HK1212365B - Polyurethane adhesive film - Google Patents

Description

Polyurethane adhesive film

Cross Reference to Related Applications

The present application claims the benefit of U.S. provisional application No.61/860,006 filed on 30/7/2013 and incorporated herein.

Background

Adhesives are commonly used to bond substrates together to maintain the two substrates in a fixed relationship to each other.

Adhesives based on polyurethane dispersions (PUDs) can be formulated with solid surface-deactivated isocyanates. Such compositions may be pre-applied to a substrate and dried such that the isocyanate remains unactivated (i.e., heat remains less than required for activation and curing). This gives the user the option of later activating the isocyanate with heat to form a bond and initiate the curing reaction between the polyurethane and the isocyanate.

In a production environment, it is convenient that the adhesive may be provided to the end user as a thin self-supporting adhesive film. The end user thus does not have to contend with the equipment and methods of applying and drying the adhesive.

SUMMARY

In one aspect, the invention features a self-supporting adhesive film comprising: a solid surface-deactivated isocyanate and greater than 70 weight percent of a first polyurethane having a weight average molecular weight (Mw) of no greater than about 90,000 and a melting enthalpy of at least about 25J/g.

In one embodiment, a self-supporting adhesive film is obtained from an aqueous composition. In another embodiment, the solid surface-deactivated isocyanate is derived from toluene diisocyanate. In yet another embodiment, the film of the first polyurethane has a melting enthalpy of at least about 35J/g.

In one embodiment, the first polyurethane is derived from a polyester derived from a polyol selected from the group consisting of 1, 4-butanediol and 1, 6-hexanediol. In a second embodiment, the first polyurethane is derived from a polyester derived from adipic acid and a mixture of 1, 6-hexanediol and neopentyl glycol; and aliphatic isocyanates.

In various embodiments, the film exhibits an adhesive strength of at least about 20N/2.5cm when tested according to the adhesion test method at an adhesive layer temperature (bond lineteparature) of about 64 ℃. In another embodiment, the film exhibits an adhesive strength of at least about 30N/2.5cm when tested according to the adhesion test method at an adhesive layer temperature of about 82 ℃.

In some embodiments, the self-supporting adhesive film has a thickness of about 1 mil to about 8 mils. In other embodiments, the self-supporting adhesive film further comprises a release liner.

In other embodiments, the self-supporting adhesive film further comprises a second polymer. In one embodiment, the sum of the solid surface-deactivated isocyanate, the first polyurethane, and the second polymer total at least about 95 weight percent of the self-supporting adhesive film.

In another aspect, the present disclosure includes a composite structure comprising a first layer and a second layer, at least one of the first layer and the second layer comprising a self-supporting adhesive film, wherein the self-supporting adhesive film comprises a solid surface deactivated isocyanate and greater than 70 weight percent of a first polyurethane having a weight average molecular weight (Mw) of not greater than about 90,000 and a melting enthalpy of at least about 25J/g.

In one embodiment, the first layer comprises a self-supporting adhesive film and the second layer is flexible and is selected from the group consisting of fabric, foil and paper.

In another aspect, the invention features a composite structure including a self-supporting adhesive film, a rigid layer, and a flexible layer, wherein the rigid layer is adhered to the flexible layer by the self-supporting adhesive film. In some embodiments, the rigid layer comprises at least one of a metal, a metal composite, a plastic composite, wood, and a wood composite. In other embodiments, the flexible layer comprises at least one of a fabric, a foil, and a paper. In yet further embodiments, the rigid layer is nylon and the soft fabric layer is microfiber.

In another aspect, the invention features a method of making a composite that includes contacting a flexible layer with a first major surface of a self-supporting adhesive film, applying heat to the film before and after applying the film to a flexible substrate; contacting the rigid layer with the second major surface of the self-supporting adhesive film such that the second major surface is in direct contact with the rigid layer to form a composite; and applying heat and pressure to the composite.

In various aspects, a self-supporting adhesive film is obtained from an aqueous composition comprising a solid surface-deactivated isocyanate and a first polyurethane dispersion having a dry film having a melting enthalpy of at least about 25J/g, wherein the self-supporting adhesive film has a thickness of about 1 mil to about 8 mils. In one embodiment, the isocyanate is derived from an aromatic isocyanate. In various embodiments, the self-supporting adhesive film has a thickness of about 2 mils to about 6 mils. In another embodiment, a composite structure is obtained comprising a self-supporting adhesive film, a first rigid layer, and a second rigid layer, wherein the rigid layers are adhered to each other by the self-supporting adhesive film. In yet further embodiments, the composite structure comprises a self-supporting adhesive film, a rigid layer, and a flexible layer, wherein the rigid layer is adhered to the flexible layer by the self-supporting adhesive film. Alternatively, the self-supporting adhesive film comprises a second polymer.

Term(s) for

A self-supporting adhesive film is an adhesive film without any matrix present.

The substrate is the final material that is bonded or coated using an adhesive. The release liner is not considered to be a matrix.

Detailed description of the invention

The inventors have found that the adhesive composition may be provided to the user as a self-supporting adhesive film with or without a release liner.

The film comprises an isocyanate-reactive polymer and a solid surface-deactivated isocyanate. The isocyanate-reactive polymer is a polyurethane. For purposes of this application, polyurethanes include polyurethanes, polyureas, and polyurethane-ureas.

Applicants have found that thin layers of self-supporting adhesive films are capable of forming strong initial bonds at low adhesive layer temperatures. This minimizes the time required to prepare each part and increases the production speed on the production line.

Self-supporting adhesive films exhibit an adhesive strength of at least about 20N/2.5cm, at least about 30N/2.5cms, at least about 50N/2.5cms, or even from about 15N/2.5cm to about 90N/2.5cm when tested according to the adhesion test method.

Aqueous composition

The self-supporting adhesive film may be derived from an aqueous composition comprising a first polymer comprising a first polyurethane dispersion and a solid surface-deactivated isocyanate crosslinker. The first polyurethane dispersion and the solid surface-deactivated isocyanate crosslinker may be provided separately as a two-component system and then mixed prior to forming a film, or alternatively, may be provided as a one-component system in which the two are already mixed.

A first polyurethane dispersion

A useful first polyurethane dispersion comprises an anionic polyurethane dispersion. The first polyurethane has a degree of crystallinity and a melting peak that is low enough to be easily activated. A useful indication of crystallinity is the enthalpy of fusion-the higher the enthalpy of fusion of a compound, the higher its crystallinity. A useful method for determining the enthalpy of fusion (Δ H) and the melting peak of polyurethanes utilizes Differential Scanning Calorimetry (DSC) using a PYRIS1DSC with a heating rate of 10 ℃/min.

The dried first polyurethane preferably has a melting enthalpy of at least about 15 joules/gram (J/g), at least about 25J/g, at least about 35J/g, or even from about 15J/g to about 70J/g. The dried first polyurethane preferably has a melting peak of no greater than about 65 ℃, no greater than about 60 ℃, or even no greater than about 55 ℃.

The first polyurethane has a relatively low weight average molecular weight (Mw). Preferably, the first polyurethane has a molecular weight of no greater than about 90,000, no greater than about 85,000, or even no greater than about 80,000.

The first polyurethane is derived from at least one diol, polyol, or combination thereof, and at least one di-and or polyisocyanate.

Examples of useful polyols include polyester polyols derived in part from aliphatic diols, including ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, and neopentyl glycol. In one embodiment, the first polyurethane portion is derived from a polyester polyol derived in part from 1, 4-butanediol or 1, 6-hexanediol.

Other useful polyester polyols are derived from linear dicarboxylic acids and/or derivatives thereof (e.g., anhydrides, esters, and acid chlorides), and aliphatic, cycloaliphatic, linear, and branched polyols, and combinations thereof. In one embodiment, the first polyurethane is derived from polyester polyols derived from dicarboxylic acids selected from adipic acid, succinic acid, sebacic acid, and dodecanedioic acid (dodecanoic diacid).

In another embodiment, the first polyurethane is derived from polyester polyols based on adipic acid and 1, 4-butanediol, or polyester polyols based on adipic acid and 1, 6-hexanediol, or polyester polyols based on adipic acid and a mixture of 1, 6-hexanediol and neopentyl glycol.

Useful di-and polyisocyanates include, for example, any organic compound having at least 2 free isocyanate groups per molecule. Preferred diisocyanates include, for example, aliphatic diisocyanates such as Hexamethylene Diisocyanate (HDI), 1-isocyanate-3, 3,5-trimethyl-5-isocyanatomethyl-cyclohexane (1-isocyanto-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, IPDI), and combinations thereof.

The first polyurethane may be present as one polyurethane or as a mixture of two or more polyurethanes.

The dry self-supporting adhesive film comprises at least about 30 wt%, at least about 50 wt%, at least about 70 wt%, at least about 80 wt%, from about 30 wt% to about 97 wt% of the first polyurethane, or even from about 50 wt% to about 95 wt% of the first polyurethane.

Useful first commercial polyurethane dispersions include, for example, DISPERCOLL U XP 2682, DISPERCOLL U56 and DISPERCOLL U2815 XP, all available from Bayer Material Science AG, germany, and WD4047, available from HB Fuller Company (st. paul, MN).

Solid surface-deactivated isocyanate crosslinking agent

The aqueous composition comprises a solid surface-deactivated isocyanate crosslinker. Useful solid surface-deactivated isocyanate crosslinkers are derived from a polyisocyanate and a passivating agent. A variety of polyisocyanates are suitable including, for example, aliphatic, cycloaliphatic, heterocyclic and aromatic polyisocyanates such as methylene diphenyl diisocyanate (MDI), Toluene Diisocyanate (TDI) and isophorone diisocyanate (IPDI), as well as those polyisocyanates such as those disclosed in US 6,348,548B1, which are incorporated herein by reference. Surface-deactivated isocyanates derived from aromatic isocyanates are preferred because they react faster than aliphatic isocyanates, allowing strong initial bonds to form at low-adhesion layer temperatures.

A variety of passivating agents are suitable, including, for example, primary and secondary aliphatic amines, diamines, polyamines, hydrazine derivatives, amidines, guanidines, and combinations thereof. Useful examples of deactivators include ethylene diamine, 1, 3-propylene diamine, diethylene triamine, triethylene tetramine, 2, 5-dimethyl-piperazine, 3' -dimethyl-4, 4' -diamino-dicyclohexylmethane, methyl nonanediamine, isophorone diamine, 4' -diamino dicyclohexylmethane, diamino and triaminopolypropylene ethers, polyamidoamines and combinations thereof, as well as those deactivators disclosed in US 6,348,548B 1.

Useful solid surface-deactivated isocyanate crosslinkers can be prepared in a variety of ways, including those described in US 6,348,548B 1.

The solid surface-deactivated isocyanate crosslinker may be in a variety of forms including, for example, aqueous suspensions and micronized particles.

Useful commercially available solid surface-deactivated isocyanates include, for example, aqueous suspensions of DISPERCOLL BL XP 2514 of latent-reactive (late-reactive) isocyanates containing about 40% TDI dimer. Useful solid particulate isocyanates that can be deactivated include DISPERCOLL LP BUEJ471, 100% solids micronized IPDI isocyanurate available from Bayer Material Science AG, Germany, and ADDOLINK TT and ADDOLINK ST available from Rhein Chemie Rheinau GmBH, Mannheim, Germany.

The solid surface-deactivated isocyanate may be mixed with the first polyurethane dispersion to form a stable aqueous composition.

Other Components

The aqueous composition optionally comprises a second polymer. Some examples of possible second polymers include, for example, second polyurethane (e.g., DISPERCOLL U53, commercially available from Bayer Material Science AG, germany), VAE (vinyl acetate ethylene), PVA (polyvinyl alcohol), acrylics, butadiene acrylonitrile, and Styrene Butadiene Rubber (SBR).

The aqueous composition optionally comprises a variety of other additives including, for example, catalysts (e.g., amine-based), preservatives, pH modifiers (e.g., ammonia), adhesion promoters (e.g., tackifiers, silane-containing compounds), pigments, surfactants, defoamers, fungicides, bactericides, thickeners, blocking and stabilizing agents (e.g., amines), fillers (e.g., carbonates, talc, starch), materials that help adhere to form a barrier for film formation (e.g., nanoclays), insulating materials (e.g., mineral fillers, glass microbubbles), conductive materials (e.g., various metals (e.g., silver)), and combinations thereof.

A useful stabilizer is JEFFAMINE T-403POLYETHERAMINE, commercially available from Huntsman Corporation (The Woodlands, Texas). Useful thickeners for aqueous dispersions include those available from OMG Borchers GmbH (Langenfeld, Germany)GEL A LA and STEROOLL HT, commercially available from BASF Chemical Company (Ludwigshafen, Germany). Useful preservatives are ACTICIDE MBS commercially available from Thor GmbH (Speyer, Germany).

Self-supporting adhesive film

The aqueous composition is dried to form a self-supporting adhesive film. The film may be formed from the aqueous composition using a variety of methods, including spraying (e.g., spiral (spray), splash (splatter), etc.) and various coating techniques (e.g., roll coating (roll), slot (slot), gravure (gravure), pattern (pattern), etc.).

In one method, the aqueous composition is roll coated onto the release liner at the desired coating weight. The aqueous composition is then passed through a drying tunnel. The drying temperature in the drying tunnel may vary but is preferably maintained at a temperature low enough to prevent activation of the solid surface deactivated isocyanate. The temperature of the adhesive film during drying is preferably maintained at a temperature of less than about 70 c, less than about 60 c, or even less than about 55 c. After the drying tunnel, the adhesive coated on the release liner may be cooled, for example by a chill roll. It can then be wound on itself, for example in a roll, and stored for a later time.

A self-supporting adhesive film may include a solid surface-deactivated isocyanate and greater than 70 weight percent of a first polyurethane having a weight average molecular weight (Mw) of not greater than about 90,000 and a melting enthalpy of at least about 25J/g. Alternatively, a self-supporting adhesive film may comprise a solid surface-deactivated isocyanate and greater than 70 weight percent of a first polyurethane having a weight average molecular weight (Mw) of not greater than about 90,000 and a melting enthalpy of at least about 25J/g, and a second polymer. The sum of the solid surface-deactivated isocyanate, the first polyurethane, and the second polymer may total at least about 90 wt.%, at least about 95 wt.%, or even at least about 98 wt.% of the self-supporting adhesive film.

The dried film has a thickness of less than about 20 mils, less than about 15 mils, less than about 10 mils, less than about 8 mils, less than about 6 mils, from about 1 mil to about 8 mils, or even from about 2 mils to about 6 mils. The thickness of the film can be obtained in a number of ways, for example by direct coating, multiple passes through a coater, or laminating two films of different thickness together.

The film can form a strong bond between two different substrates. The matrix may be layered. The strong bond may be at a bond layer temperature (i.e., the temperature of the bond as it is formed) of no greater than about 90 ℃, no greater than about 80 ℃, no greater than about 70 ℃, or even from about 50 ℃ to about 90 ℃.

Composite structure

Self-supporting adhesive films may be used to form composite structures. The composite structure comprises an adhesive film and at least one other layer (e.g., a matrix). The layer may be rigid or flexible. An adhesive film may be placed on at least one surface of the layer to cover it.

Examples of useful rigid layers include ceramic tiles, ceramics, metals (e.g., aluminum, stainless steel), plastics (e.g., polyethylene, polypropylene, polyamides (e.g., nylon), polyurethanes, polycarbonates, Acrylonitrile Butadiene Styrene (ABS), ABS/polycarbonate blends, Polyetheretherketone (PEEK), etc.), plastic composites (e.g., fiber reinforced plastics), glass, cardboard, wood, and wood-containing products. The rigid layer may comprise one layer or it may be multilayered (i.e. comprise at least two layers).

The rigid layer may be pre-treated to improve the adhesion of the self-supporting adhesive film. It can be pre-treated by a variety of methods including, for example, corona, plasma, flame, various chemical primers, and combinations thereof.

Examples of useful flexible layers include various textiles (e.g., fabrics (e.g., microfiber-based polyethylene, cotton, canvas, and non-woven fabrics), leathers and furs, foils (e.g., decorative foils), papers, films (e.g., plastic films (e.g., polyester, polyimide (i.e., Kapton), polypropylene, and polyethylene)), and combinations thereof.

Alternatively, a self-supporting adhesive film may be used to form a composite structure comprising a rigid layer and a flexible layer, with a self-supporting adhesive film layer positioned between the rigid layer and the flexible layer to bond the two layers together.

The self-supporting adhesive film may further be used to form a composite structure selected from the group consisting of a dual rigid layer and a dual flexible layer. A self-supporting adhesive film layer is positioned between the two layers to bond the two layers together. The dual rigid layer/dual flexible layer composites may comprise the same material or they may comprise different materials.

Composite structures can be formed by a number of different methods.

In one method, the flexible layer is contacted with the first major surface of the self-supporting film and heat is applied to the film, or a combination thereof, before or after the film is applied to the flexible substrate. The rigid layer is then contacted with the second major surface of the self-supporting film such that the second major surface is in direct contact with the rigid layer to form a composite. The composite is heated to a temperature of at least about 70 ℃ to activate the isocyanate and initiate the curing process. Alternatively, the composite is heated to a temperature just hot enough to form a bond. Pressure may be used to assist in forming the bond (e.g., a film or tire press). A limited time is required to form the bond.

Use of

Self-supporting adhesive films are used in the production of a variety of articles including, but not limited to, for example, shoes, automotive parts, compartment covers, textile laminates (e.g., outdoor apparel, feminine intimate apparel), various assembled goods (e.g., panels, laminates, filters, floors, etc.).

Examples

Test program

Unless otherwise indicated, the test procedures used in the examples and throughout the specification are included as follows.

Molecular weight

The GPC molecular weight distribution curves for each dried polyurethane sample were obtained by passing a 0.05M LiBr/DMF mobile phase through 2 Agilent Resipore GPC columns using a Waters 2695 separation module connected to a Waters 2414 RI detector. Molecular weight data were calculated relative to a polymethylmethacrylate standard.

Melting peak and melting enthalpy test method

The melting peak and enthalpy of fusion (Δ H) of the dried polyurethane dispersion were determined using Differential Scanning Calorimetry (DSC) using a PYRIS1DSC with a heating rate of 10 ℃/min.

Adhesion test method

Dry films were prepared from the water-based compositions in table 2. The film was drawn using a 10cm wide draw down bar with a 250 μm gap. The film was dried at a temperature of 40 ℃ for 20 minutes to form a 100 μm (3.94 mils) thick dried film.

An adhesive bond was then prepared between the polycarbonate and polyurethane based fabrics. The bonding was carried out using a specified bonding layer temperature at 5N/cm²And a bonding pressure of 60 seconds.

The bond was then aged at room temperature for 5 minutes and peeled off using a ZWICK peel tester at a rate of 300 mm/minute. The average of the two bonds is reported.

Commercially available polyurethane dispersions were tested according to the melting peak and melting enthalpy test methods and according to the molecular weight test method. The results are described in table 1 below.

TABLE 1 comparison of polyurethane dispersions

As reported by the supplier

Examples 1 to 4

Aqueous compositions were prepared by combining the components set forth in table 2 below in the amounts indicated. The resulting composition was then tested according to the adhesion test method and the results are reported in table 2.

TABLE 2 examples

Other embodiments are within the claims.

Claims (14)

1. A self-supporting adhesive film comprising:

a.) solid surface-deactivated isocyanates; and

b.) greater than 70% by weight of a first polyurethane having a weight average molecular weight of not greater than 90,000 and a melting enthalpy of at least 25J/g, the first polyurethane being present as a mixture of two or more polyurethanes.

2. A self-supporting adhesive film according to claim 1 wherein the self-supporting adhesive film is derived from an aqueous composition.

3. The self-supporting adhesive film according to claim 1 wherein the first polyurethane is derived from:

a.) a polyester derived from adipic acid and at least one of 1, 6-hexanediol and 1, 4-butanediol; and

b.) aliphatic isocyanates.

4. The self-supporting adhesive film according to claim 1 wherein the film exhibits an adhesive strength of at least 20N/2.5cm when tested according to the adhesion test method at an adhesive layer temperature of 64 ℃.

5. A composite structure comprising:

a self-supporting adhesive film according to claim 1,

a rigid layer, and

a flexible layer, which is arranged on the outer surface of the flexible layer,

wherein the rigid layer is adhered to the flexible layer by a self-supporting adhesive film.

6. The composite structure of claim 5, wherein the rigid layer comprises at least one of a metal, a metal composite, a plastic composite, a wood, and a wood composite, and wherein the flexible layer comprises at least one of a fabric, a foil, a film, and a paper.

7. The composite structure of claim 5 wherein the rigid layer is nylon and the flexible layer comprises a soft fabric layer comprising microfibers.

8. A method of making a composite comprising:

a.) contacting a flexible layer with a first major surface of a self-supporting adhesive film of claim 1;

b.) applying heat to the film before or after applying the film to the flexible substrate;

c.) contacting the rigid layer with the second major surface of the self-supporting adhesive film such that the second major surface is in direct contact with the rigid layer to form a composite; and

d.) applying heat and pressure to the composite.

9. The self-supporting adhesive film of claim 1 wherein the solid surface deactivated isocyanate, the first polyurethane and the sum selected from the group consisting of the second polyurethane, vinyl acetate ethylene, polyvinyl alcohol, acrylic polymer, butadiene acrylonitrile and styrene butadiene rubber sum to at least 95 weight percent of the self-supporting adhesive film.

10. A composite structure comprising:

a self-supporting adhesive film comprising a solid surface-deactivated isocyanate; and more than 70% by weight of a first polyurethane having a weight average molecular weight of not more than 90,000 and a melting enthalpy of at least 25J/g, the first polyurethane being present as a mixture of two or more polyurethanes,

a rigid layer, and

a flexible layer, which is arranged on the outer surface of the flexible layer,

wherein the rigid layer is adhered to the flexible layer by a self-supporting adhesive film.

11. The composite structure of claim 10, wherein the rigid layer comprises at least one of a metal, a metal composite, a plastic composite, a wood, and a wood composite, and wherein the flexible layer comprises at least one of a fabric, a foil, a film, and a paper.

12. The composite structure of claim 10 wherein the rigid layer comprises nylon and the soft fabric layer comprises microfibers.

13. A self-supporting adhesive film comprising

a) Solid surface-deactivated isocyanates; and

b) greater than 70 weight percent of a first polyurethane having a weight average molecular weight of no greater than 90,000 and a melting enthalpy of at least 25J/g, the first polyurethane being present as a mixture of two or more polyurethanes, and

c) a second polyurethane different from the first polyurethane.

14. A method of making a composite comprising:

a) contacting the flexible layer with a first major surface of a self-supporting adhesive film comprising a solid surface-deactivated isocyanate; greater than 70 weight percent of a first polyurethane having a weight average molecular weight of no greater than 90,000 and a melting enthalpy of at least 25J/g, the first polyurethane being present as a mixture of two or more polyurethanes, and a second polyurethane different from the first polyurethane;

b) applying heat to the film before or after applying the film to the flexible substrate;

c) contacting the rigid layer with the second major surface of the self-supporting adhesive film such that the second major surface is in direct contact with the rigid layer to form a composite; and

d) heat and pressure are applied to the composite.