Impervious breathable ethylene copolymer film

Abstract

An impervious breathable film made of a composition that does not include polymers having polyether units and includes one or more polymers, at least one of which is an ethylene copolymer. Said impervious breathable film is moreover made of a comonomer, having the function of an acid or one of the derivatives thereof. In said impervious breathable film, the weight of comonomers, having the function of carboxylic acid or a derivative of said acid, is greater than or equal to 21 wt % in said copolymer. Said impervious film moreover relates to a slip additive. The film has a thickness of 2 to 30 μm. Also, an impervious breathable structure, containing a fibrous material and said film, and moreover relates to a method for manufacturing said structure. Said film and said structure are advantageously usable as an impervious breathable material for, for example, construction siding.

Claims

1. Waterproof-breathable film of a composition not comprising any polymer carrying polyether units and comprising one or more polymers, at least one of which is a copolymer of ethylene and of a comonomer carrying a carboxylic acid functional group or one of its derivatives, in which the amount by weight of comonomer carrying the carboxylic acid functional group or a derivative of this acid in the said copolymer is greater than or equal to 23%, and also a slip additive, a siliceous additive selected from the group consisting of silicas, zeolites and talcs; optionally, an additive selected from the group consisting of plasticizers, antioxidants, UV stabilizers, flame retardants and mold release agents; and wherein the film, at a thickness of 25 μm, has a permeability to water vapour within the range extending from 35 to 120 g/m.sup.2/24 h, using Standard ASTM E96, method A (23° C., 50% relative humidity); and wherein an amount by weight of the copolymer of the ethylene and the comonomer is within a range extending from 80 to 100% of total weight of polymer in the composition.

2. Film according to claim 1, wherein an amount by weight of the slip additive is within a range extending from 500 to 50 000 ppm, with respect to a total weight of the composition.

3. Film according to claim 1, wherein an amount by weight of the siliceous additive is within a range extending from 500 to 100 000 ppm, with respect to a total weight of the composition.

4. Film according to claim 1, wherein the comonomer carries a functional group of a carboxylic acid derivative and is chosen from carboxylic acid vinyl esters, and alkyl (meth)acrylates, the alkyl chain of which comprises from 1 to 20 carbon atoms.

5. Film according to claim 1, wherein the copolymer of ethylene and of the comonomer carrying a carboxylic acid functional group or a derivative of this acid is manufactured by a high-pressure radical polymerization process in an autoclave reactor.

6. Waterproof-breathable film of a composition not comprising any polymer carrying polyether units and comprising one or more polymers, at least one of which is a copolymer of ethylene and of a comonomer carrying a carboxylic acid functional group or one of its derivatives, in which the amount by weight of comonomer carrying the carboxylic acid functional group or a derivative of this acid in the said copolymer is greater than or equal to 23%, and also a slip additive, the film having a thickness ranging from 2 to 30 μm, wherein the film, at a thickness of 25 μm, has a permeability to water vapour within the range extending from 35 to 120 g/m.sup.2/24 h, using Standard ASTM E96, method A (23° C., 50% relative humidity); and wherein an amount by weight of the copolymer of the ethylene and the comonomer is within a range extending from 80 to 100% of total weight of polymer in the composition.

7. Film according to claim 1, wherein the film has a thickness ranging from 2 to 30 μm and wherein the slip additive is selected from the group consisting of fatty acids comprising from 8 to 80 carbon atoms and their derivatives comprising from 8 to 80 carbon atoms.

8. Film according to claim 6, wherein the film is non-porous; and wherein the slip additive is selected from the group consisting of fatty acids comprising from 8 to 80 carbon atoms and their derivatives comprising from 8 to 80 carbon atoms.

9. Film according to claim 1, wherein the slip agent is chosen from erucamide, oleamide, stearamide, behenamide, oleylpalmitamide, stearylerucamide, N,N′-ethylenebis(stearamide) and ethylenebisoleamide.

10. Film according to claim 6, wherein the slip agent is chosen from erucamide, oleamide, stearamide, behenamide, oleylpalmitamide, stearylerucamide, N,N′-ethylenebis(stearamide) and ethylenebisoleamide.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) A first subject-matter of the invention is a waterproof-breathable film with a composition comprising a copolymer of ethylene and of a comonomer carrying a carboxylic acid functional group or a derivative of this acid, in which the amount by weight of comonomer in the said copolymer is greater than or equal to 21%.

(2) A comonomer is a monomer capable of reacting with ethylene to form a copolymer. Mention may be made, as examples of comonomer carrying an acid functional group or one of its derivatives, of: unsaturated carboxylic acids, such as acrylic acid or methacrylic acid; unsaturated carboxylic acid anhydrides or unsaturated dicarboxylic acid anhydrides, such as maleic anhydride; alkyl acrylates and alkyl methacrylates combined under the term alkyl (meth)acrylates. The alkyl chains of these (meth)acrylates can have up to 20 carbon atoms and can be linear or branched. Mention may be made, as alkyl chains, of methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl or eicosyl. Preference is given to methyl (meth)acrylate as alkyl (meth)acrylate; carboxylic acid vinyl esters. Mention may be made, as examples of carboxylic acid vinyl esters, of vinyl acetate, vinyl versatate, vinyl propionate, vinyl butyrate or vinyl maleate. Preference is given to vinyl acetate as carboxylic acid vinyl ester.

(3) Preferably, the comonomer carrying an acid functional group is an alkyl (meth)acrylate.

(4) The copolymer can comprise at least 2 comonomers carrying an acid functional group or one of its derivatives.

(5) The copolymer can additionally comprise another comonomer capable of reacting with ethylene and with the comonomer(s) carrying a carboxylic acid functional group or a derivative of this acid. The copolymer comprises an amount of greater than or equal to 21% by weight of comonomer carrying a carboxylic acid functional group or a derivative of this acid. The amounts of the various monomers present in the various polymers of the invention can be measured by infrared spectroscopy, for example using the method described in Standard ISO8985.

(6) Such copolymers are sold by the Applicant Company under the Evatane® trade name (copolymer of ethylene and of vinyl acetate) and Lotryl® trade name (copolymer of ethylene and of alkyl acrylate).

(7) These copolymers can be manufactured by radical polymerization, for example at high pressure. Industrially, these copolymers are manufactured using two types of different reactors: reactors of “autoclave” type and reactors of “tubular” type. These copolymerization processes are, for example, those described in Patent Applications FR 2 660 660, FR 2 498 609, FR 2 569 411, FR 2 569 412, US2006/0149004 A1 and US2007/0032614 A1. An “autoclave copolymer” and a “tubular copolymer” are obtained respectively. The properties for the 2 copolymers obtained are different. Without being committed to any one theory, these different properties can be explained by differences in branching and in distribution of the comonomers in the polymer chain. This in particular brings about a difference in melting point of the polymer for a copolymer obtained from the same monomers in an autoclave reactor or in a tubular reactor. Preferably, the copolymer is obtained using an autoclave reactor, which makes possible easier application to a support than a copolymer with the same composition obtained using a tubular reactor. Preferably, the copolymer exerts a melting point of less than or equal to 85° C., preferably ranging from 50 to 80° C., for example from 55 to 75° C. For example, this temperature can be measured by DSC according to Standard ISO 11357-1:2009.

(8) The composition used to form the film according to the invention can additionally comprise another polymer, such as polyolefins. Mention may be made, as examples of polyolefin, of homopolymers of ethylene or copolymers of ethylene with a second olefin, such as 1-butene, 1-hexene or 1-octene.

(9) Preferably, the composition comprises from 80 to 100% by weight of copolymer of ethylene and of a comonomer carrying a carboxylic acid functional group or a derivative of this acid, with respect to the total weight of polymer in the composition. According to one embodiment, the polymer of the combination is composed of the said copolymer.

(10) The composition forming the film additionally comprises a slip agent.

(11) It can be chosen from fatty acids comprising from 8 to 80 carbon atoms and their derivatives comprising from 8 to 80 carbon atoms, such as salts, esters or amides, or one of their mixtures. Mention may be made, as examples of carboxylic acid, of stearic acid, oleic acid or erucic acid. Mention may be made, as carboxylic acid salt, of aluminium stearate or zinc stearate. Use may be made, as fatty acid ester, of methyl stearate or ethyl stearate. Preferably, the slip agent is a fatty acid amide. It can be chosen from erucamide, oleamide, stearamide, behenamide, oleylpalmitamide, stearylerucamide, N,N′-ethylenebis(stearamide) and ethylenebisoleamide. The composition can comprise a mixture of these slip agents.

(12) The composition can additionally comprise a siliceous additive which is chosen from silica, zeolites and talc. These additives can be modified at the surface via a treatment. These siliceous additives can have a particle size ranging from several nanometres to a few microns.

(13) The composition can additionally comprise other additives which make it possible to improve one of the properties of the polymer, such as a plasticizer, an antioxidant, a UV stabilizer, a flame retardant or a mould-release agent.

(14) The composition of the film according to the invention can be manufactured by mixing its various constituents by conventional means for processing thermoplastic, such as, for example, extrusion or kneading. Use may be made of internal blade or rotor mixers, an external mixer, or single-screw or corotating or counterrotating twin-screw extruders. The processing temperature can be from 80 to 300° C.

(15) The film according to the invention preferably exhibits a thickness ranging from 2 to 30 μm, preferably from 5 to 24 μm, for example from 10 to 20 μm. Preferably, the film comprises fewer than 10 holes per m.sup.2 of film. Very preferably, the film exhibits an absence of holes.

(16) The waterproof-breathable properties of the film are measured by measuring in particular the permeability to water vapour. This depends on the thickness of the film evaluated and on the operating conditions, that is to say on the configuration, the temperature and the humidity conditions of the test. Preferably, the film is made from a composition exhibiting a permeability to water vapour included within the range extending from 35 to 120 g/m.sup.2/24 h when it is in the form of a film with a thickness of 25 μm, using Standard ASTM E96 method A (23° C., 50% relative humidity). Advantageously, the film exhibits an impermeability to water in the liquid form, measured by the water column test according to Standard NF EN 20811 of more than 1 m.

(17) Use may be made, to form the film according to the invention, of a press or a flat extruder having a film die (of cast type). Use may also be made of a continuous process in which the composition and immediately the film are formed, for example using an extruder of cast type.

(18) Another subject matter of the invention is a structure comprising a film according to the invention on a support made of fibrous material.

(19) A fibrous support is a non-continuous support which allows water to pass in the liquid and vapour form. This support made of fibrous material is preferably a woven or a non-woven. This fibrous material can be manufactured from synthetic polymer, such as polyolefins, polyester or polyamide. It can also be manufactured from natural fibre, such as cotton, flax or cellulose. Non-wovens made of polypropylene or paper or wovens made of cotton may thus be involved.

(20) The structure can be manufactured by applying the film, manufactured beforehand, to a support and by assembling it, for example by pressing.

(21) According to a highly advantageous form of the invention, the structure according to the invention is manufactured by a process of extrusion-coating of the film of the composition on the support. One of the advantages of the composition used in the present invention is that it makes possible its coating on the support in the form of a thin film, for example having a thickness of less than 30 μm, the said film exhibiting a lower number of holes than the films with the same thickness of the prior art, even using speeds of the extrusion line (forward progression of the support) of between 50 and 300 m/min.

(22) The invention thus relates to a process for the manufacture of a structure according to the invention by extrusion-coating of the film according to the invention on a support made of fibrous material. Preferably, the speed of the extrusion line is between 50 and 300 m/min.