Synergist for hyperbranched polyol polymer processing additives

Abstract

Synergists are combined with hyperbranched polyester polyols to form polymer processing additive compositions. These synergists are selected from the group consisting of polyethylene glycol, polyethylene oxide, polycaprolactone, and combinations thereof. Compositions containing a thermoplastic polymer and such polymer processing additive compositions are also described, as are methods of extruding a thermoplastic polymer containing such polymer processing additive compositions.

Description

Technical Field

[0001] The present disclosure relates to synergists for use with hyperbranched polyol polymer processing additives and thermoplastic polymer compositions containing these synergists. Summary of the Invention

[0002] Briefly, in one aspect, the present disclosure provides a composition comprising a plurality of thermoplastic polymers and an additive composition comprising a hyperbranched polyester polyol and a synergist selected from the group consisting of polyethylene glycol, polyethylene oxide, polycaprolactone, and combinations thereof.

[0003] In another aspect, the present disclosure provides methods for forming films comprising blending a thermoplastic polymer with a hyperbranched polyester polyol and a synergist selected from the group consisting of polyethylene glycol, polyethylene oxide, polycaprolactone, and combinations thereof to form a composition, and extruding the composition.

[0004] The above summary of the present disclosure is not intended to describe every embodiment of the present invention. Details of one or more embodiments of the present invention are also listed in the following detailed description. Other features, objects and advantages of the present invention will be apparent from the detailed description and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 The effect of various synergists on the reduction in melt fracture obtained with hyperbranched polyester polyol polymer processing additives is shown.

[0006] Figure 2 Shown is the effect of adding various amounts of polyethylene glycol synergist on the reduction in melt fracture obtained with a hyperbranched polyester polyol polymer processing additive.

[0007] Figure 3 The effect of adding a polycaprolactone synergist on the reduction in melt fracture obtained with a hyperbranched polyester polyol polymer processing additive is shown.

[0008] Figure 4 The effect of adding various poly(ethylene oxide) synergists on the reduction in melt fracture obtained with hyperbranched polyester polyol polymer processing additives is shown.

[0009] Figure 5 The effect of adding a hyperbranched polyester polyol polymer processing additive and a synergist as a combined masterbatch processing additive on melt fracture reduction is shown. DETAILED DESCRIPTION

[0010] The extrusion of polymeric materials during article formation and molding is an integral part of the plastic or polymeric article industry. The quality of the extruded article and the overall success of the extrusion process are influenced by the interaction of the fluid material with the extrusion die. The requirement for a smooth extrudate surface competes with the economic advantage of extruding polymer compositions at the fastest possible speeds (e.g., highest shear rates) and must be optimized relative to this economic advantage.

[0011] For any melt-processable thermoplastic polymer composition, there exists a critical shear rate above which the surface of the extrudate becomes rough or distorted, while below which the extrudate is smooth. At shear rates slightly above the critical shear rate, defects in extruded thermoplastics can take the form of "sharkskin," a loss of surface gloss, or more severely, ridges extending somewhat transverse to the direction of extrusion. At high shear rates, the extrudate can undergo "continuous melt fracture," becoming severely distorted. At rates below the point where continuous melt fracture is just observed, some thermoplastics can also experience "annular melt fracture," a process in which the extrudate surface changes from smooth to rough.

[0012] Other problems encountered during the extrusion of thermoplastic polymers include: polymer accumulation at the orifice of the die (called die buildup or die drool), high back pressure during extrusion, and excessive degradation of the polymer or low melt strength due to the need to use higher extrusion temperatures to overcome these problems. These problems slow down the extrusion process, either because the process must be stopped to clean the equipment or because the process must be carried out at a lower speed.

[0013] Additives for polymer processing (also known as "polymer processing additives" or "PPAs") have been used to address such problems. PPAs can reduce melt stagnation at the die and increase the shear rate at which thermoplastic polymers can be extruded without visible melt defects.

[0014] Fluoropolymers are commonly used as polymer processing additives. In some cases, the performance of fluorinated PPAs can be enhanced by incorporating "synergists." For example, U.S. Patent No. 6,818,695 B2 ("Extrudable Thermoplastic Compositions," Dillon et al.) describes the use of hyperbranched polyesters and hyperbranched polyesteramides as synergists for use with various fluorinated polymer processing additives. While synergists are effective in reducing the amount of fluorinated material required, in some applications, it is desirable to eliminate the use of fluorinated PPAs.

[0015] Hong et al. describe the use of functionalized hyperbranched polyesters as polymer processing additives. ( Journal of Rheology Journal of Rheol. 43(3) May / June 1999, pp. 781-93). The hydroxyl groups of the hyperbranched polyesters are reacted with C-14 alkanes to form hexadecyl-terminated polymers, or the hydroxyl groups are reacted with a mixture of eicosanoic and docosanoic acids such that 50% to 90% of the groups are terminated with C-20 / 22 alkanes. Hong and Coombs et al. also describe the use of hyperbranched polyesters functionalized with eicosanoic and docosanoic acids as polymer processing additives. ( Polymer ,41(2000),pp.7705-13).

[0016] The present inventors have discovered that the hydroxyl groups of the hyperbranched polyesters do not need to be functionalized to provide the benefits of a polymer processing additive, such as reduction of melt defects, when combined with a synergist.

[0017] Hyperbranched polymers are known in the art. Hyperbranched polymers are similar to dendritic polymers in that both are characterized by a highly branched three-dimensional structure. All bonds originate from the core, with the branching junctions being each monomer unit and multiple reactive chain ends. A branching generation consists of structural units that are radially connected to the core or to structural units of the previous generation, with these structural units extending outward. The structural unit has at least two monofunctional groups and / or at least one monofunctional group and one polyfunctional group. The term polyfunctional should be understood as having a functionality of 2 or higher. New structural units can be attached to each functional group, resulting in higher branching generations. Unlike dendritic polymers, hyperbranched polymers have an irregular structure and the positioning of their functional groups; therefore, while dendritic polymers are described as having precise "generations", hyperbranched polymers are described as having "pseudo-generations". The resulting hyperbranched polymer has a core, at least one branching pseudo-generation, and an outer surface composed of functional end groups.

[0018] Hyperbranched polymers of the polyester type are described, for example, in International Publication No. WO 96 / 12754 and US Pat. No. 6,300,424 Bl.

[0019] As used herein, "hyperbranched polyester polyol" refers to a hydroxyl-functional hyperbranched polyester in which at least 90 mole percent of the functional end groups are hydroxyl groups, for example, in some embodiments, at least 95 mole percent or even 100 mole percent of the functional end groups are hydroxyl groups. The term "hyperbranched polyester polyol" distinguishes the hydroxyl-functional hyperbranched polyesters of the present disclosure from functionalized hyperbranched polyesters in which a higher percentage (e.g., 50%, 90% or even 100%) of the hydroxyl groups are replaced by, for example, fatty acid or amine functional groups. Suitable hyperbranched polyester polyols are commercially available from Perstorp AB under the trade name BOLTRON, for example, BOLTON H20 (reported to be a pseudo-2 generation with 16 hydroxyl functional groups), H30 (reported to be a pseudo-3 generation with 32 hydroxyl functional groups), and H40 (reported to be a pseudo-4 generation with 64 hydroxyl functional groups). These hyperbranched polyester polyols are described as having 2,2-bis(hydroxymethyl)propionic acid ("bis-MPA") branching units.

[0020] As shown in the examples, when combined with thermoplastic polymers, the hyperbranched polyester polyols of the present disclosure serve as polymer processing additives. That is, the hyperbranched polyester polyols shorten the time to clear melt fracture. In some embodiments, the hyperbranched polyester polyols also reduce the pressure drop of extrusion.

[0021] The present inventors have discovered that the performance of hyperbranched polyester polyols as polymer processing additives can be improved by adding synergists to form polymer processing additive compositions. In some embodiments, the synergists further shorten the time to melt fracture. In some embodiments, the synergists further reduce the pressure drop of extrusion. In some embodiments, the synergists can be used to reduce the amount of the hyperbranched polyester polyol polymer processing additive while maintaining the same or similar performance.

[0022] Suitable synergists include polyethylene glycol, poly (ethylene oxide) and polycaprolactone. In some embodiments, polyethylene glycol has 1000 dalton to 50,000 dalton, for example, 4000 dalton to 25,000 dalton number average molecular weight. In some embodiments, poly (ethylene oxide) has 10,000 dalton to 500,000 dalton, for example, 15,000 dalton to 400,000 dalton number average molecular weight. In some embodiments, polycaprolactone has 2,000 dalton to 200,000 dalton, for example, 50,000 dalton to 150,000 dalton number average molecular weight. The number average molecular weight can be measured using polyethylene glycol and poly (ethylene oxide) standards by gel permeation chromatography (GPC). GPC equipment and standards are available from Agilent Technologies, Inc.

[0023] Typically, the weight ratio of the hyperbranched polyester polyol to the synergist in the polymer processing additive composition is from 90:10 to 10:90. In some embodiments, the weight ratio is from 75:25 to 25:75, or even from 60:40 to 40:60.

[0024] In some embodiments, the thermoplastic polymer to which the hyperbranched polyester polyol and synergist are added includes polymers obtained by homopolymerization or copolymerization of olefins. Suitable olefins have the general structure CH2=CHR, wherein R is hydrogen or an alkyl group, and generally, the alkyl group contains no more than 10 carbon atoms, and preferably one to four carbon atoms. Representative olefins are ethylene, propylene, and butene-1. Representative examples of olefin polymers include polyethylene, polypropylene, polybutene-1, poly(3-methylbutene), poly(4-methylpentene), and copolymers of ethylene with propylene, butene-1, hexane-1, octene-1, decene-1, 4-methyl-1-pentene, and octadecene-1.

[0025] In some embodiments, the thermoplastic polymer is a copolymer of one or more olefins and up to about 30 weight percent (but preferably 20 weight percent or less) of one or more monomers copolymerizable with such olefins. Representative monomers that can be copolymerized with olefins are vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl chloroacetate, vinyl chloropropionate, acrylic acid and α-alkyl acrylic acid monomers; and their alkyl esters, amides and nitriles such as acrylic acid, methacrylic acid, ethacrylic acid, methyl acrylate, ethyl acrylate, N,N-dimethylacrylamide, methacrylamide, acrylonitrile; vinyl aromatic monomers such as styrene, o-methoxystyrene, p-methoxystyrene and vinyl naphthalene; vinyl halide and vinylidene halide monomers such as vinyl chloride, vinylidene chloride, vinylidene bromide; alkyl ester monomers of maleic acid and fumaric acid such as dimethyl maleate, diethyl maleate; vinyl alkyl ether monomers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, 2-chloroethyl vinyl ether; and vinyl pyridine monomers, N-vinylcarbazole monomers and N-vinylpyrrolidone monomers.

[0026] In some embodiments, the thermoplastic polymer further comprises a metal salt of an olefin copolymer, or a blend thereof, which comprises free carboxylic acid groups. Illustrative examples of metals that can be used to provide the carboxylic acid polymer salt are monovalent, divalent, or trivalent metals such as sodium, lithium, potassium, calcium, magnesium, aluminum, barium, zinc, zirconium, beryllium, iron, nickel, and cobalt.

[0027] Representative blends of thermoplastic hydrocarbon polymers useful in the present invention are blends of polyethylene and polypropylene, blends of low density polyethylene and high density polyethylene, blends of polyethylene and olefin copolymers containing copolymerizable monomers, some of which have been described above, for example, ethylene and acrylic acid copolymers; ethylene and methyl acrylate copolymers; ethylene and ethyl acrylate copolymers; ethylene and vinyl acetate copolymers; ethylene, acrylic acid and ethyl acrylate copolymers, and ethylene, acrylic acid and vinyl acetate copolymers.

[0028] The thermoplastic polymer can be used in powder, pellets, granules or any other extrudable form.In some embodiments, the thermoplastic polymer contains other additives such as, for example, anti-blocking agents, anti-slip agents, light stabilizers and fillers.

[0029] Generally, the amount of the polymer processing additive composition (i.e., the combined amount of the hyperbranched polyester polyol polymer processing additive and the synergist) contained in the thermoplastic composition is not particularly limited. However, for compositions intended to be extruded into finished articles, it may be desirable to minimize the amount of the polymer processing additive composition while maintaining the desired processing properties. In some embodiments, such compositions and articles contain no more than 5000 ppm of the polymer processing additive composition, based on the total weight of the composition. For example, in some embodiments, such compositions or articles contain from 100 ppm to 3000 ppm, such as from 500 ppm to 1500 ppm, based on the total weight of the composition.

[0030] In some embodiments, each component of the polymer processing additive composition can be added separately to the thermoplastic polymer. In some embodiments, the hyperbranched polyester polyol polymer processing additive and the synergist can be blended, for example, in a desired ratio and then added together to the thermoplastic polymer. For example, the components of the polymer processing additive composition can be blended by physical mixing or melt blending. In such embodiments, additional amounts of the hyperbranched polyester polyol polymer processing additive or the synergist can be added to the thermoplastic polymer to adjust their amounts.

[0031] Because it can be difficult to control the amount of the polymer processing additive composition at such low levels, in some embodiments, a masterbatch can be used. Such a masterbatch contains a relatively high proportion of one or more components of the polymer processing additive composition in a host resin. The host resin is selected to be compatible with the thermoplastic polymer and can be the same as or different from the thermoplastic polymer.

[0032] In some embodiments, a separate masterbatch can be used, wherein one contains a hyperbranched polyester polyol polymer processing additive and the other contains a synergist. For example, this may be useful when it may be desirable to adjust the ratio of a hyperbranched polyester polyol polymer processing additive and a synergist. Equally, the amount of specific components in the masterbatch is not critical. In some embodiments, the masterbatch contains 0.2 % by weight to 10 % by weight, for example 0.5 % by weight to 5 % by weight of those components of the polymer processing additive composition present in the masterbatch. In some embodiments, a single combined masterbatch contains both a hyperbranched polyester polyol polymer processing additive and a synergist.

[0033] The polymer processing additive composition can be compounded into the thermoplastic polymer using known equipment and methods, and the compounded composition can be processed. For example, the polymer processing additive composition of the present disclosure can be used in the processing of thermoplastic polymers, including, for example, film extrusion, extrusion blow molding, injection molding, pipe, wire or cable extrusion, and fiber production.

[0034] Examples: The materials used to prepare the polymer processing additive compositions used in the following examples are summarized in Table 1.

[0035] Table 1: Summary of materials used in the preparation of the examples .

[0036]

[0037] Prepare the independent masterbatch of hyperbranched polyester polyol polymer processing additive (PPA) and each synergist.By mixing 60 grams (g) of required materials (that is, PPA or synergist) with 2935g2MI LLDPE (available from ExxonMobil EM 1002.09), 3.0g IRGANOX B900 heat stabilizer (available from BASF) and 2.1g zinc stearate in a bag and vigorous shaking to prepare each masterbatch.The resulting mixture is fed to a laboratory scale, intermeshing, counter-rotating, non-ventilated, air-cooled conical twin-screw (HaakeBuchler Rheomix TW-100) with a front internal diameter of 33mm.The mixture is gravity-fed to the throat of the extruder and exposed to air at a rate of 55g / min. The specific temperature profile of the extruder was 170°C / 190°C / 200°C / 200°C for the three barrel zones (feeding, metering, mixing) and the die zone, respectively. The extruder was operated at 150 RPM for the first "compounding" pass. The second compounding pass was run with the same temperature profile but at 90 RPM while the material was being fed. The 4-minute material "purge" step was omitted at the beginning of each compounding pass. Each masterbatch contained 2.0 wt% of the desired component (i.e., PPA or synergist) based on the total weight of the masterbatch.

[0038] Extrudable compositions were prepared by blending the desired masterbatch into 0.9 MI ZN LLDPE (MARFLEX 7109 from Chevron Phillips Chemicals). The reference sample contained only the hyperbranched polyester polyol polymer processing additive. The comparative example contained only the synergist. The examples contained hyperbranched polyester polyol PPA and the synergist. All extrudable compositions also contained 6000 ppm of an anti-caking additive (ABT 2500, AMPACET MB#101558) and 1000 ppm of a slip agent (ERUCAMIDE, Ampacet MB#10090).

[0039] Melt fracture and pressure drop were evaluated using a Kiefel blown film line with a 40 mm, 24 / 1 grooved feed extruder. The die was a spiral design with a 40 mm diameter, 14 L / D, and a 0.9 mm die gap. Extrusion was performed at 210°C, 10.5 kg / hour, and 220 s.

[0040] The pressure was recorded every 10 minutes, and film samples were collected. The films were inspected for the presence of melt fracture (MF) and expressed as the percentage of the film area covered by MF. The time corresponding to the disappearance of the last MF band, or the time to clear melt fracture (TTC), was recorded, at which point the test was stopped. If any MF remained at the end of two hours, the test was stopped and the final MF level was recorded. In this case, the TTC was estimated based on the shape of the curve.

[0041] The effect of various synergists was evaluated by comparing a sample containing 1000 ppm of hyperbranched polyester polyol PPA (REF-1) with samples containing 500 ppm of hyperbranched polyester polyol PPA and 500 ppm of synergist (Examples EX-1 to EX-3), where all amounts are reported in ppm by weight based on the total weight of the extruded composition. For each synergist, a comparative example containing only 1000 ppm of synergist was run (CE-1 to CE-3). The melt fracture results are summarized in Table 2 and are shown in Table 2. Figure 1 The pressure drop results are also reported in Table 2.

[0042] Table 2: Performance of various synergists in combination with hyperbranched polyol PPA .

[0043]

[0044] As shown, none of the synergists alone were effective in reducing melt fracture (CE-1 to CE-3). However, when combined with the hyperbranched polyester polyol PPA, each synergist provided good results while reducing the amount of hyperbranched polyester polyol PPA required by 50% (500 ppm of hyperbranched polyester polyol PPA in EX-1 to EX-3 compared to 1000 ppm of hyperbranched polyester polyol PPA in REF-1).

[0045] Additional samples were prepared by varying the relative amounts of hyperbranched polyester polyol PPA and PEG 8K synergist. Melt fracture results are summarized in Table 3 and are presented in Table 3. Figure 2 The pressure drop results are also reported in Table 3.

[0046] Table 3: PEG synergist and hyperbranched polyester polyol PPA .

[0047]

[0048] Reference Example 3 (REF-3) was prepared using 500 ppm of hyperbranched polyester polyol PPA based on the total weight of the extruded composition. Examples EX-9, EX-10, and EX-11 were prepared using a combination of 500 ppm of hyperbranched polyester polyol PPA and 500 ppm of polycaprolactone (PCL) or poly(ethylene oxide) (PO) synergist. Figure 3 (PCL) and Figure 4 As shown in Figure 5, the addition of the synergist improved the melt fracture reduction in each case, with the results being comparable to using 1000 ppm of the hyperbranched polyester polyol PPA (REF-2).

[0049] Table 4: Improvement of melt fracture with various synergists .

[0050]

[0051] In the previous examples, the hyperbranched polyester polyol PPA and the synergist were added as separate masterbatches to form an extrudable composition. In the following examples, a combined masterbatch was prepared. This combined masterbatch (CMB) was prepared in the same manner as the other masterbatches, except that the CMB was prepared from 30 g of the hyperbranched polyester polyol PPA and 30 g of the PEG 8K synergist, resulting in a 2.0 wt% combined PPA and synergist based on the total weight of the CMB.

[0052] This CMB was used to form the extrudable composition of Example EX-12, which contained 500 ppm of hyperbranched polyester polyol PPA and 500 ppm of PEG 8K synergist, each by weight based on the total weight of the extrudable composition. Testing was performed using a blown film line. The results are shown in Tables 5 and Figure 4In the example, the results were compared with EX-6 prepared using a separate masterbatch of hyperbranched polyester polyol PPA and PEG 8K synergist.

[0053] Table 4: Results of combined masterbatches using hyperbranched polyol PPA and synergists .

[0054]

Claims

1. A composition comprising greater than 50% by weight of a thermoplastic polymer and a polymer processing additive composition comprising: (i) a hyperbranched polyester polyol, wherein the hyperbranched polyester polyol is a hydroxyl functional hyperbranched polyester having functional end groups, wherein at least 90 mole % of the functional end groups are hydroxyl groups; and (ii) a synergist selected from the group consisting of polyethylene glycol, poly(ethylene oxide), polycaprolactone, and combinations thereof; wherein the composition does not contain a fluoropolymer.

2. The composition of claim 1, wherein the composition comprises from 100 ppm to 3000 ppm by weight of the polymer processing additive composition, based on the weight of the thermoplastic polymer.

3. The composition of claim 1 , wherein the polymer processing additive composition comprises at least 100 ppm of the hyperbranched polyester polyol and at least 100 ppm of the synergist, based on the weight of the thermoplastic polymer.

4. The composition of claim 3, wherein the weight ratio of the hyperbranched polyester polyol to the synergist is 10:90 to 90:

10.

5. The composition of claim 4, wherein the weight ratio of the hyperbranched polyester polyol to the synergist is 25:75 to 75:

25.

6. A composition according to any one of the preceding claims, wherein the synergist comprises polyethylene glycol.

7. The composition of claim 6, wherein the polyethylene glycol has a number average molecular weight of 1000 to 50,000 daltons as measured by gel permeation chromatography using polyethylene glycol and poly(ethylene oxide) standards.

8. The composition of any one of claims 1 to 5, wherein the synergist comprises poly(ethylene oxide).

9. The composition of claim 8, wherein the poly(ethylene oxide) has a number average molecular weight of 10,000 to 500,000 daltons as measured by gel permeation chromatography using polyethylene glycol and poly(ethylene oxide) standards.

10. The composition of any one of claims 1 to 5, wherein the synergist comprises polycaprolactone.

11. The composition of claim 10, wherein the polycaprolactone has a number average molecular weight of 2,000 to 200,000 Daltons as measured by gel permeation chromatography using polyethylene glycol and poly(ethylene oxide) standards.

12. The composition of any one of claims 1 to 5, wherein the hyperbranched polyester polyol comprises 2,2-bis(hydroxymethyl)propionic acid branching units.

13. The composition according to claim 12, wherein the hyperbranched polyester polyol is a pseudo 2nd generation hyperbranched polyester polyol having 16 hydroxyl functional groups.

14. The composition of any one of claims 1 to 5, wherein the thermoplastic polymer comprises a polyolefin.

15. The composition of claim 14, wherein the polyolefin comprises linear low density polyethylene.

16. A method of forming a film, the method comprising: A) blending a thermoplastic polymer with a hyperbranched polyester polyol and a synergist selected from polyethylene glycol, polyethylene oxide, polycaprolactone, and combinations thereof to form a composition, and B) extruding the composition; wherein the hyperbranched polyester polyol is a hydroxyl-functional hyperbranched polyester having functional end groups, wherein at least 90 mole % of the functional end groups are hydroxyl groups; wherein the composition does not contain a fluoropolymer.

17. The method of claim 16, wherein blending the thermoplastic polymer with the hyperbranched polyester polyol and the synergist to form the composition comprises blending the hyperbranched polyester polyol and the synergist to form a polymer processing additive composition, and blending the polymer processing additive composition with the thermoplastic polymer.

18. The method of claim 17, wherein the composition comprises from 100 ppm to 3000 ppm of the polymer processing additive composition, based on the total weight of the composition.

19. The composition of any one of claims 1 to 5, wherein the composition comprises from 100 ppm to 3000 ppm of the polymer processing additive composition, based on the total weight of the composition.

Images