CA1270451A - Apparatus and method for producing multi-layered laminates and improved multi-layered laminates produced therefrom - Google Patents
Apparatus and method for producing multi-layered laminates and improved multi-layered laminates produced therefromInfo
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- CA1270451A CA1270451A CA000599621A CA599621A CA1270451A CA 1270451 A CA1270451 A CA 1270451A CA 000599621 A CA000599621 A CA 000599621A CA 599621 A CA599621 A CA 599621A CA 1270451 A CA1270451 A CA 1270451A
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- parison
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Abstract
ATTRACT OF THE DISCLOSURE
The present invention provides a multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permeation losses, and formed by coextrud-ing in a molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said container having layers formed from said parison comprising a thermoplastic polyolefin layer; a layer functioning as a bar-rier layer to prevent product oxidation or product permeation loss, and a scrap layer, said scrap layer comprising a mixture of a regrind of all layers from previous containers of the same con-struction but said scrap layer not including the combination of scrap and an adhesive layer or bonding layer, said previous con-tainers comprising a thermoplastic polyolefin layer, a layer functioning as a barrier layer, and a scrap layer.
The present invention provides a multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permeation losses, and formed by coextrud-ing in a molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said container having layers formed from said parison comprising a thermoplastic polyolefin layer; a layer functioning as a bar-rier layer to prevent product oxidation or product permeation loss, and a scrap layer, said scrap layer comprising a mixture of a regrind of all layers from previous containers of the same con-struction but said scrap layer not including the combination of scrap and an adhesive layer or bonding layer, said previous con-tainers comprising a thermoplastic polyolefin layer, a layer functioning as a barrier layer, and a scrap layer.
Description
This invention relates ko apparatus and method for forming a multi-layered parison containing at least two rela-tively thin layers and one rela-tively thick layer. The parison may be employed for th~ formation of containers such as bottles and the like by blow molding.
This application is a divisional application of copend-ing application No. 427,503 filed May 5, Ig83.
Multi-layered laminate structures have long been used to make containers for a variety of products wherein, due to industrial requirements and specifications, it is not possible to use containers made from a single plastic material. In packaging foods, liquids such as various juices, sanitary articles and a host of other products, the container wall must withstand attack by oxygen or some of the ingredients of khe packaged product which often tend to permeate through the container wall.
It has, by now, become well known to make multi-layered laminate structures from thermoformable plastics and to make con-tainers therefrom by in~ection molding or blow molding tech-nlques, and numerous thermoplastic resins have been disclosed and recommended for this purpose. Some of these thermoplastics mate-rials and the composite laminated structures made therefrom are ~5 described in United States Patent Nos. 3,560,325; 3,595,740;
3,882,259; 3,955,697; 4,182,457 and 4,234,663, to cite a few.
As mentioned in United States Patent No. 4,234,663, which issued to Catte et al on November 18, 1980, when multi-layer foil structures are used to make containers by thermoform-ing of the foil, a considerable amount of "scrap" is obtained which may be as high as 50% of the total weight of the initially coextruded material. If the scrap cannot be included in the multi-layered laminate structure, it constitutes a waste which must be disposed of with consequent economic disadvantages.
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In thei~ aforementioned patent, Catté et al disclose reintroduction of at least part of the scrap into the multi-layer foil structure as a "supplemen-tary" layer. The scrap-containing layer of Catte et al, however, is constituted by a mixture of the scrap with sufficient amounts of adhesive, which is a graft copolymer of a styrenic monomer on a polyolefinic substrate.
In an article by Muneki Yamada entitled ~Orien-ted Multi-Layer Containers for Food: Solid Phase Pressure Formed Cups and Stretch-Blow Molded sottles~, presented on March 17-19, 1981 at the "5th Annual International Conference on Oriented Plastic Containers~, the author discusses the technology of solid phase pressure forming and stretch-blow molding in the manufacture of multi-layer containers. with reference to Figures 2 and 3, the 1~ author describes a 7-la~er structure which comprises a scrap layer interposed between a polypropylene layer and an adhesive layer with no significant reduction in clarity (transparency of the containers) provided the thickness of the scrap layer is within certain critical thickness ratio to the other layers.
At page 5, the Yamada article refers to United States Patent No. 4,182,457 for making "oriented~' containers. This patent, however, is basically concerned with making transparent containers obtained by orienting the thermoplastic polyolefin olefin layer during stretch blow molding of the parison.
So far as it is k~nown, there is not, at the present, a totally satisfactory method of utilizing all the scrap in making a satisfactory multi-layer laminate for forming containers.
Various apparatus for forming a multi-layered parison and blow molding the parison into a container of the desired shape are known. See, for example, United States Patent Nos.
4,047,868; 4,297,092; 3,802,826; 3,447,20~; 3,478,139; 3,546,743;
4,042,661; 4,125,585; 4,134,952; 4,152,104 and 4,281,981. The common features of these apparatuses include an annular discharge .
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flow passageway formed be-tween a cylindrical flow tube an~ a ~ie body, an annular discharge orif.ice at the downstream end o~ the annular discharge flow passageway through which the parison or multi-layered laminate structure is extruded, feed passageways which supply resin material to the apparatus for an individual resin layer and connecting passageways which join the feed pass-ageways to the annular discharge flow passageway at junctions where an individual resin layer is added to the multi-layered laminate flowing from upstrearn of the junction.
In U.S. 4,0~7,868 the use of pressure rings to control the relative flow of resin material in the connecting passageways and the thickness of the individual layers is taught. Use of annular accumulation chambers to distribute ma-terial flowing into the feed passageways circumferentially to form more uniform lay-ers is taught in U.S. 4,297,092; 4,152,10~; 4,042,661; 3,546,743;
3,478,139 and 3,447,204. Rotation of the die body about the man-drel to provide more uniform layers is described in U.S.
3,802,826. Methods of controlling thickness and concentricity of the layers are taught in U.S. 4,047,~68, 3,546,743 and 3,446,204.
A principal object of the various apparatus of the sev-eral patents mentioned above was to produce multi-layered struc-tures with good roll geometry, that is a gauge thickness of sub-stantially uniform depth across the width. Another ob~ect was toprovide uniform deposition of a relatively thin molten layer of polymer onto a relatively thick molten layer of polymer under conditions of laminar flow without causing turbulence leading to fusion of the molten layers, uneven laydown of one layer upon the other or aberations which ultimately lead to delaminations when the finished product is sub;ected to mechanical stress.
These problems become particularly difficult when a relatively thin layer is to be laminated to a relatively thick layer. It is nonetheless important to be able to form lamina-tes including one or more thin layers. For example, a container ~7~5~
might be formed with an inner layer, an a~hesive layer an~ an oxygen barrier layer. The inner layer may be forme~ with a ther moplastic polyolefin, the adhesive layer with a carboxylic acid modified polyolefin and the barrier layer (if oxygen is to be excluded) of a saponified copolymer of ethylene and vinyl acetate. The first mentioned polymers are rela-tively inexpen-sive. The last-mentioned polymers are specialty chemicals and quite expensive. For economic reasons, therefor, it is important that the expensive polymers be laid down in thin layers. It is e~ually important for in use performance that the thin layers have good roll geometry, that they completely cover the thick layer and that there be no weak areas subject to delamination under mechanical stress. These ends are difficult to achleve in conven~ional equipment utilized for the preparation of parisons lS for blow molding.
The present invention provides a multi-layer laminate structure including a distinct and separate layer of scrap pro-duced from the coextrudate formed during coextrusion of the dif-~erent layers of several thermoplastic materials.
The present invention also provides a method for effi-cient and economical utilization of the scrap when making con~
tainers from multi-layer laminate structure comprising several thermoplastic materials.
) The present invention again makes packaging containers from multi-layer laminated structures which include a scrap layer, wherein the container has, inter alia, excellent resis-tance to oxygen permeability and transparency.
The present invention also provides improved apparatus for making a multi-layered parison for blow molding which pro-duces parisons reliably despite variations in the thickness of the layers~
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The invention fur-ther provides an irnproved appara-tus for producing multi-layered structures wi-th layers o~ uniform thickness and concentricity.
In copending application No. 427,503 there is disclosed and claimed an apparatus for producing multi-layer parisons of polymeric materials wherein at least two of said layers are rela-tively thin compared to at leas-t one other layer, said appara-tus comprising means including a tubular channel for forming a rela-tively thick layer of a first polymeric material and laminate forming means for forming a laminate of at least two thin layers around the surface of the thick layer of polymeric material, sald laminate forming means including a segmented die block, each seg-ment being formed with a polymeric accumulation reservoir, the die block being formed aro~md said tubular channel and having a first passageway narrower than said tubular channel, said first passageway leading from an accumulation reservoir in a first seg-ment and being adapted to be charged with a second polymeric material from said accumulation reservoir, and said die block having a second passageway leading from an accumulation reservoir in a second segment and adapted to be charged wlth a third poly-meric material from said accumulation reservoir; said first and second passageways being defined between facing surfaces o~ adja-cent segments, said second passageway merging withln said first passageway to form in said die block a laminate composed of said second and third polymeric material, said first passageway there-after leading to said tubular channel whereby said laminate can be fed around said first polymeric material in said tubular chan-nel.
The copending application also discloses and claims an apparatus for producing multi-layer parisons for blow molding wherein at least two of the layers are relatively thin cornpared to at least one other relatively thick layer, the apparatus com-prising: a. a hollow flow tube having a hollow cor~ pin at itsforward end portion forming a hollow unit, b. a segmented die .. . ........
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block comprising an extrusion die block segmen-t at the end por-tion of the apparatus formed with an interior surface surrounding the core pin, but spaced apart therefrom to form a delivery chan-nel for the flow of multiple layers of polymers, the extrusion die block segment also being formed with an annular opening at its ~orward portion which surrounds, but is spaced from the for-ward position of the core pin to form an annular opening through which the multi-layer parison exits the apparatus, and c. a plu-rality of subextrusion die block segments vertically located behind the extrusion die block segment comprising at least one principal subextrusion die block segment -Eormed with an annular opening of larger diameter than the diameter of the flow tube and surrounding the flow tube to ~orm a principal tubular channel for flow of a first layer of polymeric material into the delivery channel, and at least two adjacent auxiliary subextrusion die block segments each formed with an accumulation reservoir, there being a first passageway narrower than the principal tubular channel leading from an accumulation reservoir in a first subex-trusion die block segment and adapted to be charged with a second polymeric material from said accumulation reservoir and a second passageway leading from an accumulation reservoir in a second subextrusion die block segment and adapted to be charged with a third polymeric material from said accumulation reservoir in said second subextrusion die block segment; said first and second pas-sageways being defined between facing surfaces of ad~acent subex-trusion die block segment, said second passageway merging with said first passageway, and said first passageway therea~ter lead-ing to said principal tubular channel, whereby a laminate can be formed in said auxiliary subextrusion die block segments composed o~ said second and third polymeric material and thereafter fed completely around said first polymeric material in said principal tubular channel.
According to one aspect thereof there is provided a multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permeation losses, formed by coextruding in a molten s-tate a plurality of plas-tic layers to form a parison, ~orm:ing said parison into a container by blow-molding, said container having a plurality of layers formed from said parison comprising an inner thermoplastic poly-olefin layer which is next to the product; an outer thermoplasticpolyolefin layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture o~ a regrind of all the layer~ from previous contalners of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
The invention also provides a process for making a multi-layer plastic container which comprises coextruding in the molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said con-tainer having a plurality of layers formed from said parison com-prising an inner thermoplastic polyolefin layer which is next to the product; an outer polyolefin thermoplastic layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
According to another aspect thereof the present inven-tion provides a multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to perme-ation losses, said container being formed by internal blow~mold-ing of a multi-layer tubular parison, said tubular parison having a plurality of layers coextruded in the molten state through a plurality of dies to form a parison with layers which are there-after expanded by internal blow-molding said tubular parison into . .
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a mold having the shape of the container, said plurality of lay ers of said container including an inner thermoplastic polyolefin layer which is next to the product, an outer thermoplastic poly-olefin layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of re~rind of all the layers from previous con-tainers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one a~hesive layer to adhere said barrier layer to at least one of the other layers.
The present invention again provides a process of mak-ing multi-layer plastic containers which comprises coextruding in the molten state a plurality of plastic layers through a plural-ity of dies to form a tubular parison, having a plurality of lay-ers, internally blow-molding said parison to form a container, said container having a plurality of layers formed from said parison comprising an inner thermoplastic polyolefin layer which is next to the product; and outer polyolefin thermoplastic layer;
a barrier layer to prevent product oxidation or product perme-ation loss; a scrap layer lncluding a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers. Suitably said adhe-sive is comprised of maleic anhydride-modified polypropylene.
Desirably a second adhesive layer adheres said scrap layer to said inner thermoplastic layer.
The invention again provides a multi-layer parison blow-molding plastic container comprising a container-shaped structure having a multi-layer translucent laminate wall with an outer thermoplastic polyolefin layer; an inner ther~noplastic polyolefin layer and an intermediate barrier layer; a first adhe-sive layer for adhesively joining said inner thermoplastic poly-olefin layer to said barrier layer; a scrap layer interiorly ofsaid outer thermoplastic polyolefin layer and a second adhesive layer for adhesively joining said scrap layer to said barrier layer, wherein said scrap layer includes a mixture of a regrind of all the layers from previous containers of the same construc-tion, said previous containers comprising inner and outer thermo-plastic polyolefin layers, a barrier layer, adhesive layers and a scrap lay~r. Suitably said adhesive ls comprised of maleic anhydride-modified polypropylene. Desirably said inner and outer thermoplastic layers are made of polypropylene or random copoly-mer of propylene and ethylene containing up to about 2 mol percent ethylene.
The present invention again provides a multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permea-tion losses, and formed by coextruding in a molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said container having layers formed from said parison comprising a thermoplastic polyolefin layer; a layer functioning as a barrier layer to prevent product oxidation or product perme-ation loss; and a scrap laye~, said scrap layer comprising a mix-ture of a regrind of all layers from previous containers of the same construction but said scrap layer not including the combina-tion of scrap and an adhesive layer or bonding layer, said previ-ous containers comprising a thermoplastic polyolefin layer, a layer functioning as a barrier layer, and a scrap layer. Suit-ably the container is formed from said parison so as to be translucent. Desirably said parison is blow molded into a translucent container having a neck portion and a body portion and wherein said neck portion has a smaller cross-sectional area than the cross-sectional area of the body portion. Preferably the container further includes an adhesive layer. Suitably said thermoplastic polyolefin layer is made of polypropylene or random copolymer of propylene and ethylene containing up to about 2 mol percent ethylene.
_ g _ , The present invention again provides a process of mak-ing multi-layer plastic containers which comprises coextruding in the molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-moldin~, said con-tainer having a plurality of layers formed from said parison com-prising thermoplastic polyolefin layer; a layer functioning as a barrier layer to prevent product oxidation or product permeation loss; and a scrap layer, said s~rap layer comprising a mixture of a regrind of all the layers from previous parison blow-molded containers of the same construction but said scrap layer not including the combination of scrap and an adhesive layer or bonding layer, said previous containers comprising a thermo-plastic polyolefin layer, a layer functioning as a barrier layer, and a scrap layer.
A multi-layer laminate structure is also provided which includes a separate layer of scrap made from regrind of the extrudate of the various resins used in making the laminate structure. Preferably, the mul-ti-layer laminate structure com-prises an outer thermoplastic polyolefin layer, an inner thermo-plastic polyolefin layer and an intermediate oxygen barrier layer. The outer and inner polyolefin layers are preferably made of polypropylene, particularly crystalline isotactic polypropy-lene and the intermediate barrier layer is preferably made of ethylene-vinyl alcohol copolymer. A first adhesive layer bonds the inner polyolefin layer to the intermediate barrier layer. A
separate scrap layer may be disposed interiorly of the outer polyolefin layer and a second adhesive layer bonds this scrap layer to the intermediate barrier layer. Alternatively, the sep-arate scrap layer may be interposed between the inner polyolefinlayer and the second adhesive layer, or it may be interposed at both of said positions.
In order to make a container, the multi~layer structure is coextruded into a parison tube which is then placed in a blow mold and inflated by injection of air, under pressure, to form ~o~
the container.
This invention also provides improved blow-molding apparatus for formation of parisons for blow molding into con-tainers of any desired shape.
The apparatus is especial~y useful for the pre~arationof the preferred multi-layered structures of this invention.
The present invention will be made more apparent by reference to the accompanying drawings, in which:-Figure 1 is a sectional view of a preferred embodiment of the novel apparatus of this invention for forming multi-lay-ered parisons;
Figure 2 is an enlarged sectional view of the preferred embodiment shown in Figure l;
Figure 3 is a schematic illustration of an apparatus of this invention which particularly illustrates its principal fea-tures; and Figure 4 is a schematic sectional view illustrating the arrangements of the various layers of a six layer laminate struc-ture, including a separate scrap layer, made in accordance with a preferred embodiment of this invention.
According to the broad principles of this invention, the several layers are first coextruded to form a parison tube which is then molded and shaped into the desired container form.
It must bQ mentioned, however, that the formation of the parison tube and the container are well known techniques in the plastic industry. For example, one such method is described in United States Patent No. 4,079,~50 wherein a multi-layer resin in the molten state is coextruded to form a parison. A pair of split ~7~
molds are disposed around the parison and the split molds have such a configuration that when they are in register with each other, they define a cavity which corresponds to the shape of the desired container. ~y injecting air, under pressure, the parison is blow molded to form the container.
In its broadest aspec-ts, the appara-tus of this inven-tion comprises extrusion molding apparatus in which two or rnore relatively thin layers of polymeric material are formed inko a laminate within the apparatus before being joined to one or more relatively thick layers. The principle of the invention will be well understood by reference to Figure 3. For convenience, the various parts of the apparatus will be broadly defined with ref-erence to Figure 3 and only the principal parts will be identi-fied. They will be more specifically defined with reference tothe other Figures.
Figure 3 schematically represents an apparatus of the invention including a segmented die block with an extrusion die block segment 201; principal subextrusion die block segments 202,203 and 204; subextrusion die block segments 205,206 and 207.
There is a hollow central flow tube 208 terminating in a core pin 209, the end portion of which terminates at an orifice 210 in the extrusion block 201. There is a principal tubular channel 211 around the flow tube communicating with a delivery channel 212 and with various passageways for polymer materials to be described hereinafter.
The schematic of Figure 3 is designed to produce a pre-ferred laminated structure 100 of this invention illustrated in Figure 4. In Figure 4 there is an inner thermoplastic polyolefin layer 105 and progressing outwardly a first adhesive layer 109, an oxygen barrier layer 107, a second adhesive layer 113, a scrap layer 111, and an outer thermoplastic polyolefin layer 103. The inner and outer layers and the scrap layers may be regarded as stnlctural layers and, as will be seen, they are relatively thick, of the order of 12 to 1~ mils. The adhesive and barrier layers are relatively thin, i.e. 0.5 to 2 mils. A particular advantage of the apparatus of this invention is -tha-t it makes it possible to form extremely thin layers completely around a faci.ng surface of relatively thick layers in a uniform manner while avoiding the problems aforesaid.
Reverting now to Figure 3, the inside structural layer is formed from a polymer in principal subextruder die block 204 which is formed with a polymer accumulation reservoir 213. There is a passageway 214 leading from the reservoir to the principal tubular channel 211. Adhesive layer 109 is extruded from auxil-iary subextrusion die block 206 with accumulation reservoir 217 and second passageway 218 which leads i.nto first passageway 216.
The second adhesive layer 113 is extruded from auxiliary subex-trusion die block 205 with accumulation reservoir 219 and third passageway 220 leading to first passageway 216.
After the ~uncture of first passageway 216 and thlrd passageway 220, the first passageway ~oins the principal tubular channel. There is thus formed within the extrusion apparatus a laminate composed of the thin adhesive layers and the barrier layer. This laminate is brought into confluence with the thick inner layer within the extrusion apparatus.
The scrap layer 111 is extruded from principal su~ex-truder 203 formed with accumulation reservolr 221 and passageway 222. It forms a junction with the principal tubular channel 211 at junction 223.
The principal tubular channel joins the delivery chan-nel 212 and the six layered parison exits the apparatus around pin 209 through exit orifice 210.
~s will be explained more fully hereinafter, in pre-ferred embodiments o~ th2 inven-tion the flow tube is pro-grammable, that is it can move vertically wi-thin a fixed -tube or mandrelO The size of the orifice 210 can also be adjusted.
The invention will now be explained in more detall with reference to Figures 1 and 2. While the description wlll refer principally and for purposes of illustration to the preferred embodiments, -those skilled in the art will recognize that many variations from the embodiments actually described are possible without varying from the spirit or scope of the invention. For example, certain of the layers, such as the scrap layer or the outside layer can be omitted. The apparatus can be arranged to form a three layered structure of thick structural layer and thin adhesive and barrier or other layer. The apparatus can be arranged so that the thick layer is the inner or the outer layer.
More principal subextruders can be added to the vertically arranged subextruder column to form laminated structures with more than six layers.
The preferred embodiment of the novel apparatus 1 for forming the multi-layered parison tube of this invention shown in Figures 1 and 2 comprises a segmented die block including a set of principal and auxiliary subextruders 7,3,4,5,6 and 8 mounted vertically in order from bottom to top to define a longitudinal direction on an adapter block 10 and substantially cylindrical mandrel 14 passing through coinciden-t central holes in extruders 7,3,4,5,6 and ~ and adapter block 10. The annular space between mandrel 14 and -the extruders 7,3,4,5,6 and 8 defines a principal annular discharge channel 40 through which the multi-layered lam-inate flows. The'mandrel 14 is cylindrical and has a concentriccentral cylindrical cavity through which a programming flow tube 15 passes. The flow tube is vertically moveable within the man-drel. A blow pin 11 is mounted at the downstream end portion of mandrel 14 on cylindrical pin holder 12 which is attached directly to programming flow tube 15. The pin holder 12 is held ln position by pin holder sleeve 13 a-ttached to the downstream , .
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end of mandrel 14. There is thus defined a hollow unit throuyh which air or oth~r gas may be forced to blow mold the parison.
A principal subextruder 8 comprises the downstream end of the segmented die block and, as shown, consists of an upstream cylindrical portion of substantially greater radius than a down-stream portion. The exterior surface of the end portion of top block 8 is threaded to engage and hold an end cap 26 which con-sists of a cylindrical pipe portion whose bottom interior surface is threaded and an interiorly directed top lip. A bushing rlng 21 which forms a seat for bushing 19 is conformed to be held in place by end cap 26. Bushing 19 has a central interior nozzle cavity and central annular orifice 23 surrounding but spaced from the blow pin 11 to form an exit orifice through which the multi-layered laminate can be extruded.
The cylindrical, central cavity of top extruder 8 hasadditionally three pipe-shaped pieces, a bushing adapted 24, top adapter sleeve 28, and bottom adapter sleeve 30 mounted therein in tandem from top to bottom whose interior surfaces together with the exterior surface of the mandrel 14 define the downstream portion or delivery channel of the principal tubular discharge channel 40~
he downstream end of bushing adapter 24 abuts against bushing 19 and bushing ring 21. The concentricity of the extru-date may be partially controlled by an axially disposed adapter set screws 31 passing through top block 8 to press against bush-ing adapter 24.
In the pre~erred embodiment shown, a central longitudi-nal air shaft 17 passes through programming flow tube 15, pin holder 12, and blow pin 11 and provides a means by which air or other vapor is introduced to prevent the parison walls from col-lapsing during extrusion and to blow mold the parison.
Eac~ of subex-truder die blocks 6~5,~,3 and 7 comprises a cylindrical bottom portion with a central hole therein and a downstream extending sleeve top portion so conformed ko fit into the cylindrical bottom portion of the adjacent extruder or sub-extruder so as to form annular accumulation reser~oirs 48,47,46, 45,44 and 43 in the segmented die block to hold the melted ther-moplastic resin material used for each individual layer of the six-layered laminate. Resin material is fed to the reservoirs 48,47,46 ~ 45, 44 and 43 from an external source which is not shown.
The resin is distributed circumferentially by feed passageways, flow blocks 6,5,4, 3 and 7 and adapter block 10. The annular accumulation reservoir 48 in principal subextruder die block 6 is fed by feed passageway 24 having an axially disposed inlet in adapter block 10. Annular accumulation reservoir 43 formed between flow sleeve 2 and principal subextruder die block 6 is fed by feed passageway 23.
The feed passageway can be e~uipped with a regulating system such as pressure transducer 90 and a choke pin 92 mounted in choke pin adapter 93 for regulating the flow rate of polymeric material. The accumulation reservoirs 43,~7 and 48 are connected directly to the principal tubular discharge flow channel 40 by annular connecting passageways 50,57 and 58. However, annular discharge reservoirs 44,45 and 45 are connected to an auxiliary discharge flow channel 42 which leads to principal tubular flow channel 40 by annular connecting passageways 52,53 and 55.
Auxiliary discharge flow channel 42 is substan-tially smaller in diameter than principal tubular flow channel 40 into which it is connected. The use of an auxiliary discharge flow channel 42 allows preforming a three-layered laminate consisting of two adhesive layers and a barrier layer which may be formed completely around the inner layer without causing imperfectlons in the final produc-ts.
It will be understood from the description and from the ~7~
Figures that the accumulation reservoirs and -the polymer passaye-ways leadin~ from the accumulation reservoirs to the first or auxiliary passageways and to the principal tubular channel 40 ma~
be defined by facing surfaces of ad~acent extruders. They may be, however, conveniently formed in the blocks themselves. This is especially true of the accumulation reservoirs.
The passageways are tapered~ i.e. the diameter of the downstream end is less than that of the end closer to the accumu-lation reservoirs. Therefore, the pressure of the molten polymerat the downstream end is greater than at the upstream end. As a result, the stream of molten resin becomes laminar flow so that t~lere is reduced turbulence as each polymer stream joins another polymer stream.
Heat may be supplied to the die block by any convenient means. The extruders and subextruders may be insùlated by ceramic bands 39,38,37,36,35,34,33 and 32 as shown. Thermo-couples may be mounted in the extruders and subextruders 8,6, 5,4,3 and 7; for example, thermocouple 85 is mounted in adapter 86 and senses the temperature in principal subextruder 8 and thermocouple 83 ln adapter 84 senses the temperature in au~iliary subextruder 5.
The blow pin 11 is also positioned by a pin orientation bar 75 axially attached to and holding the programming flow tube 15 by bar adapter 77. Orientation bar 75 is held in position by clamp pin 79 and bar adapter 77 is supported on the bottom of adapter block 10 by cylindrical flanged bushing 70 attached to a mounting plate 60 which is fixed to adapter block 10 by mounting bolt 63. Air may be admitted to air shaft 17 by means of the couplet 80 which passes air to the end of programming flow tube 15 through bar adapter 77 from air inlet 82.
Movement of programming flow tube 15 withln mandrel 14 may be controlled by an electronic parison programmer 65, for : : ''; ' :
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':.. ,. " , examp~e, a Hunker (trademark) Programmer available from Hunker Acroboratories, Inc. The programmer 65 is attached to programmer base plate 66 which is connected to mounting plate 60 by tie rods 62.
In the preferred practice o* this invention as illus-trated in Figure 4, the laminate struc-ture has an in-termediate gas and oxygen barrier layer of e-thylene-vinyl alcohol copolymer, outer and inner structural layers of a thermoplastic polyol~fin, a separate scrap layer adjacent to the outer polyolefin layer and two adhesive layers, one interposed between the intermediate barrier layer and the scrap layer, and the other is interposed between the intermediate barrier layer and the inner polyolefin layer.
The polyolefins which are suitable in forming the outer and inner layers of the laminate s-tructure are thermoplastic olefinic polymers such as e.g., high and low density polyethy-lene, polypropylene and blends of these.
Both adhesive layers are preferably made of maleic anhydride modified polypropylene wherein the polypropylene back-bone is modified with maleic anhydride moieties. One such adhe-sive is available from Mitsui, Japan, under the trademark ADMER
QB 530. In general, however, polypropylene modified with ethylenically unsaturated carboxylic anhydrides may be used as the adhesive layers for the present laminate structure.
It must be mentioned that the aforementioned adhesives are particularly well suited when polypropylene or propyleneethy-lene random copolymers constitute the outer and inner structural layers. However, when this layer is made of polyethylene, it is preferable to use a different adhesive such as, for example, the Plexar (trademark) adhesives manufactured by Chemplex Company, Rolling Meadows, Illinois. These adhesives are a blend of e-thy-lene-vinyl acetate copolymer and a graft copolymer of polyethy--- 1~ --.'~ ~, ., . .
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lene and a dicarboxylic acid anhydride.
The scrap layer is made of regrind of the coextrudatesof the differen-t thermoplastic layers used to form the parison tube. The nature of the scrap and its incorporation into the laminate structure will hereina~ter be described in detail in connection with the description of the process of this invention.
As mentioned above, the multi-layer laminate structure generally designated as 100 has an outer polyolefin s-tructural layer 103, an inner polyolefin structural layer 105 and an inter-mediate oxygen barrier layer 107. The inner polyolefin layer 105 is adhesively bonded to the intermediate barrier layer 107 by the adhesive layer 113.
All the layers are coextensively bonded along their respective junctions with no interlaminar separation between the respective layers of the laminate structure.
In order to form the laminate structure, the thermo-plastic resins used to make the different layers are coextruded in the molten state through an extrusion apparatus, preferably an embodiment of the apparatus described herein, to form the parison tube. The parison tube is then blow molded by in~ection of air or other vapor, under pressure, and is shaped into a container in a separate container mold. The excess materials from this blow molding operation are ground up and mixed as a homogeneous scrap and the scrap layer is reintroduced into the laminate structure.
As a practical matter, therefore, the process and appa--ratus of this invention permits utilization of all the scrap pro-duced during the container forming operations. Accordingly, the economy of the operation is considerably improved and waste dis-posal is virtually eliminated.
In addition to improving the economy of operation and -- lg --' ~7~
reduction of waste disposal, it has been found that inclusion of a separate scrap layer in the multi-layer laminate structure does not detract from the transparency of unoriented containers made of such laminate structures. The ability to make transpar0nt containers by non-oriented blow molding of a multi-layer laminate structure having a comple-tely separate layer of scrap constitutes a novel and surprising feature of the present invention.
While the invention has heretofore been described with a certain degree of particularity and illustrated by a 6-layer laminate structure, several changes and modi~ications are sug-gested from the foregoing disclosure which are nevertheless within the scope and contemplation of this invention. For example, additional layers may be used for decorative purposes or otherwise and more than one scrap layer can be reintroduced into the laminate structure, if desired.
It is also within the contemplation of this invention to make a 5-layer laminate structure, and to form containers therefrom as aforesaid. In this construc-ticn, the scrap layer may constitute the outer layer and the outer polyolefin layer may be eliminated.
Additionally, if desired, the scrap layer may be inter-posed between the inner polyolefin layer and the second adhesivelayer, or two scrap layers may be incorporated in the laminate structure; one interposed between the outer polyolefin layer and the first adhesive layer, and the other is interposed between the inner polyolefin layer and the second adhesive layer.
Containers having excellent oxygen barrier properties and good transparency can be made by varying the relative thick-nesses of the different layers. For example, excellent barrier properties and good transparency can be obtained from the multi-layer structure of this invention when the thickness of the ethy-lene-vinyl alcohol layer is between about 0.5 to about 2 mils and , ,.~ .
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the scrap layer constitutes up to about 40 weight percent of the total extrudate.
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This application is a divisional application of copend-ing application No. 427,503 filed May 5, Ig83.
Multi-layered laminate structures have long been used to make containers for a variety of products wherein, due to industrial requirements and specifications, it is not possible to use containers made from a single plastic material. In packaging foods, liquids such as various juices, sanitary articles and a host of other products, the container wall must withstand attack by oxygen or some of the ingredients of khe packaged product which often tend to permeate through the container wall.
It has, by now, become well known to make multi-layered laminate structures from thermoformable plastics and to make con-tainers therefrom by in~ection molding or blow molding tech-nlques, and numerous thermoplastic resins have been disclosed and recommended for this purpose. Some of these thermoplastics mate-rials and the composite laminated structures made therefrom are ~5 described in United States Patent Nos. 3,560,325; 3,595,740;
3,882,259; 3,955,697; 4,182,457 and 4,234,663, to cite a few.
As mentioned in United States Patent No. 4,234,663, which issued to Catte et al on November 18, 1980, when multi-layer foil structures are used to make containers by thermoform-ing of the foil, a considerable amount of "scrap" is obtained which may be as high as 50% of the total weight of the initially coextruded material. If the scrap cannot be included in the multi-layered laminate structure, it constitutes a waste which must be disposed of with consequent economic disadvantages.
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In thei~ aforementioned patent, Catté et al disclose reintroduction of at least part of the scrap into the multi-layer foil structure as a "supplemen-tary" layer. The scrap-containing layer of Catte et al, however, is constituted by a mixture of the scrap with sufficient amounts of adhesive, which is a graft copolymer of a styrenic monomer on a polyolefinic substrate.
In an article by Muneki Yamada entitled ~Orien-ted Multi-Layer Containers for Food: Solid Phase Pressure Formed Cups and Stretch-Blow Molded sottles~, presented on March 17-19, 1981 at the "5th Annual International Conference on Oriented Plastic Containers~, the author discusses the technology of solid phase pressure forming and stretch-blow molding in the manufacture of multi-layer containers. with reference to Figures 2 and 3, the 1~ author describes a 7-la~er structure which comprises a scrap layer interposed between a polypropylene layer and an adhesive layer with no significant reduction in clarity (transparency of the containers) provided the thickness of the scrap layer is within certain critical thickness ratio to the other layers.
At page 5, the Yamada article refers to United States Patent No. 4,182,457 for making "oriented~' containers. This patent, however, is basically concerned with making transparent containers obtained by orienting the thermoplastic polyolefin olefin layer during stretch blow molding of the parison.
So far as it is k~nown, there is not, at the present, a totally satisfactory method of utilizing all the scrap in making a satisfactory multi-layer laminate for forming containers.
Various apparatus for forming a multi-layered parison and blow molding the parison into a container of the desired shape are known. See, for example, United States Patent Nos.
4,047,868; 4,297,092; 3,802,826; 3,447,20~; 3,478,139; 3,546,743;
4,042,661; 4,125,585; 4,134,952; 4,152,104 and 4,281,981. The common features of these apparatuses include an annular discharge .
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flow passageway formed be-tween a cylindrical flow tube an~ a ~ie body, an annular discharge orif.ice at the downstream end o~ the annular discharge flow passageway through which the parison or multi-layered laminate structure is extruded, feed passageways which supply resin material to the apparatus for an individual resin layer and connecting passageways which join the feed pass-ageways to the annular discharge flow passageway at junctions where an individual resin layer is added to the multi-layered laminate flowing from upstrearn of the junction.
In U.S. 4,0~7,868 the use of pressure rings to control the relative flow of resin material in the connecting passageways and the thickness of the individual layers is taught. Use of annular accumulation chambers to distribute ma-terial flowing into the feed passageways circumferentially to form more uniform lay-ers is taught in U.S. 4,297,092; 4,152,10~; 4,042,661; 3,546,743;
3,478,139 and 3,447,204. Rotation of the die body about the man-drel to provide more uniform layers is described in U.S.
3,802,826. Methods of controlling thickness and concentricity of the layers are taught in U.S. 4,047,~68, 3,546,743 and 3,446,204.
A principal object of the various apparatus of the sev-eral patents mentioned above was to produce multi-layered struc-tures with good roll geometry, that is a gauge thickness of sub-stantially uniform depth across the width. Another ob~ect was toprovide uniform deposition of a relatively thin molten layer of polymer onto a relatively thick molten layer of polymer under conditions of laminar flow without causing turbulence leading to fusion of the molten layers, uneven laydown of one layer upon the other or aberations which ultimately lead to delaminations when the finished product is sub;ected to mechanical stress.
These problems become particularly difficult when a relatively thin layer is to be laminated to a relatively thick layer. It is nonetheless important to be able to form lamina-tes including one or more thin layers. For example, a container ~7~5~
might be formed with an inner layer, an a~hesive layer an~ an oxygen barrier layer. The inner layer may be forme~ with a ther moplastic polyolefin, the adhesive layer with a carboxylic acid modified polyolefin and the barrier layer (if oxygen is to be excluded) of a saponified copolymer of ethylene and vinyl acetate. The first mentioned polymers are rela-tively inexpen-sive. The last-mentioned polymers are specialty chemicals and quite expensive. For economic reasons, therefor, it is important that the expensive polymers be laid down in thin layers. It is e~ually important for in use performance that the thin layers have good roll geometry, that they completely cover the thick layer and that there be no weak areas subject to delamination under mechanical stress. These ends are difficult to achleve in conven~ional equipment utilized for the preparation of parisons lS for blow molding.
The present invention provides a multi-layer laminate structure including a distinct and separate layer of scrap pro-duced from the coextrudate formed during coextrusion of the dif-~erent layers of several thermoplastic materials.
The present invention also provides a method for effi-cient and economical utilization of the scrap when making con~
tainers from multi-layer laminate structure comprising several thermoplastic materials.
) The present invention again makes packaging containers from multi-layer laminated structures which include a scrap layer, wherein the container has, inter alia, excellent resis-tance to oxygen permeability and transparency.
The present invention also provides improved apparatus for making a multi-layered parison for blow molding which pro-duces parisons reliably despite variations in the thickness of the layers~
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The invention fur-ther provides an irnproved appara-tus for producing multi-layered structures wi-th layers o~ uniform thickness and concentricity.
In copending application No. 427,503 there is disclosed and claimed an apparatus for producing multi-layer parisons of polymeric materials wherein at least two of said layers are rela-tively thin compared to at leas-t one other layer, said appara-tus comprising means including a tubular channel for forming a rela-tively thick layer of a first polymeric material and laminate forming means for forming a laminate of at least two thin layers around the surface of the thick layer of polymeric material, sald laminate forming means including a segmented die block, each seg-ment being formed with a polymeric accumulation reservoir, the die block being formed aro~md said tubular channel and having a first passageway narrower than said tubular channel, said first passageway leading from an accumulation reservoir in a first seg-ment and being adapted to be charged with a second polymeric material from said accumulation reservoir, and said die block having a second passageway leading from an accumulation reservoir in a second segment and adapted to be charged wlth a third poly-meric material from said accumulation reservoir; said first and second passageways being defined between facing surfaces o~ adja-cent segments, said second passageway merging withln said first passageway to form in said die block a laminate composed of said second and third polymeric material, said first passageway there-after leading to said tubular channel whereby said laminate can be fed around said first polymeric material in said tubular chan-nel.
The copending application also discloses and claims an apparatus for producing multi-layer parisons for blow molding wherein at least two of the layers are relatively thin cornpared to at least one other relatively thick layer, the apparatus com-prising: a. a hollow flow tube having a hollow cor~ pin at itsforward end portion forming a hollow unit, b. a segmented die .. . ........
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block comprising an extrusion die block segmen-t at the end por-tion of the apparatus formed with an interior surface surrounding the core pin, but spaced apart therefrom to form a delivery chan-nel for the flow of multiple layers of polymers, the extrusion die block segment also being formed with an annular opening at its ~orward portion which surrounds, but is spaced from the for-ward position of the core pin to form an annular opening through which the multi-layer parison exits the apparatus, and c. a plu-rality of subextrusion die block segments vertically located behind the extrusion die block segment comprising at least one principal subextrusion die block segment -Eormed with an annular opening of larger diameter than the diameter of the flow tube and surrounding the flow tube to ~orm a principal tubular channel for flow of a first layer of polymeric material into the delivery channel, and at least two adjacent auxiliary subextrusion die block segments each formed with an accumulation reservoir, there being a first passageway narrower than the principal tubular channel leading from an accumulation reservoir in a first subex-trusion die block segment and adapted to be charged with a second polymeric material from said accumulation reservoir and a second passageway leading from an accumulation reservoir in a second subextrusion die block segment and adapted to be charged with a third polymeric material from said accumulation reservoir in said second subextrusion die block segment; said first and second pas-sageways being defined between facing surfaces of ad~acent subex-trusion die block segment, said second passageway merging with said first passageway, and said first passageway therea~ter lead-ing to said principal tubular channel, whereby a laminate can be formed in said auxiliary subextrusion die block segments composed o~ said second and third polymeric material and thereafter fed completely around said first polymeric material in said principal tubular channel.
According to one aspect thereof there is provided a multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permeation losses, formed by coextruding in a molten s-tate a plurality of plas-tic layers to form a parison, ~orm:ing said parison into a container by blow-molding, said container having a plurality of layers formed from said parison comprising an inner thermoplastic poly-olefin layer which is next to the product; an outer thermoplasticpolyolefin layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture o~ a regrind of all the layer~ from previous contalners of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
The invention also provides a process for making a multi-layer plastic container which comprises coextruding in the molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said con-tainer having a plurality of layers formed from said parison com-prising an inner thermoplastic polyolefin layer which is next to the product; an outer polyolefin thermoplastic layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
According to another aspect thereof the present inven-tion provides a multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to perme-ation losses, said container being formed by internal blow~mold-ing of a multi-layer tubular parison, said tubular parison having a plurality of layers coextruded in the molten state through a plurality of dies to form a parison with layers which are there-after expanded by internal blow-molding said tubular parison into . .
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a mold having the shape of the container, said plurality of lay ers of said container including an inner thermoplastic polyolefin layer which is next to the product, an outer thermoplastic poly-olefin layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of re~rind of all the layers from previous con-tainers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one a~hesive layer to adhere said barrier layer to at least one of the other layers.
The present invention again provides a process of mak-ing multi-layer plastic containers which comprises coextruding in the molten state a plurality of plastic layers through a plural-ity of dies to form a tubular parison, having a plurality of lay-ers, internally blow-molding said parison to form a container, said container having a plurality of layers formed from said parison comprising an inner thermoplastic polyolefin layer which is next to the product; and outer polyolefin thermoplastic layer;
a barrier layer to prevent product oxidation or product perme-ation loss; a scrap layer lncluding a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers. Suitably said adhe-sive is comprised of maleic anhydride-modified polypropylene.
Desirably a second adhesive layer adheres said scrap layer to said inner thermoplastic layer.
The invention again provides a multi-layer parison blow-molding plastic container comprising a container-shaped structure having a multi-layer translucent laminate wall with an outer thermoplastic polyolefin layer; an inner ther~noplastic polyolefin layer and an intermediate barrier layer; a first adhe-sive layer for adhesively joining said inner thermoplastic poly-olefin layer to said barrier layer; a scrap layer interiorly ofsaid outer thermoplastic polyolefin layer and a second adhesive layer for adhesively joining said scrap layer to said barrier layer, wherein said scrap layer includes a mixture of a regrind of all the layers from previous containers of the same construc-tion, said previous containers comprising inner and outer thermo-plastic polyolefin layers, a barrier layer, adhesive layers and a scrap lay~r. Suitably said adhesive ls comprised of maleic anhydride-modified polypropylene. Desirably said inner and outer thermoplastic layers are made of polypropylene or random copoly-mer of propylene and ethylene containing up to about 2 mol percent ethylene.
The present invention again provides a multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permea-tion losses, and formed by coextruding in a molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said container having layers formed from said parison comprising a thermoplastic polyolefin layer; a layer functioning as a barrier layer to prevent product oxidation or product perme-ation loss; and a scrap laye~, said scrap layer comprising a mix-ture of a regrind of all layers from previous containers of the same construction but said scrap layer not including the combina-tion of scrap and an adhesive layer or bonding layer, said previ-ous containers comprising a thermoplastic polyolefin layer, a layer functioning as a barrier layer, and a scrap layer. Suit-ably the container is formed from said parison so as to be translucent. Desirably said parison is blow molded into a translucent container having a neck portion and a body portion and wherein said neck portion has a smaller cross-sectional area than the cross-sectional area of the body portion. Preferably the container further includes an adhesive layer. Suitably said thermoplastic polyolefin layer is made of polypropylene or random copolymer of propylene and ethylene containing up to about 2 mol percent ethylene.
_ g _ , The present invention again provides a process of mak-ing multi-layer plastic containers which comprises coextruding in the molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-moldin~, said con-tainer having a plurality of layers formed from said parison com-prising thermoplastic polyolefin layer; a layer functioning as a barrier layer to prevent product oxidation or product permeation loss; and a scrap layer, said s~rap layer comprising a mixture of a regrind of all the layers from previous parison blow-molded containers of the same construction but said scrap layer not including the combination of scrap and an adhesive layer or bonding layer, said previous containers comprising a thermo-plastic polyolefin layer, a layer functioning as a barrier layer, and a scrap layer.
A multi-layer laminate structure is also provided which includes a separate layer of scrap made from regrind of the extrudate of the various resins used in making the laminate structure. Preferably, the mul-ti-layer laminate structure com-prises an outer thermoplastic polyolefin layer, an inner thermo-plastic polyolefin layer and an intermediate oxygen barrier layer. The outer and inner polyolefin layers are preferably made of polypropylene, particularly crystalline isotactic polypropy-lene and the intermediate barrier layer is preferably made of ethylene-vinyl alcohol copolymer. A first adhesive layer bonds the inner polyolefin layer to the intermediate barrier layer. A
separate scrap layer may be disposed interiorly of the outer polyolefin layer and a second adhesive layer bonds this scrap layer to the intermediate barrier layer. Alternatively, the sep-arate scrap layer may be interposed between the inner polyolefinlayer and the second adhesive layer, or it may be interposed at both of said positions.
In order to make a container, the multi~layer structure is coextruded into a parison tube which is then placed in a blow mold and inflated by injection of air, under pressure, to form ~o~
the container.
This invention also provides improved blow-molding apparatus for formation of parisons for blow molding into con-tainers of any desired shape.
The apparatus is especial~y useful for the pre~arationof the preferred multi-layered structures of this invention.
The present invention will be made more apparent by reference to the accompanying drawings, in which:-Figure 1 is a sectional view of a preferred embodiment of the novel apparatus of this invention for forming multi-lay-ered parisons;
Figure 2 is an enlarged sectional view of the preferred embodiment shown in Figure l;
Figure 3 is a schematic illustration of an apparatus of this invention which particularly illustrates its principal fea-tures; and Figure 4 is a schematic sectional view illustrating the arrangements of the various layers of a six layer laminate struc-ture, including a separate scrap layer, made in accordance with a preferred embodiment of this invention.
According to the broad principles of this invention, the several layers are first coextruded to form a parison tube which is then molded and shaped into the desired container form.
It must bQ mentioned, however, that the formation of the parison tube and the container are well known techniques in the plastic industry. For example, one such method is described in United States Patent No. 4,079,~50 wherein a multi-layer resin in the molten state is coextruded to form a parison. A pair of split ~7~
molds are disposed around the parison and the split molds have such a configuration that when they are in register with each other, they define a cavity which corresponds to the shape of the desired container. ~y injecting air, under pressure, the parison is blow molded to form the container.
In its broadest aspec-ts, the appara-tus of this inven-tion comprises extrusion molding apparatus in which two or rnore relatively thin layers of polymeric material are formed inko a laminate within the apparatus before being joined to one or more relatively thick layers. The principle of the invention will be well understood by reference to Figure 3. For convenience, the various parts of the apparatus will be broadly defined with ref-erence to Figure 3 and only the principal parts will be identi-fied. They will be more specifically defined with reference tothe other Figures.
Figure 3 schematically represents an apparatus of the invention including a segmented die block with an extrusion die block segment 201; principal subextrusion die block segments 202,203 and 204; subextrusion die block segments 205,206 and 207.
There is a hollow central flow tube 208 terminating in a core pin 209, the end portion of which terminates at an orifice 210 in the extrusion block 201. There is a principal tubular channel 211 around the flow tube communicating with a delivery channel 212 and with various passageways for polymer materials to be described hereinafter.
The schematic of Figure 3 is designed to produce a pre-ferred laminated structure 100 of this invention illustrated in Figure 4. In Figure 4 there is an inner thermoplastic polyolefin layer 105 and progressing outwardly a first adhesive layer 109, an oxygen barrier layer 107, a second adhesive layer 113, a scrap layer 111, and an outer thermoplastic polyolefin layer 103. The inner and outer layers and the scrap layers may be regarded as stnlctural layers and, as will be seen, they are relatively thick, of the order of 12 to 1~ mils. The adhesive and barrier layers are relatively thin, i.e. 0.5 to 2 mils. A particular advantage of the apparatus of this invention is -tha-t it makes it possible to form extremely thin layers completely around a faci.ng surface of relatively thick layers in a uniform manner while avoiding the problems aforesaid.
Reverting now to Figure 3, the inside structural layer is formed from a polymer in principal subextruder die block 204 which is formed with a polymer accumulation reservoir 213. There is a passageway 214 leading from the reservoir to the principal tubular channel 211. Adhesive layer 109 is extruded from auxil-iary subextrusion die block 206 with accumulation reservoir 217 and second passageway 218 which leads i.nto first passageway 216.
The second adhesive layer 113 is extruded from auxiliary subex-trusion die block 205 with accumulation reservoir 219 and third passageway 220 leading to first passageway 216.
After the ~uncture of first passageway 216 and thlrd passageway 220, the first passageway ~oins the principal tubular channel. There is thus formed within the extrusion apparatus a laminate composed of the thin adhesive layers and the barrier layer. This laminate is brought into confluence with the thick inner layer within the extrusion apparatus.
The scrap layer 111 is extruded from principal su~ex-truder 203 formed with accumulation reservolr 221 and passageway 222. It forms a junction with the principal tubular channel 211 at junction 223.
The principal tubular channel joins the delivery chan-nel 212 and the six layered parison exits the apparatus around pin 209 through exit orifice 210.
~s will be explained more fully hereinafter, in pre-ferred embodiments o~ th2 inven-tion the flow tube is pro-grammable, that is it can move vertically wi-thin a fixed -tube or mandrelO The size of the orifice 210 can also be adjusted.
The invention will now be explained in more detall with reference to Figures 1 and 2. While the description wlll refer principally and for purposes of illustration to the preferred embodiments, -those skilled in the art will recognize that many variations from the embodiments actually described are possible without varying from the spirit or scope of the invention. For example, certain of the layers, such as the scrap layer or the outside layer can be omitted. The apparatus can be arranged to form a three layered structure of thick structural layer and thin adhesive and barrier or other layer. The apparatus can be arranged so that the thick layer is the inner or the outer layer.
More principal subextruders can be added to the vertically arranged subextruder column to form laminated structures with more than six layers.
The preferred embodiment of the novel apparatus 1 for forming the multi-layered parison tube of this invention shown in Figures 1 and 2 comprises a segmented die block including a set of principal and auxiliary subextruders 7,3,4,5,6 and 8 mounted vertically in order from bottom to top to define a longitudinal direction on an adapter block 10 and substantially cylindrical mandrel 14 passing through coinciden-t central holes in extruders 7,3,4,5,6 and ~ and adapter block 10. The annular space between mandrel 14 and -the extruders 7,3,4,5,6 and 8 defines a principal annular discharge channel 40 through which the multi-layered lam-inate flows. The'mandrel 14 is cylindrical and has a concentriccentral cylindrical cavity through which a programming flow tube 15 passes. The flow tube is vertically moveable within the man-drel. A blow pin 11 is mounted at the downstream end portion of mandrel 14 on cylindrical pin holder 12 which is attached directly to programming flow tube 15. The pin holder 12 is held ln position by pin holder sleeve 13 a-ttached to the downstream , .
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end of mandrel 14. There is thus defined a hollow unit throuyh which air or oth~r gas may be forced to blow mold the parison.
A principal subextruder 8 comprises the downstream end of the segmented die block and, as shown, consists of an upstream cylindrical portion of substantially greater radius than a down-stream portion. The exterior surface of the end portion of top block 8 is threaded to engage and hold an end cap 26 which con-sists of a cylindrical pipe portion whose bottom interior surface is threaded and an interiorly directed top lip. A bushing rlng 21 which forms a seat for bushing 19 is conformed to be held in place by end cap 26. Bushing 19 has a central interior nozzle cavity and central annular orifice 23 surrounding but spaced from the blow pin 11 to form an exit orifice through which the multi-layered laminate can be extruded.
The cylindrical, central cavity of top extruder 8 hasadditionally three pipe-shaped pieces, a bushing adapted 24, top adapter sleeve 28, and bottom adapter sleeve 30 mounted therein in tandem from top to bottom whose interior surfaces together with the exterior surface of the mandrel 14 define the downstream portion or delivery channel of the principal tubular discharge channel 40~
he downstream end of bushing adapter 24 abuts against bushing 19 and bushing ring 21. The concentricity of the extru-date may be partially controlled by an axially disposed adapter set screws 31 passing through top block 8 to press against bush-ing adapter 24.
In the pre~erred embodiment shown, a central longitudi-nal air shaft 17 passes through programming flow tube 15, pin holder 12, and blow pin 11 and provides a means by which air or other vapor is introduced to prevent the parison walls from col-lapsing during extrusion and to blow mold the parison.
Eac~ of subex-truder die blocks 6~5,~,3 and 7 comprises a cylindrical bottom portion with a central hole therein and a downstream extending sleeve top portion so conformed ko fit into the cylindrical bottom portion of the adjacent extruder or sub-extruder so as to form annular accumulation reser~oirs 48,47,46, 45,44 and 43 in the segmented die block to hold the melted ther-moplastic resin material used for each individual layer of the six-layered laminate. Resin material is fed to the reservoirs 48,47,46 ~ 45, 44 and 43 from an external source which is not shown.
The resin is distributed circumferentially by feed passageways, flow blocks 6,5,4, 3 and 7 and adapter block 10. The annular accumulation reservoir 48 in principal subextruder die block 6 is fed by feed passageway 24 having an axially disposed inlet in adapter block 10. Annular accumulation reservoir 43 formed between flow sleeve 2 and principal subextruder die block 6 is fed by feed passageway 23.
The feed passageway can be e~uipped with a regulating system such as pressure transducer 90 and a choke pin 92 mounted in choke pin adapter 93 for regulating the flow rate of polymeric material. The accumulation reservoirs 43,~7 and 48 are connected directly to the principal tubular discharge flow channel 40 by annular connecting passageways 50,57 and 58. However, annular discharge reservoirs 44,45 and 45 are connected to an auxiliary discharge flow channel 42 which leads to principal tubular flow channel 40 by annular connecting passageways 52,53 and 55.
Auxiliary discharge flow channel 42 is substan-tially smaller in diameter than principal tubular flow channel 40 into which it is connected. The use of an auxiliary discharge flow channel 42 allows preforming a three-layered laminate consisting of two adhesive layers and a barrier layer which may be formed completely around the inner layer without causing imperfectlons in the final produc-ts.
It will be understood from the description and from the ~7~
Figures that the accumulation reservoirs and -the polymer passaye-ways leadin~ from the accumulation reservoirs to the first or auxiliary passageways and to the principal tubular channel 40 ma~
be defined by facing surfaces of ad~acent extruders. They may be, however, conveniently formed in the blocks themselves. This is especially true of the accumulation reservoirs.
The passageways are tapered~ i.e. the diameter of the downstream end is less than that of the end closer to the accumu-lation reservoirs. Therefore, the pressure of the molten polymerat the downstream end is greater than at the upstream end. As a result, the stream of molten resin becomes laminar flow so that t~lere is reduced turbulence as each polymer stream joins another polymer stream.
Heat may be supplied to the die block by any convenient means. The extruders and subextruders may be insùlated by ceramic bands 39,38,37,36,35,34,33 and 32 as shown. Thermo-couples may be mounted in the extruders and subextruders 8,6, 5,4,3 and 7; for example, thermocouple 85 is mounted in adapter 86 and senses the temperature in principal subextruder 8 and thermocouple 83 ln adapter 84 senses the temperature in au~iliary subextruder 5.
The blow pin 11 is also positioned by a pin orientation bar 75 axially attached to and holding the programming flow tube 15 by bar adapter 77. Orientation bar 75 is held in position by clamp pin 79 and bar adapter 77 is supported on the bottom of adapter block 10 by cylindrical flanged bushing 70 attached to a mounting plate 60 which is fixed to adapter block 10 by mounting bolt 63. Air may be admitted to air shaft 17 by means of the couplet 80 which passes air to the end of programming flow tube 15 through bar adapter 77 from air inlet 82.
Movement of programming flow tube 15 withln mandrel 14 may be controlled by an electronic parison programmer 65, for : : ''; ' :
', :
':.. ,. " , examp~e, a Hunker (trademark) Programmer available from Hunker Acroboratories, Inc. The programmer 65 is attached to programmer base plate 66 which is connected to mounting plate 60 by tie rods 62.
In the preferred practice o* this invention as illus-trated in Figure 4, the laminate struc-ture has an in-termediate gas and oxygen barrier layer of e-thylene-vinyl alcohol copolymer, outer and inner structural layers of a thermoplastic polyol~fin, a separate scrap layer adjacent to the outer polyolefin layer and two adhesive layers, one interposed between the intermediate barrier layer and the scrap layer, and the other is interposed between the intermediate barrier layer and the inner polyolefin layer.
The polyolefins which are suitable in forming the outer and inner layers of the laminate s-tructure are thermoplastic olefinic polymers such as e.g., high and low density polyethy-lene, polypropylene and blends of these.
Both adhesive layers are preferably made of maleic anhydride modified polypropylene wherein the polypropylene back-bone is modified with maleic anhydride moieties. One such adhe-sive is available from Mitsui, Japan, under the trademark ADMER
QB 530. In general, however, polypropylene modified with ethylenically unsaturated carboxylic anhydrides may be used as the adhesive layers for the present laminate structure.
It must be mentioned that the aforementioned adhesives are particularly well suited when polypropylene or propyleneethy-lene random copolymers constitute the outer and inner structural layers. However, when this layer is made of polyethylene, it is preferable to use a different adhesive such as, for example, the Plexar (trademark) adhesives manufactured by Chemplex Company, Rolling Meadows, Illinois. These adhesives are a blend of e-thy-lene-vinyl acetate copolymer and a graft copolymer of polyethy--- 1~ --.'~ ~, ., . .
. . .
lene and a dicarboxylic acid anhydride.
The scrap layer is made of regrind of the coextrudatesof the differen-t thermoplastic layers used to form the parison tube. The nature of the scrap and its incorporation into the laminate structure will hereina~ter be described in detail in connection with the description of the process of this invention.
As mentioned above, the multi-layer laminate structure generally designated as 100 has an outer polyolefin s-tructural layer 103, an inner polyolefin structural layer 105 and an inter-mediate oxygen barrier layer 107. The inner polyolefin layer 105 is adhesively bonded to the intermediate barrier layer 107 by the adhesive layer 113.
All the layers are coextensively bonded along their respective junctions with no interlaminar separation between the respective layers of the laminate structure.
In order to form the laminate structure, the thermo-plastic resins used to make the different layers are coextruded in the molten state through an extrusion apparatus, preferably an embodiment of the apparatus described herein, to form the parison tube. The parison tube is then blow molded by in~ection of air or other vapor, under pressure, and is shaped into a container in a separate container mold. The excess materials from this blow molding operation are ground up and mixed as a homogeneous scrap and the scrap layer is reintroduced into the laminate structure.
As a practical matter, therefore, the process and appa--ratus of this invention permits utilization of all the scrap pro-duced during the container forming operations. Accordingly, the economy of the operation is considerably improved and waste dis-posal is virtually eliminated.
In addition to improving the economy of operation and -- lg --' ~7~
reduction of waste disposal, it has been found that inclusion of a separate scrap layer in the multi-layer laminate structure does not detract from the transparency of unoriented containers made of such laminate structures. The ability to make transpar0nt containers by non-oriented blow molding of a multi-layer laminate structure having a comple-tely separate layer of scrap constitutes a novel and surprising feature of the present invention.
While the invention has heretofore been described with a certain degree of particularity and illustrated by a 6-layer laminate structure, several changes and modi~ications are sug-gested from the foregoing disclosure which are nevertheless within the scope and contemplation of this invention. For example, additional layers may be used for decorative purposes or otherwise and more than one scrap layer can be reintroduced into the laminate structure, if desired.
It is also within the contemplation of this invention to make a 5-layer laminate structure, and to form containers therefrom as aforesaid. In this construc-ticn, the scrap layer may constitute the outer layer and the outer polyolefin layer may be eliminated.
Additionally, if desired, the scrap layer may be inter-posed between the inner polyolefin layer and the second adhesivelayer, or two scrap layers may be incorporated in the laminate structure; one interposed between the outer polyolefin layer and the first adhesive layer, and the other is interposed between the inner polyolefin layer and the second adhesive layer.
Containers having excellent oxygen barrier properties and good transparency can be made by varying the relative thick-nesses of the different layers. For example, excellent barrier properties and good transparency can be obtained from the multi-layer structure of this invention when the thickness of the ethy-lene-vinyl alcohol layer is between about 0.5 to about 2 mils and , ,.~ .
., 5~
the scrap layer constitutes up to about 40 weight percent of the total extrudate.
~0 :.:.,. :
.. . " . ....
:, . , .:
Claims (23)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permeation losses, formed by coextruding in a molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said container having a plurality of layers formed from said parison comprising an inner thermoplastic polyolefin layer which is next to the product; an outer thermoplastic polyolefin layer;
a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
2. A process of making a multi-layer plastic container which comprises coextruding in the molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said container having a plurality of layers formed from said parison comprising an inner thermoplastic polyolefin layer which is next to the product;
an outer polyolefin thermoplastic layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
an outer polyolefin thermoplastic layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
3. A multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permeation losses, said container being formed by internal blow-molding of a multi-layer tubular parison, said tubular parison having a plurality of layers coextruded in the molten state through a plurality of dies to form a parison with layers which are thereafter expanded by internal blow-molding said tubular parison into a mold having the shape of the container, said plurality of layers of said container including an inner thermoplastic polyolefin layer which is next to the product, an outer thermoplastic polyolefin layer;
a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
4. A process of making multi-layer plastic containers which comprises coextruding in the molten state a plurality of plastic layers through a plurality of dies to form a tubular parison, having a plurality of layers, internally blow-molding said parison to form a container, said container having a plurality of layers formed from said parison comprising an inner thermoplastic polyolefin layer which is next to the product; and outer polyolefin thermoplastic layer; a barrier layer to prevent product oxidation or product permeation loss; a scrap layer including a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, an adhesive layer and a scrap layer; and at least one adhesive layer to adhere said barrier layer to at least one of the other layers.
5. A process as in claim 2 or 4 wherein said adhesive is comprised of maleic anhydride-modified polypropylene.
6. A process as in claim 2 or 4 wherein a second adhesive layer adheres said scrap layer to said inner thermoplastic layer.
7. A multi-layer parison blow-molded plastic container comprising a container-shaped structure having a multi-layer translucent laminate wall with an outer thermoplastic polyolefin layer; an inner thermoplastic polyolefin layer and an intermediate barrier layer; a first adhesive layer for adhesively joining said inner thermoplastic polyolefin layer to said barrier layer; a scrap layer interiorly of said outer thermoplastic polyolefin layer and a second adhesive layer for adhesively joining said scrap layer to said barrier layer, wherein said scrap layer includes a mixture of a regrind of all the layers from previous containers of the same construction, said previous containers comprising inner and outer thermoplastic polyolefin layers, a barrier layer, adhesive layers and a scrap layer.
8. A container as in claim 1, 3 or 7 wherein said adhesive is comprised of maleic anhydride-modified polypropylene.
9. A container as in claim 7 wherein said inner and outer thermoplastic layers are made of polypropylene or random copolymer of propylene and ethylene containing up to about 2 mol percent ethylene.
10. A container as in claim 8 wherein said inner and outer thermoplastic layers are made of polypropylene or random copolymer of propylene and ethylene containing up to about 2 mol percent ethylene.
11. A container as in claim 1, 3, or 7, wherein a second adhesive layer adheres said scrap layer to said inner thermoplastic layer.
12. A multi-layer plastic container adapted to contain oxygen sensitive products or contain products sensitive to permeation losses, and formed by coextruding in a molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said container having layers formed from said parison comprising a thermoplastic polyolefin layer; a layer functioning as a barrier layer to prevent product oxidation or product permeation loss; and a scrap layer, said scrap layer comprising a mixture of a regrind of all layers from previous containers of the same construction but said scrap layer not including the combination of scrap and an adhesive layer or bonding layer, said previous containers comprising a thermoplastic polyolefin layer, a layer functioning as a barrier layer, and a scrap layer.
13. A container as in claim 1, 3 or 12 wherein the container is formed from said parison so as to be translucent.
14. A multi-layer plastic container as in claim 1, 3, 7 or 12 wherein said parison is blow molded into a translucent container having a neck portion and a body portion and wherein said neck portion has a smaller cross-sectional area than the cross-sectional area of the body portion.
15. A container as in claim 12 further including an adhesive layer.
16. A container as in claim 12 wherein said thermoplastic polyolefin layer is made of polypropylene or random copolymer of propylene and ethylene containing up to about 2 mol percent ethylene.
17. A container as in claim 15 wherein said adhesive layer is comprised of maleic anhydride-modified polypropylene.
18. A process of making multi-layer plastic containers which comprises coextruding in the molten state a plurality of plastic layers to form a parison, forming said parison into a container by blow-molding, said container having a plurality of layers formed from said parison comprising thermoplastic polyolefin layer; a layer functioning as a barrier layer to prevent product oxidation or product permeation loss; and a scrap layer, said scrap layer comprising a mixture of a regrind of all the layers from previous parison blow-molded containers of the same construction but said scrap layer not including the combination of scrap and an adhesive layer or bonding layer, said previous containers comprising a thermoplastic polyolefin layer, a layer functioning as a barrier layer, and a scrap layer.
19. A process as in claim 2, 4 or 18 wherein the said parison is formed into a translucent container.
20. A process as in claim 2, 4 or 18 wherein said parison is blow molded into a translucent container having a neck portion and a body portion and wherein said neck portion has a smaller cross-sectional area than the cross-sectional area of the body portion.
21. A process as in claim 18 wherein said thermoplastic polyolefin layer is made of polypropylene or random copolymer of propylene and ethylene containing up to about 2 mol percent ethylene.
22. A process as in claim 18 wherein one of said layers is an adhesive comprised of maleic anhydride-modified polypropylene.
23. A process as in claim 22 wherein said adhesive layer adheres said scrap layer to said thermoplastic layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000599621A CA1270451A (en) | 1982-11-29 | 1989-05-12 | Apparatus and method for producing multi-layered laminates and improved multi-layered laminates produced therefrom |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US445,261 | 1982-11-29 | ||
| US06/445,261 US4522775A (en) | 1982-03-04 | 1982-11-29 | Apparatus and method for producing multilayered laminates |
| CA000427503A CA1258758A (en) | 1982-11-29 | 1983-05-05 | Apparatus and method for producing multi-layered laminates and improved multilayer laminates produced therefrom |
| CA000599621A CA1270451A (en) | 1982-11-29 | 1989-05-12 | Apparatus and method for producing multi-layered laminates and improved multi-layered laminates produced therefrom |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000427503A Division CA1258758A (en) | 1982-11-29 | 1983-05-05 | Apparatus and method for producing multi-layered laminates and improved multilayer laminates produced therefrom |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1270451A true CA1270451A (en) | 1990-06-19 |
Family
ID=25670025
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000599621A Expired - Lifetime CA1270451A (en) | 1982-11-29 | 1989-05-12 | Apparatus and method for producing multi-layered laminates and improved multi-layered laminates produced therefrom |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1270451A (en) |
-
1989
- 1989-05-12 CA CA000599621A patent/CA1270451A/en not_active Expired - Lifetime
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