Method for changing the optical appearance of a polymer

Abstract

The present disclosure relates to a method for altering the optical appearance of a polymer, the method comprising extruding a molten polymer comprising polypropylene and a composition comprising an acid scavenger comprised of zinc oxide and zinc carbonate.

Description

Technical Field

[0001] The present disclosure relates to a method for changing the optical appearance of a polymer containing polypropylene, and the use of a composition for changing the optical appearance of a polymer containing polypropylene and / or stabilizing the color of such a polymer over time.

Background Art

[0002] Polymers such as polypropylene produced using Ziegler-Natta catalysts may not have a satisfactory initial color at the time of production and / or may discolor over time. Also, for example, polypropylene produced using a Ziegler-Natta catalyst may have insufficient transparency and / or gloss. If the optical appearance is inferior due to one or more of these properties during processing and / or aging, it is undesirable for some applications such as extrusion, such as stretch tapes (e.g., raffia tapes or slit tapes), biaxially oriented polypropylene (BOPP) films, and thermoformed products. These applications are generally required for food packaging, but food packaging is not only easily affected by flavors and odors derived from the additive itself or the reaction product of the additive and catalyst residues, but also requires a stable optical appearance.

[0003] Discoloration is a complex phenomenon and is thought to be based on several factors such as the amount of catalyst residues in the polymer. In particular, discoloration is thought to worsen when the catalyst residues associate with other common additives, such as antioxidants used to prevent polymer degradation by reacting with radical species. Examples of antioxidants include organic phosphites and phosphonites, sterically hindered phenolic antioxidants, and amines.

[0004] Other common additives include acid scavengers. This is a chemical substance that neutralizes acidic residues formed when, for example, a Ziegler-Natta catalyst is inactivated during the production of polypropylene, contributing to the overall performance of the polymer. Acid scavengers for polypropylene include metal stearates such as sodium stearate, calcium stearate, and zinc stearate, zeolite structures, hydrotalcite, hydrocalumite, metal oxides such as calcium oxide and zinc oxide, and other salts obtained from lactic acid and benzoic acid, etc.

[0005] Zweifel, Hans, "Plastics Additives Handbook", 5 th As described in Edition, Carl Hanser Verlag, Munich 2001, pp. 492 - 493, conventional zinc oxide produced by the so-called French method based on the reaction of elemental zinc and elemental oxygen neutralizes acids in polyolefins and provides photo-stabilization. According to the description, zinc oxide neutralizes more acids compared to calcium stearate at the same mass concentration and has a better initial color than calcium stearate, but does not have the color retention ability like calcium stearate that dissolves in the polymer matrix. Therefore, it is described that conventional zinc oxide is rarely used as an acid scavenger because it is inferior in color retention ability when the extrusion process is carried out multiple times and the transparency of the material is greatly reduced. In particular, it is not acceptable in extrusion applications such as biaxially oriented polypropylene (BOPP) films or cast films, stretched tapes, or thermoformed products. However, zinc oxide is used as an acid scavenger in applications such as cast films that are treated at high temperatures where organometallic stearates are prone to discoloration in air.

[0006] On the one hand, the color retention ability of calcium stearate is not always satisfactory for at least all applications. Also, as described in WO 2019 / 057640 A1, although the transparency obtained with calcium stearate is desirable for film applications, metal stearates are migratory additives that tend to migrate to the film surface and are known to cause problems in polypropylene used in these applications. This can be a problem especially when the film is metallized and / or printed. According to WO 2019 / 057640 A1, it is considered that when zinc oxide is used in combination with an organic phosphite antioxidant, a synergistic effect of making the color of polypropylene more stable can be obtained. This is based on the fact that zinc oxide acts not only as an acid scavenger but also as a fluorescent dye, that is, by absorbing (near) ultraviolet light and emitting blue fluorescence, it can improve the initial color of polypropylene or reduce the color development during long-term or repeated heat exposure.

[0007] It is known to use hydrotalcite, which is non-migratory and does not affect the metallization or printability of the film, instead of metal stearates. However, when hydrotalcite is used in combination with a phenolic antioxidant, the color stability is poor in that the polymer to which these are added turns yellow. Furthermore, hydrotalcite is often used in BOPP and stretched tapes, but it tends to agglomerate and may result in an unacceptable optical appearance, for example, in BOPP films, after downstream processing. In addition, hydrotalcite releases crystal water at high temperatures.

[0008] Therefore, in known methods for preparing polymer resins such as polyolefin-based resins containing polypropylene, and attempts to improve their optical appearance, additives that are still unsatisfactory, especially in extrusion applications, are still being used. Thus, there is a need to identify additives that can achieve a desired balance among various properties such as initial color, color retention ability (i.e., color when the extrusion process is carried out multiple times), transparency, and gloss without degrading the performance of the polymer.

[0009] As described above, there is still a need to develop a method for changing the optical appearance of polymers containing polypropylene, which can obtain satisfactory initial color, color retention, transparency, and gloss while maintaining the performance of the polymers.

Summary of the Invention

Problems to be Solved by the Invention

[0010] Surprisingly, the applicant has found that by using a composition containing zinc oxide and zinc carbonate as the sole acid scavenger and contacting a polymer containing polypropylene with this composition under extrusion conditions, it is possible to achieve an unexpected balance of initial color, color retention, transparency, and gloss whether in the presence or absence of an antioxidant while neutralizing acidic residues and achieving the overall performance of the polymer. When one or more antioxidants are present, a synergistic effect is observed with zinc oxide and zinc carbonate on one hand and the antioxidant on the other hand.

[0011] Furthermore, the inventors have tested the compositions defined by the method according to one or more embodiments of the present disclosure, and found that the transparency and gloss exhibited by polymers containing polypropylene treated with such compositions are at least equivalent, if not better than, the transparency and gloss obtained with calcium stearate. On the other hand, regarding transparency, unlike metal stearates, there was no migration of additives to the film surface and related effects as commonly seen with metal stearates. Furthermore, color retention was also achieved with these compositions. In addition, surprisingly, polymers containing polypropylene treated with these compositions defined by the embodiments of the method according to the present disclosure have better initial color and color after multiple extrusion steps than each polymer treated with the individual components of the composition.

Means for Solving the Problems

[0012] According to a first aspect of the present disclosure, the present disclosure relates to a method of changing the optical appearance of a polymer, which includes a step of extruding a molten polymer containing polypropylene and a composition containing an acid scavenger composed of, for example, zinc oxide and zinc carbonate. The zinc oxide and the zinc carbonate are present in the same particles.

[0013] In this specification and the claims described hereinafter, the optical appearance of the polymer refers to the following properties: · The initial color of the polymer or the color development after compounding and extrusion, determined by the yellowness index (YI) of polymer pellets according to ASTM D6290; · The color retention ability or color development after compounding the polymer and after performing the extrusion process a predetermined number of times (for example, at least 3 times), determined by the yellowness index (YI) of polymer pellets according to ASTM D6290; · The glossiness determined for an injection-molded polymer product according to ISO2813; and / or · The haze value determined for an injection-molded polymer product according to ISO14782 One or more of which are indicated.

[0014] Therefore, if the optical appearance of the polymer changes, it indicates that one or more of the above-described properties have changed, and the fact that the color of the polymer remains stable even after the passage of time indicates the same as the color retention ability or color development after performing the extrusion process a predetermined number of times (for example, 3 times).

[0015] According to the present disclosure, the polymer contains polypropylene. According to one or more embodiments, the polypropylene may be selected, for example, from a homopolymer of propylene or a copolymer of propylene (for example, a copolymer of propylene and another olefin (such as an olefin having 2 to 8 carbon atoms)).

[0016] According to one or more embodiments, the polypropylene may be selected from the group consisting of a polypropylene homopolymer, a random copolymer containing propylene, a heterophasic copolymer containing propylene, and combinations thereof. For example, the polypropylene may be selected from the group consisting of a polypropylene homopolymer and a propylene copolymer of propylene and ethylene.

[0017] According to one or more embodiments, the polypropylene may include a homopolymer, a random copolymer, and a heterophasic copolymer of propylene. The copolymer of propylene may include a copolymer of propylene and other olefins (such as ethylene, 1-butene, 2-butene, and pentene isomers, and combinations thereof). A random copolymer, also known as a statistical copolymer, is a polymer in which propylene and comonomer are randomly distributed throughout the polymer chain in a ratio corresponding to the feed ratio of propylene and comonomer. A heterophasic copolymer is composed of a semi-crystalline matrix containing a homopolymer or random copolymer of propylene and rubber particles composed of a random copolymer of propylene and ethylene. The homopolymer, random copolymer, and heterophasic copolymer may be produced by known processes.

[0018] For example, the polymer may be a homopolymer or copolymer of propylene. According to one or more embodiments, the homopolymer or copolymer of propylene may have an initial MFR before extrusion of about 0.2 g / 10 min to about 200 g / 10 min, such as 1 g / 10 min to 100 g / 10 min, such as 1.5 g / 10 min to 50 g / 10 min, such as 2 g / 10 min to 20 g / 10 min, such as 2.5 g / 10 min to 10 g / 10 min, as measured at 230 °C with a load of 2.16 kg in accordance with ISO 1133.

[0019] Unless otherwise specified, the MFR in this specification and the claims is the MFR measured at a load of 2.16 kg and 230 °C in accordance with ISO 1133.

[0020] According to one or more embodiments, the homopolymer or copolymer of propylene may have a final MFR of 0.2 g / 10 min to 200 g / 10 min after extrusion in the presence of the above composition. According to one or more embodiments, the final MFR may be 1 g / 10 min to 100 g / 10 min, such as 1.5 g / 10 min to 50 g / 10 min, such as 2 g / 10 min to 20 g / 10 min, such as 2.5 g / 10 min to 10 g / 10 min.

[0021] According to one or more embodiments, the above composition is composed of, for example, zinc oxide and zinc carbonate and, optionally, one or more polymer additives, such as polymer additives other than additives that act as acid scavengers.

[0022] According to the present disclosure, the above zinc oxide and the above zinc carbonate are present within the same particles. That is, the above composition is not a mixture of zinc oxide particles and zinc carbonate particles, but a composition in which each particle contains both zinc oxide and zinc carbonate.

[0023] According to one or more embodiments, the above composition may contain basic zinc carbonate in addition to zinc oxide and zinc carbonate.

[0024] According to one or more embodiments, the zinc carbonate in the above composition containing zinc oxide and zinc carbonate may contain basic zinc carbonate.

[0025] According to one or more embodiments, the above composition may be prepared by a wet chemical precipitation method.

[0026] According to one or more embodiments, the BET surface area of the above composition is 10 m 2 / g to 100 m 2 / g, such as 20 m 2 / g to 90 m 2 / g, such as 30 m 2 / g to 60 m 2 / g, such as 40 m 2 / g to 50 m 2 / g.

[0027] According to one or more embodiments, the bulk density of the above composition ranges from 50 g / l to 400 g / l, for example from 100 g / l to 300 g / l, for example from 150 g / l to 250 g / l.

[0028] According to one or more embodiments, the above composition contains 90 to 99% by weight of zinc oxide, for example 93 to 98% by weight, for example 94 to 97.5% by weight, for example 95 to 97% by weight, and 1 to 10% by weight of zinc carbonate, for example 2 to 7% by weight, for example 2.5 to 6% by weight, for example 3 to 5% by weight.

[0029] According to one or more embodiments, the above composition contains 0.1 to 1.0% by weight of carbon, for example 0.2 to 0.6% by weight of carbon, for example 0.3 to 0.5% by weight of carbon, based on the total weight of the composition.

[0030] According to one or more embodiments, the above composition contains zinc oxide and zinc carbonate and is prepared by a wet chemical precipitation method.

[0031] According to one or more embodiments, when the above composition is prepared by a wet chemical precipitation method, the composition may be prepared, for example, in a spray dryer at a predetermined gas temperature as described in German Patent Application Publication No. 3900243. For example, the above process may have a step of mixing at least one aqueous solution of an alkali carbonate, an alkali metal hydroxide, or a mixture thereof with an aqueous solution of a zinc salt, zinc carbonate, or basic zinc carbonate to precipitate zinc carbonate or basic zinc carbonate. The resulting aqueous suspension may be dried in a high-temperature gas. The temperature of the high-temperature gas in the spray dryer may range from 450 °C to 900 °C.

[0032] According to one or more embodiments, the above composition may have a particle size distribution determined by at least one of the following average particle sizes.

[0033] According to one or more embodiments, the above composition has a D measured at room temperature and an air pressure of 3.0 bar using a Malvern Mastersizer 2000 (registered trademark). 10(10% (by volume) of the particles in the composition is equivalent to an average particle size such that the particle size is smaller than d 10 is 0.2 μm to 3.0 μm, for example 0.5 μm to 2.0 μm, for example 0.7 μm to 1.8 μm.)

[0034] According to one or more embodiments, the above composition has a D measured at room temperature and an air pressure of 3.0 bar using a Malvern Mastersizer 2000 (registered trademark). 50 (50% (by volume) of the particles in the composition is equivalent to an average particle size such that the particle size is smaller than d 50 is 2.0 μm to 15 μm, for example 3.0 μm to 13 μm, for example 3.5 μm to 12.5 μm.)

[0035] According to one or more embodiments, the above composition has a D measured at room temperature and an air pressure of 3.0 bar using a Malvern Mastersizer 2000 (registered trademark). 90 (90% (by volume) of the particles in the composition is equivalent to an average particle size such that the particle size is smaller than d 90 is 5.0 μm to 30 μm, for example 8.0 μm to 28 μm, for example 10 μm to 25 μm.)

[0036] According to one or more embodiments, the above composition further comprises at least one antioxidant. When the above composition contains at least one antioxidant, the zinc oxide and the zinc carbonate act synergistically with this at least one antioxidant to have a good initial color (low yellowness), high color retention ability when the extrusion process is carried out a plurality of times, high transparency (low haze value), and high gloss, resulting in an unexpected combination. Further, when the above composition contains at least one antioxidant, an improvement in thermal stability characterized by an increase in the oxidation induction time (Oxidation Induction Time, OIT) according to ISO 11357-6 may be observed. This is beneficial for piping applications such as pressure pipes for high-temperature and low-temperature drinking water, floor heating and wall heating systems, and joints.

[0037] According to one or more embodiments, the at least one antioxidant is selected from the group consisting of, for example, phenolic antioxidants, amine antioxidants, hydroxylamine antioxidants, phosphite antioxidants, phosphonite antioxidants, benzofuranone antioxidants, thiodipropionate antioxidants, acryloyl antioxidants, and combinations thereof.

[0038] The phenolic antioxidant may contain, for example, one or more sterically hindered phenolic compounds. Examples of the compounds include those selected from the group containing pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, and 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. The amine antioxidant may contain, for example, a hindered amine compound. Examples of the compounds include those selected from the group containing poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol-alt-1,4-butanedioic acid), bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, and poly[[6-[(1,1,3,3-tetramethylbutyl)amino]-s-triazine-2,4-diyl]-[(2,2,6,6-tetramethyl-4-piperidyl)imino]-hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl)imino]]. The hydroxylamine antioxidant may contain, for example, bis(hydrogenated tallow alkyl)amine oxides. An example of the compound is bis(octadecyl)hydroxylamine. The phosphite antioxidant may contain, for example, phosphite esters. Examples of the compounds include those selected from the group containing tris(2,4-di-tert-butylphenyl)phosphite, 3,9-bis(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-diphosphite. The phosphonite antioxidant may contain, for example, phosphonite esters. An example of the compound is tetrakis(2,4-di-tert-butylphenyl)[1,1'-biphenyl]-4,4'-diylbis(phosphonite). The benzofuranone antioxidant may contain, for example, 3-aryl-benzofuranones.Examples of the compound include 5,7 - di - tert - butyl - 3-(3,4 - dimethylphenyl)3H - benzofuran - 2 - one. The thiodipropionate - based antioxidant may contain, for example, alkyl esters of thiodipropionic acid. Examples of the compound include dioctadecyl 3,3’ - thiodipropionate. The acryloyl - based antioxidant may contain, for example, acryloyl - modified phenols. Examples of the compound include 2-(1,1 - dimethylethyl)-6 - [[3-(1,1 - dimethylethyl)-2 - hydroxy - 5 - methylphenylmethyl - 4 - methylphenyl acrylate.

[0039] According to one or more embodiments, the at least one antioxidant includes at least one primary antioxidant suitable for long - term stabilization, at least one secondary antioxidant suitable for process stabilization, or a combination thereof. The primary antioxidant may include, for example, phenolic antioxidants, amine - based antioxidants, and hydroxylamine - based antioxidants. The secondary antioxidant may include, for example, phosphite - based antioxidants and phosphonite - based antioxidants.

[0040] According to one or more embodiments, the composition contains 5 - 40 wt% zinc oxide, 0.5 - 4.0 wt% zinc carbonate, and at least one antioxidant, which may be any of the primary and / or secondary antioxidants exemplified above, in an amount of 10 - 65 wt%. All are amounts based on the total weight of the composition.

[0041] According to one or more embodiments, the composition contains 5 - 40 wt% zinc oxide, for example 10 - 35 wt%, for example 15 - 30 wt%, 0.5 - 4.0 wt% zinc carbonate, for example 1.0 - 3.5 wt%, for example 1.5 - 3.0 wt%, and 10 - 65 wt%, for example 15 - 60 wt%, for example 20 - 55 wt% of at least one primary antioxidant or at least one secondary antioxidant, or a combination thereof, all being amounts based on the total weight of the composition.

[0042] According to one or more embodiments, the composition comprises 5 to 40 wt% zinc oxide, such as 10 to 35 wt%, such as 15 to 30 wt%, 0.5 to 4.0 wt% zinc carbonate, such as 1.0 to 3.5 wt%, such as 1.5 to 3.0 wt%, 10 to 65 wt% of at least one primary antioxidant, such as 15 to 60 wt%, such as 20 to 55 wt%, and 10 to 65 wt% of at least one secondary antioxidant, such as 15 to 60 wt%, such as 20 to 55 wt%, all based on the total weight of the composition.

[0043] According to one or more embodiments, the primary antioxidant may be selected from the group consisting of sterically hindered phenolic compounds, hindered amine compounds, and hydroxylamine compounds, and the secondary antioxidant may be selected from the group consisting of phosphite compounds and phosphonite compounds.

[0044] According to one or more embodiments, the composition comprises zinc oxide, zinc carbonate, and optionally one or more antioxidants, but does not contain other acid scavengers, i.e., acid scavengers other than zinc oxide and zinc carbonate in the composition. The composition may not further contain metal salts such as sodium, calcium, zinc, and similar metal salts of acids. The composition may not contain metal stearates such as zinc stearate.

[0045] According to one or more embodiments, the method further comprises a step of adding the composition to the polymer, and the amount of the composition added to the polymer ranges from 1000 ppm to 5000 ppm, such as 1200 ppm to 3000 ppm, such as 1500 ppm to 2500 ppm, based on the amount of the polymer.

[0046] Unless otherwise specified, throughout this disclosure and the claims hereinafter, ppm represents mg / kg, i.e., weight ppm.

[0047] When the composition added to the polymer contains one or more antioxidants together with zinc oxide and zinc carbonate, the composition added to the polymer is in the range of 1000 ppm to 5000 ppm, for example 1200 ppm to 3000 ppm, for example 1500 ppm to 2500 ppm, based on the amount of the polymer.

[0048] According to one or more embodiments, the method has a plurality of extrusion steps, for example 2, 3, 4, or more extrusion steps.

[0049] According to one or more embodiments, the first extrusion step may have a step of extruding the molten polymer and the composition containing zinc oxide and zinc carbonate, and each subsequent extrusion step may have a step of extruding the material obtained in the first extrusion step.

[0050] Regardless of the number of extrusion steps, according to one or more embodiments, the method may have a step of blending the composition and the polymer before the extrusion step.

[0051] According to one or more embodiments, the extrusion step may be carried out in an extruder or in another melt processing apparatus. In either case, the extrusion step is carried out under extrusion conditions.

[0052] According to one or more embodiments, the extrusion step may be carried out in an extruder under predetermined extrusion conditions suitable for extruding the polymer, for example under a predetermined extrusion temperature and a predetermined extrusion pressure. Unless otherwise specified with respect to the extruder, the extrusion temperature and extrusion pressure exemplified in this specification and the claims hereinafter refer to the temperature and pressure of the barrel.

[0053] The extrusion step may be carried out at an extrusion temperature of, for example, 180°C to 270°C, for example 190°C to 260°C, for example 200°C to 250°C.

[0054] The extrusion process may be carried out at an extrusion pressure of 1 bar to 200 bar, for example 5 bar to 150 bar, depending on, for example, the zone of the extruder or the melting treatment apparatus.

[0055] According to one or more embodiments, the extruder may have, in this order, a supply zone, a solid transport zone, a solid compression zone, a melting zone, a melt transport zone, a decompression zone, a melt compression zone, and a die zone. In the supply zone, polymer powder is supplied to the extruder and may be held at a predetermined temperature so that the polymer powder does not become viscous or melt and so that the peroxide does not initiate a reaction. In the solid transport zone, the polymer powder is transported to the compression zone. In the solid compression zone, the polymer powder is pressurized to melt most of the polymer in the melting zone, and in the melt transport zone, the last remaining polymer particles are melted and mixed until a uniform temperature and composition are obtained. In the decompression zone, the molten polymer is decompressed. In the melt compression zone, the polymer melt is pressurized, and in the die zone, the molten polymer is shaped into a desired shape and recovered.

[0056] According to one or more embodiments, the extrusion pressure may be varied along the length of the extruder. The extrusion conditions may be, for example, that the pressure in the supply zone is 1 bar (atmospheric pressure) and the pressure in the melt compression zone is 5 bar to 150 bar. In other zones, the pressure may be between the pressures exemplified in the supply zone and the melt compression zone.

[0057] The extrusion conditions may further include strong mixing within the extruder. According to one or more embodiments, sufficient mixing may be achieved by setting the screw speed of the extruder in the range of 50 rpm to 200 rpm.

[0058] According to one or more embodiments, the extrusion process may be carried out in the presence of one or more polymer additives, for example polymer additives other than acid scavengers. Examples of the additives include fillers, antioxidants, antibacterial agents, bactericides, reinforcing agents, antistatic agents, heat stabilizers, UV stabilizers, fluidizing agents, colorants, and other additives or processing aids known to those skilled in the art.

[0059] According to one or more embodiments, the composition may be added to the polymer and then the extrusion step may be performed. According to one or more embodiments, the composition may be added to the polymer during the extrusion step.

[0060] According to one or more embodiments, the method comprises the step of extruding a molten polymer in the presence of a composition as described in one or more embodiments of the methods described herein.

[0061] According to a second aspect of the present disclosure, the present disclosure relates to a polymer composition comprising a polymer modified by a method according to any embodiment or combination thereof described herein.

[0062] According to another aspect of the present disclosure, the present disclosure relates to the use of a composition comprising zinc oxide and zinc carbonate for changing the optical appearance of a polymer comprising polypropylene. A composition defined in any embodiment of the above method may be used.

[0063] According to one or more embodiments, the use is for changing the optical appearance of a polymer under extrusion conditions.

[0064] According to one or more embodiments, the extrusion conditions may be those defined above with respect to the embodiments of the above method.

[0065] According to one or more embodiments, changing the optical appearance of the polymer may include suppressing color, retaining or stabilizing color after a period of time and / or after multiple extrusion steps, reducing the haze value (i.e., increasing transparency), increasing glossiness, and combinations thereof (e.g., consisting of) and may be selected from the group.

[0066] Changing the optical appearance may include, for example, the following properties: · The initial yellowness index is less than 5, for example less than 2; · When the extrusion process is carried out three times, the yellowness index is less than 40, for example less than 25; · The haze value is less than 60%, for example less than 45%; and / or · The gloss at 20° is more than 80, for example more than 85 and / or the gloss at 60° is more than 90, for example more than 100, may include one or more of the above.

[0067] According to one or more embodiments, the above-described method and use defined in any of the embodiments described herein may be implemented in applications of films, stretched tapes, and sheets.

[0068] Examples of film applications include biaxially oriented polypropylene (BOPP) films, cast films, tubular water quenched films, inflation films, etc. Examples of stretched tape applications include raffia, slit tapes, straps, decorative ribbons, etc. Examples of sheet applications include thermoforming, solid-phase pressure forming, melt forming, etc.

[0069] For example, in each of the above uses or combinations thereof, the above composition may be used in an extruder under one or more of the extrusion conditions defined above for the above method. The above composition and the above polymer may be any of the compositions and polymers exemplified above.

Brief Description of the Drawings

[0070]

Figure 1

Figure 2

Figure 3

DETAILED DESCRIPTION OF THE INVENTION

[0071] The following examples related to a method for changing the optical appearance of a polymer, particularly polypropylene, are for illustrative purposes and not for limiting purposes.

[0072] The examples show the properties of the polymers obtained by implementing the method for changing the optical appearance of the polymers according to the embodiments of the present disclosure. In particular, in the examples, it can be seen that the optical appearance obtained by the method according to the embodiments of the present disclosure is improved compared to the three conventional methods using conventional calcium stearate, conventional zinc oxide, and conventional zinc carbonate, respectively. Furthermore, in the examples of the method according to the embodiments of the present disclosure, the yellowness index measured according to ASTM D6290 is lower, the glossiness measured according to ISO2813 is higher, and the haze value measured according to ISO14782 is lower both after compounding the polymer and when the extrusion process is carried out multiple times, compared to the polymers treated by the conventional methods.

[0073] The following examples illustrate a method for changing the optical appearance of an isotactic polypropylene homopolymer under extrusion conditions. However, other polymers including polypropylene may be treated by the method of the present disclosure. Also, a composition containing zinc oxide, zinc carbonate, and two antioxidants is described. However, other antioxidants and common additives according to one or more embodiments of the method according to the present disclosure may be used. For example, stabilizers and / or other additives according to one or more embodiments of the method according to the present disclosure may be used.

[0074] Each of the exemplified compositions was directly fed from a hopper to an extruder together with the exemplified polymer powder. Stabilizers and / or other additives may be fed from the hopper to the extruder together with the composition and the polymer powder. The exemplified polymers and compositions were extruded using a Brabender laboratory twin-screw extruder KEDSE20 / 40D with an L / D (extruder length / screw diameter) of 40, an extrusion temperature of 230 °C, a screw speed of 120 rpm, and an extrusion pressure of 10 bar. The polymers and compositions were mixed with the screw of the extruder.

[0075] The properties reported in the examples were measured by the following methods.

[0076] The melt flow rate (MFR) was measured at 230 °C under a load of 2.16 kg in accordance with ISO 1133.

[0077] The evolution of carbon dioxide when each powder was treated with phosphoric acid (25% v / v) was detected, and the evolved gas was washed / dried with sulfuric acid / potassium permanganate / silver nitrate / silver wool in a continuous washing / drying column, and the carbon content was measured using a non-dispersive infrared (NDIR) sensor. Nitrogen was used as the carrier gas, and the powder sample was measured after encapsulation in gelatin.

[0078] Assuming that all carbon originated from zinc carbonate, the theoretical content of zinc carbonate was estimated (theoretical content of zinc carbonate = carbon content × molar mass of zinc carbonate / molar mass of carbon).

[0079] In accordance with the Brunauer-Emmett-Teller (BET) theory, the BET surface area was measured by performing linear regression with five points obtained in the pressure range p / p0 of 0.06 - 0.2 using ASAP2420 manufactured by Micromeritics (Micromeritics Operator’s Manual, Brunauer, S., Emmett, P.H., and Teller, E., J. Am. Chem. Soc. 60, 309 (1938)). The analytical adsorbate was nitrogen gas, the analytical bath temperature was 77.350 K, the ambient temperature was 22.00 °C, automatic degassing was on, temperature correction was off, and the calibration interval was 10 seconds.

[0080] For each point set for calculating the surface area, the adsorbed gas amount Q was measured and f(Q,p0 / p) was calculated.

Number

[0081] Least squares fitting was performed on the specified pair (p / p0,f(Q,p0 / p)) (where p / p0 is the independent variable and f(Q,p0 / p) is the dependent variable) to determine the following. a) Slope S (g / cm 3 STP) b) Y-intercept Y INT (g / cm 3 STP)

[0082] Using the results of the above calculations, the BET surface area SA BET was calculated.

Number

[0083] The Malvern Mastersizer 3000 was used in combination with the Malvern Aero S dry dispersion unit to determine the particle size distribution. The pressure of the dispersion unit (venturi) was set to 3.0 bar, and the metering system was adjusted so that the attenuation rate was 0.5 - 10%. In accordance with ISO13320, the experimental diffraction data was analyzed according to the Fraunhofer theory. In accordance with ISO9276, the percentiles D 10 (corresponding to x10), D 50 (corresponding to x50), D 90 (corresponding to x90) of the particle size distribution were calculated.

[0084] The compounding of the polymer pellets and the color development after extrusion were determined by the yellowness index (YI) of the polymer pellets. To determine the yellowness index, in accordance with ASTM D6290, using a LabScan XE manufactured by Hunterlab, which is a spectrophotometer of Group I, the color was determined at 400 - 700 nm, with a resolution of 10 nm, and the light source / observer arrangement set as D65 / 10°. The pellets were filled to the brim of the sample cup, placed in the sensor port, and covered with an opaque light-shielding cover. By measurement, the tristimulus values X, Y, and Z were obtained. In accordance with ASTM E313, the yellowness index was calculated using the following equation. YI = 100(CxX - CzZ) / Y (In the formula, the coefficients Cx and Cz were selected according to the settings of the light source and observer used in the measurement of the tristimulus values. In the case of light source D65 and observer 10°, Cx is 1.3013 and Cz is 1.1498.)

[0085] The haze value was measured using a Haze-gard plus manufactured by BYK in accordance with ISO14782.

[0086] The glossiness was measured using a micro-TRI-gloss manufactured by BYK at angles of 20° and 60° in accordance with ISO 2813.

[0087] Regarding the measurement of the haze value and glossiness, an injection molding plate with a thickness of 1 mm was prepared in accordance with ISO294 and measured directly during the preparation.

[0088] Comparative Examples 1 to 3 and Example 4 according to the present disclosure Each polymer was prepared by compounding an isotactic polypropylene homopolymer powder (MFR: 12 g / 10 min, ISO1133) with each composition containing an additive acting as an acid scavenger and an additive acting as an antioxidant. The isotactic polypropylene homopolymer was prepared by a vertical stirred gas-phase polymerization process using a Ziegler-Natta catalyst. The compositions are shown in Table 1.

Table 1

[0089] The following commercially available products were used as components. Phosphite-168: Tris(2,4-di-tert-butylphenyl) phosphite (Irgafos 168 (registered trademark) sold by BASF) Phenolic AO-1010: Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (Irganox 1010 (registered trademark) sold by BASF) Calcium stearate: Ligastar CA350 (registered trademark) sold by Peter Greven Zinc carbonate: Zinc carbonate RAC (registered trademark) sold by Bruggemann Zinc oxide: White Seal S (registered trademark) sold by Bruggemann Composition of zinc oxide and zinc carbonate: Zinc oxide AC45 (registered trademark) sold by Bruggemann

[0090] Prior to compounding, the components of each composition were tumble-mixed with the polymer powder for 2 hours to achieve good dispersion. The mixture of the polypropylene powder and the composition of each example was fed into the hopper of the extruder at a supply rate of 3 kg / h. The obtained extrudate was pelletized (MFR of the final pellets: 13 g / 10 min to 14 g / 10 min), and then all tests including multiple extrusion steps and measurements of yellowness, gloss, and haze values were carried out.

[0091] For each batch of zinc-based components, the parameters of carbon content, (theoretical) zinc carbonate content, BET surface area, and particle size distribution were summarized in Table 2.

Table 2

[0092] The results of measuring the yellowness index (Y-0) at the initial formulation and the increased yellowness indices (YI-1 to YI-5) during the extrusion process for the polymer compositions of Comparative Examples 1 to 3 and Example 4 are shown in Figure 1 and Table 3.

Table 3

[0093] The composition of Example 4 had the lowest initial yellowness (Y-0) after compounding, and the increase in yellowness was most suppressed when the extrusion process was carried out 1, 3, and 5 times. For example, YI-5 of Example 4 was 45% lower than YI-5 of Comparative Example 1 and 24% lower than YI-5 of Comparative Example 2. Therefore, Example 4 had the best initial color and color retention ability among all the test compositions.

[0094] The results of measuring the glossiness and haze value of the polymer compositions of Comparative Examples 1 to 3 and Example 4 are shown in FIG. 2 and Table 4.

Table 4

[0095] When the composition of Example 4 was used, it was found that the glossiness was very high compared with both Comparative Example 2 and Comparative Example 3. Therefore, the optical appearance and properties of the composition of Example 4 are particularly suitable for manufacturing articles such as slit tapes or BOPP films.

[0096] Furthermore, the composition of Example 4 exhibited a glossiness comparable to that obtained with calcium stearate, but no surface migration phenomenon occurred. Therefore, the composition of Example 4 is particularly suitable for printing and raffia applications.

[0097] The results of measuring the haze value of the polymer compositions of Comparative Examples 1 to 3 and Example 4 are shown in FIG. 3. When the composition of Example 4 was used, it was found that the properties of the haze value were also improved, and it was 25% lower than the value obtained in Comparative Example 2. Therefore, the composition of Example 4 is particularly suitable for high transparency applications such as thermoformed products.

[0098] Regarding the high gloss and low haze value in Example 4, these results were particularly unexpected. Furthermore, since the composition of Example 4 contains an inorganic additive that is insoluble in the polymer matrix, it is particularly surprising that all of these properties are improved.

[0099] From the results of changing the optical appearance of polypropylene, it can be seen that the optical appearance is improved compared to each conventional method using conventional calcium stearate, conventional zinc oxide, and conventional zinc carbonate in terms of the yellowness index, gloss, and haze value when the compounding and extrusion processes are carried out multiple times.

[0100] Although the aspects of the present disclosure have been described for only a limited number of embodiments, those skilled in the art who enjoy the benefits of the present disclosure will understand that other embodiments that do not depart from the scope of the invention disclosed herein are also conceivable. Therefore, the scope of this scope should be limited only by the appended claims.

Claims

1. A molten polymer containing polypropylene, and a composition containing an acid scavenger composed of zinc oxide and zinc carbonate are extruded, and the zinc oxide and the zinc carbonate are present within the same particles, A method for producing a polymer composition.

2. The production method according to claim 1, wherein the polymer composition is suppressed in color, retains color even after the passage of time and / or after repeating the extrusion process, has a decreased haze value, has an increased glossiness, and combinations thereof.

3. The composition has a BET surface area of 10 m ２ / g to 100 m ２ / g, and is the production method according to claim 1 or 2.

4. The production method according to any one of claims 1 to 3, wherein the composition contains 90 to 99% by weight of zinc oxide and 1 to 10% by weight of zinc carbonate.

5. The production method according to any one of claims 1 to 4, wherein the composition has a carbon content of 0.1 to 1.0% by weight of carbon based on the total weight of the composition.

6. The production method according to any one of claims 1 to 5, wherein the composition further contains at least one antioxidant.

7. The at least one antioxidant is selected from the group consisting of phenolic antioxidants, phosphite antioxidants, amine antioxidants, hydroxylamine antioxidants, phosphonite antioxidants, benzofuranone antioxidants, thiodipropionate antioxidants, acryloyl antioxidants, and combinations thereof. The production method according to any one of claims 1 to 6.

8. The production method according to any one of claims 1 to 7, wherein the method further has a step of adding the composition to the polymer, and the amount of the composition added to the polymer ranges from 1000 ppm to 5000 ppm based on the amount of the polymer.

9. The production method according to any one of claims 1 to 8, wherein the method has a plurality of extrusion steps.

10. The polypropylene is selected from the group consisting of polypropylene homopolymers, random copolymers containing propylene, heterophasic copolymers containing propylene, and combinations thereof. The production method according to any one of claims 1 to 9.

11. A polymer composition produced by the method according to any one of claims 1 to 10.

12. Use of a composition containing zinc oxide and zinc carbonate for producing a polymer composition containing polypropylene, The polymer composition is characterized by suppressed color, maintaining color after the passage of time and / or after repeated extrusion processes, a decreasing haze value, an increasing glossiness, and combinations thereof. Use.

13. When the extrusion process is carried out three times on a polymer with an initial yellowness index of less than 5, the yellowness index is less than 40. The haze is less than 60%, and The glossiness at 20° is more than 80 and / or the glossiness at 60° is more than 90. including at least one of the following. The use according to claim 12.

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