Variable vapor barrier for humidity control

[0001] This invention relates to a composition having variable moisture permeance under different ambient humidity conditions, and articles comprising the composition.

[0002] Confined spaces such as building interiors and packaging may have limited exchange of moisture vapor with adjacent or external environmental spaces. Materials having moisture permeance that is variable when exposed to different ambient conditions can provide benefits in such fields as construction, packaging, etc.

[0003] Buildings are commonly equipped with thermal insulation in order to provide comfortable living conditions inside the building. In addition to insulation, buildings are also constructed with various air barrier materials to limit air and water infiltration into the structure of the building. These air barriers minimize heat loss through draft flow.

[0004] In addition to air barriers, vapor barriers have also been used for controlling flow of moisture. For example, the moisture flow is generally from inside to outside when the exterior air is cold and dry (winter) and from outside to inside when the air is hot and humid (summer). In regions where these conditions prevail, it is common practice to use a vapor barrier such as polyethylene (PE) film on the warm side of the insulation, generally behind the gypsum wallboard, to prevent moisture diffusion from the interior heated space to the exterior cold environment. Such vapor barriers reduce the potential for moisture condensation in the interior wall cavity space as the water vapor is exposed to the cold exterior temperatures. Although the use of PE film as a vapor barrier reduces moisture condensation during exterior conditions of cold temperatures and low humidity, the same vapor barrier increases the likelihood of moisture condensation at the insulation-PE film interface during hot, humid summer conditions where moisture flow is from outside to inside. Therefore, it is desirable to have a material that acts as a vapor barrier during winter but facilitates vapor permeation during hot, humid summer conditions. It is also desirable to have a vapor barrier that can become vapor permeable under humid conditions in the wall cavity caused by unexpected uncontrolled events like water leaks into the wall cavity, to facilitate drying of the wall cavity by inward moisture flow as well as outward flow. Under conditions of low ambient humidity, low moisture permeance is desirable and under high ambient humidity, high moisture permeance is desirable.

[0005] U.S. Pat. Nos. 6,808,772; 6,878,455 and 6,890,666 disclose applications of a polyamide building liner material that has a water vapor diffusion resistance (WVDR) of from 2 to 5 meters diffusion-equivalent air space width at a relative humidity (RH) of an atmosphere surrounding the vapor barrier between 30% and 50% and a WVDR of less than 1 meter diffusion-equivalent air space width at a relative humidity between 60% and 80%. See also, US Patent Application Publication 2003/0215609 (a moisture-adaptive vapor-barrier film comprising PE and acrylic ester with a WVDR of from 0.5 to 100 meters diffusion-equivalent air space width at an RH of an atmosphere surrounding the vapor barrier between 60% and 80%) and WO2002/070351 (use of ionomers for sealing insulating materials having a WVDR of from 1 to 20 meters diffusion-equivalent air space width at an RH of an atmosphere surrounding the vapor barrier of 25% and a WVDR of from 0.02 to 0.7 meter diffusion-equivalent air space width at a relative humidity of 72.5%).

[0006] Variable vapor permeance can also be desirable of packaging. It is desirable for packaging of food items such as fresh produce to have low moisture permeance under conditions of typical cold storage (low temperatures and low humidity) to retain moisture within the package, thereby retarding desiccation of the produce and maintaining freshness. However, if the packaged produce is exposed to higher temperatures and humidity, such as in a warehouse that is not climate-controlled, increased respiration rates can lead to increased liquid water formation due to high levels of trapped moisture inside the package. Fresh fruits and vegetables also produce carbon dioxide during respiration and the carbon dioxide can react with moisture in the package to form carbonic acid. The carbonic acid formed can affect the quality of the produce. As a result, degradation of the produce by carbonic acid is accelerated. Packaging that allows moisture vapor to permeate at higher ambient humidity would allow for moisture equilibration with the exterior of the package, thereby helping to minimize formation of carbonic acid by reducing the available liquid water. As a result, the produce would be protected from degradation by carbonic acid, which could allow for extended storage of produce without loss of food quality, even under storage conditions of variable ambient temperatures.

[0007] This invention provides a composition comprising or consisting essentially of (i) one or more E/X/Y copolymers; (ii) one or more organic acids selected from carboxylic acids having fewer than 36 carbon atoms, or salts thereof; and (iii) optionally one or more optionally polymer including ethylene-containing polymers or propylene-containing polymers. The composition optionally has a ratio of wet cup permeance to dry cup permeance greater than 10, alternatively greater than 20, alternatively greater than 50, alternatively greater than 75, when measured according to ASTM E 96-00 at a temperature of 73° F. (23° C.), wherein wet cup permeance is determined at an average relative humidity of 75% and dry cup permeance is determined at an average relative humidity of 25%. The composition may be a variable vapor barrier which may be in the form of a film.

[0008] A process for producing the composition comprises combining one or more E/X/Y copolymers, one or more carboxylic acids or salts thereof, and optionally one or more optional polymers to form a mixture; and heating the mixture under a condition sufficient to produce the composition.

[0009] Many previous permeable membranes are microporous; that is, they are permeable due to the presence of microscopic pores through which vapor can pass. The composition disclosed herein can be formed into a monolithic membrane that functions as a selectively permeable barrier. Monolithic membranes, in contrast to microporous membranes, have high water-entry pressure and are waterproof and liquidproof and can provide good barriers to liquid water while still allowing permeability to water vapor under appropriate conditions. Monolithic membranes are also excellent in stopping draft flow to help minimize heat loss. A monolithic membrane can also function as a barrier to odors and possess tear strength compared to microporous membranes.

[0010] Unless stated otherwise, all percentages, parts, ratios, etc., are by weight. When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range. When a component is indicated as present in a range starting from 0, such component is an optional component (i.e., it may or may not be present).

[0011] “Consisting essentially of” means that the recited components are essential, while smaller amounts of other components may be,present to the extent that they do not detract from the operability of the present invention. The term “(meth)acrylic acid” indicates methacrylic acid and/or acrylic acid. Likewise, the term “(meth)acrylate” indicates methacrylate and/or acrylate.

[0012] Permeance is a measure of the permeability of a material to water vapor divided by its thickness in inches and can be expressed in units of Perms (grains/h·ft²·inches of Hg). The permeance of still air is 120 perms·inch (see Table 5.4, Page 158, Thermal and Moisture Protection Manual, Christine Beall, McGraw-Hill). Another measure of permeability is WVDR (S_d), which can be expressed in meters diffusion-equivalent air layer thickness. These measures can be related by the expression
3.048/S_d=Permeance in Perms.

[0013] For illustration, the diffusion resistance expressed as S_d of prior vapor barrier materials has been converted to permeance expressed in Perms and summarized below:

[0014]

Reference	Permeance (Perms)
U.S. Pat. No. 6,808,772	0.61 to 1.52 at	Greater than 3.1 at 60 to
	30 to 50% RH	80% RH
US2003/0215609	—	0.03 to 6.09 at 60 to 80% RH
WO2002/070351	0.15 to 3 at	4.35 to 152 at 72.5% RH
	25% RH

[0015] Average humidity below 50% is thought of as relatively dry conditions and average humidity above 60% is thought of as relatively humid conditions.

[0016] The amount of basic metal compound capable of neutralizing acidic groups may be provided by adding the stoichiometric amount of the basic compound calculated to neutralize a target amount of acid moieties in the acid copolymer and organic acid(s) in the blend (hereinafter referred to as “% nominal neutralization” or “nominally neutralized”). Thus, sufficient basic compound is made available in the blend so that, in aggregate, the indicated level of nominal neutralization could be achieved. Nominal neutralization levels of all acid moieties in the composition are at least 70, 80, or 90%, or even 100%.

[0017] Metal compounds can include compounds of alkali metals, such as lithium, sodium or potassium, or combinations of such cations. Melt processibility, for example in a blown film process, may be improved if a combination of alkali metal ions and transition metal ions and/or alkaline earth metal ions is employed. Examples include sodium or combinations of sodium and potassium, optionally including small amounts of other cations such as alkali metal ions, transition metal ions or alkaline earth ions. Compounds of note include formates, acetates, nitrates, carbonates, hydrogencarbonates, oxides, hydroxides or alkoxides of the ions of alkali metals, especially sodium and potassium, and formates, acetates, nitrates, oxides, hydroxides or alkoxides of the ions of alkaline earth metals and transition metals. Of particular note are sodium hydroxide, potassium hydroxide, sodium acetate, potassium acetate, sodium carbonate and potassium carbonate.

[0018] In E/X/Y copolymer, E is derived from ethylene, X is derived from at least one C₃ to C₈ α,β-ethylenically unsaturated carboxylic acid, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers. X is from about 2 to about 35, 4 to 25, or 5 to 20, weight % of the E/X/Y copolymer and Y is from 0 to about 35, about 0.1 to about 35, or 5 to 30, weight % of the E/X/Y copolymer.

[0019] The organic acids can be monobasic, dibasic, or polybasic carboxylic acids having fewer than 36 carbon atoms, or salts thereof and can be present in the composition from about 1 to about 50 weight %. The acids are optionally substituted with from one to three substituents independently selected from the group consisting of C₁-C₈ alkyl, OH, and OR¹ in which each R¹ is independently C₁-C₈ alkyl, C₁-C₆ alkoxyalkyl or COR²; and each R² is independently H or C₁-C₈ alkyl.

[0020] Greater than 70%, 80% or 90% (or even 100%) acidic groups in the E/X/Y copolymers and organic acids are nominally neutralized with metal ions; and the metal ions present in the mixture can comprise at least 50 mole % sodium ions and the preponderance of the other metal ions are alkali metal ions.

[0021] The E/X/Y copolymers are acid copolymers or “direct” acid copolymers. They include an α-olefin, such as ethylene, copolymerized with at least one monomer derived from a C_3-8 α,β-ethylenically unsaturated carboxylic acid. The acid copolymers can be described as E/X/Y copolymers where E is ethylene, X is derived from at least one α,β-ethylenically unsaturated carboxylic acid, and Y is a softening comonomer. “Softening” means that the crystallinity is disrupted (the polymer is made less crystalline). Notable are E/X/Y copolymers wherein Y is 0 weight % of the polymer. They may optionally contain a third softening comonomer.

[0022] Examples of X include unsaturated acids such as (meth)acrylic acid, maleic acid, fumaric acid, and itaconic acid; and monoesters of fumaric acid and maleic acid (maleic half esters) including esters of C₁ to C₄ alcohols such as for example, methyl, ethyl, n-propyl, isopropyl and n-butyl alcohols.

[0023] Examples of softening comonomers for use as Y include alkyl acrylate, alkyl methacrylate, or combinations thereof wherein the alkyl groups have from 1 to 8, or 1 to 4, carbon atoms

[0024] Ethylene acid copolymers with high levels of acid (X) can be produced by any methods known to one skilled in the art such as use of “co-solvent technology” disclosed in U.S. Pat. No. 5,028,674 or by employing somewhat higher pressures than those at which copolymers with lower acid levels can be prepared.

[0025] Specific acid copolymers include ethylene/(meth)acrylic acid copolymers. They also include ethylene/(meth)acrylic acid/n-butyl(meth)acrylate, ethylene/(meth)acrylic acid/iso-butyl(meth)acrylate, ethylene/(meth)acrylic acid/methyl(meth)acrylate, ethylene/(meth)acrylic acid/ethyl(meth)acrylate terpolymers, or combinations of two or more thereof. Other acid copolymers include ethylene/maleic acid and ethylene/maleic acid monoester dipolymers; and ethylene/maleic acid monoester/n-butyl(meth)acrylate, ethylene/maleic acid monoester/methyl(meth)acrylate, ethylene/maleic acid monoester/ethyl(meth)acrylate terpolymers, or combinations of two or more thereof.

[0026] The acid copolymers described above can be used to prepare unmodified, melt processible ionomers used by treatment with a metal compound disclosed above. The unmodified ionomers may be nominally neutralized to any level such as about 15 to about 90% or about 40 to about 75% of the acid moieties.

[0027] The unmodified ionomers can be mixed with organic acids or salts thereof, metal compounds, and optional ethylene- or propylene-containing polymers, by any means known to one skilled in the art, to prepare compositions,

[0028] “Monobasic” refers to acids with one carboxylic acid moiety. Examples of organic acids include C₄ to less than C₃₆ (such as C₃₄, C_4-26, C_6-22, or C_12-22). At 100% nominal. neutralization (i.e., sufficient metal compound is added such that all acid moieties in the copolymer and organic acid are nominally neutralized), volatility is not an issue. As such, organic acids with lower carbon content can be used. It is preferred that the organic acid (or salt) be non-volatile (not volatilize at temperatures of melt blending of the agent with the acid copolymer) and non-migratory (not bloom to the surface of the polymer under normal storage conditions (ambient temperatures)). Examples of organic acids include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, isostearic acid, behenic acid, erucic acid, oleic acid, and linoleic acid. Naturally derived organic fatty acids such as palmitic, stearic, oleic, erucic, behenic acids, or combinations of two or more thereof.

[0029] Saturated organic acids, such as stearic acid and behenic acid, may reduce organoleptic properties of the composition.

[0030] Acids substituted with at least one C_1-8 alkyl group are branched acids. Saturated, branched organic acids are acids comprising at least one CH (methenyl) moiety and at least two CH₃ (methyl) moieties. In contrast, saturated, linear organic acids (e.g., behenic acid) are acids comprising only one CH₃ and no CH moieties.

[0031] “Hydroxy-substituted organic acids” includes not only those organic acids substituted with a hydroxyl (—OH) moiety, but also derivatives wherein the H of the hydroxyl moiety is replaced by R¹ moieties as defined above. Hydroxy-substituted organic acid can be substituted with one OH or one OR¹. Isostearic acid and 12-hydroxystearic acid are examples of organic acids substituted with one alkyl group and one OH, respectively.

[0032] Salts of any of these organic acids may include the alkali metal salts, such that the metal ions present in the final composition comprise at least 50% sodium ions, including sodium and potassium salts. Small amounts of salts of alkaline earth metal and/or or transition metal ions may be present in addition to alkali metal salts.

[0033] The composition optionally comprise from about 0.1 to about 25, to about 15, or to about 10, weight %, or from about based on the composition, of one or more ethylene-containing polymers or propylene-containing polymers. For example, when the composition comprises 2 or 5 weight % to 25 weight % organic acids, the optional polymers may be present in the composition from 10 to 25 weight %. Blending with such polymers may provide better processibility, improved toughness, strength, flexibility, compatibility of the blend when adhering to a substrate as described below.

[0034] The optional polymers can include PE homopolymers and copolymers, polypropylene (PP) homopolymers, PP copolymers, or combinations of two or more thereof.

[0035] PE homopolymers and copolymers can be prepared by a variety of methods, for example, the well-known Ziegler-Natta catalyst polymerization (e.g., U.S. Pat. Nos. 4,076,698 and 3,645,992), metallocene catalyzed polymerization, Versipol® catalyzed polymerization and by free radical polymerization. The polymerization can be conducted as solution phase processes, gas phase processes, and the like. Examples of PE polymers can include high density PE (HDPE), linear low density PE (LLDPE), low density PE (LDPE), very low or ultralow density polyethylenes (VLDPE or ULDPE), lower density PE made with metallocene having high flexibility and low crystallinity (mPE). Metallocene technology is described in, for example, U.S. Pat. Nos. 5,272,236; 5,278,272, 5,507,475, 5,264,405, and 5,240,894.

[0036] The densities of polyethylenes suitable can range from about 0.865 g/cc to about 0.970 g/cc. Linear polyethylenes can incorporate α-olefin comonomers such as butene, hexene or octene to decrease density to within the density range so described. For example, a copolymer used may comprise a major portion (by weight) of ethylene that is copolymerized with another α-olefin having about 3 to about 20 carbon atoms and up to about 20% by weight of the copolymer. Other α-olefins are propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-tetradecene, 1-octadecene, or in admixtures of two or more.

[0037] The PE copolymer may also be an ethylene propylene elastomer containing a small amount of unsaturated compounds having a double bond. The term “PE” when used herein is used generically to refer to any or all of the polymers comprising ethylene described above.

[0038] Ethylene copolymers having small amounts of a diolefin component such as butadiene, norbornadiene, hexadiene and isoprene are also generally suitable. Terpolymers such as ethylene/propylene/diene monomer (EPDM) are also suitable.

[0039] Polypropylene polymers include homopolymers, random copolymers, block copolymers and terpolymers of propylene. Copolymers of propylene include copolymers of propylene with other olefins such as ethylene, 1-butene, 2-butene and the various pentene isomers, etc. and preferably copolymers of propylene with ethylene. Terpolymers of propylene include copolymers of propylene with ethylene and one other olefin. Random copolymers, also known as statistical copolymers, are polymers in which the propylene and the comonomer(s) are randomly distributed throughout the polymeric chain in ratios corresponding to the feed ratio of the propylene to the comonomer(s). Block copolymers are made up of chain segments consisting of propylene homopolymer and of chain segments consisting of, for example, random copolymers of propylene and ethylene.

[0040] Polypropylene homopolymers or random copolymers can be manufactured by any known process (e.g., using Ziegler-Natta catalyst, based on organometallic compounds, or on solids containing titanium trichloride).

[0041] Block copolymers can be manufactured similarly, except that propylene is generally first polymerized by itself in a first stage and propylene and additional comonomers such as ethylene are then polymerized, in a second stage, in the presence of the polymer obtained during the first. Each of these stages can be carried out, for example, in suspension in a hydrocarbon diluent, in suspension in liquid propylene, or else in gaseous phase, continuously or noncontinuously, in the same reactor or in separate reactors. See, e.g., chapters 4.4 and 4.7 of the work “Block Copolymers” edited by D. C. Allport and W. H. Janes, published by Applied Science Publishers Ltd., 1973.

[0042] The optional polymer may also include ethylene copolymers obtained from copolymerization of ethylene with at least one polar monomer such as ethylene/vinyl acetate copolymers, ethylene/acrylic ester copolymers, ethylene/methacrylic ester copolymers, ethylene/vinyl acetate/CO copolymers, ethylene/acrylic ester/CO copolymers, ethylene/maleic anhydride copolymers, and/or mixtures of any of these.

[0043] Optionally, the composition may comprise at least one ethylene/vinyl acetate copolymer, which includes copolymers derived from the copolymerization of ethylene and vinyl acetate or the copolymerization of ethylene, vinyl acetate, and an additional comonomer.

[0044] The relative amount of the vinyl acetate comonomer incorporated into ethylene/vinyl acetate copolymers can vary from a few (e.g., 3) weight % up to as high as 45 weight % of the total copolymer or even higher.

[0045] The ethylene/vinyl acetate copolymer may have 2 to 45 or 6 to 30, weight % derived from vinyl acetate. The ethylene/vinyl acetate copolymer may optionally be modified by methods well known in the art, including modification with an unsaturated carboxylic acid or its derivatives, such as maleic anhydride or maleic acid. The ethylene/vinyl acetate copolymer may have a melt flow rate, measured in accordance with ASTM D-1238, of from 0.1 to 60 g/10 or 0.3 to 30 g/10 minutes. A mixture of two or more different ethylene/vinyl acetate copolymers can be used.

[0046] Optionally, the composition may comprise at least one ethylene/alkyl(meth)acrylate copolymer, which includes copolymers of ethylene and one or more C_1-8 alkyl(meth)acrylates. Examples of alkyl(meth)acrylates include methyl acrylate, ethyl acrylate and butyl acrylate. Examples of the copolymers include ethylene/methyl acrylate copolymer ethylene/ethyl acrylate copolymer, ethylene/butyl acrylate copolymer, or combinations of two or more thereof.

[0047] Alkyl(meth)acrylate may be incorporated into an ethylene/alkyl(meth)acrylate copolymer a few weight % up to as high as 45 weight % of the copolymer or even higher such as 5 to 45, 10 to 35, or 10 to 28, weight %. Frequently used alkyl group is methyl, ethyl, iso-butyl, or n-butyl.

[0048] Ethylene/alkyl(meth)acrylate copolymers can be prepared by processes well known to one skilled in the art using either autoclave or tubular reactors. See, e.g., U.S. Pat. Nos. 2,897,183; 3,404,134; 5,028,674; 6,500,888; and 6,518,365. See also, Richard T. Chou, Mimi Y. Keating and Lester J. Hughes, “High Flexibility EMA made from High Pressure Tubular Process”, Annual Technical Conference—Society of Plastics Engineers (2002), 60^th (Vol. 2), 1832-1836. The entire disclosure of all references are incorporated by reference. Because the methods for making an ethylene/Alkyl(meth)acrylate copolymer are well known, the description of which is omitted herein for the interest of brevity. Tubular reactor produced ethylene/alkyl(meth)acrylate copolymers, are commercially available from E. I. du Pont de Nemours and Company, Wilmington, Del. (DuPont) such as Elvaloy®. The ethylene/alkyl(meth)acrylate copolymers can vary significantly in molecular weight and the selection of the melt index (MI) grade of polymer can be by balancing the properties of the ethylene/alkyl(meth)acrylate copolymer with those of the neutralized organic acid and ethylene acid copolymer to provide the desired mix of permeability and structural properties needed for a specific variable vapor barrier construction. A mixture of two or more different ethylene/alkyl(meth)acrylate copolymers can be used. Of note is a composition wherein at least one ethylene/alkyl(meth)acrylate copolymer is present in up to 15 weight %.

[0049] An anhydride-modified polymer can be used as the optional polymer and comprise a copolymer having an unsaturated dicarboxylic acid anhydride repeating unit. Monomers providing the unsaturated dicarboxylic acid anhydride repeating unit include maleic anhydride, citraconic anhydride, itaconic anhydride, tetrahydrophthalic anhydride, or combinations of two or more thereof. The modified copolymer can be obtained by known techniques, such as a process in which a polymer selected from a PE homopolymer or copolymer, a polypropylene homopolymer or copolymer, an ethylene/vinyl acetate copolymer or an ethylene/alkyl acrylate copolymer, as disclosed above, is dissolved in an organic solvent with an unsaturated dicarboxylic acid anhydride or its functional equivalent and a radical generator, followed by heating with stirring; and a process in which all the components are fed to an extruder to provide a maleic-anhydride grafted ethylene copolymer. Grafting processes provide copolymers with from 0.1 to 3 weight % of anhydride units. These graft copolymers are available commercially from DuPont under the Fusabond® or Bynel® brand names.

[0050] Ethylene copolymers that include reactive functional groups such as maleic anhydride also can be readily obtained by a high-pressure free radical process, in which an olefin comonomer and a functional comonomer are directly copolymerized. A high-pressure process suitable for use in the practice of the present invention is described, for example, in U.S. Pat. No. 4,351,931. This process allows for preparation of copolymers with greater than 3 weight %, such as up to about 15 weight %, of anhydride units. These copolymers include olefin/maleate copolymers such as ethylene/maleic anhydride.

[0051] The composition disclosed can be produced by any means known to one skilled in the art. It is substantially melt-processible and can be produced by combining one or more E/X/Y copolymers, one or more monobasic carboxylic acids or salts thereof, and optionally one or more optional polymers to form a mixture; heating the mixture under a condition sufficient to produce the composition. Heating can be carried out under a temperature in the range of from about 80 to about 350, about 100 to about 320, or 120 to 300° C. under a pressure that accommodates the temperature for a period from about 30 seconds to about 2 or 3 hours. For example, the composition can be produced by melt-blending an E/X/Y copolymer and/or ionomer thereof with one or more organic acids or salts thereof; concurrently or subsequently combining a sufficient amount of a basic metal compound capable of neutralization of the acid moieties to nominal neutralization levels greater than 70, 80, 90%, to near 100%, or to 100%; and optionally, combining an optional polymer disclosed above. A salt blend of components can be made or the components can be melt-blended in an extruder. For example, a Werner & Pfleiderer twin-screw extruder can be used to mix and treat the acid copolymer and the organic acid (or salt) with the metal compound at the same time. It is desirable that the mixing is conducted so that the components are intimately mixed, allowing the metal compound to neutralize the acidic moieties. Actual neutralization levels can be determined using infra red spectroscopy by comparing an absorption peak attributable to carboxylate anion stretching vibrations at 1530 to 1630 cm⁻¹ and an absorption peak attributable to carbonyl stretching vibrations at 1690 to 1710 cm⁻¹.

[0052] Treatment of acid copolymers and organic acids with metal compounds in this manner (concurrently or subsequently), such as without the use of an inert diluent, may produce composition without loss of processibility or properties such as toughness and elongation to a level higher than that which would result in loss of melt processibility and properties for the ionomer alone.

[0053] The composition can additionally comprise small amounts of additives commonly used and well known in the adhesive art including plasticizers, stabilizers including viscosity stabilizers and hydrolytic stabilizers, primary and secondary antioxidants, ultraviolet ray absorbers, anti-static agents, dyes, pigments or other coloring agents, inorganic fillers, fire-retardants, lubricants, reinforcing agents such as glass fiber and flakes, synthetic (for example, aramid) fiber or pulp, foaming or blowing agents, processing aids, slip additives, antiblock agents such as silica or talc, release agents, tackifying resins, or combinations of two or more thereof. These additives are described in the Kirk Othmer Encyclopedia of Chemical Technology.

[0054] These additives may be present in the compositions in quantities ranging from 0.01 to 15, 0.01 to 10, or 0.01 to 5, weight %. The incorporation of the additives can be carried out by any known process such as, for example, by dry blending, by extruding a mixture of the various constituents, by the conventional masterbatch technique, or the like.

[0055] The composition as described herein has a permeance (water vapor diffusion) that is dependent on the ambient humidity, allowing it to be used to prepare a variable vapor barrier. The variable vapor barrier can also be termed a “humidity-adaptive smart vapor barrier.”

[0056] Compositions of this invention have moisture vapor transmission as measured by water vapor permeation values (WVPV) above 200 g-mil/m²-24 h, and may have WVPV above 1000, above 5000, or above 10,000 g-mil/m²-24 h when measured at 100% relative humidity. For some applications, such as packaging films, it may be desirable to have relatively low WVPV, while for other applications, such as variable vapor barriers for moisture control in buildings, it may be desirable to have higher WVPV.

[0057] In another embodiment, the composition may be applied to a substrate comprising a carrier material. For example, the composition may be applied as a coating or a laminate to the carrier material. Alternatively, a film comprising the variable vapor barrier composition may be laminated to a substrate of the carrier material. Substrate can be any materials providing support, shape, esthetic effect, protection, surface texture, bulk volume, weight, or combinations of two or more thereof to enhance the functionality and handability of variable vapor barrier composition.

[0058] For example, the composition, either in the form of a film or combined with a substrate, can be applied to a wall, ceiling or roof of a building between the interior sheathing material (such as gypsum wallboard) and the insulation. Articles comprising the composition and a substrate can be used to provide structural components that can be used in the construction or renovation of a building. The variable vapor barrier composition may be used as a surface for building panels or as a backing sheet for insulation. Also, films and structures prepared from the composition have sufficient strength and toughness for use in buildings as they are being built or renovated. When used as part of a building, the variable vapor barrier can be applied between the interior sheathing and the insulating material in a wall, ceiling and/or roof of a building in accordance with the invention. It can also be used with metal roofs or timber post constructions and can also lead to a reduction in building costs along with an improvement in moisture and temperature control.

[0059] The humidity-dependent behavior of the variable vapor barrier leads to a lower permeance being achieved under cold, dry exterior conditions than under hot humid exterior conditions. In this way, the variable vapor barrier material is effective in preventing moisture from diffusing from the interior of the building into the wall cavity and condensing into liquid water under winter conditions. Under conditions of high exterior humidity, the humidity-dependent behavior of the material provides moisture flow out of the wall cavity in either directions (particularly into the air-conditioned interior of the building) when needed, to facilitate a drying out process and to avoid water condensation in the wall cavity due to cooling by the building air conditioning. This behavior fosters peak insulation performance and reduces the risk of damage to building components due to excess moisture retention.

[0060] In one embodiment according to the invention, the variable vapor barrier is a film that can be applied as part of the wall, ceiling or roof construction of a building. For example, the film may be attached to the framing members so that the film is between the insulating material and the interior sheathing.

[0061] In another embodiment according to the invention, the variable vapor barrier is part of a structural component of the house that has a carrier material for the variable vapor barrier composition.

[0062] Cellulose materials such as paper webs (for example Kraft paper), membranes made from synthetic fiber spun fabrics such as nonwoven textiles, or even perforated films having large percentages of open areas such as perforated PE films, may be used as materials for the carrier(s), for example. These carrier materials may be reinforced with fibers. Other examples of suitable carrier materials for purposes of the present invention include particle board, chip board, oriented strand board, plywood paneling, gypsum board (standard or fiber reinforced), fiber board, cement board, cementitious wood wool board, calcium silica board, fiber insulation batts or slabs, foam insulation slabs, cloth, or combinations of two or more thereof. The variable vapor barrier itself may be applied to any of these carrier materials as a film or membrane or as a coating (via extrusion coating, spraying, painting or other appropriate application methods).

[0063] Of note is a variable vapor barrier wherein at least one layer of carrier material is thermal insulation selected from the group consisting of fiber insulation bafts, fiber insulation slabs, foam insulation slabs, or combinations of two or more thereof. The at least one layer can also be gypsum board, a cellulose material such as Kraft paper, a nonwoven textile, or combinations of two or more thereof.

[0064] For example, the variable vapor barrier material is applied to a carrier material as a film, a coating or a laminated layer. The coating or laminate can be applied to one side or both sides of the carrier material but, in special cases, it can also be accommodated between two layers of the carrier material in a sandwich-like manner. In the latter embodiment, the coating or laminate material is effectively protected from both sides from mechanical wear and it can therefore ensure the desired water vapor diffusion properties over an extended period of time. To avoid hindering drying, the carrier of these embodiments is such that the carrier material has a water vapor diffusion that is greater than the water vapor diffusion of the variable vapor barrier material so that the water vapor diffusion characteristics of the structure are essentially provided by the variable vapor barrier material. Several such layer assemblies can also be assembled one above the other.

[0065] In the case where the carrier material is coated or laminated on one side, this coating or laminate can be applied to the side on which little or no protection is required against mechanical influences. The installation of the variable vapor barrier in accordance with the invention can take place in such a way in this case that the protective carrier material points toward the side facing the room.

[0066] Of note is an embodiment wherein the variable vapor barrier material is applied to a paper web by, for example but not limitation, extrusion coating. For example, extrusion coating the variable vapor barrier material onto paper can be done as follows: dried granulates of the blend (and granulates of compositions for other layers, if present) are melted in single screw extruder(s). The molten polymer(s) are passed through a flat die to form a molten polymer curtain wherein the compositions of the individual layers are present in a laminar flow. The molten curtain drops onto the moving paper substrate to be immediately pressed into that substrate and quenched by a quench drum.

[0067] A film of the variable vapor barrier material can also be laminated to a paper web by means of an inner layer applied in molten form to adhere the film to the substrate. The process involves laying down a molten curtain of the inner layer composition between the film and the substrate moving at high speeds as they come into contact with a cold (chill) roll. The melt curtain is formed by extruding the inner layer composition through a flat die.

[0068] Use of paper coated with the variable vapor barrier material is particularly advantageous for production of building materials in continuous processes wherein the coated paper is supplied as a continuous web and is incorporated as part of a multilayer structure. An example embodiment further comprises insulation batts or slabs, wherein the paper coated with the variable vapor barrier is a facing sheet for the insulation. In another embodiment, the coated paper can be applied as a backing sheet for a building panel comprising, for example but not limitation, particle board, chip board, oriented strand board, plywood paneling, gypsum board (standard or fiber reinforced), fiber board, cement board, cementitious wood wool board, or calcium silica board.

[0069] These embodiments allow for the installation of the variable vapor barrier and an additional building material, such as insulation or a building panel, in a single operation. In an alternative embodiment, a fiberglass batt may be encased in an envelope prepared from a variable vapor barrier film of this invention. This embodiment also allows for the installation of insulation and the variable vapor barrier, such as in between the framing members in a wall cavity, in a single operation.

[0070] The following Examples are presented to illustrate the invention, but are not meant to be unduly limiting.

[0071] To illustrate variable moisture permeance associated with a film layer, cast films were prepared from the materials listed below.

• [0072] EMAA-1: An ethylene/methylacrylic acid (19 weight %) copolymer with MI of 300 g/10 minutes.
• [0073] EMAA-2: An ethylene/methylacrylic acid (11 weight %) copolymer with MI of 100 g/10 minutes.
• [0074] EMAA-3: An ethylene/methylacrylic acid (19 weight %) copolymer with MI of 60 g/10 minutes.
• [0075] EMA-1: An ethylene/methyl acrylate (24 weight %) copolymer with MI of 20 g/10 minutes.
• [0076] EMA-2: An ethylene/methyl acrylate (24 weight %) copolymer with MI of 2 g/10 minutes.
• [0077] Ionomer-1: An ethylene/methylacrylic acid (19 weight %) copolymer neutralized with sodium (37% nominally neutralized) with MI of 2 g/10 minutes.
• [0078] HSA: 12-hydroxystearic acid commercially supplied by ACME-Hardesty Co.
• [0079] ISA: Iso-stearic acid commercially supplied by Arizona Chemical.
• [0080] Base MB-1: A blend of 59.5 weight % Na₂CO₃ in an ethylene/methylacrylic acid (10 weight %) copolymer with MI of 450 g/10 minutes.
• [0081] Base MB-2: A blend of 50% K₂CO₃ in an E/methyl acrylate (24 weight %) copolymer with MI of 20 g/10 minutes.

[0082] The materials were melt-blended in a twin-screw extruder at 20 lb/h (about 9 kg/h) throughput rate to provide compositions summarized in Table 1 below. In Table 1, Examples 2 and 4 are Examples 1 and 3, respectively, diluted with additional ionomer, but no additional modifier or base. Unless noted otherwise in Table 2, the compositions were cast into films of 2 to 2.5 mils thickness via a 28 mm W&P twin screw extruder.

[0083] For comparison, various known building membranes were tested. They include a nylon 6 vapor barrier film, commercially available as Membrain® from Certain Teed® (Comparative Example C20); PE film (Comparative Example C21); and flashspun HDPE nonwoven, commercially available as Tyvek® Home Wrap from DuPont (Comparative Example C22). In the Tables, “NA” stands for “not applicable.”

[0084]

TABLE 1
	Acid copolymer or	Additional		Neutralizing
	ionomer	Polymer	Modifier	Agent	Nominal
Example	(wt %)	(wt %)	(wt %)	(wt %)	Neutralization
1	Ionomer-1 (72.57)	0	ISA (18.14)	KOH (8.89)	100
2	Ex. 1 + Ionomer-1	0	—	—	—
	(25:75 by weight)
3	Ionomer-1 (83.33)	0	HSA (9.26)	KOH (7.41)	90
4	Ex. 3 + Ionomer-1	0	—	—	—
	(50:50 by weight)
5	Ionomer-1 (61.70) + EMAA-	EMA-2 (7.22)	HSA (3.25)	Base MB-2 (12.84)	80
	3 (15.0)
6	Ionomer-1 (58.76) + EMAA-	EMA-2 (10.92)	HSA (3.09)	Base MB-2 (12.23)	79
	3 (15.0)
7	Ionomer-1 (55.78) + EMAA-	EMA-2 (14.68)	HSA (2.94)	Base MB-2 (11.61)	78
	3 (15.0)
8	EMAA-1 (75.37)	0	HSA (3.14)	K2CO3 (21.49)	88
9	EMAA-1 (78.38)	0	HSA (3.27)	K2CO3 (11.17) + Base	88
				MB-1 (7.18)
10	EMAA-1 (59.71)	EMA-1 (21)	HSA (3.36)	K2CO3 (9.67) + Base	98
				MB-1 (6.22)
11	EMAA-1 (57.72)	EMA-1 (20.3)	HSA (3.25)	K2CO3 (18.71)	98
12	EMAA-2 (68.05)	EMA-1 (25)	HSA (1.39)	K2CO3 (5.56)	88
13	EMAA-2 (60.92)	EMA-1 (24.70)	HSA (6.77)	K2CO3 (7.61)	91
14	EMAA-1 (81.60)	0	HSA (3.40)	Base MB-1 (15.0)	88
15	EMAA-1 (73.70)	0	HSA (10.05)	Base MB-1 (16.25)	93
16	EMAA-1 (71.55)	EMA-1 (10.70)	HSA (3.43)	Base MB-1 (14.31)	95
17	EMAA-1 (61.82)	EMA-1 (21.8)	HSA (3.48)	BaseMB-1 (12.93)	98
18	EMAA-1 (58.32)	EMA-1 (17.20)	HSA (10.29)	Base MB-1 (14.24)	98
19	EMAA-1 (58.98)	EMA-1 (21.70)	HSA (6.07)	Base MB-1 (13.27)	99
C20	Nylon 6 (100)	NA	NA	NA	NA
C21	PE (100)	NA	NA	NA	NA
C22	HDPE (100)	NA	NA	NA	NA

[0085] The moisture permeance was measured for each cast film using protocols according to ASTM E 96-00. Dry Cup permeance was measured according to Procedure A, using an average relative humidity (RH) of 25%, with the RH on one side of the film at 0% and the RH on the other side at 50% at a temperature of 73° F. (23° C.). Wet Cup permeance was measured according to Procedure B, using an average RH of 75%, with the RH on one side of the film at 50% and the RH on the other side at 100% at a temperature of 73° F. (23° C.).

[0086] The resulting data expressed as Permeance are presented in Table 2 below. In Table 2, “Ratio” is the Wet cup permeance divided by the Dry cup permeance and is an indication of the variability in permeance for the different humidity protocols. When films of different thickness were used for a composition, the average ratio was calculated.

[0087] Some samples were also tested for water vapor transmission (permeation) values (WVPV), following ASTM D6701-01, at 37.8° C. and 100% RH on a Mocon Permatran-W® 101K. These results are also reported in Table 2.

[0088]

	TABLE 2
	Measured Permeance
	(perms)
Example	Dry cup	Wet cup	Ratio	WVPV (g-mil/m2-24 h)
1	0.59	40	68	1738
2	0.37	5.4	15	231
3	3.32	91.4	28	5188
4	0.43	21.3	50	718
5 (1 mil)	1.5	64.5	43	—
5 (2 mil)	0.97	48.1	50	3383
5 (4 mil)	0.76	46.3	61	—
		Average Ratio	51
6 (1 mil)	1.45	52.2	36	—
6 (2 mil)	1.13	42.2	37	4219
6 (4 mil)	0.86	36.9	43	—
		Average Ratio	39
7 (1 mil)	0.9	34.7	39	—
7 (2 mil)	0.51	34	67	2183
7 (4 mil)	0.34	24.6	72	—
		Average Ratio	59
8 (4 mil)	1.3	70.8	54	10333
8 (6 mil)	1.3	72.0	58	—
		Average Ratio	56
9 (4 mil)	0.7	59.3	85	5079
9 (6 mil)	0.7	54.0	81	—
		Average Ratio	83
10 (4 mil)	0.8	55.5	70	5006
10 (6 mil)	0.7	43.3	62	—
		Average Ratio	66
11 (4 mil)	2.5	34.3	14	4415
11 (6 mil)	2.2	33.3	15	—
		Average Ratio	14.5
12	0.7	7.1	10	771
13	0.72	11.8	16	1111
14	0.26	48.1	185	2347
15	0.29	48.4	167	3528
16	0.38	47.1	124	4627
17	0.53	30.4	57	1996
18	0.46	43.9	95	3185
19	0.39	24.5	63	2546
C20	0.63	10.5	17	—
C21	0.07	0.16	2.3	—
C22	30.7	39.9	1.3	—

[0089] Table 2 reveals that the permeance of PE film (C21) and flashspun HDPE (C22) were relatively unaffected by changes in humidity. PE film provided low permeance while flashspun HDPE provided somewhat higher permeance. Nylon 6 film (C20) provided some variability in permeance depending on humidity, with a wet cup to dry cup ratio less than 20.

[0090] Water vapor permeance is dependent on thickness, the permeance of the test films of a given thickness can be related to permeance of other thicknesses. For example, the permeance of Examples 1-3 can be converted to permeance of thicker films as shown in Table 3.

[0091]

	TABLE 3
	Measured Permeance		Calculated Permeance
	(perms)		For 4X thickness
Example	Dry cup	Wet cup	Ratio	Dry cup	Wet cup
1	0.26	48.1	185	0.07	12.0
2	0.29	48.4	167	0.07	12.1
3	0.38	47.1	124	0.095	11.8