Masterbatch Composition

Abstract

Masterbatch compositions containing a polyolefin polymer and an additive can be made with high levels of additive and low dust formation when the additive comprises at least 2 weight percent of a fatty acid metal salt.

Description

[Technical field]

[0001] The present invention relates to masterbatch compositions for polyolefin polymers and processes for their use. [Background technology]

[0002] Polyolefin polymers are generally mixed with additives before being molded or extruded into their intended shape. Known examples of useful additives include antioxidants, light stabilizers, flame retardants, colorants, and processing agents such as lubricants, plasticizers, slip agents, and antiblocking agents. The final concentration of additives (other than fillers and colorants) is usually 100 ppmw to 5000 ppmw of the blend composition.

[0003] Additives are difficult to add precisely to polyolefin polymers at low concentrations and blend uniformly. To make the process easier, the additive package is first blended with a higher concentration of polymer to form a masterbatch. For example, the article "An Overview-Masterbatch" describes masterbatches that typically contain 40-65 percent additive, but at outer limits may contain 15-80 percent additive (https: / / www.plastics-technology.com / articles / an-overview-masterbatch-plastics-technology). Masterbatches are generally formed into pellets, as are the resins to which they are added. Masterbatch pellets are easy to meter into extrusion equipment in precise amounts and to disperse uniformly in the polymer melt within the equipment.

[0004] Masterbatch pellets are desirably tough (rather than brittle) so that they can be transported and used without forming excessive dust. Dust from additives used in masterbatches can pose a fire or explosion hazard or can cause breathing problems. Masterbatch compositions can be shipped in bags and transported on-site using pneumatic conveyors. Shipping and handling can subject the pellets to repeated physical impacts that can cause dust to form in brittle pellets.

[0005] It is also desirable that the masterbatch be inexpensive, as the formation of the masterbatch requires an extra processing step for the additives, thereby increasing the cost of the masterbatch. Summary of the Invention

[0006] The cost of the masterbatch composition can be reduced by increasing the concentration of additives and decreasing the concentration of polymer in the masterbatch. Increasing the concentration of additives in the masterbatch reduces the overall amount of masterbatch compounded and used, thereby reducing compounding costs. However, decreasing the concentration of polymer increases the brittleness of the masterbatch pellets and the risk of generating dust. The formation of dust can be minimized by including fatty acid metal salts, such as calcium stearate, among the additives in the masterbatch. Metal salts of fatty acids are generally added to polymers as lubricants, release agents and / or acid scavengers, and they can also improve the toughness of the masterbatch pellets.

[0007] One embodiment of the present invention is a masterbatch composition comprising: (i) from 2 weight percent to 30 weight percent of a polyolefin polymer; and (ii) from 98 weight percent to 70 weight percent of an additive for polyolefin polymer formulations; a. the additive comprises at least 2 weight percent of a fatty acid metal salt; b. the additive comprises less than 70 weight percent of a filler; c. All weight percentages are masterbatch composition based on the total weight of the masterbatch composition.

[0008] A second embodiment of the present invention is a process for making a polyolefin polymer formulation comprising co-extruding a polyolefin polymer with a masterbatch composition of the present invention under conditions to homogeneously blend the masterbatch composition into the polyolefin polymer.

[0009] A third embodiment of the present invention is a method of conveying the masterbatch composition of the present invention within a facility, wherein the masterbatch composition is conveyed in an air atmosphere using a pneumatic device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The masterbatch composition of the present invention contains a polyolefin polymer and an additive.

[0011] Polyolefin Polymer Polyolefin polymers and their methods of manufacture are well known. They are typically made by polymerizing ethylene and / or propylene monomers, optionally with small amounts of comonomers.

[0012] In some embodiments, the polyolefin polymer is a polyethylene homopolymer or copolymer and contains at least 50 mole percent repeat units derived from ethylene, or at least 80 mole percent or at least 85 mole percent ethylene, or at least 90 mole percent and up to 100 mole percent repeat units derived from ethylene. For polyethylene copolymers, typical examples of suitable comonomer units include repeat units derived from butylene, pentene, hexene, heptane, and / or octene, although other unsaturated olefin comonomers are also suitable.

[0013] In some embodiments, the polyolefin polymer is a polypropylene homopolymer or copolymer and contains at least 50 mole percent repeat units derived from propylene, or at least 80 mole percent or at least 85 mole percent ethylene, or at least 90 mole percent and up to 100 mole percent repeat units derived from propylene. In polypropylene copolymers, the comonomer units are generally derived from ethylene, although other unsaturated olefin comonomers are also suitable.

[0014] The masterbatch composition contains between 2 weight percent and 30 weight percent polyolefin polymer. In some embodiments, the masterbatch composition contains at least 3 or weight percent 4 or weight percent 5 or weight percent 6 or weight percent 7 or weight percent 8 or weight percent 9 or weight percent 10 weight percent polyolefin polymer. In some embodiments, the masterbatch composition contains up to 25 or weight percent 22 or weight percent 20 or weight percent 18 or weight percent 15 or weight percent 12 or weight percent 10 weight percent polyolefin polymer. In some embodiments, the masterbatch composition contains less than 20 weight percent polyolefin polymer. All weight percentages are based on the total weight of the masterbatch composition.

[0015] Additives Additives for polyolefin polymers are well known.Examples of common additives include antioxidants, light stabilizers, acid scavengers, processing aids (such as lubricants, rheology control agents, mold release agents, antiblocking agents and slip agents), antistatic agents, flame retardants, colorants and fillers.The preferred choice of additives varies depending on the polyolefin polymer that the masterbatch composition is blended with, as well as the intended use of the final product.

[0016] Many potential additives can serve more than one purpose. For example, calcium stearate can act as both a lubricant and an acid scavenger in polyolefins, and hindered amine antioxidants are also often used in light stabilizer packages. Fatty acid amides can be useful as lubricants, slip agents, and antiblocking agents.

[0017] Additives for polyolefin polymers are described in numerous publications, such as the pamphlet: Tolinski, "Additives for Polyolefins. Getting the Most out of Polypropylene, Polyethylene and TPO (Second Edition)" published by Plastics Design Library in 2015. Those working with other polyolefin polymers can easily find references listing the appropriate additives and proportions for those polymers and their intended uses.

[0018] The following examples of additives are non-limiting. They do not exclude the presence of other additives in the masterbatch composition. Furthermore, except for the fatty acid metal salt, the masterbatch composition of the present invention is not required to contain any of the examples listed below. The masterbatch composition may contain all of the examples listed below, some of the examples listed below, or none of the examples listed below, except for the fatty acid metal salt.

[0019] Antioxidants are generally classified as primary antioxidants (radical scavengers) and secondary antioxidants (hydroperoxide scavengers).

[0020] Examples of common primary antioxidants include: hindered phenols, such as pentaerythrityl tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenol)propionate), available under the name Irganox 1010, or octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, available under the name Irganox 1076. Hindered amines, for example the polyamines sold under the names Chimassorb 944 or Chimassorb 2020. · Vitamin E, either natural or synthetic. Lactones.

[0021] Examples of common secondary antioxidants include: Phosphites, for example tris(2,4-di-tert-butylphenyl)phosphite, sold under the name IRGAFOS® 168, or tris(nonylphenyl)phosphite. Thioesters, for example, distearyl thiodipropionate.

[0022] Light stabilizers generally work by blocking light (especially ultraviolet light) or absorbing damaging light and releasing the energy in a less damaging form. Examples of common light stabilizers include: Carbon black. Pigments, for example titanium dioxide. Benzophenones, for example 2-hydroxy-4-n-octoxybenzophenone, available commercially as Chimassorb 81 and Cyasorb UV-531. Benzotriazoles, for example 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol, commercially available as Tinuvin 326. cyanoacrylates, for example 1,3-bis-((2'-cyano-3',3'-diphenylacryloyl)oxy)-2,2-bis-(((2'-cyano-3',3'-diphenylacryloyl)oxy)methyl)-propane, commercially available as Uvinul 3030; and Phenyl- or aryl esters, for example benzoic acid, 3,5-(1,1-dimethylethyl)-, 2,4-bis(1,1-dimethylethyl)phenyl ester, commercially available as Tinuvin 120.

[0023] Some of the primary antioxidants mentioned above can be used in conjunction with light stabilizers to scavenge free radicals that may be generated by the light stabilizer absorbing light. Hindered amine stabilizers are sometimes used for this purpose.

[0024] Examples of acid scavengers include hydrotalcites (such as those commercially available under the name DHT-4A), metal stearates (such as calcium stearate and zinc stearate), and zinc oxide.

[0025] Examples of processing aids include: Lubricants. Some lubricants are metal salts of fatty acids, e.g., metal stearates such as calcium stearate and zinc stearate. Some lubricants are fatty amides, esters, acids or alcohols, e.g., glycerol monostearate, erucamide, oleamide, and ethylene bis(stearamide). Some lubricants are polymers, e.g., silicones, fluoropolymers, and polyolefin plastomers or oligomers. Rheology control agents. For example, peroxides may be added to polypropylene to reduce the viscosity during molding. Other examples include polymer processing aids such as 3M Dynamar™ products. Mold release agents. Mold release agents reduce the adhesion of the polyolefin polymer to the mold. Examples of mold release agents include fatty acids or esters such as glycerol monostearate; amides such as erucamide and oleamide; hydrocarbon microcrystalline waxes; and partially oxidized polyethylene. Slip agents. Slip agents reduce friction between the polyolefin polymer and the processing equipment. Examples of slip agents include fatty acid amides such as erucamide, oleamide, stearamide, ethylene bisstearamide, and stearyl stearamide. Antiblocking agents. Antiblocking agents prevent layers of polyolefin polymer from sticking to each other. Examples of antiblocking agents include inorganic materials that roughen the surface of the film, such as diatomaceous earth, silica or talc, and fatty acid amides, such as behanamide, erucamide or stearamide.

[0026] Examples of antistatic agents include: Some non-ionic compounds, for example, glycerol esters such as glycerol monostearate, lauric acid diethanolamide (sold as Chemstat LD-100) and ethoxylated amines (sold as Chemstat 122). Dissipative polymers, such as polyester block amides and ethylene ionomers. Conductive fillers, such as carbon black, graphene, graphite, metal particles and coated inorganic particles. Conductive fibres, for example metal fibres or carbon fibres.

[0027] Examples of flame retardants include the following: Brominated or chlorinated compounds, such as decabromodiphenyl ether (sold commercially as FR-1210), tetrabromobisphenol A bis(2,3-dibromopropyl) ether (sold commercially as FR-720) and chlorinated paraffins (sold commercially as Chlororez 700). · Phosphate flame retardants, typically containing an acid source such as ammonium polyphosphate (commercially available as Exolit AP-570), a crosslinking agent such as pentaerythritol, and a blowing agent such as melamine.

[0028] Examples of colorants include: White colouring agents, such as titanium dioxide, zinc sulphide and barium sulphide. Black colorants, such as carbon black, copper chromate and brown hematite. Colour pigments, e.g. azo dyes for a wide range of colours, iron oxides or quinacridones for red, cadmium sulphide for yellow, chromium(III) oxide for green or cobalt aluminate for blue. Metal flakes for a metallic look. Mica flakes to add a pearlescent or speckled look.

[0029] Examples of common fillers include calcium carbonate, talc, mica, wollastonite, silica and glass spheres. Many common fillers have an average particle size of 1 to 100 microns or 2 to 50 microns.

[0030] The masterbatch composition of the present invention contains from 70 weight percent to 98 weight percent of additive. In some embodiments, the concentration of additive can be at least 75 weight percent, or at least 78 weight percent, or at least 80 weight percent, or at least 82 weight percent, or at least 85 weight percent, or at least 88 weight percent, or at least 90 weight percent. Desirably, the concentration of additive can be up to 97 weight percent, or 96 weight percent, or 95 weight percent, or 94 weight percent, or 93 weight percent, or 92 weight percent, or 91 weight percent, or 90 weight percent. In some embodiments, the concentration of additive is greater than 80 weight percent. All weight percentages are based on the weight of the masterbatch composition.

[0031] In the masterbatch composition of the present invention, the additive comprises at least 2 weight percent of a fatty acid metal salt. In some embodiments, the concentration of the metal fatty acid salt is at least 5 weight percent, or at least 8 weight percent, or at least 10 weight percent, or at least 15 weight percent. In some embodiments, the concentration of the metal fatty acid salt is up to 30 weight percent, or up to 28 weight percent, or up to 26 weight percent. All weight percentages are based on the total weight of the masterbatch composition.

[0032] Examples of suitable metals for the fatty acid metal salts include calcium, zinc, sodium, potassium, magnesium, lithium, copper and silver, hi some embodiments the metal is calcium, and in some embodiments the metal is zinc.

[0033] Examples of fatty acids suitable for metal salts include acids containing at least 12 carbon atoms, or at least 14 carbon atoms, or at least 16 carbon atoms, or at least 18 carbon atoms. Examples of fatty acids suitable for metal salts include acids containing up to 30 carbon atoms, or up to 26 carbon atoms, or up to 22 carbon atoms, or up to 20 carbon atoms. Suitable fatty acids can be saturated, monounsaturated, or polyunsaturated. In some embodiments, the fatty acid can be myristic acid, palmitic acid, stearic acid, arachidic acid, or behenic acid. In some embodiments, the fatty acid is stearic acid.

[0034] In some embodiments, the fatty acid metal salt is calcium stearate or zinc stearate.

[0035] The masterbatch compositions of the present invention contain less than 70 weight percent filler. In some embodiments, the masterbatch compositions contain 50 weight percent or less filler, or 40 weight percent or less filler, or 30 weight percent or less filler, or 20 weight percent or less filler. Some embodiments contain essentially no filler (0 weight percent).

[0036] In some embodiments, the masterbatch composition contains 70 weight percent or less of colorant, or 50 weight percent or less of colorant, or 30 weight percent or less of colorant, or 20 weight percent or less of colorant. Some embodiments contain essentially no colorant (0 weight percent).

[0037] In some embodiments, the masterbatch composition contains 70 weight percent or less calcium carbonate, or 50 weight percent or less calcium carbonate, or 30 weight percent or less calcium carbonate, or 20 weight percent or less calcium carbonate. Some embodiments contain essentially no calcium carbonate (0 weight percent).

[0038] In some embodiments, the total concentration of filler (including calcium carbonate) and colorant in the masterbatch composition is 50 weight percent or less, or 30 weight percent or less, or even 20 weight percent or less. Some embodiments contain essentially no fillers or colorants.

[0039] The masterbatch composition of the present invention can be prepared by co-extruding the ingredients under conditions suitable for melting the polyolefin polymers and for homogeneously blending the ingredients. Suitable extruders and their uses are known. In some embodiments, the cylinder temperature for extruding the masterbatch containing polyethylene is 175°C to 270°C or 180°C to 210°C. In some embodiments, the cylinder temperature for extruding the masterbatch containing polypropylene is 180°C to 250°C or 200°C to 230°C.

[0040] After the ingredients are homogeneously blended, the molten masterbatch may be extruded and formed into a useful shape for the masterbatch. For example, the masterbatch may be formed into pellets by extruding as strands, cooling the strands, and then chopping the strands into pellets. Some masterbatch pellets may have a diameter of 1 mm to 5 mm and a length of 1 mm to 10 mm.

[0041] In many embodiments, the masterbatch pellets of the present invention after handling contain 500 ppm or less of dust by weight, or 400 ppm or less of dust by weight, or 300 ppm or less of dust by weight, or 200 ppm or less of dust by weight, or 150 ppm or less of dust by weight. By "dust" is meant particles in the masterbatch that can pass through a 500 μm sieve. The low dust content in the masterbatch pellets of the present invention allows the pellets to be transported and handled with pneumatic equipment that uses air as a medium rather than nitrogen as a medium. Pneumatic equipment is cheaper to install and operate than nitrogen gas pressure equipment, but may pose a higher risk of fire if the material being transported contains high levels of dust.

[0042] The masterbatch compositions of the present invention can be blended with a molten polyolefin polymer ("base polymer") by known methods to disperse the additives of the masterbatch composition throughout the base polymer. In some embodiments, the masterbatch composition is homogeneously blended with the base polymer in an extruder, and the resulting blend is extruded to form a useful shaped article, such as a film or molded article.

[0043] The description of the potential base polymer is similar to that of the polyolefin polymer used in the masterbatch composition. The polyolefin polymer in the masterbatch composition should be compatible with the base polymer so that the two polymers can be homogeneously combined together. In some embodiments, the polyolefin polymer in the masterbatch composition is different from the base polymer but is compatible with the base polymer. In some embodiments, the polyolefin polymer in the masterbatch composition and the base polymer are of similar classes of polymers, for example, both are polyethylene homopolymers or copolymers, or both are polypropylene homopolymers or copolymers. In some embodiments, the weight average molecular weight of the polyolefin polymer in the masterbatch composition is 25 percent to 400 percent, or 35 percent to 300 percent, or 50 percent to 200 percent of the weight average molecular weight of the base polymer.

[0044] The ratio of masterbatch to base resin varies depending on the additive content of the masterbatch and the desired additive content of the base resin. Those familiar with compounding polyolefin polymers can easily calculate the desired amount. In some embodiments, the masterbatch may be blended with the base resin at a ratio of 0.01 to 5 parts by weight of masterbatch per 100 parts by weight of base resin, although higher levels may be used if the masterbatch contains fillers or colorants.

[0045] Some embodiments of the present invention are illustrated by the following non-limiting examples. EXAMPLES

[0046] Sample masterbatches are made by melt co-extruding polyethylene resin (DOWLEX™ 2035G), calcium stearate, Irgafos 168 additive, and Irganox 1076 at extrusion zone temperatures of 210° C. to 260° C. in the proportions shown in Table 1. Some samples are for comparison and omit the polyethylene resin or calcium stearate.

[0047] Each sample is passed through a KICE Multi-Aspirator 6DT4-1 three times to simulate handling. The recovered material is sieved using a 500 μm sieve and a 63 μm sieve using a vibrating sieve for 10 minutes at 20° C. under laboratory controlled conditions. The amount of dust recovered from the sieving is listed in Table 1 as parts per million (ppm) based on the weight of each sample. The results show that the inventive examples have less dust than the comparative examples.

[0048] [Table 1]

Claims

1. 1. A masterbatch composition comprising: (i) 2 to 30 weight percent of a polyolefin polymer; and (ii) 98 to 70 weight percent of an additive for polyolefin polymer formulations; a) the additive comprises at least 2 weight percent of a fatty acid metal salt; b) the additive comprises less than 70 weight percent of a filler; c) A masterbatch composition, wherein all weight percentages are based on the total weight of said masterbatch composition.

2. 10. The masterbatch composition of claim 1, wherein the composition contains up to 25 weight percent of the polyolefin polymer and at least 75 weight percent of the additive.

3. 10. The masterbatch composition of claim 1, wherein the composition contains less than 20 weight percent polyolefin polymer and more than 80 weight percent additive.

4. 10. The masterbatch composition of claim 1, wherein the composition contains 15 weight percent or less of a polyolefin polymer.

5. 10. The masterbatch composition of claim 1, wherein the composition contains at least 8 weight percent polyolefin polymer.

6. 10. The masterbatch composition of claim 1, wherein the polyolefin polymer comprises a polyethylene homopolymer or copolymer.

7. 10. The masterbatch composition of claim 1, wherein the polyolefin polymer comprises a polypropylene homopolymer or copolymer.

8. 10. The masterbatch composition of claim 1, wherein the composition comprises at least 8 weight percent fatty acid metal salt and up to 30 weight percent fatty acid metal salt.

9. 10. The masterbatch composition of claim 1, wherein the fatty acid metal salt comprises a metal stearate.

10. 10. The masterbatch composition of claim 1, wherein the fatty acid metal salt comprises calcium stearate or zinc stearate.

11. 10. The masterbatch composition of claim 1, wherein the composition comprises a total of 50 weight percent or less of filler and colorant.

12. 10. The masterbatch composition of claim 1, wherein the composition is essentially free of fillers and colorants.

13. 10. The masterbatch composition of claim 1, wherein the composition is in the form of pellets.

14. A method for conveying the masterbatch composition according to any one of claims 1 to 13 within a facility, wherein the masterbatch composition is conveyed in an air atmosphere using a pneumatic device.

15. 14. A process for making a polyolefin polymer formulation, comprising co-extruding said polyolefin polymer with the masterbatch composition of any one of claims 1 to 13 under conditions to homogeneously blend said masterbatch composition into the polyolefin polymer.