate)- ASTM D638 is performed by applying a tensile force to a sample specimen and measuring various properties of the specimen under stress. It is conducted on a universal testing machine (also called a tensile testing machine) at tensile rates ranging from 1 to 500 mm/min until the specimen fails (yields or breaks).

[0050] Experimental conditions: [0051] 1" (25.4mm) width samples [2" (50.8) width would elongate to the maximum length and never break];

[0052] Grip separation of 1" (25.4 mm);

[0053] 20"/minute (508 mm/minate) test speed; and

[0054] Recorded Ibf at break, elongation at break (inches and mms), and elongation at maximum extension (inches and mms).

[0055] Dynamic Mechanical Analysis (DMA) - DMA was performed on cured adhesives (FIG. 1). The blended formulation was found to have a single Glass Transition Temperature (Tg). The effectiveness the Isocyanate crosslinker was evidenced by the increase in modulus with increasing crosslinker. Regarding polymer compatibility, if the polymer pair are miscible, forming one phase, then one glass transition temperature will be observed. If the polymers are totally immiscible, then two glass transitions will be observed at the glass transitions of the homopolymers.

[0056] DMA procedure -Sample Preparation

[0057] Adhesive films

[0058] Coatings of ~4-5mil (~.1-.13 mm) were made with a drawdown bar onto polypropylene film;

[0059] Films were dried at 75°C for 1.5h (conditions for lot A034KR008 may differ); and

[0060] A ball of adhesive (~0.14g) was made from the dry adhesive film.

[0061] Rheology

[0062] Instrument-Discovery Hybrid 2 rheometer from TA Instruments;

[0063] 8mm parallel plates, disposable aluminum;

[0064] Approx. 2mm gap;

[0065] Oscillation Temperature Ramp: -80°C to 175°C at 3°C/min;

[0066] 0.05% strain, 1 Hz;

[0067] Sample was loaded at 90°C to allow for good adhesion to plates and shaping before method was started; some samples required trimming.

[0068] The results are provided in Table 2 (FIG. 2), wherein:

[0069] MD-Machine Direction

[0070] XD-Cross Direction [0071] Cured T-peel bonds measured > 72 hours after lamination

[0072] T = Average of 10

[0073] rr = Average of 9

[0074] Tensile Strength [2 inch (50.8 mm) wide strip] = No failure at >1000% Elongation

[0075] Tensile

[0076] Strength [1 inch (25.4 mm) wide strip] = 24.5 pounds (109 Newtons) at greater than 700% elongation.

[0077] FIG. 1 shows a graph of complex viscosity (Complex Modulus divided by Angular Frequency) vs. temperature (upper points) and Tan (5) (Ratio of Loss Modulus to Storage Modulus) (lower points) for the inventive adhesive. A single glass transition between about -60°C and about -35°C indicates compatibility between the PA-PU polymers, both with and without cross-linkers.

[0078] High Strength and High Elongation Laminates.

[0079] Laminates of two or more layers have been produced with enhanced tensile, elongation, puncture and tear resistance. These laminates find utility in the building and construction industries as roofing and waterproofing membranes, packaging, and as print media. One layer is a Polyolefin film with enhanced puncture and tear resistance and the other layer is chosen from olefins, polyesters, and polyurethanes, polypropylene, PVC, nylon, vinyl, nonwovens, additives for UV resistance for outdoor applications. The olefins used can be LDPE, HDPE, LLDPE, HDPE and LDPE blends, and orientated versions of these materials. The layers are bonded to each other with an adhesive. Typical values would be:

[0080] Tensile strength > 20 Pounds per inch (89 Newtons/ 25.4 mm) width with 500% elongation without delamination;

[0081] Tear resistance (Graves)> 25 Newtons;

[0082] Tear resista nee (Tro user) > 15 Newtons (MD) and 22 Newtons (XD); and [0083] Puncture resistance > 6 Ibf (27.24 Newtons).

[0084] Table 3.

[0085] T = High density polyethylene

[0086] rr= Low density polyethylene

[0087] TTT=Linear low density polyethylene

[0088] Example 2. Samples produced similiarly to Example 1.

[0089] Table 4.

[0090] Example 3. Samples produced similiarly to Example 1.

[0091] Table 5. [0092] Example 4. Samples produced similiarly to Example 1.

[0093] Table 6.

[0094] Example 5. Samples produced similiarly to Example 1.

[0095] Table 7. Tensile and elongation from Example 1 vs commercially available material.

[0096] Table 7. Tensile Procedure:

[0097] 1" (25.4 mm) Wide samples;

[0098] 1" (25.4 mm) Grip separation; and

[0099] 20"/minute (508 mm/minute) jaw separation speed. [00100] Data Recorded: Ibf and N at break, elongation at break (inches and mm), and elongation at maximum extension (inches and mm).

[00101] Results: The elongation at break is 280% more than the competitive material.

[00102] Example 6

[00103] Adhesive from Example 2:

[00104] 34.7 grams E5721

[00105] 58.5 grams L3941

[00106] 3.7 grams Desmodur N3900

[00107] 3.1 grams KW3720

[00108] FIGS. 3 and 3A provide tables of break force, elongation at maximum load, and elongation at maximum extension for 1.2 Mil (.03 mm) MTI Black/Grey Polypropylene Laminated onto Raven F450WB and .004" (0.1 mm) Black Valeron, respectively.

[00109] Multi-layer laminate- First two layers:

[00110] The above formulation was mixed with mild agitation and coated with a mayer rod onto .0029 inch (.07 mm) thick aluminum foil and dried in an oven at 75°C for 5 minutes prior to lamination. The dried adhesive had an applied coat weight of 3.9lbs/ream (1.78 Kgs/279 square meters). The adhesive coated aluminum was laminated to a corona treated .92 Mil (.023 mm) Polyester film by passing the films though a Cheminstruments HL-100 laminator with a rubber and a heated steel roll. The laminating conditions were 121°C steel roll temperature, a speed of 250 inches/minute, and a laminating pressure of 70 PSI (482,650 Pascals).

[00111] The same adhesive used on the first two layers was coated onto the polyester side of laminate produced above and dried in an oven at 75°C for 5 minutes prior to lamination. The dried adhesive had an applied coat weight of 3.9 Ibs/ream (1.77 Kg/279 square meters). The same laminating conditions described above were used to bond a .0005 inch (.013 mm) thick polyethylene film with a polyethylene-acrylic acid heat sealable layer. The aluminum-polyester layers were bonded to the non-heat sealable side of the polyethylene film preserving the heat sealable layer for further bonding. The final multilayer laminate consisted of the following layers: .0029 inch (.074 mm) aluminum foil/.92 mil (.023 mm) polyester/.0005 inch (.013 mm) polyethylene w/heat seal layer. The pull test results, in PSI and Pascals) for this laminate are in Table 8 below.

[00112] Table 8.

[00113] T = bond strength between the polyester and polyethylene layers was greater than the strength of the polyethylene film.

[00114] rr = elongation at break

The above example demonstrates the adhesive's ability to bond dissimilar materials.

[00115] It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this invention may be made by those skilled in the art without departing from the scope of the invention as expressed in the following claims.