CA1118567A - Method for making flat cellular vinyl sheet - Google Patents
Method for making flat cellular vinyl sheetInfo
- Publication number
- CA1118567A CA1118567A CA000309073A CA309073A CA1118567A CA 1118567 A CA1118567 A CA 1118567A CA 000309073 A CA000309073 A CA 000309073A CA 309073 A CA309073 A CA 309073A CA 1118567 A CA1118567 A CA 1118567A
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- CA
- Canada
- Prior art keywords
- sheet
- capstock
- cellular
- vinyl
- polyolefin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Extrusion Moulding Of Plastics Or The Like (AREA)
Abstract
A METHOD FOR MAKING FLAT
CELLULAR VINYL SHEET
Abstract of the Invention Flat cellular vinyl chloride and vinylidene chloride polymer sheets are made by coextruding a cellular forming chloride or vinylidene chloride polymer material with a noncellular, incompatible polyolefin capstock.
The noncellular, incompatible capstock restricts the expansion of the cellular material in the lateral direction, thus maintaining the sheet in a flat condition. Since the capstock is incompatible, it can be easily stripped off the cellular sheet after cooling or after the sheet is converted into the final product.
CELLULAR VINYL SHEET
Abstract of the Invention Flat cellular vinyl chloride and vinylidene chloride polymer sheets are made by coextruding a cellular forming chloride or vinylidene chloride polymer material with a noncellular, incompatible polyolefin capstock.
The noncellular, incompatible capstock restricts the expansion of the cellular material in the lateral direction, thus maintaining the sheet in a flat condition. Since the capstock is incompatible, it can be easily stripped off the cellular sheet after cooling or after the sheet is converted into the final product.
Description
The invention is concerned with the production of a flat sheet.
Upon exiting the extrusion die, a cellular vinyl chloride or vinylidene chloride polymer extrudate expands three dimensionally. The expansion in length direction is picked up by a speed differential between the exiting material and the puller. Expansion in the other two directions, width and thickness, results in an increase in width and thickness of the extruded profile. In cases where the width is much greater than the thickness, such as in the case of a sheet, the lateral expansion leads to the forma-tion of folds in the machine direction. These folds are undesirable for producing a flat sheet.
With certain cellular thermoplastics, these folds are eliminated by mechanically stretching the extrudate to take up the slack. In an existing process for making very low density polystyrene foam sheet, such as is used for egg carton stock, this is achieved by extruding through an annular die opening and by stretching the tubular extrudate over a conical mandrel prior to cutting and flattening the sheet. This process is difficult to apply to thermo-plastic materials such as rigid cellular vinyl in the 0.50 to 1.0 gram/cc. gravity range, because of the higher stiff-ness of these materials. A meth~d for producing flat cellular vinyl sheeting is desirable.
U.S. Patents 3,479,425, 3,398,431, 3,476,627 and 3,833,704 disclo~e coextrusion of thermoplastic materials.
In accordance with the invention there is provided a method for producing flat vinyl chloride or vinylidene ;, ', , ' , ' ~18S67 chloride polymer cellular sheet comprising coextruding a heated polyolefin capstock with a heated vinyl chloride or vinylidene chloride polymer sheet containing at least one blowing agent, expanding said sheet into a cellular sheet, and then cooling said cellular sheet and said poly-olefin capstock below their softening temperature, to form a product comprising said cellular sheet with said cap-stock attached thereto, said capstock being incompatible with said sheet and being readily strippable therefrom, said capstock being effective during said expanding, to restrict the expansion of the sheet in the width direction, while allowing expansion in the height direction.
In another aspect of the invention there is pro-vided a co-extruded combination comprising a polyolefin capstock and a uinyl chloride or vinylidene chloride polymer, cellul-ar sheet, said capstock being attached to but incompatible with said sheet and being readily ~trippable from the sheet, said capstock being effective, during expansion of said sheet to restrict the expansion of the sheet in the width direction, while allowing expansion in the height direction.
, . .
' .:
, '` ~ ~ ". - : ' ~8567 Thus the invention provides flat sheets of vinyl chloride or vinylidene chloride polymer cellular material made by coextruding a cellular forming vinyl or vinylidene chloride material, such as a rigid polyvinyl chloride containing a chemical blowing agent, with a noncellular, nonadhering polyolefin capstock. The polyolefin capstock allows the blowing agent in the vinyl material to expand the vinyl material in the height (thickness) direction while restricting the expansion in the width direction.
After the vinyl chloride or vinylidene chloride polymer material has expanded into a cellular sheet, the incom-patible polyolefin capstock can be stripped .
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~ ~1185~7 off the cellular sheet giving a flat vi~yl chloride or vinylidene chloride polymer cellular sheet. If desirable, - the capstock may remain on the cellular sheet until after the final product is produced such as by vacuum-forming and then may be easily removed from the cellular sheet.
DETAILED DESCRIPTION
The flat cellular vinyl chloride or vinylidene chloride polymer sheets of this invention are made by incorporating a gas generating substance (blowing agent) in the vinyl or vinylidene material~ The vinyl chloride or vinylidene chloride polymer material containing the blowing agent is then coextruded at a temperature above their thermoplastic temperature with the noncellular non-adhering capstock on one side of the vinyl material. Upon exit from the extruder die, the vinyl or vinylidene material is at a temperature sufficiently high to decompose the blow-ing agent into a gaseous state thereby causing the viny~ or vinylidene material to expand creating a cellular sheet.
The noncellular capstock restricts the expansion of the cellular sheet in the width direction but allows expansion in the height direction. The incompatible capstock can be stripped off the cellular sheet after expansion and cooling of the cellular sheet below its softening temperature or even after the cellular sheet is converted into its final product such as by vacuum forming. In some cases, it may be desirable to leave the capstock on the cellular sheet as a protective film until the product has been shipped to its final destination and then remove the capstock.
Vinyl chloride and vinylidene chloride polymers used in this invention include homopolymers, copolymers and blends of homopolymers and/or copolymers. The vinyl chloride and vinylidene chloride polymers may contain from 0 up to about 50~ by weight of at least one other olefinically unsaturated monomer, more prçferably at least one other vinylidene monomer (i.e., a monomer containing at least one terminal CH2=C< group per molecule) copolymerized therewith, even more prererably up to about 20~ by weight of such monomer.
: ' . -, , .
85~7 Suitable monomers include l-olefins containing from 2 to 12 carbon atoms, more preferably from 2 to 8 carbon atoms, such as ethylene, propylene, l-butene, isobutylene, l-hexene, 4-methyl-1-pentene and the like; dienes containing from 4 to 10 carbon atoms including conjugated dienes as butadiene, isoprene, piperylene, and the like; ethylidene norbornene and dicyclopentadiene; vinyl esters and allyl esters such as vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl laurate, allyl acetate and the like; vinyl aromatics such as styrene, -methylstyrene, chlorostyrene, vinyl toluene, vinyl naphthalene and the like; ~inyl and allyl ethers and ketones such as vinyl methyl ether, allyl methyl ether, vinyl isobutyl ether, vinyl n-butyl ether, vinyl . chloroethyl ether, methyl vinyl ketone and the like; vinyl 15 nitriles such as acrylonitrile, methacrylonitrile and the ..
like; cyanoalkyl acrylates such as ~-cyanomethyl acrylate, the -, ~- and y- cyanoprcpyl acrylates and the like; ole-finically unsaturated carboxylic acids and esters thereof, including a,~-olefinically unsaturated acids and esters thereof such as methyl acrylate, ethyl acrylate, chloropropyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, glycidyl acrylate, methoxyethyl acrylate, ethoxy-ethyl acrylate, hexylthio-ethyl acrylate, methylmethacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate and the like, and including esters of maleic and fumaric acid and the like; amides of the olefinically unsaturated carboxylic aci.ds such as acrylamide and the like; divinyls, diacrylates and other polyfunctional monomers such as divinyl benzene divinyl ether, diethylene glycol diacrylate, ethylene glycol dimethacrylate, methylene-biR-acrylamide, al~yl pentaerythritol, and the like; and bis (~-haloalkyl) alkenyl phosphonate such as bis (~-chloro-ethyl) vinyl phosphonate and the like.
More preferred monomers include l-olefins contain-; ing from 2 to 12 carbon atoms, more preferably from 2 to 8 ` carbon atoms, such as ethylene, propylene, l-butene, iso-,' , "''-' - 1~18S~7 butylene, l-hexene, 4-methyl-1-pentene and the like; vinyl esters and allyl esters such as vinyl acetate, vinyl chloro-acetate, vinyl propionate, vinyl laurate, allyl acetate and the like; ole~inically unsaturated carboxylic acids and esters thereof, including a,~,-olefinically unsaturated acids - - and esters thereof containing from 3 to 24 carbon atoms such as methyl acrylate, ethyl acry~ate, chloropropyl acrylate, ; butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, glycidyl acrylate, methoxyethyl acrylate, ethoxy-ethyl acrylate, hexylthioacrylate, methyl methacrylate and the like, and including esters of maleic and fumaric acid and the like; and amides of a,~ olefinically unsaturated carboxylic acids such as acrylamide and the like.
The vinyl chloride and vinylidene chloride polymers may be prepared by any method known to the art such as by emulsion, suspension, bulk or solution polymerization.
At least one blowing agent is mixed with the polyvinyl chloride or polyvinylidene chloride material to give a cellular product. The blowing agent is used in amounts from about 0,1 to 3 weight parts per 100 weight parts of vinyl material, preferably about 0.2 to less than 1.5. Cellular polyvinyl chloride compositions having densities of about 0.7 to 0.8 have been obtained with 0.2 to 0.3 weight parts of chemical blowing agent and cellular polyvinyl chloride com-pos~,itions having densities of about 0.57 have been made with i about 1.0 weight part of blowing agent. A variety of chemical blowir.g agents are satisfactory in obtaining the cellular poly-vi~y~1 chloride or polyvinylidene chloride sheets of this inven-tion. The nitrogen releasing agents, for example, including azobis-formamide, azobis-iso-butyronitrile, diazoaminobenzene, p,p'-oxybis-(benzenesulfonylhydrazide), N,N'-dinitrosopenta-~; methylenetetraamine, p,p'-azobis-(benzene-sulfonylsemicarbon-amide), diethylazoisobutyrate, 1,3-bis-(xenyl) triazine, 4,4'-oxybis-(benzenesulfonylhydrazide) and the like have been found to be useful. These generally are azo-, N-nitroso- and ~ sulfonyl hydrazide compounds.
,~ 5 ,, ,, : . .
. ' ~ , , 11185~7 Catalysts based on lead, barium, cadmium, zinc salts and the like may be used. These catalysts are activa-tors and generally lower the temperatures of gas release of the blowing agent. Excellent results have been obtained with blowing agents releasing gas at temperature above 300F, particularly above 350F.
~ ubricants ana lubricant mixtures may be included in the compounds in amounts from about 1 to 5, preferably
Upon exiting the extrusion die, a cellular vinyl chloride or vinylidene chloride polymer extrudate expands three dimensionally. The expansion in length direction is picked up by a speed differential between the exiting material and the puller. Expansion in the other two directions, width and thickness, results in an increase in width and thickness of the extruded profile. In cases where the width is much greater than the thickness, such as in the case of a sheet, the lateral expansion leads to the forma-tion of folds in the machine direction. These folds are undesirable for producing a flat sheet.
With certain cellular thermoplastics, these folds are eliminated by mechanically stretching the extrudate to take up the slack. In an existing process for making very low density polystyrene foam sheet, such as is used for egg carton stock, this is achieved by extruding through an annular die opening and by stretching the tubular extrudate over a conical mandrel prior to cutting and flattening the sheet. This process is difficult to apply to thermo-plastic materials such as rigid cellular vinyl in the 0.50 to 1.0 gram/cc. gravity range, because of the higher stiff-ness of these materials. A meth~d for producing flat cellular vinyl sheeting is desirable.
U.S. Patents 3,479,425, 3,398,431, 3,476,627 and 3,833,704 disclo~e coextrusion of thermoplastic materials.
In accordance with the invention there is provided a method for producing flat vinyl chloride or vinylidene ;, ', , ' , ' ~18S67 chloride polymer cellular sheet comprising coextruding a heated polyolefin capstock with a heated vinyl chloride or vinylidene chloride polymer sheet containing at least one blowing agent, expanding said sheet into a cellular sheet, and then cooling said cellular sheet and said poly-olefin capstock below their softening temperature, to form a product comprising said cellular sheet with said cap-stock attached thereto, said capstock being incompatible with said sheet and being readily strippable therefrom, said capstock being effective during said expanding, to restrict the expansion of the sheet in the width direction, while allowing expansion in the height direction.
In another aspect of the invention there is pro-vided a co-extruded combination comprising a polyolefin capstock and a uinyl chloride or vinylidene chloride polymer, cellul-ar sheet, said capstock being attached to but incompatible with said sheet and being readily ~trippable from the sheet, said capstock being effective, during expansion of said sheet to restrict the expansion of the sheet in the width direction, while allowing expansion in the height direction.
, . .
' .:
, '` ~ ~ ". - : ' ~8567 Thus the invention provides flat sheets of vinyl chloride or vinylidene chloride polymer cellular material made by coextruding a cellular forming vinyl or vinylidene chloride material, such as a rigid polyvinyl chloride containing a chemical blowing agent, with a noncellular, nonadhering polyolefin capstock. The polyolefin capstock allows the blowing agent in the vinyl material to expand the vinyl material in the height (thickness) direction while restricting the expansion in the width direction.
After the vinyl chloride or vinylidene chloride polymer material has expanded into a cellular sheet, the incom-patible polyolefin capstock can be stripped .
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, , , .
. . . :, . .
~ ~1185~7 off the cellular sheet giving a flat vi~yl chloride or vinylidene chloride polymer cellular sheet. If desirable, - the capstock may remain on the cellular sheet until after the final product is produced such as by vacuum-forming and then may be easily removed from the cellular sheet.
DETAILED DESCRIPTION
The flat cellular vinyl chloride or vinylidene chloride polymer sheets of this invention are made by incorporating a gas generating substance (blowing agent) in the vinyl or vinylidene material~ The vinyl chloride or vinylidene chloride polymer material containing the blowing agent is then coextruded at a temperature above their thermoplastic temperature with the noncellular non-adhering capstock on one side of the vinyl material. Upon exit from the extruder die, the vinyl or vinylidene material is at a temperature sufficiently high to decompose the blow-ing agent into a gaseous state thereby causing the viny~ or vinylidene material to expand creating a cellular sheet.
The noncellular capstock restricts the expansion of the cellular sheet in the width direction but allows expansion in the height direction. The incompatible capstock can be stripped off the cellular sheet after expansion and cooling of the cellular sheet below its softening temperature or even after the cellular sheet is converted into its final product such as by vacuum forming. In some cases, it may be desirable to leave the capstock on the cellular sheet as a protective film until the product has been shipped to its final destination and then remove the capstock.
Vinyl chloride and vinylidene chloride polymers used in this invention include homopolymers, copolymers and blends of homopolymers and/or copolymers. The vinyl chloride and vinylidene chloride polymers may contain from 0 up to about 50~ by weight of at least one other olefinically unsaturated monomer, more prçferably at least one other vinylidene monomer (i.e., a monomer containing at least one terminal CH2=C< group per molecule) copolymerized therewith, even more prererably up to about 20~ by weight of such monomer.
: ' . -, , .
85~7 Suitable monomers include l-olefins containing from 2 to 12 carbon atoms, more preferably from 2 to 8 carbon atoms, such as ethylene, propylene, l-butene, isobutylene, l-hexene, 4-methyl-1-pentene and the like; dienes containing from 4 to 10 carbon atoms including conjugated dienes as butadiene, isoprene, piperylene, and the like; ethylidene norbornene and dicyclopentadiene; vinyl esters and allyl esters such as vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl laurate, allyl acetate and the like; vinyl aromatics such as styrene, -methylstyrene, chlorostyrene, vinyl toluene, vinyl naphthalene and the like; ~inyl and allyl ethers and ketones such as vinyl methyl ether, allyl methyl ether, vinyl isobutyl ether, vinyl n-butyl ether, vinyl . chloroethyl ether, methyl vinyl ketone and the like; vinyl 15 nitriles such as acrylonitrile, methacrylonitrile and the ..
like; cyanoalkyl acrylates such as ~-cyanomethyl acrylate, the -, ~- and y- cyanoprcpyl acrylates and the like; ole-finically unsaturated carboxylic acids and esters thereof, including a,~-olefinically unsaturated acids and esters thereof such as methyl acrylate, ethyl acrylate, chloropropyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, glycidyl acrylate, methoxyethyl acrylate, ethoxy-ethyl acrylate, hexylthio-ethyl acrylate, methylmethacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate and the like, and including esters of maleic and fumaric acid and the like; amides of the olefinically unsaturated carboxylic aci.ds such as acrylamide and the like; divinyls, diacrylates and other polyfunctional monomers such as divinyl benzene divinyl ether, diethylene glycol diacrylate, ethylene glycol dimethacrylate, methylene-biR-acrylamide, al~yl pentaerythritol, and the like; and bis (~-haloalkyl) alkenyl phosphonate such as bis (~-chloro-ethyl) vinyl phosphonate and the like.
More preferred monomers include l-olefins contain-; ing from 2 to 12 carbon atoms, more preferably from 2 to 8 ` carbon atoms, such as ethylene, propylene, l-butene, iso-,' , "''-' - 1~18S~7 butylene, l-hexene, 4-methyl-1-pentene and the like; vinyl esters and allyl esters such as vinyl acetate, vinyl chloro-acetate, vinyl propionate, vinyl laurate, allyl acetate and the like; ole~inically unsaturated carboxylic acids and esters thereof, including a,~,-olefinically unsaturated acids - - and esters thereof containing from 3 to 24 carbon atoms such as methyl acrylate, ethyl acry~ate, chloropropyl acrylate, ; butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, glycidyl acrylate, methoxyethyl acrylate, ethoxy-ethyl acrylate, hexylthioacrylate, methyl methacrylate and the like, and including esters of maleic and fumaric acid and the like; and amides of a,~ olefinically unsaturated carboxylic acids such as acrylamide and the like.
The vinyl chloride and vinylidene chloride polymers may be prepared by any method known to the art such as by emulsion, suspension, bulk or solution polymerization.
At least one blowing agent is mixed with the polyvinyl chloride or polyvinylidene chloride material to give a cellular product. The blowing agent is used in amounts from about 0,1 to 3 weight parts per 100 weight parts of vinyl material, preferably about 0.2 to less than 1.5. Cellular polyvinyl chloride compositions having densities of about 0.7 to 0.8 have been obtained with 0.2 to 0.3 weight parts of chemical blowing agent and cellular polyvinyl chloride com-pos~,itions having densities of about 0.57 have been made with i about 1.0 weight part of blowing agent. A variety of chemical blowir.g agents are satisfactory in obtaining the cellular poly-vi~y~1 chloride or polyvinylidene chloride sheets of this inven-tion. The nitrogen releasing agents, for example, including azobis-formamide, azobis-iso-butyronitrile, diazoaminobenzene, p,p'-oxybis-(benzenesulfonylhydrazide), N,N'-dinitrosopenta-~; methylenetetraamine, p,p'-azobis-(benzene-sulfonylsemicarbon-amide), diethylazoisobutyrate, 1,3-bis-(xenyl) triazine, 4,4'-oxybis-(benzenesulfonylhydrazide) and the like have been found to be useful. These generally are azo-, N-nitroso- and ~ sulfonyl hydrazide compounds.
,~ 5 ,, ,, : . .
. ' ~ , , 11185~7 Catalysts based on lead, barium, cadmium, zinc salts and the like may be used. These catalysts are activa-tors and generally lower the temperatures of gas release of the blowing agent. Excellent results have been obtained with blowing agents releasing gas at temperature above 300F, particularly above 350F.
~ ubricants ana lubricant mixtures may be included in the compounds in amounts from about 1 to 5, preferably
2 to 4, weight parts including for example, paraffin, poly-ethylene, calcium stearate, ethylenebis stearylamide a~dother lubricants known to and used by those skilled in the art. High melting point lubricants, above 250F are pre-ferred. Amide waxes and metal salts of fatty acids are of this type.
Fine particle size inorganic fillers may also be included in amounts from about 1 to 15 weight parts includ-ing for example titanium dioxide, iron oxide, calcium carbon-ate, silicas and the like.
Group IIA metal oxides and hydroxides particularly calcium and magnesium oxide and hydroxide have been employed in amounts from about 0.1 to 5 weight parts. Any of the usual color pigments may be added to obtain desirable color in the cellular sheets.
Stabilizers known to those skilled in the art as the tin stabilizers, particularly the tin mercaptides, for example, dibutyltinthioethyldiglycolate and the lauryl derivative have been found useful in amounts from about 0.5 to 4 parts. Some synergism with the blowing agent has been observed with these materials.
3Q The noncellular incompatible capstock is coextruded with the cellular vinyl or vinylidene material. Materials suitable for the incompatible capstock includes polyolefins such as polyethylene, polypropylene, polyisobutylene and the like. Polyethylene was found to be an excellent choice as a capstock material. The thickness of the capstock will normally be much less than the thickness of the cellular sheet. The thickness of capstock used is tbat necessary to ~18S~q provide enough lateral resistance to prevent the cellular material from expanding in the width direction. For example, a cellular sheet having a thickness of about 0.1 inch requires a capstock having a thickness of rrom about 0.001 to about 0.005 inch to restrict expansion in the lateral direction.
- The vinyl or vinylidene material and the polyolefin capstock may be coextruded using any of the well known methods of coextrusion. Coextrusion is a process whereby at least two separate materials are extruded through a common die resulting in a composite. A suitable method of coextrusion for use in this invention is described in U.S. Patent 3 t 833,704 Other suitable methods of co-extruding thermoplastics are described in U.S. Patents
Fine particle size inorganic fillers may also be included in amounts from about 1 to 15 weight parts includ-ing for example titanium dioxide, iron oxide, calcium carbon-ate, silicas and the like.
Group IIA metal oxides and hydroxides particularly calcium and magnesium oxide and hydroxide have been employed in amounts from about 0.1 to 5 weight parts. Any of the usual color pigments may be added to obtain desirable color in the cellular sheets.
Stabilizers known to those skilled in the art as the tin stabilizers, particularly the tin mercaptides, for example, dibutyltinthioethyldiglycolate and the lauryl derivative have been found useful in amounts from about 0.5 to 4 parts. Some synergism with the blowing agent has been observed with these materials.
3Q The noncellular incompatible capstock is coextruded with the cellular vinyl or vinylidene material. Materials suitable for the incompatible capstock includes polyolefins such as polyethylene, polypropylene, polyisobutylene and the like. Polyethylene was found to be an excellent choice as a capstock material. The thickness of the capstock will normally be much less than the thickness of the cellular sheet. The thickness of capstock used is tbat necessary to ~18S~q provide enough lateral resistance to prevent the cellular material from expanding in the width direction. For example, a cellular sheet having a thickness of about 0.1 inch requires a capstock having a thickness of rrom about 0.001 to about 0.005 inch to restrict expansion in the lateral direction.
- The vinyl or vinylidene material and the polyolefin capstock may be coextruded using any of the well known methods of coextrusion. Coextrusion is a process whereby at least two separate materials are extruded through a common die resulting in a composite. A suitable method of coextrusion for use in this invention is described in U.S. Patent 3 t 833,704 Other suitable methods of co-extruding thermoplastics are described in U.S. Patents
3,476,627 and 3,479,425. During the extrusion process, the materials are heated above their softening temperatures in order to allow them to conform to the shape of the extrusion die. The need for heating thermoplastic materials in order to extrude them is well known in the art.
The cellular material together with the attached capstock is cooled below their softening temperature before the capstock is removed. For purposes of keeping the cellu-lar material clean, it is preferred to not remove the capstock until after shipment to its final destination. The capstock can even be removed after the cellular material has been shaped by vacuum forming into its final product or after shipment of the product to its final destination.
; The cellular sheet of this invention will normally have a density of from about 0.4 to about l.l grams per cubic centimeter, preferably from about 0.5 to about 1.0 gram per cubic centimeter.
The following example is presented to more fully illustrate the present invention.
, EXAMPLE
; A rigid polyvinyl chloride resin having an inherent viscosity of about 0.92; and containing one part by weight of azobisformamide blowing agent per 100 parts by weight of polyvinyl chloride, was coextruded in sheet form with a high :, .
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density polyethylene (sp.gr. 0.95). The following extrusion conditions were used:
Polyvinyl Chloride Material Extruder: 2 1/2 inch Davis Standard Extruder 24:1 Screw: Mixing Screw, 0.185 inch Exit Depth, Compression Ratio 2.7:1 Die: 15 inch Wide Flex Lip Die Temperatu~e Zones-Barrel: 340F, 350F, 360F, 360F, 360F
10 Temperature Zones-Die: 355F, 360F, 355F
Head Pressure: 4000 PSI
Screw Speed: 15 RPM
Amperage: 30 Polyethylene Material 15 Extruder: 1 3/4 inch Screw: Single Stage Mixing Screw -~
Die: Feed Block, Connected to 15 inch Sheet Die Temperature Zones: 330F, 330F, 330F, 350F -20 Screw Speed: 2 RPM
Amperage: 5 - Using the above equipment and conditions, a 15 inch wide flat cellular extrudate was obtained having a density of 0.57 g/cc. The cellular polyvinyl chloride layer was 75 mils thick while the polyethylene layer was 2 mils thick. The ex-trudate was cooled to a temperature below the thermoplastic temperature of the polyvinyl chloride and the polyethylene.
After cooling, the polyethylene layer was easily removed resulting in a flat cellular sheet of rigid polyvinyl chloride.
The flat cellular sheeting of this invention have may uses, for example, they can be vacuum formed to produce packaging containers or decorative articles.
The cellular material together with the attached capstock is cooled below their softening temperature before the capstock is removed. For purposes of keeping the cellu-lar material clean, it is preferred to not remove the capstock until after shipment to its final destination. The capstock can even be removed after the cellular material has been shaped by vacuum forming into its final product or after shipment of the product to its final destination.
; The cellular sheet of this invention will normally have a density of from about 0.4 to about l.l grams per cubic centimeter, preferably from about 0.5 to about 1.0 gram per cubic centimeter.
The following example is presented to more fully illustrate the present invention.
, EXAMPLE
; A rigid polyvinyl chloride resin having an inherent viscosity of about 0.92; and containing one part by weight of azobisformamide blowing agent per 100 parts by weight of polyvinyl chloride, was coextruded in sheet form with a high :, .
; ~ ~ 7 ,..
~ .
, , :
: - , . ,, ~, ,, -- ~ 5~
density polyethylene (sp.gr. 0.95). The following extrusion conditions were used:
Polyvinyl Chloride Material Extruder: 2 1/2 inch Davis Standard Extruder 24:1 Screw: Mixing Screw, 0.185 inch Exit Depth, Compression Ratio 2.7:1 Die: 15 inch Wide Flex Lip Die Temperatu~e Zones-Barrel: 340F, 350F, 360F, 360F, 360F
10 Temperature Zones-Die: 355F, 360F, 355F
Head Pressure: 4000 PSI
Screw Speed: 15 RPM
Amperage: 30 Polyethylene Material 15 Extruder: 1 3/4 inch Screw: Single Stage Mixing Screw -~
Die: Feed Block, Connected to 15 inch Sheet Die Temperature Zones: 330F, 330F, 330F, 350F -20 Screw Speed: 2 RPM
Amperage: 5 - Using the above equipment and conditions, a 15 inch wide flat cellular extrudate was obtained having a density of 0.57 g/cc. The cellular polyvinyl chloride layer was 75 mils thick while the polyethylene layer was 2 mils thick. The ex-trudate was cooled to a temperature below the thermoplastic temperature of the polyvinyl chloride and the polyethylene.
After cooling, the polyethylene layer was easily removed resulting in a flat cellular sheet of rigid polyvinyl chloride.
The flat cellular sheeting of this invention have may uses, for example, they can be vacuum formed to produce packaging containers or decorative articles.
Claims (16)
1. A method for producing flat vinyl chloride or vinylidene chloride polymer cellular sheet comprising coextruding a heated polyolefin capstock with a heated vinyl chloride or vinylidene chloride polymer sheet con-taining at least one blowing agent, expanding said sheet into a cellular sheet, and then cooling said cellular sheet and said polyolefin capstock below their softening temperature, to form a product comprising said cellular sheet with said capstock attached thereto, said capstock being incompatible with said sheet and being readily strippable therefrom said capstock being effective during said expanding, to restrict the expansion of the sheet in-the width direction, while allowing expansion in the height direction.
2. A method of claim 1, including a step of removing said capstock from said cellular sheet.
3. A method of claim 1, wherein said cellular sheet has a density of from-about 0.4 to about 1.1 grams per cubic centimeter.
4. A method of claim 2, wherein said cellular sheet has a density of from about 0.4 to about 1.1 grams per cubic centimeter.
5. A method of claim 1, 2 or 4, wherein said cap-stock is non-cellular.
6. A method of claim 3, wherein said vinyl chloride or vinylidene chloride polymer contains copolymerized therewith up to about 50% by weight of at least one other olefinically unsaturated monomer.
7. A method of claim 6, wherein said other monomer is selected from the group consisting of 1-olefins con-taining from 2 to 12 carbon atoms, vinyl esters, .alpha.,.beta.-olefinically unsaturated carboxylic acids and esters thereof, amides of .alpha.,.beta.-olefinically unsaturated carboxylic acids, and esters of fumaric and maleic acid.
8. A method of claim 3, wherein said polyolefin capstock is polyethylene or polypropylene.
9. A method of claim 8, wherein said blowing agent is a nitrogen releasing chemical blowing agent.
10. A method of claim 9, wherein said cellular sheet has a density of from about 0.5 to about 1 gram per cubic centimeter.
11. A method of claim 10, wherein said polyolefin capstock is polyethylene.
12. A method of claim 11, wherein said blowing agent is azobisformamide.
13. A coextruded combination comprising a polyolefin capstock and a vinyl chloride or vinylidene chloride polymer, cellular sheet, said capstock being attached to but incompatible with said sheet and being readily strippable from the sheet, said capstock being effective, during expansion of said sheet to restrict the expansion of the sheet in the width direction, while allowing expansion in the height direction.
14. A combination according to claim 13, wherein said capstock is non-cellular.
15. A combination according to claim 13 or 14, wherein said polyolefin capstock is polyethylene or polypropylene and said cellular sheet has a density of from about 0.4 to about 1.1 grams per cubic centimeter.
16. A combination according to claim 13 or 14, wherein said cellular sheet has a density of from about 0.5 to 1 gram per cubic centimeter.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US83841377A | 1977-09-30 | 1977-09-30 | |
| US838,413 | 1977-09-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1118567A true CA1118567A (en) | 1982-02-23 |
Family
ID=25277035
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000309073A Expired CA1118567A (en) | 1977-09-30 | 1978-08-10 | Method for making flat cellular vinyl sheet |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1118567A (en) |
-
1978
- 1978-08-10 CA CA000309073A patent/CA1118567A/en not_active Expired
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| MKEX | Expiry |