Polyhydroxy polymer processing additives

Abstract

Polymer processing additive compositions comprising a polyhydroxy compound and, optionally, a synergist are described. The polyhydroxy compounds consist of carbon, hydrogen and oxygen, and comprise either (i) from 4 to 10 hydroxy groups or (ii) two hydroxy groups and one carboxylic acid group. Compositions of thermoplastic polymers combined with such polymer processing additive compositions, methods of preparing such compositions, and methods of forming articles such as blown films from such compositions are also described.

Description

POLYHYDROXY POLYMER PROCESSING ADDITIVESFIELD

[0001] The present disclosure relates to formulations containing a polyhydroxy compound and, optionally, a synergist, and their use as polymer processing additives in compositions comprising thermoplastic polymers.SUMMARY

[0002] Briefly, in one aspect, the present disclosure provides compositions comprising greater than 50% by weight of a thermoplastic polymer and a polymer processing additive formulation. The polymer processing additive formulation comprises (i) a polyhydroxy compound consisting of carbon, hydrogen, and oxygen, wherein the polyhydroxy compound comprises from 4 to 10 hydroxy groups; and, optionally, (ii) a synergist.

[0003] In another aspect, the present disclosure provides compositions comprising greater than 50% by weight of a thermoplastic polymer and a polymer processing additive formulation. The polymer processing additive formulation comprises (i) a polyhydroxy compound consisting of carbon, hydrogen, and oxygen, wherein the polyhydroxy compound comprises 2 hydroxy groups and one carboxylic acid group; and, optionally, (ii) a synergist.

[0004] In another aspect, the present disclosure provides methods of producing articles comprising forming and extruding such compositions.DETAILED DESCRIPTION

[0005] Extrusion of polymeric materials in the formation and shaping of articles is a major segment of the plastic or polymeric articles 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 desire for a smooth extrudate surface competes with and must be optimized with respect to the economic advantages of extruding a polymer composition at the fastest possible speed (for example at high shear rates).

[0006] For any melt-processable thermoplastic polymer composition, there exists a critical shear rate above which the surface of the extrudate becomes rough or distorted and below which the extrudate will be smooth. At shear rates slightly above the critical shear rate, defects in extruded thermoplastics may take the form of "sharkskin" which is a loss of surface gloss that in more serious manifestations appears as ridges running more or less transverse to the extrusion direction. At higher shear rates, the extrudate can undergo "continuous melt fracture" becoming grossly distorted. At rates lower than those at which continuous melt fracture is first observed, certain thermoplastics can also suffer from "cyclic melt fracture" in which the extrudate surface varies from smooth to rough.

[0007] Other problems encountered during extrusion of thermoplastic polymers include build-up of polymer at the orifice of the die (known as die build up or die drool), high extrusion pressure, and excessive degradation or low melt strength of the polymer due to the need to use higher extrusion temperatures to overcome these issues. These problems slow down the extrusion process either because the process must be stopped to clean the equipment or because the process must be run at a lower speed.

[0008] Additives for polymer processing (also referred to as “polymer processing additives” or “PPA”) have been used to address such problems. For example, when starting the process of extruding films with a thermoplastic polymer at desired production speeds resulting in conditions above the critical shear rate of the polymer, high levels of melt fracture (e.g., 100% MF) occur resulting in unusable material until the melt fracture can be eliminated. PPAs can reduce melt stagnation at the die and increase the shear rates at which thermoplastic polymers may be extruded without visible melt defects. Generally, it is desired to reduce melt fracture to less than 10%, less than 5%, less than 1% or even to 0% in no greater than 120 minutes, preferably no greater than 100 minutes, or even no greater than 60 minutes.

[0009] The chemistry principle "like dissolves like" states that compounds with similar chemical properties e.g., polarity, will dissolve in each other. The solubility parameter can be used to estimate the polarity of a molecule. The solubility of parameter of materials may be obtained in the literature and may be measured according to a variety of methods including solvent interaction methods and differential scanning calorimetry. Hildebrand solubility parameters may also be measured according to ASTM D7222 “Standard Test Method for Determining the Solubility Parameter of Polymers by Inverse Gas Chromatography.” Group contributions methods may also be used to calculate the Hildebrand solubility parameter of polymers. The Hildebrand solubility parameters of some common polymers are provided in Table 1.Table 1: Hildebrand Solubility Parameter of polymers.

[0010] A polymer processing additive (PPA) can be a material having a different solubility parameter from the host resin. This dissimilarity can be helpful to drive phase separation from the host resin, allowing the PPA to migrate to the surface of the plastic extrudate during polymer processing, such as extrusion, forming an interface between the host resin and the process equipment (typically made of metal). Especially for low molecular weight PPA, the dissimilar PPA can migrate easily based on phase separation, and the PPA does not need to be present in high concentrations; e.g., as little as 0.5%, 0.2%, or even as low as 0.1 wt.% can work effectively as a polymer processing additive. Even this smallamount of polymer processing additive can help improve processing by reducing melt fracture and pressure since melt fracture and pressure can be generated by the interaction between metal and the host resin.

[0011] Fluorinated organic compounds such as fluoropolymers are commonly used as polymer processing additives with, e.g., polyolefins. Common fluorinated PPA have a Hildebrand solubility parameter of about 12 to 17 MPa^ To be effective as PPAs, such fluorinated organic compounds are typically present at amounts of at least 100, e.g., at least 500 ppm by weight based on the weight of the composition. There is a desire to eliminate the use of fluorinated organic compounds even at these low concentrations. For example, compositions containing no greater than 1 ppm, no greater than 1 ppb, or even undetectable amounts of fluorinated organic compounds may be desired.

[0012] Silicone based compounds have also been used as polymer processing additives. Common silicone-based PPA have a Hildebrand solubility parameter of about 15 to 18 MPa^ However, in some cases the presence of silicone materials may impact the properties of extruded compositions. For example, in some cases the silicone materials may migrate to exposed surfaces reducing adhesion to inks, coatings and adhesives. There is a desire to avoid the use of silicone compounds. For example, compositions containing no greater than 1 ppm by weight based on the weight of the composition may be desired.

[0013] Hyperbranched polyester polyols have been used as non-fluorinated polymer processing additives, alone or with synergists. For example, WO 2023 / 089434 Al (“Synergists for Hyperbranched Polyol Polymer Processing Additives”) describes hydroxy-functional hyperbranched polyesters in which at least 90 mole% of the functional end groups are hydroxy groups and their use as PPAs. Suitable hyperbranched polyester polyols included those having 16, 32 or 64 hydroxy groups in pseudo generation 2, 3 and 4 hyperbranched structures, respectively. Commercially available hyperbranched polyester polyols such as BOLTORN H20, H30 and H40 (available from Perstorp) are believed to have a solubility parameter of about 20 MPa^

[0014] 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.) Hyperbranched polyesters are either reacted with C-14 alkanes to form hexadecanote -terminated polymers or the hydroxy groups are reacted with a mixture of eicosanoic and docosanoic acid such that 50 to 90% of the groups are terminated with C-20 / 22 alkanes.

[0015] Mixtures of polyethylene glycol reacted with organic polyacids, phosphoric acid, and polyesters of oxyacids of phosphorus have been used as non-fluorinated polymer processing additives. For example, see “Thermoplastic Polymer Material” (RU2376331C, describing the use of polyhydroxl aliphatic polyesters (copolymers of polyethylene glycols and polyhydric alcohols)); “Low Viscous Hydrophilic Processing Additives for Extrusion of Polyethylene at Reduced Temperatures” (Polymer Engineering and Science, 50(6) (2010), pp. 1236-1252, describing low viscous PPA made from reactingmixtures of polyethylene glycol with organic polyacids, phosphoric acid and polyesters of oxiacids of phosphorus); and “Impact of Elasticity on Lubrication. Esters of PEG, Silanol and their Blends as Polymer Processing Additives” (International Congress on Rheology, The Society of Rheology 80thAnnual Meeting, pp. 63-65, exemplify the use of PEG with sorbitol and silica fume cured by phosphoric acid). RU2376331C1 also describes (i) polycondensation reaction products between hardeners containing boron and oxygen and polyhydroxl compounds, and (ii) esters of phosphorous acids and polyhydroxl compounds as hardeners or thickeners.

[0016] U.S. Patent 6,048,937 (“Thermoplastic Molding Compounds Based on Ethylene Polymers and Thermoplastic Polyesters”) describes the use of polyesters obtained by reacting a mixture of components including 0 to 5 percent by weight a compound having at least three groups capable of forming an ester, preferably hydroxyl or carboxyl groups.

[0017] Despite these advancements, a need remains for nonfluorinated PPAs that meet demanding performance requirements. For example, PPAs are commonly used in fdm extrusion, e.g., blown fdm operations, that can operate at high temperatures and speeds and may produce fdms requiring food contact approvals. In addition to film extrusion, PPAs are also used in high speed tube extrusion, and high speed cable and wire coating. The presence of water and charring can produce unacceptable results in each of these applications. Note that blown film processes are to be distinguished from blow molding operations. Although PPAs may also be useful in such applications, the melt defects associated with high speed blown film operations are less prevalent. Melt defects are also less critical in film extrusion and film casting processes. However, PPAs are still valuable in reducing pressure allowing for higher speed operations.

[0018] A broad range of polyhydroxy compounds have been used in combination with thermoplastic polymers for a variety of purposes. For example, such compounds have been used to plasticize PVOH (GB 2409204), to stabilize recycled polyolefins by reacting with carbonyl groups to form acetals (US 11,591,450 B2), to impact the crystallization speed of (i) polyhydroxyalkanoates (US 9,475,934), (ii) polylactic acids (US 20210363345 Al), or (iii) PVC and CPVC homopolymer and copolymers (JPH11- 12420A), and as binders or carriers to form tablets containing a polymer property modifying agent for use in extrusion operations (US 9,701,814 B2).

[0019] Surprisingly, the present inventors discovered that formulations containing certain polyhydroxy compounds can be used as PPA in thermoplastic compositions. These polyhydroxy compounds have a substantially higher Hildebrand solubility parameter than convention fluorinated PPA and silicone PPA. These compounds also avoid the complex synthesis and associated costs and contain far fewer hydroxy groups than the hyperbranched options. These compounds offer various additional advantages. For example, some such compounds are authorized for indirect food contact, show low levels of water absorption, can be processed at high temperatures without charring, and can be easier to produce at higher purity.

[0020] In some cases, the polyhydroxy compounds of the present invention consist of carbon (C), hydrogen (H) and oxygen (O), and comprise at least four hydroxy groups (-OH). Suitable polyhydroxy compounds comprise 4 to 10, e.g., 4 to 6, 5 to 6, or even 6 hydroxy groups. Linear polyhydroxy compounds include sugar alcohols, which can be represented by the formula below:wherein n is an integer from 2 to 8. Exemplary linear polyhydroxy compounds include erythritol (four hydroxy groups), xylitol (five hydroxy groups), and sorbitol and mannitol (six hydroxy groups).Exemplary branched polyhydroxy compounds include pentaerythritol (four hydroxy groups). Exemplary cyclic polyhydroxy compounds include inositol (six hydroxy groups). Isomers of these linear, branched, and cyclic materials may also be used.

[0021] Suitable polyhydroxy compounds may also include one or more ether oxygen. Exemplary polyhydroxy compounds comprising ether oxygens include linear compounds and branched compounds such as dipentaerythritol, tripentaerythritol, maltitol, isomalt, and their respective isomers.

[0022] In some cases, the polyhydroxy compounds of the present invention consist of carbon (C), hydrogen (H) and oxygen (O), and include at least two hydroxy groups and only one carboxylic acid group. Exemplary polyhydroxy compounds comprising a single carboxylic acid group include polyalkyol alkanoic acids, including, e.g., dimethylol alkanoic acids. Dimethylol alkanoic acids include, e.g., dimethylol propionic acid (2,2-bis(hydroxymethyl)propionic acid) and dimethylol butanoic acid (2,2- bis(hydroxymethyl)butanoic acid). Additional exemplary polyhydroxy compounds comprising a single carboxylic acid group and two or more hydroxy groups include glyceric acid (two hydroxy groups) and gluconic acid (five hydroxy groups).

[0023] The typical processing temperature for thermoplastic polymers is at least 150 °C, and more commonly above 200 °C, sometimes approaching 300 °C. It is desirable to avoid degradation during processing. The thermal stability of polymer processing additives can be a critical property, and can be assessed through thermogravimetric analysis (TGA). Thermal stability is indicated by the onset temperature of the PPA, with a higher onset temperature being desirable. An onset temperature of at least 200°C is good, but at least 300 °C will provide a wider operating window.

[0024] Discoloration during processing may happen due to poor thermal stability of PPAs. Also, during the extrusion of thermoplastic polymers, black specks may form due to the gradual thermal degradation of the PPAs, which leads to the formation of carbon residues. This issue is particularly common during machine shutdowns or startups. Caramelization of polyhydroxy compounds is known to occur in sugars, such as glucose and sucrose, during heating, which typically results in a brown color. The discoloration and black specks may be related to the extent of carbon residue formation, which canbe quantified by the char yield, as determined by TGA. The char yield represents the percentage of solid residue remaining after heating the PPA to 600°C under a nitrogen atmosphere. A lower char yield is preferable, e.g., no greater than 5 wt.%, no greater than 1 wt.%, or even undetectable (i.e., 0 %).

[0025] Thermoplastic polymers processed with excessive moisture can lead to defects. Common defects when the resin is under-dried include sink marks or voids, cloudiness, splay, streaks, air bubbles on the product's surface, shrinkage, or irregular shapes. If polymer processing additives contain moisture, they may cause such defects during processing. Additionally, if the PPA material is moist, it can result in agglomeration, which affects product flow, especially in areas with high humidity. The moisture content can be sensitive to the humidity level if the material is hygroscopic or prone to absorbing moisture. Moisture sensitivity can be assessed using a moisture analyzer after exposure at 40 °C with 85% relative humidity (RH) in an oven. A lower moisture content after exposure is desired, e.g., no greater than 10 wt.%, no greater than 5 wt.%, or even no greater than 0.5 wt.%, based on the total weight of the PPA sample.

[0026] In some cases, a synergist can be used to (a) reduce the amount of the polyhydroxy compound required to achieve similar performance, (b) to improve the melt fracture elimination, (c) to further reduce the pressure during extrusion, or (d) a combination of these benefits. Although not always required, suitable synergists include polyethylene glycol, polyethylene glycol / polypropylene glycol block polymer, polyethylene oxide) and polycaprolactone. In some cases, the polyethylene glycols have a number average molecular weight of 1000 to 50,000 Daltons, e.g., 4000 to 25,000 Daltons. In some cases, the polyethylene oxide)s have a number average molecular weight of 10,000 to 500,000 Daltons, e.g., 15,000 to 400,000 Daltons. In some cases, the polycaprolactones have a number average molecular weight of 2,000 to 200,000 Daltons, e.g., 50,000 to 150,000 Daltons. In some cases, the polyethylene glycol / polypropylene glycol block polymers have a number average molecular weight of 1000 to 50,000 Daltons, e.g., 4000 to 25,000 Daltons. The number average molecular weight may be measured by Gel Permeation Chromatography (GPC) using appropriate standards, e.g., polyethylene glycol and poly(ethylene oxide). For example, ASTM D6474-20 may be used. GPC equipment and standards are available from Agilent Technologies, Inc.

[0027] In some cases, a multimodal, e.g., a bimodal distribution molecular weight synergists may be used. In some cases, the ratio of the number average molecular weights of the first and second synergist may be from 2: 1 to 10: 1, e.g., 2: 1 to 5: 1, or 3: 1 to 5: 1. In some cases, the two synergists may have different chemical compositions. In some cases, the synergists may have the same chemical composition, e.g., two polyethylene glycols with different molecular weights. For example, in some cases, the first synergist may comprise a first polyethylene glycol have a number average molecular weight of 1000 to 8000 Daltons, e.g., 2000 to 5000 Daltons; and a second polyethylene glycol have a number average molecular weight of 9000 to 25,000, e.g., 9000 to 15,000 Daltons.

[0028] Although other components may be present, the polymer processing additive formulations comprise at least 90 wt.%, e.g., at least 95 wt.%, at least 99 wt.% or even 100 wt.% of the polyhydroxy compound(s) and the optional synergist based on the total weight of the polymer processing additive formulation. If the polymer processing additive formulation does not include a synergist, the polymer processing additive formulation comprises at least 90 wt.%, e.g., at least 95 wt.%, at least 99 wt.% or even 100 wt.% of the polyhydroxy compound(s). If the polymer processing additive formulations comprise both at least one polyhydroxy compound and at least one synergist, the polyhydroxy compound and the synergist may be included in any desired ratio. In some cases, the weight ratio of the polyhydroxy compound to the synergist is 99: 1 to 1:99, 95:5 to 5:95, 90: 10 to 10:90, 75:25 to 25:75, or 60:40 to 40:60. It may be desirable to use higher amounts of the synergist. In some cases, the weight ratio of the polyhydroxy compound to the synergist is from 40:60 to 10:90, e.g., 20:80 to 10:90.

[0029] The amount of the polymer processing additive formulation (i.e., the combined amounts of the PPA and optional synergist) will depend on a variety of factors including the compositions of the extruded polymer, the PPA, and the synergist. Generally, the amount of the polymer processing additive formulation contained in the thermoplastic composition is not particularly limited. However, for compositions intended for extrusion into finished articles, it may be desirable to minimize the amount of the polymer processing additive composition, while maintaining the desired processing benefits such as pressure reduction.

[0030] In some cases, the compositions will contain at least 500 ppm of the polymer processing additive formulation based on the total weigh to the composition, e.g., at least 750 ppm, or even at least 1000 ppm. Generally, there is a desire to minimize the amount of PPA used. Although greater amounts could be used, the polymer processing additive formulations are effective even at concentrations of no greater than 5000 ppm, e.g., no greater than 3000 ppm, or even no greater than 1500 ppm, based on the total weigh to the composition. As result, compositions containing 500 to 5000 ppm, e.g., 750 to 3000 ppm, 1000 to 3000 ppm, 1000 to 2000 ppm, or even 1000 to 1500 ppm of the polymer processing additive formulation based on the total weigh to the composition may be useful.

[0031] Surprisingly, in some cases, a very small amount of the polyhydroxy compound can be enough to maintain the desired processing benefits such as pressure reduction when a synergist is included. For example, such compositions or articles may contain less than 500 ppm, less than 100 ppm, or even less than 25 ppm, and in some instances, less than 10 ppm of the polyhydroxy compounds based on the total weight of the composition or article. Such compositions contain at least 3, e.g., at least 5 ppm of the polyhydroxy compound. For example, compositions containing 3 to 100, 3 to 25 or 3 to 10 ppm of the polyhydroxy compound may be used.

[0032] The polymer processing additive formulations are substantially free of fluorinated organic compounds, i.e., the formulations comprise no greater than 1 ppm by weight of fluorinated organic compounds based on the total weight of polymer processing additive formulations. Generally, nofluorinated organic materials are required; therefore, no fluorinated organic materials are intentionally added. Therefore, in some cases, the polymer processing additive formulations contain no greater than 5 ppb, e.g., no greater than 1 ppb of fluorinated organic compounds. In some cases, the polymer processing additive formulations contain no fluorinated organic compounds, i.e., undetectable amounts of fluorinated organic compounds.

[0033] Fluorinated organic compounds can be measured using “3M Standard Test Method” (Edition 1.2 June 2020) using LC-MS quantitative analysis. For example, polymer samples may be pulverized to a fine powder in a cryogrinder before undergoing extraction with methanol on a mechanical shaker.Then, 1.0 g of each powdered sample is extracted using 9 ml of methanol. The samples are spiked a known amount ofas internal standard are measured using LC / MS (model G6550A available from, Agilent Technologies, Santa Clara, CA, United States). For the quantitation, standard solutions including a known amount of PFOA andare prepared and measured as the same manner.

[0034] In some cases, the polymer processing additive formulations are also substantially free of silicone-based compounds, i.e., the formulations comprise no greater than 1 ppm by weight, e.g., no greater than 1 ppb, or even undetectable amounts of silicone-based compounds based on the total weight of polymer processing additive formulations.

[0035] While the prior art fluorinated and silicone-based PPA have Hildebrand solubility parameters of about 16 to 18, as shown in the Examples, the Hildebrand solubility parameter of the polymer processing additives of the present invention are at least 22, e.g., 22 to 30, or 23 to 28 MPa^ As a result, the polymer processing additive formulations are particularly suited for use with non-polar polymers. As used herein, non-polar polymers are those with a Hildebrand solubility parameter of no greater than 18 MPa^ For example, in some cases the non-polar thermoplastic polymers have a Hildebrand solubility parameter of 14 to 18, e.g., 15 to 17 MPa^

[0036] In some cases, the thermoplastic polymers to which the polymer processing additive formulations are added comprise polymers obtained by the homopolymerization or copolymerization of olefins. Suitable olefins have the general structure CH2=CHR, where R is a hydrogen or an alkyl radical, and generally, the alkyl radical contains not more than 10 carbon atoms and preferably one to four carbon atoms. Representative olefins are ethylene, propylene, and butene-1. Representative examples of olefinic 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.

[0037] In some cases, the thermoplastic polymer is a homopolymer. In view of the processes used to generate homopolymers, as used herein, a homopolymer comprises no greater than 1 mole%, e.g., no greater than 0.5, or even no greater than 0.1 mole% of a comonomer. In some cases, the homopolymer is a polypropylene, i.e., a polymer comprising at least 99 mole% of propylene repeat units. In some cases,the homopolymer is a polyethylene, i.e., a polymer comprising at least 99 mole% of ethylene repeat units. The polyethylene may be a high density polyethylene (HDPE), a medium density polyethylene (MDPE), or a low density polyethylene (LDPE). In some cases, the LDPE is a linear low density polyethylene (LLDPE), for example, a metallocene-catalyzed LLDPE.

[0038] The Hildebrand solubility parameter of polypropylene has been reported as about 16.8 MPa^2, while reported values for polyethylenes are about 16.2 MPa^2.

[0039] In some cases, the thermoplastic polymers are copolymers of one or more olefins and up to about 30 weight percent, but preferably 20 weight percent or less, of one or more monomers which are copolymerizable with such olefins. Representative monomers which are copolymerizable with olefins are vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl chloroacetate, vinyl chloropropionate, acrylic and alpha-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- dimethyl acrylamide, methacrylamide, acrylonitrile, vinyl aryl monomers such as styrene, o- methoxy styrene, p-methoxy styrene, and vinyl naphthalene, vinyl and vinylidene halide monomers such as vinyl chloride, vinylidene chloride, vinylidene bromide, alkyl ester monomers of maleic 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-vinyl carbazole monomers, and N-vinyl pyrrolidone monomers.

[0040] The comonomers and their amounts may be selected such that the resulting copolymer remains non-polar, i.e., has a Hildebrand solubility parameter of no greater than 18 MPa^2,e.g., 15 to 18 MPa1 / 2.

[0041] In some cases, the thermoplastic polymers also include the metallic salts of olefin copolymers, or blends thereof, which contain free carboxylic acid groups. Illustrative of the metals which can be used to provide the salts of said carboxylic acid polymers are the one, two and three valence metals such as sodium, lithium, potassium, calcium, magnesium, aluminum, barium, zinc, zirconium, beryllium, iron, nickel and cobalt.

[0042] Representative blends of thermoplastic hydrocarbon polymers include polyethylene and polypropylene, low-density polyethylene and high-density polyethylene, metallocene linear low density and low density polyethylene, linear low density polyethylene and low density polyethylene, and polyethylene and olefin copolymers containing copolymerizable monomers, some of which are described above, e.g., 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.

[0043] The thermoplastic polymers may be used in the form of powders, pellets, granules, or any other extrudable form. In some cases, the thermoplastic polymer may contain other additives such as,e.g., antioxidants, anti-blocking agents, slip agents, light stabilizers (e.g., hindered amine light stabilizers “HALS”), nucleating agents, clarifying agent, and fillers.

[0044] An antiblocking agent is a compound that prevents adhesion between film layers by creating a rough surface, reducing contact area. Polyolefin films tend to stick to themselves under slight compression, which can cause deformation and tearing during manufacture. Adding inorganic fillers like talc can reduce blocking, but too much filler can harm the film's optical properties. Exemplary inorganic antiblocking agents include talc, silica, and zeolite.

[0045] Talc has been used in polymer processing as an anti-blocking agent. It can improve the stiffness of polymers, especially when used in polypropylene, polyethylene, and polyamide. Additionally, talc's fine particle size and lamellar structure can give plastic surfaces a smooth, matte appearance, which is useful in applications like automotive parts, consumer goods, and household appliances. Talc can also reduce the visibility of imperfections and improve the overall surface quality of plastic products. However, talc mined for commercial use can be contaminated with asbestos.

[0046] In the manufacture of polyolefin and related copolymer films, it is common practice to include slip agents in the polymer formulation. The slip characteristic of a polyolefin film or layer is a measure of its ability to slide one layer over another and is commonly expressed in terms of the film’s coefficient of friction. The slip agents migrate to the surface of the polymer film and decrease the coefficient of friction between the film and the rollers over which it passes, thus facilitating the processing of the film. Furthermore, the slip agents decrease the coefficient of friction between layers of the film when it is wound into rolls, thereby facilitating the unwinding of the rolls for further processing. In the manufactured polyolefin film, the presence of slip agents facilitates handling in, for example, automatic packaging machinery.

[0047] Fatty acid amides are well recognized in the plastics industry as conventional slip and / or antiblocking agents for use in polyolefin and related copolymer formulations. They are generally derived from aliphatic saturated and / or unsaturated fatty acids containing between 16 and 22 carbon atoms. Examples of such fatty acid amides include erucamide, behenamide, oleamide, stearamide, and isostearamide.

[0048] In some cases, each component of the polymer processing additive formulation may be added separately to the thermoplastic polymer. In some cases, the polyhydroxy compound and the synergist may be blended, e.g., in the desired ratio, and then added together to the thermoplastic polymer. For example, the components of the polymer processing additive composition may be blended by physical mixing or melt-blending. In such cases, additional amounts of the polyhydroxy compound or the synergist may be added to the thermoplastic polymer to adjust their amounts.

[0049] As it may be difficult to control the amount of the polymer processing additive composition at such low levels, in some cases, master batches may be used. Such a master batch contains a higherproportion of one or more of the components of the polymer processing additive composition in a host resin. The host resin is elected to be compatible with the thermoplastic polymer and may be the same or different than the thermoplastic polymer.

[0050] In some cases, separate master batches may be used with one containing the polyhydroxy compound and one containing the synergist. This may be useful when, e.g., it may be desirable to adjust the ratio of the polyhydroxy compound and the synergist. Again, the amount of the specific component in the master batch is not critical. In some cases, the master batches contain 0.2 to 10 wt.%, e.g., 0.5 to 5 wt.% of those components of the polymer processing additive composition present in the master batch.

[0051] Known equipment and methods may be used both to compound the polymer processing additive composition into the thermoplastic polymer and to process the compounded composition. For example, the polymer processing additive compositions of the present disclosure are useful in the processing of thermoplastic polymers, which includes for example, extrusion of films, blown film extrusion, extrusion blow molding, injection molding, and extrusion of pipe, fibers, and sheaths for cable and wire.

[0052] Examples. The materials used to prepare the polymer processing additive compositions used in the following samples are summarized in Tables 2 and 3. The polyhydroxy and carboxylic acid compounds listed in Table 3 are available from commercial sources such as from Sigma-Aldrich Chemical Company; Milwaukee, Wisconsin U.S.A.Table 2: Summary of materials used in the preparation of the examples.Table 3: Summary of polyhydroxy and carboxylic acid compounds.

[0053] TGA Procedure (Thermogravimetry Analysis). Onset temperature was determined using aTGA (Thermogravimetry Analysis TGA 5500 by TA Instrument) from the thermogravimetric curve as the intersection of the inflectional tangent with the tangent extrapolated from temperatures in accordance with ASTM E 2550-21. The sample size for the test was 10.0 ± 1 mg. The sample was heated to 600° C at a 20° C / minute under a nitrogen flow and then held at 600 °C for 10 minutes under air flow. The char yield has been defined as the amount of solid residue after completion of the TGA Procedure. Onset temperatures and char yields of the polyhydroxy and carboxylic acid materials are shown in Table 4.

[0054] Moisture Test Procedure. Moisture content was determined using a Sartorius moisture analyzer, LMA100P Model Mark 3, at 120°C in automatic endpoint mode to reach a slope of 0.005% of initial weight change in a 1-minute window. The sample size for the moisture test was 1.0 ± 0.1 g. Samples were aged in a Memmert HCP108 humidity oven at 40°C and 85% relative humidity (RH) for 24 hours. Moisture contents before and after aging in the humidity oven were summarized in Table 4.Table 4: Summary of TGA and moisture content analysis of various compounds.

[0055] Powder Blend Master batch preparation. Each polymer processing additive composition used in the following samples was prepared as a separate master batch. The master batch contained the desired level of polymer processing additive and synergist, if any, in the desired weight ratio (e.g., 500 ppm of the polymer processing additive and 500 ppm of the synergist) in a host resin. Each 1000 g master batch was prepared by shaking vigorously in a bag: the desired amounts of polymer processing additive and optional synergist, along with 1.0 g of IRGANOX B900 antioxidant, and 0.7 g of zinc stearate (a slip and antiblocking agent), and the host resin, granular resin (2MI LLDPE, EM 1002.09 available from Exxon Mobil), as the balance. The shaken powder blend was fed to a laboratory scale, intermeshing, co-rotating, unvented, air cooled, conical twin screw extruder (Brabender Plasti -corder) with a front inside diameter of 33 mm. The powder blend was gravity fed to the throat of the extruder, exposed to air, at a rate of 55 g / minute. The extruder specific temperature profile of the 3-barrel zones (feed, metering, mixing), and die zone was 170°C / 190°C / 200°C / 200°C respectively. The extruder was run at 150 RPM for the first "compounding" pass. The second pass was run with the same temperature profile but at 100 RPM while flood feeding the material produced in the first compounding pass and formed into pellets. A four-minute "purge" of material was discarded at the beginning of each pass. All polymer processing additive amounts of the formulation used in the Samples are ppm by weight in the primary resin.

[0056] Blown Film Extrusion Test Procedure. The blown film extrusion tests were conducted using an extruder with film die from Optical Control Systems GmbH. The melt fracture performance was assessed using a 0.9 MI ZN LLDPE as the primary resin (MARFLEX 7109 available from Chevron Philips Chemicals). Trials were conducted using a LabTech blown film line with a 40 mm, 24 / 1, grooved feed extruder. The die was of spiral design with a 40-mm diameter and 0.9-mm die gap (36 mil). Testing was done by diluting the separate master batches of the PPA components to the total target levels in the host resin at 210 °C (410 °F), 0.9 mm (36 mil) gap, 14 L / D, 10.5 kg / h (23 Ib / h), and 220 / s, in combination with an antiblock additive (6000 ppm of ABT 2500) and a slip agent (1000 ppm of erucamide) based on the weight of the primary resin.

[0057] The primary resin without any polymer processing additive formulation was charged for thirty minutes. The feed was then switched to the primary resin containing a PPA masterbatch for investigating the melt fracture performance. At 10 minute intervals, a film sample was taken and inspected visually for the presence of melt fracture (MF) and expressed as a percentage of the film area covered with melt fracture (% MF) until the film was free of MF or until the 120 min mark.

[0058] Prior to each evaluation it was necessary to ensure that the blown film line was free of residual additives from the previous trial. This was accomplished by extruding abrasive silica-containing purging compound, followed by an equal amount of the LLDPE resin with additives, but without any polymer processing additive formulation. This procedure was performed before each blown film line evaluation. Prior to beginning each trial, 100% Melt Fracture was verified.

[0059] Melt fracture procedure. The percent melt fracture was determined by taking a collected section of the film, laying it flat, opening it along the edge, measuring the width of individual bands (regions) of melt fracture in the transverse direction of the film, summing their total, and then dividing by the total width of the opened lay flat film.

[0060] Polymer processing additives are also used to reduce the melt pressure during extrusion. The initial pressure was calculated of average pressure of baseline run at -30, -20 and -10 minutes before introducing polymer processing additive and the final pressure was taken at the point of clearing melt fracture (0% of melt fracture) or the pressure at 120 minutes. The pressure reduction is the difference between the initial pressure and the final pressure expressed as a percentage of the initial pressure, and was calculated using the equation below: initial pressure — final pressure Pressure reduction (%) = - - - x 100 initial pressure

[0061] Samples Al to A6 were prepared using a processing additive formulation comprising sorbitol as the polyhydroxy compound. As shown in Table 5, this linear polyhydroxy compound was effective at eliminating melt fracture and providing pressure reduction alone (Al); and was even more effective in combination with various synergists (A2 to A5). For this particular polyhydroxy compound, poorerperformance was observed when using a 200 MW polyethylene glycol synergist (A6) even though excellent performance was obtained using a higher MW polyethylene glycol synergist (A2 to A4).Table 5: Summary of extrusion results for Samples Al to A6.

[0062] Samples B 1 to B5 were prepared using other polyhydroxy compounds in combination with a synergist. The polyhydroxy compounds were xylitol (Bl), erythritol (B2), maltitol (B3), isomalt (B4), and inositol (B5). As shown in Table 6, excellent melt fracture elimination and pressure reduction were observed in all cases.Table 6: Summary of extrusion results for Samples Bl to B5.

[0063] Samples Cl to Cl were prepared using a polymer processing additive formulation comprising mannitol as the polyhydroxy compounds with varying amounts of a synergist. As shown in Table 7, large pressure reductions were obtained at all levels of mannitol, less than 20% MF was achieved at 100 minutes for mannitol contents of 200 and 1000 ppm, and excellent melt fracture elimination (0% MF) and pressure reduction could be achieved at certain ratios of mannitol to PEG 8000 synergist (C2 and C3).For this particular polyhydroxy compound and synergist, poor results were obtained if the total amount of polyhydroxy compound and synergist was too low (C6 and C7).Table 7: Summary of extrusion results for Samples Cl to C7.

[0064] Samples D 1 to D6 were also prepared using a polymer processing additive formulation comprising mannitol as the polyhydroxy compound. As shown in Table 8, at different ratios of mannitol to synergist, excellent melt fracture elimination and pressure reduction could be achieved even with very low amounts of mannitol (D3 and D4) even though neither mannitol alone at this low level (DI) nor the synergist alone (D6) reduced melt fracture.Table 8: Summary of extrusion results for Samples DI to D6.

[0065] Samples Fl to F7 were prepared and tested using other polyhydroxy compounds and polyethylene glycol polymer processing additive formulations, as summarized in Table 9. Polyhydroxy compounds with only hydroxy groups (Fl to F3); with hydroxy groups and ether oxygens (F4 to F6); and with hydroxy groups and one carboxylic acid group (F7 and F8) were tested. Sample F8 contained two polyhydroxy compounds as well as a synergist. The compositions, melt fracture reduction and pressure reduction are summarized in Table 9.Table 9: Summary of extrusion results for Samples Fl to F7.

[0066] Samples were prepared using polyethylene glycol in combination with a compound containing one carboxylic acid group and only one hydroxy group (Gl); a compound containing two carboxylic acid groups and two hydroxy groups (G2); a polyhydroxy compound containing one carboxylic acid group and no hydroxy groups (G3), and a polyhydroxy compound containing two carboxylic acid groups and no hydroxy groups (G4). None of these compositions provided melt fraction reduction, as 70 to 100% MF remained even after 120 minutes.Table 10: Summary of extrusion results for Samples Gl to G4.

[0067] Samples Hl to H3. Master batches (3 wt.%) were prepared from blends of dimethylol propionic acid powder and PEG 8000 powder for use as a polymer processing additive composition at the weight in ppm of the materials in the host resin as shown in Table 11. The color of the master batches was translucent or white. As shown, dimethylol propionic acid, with a TGA onset temperature of 207 °C, showed some signs of discoloration at higher loading levels. As a result, its desirability in some applications may be limited. Example H4 was prepared using only the polyhydroxy compound (dimethylol propionic acid). Example H5 was prepared and tested using polycaprolactone as the synergist. Example H6 was prepared using glucose as the polyhydroxy compound with PEG 8000 powder.

[0068] The resulting polymer processing additive formulation master batches were evaluated according to the blown film extrusion test procedure. At ten-minute intervals, a film sample was inspected visually for the presence of melt fracture following the melt fracture procedure. The compositions, melt fracture reduction and pressure reduction are summarized in Table 11.Table 11: Summary of extrusion results for Samples Hl to H6.

[0069] Sample JI was prepared using only polyethylene glycol. Sample J2 was prepared using only polycaprolactone. Following the blown film extrusion test, both samples were white but neither synergist alone reduced melt fracture (both showed 100% MF at 120 minutes) and both provided only a small pressure reduction (2.2% for JI and 3.2% for J2).

[0070] Melt Blend Master batch procedure. Samples KI to K3 were prepared using an alternate method to prepare the polymer processing additive compositions. In the prior examples, individual powders or granules of the polymer processing additive and synergist were blended with powders or granules of the IRGANOX B900 antioxidant, the zinc stearate (a slip and antiblocking agent) and host resin, then fed into an extruder to form pellets. In Samples KI to K3, the polymer processing additive and synergist were first melt blended and formed into flakes. These flakes were then powder mixed with host resin and other components (described below) and extruded into pellets for subsequent using the same procedures as described above.

[0071] The melt blend of mannitol and polyethylene glycol was prepared in 200 g batches by mixing the powder forms of mannitol and polyethylene glycol at the desired ratios, along with an antioxidant (IRGANOX B225). The powder mixture was placed on an aluminum pan in an oven for 20 minutes at 200 °C, a temperature higher than the melting point of both the mannitol and the polyethylene glycol. Then the melted mannitol and polyethylene glycol were stirred using a spatula to form the melt blend. The pan was then cooled to room temperature and the melt-blended composition was ground in a plastic bag using a hammer. The resulting flakes were used as a polymer processing additive composition for masterbatch compounding as follows.

[0072] The flakes were compounded into masterbatches at a level of 3 wt.%. The master batches were prepared in 2000 g batches by shaking vigorously in a bag: 60 g of the melt blended polymer processingadditive flakes, 1936.6 g of granular host resin (2MI LLDPE, EM 1002), 2.0 g of IRGANOX B900, and 1.4 g of zinc stearate. The resulting formulation was fed to a laboratory scale, intermeshing, counter rotating, unvented, air cooled, conical twin screw (Brabender Plasti-corder Single Screw extruder) with a front inside diameter of 33 mm. The mixture was gravity fed to the throat of the extruder, exposed to air at a rate of 55 g / min. The extruder specific temperature profile of the 3-barrel zones (feed, metering, mixing), and die zone was 170°C / 190°C / 200°C / 200°C respectively. The extruder was run at 150 RPM for the first "compounding" pass. The second pass was run with the same temperature profile but at 100 RPM while flood feeding the material to form pellets. A 4 minute "purge" of material was discarded at the beginning each pass.

[0073] Sample K4 was prepared as a powder blend using the Powder Blend Master batch procedure described above, as was used for Sample C2, to form pellets.Samples KI to K4 were then processed according to the Blown Film Extrusion Test Procedure except that for samples KI, K2 and K4, the blown film composition did not include the additional antiblock additive (ABT 2500 Talc) or the additional slip agent (erucamide), while both were used in Samples C2 and K3. The results are summarized in Table 12, along with results of Sample C2, for comparison.Table 12: Summary of extrusion results for Samples KI to K4 and C2.

[0074] Hybrid Powder / Melt Master batch procedure. Sample LI was prepared using a hybrid preparation procedure. Samples K1-K3 were prepared by melt blending the polymer processing additive and synergist at a temperature greater than the melting temperature of both components. In contrast, Sample LI was prepared by melting the synergist (PEG) at 100 °C then adding the powder form of the PPA (mannitol) and mixing below the melting temperature of the mannitol.

[0075] The hybrid blend of mannitol and polyethylene glycol of Sample LI was prepared in a 200 g batch. First, 100 g of polyethylene glycol along with an antioxidant (IRGANOX B225) were placed on an aluminum pan in an oven for 20 minutes at 100 °C. Then the powder form of mannitol was added to the melted polyethylene glycol and stirred using a spatula. The pan was then cooled to room temperature and the contents were ground using a hammer in a plastic bag. The resulting flakes were used as a polymer processing additive (PPA) for masterbatch compounding as follows.

[0076] The master batch was prepared in a 2000 g batch by shaking vigorously in a bag: 60g of the flakes (mannitol / PEG), 1936.6 g of granular resin (2MI LLDPE, EM 1002.09 available from Exxon Mobil), 2.0 g of Irganox B900 antioxidant, and 1.4 g of Zinc Stearate. The formulation was fed to a laboratory scale, intermeshing, counter rotating, unvented, air cooled, conical twin screw (Brabender Plasti-corder Single Screw extruder) with a front inside diameter of 33 mm. The mixture was gravity fed to the throat of the extruder, exposed to air at a rate of 55 g / min. The extruder specific temperature profile of the 3-barrel zones (feed, metering, mixing), and die zone was 170°C / 190°C / 200°C / 200°C respectively. The extruder was run at 150 RPM for the first "compounding" pass. The second pass was run with the same temperature profile but at 100 RPM while flood feeding the material. A 4 minute "purge" of material was discarded at the beginning each pass.

[0077] The resulting pellets then processed according to the Blown Film Extrusion Test Procedure except that the blown film composition did not include the additional antiblock additive (ABT 2500 Talc) or the additional slip agent (erucamide). Melt fracture was eliminated in only 50 minutes with a pressure reduction of 17.9% with the hybrid approach, as reported in Table 12.

[0078] Surprisingly, when the additional antiblocking agent (Talc as ABT 2500) was present, the powder blending (Sample C2) and melt blending (Sample K3) results were similar. However, when those ingredients were not present, the melt blend samples (KI and K2) and the hybrid blend sample (LI) performed better than the powder blended sample (K4). While not wishing to be bound by theory, it is possible a more uniform distribution of the PPA (mannitol) and synergist (PEG) was obtained with melt blending then with powder blending. It is also possible the presence of the talc in sample C2 helped ensure a more uniform distribution of the mannitol in the primary resin, leading to better results.

[0079] Optical scanning microscopy (BX51 microscope by Olympus) in transmission mode at 12.6x magnification was used to examine LLDPE master batch samples prepared using various synergist (PEG) and polyhydroxy compound (mannitol) blending approaches. The samples were prepared as about 0.5 mm thick sections sliced from pellets of the target masterbatch composition.

[0080] First, reference samples of masterbatches containing either only PEG (Sample D6, Table 8) or only mannitol (Sample Cl, Table 7) were examined. The PEG reference sample from showed well dispersed, circular to oval PEG domains with a low aspect ratio of major axis to minor axis as shown in the cross-sectional images. The mannitol reference samples showed much larger domains of mannitol. The domains ranged from circular to elongated ovals with larger aspect ratios.

[0081] Sample K4, which was prepared from a powder blend of PEG and mannitol, also showed large, elongated oval (higher aspect ratio) mannitol domains and small circular PEG domains. In addition, while the PEG domains appeared evenly distributed throughout the sample, the mannitol domains were less uniformly dispersed.

[0082] Improved dispersion was shown in Sample KI, which was prepared from a melt blend of PEG and mannitol at a temperature greater the melting point of both components. Although elongated domains of mannitol were still present, their aspect ratio was reduced compared to Sample K4. Slightly larger, but still circular, domains of PEG were also observed. It appeared that the PEG domains were more evenly distributed throughout the sample compared to the mannitol, but the mannitol domain distribution was significantly better than from Sample K4.

[0083] The best dispersion was obtained with Sample LI, which was prepared from a hybrid approach in which the PEG and mannitol were melt blended at a temperature greater than the melting point of the PEG, but below the melting point of the mannitol. In this sample, the mannitol domains were circular to oval with the smallest aspect ratio of all samples. The shapes of the PEG domains remained similar to those observed for sample K4. However, both the mannitol and PEG domains appeared evenly distributed throughout the sample, indicating the best dispersion.

[0084] Bimodal Synergists. Samples Ml to M4 were prepared using two different PEG synergists. The PEG materials had different number average molecular weights, resulting in a bimodal distribution. These samples were prepared without talc, as this component may be undesirable in some applications.

[0085] The master batch was prepared in a 1000 g batches by shaking vigorously in a bag: 60 g of the blend of mannitol and PEG including Irganox B225 (2.5% to PEG), 1936.6 g of granular resin (2MI LLDPE, EM 1002.09 available from Exxon Mobil), 2.0 g of Irganox B900, and 1.4 g of Zinc Stearate. The formulation was fed to a laboratory scale, intermeshing, counter rotating, unvented, air cooled, conical twin screw (Brabender Plasti -corder Single Screw extruder) with a front inside diameter of 33 mm. The mixture was gravity fed to the throat of the extruder, exposed to air at a rate of 55 g / min. The extruder specific temperature profile of the 3-barrel zones (feed, metering, mixing), and die zone was 170°C / 190°C / 200°C / 200°C respectively. The extruder was run at 150 RPM for the first "compounding" pass. The second pass was run with the same temperature profile but at 100 RPM while flood feeding the material. A four minute "purge" of material was discarded at the beginning each pass.

[0086] The melt fracture performance was assessed using a 0.9 MI ZN LLDPE as a host resin (Marflex 7109 available from Chevron Philips Chemicals). Trials were conducted using a LabTech blown film line with a 40 mm, 24 / 1, grooved feed extruder. The die was of spiral design with a 40-mm diameter and 0.9-mm die gap (36 mil). Testing was done by diluting the separate MBs of the PPA components to a total target level of 1,000 ppm of the materials in the host resin at 210°C (410°F), 0.9 mm (36 mil) gap, 14 L / D, 10.5 kg / h (23 Ib. / h), and 220 / s.

[0087] The host resin in combination with 6000 ppm of ABT 2500 (Ampacet MB #101558) and 1000 ppm of Erucamide (Ampacet MB #10090), but without the polymer processing additive masterbatch, was charged for 30 minutes as the baseline. Then, the feed was switched to the host resin containing the PPAmasterbatch, but without ABT 2500 and Erucamide, for investigating the melt fracture performance. At 10 minute intervals a fdm sample was taken and inspected visually for the presence of melt fracture (MF) and expressed as a percentage of the fdm area covered with melt fracture (% MF) until the fdm was free of MF or until the 120 minute mark.

[0088] Prior to each evaluation it was necessary to ensure that the blown fdm line was free of residual additives from the previous trial. This was accomplished by extruding abrasive silica-containing purging compound, followed by an equal amount of the LLDPE resin with additives, but without PPA. This procedure was maintained before each blown fdm line evaluation. Prior to beginning each trial, 100% Melt Fracture was verified.

[0089] The percent melt fracture was determined by taking a section of the fdm lay flat, opening it along the edge, measuring the individual bands (regions) of melt fracture in the transverse direction of the fdm, summing their total, and then dividing by the total width of the opened lay flat fdm.

[0090] For Sample Ml, a blend was prepared by 30 grams of mannitol powder and 30 grams of PEG blend (5.85 grams of PEG 3350 powder (Polyethylene glycol, Mn=3350) and 23.4 grams of PEG 12000 powder (Polyethylene glycol, Mn=12000) with 0.75 grams of Irganox B225) as a polymer processing additive (PPA), 968.3 g of granular resin EM 1002.09 (2MI LLDPE, available from Exxon Mobil), 2.0 g of Irganox B900, and 1.4 g of Zinc Stearate. The blend was extruded to make a masterbatch according the masterbatch preparation method described above. The resin containing the PPA masterbatch (1,000 ppm) was charged to the blown fdm extruder for melt fracture. At 10-minute intervals a fdm sample was taken and inspected visually for the presence of melt fracture (MF) and expressed as a percentage of the fdm area covered with MF. The melt fracture of samples was cleared in 30 minutes.

[0091] Sample M2 was prepared and tested as Sample Ml except that 14.625 grams of PEG 3350 and 14.625 grams of PEG 12000 were combined and used as he synergist. The melt fracture of samples was cleared in 50 minutes

[0092] Sample M3 was prepared and tested as Sample Ml except that only PEG 3350 was used as the synergist. The melt fracture of samples was cleared in 90 minutes. Sample M4 was prepared as Sample Ml except that only PEG 12000 was used as the synergist. The melt fracture of samples was cleared in 50 minutes.Table 13: Summary of extrusion results for Samples Ml to M4.

[0093] As shown, the use of a bimodal distribution of synergist can lead to improved melt fracture elimination and pressure reduction.

[0094] Due in part to their high melt strength, polyethylenes are often used in blown film processes. While linear low density polyethylene (LLDPE) is the most common, low density (LDPE), medium density (MDPE) and high density (HDPE) polyethylenes are also used.

[0095] Polypropylene (PP) is one of the largest volume thermoplastics produced globally, offering advantageous physical properties, good processability, and low cost. Compared to polyethylene (PE), a repeat unit of polypropylene (PP) contains one methyl group in place of a hydrogen atom. Other than a potentially higher temperature profile (melt temperature = 330 °F, 165 °C), processing PP is similar in ease to processing PE. Both materials are thermally stable compared to other polymers, do not require drying, and exhibit a decrease in viscosity readily at higher screw speeds (shear thinning). One notable exception, however, is that PP generally has a lower melt strength than PE, particularly when compared with LDPE. In blown film processing, this can lead to difficulties with bubble stability. However, PP can be used in both monolayer specialty films and as part of a multilayer coextruded structure. In some PP applications, the use of a PPA to reduce the pressure can be more important.

[0096] Recently, many new polypropylene grades have been synthesized using metallocene technology, similar to that used for ethylene. This has widened the range of property offerings in areas such as stiffness, impact strength, melting point, and clarity. Additional property sets are available from PE / PP copolymers, materials synthesized using both ethylene and propylene monomers. These find many applications in food packaging because of their good clarity resulting from low crystallinity.

[0097] The attractive properties of polypropylene (PP) have established this polyolefin as one of the leading thermoplastic materials. The combination of low density, excellent chemical and thermal resistance, good mechanical and optical properties, low cost, and versatile processing conditions has enabled a vast range of applications. The material properties are contingent on the semi -crystalline arrangement of the polymer chains. During processing, the crystallization behavior of the polymer can be tuned by the addition of a nucleating agent. Such additives expose a heterogeneous surface that promotesnucleation and yields the formation of small crystalline domains with a narrow size distribution. In addition, an increase in the crystallization temperature enables shorter cycle times and energy efficiency.

[0098] Samples containing 1000 g of polypropylene were prepared with different concentrations of mannitol, using ProFax 6523 polypropylene homopolymer (available from LyondellBasell) as the base material. The polypropylene compositions were flood-fed into a single screw extruder (ME-20 2800 V4 Measuring Extruder from Optical Control Systems GmbH) equipped with a 15 -inch (38 cm) wide film die. The specific temperature profile for the three barrel zones (feed, metering, mixing) and the die zone was set at 190°C, 220°C, 230°C, and 245°C, respectively. The extruder was operated at 70 RPM. A baseline run was performed using only polypropylene for 30 minutes and the pressure reading was recorded as 6.8 MPa (986 psi). Then, 10 ppm of mannitol (El) was introduced, and the pressure reduction was measured based on the difference from the baseline pressure after 20 minutes. The polypropylene compound was drained from the hopper, and 100 ppm of mannitol (E2) was added; the pressure reduction was measured after a 20-minute run. The same procedure was repeated for 1000 ppm of mannitol (E3). As shown in Table 14, significant pressure reductions could be obtained.Table 14: Summary of extrusion results for Samples El to E3.

[0099] Generally, materials having a TGA onset of less than 200 °C or a char of greater than 5% are not suitable for use as a PPA in many applications. In addition, materials having a moisture content after 24 hours @ 40°C / 85RH (%) of greater than 10% may pose handling challenges, e.g., clumping and excess moisture in extrusion operations) making them more difficult to use; however, such materials can be suitable for some applications, and may be pre-processed (e.g., dried) such that they may be suitable for all applications. Generally, compounds have at least two, and preferably all three of the following properties would be most desirable for use as a PPA: (a) a TGA onset of at least 240 °C (preferably at least 300 °C), (ii) a char of no greater than 1% (preferably, 0%) and (c) a moisture content after 24 hours @ 40°C / 85RH (%) of no greater than 5% (preferably no greater than 1%).

[0100] Optimally, melt fracture should be eliminated completely (i.e., 0% MF). Ideally, the melt fracture should be reduced as quickly as possible, e.g., no greater than 120 minutes, preferably, no greater than 100 minutes, and most preferably, no greater than 60 minutes. As a result, MF% at 100 minutes should be no greater than 40%, preferably, no greater than 10%, and most preferably, 0%. In the present application, the tests were stopped at 120 minutes regardless of the progress, and MF was reported at the 100 minute mark. Therefore, a composition that results in a time to clear melt fracture of greater than 120 minutes may still be acceptable provided the precent melt fracture at 100 minutes is low, and providedthat melt fracture is ultimately reduced to an acceptable level for the product (e.g., less than 10%) in a commercially reasonable time (e.g., less than 180 minutes).

[0101] Table 15 summarizes various properties that are considered when selecting PPA compositions, and levels that may be desired for specific applications. Not all properties are required for every application. For example, in some applications food contact compliance is not required, while in others, drying the PPA composition to reduce moisture may be acceptable.Table 15: Relevant properties when selecting a polymer processing additive composition.* After 24 hours @ 40°C / 85 RH (%)

[0102] Table 16 summarizes the properties and performance of the polymer processing additives evaluated in the present application using the scale of Table 15. A property value of “A” indicates the PPA is more robust in that feature than a lower score, e.g., B, and so forth. Thus, for applications where that property is important, the PPA may be suitable for a broader range of requirements for that property. For example, a PPA with a score of “A” for TGA Onset temperature may be used in applications requiring a higher operating temperature than a PPA with a score of “B” for TGA onset temperature. The scores shown in Table 16 reflect optimum values obtained for the specified PPA when considering samples with and without the use of synergists.Table 16: Qualitative summary of performance and properties.

[0103] Considering these results as whole, certain compounds were found to be unsuitable as polymer processing additives. First, although glycerol eliminated melt fracture, the combination of low TGA onset temperature and high moisture content would impose significant limitations for its use in many important applications. Glucose did not function as a PPA with little melt fracture reduction even after 120 minutes. Although fructose, sucralose, and sucrose were not tested as PPAs, these sugars, like glucose, had excessively high char values.

[0104] In contrast, mannitol and inositol showed excellent results for all parameters. Both are sugar alcohols containing six hydroxy groups. Sorbitol is also a sugar alcohol comprising six hydroxy groups. Again, excellent performance as a PPA was observed; however, the high moisture content may require special handling and could make sorbitol a less attractive choice in some applications.

[0105] Erythritol (four hydroxy groups), pentaerythritol (four hydroxy groups), xylitol (five hydroxy groups), and maltitol (nine hydroxy groups) also showed excellent melt fracture elimination, but they had a lower TGA onset temperature or higher charring than mannitol and inositol. Such materials are still excellent PPAs for many applications, although higher processing temperatures, e.g., greater than 250 to 300 °C, may need to be avoided.

[0106] Dipentaerythritol (six hydroxy groups) and tripentaerythritol (eight hydroxy groups) also performed well as PPAs, but with slightly longer times expected for melt fracture elimination and less pressure reduction compared to other PPAs. Although they may be less preferred for these reasons, they are still suitable for many applications.

[0107] Isomalt (nine hydroxy groups) showed excellent melt fracture elimination and pressure reduction and had a high TGA onset temperature. However, the higher moisture content and char yield may limit its applications.

[0108] Considering compounds containing one carboxylic acid group, stearic acid (no hydroxy groups), glutaric acid (no hydroxy groups), glycolic acid (one hydroxy group) all failed to reduce melt fracture and did not function as PPAs. Similarly, tartaric acid, which contained two hydroxy groups and two carboxylic acid groups also failed to reduce melt fracture.

[0109] In contrast, both dimethylol propionic acid and dimethylol butanoic acid, which contained two hydroxy groups and only one carboxylic acid group, showed good melt fracture elimination, although longer times may be required. These materials also showed lower pressure reductions and lower TGA onset temperature, so they may be less desirable in some applications.

Claims

What is Claimed is:

1. A composition comprising greater than 50% by weight of a thermoplastic polymer and a polymer processing additive formulation comprising a polyhydroxy compound consisting of carbon, hydrogen and oxygen, wherein the compound comprises either(i) from 4 to 10 hydroxy groups or(ii) two hydroxy groups and one carboxylic acid group.

2. The composition of claim 1, wherein the polyhydroxy compound comprises 4 to 10 hydroxy groups.

3. The composition of claim 2, wherein the polyhydroxy compound is a linear compound comprising from 4 to 6 hydroxy groups.

4. The composition of claim 3, wherein the polyhydroxy compound comprises mannitol.

5. The composition of claim 2, wherein the polyhydroxy compound comprises isomalt.

6. The composition of claim 2, wherein the polyhydroxy compound is selected from the group consisting of sorbitol, erythritol, pentaerythritol, xylitol, maltitol, and combination thereof.

7. The composition of claim 2, wherein the polyhydroxy compound further comprises at least one ether oxygen.

8. The composition of claim 7, wherein the polyhydroxy compound is selected from the group consisting of dipentaerythritol, tripentaerythritol, and combinations thereof.

9. The composition of claim 1, wherein the polyhydroxy compound comprises two hydroxy groups and one carboxylic acid group.

10. The composition of claim 9, wherein the polyhydroxy compound is a dialkyol alkanoic acid.

11. The composition of claim 10, wherein the dimethylol alkanoic acid is selected from the group consisting of dimethylol propionic acid, dimethylol butanoic acid, and combinations thereof.

12. The composition according to any one of the preceding claims, wherein the polymer processing additive formulation further comprises a synergist.

13. The composition according to any one of the preceding claims, wherein the composition comprises 500 to 5000 ppm by weight of the polymer processing additive formulation.

14. The composition of claim 12 or 13, wherein the weight ratio of the polyhydroxy compound to the synergist is from 10:90 to 90: 10.

15. The composition according to any one of claims 12 to 14, wherein the composition comprises 3 to 100 ppm of the polyhydroxy compound, based on the total weight of the composition.

16. The composition of claim 15, wherein the polyhydroxy compound comprises mannitol and the composition comprises 3 to 25 ppm of the polyhydroxy compound, based on the total weight of the composition.

17. The composition according to any one of claims 12 to 16, wherein the synergist is a selected from the group consisting of polyethylene glycol, polyethylene glycol / polypropylene glycol block polymer, poly(ethylene oxide) and poly caprolactone.

18. The composition according to any one of claims 12 to 17, wherein the synergist comprises a first synergist and a second synergist, wherein a ratio of the number average molecular weights of the first and second synergist is from 2: 1 to 10: 1, inclusive.

19. The composition of claim 18, wherein the ratio of the number average molecular weights of the first and second synergist is from 2: 1 to 5 : 1.

20. The composition of claim 18 or 19, wherein the first synergist is a polyethylene glycol and the second synergist is a polyethylene glycol.

21. The composition according to any one of claims 12 to 20, wherein the polymer processing additive formulation comprises a melt blend of the polyhydroxy compound and the synergist.

22. The composition of claim 21, wherein the polyhydroxy compound and the synergist were melt- blended at a temperature greater than the melting temperature of both the polyhydroxy compound and the synergist.

23. The composition of claim 21, wherein the polyhydroxy compound and the synergist were melt- blended at a temperature greater than the melting temperature of the synergist and below the melting temperature of the polyhydroxy compound.

24. The composition according to any one of the preceding claims, wherein the thermoplastic polymer comprises a polyolefin.

25. The composition of claim 24, wherein the polyolefin comprises a polyethylene.

26. The composition of claim 25, wherein the polyethylene comprises at least one of a linear low- density polyethylene and a metallocene linear low-density polyethylene.

27. The composition of claim 24, wherein the polyolefin comprises a polypropylene.

28. The composition according to any one of the preceding claims, wherein the thermoplastic polymer has a Hildebrand solubility parameter of 15 to 17 MPa^ and the polyhydroxy compound has a Hildebrand solubility parameter of 22 to 30 MPa 1 / 229. The composition according to any one of the preceding claims, wherein the composition comprises no greater than 1 ppm by weight of fluorinated organic compounds based on the total weight of the composition.

30. The composition according to any one of the preceding claims, wherein the composition comprises no greater than 1 ppm by weight of a silicone based on the total weight of the composition.

31. A method for forming an article comprising: forming the composition according to any one of the preceding claims; and extruding the composition to form the article.

32. The method of claim 31, wherein the article comprises a film, and extruding comprises blown film extrusion.

33. A method of eliminating melt fracture in an extrusion process comprising:(i) preparing a composition according to any one of claims 1 to 30;(ii) extruding the composition at a shear rate above the critical shear rate of the thermoplastic polymer such that melt fracture occurs; and(iii) continuing to extrude the composition for time sufficient to reduce melt fracture to no greater than 10%, where in the time is no greater than 120 minutes.

34. The method of claim 33, where the melt fracture is reduced to 0%.

35. The method of claim 34, wherein the time is no greater than 100 minutes.

36. The method of claim 35, where in the time is no greater than 60 minutes.

37. The method of any one of claims 33 to 36, wherein extruding comprises blown film extrusion.

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