WO2008144171A1

WO2008144171A1 - Multi-layer composite having a functionalized acrylic layer

Info

Publication number: WO2008144171A1
Application number: PCT/US2008/061710
Authority: WO
Inventors: Amy A. Lefebvre; Leslie A. Cohen; Harold Reid Banyay
Original assignee: Arkema France
Priority date: 2007-05-18
Filing date: 2008-04-28
Publication date: 2008-11-27

Abstract

The invention relates to a multi-layer composite having a functionalized acrylic layer directly adhered to a polymeric substrate without the use of any adhesive. The functionalized acrylic layer may be a capstock or a tie layer. The polymeric substrate is one having some functionality that chemically interacts with the functional groups on the functionalized acrylic, such as polyethylene terephthalate, polycarbonate, polyamides, polyurethanes and polyesters The functionalized acrylic polymer is adhered to the substrate though a heat and/or pressure process.

Description

MULTI-LAYER COMPOSITE HAVING A FUNCTIONALIZED ACRYLIC LAYER

Field of the Invention: The invention relates to a multi-layer composite having a functionalized acrylic layer directly adhered to a polymeric substrate without the use of any adhesive. The functionalized acrylic layer may be a capstock or a tie layer. The polymeric substrate is one having some functionality that chemically interacts with the functional groups on the functionalized acrylic. The functionalized acrylic polymer is adhered to the substrate though a heat and/or pressure process.

Background of the Invention

Acrylic compositions and articles made from them are well known for their clarity, sparkling color, surface gloss and weather resistance. These acrylic compositions are often used as thin capstocks to provide protection and enhanced appearance to substrate polymers that lack outdoor weatherability, solvent resistance or surface hardness. These capstocks may be impact modified. Current protective acrylic capstocks are generally comprised of methyl methacrylate (MMA) and non- functionized acrylate comonomers such as ethyl acrylate (EA), methyl acrylate (MA), and butyl acrylate (BA). In co-extruded products, the use of acrylic capstocks is generally limited to compatible substrate thermoplastic materials, such as polyvinyl chloride (PVC) and styrene-acrylonitrile containing materials.

One approach to compatibilize a PMMA capstock with incompatible substrate thermoplastics such as poly(styrene) involves the use of additives, as described in US 6,852,405. Such additives are expensive and may reduce properties of the capstock and resulting multi-layer material. Additionally, no such additive approach is known to adhere PMMA based protective capstocks to substrates such as pultruded fiberglass reinforced polyurethane, pultruded fiberglass reinforced polyester, thermoplastic polyester, or thermoplastic polyester substrates. Another approach is through the use of surface treatments that provide surface energy and allow some adhesion between substrates. Adhesives and tie layers present another solution. However, these solutions require extra processing steps, as well as additional costs and concerns. Functionalized acrylics have been used in coating compositions to improve adhesion, such as described in US 6,420,429 for high weatherability (meth)acrylic paints having alkenyl or silyl groups. US 6,388,021 describes acrylic resins functionalized with an amino group, an ammonium group, or a hydroxyl group, for use as films having excellent metal adhesion.

It has now been found that a functionalized acrylic polymer layer can be directly adhered to a substrate layer that typically does not adhere to acrylic polymers, with good adhesion.

Summary of the Invention

A multi-layer composite comprising a layer of funcitionalized acrylic polymer of at least 1 mil in thickness directly adhered to a polymeric substrate layer with out the use of an adhesive, wherein said acrylic polymer comprises from 50 to 99.9 weight percent of methyl methacrylate units.

Detailed Description of the Invention

The invention relates to a multi-layer composite having a functionalized acrylic layer directly adhered to a polymeric substrate. The functionalized acrylic layer may be a capstock or a tie layer. The functionalized acrylic polymer provides good adhesion properties, without the need for other adhesive or tie layers.

The functionalized acrylic layer is formed using a functionalized acrylic resin, or a mixture containing a functionalized acrylic resin and non-functionalized resin. By "functionalized acrylic" resin is meant a resin having an acrylic backbone and containing from 0.1 to 100.0 percent functionalized units, preferably 0.1 to 20 percent functional units, more preferably from 1 to 10 percent, and most preferably from 1.5 to 7 percent functional units. The functionalized acrylic resin may contain a single type of functionality, may be a mixture of two or more functionalities within the same polymer, or may be a mixture of two or more separate resins having different functionalities. The functionalized acrylic resin may be formed in several different ways, as known in the art. These include polymerization of one or more functionalized monomers, copolymerization of one or more functional monomers with one or more non- functional monomers, post-polymerization functionalization of an acrylic polymer, or a combination of the above. "Acrylic" resin, as used herein, includes polymers formed from alkyl methacrylate and alkyl acrylate monomers, and mixtures thereof. The alkyl methacrylate monomer is preferably methyl methacrylate, which makes up from 50 to 99.9 percent of the monomer mixture. 0 to 50 percent of other acrylate and methacrylate monomers or other ethylenically unsaturated monomers, included but not limited to, styrene, alpha methyl styrene, acrylonitrile, and crosslinkers may also be present in the monomer mixture. Other methacrylate and acrylate monomers useful in the monomer mixture include, but are not limited to, methyl acrylate, 2-ethyl hexyl acrylate and methacrylate, ethyl acrylate and ethyl methacrylate, butyl acrylate and butyl methacrylate, iso-octyl methacrylate and acrylate, lauryl acrylate and lauryl methacrylate, stearyl acrylate and stearyl methacrylate, isobornyl acrylate and methacrylate, methoxy ethyl acrylate and methacrylate, 2-ethoxy ethyl acrylate and methacrylate, dimethylamino ethyl acrylate and methacrylate monomers.

Functional monomers useful as comonomers to add functionality to the acrylic polymer include, but are not limited to, those containing acid, anhydride, maleic anhydride, hydroxy, epoxy, and amine groups. Examples of useful functional comonomers include, but are not limited to, amine functional: N,N- dimethylaminoethyl(meth)acrylate, N,N-diethylaminoethyl(meth)acrylate, (meth)acrylamide, N,N-dimethylacrylamide, N-methylolacrylamide, N- methylaminopropyl(meth)acrylamide, N,N-dimethylarninopropyl(meth)acrylamide, N-ethylamino propyl(meth)acrylamide, N,N-diethylaminopropyl (meth)acrylamide, or chlorides of these compounds; hydroxyl functional: 2-hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, 4-hydroxybutyl (meth)acrylate, or 2,3- dihydroxypropyl(meth)acrylate; carboxylic acid and anhydride functionality: maleic anhydride, maleic acid, substituted maleic anhydride, mono-ester of maleic anhydride, itaconic anhydride, itaconic acid, substituted itaconic anhydride, monoester of itaconic acid, fumaric acid, fumaric anhydride, substituted fumaric anhydride, monoester of fumaric acid, crotonic acid and its derivatives, acrylic acid, and methacrylic acid. The polymers may be made by methods known in the art including emulsion polymerization, suspension polymerization, bulk polymerization, and solution polymerization.

The molecular weight of the functionalized acrylic polymer is in the range of at least 10,000 weight average molecular weight, and Tg of at least 25⁰C. The functionalized acrylic layer may also contain additives, such as UV absorbers, lubricants, antioxidants, pigments, matting agents, fillers, and dyes. For end-use applications in which the functionalized acrylic layer will be exposed to the environment, it is preferred to have from 0.5 to 10 weight percent, and more preferably from 1 to 5 weight percent of UV absorbers, based on the weight of the acrylic polymer. Additionally, the functionalized acrylic layer may contain from 0.1 and 99.9 percent of an elastomeric impact modifier, preferably 5 to 60.0 weight percent of an elastomeric impact modifier.

The functionalized acrylic layer is in direct contact with a polymeric substrate, without the use of an adhesive or other intermediate material. The polymeric substrate includes some functionality that can chemically interact with the functionality on the functionalized acrylic layer. That interaction could be due the formation of covalent, polar-covalent, or ionic bonds, or intermolecular interactions such as hydrogen bonding or van der Waals forces. The polymeric substrate can be a thermoplastic, a thermosetting polymer or a mixture. Examples of polymeric substrates useful in the invention include polyethylene terephthlate (PET), polycarbonate (PC), polyamides, thermosetting polyurethane, thermosetting polyester, thermoplastic polyurethane, other thermoplastic polyesters including co-polyesters, cellulosic polymers, wood- polymer composites, urethanes, epoxies, maleic anhydride/styrene copolymers, polyethylene naphthalate (PEN), vinyl acetate copolymers, glycol modified polyethylene terephthlate (PETG), or mixtures of the above. No adhesive is required for good bonding between the polymeric substrate and the functionalized acrylic layer.

The substrate layer may or may not contain other additives and fillers for property improvement such as glass fibers, glass strands, clay nanostructures, calcium carbonate and other fillers, glass beads, cross-linked polymeric beads, flame retardants etc.

In addition to the functionalized acrylic layer and polymeric substrate layer, the multi-layer composite of the invention may contain one or more additional layers. In one embodiment, the functionalized acrylic layer may serve as a tie layer to adhere an outer layer (such as a non- functional acrylic, a fluoropolymer, a fluorpolymer/acrylic blend, a terpolymers of acrylonitrile-styrene-acrylate elastomer, or a terpolymers of acrylonitrile-styrene-olefin elastomer) to a polymeric substrate. The outer layer, and functional acrylic tie layer could be transparent, translucent, or opaque. In another embodiment, the outer layer, and/or functional acrylic tie layer contain from 0.1 to 10 weight percent of UV absorber, based on the weight of the polymer matrix layer. The outer layer could optionally contain other additives, such as impact modifiers, matting agents, or fillers. The multi-layer composite is formed without adhesive between the functional acrylic layer and polymeric substrate. The multi-layer composite is formed by a combination of heat and pressure, applied to either the substrate, functional acrylic layer, or preferably both. Examples of processes useful in forming the multi-layer composite of the invention include, but are not limited to pultrusion, multi-layer extrusion, film lamination, insert molding, and compression molding.

The resulting multi-layer polymeric structure displays physical properties representative of the engineering thermoplastic or thermoset substrate and enhanced surface properties such as outdoor weatherability.

The functionalized acrylic layer of the multi-layer composite is generally greater than 1 mil thick, generally from 1 to 20 mils in thickness, preferably 3 to 15 mils in thickness. The substrate layer could be thick enough to provide support for the thin acrylic layer (generally from 5 mils to 6 inches thick) or could be thin enough to form a multi-layer film having a total film thickness of from 0.5 to 20 mil in thickness. In one embodiment, the substrate may have some direct adhesion to a non- functionalized acrylic polymer, however the combination of the substrate with a functionalized acrylic layer provides benefits such as increased adhesion, or processing advantages such as a widening of the processing window.

One of skill in the art can conceive of many uses for the multi-layer composite of the invention, based on the description and the non- limiting examples provided. The multi-layer composite can be used as a capstock material for weatherable applications.

The composite may also be used in "in-mold decorating" where films of clear acrylic polymers are die-cut to the desired size and shape. The following examples are illustrative of the invention but are not intended to be exhaustive or to limit the invention to the precise form disclosed. Many other variations and modifications are possible in light of the specification and examples. Examples:

To determine the relative adhesion between two different polymers melts pressed together, a compression molding study was conducted on the Carver Press in the Arkema labs, in building 14, in King of Prussia, PA. Plaques of each composition were pressed together at the tabulated temperatures. Adhesion was tested, by wedging a sharp instrument between the layers after compression, and physical separation was attempted by physically attempting to pull the two layers apart. Two different operators repeated each test and a rating consensus was determined. Ratings are tabulated as Excellent, Good, Fair, and Poor, and in some cases a rating between each category such as Good/Fair, Fair/Good, and Fair/Poor.

The PMMA Samples are labeled as: NA = No Acid (100% polymethyl methacrylate - PMMA) LA= Low Acid (contains 1.5 wt % methacrylic acid (MAA)) monomer units) MA = Medium Acid (contains 4.5 wt % MAA) PC = Polycarbonate

PETG = Polyethylene terephthalate, glycol modified PBT 315 - Polybutylene terephthalate

Example 1 and 2 show the improved adhesion of functionalized acrylic to PETG with higher MAA levels, with the MA sample demonstrating higher adhesion vs. the LA sample. This example also shows increased adhesion with higher temperatures. While not being bound to any particular theory, it is believed that he increased adhesion at the higher temperatures is related to intermolecular interactions between the PETG and functionalized acrylic.

Example 3 illustrates that higher PMAA levels in a p(MMA/MAA) copolymer coupled with higher temperatures leads to improved adhesion to a polybutylene terephthalate substrate. Example 1:

Claims

What is claimed is:

1. A multi-layer composite comprising a layer of funcitionalized acrylic polymer of at least 1 mil in thickness directly adhered to a polymeric substrate layer with out the use of an adhesive, wherein said acrylic polymer comprises from 50 to 99.9 weight percent of methyl methacrylate units.

2. The multi-layer composite of claim 1, wherein said functionalized acrylic layer comprises from 0.1 to 100.0 weight percent functionality.

3. The multi-layer composite of claim 2, wherein said functionalized acrylic layer comprises from 0.1 to 20 weight percent functionality.

4. The multi-layer composite of claim 2, wherein said functionalized acrylic layer comprises from 1 to 10 weight percent functionality.

5. The multi-layer composite of claim 1, wherein said functionalized acrylic layer comprises one or more functionalities selected from acid, anhydride, hydroxy, epoxy, and amine groups.

6. The multi-layer composite of claim 1 wherein said functionalized acrylic polymer comprises from 0.1 to 49.9 weight percent of one or more acrylic comomer units.

7. The multi-layer composite of claim 6, wherein said acrylic comonomers comprise one or more of ethyl acrylate, methyl acrylate and/or butyl acrylate.

8. The multi-layer composite of claim 1, wherein said substrate is selected from the group consisting of polyethylene terephthlate (PET), polybutylene terephthlate (PBT), polycarbonate (PC), polyamides, thermosetting polyurethane, thermosetting polyester, thermoplastic polyurethane, other thermoplastic polyesters, cellulosic polymers, wood-polymer composites, urethanes, epoxies, maleic anhydride/styrene copolymers, polyethylene naphthalate (PEN), glycol modified polyethylene terephthlate (PETG, vinyl acetate copolymers, or mixtures thereof.

9. The multi-layer composite of claim 1 wherein said functionalized acrylic layer comprises from 0.1 to 20.0 weight percent UV absorbers.

10. The multi-layer composite of claim 1 wherein said functionalized acrylic layer comprises from 0.1 to 99.9 weight percent impact modifiers, based on the weight of the functional functionalized acrylic polymer.

11. The multi-layer composite of claim 10 wherein said functionalized acrylic layer comprises from 0.1 to 60.0 weight percent impact modifiers, based on the weight of the functional acrylic polymer.

12. The multi-layer composite of claim 8 wherein said functionalized acrylic layer is transparent, and said functionalized acrylic layer matrix and impact modifiers have refractive indexes within 0.02 of each other.

13. The multi-layer composite of claim 1, wherein said substrate layer further comprises oneor more of glass fibers, glass strands, clay nanostructures, flame retardants, UV absorbers, glass beads, calcium carbonate, crosslinked polymeric beads, lubricants, antioxidants, pigments, matting agents, fillers, and dyes.

14. The multi-layer composite of claim 1, wherein said composite contains 3 or more layers, with one or more layers on the side of the functionalized acrylic layer away from the polymeric substrate.

15. The multi-layer composite of claim 1, wherein said functionalized acrylic layer is on the side of the substrate facing the environment.

16. The multi-layer composite of claim 1, wherein a layer on top of the said functionalized acrylic layer is on the side of the substrate facing the environment.

17. The multi-layer composite of claim 1 , wherein said functionalized acrylic layer is on the side of the substrate oriented toward the environment.

18. A process for adhering an acrylic polymer to a substrate polymer comprising: a) forming a functional acrylic polymer having from 0.1 to 100 weight percent functionality; b) selecting a substrate polymer selected from the group consisting of polyethylene terephthlate (PET), polycarbonate (PC), polyamides, thermosetting polyurethane, thermosetting polyester, thermoplastic polyurethane, other thermoplastic polyesters, co-polyesters, cellulosic polymers, wood-polymer composites, urethanes, epoxies, maleic anhydride/styrene copolymers, polyethylene terephthlate - glycol modified (PETG), PEN (polyethylene naphthalate), vinyl acetate copolymers, or mixtures of the above; c) directly contacting the functionalized acrylic polymer and the substrate polymer through the use of heat and/or pressure to adhere the layers together.

19. The process of claim 18, wherein the heat and/or pressure process is pultrusion, multi-layer extrusion, film lamination, insert molding, compression molding, or in-mold decorating.