CA1292850C - Seamless laminar article - Google Patents

Abstract

TITLE SEAMLESS LAMINAR ARTICLE Seamless, molded, thermoplastic articles are disclosed having a laminar, multi-component composition with a heterogeneous blend of incompatible polymers - at least one as a matrix and at least one as a discontinuous phase. Knit lines in the article are curved to obscure seams and increase strength.

Description

~Z9ZE~50 TITLE
SEAMLESS LAMINAR ARTICLE
~ACKGR~UND OF THE INVEN'lIO~
Field of the Invention This inventior relates to thermoplastic articles malded from a heterogeneous blenu of incompatible polvmers. Especially preferrea poiymers are a polyolefin first polymer anù a secona ~olymer, incompati~le with the polyolefin. Tne invention, additionally, relates to processes for making such articles. The invention specifically relates to suc~
articles having substantially uniform wall thicknesses around the circumference of a g~nerally cylindrical shape with resulting improvea barrieL
properties and strength.
Description of Prior Art U.S. Patent No. 4,410,482 discloses manufacture of thermoplastic articles from a heterogeneous blend of a polyolefin first polymer anù
an incompatible second polymer. The articles o~ that patent have the polymer components present as a multitude of thin, substantially two-dimensional, parallel and overlapping layers and such art~cles in the form of containers are aisclosea to exhibit permeation barrier characteristlcs greatiy increase~
in comparison with containers made fron, pol~olefin, alone. Other patents which aisclose articles havlng a similar construction incluae U.~. Patents No.
4,444,817 and 4,416,94~.
U.S. Patent No. 3,~99,8~ aiscloses an extrusion device for making tubing of homogeneous wall construction whereoy molten moldiny material is conducted through the device by streamlining su~port fins to reduce the existence of flow lines causea by 9D-5441 35 separation of the material in the so-called nozzle ~Z92850 head. This patent also discloses a steplike offset of the support to assure effective mixing of the molten material.
U.S. Patents No. 3,~79,501 and 3,404,~03 disclose manufacture of tubing with orientea internal and external surfaces wherein the mold surfaces are counter-rotated during extrusion of the molten material.
U.S. Patent ~o. 3,~56,560 discloses a di~
for orienting the internal anc external surfaces of an extrudate by means of grooves cut in the respective surfaces of the die to direct the flow of molten material in opposite directlons.
SUMMARY OF THE INVENTIG~
According to this invention there is provided a process for manufacturing a lan,inar, molded, hollow, article of polymeric materla comprising the steps of establishing a molten, heterogeneous, blend of incompatible polymers by heating the blend above the melting point of the highest melting polymer component and, then, molaing the melted blend by extruding a body of the blend through a die wherein internal surfaces of the die have streamlined irregularities positioned to ~isplace surface material of the blend relative to core material of the blend and cooling the extruaed body to below the melting point of the lowest meltins polymer component. In a preferre~, continuous, blow molding process of this invention, the extruaea boay is blown before cooling. The blend o~ incompati~le polymers preferred and most often usea incluaes a polyolefin as a continuous or matrix phase ana a second polymer incompatible with the polyolefln as a discontinuous or distributed phase.

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A laminar, moldea, hollow artlcle is also - provided which comprises a combination of incompatible polymers wherein the polymers are present as thin, substantially two-dimensional, parallel ana overlapping layers of material and wherein melt seams or knit lines in the artlcle are c~rved to provide such overlapping layers in any radial section through a wall of the hollow article.
Such laminar hollow article, when blow molded, has overlapping layers in any radial section and has walls of substantially uniform thickness around the perimeter or circumference of the article.
An important and critical aspect of the present invention resides in the aisplacement of surface material during manufacture of articles molded using the heterogeneous blend such that, when the blend is stretchea, all components of the blen~
remain relatively uniformly distribute~ throughout the article and the thickness of the article does not undergo thinning at one area out of proportlon with other areas of the article.
BRIEE DESCRIPTON OF T~ DRA~lNGS
Fig. 1 is a cross-sectional representatlon of an extrusion device with a grooved spiral head useul for practicing the present invention.
Fig. 2 is a cross-sectional representation of an extrusion device with a rotating extrusion heao useful for practicing the present invention.
Fig. 3 is a cross-sectional representation of a ribbed spiral head to be used in an extrusion ~evice for practice of the present invention.
Fig. 4 is a cross-sectional representation of a blow mol~ed lamellar container wall of the prior art displaying a greatly magnifiea melt seam volume.

Fig. 5 is a cross-sectional representation of a blow molded lamellar container wall of the present invention having one wall surface displacea and displaying a greatly magnified melt seam volu~,e.
Fig. 6 is a cross-sectional repr-esentation of a blow molded lamellar container wall of the present invention having two wall surfaces aisplacea and displaying a greatly magnified melt seam voiume.
DESCRIPTION O~ E I~iVENl IOI~I
Laminar, shaped, articles are well known which are maae from a n,ixture of incompatible polymers wherein one polyn,er is in the form of a continuous matrix phase and another polymer is in the form of a discontinuous distributea phase. The laminar articles are made by mixing together particles of the polymers, heating the mixture to yield a heterogeneous melt of material, an~ forming the melt in a way which results in stretching the melt to yielà an elongated discontinuous polymer phase.
In one embodiment, the polymer partlcles, in unmelted form, are mixed thoroughly so as to proviae a statistically homogeneous distribution ana care is exercised to avoid substantiai aaditlonal n,lxing after the polymers have been heatea to a melt. lr, another embodiment, the ~olymer particles can be combined in softened or molten form so lons as the combination of polymers maintains a heterogeneous character. The blend can, also, be establishea by combining the polymers such that the highest melting of the polymers is not softened or molten and then heating the combination. The success of the invention depends on establishing a melted heterogeneous blend of incompatible polymers so that, when the melt is stretched, such as b~ blow molding `` 12928S~) forces, one polymer is in the form of a continuous ~atrix phase and another polymer is in the for~l ol 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.
The thin, substantially two-dimensional, parallel and overlapping layers operate, in concert, to provide strength and permeation barrier qualitles to the article so-formea. To the extent that the layers overlap, the strength and the barrier qualities are enhanced by providing a briage of discontinuous material across the matrix phase.
The strengthening èffect o~ overlappeo layers is especially pronounced in the manufacture of laminar articles by blow molding means although the effect is, also, exhibited when the laminar articles are made by other means, such as by the stretching forces which are associated with simple extrusion.
In blow molding manufacture of laminar articlec, such as in blow molding bottles, a parison is generally made and then the parison is ~lown to a final bottle shape. Parisons are manufactured by extrusion from dies which form tubing an~ sucr, oles must be constructed with support elements or materiaï
flow components which divide the molten material as it flows to the die lip opening. In the laminar, heterogeneous, article of the present inventlon, an~
division of the molten material prevents overlap of layers in the distributed phase at the points of division and causes weakening of the article unless the overlap can somehow be reinstitute~.
Fig. 1 depicts an extrusion device with a body 1 and a mandrel 2 centrally positioned within a --` 129Z850 cavity 3 in body 1. Outer die lip element 4 is affixed to body 1 by means of bolts 5 and ring 6 and its position is adjusted by means of bolts 7. Outer die lip element 4 includes a cavity 8 in which mandrel 2 is also centrally positioned. Mandrel ~
ends in an inner die lip surface 9 at the point where mandrel 2 is in closest proximity with exit 10 from outer die lip element 4 to form outer die lip surface 11. Mandrel 2, centrally located in cavities ~ ana 8, are supported by spiders 12 which are rigid struts from about two to twelve in number arrangea equidistant from each other fixea between manarel and the inner wall 13 of boay 1. In Fig. 1, two of the spiders 12 are shown. One spiàer 12 is shown in cross section as a part ol mandrel 2 ana another spider 12 is shown as it radiates from manarel 2 into the plane of the figure to boay 1. ~xtrusion aevices 5uch as are depicted in Fig. 1 and in Fig. ~ are often used without spiders but are shown here to afford the aaded stability provided thereby.
The inner wall 14 of outer die li~ element 4 has grooves 15 which serve as streamlined irregularities for spirally displacing molten material passing through the device. l~he manarel 2 may have grooves 16 which, also, serve as streamlinea irreaularities for spirally displacing molten material. Grooves 15 and 16 are, generally, locatea with opposite spirals.
In operation, a molten, heterogeneous, blend of incompatible polymers is intro~uced into the extrusion device through iniet port 17 ana arouna mandrel 2. The molten material passes arouna both sides of mandrel 2 and where the material meets itself on the side opposite the inlet port 17, a knit line is formed. The knit line is so-callea because lZ928~0 the molten material must knit together an~ forn, a weld or joint in the final moldea artlcle. ~ithout the benefit of the present invention, the continuous or matrix phase of the heterogeneous blena of polymers can be successfully knit together; but the discontinuous or distributed phase cannot ~orm an adequate joint because the parallel layers of distributed material cannot overlap across the knit line.
The molten blend, complete with knit line, continues into cavity 3 ana passes spiders 12 whereupon the blend is cut by each of the spiders 12. At each cut, the molten material is separated;
an~, after each spider, the molten material is rejoined with itself and results in a melt seam wherein the continuous or matrix phase is successf~lly joined but the distributed phase is not overlapped across the seam.
The molten blend, with knit line ana melt seams, advances through cavlty 3 and into cavity 8.
For purposes of describing this lnvention, knit llnes and melt seams are equivalent ana either designation can be taken to mean both. At cavity ~, the molten blend encounters streamlined irregularities in the form of grooves 15 in outer die lip element 4 an~
orooves 16 in mandrel 2. ~he grooves 15 and 16 are spirally placed in opposing directions on outer ~le lip element 4 and mandrel 2, res~ectively, and the grooves cause gentle displacement of surface layer~
of the molten material such that the melt seams are curved and particles of the distributed phase are overlapped in the sense that such particles are present in any radial section through the molten material.

The molten blend, with displaced surface layers, is extruded ~etween inner die lip surface 9 and outer die lip surface 11 to yield a shaped article having curved knit lines ana overlapping particles of the distributed phase. It shoui~ be noted that the benefits of this inventlon can be realizea even if the streamlined irregularities are present on only one surface of the extrusion devlce, for example, on only the outer die lip element 4 o~
on only the mandrel 2. Moreover, the streamllnea irregularities can be locatea, generally, on any surface of cavity 3 or cavity b so long as they are aownstream from the spiders 12 and they can take the form of either grooves or ridges.
Thè grooves or ridges -- the streamlined irregularities -- should be shapea such that the irregularities cause displacement of less than about one-third of the thickness of the molten material on the affected side and the displacement should be géntle in that the displaced material is maintainea in its heterogeneous condition and is not mixea exce~sively, causing homogenization of the displace~
blend.
Fig. 2 depicts an alternative embo~iment of an extru~ion devlce useful in practice of this invention. l'he device comprises boay lb ana manarel 19 with c~vity ~O in boày 1~. In thls aevice, outer die lip element 21 is rotatably mounted agalnst booy 18 such that cavity 20 matches with cavity ~2 in outer die lip element 21. Outer die lip element 21 is held against body 18 by means of bolts 23 ana ring 24 and rotatability is maintained by bearings 2~.
Seal 26 is providea to prevent leakage of molten molding material. Outer die lip element 21 has rlng gear 27 mounted thereon and it is rotated by drivlng gear 28. A molten, heterogeneous, blend of incompatible polymers is introduced at inlet port ~, forms a knit line at mandrel 19, and traverses the cavities 20 and 22 being separated during its travels b~ spiders 30 and then rejoined. In Fig. 2, two of the spiders 30 are shown. One spiaer 30 is shown in cross section as a part of mandrel 19 ana another spider 30 is shown as it radiates from manarel 19 into the plane of the figure to body 18. Outer aie lip element 21 is rotated and the rotation causes shear forces between the inner surface 31 of outer die lip element 21 ana tne molten blend. In tt,is case, the streamlinea irregularities can be as small as the slight irregularities usually foun~ on machined surfaces or they can be more pronouncea grooves or ridges placea on the inner surface 31.
Rotation of the outer die lip element ~1 intensifles the effect of the irregularities. The rotation of the outer die lip element 21 causes displacement of a

2~ surface layer of the molten material resulting in curved knit lines and melt seams and in overlappiny of particles of the dispersèd phase in the shapea article which is extruded between inner die lip surface 32 and outer die lip surface 33.
@ig. 3 depicts an outer die lip element 40 which can be usea in the extrusion devices of Fig. 1 and, if fitted with a ring gear, Fig. ~. Ihe element 4~ of Fig. 3 is fitted with ridges 41 as streamlinea irregularities.
Fig. 4 àepicts a cross section of laminar, molded, hollow article 4~ of a molten, hetero~eneous, blend of incompatible polymers after the article has undergone stretching. The Fig. 4 àepicts a stretchea laminar, molded, article made without the beneflt of the present invention. An inset is drawn to show an ~Z~;~850 exaggerated representation of a knit line or melt seam 43 in the hollow article 42. Particles of polymeric material 44, shown as thin, substantially two-dimensional, parallel and overlapping layers are 5 distributed in continuous, matrix, material 45.
Before stretching, article 42 has a substantially constant thickness all around its circumference. At knit line 43, matrix material 45 is thoroughly fusea to yield a successful melt seam of the matrix 10 material; but there is no overlap of particles of polymeric material 44 across knit line or melt seam 43.
Particles of polymeric material 44 leno strength and reinforcement to the blend; ana, when 15 the article (or tube or bottle) is stretchea there will be less stretching in a section or volume which contains the particles 44 than there will be in a section or volume which has none of the particles 44. The portion of the article directly surroun~ing 20 knit line 43 has no overlapping particles of polymeric material 44 and, therefore, is subjectea to more stretching than the portion of the article farther away from the knit line. By being stretched more, the resulting article wall is thinner and the 25 product âevelops a thin, weak, area which follows the knit line and the seams all along the wall of the article.
The distributed particle 44, in ~ig. 4, ana 49 and 54 in Figs. 5 and 6, respectively, are 30 depicted as having a length on the order of the thickness of the article itself. While determination of the length of the particles 44 is very difflcult and while the lengths are expected to vary considerably from one particle to another, it is 35 believed that the particles actually have a lerlgth of ~z928~;~

about 5 to 50 and most usually 10 to 30 times the thickness of an article such as is presentea in Figs.
4, 5, and 6. The particles 44 are shown out of scale for the purpose of providing an accurate impression of the large number of two-dimension31, parallel and overlapping, layers present in the article of this invention.
Fig. 5 depicts â cross section of a laminar, moldea, hollow article 47 of a molten, heterogeneous, blend of incompatible polymers after the article has undergone stretching. The article of Fig. 5 lS an article of the present invention. An inset is ~rawn to show an exaggeratea representation of a knit l~rle or melt seam 48 in the article 47. As in Fig. 4, particles of polymeric material 49 are shown distributed in continuous, matrix, material ~0. As stated, the article 47 was made by the present invention wherein the inner surface of the extrusion device was fitted with streamlined irregularities to cause displacement of an inner surface layer of the extruded blend of materials. Before stretching, matrix material 50 is thoroughly fused at knit line 48 to yield â seam of the matrix material. T~e knit line 48 is, however, curveâ at one end resulting in overlap of particles of incompatible polymeric material 49. By overlap, is meant that overlapping layers of the distributea material 49 will be included in any radial section through the wall of the article.
When the article 47 is stretche~, tr~e curvea portion of the knit line 48 wlll stretch. Because, as noted above, particles of incompati~le polymeric material 49 lend strength to the blend, t~le portion of the article 47 which is directly surrounding the curved end of knit line 48 will stretch at about the lZ9~8~0 same rate and to about the same degree as ~ortions of the article 47 located some distance from the knit line 48. On the other hana, the portion of the article 47 which is directly surrounding the undisturbed end of knit line 48 will stretch more and at a greater rate than other portions of article 47.
Such greater degree of stretching causes some thinning and weakening of the wall of article 47 but the wall is not thinned or weakened in the areas wherein the knit line 48 has been curved and the particles of incompatible polymeric material 49 have been caused to overlap by the practice of the present invention.
Fig. 6 depicts a cross section of a laminar, molded, hollow article 52, of this invention, after the article has undergone stretching. An inset is drawn to show an exaggerated representatiGn of a knit line or seam 53 in the article 52. Particles of incompa~ible polymeric material 54 are distributea in continuous matrix material 55 ana the knit line 53 has been curved at both ends as a result of using an extrusion device having streamlined irregularities on both the inner and the outer surfaces to cause displacement o both surface layers of the extruded blend of materials. Because the knit line 53 is curved at both ends, particles of incompatible polymeric material S4 form overlapping layers and the overlapping layers increase the strength of the article and prevent thinning at the seam.
Overlapping layers of particles of incompatible polymeric material 54 are included in any radial section through the wall of article 52. As a result of the practice of this invention, a molded article has a substantially uniform thickness from the knit line area to areas adjacent the knit line area.

lZ~28~0 The article of this invention includes a first polymer present as a continuous or matrix phase and a second polymer, incompa~ible with the first, present as a discontinuous phase. Also useful in the practice of this invention, is a polymer which is believe~ to adhere together adjacent layers or domains of the incompatible polymers. In view of its believed purpose, that polymer can be termeu a compatibilizer; but the actual mechanism of its operation is not completely unaerstood. 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 together. Without the compatibilizer, shaped articles formed from heterogeneous melts of incompatible polymer sometimes have poor mechanlcal properties and, sometimes, 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 preferrea that the second polymer used in practice of this invention is, as stated, in particulate form; anu it is desired that both, the first polymer and the second polymer should be mixed as particles. I~he 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, lZ9Z~3SO

even though not excessively mixed, tends to function as a homogeneous composition because the individual 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 a~ticles having a marbleized structure rather than a laminar structure. 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 lS
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 constitute 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.
Mixing particles of polymers can be accomplished by any well-known means such as by means of a vee-blender or a tun,ble mixer or, on a larger scale, by means of a double-cone blender. Continuous mixing of the particles can be accomplished by any of lZ9Z8SO

several well-known methods. ~f course, the partic~es can also be mixed by hand; -- the only requirement o~
the mixing being that any two statistical samplings of the mixture in a given mass of material shoula 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 mixture is, thus, ready for the heatina 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 softenea or meltea blena.
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 re~uired to stretch each of thè 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. 1`he heating can be conducted by any of several well-known means and is usually conducted in an extruaer. 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 ~92850 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 ana 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 of 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 shapefl articles, the stretching can be accomplished ~0 by a combination of extruding a blend of the heterogeneous melt to yield a container pre~orm or parison followed by blow molding the parison into a finished container.
The stretching can be in one airection or in two, preferably perpen~icular, directions. Whether the stretching is conducted in one direction or two, there should be an elongation of from lO0 to 2000 percent in at least one direction; and an elongation of from lO0 to 1500 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.

129~50 Stretchlng 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 conducte~ by any desired means and S at any convenient rate. In the case of stretching by blow molding, the mold is often chilled to cool tne article; and, in the case of extruding a film, cooling can be accomplished by exposure to cool air or by contact with a quenchiny roll.
As to the proportions of the components for practicing the invention, the incompatible, second, polymer which is to be a discontinuous 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 4~ weight percent of the mixture and about 2 to 20 weight percent is preferrea. The continuous, first, polymer shoula be present in more than about ~0 weight percent an~ less than about 99.5 weight percent of tne mixture an~ 7 to 98 weight percent is preferred. The compatibilizer should be present in about 5 to :~5 weight percent of the discontinuous phase and about 10 to 2S 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 apacifiers, 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.

lZ9Z850 The first polymer, forming a continuous or matrix phase in the composition of this invention, can be any thermoplastic material having a melt viscosity, at forming and stretching temperatures, lower than the melt viscosity of the secon~ polymer, described below. Polyolefins are preferred as the first polymers and preferred polyoleflns are polyethylene, polypropylene, polybutylene, copolymers of those n,aterials, and the like. Polyethylene is preferred and may be high, medium, or low density.
The second polymer, forming a aiscontinuous phase in the composition of this invention, can be any thermoplastic material having a melt viscosity at forming and stretching temperatures, higher than the melt viscosity of the first polymer, descri~ed above. Examples of second polymers which can be usea in this invention are polyamides, polyvinyl alcohols, and olefin copolymers such as ethylene/vinyl alcohol, nitrile copolymers such as acrylonitrile/methylacrylate and styrene/acrylonitrile, polyvinylidene chloride, polycarbonates and other polyesters such as polyethylene terephthalate and polybutylene terephthalate, and the like. Polycondensation polymers such as polyamides an~ polyesters are preferred as second polymers.
The compatibilizer lS a polyolef1n which has carboxylic moieties attached thereto, either on the polyolefin backbone itself or on side chains. By "carboxylic moiety" is meant carboxylic ~roups 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 inclu~es the carboxylic acid of that salt. Such lZ~8~0 compatibilizers are termed ionomeric polymers.
Additional description of compatibilizers is foun~ in U.S. 4,410,482.
DESCXI PTION OF TH~ PREFERRED EMBODIME;NTS
Polyolefin, polyamide, and a compatibilizer were mixed to make a blend, parisons were extruoed from the blend, and bottles were blow molded from the parisons. The parisons were extruded through heaas with no streamlined irregularities, as a control, and through heads with streamlined irregularities such as are indicated in Fig. 3, as an example of this invention.
The polyolefin was a linear polyethylene having a density of 0.955 gram per cubic centimeter, a melt index of 0.35 as determined according to ASTM
D-1238, and is commercially available from Phillips Petroleum Company under the trademark designation "Marlex" 5502. Particles of the polyamide and the polyethylene were generally aisk-shaped and were 20 about 3-4 millimeters in diameter.
The polyamide was prepared by condensing hexamethylene diamine, adipic acid, and caprolactam to obtain a composition of 80 weight parts of polyhexamethylene adipamide and 20 weight parts o~
25 polycaproamide. That polyamide exhibited a melting point of about 220C.
The alkylcarboxyl-substituted polyolefin compatibili~er 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 ASTI~] 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 35 U.S. Patent No. 4,026,967. Particles of the 1~

129;~850 .

compati~ilizer ~ere generally cubical and were about 2-3 millimeters on a side. The material exhibitea a melting point of about 135C.
The mixture was tumbled in a drum to achieve complete, even, particle distribution and was then fed directly into an extrusion blow molding macnine such as that soid by Rocheleau Tool & Die Co., Inc., of Fitchburg, MA, ~.S.A., identified âS Model R7A anc equipped with a low mixing screw and toollng. In initial operations, the mandrel and extrusion heac of the extrusion aevice were smooth, ano bottles made using those elements were tested as comparative examples. To make the articles of this inventlon, the smooth-walled extrusion head was exchanged for a head having 8 ridges, 1/8 inches high and ~`ixed at a spiral angle of about 45 degrees from the vertical equally spaced around the upper, cone-convergent, area as shown in Fig. 3. The converged throat of the extrusion was about 1.5 centimeters in diameter.
Bottles with a capacity of about 900 milliliters (quart) were blow molded at an extrusion temperature of about 230C.
As controls, bottles of pure poiyethylene ~H~PE in Table, below) were, also, blow mol~ed in sizes and using equipment as will be described below. ~he mixture of polymers used in these examples was a~out 85 weight percent polyethylene, 12.5 weight percent polyamide, and 2.5 weight percent compatibilizer (INV in Table, below).
Bottles were tested for permeatlon and arop height.
The permeation test provides inalcation of the containing quality of bottle walls. The permeability test is conducted in accordance with 35 ASTM D-2684-73R79 wherein bottles are filled to 20 percent of their volume with xylene and are stored in circulating-air ovens at 60C and weighed periodically to determine xylene loss from the bottles. The weight loss is plotted against time and, from that plot, the rate of loss (R) is determined. The permeability factor (P) is determined from the following equation:
P = RT/A wherein R is the rate of loss as above-noted;
T is the average bottle wall thickness; and A is the bottle s~rface area.
The drop height test provides indication of wall strength in blow molded containers. The drop height test is conducted in accordance with ASTM
D-2463-74R83 wherein bottles filled with water are dropped to a solid flat floor surface in an order which involves decreasing the drop height by 0.3 meters after èach fall which results in failure and increasing the drop height by 0.3 meters after each fall where the dropped bottle does not fail. The first drop is made from about the expected height of failure and the mean failure drop height is calculated from a total testing of twenty dropped bottles.
The mean failure drop height can be 5 calculated as follows:
h - h + dt(A/N)I 1/2] wherein o h - mean failure drop height d = increment in height of drop N - number of failures or nonfailures, whichever is lesser.
ho = lowest height at which any of N occurs.
( hl) (nl)+(dh2) (n2)~- - (dhi) (ni) dhi is the number of increments apart from the height of ho and nl is the number of failures or nonfailures occurring at dhi.

129.'Z85(~

When failures are countea, the negative 1/~
is used. For counting nonfailures, the positive 1/2 is used.
Results are shown in the Table, below.
5 Example I II
Head Smooth Spiral Spiral Material INV HDPE INV
Bottle wt. (gm) 63.3 61.8 60.7 Permeation 4.11 176 1.2 Drop Height (m) 1.58 5.49 3.20 *Units for permeation are gram-mils per day-100 square inches.
It should be notea that Example I is useful as a comparison between bottles maae using a smoGtn extrusion head and bottles made using a spiral hea~
in accordance with this invention. Example II is useful as a comparison between bottles made using high density polyethylene (HDPE) and bottles made using the combination of component materials in accordance with this invention. Example 1 is data from testing bottles made in accordance with this invention.

Claims (20)

What is Claimed Is:

1. A laminar, molded, hollow, article comprising a combination of a first polymer component and a second polymer component incompatible with the first wherein the first polymer is present in the article as a continuous matrix phase and the second polymer is present in the article as thin, substantially two-dimensional, parallel and overlapping layers of material wherein knit lines in the article are curved to provide such overlapping layers in any radial section through a wall of the hollow article.

2. The article of Claim 1 wherein the first polymer component is a polyolefin.

3. The article of Claim 1 wherein there is also included an alkylcarboxyl-substituted polyolefin as a compatibilizer.

4. The article of Claim 1 in the form of a parison.

5. The article of Claim 1 in the form of a blow-molded container having a substantially uniform wall thickness around the perimeter of the container from the knit line area to areas adjacent the knit line area.

6. The article of Claim 1 wherein the first polymer component is present in the article as a continuous matrix phase and the second polymer component is present in the article as a discontinuous distribution of layers.

7. The article of Claim 6 wherein there is an alkylcarboxyl-substituted polyolefin present in the article between the matrix and the discontinuous layers and adheres the matrix and the discontinuous layers together.

8. The article of claim 2 wherein the second polymer component is a condensation polymer.

9. The article of Claim 8 wherein the condensation polymer is a polyamide or a polyester.

10. The article of Claim 8 wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene, and copolymers of those materials.

11. A laminar, moloed, hollow, article comprising a combination of 60-99.5 weight percent polyolefin, 0.5-40 weight percent of a condensation polymer incompatible with the polyolefin, and 0.1-10 weight percent of an alkylcarboxyl-substituted polyolefin wherein the polyolefin is present as a continuous matrix phase, the condensation polymer is present as a discontinuous distribution of thin, substantially two-dimensional, parallel and overlapping layers and wherein mold knit lines in the article are curved to provide such overlapping layers in any radial section through a wall of the hollow article.

12. A process for manufacturing a laminar, molded, hollow, article of polymeric material comprising the steps of: (i) establishing a molten, heterogeneous, blend of a first polymer component and a second polymer component incompatible with the first by heating the blend above the melting point of the highest melting polymer component and (ii) molding the melted blend to have a knit line curved through the thickness of the melted blend by (a) extruding a body of the melted blend through a die wherein internal surfaces of the die have streamlined irregularities positioned to displace surface material of the melted blend relative to core material of the melted blend and (b) cooling the extruded body to below the melting point of the lowest melting polymer component.

13. The process of Claim 12 wherein the first polymer component is a polyolefin.

14. The process of Claim 12 wherein there is also included an alkylcarboxyl-substituted polyolefin as a compatibilizer.

15. The process of Claim 12 wherein the extruded material of step (a) is blow molded into the shape of a bottle before the cooling of step (b).

16. The process of Claim 15 wherein the blow-molded bottle has a substantially uniform wall thickness from the knit line area to areas adjacent the knit line area.

17. The process of Claim 12 wherein the first polymer component is present in the molten blend as a continuous matrix phase and the second polymer component is present in the molten blend as a discontinuous phase.

18. The process of Claim 13 wherein the second polymer component is a condensation polymer.

19. The process of Claim 18 wherein the condensation polymer is a polyamide or a polyester.

20. The process of Claim 18 wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene, and copolymers of those materials.