CA2176057A1 - Melt fracture reduction with uv additive - Google Patents
Melt fracture reduction with uv additiveInfo
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- CA2176057A1 CA2176057A1 CA002176057A CA2176057A CA2176057A1 CA 2176057 A1 CA2176057 A1 CA 2176057A1 CA 002176057 A CA002176057 A CA 002176057A CA 2176057 A CA2176057 A CA 2176057A CA 2176057 A1 CA2176057 A1 CA 2176057A1
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- 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
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- 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
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- 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
- C08L23/10—Homopolymers or copolymers of propene
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- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
- C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
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- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
- C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
- C08L27/16—Homopolymers or copolymers or vinylidene fluoride
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
- C08L51/003—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
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- 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
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- C—CHEMISTRY; METALLURGY
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- 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
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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
- 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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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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- 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
- C08L2666/24—Graft or block copolymers according to groups C08L51/00, C08L53/00 or C08L55/02; Derivatives thereof
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Abstract
Thermoplastic polyolefins used in "outdoor" applications are often compounded with hindered amine light stabilizers ("HALS") in order to improve their resistance to ultra violet (UV) rays. These thermoplastic compounds may also contain inorganic antiblocks (e.g. talc; silica) to reduce the blocking of films extruded from the compounds. The combined use of HALS and antiblocks is well known to be very antagonistic towards the effectiveness of many conventional processing additives. However, the extrusion of such thermoplastic polyolefin compounds, especially those based on linear low density polyethylene ("LLDPE"), has been discovered to be improved by the use of a processing additive comprising a blend of a thermoplastic acrylic polymer and a fluorocarbon polymer. In a preferred embodiment, the processing additive is a homogeneous blend of a thermoplastic styrene/methyl methacrylate polymer and a thermoplastic copolymer of vinylidene fluoride and hexafluoropropylene.
The polyolefin extrudates produced according to this invention have reduced levels of melt fracture when extruded in conventional polymer extrusion equipment.
The polyolefin extrudates produced according to this invention have reduced levels of melt fracture when extruded in conventional polymer extrusion equipment.
Description
217~0~7 Patent Hindered Amine / Polyolefin Compositions FIELD OF THE INVENTION
The present invention generally relates to polyolefin blends 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. The invention further relates to a novel composition of matter consisting of a blend of a thermoplastic, acrylic-containing polymer and a thermoplastic fluorocarbon polymer which is useful as an additive for extrudable polyolefin compositions.
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 elastomeric fluoropolymers to provide a smooth surface on extrudate at high extrusion speeds.
psG~ s~ S120Gan.doc - 2 -2:176n~7 Patent United States patent 4,753,995, assigned to Mobil Oil Corporation, discloses the use of vinylidene fluoride homopolymer to improve the extrusion of low density polyethylene.
It is well known to those skilled in the art that the use of hindered amine light stabilizers ("HALS") has a detrimental effect upon the effectiveness of fluoropolymers as a polyethylene processing additive. (It is also known that such fluoropolymers are prone to dehydrofluorination in the presence of bases - such as amines. Accordingly, a non-binding theory is that the HALS reacts with the fluoropolymers so as to produce a reaction product which is a less effective processing additive.) 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 linear low density polyethylene ("LLDPE") having a narrow molecular weight distribution.
Acrylic polymers are generally much less expensive than fluoropolymers. Accordi,)gly, there is an economic incentive to employ acrylics rather than fluoropolymers as processing additives. However, the simple addition of an acrylic polymer and a fluoropolymer to a polyethylene extrusion process has been observed to produce antagonistic results (i.e. the performance produced by one has been observed to be adversely affected by the simple addition of the other).
~sc~].,Js~.eG/S120can.doc - 3 -2176~7 Patent We have now surprisingly discovered that a premixed acrylic/fluoropolymer blend improves the extrusion of a thermoplastic compound which contains polyolefin, HALS and antiblock agents.
SUMMARY OF THE INVENTION
In one embodiment, the present invention provides:
An extrudable composition comprising:
A) a major component of a thermoplastic polyolefin;
B) less than 1 weight percent, based on the weight of said thermoplastic polyolefin, of a blend of a fluorocarbon polymer and an acrylic-containing thermoplastic polymer;
and C) from 100 to 5000 parts per million, based on the weight of 2 o said thermoplastic polyolefin, of a hindered amine light stabilizer.
In a pre~lled er"bodi",ent, the composition further contains:
D) from 100 to 5000 parts per million, based on the weight of said thermoplastic polyolefin, of an inorganic antiblock agent.
The compositions of this invention are particularly preferred for use in well known methods to prepare blown film (typically having a thickness of from 0.2 to 30 mils) and polyolefin-coated wire and cable. The compositions may also be useful for the extrusion of profiles such as pipes or tubing and/or the extrusion of thick films (typically greater than 20 mils) such as those used in so-called geomembranes.
c/9120can.doc - 4 -21760~7 Patent DETAILED DESCRIPTION
This invention is generally directed towards improvements in the extrusion of thermoplastic polyolefin compounds (especially those based on LLDPE) which contain antiblock and UV stabilizers. This improvement is achieved by the use of a processing additive which is a polymeric blend of an acrylic-containing ll ,er" ,oplastic and a fluorocarbon polymer.
The term thermoplastic polyolefin encompasses a number of widely used plastics which are prepared by olefin polymerization. Examples of such thermoplastic polyolefins include polyethylene homopolymer, polypropylene homopolymer, and copolymers of ethylene with small amounts of at least one other olefin - such as propylene, butene-1, hexene-1 or octene-1.
The invention is useful for thermoplastic polyolefins in general but is particularly well suited for improving the extrusion of linear low density polyethylene. LLDPE is a copolymer of ethylene with another alpha olefin (such as the aforementioned butene, hexene or octene) which has a density of less than 0.940 grams per cubic centimeter. Such LLDPEs are well known items of commerce and may be prepared by conventional polymerization processes. The polymerization may be in the gas phase (that is, at relatively low pressures below 500 psi, prererably below about 250 psi; at te""~eral.lres 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 - typically 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 ~,c~ ~/S120can.doc - 5 -~l7~n~7 Patent 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. The so-called metallocene catalysts may be used in all of these polymerization processes and the details of such types of poly",eri~alion are generally well known.
Depending on the type of polymerization, the olefin polymer may have a molecular weight (weight average - "Mw") from about 10,000 up to 1,000,000, typically from about 100,000 to 350,000. More than one type of polyolefin may be present in the extrudable compositions. For example, blends of LLDPE with LDPE are often used to prepare film and are suitable for use according to this invention.
This invention generally encompasses the use of certain blends of a fluorocarbon polymer and an acrylic polymer as additives to improve polyolefin extrusion. The term "acrylic polymer" is widely known but may mean different things to different people. Accordingly, we have used the term "acrylic-containing thermoplastic polymer" to describe polymers which are suitable. As used herein, the "acrylic-containing thermoplastic polymer", (or "ACTP"), is a polymer which:
(a) is polymeric (i.e. it has a weight average molecular weight of greater than 500);
(b) is thermoplastic (i.e. it will soften when heated and harden when cooled and will do so for more than one heaVcool cycle);
(c) is prepared using an "acrylic monomer: (i.e. acrylic acid, or an ethylenically unsaturated derivative thereof such as methyl methacrylate, ethyl methacrylate or butyl methacrylate); and ~"J~,dc/9120can.doc - 6 -2~7~057 Patent (d) contains at least 20 weight percent of polymer units (or "bound"
units) of the above defined monomer (c).
Thus, the defined term does include the well known polymer methyl methacrylates (such as those sold under the trademark PLEXIGLAS by Rohm and Haas); the so-called acrylic process aids which are well known to those skilled in the art of preparing polyvinyl chloride compounds (such as those sold under the trademarks PARALOID and/or ACRYLOID by Rohm and Haas - which PARALOID and ~CRYLOID process aids are reported to be copolymers of methyl methacrylate, butyl acrylate and styrene); and the well known styrene/methyl methacrylate copolymers such as those sold under the trademark NAS by Novacor Chemicals Inc.
of Leominster, MA. However, the term does not include polymers which contain less than about 15 weight percent of the acrylic monomer - such as, for example, copolymers of a major portion (typically greater than 90 weight percent) ethylene with a minor amount of a lower alkyl acrylate or the so-called "carboxylated polyolefins" (which typically contain less than 2 weight percent of an acid or acrylate monomer which is grafted to the polyolefin). Styrene/methyl methacrylate copolymers having from about 80 to about 45 weight percent bound styrene and from about 20 to about 55 weight percent of bound methyl methacrylate are highly preferred.
The term "fluorocarbon polymer" is meant to convey its conventional meaning, namely homopolymers and copolymers of the fluorinated olefins having a fluorine: carbon atom ratio of at least 1:2 and prereral~ly at least 1:1.
'9120carl.doc - 7 -2176057 Patent Suitable homopolymers may be prepared from vinylidene fluoride or vinyl fluoride. Copolymers may further include a fluorinated olefin (such as hexafluoropropylene) or a non-fluorinated olefin. This term includes both elastomeric and thermoplastic polymers.
"Fluoroelastomers" may be synthesized, for example by copolymerizing vinylidene fluoride ("VdF") and hexafluoropropylene ("HFP") so as to produce a polymer containing about 25 to 50 weight percent of "bound"
hexafluoropropylene. These bound hexafluoropropylene units disrupt the crystallinity of the polymer and thus help to provide an elastomeric polymer. Such fluoroelastomers are sold under the trademark VITON by E.l. DuPont de Nemours and by Minnesota Mining and Manufacturing ("3M") under the trademark DYNAMAR.
2 o It should be further noted that VdF/HFP copolymers which contain greater than 85 weight percent VdF and less than about 15 weight percent HFP may be thermoplastic. Elf Atochem of Philadelphia, PA sells different thermoplastic fluorocarbon polymers under the trademark KYNAR which include both vinylidene fluoride homopolymers and VdF/HFP copolymers containing low levels of HFP.
The acrylic-containing thermoplastic polymer and the fluorocarbon polymer must be blended together prior to the use of the blend to improve polyolefin extrusion. Accordingly, it is especially preferred to:
(1 ) use an ACTP with good "processibility" (i.e. an ACTP which is readily melt processed when subjected to heat and shear);
(2) use a combination of an ACTP and fluorocarbon polymer with similar"processibility" characteristics; and psc~ s~~~lS120can.doc ~ 8 -2~ 7G~S7 ~ ~ Patent (3) in the ideal case, use an ACTP and fluorocarbon polymer which satisfy the above two criteria and which are at least partly miscible with each other.
It has been, epo, Led that polymethylmethacrylate ("PMMA") is miscible with polyvinylidene fluoride (Ref: Kirk-Othmar Encyclopedia of Chemical Technology, 3rd Edition, Volume 18, p. 464). However, PMMA
can be difficult to melt process.
We have discovered that SMMA may be conveniently blended with thermoplastic VdF/HFP using conventional polymer mixing equipment and that it is possible to prepare "homogeneous" blends in this manner.
The term "homogeneous" may mean different things to different people, but as used herein it refers to a polymer blend which:
(a) has a uniform visual appearance (with respect to a uniform color and an essential lack of visible physical occlusions); and/or (b) has a well mixed, "matrix/domain" morphology which is apparent upon examination by scanning electron microscopy -as evidenced by the existence of discrete particles having a size of less than 4 microns.
Thus, we have discovered that a "premixed" blend of an ACTP and fluorocarbon polymer is useful as an additive to improve the extrusion of polyolefin compounds which contain UV additives and antiblocks. The weight ratio of ACTP/fluorocarbon polymer may be from 95/5 to 5/95, with preferred blends having a weight ratio of from 10/90 to 25/75. The most highly preferred blends contain SMMA and a thermoplastic VdF/HFP
copolymer in these weight ratios.
1,:,c~ spec/9120can.doc - 9 -2~7~0~7 Patent The blend is added to the thermoplastic polyolefin in an amount sufficient to provide from 0.01 weight percent (100 ppm) to 0.2 weight percent (2000 ppm) of the fluorocarbon polymer, based on the weight of the thermoplastic polyolefin.
Amounts less than 0.01 weight percent may not provide consistent improvements in the extrusion of polyolefins. Amounts greater than 0.2 weight percent may be employed but are expensive and wasteful.
The thermoplastic polyolefin-containing compositions of the present invention contain hindered amine light stabilizers (HALS) and antiblock agents (such as silica or talc) and may further include fillers, antioxidants (at least a primary and optionally a secondary antioxidant), pigments, opacifying agents, static control agents such as glycerol monostearate 2 o and/or low molecular weight polyethylene glycol (e.g. CARBOWAX 3350, sold by Union Carbide Corporation). The amount of HALS is from 100 to 5000 ppm (preferably 1500 to 3000 ppm) and the amount of antiblock is from 1000 to 5000 ppm (preferably 1000 to 3000 ppm).
For film applications, prererably 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 gldrL6d by extrusion with a functional ethylenically unsaturated monomer such as maleic anhydride in the presence of a free radical agent such as a peroxide).
Primary and secondary antioxidants may be used in an amount from about 0.01 to 2, ~ erer~bly 0.01 to about 1 weight %. Fillers may be ~Gfi"~"~c/9120can.doc - 10 -2~76~57 Patent incorporated into the compositions of the present invention in amounts up to about 50%, prererdbly less than about 30%.
Typically, the extrudable polymer compositions of the present invention will be prepared ("compounded") by melt blending. There are several methods which could be used to produce the compositions of the present invention. All the components, including the premixed o ACTP/fluorocarbon polymer blend, may be dry blended in the requiredweight 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
masterbatch could be prepared with some of the polyolefin and the other ingredients. The masterbatch is then fed to an extruder and melt blended.
In a third method the dry co" IpGi ,ents 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-rotaliny 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, prererably from 190 to 200~C. The screw speed will normally be from 50 to 150, preferably from 100 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 ~a~,r~ ~/8120can.doc - 11 -~ 2~76~7 Patent 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 blend about a stable bubble of air. The film is collapsed after passing over or about the bubble.
Example 1 P~ e~aralion of ACTP/Fluorucarl,o, I Polvmer Blend The ACTP polymer used in this example was a styrene/methyl methacrylate copolymer sold under the trademark NAS 30 by Novacor Chemicals Inc. and was reported to contain about 30 weight percent bound methyl methacrylate and about 70 weight percent bound styrene.
The melt flow rate (as determined by ASTM D1238 at 230~C under a load of 3.8 kilograms) was reported to have a typical value of 8.6 grams per 10 minutes.
The fluorocarbon polymer used in this example was a thermoplastic copolymer of vinylidene fluoride and hexafluoropropylene sold in powder form under the trademark KYNAR 2751 by Elf Atochem of Philadelphia, PA. Reported (typical) physical properties of KYNAR 2751 are given below:
,~sc~"Js~2c/8120can.doc -1 2 -1~ 21760~7 Patent Melting Point: 135~C
Melt Viscosity at 230~C: 20,000 - 25,000 Poise Melt Flow Rate:
(ASTM D1238 at 230~C
under 12.5 kg load) 4 - 10 grams / 10 minutes Two blends of the NAS 30 / KYNAR 2751 were then prepared in a lab scale Brabender-type ("mixing bowl") polymer mixer under conditions of heat and shear.
The first blend contained 25 weight percent NAS 30 and 75 weight percent of KYNAR 2751 (blend "1A").
The second blend contained 10 weight percent NAS 30 and 90 weight percent of KYNAR 2751 (blend "1 B").
Both of the blends appeared homogeneous by visual inspection as evidenced by uniform color and a lack of occlusions (i.e. no "chunks" or "specks" were observed).
Example 2 A laboratory scale twin screw extruder was used to prepare compounds containing LLDPE, conventional stabilizers, other conventional adjuvants, a process aid consisting of the KYNAR 2751 /
NAS 30 blends from Example 1 plus HALS and antiblock.
A blend made with a fluoroelastomer sold by 3M under the trademark DYNAMAR FX 9613 (a conventional process aid) was prepared for a control.
The formulations are shown in Table 10. All figures are shown as weight percentages.
,~sc~."~s~c/9120can.doc - 13 -J~ Patent Component: Ex. 100 Ex. 200 Ex. 300 LLDPE1 99.305 99.24 99.265 AO-12/AO-23 0.03/0.12 0.03/0.12 0.03/0.12 Zinc Oxide 0.015 0.015 0.15 FE4 0.08 ---PEG5 0.05 0.06 0.06 Blend 1A6 0.135 ----Blend 1 B7 ---- ---- 0.11 HALS8 0.15 0.15 0.15 Silica9 0.25 0.25 0.25 Notes:
1. Ethylene-hexene LLDPE having a density of about 0.918 g/cc and a melt index (ASTM D1238 at 190~C under a load of 2.16 kg) of about 1.
2. AO-1 = hindered phenol antioxidant (sold under the trademark IRGANOX 1076 by Ciba Geigy).
3. AO-2 = phosphite antioxidant (sold under the trademark WESTON
339 by General Electric Company).
4. FE = fluoroelastomer sold under the trademark DYNAMAR FX
9613 by 3M.
The present invention generally relates to polyolefin blends 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. The invention further relates to a novel composition of matter consisting of a blend of a thermoplastic, acrylic-containing polymer and a thermoplastic fluorocarbon polymer which is useful as an additive for extrudable polyolefin compositions.
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 elastomeric fluoropolymers to provide a smooth surface on extrudate at high extrusion speeds.
psG~ s~ S120Gan.doc - 2 -2:176n~7 Patent United States patent 4,753,995, assigned to Mobil Oil Corporation, discloses the use of vinylidene fluoride homopolymer to improve the extrusion of low density polyethylene.
It is well known to those skilled in the art that the use of hindered amine light stabilizers ("HALS") has a detrimental effect upon the effectiveness of fluoropolymers as a polyethylene processing additive. (It is also known that such fluoropolymers are prone to dehydrofluorination in the presence of bases - such as amines. Accordingly, a non-binding theory is that the HALS reacts with the fluoropolymers so as to produce a reaction product which is a less effective processing additive.) 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 linear low density polyethylene ("LLDPE") having a narrow molecular weight distribution.
Acrylic polymers are generally much less expensive than fluoropolymers. Accordi,)gly, there is an economic incentive to employ acrylics rather than fluoropolymers as processing additives. However, the simple addition of an acrylic polymer and a fluoropolymer to a polyethylene extrusion process has been observed to produce antagonistic results (i.e. the performance produced by one has been observed to be adversely affected by the simple addition of the other).
~sc~].,Js~.eG/S120can.doc - 3 -2176~7 Patent We have now surprisingly discovered that a premixed acrylic/fluoropolymer blend improves the extrusion of a thermoplastic compound which contains polyolefin, HALS and antiblock agents.
SUMMARY OF THE INVENTION
In one embodiment, the present invention provides:
An extrudable composition comprising:
A) a major component of a thermoplastic polyolefin;
B) less than 1 weight percent, based on the weight of said thermoplastic polyolefin, of a blend of a fluorocarbon polymer and an acrylic-containing thermoplastic polymer;
and C) from 100 to 5000 parts per million, based on the weight of 2 o said thermoplastic polyolefin, of a hindered amine light stabilizer.
In a pre~lled er"bodi",ent, the composition further contains:
D) from 100 to 5000 parts per million, based on the weight of said thermoplastic polyolefin, of an inorganic antiblock agent.
The compositions of this invention are particularly preferred for use in well known methods to prepare blown film (typically having a thickness of from 0.2 to 30 mils) and polyolefin-coated wire and cable. The compositions may also be useful for the extrusion of profiles such as pipes or tubing and/or the extrusion of thick films (typically greater than 20 mils) such as those used in so-called geomembranes.
c/9120can.doc - 4 -21760~7 Patent DETAILED DESCRIPTION
This invention is generally directed towards improvements in the extrusion of thermoplastic polyolefin compounds (especially those based on LLDPE) which contain antiblock and UV stabilizers. This improvement is achieved by the use of a processing additive which is a polymeric blend of an acrylic-containing ll ,er" ,oplastic and a fluorocarbon polymer.
The term thermoplastic polyolefin encompasses a number of widely used plastics which are prepared by olefin polymerization. Examples of such thermoplastic polyolefins include polyethylene homopolymer, polypropylene homopolymer, and copolymers of ethylene with small amounts of at least one other olefin - such as propylene, butene-1, hexene-1 or octene-1.
The invention is useful for thermoplastic polyolefins in general but is particularly well suited for improving the extrusion of linear low density polyethylene. LLDPE is a copolymer of ethylene with another alpha olefin (such as the aforementioned butene, hexene or octene) which has a density of less than 0.940 grams per cubic centimeter. Such LLDPEs are well known items of commerce and may be prepared by conventional polymerization processes. The polymerization may be in the gas phase (that is, at relatively low pressures below 500 psi, prererably below about 250 psi; at te""~eral.lres 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 - typically 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 ~,c~ ~/S120can.doc - 5 -~l7~n~7 Patent 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. The so-called metallocene catalysts may be used in all of these polymerization processes and the details of such types of poly",eri~alion are generally well known.
Depending on the type of polymerization, the olefin polymer may have a molecular weight (weight average - "Mw") from about 10,000 up to 1,000,000, typically from about 100,000 to 350,000. More than one type of polyolefin may be present in the extrudable compositions. For example, blends of LLDPE with LDPE are often used to prepare film and are suitable for use according to this invention.
This invention generally encompasses the use of certain blends of a fluorocarbon polymer and an acrylic polymer as additives to improve polyolefin extrusion. The term "acrylic polymer" is widely known but may mean different things to different people. Accordingly, we have used the term "acrylic-containing thermoplastic polymer" to describe polymers which are suitable. As used herein, the "acrylic-containing thermoplastic polymer", (or "ACTP"), is a polymer which:
(a) is polymeric (i.e. it has a weight average molecular weight of greater than 500);
(b) is thermoplastic (i.e. it will soften when heated and harden when cooled and will do so for more than one heaVcool cycle);
(c) is prepared using an "acrylic monomer: (i.e. acrylic acid, or an ethylenically unsaturated derivative thereof such as methyl methacrylate, ethyl methacrylate or butyl methacrylate); and ~"J~,dc/9120can.doc - 6 -2~7~057 Patent (d) contains at least 20 weight percent of polymer units (or "bound"
units) of the above defined monomer (c).
Thus, the defined term does include the well known polymer methyl methacrylates (such as those sold under the trademark PLEXIGLAS by Rohm and Haas); the so-called acrylic process aids which are well known to those skilled in the art of preparing polyvinyl chloride compounds (such as those sold under the trademarks PARALOID and/or ACRYLOID by Rohm and Haas - which PARALOID and ~CRYLOID process aids are reported to be copolymers of methyl methacrylate, butyl acrylate and styrene); and the well known styrene/methyl methacrylate copolymers such as those sold under the trademark NAS by Novacor Chemicals Inc.
of Leominster, MA. However, the term does not include polymers which contain less than about 15 weight percent of the acrylic monomer - such as, for example, copolymers of a major portion (typically greater than 90 weight percent) ethylene with a minor amount of a lower alkyl acrylate or the so-called "carboxylated polyolefins" (which typically contain less than 2 weight percent of an acid or acrylate monomer which is grafted to the polyolefin). Styrene/methyl methacrylate copolymers having from about 80 to about 45 weight percent bound styrene and from about 20 to about 55 weight percent of bound methyl methacrylate are highly preferred.
The term "fluorocarbon polymer" is meant to convey its conventional meaning, namely homopolymers and copolymers of the fluorinated olefins having a fluorine: carbon atom ratio of at least 1:2 and prereral~ly at least 1:1.
'9120carl.doc - 7 -2176057 Patent Suitable homopolymers may be prepared from vinylidene fluoride or vinyl fluoride. Copolymers may further include a fluorinated olefin (such as hexafluoropropylene) or a non-fluorinated olefin. This term includes both elastomeric and thermoplastic polymers.
"Fluoroelastomers" may be synthesized, for example by copolymerizing vinylidene fluoride ("VdF") and hexafluoropropylene ("HFP") so as to produce a polymer containing about 25 to 50 weight percent of "bound"
hexafluoropropylene. These bound hexafluoropropylene units disrupt the crystallinity of the polymer and thus help to provide an elastomeric polymer. Such fluoroelastomers are sold under the trademark VITON by E.l. DuPont de Nemours and by Minnesota Mining and Manufacturing ("3M") under the trademark DYNAMAR.
2 o It should be further noted that VdF/HFP copolymers which contain greater than 85 weight percent VdF and less than about 15 weight percent HFP may be thermoplastic. Elf Atochem of Philadelphia, PA sells different thermoplastic fluorocarbon polymers under the trademark KYNAR which include both vinylidene fluoride homopolymers and VdF/HFP copolymers containing low levels of HFP.
The acrylic-containing thermoplastic polymer and the fluorocarbon polymer must be blended together prior to the use of the blend to improve polyolefin extrusion. Accordingly, it is especially preferred to:
(1 ) use an ACTP with good "processibility" (i.e. an ACTP which is readily melt processed when subjected to heat and shear);
(2) use a combination of an ACTP and fluorocarbon polymer with similar"processibility" characteristics; and psc~ s~~~lS120can.doc ~ 8 -2~ 7G~S7 ~ ~ Patent (3) in the ideal case, use an ACTP and fluorocarbon polymer which satisfy the above two criteria and which are at least partly miscible with each other.
It has been, epo, Led that polymethylmethacrylate ("PMMA") is miscible with polyvinylidene fluoride (Ref: Kirk-Othmar Encyclopedia of Chemical Technology, 3rd Edition, Volume 18, p. 464). However, PMMA
can be difficult to melt process.
We have discovered that SMMA may be conveniently blended with thermoplastic VdF/HFP using conventional polymer mixing equipment and that it is possible to prepare "homogeneous" blends in this manner.
The term "homogeneous" may mean different things to different people, but as used herein it refers to a polymer blend which:
(a) has a uniform visual appearance (with respect to a uniform color and an essential lack of visible physical occlusions); and/or (b) has a well mixed, "matrix/domain" morphology which is apparent upon examination by scanning electron microscopy -as evidenced by the existence of discrete particles having a size of less than 4 microns.
Thus, we have discovered that a "premixed" blend of an ACTP and fluorocarbon polymer is useful as an additive to improve the extrusion of polyolefin compounds which contain UV additives and antiblocks. The weight ratio of ACTP/fluorocarbon polymer may be from 95/5 to 5/95, with preferred blends having a weight ratio of from 10/90 to 25/75. The most highly preferred blends contain SMMA and a thermoplastic VdF/HFP
copolymer in these weight ratios.
1,:,c~ spec/9120can.doc - 9 -2~7~0~7 Patent The blend is added to the thermoplastic polyolefin in an amount sufficient to provide from 0.01 weight percent (100 ppm) to 0.2 weight percent (2000 ppm) of the fluorocarbon polymer, based on the weight of the thermoplastic polyolefin.
Amounts less than 0.01 weight percent may not provide consistent improvements in the extrusion of polyolefins. Amounts greater than 0.2 weight percent may be employed but are expensive and wasteful.
The thermoplastic polyolefin-containing compositions of the present invention contain hindered amine light stabilizers (HALS) and antiblock agents (such as silica or talc) and may further include fillers, antioxidants (at least a primary and optionally a secondary antioxidant), pigments, opacifying agents, static control agents such as glycerol monostearate 2 o and/or low molecular weight polyethylene glycol (e.g. CARBOWAX 3350, sold by Union Carbide Corporation). The amount of HALS is from 100 to 5000 ppm (preferably 1500 to 3000 ppm) and the amount of antiblock is from 1000 to 5000 ppm (preferably 1000 to 3000 ppm).
For film applications, prererably 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 gldrL6d by extrusion with a functional ethylenically unsaturated monomer such as maleic anhydride in the presence of a free radical agent such as a peroxide).
Primary and secondary antioxidants may be used in an amount from about 0.01 to 2, ~ erer~bly 0.01 to about 1 weight %. Fillers may be ~Gfi"~"~c/9120can.doc - 10 -2~76~57 Patent incorporated into the compositions of the present invention in amounts up to about 50%, prererdbly less than about 30%.
Typically, the extrudable polymer compositions of the present invention will be prepared ("compounded") by melt blending. There are several methods which could be used to produce the compositions of the present invention. All the components, including the premixed o ACTP/fluorocarbon polymer blend, may be dry blended in the requiredweight 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
masterbatch could be prepared with some of the polyolefin and the other ingredients. The masterbatch is then fed to an extruder and melt blended.
In a third method the dry co" IpGi ,ents 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-rotaliny 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, prererably from 190 to 200~C. The screw speed will normally be from 50 to 150, preferably from 100 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 ~a~,r~ ~/8120can.doc - 11 -~ 2~76~7 Patent 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 blend about a stable bubble of air. The film is collapsed after passing over or about the bubble.
Example 1 P~ e~aralion of ACTP/Fluorucarl,o, I Polvmer Blend The ACTP polymer used in this example was a styrene/methyl methacrylate copolymer sold under the trademark NAS 30 by Novacor Chemicals Inc. and was reported to contain about 30 weight percent bound methyl methacrylate and about 70 weight percent bound styrene.
The melt flow rate (as determined by ASTM D1238 at 230~C under a load of 3.8 kilograms) was reported to have a typical value of 8.6 grams per 10 minutes.
The fluorocarbon polymer used in this example was a thermoplastic copolymer of vinylidene fluoride and hexafluoropropylene sold in powder form under the trademark KYNAR 2751 by Elf Atochem of Philadelphia, PA. Reported (typical) physical properties of KYNAR 2751 are given below:
,~sc~"Js~2c/8120can.doc -1 2 -1~ 21760~7 Patent Melting Point: 135~C
Melt Viscosity at 230~C: 20,000 - 25,000 Poise Melt Flow Rate:
(ASTM D1238 at 230~C
under 12.5 kg load) 4 - 10 grams / 10 minutes Two blends of the NAS 30 / KYNAR 2751 were then prepared in a lab scale Brabender-type ("mixing bowl") polymer mixer under conditions of heat and shear.
The first blend contained 25 weight percent NAS 30 and 75 weight percent of KYNAR 2751 (blend "1A").
The second blend contained 10 weight percent NAS 30 and 90 weight percent of KYNAR 2751 (blend "1 B").
Both of the blends appeared homogeneous by visual inspection as evidenced by uniform color and a lack of occlusions (i.e. no "chunks" or "specks" were observed).
Example 2 A laboratory scale twin screw extruder was used to prepare compounds containing LLDPE, conventional stabilizers, other conventional adjuvants, a process aid consisting of the KYNAR 2751 /
NAS 30 blends from Example 1 plus HALS and antiblock.
A blend made with a fluoroelastomer sold by 3M under the trademark DYNAMAR FX 9613 (a conventional process aid) was prepared for a control.
The formulations are shown in Table 10. All figures are shown as weight percentages.
,~sc~."~s~c/9120can.doc - 13 -J~ Patent Component: Ex. 100 Ex. 200 Ex. 300 LLDPE1 99.305 99.24 99.265 AO-12/AO-23 0.03/0.12 0.03/0.12 0.03/0.12 Zinc Oxide 0.015 0.015 0.15 FE4 0.08 ---PEG5 0.05 0.06 0.06 Blend 1A6 0.135 ----Blend 1 B7 ---- ---- 0.11 HALS8 0.15 0.15 0.15 Silica9 0.25 0.25 0.25 Notes:
1. Ethylene-hexene LLDPE having a density of about 0.918 g/cc and a melt index (ASTM D1238 at 190~C under a load of 2.16 kg) of about 1.
2. AO-1 = hindered phenol antioxidant (sold under the trademark IRGANOX 1076 by Ciba Geigy).
3. AO-2 = phosphite antioxidant (sold under the trademark WESTON
339 by General Electric Company).
4. FE = fluoroelastomer sold under the trademark DYNAMAR FX
9613 by 3M.
5. PEG - polyethylene glycol sold under the trademark CARBOWAX
3350 by Union Carbide Corporation.
3350 by Union Carbide Corporation.
6. Blend 1A = 25/75 weight ratio blend of NAS 30 / KYNAR 2751 from Example 1.
7. Blend 1 B = 10/90 weight ratio blend of NAS 30 / KYNAR 2751 from Example 1.
psc~ la~aGls12ocan.doc - 14 -2~76~7 Patent 8. HALS = hindered amine light stabilizer (sold under the trademark CHIMASORB 944) 9. Silica antiblock agent The amount of blends 1A and 1 B were chosen so as to provide about 1.0 x 103 ppm of the KYNAR (on an LLDPE basis).
The compounds were mixed in a laboratory extruder under conventional mixing conditions.
These three compounds were then individually extruded through a capillary rheometer at 21 0~C. The capillary had a length/diameter ratio of 20/1. The shear rate in the rheometer was adjusted during each test from a range of less than 100 reciprocal seconds (s~') to a shear rate of about 1 350 s~'.
It will be appreciated by those skilled in the art that this type of extrusion through a capillary will typically cause surface defects ("melt fracture") in LLDPE extrudates in the absence of a processing additive at a shear rate of less than 200 s~'.
The control experiment (Ex. 100 in Table 10; using a conventional fluoroelastomer as the processing additive) showed some "sharkskin" melt fracture at a shear rate of about 150 s~' and gross melt fracture (as 3 o evidenced by an extremely rough, distorted extrudate) at a shear rate of about 800 s~'.
The use of blend "1A" (25% SMMA / 75% fluoroplastic; Ex. 200) provided excellent results, with essentially no "sharkskin" melt fracture at low shear rates, and with gross melt fracture not occurring until a shear rate of about 1200 s~'.
psc,r, Js~ c/9120c3n.doc - 15-2176~)~7 ~ ~ Patent The use of blend 1 B (90% fluoroplastic / 10% SMMA; Ex. 300) provided another excellent result, with gross melt fracture not occurring until a shear rate of about 1200 s~'.
Additional data, which illustrate the improved shear viscosity of the inventive compounds of Ex. 200 and 300 in comparison to the control compound of Ex. 100, are shown in Table 20.
o TABLE 20 Apparent Shear Viscosity (Pa.s) Shear Rate (1/s) Ex.100 Ex. 200 Ex. 300 ' 9.2 ~,729.7 ~96 ~.6 ~939.8 38.4 vO 8.8 "1~".5 2165.8 ~7.6 Z.~S9.~ ~ 6-v.O ~ 80.6 76.8 2221. ~ ~9 .8 ~ 030 7 96.0 ~ 946.0 ' 222.7 ~ ' 61.4 ~ ~ .2 ~ '17.9 ~ 1~ 0.9 ~ 050.3 . ~.4 533.9 ' 0"1.2 972.8 v.6 ",9'.6 9~.7 9' ,.6 9.~.0 9".3 86~.8 82~.9 o.~- ~ 59.7 801-~.4 76 ~ 7.2 879.~ 70. .6 679.
_~ 4.U 770.~ 64~.0 ~''2 ~0.0 ~92.3 .,90.~ .~'8.
600.0 88.8 20. ~)4 750.0 99.7 ~69.; ~59.~
900.0 ~ 3. 9 ~25.9 1050.0 ---- 38~ .6 387.' 1200.0 ---- 340.7 348.2 3 o 1350.0 ---- 294.0 302.6 Notes:
Ex, 100, the control experiment (using a conventional fluoroelastomer as the processing additive), began to exhibit sharkskin melt fracture at a shear rate of about 150 s~'. Gross melt fracture, as evidenced by an extremely rough, distorted extrudate, was observed to start at a shear rate of about 800 s~'.
~s~l~"/s~20can.doc - 16 -2176~7 Patent Ex. 200 produced no sharkskin melt fracture and began to exhibit gross melt fracture at a shear rate of about 1200 s~', as compared to about 800 s~' for Ex.100.
Ex. 300 showed similar results with the onset of gross melt fracture also occurring at a shear rate of about 1200 s~', as compared to about 800 s-' for Ex.100.
Example 3 (Comparative) Three different types of vinylidene fluoride-based fluoroplastics were evaluated as process additives for the extrusion of polyethylene in a "blown film compound".
The fluoroplastics included a homopolymer vinylidene fluoride (sold under the trademark KYNAR 721), the KYNAR 2751 (described in example 1) and another vinylidene fluoride/hexafluoropropylene sold under the trademark KYNAR 2801.
Each of these three fluoroplastics was used - in the absence of any acrylic-containing thermoplastic - to prepare compounds with an LLDPE
(similar to the LLDPE used in examples 1 and 2). A total of six compounds were prepared, (two for each of the three fluoroplastics, with one blend containing 500 ppm fluoroplastic and the second containing 1000 ppm fluoroplastic on the basis of the LLDPE). The compounds also contained minor, conventional amounts of other adjuvants including: a slip agent (750 ppm Erucamide), antioxidant (Irganox 1076 and Weston 399), an amine (sold under the trademark Kemamine), and zinc stearale (500 ppm). More significantly, the compounds further contained about 3150 ppm of silica as an antiblock agent.
The six compounds were then used on a commercial-sized blown film line (operating at a throughput rate of between about 32 and 33 kg ~J~r~"~s~ 12ocan.doc - 17 -~ 2~76(~57 Patent per hour). All six compounds showed unacceptable levels of surface defects, with between 60 and 100% of the film surface showing melt fracture defects.
In order to ensure that there was not a machine problem causing these poor results, a control experiment was performed with a conventional fluoroelastomer based additive. This control experiment resulted in the complete elimination of melt fracture at a fluoroelastomer level of less than 1000 ppm.
These data indicate that silica antiblocks are very antagonistic towards the e~fectiveness of vinylidene fluoride-containing thermoplastics in the absence of acrylic-containing thermoplastics.
Example 4 (Com,~ al dli~e) comPositions Containinq Hindered Amine Li~ht Stabilizers This example illustrates that hindered amine light stabilizer additives (also known as "UV" additives) are antagonistic towards fluorocarbon polymer additives.
A polyethylene compound containing conventional, minor amounts of adjuvants (including 450 ppm of a fluoroelastomer sold under the trademark DYNAMAR FX 9613 by 3M) was prepared without a UV
additive. A second blend (otherwise identical to the first blend, except for the addition of 4000 ppm of a UV additive, believed to be a hindered amine, sold under the trademark CHIMASORB 944) was also prepared.
No ACTP was present in these compounds.
The two compounds were then extruded through a capillary rheometer (as described in Example 2).
"~ls120can.d0c - 18-2l7~n~7 ~ ~ Patent Data describing shear viscosity (Pa.s) versus shear rate (s~') are given in Table 30.
As shown in Table 30, the UV additive-containing compositions have substantially higher shear viscosities at equivalent shear rates.
More significantly, the blend containing the UV additive demonstrated onset of melt fracture at a shear rate of about 530 s~' whereas the blend without the UV additive did not demonstrate onset of melt fracture until a shear rate of greater than 900 s~'.
Effect of UV Additive on Shear Viscosity Shear Rate, s~' Shear Viscosity, Pa.s No ~ V ~dditive With UV Additive ~7.6 9~7 20~5 6.8 ~'2 7o 9~ 2'8 ~5'0 ' 1. ~.'' ' 07~ ~ 383 3~.2 962.1 ' 272 ' 5~.7 88~.6 ' ' ~5 9' .8 790.~ ' 0~6 230.3 7''4.~ 9~5.1 v07. 6~,8.- 80n.s 8~.~ 9.6 70 .9 6 . ,: -9. 6_~.0 . . 06.3 . .8 . ~ ,.5 ' 90.2 5 1.7 66 .0 ~5fi.~ 506.4 729.8 ~'' .' ' 72.8 810.8 ~22. ~35.8 848.2 ~ 1~........... 19.4 ps."~ c/9120can.doc - 19 -
psc~ la~aGls12ocan.doc - 14 -2~76~7 Patent 8. HALS = hindered amine light stabilizer (sold under the trademark CHIMASORB 944) 9. Silica antiblock agent The amount of blends 1A and 1 B were chosen so as to provide about 1.0 x 103 ppm of the KYNAR (on an LLDPE basis).
The compounds were mixed in a laboratory extruder under conventional mixing conditions.
These three compounds were then individually extruded through a capillary rheometer at 21 0~C. The capillary had a length/diameter ratio of 20/1. The shear rate in the rheometer was adjusted during each test from a range of less than 100 reciprocal seconds (s~') to a shear rate of about 1 350 s~'.
It will be appreciated by those skilled in the art that this type of extrusion through a capillary will typically cause surface defects ("melt fracture") in LLDPE extrudates in the absence of a processing additive at a shear rate of less than 200 s~'.
The control experiment (Ex. 100 in Table 10; using a conventional fluoroelastomer as the processing additive) showed some "sharkskin" melt fracture at a shear rate of about 150 s~' and gross melt fracture (as 3 o evidenced by an extremely rough, distorted extrudate) at a shear rate of about 800 s~'.
The use of blend "1A" (25% SMMA / 75% fluoroplastic; Ex. 200) provided excellent results, with essentially no "sharkskin" melt fracture at low shear rates, and with gross melt fracture not occurring until a shear rate of about 1200 s~'.
psc,r, Js~ c/9120c3n.doc - 15-2176~)~7 ~ ~ Patent The use of blend 1 B (90% fluoroplastic / 10% SMMA; Ex. 300) provided another excellent result, with gross melt fracture not occurring until a shear rate of about 1200 s~'.
Additional data, which illustrate the improved shear viscosity of the inventive compounds of Ex. 200 and 300 in comparison to the control compound of Ex. 100, are shown in Table 20.
o TABLE 20 Apparent Shear Viscosity (Pa.s) Shear Rate (1/s) Ex.100 Ex. 200 Ex. 300 ' 9.2 ~,729.7 ~96 ~.6 ~939.8 38.4 vO 8.8 "1~".5 2165.8 ~7.6 Z.~S9.~ ~ 6-v.O ~ 80.6 76.8 2221. ~ ~9 .8 ~ 030 7 96.0 ~ 946.0 ' 222.7 ~ ' 61.4 ~ ~ .2 ~ '17.9 ~ 1~ 0.9 ~ 050.3 . ~.4 533.9 ' 0"1.2 972.8 v.6 ",9'.6 9~.7 9' ,.6 9.~.0 9".3 86~.8 82~.9 o.~- ~ 59.7 801-~.4 76 ~ 7.2 879.~ 70. .6 679.
_~ 4.U 770.~ 64~.0 ~''2 ~0.0 ~92.3 .,90.~ .~'8.
600.0 88.8 20. ~)4 750.0 99.7 ~69.; ~59.~
900.0 ~ 3. 9 ~25.9 1050.0 ---- 38~ .6 387.' 1200.0 ---- 340.7 348.2 3 o 1350.0 ---- 294.0 302.6 Notes:
Ex, 100, the control experiment (using a conventional fluoroelastomer as the processing additive), began to exhibit sharkskin melt fracture at a shear rate of about 150 s~'. Gross melt fracture, as evidenced by an extremely rough, distorted extrudate, was observed to start at a shear rate of about 800 s~'.
~s~l~"/s~20can.doc - 16 -2176~7 Patent Ex. 200 produced no sharkskin melt fracture and began to exhibit gross melt fracture at a shear rate of about 1200 s~', as compared to about 800 s~' for Ex.100.
Ex. 300 showed similar results with the onset of gross melt fracture also occurring at a shear rate of about 1200 s~', as compared to about 800 s-' for Ex.100.
Example 3 (Comparative) Three different types of vinylidene fluoride-based fluoroplastics were evaluated as process additives for the extrusion of polyethylene in a "blown film compound".
The fluoroplastics included a homopolymer vinylidene fluoride (sold under the trademark KYNAR 721), the KYNAR 2751 (described in example 1) and another vinylidene fluoride/hexafluoropropylene sold under the trademark KYNAR 2801.
Each of these three fluoroplastics was used - in the absence of any acrylic-containing thermoplastic - to prepare compounds with an LLDPE
(similar to the LLDPE used in examples 1 and 2). A total of six compounds were prepared, (two for each of the three fluoroplastics, with one blend containing 500 ppm fluoroplastic and the second containing 1000 ppm fluoroplastic on the basis of the LLDPE). The compounds also contained minor, conventional amounts of other adjuvants including: a slip agent (750 ppm Erucamide), antioxidant (Irganox 1076 and Weston 399), an amine (sold under the trademark Kemamine), and zinc stearale (500 ppm). More significantly, the compounds further contained about 3150 ppm of silica as an antiblock agent.
The six compounds were then used on a commercial-sized blown film line (operating at a throughput rate of between about 32 and 33 kg ~J~r~"~s~ 12ocan.doc - 17 -~ 2~76(~57 Patent per hour). All six compounds showed unacceptable levels of surface defects, with between 60 and 100% of the film surface showing melt fracture defects.
In order to ensure that there was not a machine problem causing these poor results, a control experiment was performed with a conventional fluoroelastomer based additive. This control experiment resulted in the complete elimination of melt fracture at a fluoroelastomer level of less than 1000 ppm.
These data indicate that silica antiblocks are very antagonistic towards the e~fectiveness of vinylidene fluoride-containing thermoplastics in the absence of acrylic-containing thermoplastics.
Example 4 (Com,~ al dli~e) comPositions Containinq Hindered Amine Li~ht Stabilizers This example illustrates that hindered amine light stabilizer additives (also known as "UV" additives) are antagonistic towards fluorocarbon polymer additives.
A polyethylene compound containing conventional, minor amounts of adjuvants (including 450 ppm of a fluoroelastomer sold under the trademark DYNAMAR FX 9613 by 3M) was prepared without a UV
additive. A second blend (otherwise identical to the first blend, except for the addition of 4000 ppm of a UV additive, believed to be a hindered amine, sold under the trademark CHIMASORB 944) was also prepared.
No ACTP was present in these compounds.
The two compounds were then extruded through a capillary rheometer (as described in Example 2).
"~ls120can.d0c - 18-2l7~n~7 ~ ~ Patent Data describing shear viscosity (Pa.s) versus shear rate (s~') are given in Table 30.
As shown in Table 30, the UV additive-containing compositions have substantially higher shear viscosities at equivalent shear rates.
More significantly, the blend containing the UV additive demonstrated onset of melt fracture at a shear rate of about 530 s~' whereas the blend without the UV additive did not demonstrate onset of melt fracture until a shear rate of greater than 900 s~'.
Effect of UV Additive on Shear Viscosity Shear Rate, s~' Shear Viscosity, Pa.s No ~ V ~dditive With UV Additive ~7.6 9~7 20~5 6.8 ~'2 7o 9~ 2'8 ~5'0 ' 1. ~.'' ' 07~ ~ 383 3~.2 962.1 ' 272 ' 5~.7 88~.6 ' ' ~5 9' .8 790.~ ' 0~6 230.3 7''4.~ 9~5.1 v07. 6~,8.- 80n.s 8~.~ 9.6 70 .9 6 . ,: -9. 6_~.0 . . 06.3 . .8 . ~ ,.5 ' 90.2 5 1.7 66 .0 ~5fi.~ 506.4 729.8 ~'' .' ' 72.8 810.8 ~22. ~35.8 848.2 ~ 1~........... 19.4 ps."~ c/9120can.doc - 19 -
Claims (8)
1. An extrudable composition comprising:
A) a major component of a thermoplastic polyolefin;
B) less than 1 weight percent, based on the weight of said thermoplastic polyolefin, of a blend of a fluorocarbon polymer and an acrylic-containing thermoplastic polymer;
and C) from 100 to 5000 parts per million, based on the weight of said thermoplastic polyolefin, of a hindered amine light stabilizer.
A) a major component of a thermoplastic polyolefin;
B) less than 1 weight percent, based on the weight of said thermoplastic polyolefin, of a blend of a fluorocarbon polymer and an acrylic-containing thermoplastic polymer;
and C) from 100 to 5000 parts per million, based on the weight of said thermoplastic polyolefin, of a hindered amine light stabilizer.
2. The composition of claim 1 which further contains:
D) from 100 to 5000 parts per million, based on the weight of said thermoplastic polyolefin, of an inorganic antiblock agent.
D) from 100 to 5000 parts per million, based on the weight of said thermoplastic polyolefin, of an inorganic antiblock agent.
3. An extrudable composition comprising:
A) a thermoplastic polyolefin; and B) from 0.01 to 0.2 weight percent, based on the weight of said thermoplastic polyolefin, of a fluorocarbon polymer, with the provisos that:
(a) said fluorocarbon polymer is provided as a component of a premixed blend with an acrylic-containing thermoplastic polymer; and (b) the weight ratio of said fluorocarbon polymer to said acrylic-containing thermoplastic polymer in said premixed blend is from about 95/5 to 5/95.
A) a thermoplastic polyolefin; and B) from 0.01 to 0.2 weight percent, based on the weight of said thermoplastic polyolefin, of a fluorocarbon polymer, with the provisos that:
(a) said fluorocarbon polymer is provided as a component of a premixed blend with an acrylic-containing thermoplastic polymer; and (b) the weight ratio of said fluorocarbon polymer to said acrylic-containing thermoplastic polymer in said premixed blend is from about 95/5 to 5/95.
4. The composition of claim 3 wherein said fluorocarbon polymer is a copolymer of vinylidene fluoride and hexafluoropropylene.
5. The composition of claim 3 wherein said fluorocarbon polymer is a thermoplastic copolymer of a major portion of vinylidene fluoride and up to about 15 weight percent of bound hexafluoropropylene.
6. The composition of claim 5 wherein said acrylic-containing thermoplastic copolymer is a copolymer of from about 45 to about 80 weight percent of bound styrene and from about 20 to about 55 weight percent of bound methyl methacrylate.
7. The composition according to claim 5 wherein said copolymer contains from about 20 to about 35 weight percent of bound methyl methacrylate and from about 80 to about 65 weight percent of bound styrene and wherein the weight ratio of said acrylic-containing thermoplastic copolymer to said fluorocarbon polymer is from about 10/90 to 25/75.
8. The composition of claim 7 wherein said premixed blend is homogeneous as indicated by:
A) having an essentially uniform color by visual inspection;
and/or B) the existence of a matrix/particle morphology as determined by microscopy and wherein particles having a size of less than 4 microns are observable by scanning electron microscopy.
A) having an essentially uniform color by visual inspection;
and/or B) the existence of a matrix/particle morphology as determined by microscopy and wherein particles having a size of less than 4 microns are observable by scanning electron microscopy.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002176057A CA2176057A1 (en) | 1996-05-08 | 1996-05-08 | Melt fracture reduction with uv additive |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002176057A CA2176057A1 (en) | 1996-05-08 | 1996-05-08 | Melt fracture reduction with uv additive |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2176057A1 true CA2176057A1 (en) | 1997-11-09 |
Family
ID=4158161
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002176057A Abandoned CA2176057A1 (en) | 1996-05-08 | 1996-05-08 | Melt fracture reduction with uv additive |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2176057A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2006015026A1 (en) * | 2004-07-29 | 2006-02-09 | Dupont Dow Elastomers L.L.C. | Process aid for melt processable polymers that contain hindered amine light stabilizer |
| US7402625B2 (en) | 2003-06-11 | 2008-07-22 | 3M Innovative Properties Company | Compositions and method for improving the processing of polymer composites |
| WO2010053578A1 (en) * | 2008-11-10 | 2010-05-14 | Chevron Phillips Chemical Company Lp | Polymer compositions containing a polymer processing aid and a hindered amine light stabilizer |
| US8236874B2 (en) | 2003-06-11 | 2012-08-07 | 3M Innovative Properties Company | Compositions and method for improving the processing of polymer composites |
-
1996
- 1996-05-08 CA CA002176057A patent/CA2176057A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7402625B2 (en) | 2003-06-11 | 2008-07-22 | 3M Innovative Properties Company | Compositions and method for improving the processing of polymer composites |
| US8236874B2 (en) | 2003-06-11 | 2012-08-07 | 3M Innovative Properties Company | Compositions and method for improving the processing of polymer composites |
| WO2006015026A1 (en) * | 2004-07-29 | 2006-02-09 | Dupont Dow Elastomers L.L.C. | Process aid for melt processable polymers that contain hindered amine light stabilizer |
| WO2010053578A1 (en) * | 2008-11-10 | 2010-05-14 | Chevron Phillips Chemical Company Lp | Polymer compositions containing a polymer processing aid and a hindered amine light stabilizer |
| US8110262B2 (en) | 2008-11-10 | 2012-02-07 | Chevron Phillips Chemical Company Lp | Polymer compositions containing a polymer processing aid and a hindered amine light stabilizer |
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Legal Events
| Date | Code | Title | Description |
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| FZDE | Discontinued |