WO2017205172A1

WO2017205172A1 - Reformable resin materials and uses therefor

Info

Publication number: WO2017205172A1
Application number: PCT/US2017/033282
Authority: WO
Inventors: Sylvain Gleyal; Brandon Madaus; Craig Chmielewski
Original assignee: Zephyros, Inc.
Priority date: 2016-05-24
Filing date: 2017-05-18
Publication date: 2017-11-30

Abstract

Reformable epoxy resins are disclosed for use in films, composites, and tapes and more particularly for uses of such materials for reinforcing, surface treating, adhering, laminating and stiffening.

Description

REFORMABLE RESIN MATERIALS AND USES THEREFOR

Technical Field

[0001] The present teachings pertain generally to reformable resins for use in films, composites, and tapes and more particularly to uses of such materials for reinforcing, surface treating, adhering, laminating and stiffening.

Background

[0002] The use of composite structures in the protective armor field frequently requires materials that are capable of adhering adjacent layers of the composite structures. Such composites are often similar to composite materials utilized in building construction, sporting equipment, furniture construction, automotive vehicles, trains, and aerospace vehicles (and other transportation vehicles), among others. However, the adhesives generally used in these industries are thermoset adhesives due to their improved strength as compared to thermoplastic adhesives. Thermoplastic adhesives generally do not have the strength characteristics of epoxy-based thermoset materials. However, the use of thermoset adhesives in composite structures often presents significant limitations on the ability to curve, mold and form the composite structures, dues to the strength and stiffness of the thermoset adhesive.

[0003] Many of the composite structures utilized for protective armor include ceramic plates. While the ceramic material is effective against ballistic penetration, the plates have a curved surface that is often uneven. As a result, when the plates are located in contact with an adjacent layer, gaps between the layers are common which can reduce the efficacy of the composite.

[0004] There is thus a need for reformable (e.g., non-thermoset) epoxy-based adhesives that are easily formed into a wide variety of formats, capable of filling gaps between and within adjacent layers, require minimal time and heat to soften and adhere, and yet maintain the high strength of typical epoxy-based thermoset adhesives. There is a further need for such epoxy-based adhesives that are substantially free of any mixing with thermoset components.

Summary of the Invention

[0005] The teachings herein are directed to a variety of formats and uses for reformable epoxy resin adhesives including composites comprising a ceramic layer; a polyethylene layer; a reformable epoxy resin adhesive layer located in contact with at least one of the ceramic layer or polyethylene layer; and an optional structural adhesive layer having an embedded material l located within or adjacent the structural adhesive layer. The reformable epoxy resin adhesive layer has a glass transition temperature higher than room temperature but lower than 200°C and upon exposure to temperatures at or above its glass transition temperature, the reformable epoxy resin adhesive layer bonds to one or more of the ceramic layer and polyethylene layer.

[0006] The composite may be free of any adhesive that is liquid at 25°C (e.g., any adhesive having a viscosity of less than 100 P s at 25°C). The reformable epoxy resin adhesive layer may be a film. The structural adhesive layer may be an activatable material. The reformable epoxy resin adhesive layer may be a heat activated expandable material. The reformable epoxy resin adhesive layer may fall below its glass transition temperature upon exposure to ambient temperature in less than 5 minutes. After the reformable epoxy resin layer falls below its glass transition temperature, it can be heated multiple times above its glass transition temperature for molding into a non-planar composite structure. The reformable epoxy resin layer may be stored at room temperature prior to use. The reformable epoxy resin layer may be formed of a reaction product of a mono-functional or di-functional species (i.e., respectively, a species having one or two reactive groups, such as an amide containing species), with an epoxide-containing moiety, such as a diepoxide (i.e., a compound having two epoxide functionalities), reacted under conditions for causing the hydroxyl moieties to react with the epoxy moieties to form a generally linear backbone polymer chain with ether linkages. The shelf life of the reformable epoxy resin material may be at least about 3 months, at least about 6 months, at least about 1 year, or even at least about 5 years. The reformable epoxy resin layer may be formed of a reaction product of bisphenol A diglycidyl ether (BADGE) and monoethanolamine. The reformable epoxy resin material may be recyclable. The stiffness of the reformable epoxy resin material may be substantially higher than the stiffness of a thermoplastic material without an epoxy component.

[0007] The reformable epoxy resin material may be capable of receiving printed material prior to forming the composite structure whereby the printed material can be clearly viewed after formation of the composite structure. The resulting composite structure may be stampable. The composite may be utilized as part of a protective garment. The protective garment may be a bullet proof vest. The polyethylene may be an ultra-high molecular weight polyethylene (UHMWPE). The reformable epoxy resin material may substantially prevent fragments of broken ceramic layer from contacting the polyethylene layer. The composite may include one or more of a glass material, carbon material, and aramid material. The ceramic layer may be wrapped in the reformable epoxy resin layer. The ceramic layer may be repaired by exposing the reformable epoxy resin layer to temperatures above its glass transition temperature to remove the reformable epoxy resin layer. The composite may be used to form a helmet. The composite may be substantially free of any additional layer for reinforcement. The composite may be substantially free of any polyurethane or polyvinyl butyral.

[0008] The teachings herein further provide for a composite structure that consists essentially of a ceramic layer, a polyethylene layer and a reformable epoxy resin layer. The teachings herein also provide for a composite structure consisting essentially of a ceramic layer, a polyethylene layer, a reformable epoxy resin layer, and a structural adhesive layer. The reformable epoxy resin layer may be a film layer.

Detailed Description

[0009] The present teachings meet one or more of the above needs by the improved composite structures and methods described herein. The explanations and illustrations presented herein are intended to acquaint others skilled in the art with the teachings, its principles, and its practical application. Those skilled in the art may adapt and apply the teachings in its numerous forms, as may be best suited to the requirements of a particular use. Accordingly, the specific embodiments of the present teachings as set forth are not intended as being exhaustive or limiting of the teachings. The scope of the teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. Other combinations are also possible as will be gleaned from the following claims, which are also hereby incorporated by reference into this written description.

[0010] This application claims the benefit of the filing date of U.S. Provisional Application Serial Nos. 62/341 ,044, filed May 24, 2016 and 62/441 ,780, filed January 3, 2017, the contents of these applications being hereby incorporated by reference herein for all purposes. The teachings herein make advantageous use of a reformable epoxy resin epoxy adhesive that hardens and adheres when it cools. The teachings herein contemplate a method for providing composite structures that are formable and moldable after the reformable epoxy resin material is heated and subsequently falls below its glass transition temperature. The reformable epoxy resin adhesive provides structural toughness associated with epoxy materials, but is amenable to molding and re-molding after cure unlike other epoxy-based adhesive materials. Thermoplastic films are known in the art of composite structure formation, but such films typically fail to provide sufficient adhesion and stiffness. Reformable epoxy resin adhesives for use in the structures described herein provide additional stiffness, adhesion and allow for reforming and are therefore useful for composites utilized in protective materials. [0011] Currently, many composite materials utilized in protective gear (body armor, helmets and other bullet-proof gear) are formed using liquid adhesives having a relatively low viscosity at room temperature (e.g., viscosities that are less than 100 P s at 25°C). Such liquid adhesives are difficult to process and require lengthy cure times. Further, such adhesives lack sufficient toughness to form a barrier between ceramic layers and adjacent polyethylene layers. As such, when the ceramic layer fractures, occasional fragments of the ceramic pierce through the polyethylene layer.

[0012] The reformable epoxy resin material described herein may be formed as a film and easily applied to one or more layers in a composite structure. Cure time for the deformable epoxy resin material is less than 1 hour, less than 30 minutes, or even less than 10 minutes upon exposure to ambient temperature. The reformable epoxy resin material falls below its glass transition temperature upon exposure to ambient temperature in less than 5 minutes. After the reformable epoxy resin material falls below its glass transition temperature, it may be heated multiple times above its glass transition temperature for molding into a shape that differs from an original shape.

[0013] The reformable resin adhesives disclosed herein are also easily printed on and can thus be applied to a visible surface with desired print material already located on the film. Alternatively, the film can receive print after being applied to a desired surface. The reformable epoxy resin adhesives may also be stampable or otherwise capable of receiving an imprint.

[0014] The materials and methods taught herein include possible uses for reformable epoxy resin materials in composite structures. It is possible that the reformable epoxy resin materials may be provided initially in a pellet form and then formed into a reformable epoxy resin film. The film may then be applied as a layer to a surface or may be applied to surround the entirety of a layer. The film may be applied to a ceramic layer of a composite. The film may substantially surround a ceramic layer. The film may be applied to a polymeric layer. The film may be applied to a polyethylene layer. The film may be applied so that it lies in between a polyethylene layer and a ceramic layer. An additional adhesive layer may be utilized within the composite structure. As a result the film may be applied on a surface of the additional adhesive layer. The additional adhesive layer may be a structural adhesive, which may be tacky to the touch. The additional adhesive layer may also be dry to the touch.

[0015] An advantage of the present teachings over existing epoxy materials used for adhesives is that the materials herein have improved strength and adhesion as compared to other thermoplastic materials and are also significantly more flexible than other epoxy-based adhesives. Further, the reformable epoxy resin adhesive can be easily and selectively removed and reformed by the addition of heat. Additional benefits of the reformable epoxy resin material include fast hardening and adhesion, and also the ability to re-form and re-mold the adhesive. Adhesion, hardening, and returning to a solid state upon cooling of the reformable epoxy resin adhesive begins almost immediately after heating is stopped and full adhesion can occur within about 10 seconds to about 60 seconds (e.g., about 30 seconds). It is contemplated that allowing the adhesive to return to ambient temperature is sufficient for adhesion, and additional hardening steps are possible, but not necessary. In addition, a reformable epoxy resin may be desirable because of its long shelf life. It also may not require storage at a refrigerated temperature, unlike some alternative materials.

[0016] In use of the reformable epoxy resin adhesive in protective structures, in addition to providing improved, quick adhesion (as compared to typical adhesives used to form such composites), the reformable epoxy resin may act as a barrier to prevent unwanted composite materials from contacting an underlying polymeric layer upon breaking of one or more composite layers.

[0017] Exemplary reformable epoxy resin materials are made using bisphenol A diglycidyl ether (BADGE) and monoethanolamine. For some applications that may require a higher glass transition temperature (T_g), it is contemplated that BADGE may be replaced by an epoxy monomer with less mobility. Such epoxy monomers may include diglycidylether of fluoren diphenol or 1 ,6 napthalene diepoxy. Also, it is contemplated that where fire resistance is desired, BADGE can be replaced by a brominated bisphenol A epoxy resin. The reformable epoxy resin material having at least one epoxide group may be hydroxy-phenoxyether polymer, such as a polyetheramine thermoplastic material as described herein. For example, such thermoplastic polymeric material having at least one epoxide group may be a product (e.g., a thermoplastic condensation reaction product) of a reaction of a mono-functional or di-functional species (i.e., respectively, a species having one or two reactive groups, such as an amide containing species), with an epoxide-containing moiety, such as a diepoxide (i.e., a compound having two epoxide functionalities), reacted under conditions for causing the hydroxyl moieties to react with the epoxy moieties to form a generally linear backbone polymer chain with ether linkages.

[0018] Though other functional species may be employed, as is taught in U.S. Patent No. 6,011 , 11 1 (incorporated by reference; see, e.g., Cols. 6-8) and WO 98/14498 (incorporated by reference; see, e.g., pages 8-11) examples of such mono-functional or di-functional species may include a dihydric phenol, a secondary amine (e.g., a bis-secondary amine), a primary amine, or any combination thereof. Any amine of the functional species can be an aromatic amine, an aliphatic amine or a combination thereof. The mono-functional or di-functional species may have one or two functionalities capable of reacting with epoxide groups to form a generally non-cross- linked polymer. Some particular examples, without limitation, of functional species for reaction with an epoxy moiety in accordance with the present teachings includes an ethanolamine (e.g., monoethanolamine), piperazine or a combination thereof. Any of the illustrative functional species may be substituted or unsubstituted.

[0019] Other examples of illustrative materials, functional species and diepoxides are described in U.S. Patent Nos. 5, 115,075; and 4,438,254, all incorporated by reference herein (see also U.S. Patent No. 3,317,471 and 4,647,648, also incorporated by reference herein). Examples of such materials also can be found, without limitation at paragraphs 15-25 of Published U.S. Patent Application No. 20070270515 (Chmielewski et al), incorporated by reference for all purposes.

[0020] The teachings herein also relate to a method for making a variety of composites. In general, a method in accordance with the present teachings may employ a step of contacting a plurality of segmented forms provided for defining a distributed with a thermoplastic epoxy resin, such as an hydroxy-phenoxyether polymer (e.g., a generally thermoplastic reaction product of an epoxy and an amine) that is in a softened state (e.g., in a liquefied molten state). For instance, a method in accordance with the present teachings may employ forming a composite material by extrusion, injection molding, or a combination of both. Thus, it is envisioned for the teachings herein that there is method of making the articles that includes contacting an epoxy/amine reaction product material (e.g., a material that is a reaction product of a diepoxide and a primary amine, such as monoethanolamine) during a step of extrusion, molding, pultrusion or any combination thereof. The contacting may be only after the reaction has completed between the epoxy and the amine (e.g., only after the reaction of epoxy and amine). Thus it is possible that the method herein will involve no chemical reaction between any epoxy and amine reactants that occurs with an injection molding machine and/or an extruder. That is, the method may include advancing a thermoplastic polymer having at least one epoxide functional group reaction product along a rotating feed screw within a barrel of a polymeric material shaping apparatus.

[0021] Reformable epoxy resin adhesives are advantageous as they allow for faster hardening and adhesion, thereby reducing the need for extended periods of time and large areas of space for curing adhesives in composite structures. While reformable epoxy resin adhesives may be workable at ambient temperature, it is often desirable to have a heat applying step to soften or melt the reformable epoxy resin adhesive to allow it to move or become more workable. Heating the resulting structure allows for ease of formability into a desired shape. Adhesion and hardening of the reformable epoxy resin adhesive begins almost immediately after heating is stopped and full adhesion can occur within about 10 seconds to about 5 minutes (e.g., about 2 minutes). It is contemplated that allowing the adhesive to return to ambient temperature is sufficient for adhesion, and additional hardening steps are possible, but not necessary. With a reformable epoxy resin adhesive, it is also possible that the bond formed between the adhesive and any adjacent substrate can be debonded by increasing the temperature over the glass transition temperature (T_g) of the reformable epoxy resin adhesive to allow the bonded substrates to be separated.

[0022] As used herein, unless otherwise stated, the teachings envision that any member of a genus (list) may be excluded from the genus; and/or any member of a Markush grouping may be excluded from the grouping.

[0023] Unless otherwise stated, any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component, a property, or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that intermediate range values such as (for example, 15 to 85, 22 to 68, 43 to 51 , 30 to 32 etc.) are within the teachings of this specification. Likewise, individual intermediate values are also within the present teachings. For values which are less than one, one unit is considered to be 0.0001 , 0.001 , 0.01 or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner. As can be seen, the teaching of amounts expressed as "parts by weight" herein also contemplates the same ranges expressed in terms of percent by weight. Thus, an expression in the of a range in terms of at "'χ' parts by weight of the resulting polymeric blend composition" also contemplates a teaching of ranges of same recited amount of "x" in percent by weight of the resulting polymeric blend composition."

[0024] Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. The use of "about" or "approximately" in connection with a range applies to both ends of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", inclusive of at least the specified endpoints.

[0025] The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for ail purposes. The term "consisting essentially of to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, ingredients, components or steps herein also contemplates embodiments that consist of, or consist essentially of the elements, ingredients, components or steps.

[0026] Plural elements, ingredients, components or steps can be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step might be divided into separate plural elements, ingredients, components or steps. The disclosure of "a" or "one" to describe an element, ingredient, component or step is not intended to foreclose additional elements, ingredients, components or steps.

[0027] It is understood that the above description is intended to be illustrative and not restrictive. Many embodiments as well as many applications besides the examples provided will be apparent to those of skill in the art upon reading the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The omission in the following claims of any aspect of subject matter that is disclosed herein is not a disclaimer of such subject matter, nor should it be regarded that the inventors did not consider such subject matter to be part of the disclosed inventive subject matter.

Claims

What is claimed is:

1) A composite comprising:

i. a ceramic layer;

ii. a polyethylene layer;

iii. a reformable epoxy resin adhesive layer located in contact with at least one of the ceramic layer or polyethylene layer;

iv. an optional structural adhesive layer having an embedded material located within or adjacent the structural adhesive layer;

wherein the reformable epoxy resin adhesive layer has a glass transition temperature higher than room temperature but lower than 200°C and upon exposure to temperatures at or above its glass transition temperature, the reformable epoxy resin adhesive layer bonds to one or more of the ceramic layer and polyethylene layer.

2) The composite of claim 1 , wherein the composite is free of any adhesive that is liquid at 25°C (e.g., any adhesive having a viscosity of less than 100 P s at 25°C).

3) The composite of claim 1 or claim 2, wherein the reformable epoxy resin adhesive layer is a film.

4) The composite of any of the preceding claims, wherein the structural adhesive layer is an activateable material.

5) The composite of claim 4, wherein the reformable epoxy resin adhesive layer is a heat activated expandable material.

6) The composite of any of the preceding claims, wherein the reformable epoxy resin

adhesive layer falls below its glass transition temperature upon exposure to ambient temperature in less than 5 minutes.

7) The composite of any of the preceding claims, wherein after the reformable epoxy resin layer falls below its glass transition temperature, it can be heated multiple times above its glass transition temperature for molding into a non-planar composite structure.

8) The composite of any of the preceding claims, wherein the reformable epoxy resin layer is stored at room temperature prior to use.

9) The composite of any of the preceding claims, wherein the reformable epoxy resin layer is formed of a reaction product of a mono-functional or di-functional species (i.e., respectively, a species having one or two reactive groups, such as an amide containing species), with an epoxide-containing moiety, such as a diepoxide (i.e., a compound having two epoxide functionalities), reacted under conditions for causing the hydroxyl moieties to react with the epoxy moieties to form a generally linear backbone polymer chain with ether linkages.

10) The composite of any of the preceding claims, wherein the shelf life of the reformable epoxy resin material is at least about 3 months, at least about 6 months, at least about 1 year, or even at least about 5 years.

11) The composite of any of the preceding claims, wherein the reformable epoxy resin layer is formed of a reaction product of bisphenol A diglycidyl ether (BADGE) and

monoethanolamine.

12) The composite of any of the preceding claims, wherein the reformable epoxy resin

material is recyclable.

13) The composite of any of the preceding claims, wherein the stiffness of the reformable epoxy resin material is substantially higher than the stiffness of a thermoplastic material without an epoxy component.

14) The composite of any of the preceding claims, wherein the reformable epoxy resin

material is capable of receiving printed material prior to forming the composite structure whereby the printed material can be clearly viewed after formation of the composite structure.

15) The composite of any of the preceding claims, wherein the resulting composite structure is stampable.

16) The composite of any of the preceding claims, wherein the composite is utilized as part of a protective garment.

17) The composite of claim 16, wherein the protective garment is a bullet proof vest.

18) The composite of any of the preceding claims, wherein the polyethylene is an ultra high molecular weight polyethylene (UHMWPE).

19) The composite of any of the preceding claims, wherein the reformable epoxy resin

material substantially prevents fragments of broken ceramic layer from contacting the polyethylene layer.

20) The composite of any of the preceding claims, wherein the composite includes one or more of a glass material, carbon material, and aramid material.

21) The composite of any of the preceding claims, wherein the ceramic layer is wrapped in the reformable epoxy resin layer. 22) The composite of any of the preceding claims, wherein the ceramic layer can be repaired by exposing the reformable epoxy resin layer to temperatures above its glass transition temperature to remove the reformable epoxy resin layer.

23) The composite of any of the preceding claims, wherein the composite is used to form a helmet.

24) The composite of any of the preceding claims, wherein the composite is substantially free of any additional layer for reinforcement.

25) A composite structure consisting essentially of a ceramic layer, a polyethylene layer and a reformable epoxy resin layer.

26) A composite structure consisting essentially of a ceramic layer, a polyethylene layer, a reformable epoxy resin layer, and a structural adhesive layer.

27) The composite of claim 25 or 26, wherein the reformable epoxy resin layer is a film layer.

28) The composite of any of the preceding claims, wherein the composite is substantially free of any polyurethane or polyvinyl butyral.