Halogen-free flame-retardant compositions with ethylene-alkyl acrylate copolymer, halogen-free flame retardant, and low-density polyethylene

Abstract

Embodiments are directed to a halogen-free flame retardant composition comprising, in relation to the total weight of the halogen-free flame retardant composition, 5 wt.% to 35 wt.% of ethylene-alkyl acrylate copolymer, 60 wt.% to 75 wt.% of halogen-free flame retardant, and 5 wt.% to 25 wt.% of low-density polyethylene (LDPE). The ethylene-alkyl acrylate copolymer comprises 8 wt.% to 35 wt.% alkyl acrylate, in relation to the total weight of the ethylene-alkyl acrylate copolymer, and a melt flow index (I2) of 1 gram per 10 minutes (g / 10 min) to 50 g / 10 min. The LDPE has a melt flow index (I2) of 1 g / 10 min to 50 g / 10 min. Further embodiments are directed to recycling processes for the halogen-free flame retardant composition.

Description

[0001] HALOGEN-FREE FLAME RETARDANT COMPOSITIONS WITH ETHYLENE-ALKYL ACRYLATE COPOLYMER, HALOGEN-FREE FLAME RETARDANT AND LOW-DENSITY POLYETHYLENE

[0002] TECHNICAL FIELD

[0003] [1] The embodiments described herein relate generally to halogen-free flame retardant compositions and relate specifically to halogen-free flame retardant compositions with ethylene-alkyl acrylate copolymer, halogen-free flame retardant and low-density polyethylene.

[0004] BACKGROUND

[0005] [2] Aluminum composite panels (ACPs) are rigid composite designs made of a polymer core bonded with adhesive bonding layers to aluminum surface sheets. ACPs are commonly used in exposed facade systems due to their insulating and aesthetic properties. This application in building and construction requires the inclusion of a flame-retardant core. Unfortunately, conventional flame-retardant cores, such as those containing ethyl vinyl acetate, can be energy-intensive to produce with relatively high screw torque. Furthermore, conventional flame-retardant cores may not retain the desired flame-retardant effect after recycling.

[0006] [3] Therefore, there is a need for improved halogen-free flame retardant compositions that reduce thyme torque, even after recycling, while maintaining the flame retardant effect.

[0007] SUMMARY

[0008] [4] The embodiments described herein satisfy this need by using a combination of ethylene-alkyl acrylate copolymer, halogen-free flame retardant, and low-density polyethylene. This resulted in a halogen-free flame retardant composition with reduced screw torque compared to a halogen-free flame retardant composition lacking an ethylene-alkyl acrylate copolymer, even after at least 5 recycling stages, while maintaining the flame retardant effect (e.g., a maximum effective heat of combustion that is less than 25% higher than the maximum effective heat of combustion of a first halogen-free flame retardant article).

[0009] [5] In one embodiment, a halogen-free flame retardant composition comprises, based on a total weight of the halogen-free flame retardant composition, 5 wt% to 35 wt% of ethylene-alkyl acrylate copolymer, 60 wt% to 75 wt% of halogen-free flame retardant, and 5 wt% to 25 wt% of low-density polyethylene (LDPE). The ethylene-alkyl acrylate copolymer comprises 8 wt% to 35 wt% of alkyl acrylate, based on a total weight of the ethylene-alkyl acrylate copolymer, and a melt flow index (I2) of 1 gram per 10 minutes (g / 10 min) to 50 g / 10 min. LDPE comprises a melt flow index (I2) of 1 g / 10 min to 50 g / 10 min.

[0010] [6] In another embodiment, a recycling process comprises heating a first halogen-free flame retardant article to a recycling temperature to form a first recyclable halogen-free flame retardant composition, extruding the heated recyclable first halogen-free flame retardant composition, and cooling the extruded recyclable first halogen-free composition to form a second halogen-free flame retardant article. The first halogen-free flame retardant article comprises ethylene-alkyl acrylate copolymer, halogen-free flame retardant, and low-density polyethylene (LDPE). The second halogen-free flame retardant article differs from the first halogen-free flame retardant article and comprises the ethylene-alkyl acrylate copolymer, the halogen-free flame retardant, and the LDPE.

[0011] [7] Additional features and advantages will be set forth in the detailed description that follows, and some will be readily apparent to those skilled in the art from that description or recognized through the practice of the embodiments described herein, including the detailed description that follows and the claims.

[0012] [8] It should be understood that both the above general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] [9] The following detailed description of specific embodiments of the present description may be better understood when read in conjunction with the following drawings, where similar structure is indicated by similar reference numbers.

[0010] FIG. 1 is a schematic representation of a composite panel, according to the embodiments described in this description.

[0015]

[0011] Reference will now be made in detail to several realizations, some of which are illustrated in the accompanying drawings.

[0016] DETAILED DESCRIPTION

[0017]

[0012] Specific embodiments of this application will be described below. These embodiments are provided in such a way that this description will be exhaustive and complete and will fully convey the scope of the subject matter to those skilled in the art. The terminology as set forth herein is for the description of the embodiments only and should not be construed as limiting the scope of the description as a whole.

[0018]

[0013] DEFINITIONS

[0019]

[0014] Unless otherwise stated, implied in the context or customary in the art, all test methods are current as of the date of submission of this description.

[0020]

[0015] Intervals may be expressed herein as from "approximately" a particular value and / or to "approximately" another particular value. When such an interval is expressed, another realization includes from one particular value and / or to the other particular value. Similarly, when values ​​are expressed as approximations, by using the antecedent "approximately," the particular value is understood to form another realization. It is further understood that the endpoints of each interval are significant both in relation to and independently of the other endpoint.

[0021]

[0016] The terms "comprising," "including," "having," and their derivatives are not intended to exclude the presence of any additional component, step, or process, whether or not specifically described. For the avoidance of doubt, all compositions claimed by using the term "comprising" may include any additive, adjuvant, or additional compound, whether polymeric or otherwise, unless otherwise stated. Conversely, the expression "consisting essentially of" excludes from the scope of any subsequent enumeration any other component, step, or process, except those not essential to operability. The expression "consisting of" excludes any component, step, or process that is not specifically defined or stated.

[0017] The quantity of a component (e.g.The percentage of the halogen-free flame retardant composition (ethylene-alkyl acrylate copolymer, halogen-free flame retardant, low-density polyethylene, polyethylene grafted with maleic anhydride and calcium carbonate) in the halogen-free flame retardant composition is provided herein as a weight percentage (% wt), based on the total weight of the halogen-free flame retardant composition, unless otherwise stated.

[0022]

[0018] The term "polymer", as used herein, refers to a polymeric compound prepared by catalytic reaction (i.e., polymerization) of at least two monomers, whether of the same or different type.

[0023]

[0019] Therefore, the generic term polymer encompasses the term "homopolymer," which refers to a polymer prepared from a single type of monomer, as well as "copolymer," which refers to a polymer prepared from two or more different monomers. The term "interpolymer," as used herein, refers to a polymer prepared by the polymerization of at least two different types of monomers. Therefore, the generic term interpolymer includes a copolymer or polymer prepared from more than two different types of monomers, such as terpolymers.

[0024]

[0020] The term "article," as used herein, refers to a halogen-free flame retardant composition for recycling. The term "recycling," as used herein, refers to a process comprising the steps of heating, extruding, and cooling a halogen-free flame retardant composition. This includes a halogen-free flame retardant composition comprising ethylene-alkyl acrylate copolymer, halogen-free flame retardant, and low-density polyethylene.

[0025]

[0021] "Polyethylene" or "ethylene-based polymer," as used herein, refers to polymers comprising more than 50% by weight of units derived from the monomer ethylene, based on the total weight of the polymer. This includes ethylene-based homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of ethylene-based polymers known in the art include, but are not limited to, low-density polyethylene (LDPE); linear low-density polyethylene (LLDPE); recycled low-density polyethylene (rLDPE); ultra-low-density polyethylene (ULDPE); very low-density polyethylene (VLDPE); single-site catalyzed linear low-density polyethylene, including both linear and substantially linear low-density resins (m-LLDPE); medium-density polyethylene (MDPE); and high-density polyethylene (HDPE).

[0026]

[0022] "Ethylene-alkyl acrylate copolymer" or "ethyl-alkyl acrylate copolymer," as used herein, refers to polymers comprising at least 8 wt% of acrylate monomer-derived units, based on the total weight of the copolymer. This includes homopolymers or ethylene-based copolymers (meaning units derived from two or more comonomers). Common forms of ethylene-alkyl acrylate polymers known in the art include, but are not limited to, ethylene-ethyl acrylate copolymer (EEA), n-butyl ethylene-acrylate (EnBA), and ethylene-methyl acrylate copolymer (EMA).

[0027]

[0023] The expressions "similar halogen-free flame retardant composition" and "similar halogen-free flame retardant article", as used herein, refer to a composition or article that lacks an ethylene-alkyl acrylate copolymer and has a similar melt flow index (I2).

[0028]

[0024] The expression "that maintains the flame retardant effect", as used herein, refers to a recycled article (e.g., the sixth article) that has a maximum effective heat of combustion that is less than 25% greater than the maximum effective heat of combustion of a first halogen-free flame retardant article.

[0029]

[0025] REALIZATIONS

[0030]

[0026] The embodiments of the present description are directed to a halogen-free flame retardant composition comprising ethylene-alkyl acrylate copolymer, halogen-free flame retardant and LDPE.

[0031]

[0027] Ethylene-alkyl acrylate copolymer

[0032]

[0028] The ethylene-alkyl acrylate copolymer imparts reduced torque, even after recycling, while maintaining its flame-retardant effect. The ethylene-alkyl acrylate copolymer can also impart desirable mechanical properties, such as tensile strength and elongation at break.

[0033]

[0029] Non-limiting examples of suitable ethylene-alkyl acrylate copolymers may include ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, ethylene-methacrylic acid copolymers, ethylene-acrylate copolymers of (ethyl, methyl, butyl, n-butyl, 2-ethylhexyl) or combinations thereof. In embodiments, the ethylene-alkyl acrylate copolymer may be ethylene-based and may include ethylene and methyl acrylate.

[0030] In embodiments, the ethylene-alkyl acrylate copolymer may comprise ethylene-methyl acrylate copolymer.

[0034]

[0031] In embodiments, the halogen-free flame retardant compositions described herein may include from 5 wt% to 35 wt% of ethylene-alkyl acrylate copolymer comprising a melt flow index (I2) of 1 gram per 10 minutes (g / 10 min) to 50 g / 10 min and from 8 wt% to 35 wt% of alkyl acrylate, based on a total weight of the ethylene-alkyl acrylate copolymer.

[0035]

[0032] The halogen-free flame retardant composition may comprise a minimum amount of ethylene-alkyl acrylate copolymer (e.g., 5 wt. or greater) so that the halogen-free flame retardant compositions achieve a desired reduced torque. The amount of ethylene-alkyl acrylate copolymer may be limited (e.g., 35 wt. or less) to ensure that other components can be included to impart the desired properties. Accordingly, in embodiments, the halogen-free flame retardant compositions may include from 5 wt. to 35 wt. of the ethylene-alkyl acrylate copolymer. For example, in embodiments, the amount of ethylene-alkyl acrylate copolymer in the halogen-free flame retardant composition can be from 5% to 35% by weight, from 5% to 30% by weight, from 5% to 25% by weight, from 5% to 20% by weight, from 5% to 15% by weight,from 5% by weight to 13% by weight; from 5% by weight to 11% by weight; from 7% by weight to 35% by weight, from 7% by weight to 30% by weight, from 7% by weight to 25% by weight, from 7% by weight to 20% by weight, from 7% by weight to 15% by weight, from 7% by weight to 13% by weight, from 7% by weight to 11% by weight, from 9% by weight to 35% by weight; from 9% by weight to 30% by weight, from 9% by weight to 25% by weight, from 9% by weight to 20% by weight, from 9% by weight to 15% by weight; from 9% by weight to 13% by weight; from 9% by weight to 11% by weight; from 11% by weight to 35% by weight, from 11% by weight to 30% by weight, from 11% by weight to 25% by weight, from 11% by weight to 20% by weight, from 11% by weight to 15% by weight, or even from 11% by weight to 13% by weight, based on the total weight of the halogen-free flame retardant composition.

[0036]

[0033] The ethylene-alkyl acrylate copolymer may comprise a minimum amount of ethylene (e.g., greater than or equal to 65 wt.) so that the halogen-free flame compositions achieve the desired hydrophobicity. Accordingly, in embodiments, the ethylene-alkyl acrylate copolymer may include from 65 wt. to 80 wt. of ethylene. For example, in embodiments, the amount of ethylene in the ethylene-alkyl acrylate copolymer can be 65% to 80% by weight, 65% to 75% by weight, 65% to 70% by weight, 70% to 85% by weight, 70% to 80% by weight, 70% to 75% by weight, or 75% to 80% by weight of ethylene, based on the total weight of the ethylene-alkyl acrylate copolymer.

[0037]

[0034] The ethylene-alkyl acrylate copolymer may comprise a minimum amount of copolymerized alkyl acrylate (e.g., 8 wt. or greater) so that halogen-free flame compositions achieve improved processability, charge acceptance, and the required flame-retardant effect. Accordingly, in embodiments, the ethylene-alkyl acrylate copolymer may include from 8 wt. to 35 wt. of copolymerized alkyl acrylate.For example, in embodiments, the amount of copolymerized alkyl acrylate in the ethylene-alkyl acrylate copolymer can be from 8% to 35% by weight, from 8% to 30% by weight, from 8% to 25% by weight, from 10% to 35% by weight, from 10% to 30% by weight, from 10% to 30% by weight, from 10% to 25% by weight, from 15% to 35% by weight, from 15% to 30% by weight, from 15% to 25% by weight, from 20% to 35% by weight, from 20% to 30% by weight, from 20% to 25% by weight, from 25% to 35% by weight, from 25% to 30% by weight, or from 30% to 35% by weight, based on the total weight of the copolymer.

[0038]

[0035] The ethylene-alkyl acrylate copolymer may comprise a minimum melt flow index (e.g., greater than or equal to 1 g / 10 min) to minimize energy consumption, mixing time, and to ensure proper mixing with the feed. The melt flow index of the ethylene-alkyl acrylate copolymer may be limited (e.g., less than or equal to 50 g / 10 min) to permit extrusion of the halogen-free flame retardant composition.Therefore, in embodiments, the ethylene-alkyl acrylate copolymer can have a melt flow index of 1 g / 10 min to 50 g / 10 min, from 1 g / 10 min to 40 g / 10 min, from 1 g / 10 min to 30 g / 10 min, from 1 g / 10 min to 20 g / 10 min, from 1 g / 10 min to 10 g / 10 min, from 1 g / 10 min to 5 g / 10 min, from 5 g / 10 min to 50 g / 10 min, from 5 g / 10 min to 40 g / 10 min, from 5 g / 10 min to 30 g / 10 min, from 5 g / 10 min to 20 g / 10 min, from 5 g / 10 min to 10 g / 10 min, from 10 g / 10 min to 50 g / 10 min, from 10 g / 10 min to 40 g / 10 min, 10 g / 10 min to 30 g / 10 min, 10 g / 10 min to 20 g / 10 min, 20 g / 10 min to 50 g / 10 min, 20 g / 10 min to 40 g / 10 min, or 20 g / 10 min to 30 g / 10 min.

[0039]

[0036] In embodiments, the ethylene-alkyl acrylate copolymer can have a density of 0.920 grams per cubic centimeter (g / cm³). 3 ) at 0.960 g / cm 3 , of 0.920 g / cm 3 at 0.950 g / cm 3 , of 0.930 g / cm 3 at 0.960 g / cm 3 , of 0.930 g / cm 3 at 0.950 g / cm3 , of 0.940 g / cm 3 at 0.960 g / cm 3 , or 0.940 g / cm 3 at 0.950 g / cm 3 , measured according to ASTM D1238.

[0037] Several commercial embodiments are considered suitable. For example, suitable ethylene-alkyl acrylate copolymers may be commercially available from The Dow Chemical Company under the brand name ELVALOY™ AC, such as Class 1330 and 12024S ethylene-methyl acrylate copolymers, Class 2116 and 22534 ethylene-ethyl acrylate copolymers, and Class 3117 and 3427 ethylene-butyl acrylate copolymers.

[0040]

[0038] Halogen-free flame retardants

[0041]

[0039] The halogen-free flame retardant imparts a desired flame retardant effect.

[0042]

[0040] The halogen-free flame retardant composition may comprise a minimum amount of halogen-free flame retardant (e.g., greater than or equal to 60% by weight) so that the halogen-free flame retardant compositions achieve the desired flame retardant effect and fire resistance class. The amount of halogen-free flame retardant may be limited (e.g., less than or equal to 75% by weight) to achieve a desired screw torque, improved processability, and to ensure that other components can be included to impart the desired properties.

[0043]

[0041] Accordingly, in embodiments, halogen-free flame retardant compositions may include from 60% by weight to 75% by weight of the halogen-free flame retardant. For example, in embodiments, the amount of halogen-free flame retardant in the composition may be 60% to 75% by weight, 60% to 73% by weight, 60% to 70% by weight, 63% to 75% by weight, 63% to 73% by weight, 63% to 70% by weight, 65% to 75% by weight, 65% to 73% by weight, 65% to 70% by weight, 67% to 75% by weight, 67% to 73% by weight, or 67% to 70% by weight of halogen-free flame retardant, based on the total weight of the halogen-free flame retardant composition.

[0044]

[0042] In embodiments, the halogen-free flame retardant described herein may include a metal hydroxide. In some embodiments, the metal hydroxide comprises at least one of an alkali metal, an alkaline earth metal, aluminum, or combinations thereof. In further embodiments, the alkaline earth metal comprises sodium, potassium, or combinations thereof. The alkaline earth metal may contain magnesium, calcium, or combinations thereof. In embodiments, the halogen-free flame retardant may contain magnesium hydroxide.

[0043] In embodiments, the halogen-free flame retardant may comprise a dso of 1.6 pm to 2.0 pm. In embodiments, the halogen-free flame retardant may comprise a dso of 1.6 pm to 2.0 pm (e.g., 1.6 pm to 1.9 pm, 1.6 pm to 1.8 pm, or 1.6 pm to 1.7 pm).

[0045]

[0044] In embodiments, the halogen-free flame retardant may comprise a dgo of 2.4 pm to 4.4 pm, 2.4 pm to 4.0 pm, 2.4 pm to 3.4 pm, 2.4 pm to 3.0 pm, 3.0 pm to 4.4 pm, 3.0 pm to 4.0 pm, 3.0 pm to 3.4 pm, 3.4 pm to 4.4 pm, or 4.0 pm to 4.4 pm.

[0046]

[0045] In some embodiments, the nanoparticle dispersion may include magnesium or hydroxide nanoparticles having a specific BET surface area of ​​4 square meters per gram (m²). 2 / g) at 6 m 2 / g. As used herein, the term "specific surface area" may refer to the surface area of ​​the magnesium / hydroxide nanoparticles as measured by ASTM D-1993. In some embodiments, the metal hydroxide nanoparticles may have a specific surface area BET of 4 m². 2 / ga 6 m 2 / g, of 4 m 2 / ga 5 m 2 / g, or 5 m 2 / ga 6 m 2 / g.

[0047]

[0046] Several commercial embodiments are considered suitable. For example, suitable halogen-free flame retardants may be commercially available from Huber Engineered Materials under the MANIFIN® brand, such as H-5 class magnesium hydroxide.

[0048]

[0047] Low-density polyethylene (LDPE)

[0049]

[0048] LDPE imparts processability to halogen-free flame retardant compositions.

[0050]

[0049] Non-limiting examples of suitable low-density polyethylenes include linear low-density polyethylene (LLDPE); recycled low-density polyethylene (rLDPE); ultra-low-density polyethylene (ULDPE); very low-density polyethylene (VLDPE); single-site catalyzed linear low-density polyethylene, including linear and substantially linear low-density resins (m-LLDPE); and combinations thereof.

[0051]

[0050] In embodiments, low-density polyethylene may comprise post-consumer recycled ethylene. In specific embodiments, low-density polyethylene may comprise rLDPE.

[0052]

[0051] In embodiments, the halogen-free flame retardant compositions described herein may include, based on a total weight of ethylene-alkyl acrylate copolymer, from 5 wt% to 25 wt% of low-density polyethylene comprising a melt flow index (I2) of 1 gram per 10 minutes (g / 10 min) to 50 g / 10 min.

[0053]

[0052] Halogen-free flame retardant compositions may comprise a minimum amount of low-density polyethylene (e.g., 5 wt. or greater) so that the halogen-free flame retardant compositions achieve the desired processability. The amount of low-density polyethylene in the halogen-free flame retardant composition may be limited (e.g., 25 wt. or less) to maintain filler acceptance and flame retardant effect and to ensure that other components can be included to impart the desired properties. Accordingly, in embodiments, halogen-free flame retardant compositions may include from 5 wt. to 25 wt. of low-density polyethylene, based on the total weight of the halogen-free flame retardant composition.For example, in some embodiments, the amount of low-density polyethylene in the composition may be from 5% to 25% by weight, from 5% to 20% by weight, from 5% to 15% by weight, from 10% to 25% by weight, from 10% to 20% by weight, from 10% to 15% by weight, from 15% to 25% by weight, or from 15% to 20% by weight, based on the total weight of the halogen-free flame retardant composition.

[0054]

[0053] Low-density polyethylene may comprise a minimum amount of recycled low-density polyethylene (e.g., greater than or equal to 50% by weight). Accordingly, in embodiments, low-density polyethylene may include from 50% to 100% by weight of recycled low-density polyethylene, based on the total weight of the low-density polyethylene. For example, in some embodiments, the amount of recycled low-density polyethylene in the low-density polyethylene may be 50% by weight to 100% by weight, 50% by weight to 75% by weight, 50% by weight to 60% by weight, 60% by weight to 100% by weight, 60% by weight to 75% by weight, 70% by weight to 100% by weight, 70% by weight to 75% by weight, 80% by weight to 100% by weight, or 90% by weight to 100% by weight, based on the total weight of the low-density polyethylene.

[0055]

[0054] In embodiments, low-density polyethylene can have a melt flow index of 1 g / 10 min to 50 g / 10 min, from 1 g / 10 min to 40 g / 10 min, from 1 g / 10 min to 30 g / 10 min, from 1 g / 10 min to 20 g / 10 min, from 1 g / 10 min to 10 g / 10 min, from 1 g / 10 min to 5 g / 10 min, from 5 g / 10 min to 50 g / 10 min, from 5 g / 10 min to 40 g / 10 min, from 5 g / 10 min to 30 g / 10 min, from 5 g / 10 min to 20 g / 10 min, from 5 g / 10 min to 10 g / 10 min, from 10 g / 10 min to 50 g / 10 min, from 10 g / 10 min to 40 g / 10 min, 10 g / 10 min to 30 g / 10 min, 10 g / 10 min to 20 g / 10 min, 20 g / 10 min to 50 g / 10 min, 20 g / 10 min to 40 g / 10 min, or 20 g / 10 min to 30 g / 10 min.

[0055] In some embodiments, recycled low-density polyethylene may comprise a melt flow index (MFI) of 0.3 g / 10 min to 3 g / 10 min, 0.3 g / 10 min to 2.5 g / 10 min, 0.3 g / 10 min to 2 g / 10 min, 0.3 g / 10 min to 1.5 g / 10 min, 0.3 g / 10 min to 1 g / 10 min, 0.3 g / 10 min to 0.5 g / 10 min, 0.4 g / 10 min to 3 g / 10 min, 0.4 g / 10 min to 2.5 g / 10 min, 0.4 g / 10 min to 2 g / 10 min, 0.4 g / 10 min to 1.5 g / 10 min, 0.4 g / 10 min to 1 g / 10 min, 0.4 g / 10 min to 0.5 g / 10 min, 0.5 g / 10 min to 3 g / 10 min, 0.5 g / 10 min to 2.5 g / 10 min, 0.5 g / 10 min to 2 g / 10 min, 0.5 g / 10 min to 1.5 g / 10 min, 0.5 g / 10 min to 1 g / 10 min, from 1 g / 10 min to 3 g / 10 min, from 1 g / 10 min to 2.5 g / 10 min, from 1 g / 10 min to 2 g / 10 min, from 1 g / 10 min to 1.5 g / 10 min, from 1.5 g / 10 min to 3 g / 10 min, from 1.5 g / 10 min to 2.5 g / 10 min, from 1.5 g / 10 min to 2 g / 10 min, 2 g / 10 min to 3 g / 10 min, 2 g / 10 min to 2.5 g / 10 min, or even 2.5 g / 10 min to 3 g / 10 min.

[0056]

[0056] In embodiments, low-density polyethylene can have a density of 0.916 grams per cubic centimeter (g / cm³). 3 ) at 0.928 g / cm 3 , such as 0.917 g / cm 3 at 0.927 g / cm 3 , of 0.918 g / cm 3 at 0.926 g / cm 3 , or 0.920 g / cm 3 at 0.924 g / cm 3 .

[0057]

[0057] Several commercial embodiments are considered suitable. For example, suitable low-density polyethylene may be commercially available from The Dow Chemical Company under the brand name DOW™ LDPE, such as Class 352E and 780E low-density polyethylene.

[0058]

[0058] Polyethylene grafted with maleic anhydride (MAH-g)

[0059]

[0059] In embodiments, halogen-free flame retardants may further comprise MAH-g to improve the adhesion and mechanical properties of aluminum composite panels.

[0060]

[0060] Non-limiting examples of suitable maleic anhydride-grafted polyethylene may be an ethylene-based polymer with a maleic anhydride graft monomer grafted thereon. Suitable ethylene-based polymers for maleic anhydride-grafted polyolefin include, without limitation, polyethylene homopolymers and copolymers with α-olefins. In embodiments, the maleic anhydride-grafted polyethylene may comprise one or more of a maleic anhydride-grafted linear low-density polyethylene (LLDPE), a maleic anhydride-grafted polyethylene elastomer, or a combination thereof.

[0061]

[0061] In embodiments, the halogen-free flame retardant compositions described herein may include, based on the total weight of the halogen-free flame retardant composition, from 1 wt% to 5 wt% of a maleic anhydride-grafted polyethylene comprising a melt flow index (I2) of 0.5 g / 10 min to 10 g / 10 min, and wherein the maleic anhydride-grafted polyethylene comprises from 0.5 wt% to 2.5 wt% of maleic anhydride based on the total weight of the maleic anhydride-grafted polyethylene.

[0062]

[0062] The halogen-free flame retardant composition may comprise a minimal amount of MAH-g (e.g., greater than or equal to 1 wt.%) so that the halogen-free flame retardant compositions are recyclable and so that the fillers can be homogeneously dispersed in the core to provide the desired flame retardant properties. The amount of MAH-g may be limited (e.g., less than or equal to 5 wt.%) to ensure the processability of the composition with respect to viscosity. In halogen-free flame retardant compositions comprising more than 5 wt.% of MAH-g, the MAH-g may react with the halogen-free flame retardant (e.g., magnesium hydroxide) to generate a product with a higher viscosity, which may be undesirable; therefore, the amount of MAH-g used in the halogen-free flame retardant composition may be limited.Therefore, in embodiments, halogen-free flame retardant compositions may include from 1 wt% to 5 wt% of MAH-g. For example, in embodiments, the amount of the copolymer in the composition may be from 1 wt% to 5 wt%, from 1 wt% to 3 wt%, 1 wt% to 2 wt%, from 2 wt% to 5 wt%, from 2 wt% to 3 wt%, or from 3 wt% to 5 wt%, based on the total weight of the halogen-free flame retardant composition.

[0063]

[0063] Maleic anhydride grafted polyethylene may contain a minimum amount of maleic anhydride graft monomer (e.g., greater than or equal to 0.5 wt%) to ensure filler compatibility with the polymer matrix. Accordingly, in embodiments, halogen-free flame retardant compositions may include from 0.5 wt to 2.5 wt of the maleic anhydride graft monomer. For example, in embodiments, the amount of maleic anhydride in the composition may be from 0.5 wt to 2.5 wt, from 0.5 wt to 2.0 wt, from 0.5 wt to 1.5 wt, from 0.5 to 1.0 wt, from 1.0 wt to 2.5 wt, from 1.0 wt to 2.0 wt, from 1.0 wt to 1.5 wt, or from 1.5 wt to 2.0 wt of the maleic anhydride graft monomer, based on the total weight of the halogen-free flame retardant composition.

[0064]

[0064] In embodiments, the polyethylene grafted with maleic anhydride can have a melt flow index of 0.5 g / 10 min to 10 g / 10 min, 0.5 g / 10 min to 8 g / 10 min, or 0.5 g / 10 min to 5 g / 10 min, 0.5 g / 10 min to 3 g / 10 min, 0.5 to 2 grams per 10 minutes (g / 10 min), 1 g / 10 min to 10 g / 10 min, 1 g / 10 min to 8 g / 10 min, 1 g / 10 min to 5 g / 10 min, 1 g / 10 min to 3 g / 10 min, 1.75 g / 10 min to 10 g / 10 min, 1.75 g / 10 min to 5 g / 10 min, or 1.75 g / 10 min to 3 g / 10 min, determined according to ASTM D1238 at 190 °C and 2.16 kg. In some embodiments, the polyethylene grafted with maleic anhydride comprises a melt flow index of 1.0 g / 10 min to 2.0 g / 10 min.

[0065]

[0065] In further embodiments, the polyethylene grafted with maleic anhydride may comprise a density of 0.920 g / cm³ 3 at 0.940 g / cm 3 , of 0.925 g / cm 3 at 0.935 g / cm 3 , of 0.920 g / cm 3 at 0.930 g / cm 3 , or 0.930 g / cm 3at 0.940 g / cm 3 .

[0066]

[0066] Several commercial embodiments are considered suitable. For example, suitable maleic anhydride-grafted polyethylenes may be commercially available from The Dow Chemical Company under the FUSABOND™ brand, such as maleic anhydride-grafted polyethylene of classes E528, E226, and E528, and maleic anhydride-grafted ethylene copolymer of class N525.

[0067]

[0067] Fillers - Calcium Carbonate (CaCCh)

[0068]

[0068] Halogen-free flame retardant compositions, as described herein, may further comprise components that may be collectively referred to herein as "fillers." Non-limiting examples of suitable fillers may include inorganic fillers, talc, calcium carbonate, chalk, calcium sulfate, clay, kaolin, silica, glass, fumed silica, mica, wollastonite, feldspar, aluminum silicate, calcium silicate, alumina, hydrated alumina such as alumina trihydrate, glass microspheres, ceramic microspheres, thermoplastic microspheres, barite, wood flour, glass fibers, carbon fibers, marble dust, cement dust, magnesium oxide, antimony oxide, zinc oxide, barium sulfate, titanium dioxide, titanates, and combinations thereof. Inorganic fillers may include anhydrous inorganic fillers or at least a majority of anhydrous inorganic fillers (by weight).In some formulations, the charge may contain calcium carbonate.

[0069]

[0069] Calcium carbonate can be used to limit the amount of flammable components in a halogen-free flame retardant composition. Calcium carbonate can also be added to a halogen-free flame retardant composition to achieve price competitiveness in the compound.

[0070]

[0070] In embodiments, the halogen-free flame retardant composition may include from 0% by weight to 30% by weight of calcium carbonate, based on the total weight of the halogen-free flame retardant composition.

[0071] The halogen-free flame retardant composition may comprise a minimal amount of calcium carbonate (e.g., greater than or equal to 0% by weight). The amount of calcium carbonate may be limited (e.g., less than or equal to 30% by weight). Accordingly, in embodiments, halogen-free flame retardant compositions may include from 0% to 30% by weight of calcium carbonate.For example, in embodiments, the amount of calcium carbonate in the composition may be from 0% to 30% by weight, from 0% to 25% by weight, from 0% to 20% by weight, from 0% to 15% by weight, from 5% to 30% by weight, from 5% to 25% by weight, from 5% to 20% by weight, from 5% to 15% by weight, from 10% to 30% by weight, from 10% to 25% by weight, from 10% to 20% by weight, from 10% to 15% by weight, from 15% to 30% by weight, from 15% to 25% by weight, or from 15% to 20% by weight of calcium carbonate, based on the weight total of the halogen-free flame retardant composition.

[0071]

[0072] In realizations, calcium carbonate can comprise a dso of 1.0 pm to 2.0 pm.

[0072]

[0073] In realizations, calcium carbonate can comprise a dgo of 4.0 pm to 6.0 pm.

[0073]

[0074] In practical applications, calcium carbonate can have a specific surface area of ​​3 square meters per gram (m²). 2 / g) at 5 m 2 / g, of 3 m 2 / ga 4 m 2 / g, or 4 m 2 / ga 5 m 2 / g.

[0074]

[0075] In some embodiments, the filler may comprise a surface coating. In specific embodiments, the calcium carbonate may comprise a surface coating.

[0075]

[0076] Not being limited by theory, halogen-free flame retardant compositions comprising MAH-g as described herein may comprise uncoated CaCCh to achieve lower costs of the halogen-free flame retardant composition without compromising the desired performance of the charge.

[0076]

[0077] Several commercial realizations are considered suitable. For example, suitable fillers may be commercially available from Omya under the brand name OMYAFILM, such as Class 753 calcium carbonate.

[0077]

[0078] Additives

[0078]

[0079] Additives can improve the performance, compatibility, and stability of halogen-free flame retardant compositions.

[0080] Halogen-free flame retardant compositions, as described herein, may further comprise one or more optional components, which may be collectively referred to herein as "additives." Non-limiting examples of suitable additives include antioxidants, coupling agents, synergistic agents, polymer processing aids (PPAs), waxes, grafting initiators, crosslinking catalysts, blowing agents, blowing agent activators (e.g., zinc oxide, zinc stearate, and the like), co-agents (e.g., trialyl cyanurate), plasticizers, processing oils, carbon black, colorants or pigments, stability control agents, nucleating agents, acid scavengers, ultraviolet (UV) stabilizers, lubricants, extrusion aids, and combinations thereof.When present, the total amount of additive can be from 0% by weight to 2.0% by weight of additives, based on the total weight of the halogen-free flame retardant composition. For example, in embodiments, the amount of additives in the composition may be from 0% by weight to 2.0% by weight, from 0% by weight to 1.5% by weight, from 0% by weight to 1.0% by weight, from 0% by weight to 0.5% by weight, from 0.5% by weight to 2.0% by weight, from 0.5% by weight to 1.5% by weight, from 0.5% to 1.0% by weight, from 1.0% by weight to 2.0% by weight, from 1.0% by weight to 1.5% by weight, from 1.5% by weight to 2.0% by weight of the additives, or any and all sub-intervals formed from these endpoints, based on the total weight of the halogen-free flame retardant composition.

[0079]

[0081] In embodiments, halogen-free flame retardant compositions may further comprise antioxidants, coupling agents, synergistic agents, polymer processing aids, waxes, or combinations thereof.

[0080]

[0082] In some embodiments, the halogen-free flame retardant composition may include an antioxidant. While not limited by theory, it is believed that antioxidants can be used to help prevent the oxidative degradation of polymers, extending the material's service life. Non-limiting examples of suitable antioxidants include compounds comprising phenol, phosphorus, and any combination thereof. Several commercial embodiments are considered suitable. For example, suitable antioxidants may be commercially available from BASF under the Irganox® brand, such as antioxidants in classes 1010, MD 1024, and 1076, or under the Irgafos brand, such as the class 168 antioxidant.

[0081]

[0083] In some embodiments, the halogen-free flame retardant composition may include a coupling agent. The coupling agent can act to improve adhesion between different phases in a composite material, such as between the polymer matrix and fillers or reinforcements, and to mitigate phase separation of the components in the corrosion inhibitor formulation. The risk of phase separation can be particularly acute in environments with a wide temperature range. Non-limiting examples of suitable coupling agents include organofunctional silanes, fatty acids, fatty acid salts, and combinations thereof. Several commercial embodiments are considered suitable. For example, suitable silane coupling agents may be commercially available from The Dow Chemical Company under the brand name XIAMETER™, such as the OFS-6341 Silane and OFS-6665 Silane coupling agents.

[0082]

[0084] In some embodiments, the halogen-free flame retardant composition may include a synergistic agent. Synergistic agents can enhance the effectiveness of flame retardants or other additives, allowing for improved flame resistance at lower concentrations of these agents. While not limited by theory, it is believed that the synergistic agent adsorbs onto a metal surface while simultaneously attracting an active component comprising a quaternary ammonium or pyridinium substituent. Non-limiting examples of suitable synergistic agents include compounds comprising silicon (e.g., organosilicon and organofunctional siloxane polymers), nitrogen (e.g., triazine), phosphoric acid (e.g., ammonium polyphosphate), and combinations thereof.

[0083]

[0085] In some embodiments, the halogen-free flame retardant composition may include a polymer processing aid. Polymer processing aids (PPAs), or processing aids, are often used for their flame-retardant properties. They can improve the thermal stability of polymers and promote char formation during combustion, which helps insulate the underlying material from heat. Furthermore, polymer processing aids can provide a balance of thermal and mechanical properties, making them valuable for applications requiring both flame resistance and structural integrity. Several commercial embodiments are considered suitable. For example, suitable processing aids may be commercially available from Struktol under the Struktol® brand, such as W33 class dispersant and processing flakes.

[0084]

[0086] In some applications, the halogen-free flame retardant composition may include a wax. Waxes can improve flow characteristics in processes such as extrusion and injection molding, leading to smoother operation and better surface finishes.

[0085]

[0087] Composite panel

[0086]

[0088] The halogen-free flame retardant compositions described herein can be used in various applications, such as composite panels for, for example, the facade of a building.

[0087]

[0089] Referring now to the embodiment of FIG. 1, the composite panel (100) may include a first metallic layer (110); a second metallic layer (110), a central layer (130) disposed between the first metallic layer (110) and the second metallic layer (110), a first bonding layer (120) disposed between the first metallic layer (110) and the central layer (130); and a second bonding layer (120) disposed between the second metallic layer (110) and the central layer (130).

[0088]

[0090] In embodiments, the first metallic layer (100), the second metallic layer (200), or both may include aluminum, stainless steel, painted steel, titanium, copper, zinc, or combinations thereof. In embodiments, the first metallic layer (100) and the second metallic layer (200) comprise aluminum.

[0089]

[0091] In embodiments, the first metallic layer, the second metallic layer, or both may have a width of 0.2 mm to 0.5 mm. For example, in embodiments, the first metallic layer, the second metallic layer, or both may have a width of 0.2 mm to 0.5 mm, 0.2 mm to 0.4 mm, 0.2 mm to 0.3 mm, 0.3 mm to 0.5 mm, 0.3 mm to 0.4 mm, or 0.4 mm to 0.5 mm.

[0090]

[0092] In some embodiments, the adhesive bonding layers may include one or more adhesive resins. In other embodiments, the adhesive bonding layers may include an anhydride-modified polymer. Based on the manufacturing process of the metal composite panels, the adhesive bonding layers may be co-extruded or applied by film lamination. Depending on the manufacturing process and the requirements of the final product, the adhesive bonding layers may be based on low-crystallinity polyolefin elastomers or have a relatively more crystalline linear low-density polyethylene structure. In some embodiments, the adhesive bonding layers may also be based on low-density polyethylene. Several commercial embodiments are considered suitable for the adhesive bonding layers.For example, suitable polymers may be commercially available from The Dow Chemical Company under the brand name BYNEL™, such as the ethylene-vinyl acetate-based copolymer of class 30E753.

[0093] In one or more embodiments, the first adhesive bonding layer (120), the second adhesive bonding layer (120), or both, may have a thickness of 20 pm to 100 pm.In other embodiments, the first adhesive bonding layer, the second adhesive bonding layer, or both, may have a thickness of approximately 20 pm to 100 pm, approximately 20 pm to approximately 90 pm, approximately 20 pm to approximately 80 pm, approximately 20 pm to approximately 60 pm, approximately 20 pm to approximately 40 pm, approximately 30 pm to approximately 100 pm, approximately 30 pm to approximately 90 pm, 30 pm to approximately 80 pm, approximately 30 pm to approximately 60 pm, approximately 30 pm to approximately 40 pm, approximately 40 pm to approximately 100 pm, approximately 40 pm to approximately 80 pm, approximately 40 pm to approximately 60 pm, approximately 60 pm to approximately 100 pm, approximately 60 pm to approximately 80 pm, or approximately 80 pm to approximately 100 pm.

[0091]

[0094] In embodiments, the core layer (300) may comprise embodiments of the halogen-free flame retardant compositions described herein. In embodiments, the core layer may have a thickness of 1 mm to 5 mm. In other embodiments, the core layer may have a thickness of 2 mm to 4 mm, approximately 2 mm to 3 mm, 3 mm to 5 mm, 3 mm to approximately 4 mm, or 4 mm to 5 mm.

[0092]

[0095] The production methods for composite panel embodiments comprising the halogen-free flame-retardant compositions described herein may include extrusion of the core layer. It is believed that providing an extrudable core layer material, including embodiments of the halogen-free flame-retardant compositions described herein, may enable cost-effective and simplified procedures for the production of composite panels.

[0093]

[0096] In one embodiment, the composite panels can be produced by extruding the halogen-free flame-retardant compositions described herein through a flat slit die and shaping the compositions in a roller press to form the core layer (130) and manufacture the final dimensions. The core layer (130) can then be fed in-line to a lamination stage or rolled for further processing. In additional embodiments, the production methods for the composite panels may include co-extruding the first bonding layer (120) and the second bonding layer (120) onto the core layer (130). In other embodiments, the production methods for the composite panels may include laminating the first bonding layer (120) and the second bonding layer (120) onto the core layer (130).In embodiments, the production methods of composite panels may include the in-line lamination of the first metallic layer (110) and the second metallic layer (110) onto the first bonding layer (120) and the second bonding layer (120), thereby producing the composite panel (100).

[0094]

[0097] In further embodiments, the halogen-free flame-retardant compositions used for the core layer (130) may include one or more pre-combination stages. Not limited by theory, one or more pre-combination stages can improve the processability and conformity of the polyolefin base for direct extrusion of the core layer (100). During direct extrusion, additional charges can be fed by side feeders into the molten pre-combinations (or "pre-batches") of the halogen-free flame-retardant compositions, potentially enabling further processes for the production of composite panels.

[0095]

[0098] Recycling procedure

[0096]

[0099] According to the embodiments described herein, a recycling procedure is provided. The halogen-free flame retardant compositions described herein have a reduced screw torque relative to a halogen-free flame retardant composition lacking an ethylene-alkyl acrylate copolymer, even after at least 5 recycling steps, while maintaining the flame retardant effect (e.g., a maximum effective heat of combustion that is less than 25% higher than the maximum effective heat of combustion of a first halogen-free flame retardant article).

[0097]

[0100] In embodiments, the recycling process comprises heating a first halogen-free flame retardant article to a recycling temperature to form a first recyclable halogen-free flame retardant composition. The first halogen-free flame retardant article may comprise ethylene-alkyl acrylate copolymer, halogen-free flame retardant, and LDPE, as described herein. The heating may occur in an extruder, such as a twin-screw extruder. The first recycling temperature may be from 130 °C to 260 °C.In other embodiments, a first halogen-free flame retardant article can be heated to a first recycling temperature of 130°C to 260°C, 130°C to 150°C, 140°C to 160°C, 150°C to 170°C, 160°C to 180°C, 170°C to 190°C, 180°C to 200°C, 190°C to 210°C, 200°C to 220°C, 210°C to 230°C, 220°C to 240°C, 230°C to 250°C, or even 240°C to 260°C to form a first recyclable halogen-free flame retardant composition. For example, a first halogen-free flame retardant article can be heated to a stress temperature profile of 240 °C / 240 °C / 256 °C / 245 °C / 225 °C / 192 °C. During heating, the extruder screw speed can be from 140 rpm to 170 rpm.In other embodiments, the extruder screw speed during heating can be from 140 rpm to 170 rpm, from 140 rpm to 150 rpm, from 145 rpm to 155 rpm, from 150 rpm to 160 rpm, from 155 rpm to 165 rpm, from 160 rpm to 170 rpm, or even from 165 rpm to 170 rpm.

[0098]

[0101] In implementations, the recycling process continues with the extrusion of the first heated recyclable halogen-free flame retardant composition.

[0099]

[0102] In embodiments, the recycling process continues with the cooling of the first extruded recyclable halogen-free composition to form a second halogen-free flame retardant article. The second halogen-free flame retardant article may be different from the first halogen-free flame retardant article. The second halogen-free flame retardant article may comprise ethylene-alkyl acrylate copolymer, halogen-free flame retardant, and LDPE.

[0100]

[0103] In embodiments, the recycling process further comprises repeating the heating, extrusion, and cooling steps an additional time (i.e., once, twice, three times, etc.) to form additional halogen-free flame retardant articles (e.g., third, fourth, fifth halogen-free flame retardant articles). These additional halogen-free flame retardant articles may have a lower screw torque compared to a similar additional halogen-free flame retardant article lacking an ethylene-alkyl acrylate copolymer.

[0101]

[0104] For example, in embodiments, the recycling process may further comprise repeating the heating, extrusion, and cooling steps an additional time to form a third halogen-free flame retardant article, a fourth halogen-free flame retardant article, a fifth halogen-free flame retardant article, and a sixth halogen-free flame retardant article. The sixth halogen-free flame retardant article may differ from the first through fifth halogen-free flame retardant articles and comprises: the ethylene-alkyl acrylate copolymer; the halogen-free flame retardant; and LDPE. The sixth halogen-free flame retardant article may have a lower screw torque compared to a similar sixth halogen-free flame retardant article lacking an ethylene-alkyl acrylate copolymer.

[0102]

[0105] The measurement of applied screw torque depends on the equipment used, including the torque wrench, the materials used to manufacture the screw, and the parts being assembled. As shown in the examples below, the sixth example halogen-free flame retardant item has a screw torque range of 18 Nm to 42 Nm; however, other values ​​and ranges can be achieved with different equipment and parameters.

[0103]

[0106] In some embodiments, the additional halogen-free flame retardant article, such as the sixth halogen-free flame retardant article, comprises a maximum effective heat of combustion of less than 76 MJ / kg, or even less than 75 MJ / kg.

[0104]

[0107] As described herein, the halogen-free flame retardant compositions retain their flame retardant properties after at least five recycling stages. For example, in certain embodiments, the additional halogen-free flame retardant article, such as the sixth halogen-free flame retardant article, comprises a maximum effective heat of combustion that is less than 25% greater than the maximum effective heat of combustion of the first halogen-free flame retardant article. In further embodiments, the additional halogen-free flame retardant article, such as the sixth halogen-free flame retardant article, comprises a maximum effective heat of combustion that is less than 20% greater, less than 15% greater, less than 10% greater, or even less than 5% greater than the maximum effective heat of combustion of the first halogen-free flame retardant article.

[0105]

[0108] In embodiments, the additional halogen-free flame retardant article, such as the sixth halogen-free flame retardant article, comprises higher tensile strength and elongation at break compared to the first halogen-free flame retardant article. In some embodiments, the additional halogen-free flame retardant articles, such as the sixth halogen-free flame retardant article, may comprise a tensile strength of at least 10 MPa, at least 13 MPa, at least 15 MPa, or even at least 17.0 MPa and an elongation at break of at least 2%, at least 4%, or even at least 6%. In further embodiments, the first halogen-free flame retardant article comprises a tensile strength of at least 8 MPa, at least 10 MPa, at least 12 MPa, or even at least 14 MPa and a tensile elongation at break of at least 1%, at least 3%, or even at least 5%.

[0106]

[0109] TEST METHODS

[0107]

[0110] The test methods used in this document include the following:

[0108]

[0111] Density

[0109]

[0112] Density was measured according to ASTM D792 with results presented in grams per cubic centimeter (g / cm³). 3 ) at 25 °C.

[0110]

[0113] Screw torque

[0111]

[0114] The screw torque was measured with a torque meter during twin screw extrusion with the results presented in newton-meter (Nm).

[0112]

[0115] yellowness index

[0113]

[0116] The yellowness index (YI) was measured according to ASTM E313 using the D65 / 1O illuminant-observer combination 0 .

[0114]

[0117] Particle size distribution

[0115]

[0118] The particle size distribution (for metal hydroxide and calcium carbonate) was measured according to ISO 13320 at dso (median diameter) and dgo with the results presented in micrometers (pm).

[0116]

[0119] Specific surface area BET

[0117]

[0120] The Brunauer Emmett Teller (BET) specific surface area (for metal hydroxide and calcium carbonate) was measured according to ASTM D-1993 with the results presented in square meters per gram (m²). 2 / g).

[0118]

[0121] Average effective heat of combustion

[0119]

[0122] The mean effective heat of combustion was measured according to ASTM D 6556 with the results presented in megajoules / kilogram (MJ / kg).

[0120]

[0123] Maximum effective combustion heat

[0121]

[0124] The maximum effective heat of combustion was measured according to ASTM D 6556 with the results presented in megajoules / kilogram (MJ / kg).

[0122]

[0125] Tensile strength

[0123]

[0126] Tensile strength was measured according to ASTM D638 at 23 °C and a strain rate of 0.85 mm / s with the results presented in megapascals (MPa).

[0127] Tensile break elongation

[0124]

[0128] The tensile elongation at break was measured according to ASTM D638 at 23 °C and a strain rate of 0.85 mm / s, with the results presented as a percentage (%).

[0125]

[0129] fluency index (MI eh )

[0126]

[0130] The MI was measured according to ASTM D 1238, Conditions 190 °C / 2.16 kg with the results presented in grams per 10 minutes (g / 10 min).

[0127]

[0131] Melting point

[0128]

[0132] The melting temperature (T m ) was measured according to ASTM D1238 with the results presented in degrees Celsius (°C).

[0129]

[0133] EXAMPLES

[0130]

[0134] The following examples illustrate features of this description, but are not intended to limit its scope. The following experiments analyzed the performance of halogen-free flame retardant compositions described herein.

[0131]

[0135] The materials used in comparative examples CE1 and CE2 and in inventive examples IE1-IE3 are provided in Table 1 below.

[0136] Table 1

[0132]

[0133]

[0137] Preparation of halogen-free flame retardant compositions

[0134]

[0138] A feeding system for a co-rotating twin-screw extruder included two feeders, one for pellets and one for the filler. Comparative examples CE1 and CE2 and inventive examples IE1 and IE2 were combined into a two-stage process. The first stage was to combine the materials in the twin-screw extruder in the quantities indicated in Table 2 (wt. %) to achieve a filler level of 53.8 wt. at a feed rate of 4 kg / h. The second stage was to feed the pellets, now filled with 53.8 wt. filler, back into the extruder to achieve a filler level of 70 wt. at a feed rate of 2–3 kg / h. The screw speed was set to 150 rpm, and the temperature profile was set as follows: 180 °C / 180 °C / 195 °C / 185 °C / 170 °C / 132 °C. The extruded products from the spinneret were cooled in a water bath set to 6.9 °C connected to an auxiliary cooling system.

[0135]

[0139] After blending, the recycling process was simulated to mimic thermomechanical stress by feeding the blended materials into the twin-screw extruder to form a closed circuit (i.e., the "example recycling stage"). To accelerate the thermomechanical stress effect, the screw speed was set to 160 rpm and the temperature profile was adjusted as follows: 240 °C / 240 °C / 256 °C / 245 °C / 225 °C / 192 °C. Similar to the blended materials, after extrusion, the recycled products were cooled in a water bath at 6.9 °C connected to an auxiliary cooling system.

[0136]

[0140] Table 2

[0137]

[0138]

[0141] Screw torque of halogen-free flame retardant compositions

[0139]

[0142] Referring to Table 3, the screw torques of inventive examples IE1 and IE3 and comparative examples CE1 and CE2 are shown after a first extrusion (i.e., combined) and after 9 example recycling stages (i.e., from the second to the tenth article). Inventive examples IE1 and IE3 were compared with comparative examples CE1 and CE2, respectively, due to the similarities in the melt flow indices of the copolymers included in them. As shown, inventive example IE1, a composition including ELVALOY™ AC 1330 (ethylene-methyl acrylate copolymer), had a lower screw torque after a first extrusion and after 6 example recycling stages (i.e., from the first to the seventh article) compared to comparative example CE1, a composition including ELVAX™ 265 (ethylene-vinyl acetate copolymer).Furthermore, inventive example IE3, a composition including ELVALOY™ AC 12024S (ethylene-methyl acrylate copolymer), had a lower screw torque after a first extrusion and after 9 example recycling steps (i.e., from the first to the tenth article) compared to comparative example CE2, a composition including ELVAX™ 250A (ethylene-vinyl acetate copolymer). As shown in Table 3, the halogen-free flame retardant compositions as described herein have lower screw torque compared to a halogen-free flame retardant composition lacking an ethylene-alkyl acrylate copolymer, even after at least a first extrusion (i.e., combined) and after 4 example recycling steps (i.e., from the first to the fifth article).

[0140]

[0143] Table 3

[0141]

[0142]

[0144] Flame retardant properties of halogen-free flame retardant compositions TI

[0143]

[0145] Referring now to Table 4, the maximum effective heat of combustion of the comparative example CE1 and the inventive example IE1 are shown after a first extrusion (i.e., combined) and after a 9 aexample recycling stage (i.e., tenth item). Inventive example IE1, a composition including ELVALOY™ AC 1330 (ethylene-methyl acrylate copolymer), had a lower percentage increase in maximum effective heat of combustion than comparative example CE1, a composition including ELVAX™ 265 (ethylene-vinyl acetate copolymer).As shown in Table 4, although both a composition including ethylene-methyl acrylate copolymer and a composition lacking ethylene-methyl acrylate copolymer can maintain the flame retardant effect (i.e., a maximum effective heat of combustion that is less than 25% greater than the maximum effective heat of combustion of a first halogen-free flame retardant article), the halogen-free flame retardant compositions as described herein have less decrease in the flame retardant effect compared to a halogen-free flame retardant composition lacking ethylene-alkyl acrylate copolymer.

[0144]

[0146] Table 4

[0145]

[0146]

[0147] Color, tensile strength and elongation at break of halogen-free flame retardant compositions

[0147]

[0148] Referring to Table 5, the yellowness indices for the comparative example CE1 and the inventive example IE1 are shown after a first extrusion (i.e., combined), after 4 recycling stages (i.e., fifth article), after 5 recycling stages (i.e., sixth article), and after 9 recycling stages (i.e., tenth article). The inventive example IE1, a composition including ELVALOY™ AC 1330 (ethylene-methyl acrylate copolymer), exhibited a delta of 3 YI after a first extrusion (i.e., combined) and after 4 example recycling stages (i.e., from the first to the fifth article). The comparative example CE1, a composition that includes ELVAX™ 265 (ethylene-vinyl acetate copolymer), had a delta of 16 YI after a first extrusion (i.e., combined) and after 4 example recycling stages (i.e., fifth item).As indicated in Table 5, the halogen-free flame retardant composition as described herein has less color change after at least one first extrusion (i.e., combined) and after 4 example recycling stages (i.e., from the first to the fifth item) compared to a halogen-free flame retardant composition lacking an ethylene-alkyl acrylate copolymer.

[0148]

[0149] Table 5

[0149]

[0150]

[0150] Referring to Table 6, the tensile strength and elongation at break for Comparative Example CE1 and Inventive Example IE1 are shown after a first extrusion (i.e., combined), after 4 recycling stages (i.e., fifth article), after 5 recycling stages (i.e., sixth article), and after 9 recycling stages (i.e., tenth article). As shown, Inventive Example IE1, a composition including ELVALOY™ AC 1330 (ethylene-methyl acrylate copolymer), exhibited an increase in both tensile strength and elongation at break during at least a first extrusion (i.e., combined) and after 5 example recycling stages (i.e., sixth article).Furthermore, in comparative example 1 CE1, a composition including ELVAX™ 265 (ethylene-vinyl acetate copolymer) showed a decrease in tensile elongation at break after a first extrusion (i.e., combined) and after four example recycling stages (i.e., fifth article). Additionally, inventive example IE1 showed less variability in tensile properties, as evidenced by the lower standard deviation compared to comparative example CE1 after a first extrusion (i.e., combined) and after five and six example recycling stages (i.e., fifth and sixth articles).As indicated in Table 6, the halogen-free flame retardant composition as described herein has higher tensile strength and elongation at break after at least one first extrusion (i.e., combined) and after 4 example recycling stages (i.e., from the first to the fifth item) and may have less variable tensile properties compared to a halogen-free flame retardant composition lacking an ethylene-alkyl acrylate copolymer.

[0151]

[0151] Table 6

[0152]

[0153]

[0152] Although particular embodiments of the present description have been illustrated and described, it would be obvious to those skilled in the art that some other changes and modifications can be made without departing from the spirit and scope of the description. Therefore, it is intended to cover in the appended claims all such changes and modifications that are within the scope of this description.

Claims

CLAIMS 1. A halogen-free flame retardant composition comprising, based on a total weight of the halogen-free flame retardant composition: from 5% by weight to 35% by weight of ethylene-alkyl acrylate copolymer, comprising the ethylene-alkyl acrylate copolymer from 8% by weight to 35% by weight of alkyl acrylate, based on a total weight of the ethylene-alkyl acrylate copolymer, and a melt flow index (L) from 1 gram per 10 minutes (g / 10 min) to 50 g / 10 min; from 60% by weight to 75% by weight of halogen-free flame retardant; and from 5% by weight to 25% by weight of low-density polyethylene (LDPE) comprising a melt flow index (I2) of 1 g / 10 min to 50 g / 10 min.

2. The halogen-free flame retardant composition of claim 1, wherein the halogen-free flame retardant comprises metal hydroxide.

3. The halogen-free flame retardant composition of claim 1 or claim 2, wherein the LDPE comprises at least 50% by weight of recycled LDPE, based on the total weight of the LDPE.

4. The halogen-free flame retardant composition of claim 3, wherein the recycled LDPE comprises a melt flow index (I2) of 0.3 g / 10 min to 3 g / 10 min.

5. The halogen-free flame retardant composition of any one of claims 1-4, wherein the halogen-free flame retardant composition further comprises 1 wt% to 5 wt% of a polyethylene grafted with maleic anhydride, the polyethylene grafted with maleic anhydride comprising 0.5 wt% to 2.5 wt% of maleic anhydride and a melt flow index (I2) of 0.5 g / 10 min to 10 g / 10 min.

6. The halogen-free flame retardant composition of any one of claims 1-5, wherein the halogen-free flame retardant composition further comprises from 0% by weight to 30% by weight of calcium carbonate.

7. The halogen-free flame retardant composition of any one of the claims 1-6, further comprising antioxidants, coupling agents, synergistic agents, polymer processing aids, waxes or combinations thereof.

8. The halogen-free flame retardant composition of any one of claims 1-7, wherein the halogen-free flame retardant composition comprises a lower worm torque with respect to a similar halogen-free flame retardant composition lacking an ethylene-alkyl acrylate copolymer.

9. A composite panel comprising: a first metallic layer; a second metallic layer; a central layer disposed between the first metallic layer and the second metallic layer, a first bonding layer disposed between the first metallic layer and the central layer; and a second bonding layer disposed between the second metallic layer and the central layer, wherein the central layer comprises the halogen-free flame retardant composition of any one of claims 1-8.

10. A recycling procedure comprising heating a first halogen-free flame retardant article to a recycling temperature to form a first recyclable halogen-free flame retardant composition, the first halogen-free flame retardant article comprising: ethylene-alkyl acrylate copolymer; halogen-free flame retardant; and low-density polyethylene (LDPE); extrude the first heated recyclable halogen-free flame retardant composition; and cooling the first extruded recyclable halogen-free composition to form a second halogen-free flame-retardant article, the second halogen-free flame-retardant article being different from the first halogen-free flame-retardant article and comprising: the ethylene-alkyl acrylate copolymer; the halogen-free flame retardant; and LDPE.

11. The method of claim 10, wherein the recycling process further comprises repeating the heating, extrusion, and cooling steps four additional times to form a third halogen-free flame retardant article, a fourth halogen-free flame retardant article, a fifth halogen-free flame retardant article, and a sixth halogen-free flame retardant article, the sixth halogen-free flame retardant article being different from the first through fifth halogen-free flame retardant articles and comprising: the ethylene-alkyl acrylate copolymer; the halogen-free flame retardant; and LDPE, wherein the sixth halogen-free flame retardant article comprises a lower screw torque with respect to a similar sixth halogen-free flame retardant article lacking an ethylene-alkyl acrylate copolymer.

12. The method of claim 11, wherein the sixth halogen-free flame retardant article comprises a maximum effective heat of combustion that is less than 25% greater than the maximum effective heat of combustion of the first halogen-free flame retardant article.

13. The method of claim 12, wherein the sixth halogen-free flame retardant article comprises a maximum effective heat of combustion of less than 76 MJ / kg.

14. The method of any one of claims 11-13, wherein the sixth halogen-free flame retardant article comprises increased tensile strength and increased tensile elongation with respect to the first halogen-free flame retardant article.

15. The method of any one of claims 10-14, wherein the Heating and extrusion are carried out in a twin-screw extruder at a temperature profile of 130 °C to 260 °C and a screw speed of 140 rpm to 170 rpm.

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