Polymeric blends containing a block poly(ether-co-amide).

DESCRIPTION

GIVES

PATENT OF INVENTION

No. 98 989

APPLICANT: CHICOPEE, NORTH AMERICAN, ESTABLISHED AT 317 George Street, New Brunswick, New Jersey 08903, United States of America.

EPIGRAPH: PROCESS FOR PREPARING POLYMERIC MIXTURES CONTAINING A BLOCK POLY (Ether-COAMIDE)

INVENTORS: SHMUEL DABI AND BRUCE JOHNSON.

Claim of right of priority under Article 4 of the Paris Convention of 20 March 1883.

United States of America on September 18, 1990, under serial number 584,301.

INPI MOD. 113 RF 18732

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Description for the U.S. industrial and commercial CHICOPEE invention patent, established at 317 George Street, New Brunswick, New Jersey, United States of America (inventors: Shmuel Dabi and Bruce Johnson, USA), to : PROCESS FOR PREPARING POLYMERIC MIXTURES CONTAINING A POLY (CQ-AMIDE)

BLOCKS.

DESCRIPTION

BACKGROUND OF THE INVENTION

This invention relates to polymeric blends that can be molded or extruded to prepare non-porous and moisture permeable films. More specifically, it refers to polymeric mixtures containing a block poly (ether-co-amide) as one of the polymeric components.

The preparation of non-porous polymeric films which act as a barrier to liquids, especially water, while being permeable to water vapor, is desirable for numerous applications. These films can be used to make surgical gowns and dressings, occlusive wound dressings, disposable absorbent articles such as diapers and sanitary towels, and a variety of health care products. These films may be conventionally prepared by extruding or molding a particular polymer composition.

Films exhibiting a high water vapor transmission rate (MVTR) are usually prepared from hydrophilic polymers. Unfortunately, hydrophilic polymer films are sensitive to water contact and therefore lose a significant amount of their resistance when wet.

In order to overcome the problem associated with the poor strength of hydrophilic polymeric films, attempts have been made to laminate these films onto a fabric backing. For example, U.S. Patent 4,713,068 discloses a non-porous polyvinyl alcohol film laminated to a porous tissue-like porous substrate. U.S. Patent 4,808,675 discloses a breathable film made of a laminated block copolyether amide on textile fibers of a hydrophilic hydrophobic laminate. While these laminates attempt to increase the wet strength of breathable films by reinforcing these films with a water resistant fabric, the laminates still have poor wet strength and swell in aqueous fluids.

To combat the difficulty that appears to exist between preparing a retaining film when wetted and preparing a film which exhibits high MVTR, numerous attempts have been made to synthesize polymers containing a hydrophilic portion and a hydrophobic portion. In this way, the hydrophilic portion of the polymer serves to improve the MVTR characteristics of the film and the hydrophobic portion serves to enhance the wet strength characteristics of the film. Most commonly, the hydrophilic moiety is given by a polyethylene glycol (PEG) segment. Examples of newly developed hydrophilic / hydrophobic polymers with PEG segments may be PEG units linked via an amide bond (U.S. Patent 4,808,675),

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ester (U.S. Patent 4,622,263), a urethane bond (U.S. Patent 4,868,062), and esteramide bonds (British Patent Application 2,112,789).

Unfortunately, the preparation of films exhibiting the required balance of acceptable wet strength and high MVTR from hydrophilic / hydrophobic polymers is not always achieved. Also, working these polymers in certain specific applications is difficult and time consuming. Therefore, in view of the shortcomings of the prior art, it is desirable to prepare polymeric compositions which can be extruded or molded using conventional non-porous film preparation means having an excellent balance of properties.

SUMMARY OF THE INVENTION

The invention is a polymeric mixture comprising a mixture of a hydrophilic block poly (ether-co-amide) containing from about 20 to about 80 weight percent PEG blocks and a hydrophobic polymer. The hydrophobic polymer may be any of the following:

(a) poly (ether-co-amide) blocks containing virtually no PEG blocks;

b) a polyamide;

c) a polyester; or

d) a polyurethane.

The hydrophilic and hydrophobic polymer blends of this invention may be melt treated using conventional extrusion or molding techniques to prepare non-porous breathable films. Surprisingly, films prepared from these mixtures exhibit a high MVTR and a significantly higher wet strength than the wet strength exhibited by a film prepared from the hydrophilic polymer alone.

Films prepared from polymeric mixtures may be used in a variety of medical applications, such as for the preparation of gowns and surgical ornaments and for the preparation of dressings for occlusive injuries. In addition, these films may find use in other applications requiring a breathable barrier layer. For example, the films may be employed for the preparation of disposable articles including disposable diapers and sanitary napkins.

DETAILED DESCRIPTION OF THE INVENTION

Hydrophilic block poly (ether-co-amide) is a block copolymer with a repeatability of soft polyether blocks and hard polyamide blocks. Soft polyether blocks increase copolymer flexibility, hydrophilicity and thermoplasticity, and hard polyamide blocks enhance the physical properties of the copolymer. The term hydrophilic refers to the ability of copolymers to swell in water and to absorb at least 50 weight percent of water at equilibrium.

The copolymer polyether blocks contain PEG blocks. The amount of PEG in the block copolymer ranges from about 20 to about 80 weight percent. An amount of PEG in the block copolymer of less than 20 weight percent may not impart the desired degree of hydrophilicity to the copolymer and therefore the polymeric mixtures treated to prepare films from these copolymers may not have an acceptable MVTR. An amount of PEG in the block copolymer greater than 80 weight percent may result in films with poor dimensional integrity.

Polyether blocks may contain not only PEG block repeat units, but also separate repeat units from other polyalkylene oxides such as polypropylene oxide, provided that the total amount of PEG in the copolymer is between about 20 and about 80 percent. In a unique manner, PEG may be copolymerized with other polyalkylene oxides to form suitable polyether blocks.

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Preferably, the copolymer polyether blocks consist only of PEG repeating units. The average molecular weight of each of the PEG blocks desirably ranges from about 600 to 8000, preferably from about 800 to 3000. A molecular weight of less than about 600 may result in vapor impermeable films and molecular weights greater than about 8000 can result in dimensionally unstable films.

The polyamide blocks of the copolymer may be polyamides such as nylon 6, 66, 612, 11 or 12. The polyamide blocks may contain repeating units of dissimilar polyamides, or copolyamides prepared by reacting at least two different polyamides.

The total average molecular weight of the hydrophilic block copolymer should be large enough to prepare films having acceptable dimensional stability. Preferably, the weighted average molecular weight as determined by gel permeation chromatography should be greater than 20,000.

Hydrophilic block copolymers within the scope of this invention are already known. In one case, the polyether blocks are attached to the polyamide blocks via ester bonds, as described in U.S. Patent 4,252,920, U.S. Patent 4,115,475 and U.S. Patent 4,208,493. In another case, the polyether blocks terminate with amino groups and are attached directly to the polyamide blocks, as described in U.S. Patent 4,808,675. 0 Most preferred block copolymer is TM block poly (ether-co-amide).

4011MA PEBAX provided by Atochem of North America.

The amount of hydrophilic block poly (ether-co-amide) required in the polymer blend will depend on the desired MVTR for films prepared from mixtures, as well as the molecular weight and percent weight of PEG in the block copolymer. The amount of beaker block blocks in the mixture can be determined quickly and empirically, and desirably ranges from about 20 to about 90 weight percent, preferably from about 20 to about 90 percent by weight.

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about 30 and about 80 percent of the polymer mixture. The hydrophobic polymeric component of the polymeric mixture, in a manner similar to that of hydrophilic block poly (ether-co-amide), must have an average weight weighted molecular weight greater than 20,000, so that it is suitable for the preparation of stable films. dimensionally. The term hydrophobic refers to a polymer characterized by reduced water absorption of less than 10 weight percent at equilibrium.

One of the hydrophobic polymers that can be used in the polymer blend is a block poly (ether-co-amide) that contains virtually no PEG blocks. The term is essentially intended to cover the minimum amounts of PEG that will not increase the amount of water absorption of the block poly (ether-co-amide) below 10 weight percent. Preferably, the block copolymer contains no PEG blocks and contains polytetramethyl oxide or polypropylene oxide blocks. These copolymers are known and described in U.S. Patent 4,252,920. Preferred copolymers are PEBAX ™ block poly (ether-co-amides) 2533, 4033 and 3533.

Other hydrophobic polymers that may be used include polyethers, polyamides and polyurethanes. Polyesters which may be used are conveniently prepared by reacting a poly (alkylene oxide) with a dicarboxylic acid and are described, for example, in U.S. Patent 4,725,481. Particularly preferred examples of polyester include p olicaprolactone and poly (tetramethyl glycol) terephthalate. The most preferred polyester is polycaprolactone. Examples of polyamides which may be used include nylon 6, 66, 11 and 12, as well as copolyamides prepared by copolymerization of two or more thereof. The polyurethanes which may be employed in this invention are conventional hydrophobic polyether or polyester urethanes. Generally, these polyurethanes are prepared by reacting the excess diisocyanate with a hydroxyl terminated polyether or polyester which is of extended chains by low molecular weight diols or diamines. Examples of diisocyanates include toluene dicyanate (TPI), 4,4-diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI) Examples of polyether polyols include polypropylene glycol and polytetramethylene glycol. Examples of polyester polyols are ethylene glycol adipate, butane diol succinate and neopentyl glycol azelate.

Preferred hydrophobic polymers are block poly (ether-co-amides) which contain virtually no PEG blocks, polyamides and polyurethanes. The most preferred hydrophobic polymers are block poly (ether-co-amides) and polyamides.

Additional components may be added to the polymer blend without departing from the spirit or scope of the invention. For example, polyolefins, for example polyethylene, or isomeric resins, such as Surlyn ™ isomer resin, may be incorporated into the polymer blend. A highly viscous polyolefin, such as a linear low density polyethylene with a melt index of less than 3, may be incorporated into the polymer blend in amounts up to 30 weight percent to enhance the treatment characteristics of the blend. Isomeric resins may be added to the mixture to increase compatibility of polymeric components. Additionally, additives such as antioxidants, lubricants, pigments, etc. may be added to improve the overall properties of films prepared from polymeric mixtures.

Another example of an additional component which may be added to the polymer mixture without departing from the spirit or scope of the invention is a grafted polyolefin prepared by reacting a polyolefin with an ethylenically unsaturated alpha-beta polycarboxylic acid or anhydride. Examples of polyolefins are polyethylene, polypropylene, ethylene propylene rubber, etc. Examples of ethylenically unsaturated alpha-beta pollcarboxylic acids or anhydrides are maleic anhydride, maleic acid

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and fumaric acid. Grafted polyolefins may be incorporated into the polymer blend in amounts up to 40 percent by weight, preferably from about 5 to about 25 percent by weight. Incorporation of a grafted polyolefin into the polymer blend can significantly improve the compatibility of the blend components and enhance the treatment characteristics.

The polymeric mixture may be melt treated to prepare non-porous breathable films, for example by conventional extrusion or molding techniques. The prepared films may be further treated to prepare a number of devices. For example, the film may be fused or bonded to fabric liners to prepare surgical gowns and dressings, wound dressings and disposable articles.

The following examples are illustrative only and are not intended to limit the. scope of the claimed invention. The numerous additional embodiments within the scope of the invention will readily become apparent to those skilled in the art.

EXAMPLES

Hydrophilic block poly (ether-co-amide) PEBAX ™ 4011MA is melt-blended separately with nylon 6, hydrophobic poly (ether-co-amide) PEBAX ™ 2533, hydrophobic poly (ether-co-amide) 4033 PEBAX ™ and polycaprolactone, in the proportions listed in Table I below. The polymers are mixed in a Plastic-Corder mixer (a Brabender melt mixer) at 50 rpm at 2252 ° C. Each mixture is compression molded to film in a Pasadena press at 2352C and 703 kg / cm²(10,000 psi).

The following measurements were taken to assess the water vapor resistance and permeability of each sample:

a) Buffer plug - Instron testing machine is used with a crosshead speed of 12.7 cm

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per minute (5 inches per minute) and a clearance of

25.4 mm (1 inch); The sample size is 2.54 cm x 10.16 cm with a thickness of 5 mils.

b) MVTR - A Permatran-W moisture permeation testing machine from Modern Controls Inc. is employed following the manufacturer's recommended procedures. Measurements are made on 1 mil thick films, laminated tightly between two aluminum sheets with a 25.4 mm (1 inch) diameter circular opening.

c) Wet yield stress - films are soaked in water for 90 minutes at room temperature. The swollen wet films are then drawn on the Instron as described above for the dried samples.

d) Water absorption - 2.54 cm x 2.54 cm samples are immersed in water for 90 minutes and the weight again recorded.

These measurements are compared to measurements made on films molded from PEBAX ™ 4011MA hydrophilic block poly (ether-co-amide) alone. The compositions and their properties are given in the following table.

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PAINTING

PHYSICAL PROPERTIES OF FILMS PREPARED FROM POLYMERIC MIXTURES CONTAINING A HYDROPHILIC BLOCK POLY (Ether-COAMIDE)

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As illustrated in the Table, polymeric blends (Examples 2-7) offer a wide variety of properties with better wet strength and higher MVTR when compared to PEBAX ™ hydrophilic block poly (ether-co-amide) alone (Example 1 ). It can also be seen from the Table that the degree of swelling of PEBAX ™ hydrophilic block poly (ether-coamide) can be significantly reduced by mixing with hydrophobic polymers while maintaining high MVTR values. The flexibility of controlling properties by simply varying the components and their ratio in mixtures creates an easy way to work new bespoke films.