CA1293077C - Extrudable blends of polyethylene and films thereof - Google Patents
Extrudable blends of polyethylene and films thereofInfo
- Publication number
- CA1293077C CA1293077C CA000544666A CA544666A CA1293077C CA 1293077 C CA1293077 C CA 1293077C CA 000544666 A CA000544666 A CA 000544666A CA 544666 A CA544666 A CA 544666A CA 1293077 C CA1293077 C CA 1293077C
- Authority
- CA
- Canada
- Prior art keywords
- ethylene
- low density
- films
- linear low
- polyvinylidene fluoride
- 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 - Lifetime
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- Manufacture Of Macromolecular Shaped Articles (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
EXTRUDABLE BLENDS OF POLYETHYLENE
AND FILMS THEREOF
ABSTRACT
The extrudability of linear polymers of ethylene such as low density copolymers of ethylene and C4 to C10 olefins (LLDPE) into thin films is improved by adding small amounts, e.g., 0.02 to 2 weight percent polyvinylidene fluoride to reduce melt fracture, head pressure and to obtain films having excellent anti-blocking characteristics.
AND FILMS THEREOF
ABSTRACT
The extrudability of linear polymers of ethylene such as low density copolymers of ethylene and C4 to C10 olefins (LLDPE) into thin films is improved by adding small amounts, e.g., 0.02 to 2 weight percent polyvinylidene fluoride to reduce melt fracture, head pressure and to obtain films having excellent anti-blocking characteristics.
Description
E~iRDnPlLE ELEND6 OF P3IYE3NYIENE
Linear ethylene polymers such a linear low density polyethylenes (LLDPE) are widely used in the extrusion of films because of their superior properties when ccmpqred with high pressure polyethylene (LDPE). However, there are persistent prcblems in the ocmmercial exploitation of mTnpE
resins due to difficulties in extrusion. For example, high back pressure and torque due to extremely high shear viscosity of the linear ethylene polymer axe encountered.
rurthermore, the extruded films exhibit surface distortion relatj~d to m~lt fracture. Accordingly, much effort has been devoted to finding additives, modifying extrusion conditions and changing die materials in order to alleviate some of the problems. For example, U.S. Patent 3,125,547 discloses the use of, i r alia, hexafluoropropylene-vinylidene fluoride oopolymer as a film processing aid.
m is invention relates to the use of a semi-crys~alline polymer of vinylidene fluoride, for example, polyvinylidene fluoride, which impruves the extrusion characteristics of linear ethylene polymers by reducing melt fracture and head pressure, and results in a film thereof having exoellent anti-blocking characteristics.
According to the present invention, there is prcvided an extruded film ocmprising:
(1) a linear low density polyethylene, viz, a linear oopolymer of ethylene and a higher olefin oontain mg 4 to 10 carbon atoms, having a density of 0.90 to 0.94; and (2) 0.02 to 2 weight percent of polyvinylidene fluoride hamopolymer. & id film has reduoed blocXing oompqred to a film of the same oopolymer of ethylene containing the same weiqht of hexafluoropropylene-vinylidene fluoride copolymer.
m e linear ethylene polymers (i) which are suitable for use in this invention are kncwn materials which are widely commercially available. me preparation of suitable polymers is described in U.S. Patent 4,076,698. Suitable polymers are generally prepared , lZ~3a1~i7 under low pressure conditions using Ziegler-Natta catalysts or chromium oxide catalysts. The linear polymers are either homopolymers of ethylene or copolymers of ethylene and alpha-olefins containing from 4 to lO carbon atoms such as butene, hexene or octene. This invention is particularly concerned with linear low density polyethylenes which are copolymers as aforesaid and having a density between 0.90 and 0.94, preferably between O.9l and 0.93.
The semicrystalline polymer of vinylidene fluoride (ii) is preferably polyvinylidene fluoride homopolymer and should have melt flow characteristics similar to that of the linear polyethylene polymer so that it can be easily dispersed in the polyethylene. The weight average molecular weight of (ii) should be in the range of 20,000 to l,000,000, preferably between 40,000 to 500,000.
Desirably, (ii) should be present in an amount from 0.02 to 2 percent by weight.
The semicrystalline polymer (ii) can be blended with the linear ethylene polymer in any suitable manner. It has been found to be advantageous to prepare a masterbatch containing the linear ethylene polymer (i) which is rich in the semicrystalline polymer (ii) for blending with additional ethylene polymer to achieve the desired concentration of the additives.
This invention also provides an extruded film comprlsing a composition as herein defined.
The following non-limiting Examples illustrate the invention.
EXAMPLES 1 to 6 The linear low density polyethylene (LLDPE) used in all of the Examples was an ethylene-butene copolymer having a density of O.9l~ and a melt index of l which exhibits severe melt fracture under commercial narrow die gap extrusion conditions. The polyvinylidene fluoride used in the examples had a weight average molecular weight of about 50,000 (Kynar 720 obtained from the ~.
Linear ethylene polymers such a linear low density polyethylenes (LLDPE) are widely used in the extrusion of films because of their superior properties when ccmpqred with high pressure polyethylene (LDPE). However, there are persistent prcblems in the ocmmercial exploitation of mTnpE
resins due to difficulties in extrusion. For example, high back pressure and torque due to extremely high shear viscosity of the linear ethylene polymer axe encountered.
rurthermore, the extruded films exhibit surface distortion relatj~d to m~lt fracture. Accordingly, much effort has been devoted to finding additives, modifying extrusion conditions and changing die materials in order to alleviate some of the problems. For example, U.S. Patent 3,125,547 discloses the use of, i r alia, hexafluoropropylene-vinylidene fluoride oopolymer as a film processing aid.
m is invention relates to the use of a semi-crys~alline polymer of vinylidene fluoride, for example, polyvinylidene fluoride, which impruves the extrusion characteristics of linear ethylene polymers by reducing melt fracture and head pressure, and results in a film thereof having exoellent anti-blocking characteristics.
According to the present invention, there is prcvided an extruded film ocmprising:
(1) a linear low density polyethylene, viz, a linear oopolymer of ethylene and a higher olefin oontain mg 4 to 10 carbon atoms, having a density of 0.90 to 0.94; and (2) 0.02 to 2 weight percent of polyvinylidene fluoride hamopolymer. & id film has reduoed blocXing oompqred to a film of the same oopolymer of ethylene containing the same weiqht of hexafluoropropylene-vinylidene fluoride copolymer.
m e linear ethylene polymers (i) which are suitable for use in this invention are kncwn materials which are widely commercially available. me preparation of suitable polymers is described in U.S. Patent 4,076,698. Suitable polymers are generally prepared , lZ~3a1~i7 under low pressure conditions using Ziegler-Natta catalysts or chromium oxide catalysts. The linear polymers are either homopolymers of ethylene or copolymers of ethylene and alpha-olefins containing from 4 to lO carbon atoms such as butene, hexene or octene. This invention is particularly concerned with linear low density polyethylenes which are copolymers as aforesaid and having a density between 0.90 and 0.94, preferably between O.9l and 0.93.
The semicrystalline polymer of vinylidene fluoride (ii) is preferably polyvinylidene fluoride homopolymer and should have melt flow characteristics similar to that of the linear polyethylene polymer so that it can be easily dispersed in the polyethylene. The weight average molecular weight of (ii) should be in the range of 20,000 to l,000,000, preferably between 40,000 to 500,000.
Desirably, (ii) should be present in an amount from 0.02 to 2 percent by weight.
The semicrystalline polymer (ii) can be blended with the linear ethylene polymer in any suitable manner. It has been found to be advantageous to prepare a masterbatch containing the linear ethylene polymer (i) which is rich in the semicrystalline polymer (ii) for blending with additional ethylene polymer to achieve the desired concentration of the additives.
This invention also provides an extruded film comprlsing a composition as herein defined.
The following non-limiting Examples illustrate the invention.
EXAMPLES 1 to 6 The linear low density polyethylene (LLDPE) used in all of the Examples was an ethylene-butene copolymer having a density of O.9l~ and a melt index of l which exhibits severe melt fracture under commercial narrow die gap extrusion conditions. The polyvinylidene fluoride used in the examples had a weight average molecular weight of about 50,000 (Kynar 720 obtained from the ~.
3(~77 Pennwalt Corporation). The hexafluoropropylene-vinylidene fluoride polymer used in the control examples was Viton A from E.I. du Pont de Nemours and Company.
Blocking force of the films containing various amounts of the fluoropolymer was measured according to the ASTM method (D-3354) on five samples of each film, averaged and reported in the Table below.
T _ (Control) lo Grams Grams Blocking Force Blocking Force Example Wt. % (KYNAR) (VITO~ A) 1 2.0 27.9 94.7 2 1.0 55.9 101 3 0.5 85.5 108 4 .25 115 120 0.1 119 130 6 0.04 130 133 All samples exhibited the absence of melt fracture which is obtained when the same polymer is extruded under the same conditions without fluorocarbon polymer but the"Kynar"(polyvinylidene fluoride) examples give films having less blocking than the Viton counterparts.
("KYNAR" and "VITON" are registered Trademarks.) . ~
Blocking force of the films containing various amounts of the fluoropolymer was measured according to the ASTM method (D-3354) on five samples of each film, averaged and reported in the Table below.
T _ (Control) lo Grams Grams Blocking Force Blocking Force Example Wt. % (KYNAR) (VITO~ A) 1 2.0 27.9 94.7 2 1.0 55.9 101 3 0.5 85.5 108 4 .25 115 120 0.1 119 130 6 0.04 130 133 All samples exhibited the absence of melt fracture which is obtained when the same polymer is extruded under the same conditions without fluorocarbon polymer but the"Kynar"(polyvinylidene fluoride) examples give films having less blocking than the Viton counterparts.
("KYNAR" and "VITON" are registered Trademarks.) . ~
Claims (8)
1. An extruded film comprising:
(1) a linear low density polyethylene, viz, a linear copolymer of ethylene and a higher olefin containing 4 to 10 carbon atoms, having a density of 0.90 to 0.94; and (2) 0.02 to 2 weight percent of polyvinylidene fluoride homopolymer.
(1) a linear low density polyethylene, viz, a linear copolymer of ethylene and a higher olefin containing 4 to 10 carbon atoms, having a density of 0.90 to 0.94; and (2) 0.02 to 2 weight percent of polyvinylidene fluoride homopolymer.
2. The film of claim 1 in which said linear low density polyethylene is a copolymer of ethylene and butene.
3. The film of claim 1 in which said linear low density polyethylene is a copolymer of ethylene and hexene.
4. The film of claim 1 in which said linear low density polyethylene is a copolymer of ethylene and octene.
5. An extruded film according to claim 1 in which the polyvinylidene fluoride homopolymer has a weight average molecular weight of from 20,000 to 1,000,000.
6. An extruded film according to claim 1 in which the polyvinylidene fluoride homopolymer has a weight average molecular weight of from 40,000 to 500,000.
7. An extruded film according to any one of claims 1-6 wherein the linear low density polyethylene has a density of from 0.91 to 0.93.
8. An extruded film according to claim 1 or claim 2 wherein said linear low density polyethylene is an ethylene-butene copolymer having a density of 0.918 and a melt index of 1, and wherein said polyvinylidene fluoride has a weight average molecular weight of about 50,000.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000544666A CA1293077C (en) | 1987-08-17 | 1987-08-17 | Extrudable blends of polyethylene and films thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000544666A CA1293077C (en) | 1987-08-17 | 1987-08-17 | Extrudable blends of polyethylene and films thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1293077C true CA1293077C (en) | 1991-12-10 |
Family
ID=4136287
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000544666A Expired - Lifetime CA1293077C (en) | 1987-08-17 | 1987-08-17 | Extrudable blends of polyethylene and films thereof |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1293077C (en) |
-
1987
- 1987-08-17 CA CA000544666A patent/CA1293077C/en not_active Expired - Lifetime
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |