WO2006035364A1

WO2006035364A1 - Gas-barrier material

Info

Publication number: WO2006035364A1
Application number: PCT/IB2005/053097
Authority: WO
Inventors: Yves Leterrier; Jérôme BOUCHET; Jae Manson
Original assignee: Ecole Polytechnique Federale De Lausanne (Epfl)
Priority date: 2004-09-30
Filing date: 2005-09-20
Publication date: 2006-04-06

Abstract

The invention relates to novel gas-barrier materials for food packaging, based on transparent nanosized hybrid organic/inorganic films on polymer substrates. By contrast with current brittle oxides, these new materials combine extremely high cohesive strength (with a corresponding crack onset strain larger than 5%) and considerably improved barrier properties (oxygen transmission rates lower than 1 cm3(STP)/m2/day/bar).

Description

Gas-barrier material

Field of the invention

This invention relates to composites of substrate material and more particularly to composites of substrate material coated with a barrier film. The coated composite substrate material is substantially impermeable to gases and water vapor. The invention also relates to methods to produce these composites. Such composites can be used as barrier materials for food packaging and pharmaceutical packaging, as well as encapsulation and protective materials for a broad range of applications including adhesives. opto-electronic systems, displays, batteries, solar cells, in fields of use as diverse as automotive, aerospace, construction and building.

General description of the invention The composite according to the invention is made of at least one polymeric substrate having a thin oxide Him on its surface and a thin layer of a silane on the oxide Him.

The invention will be better understood with the detailed description below.

Short description of the figure

Fig I . shows an exemplary embodiment of a polymer substrate with a PECVD coated SiO_x coating and a protective silane layer.

Detailed description of the invention The silane film preferably contains terminal amino group(s) (see Fig. 1 ). The polymeric substrate may be a thermoplastic polymer Him such as a polyester film. The oxide Him, e.g. SiO_x. may have a thickness of 10- 100 nm. I he amino-silane is e.g.. gamma-aminopropyl tricthoxysilanc (GAPS). Spin-coated films were prepared from fresh and basic solutions (pH ~ 1 1 .4) of 5 wt% GAPS/ethanol. Spin coating was carried out at 1000 rpm for 20 s yielding silane coatings of thickness comprised between 50 and 70 nm. The formation mechanism of the amino-silane/oxide interphase was determined in a first step using various analytical techniques such as DSC, FTIR, ICP. AFM. XPS and XRF. When the liquid GAPS is applied onto a metal oxide (or hydroxide) surface, an interphase having chemical and physical properties quite different to those of the bulk polymer is created. The interphase formation results from a dissolution phenomenon of the oxide controlled by the basic behavior of the GAPS. When the liquid GAPS controlled at pH 8 was applied onto the metal oxide or hydroxide surfaces or when pure GAPS at pH I 1.4 were applied onto gold coated substrates, no chemical reaction was observed. On the contrary, when pure GAPS at pH 1 1.4 is applied onto metal oxide or hydroxide surfaces, chemical reactions occurred. Following the amine chemical sorption onto oxided or hydroxilated metallic surfaces, a partial dissolution of the surface oxide and/or hydroxide metallic substrate was observed according to the basic behavior of silane oligomer. Metallic ions then diffuse within the liquid oligomer and react probably by coordination with the amine groups of the amino-silane oligomer to form organo-metallic complexes (or chelates). When the complex concentration is higher than its solubility limit, complexes (or chelates) crystallize as sharp particles. These crystals are mainly formed close Io the metallic surfaces leading to an oriented crystalline layer. Crystals act as short fibers in an organic matrix leading to a local increase of the mechanical properties. Also, since dissolution and diffusion phenomena are expected, the extent of interphase formation should be related to either the duration of contact between the basic liquid and metallic substrates and/or the viscosity of the liquid oligomer or the pH value.

The resulting oxygen permeability and cohesive properties of the nanocomposite barrier coating were investigated in a second step by means of tensile tests carried out in-situ in a scanning electron microscope and a permeation cell respectively:

• Initially, for the as received film we have a thick SiO_x coating of 50 nm with a permeation value of 1 .9 cm^J(STP)/m7day/Pa and the very first cracks in the oxide coating were detected at a strain equal to 2%.

• For the treated film, irrespective of the pH value, we have a thick amino-silane of 70 nm with a permeation value of 0.35 cm^STPymVday/Pa and the very first cracks in the silane layer were detected at 10% strain.

• For the as received film elongated at 8% strain we have a permeation value of 96 cm³(STP)/m²/day/Pa. • For the treated film controlled at pH= l l .4 elongated at 8% strain, we have a permeation value of 4 cm³(STP)/m²/da\/Pa.

• For the treated film controlled at pH=8 elongated at 8% strain, we have a permeation value of 81 .6 cm '(STP)/m²/day/Pa.

The surface treatment can comprise at least a second component such as a hypcrbranched polymer. I he second component is preferably present in a concentration lower than 20 wt%. More preferably, the concentration of the second component is lower than I 5wt%, for example I O vvt% or 5 wt%.

Organojunctional silanes

I he orgnofunctional silanes are compounds according to the follow ing formula:

Y-(CH₂VSiXi Wherein

Y represents an organofonctional group selected from -NH₂- R-NM-. CM₂=CH-,

CH₂=C(CH₃)COO-. 2.3. epoxypropo\\, HS- and Cl-

X represents a silicon functional group selected from -OR, -OC(=O)R'. -Cl wherein R and R^* are independently selected from Ci-C₄ alkyls, preferably -Cl h and -C₂H, : and n is an integer from 0 to 20, preferably from 0 to 10 and most preferably from 0 to 3.

Preferred silanes are amino-organofunctional silanes having at least one aminofunctional group

Hyperhranched polymers

Hypcrbranched polymers can generally be described as three-dimensional highly branched molecules ha\ ing a tree-like structure. 1 hey are characterized by a great number of end groups, which can be functionalized with tailored groups to ensure compatibility and reactivity. For the purpose of this invention the term "hyperbranched poly mers^" also includes dendrimers, monodisperse variations of hyperbranched polymers. Hyperbranched polymers normally consist of an initiator or nucleus having one or more reactive sites and a number of branching layers of chain extending molecules and optionally a layer of one or more chain terminating molecules. The layers are usually called generations. In general, hyperbranched polymers have an average of at least 16 end groups per molecule for 2^nd generation materials. increasing by a factor of at least 2 for each successive generation. Number average molar masses of 2^nd generation hypcrbranched polymers are usually greater than about 1 500 g/mol. and the molar masses increase exponentially in generation or pseudo-generation number, reaching about 8000 g/mol for a 4 pseudo-generation polymer. Typically the molecular weight of the dcndrimers will be about 1 00 g/mol per end group, although this wil l vary according to the exact formulation.

The nucleus of the hyperbranched polymers is preferably selected from the group consisting of a mono. di. tri or poK functional alcohol; a reaction product between a mono. di. tri or poly functional alcohol and ethylene oxide, propylene oxide, butylene oxide, phenylethylene oxide or combinations thereof; a mono, di, tri or poly functional epoxide: a mono. di. tri or pol\ functional carboxylic acid or anhydride: a hv droxy functional carboxy lic acid or anhydride.

Chain termination is preferably performed by addition of at least one monomeric or polymeric chain stopper to the hyperbranched polymer. A chain stopper is preferably selected from the group consisting of aliphatic or cycloaliphatic saturated or unsaturated monofunctional carboxylic acid or anhydride having 1 - 24 carbon atoms: aromatic monofunctional carboxy lic acid or anhydride, a diisocyanate. an oligomer or an adduct thereof, a glycidyl ester of a monofunctional carboxylic acid or anhydride having I - 24 carbon atoms; a glycidyl ether of a monofunctional alcohol with I - 24 carbon atoms, an adduct of an aliphatic or cycloaliphatic saturated or unsaturated mono. di. tri or poly functional carboxy lic acid or anhydride hav ing I - 24 carbon atoms: an adduct of an aromatic mono. di. tri or poh functional carboxylic acid or anhydride: an epoxide of an unsaturated monocarboxj lic acid or corresponding triglyceride, which acid has 3 - 24 carbon atoms and an amino acid.

Oxide(s) and or Hydroxkle(s)

Metals or metal alloys, ceramics covered by an oxide and/or hydroxide can be considered.

Polymer s iibstrute

Any thermoset and thermoplastic material, either in glassy or rubbery, amorphous or semi- crystalline states, can be considered as polymer substrate. Examples of thermoset materials comprise those based on epoxides, acry lates, polyurethanes. Examples of thermoplastic materials comprise polyesters such as poly (ethylene terephthalate), poly(ethylene naphthalene); polyolefins such as polyethylene or polypropylene; polyamides: polyurethanes: ABS (acrylonilrile butadiene styrene) and PVC. and copolymers thereof. Examples of rubbers comprise polyisoprene, chloroprene, styrene-butadiene, butyl rubber, nitrile and hydrogenctatcd nitrile rubbers, EPDM.

Process

Since dissolution and diffusion phenomena were observed clue to the acid or basic behavior o\^' liquid prepolymer. polymer or oligomer, the interphase or the new material formed is related to the duration of contact between liquid prepolymer, polymer or oligomer and the metallic substrate covered by their oxide or hydroxide layers before the polymerization cycle (thermal or UV).

The barrier film containing the oxide can be applied by vapor deposition. The barrier Him containing the silane can be applied by spraying, centrifugal or doctor processes. The film may be subsequently cured by. e.g. heat, photochemical induction or thermal induction.

Applications - Polymer material gas-barrier

. Food packaging

. Pharmaceutical

. Opto-electronic

. Encapsulation for opto-electronic systems . Solar cell, screen

Polymer composite . Automotive . Aerospace . Adhesive

. Construction

Claims

5 1. A method for the manufacture of a composite with barrier properties and extremely high cohesive strength characterized by the following steps :

AppK ing to a polymeric substrate a first barrier film comprising an oxide or an hydroxide.

Applying to said first barrier film a second film comprising a silane. I O

2. A method according to claim I wherein the polymeric has a thickness between I micrometer and 2 millimeters.

3. A method according to claim I or 2 wherein the first barrier film has a thickness between 5 15 and 1000 nanometers.

4. Λ method according to claim I , 2 or 3 wherein the second barrier film has a thickness between I and 500 nanometers.

20 5. Λ composite formed according to the method of anyone of claim I to 4, characterized by the fact that it has an ov/gen permeability of less than I cm3/(m2 day bar) at 23°C and about 75% relative humidity combined w ith a strain to failure of the barrier larger than 4%.

25 6. Use of a composite formed according to the method of anyone of claim I to 4 as a gas barrier-material.