MXPA02006718A - Antibacterial microporous film and method of making. - Google Patents

Abstract

Antibacterial unembossed and microembossed film products permeable to moisture vapor and which act as barriers to bacteria and liquid are made by a high speed method. The antibacterial microembossed microporous films have impact strengths greater than 150 grams according to ASTM D1709 and high moisture vapor transmission rates (MVTRs) on the order of about 1000 to about 4500 gmsm2day according to ASTM E96E.

Description

MICROPOROSE ANTIBACTERIAL FILM. AND METHOD TO MANUFACTURE THE SAME RELATED REQUESTS This application is a request that is a continuation in part of the serial application No. 09 / 480,374, filed on January 10, 2000, which, in turn, is a request that is a continuation in part of the serial application No. 09 / 080,063, filed on May 15, 1998, now US patent No. 6,013,151, and serial application No. 09 / 395,627, filed September 14, 1999. All of the foregoing applications are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION This invention relates to microporous antibacterial films, and to a high speed method for manufacturing them.

BACKGROUND OF THE INVENTION The methods of making plastic films date back many years. For example, the patent of E.U.A. No. 3,484,835 (1968), issued to Trounstine, et al., Dates back more than 30 years and is directed to a relief plastic film having desirable handling characteristics, as well as to the manufacture of useful articles such as diapers. Since that time, many patents have been issued in the field. The patent of E.U.A. No. 4,376,147 (1983), discloses a film with relief in the transverse direction (CD) and machine direction (MD). The patents of E.U.A. Nos. 5,202,173 (1993) and 5,296,184 (1994) describe an ultra-smooth thermoplastic film that was obtained by progressively stretching the film with relief, and the formation of perforations to achieve breathing capacity. The movie may include fillers. Polycaprolactone (PCL) polymer films and starch or polyvinyl alcohol (PVOH) polymer after progressive stretching also produce respirable products, as described in the U.S. Patents. Nos. 5,200,247 and 5,407,979. More recently, the patent of E.U.A. No. 5,865,926 was issued for a method of manufacturing a microporous cloth-like laminate of a fibrous non-woven fabric and thermoplastic film having moisture and air vapor permeabilities with liquid barrier properties. Methods of manufacturing microporous film products have also been known for some time. For example, the patent of E.U.A. No. 3,832,267 to Liu, describes the melt-print of a polyolefin film containing an amorphous polymer phase dispersed before stretching or orientation, to improve the transmission of moisture vapor and gases from the film. According to the Liu patent, a crystalline polypropylene film having a dispersed amorphous polypropylene phase is first stamped before being biaxially stretched to produce a non-perforated oriented film having greater permeability. The dispersed amorphous phase serves to provide microvoids that otherwise improve the permeability of the film without perforations to improve the transmission of moisture vapor (MVT). The embossed film is preferably stamped with at least about 4, and no more than about 600 embossments by 6.45 cm2, and drawn sequentially. The 4 to 600 highlights by 6.45 cm2, are equivalent to approximately 2 to 25 lines stamped by 2.54 cm. In 1976, Schwarz published an article describing mixtures and polymer compositions to produce microporous substrates (Eckhard CA Schwartz (Biax-Fiberfilm), "New Fibrillated Film Structures, Manufacture and Uses", Pao Synth Conf. (TAPPI). , pages 33-39). According to this article, a film of two or more incompatible polymers, wherein a polymer forms a continuous phase and a second polymer forms a discontinuous phase, after being stretched, is separated in its phases, thus leading to gaps in the polymer matrix, and increased the porosity of the film. The continuous film matrix of a crystallizable polymer can also be filled with inorganic filler such as clay, titanium dioxide, calcium carbonate, etc., to provide microporosity in the stretched polymeric substrate. Many other patents and publications describe the phenomenon of manufacturing porous thermoplastic film products. For example, European patent 141592, describes the use of a polyolefin, in particular ethylene vinyl acetate (EVA) containing a dispersed polystyrene phase which, when stretched, produces a hollow film that improves the permeability of the film to moisture vapor . Said patent also describes sequential steps of embossing the EVA film with thick and thin areas, followed by stretching, to first provide a film having voids which, when stretched further, gives a product in the form of a network. The patents of E.U.A. Nos. 4,452,845 and 4,596,738, also disclose stretched thermoplastic films wherein the dispersed phase may be a polyethylene filled with calcium carbonate, to provide the microvoids after stretching. The patents of E.U.A. Nos. 3,137,746; 4,777,073; 4,814,124; and 4,921, 653, describe the same procedures described by the publications mentioned above, including the steps of first stamping a polyolefin film containing a filler, and then stretching that film to provide a microporous product. In the case of the patent No. 3,137,746, the embossing is up to 300 embossments by 6.45 cm2, equivalent to approximately 17 embossed lines by 2.54 cm. The patent 4,777,073 does not describe the geometry of the stamp. The patents 4,814,124 and 4,921,653 describe embossing to improve tear resistance. The patent of E.U.A. No. 4,308,303, discloses a bacterial barrier of a microporous film having a pore size no greater than about 0.2 microns, which is prepared by stretching a filler-containing film with two series of 4-roller guide pulleys operating at different speeds. The patents of E.U.A. Nos. 4,344,999; 4,353,945 and 4,713,068, are other examples of patents that describe the stretching of polyolefin and filler precursors to provide microporosities less than about 0.2 microns. Notwithstanding the great advances in the art for manufacturing plastic films and breathable microporous films to provide moisture vapor and air permeabilities with liquid barrier properties, further improvements are required. In particular, improvements are desired to obtain microporous film products having antibacterial properties and other desirable properties.

BRIEF DESCRIPTION OF THE INVENTION This invention is directed to microporous antibacterial thermoplastic films, and to a method for manufacturing them. The product can be made using high speed production machinery at speeds of at least about 165 m / min, preferably about 210 m / min - 360 m / min. In the patent applications mentioned above, thin stretched and non-patterned microprocessed films having high MVTRs, ie, greater than 1000 gms / m2 / day, preferably from about 2000 to 4500 gms / m2 / day were described (method E96E of ASTM). This invention is directed to further enhancements of progressively stretched microstamped and non-patterned thin films having antibacterial properties. These films also have high MVTRs and high impact resistance. Laminates of antibacterial microporous patches or strips of non-woven fabrics with the microporous film are also produced at high speeds in accordance with this invention. This invention provides an antibacterial microporous film having a high moisture vapor transmission rate (MVTR), comprising a thermoplastic polymer film containing a dispersed phase of particles selected from the group consisting of an inorganic filler and an organic material. An antibacterial agent may also be added to the composition to achieve additional protection against bacteria. The film has a thickness of about 0.002 cm to about 0.005 cm, with areas stretched progressively in the film to provide microporosity in the film with a MVTR of greater than about 1000 gms / m2 / day according to the E96E method of ASTM. The microporosity of the film has a pore size distribution, where the largest pore size is around 0.22 microns, as determined by capillary flow porosimetry of PMI. Preferably, the smallest pore size is about 0.05 microns, and about 80% of the pores vary from about 0.05 to about 0.08 microns.

It has been found that a progressively drawn microporous thin thermoplastic film having a rectangular micro-patterned engraving of intersecting and machine direction (MD) transverse direction (CD) lines of about 165 to 300 lines by 2.54 cm in both directions provides Greater impact resistance than a non-stamped film. Impact strengths greater than about 150 g are achieved (ASTM method D1709). The thin film has a thickness of about 0.002 cm to about 0.005 cm, and a depth of engraving of about 0.002 cm to about 0.005 cm. In a preferred rectangular embossed film, approximately 250 lines by 2.54 cm are stamped on the width (CD) and length (MD) of the film. Laminates of antibacterial patches or strips of non-woven fabrics and the progressively stretched micro-patterned film are also provided, wherein only a portion of the film is laminated to the non-woven fabric. In the case of these laminates, the exclusive film portion with improved impact resistance is provided, and the resulting laminate has improved impact and general tear resistance. The method of this invention involves the extrusion of a microporous formable thermoplastic film into a grip of CD and MD stamping rolls, wherein the roll is etched with a rectangular pattern of CD and MD lines of about 165-300 by 2.54 cm in both directions. The microporous formable thermoplastic composition of the film may comprise a blend of a thermoplastic polymer and a mechanical pore-forming agent, such as an inorganic filler (CaCO3). The pore-forming agent in the film is then activated after progressive stretching to form a microporous film. This unique method not only provides economy in the manufacture of breathable laminates, but also allows its production in high speed machinery in the order of around 210 m / min-360 m / min. The method consists of melting a microporous, formable thermoplastic composition and extruding into grooved die a fabric of that composition through a cooling zone in a stamping roll grip, to form a film at a rate of preferably greater than about 210 m. / min. A stream of cooling gas (air) is directed to the film during its extraction in a film. The flow of air through the cooling zone is substantially parallel to the surface of the fabric to cool it, and form a film without stretch resonance. In the preferred embodiment of the method, the efficiency of the cooling gas is improved by creating a plurality of gas vortices as the current moves through the zone to cool the fabric. The vortices improve the efficiency of the cooling gas by mixing the cooling gas, and causing the flow of the cooling gas to be turbulent in the cooling zone. A cooling device is used to create the vortices and cause the gas stream to move in different directions parallel to the movement of the fabric. Alternatively, the gas stream moves mainly in the same direction as the movement of the fabric, or in a direction opposite to the movement of the same. Alternatively, when it is desired to achieve impact resistance of the microporous film in a strip laminate with a nonwoven, a strip of fibrous non-woven fabric is introduced into the grip of the embossing rolls with the extruded film, and the temperature The lamination is controlled by the cooling gas to control the target bonding levels at high extrusion lamination speeds. For example, objective bonding levels are achieved between the plastic film and the non-woven fabric at speeds exceeding about 210 m / min, or even up to about 360 m / min, or more. Target binding levels of, for example, 100 gms / cm (approximately 250 grams / 2.54 cm) between the film and the nonwoven, are achieved at line speeds in the order of 270 m / min for commercial purposes. The compressive force between the fabric and the film in the grip is controlled to join the surface of the fabric to form a laminated sheet. In addition, even at high line speeds, the film gauge is controlled without stretch resonance. For example, a fixed basis weight of the film of about 40 grams per square meter (gsm) at 270 m / min is achieved. In this way, the cooling method eliminates the stretch resonance that would otherwise normally be encountered under such conditions.

In accordance with the invention, breathable micro-patterned films and laminates are produced which are permeable to air and water vapor, but which are a barrier to bacteria and liquids. These bacterial products are obtained from a microporous formable thermoplastic composition comprising a thermoplastic polymer and filler particles. Antibacterial agents may optionally be included. After extrusion into slotting and micro-stamping of said composition, followed by the application of a stretching force to the film at high speeds along lines substantially and uniformly through the film and through its depth, a film is formed microporosa microstamp that has improved resistance to impact. Breathable strip and patch laminates are obtained when a non-woven fibrous web is laminated to a portion of the micro-patterned film during extrusion. The efficiency of the cooling gas is improved by creating a plurality of gas vortices as the current moves through the cooling zone to cool the fabric during extrusion lamination. Then, a progressive stretching force is preferably applied to the micro-patterned film or the laminate at high speeds substantially and uniformly through the film, and through its depth to provide a microporous film and non-woven laminate. Branching can also be used to stretch the laminate. Other benefits, advantages and objectives of this invention will be better understood in relation to the following detailed description.

DETAILED DESCRIPTION OF THE INVENTION A principal objective of this invention is to produce thin antibacterial microporous films with improved properties, such as impact resistance, in high speed production machinery. Another objective of the method is to obtain regular caliber antibacterial breathable strip and patch rolled products without stretch resonance. Another objective is to produce said laminates having satisfactory bond strengths, while maintaining the appearance of a cloth or cloth having adequate air permeability and moisture vapor transmission rates, while maintaining antibacterial and liquid barrier properties. The antibacterial properties are achieved by progressively stretching an extruded film containing filler particles to provide a pore size distribution, where the largest pore size is around 0.22 microns, to prevent the passage of bacteria. Preferably, the smallest pore size is about 0.05 microns, and about 80% of the pores vary from about 0.05 to about 0.08 microns. The high speed method for manufacturing an antibacterial film or a strip laminate (patch) of a fibrous web nonwoven with the film comprises melt blending a thermoplastic polymer and filler particles to form a thermoplastic polymer composition. A fabric of the molten thermoplastic composition is extruded from a slotted die through a cooling zone in a roller grip to form a film at a rate of preferably greater than about 210 m / min, and introducing strips of a cloth fibrous non-woven in said roller grip, and controlling the temperature and the compressive force between the cloth and the film in the grip, to bond the surfaces of the cloth strips to the film, and to form a laminated sheet having a force between the film and the fabric, from about 100 grams / 2.54 cm to about 600 grams / 2.54 cm when measured at almost room temperature. Preferably, the bonding forces are from about 200 grams / 2.54 cm to about 500 grams / 2.54 cm, to facilitate progressive stretching at about 210 m / min-360 m / min, to provide a microporous laminate. The progressive stretching force is applied through the laminated sheet, to provide a microporous cloth-like laminate having a binding strength of the fabric to the film of about 100 grams / 2.54 cm to about 200 grams / 2.54 cm. In a preferred embodiment, the high speed method for manufacturing a microporous antibacterial thermoplastic film involves melt blending a composition comprising: (a) from about 30% to about 45% by weight of a linear low density polyethylene (LLDPE) ), (b) from about 1% to about 10% by weight of a low density polyethylene (LDPE), (c) from about 40% to about 60% by weight of calcium carbonate filler particles around from 0.1 microns to 1 miera, and optionally (d) an antibacterial agent in an effective amount of from about 0.3 to about 1% by weight. The melt-blended composition is extruded into a slotted die as a fabric through a cooling zone in an engraved embossed metal roll and rubber roller grip. The embossing roll has a rectangular engraved pattern of about 165 to 300, preferably about 250, lines by 2.54 cm, to provide a film with relief on CD and MD 250 lines by 2.54 cm in both directions. The thickness of the film is usually around 0.002 cm to 0.005 cm, with a stamping depth of about 0.002 cm to 0.005 cm. More preferably, the thickness of the film is about 0.002 cm, with the 250 lines by 2.54 cm of the rectangular patterned pattern and a stamping depth of about 0.002 cm to about 0.003 cm. After this micro-patterned film is progressively stretched, a microporous film having an unexpectedly greater impact resistance is produced when compared to an unprinted film. The relief film is obtained at speeds in the order of about 165 m / min to about 360 m / min without stretching resonance. A device for directing a stream of cooling gas to flow in the cooling zone substantially parallel to the surface of the fabric is shown, for example, in U.S. Pat. Nos. 4,718,178 and 4,779,355. The full descriptions of these patents are incorporated herein by reference, as examples of devices that can be employed to provide improved efficiency of the cooling gas by creating a plurality of gas vortices as the current moves through the cooling zone to cool the cloth. Then, a progressive stretching force is applied to the micro-printed film at high speeds along lines substantially and uniformly throughout the film and throughout its depth, to provide a microporous micro-patterned film. The mixture of LLDPE and LDPE within the approximate ranges of above components allows the production of the microporous film at high speed when equilibrated with the prescribed amount of calcium carbonate. In particular, LLDPE is present in an amount of from about 30% to about 45% by weight, to provide a sufficient amount of matrix to carry the calcium carbonate filler particles, thereby allowing the film to be handled and stretched without porosity and breaking. The LDPE in an amount of about 1% to about 10% by weight also contributes to the production of film without any porosity, and allows high speed production without stretch resonance. The polymer matrix is balanced with an amount of about 40% to about 60% by weight of calcium carbonate particles having an average particle diameter preferably of about 1 miera, to achieve a moisture vapor transmission rate (MVTR) sufficient in the scale of around 1000 gms / m2 / day to 4500 gms / m2 / day, as measured by the E96E method of ASTM. In addition, the melt-mixed composition can include a three-block polymer in an amount of from about 0% to about 6% by weight, to facilitate stretching in high speed production without breaking. Other components are used such as about 5% by weight of high density polyethylene (HDPE) and about 1% by weight of antioxidants / processing aids. A progressive stretching force can be applied in line to the film formed under ambient conditions, or at an elevated temperature at speeds greater than about 210 m / min along lines substantially uniformly through the film and throughout its entire length. depth, to provide a microporous film. The method of this invention also involves the lamination of the microporous formable thermoplastic film to a strip or patch of fibrous non-woven fabric during extrusion. The extrusion lamination is carried out at the same high speeds, where a fibrous non-woven fabric is introduced into the stamping roll grip along with the microporous formable thermoplastic extrudate. The compression force between the fibrous web and the extruded material is controlled to bond a surface of the fabric to the film and form a patch or strip laminate. The laminate is then stretched progressively along lines substantially uniformly through the laminate and through its full depth, in one direction, to obtain the microporous micro-patterned film. The laminate can be stretched in the transverse direction and direction of the machine, to provide barriers to breathable cloth-type liquids capable of transmitting moisture and air vapor.

A. Materials for the method The thermoplastic polymer for the film is preferably of the polyolefin type, and can be any of the class of thermoplastic polyolefin polymers or copolymers that are processable in a film or for direct lamination, by melt extrusion in the fibrous fabric. Various thermoplastic copolymers suitable in the practice of the invention are the oxyalkanoyl polymers or normally solid dialkanole polymers represented by poly (caprolactone) mixed with polyvinyl alcohol or starch polymers, which can be formed into a film. Olefin-based polymers include the most common polymers based on ethylene or propylene, such as polyethylene, polypropylene, and copolymers such as ethylene vinyl acetate (EVA), ethylene methyl acrylate (EMA) and ethylene acrylic acid (EAA), or mixtures thereof. polyolefins. Other examples of polymers suitable for use as films include elastomeric polymers. Suitable elastomeric polymers can also be biodegradable or degradable by the environment. Suitable elastomeric polymers for the film include poly (ethylene-butene), poly (ethylene-hexene), poly (ethylene-octene), poly (ethylene-propylene), poly (styrene-butadiene-styrene), poly (styrene-isoprene-) styrene), poly (styrene-ethylene-butylene-styrene), poly (ether-ether), poly (ether-amide), poly (ethylene-vinyl acetate), poly (ethylene-methyl acrylate), poly (ethylene- acrylic acid), poly (ethylene-butyl acrylate), polyurethane, poly (ethylene-propylene-diene) and ethylene-propylene-rubber. This new class of rubber-type polymers can also be used, and are generally referred to herein, as metallocene polymers or polyolefins produced from single-site catalysts. Most preferred catalysts are known in the art as metallocene catalysts, whereby ethylene, propylene, styrene and other olefins can be polymerized with butene, hexene, octene, etc., to provide suitable elastomers for use in accordance with Principles of this invention, such as poly (ethylene-butene), poly (ethylene-hexene), poly (ethylene-octene), poly (ethylene-propylene) and / or polyolefin terpolymers thereof. Suitable antibacterial agents for use are 2-alkyl-1,2-benzisothiazolin-3-ones (hereinafter referred to as BIT), such as 2- (n-hexyl) -BIT, 2- (2-ethylbutyl) -BIT , 2- (2-ethylhexyl) -BIT, 2-octylisothiazolin-3-one, oxy-bis-10,10-phenoxarsine, trichloromethyl mercaptophthalimide; ureas such as 2- (3,4-dichlorophenyl) -1,1-dimethylurea and 2- (4-isopropylphenyl) -1,1-dimethylurea; halogenated pyridines with 4-alkylsulfonyl, such as 2,3,5,6-tetrachloro-4 (methylsulfonyl) -pyridine and 2,3,6-trichloro-4 (isopropylsulfonyl) -pyridine; tetrachloro-isophthalonitrile; benzimidazomethyl carbamate; thiocyanatomethylthiobenztriazole; methylene bisthiocyanate, iodopropargyl-n-butyl carbamate; triazines such as 2-tert-butylamino-4-ethylamino-6-methylmercapto-1, 3,5-triazine and 2-methylthio-4-tert-butylamino-6-cyclopropylamino-1, 3,5-triazine; N- (1-methyl-1-naphthyl) maleamide; dichlorofluanide, (fluoro) -captan and (fluoro) -folpet. Other microbiocidal compounds that can be employed include phenoxarsines (including bispheno-arsines), fenarsazines (including bisphenarsazines), maleimides, isoindole dicarboximides having a sulfur atom attached to the nitrogen atom of the dicarboximide group, aryl halogenated alkanols, and isothiazolinone compounds. Examples of these phenoxarsines and fenarsazines include 10-chloro-phenoxarsine; 10-iodophenoxarsine; and 10-bromophenox-arsine. Microbiocidal maleimides are exemplified by N- (2-methylnaphthyl) maleamide. Isoindole dicarboximides are exemplified by N-trichloromethylthio phthalimide. The halogenated aryl alkanols are exemplified by 2,4-dichlorobenzyl alcohol. An isothiazolinone compound is exemplified by 2- (n-octyl-4-isothiazolin-3-one). The bisphenoxarsines and bisphenarsazines are exemplified by 10, 10'-oxybisfenoxarsine and 10,10'-oxybisfenarsazine. The amounts are preferably in the general scale of 0.3 to 1% by weight. The microporous formable film composition can be obtained by formulating a thermoplastic polymer with suitable pore-forming fillers and additives, to provide an extruded material or film for stamping and lamination with the non-woven fabric. The particles of calcium carbonate and barium sulfate are the most common fillers. Microporous formable compositions of polyolefins, organic or inorganic pore forming fillers and other additives are known to obtain microporous sheet materials. This method can be carried out online, and provides savings in manufacturing and / or materials, compared to known methods for forming laminates. In addition, as mentioned above, metrroporous formable polymer compositions can be obtained from polymer blends such as a mixture of an alkanoyl polymer and polyvinyl alcohol, as described in U.S. Pat. No. 5,200,247. In addition, mixtures of an alkanoyl polymer, destructurized starch and an ethylene copolymer can be used, such as the microporous formable polymer composition as described in the U.S.A. No. 5,407,979. By using these polymer blends, it is not necessary to use pore-forming fillers to provide microporosity after progressive stretching. Rather, the different polymer phases themselves in the film, when the film is stretched at room temperature, produce microvoids. The non-woven fibrous web may comprise fibers of polyethylene, polypropylene, polyesters, rayon, cellulose, nylon, and blends of said fibers. Various definitions have been proposed for fibrous non-woven fabrics. The fibers are usually discontinuous fibers or continuous filaments. As used herein, "fibrous non-woven fabric" is used in its generic sense to define a generally planar structure that is relatively flat, flexible and porous, and is formed of discontinuous fibers or continuous filaments. For a detailed description of nonwovens, see "Nonwoven Fabric Primer and Reference Sampler," by E. A. Vaughn, Association of the Nonwoven Fabrics Industry, 3a. edition (1992).

In a preferred embodiment, the microporous micro-patterned or non-patterned film has a caliper or thickness between about 0.002 cm and 0.005 cm and, more preferably, about 0.002 cm. The non-woven fibrous webs of the laminated sheet of strips or patches, typically have a weight of about 5.95 g / m2 to 89.25 g / m2, preferably from about 23.8 g / m2 to about 47.6 g / m2. The mixed or rolled material can be stretched progressively in the transverse direction (CD), to form a mixed material stretched on CD. In addition, CD stretching can be followed or preceded by stretching in the machine direction (MD), to form a mixed material that is stretched in both directions, ie CD and MD. As indicated above, microporous laminates or micro-patterned films can be used in many different applications, such as baby diapers, baby training diapers, garments and menstruation pads, and the like, where air-transmitting properties are required and moisture vapor, as well as fluid barrier properties.

B. Stretchers for the microporous formable laminates Various extruders and different techniques can be employed to stretch the starting or original laminate of a non-woven fibrous web and microporous formable film. These laminates of woven fibrous non-woven fabrics of staple fibers or non-woven spunbonded fibrous fabrics can be stretched with the extruders and techniques described below: 1. Diagonal gear stretcher The diagonal gear extruder consists of a pair of left and right helical gear elements on parallel arrows. The arrows are arranged between two machine side plates, the lower arrow being located on fixed supports, and the upper arrow being located on supports in vertically slidable members. The sliding members are adjustable in vertical direction by means of wedge-shaped elements operable by adjustment worms. Screwing or dismilling the wedges will move the vertically slidable member in a downward or upward direction to further engage or disengage the meshing-type teeth of the upper gear roller with the lower gear roller. Micrometers mounted to the side frames, are operable to indicate the depth of engagement of the teeth of the gear roller. Air cylinders are used to firmly hold the collapsible members in their lowest engaged position, against the adjustment wedges to oppose the upward force exerted by the material being stretched. These cylinders can also be retracted to disengage the upper and lower gear rollers from each other for the purpose of threading material through the gear, or in conjunction with a safety circuit that would open all the grip points of the machine when it is triggered Impulse means are typically used to drive the stationary gear roller. If the upper gear roller is to be disengaged for machine screwing or safety purposes, it is preferred to use an anti-recoil gear arrangement between the upper and lower gear rollers to ensure that after re-engagement, the teeth of a roller Gear always fall between the teeth of the other gear roller, and potentially harmful physical contact between the projections of the gear teeth is avoided. If the gear rollers will be kept in constant gear, the upper gear roll typically does not need to be driven. The impulse can be achieved by the driven gear roller through the material being stretched. The gear rollers closely resemble fine pitch helical gears. In the preferred embodiment, the rollers are 15.07 cm in diameter, angle of advance of 45 °, a normal pitch of 0.25 cm, diametral pitch 30, pressure angle of 14.5 °, and are basically a gear with a long protrusion. This produces a deep and narrow tooth profile that allows up to approximately 0.22 cm of mesh, and approximately 0.01 cm of free space on the sides of the teeth for material thickness. The teeth are not designed to transmit rotating torque, and they do not contact metal to metal in the normal operation of gear stretching. 2. Transverse direction gear stretcher The CD gear stretch equipment is identical to the diagonal gear extruder, with differences in the design of the gear rollers and other minor areas described below. Since the CD gear elements are capable of great meshing depths, it is important that the equipment incorporate means to make the arrows of the two gear rollers remain parallel when the upper arrow goes up or down. This is necessary to ensure that the teeth of one gear roller always fall between the teeth of the other gear roller, and potentially damaging physical contact between the gear teeth is avoided. This parallel movement is ensured by a rack and mesh arrangement, wherein a stationary gear rack is fixed to each side frame in juxtaposition with the vertically slidable members. An arrow traverses the side frames, and operates on a support in each of the vertically slidable members. A gear resides at each end of this arrow, and operates in mesh with the racks, to produce the desired parallel movement. The drive for the CD-gear puller must operate the upper and lower gear rolls, except in the case of gear-stretching of materials with a relatively high coefficient of friction. However, the impulse does not need to be anti-recoil, because a small amount of misalignment of the machine direction or impulse slip will not cause any problems. The reason for this will be evident from a description of the gear elements in CD. The CD gear elements are machined from solid material, but can best be described as an alternative stack of two discs of different diameter. In the preferred embodiment, the gear discs would be 15.24 cm in diameter, 0.07 cm thick, and have a total radius at their edge. The separating discs that separate the gear discs would be 13.97 cm in diameter and 0.17 cm thick. Two rollers of this configuration would be able to be geared up to 0.58 cm, leaving a free space of 0.04 cm for material on all sides. As in the case of the diagonal gear extruder, this configuration of a CD gear element would have a pitch of 0.25 cm. 3. Gear Stretcher in Machine Direction The MD Stretch gear is identical to the diagonal gear puller, except for the design of the gear rolls. The gear rollers in MD closely resemble straight-pitch gears. In the preferred embodiment, the rollers are 15.06 cm in diameter, 0.25 cm in normal pitch, diametral pitch 30, pressure angle of 14.5 °, and are basically a gear with a long protrusion. A second step was carried out on these rollers, where the matrix mill displaced 0.02 cm, to provide a reduced tooth with more free space. With approximately 0.22 cm of mesh, this configuration will have approximately 0.02 cm of free space on the sides for material thickness. 4. Progressive Stretching Technique The CD or MD diagonal gear extruders described above can be employed to produce the progressively drawn laminate of non-woven fibrous fabric and microporous formable film, to form the microporous laminate of this invention. The stretching operation is usually employed in an extrusion laminate of a non-woven fibrous web of discontinuous fibers or spunbond filaments and microporous formable thermoplastic film. In one of the unique aspects of this invention, a laminate of a non-woven fibrous web of spunbonded filaments can be progressively stretched, to provide a very soft fibrous finish for the laminate having a cloth-like appearance. Non-woven fibrous fabric laminate and microporous formable film, is stretched progressively using, for example, the gear extruder in CD and / or MD with a passage through the extruder with a roller engagement depth of about 0.06 cm to 0.30 cm, at speeds of about 210 m / min at 360 m / min, or greater. The results of such progressive or gear stretching produce laminates that have excellent liquid barrier and breathability properties, and still provide superior bond strengths and soft cloth-like textures.

The following example illustrates the method for manufacturing antibacterial films and laminates of this invention. In light of these examples and this further detailed description, it is apparent to those skilled in the art that variations thereof can be made without departing from the scope of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in relation to the drawings, in which: Figure 1 is a schematic representation of a progressive extrusion rolling and inline extrusion apparatus for manufacturing the microporous laminate of this invention. Figure 2 is a cross-sectional view taken along line 2-2 of Figure 1, illustrating the gear rollers in schematic form. Figure 3 is a graph showing the line speeds for examples 1 to 5. Figure 4 is a graph showing the moisture vapor transmission properties of the microporous flat and micro-patterned films.

Figure 5 is a graph showing that the moisture vapor transmission rate can be adjusted by heating the precursor film. Figure 6 is a graph showing the impact strengths of the flat and micro-printed films that have been progressively stretched. Figure 7 is a graph showing the tear resistance of flat and micro-printed films that have been progressively stretched.

EXAMPLES 1 TO 5 Mixtures of LLDPE and LDPE having the compositions reported in Table 1 below were extruded to form antibacterial flat films (unprinted) and micro-patterned films, and the films were then progressively drawn to provide antibacterial microporous films. The antibacterial micro-stamped film was made with a metal stamping roll that has a rectangular engraving of CD and MD lines with approximately 165-300 lines by 2.54 cm, preferably 250 lines by 2.54 cm, with etching depth to produce around from 0.002 cm to 0.005 cm, preferably from about 0.002 cm to 0.003 cm, depth of stamping, in a 0.002 cm thick film. This pattern is described, for example, in the patent of E.U.A. No. 4,376,147, which is incorporated herein by reference. This micro-patterned pattern provides a matte finish to the film, but is imperceptible to the naked eye. The flat film was made with a flat roller of chrome.

TABLE 1 * Other components include 2.5% by weight of a three-block styrene-butadiene-styrene (SBS) polymer, Shell Kraton 2122X, which is a SBS copolymer with less than 50% by weight + mineral oil less than 30% by weight. weight, EVA copolymer less than 15% by weight, polystyrene less than 10% by weight, hydrocarbon resin less than 10% by weight, antioxidant / stabilizer less than 1% by weight, and amorphous hydrated silica less than 1% by weight . Each of formulations 1 to 5 was extruded into films using an extrusion apparatus as shown schematically in Figure 1. As shown, the apparatus can be used to extrude films with and without lamination. In the case of extrusion of the film, the formulations of Examples 1 to 5 were fed from an extruder 1 through the slotted die 2, to form the extruded material 6 in the grip of a rubber roller 5 and a metal roller 4 with a pneumatic blade 3. A micro-stamped metal roller and a flat chrome roller were used to obtain the micro-stamped and flat films, respectively, for comparative purposes. When extrusion lamination is practiced, there is a strip of incoming cloth of fibrous material 9 of the roll 13, which is also introduced into the grip of the rubber roll 5 and metal roll 4. In examples 1 to 5, the thermoplastic film for subsequent progressive stretching, to form microporous non-stamped and micro-printed films. As shown in table 1, at speeds of about 165 m / min at 360 m / min, a polyethylene film 6 was obtained in the order of about 45 gms / m2 thickness, which was extracted in the roller 7. The pneumatic blade 3 has a length of about 304.8 cm and an opening of about 0.08 cm-0.15 cm, and air is blown through the opening and against the extruded material 6 at about 5 cfm / 2.54 cm at 25 cfm / 2.54 cm. The compressive force in the grip and the pneumatic blade is kept under control, so that the film is obtained without porosity and without stretch resonance in the case of examples 2 to 5. When the LDPE was included in the composition to a At a level of 1.5% by weight, a stretch resonance was found at a line speed of 165 m / min. However, when the LDPE was included in the formulation at a level of 3.7% by weight with the LLDPE at a level of 44.1-44.9% by weight, production of the film at high speeds greater than 165 m / min could be achieved. up to 360 m / min, without stretching resonance. The melting temperatures from the feed zone to the worm tip of the extruders A and B, were maintained at about 204.4 ° C -221.1 ° C, with die temperatures of about 232.2 ° C, to extrude the precursor film to around 45 gms / m2. Figure 3 is a graph showing the line speeds for examples 1 to 5. Example 1, which contained only 1.5% by weight of LDPE, resulted in poor control of the film size with stretch resonance even with the pneumatic blade 3. However, when the LDPE was increased to about 3.7% by weight, excellent fabric stability without stretch resonance was achieved, even when the line speeds were increased to approximately 360 m / min. This is shown schematically in Figure 3.

Figure 4 is a graph demonstrating the moisture vapor transmission properties of the flat and micro-patterned films that result from progressively stretching the precursor films of Examples 2 to 5 under different temperatures and conditions of engagement of the draw roller. As shown schematically in Figure 1, when the incoming film 12 at room temperature was passed through the controlled temperature rolls 20 and 21 before the stretching rolls (10 and 11 and 10 'and 11') progressive on CD and MD, temperatures and depths of mesh could be controlled. Notably, the MVTR of the flat film exceeded the MVTR of the relief film as shown in Figure 4. In summary, MVTRs were obtained for the embossed film in the order of about 1200-2400 gms / m2 / day, while MVTRs were obtained for the flat film in the order of about 1900-3200 gms / m2 / day. Unexpectedly, as also shown in Figure 5, the MVTR of the microporous film could also be controlled by the temperature of the fabric during stretching. Figure 5 shows the film when it is heated to different temperatures, before the CD stretch can produce different MVTRs. The data reported in Figure 5 were for a 0.16 cm depth of engagement of the CD rollers, and 0.10 cm depth of engagement of the MD rolls, where the temperature of the roll 21 was maintained at room temperature. As mentioned above, the relief film was obtained with a metal stamping roll having a rectangular engraving of CD and MD lines with approximately 165-300 lines by 2.54 cm. This pattern is described, for example, in the patent of E.U.A. No. 4,376,147, which is incorporated herein by reference. This micro-patterned pattern provides a matte finish to the film, but is imperceptible to the naked eye.

EXAMPLE 6 Other blends of LLDPE, LDPE and HDPE having the compositions reported in Table 2 below, were extruded to form flat films, and the films were then progressively drawn to provide microporous films having high MVTRs greater than about 2000 gms / m2 / day, for example, from around 2000 to 4500 gms / m2 / day.

TABLE 2 The formulation of Table 2 was extruded into films using an extrusion apparatus similar to that shown schematically in Figure 1. As shown, the apparatus can be used to extrude films with and without lamination. In the case of extrusion of films, the formulation of Example 6 is fed from an extruder 1 through the slotted die 2, to form the extruded material 6 in the grip of a rubber roller 5 and a metal roller 4. The roller Metal is a polished chrome roller. Instead of the air knife, two air cooling devices (ACD), ACD No. 1 and ACD No. 2 are used, which are not shown in the drawing. Again, when extrusion lamination is practiced, there is an incoming cloth of fibrous material 9 from the roll 13 which is also inserted in the grip of the rubber roll 5 and metal roll 4. In the example 6, the thermoplastic film is produced for subsequent progressive stretching to form the microporous film. As shown in table 2, a polyethylene film 6 is obtained in the order of about 27 gms / m2 thickness at a speed of about 270 m / min, which is extracted in roller 7. The ACDs have dimensions that approximate the width of the fabric with a multiple dimensioned enough to release the cooling air. As mentioned above, these ACDs are described in more detail in the aforementioned patents 4,718,178 and 4,779,355. The velocity of the air blown through the nozzle of the ACD No. 1 and against the extruded material 6 is about 1200 m / min at the exit of the nozzle, and the volume of air is 20.4 m / min per .305 m. The air velocity of ACD No. 2 is around 2040 m / min at the outlet of the nozzle, and the air volume is 33.9 m / min per .305 m. The ACD No. 1 is located approximately 95 mm from the die, and approximately 25 mm from the cloth 6. The ACD No. 2 is located on the opposite side of the cloth 6 at approximately 2.85 mm from the die, and at approximately 15 mm from the the fabric The grip of the rubber roller 5 and the metal roller 4 is located approximately 736 mm from the die. The compression force in the grip and the ACDs is kept under control, so that the film is obtained without porosity and without stretching resonance. The melting temperatures from the feed zone of the slotted die to the worm tip of extruders A and B (not shown) were maintained to provide a temperature of the extruded material of about 243 ° C with refrigerant gas from the ACDs. .1 and No. 2, decreasing fabric temperatures to 211 ° C - 181 ° C before entering the grip. In this example 6, with reference to figure 1, wherein the incoming film 12 at room temperature is passed through the controlled temperature rollers 20 and 21 before the rollers (10 and 11 and 10 'and 11') of progressive stretching in CD and MD, temperatures and depths of mesh can be controlled. In summary, moisture vapor transmission rates (MVTRs) for the flat film are achieved, in the order of about 2000-4500 gms / m2 / day. The MVTR of the microporous film can also be controlled by the temperature of the fabric during stretching. When the film is heated to different temperatures before stretching on CD, different MVTRs can be obtained.

EXAMPLES 7 TO 16 Mixtures of LLDPE and LDPE having a composition of Example 2 described above, were extruded in slotted die according to the same procedure for Examples 1 to 5, to produce flat (unstamped) films and micro-prints which were then progressively stretched to provide microporous films. In the case of Examples 7 to 11, Example 7 was a 0.002 cm film obtained for comparative purposes with Examples 8 to 11 of the microporous micro-printed film of this invention. The micro-patterned film had a rectangular pattern of 250 lines by 2.54 cm in CD and MD with a depth of engraving of about 0.002 cm to about 0.003 cm, and about 0.002 cm in thickness. In the case of Examples 13 to 16, a flat roller of chromium metal was used to produce the unprinted microporous films about 0.002 cm thick, and Example 12 was obtained for comparative purposes. The conditions of progressive stretching, base weight resulting from the film, air cooling conditions, impact film resistance and notch tear resistance are given in Table 3 below. & * TABLE 3 Figures 6 and 7 are graphs showing the impact strengths of the non-patterned microporous films and microstamps that have been stretched progressively in accordance with the procedures of examples 8 to 11 and 13 to 16. With reference to table 3, examples 13 to 16, where the non-patterned films were progressively stretched to produce micropores in the films, the microporous films lost their mechanical properties, such as elongation at break and impact resistance. However, in contrast, examples 8 to 11 demonstrate that the micro-stamped films of this invention, after progressive stretching, provide micro-porosities that did not lose their impact resistance to the same extent as the flat film. In this way, Table 3 and Figures 6 and 7 show unexpectedly hi impact strengths for the microporous microstamped film that has been stretched progressively, when compared to the unprinted film. In addition, the tear resistance of the micro-printed film, as well as the unprinted film, is comparable, as shown in Table 3 and Figures 6 and 7. As reported in Patent Patent Publication No. 09 / 395,627 , presented on September 14, 1999, it has been found that ACDs that provide a cooling air flow substantially parallel with vortices on the surface of the fabric, efficiently cool the fabric. Surprisingly, the stretch resonance of the fabric that can normally be found in the prior art has been removed or controlled at high speeds of about 150 m / min - 360 m / min from the fabric. In addition, as also reported in that application, when film and non-woven laminates are obtained, bonding forces are achieved very efficiently on targets, which have not been possible with other known methods of cooling, while at the same time time they maintain the controls of the caliber of the film, even at high speeds of the fabric. In view of the above detailed description, it will be understood that variations will occur in employing the principles of this invention, depending on the materials and conditions, as will be understood by those skilled in the art.

Claims (18)

NOVELTY OF THE INVENTION CLAIMS

1. - A microporous film having a high moisture vapor transmission rate (MVTR), comprising a thermoplastic polymer film containing a dispersed phase of particles selected from the group consisting of an inorganic filler and an organic material, the film having (a) a film thickness of about 0.002 cm to about 0.005 cm with areas stretched progressively in the film to provide microporosity in the film with a MVTR of greater than about 1000 gms / m2 / day according to the E96E method of ASTM , and (b) a rectangular micro-patterned pattern, characterized in that (c) the pattern comprises approximately 250 lines stamped by 2.54 cm across the width of the film intersecting with stamped lines of about 250 lines by 2.54 cm across the length of the film, and the pattern has a stamping depth of about 0.002 cm to about 0.005 cm, and because the film ula has (d) an impact strength greater than about 150 grams according to ASTM method D1709.

2. The film according to claim 1, further characterized in that the microporosity of the film has a pore size distribution in which the largest pore size is around 0.22 microns, as determined by capillary flow porosimetry. of PMI.

3. The film according to claim 2, further characterized in that the smallest pore size is around 0.05 microns.

4. The film according to claim 2 or 3, further characterized by approximately 80% of the pores. They vary from around 0.05 to about 0.08 microns.

5. The film according to any of the preceding claims, further characterized in that the MVTR is in the order of about 2000 to about 4500 gms / m2 / day according to the E96E method of ASTM.

6. The film according to any of the preceding claims, further characterized in that the thermoplastic composition is a polymer selected from the group consisting of polyethylene, polypropylene, and copolymers thereof.

7. The film according to any of claims 1 to 5, further characterized in that said thermoplastic composition is an elastomeric polymer.

8. The film according to claim 7, further characterized in that said elastomeric polymer is selected from the group consisting of poly (ethylene-butene), poly (ethylene-hexene), poly (ethylene-octene), poly (ethylene- propylene), poly (styrene-butadiene-styrene), poly (styrene-isoprene-styrene), poly (styrene-ethylene-butylene-styrene), poly (ether-ether), poly (ether-amide), poly (ethylene- vinyl acetate), poly (ethylene-methyl acrylate), poly (ethylene-acrylic acid), poly (ethylene-butyl acrylate), polyurethane, poly (ethylene-propylene-diene) and ethylene-propylene-rubber.

9. The film according to any of the preceding claims, further characterized in that said inorganic filler is selected from the group consisting of calcium carbonate and barium sulfate.

10. The film according to any of claims 1 to 5, further characterized in that the composition of the film comprises: (a) from about 30% to about 45% by weight of a linear low density polyethylene, (b) ) from about 1% to about 10% by weight of a low density polyethylene, and (c) from about 40% to about 60% by weight of calcium carbonate filler particles.

11. The film according to claim 10, further characterized in that the composition also contains high density polyethylene and titanium dioxide.

12. The film according to claims 10 or 11, further characterized in that the composition additionally contains an antibacterial agent.

13. - The film according to any of the preceding claims, further characterized in that it has a portion thereof laminated to a strip or patch of a fibrous web.

14. The film according to claim 13, further characterized in that the fibers of said fibrous web are selected from the group consisting of polypropylene, polyethylene, polyesters, cellulose, rayon, nylon, and mixtures or coextrusions of two or more of said fibers.

15. The film according to claim 13 or 14, further characterized in that the fibrous web has a weight of about 5.95 g / m2 to about 83.3 g / m2.

16. A method of manufacturing at high speed a microporous thermoplastic film, comprising melt-blending a thermoplastic polymer and filler particles to form a thermoplastic polymer composition, extruding a web of said molten thermoplastic composition from a die slotted through a cooling zone in a roll grip to form a film having a thickness of about 0.002 cm to about 0.005 cm at a speed in the order of at least about 165 m / min to about 360 m / min without stretch resonance, said roller grip comprising a metal embossing roller having a rectangular etching of a pattern of intersecting CD and MD lines and a rubber roller, the compression force between the rollers being controlled to form a film with relief, and applying a progressive stretching force to said film with - embossing at said speeds along lines substantially uniformly through said film and throughout its depth, to provide a microporous film with an MVTR of greater than about 1000 gms / m2 / day according to the E96E method of ASTM, characterized in that the pattern comprises approximately 250 lines by 2.54 cm in each direction and has a stamping depth of about 0.002 cm to about 0.005 cm, and because the film has a greater impact strength of about 150 grams according to with ASTM method D1709.

17. The high-speed method according to claim 16, further characterized in that it comprises introducing a strip of fibrous non-woven fabric into said roller grip, and controlling the compressive force between the strip and the film in the grip, to Attach the strip surface to only a portion of the film to form a laminated microporous sheet.

18. The high-speed method according to claim 16 or 17, further characterized in that said step of progressive stretching is carried out at room temperature.