RU2256673C2 - Air- and steam-permeable biodegradable films and a method for manufacturing thereof - Google Patents

Abstract

FIELD: sanitary and hygienic facilities.

SUBSTANCE: invention relates to biodegradable film materials for manufacture of such articles as baby swaddling bands, female hygienic products, hospital bed-sheets, and the like. Film subjected to stepped stretching is made from polyester containing disperse phase constituted by inorganic filler. Film is characterized by steam passage above 1000 g/m²/day according to ASTM E96E and air permeability 30 cm³/cm²/min at air pressure 620.52 kN/m². Film is manufactured by extruding polymer melt mixed with filler through slot extrusion die into cooling zone. Film is impermeable for liquids.

EFFECT: enhanced hygienic properties.

17 cl, 5 dwg, 2 tbl, 10 ex

Description

RELATED APPLICATIONS

This application is a partial continuation of the application with serial number 09/480374, filed January 10, 2000, which, in turn, is a partial continuation of the application with serial number 09/080063, filed May 15, 1998, which is currently US Patent No. 6013151, and applications with serial number 09/395627, filed September 14, 1999. All of the above applications in their entirety are included in this document.

FIELD OF TECHNOLOGY

The present invention relates to biodegradable plastic films, permeable to air and water vapor, and to methods for their preparation.

BACKGROUND OF THE INVENTION

Methods for producing a film of plastic have been known for many years. For example, more than thirty years ago by Trounstine, et al. U.S. Patent No. 3,448,485 (1968) was issued, and it was directed to a profiled plastic film having desirable characteristics for working with it, and to the manufacture of useful products, such as diapers. Since then, many patents have been granted in this field. US patent No. 4376147 (1983) describes a profiled film elongated in the direction perpendicular to the direction of extrusion, (CD) and in the direction of extrusion (MD). U.S. Patent Nos. 5,202,173 (1993) and 5,296,184 (1994) describe an ultra-soft thermoplastic film that is obtained by stepwise stretching a profiled film and creating perforations to achieve gas permeability. The film may include fillers. Polymeric films of polycaprolactone (PCL) and polymer starch or polyvinyl alcohol (PVOH) by stepwise stretching also provide gas-permeable products, as described in US Pat. Nos. 5,200,247 and 5,407,979. Closer to our time, US patent No. 5865926 was issued for A method for producing a tissue-like microporous laminate of a non-woven fibrous web and a thermoplastic film with permeability to air and water vapor and with properties that provide impermeability to liquids.

Methods for producing products from microporous films are also well known for some time. For example, US Patent No. 3,832,267, issued to Liu, describes melt profiling of a polyolefin film containing a dispersed amorphous polymer phase before stretching or orientation, which improves the film's transmission of gas and water vapor. According to the Liu-267 patent, in order to obtain an oriented non-perforated film with higher permeability, a crystalline polypropylene film containing a dispersed phase of amorphous polypropylene was first subjected to profiling before biaxial stretching. The dispersed amorphous phase served as a source of microcavities to increase the permeability of the otherwise non-perforated film, which improved the passage of water vapor (MVT).

In 1976, Schwarz published a paper describing polymer blends and compositions for microporous substrates (Eckhard CA, Schwartz (Biax-Fiberfilm), “New Fibrillated Film Structures, Manufacture and Uses”, Pap. Synth. Conf. (TAPPI), 1976 pg. 33-39). In accordance with this work, in a film of two or more incompatible polymers, where one polymer forms a continuous phase and the second polymer forms a discrete phase, phase separation will occur during stretching, which will lead to the formation of cavities in the polymer matrix and increase the porosity of the film . The continuous film matrix of the crystallizable polymer can also be filled with an inorganic filler such as clay, titanium dioxide, calcium carbonate and the like, which will create microporosity in the stretched polymer substrate.

The phenomenon of obtaining products from microporous thermoplastic films is also described by many other patents and publications. For example, European Patent No. 141592 describes the use of a polyolefin, in particular a copolymer of ethylene-vinyl acetate (EVA), containing a dispersed polystyrene phase, which when stretched allows to obtain a cavity-containing film, which improves the permeability of the film for water vapor. This EP-592 patent also describes successive steps for profiling an EVA film to produce thick and thin regions, followed by stretching in order to first produce a film with cavities which, upon subsequent stretching, will provide a network-like product. US patents Nos. 4452845 and 4596738 also describe stretched thermoplastic films, where the dispersed phase may be polyethylene filled with calcium carbonate to create micro-cavities under tension. U.S. Patent Nos. 3,137,746; 4,777,073; 4814124 and 4921653 describe the same methods described in the above publications, including the steps of first profiling the polyolefin film containing the filler, and then stretching the film to obtain a microporous product. Other patent publications were published, including WO 98/23673, which were directed to thermoplastic films based on complex copolyesters with improved water vapor transmission rates obtained by mixing a resin based on a copolyester and an inorganic filler.

Biodegradable and / or compostable products help conserve environmental resources and prevent additional waste. Both producers and consumers are aware of the limited space available at landfills and other waste disposal sites and can constructively use biodegradable and / or compostable products in comparison with products that are biodegradable and / or unsuitable for composting. The need for biodegradability and / or suitability for making compost is especially important in the case of recyclable products characterized by increased use, such as baby diapers, feminine hygiene products, hospital sheets and the like.

Thermoplastic films that are biodegradable and / or suitable for making compost have been known in the prior art. The above-mentioned US patent No. 5407979 describes a biodegradable thermoplastic film consisting of three components: an alkanoyl polymer, degraded starch and an ethylene copolymer. The components can be extruded, and the film can be stretched to obtain a gas permeable film. US patent No. 5200247 describes a biodegradable thermoplastic film containing a mixture of alkanoyl polymer / polyvinyl alcohol (PVA). US Patent No. 5,196,247 describes a sheet of a polymer composite suitable for composting and a method for producing or making compost from it.

Fully biodegradable and / or compostable soft tissue-like composites are described in US Pat. No. 5,851,937. Composites are obtained by stepwise stretching one or more layers of completely biodegradable and / or nonwoven webs and plastic films suitable for composting to obtain a soft fabric-like neck.

There are still obstacles to the production of gas permeable films and laminates that are impervious to liquids. It is difficult to obtain a film that is impervious to liquid, having sufficient strength while maintaining the properties of biodegradability, permeability to air and the transmission of water vapor.

SUMMARY OF THE INVENTION

This invention relates to a biodegradable film that is permeable to both air and water vapor, and which is impervious to liquid. These films differ in water vapor transmission rates (MVTR) exceeding approximately 1000 grams (g) per m ² per day at 100 ° F and 95% relative humidity (RH) in accordance with ASTM E96E, and air permeabilities exceeding approximately 30 cc / cm ² / min under air pressure 90 lb / ^in2.

The above patent applications with registration numbers 09/080063 and 09/480374 describe stepwise stretched films characterized by high MVTR. These applications were aimed at improving stepwise stretched profiled and non-profiled films differing in MVTR values, preferably on the order of magnitude, in the range of from about 1200 to about 4500 g / m ² / day. Gas-permeable laminates of these films with nonwoven substrates have also been described.

The present invention aims to further improve biodegradable films and laminates that are permeable to both air and water vapor. In the broad context of the present invention, a biodegradable film comprises a mixture of a biodegradable thermoplastic polymer and a mechanical pore-forming agent, such as inorganic fillers, namely calcium carbonate, silicon dioxide and zeolite. The pore-forming agent in the film or laminate is activated during stretching, preferably stepwise stretching, resulting in a microporous film or laminate from a fibrous web and film. Biodegradable polymers such as polycaprolactone (PCL) mixed with polymer starches or polyvinyl alcohol (PVA), which can be formed into films, are suitable. Other biodegradable polymers include polylactide (PLA), polyesters and copolyesters.

Biodegradable films and laminates can be used to make back layers of diapers, sanitary napkins and pads, and for other medical, packaging and clothing applications. The biodegradable film is particularly suitable for data and other similar applications due to its permeability to air, permeability to water vapor and impermeability to water. The advantages and properties of the biodegradable film of the present invention and the method for its preparation will be better understood in connection with the following detailed description.

DETAILED DESCRIPTION OF THE INVENTION

The main object of the present invention is to provide permeable to air and water vapor biodegradable film with a permeability to air of at least approximately equal to 30 cc / cm ² / min at an air pressure 90 lb / ^in2, and MVTR, greater than about 1000 g per m ² in one day at 100 ° F and 95% relative humidity (RH) in accordance with ASTM E96E. Another objective of this invention is to obtain a stepwise stretched biodegradable thermoplastic film having these properties with respect to gas permeability and characterized by normal thickness, uniform porosity and the absence of damage.

A. Materials for biodegradable film and laminate.

A biodegradable film composition can be obtained by combining a biodegradable thermoplastic polymer with suitable additives and pore-forming fillers to form an extrudate or film. The film can be laminated onto a non-woven fabric. The most commonly used fillers are particles of calcium carbonate, barium sulfate, silicon dioxide and zeolite. As described above, it was already known to obtain biodegradable films with various polymer phases in the film, such that when the film is stretched at ambient temperature or at room temperature microcavities are formed that provide gas permeability and the passage of water vapor. These methods are described in US patent No. 5200247 and 5407979. In contrast, this invention is directed to the use of inorganic fillers to obtain high permeability to air and high MVTR from biodegradable films in the presence of properties that provide impermeability to liquids.

As described above, these and other objectives are achieved in a preferred form of the invention by first melt-mixing the composition (a) from about 40% to about 75% (mass.) Of a biodegradable polymer of the type indicated above, and (b) from about 25% to about 60% (mass.) particles of an inorganic filler, for example, calcium carbonate, zeolite, silicon dioxide, talc, barium sulfate, mica and the like, then extruding said composition melt mixed together with others to Avkam in the roll gap to obtain a film at a speed of the order of magnitude in the range of at least about 550 feet per minute to about 1200 feet per minute without resonance when the extrudate is drawn and applying stepwise tensile forces to said film at said speed along the lines, extending substantially uniformly across the film and throughout its depth, until a biodegradable microporous film is obtained.

More specifically, in a preferred form, the melt-blended composition essentially comprises from about 60% to about 75% polyester, such as aliphatic-aromatic copolyesters, which are described in WO 98/23673, and this description is included in the present reference document. In particular, these thermoplastic copolyesters may include at least one aliphatic dibasic carboxylic acid, at least one aromatic dibasic carboxylic acid, and at least one aliphatic diol containing from 4 to about 12 carbon atoms. Alternatively, the thermoplastic copolyester may include at least one aromatic dibasic carboxylic acid, at least one aliphatic diol, and a polyalkylene ether. Aliphatic dibasic carboxylic acid is selected from the group consisting of adipic acid, glutaric acid, cyclohexanoic acid and mixtures thereof; at least one of said aromatic dibasic carboxylic acids is selected from the group consisting of terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and mixtures thereof; and at least one of said aliphatic diols is selected from the group consisting of 1,4-butanediol, cyclohexanedimethanol, a polyalkylene ether derivative selected from the group consisting of poly (ethylene glycol), poly (tetramethylene glycol) and poly (propylene glycol) and mixtures thereof. The thermoplastic copolyester may contain various combinations of aromatic dibasic carboxylic acid, aliphatic diols, cyclic aliphatic dibasic carboxylic acids, polyalkylene ethers and the like, all of which are described in WO 98/23673 as examples of copolyesters within the scope of this invention.

Other polymers include an ester-ether polyester (Hytrel and Armtel); polyester based on nylon - ether (Pebax); polyethylene terephthalate (PET); polyvinyl alcohol (PVA); polycaprolactone (PCL); starch; polylactide (PLA); a mixture of starch and PVA, PCL or PLA; polyesters such as polyhydroxy (butyrate) (PHB), polyhydroxy (valerate) (PHV); and mixtures thereof. Preferably, about 25-40% of calcium carbonate, silicon dioxide, barium sulfate or zeolite is used with an average particle size in the range of from about 1 to about 10 microns.

Biodegradable nonwoven materials can be laminated onto films, and they preferably include melt stable lactide polymers of the type described in US Pat. No. 5,593,081, that is, polylactide nonwoven materials (PLA). All elementary fibers of the nonwoven material are obtained entirely from a polymer or a mixture of polymers formed from lactic acid, that is, from L-lactic acid, D-lactic acid or a mixture of L- and D-lactic acids. Other nonwoven materials that are biodegradable and / or suitable for making compost include cotton nonwovens, cellulose nonwovens, aliphatic-aromatic copolyesters, and mixtures thereof.

In the above method, the melt-blended composition is extruded through a slotted extrusion die in the form of a web going through a cooling zone equipped with a pneumatic knife, then the rollers are fed into the gap to produce a film with high speeds. You can get profiled or flat (non-profiled) film. The use of a pneumatic knife, as mentioned above, helps to eliminate the occurrence of resonance when extruding the extrudate, which is known, for example, from such a reference as US patent No. 4626574. In addition, as described in U.S. pending application Serial No. 09/395627, filed September 14, 1999, which is incorporated herein by reference in its entirety, devices that direct the flow of cooling gas so that in the cooling stream would move substantially parallel to the surface of the web. For example, you can use the devices shown in US patent No. 4718178 and 4779355, and full descriptions of these patents are also included in this document for reference. After cooling, a stepwise tensile force is applied to the film or laminate at high speeds along lines extending substantially uniformly across the film and throughout its depth, until a stepwise stretched shaped or flat film is obtained characterized by high MVTR and air permeability.

Flat films are prepared in accordance with the principles of the present invention after extruding the web into a roll gap that has a polished chrome surface to form a flat film. Flat film with stepwise stretching at high speeds allows you to get products from microporous films, characterized by high MVTR in excess of 1000 g / m ² / day. It has been found that a flat film can be subjected to stepwise stretching more evenly than a profiled film. The stretching method can be implemented at ambient temperature, room temperature or at elevated temperature, as is understood at the present level of technology. As is also understood at the present level of technology, “ambient temperature” refers to the temperature of the environment or atmosphere that may occur, whatever the conditions for the implementation of the method may exist in the environment of the film. As already described above, it is possible to obtain laminates of a microporous film and non-woven fibrous webs.

In a preferred form, a film is used in the microporous laminate whose assortment or thickness is in the range of about 0.25 to 10 mils, and depending on the use, the film thickness will vary, and for utilized applications, it will most preferably have a thickness in the order of magnitude in the range of from about 0.25 to 2 mil. Non-woven fibrous webs of the laminated sheet typically have a mass in the range of from about 5 g / yard ² to 75 g / yard ² , preferably from about 20 to about 40 g / yard ² . The composite or laminate can be subjected to stepwise stretching in the direction perpendicular to the direction of extrusion (CD) to obtain a composite subjected to CD-stretching. In addition, CD stretching can be followed by stretching in the direction of extrusion (MD) to obtain a composite that has been stretched in both CD and MD directions. As mentioned above, a microporous film or laminate can be used in many different applications, such as baby diapers, children's training underwear, panty liners and clothing for use during menstruation and the like, where properties are required that allow the passage of water vapor and air, as well as liquid tightness properties.

B. Exhaust devices for microporous film and laminates

For stretching a film or laminate of a non-woven fibrous web and formed as a microporous film, several different exhaust devices and techniques can be used. These laminates of non-woven fibrous webs from staple fiber webs or non-woven fibrous webs with fiber forming with ejection by a high-speed stream of air can be stretched using exhaust hoods and techniques described as follows:

1. Exhaust hood with diagonal interlocking

An exhaust device with diagonal interlocking consists of a pair of elements similar to a helical spur gear with a left tooth and a right tooth on parallel shafts. The shafts are located between the two side plates of the machine, with the lower shaft located in the fixed bearings, and the upper shaft located in the bearings in vertically movable elements. The position of the movable elements can be adjusted in the vertical direction using wedge-shaped elements controlled by adjusting screws. Unscrewing or screwing in the wedges will move the vertically movable element, respectively, up or down to additionally engage or disengage the gear-like teeth of the upper intermeshing roller and the lower intermeshing roller. Micrometers mounted on the sidewalls can be controlled by indicating the tooth engagement depth for the intermeshing roller.

Pneumatic cylinders are used to hold the movable elements firmly in the lower engagement position with respect to the control wedges while counteracting the upwardly generated force exerted by the material being stretched. These cylinders can also be retracted to disengage the upper and lower intermeshing rollers for the purpose of loading material through intermeshing equipment or in connection with the action of the protective circuit, which will open all areas with gaps in the machine when it is activated.

A drive device is typically used to drive a stationary intermeshing roller. If the upper interlock gear needs to be able to disengage for refueling purposes or for safety reasons, it is preferable to use a backlash-free gear arrangement between the upper and lower interlock shafts, which will ensure that when teeth re-engage, the teeth of one interlock shaft will always be between the teeth of the other interlock shaft, and potential destructive physical contact between the heads of the teeth of the intermeshing will be prevented. If the intermeshing rollers must remain in constant engagement, then the upper intermeshing roller usually does not need to be driven. The propulsion can be accomplished by the drive roller intermeshing due to the material subjected to stretching.

Intermeshing rollers very much resemble helical gears with a small pitch. In a preferred embodiment, the rollers have a diameter of 5.935 ”, an angle of inclination of the tooth line of 45 °, a normal pitch of 0.100”, a pitch of 30, an angle of engagement of 14 °, and basically they are a gear with a protruding long tooth head. As a result, we get a narrow, deep tooth profile, which makes it possible with intermesh engagement up to about 0.090 ”and a gap on the sides of the tooth for a material thickness of approximately 0.005”. The teeth are not designed to transmit rotational moment, and in the usual execution of tension with intermeshing, they do not interact in contact of metal with metal.

2. An exhaust device with interlocking in a direction perpendicular to the direction of extrusion.

The equipment for stretching with CD intermeshing is identical to a draft unit with diagonal intermeshing with differences in the design of the intermeshing rollers and other minor elements noted below. Since CD interlocking elements are capable of reaching large depths of engagement, it is important that the equipment includes devices that cause the shafts of the two interlocking rollers to remain parallel when the upper shaft rises or falls. This is necessary in order to ensure that the teeth of one interlocking roller always fall between the teeth of the other interlocking roller and to prevent potential destructive physical contact between the interlocking teeth. This parallel movement is ensured by the arrangement of the gear rack and the gear wheel, where, in the overlay position on vertically moving elements, a stationary gear rack is attached to each sidewall. The shaft passes the sidewalls and acts in the bearing in each of the vertically moving elements. There is a gear at each end of the shaft, and it is engaged with the gear racks to obtain the desired parallel movement.

The drive of the exhaust device with CD intermeshing should act on both the upper and lower intermeshing rollers, with the exception of the case of stretching with intermeshing for materials with a relatively high coefficient of friction. However, the drive should not be backlash-free, because a small degree of misalignment in the direction of extrusion or slipping of the drive will not cause problems. The reason for this will become apparent from the description of the elements of CD interlinking.

The CD intermeshing elements are machined from solid material, but can best be described as an alternating stack of disks with two different diameters. In a preferred embodiment, the disengagement disks will have a diameter of 6 ”, a thickness of 0.031” and will have a full radius at their edge. Spacer disks separating the intermeshing disks will be 5Ѕ “in diameter and 0.069” in thickness. Two rollers of this configuration will be able to provide interlocking up to 0.231 ”, leaving a gap of 0.019” for the material from all sides. As with an exhaust device with diagonal interlocking, this configuration of the CD interlocking member will have a step of 0.100 ”.

3. Extraction device with intermeshing in the direction of extrusion

The MD stretching equipment is identical to a diagonal interlock extractor, with the exception of the design of the intermeshing rollers. Shafts with MD interlocks very much resemble spur gears with fine pitch. In a preferred embodiment, the rollers have a diameter of 5.933 ”, a pitch of 0.100”, a diametrical pitch of 30, an angle of engagement of 14 °, and basically they are a gear wheel with a protruding long tooth head. To obtain a narrower tooth with a larger clearance for these rollers, a second pass of the gear cutting worm cutter was made at an offset of 0.010 ”. When engaging approximately equal to 0.090 ”, for the thickness of the material, this configuration on the sides will have a clearance of approximately equal to 0.010”.

4. The method of incremental stretching

The diagonal, CD or MD interlocking hoods described above can be used to make stepwise stretched film or nonwoven fibrous web laminate and formable as a microporous film to produce microporous film products of the present invention. For example, a stretching operation can be used for an extruded laminate of a nonwoven fibrous web of staple fiber or elementary fibers with fiber forming with ejection by a high-speed air stream and formed as a microporous thermoplastic film. In one of the unique aspects of the present invention, a laminate of a nonwoven fibrous web of fiber spun fibers with ejection by a high-speed stream of air can be stretched step by step to obtain a laminate with a very soft lint finish that has the appearance of a fabric. A nonwoven fibrous web laminate and a microporous film formed is subjected to stepwise stretching using, for example, an exhaust device with CD and / or MD interlocking in a single pass through the exhaust device at an engagement depth of the rollers in the range of from about 0.060 inches to 0.120 inches at speeds in ranging from approximately 550 feet per minute to 1200 feet per minute or faster. The results of such stepwise stretching or interlocking stretching are laminates which have excellent gas permeability and liquid impermeability properties, while excellent adhesion strengths are achieved and soft fabric-like textures are formed.

The following examples illustrate the method for producing the microporous film and laminates of the present invention. In the light of these examples and this additional detailed description, it will be apparent to those skilled in the art that variations in the present invention can be made without departing from the scope of this invention.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a micrograph of the surface of the film of example 1A at 1000X.

Figure 2 is a micrograph of the cross section of the film from example 1A at 2000X.

Figure 3 is a micrograph of the surface of the film of Example 1B at 1000X in the unstretched region due to interlocking.

Figure 4 is a micrograph of the surface of the film of Example 1B at 1000X in the stretched region due to stretching with intermeshing.

Figure 5 is a micrograph of the cross section of the film from example 1B at 2000X for the stretched surface region.

Examples 1A and 1B

In these examples, a biodegradable aromatic - aliphatic type copolyester was used, which is fully described in the examples in WO 98/23673. More specifically, a film containing representative biodegradable copolyesters described in the examples of this publication, containing from about 25% to about 40% zeolite or calcium carbonate, was extruded using a conventional solution cast film extrusion technique through a slit die, which well known to those skilled in the art. In particular, films having thicknesses of approximately 2 miles (50 g per square meter) were extruded at melt temperatures of the order of about 425-475 ° F. A micrograph of such a film surface is shown in Figure 1, and a cross section is shown in Figure 2. The film was tested and was not found to be air permeable, but according to ASTM E96E testing method, its MVTR (water vapor transmission rate) was 939 g / m ² /day.

The film from Example 1A, after stepwise stretching at a temperature of approximately 72 ° F, with a CD gear of 0.070 inches, followed by an MD gear of 0.050 inches, became air permeable using the apparatus described above, and the passage speed her water vapor increased. MVTR increased from 939 g / m ² / day (Example 1A) to 2350 g / m ² / day (Example 1B). The permeability to air of the film originally zero permeability (Example 1A) has become equal to 570 cc air / ^cm2 / min at an air pressure of 90 lbs / inch ² (Example 1B).

Microphotographs of the surfaces and cross sections of the film from examples 1A and 1B actually showed inorganic particles (see figures 1-5). Biodegradable film, characterized by high MVTR and permeability to air, of this invention was actually characterized by the formation of pores in the vicinity of inorganic particles during stepwise stretching (see figures 4 and 5). However, no pore formation was observed in the unstretched region (see figure 3). The cross section of the film from example 1B (see figure 5) clearly shows that the pores are connected, which allows air to flow through them. In the film of Example 1A (see Figure 2, cross section), there are no pore compounds that allow air to flow through them.

The mechanical properties of the film from example 1A are as follows (see table 1).

Table 1

Example A. Example B. The ratio of 1B / 1A. The total density of the canvas (g / m ² ) fifty 35 0.7 Airflow cc / cm ² / min at 90 lb / ⁱⁿ² 0 570 ∞ MVTR (g / m ² / day), ASTM E96E 939 2350 2,5 MD tensile strength (gram / inch) 1116 885 CD tensile strength (gram / inch) 756 661 Elongation at MD break (%) 707 494 Elongation at CD break (%) 539 436

The biodegradable film of Example 1B is suitable for back layers of diapers, sanitary napkins, and health care apparel applications where air-to-skin passage (ventilation), high water vapor transmission, and impermeability properties are required when wearing a skin care and comfort sock. for fluid.

Examples 2A-2H

In these examples, the aromatic-aliphatic-type copolyesters used in Example 1A were similarly extruded to obtain a film. These films from examples 2A-2H were subjected to CD and / or MD stretching at room temperature to obtain biodegradable films with permeability to air and water vapor, as shown in table 2.

table 2

Example Interlocking Stretch (inches) Air flow, cc / cm ² / min of air at 90 lb / ⁱⁿ² The speed of passage of water vapor, E96E, g / m ² / day The density of the canvas (g / m ² ) Extraction rate (before / after) CD MD 1A (comparative) 0 0 0 939 fifty 0 2A 0,040 0 fifty 1365 48 1.05 2B 0,040 0,040 110 1665 45 1,11 2C 0,050 0 140 1665 45 1,11 2D 0,050 0,050 280 2122 39 1.28 2E 0,060 0 200 1895 40 1.25 2F 0,060 0,060 490 2350 33 1.51 2G 0,070 0 310 2122 36 1.39 2H 0,070 0,070 720 2652 29th 1.72

Other biodegradable polymers such as polylactides, polycaprolactones, starch, polyvinyl alcohols, polyesters and copolyesters can be processed to produce films with air and moisture permeability in light of the above description with inorganic filler particles.

In view of the above detailed description, it is necessary to understand that, depending on the materials and conditions, as one skilled in the art would understand, variations will occur in using the principles of this invention.

Claims (17)

1. Biodegradable thermoplastic film, permeable to air and moisture, containing a biodegradable thermoplastic polymer containing a dispersed phase of inorganic filler particles, said film having a liquid impermeable thickness in the presence of stretched regions, and said particles form pores in said film, creating microporosity in the film , characterized in that the polymer is a biodegradable thermoplastic complex polyester, the film is subjected to stepwise stretching and it has a speed s moisture vapor transmission (MVTR) greater than about 1000 g / ^m2 / day according to ASTM E96E, and air permeability of above about 30 cm ³ / cm ² / min at an air pressure 90 lb / ⁱⁿ² (620.52 kN / m ² ). 2. The film according to claim 1, where the biodegradable thermoplastic polymer is an aliphatic - aromatic complex copolyester. 3. The film according to claim 1 or 2, where the aforementioned filler is selected from the group consisting of calcium carbonate, silicon dioxide, talc, barium sulfate, zeolite and mica and mixtures thereof. 4. The film according to any one of the preceding paragraphs, where the microporous film has a thickness of the order of magnitude in the range from about 0.25 to about 10 mils (6.35 to 254 microns). 5. The film according to any one of the preceding paragraphs, where the microporous film has a thickness of the order of from about 0.25 to about 2 mils (from 6.35 to 50.8 microns). 6. The film according to any one of the preceding paragraphs, where the water vapor transmission rate (MVTR) is in the range from about 2000 to about 4500 g per 1 m ² per day in accordance with ASTM E96E, and the air permeability is in the range from about 200 to about 1600 cm ³ / cm ² / min under air pressure 90 lb / ⁱⁿ² (620.52 kN / m ^2). 7. The film according to any one of the preceding paragraphs, intended for application to a biodegradable fibrous web. 8. The film according to claim 7, where the fibers in said fibrous fabric are selected from the group consisting of cellulosic polymer, polyester, copolyester, polymer fully formed from L-lactic acid, polymer fully formed from D-lactic acid, copolymer L-lactic acid and D-lactic acid and a mixture of polymers of L-lactic acid and D-lactic acid. 9. A high-speed method for producing a biodegradable thermoplastic film, permeable to air and moisture, having properties that impermeable to liquids, including mixing in a melt of a biodegradable thermoplastic polymer and particles of an inorganic filler to form a composition of a biodegradable thermoplastic polymer, extruding the fabric of said molten thermoplastic composition into a gap to obtain a film having a thickness of from about 0.25 to about 10 mi (from 6.35 to 254 microns), applying a stepwise tensile force to said film along lines extending substantially uniformly across the film and throughout its depth, characterized in that the method comprises melt mixing from about 40% to about 75 wt. % polymer based on biodegradable thermoplastic polyester and from about 25% to about 60 wt.% particles of inorganic filler; the web is extruded from the slit die through the cooling zone into the gap to form a biodegradable microporous film with an MVTR of more than about 1000 g / m ² / day in accordance with ASTM E96E and an air permeability of more than about 30 cm ³ / cm ² / min under air pressure 90 lb / ⁱⁿ² (620.52 kN / m ^2). 10. The method according to claim 9, where the MVTR is in the order of magnitude in the range from about 2000 to about 4500 g / m ² / day in accordance with ASTM E96E, and the permeability to air is in the range from about 200 to about 1600 cm ³ / cm ² / min under air pressure 90 lb / ⁱⁿ² (620.52 kN / m ^2). 11. The method according to claim 9 or claim 10, wherein the biodegradable thermoplastic polymer is an aliphatic - aromatic complex copolyester. 12. The method according to any one of claims 9 to 11, wherein said filler is selected from the group consisting of calcium carbonate, silicon dioxide, talc, barium sulfate, zeolite and mica, and mixtures thereof. 13. The method according to any one of claims 9-12, wherein the average particle size of said inorganic filler is in the range of from about 1 to about 10 microns, and said inorganic filler is selected from the group consisting of calcium carbonate, barium sulfate, silicon dioxide and zeolite. 14. The method according to any one of claims 9 to 13, where the microporous film has a thickness of the order of magnitude in the range from about 0.25 to about 2 mils (6.35 to 50.8 μm). 15. The method according to any one of claims 9-14, comprising introducing a biodegradable nonwoven fibrous web into said roll gap, adjusting the compressive force to adhere the web to the film and stretching to form a laminated biodegradable film. 16. The method according to clause 15, where the fibers in said fibrous fabric are selected from the group consisting of cellulosic polymer, complex polyester, complex copolyester, a polymer completely formed from L-lactic acid, a polymer completely formed from D-lactic acid, a copolymer L-lactic acid and D-lactic acid and a mixture of polymers of L-lactic acid and D-lactic acid. 17. The method according to any one of paragraphs.9-16, where the film is formed at a speed of the order of magnitude, at least in the range from about 550 feet per minute to about 1200 feet per minute (from 2.80 to 6.10 m / c) without resonance during extrudate drawing.

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