KR20020095261A - Polyolefin/copolyamide RF active adhesive film - Google Patents

Abstract

Flexible, halogen-free, high frequency-sealable films fabricated from a blend of a copolyamide and a polyolefin having a carboxylic acid or carboxylic acid anhydride functionality have sufficient copolyamide to yield a DLF of at least 0.05 at a frequency of 27 megahertz and serve as effective substitutes for flexible polyvinyl chloride films. The films may be mono-layer films or multi-layer films, especially where the high frequency-sealable films serve as outer or skin layers in multi-layer films. Products made from such mono- layer and multi-layer films find utility in a number of applications, especially for medical device applications.

Description

Polyolefin / copolyamide wireless frequency active adhesive film {Polyolefin / copolyamide RF active adhesive film}

The present invention relates to wireless frequency sensitive film forming polymer blend compositions, in particular polymer blend compositions that are substantially free of halogen containing polymers such as poly (vinyl chloride) or PVC. In other words, current analytical techniques do not indicate that chemically bound halogens are present in detectable amounts. The present invention particularly relates to monolayer films made from such compositions and coextruded multilayer film structures incorporating one or more layers made from such compositions. The present invention more particularly relates to compositions comprising copolyamides and acid-functionalized polyolefins and their use in the films and structures described above.

Products made from flexible PVC (f-PVC) have long been used in a variety of purpose applications, including those that depend on their radio frequency sealing ability, vapor or gas barrier properties or flexibility. Concerns about environmental impacts by halogenated polymers, such as f-PVC, in particular during their preparation and disposal, are stimulating efforts to develop halogen-free alternatives. When f-PVC is used for medical goods, children's toys, and food packaging applications, consideration is given to using phthalate plasticizers in f-PVC at levels typically of 10 to 40 weight percent based on the weight of the composition. Getting started. This consideration focuses on the tendency for plasticizers to move out of or flee out of the f-PVC as it is used or over time.

Efforts to address the above concerns about environmental impacts include olefin polymers such as polypropylene (PP), polyethylene (PE), styrene block copolymers such as styrene / ethylene butene / styrene or (SEBS). And ethylene copolymers such as ethylene / octene-1 or ethylene / vinyl acetate (EVA) copolymers. Olefin polymers meet or are close to many of the physical properties exhibited by f-PVC and can be achieved at similar cost. Films produced from such polymers require heat sealing because they generally have a very low dielectric loss rate (DLF) that makes it difficult to facilitate high frequency (HF) sealing or especially radio frequency sealing.

Various halogen-free polymers with dielectric properties that allow high frequency (HF) or radio frequency (RF) welding or sealing are described in the references. These polymers include, for example, thermoplastic polyurethanes (TPUs); Polyamide (nylon) and glycol modified polyester (PETG). However, these polymers are more expensive than PVC, making them economically unattractive to replacing f-PVC. In addition, other radio frequency active polymers have significantly higher tensile modulus or hardness than f-PVC, making it impractical to replace in use as flexible film packaging or bags.

Copolyamides, known as high frequency activity, suffer from disadvantages due to inadequate physical properties and high cost compared to f-PVC. Polyamides having a high number average molecular weight (M _n ), also known as nylon, generally have a modulus high enough to classify them as strong compared to f-PVC, and are difficult to seal and expensive. . Copolyamides having a low number average molecular weight (M _n ), for example those used in the present invention, are commonly used in low viscosity hot melt adhesives. As such, they have low melt strength, low tensile strength, inferior processing in conventional extrusion equipment, adhesive type tack and are excessively expensive.

Another effort to replace f-PVC with halogen-free polymers uses copolymers of olefins with acrylic esters (acrylates) or vinyl esters, such as vinyl acetate (VA). Copolymers of ethylene with higher levels (typically greater than 15% by weight based on copolymer weight) of VA or methyl acrylate provide significant high frequency activity. These olefin copolymers exhibit tensile and modulus properties similar to the tensile and modulus properties of f-PVC and are less expensive than TPU, nylon and PETG, while having significantly lower dielectric losses than f-PVC. Lower dielectric loss rates actually require an increase in the size of the high frequency generator, leading to a concomitant increase in capital costs and power usage. In conjunction with longer welding times, these increases will raise the price of the final molded part.

Efforts to avoid relying on larger high frequency generators include blending high frequency active inorganic or organic particulate additives into the olefinpolymer composition for film formation, typically at high packing levels. EP 193,902 describes high frequency compositions containing inorganic additives such as zinc oxide, bentonite clay and alkaline earth metal aluminosilicates at levels of 1 to 20% by weight, based on the weight of the composition. International Publication No. 92/09415 discloses incorporation of high frequency receptors such as phosphonate compounds, phosphate compounds, quaternary ammonium salts, polystyrene sulfonate sodium salts, alkaline earth metal sulfates and aluminum trihydrates into thermosetting compounds and films. It is described. U.S. Patent No. 5,627,223 describes the addition of 1 to 50% by weight starch (to impart high frequency weldability) to a polyolefin blend that also contains a coupling agent. These additives improve high frequency weldability, but adversely affect other properties such as optical properties and clarity, tensile strength and toughness of the film.

International Publication No. 95/13918 describes a multilayer structure comprising a high frequency sensitive layer based on four components. These components are propylene-based polymers, nonpropylene polyolefins, high frequency sensitive polymers and polymeric compatibilizers. The high frequency sensitive polymer is any of EVA, EMA, ethylene / vinyl alcohol (EVOH), polyamide (including nylon), PVC, vinylidene chloride polymer, vinylidene fluoride polymer and copolymer of bisphenol A and epichlorohydrin. Also good. Compatibilizers are SEBS block copolymers modified with styrene / hydrocarbon block copolymers, preferably maleic anhydride (MAH), epoxy or carboxylate functional groups.

International Publication No. 96/40512 describes a multilayer structure comprising a skin layer, a blocking layer and a high frequency sensitive layer. Four polymers are combined to obtain a high frequency sensitive layer. These polymers are propylene polymers, nonpropylene polyolefins, high frequency sensitive polymers and polymeric compatibilizers. The high frequency sensitive polymer may be an EVA or EMA copolymer, polyamide, EVOH copolymer, PVC, vinylidene chloride, fluoride or a copolymer of bisphenol-A and epichlorohydrin with sufficient comonomer content. Styrene / hydrocarbon block copolymers, in particular SEBS block copolymers modified with maleic anhydride (MAH), epoxy or carboxylate functionality, function as suitable compatibilizers.

International Publication No. 95/14739 describes polymer compositions suitable for the use of items such as medical packaging. The composition comprises a heat resistant polymer, a high frequency sensitive polymer and a compatibilizing polymer. The high frequency sensitive polymer can be selected from one of two polar polymer groups. One group includes ethylene copolymers in which the comonomer is selected from ester derivatives of alcohols having 1 to 10 (C ₁ -C ₁₀ ) carbon atoms of acrylic acid, methacrylic acid, acrylic acid or methacrylic acid, vinyl acetate and vinyl alcohol . The other group includes copolymers having polyurethane, polyester, polyurea, polyimide, polysulfone or polyamide segments. The compatibilizer may be a styrene block copolymer (eg SEBS), preferably a MAH-functionalized.

EP 0 688 821 describes polyolefin compositions which can be produced from sheets and films sealable with high frequency-generated dielectric heat. The composition comprises a heterophasic olefin polymer and 3-15% of one or more polymers having a dielectric heat loss rate (DHLF or DLF) of at least 0.01. Heterophasic olefin polymers include crystalline propylene homopolymers or copolymers, optional crystalline ethylene copolymers and elastic ethylene / propylene (EP) copolymers. The heterophasic olefin polymer may be modified with one or more polar monomers, for example 0.03 to 0.3% MAH. Polymers that meet the DHLF requirement include polyamides, vinyl polymers, polyesters and polyurethanes. Preference is given to polyamides, in particular M _n of at least 1000.

A first aspect of the invention is a polymer composition suitable for producing high frequency weldable film structures, which composition consists essentially of blends of copolyamides with polyolefins having carboxylic or carboxylic anhydride functionality, the DLF of the blend being frequency And at least 0.05 at 27 MHz and 23 ° C., the copolyamide is present in an amount of from 20 to 80 weight percent based on the total weight of the blend.

Such a polymer composition combines the desirable properties of the polyolefin (physical strength, processability and relatively low price) with the high frequency activity of the copolyamide to provide a novel high frequency weldable film structure. Acid or acid anhydride functional groups impart desirable blend homogeneity by conferring compatibility between two polymers that, if they are not present, cannot dissolve with each other, resulting in equal amounts of the same copolyamide and non-functionalized polyolefin It is believed to result in improved film properties compared to blends made from the same polyolefins used in the invention but without acid or acid anhydride functional groups).

A second aspect of the invention is a high frequency weldable film structure comprising one or more layers produced from the polymer composition of the first aspect. The film structure may be monolayer or multilayer. The multilayer structure may include one or more layers having a DLF of less than 0.05 at frequencies 27 MHz and 23 ° C.

A third aspect of the invention is a product made from the film structure of the second aspect, which is selected from the group consisting of bags, containers, packaging materials, automotive interior fabrics and parts, flotation devices, tarpaulins and tent sheaths. Other suitable applications of more specific examples than those described above include, for example, medical or urological collection bags, medical ostomy bags, medical infusions or intravenous bags. bags, inflatable devices such as air mattresses, flotation devices or toys, food packaging materials, retail blister packaging materials, children's products and toys, reinforcement laminates for tents and tarpaulins, roofing membranes and geotextiles ( geotextiles) and for use in fastening devices, such as binder covers. The composition providing the film of the invention can also be extruded into a tube having a high frequency active outer layer. Such tubing is easy to use with high frequency weldable films to provide a finished high frequency weldable polyolefin film structure, such as a medical collection bag. Those skilled in the art will readily be able to broaden the list of products illustrated above to include substantially any device or use that requires a high frequency or radio frequency sealable flexible monolayer or multilayer film structure. The relatively low price of the polyolefin materials used to make the films of the present invention, as compared to f-PVC, and the performance characteristics of the films of the present invention may replace flexible plastic halide films such as f-PVC. Provide many opportunities.

Unless stated otherwise, each range includes both terminal values used to set the range.

The blend has a polyamide content sufficient to provide a blend with a DLF of at least 0.05, preferably at least 0.10 at 27 MHz when tested at 23 ° C. The polyamide content is suitably at least 20% by weight based on the blend weight and preferably at least 30% by weight. Blends with such polyamide content shorten the high frequency welding time when using a standard high frequency welding device when compared to blends with lower polyamide content. The high frequency welding time operates at a frequency of 27.12 MHz and is a Callan Company, equipped with a brass sealing bar that is 0.5 in (1.3 cm) wide, 8 in (20.3 cm) long and 4 square in (26.4 cm ² ) in area. It can be shortened to about 0.5 to 1.0 seconds using a 2kW high frequency welding apparatus sold by Callanan Company.

"DLF" is a calculated value calculated by multiplying the dielectric constant (DC) of a material by the dielectric loss coefficient (DDF) (or loss tangent) of the material. DC and DDF are easily measured by the dielectric constant test method by the instrument. Particularly preferred test equipment uses the Hewlett-Packard dielectric constant test facility, the Hewlett-Packard Impedance / Material Analyzer in conjunction with Model 16453A, Model 4291B. Dielectric properties can be measured on compression molded plaques (2.5 mm (64 mm) in diameter and 0.050 in (1.3 mm) in thickness) produced from materials such as polymers or blended polymer compounds.

"High frequency sealability" relates to bonding a sealable polymer to its portion or other material using electromagnetic energy or waves over a wide frequency range of 0.1 to 30,000 MHz. This includes high frequency heating and microwave (MW) heating rather than conventional heat sealing. The high frequency range typically includes three frequency ranges called the ultrasonic frequency range (18 KHz to 1000 KHz), the high frequency range (1 MHz to 300 MHz), and the microwave frequency range (300 MHz to 10,000 MHz). High frequency and microwave ranges are particularly important. The terms "activation", "seal", "bond" and "welding" (and variations of each word) may be used interchangeably herein.

By “high frequency activity” is meant a material that is sensitive to dielectric activity through energy in the high frequency range, the application of which causes rapid heating of the material. Similarly, "high frequency activity" means a material that is sensitive to dielectric activity through energy in the high frequency range.

In general, those skilled in the art regard materials with a DLF less than 0.05 as radio frequency or radio frequency inert. They classify substances with DLF between 0.05 and 0.1 as weak radio frequency or high frequency activity. They believe that materials with a DLF greater than 0.1 have good radio frequency or high frequency activity and materials with a DLF greater than 0.2 are very radio frequency or high frequency active. A satisfactory result can be obtained if the DLF is 0.05, but the skilled person generally more preferably has a DLF of more than 0.1, more typically more than 0.2, in order to obtain sufficient sealing using high frequency wavelengths, especially radio frequency wavelengths. Here it is.

Dimer acid copolyamides are typically produced by polymerization reactions between dimer fatty acids such as azelaic acid and one or more alkyl or cyclic diamines such as ethylenediamine, hexamethylenediamine, piperazine, or propylene glycol diamine. do. Copolyamides preferably have an acid value in the range of 0.5 to 15 (mg potassium hydroxide per gram of resin) and an amine value in the range of 1 to 50 (mg KOH / g resin). Copolyamides advantageously have a ring and ball softening point (ASTM E-28) in the range of 80 to 190 ° C, more preferably 90 to 150 ° C. Low molecular weight copolyamides also have low viscosity and M _n values of 5,000 to 15,000. Typical Brookfield melt viscosities of low M _n copolyamides range from about 900 to about 13,000 cps when tested at 190 ° C. according to ASTM D-3236. Copolyamides meeting these criteria are commonly used in hot melt adhesive compositions, such as MACROMOMELT ^R (Henkel) and UNIREZ ^R (Union Camp). To be suitable for use in the present invention, the copolyamide should have a DLF of at least 0.05, preferably at least 0.1 at 27 MHz when tested at 23 ° C.

Further satisfactory low M _n copolyamides are derived from the reaction product of caprolactam or lauryllactam with water or hexamethylenediamine and adipic acid. These copolyamides are chemically similar to the high M _n polymers known as nylon 6 or nylon 12, but are mainly amorphous and have significantly lower melting points and M _n values than conventional nylon resins. Preferred amorphous copolyamides have a melting point of 90 to 140 ° C. and an average molecular weight (M _W ) of 10,000 to 25,000. These are commercially available under the trade name GRILTEX ^R (EMS-American Grilon or EMS-Chemie) as a hot melt adhesive.

Due to the relatively low M _n and low viscosity of the copolyamide resins described herein, they are difficult to process in conventional film or sheet extrusion equipment designed for high molecular weight polymers. In addition, the resins exhibit relatively low tensile and tear strength properties and become sticky or sticky when extruded into a monolayer film. The blend composition overcomes the inherent limitations of the low molecular weight copolyamide resins used in the present invention.

For polymers, “acid functionality” means a polymer, especially an olefin polymer which polymerizes ethylenically unsaturated carboxylic acid in an olefin polymer, as well as a polymer resulting from the reaction of grafting the acid on the polymer backbone. Suitable acids are acrylic acid (AA) and methacrylic acid (MAA). Particularly preferred acid functional olefin polymers include those produced from ethylene based polymers and copolymers. Commercially available ethylene / acrylic acid (EAA) copolymer comprises a creamer cor (PRIMACOR) ^* resins ^(* trademark of The Dow Chemical Company,). Commercially available ethylene / methacrylic acid (EMAA) copolymer is a child under the trade name of press Krell (NUCREL ^R). Includes those sold by EI du Pont de Nemours and Company. Commercially available ethylene / methyl acrylate / acrylic acid terpolymers (EMAAA) include those sold by Exxon Chemical under the trade name ESCOR ^R ATX resin. The acid comonomer should be present at least 3% by weight, preferably at least 6% by weight based on the weight of the polymer to provide sufficient compatibility with the copolyamide of the olefin. Particularly preferred acid copolymers have AA or MAA in an amount of 9 to 20% by weight. Polyolefins grafted with acrylic acid include those sold by BP Chemical under the trade name POLYBOND ^R.

Similarly, "anhydride functional group" means a polymer resulting from the reaction of grafting ethylenically unsaturated carboxylic anhydrides such as maleic anhydride (MAH) to the polymer backbone. Polyethylene (PE), polypropylene (PP) and ethylene copolymers such as EVA function as suitable backbone polymers. Commercial MAH-graft (MAH-g) polyolefins include BYNEL ^R CXA and HUSABOND ^R resins (E. DuPont de Nemoir & Company), PLEXAR ^R [equ] Equistar Chemicals] and LOTADER ^R (Elf Atochem). The MAH content of conventional MAH-g polymers is 0.05 to 1.5 weight percent based on the total amount of polymer.

Ionomers function as suitable substitutes for acid functionalized and acid anhydride functionalized polyolefins. "Ionomo" typically means ionomerized metal salts of carboxylic acid copolymers, such as sodium, potassium or zinc ionomers of EAA or EMAA. Commercial ionomers include E.I. Some are sold under the trade name SURLYN ^R by DuPont de Nemoir & Company.

Ionomers and acid or acid anhydride functional olefin polymers typically have a density of 0.86 to 0.99 grams per cubic centimeter (g / cc), preferably 0.89 to 0.97 g / cc, and a melt index or I ₂ value of 190 ° C., 2.16. When tested in kg (ASTM D-1238), it is 0.5 to 300 grams (g / 10 min), preferably 2 to 20 g / 10 min, per 10 minutes.

The polymer blend preferably has a copolyamide content of at least 20% by weight and an acid or acid anhydride functional polymer content of at most 80% by weight based on the blend weight. The copolyamide content is preferably in the range of 20 to 80% by weight when the supplemental content of the acid or acid anhydride functional polymer is in the range of 80 to 20% by weight. More preferably the copolyamide content of the blend is 30 to 70% by weight, based on the blend weight. If copolyamides are used at levels below 20% by weight, in particular below 10% by weight, the blend has a DLF that is too low to allow easy high frequency welding. If the copolyamide level is above 80% by weight, in particular above 90% by weight, the blend is processed like a low melt strength copolyamide, making it difficult to extrude in conventional extrusion equipment, inferior melt strength, high tack or film blocking and general Inferior physical properties such as tensile strength, tear and impact strength.

Acid or acid anhydride functionalized polymers exhibit increased melt viscosity and increase film strength and flexibility during extrusion, as compared to blends that do not contain such functionalized polyolefins, improve adhesive peel strength and bond durability, Provides blends with improved moisture resistance. The copolyamide component provides a blend with sufficient DLF properties to impart high frequency weldability. Copolyamides can also impart improved oxygen and carbon dioxide barrier to the blend. In addition, copolyamides mostly have a softening point above 100 ° C. and many above 120 ° C., and the melting point of most acid functional ethylene polymers is slightly higher or lower than 100 ° C. Thus, the copolyamide component of the blend can improve temperature stability and bond strength at elevated temperatures (above 100 ° C.).

The polymer blends that produce the films of the present invention may also include one or more conventional additives that impart functionality to the film but do not significantly degrade the film sealing ability through exposure to high frequency or radio frequency radiation. Such additives include, but are not limited to, antioxidants or processing stabilizers, ultraviolet stabilizers, tackifiers, flame retardants, inorganic fillers, insecticides and pigments.

In addition to the copolyamide and acid functional olefin polymers required for the polymer compositions of the present invention, as long as the composition contains at least 20% by weight of copolyamides, large amounts of olefin polymers and copolymers may be added to achieve the desired film properties. Can be. Olefin polymers suitable for the purposes of the present invention are homopolymers such as PE or PP, and copolymers such as ethylene / butene-1 (EB), ethylene / octene-1 (EO) or ethylene / propylene ( EP). Useful nonpolar olefin polymers include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE), high density polyethylene (HDPE), polyethylene plastomer (metallocene catalyst, 0.86 to 0.92 grams per cubic centimeter ( g / cc) density, (mPE), PP homopolymer, PP copolymer (co-PP), EVA, EMA, ethylene / n-butyl acrylate (EnBA), ethylene / ethyl acrylate (EEA), EAA, EMAA , EMAAA, ionomerized metal salts of carboxylic acid copolymers such as sodium, potassium or zinc ionomers of EAA or EMAA, ethylene / propylene / diene copolymers (EPDM), ethylene / styrene copolymers (ESI), EVOH , Polybutene (PB), polyisobutene (PIB), styrene / butadiene (SB) block copolymer, styrene / isoprene / styrene (SIS) block copolymer, styrene / ethylene-butene / styrene (SEBS) block copolymer or MAH-g olefin polymers such as MAH-g-EVA, MAH-g-PE and MAH-g-PP And MAH-g styrene block copolymers, for example SEBS-g-MAH.

The film of the present invention may be any gauge according to certain needs, but is typically in the range of 1 to 100 mils (25 to 2500 μm), preferably 2 to 20 mils (50 to 500 μm). Conventional film production processes can be used to produce such films. Exemplary processes include, but are not limited to, an annular extrusion blown film process, a slot die cast extruded film process, and one or more layers of extrusion coating on a film or substrate. The film of the invention functions as a single layer film or as one or more layers of a multilayer film structure. Such multilayer films are preferably produced from lamination processes as well as coextrusion processes. In addition, the high frequency active blend composition of the present invention may be prepared in an extruded form such as a tube. For example, high frequency weldable monolayers or coextruded multilayer tubular structures can be bonded to a film or other substrate to produce a composite molded article, such as a medical collection bag. In addition, the polymer blend compositions described herein may be coated in the liquid phase using conventional liquid coating processes after being dissolved in a solvent or dispersed as an aqueous dispersion or emulsion.

In a preferred embodiment of the invention, the polymer composition or high frequency active polymer blend can be assembled into a multilayer composite having a polymer layer that is coextruded, not high frequency active or weakly high frequency active. The incorporation of a high frequency active layer having a high frequency inactive layer into the coextruded film structure preferably allows the entire film to be high frequency welded. Particularly preferred film structures of the present invention are "AB" or "ABA" or "BAB", where the "A" layer is high frequency inactive or weak high frequency active and the "B" layer is the high frequency active polymer blend composition of the present invention. I can display it. For example, in "ABC" coextrusion, additional high frequency inert or weak high frequency active layer "C" may also be incorporated. Those skilled in the art will readily appreciate that these structures merely illustrate a wide variety of predictable structures.

Any film described herein may be sealed or welded to itself or another substrate using conventional high frequency sealing agents, such as radio frequency sealing agents. Commercially available high frequency welders, such as the Callanan Company, Weldan, Colpitt, Kiefel Technologies, Thermatron, Radyne Commercially available ones, etc. typically operate at the frequency 27.12 MHz. Two rarely used radio frequencies are 13.56 MHz and 40.68 MHz. Conventional microwave sealing or welding devices operate at frequencies 2450 MHz (2.45 GHz), 5.8 GHz and 24.12 GHz. When using a high frequency sealing agent, the die or tool may be operated at ambient room temperature (nominal 23 ° C.) or preheated to a temperature such as 40 ° C. or 60 ° C. Slightly elevated temperatures can improve high frequency activity and reduce sealing time.

Radio frequency or microwave activation (sealing and bonding) offers performance advantages over conventional heat sealing where rapid sealing is a major factor, such as in the case of high speed manufacturing. High frequency (including radio frequency and microwave) bonding techniques eliminate the need to transfer heat into the entire structure by allowing energy to concentrate on the high frequency active layer. This advantage is increased film gauge, especially relatively thick (gauge> 5 mils or 125 μm), which requires relatively long contact times (compared to high frequency sealing) in order to allow heat to transfer through the film to the contact interface in conventional heat sealing techniques ) Becomes more apparent in the case of a film. For example, high frequency sealing can occur within 0.4 seconds, while conventional thermal contact or impulse sealing of films of the same thickness conventionally takes at least a few seconds to achieve comparable sealing. High frequency bonding or sealing also has the advantage over conventional heat sealing when the composite structure contains heat sensitive materials such as color sensitive dyed fabrics or nonwoven materials or orientation films that soften and undesirably shrink upon heating. Have High frequency dies may also be manufactured in very complex shapes, which can be difficult to work with when treated with a heat sealing device.

The film of the present invention facilitates the production of various structures through high frequency sealing. For example, the film may be folded to form a bag or pouch by at least partially high frequency sealing to the film itself. Using two layers of the same film makes it easy to produce similar bags or pouches without grounding. High frequency sealing also promotes adhesion of the above films to substrates, such as different films, nonwovens, injection molded or extruded parts, or paper. In most applications, sufficient high frequency sealing or adhesion corresponds to an adhesive strength of at least 4 pounds per inch (lb / in) (0.72 Newtons per millimeter (N / mm)). A medical collection bag or body drain pouch requires that the high frequency weld strength between the two film layers exceeds the tear strength of the film itself. In other words, one or more films are required to tear by an effort to peel the film. When tested by the 180 ° peel test of ASTM D-903, high frequency welding or sealing adhesive strength of 4 lb / in (0.72 N / mm) meets these requirements. Thicker film structures, such as those used in inflatable applications, generally require better welding or adhesive strength. Films similar to the present invention but with a DLF of less than 0.05 do not facilitate high frequency sealing and typically yield peelable seals that do not meet the above adhesive strength requirements when exposed to the same level of high frequency radiation.

Despite the emphasis on high frequency weldability, film structures or films made of the compositions of the present invention may also be thermally laminated, sealed using conventional thermal processes such as hot rolllamination, flame lamination and heat sealing. Or may be welded. This possibility allows the thermal process to be combined with high frequency welding. One example of such a combination is the first step of thermally laminating the film of the present invention on a substrate, such as a fabric, to produce a film / fabric composite, and the high frequency welding of the two composites together at the film / film interface to produce a film inner surface and A subsequent second step of providing the fabric outer surface. Further interesting substrates on which the films of the present invention may be laminated include bubble foams, such as polyurethane or polyolefin foams, textiles or nonwovens, paper or cardboard products, thermoplastic films or sheets, wood veneers or wooden products. And wood or cellulose composites.

The following examples illustrate the invention but are not limited thereto. Arabic numerals or a combination of Arabic numerals and alphabetic characters represent an embodiment Ex of the present invention. Only alphabetical letters indicate a comparative example (Comp Ex.).

Example 1-DLF Measurement

Several polymeric materials are tested for DLF using the apparatus and procedure described above. The material and corresponding DLF values are as follows: LDPE (LDPE 501, 0.922 g / cc density, Melt Index 1.9 g / 10 min, The Dow Chemical Company) <0.001; EAA (EAA-1) (primacor ^* 1430, melt index 5 g / 10 min, The Dow Chemical Company) having a 9.7 weight percent acrylic acid (AA) content = 0.003; EAA (EAA-2) (primacor ^* 5980, melt index 300 g / 10 min, The Dow Chemical Company) with 20 wt% AA content = 0.07; EAA (EAA-3) (primacor ^* 3460, melt index 20 g / 10 min, The Dow Chemical Company) having a 9.7 wt.% AA content = 0.07; Copolyamide number 1 (CPA-1) (Macromelt ^R 6211, Henkel) = 0.221; CPA-2 (Macromelt ^R 6238, Henkel) = 0.082; CPA-3 (Macromelt ^R 6206, Henkel) = 0.057; CPA-4 (Grilltex ^R 1G, EMS-Kemi) = 0.11; CPA-5 (Grilltex ^R D1330, EMS-Kemi) = 0.07; CPA-6 (Grilltex ^R D1472, EMS-Kemi) = 0.08; Blend of blend number 1 (B-1), 80% EAA-1 and 20% CPA-1 = 0.03; Blend of B-2, 60% EAA-1 and 40% CPA-1 = 0.06; Blend of B-3, 40% EAA-1 and 60% CPA-1 = 0.083; Ionomer-1 (Sullin ^R 1605, E. Dupont de Nemoir and Company) = 0.008; Ionomer-2 (Sullin ^R 1702, E.I. Dupont de Nemoir and Company) = 0.003. ^* Stands for Dow Chemical Company's trademark.

Example 2 Single Layer Film Sealing Test

Conventional 2.5 inch (6.4 cm) slot die cast film line, single screw extruder with ratio of length to diameter (L / D) operating at 300 ° F. (149 ° C.) and 300 ° F. (149 ° C.) The melt processable polymer composition was cast on a chilled (75 ° F. (25 ° C.)) cast roll using a 28 inch (71 cm) wide slot die operating at) to produce a 4 mil (102 μm) monolayer film. Wind up on a roll. The meltable polymer composition comprises 3 parts by weight of CN-744 anti-stick concentrate (20% by weight SiO _{2 in} LDPE) and 100 parts by weight of CN-4420 slip / anti-stick concentrate (SiO _{2 in} EVA carrier). 20 parts by weight, 4% by weight stearamide and 4% by weight erusilamide). Southwest Plastics supplies the latter two materials.

Two layers of film each using a 50% set power with a 0.5 in. (1.25 cm) wide, 8 in. (20.3 cm) unheated bar sealing die and a Callanan 2.0 kW high frequency welder operating at 1 sec sealing time Are genetically sealed together. The film is cut into strips of 1 inch (2.5 cm) wide perpendicular to the seal. The strip is subjected to a 180 ° peel test using an Instron tensile tester at a tensile rate of 12 in / min (30.5 cm / min) in accordance with ASTM test D-903.

The film composition and corresponding yarn strength are as follows: 100% EAA-1-Unmeasurable yarn; 80% EAA-1 / 20% CPA-1 = 4.15 lb / in (lb / in) /0.73 Newtons / millimeter (N / mm); 60% EAA-1 / 40% CPA-1 = 4.75 lb / in (0.83 N / mm); And 40% EAA-1 / 60% CPA-1 => 6 lb / in (1.05 N / mm). CPA-1 has a ring and ball softening point of 145 ° C, an acid value of 2 to 10 mgKOH / g resin, an amine value of less than 2 mgKOH / g resin and a melt viscosity of about 5,000 cps at 190 ° C.

Peel test data demonstrates that polyolefin films without copolyamides are typically incapable of high frequency sealing, while blending 20% by weight of copolyamide with polyolefins results in satisfactory adhesive strength. Increased copolyamide levels (eg, 40 wt% and 60 wt% CPA-1) result in stronger adhesive strength grades.

Example 3

Single layer copolyamide / polyolefin blend 5.0 mil (125 μm) films are prepared on a conventional blown film line using a 1 inch (2.5 cm) diameter extruder introduced into a 1 inch (2.5 cm) diameter die. The extruder zone temperature is from 280 ° F. (138 ° C.) to 330 ° F. (165 ° C.) while operating the die at 330 ° F. (165 ° C.). The film was 55% BYNEL CXA 3101 (E. Dupont de Nemoir & Company, acid-modified EVA resin with a melt index of 3.5 g / 10 min, 0.96 g / cc density), 30% CPA-1, 10% LDPE 501I (same as Example 1) and 5% CN734 anti-stick concentrate (Southwest Plastic, 15% SiO _{2 in} LDPE). As a result, the obtained film was 1360psi (9.4N / mm ²⁾ in the MD (machine direction) Final tensile strength, 560% elongation of the ^{final, 5,020psi (34.6N / mm 2)} 2% secant modulus, 160g / mil (6.3 in g / μm) Elmendorf tear strength and 270g / mil (10.5g / μm) Spencer impact strength. The DLF of the film is 0.08.

As in Example 2, the two film layers are dielectrically sealed together with a low power preheat of 0.5 seconds and a high frequency sealing time of 1.0 seconds, followed by a pause time of 0.5 seconds (no power) and a Clayton air capacitor plate set to 22. This produces high strength yarns (greater than 6.0 lb / in (1.05 N / mm)). The yarn has sufficient strength to promote breakage of the film before the yarn breaks.

Example 4

Same as Example 3, but a blend of 40% by weight of EAA-1, 40% by weight of CPA-1, 15% by weight of the same LDPE as Example 3 and 5% by weight of the same anti-stick concentrate as in Example 3. The film has an MD final tensile strength of 1560 psi (10.8 N / mm ² ), a final elongation of 530%, a 2% secant modulus of 7,050 psi (48.6 N / mm ² ), and an Elmendorf tear of 160 g / mil (6.2 g / μm). Strength and Spencer impact strength of 260 g / mil (10.1 g / μm).

The two film layers are hermetically sealed together to yield peel strengths in excess of 5.5 lb / inch (1.0 N / mm).

Example 5

Same as Example 3, but using a blend of 75% by weight of Sullin ^R 1605 (E. DuPont de Nemoir & Company), 20% by weight CPA-1 and 5% by weight of the same anti-stick concentrate as in Example 3. do. The film has an MD final tensile strength of 2640 psi (18.2 N / mm ² ), a final elongation of 215%, 2% secant modulus of 27,300 psi (188.3 N / mm ² ), and a Spencer impact strength of 300 g / mil (11.7 g / μm) Indicates. The film's DLF is 0.06.

Example 6

The three layer 7.4 mil (188 μm) film is coextruded using a conventional upward blown film line equipped with a 5 inch (12.7 cm) diameter die and three 2.5 inch (6.4 cm) extruders. The film has an ABA symmetry structure in which the innermost and outermost layers "A" constitute 15% of the total film gauge, respectively, and the central layer "B" constitutes 70% of the film thickness (5.2 mil, 131 mu m). The surface “A” layer comprises 95% by weight EAA-1 and 5% by weight of the same anti-stick concentrate as in Example 3. “B” or the core layer comprises 60% by weight EAA-1 and 40% by weight CPA-1. All three extruders are areas ramped from 275 ° F. (135 ° C.) to 330 ° F. (166 ° C.), with a die area set at 330 ° F. (166 ° C.). This creates a lay-flat bubble of 16 inches (41 cm) wide. The resulting film had a Spencer impact strength of 595 g / mil (23.2 g / μm), an oxygen transmission rate (O ₂ TR) of 375 cc-mil / 100 in ² -day (147 cc-mm / m ² -day) and 4.1 / g It has a water vapor transmission rate (WVTR) of -mil / 100in ² -day (1.62 g-mm / m ² -day). Table 1 below shows additional physical property data of the film (measured in MD and TD (transverse direction)).

MD TD Final Tensile Strength (psi / (N / mm ² )) 2640 / 18.2 2295 / 15.8 % Final elongation 470 540 2% secant modulus (psi / (N / mm ² )) 7540 / 52.0 7520 / 51.9 Elmendorf Tear Strength (g / mil / (g / μm)) 250 / 9.8 350 / 13.6

The DLF of the center layer "B" is 0.06. The two film layers are dielectrically sealed together with a high frequency sealing time of 1.5 seconds and a Clayton air capacitor plate set to 23 as in Example 3. The resulting peel strength of the yarn exceeds 7.1 lb / in (1.2 N / mm) and the film breaks before the yarn breaks.

Example 7

Example 6 was repeated but two extruders were used rather than three to produce a coextruded 9.0 mil (228 μm) asymmetric (AB configuration) bilayer film. The “A” layer, the nominal innermost layer, provides 50% (4.5 mil, 114 μm) of the total film gauge and has the same composition as the layer A of Example 6. The “B” layer, nominal outermost layer, provides 50% (4.5 mil, 114 μm) of the total film gauge, 55% by weight of EAA-1, 40% by weight of CPA-1 and 5% of the antistick concentrate of Example 3. Including%. The resulting film had a Spencer impact strength of 590 g / mil (23.0 g / μm), O ₂ TR of 330 cc-mil / 100 in ² -day (130 cc-mm / m ² -day) and 2.4 g-mil / 100 in ² It has a WVTR of -day (0.95 g-mm / m ² -day). Table 2 below shows additional physical property data (MD and TD) of the film.

MD TD Final Tensile Strength (psi / (N / mm ² )) 2930 / 20.2 2670 / 18.4 % Final elongation 475 495 2% secant modulus (psi / (N / mm ² )) 9970 / 68.8 9620 / 66.3 Elmendorf Tear Strength (g / mil / (g / μm)) 240 / 9.4 295 / 11.5

The outer layer "B" has a DLF of 0.06. Two strands of film were dielectrically sealed together using the same conditions as Example 6, with the "B" layers adjacent to each other, to yield a peel strength of 5.0 lb / in (0.9 N / mm).

Claims (13)

Consisting essentially of a blend of a copolyamide with a polyolefin having a carboxylic acid or carboxylic anhydride functional group, the dielectric loss rate of the blend being at least 0.05 at a frequency of 27 MHz and 23 ° C., the copolyamide being based on the total weight of the blend, A polymer composition suitable for making into a radio frequency weldable film structure present in an amount from 20 to 80% by weight. The composition of claim 1 wherein the copolyamide is derived from dimeric fatty acids. The composition according to claim 1, wherein the polyolefin polymerizes at least one monomer which is an ethylenically unsaturated carboxylic acid or an ethylenically unsaturated carboxylic anhydride in the polyolefin. 4. The composition of claim 3 wherein the polyolefin is an ethylene / acrylic acid copolymer or an ethylene / methacrylic acid copolymer having an acid comonomer content of at least 3% by weight based on the total weight of the polymer. The composition of claim 1 wherein the polyolefin is a base polyolefin grafted with at least one monomer selected from the group consisting of ethylenically unsaturated carboxylic acids and ethylenically unsaturated carboxylic anhydrides. 6. The base polyolefin of claim 5 wherein the base polyolefin is a linear low density polyethylene, a low density polyethylene, an ultra low density polyethylene, a copolymer of ethylene with at least one α-olefin monomer, a linear ethylene / α-olefin copolymer, a substantially linear ethylene / α-olefin A composition selected from the group consisting of copolymers, propylene polymers and copolymers, and copolymers of ethylene with less than 30% by weight of polar monomers, based on the weight of the copolymer. The composition of claim 6 wherein the polar monomer is selected from the group consisting of vinyl acetate, methyl acrylate, acrylic acid and methacrylic acid. The composition of claim 6 wherein the α-olefin monomer has 3 to 20 carbon atoms. The composition of claim 6 wherein the polyolefin is an ethylene / α-olefin copolymer having a density range of 0.86 to 0.94 g / cm ³ . 10. A radio frequency weldable film structure comprising at least one layer produced from a composition according to any of the preceding claims. The structure of claim 10, further comprising at least one layer of polymer composition having a dielectric loss rate of less than 0.1 when exposed to radiation at 27 MHz at 23 ° C. 12. The structure of claim 10, wherein the seam strength is at least 3 pounds per inch (0.56 N / mm) when the film structure is sealed to the film structure itself using a high frequency sealer operating at 27.12 MHz. An article of manufacture made from the structure of claim 10 selected from the group consisting of bags, containers, packaging materials, automotive interior fabrics and components, textile laminates, air inflation devices, flotation devices, tarpaulins and tent envelopes.