CA2161906A1 - Lld-polyethylene with reduced melt fracture - Google Patents
Lld-polyethylene with reduced melt fractureInfo
- Publication number
- CA2161906A1 CA2161906A1 CA002161906A CA2161906A CA2161906A1 CA 2161906 A1 CA2161906 A1 CA 2161906A1 CA 002161906 A CA002161906 A CA 002161906A CA 2161906 A CA2161906 A CA 2161906A CA 2161906 A1 CA2161906 A1 CA 2161906A1
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- Prior art keywords
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- composition according
- processing aid
- polyethylene
- composition
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/08—Copolymers of ethene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/06—Polyethene
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/08—Copolymers of ethene
- C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
- C08L23/0815—Copolymers of ethene with aliphatic 1-olefins
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/08—Copolymers of ethene
- C08L23/0846—Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
- C08L23/0869—Acids or derivatives thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L71/00—Compositions of polyethers obtained by reactions forming an ether link in the main chain; Compositions of derivatives of such polymers
- C08L71/02—Polyalkylene oxides
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
- C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
- C08L2666/04—Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
- C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
- C08L2666/04—Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
- C08L2666/06—Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
Abstract
The present invention relates to a polyolefin composition, having good extrusion characteristics. The composition comprises one or more low molecular weight poly C2-4 alkylene oxides; an acrylic processing aid and the polyolefin. The blend is fluoropolymer-free and is suitable for making blown film.
Description
21619û~ Patent LLD-Polyethylene With Reduced Melt Fracture FIELD OF THE INVENTION
The present invention relates to polyolefins suitable for use in extrusion processes. More particularly the present invention relates to polyolefin compositions suitable for the manufacture of blown film having a good surface appearance.
BACKGROUND OF THE INVENTION
In the manufacture of extruded polymers there are a number of surface defects referred to as sharkskin, snakeskin and orange peel which all are related to the rheology of the polymer melt and in particular the melt fracture of the polymer. Melt fracture arises when the shear rate at the surface of the polymer is sufficiently high that the surface of the polymer begins to fracture. That is there is a slippage of the surface of the extruded polymer relative the body of the polymer melt. The surface generally can't flow fast enough to keep up with the body of the extrudate and a fracture in the melt occurs generally resulting in a loss of surface properties for the extrudate.
United States Patent 3,125,547 issued March 17, 1964 assigned to E.l. DuPont de Nemours and Company discloses blends of polyethylene and small amounts of fluoropolymers to provide a smooth surface on extrudate at high extrusion speeds.
United States Patent 3,222,314 issued December 7, 1965, assigned to E.l. DuPont de Nemours and Company discloses blends of polyethylene and low molecular weight polyethylene glycol to provide a heat sealable film suitable for printing.
ps~"~opecls11ocan doc - 2 -216 I 9 0 ~ Patent European Patent Application 0 060 673 published 22.09.82 discloses the use of low molecular weight polyalkylene oxides as a processing aid in the manufacture of extruded polyolefins.
There are a series of patents in the name of the Minnesota Mining and Manufacturing Company relating to the use of a combination of polyalkylene oxides and fluorocarbon polymers as a process aid in extrusion of polyolefins. These patents include U.S. 4,855,360 issued August 8, 1989 which discloses and claims a composition of matter comprising the polyolefin and the process aid; U.S. 5,015,693 which claims the process aid per se; U.S. patent 4,863,983 issued September 5, 1989 and U.S. patent 4,983,677 issued January 8,1991 which patents disclose and claim the use of an organophosphite in conjunction with the 20 fluoropolymer as a process aid.
The first two 3M patents teach that the ratio of fluoropolymer to glycol must be from 1 :1 to 1 :10. That is the glycol must always be used in excess of the fluoropolymer.
U.S. patent 4,829,116, issued May 9,1989 discloses a polyolefin molding composition comprising linear low density polyethylene (LLDPE);
a fluorine containing polymer such as a polymer of vinylidene fluoride and hexafluoropropylene; and a wax such as an ester of montanic acid.
The aforementioned patents all require the use of one or more fluoropolymers to improve processibility of the polyolefin. These fluoropolymers are very expensive so there is a clear economic incentive to reduce or eliminate the use thereof.
psc,j",'i"~cl9110can.doc - 3 -2 1 6 1 9 ~ 6 Patent In U.S. patent 4,963,622, assigned to Union Carbide Corporation, it is disclosed that the use of an acrylic processing aid improves the extrusion of high density polyethylene (HDPE). However, the use of this processing aid provides only a marginal improvement in the extrusion of LLDPE. We have now discovered that the combination of an acrylic processing aid and a polyalkylene oxide substantially improves the extrusion of LLDPE.
SUMMARY OF THE INVENTION
In accordance with the broadest aspects of the present invention there is provided a fluoropolymer-free extrudable composition comprising:
(i) a predominant component which contains at least 50 weight % of linear low density polyethylene;
(ii) from 0.01 to 1 weight % of at least one polyalkylene oxide or ether and mixtures thereof; and (iii) from 0.05 to 1 weight % of an acrylic processing aid.
The present invention also provides blown film (typically from 0.20 to 30 mils thick), and coated wire or optical cable made using the above compositions.
The compositions of the present invention may also be useful in extrusion of pipes or tubing and the extrusion of a thick film (typically greater than 20 mils) or geomembranes.
The invention also encompasses processes to extrude the above compositions.
psGrJ~ G/s11oGan doc - 4 -216190~ Patent DETAILED DESCRIPTION
The major or predominant component in the compositions of the present invention is an extrudable composition which contains linear low density polyethylene (LLDPE). The predominant component is present in an amount of at least about 98% by weight (weight %) of the base composition. That is, the composition may include pigments and fillers in 10 a typical amount but they would not be considered a part of the base component. The predominant composition contains at least 50% by weight of LLDPE and may also contain other extrudable polymers such as HDPE, polypropylene and/or "high pressure low density polyethylene".
The LLDPE used in this invention is a copolymer of ethylene with another alpha olefin (such as butene, hexene or octene) which has a 20 density of less than 0.940 grams per cubic centimeter (g/cc). Such LLDPE products are widely available articles of commerce and may be prepared by conventional polymerization processes. The polymerization may be in gas phase (that is, at relatively low pressures below 500 psi, preferably below about 250 psi; at temperatures below about 1 30~C; and using a fluidized bed catalyst (such as the process patented by Union Carbide Corporation)); in solution (a process at high temperatures -30typically from about 130 to 300~C, by dissolving ethylene and other comonomer(s) in a solvent such as hexane and in the presence of a coordination catalyst such as those disclosed in a number of patents in the name of DuPont) or slurry polymerization initiated by a coordination catalyst or in the case of high pressure polymerization by free radicals.
ps~"~ ,e~110can.doc -5-Patent The details of such types of polymerization are generally known to those skilled in the art of polymerization.
Depending on the type of polymerization the olefin polymer may have a molecular weight (weight average - Mw) from about 100,000 up to 1,000,000 typically from about 100,000 to 350,000. More than one type of LLDPE may be present.
The second component in the compositions of the present invention is a polyalkylene oxide (PAO) having a molecular weight less than 20,000. Preferably the weight average molecular weight (Mw) of the PAO is less than 10,000. Most preferably the PAO has a molecular weight (Mw) from 2,500 to 6,000. The alkyl ethers of PAO may also be used. Suitable ethers include methyl ethers comprising on average from 30 to 80 ethylene oxide units. Applicants are using the phrase "on average" as the PAOs are mixtures and are best characterized by an average number of alkylene oxide units in the composition while there may be in the composition individual glycol molecules having a greater or lesser number of alkylene oxide units.
The PAOs or their alkyl ethers may be used in the compositions of the present invention in an amount from 0.01 to 1, preferably 0.01 to 0.18% based on the weight of the total composition (weight %). The preferred PAOs are polyethylene glycols and their alkyl ethers The third component in the compositions of the present invention is an acrylic processing aid. The term acrylic processing aid is generally meant to refer to those acrylic polymers prepared from alkyl acrylates or alkyl methacrylates and/or other monomers which are copolymerizable psG,~ /s~JeGIs11OGan.dOG - 6 -2161906 Patent therewith (such as styrene), which are known to improve the processibility/
extrusion of polyvinyl chloride (PVC). Preferred examples of such acrylic processing aids are copolymers of methyl methacrylate and styrene (optimally containing additional, higher acrylates such as ethyl acrylate or butyl acrylate), blends of such polymers with homopolymer polymethymethacrylate; and/or"core-shell" polymers prepared from these monomers. Specific examples include acrylic processing aids sold by Rohm and Haas under the trademarks PARALOID and/or ACRYLOID, which processing aids are reported to be polymers prepared predominantly with methyl methacrylate, butyl acrylate and styrene and having a molecular weight (Mw) of between 50,000 and 250,000.
The acrylic processing aid component is present in the 2 o compositions of the present invention in an amount from 0.05 to 1, preferably from 0.40% to 0.80 % by weight based on the total weight of the composition (weight %).
The present inventions preferably contain a weak metal base. The metal base may be a weak oxide of an alkaline earth or a transition metal or hydrotalcite (Mg6AI2(OH),6 CO3. 4H20). A particularly useful metal base is zinc oxide. The zinc oxide may be incorporated into the composition in an amount from at least 25, preferably from 50 to 500, most preferably from 100 to 300 parts per million (ppm). Useful metal bases include hydrotalcite (Mg6AI2(OH)16 CO3. 4H20) and zinc oxide, preferably zinc oxide. The zinc oxide may be included in a master batch comprising antioxidant, and PAO. A suitable masterbatch composition might comprise from 20 to 30 weight % of an antioxidant (such as IRGANOXTM
psclï,.,/spec/9110can.doc - 7 -2161906 Patent (of Ciba Geigy)), from 10 to 20 weight % of zinc oxide and the balance of PAO (such as the PAO sold under the name CARBOWAXTM 5000 by Carbide Corporation).
The compositions of the present invention may further include fillers, antioxidants (at least a primary and optionally a secondary antioxidant), pigments, opacifying agents and other adjuvants. For film lo applications preferably no pigment or filler is added and the film is clear or relatively clear. In other applications such as wire and cable (electrical or optical) the compound may contain a pigmenVfiller such as carbon black and other adjuvants (in these types of applications the unsubstituted olefin polymer may be grafted by extrusion with a functional ethylenically unsaturated monomer such as maleic anhydride in the presence of a free 20 radical agent such as a peroxide).
Typically if an antioxidant (primary alone or optionally in combination with a secondary antioxidant) is used it is used in an amount from about 0.01 to 2, preferably 0.01 to about 1 weight %. Fillers may be incorporated into the compositions of the present invention in amounts up to about 50%, preferably less than about 30%.
Typically, the polymer compositions of the present invention will be prepared by melt blending. There are several methods which could be used to produce the compositions of the present invention. All the components may be dry blended in the required weight ratio in a suitable device such as a tumble blender. The resulting dry blend is then melted in suitable equipment such as an extruder. A master batch could be prepared with some of the olefin and the other ingredients. The psc~ pecl9110can.doc - 8 -~ 216190G ~,161~0~ Patent masterbatch is then fed to an extruder and melt blended. In a third method the dry components of the blend may be metered directly into an extruder.
The extruder may be a twin or single screw extruder. If it is a twin screw extruder it may be operated in a co-rotating mode (i.e. both screws turning in the same direction) or in a counter rotating mode (i.e. the screws rotate in opposite directions).
The specific conditions for operation of any extruder will differ from that of any other extruder. The variations between machines may usually be resolved by non-inventive testing. Typically, laboratory twin screw extruders will operate within the following envelope of conditions. The barrel will be heated to a temperature from about 180 to 210, preferably from 190 to 200~C. The screw speed will be from 120 to 150, preferably from 120 to 130 RPM's. The back pressure on the extruder will be from about 1000 to 1300, preferably from 1 100 to 1250 psi. As noted above the specific conditions for the operation of any specific extruder can readily be determined by one skilled in the art by non-inventive testing in view of the above envelope of conditions.
The extruder will typically extrude the polymer composition as strands which are then cooled and cut into pellets for subsequent use, typically film extrusion.
The film extruder may also be a single or twin screw extruder. The die may be a slot die or it may be an annular ring die extruding a film of the polymer alloy about a stable bubble of air. The film is collapsed after passing over or about the bubble. For laboratory scale film extrusion the 311Ocan.doc - 9 -21619 0 ~ Patent extruder may be operated within the envelope of parameters as set forth in the examples.
Examples The following ingredients were used in the Examples. LLDPE-1 was a commercially available LLDPE prepared from ethylene and hexene (having a density of about 0.917 g/cc and a "melt index" of about 1.0 [as determined by ASTM D-1238, at a load of 2.16 kg and a temperature of 1 90~C]) sold under the trademark NOVAPOL by Novacor Chemicals.
LLDPE-2 was a similar, hexene based LLDPE having a density of about 0.924 g/cc and "melt index" of about 0.80 sold under the trademark NOVAPOL by Novacor Chemicals.
The fluoroelastomer used in the comparative examples was a commercial product (DYNAMARTM FX-9613 sold by Minnesota Mining and Manufacturing Company) and is reported to be a mixture of elastomeric copolymer (of vinylidene fluoride and hexafluoropropylene) with a minor about (about 10%) of an anti-agglomerate.
The PAO was a commercialiy available polyethylene glycol having an Mw of about 5000 sold under the trademark CARBOWAX 5000.
The acrylic processing aid was a commercially available product (believed to be polymerized from methyl methacrylate, butyl acrylate and styrene) sold under the trademark PARALOID K-175 by Rohm and Haas.
Other conventional ingredients include a hundred phenolic antioxidant (sold under the trademark "IRGANOX 1076" by Ciba); a phosphate-based secondary antioxidant ("WESTON 399"); zinc oxide; an pscr~us~ecls11ocan~doc - 10-21 ~19 ~ G Patent amine-based ultraviolet stabilizer ("KEMAMINE AS-990") and a binding agent for other additives ("SYLOID 279").
A series of compounds having the formulations shown in Table 1 were prepared.
The compounds were then processed on a blown film line under the following conditions:
Melt temperature: 380-425~F (about 195 to 220~C) Output (kg/hr): indicated in Table 1 Film thickness (aiming point): 1.5 mils Control example 1 illustrates that melt fracture (MF) occurs in the absence of any processing aid.
Comparative example 2 demonstrates that the addition of 0.5 weight % acrylic processing aid is insufficient to eliminate melt fracture under the test conditions.
Comparative example 3 shows that the combination of acrylic processing aid and fluoroelastomer is also insufficient to eliminate melt fracture under the test conditions.
Inventive example 4 show that the combination of acrylic processing aid and PAO completely eliminated melt fracture outputs of about 100, 157 and 177 pounds of polyethylene per hour (and of equal significance, the film was clear and visually grain-free at outputs of 100 and 157 pounds/hr).
Comparative example 5 surprisingly demonstrates that the addition of fluoroelastomer to the composition of inventive Example 4 causes deterioration of extruder performance. Specifically, the film produced with ps~"l.,,b~cl91 10can.doc 216190G Patent the fluoroelastomer additive was visually "grainy" at all output rates tested.
This is a highly unusual result as the addition of fluoroelastomer typically improves the extrusion of polyethylene film.
Inventive example 6 illustrates that the combination of the acrylic processing aid and polyethylene glycol provides a comparatively good quality film even when silica is present. (It will be appreciated by those skilled in the art that silica typically causes problems with the production of melt fracture-free, clear polyethylene films.) psclj.~ GI911Ocan.do~ -12-Patent ~ ~ 1' o O O
Melt Fracture Trials Results/Formulation MELT FRACTURE-EST
COMPOSITION OUT-PUT uy., MELT F
BLEND # (Weight %) LBS/HR UND NO MELT F COMMENT
1. (Control) LLDPE-1 99.750 51 Y Control IRGANOX-1076 0.030 No PPA
KEMAMINE AS-990 0.050 ZINC STEARATE 0.050 98 Y Port Fracture WESTON 399 0.120 SYLOID 279 1.005 2. (Comparative) LLDPE-1 99.375 100 y MF - Grainy Grainy K-175 0.500 WESTON 399 0.125 118 Y MF - Grainy Grainy 3. (Comparative) LLDPE-1 99.330 100 y MF - Grainy Grainy K-175 0.500 cs:, WESTON 399 0.125 160 Y MF - Grainy Grainy FX-9613 0.045 c~
180 Y MF - Grainy Grainy c:~
psc~mispe~/911Ocan.d~c - 13-Patent w ~ ,--o o o TABLE 1 (Continued) MELT FRACTURE -EST
COMPOSITION OUT-PUT uy,, MELT F
BLEND # (Weight %) LBS/HRUN~ NO MELT F COMMENT
The present invention relates to polyolefins suitable for use in extrusion processes. More particularly the present invention relates to polyolefin compositions suitable for the manufacture of blown film having a good surface appearance.
BACKGROUND OF THE INVENTION
In the manufacture of extruded polymers there are a number of surface defects referred to as sharkskin, snakeskin and orange peel which all are related to the rheology of the polymer melt and in particular the melt fracture of the polymer. Melt fracture arises when the shear rate at the surface of the polymer is sufficiently high that the surface of the polymer begins to fracture. That is there is a slippage of the surface of the extruded polymer relative the body of the polymer melt. The surface generally can't flow fast enough to keep up with the body of the extrudate and a fracture in the melt occurs generally resulting in a loss of surface properties for the extrudate.
United States Patent 3,125,547 issued March 17, 1964 assigned to E.l. DuPont de Nemours and Company discloses blends of polyethylene and small amounts of fluoropolymers to provide a smooth surface on extrudate at high extrusion speeds.
United States Patent 3,222,314 issued December 7, 1965, assigned to E.l. DuPont de Nemours and Company discloses blends of polyethylene and low molecular weight polyethylene glycol to provide a heat sealable film suitable for printing.
ps~"~opecls11ocan doc - 2 -216 I 9 0 ~ Patent European Patent Application 0 060 673 published 22.09.82 discloses the use of low molecular weight polyalkylene oxides as a processing aid in the manufacture of extruded polyolefins.
There are a series of patents in the name of the Minnesota Mining and Manufacturing Company relating to the use of a combination of polyalkylene oxides and fluorocarbon polymers as a process aid in extrusion of polyolefins. These patents include U.S. 4,855,360 issued August 8, 1989 which discloses and claims a composition of matter comprising the polyolefin and the process aid; U.S. 5,015,693 which claims the process aid per se; U.S. patent 4,863,983 issued September 5, 1989 and U.S. patent 4,983,677 issued January 8,1991 which patents disclose and claim the use of an organophosphite in conjunction with the 20 fluoropolymer as a process aid.
The first two 3M patents teach that the ratio of fluoropolymer to glycol must be from 1 :1 to 1 :10. That is the glycol must always be used in excess of the fluoropolymer.
U.S. patent 4,829,116, issued May 9,1989 discloses a polyolefin molding composition comprising linear low density polyethylene (LLDPE);
a fluorine containing polymer such as a polymer of vinylidene fluoride and hexafluoropropylene; and a wax such as an ester of montanic acid.
The aforementioned patents all require the use of one or more fluoropolymers to improve processibility of the polyolefin. These fluoropolymers are very expensive so there is a clear economic incentive to reduce or eliminate the use thereof.
psc,j",'i"~cl9110can.doc - 3 -2 1 6 1 9 ~ 6 Patent In U.S. patent 4,963,622, assigned to Union Carbide Corporation, it is disclosed that the use of an acrylic processing aid improves the extrusion of high density polyethylene (HDPE). However, the use of this processing aid provides only a marginal improvement in the extrusion of LLDPE. We have now discovered that the combination of an acrylic processing aid and a polyalkylene oxide substantially improves the extrusion of LLDPE.
SUMMARY OF THE INVENTION
In accordance with the broadest aspects of the present invention there is provided a fluoropolymer-free extrudable composition comprising:
(i) a predominant component which contains at least 50 weight % of linear low density polyethylene;
(ii) from 0.01 to 1 weight % of at least one polyalkylene oxide or ether and mixtures thereof; and (iii) from 0.05 to 1 weight % of an acrylic processing aid.
The present invention also provides blown film (typically from 0.20 to 30 mils thick), and coated wire or optical cable made using the above compositions.
The compositions of the present invention may also be useful in extrusion of pipes or tubing and the extrusion of a thick film (typically greater than 20 mils) or geomembranes.
The invention also encompasses processes to extrude the above compositions.
psGrJ~ G/s11oGan doc - 4 -216190~ Patent DETAILED DESCRIPTION
The major or predominant component in the compositions of the present invention is an extrudable composition which contains linear low density polyethylene (LLDPE). The predominant component is present in an amount of at least about 98% by weight (weight %) of the base composition. That is, the composition may include pigments and fillers in 10 a typical amount but they would not be considered a part of the base component. The predominant composition contains at least 50% by weight of LLDPE and may also contain other extrudable polymers such as HDPE, polypropylene and/or "high pressure low density polyethylene".
The LLDPE used in this invention is a copolymer of ethylene with another alpha olefin (such as butene, hexene or octene) which has a 20 density of less than 0.940 grams per cubic centimeter (g/cc). Such LLDPE products are widely available articles of commerce and may be prepared by conventional polymerization processes. The polymerization may be in gas phase (that is, at relatively low pressures below 500 psi, preferably below about 250 psi; at temperatures below about 1 30~C; and using a fluidized bed catalyst (such as the process patented by Union Carbide Corporation)); in solution (a process at high temperatures -30typically from about 130 to 300~C, by dissolving ethylene and other comonomer(s) in a solvent such as hexane and in the presence of a coordination catalyst such as those disclosed in a number of patents in the name of DuPont) or slurry polymerization initiated by a coordination catalyst or in the case of high pressure polymerization by free radicals.
ps~"~ ,e~110can.doc -5-Patent The details of such types of polymerization are generally known to those skilled in the art of polymerization.
Depending on the type of polymerization the olefin polymer may have a molecular weight (weight average - Mw) from about 100,000 up to 1,000,000 typically from about 100,000 to 350,000. More than one type of LLDPE may be present.
The second component in the compositions of the present invention is a polyalkylene oxide (PAO) having a molecular weight less than 20,000. Preferably the weight average molecular weight (Mw) of the PAO is less than 10,000. Most preferably the PAO has a molecular weight (Mw) from 2,500 to 6,000. The alkyl ethers of PAO may also be used. Suitable ethers include methyl ethers comprising on average from 30 to 80 ethylene oxide units. Applicants are using the phrase "on average" as the PAOs are mixtures and are best characterized by an average number of alkylene oxide units in the composition while there may be in the composition individual glycol molecules having a greater or lesser number of alkylene oxide units.
The PAOs or their alkyl ethers may be used in the compositions of the present invention in an amount from 0.01 to 1, preferably 0.01 to 0.18% based on the weight of the total composition (weight %). The preferred PAOs are polyethylene glycols and their alkyl ethers The third component in the compositions of the present invention is an acrylic processing aid. The term acrylic processing aid is generally meant to refer to those acrylic polymers prepared from alkyl acrylates or alkyl methacrylates and/or other monomers which are copolymerizable psG,~ /s~JeGIs11OGan.dOG - 6 -2161906 Patent therewith (such as styrene), which are known to improve the processibility/
extrusion of polyvinyl chloride (PVC). Preferred examples of such acrylic processing aids are copolymers of methyl methacrylate and styrene (optimally containing additional, higher acrylates such as ethyl acrylate or butyl acrylate), blends of such polymers with homopolymer polymethymethacrylate; and/or"core-shell" polymers prepared from these monomers. Specific examples include acrylic processing aids sold by Rohm and Haas under the trademarks PARALOID and/or ACRYLOID, which processing aids are reported to be polymers prepared predominantly with methyl methacrylate, butyl acrylate and styrene and having a molecular weight (Mw) of between 50,000 and 250,000.
The acrylic processing aid component is present in the 2 o compositions of the present invention in an amount from 0.05 to 1, preferably from 0.40% to 0.80 % by weight based on the total weight of the composition (weight %).
The present inventions preferably contain a weak metal base. The metal base may be a weak oxide of an alkaline earth or a transition metal or hydrotalcite (Mg6AI2(OH),6 CO3. 4H20). A particularly useful metal base is zinc oxide. The zinc oxide may be incorporated into the composition in an amount from at least 25, preferably from 50 to 500, most preferably from 100 to 300 parts per million (ppm). Useful metal bases include hydrotalcite (Mg6AI2(OH)16 CO3. 4H20) and zinc oxide, preferably zinc oxide. The zinc oxide may be included in a master batch comprising antioxidant, and PAO. A suitable masterbatch composition might comprise from 20 to 30 weight % of an antioxidant (such as IRGANOXTM
psclï,.,/spec/9110can.doc - 7 -2161906 Patent (of Ciba Geigy)), from 10 to 20 weight % of zinc oxide and the balance of PAO (such as the PAO sold under the name CARBOWAXTM 5000 by Carbide Corporation).
The compositions of the present invention may further include fillers, antioxidants (at least a primary and optionally a secondary antioxidant), pigments, opacifying agents and other adjuvants. For film lo applications preferably no pigment or filler is added and the film is clear or relatively clear. In other applications such as wire and cable (electrical or optical) the compound may contain a pigmenVfiller such as carbon black and other adjuvants (in these types of applications the unsubstituted olefin polymer may be grafted by extrusion with a functional ethylenically unsaturated monomer such as maleic anhydride in the presence of a free 20 radical agent such as a peroxide).
Typically if an antioxidant (primary alone or optionally in combination with a secondary antioxidant) is used it is used in an amount from about 0.01 to 2, preferably 0.01 to about 1 weight %. Fillers may be incorporated into the compositions of the present invention in amounts up to about 50%, preferably less than about 30%.
Typically, the polymer compositions of the present invention will be prepared by melt blending. There are several methods which could be used to produce the compositions of the present invention. All the components may be dry blended in the required weight ratio in a suitable device such as a tumble blender. The resulting dry blend is then melted in suitable equipment such as an extruder. A master batch could be prepared with some of the olefin and the other ingredients. The psc~ pecl9110can.doc - 8 -~ 216190G ~,161~0~ Patent masterbatch is then fed to an extruder and melt blended. In a third method the dry components of the blend may be metered directly into an extruder.
The extruder may be a twin or single screw extruder. If it is a twin screw extruder it may be operated in a co-rotating mode (i.e. both screws turning in the same direction) or in a counter rotating mode (i.e. the screws rotate in opposite directions).
The specific conditions for operation of any extruder will differ from that of any other extruder. The variations between machines may usually be resolved by non-inventive testing. Typically, laboratory twin screw extruders will operate within the following envelope of conditions. The barrel will be heated to a temperature from about 180 to 210, preferably from 190 to 200~C. The screw speed will be from 120 to 150, preferably from 120 to 130 RPM's. The back pressure on the extruder will be from about 1000 to 1300, preferably from 1 100 to 1250 psi. As noted above the specific conditions for the operation of any specific extruder can readily be determined by one skilled in the art by non-inventive testing in view of the above envelope of conditions.
The extruder will typically extrude the polymer composition as strands which are then cooled and cut into pellets for subsequent use, typically film extrusion.
The film extruder may also be a single or twin screw extruder. The die may be a slot die or it may be an annular ring die extruding a film of the polymer alloy about a stable bubble of air. The film is collapsed after passing over or about the bubble. For laboratory scale film extrusion the 311Ocan.doc - 9 -21619 0 ~ Patent extruder may be operated within the envelope of parameters as set forth in the examples.
Examples The following ingredients were used in the Examples. LLDPE-1 was a commercially available LLDPE prepared from ethylene and hexene (having a density of about 0.917 g/cc and a "melt index" of about 1.0 [as determined by ASTM D-1238, at a load of 2.16 kg and a temperature of 1 90~C]) sold under the trademark NOVAPOL by Novacor Chemicals.
LLDPE-2 was a similar, hexene based LLDPE having a density of about 0.924 g/cc and "melt index" of about 0.80 sold under the trademark NOVAPOL by Novacor Chemicals.
The fluoroelastomer used in the comparative examples was a commercial product (DYNAMARTM FX-9613 sold by Minnesota Mining and Manufacturing Company) and is reported to be a mixture of elastomeric copolymer (of vinylidene fluoride and hexafluoropropylene) with a minor about (about 10%) of an anti-agglomerate.
The PAO was a commercialiy available polyethylene glycol having an Mw of about 5000 sold under the trademark CARBOWAX 5000.
The acrylic processing aid was a commercially available product (believed to be polymerized from methyl methacrylate, butyl acrylate and styrene) sold under the trademark PARALOID K-175 by Rohm and Haas.
Other conventional ingredients include a hundred phenolic antioxidant (sold under the trademark "IRGANOX 1076" by Ciba); a phosphate-based secondary antioxidant ("WESTON 399"); zinc oxide; an pscr~us~ecls11ocan~doc - 10-21 ~19 ~ G Patent amine-based ultraviolet stabilizer ("KEMAMINE AS-990") and a binding agent for other additives ("SYLOID 279").
A series of compounds having the formulations shown in Table 1 were prepared.
The compounds were then processed on a blown film line under the following conditions:
Melt temperature: 380-425~F (about 195 to 220~C) Output (kg/hr): indicated in Table 1 Film thickness (aiming point): 1.5 mils Control example 1 illustrates that melt fracture (MF) occurs in the absence of any processing aid.
Comparative example 2 demonstrates that the addition of 0.5 weight % acrylic processing aid is insufficient to eliminate melt fracture under the test conditions.
Comparative example 3 shows that the combination of acrylic processing aid and fluoroelastomer is also insufficient to eliminate melt fracture under the test conditions.
Inventive example 4 show that the combination of acrylic processing aid and PAO completely eliminated melt fracture outputs of about 100, 157 and 177 pounds of polyethylene per hour (and of equal significance, the film was clear and visually grain-free at outputs of 100 and 157 pounds/hr).
Comparative example 5 surprisingly demonstrates that the addition of fluoroelastomer to the composition of inventive Example 4 causes deterioration of extruder performance. Specifically, the film produced with ps~"l.,,b~cl91 10can.doc 216190G Patent the fluoroelastomer additive was visually "grainy" at all output rates tested.
This is a highly unusual result as the addition of fluoroelastomer typically improves the extrusion of polyethylene film.
Inventive example 6 illustrates that the combination of the acrylic processing aid and polyethylene glycol provides a comparatively good quality film even when silica is present. (It will be appreciated by those skilled in the art that silica typically causes problems with the production of melt fracture-free, clear polyethylene films.) psclj.~ GI911Ocan.do~ -12-Patent ~ ~ 1' o O O
Melt Fracture Trials Results/Formulation MELT FRACTURE-EST
COMPOSITION OUT-PUT uy., MELT F
BLEND # (Weight %) LBS/HR UND NO MELT F COMMENT
1. (Control) LLDPE-1 99.750 51 Y Control IRGANOX-1076 0.030 No PPA
KEMAMINE AS-990 0.050 ZINC STEARATE 0.050 98 Y Port Fracture WESTON 399 0.120 SYLOID 279 1.005 2. (Comparative) LLDPE-1 99.375 100 y MF - Grainy Grainy K-175 0.500 WESTON 399 0.125 118 Y MF - Grainy Grainy 3. (Comparative) LLDPE-1 99.330 100 y MF - Grainy Grainy K-175 0.500 cs:, WESTON 399 0.125 160 Y MF - Grainy Grainy FX-9613 0.045 c~
180 Y MF - Grainy Grainy c:~
psc~mispe~/911Ocan.d~c - 13-Patent w ~ ,--o o o TABLE 1 (Continued) MELT FRACTURE -EST
COMPOSITION OUT-PUT uy,, MELT F
BLEND # (Weight %) LBS/HRUN~ NO MELT F COMMENT
4. (Inventive) LLDPE-1 99.285 100 N Good Appearance K-175 0.500 WESTON 399 0.125 157 N Good Appearance CW 5000 0.045 IRGANOX-1076 0.030 177 N Some Grain Minute Grain ZINC OXIDE 0.015 5. (Comparative) LLDPE-1 99.24 100 N Some Grain Clear Grain K-1 75 0.500 FX-9613 0.045 156 N Some Grain Clear Grain WESTON 399 0.125 CW 5000 0.045 170 N MF - Grainy Grainy IRGANOX-1076 0.030 ZINC OXIDE 0.015 6. (Inventive) LLDPE-2 98.905 102 N Some Grain Good K-1 75 0.500 CW 5000 0.080 152 Y Some Grain Grain WESTON 399 0.120 ZINC OXIDE 0.015 171 Y Some Grain Grain IRGANOX-1076 0.030 ~_"SILICA 0.350 c~
c~
psc~"~/91 lOcan.doc - 14 -216190~
Patent NOTES:
K-175 = PARALOIDTM K-175acrylicprocessingaid WESTONTM 399 = phosphate secondary antioxidant CW5000 = CARBOWAXTM 5000 (PAO) IRGANOXTM 1076 = phenolicantioxidant FX 9613 = DYNAMARTM FX 9613 fluoroelastomer SYLOIDTM = binding agent for additives KEMAMINETMAS-990 = amine-basedUVstabilizer p5c~lnJ~pecl91 10can.doc -1 5 -
c~
psc~"~/91 lOcan.doc - 14 -216190~
Patent NOTES:
K-175 = PARALOIDTM K-175acrylicprocessingaid WESTONTM 399 = phosphate secondary antioxidant CW5000 = CARBOWAXTM 5000 (PAO) IRGANOXTM 1076 = phenolicantioxidant FX 9613 = DYNAMARTM FX 9613 fluoroelastomer SYLOIDTM = binding agent for additives KEMAMINETMAS-990 = amine-basedUVstabilizer p5c~lnJ~pecl91 10can.doc -1 5 -
Claims (10)
1. An fluoropolymer-free extrudable composition comprising:
(i) a predominant component which contains at least 50 weight % of linear low density polyethylene;
(ii) from 0.01 to 1 weight % of at least one polyalkylene oxide or ether and mixtures thereof; and (iii) from 0.05 to 1 weight % of an acrylic processing aid.
(i) a predominant component which contains at least 50 weight % of linear low density polyethylene;
(ii) from 0.01 to 1 weight % of at least one polyalkylene oxide or ether and mixtures thereof; and (iii) from 0.05 to 1 weight % of an acrylic processing aid.
2. The composition according to claim 1, wherein said (i) comprises at least 98 weight % of linear low density polyethylene which is a copolymer of ethylene and hexene having a density of less than 0.940 grams per cubic centimeter.
3. The composition according to claim 2, wherein component (ii) has a weight average molecular weight less than 10,000.
4. The composition according to claim 3, wherein said at least one polyalkylene oxide is a polyethylene glycol.
5. The composition according to claim 4, wherein said acrylic processing aid is a polymer prepared from methyl methacrylate, butyl acrylate and styrene.
6. The composition according to claim 5, wherein said acrylic processing aid is present in an amount from 0.4 to 0.80 weight %.
7. The composition according to claim 1, wherein the metal oxide is zinc oxide and is present in an amount from 100 to 300 ppm.
8. The composition according to claim 1, in the form of a blown film.
9. The composition according to claim 1, in the form of an extruded coating on a wire or optical cable.
10. The composition according to claim 1, in the form of an extruded sheet or geomembrane.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002161906A CA2161906A1 (en) | 1995-10-26 | 1995-10-26 | Lld-polyethylene with reduced melt fracture |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002161906A CA2161906A1 (en) | 1995-10-26 | 1995-10-26 | Lld-polyethylene with reduced melt fracture |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2161906A1 true CA2161906A1 (en) | 1997-04-27 |
Family
ID=4156892
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002161906A Abandoned CA2161906A1 (en) | 1995-10-26 | 1995-10-26 | Lld-polyethylene with reduced melt fracture |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2161906A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2023138374A1 (en) * | 2022-01-18 | 2023-07-27 | 熵能创新材料(珠海)有限公司 | Polyalkane acrylate processing auxiliary agent, and melt-processable composition containing processing auxiliary agent |
-
1995
- 1995-10-26 CA CA002161906A patent/CA2161906A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2023138374A1 (en) * | 2022-01-18 | 2023-07-27 | 熵能创新材料(珠海)有限公司 | Polyalkane acrylate processing auxiliary agent, and melt-processable composition containing processing auxiliary agent |
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