LAMINAR ARTICLES OF POLYOLEFIN AND A SECOND POLYMER AND PROCESS FOR MAKING THEM

Abstract: A process for manufacturing laminar articles by form­ ing heterogeneous melts of a combination of a polyolefin and a second polymer with a alkylcarboxyl-substituted polyolefin as a compatibilizing material. Also, the laminar articles wherein the second polymer is a discontinuous phase and the polyolefin is continuous.

Description: LMINER ARTICLES OF POLYOLEFIN AND A SECOND POLYMER AND PROCESS FOR BURKING THSM Description Technical Field - This invention relates to manufacture of laminar, shaped, articles of a heterogeneous blend of a polyolefin and a second polymer, incompatible with the polyolefin, and to such articles especially in the form of barriers to permeation of fluid, liquid and gaseous, materials. Background Art - United States Patent No. 3,873,667 discloses a heat treatment process for decreasing the permeability of gases through a homogeneous composition of polyolefin and polyamide. That composition is disclosed to include an ionic hydrocarbon copolymer of ethylene and either acrylic or methacrylic acid. There is no suggestion that heterogeneous blends would exhibit improvement over homogeneous blends. United States Patent No. 3,093,255 discloses compositions of polyolefin combined with polyamide. The patent clearly discloses that the polyolefin and the polyamide must be subjected to intensive mixing under high pressures and that homo- geneity is desired over heterogeneity. United States Patents Nos. 3,373,222; 3,373,223; and 3,373,224 all disclose homogeneous polymeric blends of polyolefin, polyamide and some dispersant material to obtain homogeneous blends exhibiting decreased permeability and improved mechanical properties as compared with blends having no dispersant. U.S. 3,373,222 discloses carboxylated polyethylene; U.S. 3,373,223 discloses a copolymer of ethylene with acrylic acid or methacrylic acid; and 3,373,224 discloses a metal ion containing copolymer of ethylene and an a,5-ethyl- enically unsaturated monocarboxylic acid. All of those patents disclose the benefit of utilizing the dispersant to obtain a homogeneous blend and none suggests that heterogeneous blends would be useful. German published Application No. 2,746,181 discloses that a dispersion of polyvinylchloride partially dissolved in polyvinyl alcohol can be gelled and then subjected to laminar flow by rolling,molding or extruding the gel to yield a multilayer structure of low permeability to gases. The German Application discloses initial use of a homogeneous blend of the polymers and does not disclose use of either, a polyolefin as one polymer component, or a dispersant such as was required in the other, previouslyconsidered, patents. Summary of the Invention - According to this invention there is provided a process for manufacturing a laminar, shaped, article of polymeric material comprising the steps of establishing a melted, heterogeneous, blend of a polyolefin1 a second polymer, incompatible with the polyolefin, and an alkylcarboxyl-substituted polyolefin; and forming the melted blend by stretching a body of the melt and cooling the stretched body to below the melting point of the lowest melting polymer component. There is also provided a laminar, shaped, article comprising a combination of the polyolefin, the second polymer, and the alkylcarboxyl-substituted polyolefin wherein the polyolefin and the second polymer are present, in the article, as a multitude of thin, substantially two-dimensional, parallel and overlapping layers of material and the alkylcarboxylsubstituted polyolefin is believed to be present between the layers and adheres the layers together. Description of the Invention - Films, filaments, sheets, containers and other shaped articles have long been made from polymeric compositions. Special qualities desired for shaped articles have required special polymers or specially formulated polymeric compositions. This invention utilizes a special process and a special formulation of polymers to yield a composition which exhibits improved barrier to fluid permeation and improved mechanical properties. The general product of this invention is a laminar shaped article made from a mixture of two incompatible polymers and one polymer which serves to adhere together laminar domains of the incompatible polymers. The product is made by mixing together particles of the polymers, heating the mixture to yield a heterogeneous melt of material, and form ing the melt in a way which results in stretching the e melt to yield an elongated discontinuous polymer phase. In one embodiment, the polymer particles, in unmelted form, are mixed thoroughly so as to provide a statistically homogeneous distribution and care must be exercised -to avoid substantial additional mixing after the polymers have been heated to a melt. In another embodiment, the polymer particles can be combined in softened or molten form so long as the combination of polymers maintains a heterogeneous character. The blend can, also, be established by combining the polymers at a temperature such that one of the polyolefin or the second polymer is not softened or molten and then heating the combination. The success of the invention depends on establishing a melted heterogeneous blend of incompatlble polymers so that, when the melt is stretched, such as by extrusion forces, one polymer is in the form of a continuous matrix phase and another polymer is in the form of a discontinuous distributed phase. The polymer comprising the discontinuous phase is present as a multitude of thin, substantially two dimensional, parallel and overlapping layers embedded in the continuous phase. Also necessary for the success of this invention, is the copolymer which adheres together adjacent layers or domains of the incompatible polymers. In view of its believed purpose, that polymer can be termed a compatibilizer; but the actual mechanism of its operation is not completely understood. It is believed that at least some of the compatibilizer is concentrated, in the laminar shaped article of this invention, between the adjacent layers of incompatible polymer joined partially with one layer and partially with an adjacent layer, thus adhering the layers to gather. Without the compatibilizer, shaped articles formed from heterogeneous melts of incompatible polymer have poor mechanical properties and, generally, cannot even be extruded or molded to yield unitary articles For the purposes of this invention, "incompatible polymers" mean polymeric materials which have substantially no mutual miscibility in the melt form. Although it is not required, it is preferred that the second polymer used in practice of this invention is, as stated, in particulate form; and it is desired that both, the polyolefin and the second polymer should be mixed as particles. The particles should, as a general rule, be of a size such that, the molten blend of incompatible polymers, when introduced to some melt stretching means, such as extrusion die lips, exhibits the heterogeneity necessary for practice of the invention. When the particles, especially particles of the second polymer, are of too small a size, the melted blend, even though not excessively mixed, tends to function as a homogeneous composition because the domains of material making up the discontinuous polymer phase are so small When the particles, especially particles of the second polymer, are of too large a size, the melted blend tends to form into shaped articles having a marbleized structure rather than a laminar structure; -- the large domains of the materials which would make up the discontinuous phase extending to opposite boundaries of the shaped articles and causing disruption of the material which would make up the continuous phase. The particles are preferably generally regular in shape , such as cubical or spherical or the like. The particles may, however, be irregular; and they may have one dimension substantially greater than another dimension such as would be the case, for example, when flakes of material are used. When each of the incompatible polymers is present as individual particles, the particles are generally of approximately the same size although such is not required The compatibilizer can be provided by itself as individual particles or it can be mixed into,coated onto, or otherwise combined with one or both of the incompatible polymers. The thickness of the layers of material in the discontinuous phase is a function of the particle size combined with the degree of stretching in the forming step. The particle size of the polymer which will be the discontinuous phase is generally selected with a view toward resulting, after stretching, in overlapping layers which can be from about 0.5 to 50 micrometers thick and perhaps, sometimes slightly thicker. fixing particles of polymers can be accomplished by any well-known means such as by means of a vee-blender or a tumble mixer or, on a larger scale, by means of a double-cone blender. Continuous mixing of the particles can be accomplished by any of several well-known methods. Of course, the particles can also be mixed by hand; -- the only requirement of the mixing being that any two statistical samplings of the mixture in a given mass of material should yield substantially the same composition. The mixing of the incompatible polymers can be accomplished by adding particles of the higher melting polymer to a melt of the lower melting polymer maintained at a temperature below the higher melting point. In that case, the melt is agitated to obtain an adequate mixture; and the mix ture is, thus, ready for the heating step. Once mixed, the incompatible polymers are heated to a temperature greater than the melting point of the highest melting polymer component. It is noted that the heating is conducted for the purpose of stretching the softened or melted blend. In the case of an incompatible polymer which exhibits no well-defined melting temperature, "melting temperature", as used here, refers to a temperature at least high enough that the polymers have been softened to the degree required to stretch each of the polymers in the blend. That heating results in a softened or melted, heterogeneous blend of materials and the heating must be conducted in a manner which avoids substantial additional mixing of the incompatible polymers because such mixing could cause a homogenization and combination of the melted particles and could result in a melt and a shaped article of homogeneous, unlayered, composition. The heating can be conducted by any of several well-known means and is usually conducted in an extruder. It has been learned that a single-screw extruder of the type which is designed for material transport and not material mixing can be used between the heating and forming steps of this invention without causing homogenization of the two phase incompatible polymer composition. To the extent that the composition retains an aspect of heterogeneity, to that extent the process and the product of this invention can be realized. The forming step requires stretching of the melted blend followed by cooling. Stretching is an elongation of the two phase melt to cause a substantial change in the dimensions of the particles in the discontinuous phase. Stretching can be accomplished by any of several means, or by a combination oft more than one such means. For example, the melt can be stretched by being squeezed between rollers or pressed between platens or extruded between die lips. Molding processes such as blow molding also cause stretching in accordance with this process. In the manufacture of containers as shaped articles, the stretching can be accomplished by a combination of extruding a blend of the heterogeneous melt to yield a container preform or parison followed by blow molding the parison into a finished container. The stretching can be in one direction or in perpendicular directions. Whether the stretching is conducted in one direction or two, there should be an elongation of from 100 to 500 percent in at least one direction; and an elongation of from 100 to 300 percent is preferred. While the upper limit set out herein is not critical, the lower limit is critical insofar as inadequate stretching does not yield the improved barriers to fluid permeation which characterize this invention. Avoidance of excessive stretching is important only insofar as excessive elongation of the melt may lead to weakening or rupture of the article. Stretching is followed by cooling to below the temperature of the melting point of the lowest melting component to solidify the shaped article. The cooling can be conducted by any desired means and at any convenient rate. In the case of stretching by blow molding, the mold is often chilled to cool the article; and, in the case of extruding a film, cooling can be accomplished by exposure to cool air or by cqntact with a quenching roll. As to the proportions of the components for practicing the invention, the incompatible, second, polymer which is to be a diseontinuous phase in the shaped articles should be present in generally less than about 40 weight percent of the mixture. It has been found that the incompatible, second, polymer should be present in more than about 5 weight percent and less than about 40 weight percent of the mixture and about 10 to 30 weight percent is preferred. The polyolefin should be present in more than about 60 weight percent and less than about 95 weight percent of the mixture and 70 to 90 weight percent is preferred. The compatibilizer should be present in about 5 to 30 weight percent of the discontinuous phase and about 10 to 20 weight percent is preferred. Any of the components can be used to introduce inert fillers into the composition provided only that the fillers are not of a kind or in an amount which would interfere with formation of the layered construction or with the desired or required properties of the composition. Amounts of opacifiers, colorants, lubricants, stabilizers and the like which are ordinarily used in structural polymeric materials can be used herein. The amount of such filler is not included in the calculation of amounts of incompatible polymers and compatibilizers. The polyolefins used in the composition of the invention include polyethylene, polypropylence, polybutylene, copolymers of those materials, and the like. Polyethylene is preferred and may be high, medium, or low density. The second polymer, incompatible with the polyolefin, includes polyamides, polyvinyl alcohols, poly(ethylene-co-vinyl alcohols), and polyesters such as polyethylene terephthalate and polybutylene terephthalate. Polyamides and copolyamides are well known and are made by reacting carboxylic acids with primary amines under well-known conditions. Examples of carboxylic acids are adipic acid, suberic acid, sebacic acid, azelaic acid, malonic acid, glutaric acid, pimelic acid, and the like. Examples of primary amines are tetramethylene diamine, pentamethylene diamine, hexamethylene diamine, octamethylene diamine, and the like. Exemplary polyamides include polypentamethylene adipamide, polyhexamethylene adipamide, polyhexamethylene sebacamide, polyamides obtained from lactams such as caprolactams and from amino acids such as 11aminoundecanoic acid, and the like. Polyhexamethylene adipamide and polycaproamide are preferred. Polyvinyl alcohols are well known and are made by hydrolysis or alcoholysis of vinyl acetate homopolymers or copolymers of a degree of polymerization of 200-2500, preferably 1000-2000. Preferred polyvinyl alcohols are polyvinyl acetate in which about 50 to substantially 100 and, most preferred, 80 to 99.5 percent of the acetate groups have been hydrolyzed or alcholized. Polyvinyl alcohols are disclosed in U. S. 3,541,069. Poly(ethylene-co-vinyl alcohols) are made by hydrolysis or alcoholysis of ethylene-vinyl acetate copolymers containing 5 to 80, preferably 15 to 25, weight percent ethylene. Exemplary poly(ethylene-co-vinyl alcohols) are disclosed in U.S. 3,487,059 and U.S. 3,519,701. Polyesters are disclosed in U.S. 2,465,319. The alkylcarboxyl-substituted polyolefin compatibilizer is a polyolefin which has carboxylic moieties attached thereto, either on the polyolefin backbone itself or on side chains. By "carboxylic moiety" is meant carboxylic groups from the group consisting of acids, esters, anhydrides, and salts. Carboxylic salts are neutralized carboxylic acids and a compatibilizer which includes carboxylic salts as a carboxylic moiety also includes the carboxylic acid of that salt. Such compatibilizers are termed ionomeric polymers. Compatibilizers can be prepared by direct synthesis or by grafting. An example of direct synthesis is the polymerization of an a-olefin with an olefinic monomer having a carboxylic moiety; and an example of grafting is the addition of a monomer having a carboxylic moiety to a polyolefin backbone. In the compatibilizer made by grafting, the polyolefin is polyethylene or a copolymer of ethylene and at least one a-olefin of 3-8 carbon atoms such as propylene, and the like, or a copolymer including at least one a-olefin of 3-8 carbon atoms and a diolefin, such as 1,4-hexadiene, and the like. The polyolefin is reacted with an unsaturated carboxylic acid, anhydride, or ester monomer to obtain the grafted polymer. Representative eligible acids, anhydrides, and esters include: methacrylic acid; acrylic acid; ethacrylic acid; glycidyl methacrylate; 2-hydroxy ethylacrylate; 2-hydroxy ethyl methacrylate; diethyl maleate; monoethyl maleate; di-n-butyl maleate; maleic anhydride; maleic acid; fumaric acid; itaconic acid; monoesters of such dicarboxylic acids; dodecenyl succinic anhydride; 5norbornene-2,3-anhydride; nadic anhydride (3,6 endomethylene-1,2,3,6-tetrahydrophthalic anhydride); and the like. Generally, the graft polymer will have from about 0.01 to about 20, preferably about 0.1 to about 10, and most preferably about 0.2 to about 5, weight percent graft monomer. Grafted polymers are described in greater dtiin" U.S. 4,026,967 and U.S. 3,953,655. In the compatibilizer made by direct synthesis, the polymeric material is a copolymer of an a-olefin of 2-10 carbon atoms and an ,3- ethylenically unsaturated carboxylic acid, ester, anhydride, or salt having 1 or 2 carboxylic moieties. The directly synthesized compatibilizer is made up of at least 75 mole percent of the olefin component and from about 0.2 to 25 mole percent of the carboxylic component. Ionomeric compatibilizer is preferably made from directly synthesized compatibilizer and is preferably made up of bout 90 to 99 mol percent olefin and about 1 to 10 mol percent a,6- ethylenically unsaturated monomer having carboxylic moieties wherein the moieties are considered as acid equivalents and are neutralized with metal ions having valences of 1 to 3, inclusive, where the carboxylic acid equivalent is monocarboxylic and are neutralized with metal ions having a valence of 1 where the carboxylic acid equivalent is dicarboxylic. To control the degree of neutralization, metal ions are present in an amount sufficient to neutralize at least 10 percent of the carboxyl moieties. Representative eligible a-olefins and unsaturated carboxylic acid, anhydride, and ester monomers are those previously herein described. Ionomeric polymers are described in greater detail in U.S. 3,264,272. The compatibilizer is generally about 0.5 to 3.0 weight percent carboxylic component. In making shaped articles of this invention, the polyolefin is generally taken to provide the continuous phase and is used in an amount of about 60 to 95 weight percent of the total composition while the second, incompatible, polymer is taken to provide the discontinuous phase and is used in an amount of about 5 to 40 weight percent of the total composition. The alkylcarboxylsubstituted polyolefin is used in an amount of about 0.5 to 3 weight percent of the total composition. Description of the Preferred Embodiments Example 1. In this example, polyolefin, polyamide, and compatibilizer were mixed:(a) to make a heterogeneous blend in accordance with the present invention; and (b) to make a homogeneous blend. The polyamide was prepared by condensing hexamethylene diamine, adipic acid, and caprolactam to obtain a composition of 77.5 weight parts of polyhexamethylene adipamide and 22.5 weight parts of polycaproamide. That polyamide exhibited a melting point of about 2150C. The polyolefin was a linear polyethylene having a density of 0.944 gram per cubic centimeter, a melt index of 0.24 as determined according to ASTM D-1238, and is commercially available from E. I. du Pont de Nemours and Company under the trademark designation "Alathon" PE 5593. Particles of the polyamide and the polyethylene were generally cubical and were about 3-4 millimeters on each side. The alkylcarboxyl-substituted polyolefin compatibilizer was obtained by melt grafting fumaric acid onto polyethylene having a density of 0.958 gram per cubic centimeter and a melt index of about 10, as determined according to ASTM D-1238. The fumaric acid was grafted onto the polyethylene in an amount of about 0.9 weight percent based on the total weight of the polymer in accordance with the teaching of U.S. Patent No. 4,026,967. Particles of the compatibilizer were generally cubical and were about 2-3 millimeters on a side. The material exhibited a melting point of about 1350C. The mixture included 77 weight percent polyolefin, 20 weight percent polyamide, and 3 weight percent compatibilizer and was tumbled in a drum to achieve complete, even, particle distribution. Example 1. A portion of the mixture was fed directly into an extrusion blow molding machine such as that solid by Voith-Fischer Plastic Machines, Inc. of Paramus, New Jersey, U.S.A., identified as model FBE 1000 and equipped with a low mixing screw and tooling. Bottles with a capacity of about 450 milliliters (16 ounces) were blow molded at an extrusion temperature of about 2400C. Comparative 1. A portion of the mixture was homogenized in a Werner & Pfleiderer twin screw extruder at a temperature of about 250eC and was then fed directly to the same extrusion blow molding machine used in Example 1, above, to make bottles of homogeneous wall structure. Control 1. As a control, bottles were also made using the polyolefin alone in the same extrusion blow molding machine at an extrusion temperature of about 1900C. Bottles from each of the three categories were tested visually and were tested for barrier to permeation of unleaded gasoline and pneumatic impact strength of the walls. Test results are in Table I. Table I Pneumatic impact Permeation strength barrier Visual (ka-cm/mil) (g-loss) Example 1, this in- laminar vention distrib ution of polyamide 2.40 0.25 Comparative 1, homogeneous homogeneous structure material distribution 1.75 9.8 Control 1, poly- same maethylene terial throughout 2.14 19 Visual testing was conducted by inspection, with and without the use of an optical microscope, of edge slices of material from the bottles. As indicated in the Table, bottles from Comparative 1 and Control 1 exhibited no laminar structure. Bottles from Example 1 did exhibit a laminar structure of polyamide layers distributed through the bottle wall thickness. Edge slices of the bottle walls viewed through cross polarized light filters clearly evidenced laminar distribution of the polyamide in bottles of Example 1 and evidenced homogeneous distribution of polyamide in bottles of Comparative 1. The polyamide layers were estimated to be about 0.5 to 15 micrometers thick, distributed as multiple, overlapping, layers across the bottle wall which was about 1 millimeter thick. Pneumatic impact was determined by adapting the procedure of ASTM D-3099 to test wall sections of the bottles. The procedure, generally described, involves determination of the energy absorbed by a test portion of the wall material where it is struck by a pneumatically driven steel ball. Barrier to permeation was tested by adding 100 cubic centimeters of unleaded gasoline to bottles from each category, sealing the bottles, and then determining weight loss after 500 hours at about 230C and about 50 percent relative humidity. It is noted that the bottles of the invention exhibited barrier to permeation of gasoline almost forty times as great as bottles of the same material with homogeneous walls and more than seventyfive times as great as the polyethylene control. Examples 2 - 7. Using the same poly olef in, polyamide and compatibilizer as in Example 1, several different weight ratios of the materials were mixed and 450 milliliter (16 ounce) bottles were blown using the same blow molding and extruding machinery as under Example 1, above. The bottles were blown to have walls of about 0.75-1 millimeter thickness -- slightly less than the bottles under Example 1, above. For comparative purposes, Comparative 2 and 3 and Control 2 were also run. Except for the slightly thinner bottle wall thickness, Example 2, Comparative 2, and Control 2 represent repeat runs of the bottles made under Example 1, above. The bottles were tested visually. and barrier to permeation of fluid was tested by the gasoline loss test described under Example 1, above, except that the test was run for 34 days. Results of the tests are shown Laminar walls means that sections of the walls could be delaminated or pulled apart in layers without cohesive failure. Bottles from Comparative and Control examples had uniform walls which could not be sodelaminated. Table II Polyolefin/ polyamide/ compatibil- Nature Nature Permeation Run izer of of barrier Number (weight ratios) blend walls (g-loss) Example 2 77/20/3 Heterogeneous Laminar 0.39 " 3 79/20/1 " " 0.36 " 4 82/15/3 " " 0.38 5 5 84/15/1 " " 0.36 " 6 87/10/3 ' " 0.43 " 7 89/10/1 " " 0.46 Comparative 2 77/20/3 Homogeneous Uniform 15.1 Comparative 3 79/20/1 " " 10.2 Control 2 100/0/0 " " 27.2 Example 8. In this example, bottles were made using the same polyethylene and polyamide as in previous examples along with a compatibilizer of zinc-neutralized copolymer of ethylene and methacrylic acid. The compatibilizer was about 90.weight percent ethylene and about 10 weight percent methacrylic acid wherein about 70 percent of the methacrylic acid groups were neutralized by zinc ions. The compatibilizer exhibited a melt index of about 1.1 as determined at 1900C in accordance with ASTM D-1238. Bottles having laminar walls were blown using the same equipment as previously described and a heterogeneous mixture of component materials made up of 82 weight parts polyethylene, 15 weight parts polyamide, and 3 weight parts compatibilizer. Fluid permeation was determined, as previously described, using unleaded gasoline; and, in 25 days, bottles of this example exhibited a loss of about 0.5 grams compared with a loss of about 25 grams from polyethylene control bottles made during the same runs. Example 9. Example 8 was repeated except that the compatibilizer was a polymer made by grafting fumaric acid to a copolymer of ethylene, propylene, and 1,4-hexadiene (71/25/4, weight ratio) such that the compatibilizer contained about 1.8 weight percent fumaric anhydride functionality. The material and its preparation is described in more detail in U.S. 4,026,967. Bottles prepared using that compatibilizer exhibited loss of about 0.5 grams of unleaded gasoline in the previously described fluid permeation test, after 25 days. Example 10, as an extension of Example 4, the same mixture of materials, including the fumaricgrafted compatibilizer, in the same weight ratio, was used to blow mold containers having a capacity of about 18 liters (5 gallons) and a wall thickness of about 3 millimeters (125 mils). The bottlemaking equipment used was sold by Ingersoll Rand of Nashua, New Hampshire, U.S.A. and was identified as model B-30 with a barrier flighted screw and reciprocating action. The extrusion temperature was about 2430C (4700F). To test the fluid permeation barrier, about three liters of unleaded gasoline were placed in these bottles and in polyethylene control bottles of the same size made in the same sequence of runs. The bottles were located outdoors, in ambient conditions, shaded from direct overhead sun exposure, for 72 das through summer-autumn weather in Wilmington, Delaware, U.S.A. During that period, the bottles of this invention exhibited a loss of about 3.5 grams of gasoline and the control bottles exhibited a loss of about 123 grams of gasoline. Example 11. In this example, laminar film was made by the blown tubular film process of film manufacture using an extruder such as that sold by Killion Extruders, Inc. of Verona, N.J., U.S.A., identified as model K-100 and equipped with a low mixing screw and die without mixing torpedoes, pins, or rings and the like. The material of the film was polyolefin, polyvinyl alcohol and a compatibilizer in a weight ratio of 65/30/5, respectively. The polyolefin was a linear polyethylene having a density of 0.944 gram per cubic centimeter, a melt index of 0.45 as determined according to ASTM D-1238. The polyvinyl alcohol was polyvinyl acetate more than 99 weight percent hydrolyzed, exhibiting a viscosity of 13 centipoises at 200C in a 4 weight percent aqueous solution, and was commercially available from E. I. du Pont de Nemours and Company under the trademark designation "Elvanol" 90-50. The compatibilizer was the same as that used in Example 1. The material was extruded and blown into film having a final thickness of about 50-75 micrometers (2-3 mils) thick; -- the extrusion and blowing providing stretching for formation of the laminar structure of this invention. The film had a laminar structure and could be delaminated into individual layers without cohesive failure. As a test of the barrier to fluid permeation, the film was subjected to an oxygen transmission in accordance with the procedure of ASTM D1434. The laminar film of this example exhibited an oxygen transmission of 335 cubic centimeters O2 per square meter per day per mil of film thickness while a polyethylene control film made during the same runs exhibited a transmission of 760 in the same units. Examples 12 and 13. In this example, laminar films were extruded using a mixture of polyolefin, poly(ethylene-co-vinyl alcohol), and compatibilizer. The polyolefin was the same material as was used in Example 11. The poly (ethylene-co-vinyl alcohol) was a hydrolyzed random copolymer of ethylene and vinyl acetate having a melting point of 1800C, a density of 1.19 grams per cubic centimeter, a melt index of 1.5 at 1900C as determined in accordance with ASTM D-1238, and is commercially available from Kuraray Company, Ltd., Osaka, Japan, under the trade designation "EVAL Resin EP-F". The compatibilizer in Example 12 was the same as that used in Example 1. The compatibilizer in Example 13 was the same as that used in Example 8. The film manufacturing equipment was the same as that of Example 11; and the films had the laminar structure of this invention. As a test of fluid permeation barrier, the films were subjected to the oxygen transmission test (ASTM D-1434) and to a water vapor barrier test identified as ASTM E-96. Results of the tests are shown in Table III. Table III Polyolefin/ Oxygen Water vapor second polymer/ transmission barrier Run compatibilizer (g/100 in2/day/ (g/100 in2/day/ number (weight ratios) mil) mil) Example 12 65/30/5 41 0.12 13 65/30/5 1 0.09 Control 100/0/0 116 0.03

Claims: Claims 1. A process for manufacturing a laminar, shaped, article of polymeric material comprising the steps of: (i) establishing a melted, heterogeneous, blend of polyolefin, a second polymer incompatible with the polyolefin, and an alkylcarboxyl-substituted polyolefin; and (ii) forming the melted blend by (a) stretching a body of the melt and (b) cooling the stretched body to below the melting point of the lowest melting polymer component. 2. The process of Claim 1 wherein the melted, heterogeneous, blend is established by heating particles of the polyolefin, the second polymer, and the alkylcarboxyl-substituted polyolefin, without substantial additional mixing, to a temperature above the melting point of the highest melting polymer component. 3. The process of Claim 1 wherein the melted, heterogeneous, blend is established by combining the polyolefin, the second polymer, and the alkylcarboxyl-substituted polyolefin at a temperature such that one of the polyolefin or the second polymer is not softened or molten and heating the combination to a temperature above the melting point of the highest melting polymer component. 4. The process of Claim 1 wherein the melted, heterogeneous, blend is established by heating particles of a combination of the polyolefin and the alkylcarboxyl-substituted polyolefin and particles of the second polymer, without substantial additional mixing, to a temperature above the melting point of the highest melting polymer component. 5. The process of Claim 1 wherein the melted, heterogeneous, blend is established by heating particles of the polyolefin and particles of a combination of the second polymer and the alkylcarboxylsubstituted polyolefin, without substantial additional mixing, to a temperature above the melting point of the highest melting polymer component. 6. The process of Claim 1 wherein the alkylcarboxyl-substituted polyolefin is selected from the group consisting of polyolefins which have carboxylic moieties attached thereto, either on the polyolefin backbone itself or on side chains. 7. A laminar, shaped, article comprising a combination of polyolefin, a second polymer incompatible with the polyolefin, and an alkylcarboxyl-substituted polyolefin wherein the polyolefin and the second polymer are present in the article, as thin, substantially two-dimensional, parallel and overlapping layers of material and the alkylcarboxylsubstituted polyolefin is present between the layers and adheres the layers together. 8. The article of Claim 7 wherein the alkylcarboxyl-substituted polyolefin is selected from the grbup consisting of polyolefins which have carboxylic moieties attached thereto, either on the polyolefin backbone itself or on side chains. 9. The article of Claim 7 wherein the second polymer is polyamide and is a discontinuous phase and is present in layers of material more than about 0.5 and less than about 50 micrometers thick. 10. The article of Claim 7 wherein the second polymer is present in about 5 to 40 weight percent, the polyolefin is about 60 to 95 weight percent, and the alkylcarboxyl-substituted polyolefin is about 0.5 to 3 weight percent, of the article.

Inventors: SUBRAMANIAN, PALLATHERI MANACKAL
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1980
Main classification: C08L23
IPC codes: C08J3, B29B7, B29C61, B29C45, C08L23, C08L21, B29C55, B29C65, B29C49