WO2025050288A1

WO2025050288A1 - Black polymer compound for near infrared sorting

Info

Publication number: WO2025050288A1
Application number: PCT/CN2023/117019
Authority: WO
Inventors: Aihua Pei
Original assignee: Cabot Corp
Current assignee: Cabot Corp
Priority date: 2023-09-05
Filing date: 2023-09-05
Publication date: 2025-03-13
Anticipated expiration: 2026-03-05
Also published as: WO2025054092A1

Abstract

Provided are a black polymer compound for near infrared sorting. The black polymer compound comprises: a base resin; 0.01% to 0.08% of an aggregated black pigment selected from carbon black, silica coated carbon black, and silicon treated carbon black; a first pigment having near infrared reflectivity; and optionally a second pigment, reinforcing filler, and additive, wherein a ratio of the aggregated black pigment and all near infrared pigments in the polymer compound is from 1: 12 to 1: 100, an NIR reflectance of the polymer compound from 1200 to 1500 nm is at least 10% and the jetness L* of the polymer compound is at most 27.

Description

BLACK POLYMER COMPOUND FOR NEAR INFRARED SORTING

TECHNICAL FIELD

The present invention relates to a black polymer compound for near infrared sorting, in particular, a black polymer compound which can be effectively detected by a near infrared sorting system while having good black coloring effect.

BACKGROUND ART

Automatic near infrared (NIR) spectroscopy sorting systems is the dominant technology being used at Plastics Recovery Facilities (PRFs) to separate plastics waste into various polymer type for reprocessing into valuable materials. Carbon black is the most common black pigment used in plastics because of its low cost and excellent coloring performance. However, since carbon black (CB) absorbs strongly in near infrared spectral range, it is difficult to detect black plastic packaging by NIR, and much of this material therefore ends up in unsorted residue or landfill.

Some black colorants, such as PBr29 and PBk33, with little absorption or reflection in the NIR spectrum have been used as alternative solutions to address the non-recyclable nature of carbon black plastic. Plant trials at sorting facility confirmed that food trays colored with above colorants could be effectively identified and sorted into correct polymer streams on existing NIR equipment. However, NIR detectable black colorants are much more expensive than conventional carbon black, and more importantly, these colorants generally have much worse coloring strength and opacity than that of carbon black.

Thus, there is a need for a black plastic which can be effectively detected by the near infrared sorting system and have good black coloring effect at a low cost.

SUMMARY

A black polymer compound for near infrared sorting which is at least partially visible or totally visible in a near infrared sorting system and has good black coloring effect (jetness L*of less than or equal to 29.5 and preferably lower undertones a*and b*) is provided.

According to an embodiment, a black polymer compound for near infrared sorting comprising: a base resin, 0.01%to 0.08%of an aggregated black pigment selected from carbon black, silica coated carbon black, and silicon treated carbon black, a first pigment having near infrared reflectivity, and optionally a second pigment, reinforcing filler, and additive, wherein a ratio of the aggregated black pigment and all near infrared pigments in the polymer compound is from 1: 12 to 1: 100 by weight, an NIR reflectance of the polymer compound is at least 10%in the range of from 1200 to 1500 nm, preferably from 1100 to 1500 nm, and more preferably from 1000 to 1500 nm and the polymer compound has L*of at most 29.5.

In an embodiment, the aggregated black pigment may be selected from silica coated carbon black and silicon treated carbon black, and preferably silicon treated carbon black.

In an embodiment, the silicon treated carbon black may be in the form of dual phase filler.

In an embodiment, the first pigment having near infrared reflectivity may be selected from a black or brown pigment, preferably selected from pigment brown 29, pigment black 33, and pigment black 30.

In an embodiment, the ratio of the aggregated black pigment and all near infrared pigments in the polymer compound may be from 1: 12 to 1: 100, for example, 1: 15 to 1: 30, 1: 19 to 1: 70, or 1: 12 to 1: 50.

In an embodiment, the amount of the aggregated black pigment may be in the range of 0.02 to 0.07 wt%, based on the total weight of the black polymer compound.

In an embodiment, the NIR reflectance of the polymer compound may be in the range of 10%to 27%, for example in the range of 11%to 18%, and the polymer compound may have L*of at most 27, and preferably in the range of 25 to 27.

In an embodiment, the black polymer compound may further comprise an additional pigment which does not absorb in the near infrared spectral range, preferably selected from blue pigment, brown pigment, and yellow pigment.

In an embodiment, the black polymer compound may further comprise a reinforcing filler, preferably selected from mica, graphite, and glass bead.

In an embodiment, the black polymer compound may further comprise an additive, preferably selected from an antioxidant, a dispersant, and a lubricant.

In an embodiment, the base resin may be selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, polystyrene, polyethylene terephthalate, polypropylene, or polyvinyl chloride.

In an embodiment, the base resin may be selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, or polypropylene, and the polymer compound may have L*of at most 27, and preferably in the range of 25 to 27.

In an embodiment, the base resin may be selected from the group consisting of polystyrene or polyethylene terephthalate, and the polymer compound may have L*of at most 29, and preferably in the range of 27.5 to 29.

In an embodiment, the carbon black may have an STSA of 10 to 160 m²/g, an iodine number of 10 to 270 g/kg, or both, preferably the carbon black has the STSA of 10 to 50 m²/g, preferably 10 to 30 m²/g, and more preferably 10 to 20 m²/g, the iodine number of 10 to 50 g/kg, preferably 10-35 g/kg, more preferably 10-20 g/kg, or both.

In an embodiment, the polymer compound may have a*of at most 1.9, preferably at most 1.8, and more preferably at most 1.7, b*of at most 0.5, and preferably of at most 0.4, or both.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing NIR reflectance of black LDPE compounds with different compositions in Example 1.

FIG. 2 is a graph showing NIR reflectance of black LDPE compounds with different compositions in Example 2.

FIG. 3 is a graph showing NIR reflectance of black LDPE compounds with different compositions in Example 3.

FIG. 4 is a graph showing NIR reflectance of black LDPE compounds with different compositions in Example 4.

FIG. 5 show photos of black LDPE compounds with different compositions in Example 4.

FIG. 6 is a graph showing NIR reflectance of the black LDPE compound with CSX691 in Example 1 and the black LDPE compound with CRX4210 in Example 4.

FIG. 7 is a graph showing jetness L*and undertone a*and b*of the black LDPE compound with CSX691 in Example 1 and the black LDPE compound with CRX4210 in Example 4.

FIG. 8 is a graph showing NIR reflectance of black LDPE compounds comprising masterbatch in different amounts in Example 5.

FIG. 9 is a graph showing NIR sorting result of the black LDPE compounds comprising the masterbatch in different amounts in Example 5.

FIG. 10 is a graph showing NIR reflectance of Black PP-2#in Example 6.

FIG. 11 is a graph showing NIR reflectance of black PS compounds with different compositions in Example 7.

FIG. 12 is a graph showing NIR reflectance of black PET compounds with different compositions in Example 8.

DESCRIPTION OF EMBODIMENTS

The present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. The drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

Hereinafter, a black polymer compound for near infrared sorting according to an embodiment will be described.

As stated above, in the prior art, the black plastic is difficult to detect and sort by the automatic NIR spectroscopy sorting systems when it has excellent black coloring performance, for example, by being colored with carbon black, while the black plastic has worse black coloring performance when it is colored with the near infrared reflective black pigments such as PBr29 and PBk33 and thus can be detected and sorted by the automatic NIR spectroscopy sorting systems. Thus, there is a need for a black plastic which can be effectively detected by the near infrared sorting system and have good black coloring effect at a low cost.

The present inventors have found that the black polymer compound for near infrared sorting which can be effectively detected by the near infrared sorting system and have good black coloring effect can be provided by using an aggregated black pigment selected from carbon black, silica coated carbon black, and silicon treated carbon black in a specific amount and using the aggregated black pigment with a first pigment having near infrared reflectivity in a specific ratio in a black polymer compound, making the black polymer compound have specific NIR reflectance and jetness L*, and preferably specific undertone a*and/or undertone b*. In particular, the black polymer compound for near infrared sorting is at least partially visible or totally visible in the NIR sorting system and has good black coloring effect (L*of at most 29.5, preferably of at most 27, and more preferably in the range of 25 to 27, and preferably at least one of a*of at most 1.9, preferably of at most 1.8, and more preferably of at most 1.7, and b*of at most 0.5, and preferably of at most 0.4, and more preferably all of the above L*, a*, and b*) .

According to an embodiment of the invention, a black polymer compound for near infrared sorting comprises: a base resin; about 0.01%to 0.08%of an aggregated black pigment selected from carbon black, silica coated carbon black, and silicon treated carbon black; and a first pigment having near infrared reflectivity. In the black polymer compound, a ratio of the aggregated black pigment and all the pigments having near infrared reflectivity is from 1: 12 to 1: 100 by weight. The black polymer compound has an NIR reflectance of at least 10%in the wavelength range of from 1200 to 1500 nm, preferably from 1100 to 1500 nm, and more preferably from 1000 to 1500 nm. Moreover, the black polymer compound has L*of at most 29.5, and preferably at least one of a*of at most 1.9 and b*of at most 0.5.

In the black polymer compound according to the embodiment, the amount of the aggregated black pigment is in the range of about 0.01 to about 0.08 wt%, preferably about 0.02 to about 0.07 wt%, and more preferably about 0.02 to about 0.04 wt%, for example, about 0.03 to about 0.05 wt%, or about 0.05 to about 0.065 wt%, based on the total weight of the black polymer compound. If the amount of the aggregated black pigment is less than about 0.01 wt%, the black polymer compound may not achieve good black coloring effect, for example, undertone a*and b*may not be substantially improved. If the amount of the aggregated black pigment is greater than about 0.08 wt%, the black polymer compound may not be detected by the NIR spectroscopy sorting systems. When the amount of the aggregated black pigment is within the above ranges, it can provide the black polymer compound which can be effectively detected by the near infrared sorting system and have good black coloring effect at the same time.

In the black polymer compound according to the embodiment, the ratio of the aggregated black pigment and all the pigments having near infrared reflectivity is from 1: 12 to 1: 100, preferably 1: 12 to 1: 50, more preferably 1: 15 to 1: 30, and most preferably 1: 15 to 1: 20, by weight. If the ratio of the aggregated black pigment and all the pigments having near infrared reflectivity is less than 1: 100, the black polymer compound may not achieve good black coloring effect, for example, undertone a*and b*may not be substantially improved. If the ratio of the aggregated black pigment and all the pigments having near infrared reflectivity is greater than 1: 12 (i.e., higher relative amount of aggregated black pigment) , the black polymer compound may not be detected by the NIR spectroscopy sorting systems. When the ratio of the aggregated black pigment and all the pigments having near infrared reflectivity is within the above ranges, it can provide the black polymer compound which can be effectively detected by the near infrared sorting system and have good black coloring effect at the same time.

The black polymer compound according to the embodiment has the NIR reflectance of at least 10%, preferably 10%to 27%, and more preferably 11%to 18%in the wavelength range of from 1200 to 1500 nm, preferably from 1100 to 1500 nm, and more preferably from 1000 to 1500 nm. If the NIR reflectance of the black polymer compound is greater than 10%, the black polymer compound is more readily detected by the NIR spectroscopy sorting systems.

The black polymer compound according to the embodiment has the jetness L*of at most 29.5, preferably of at most 29, for example, in the range of 27.5 to 29, and more preferably of at most 27, for example, in the range of 25 to 27. If the jetness L*of the black polymer compound is greater than 29.5, the black polymer compound may not have good black coloring effect. Jetness and undertone are measured according to the CIELAB standard of colorimetry using a D65 illuminant, measurement geometry of d/8°, and 10°observer under under specular reflection included (SCI) mode.

In an embodiment, preferably, the black polymer compound may have undertone a*of at most 1.9, for example, at most 1.8, at most 1.7, less than or equal to 1.65, preferably less than or equal to 1.60, more preferably less than or equal to 1.55, for example, less than or equal to 1.50, or less than or equal to 1.40, and/or underone b*of at most 0.5, for example, at most 0.4, less than or equal to 0.3, preferably less than or equal to 0.27, more preferably less than or equal to 0.26, for example, less than or equal to 0.25, or less than or equal to 0.24. When the undertone a*and b*of the black polymer compound are within the above ranges, it can provide the black polymer compound which has good black coloring effect.

In an embodiment, the aggregated black pigment may be selected from silica coated carbon black and silicon treated carbon black, and preferably silicon treated carbon black. When the aggregated black pigment is selected as above, it may achieve better improvement in terms of the NIR reflectance and/or the black coloring effect of the black polymer compound.

Carbon black aggregates may be modified by depositing silicon-containing species, such as silica, on at least a portion of the surface of the carbon black aggregates. The result may be described as silica coated carbon blacks. Examples of the reaction steps to form the silica coated carbon black can be found in U.S. Pat. Nos. 6,541,113 and 5,679,728, incorporated in their entirety by reference here.

The silicon treated carbon black may be in the form of dual phase filler. In the dual phase filler, a silicon containing species, such as an oxide or carbide of silicon, for instance, a silica phase (s) , is distributed through at least a portion of the filler as an intrinsic part of the filler. Similarly, the carbon phase (s) is distributed through at least a portion of the filler as an intrinsic part of the filler. The carbon phase is essentially a carbon black region (s) which exists as a carbon phase in the filler. Conventional carbon blacks exist in the form of aggregates, with each aggregate consisting of a single phase, which is carbon. This phase may exist in the form of a graphitic crystallite and/or amorphous carbon, and is usually a mixture of the two forms. The silica-coated carbon black as mentioned above is different from the dual phase filler.

The dual phase filler is not carbon black aggregates which have been coated or otherwise modified, but actually represent a different kind of aggregate having two phases. One phase is carbon, which will still be present as graphitic crystallite and/or amorphous carbon, while the second phase is silica (and possibly other silicon-containing species) . Thus, the silicon-containing species phase of the dual phase filler is an intrinsic part of the aggregate; it is distributed throughout at least a portion of the aggregate. It will be appreciated that the dual phase fillers are quite different from the silica-coated carbon blacks, which consist of pre-formed, single phase carbon black aggregates having silicon-containing species deposited on their surface. Such carbon blacks may be surface-treated in order to place a silica functionality on the surface of the carbon black aggregate as described in, e.g., U.S. Pat. No. 6,929,783. Methods of making various types of dual phase fillers or silicon-treated carbon blacks and various compositions containing the same that can be used in the present application are described in U.S. Pat. Nos. 9,267,048; 7,199,176; 6,709,506; 6,686,409; 6,534,569; 6,469,089; 6,448,309; 6,364,944; 6,323,273; 6,211,279; 6,169,129; 6,057,387; 6,028,137; 6,008,272; 5,977,213; 5,948,835; 5,919,841; 5,904,762; 5,877,238; 5,869,550; 5,863,323; 5,830,930; 5,749,950; 5,747,562; and 5,622,557, and U.S. Published Patent Application No. 2002/0027110, all incorporated in this application in their entirety by reference herein.

The dual phase filler can include silicon-containing regions (e.g., silica regions) primarily at the aggregate surface of the filler, but still be part of the filler, and/or the dual phase filler can include silicon-containing regions (e.g., silica regions) distributed throughout the filler. The dual phase filler can be oxidized. The dual phase filler can have a total silica phase amount in the dual phase filler that ranges from 1 wt%to 90 wt%or more, based on the weight of the dual phase filler. The silica phase can be present in an amount of from 5 wt%to 90 wt%, from 10 wt%to 85 wt%, from 15 wt%to 80 wt%, from 20 wt%to 75 wt%, from 25 wt%to 70 wt%, from 30 wt%to 65 wt%, from 35 wt%to 65 wt%, from 40 wt%to 85 wt%, from 50 wt%to 80 wt%, and the like, based on the total weight of the dual phase filler.

The dual phase filler, as an option, has at least part of the silica phase on the surface of the dual phase filler. In other words, the dual phase filler has an exposed outer surface and at least part of the silica phase, as an option, is present on the exposed surface of the dual phase filler. The amount of exposed surface coverage that is the silica phase can be varied. The amount of the silica phase present on the exposed surface area of the dual phase filler can be less than 100%by surface area. In other words, at least 0.1%by surface area of the exposed surface area of the dual phase filler can be a carbon phase. The amount of surface coverage of the silica phase on the exposed surface area of the dual phase filler can range, for instance, from 10%to 99.9%, 15%to 99%, 15%to 95%, 15%to 90%, 20%to 85%, 20%to 80%, 20%to 75%, 25%to 70%, 25%to 65%, 25%to 60%, 10%to 55%, or 15%to 50%by surface area. The surface coverage amount of the silica phase that is part of the exposed surface area of the dual phase filler can be the following: 15%to 20%; 20%to 25%; 25%to 30%; 30%to 35%; 35%to 40%; 40%to 45%; 45%to 50%; 50%to 55%; 55%to 60%; 60%to 65%; 65%to 70%; 70%to 75%; 75%to 80%; 80%to 85%; 85%to 90%, wherein the percent is a reference to the percent surface area based on the total exposed surface area of the dual phase filler. A test that can be used to determine the amount of silica surface coverage is provided in the paper entitled “New Generation Carbon-Silica Dual Phase Filler Part I. Characterization And Application To Passenger Tire” Rubber Chemistry And Technology, Vol 75 (2) , pp. 247-263 (2002) , incorporated in its entirety by reference herein.

The silicon treated carbon black in the form of dual phase filler may be commercially available, for example, under the name of CRX4210 from Cabot Corporation.

In an embodiment, the aggregated black pigment may be selected from the carbon black (i.e., non-mofidied carbon black) . In this case, the carbon black may have an STSA of 10 to 160 m²/g, an iodine number of 10 to 270 g/kg, or both. Preferably, the carbon black may have the STSA of 10 to 50 m²/g, preferably 10 to 30 m²/g, and more preferably 10 to 20 m²/g, the iodine number of 10 to 50 g/kg, preferably 10 to 35 g/kg, and more preferably 10 to 20 g/kg, or both. When the iodine number of the carbon black is within the above preferable ranges, it may achieve better improvement in terms of the NIR reflectance of the black polymer compound.

In addition, the carbon black may have an OAN number of 50 to 150 mL/100g, preferably 65 to 120 mL/100g, more preferably 80 to 110 mL/100g, and most preferably 90 to 100 mL/100g.

The carbon black may be commercially available. Some commercially available carbon blacks are sold under theBlack andtrademarks and are available from Cabot Corporation, for example, under the name of Black Pearls 120, Black Pearls 2, CSX 863, Vulcan 10H, CSX 691, or Black Pearls 46 from Cabot Corporation. Of these, the carbon black is preferably selected from Black Pearls 120, Black Pearls 2, and CSX 691 carbon black, and more preferably CSX 691 carbon black. Other commercially available carbon blacks include but are not limited to carbon blacks sold under theand trademarks, the CD and HV lines available from Columbian Chemicals, and the andproducts available from Orion Engineered Carbons.

In an embodiment, the first pigment having near infrared reflectivity is a pigment having a reflectance of greater than 50%, preferably greater than or equal to 60%, more preferably preferably greater than or equal to 70%, for example, preferably greater than or equal to 80%or 90%, in the infrared spectral range, for example, of 780 to 2500 nm, or 1000 to 1500 nm. Alternatively or in addition, the first pigment having near infrared reflectivity is an NIR reflective pigment having a total solar reflectance (TSR) of greater than or equal to 15%, preferably greater than or equal to 20%, more preferably greater than or equal to 30%, for example, from 15 to 70%or from 20 to 80%. Preferably, the first pigment having near infrared reflectivity may be selected from a black or brown pigment, preferably selected from pigment brown 29, pigment black 33, and pigment black 30.

In an embodiment, an amount of the first pigment having near infrared reflectivity in the black polymer compound may be adjusted, depending on the amount of the aggregated black pigment and the ratio of the aggregated black pigment and the pigments having near infrared reflectivity. For example, the amount of the first pigment having near infrared reflectivity in the black polymer compound may be within the range of about 0.3 wt%to about 12 wt%, preferably about 0.5 wt%to about 10 wt%, more preferably about 0.5 wt%to about 5 wt%, and most preferably about 1 wt%about 3 wt%, based on the total weight of the black polymer compound.

In an embodiment, the black polymer compound may further comprise an additional pigment (second pigment) which does not absorb in the near infrared spectral range. The additional pigment is not particulary limited, and may be any suitable pigment available in the art. The additional pigment may be non-black pigments that do not absorb in the NIR spectral range. Preferably, the additional pigment may be selected from blue pigment, brown pigment, and yellow pigment, such as Pigment Blue 29, Pigment Brown 24, or Pigment Yellow 164, etc., which may be used to adjust the undertone of the compound when necessary.

In an embodiment, an amount of the additional pigment in the black polymer compound is not particularly limited, and may be selected within a range which does not affect the effect of the black polymer compound of the invention. For example, the amount of the additional pigment in the black polymer compound may be within the range of about 0.01 wt%to about 5 wt%, preferably about 0.1 wt%to about 3 wt%, and more preferably about 0.2 wt%to about 2 wt%, based on the total weight of the black polymer compound.

In an embodiment, the black polymer compound may further comprise a reinforcing filler. The reinforcing filler is not particulary limited, and may be any suitable reinforcing filler available in the art. Preferably, the reinforcing filler may be selected from mica, graphite, and glass bead.

In an embodiment, an amount of the reinforcing filler in the black polymer compound is not particularly limited, and may be selected within a range which does not affect the effect of the black polymer compound of the invention. For example, the amount of the reinforcing filler in the black polymer compound may be within the range of about 0.01 wt%to about 10 wt%, preferably about 0.1 wt%to about 5 wt%, and more preferably about 0.5 wt%to about 2 wt%, based on the total weight of the black polymer compound.

In an embodiment, the black polymer compound may further comprise an additive. The additive is not particulary limited, and may be any suitable additive available in the art. Preferably, the additive may be selected from an antioxidant, a dispersant, and a lubricant.

In an embodiment, an amount of the additive in the black polymer compound is not particularly limited, and may be selected within a range which does not affect the effect of the black polymer compound of the invention. For example, the amount of the additive in the black polymer compound may be within the range of about 0.01 wt%to about 3 wt%, preferably about 0.05 wt%to about 2 wt%, and more preferably about 0.2 wt%to about 0.5wt%, based on the total weight of the black polymer compound.

In an embodiment, the base resin is not particularly limited, and may be any suitable base resin available in the art. Preferably, the base resin may be selected from the group consisting of high density polyethylene (HDPE) , low density polyethylene (LDPE) , linear low density polyethylene (LLDPE) , polystyrene (PS) , polyethylene terephthalate (PET) , polypropylene (PP) , or polyvinyl chloride (PVC) . When the base resin is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, or polypropylene, the polymer compound may have L*of at most 27, and preferably in the range of 25 to 27. When the base resin is selected from the group consisting of polystyrene or polyethylene terephthalate, the polymer compound may have L*of at most 29, and preferably in the range of 27.5 to 29.

In an embodiment, an amount of the base resin in the black polymer compound is not particularly limited, and may be selected by those skilled in the art without undue experment. For example, the amount of the base resin in the black polymer compound may be within the range of about 70 wt%to about 99.5 wt%, preferably about 80 wt%to about 99 wt%, and more preferably about 90 wt%to about 97 wt%, based on the total weight of the black polymer compound.

As described above, the black polymer compound according to an embodiment comprises the aggregated black pigment in the specific amount and the aggregated black pigment with the first pigment having near infrared reflectivity in the specific ratio, and has the specific NIR reflectance and jetness L*. As a result, the black polymer compound can be effectively detected by the near infrared sorting system and have good black coloring effect at the same time.

Hereinafter, a method of preparing the black polymer compound according to an embodiment to an embodiment will be described.

The method of preparing the black polymer compound comprises: firstly preparing a concentrated masterbatch, and then diluting the concentrated masterbatch in a base resin to prepare the black polymer compound.

In the preparation of the concentrated masterbatch, the aggregated black pigment and the base resin can be mixed to prepare a masterbatch of CB, and the first pigment having near infrared reflectivity and the base resin can be mixed to prepare a masterbatch of NIR reflective pigment. Alternatively, the aggregated black pigment, the first pigment having near infrared reflectivity, and the base resin can be mixed together to prepare a masterbatch of CB and NIR reflective pigment. Further, the second pigment, reinforcing filler, and additive may be optionally added in the preparation of the concentrated masterbatch.

Amounts of various components in the masterbatch such as the aggregated black pigment, the first pigment having near infrared reflectivity, and optionally the second pigment, reinforcing filler, and additive are not particularly limited, and may be calculated according to the desired contents in the black polymer compound. For example, the amount of the pigment in the masterbatch may be 10 wt%to 70 wt%, 20 wt%to 60 wt%, or 30 wt%to 50 wt%, the amount of the base resin in the masterbatch may be 30 wt%to 90 wt%, 40 wt%to 80 wt%, or 50 wt%to 70 wt%, and the amount of the second pigment, reinforcing filler, and additive in the masterbatch may be 0 to 10 wt%, 0 wt%to 5 wt%, or 0 wt%to 3 wt%, based on the total weight of the masterbatch. In an embodiment, the masterbatch may comprise 60 wt%of the base resin and 40 wt%of the pigment.

The mixing of the pigment, the base resin, and the optionally the second pigment, reinforcing filler, and additive may be carried out by any suitable method available in the art, for example, in a Banbury internal mixer or twin-screw extruder.

In the dilution of the concentrated masterbatch in the base resin, the materbatch is melt blended with the base resin according to the desirable concentration of the pigment in the final black polymer compound. The dilution may be carried out by any suitable method available in the art, for example, in a single screw extruder or twin-screw extruder.

Hereinafter, the embodiments are illustrated in more detail with reference to examples. These examples, however, are not in any sense to be interpreted as limiting the scope of the invention.

(Test Methods)

(1) NIR reflectance

The NIR spectra were measured on a Perkin Elmer Lambda 950 UV-VIS-NIR spectrophotometer with an integrating sphere attachment. A NIR spectrum of each sample was collected in reflection mode in the wavelength range of 800-2500nm at a scan speed of 550 nm/min and data interval of 2nm.

(2) L*, a*, and b*

The color data are generated using DATACOLOR 850 which is in conformance with the CIELAB standard of colorimetry. The protocol of color measurement is D65 illuminant, measurement geometry of d/8°, and 10° observer. L*, a*, b*data under specular reflection included (SCI) mode were recorded.

(3) NIR sortability

The NIR sortability was tested by using a UniSort PR NIR sorting unit (Steinert) according to the manufacturer’s instructions to measure visibility of the black polymer compound.

(General procedures for preparation of masterbatch, black polymer compound, and sheet)

(1) Preparation of PE and PP masterbatch by using Banbury internal mixer

The aggregated black pigment (CB pigment) or the first pigment having near infrared reflectivity (NIR reflective pigment) and the base resin were mixed by using Farrel 1.57 L Banbury internal mixer with following mixing protocol (Table 1) to prepare the masterbatch (MB) comprising 60 wt%of the base resin and 40 wt%of the pigment.

Table 1. Banbury process settings to produce MB

(2) Preparation of black polymer compound by using single screw extruder

The black PE and PP polymer compound was prepared by using a single screw extruder (SSE) BETOL A2520J with screw diameter of 25mm and L/D ratio of 25: 1, temperature setting in all zones at 190℃, and screw speed setting at 100rpm. The CB masterbatch, the NIR reflective pigment masterbatch, and the base resin were firstly dry blended and then extruded twice by the SSE to ensure a homogeneous compound. The weight of each ingredient was calculated according to the desired pigment content and ratio between CB and NIR reflective pigments.

(3) Preparation of PE sheet

The prepared black polymer compound was then extruded using a film blowing machine (Collin E20T) with temperature setting in all zones at 165℃ and screw speed setting in range of 80-100 rpm, in order to obtain a sheet with thickness about 800 μm and width about 5cm.

(4) Preparation of PP sheet

The PP sheet was prepared by using a tape extrusion equipment, which is a combination of a single screw extruder and a haul-off and collecting device. A typical tape extrusion process profile setting is shown in Table 2. The prepared black PP compound was fed into the hopper and then extruder into tapes with thickness about 500 μm.

Table 2. Typical tape extrusion processing profile

(5) Preparation of masterbatches and black compounds by using twin-screw extruder

Co-rotating twin-screw extruder (TSE) Leistritz ZSK27 iMAXX with screw diameter of 28mm and L/D ratio of 48: 1 was used to prepare PS-and PET-based masterbatches. A screw configuration with the ratio of the length of the mixing blocks versus the total length of the screw from 20-40%was used during the compounding. CB and reflective pigment were firstly premixed and then the resin and pigment mixture were fed separately into extruder from main throat. Compounding parameter settings are listed in Table 3.

PS black compounds were made by letting down PS masterbatches in PS resin. PS MB was first dry blended with resin according to the designed concentration and then compounded in extruder. In all cases, the mixture of MB and let-down resin was fed through the main throat.

PET compounds were prepared by following the same approach. The TSE parameter settings for preparing of compounds are consistent with those to produce masterbatch.

Table 3. Compounding parameters setting of Leistritz ZSK27 iMAXX extruder for masterbatch and compound

(6) Preparation of PS and PET Plaques

PS and PET plaques with dimension of 90mm x 65mm x 2mm were injection molded for NIR reflectance assessment. PS and PET black compounds were firstly dried at 90℃ for 2 hours before injection molding using 36mm injection-molding machine SE100EV-A from Sumitomo Demag. PET and PS black specimens are prepared by applying the same approach but under different injection molding parameters as listed in Table 4.

Table 4. Injection molding parameter setting for PS and PET compounds

(Materials used in Examples)

Table 5 below shows the material used in Examples.

Table 5

Example 1: black LDPE compounds with different compositions of CB pigment and NIR reflective pigment

In Example 1, CSX 691 as the CB pigment and LDPE as the base resin were mixed in the Banbury internal mixer to prepare the CB masterbatch (MB) , PBr29 (Sicopal Black K 0098) as the NIR reflective pigment and LDPE as the base resin were mixed in the Banbury internal mixer to prepare the NIR reflective pigment masterbatch (MB) , and then CB masterbatch, the NIR reflective pigment masterbatch, and the base resin were dry blended and extruded twice by the SSE to prepare the black LDPE compounds. In the black LDPE compounds, the concentration of the pigment was 1 wt%, and the ratio of the CB pigment and the NIR reflective pigment was shown in Table 6.

The black LDPE compounds were then extruded into a sheet by using the film blowing machine.

The NIR reflectances, the jetness L*and the undertone a*and b*of the black LDPE compounds were measured. The results were shown in Fig. 1 and Table 6.

Table 6

As can be seen from Fig. 1 and Table 6, in black PE -2#to black PE -5#, when the amount of the CB pigment was within the range of 0.01 to 0.08 wt%and the ratio of the CB pigment and the NIR reflective pigment is within the range of 1: 12 to 1: 100, the black polymer compound according the invention having NIR reflectance of at least 10%and the jetness L*of at most 27 could be provided, while the undertone a*and b*were substantially improved.

In black PE -6#, when the ratio of the CB pigment and the NIR reflective pigment is greater than 1: 12, for example, 1: 9, the black polymer had NIR reflectance of less than 10%, and thus could not be effectively sorted by the NIR sorting system.

In black PE -1#, when the amount of the CB pigment was less than 0.01 wt%, the jetness L*and the undertone a*and b*were not substantially improved, and thus the black polymer compound did not achieve good black coloring effect.

Example 2: black LDPE compounds with different kinds of CB pigments

In Example 2, the CB pigment of different kinds and LDPE as the base resin were mixed in the Banbury internal mixer to prepare the CB masterbatch (MB) , PBr29 (SPP 3080) as the NIR reflective pigment and LDPE as the base resin were mixed in the Banbury internal mixer to prepare the NIR reflective pigment masterbatch (MB) , and then CB masterbatch, the NIR reflective pigment masterbatch, and the base resin were dry blended and extruded twice by the SSE to prepare the black LDPE compounds. In the black LDPE compounds, the concentration of the pigment was 1 wt%, and the kind of the CB pigment and the ratio of the CB pigment and the NIR reflective pigment were shown in Table 7 and Fig. 2.

The NIR reflectances, the jetness L*and the undertone a*and b*of the black LDPE compounds were measured. The results were shown in Fig. 2 and Table 7.

Table 7

As can be seen from Fig. 2 and Table 7, when the amount of the CB pigment was within the range of 0.01 to 0.08 wt%, the black polymer compound according the invention having NIR reflectance of at least 10%and the jetness L*of at most 27 could be provided. Rather, when the amount of the CB pigment was greater than 0.08 wt%, the black polymer had NIR reflectance of less than 10%, and thus could not be effectively sorted by the NIR sorting system.

Further, from the result of Fig. 2, it was confirmed that when the carbon black used had the STSA of 10 to 50 m²/g, preferably 10 to 30 m²/g, and more preferably 10 to 20 m²/g, the iodine number of 10 to 50 g/kg, preferably 10 to 35 g/kg, and more preferably 10 to 20 g/kg, or both (Black Pearls 120, Black Pearls 2, and CSX 691, in particular, CSX 691) , better improvement in terms of the NIR reflectance of the black polymer compound could be achieved, which would contribute to the NIR sortability.

Example 3: black LDPE compounds with different kinds of pigments

In Example 3, CRX 4210 or CSX 691 as the CB pigment and LDPE as the base resin were mixed in the Banbury internal mixer to prepare the CB masterbatch (MB) , PBk33 as the NIR reflective pigment and LDPE as the base resin were mixed in the Banbury internal mixer to prepare the NIR reflective pigment masterbatch (MB) , and then CB masterbatch, the NIR reflective pigment masterbatch, and the base resin were dry blended and extruded twice by the SSE to prepare the black LDPE compounds. In the black LDPE compounds, the concentration of the pigment was 1 wt%, and the ratio of the CB pigment and the NIR reflective pigment was shown in Table 8 and Fig. 3.

The NIR reflectances, the jetness L*, and the undertone a*and b*of the black LDPE compounds were measured. The results were shown in Fig. 3 and Table 8.

Table 8

As can be seen from Fig. 3 and Table 8, use of the silicon treated carbon black (CRX4210) could achieve better improvement in terms of the NIR reflectance and/or the black coloring effect, as compared to use of the carbon black (CSX691) .

Example 4: black LDPE compounds with different kinds of NIR reflective pigments

In Example 4, CRX4210 as the CB pigment and LDPE as the base resin were mixed in the Banbury internal mixer to prepare the CB masterbatch (MB) , PBr29 (Sicopal Black K 0098) or TiO₂ as the NIR reflective pigment and LDPE as the base resin were mixed in the Banbury internal mixer to prepare the NIR reflective pigment masterbatch (MB) , and then CB masterbatch, the NIR reflective pigment masterbatch, and the base resin were dry blended and extruded twice by the SSE to prepare the black LDPE compounds. In the black LDPE compounds, the concentration of the pigment was 1 wt%, and the kind of the NIR reflective pigment and the ratio of the CB pigment and the NIR reflective pigment were shown in Table 9 and Fig. 4.

Further, as reference, black LDPE compounds with 0.1 wt%or 0.05 wt%of CRX4210 alone were prepared.

The NIR reflectances, the jetness L*and the undertone a*and b*of the black LDPE compounds were measured. The results were shown in Fig. 4 and Table 9. Also, photos of the black LDPE compounds in Example 4 were shown in Fig. 5.

Table 9

As can be seen from Fig. 4 and Table 9, when TiO₂ was used as the NIR reflective pigment, although it achieved improvement in terms of NIR reflectance, it did not achieve the jetness L*of less than or equal to 29.5, and thus did not achieve good black coloring effect.

Further, like in Example 1, it could be seen from the result of Fig. 4 that when the ratio of the CB pigment and the NIR reflective pigment is greater than 1: 12, for example, 1:9, the black polymer had NIR reflectance of less than 10%, and thus could not be effectively sorted by the NIR sorting system.

In addition, the NIR reflectances of the black LDPE compounds in Example 1 and Example 4 comprising the CB pigment and the NIR reflective pigment in the ratios of 1: 9 and 1: 19 were summarized and shown in Fig. 6, and the jetness L*and the undertone a*and b*of the black LDPE compounds in Example 1 and Example 4 comprising the CB pigment and the NIR reflective pigment in the ratios of 1: 9 and 1: 19 were summarized and shown in Fig. 7.

As can be seen from Figs. 6 and 7, use of the silicon treated carbon black (CRX4210) could achieve better improvement in terms of the NIR reflectance and/or the black coloring effect, as compared to use of the carbon black (CSX691) .

Example 5: black LDPE compounds with different concentrations of masterbatch

In Example 5, CSX691 as the CB pigment and PBr29 (Sicopal Black K 0098) as the NIR reflective pigment and LLDPE as the base resin were mixed in the Banbury internal mixer to prepare the CB containing NIR reflective masterbatch (MB) . In the CB containing NIR reflective MB, the ratio of the CB pigment and the NIR reflective pigment was 1: 19, and the total pigment content is 40 wt%and the rest component is LLDPE, the concentration of each component was shown in below Table 10.

Table 10

Then, the CB containing NIR reflective MB and the base resin were dry blended and extruded by the SSE to prepare the black LDPE compounds. In the black LDPE compounds, the ratio of the CB pigment and the NIR reflective pigment was 1: 19, and the concentration of the pigment was shown in Table 11.

The NIR reflectances of the black LDPE compounds were measured. The results were shown in Fig. 8.

The black LDPE compounds were also tested for the NIR sortability. The results were shown in Fig. 9 and Table 11.

Table 11

As can be seen from Figs. 8 and 9 and Table 11, when the amount of the CB pigment was greater than 0.08 wt%, the black LDPE compound was not NIR visible, although it still had the NIR reflectance of at least 10%.

It was confirmed that when the amount of the CB pigment was within the range of 0.01 to 0.08 wt%, the black LDPE compound was at least partially detectable in the NIR sorting system, and thus could effectively sorted by the NIR sorting system. Preferably, when the amount of the CB pigment was within the range of 0.02 to 0.04 wt%, in particular, 0.03 wt%, the black LDPE compound was completely visible in the NIR sorting system, and the sortability thereof was further improved.

Example 6: black PP compounds with different compositions of CB pigment and NIR reflective pigment

In Example 6, NIR reflective pigment PBr29 (Sicopal Black K 0098) and LLDPE as the base resin were mixed in the Banbury internal mixer to prepare the PBr29 masterbatch (MB-2#) . The compositions of the masterbatches were shows in Table 12. Then CB containing masterbatch PE MB-1#prepared under Example 5 or pure PBr29 MB (MB-2#) and PP as the base resin were dry blended and extruded by the SSE to prepare the black PP compounds. In the black PP compounds, the concentration of the pigment was shown in Table 13. In Fig. 10, the matsterbatch used was MB-1#prepared under Example 5.

The black PP compounds were then extruded by tape extruder into PP tape with thickness of about 500 μm.

The NIR reflectances, the jetness L*and the undertone a*and b*of the black PP compounds were measured. The results were shown in Fig. 10 and Table 13.

Table 12

Table 13

As can be seen from Fig. 10 and Table 13, when PP was used as the base resin, the black polymer compound according the invention having NIR reflectance of at least 10%and the jetness L*of at most 27 could be also provided.

Example 7: black PS compounds with different compositions of CB pigment and NIR reflective pigment

In Example 7, CSX 691 or Black Pearls 2 as the CB pigment and PBr29 (SPP-3080) as the NIR reflective pigment and GPPS N1841 as the base resin were compounded in the twin-screw extruder to prepare the CB containing masterbatch (MB) . The compositions of the masterbatches were shows in Table 14. Then CB containing masterbatch and GPPS 353 as the base resin were dry blended and extruded by the twin-screw extruder to prepare the black PS compounds. The compositions of the masterbatches were shows in Table 14. In the black PS compounds, the concentration of the pigment was shown in Table 15 and Fig. 11, and the ratio of the CB pigment and the NIR reflective pigment was shown in Table 15 and Fig. 11.

The black PS compounds were then injection molded by using the injection molded machine into a plaque.

The NIR reflectances, the jetness L*and the undertone a*and b*of the black PS compounds were measured. The results were shown in Fig. 11 and Table 15.

Table 14

Table 15

As can be seen from Fig. 11 and Table 15, when PS was used as the base resin, the black polymer compound according the invention having NIR reflectance of at least 10% and L*of at most 29.5, in particular in the range of 27.5 to 29, and prefererably a*of at most 1.9 and b*of at most 0.5 could be also provided.

Example 8: black PET compounds with different compositions of CB pigment and NIR reflective pigment

In Example 8, CSX 691 or BLACK PEARLS 2 as the CB pigment and PBr29 (SPP-3080) as the NIR reflective pigment and PET as the base resin were compounded in a twin-screw extruder to prepare the CB containing masterbatch (MB) . The compositions of the masterbatches were shows in Table 16. Then CB containing masterbatch and PET resin were dry blended and extruded by the twin-screw extruder to prepare the black PET compounds. The compositions of the masterbatches were shows in Table 16. In the black PET compounds, the concentration of the pigment was shown in Table 13 and Fig. 16, and the ratio of the CB pigment and the NIR reflective pigment was shown in Table 17 and Fig. 12.

The black PET compounds were then injection molded by using the injection molded machine into a plaque.

The NIR reflectances, the jetness L*and the undertone a*and b*of the black PET compounds were measured. The results were shown in Fig. 12 and Table 17.

Table 16

Table 17

As can be seen from Fig. 12 and Table 17, when PET was used as the base resin, the black polymer compound according the invention having NIR reflectance of at least 10%and L*of at most 29.5, in particular in the range of 27.5 to 29, and preferably a*of at most 1.9 and b*of at most 0.5 could be also provided.

While this invention has been described in connection with what is presently considered to be practical example embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

A black polymer compound for near infrared sorting comprising:

a base resin,

0.01 wt%to 0.08 wt%of an aggregated black pigment selected from carbon black, silica coated carbon black, and silicon treated carbon black,

a first pigment having near infrared reflectivity, and

optionally a second pigment, reinforcing filler, and additive,

wherein a ratio of the aggregated black pigment and all near infrared pigments in the polymer compound is from 1: 12 to 1: 100 by weight,

an NIR reflectance of the polymer compound is at least 10%in the wavelength range of from 1200 to 1500 nm, preferably from 1100 to 1500 nm, and more preferably from 1000 to 1500 nm and the polymer compound has L*of at most 29.5.
The black polymer compound of claim 1, wherein the aggregated black pigment is selected from silica coated carbon black and silicon treated carbon black, and preferably silicon treated carbon black.
The black polymer compound of claim 1 or 2, wherein the silicon treated carbon black is in the form of dual phase filler.
The black polymer compound of any of claims 1 to 3, wherein the first pigment having near infrared reflectivity is selected from a black or brown pigment, preferably selected from pigment brown 29, pigment black 33, and pigment black 30.
The black polymer compound of any of claims 1 to 4, wherein the ratio of the aggregated black pigment and all near infrared pigments in the polymer compound is from 1: 12 to 1: 100, for example, 1: 15 to 1: 30.
The black polymer compound of any of claims 1 to 5, wherein the amount of the aggregated black pigment is in the range of 0.02 to 0.07 wt%, based on the total weight of the black polymer compound.
The black polymer compound of any of claims 1 to 6, wherein the NIR reflectance of the polymer compound is in the range of 10%to 27%, for example in the range of 11%to 18%, and the polymer compound has L*of at most 27, and preferably in the range of 25 to 27.
The black polymer compound of any of claims 1 to 7, wherein the black polymer compound further comprises an additional pigment which does not absorb in the near infrared spectral range, preferably selected from blue pigment, brown pigment, and yellow pigment.
The black polymer compound of any of claims 1 to 8, wherein the black polymer compound further comprises a reinforcing filler, preferably selected from mica, graphite, and glass bead.
The black polymer compound of any of claims 1 to 9, wherein the black polymer compound further comprises an additive, preferably selected from an antioxidant, a dispersant, and a lubricant.
The black polymer compound of any of claims 1 to 10, wherein the base resin is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, polystyrene, polyethylene terephthalate, polypropylene, or polyvinyl chloride.
The black polymer compound of claim 11, wherein the base resin is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, or polypropylene, and the polymer compound has L*of at most 27, and preferably in the range of 25 to 27, or

the base resin is selected from the group consisting of polystyrene or polyethylene terephthalate, and the polymer compound has L*of at most 29, and preferably in the range of 27.5 to 29.
The black polymer compound of any of claims 1-12, wherein the carbon black has an STSA of 10 to 160 m²/g, an iodine number of 10 to 270 g/kg, or both, preferably the carbon black has the STSA of 10 to 50 m²/g, preferably 10 to 30 m²/g, and more preferably 10 to 20 m²/g, the iodine number of 10 to 50 g/kg, preferably 10-35 g/kg, more preferably 10-20 g/kg, or both.
The black polymer compound of any of claims 1-13, wherein the polymer compound has a*of at most 1.9, preferably at most 1.8, and more preferably at most 1.7, b*of at most 0.5, and preferably of at most 0.4, or both.