Polyolefin elastomers and their use in photovoltaic encapsulant films with improved resistance to scorch

Abstract

Embodiments are directed to polyolefin elastomers comprising a unimodal ethylene-octene copolymer, wherein the polyolefin elastomer has: a density from 0.860 g / cc to 0.900 g / cc; an I10 / I2 greater than 9, wherein I2 is measured according to ASTM D1238 (190°C, 2.16 Kg) and I10 is measured according to ASTM D1238 (190°C, 10 Kg); a percentage of ethylene groups in total unsaturation greater than or equal to 55%; and greater than or equal to 0.2 unsaturations per 1000 carbons. Additional embodiments are directed to crosslinkable polyolefin elastomer formulations and crosslinked polyolefin elastomers and articles produced therefrom.

Description

Technical Field

[0001] The embodiments disclosed herein generally relate to polyolefin elastomers, and more specifically to polyolefin elastomers used in photovoltaic encapsulants to impart scorch resistance and crosslinking. Background Technology

[0002] In photovoltaic (PV) applications, two types of resins are widely used in encapsulation films: ethylene vinyl acetate (EVA) and polyolefin elastomer (POE). While POE's high volume resistivity (VR) is crucial for the potential-induced degradation (PID) resistance of solar cells, its processability (film extrusion rate) and curing reaction are not as good as EVA. For conventional POE, organic peroxides with faster decomposition rates can be used to accelerate the curing rate, but this faces potential scorch problems.

[0003] Therefore, there is a need for improved polyolefin elastomers that achieve the required anti-PID properties while also achieving the required processability and curing reaction. Summary of the Invention

[0004] The embodiments disclosed herein satisfy the need to introduce both long-chain branching (LCB) and chain-terminal unsaturation into POE resins. The resulting POE resins exhibit improved processability, faster curing rates, higher curing densities, and improved scorch resistance (i.e., longer ts0.5 time).

[0005] According to one embodiment, the polyolefin elastomer comprises a unimodal ethylene-octene copolymer, wherein the polyolefin elastomer has: a density of 0.860 g / cc to 0.900 g / cc; and an I content greater than 9. 10 / I2, where I2 is measured according to ASTM D1238 (190°C, 2.16 kg), and I 10 Measured according to ASTM D1238 (190°C, 10 kg); percentage of vinyl in total unsaturation greater than or equal to 55%; and greater than or equal to 0.2 unsaturation / 1000 carbon.

[0006] Additional features and advantages will be set forth in the following detailed description and will in part become apparent to those skilled in the art from those description or by practice of the embodiments described herein, including the following detailed description and claims.

[0007] It should be understood that both the foregoing general description and the following detailed description describe various implementation schemes and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. Attached Figure Description

[0008] The following detailed description of specific embodiments of this disclosure is best understood in conjunction with the following drawings, in which similar reference numerals indicate similar structures and in the drawings:

[0009] Figure 1 The figure illustrates the relationship between the gel content of a crosslinked polyolefin elastomer according to one or more embodiments described in this disclosure after lamination time (4+12 min) and scorch time at 150°C (ts0.5).

[0010] Figure 2 The figure illustrates the relationship between the gel content of a crosslinked polyolefin elastomer according to one or more embodiments described in this disclosure after lamination time (4+12 min) and scorch time at 120°C (ts0.5); and

[0011] Figure 3 This is a schematic diagram of the inter-battery displacement assembly.

[0012] Various implementation schemes will now be discussed in detail, some of which are illustrated in the accompanying drawings. Detailed Implementation

[0013] Specific embodiments of this application will now be described. This disclosure may be implemented in various forms and should not be construed as limiting it to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

[0014] definition

[0015] Unless stated to the contrary, implied by the context or customary in the art, all parts and percentages are by weight, and all test methods are current methods as of the date of this disclosure.

[0016] As used herein, the term "polymer" refers to a polymeric compound prepared by polymerizing monomers of the same or different types. The general term polymer includes the terms homopolymer (used to refer to a polymer prepared from only one type of monomer; it should be understood that trace impurities may be incorporated into the polymer structure) and interpolymer, as defined below. Trace impurities (such as catalyst residues) may be incorporated into and / or within the polymer. Typically, polymers are stabilized with one or more stabilizers in very low amounts ("ppm").

[0017] As used herein, the term "interpolymer" refers to a polymer prepared by the polymerization of at least two different types of monomers. The term interpolymer therefore includes the term copolymer (used to refer to polymers prepared from two different types of monomers) and polymers prepared from more than two different types of monomers.

[0018] As used herein, the term "polyolefin" refers to a polymer that contains 50% by weight or most of a weight of an olefin (such as ethylene or propylene) in polymeric form (based on the weight of the polymer) and optionally may contain one or more comonomers.

[0019] As used herein, the terms "ethylene-based polymer" or "polyethylene" refer to a polymer that contains 50% by weight or most of a weight of ethylene (based on the weight of the polymer) in polymeric form and optionally may contain one or more comonomers.

[0020] As used herein, the term "ethylene / α-olefin copolymer" refers to a copolymer in polymeric form comprising 50% by weight or a majority weight percentage of ethylene (based on the weight of the copolymer) and α-olefin as the only two monomer types. Preferably, the ethylene / α-olefin copolymer is a random copolymer (i.e., comprising a random distribution of its monomer components).

[0021] As used herein, "single peak" refers to the molecular weight distribution (MWD) indicated by a gel permeation chromatography (GPC) curve, which exhibits a single peak defined by a single positive inflection point at which the derivative of the MWD GPC curve increases with increasing value. The ratio increases from positive to negative within the range of 2 to 8, or 3 to 7. Preferably, the resin has a Mw / Mn ratio of less than about 3.5, and further less than 2.8. More preferably, the resin composition is the result of a single-reactor, single-catalyst polymerization process.

[0022] As used herein, the terms "crosslinked composition" and "crosslinked polyolefin elastomer" refer to compositions having a network structure due to the formation of chemical bonds between polymer chains. The degree of this network structure formation is indicated by the increase in the "MH-ML" difference relative to a non-crosslinked composition. Based on the weight of the crosslinked composition, it typically has a gel content of ≥50% by weight, further ≥60% by weight, further ≥70% by weight, and further ≥80% by weight. See gel testing below.

[0023] The terms “comprising,” “including,” “having,” and their derivatives are not intended to exclude the presence of any additional components, steps, or procedures, whether or not such components, steps, or procedures are specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all compositions claimed using the term “comprising” may include any additional additives, adjuvants, or compounds, whether in polymeric or other forms. In contrast, the term “consistently comprising” excludes any other components, steps, or procedures from any subsequently listed scope, except those that are not essential for operability. The term “consisting of” excludes any components, steps, or procedures not specifically described or listed.

[0024] Implementation Plan

[0025] Polyolefin elastomers

[0026] Embodiments of this disclosure relate to polyolefin elastomers comprising a unimodal ethylene-octene copolymer, wherein the polyolefin elastomer has: a density of 0.860 g / cc to 0.900 g / cc; and an I content greater than 9. 10 / I2, where I2 is measured according to ASTM D1238 (190°C, 2.16 kg), and I 10 Measured according to ASTM D1238 (190°C, 10 kg); the percentage of vinyl in the total unsaturation is greater than or equal to 55%; and greater than or equal to 0.2 unsaturation / 1000 carbon. Further embodiments relate to crosslinkable polyolefin elastomer formulations and crosslinked polyolefin elastomers, and articles produced therefrom.

[0027] Polyolefin elastomers may have densities of 0.860 g / cc to 0.900 g / cc, 0.860 g / cc to 0.880 g / cc, or 0.865 g / cc to 0.875 g / cc.

[0028] The polyolefin elastomer may have a melt index (I2) ranging from 0.5 dg / min to 30 dg / min, wherein I2 is measured according to ASTM D1238 (190°C, 2.16 kg), and in other embodiments, may have an I2 ranging from 1.0 dg / min to 25 dg / min, 2.0 dg / min to 20 dg / min, or 3 dg / min to 18 dg / min. In other embodiments, I2 may have a lower limit extending from 0.5 dg / min, 1.0 dg / min, 2.0 dg / min, 3.0 dg / min, 4.0 dg / min, 5.0 dg / min, 6.0 dg / min, 7.0 dg / min, 8.0 dg / min, 9.0 dg / min, 10.0 dg / min, 11.0 dg / min, or 12.0 dg / min to 7.0 dg / min. in, 8.0dg / min, 9.0dg / min, 10.0dg / min, 11.0dg / min, 12.0dg / min, 13.0dg / min, 14.0dg / min, 15 The range of the upper limit of .0dg / min, 16.0dg / min, 17.0dg / min, 18.0dg / min, 20.0dg / min, 25.0dg / min or 30.0dg / min.

[0029] Polyolefin elastomers can have an I value greater than 9. 10 / I2, and in other embodiments, may have 9 to 20, 9 to 15, 9.1 to 12, or 9.1 to 11 I. 10 / I2. Unrestricted by theory, this I 10 The / I2 range is associated with increased long-chain branching, which contributes to the processability of POE resins.

[0030] Polyolefin elastomers may have high vinyl unsaturation, as demonstrated by having 0.2 vinyls / 1000 carbons or more, and in other embodiments may include 0.2 to 1 vinyl / 1000 carbon, 0.2 to 0.8 vinyls / 1000 carbons or 0.2 to 0.6 vinyls / 1000 carbons.

[0031] The polyolefin elastomer may have a degree of unsaturation greater than or equal to 0.2 degrees of unsaturation per 1000 carbons, or a degree of unsaturation greater than or equal to 0.4 degrees of unsaturation per 1000 carbons, and in other embodiments, may have a degree of unsaturation from 0.4 to 2 degrees of unsaturation per 1000 carbons, from 0.4 to 1 degree of unsaturation per 1000 carbons, or from 0.40 to 0.80 degrees of unsaturation per 1000 carbons.

[0032] In addition, the percentage of vinyl in the total unsaturation of the polyolefin elastomer is at least 55%, at least 60%, at least 65%, or at least 70%.

[0033] In addition, the polyolefin elastomer may have a number-average molecular weight (Mn) of 20 kg / mol to 30 kg / mol, or 22 kg / mol to 28 kg / mol, wherein Mn is measured according to conventional gel permeation chromatography (GPC). The polyolefin elastomer may have a Mw / Mn ratio of 2.0 to 3.0, 2.4 to 3.0, or 2.5 to 2.6, wherein Mw (weight-average molecular weight) is measured according to conventional GPC.

[0034] Crosslinkable polyolefin elastomer formulations

[0035] This disclosure also relates to crosslinkable polyolefin elastomer formulations comprising a polyolefin elastomer and a curing package. The curing package may contain an organic peroxide. In another embodiment, the curing package may also contain a crosslinking aid. In yet another embodiment, the crosslinking package may also contain a silane coupling agent.

[0036] Unrestricted by theory, it was surprisingly found that introducing both LCB (I10 / I2>9) and chain-terminal unsaturation (vinyl percentage ≥55% and unsaturation ≥0.2 / 1000C) into unimodal POE resins resulted in excellent curing, scorch resistance (longer ts0.5), faster curing rate, and higher curing density when curing POE resin peroxide curing packages.

[0037] Various organic peroxides are considered suitable. Available peroxides include, but are not limited to, peroxycarbonates, such as tert-amyl peroxycarbonate-2-ethylhexyl ester (TAEC); and peroxyketals, such as, for example, 1,1-di(tert-amylperoxy)cyclohexane. Examples of organic peroxides may include tert-butyl peroxyisopropyl carbonate; tert-butyl peroxycarbonate-2-ethylhexyl ester (TBEC); tert-amyl peroxycarbonate-2-ethylhexyl ester (TAEC); tert-butyl peracetic acid ester; tert-butyl peroxybenzoate; dicumyl peroxide; 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; di-tert-butyl peroxide; 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3; 1,1-di(tert-butylperoxy)-3,3,5-trimethyl-cyclohexane; 1,1-di-(tert-butylperoxy)-cyclohexane; methyl ethyl ketone peroxide; 2, 5-Dimethyl-hexyl-2,5-disperoxybenzoate; tert-butyl hydroperoxide; p-menthane hydroperoxide; benzoyl peroxide; p-chlorobenzoyl peroxide; tert-butylperoxyisobutyrate; heptyl peroxide; and dicyclohexanone peroxide. In one embodiment, the organic peroxide includes at least one of TBEC and TAEC.

[0038] Similarly, various silane coupling agents are considered suitable. For example, silane coupling agents may include one or more alkoxysilane coupling agents, such as vinyltrimethoxysilane (VTMS), 3-(trimethoxysilyl)-propyl-methacrylate (VMMS), tetraethoxysilane (TEOS), or combinations thereof. In one or more embodiments, the silane coupling agent includes VTMS, VMMS, or combinations thereof.

[0039] Various crosslinking aids were also considered. These may include crosslinking aids such as triallyl isocyanurate (TAIC), triallyl phosphate (TAP), triallyl cyanurate (TAC), triallyl trimellitate (TATM), 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (vinyl D4), N,N,N',N',N'',N''-hexamyl-1,3,5-triazine-2,4,6-triamine, triallyl trimellitate, trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), 1,6-hexanediol diacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, trivinylcyclohexane (TVCH), or combinations thereof.

[0040] Further examples of organic peroxides, silane coupling agents and crosslinking aids are provided in PCT Publication WO2023272545A1, which is incorporated herein by reference in its entirety.

[0041] As described above, the polyolefin elastomer of this disclosure allows for the use of lower amounts of curing packets in crosslinkable polyolefin elastomer formulations or crosslinkable polyolefin elastomers produced therefrom. For example, the curing packets may be present in the crosslinkable polyolefin elastomer formulation in an amount of 0.2% to 3.0% by weight, or in other embodiments in an amount of 1.0% to 2.0% by weight, or 1.5% to 2.0% by weight. Furthermore, the crosslinkable polyolefin elastomer formulation comprises 85% to 99.5% by weight, 90% to 99.5% by weight, or 98% to 99% by weight of polyolefin elastomer.

[0042] Organic peroxides may be present in the crosslinkable polyolefin elastomer formulation at an amount of 0.1 wt% to 2.0 wt%, or in other embodiments at an amount of 0.2 wt% to 1.0 wt%, or 0.5 wt% to 1.0 wt%. Silane coupling agents may be present in the crosslinkable polyolefin elastomer formulation at an amount of 0.05 wt% to 1.0 wt%, or in other embodiments at an amount of 0.1 wt% to 0.5 wt%, or 0.1 wt% to 0.3 wt%. Crosslinking aids may be present in the crosslinkable polyolefin elastomer formulation at an amount of 0.1 wt% to 2.0 wt%, or in other embodiments at an amount of 0.2 wt% to 1.0 wt%, or 0.5 wt% to 1.0 wt%.

[0043] Additional additives or fillers that may be added during polymerization, granulation, curing, etc., may include UV absorbers and / or stabilizers, such as hindered amine light stabilizers like TINUVIN 770; TiO2; one or more antioxidants; processing aids such as fluoropolymers, polydimethylsiloxane (PDMS), ultra-high molecular weight PDMS; ion scavengers, potential-induced degradation (PID) inhibitors; other siloxanes; fumed silica, nano-Al2O3, nano-clay, and one or more other fillers. In one embodiment, the additives are present in amounts of ≥0.20% by weight, or ≥0.40% by weight, or ≥0.60% by weight, or ≥0.80% by weight, and / or ≤5.0% by weight, or ≤4.0% by weight, or ≤3.0% by weight, or ≤2.0% by weight, or ≤1.5% by weight, or ≤1.0% by weight, based on the weight of the composition.

[0044] Crosslinked polyolefin elastomers and products

[0045] Crosslinkable polyolefin elastomers can be produced from crosslinkable polyolefin elastomer formulations via curing methods known to those skilled in the art. In some embodiments, curing can be initiated by heat, radiation, electron beam radiation, or ultraviolet (UV) radiation.

[0046] Crosslinked polyolefin elastomers can be incorporated into various articles. These crosslinked polyolefin elastomers can be contained in films, such as multilayer films. Multilayer films can contain layers of the same or different compositions. For example, the polymer used in each layer can be different, or the level of the curing agent component in each layer composition can be different. Multilayer films can contain two or more layers, such as 2 to 5 layers. An exemplary multilayer film is an EVA-POE-EVA three-layer film, wherein the polyolefin elastomer of the present invention is used in the middle POE layer. Additionally, as described above, the article can be an encapsulant for photovoltaic modules.

[0047] refer to Figure 1 The relationship between the scorch time (ts0.5 at 150°C, in minutes) and the gel content (in percentage) (G) after lamination time of 4 + 12 minutes for the crosslinked polyolefin elastomer can be defined by the following equation: G ≥ -0.150 * (ts0.5 at 150°C) + 1.110. In another embodiment, the crosslinked polyolefin elastomer can be defined by the following equation: G ≥ -0.150 * (ts0.5 at 150°C) + 1.150.

[0048] refer to Figure 2 The relationship between the scorch time (ts0.5 at 120°C, in minutes) of the crosslinked polyolefin elastomer and the gel content (in percentage) (G) after lamination time of 4 + 12 minutes can be defined by the following equation: G ≥ -0.012 * (ts0.5 at 120°C) + 0.990. In another embodiment, the crosslinked polyolefin elastomer can be defined by the following equation: G ≥ -0.005 * (ts0.5 at 120°C) + 0.926.

[0049] Test methods

[0050] density

[0051] Density was measured according to ASTM D792 and expressed in grams per cubic centimeter. 3 (g / cm) 3 )express.

[0052] Melt index (I2) and (I 10 )

[0053] Melt index (I2) was measured according to ASTM D-1238 (190℃ / 2.16kg). 10) Measured according to ASTM D-1238 (190℃ / 10kg).

[0054] Gel permeation chromatography (GPC)

[0055] The chromatographic system consisted of a PolymerChar GPC-IR (Valencia, Spain) high-temperature GPC chromatograph equipped with an internal IR5 infrared detector (IR5). The autosampler oven chamber was set to 160°C, and the column and detector chambers were set to 150°C. The columns used were four Agilent “Mixed A” 30 cm 20 μm linear mixed-bed columns. The chromatographic solvent used was 1,2,4-trichlorobenzene containing 200 ppm of butylated hydroxytoluene (BHT). The solvent source was nitrogen injection. The injection volume was 200 μL, and the flow rate was 1.0 mL / min.

[0056] The GPC column assembly was calibrated using 21 polystyrene standards with narrow molecular weight distributions, ranging from 580 to 8,400,000, arranged in six “cocktail” mixtures, with individual molecular weights spaced at least tenfold apart. The standards were purchased from Agilent Technologies. For molecular weights equal to or greater than 1,000,000, 0.025 g of polystyrene standard was prepared in 50 mL of solvent; for molecular weights less than 1,000,000, 0.05 g of polystyrene standard was prepared in 50 mL of solvent. The polystyrene standards were pre-dissolved at 80 °C with gentle stirring for 30 min, then cooled, and the room temperature solution was transferred to a 160 °C autosampler dissolution oven for 30 min. The peak molecular weights of the polystyrene standards were converted to polyethylene molecular weights using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)).

[0057] (Equation 1)

[0058] Where M is the molecular weight, A has a value of 0.4163, and B equals 1.0.

[0059] A fifth-order polynomial is used to fit the calibration point for the corresponding polyethylene equivalent.

[0060] Total plate counts of the GPC column setup were performed using decane, which was introduced into the blank sample via a micropump controlled by a PolymerChar GPC-IR system. For four Agilent “Mixed A” 30 cm 20 μm linear mixed-bed columns, the plate count of the chromatographic system should be greater than 18,000.

[0061] Samples were prepared semi-automatically using PolymerChar Instrument Control software, with a target sample weight of 2 mg / ml. Solvent (containing 200 ppm BHT) was added to a pre-bubbled, diaphragm-capped vial via a PolymerChar high-temperature autosampler. The sample was then dissolved at 160°C for 2 hours under "low-speed" oscillation.

[0062] Based on the GPC results measured using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph, according to Equation 2-4, the PolymerChar GPCOne was used... ™ The software uses baseline-subtracted IR chromatograms from data collection points (i) at equidistant points and polyethylene equivalent molecular weight (Mn) obtained from the narrow standard calibration curve at point (i) according to Equation 1. (GPC) Mw (GPC) and Mz (GPC) The calculation.

[0063] (Equation 2)

[0064] (Equation 3)

[0065] (Equation 4)

[0066] To monitor deviations over time, a flow rate marker (decane) was introduced into each sample via a micropump controlled by a PolymerChar GPC-IR system. This flow rate marker (FM) was used to linearly correct the pump flow rate (nominal flow rate) for each sample by comparing the RV (RV(FM sample)) of the corresponding decane peak within the sample with the RV (RV(FM calibrated)) of the decane peak within the narrow standard calibration. It was then assumed that any variation in the decane marker peak time was linearly related to the flow rate (effective flow rate) throughout the run. After calibration based on the flow rate marker peak, the effective flow rate (relative to the narrow standard calibration) was calculated according to Equation 5. Via PolymerChar GPC One ™ The software processes the flow marker peaks. Acceptable flow correction ensures that the effective flow rate is within + / - 0.5% of the nominal flow rate.

[0067] Flow rate (effective) = Flow rate (nominal) * (RV (FM calibration) / RV (FM sample)) (Equation 5)

[0068] Dynamic Modulus Rheometer (MDR) Curing Test

[0069] MDR tests were performed on MDR 2000 at 150°C and 120°C according to ASTM 5289. Time-to-torque (MTT) curves were generated for each given time interval in all cases. The key parameter for understanding the degree of curing of the formulation is MH-ML (dNm): a higher MH-ML value is associated with a more highly cross-linked polymer network. Here, MH (dNm) refers to the maximum torque applied by the MDR during the test interval; and ML (dNm) refers to the minimum torque applied by the MDR during the test interval. Other parameters measured were scorch time (ts0.5) and curing time (T90). Ts0.5 is defined as the time required to reach a value 0.5 dNm above the ML value during the test interval. T90 is defined as the time required to reach 90% of the maximum torque (MH) measured during the test interval.

[0070] gel measurement

[0071] Crosslinked samples were prepared by lamination: each plate (3cm × 3cm × 0.5mm) was placed on a PTFE membrane (0.15mm thick), which was then placed on a glass substrate (3.2mm thick) within a metal frame (3cm × 3cm × 0.5mm) (9 plates in one mold), and another PTFE membrane (0.15mm thick) was placed on top of the plates. Lamination was performed at 150°C using a two-step method: 1) preheating under vacuum without pressure (at 150°C) for four minutes; and 2) curing at 150°C and 1 bar pressure for 6 to 16 minutes. Therefore, for a typical single-chamber process, the total lamination time is 4 + x minutes. The laminated samples were used for gel testing.

[0072] Xylene extraction: Cut the cured plate into 3mm*3mm pieces. Then seal approximately 0.5g of sample (Ws) in a metal mesh (120 mesh, weight Wt1), and place the filled sample in a 250mL glass bottle containing 100mL xylene for 24 hours. Then, transfer the filled sample to a 500mL flask equipped with a condenser and containing 350mL xylene. After reflux for 5 hours, remove the filled sample from the xylene, place it in a vacuum oven, and heat at 120°C under vacuum for 2 hours. Remove the filled sample from the metal mesh and weigh it (Wt2). The gel content is calculated using the following equation: Gel content = (Wt2 - Wt1) / Ws * 100%.

[0073] Transmittance measurement

[0074] Transmittance was measured on a 0.5 mm thick sample using a Perkin Elmer Lambda 950 equipped with an integrating sphere. Transmission wavelengths ranged from 380 nm to 1000 nm. The compression molding process was as follows:

[0075] 1) Preparation of cross-linked film by compression molding: preheat at 120°C for 5 minutes, then preheat at 150°C for 15 minutes, cross-link at 10MPa, and cool to room temperature for 5 minutes with 40°C cooling water circulation.

[0076] 2) Preparation of thermoplastic film by compression molding: Preheat at 150°C for 5 minutes, then preheat at 150°C and 10MPa for 3 minutes, and cool to room temperature for 5 minutes with 40°C cooling water circulation.

[0077] 1 H NMR studies .

[0078] Samples were prepared as follows: Approximately 130 mg of sample was added to 3.25 g of 50 / 50 (by weight) tetrachloroethane-d2 / perchloroethylene containing 0.001 M Cr(AcAc)3 and 100 ppm antioxidant (Irganox 168) in a 10 mm NMR tube of NORELL 1001-7. The sample was purged by bubbling N2 through the solvent for approximately five minutes via a pipette inserted into the tube to prevent oxidation. The tube was then capped, sealed with Teflon tape, and subsequently soaked overnight at room temperature to promote sample dissolution. The sample was kept in an N2 purge chamber during storage, before and after preparation, to minimize O2 exposure. The sample was heated and vortexed at 110 °C to ensure homogeneity.

[0079] The samples were analyzed on a Bruner Avance 400MHz or 600MHz spectrometer equipped with a Bruner cryogenic probe and at a sample temperature of 120°C. 1 H NMR. Two experiments were performed to obtain spectra: a control spectrum for quantifying total polymer protons, and a double presaturation experiment to suppress strong peaks associated with the polymer backbone and achieve high sensitivity for quantifying end groups. The control was run with ZG pulses, TD 16384, NS 16, DS 4, SWH 10,000 Hz, AQ 1.64 s, D1 14 s. The control was run with a modified pulse sequence lc1prf2.zz, TD 16384, NS 64 scan, DS 4, SWH 10,000 Hz, AQ 1.64 s, D1 1 s, D... 13A double presaturation experiment was conducted in 13s. Unsaturation was measured according to the following method. The area under the resonance of the polymer chains (i.e., CH, CH2, and CH3 in the polymer) was measured from the spectrum obtained during the first experiment (control spectrum), as described above. The areas under the four key types of unsaturation (i.e., vinyl, vinylene, trisubstituted, and vinylene derivatives) were measured from the spectrum obtained during the second (presaturation) experiment described above. Both spectra were normalized to areas under the solvent resonance. The molar number of each unsaturation was calculated by dividing the area under the unsaturated resonance by the number of protons contributing to that resonance. The number of carbon moles in the polymer was calculated by dividing the area under the polymer chain (i.e., CH, CH2, and CH3 in the polymer) peaks by two. The total degree of unsaturation was then expressed as the relative ratio of the total number of moles of unsaturation in the polymer to the number of moles of carbon, expressed as the degree of unsaturation per 1000 carbons.

[0080] Battery connection measurement

[0081] like Figure 3 As shown, the component comprises two encapsulation films (0.5 mm), two half-cut solar cells, two backsheets (0.15 mm), and two glass substrates. The component was laminated at 125°C, preheated for 330 seconds, and then vacuum-laminated for 330 seconds. The distance between the two half-cut solar cells was then measured using a high-resolution camera with a scale.

[0082] Single-cell module lamination

[0083] The glass / glass bifacial module used in this study was fabricated using the following procedure:

[0084] Wash a 4×6 square inch glass sample with water and then dry it before use. Cut the POE film into sheets to fit the glass dimensions. Stack the front glass, encapsulation film, solar cell, encapsulation film, and back glass together in the order described above. The lamination process is performed on a PENERGY L036 laminator at 150°C for 20 minutes, including a 4-minute vacuum process and a 16-minute pressing. Use the laminated sample for the following PID stress test. Prepare two identical single-cell module samples for the PID test to obtain an average value.

[0085] PID test

[0086] Module-level PID (potential-induced degradation) testing was performed according to the procedure described in IEC 62804-1. The initial power output of the module samples was recorded using a pulsed solar simulator (Burger PS8 / PSS8) according to the procedure described in IEC 60904. The PID stress process was conducted in an environmental chamber at 85°C / 85% RH. The module samples were connected to a power source to generate a typical negative bias voltage of 1500V. The standard test lasted 96 hours.

[0087] Following the stress process, the power output of all module samples was retested. The results were compared with the initial measurements to further calculate the power loss.

[0088] The IEC standard for power loss after 96 hours of PID testing is less than 5% for both the front and rear sides of the PV module.

[0089] Example

[0090] Commercially available polymers and additives

[0091] 2-Ethylhexyl tert-butylperoxycarbonate (TBEC) [CAS 34443-12-4] is commercially available from Arkema.

[0092] 2-Ethylhexyl peroxycarbonate (TAEC) [CAS 70833-40-8] is commercially available from Arkema.

[0093] Triallyl isocyanurate (TAIC) [CAS 1025-15-6] is commercially available from Hunan Fangruida Technology Co., Ltd.

[0094] 3-(trimethoxysilyl)propyl methacrylate (VMMS) [CAS 2530-85-0] is a silane coupling agent available from The Dow Chemical Company, Midland, MI.

[0095] TINUVIN 770 [CAS 52829-07-9] is a UV stabilizer purchased from BASF.

[0096] ENGAGE ™ PV 8660 and ENGAGE ™ PV 8669 is a polyolefin elastomer available from The Dow Chemical Company, Midland, MI.

[0097] Polyolefin elastomers

[0098] The polyolefin elastomers used in the examples are provided in Table 1 below.

[0099] Table 1

[0100]

[0101] Preparation of polyolefin elastomers

[0102] The polyolefin elastomers (POE) AE in Table 1 were prepared in a well-mixed, all-liquid polymerization reactor operated under steady-state conditions. All feedstocks (ethylene monomer and 1-octene comonomer) and process solvent (narrow-boiling-range high-purity isoparaffin solvent, product name Isopar-E, supplied by ExxonMobil Chemical Company) were purified with molecular sieves before being introduced into the reaction environment. Hydrogen was supplied pressurized at a high purity level without further purification. The ethylene flow rate and reactor volume were selected to achieve the residence times specified in Table 2A. The catalysts and cocatalysts used are listed in Table 3. The solvent, comonomer, hydrogen, catalyst, and cocatalyst were fed into the reactor according to the method conditions outlined in Tables 2A and 2B. The catalyst flow rate was adjusted to achieve the desired ethylene conversion. The reactor temperature was measured at or near the reactor outlet. The interpolymers were separated and granulated.

[0103] Table 2A: Process Conditions

[0104]

[0105] Table 2B: Process Conditions (Continued)

[0106]

[0107] Table 3: Catalysts and Co-catalysts

[0108]

[0109] Preparation of crosslinkable polyolefin granules

[0110] Referring to Tables 4 through 9, the polyolefin elastomer granules from Table 1 are mixed with curing additives (peroxides, crosslinking aids, and silane coupling agents) in a fluorinated HDPE bottle to form crosslinkable polyolefin elastomer granules. If T770 is present in the formulation, an additional step is required to dissolve T770 in the peroxides and aids at 40°C for 20 minutes before mixing with the POE granules. The soaking process is carried out by rolling the bottle and absorbing at 50°C for 5 hours until all additives are completely diffused into the granules.

[0111] The preparation of cross-linked samples used for gel and transmittance testing is described in the testing section above.

[0112] Table 4

[0113]

[0114] Table 5

[0115]

[0116] Table 6

[0117]

[0118] Table 7

[0119]

[0120] Referring to Tables 4 to 6 above, the MDR and gel content of all samples were measured. ts0.5 is an indicator of scorch resistance time; a shorter ts0.5 indicates a higher tendency for scorching during film extrusion. Gel content is an indicator of crosslinking density. Gel content at different lamination times is an indicator of curing rate. Generally, a faster curing rate and higher crosslinking density result in a shorter ts0.5. For example, comparing CE-A in Table 4 with CE-E in Table 5, CE-E has a longer ts0.5, a lower curing rate, and a lower crosslinking density than CE-A. Similarly, when comparing CE-B in Table 4 with CE-F in Table 5, CE-F exhibits a longer ts0.5, a lower curing rate, and a lower crosslinking density than CE-B. However, it was observed that by introducing both long-chain branching (LCB) and chain-end unsaturation, a longer ts0.5, a faster curing rate, and a higher crosslinking density can be achieved.

[0121] As shown in Table 4, IE-1 (which includes a melt index (I2) of approximately 5 dg / min and an I2 greater than 9) 10 POEA with I2 showed better performance than CE-A (which includes POEA with a melt index of 5 dg / min and I2 of 7). 10 IE-1 exhibits a larger LCB and chain-terminal unsaturation (POE F) and thus a longer ts0.5 value (1.5 min vs. 1.7 min), while CE-A has significantly less LCB and chain-terminal unsaturation. In addition to the longer ts0.5 value, the gel content after different lamination times indicates that IE-1 achieves a faster curing rate and higher crosslinking density than CE-A.

[0122] Further, as shown in Table 4, IE-2 (which includes a melt index (I2) of approximately 13 dg / min and an I2 of greater than 9)10 POE B of / I2) and IE-3 (which includes a melt index (I2) of about 13 dg / min and an I2 of greater than 9) 10 / I2 of POE C) has a higher melt index than CE-B (which includes a melt index (I2) of about 14 dg / min and an I of 7. 10 / I2 of POE G) and CE-D (which includes a melt index (I2) of about 13 dg / min and an I of 7.4) 10 IE-2 and IE-3 exhibit larger LCB and chain-terminal unsaturation (I2), resulting in longer ts0.5 values. In addition to the longer ts0.5 values, gel content after different lamination times indicates that IE-2 and IE-3 achieve faster curing rates and higher crosslinking densities than CE-B and CE-D. CE-C (which includes a melt index (I2) of approximately 15 dg / min and an I2 of 8.9) shows higher crosslinking density. 10 / I2's POE E) exhibited a curing rate and crosslinking density comparable to IE-2 and IE-3; however, CE-C's ts0.5 was lower than that of IE-2 and IE-3, specifically 2 min vs. 2.1 min and 2.2 min, respectively.

[0123] The inter-cell displacement results in Table 4 show that, compared with a comparative example having a similar melt index, the embodiment of the present invention with LCB achieves better resistance to inter-cell displacement during lamination.

[0124] Tables 4 to 6 show that both LCB and chain-terminal unsaturation in polyolefin elastomers can achieve the desired balance between curing rate and scorch resistance. Furthermore, the desired balance between curing rate and scorch resistance is as follows: Figure 1 and Figure 2 As shown, this is a graph illustrating the relationship between crosslinking density (gel content after 4+12 minutes of lamination time) and scorch time.

[0125] Further, as shown in Table 7, after crosslinking, resins with terminal unsaturation exhibit significantly higher transmittance compared to conventional POE resins with minimal or no terminal unsaturation. Furthermore, TAEC peroxide performs better than TBEC peroxide in achieving higher transmittance after curing, as shown in Table 7. Without theoretical limitations, it appears that the network formed by terminal unsaturation reduces the chain mobility of the network, resulting in smaller crystals. Moreover, without theoretical limitations, TAEC exhibits higher transmittance after curing compared to TBEC, partly because the ethyl radicals generated from TAEC decomposition tend to react with the terminal unsaturation in POE to build more network from the chain ends.

[0126] In addition, as shown in Table 8 below, POE resin blends using POE with high LCB and high chain-terminal unsaturation exhibit high transmittance, rapid curing and scorch resistance even when blended with conventional POE resins such as POE F and POE G.

[0127] Table 8 - Resin Blends

[0128]

[0129] Additionally, as shown in Table 9, a single-cell module was fabricated using a membrane made of IE-22. As shown in Table 9, the Pmax loss after PID testing was very low.

[0130] Table 9 PID

[0131]

[0132] As shown above, the average front-end PID loss and average rear-end PID loss are far below the typical industrial requirement of <5%.

[0133] While specific embodiments of this disclosure have been described and illustrated, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of this disclosure. Therefore, it is intended that all such changes and modifications be covered within the scope of this disclosure in the appended claims.

Claims

1. A polyolefin elastomer comprising a unimodal ethylene-octene copolymer, wherein the polyolefin elastomer has: Density ranging from 0.860 g / cc to 0.900 g / cc; I greater than 9 10 / I2, where I2 is measured according to ASTM D1238 (190°C, 2.16 kg), and I 10 Measured according to ASTM D1238 (190℃, 10Kg); The percentage of vinyl groups in the total unsaturation that is greater than or equal to 55%; and Greater than or equal to 0.2 degrees of unsaturation per 1000 carbons.

2. The polyolefin elastomer according to claim 1, wherein the polyolefin elastomer has a degree of unsaturation greater than or equal to 0.4 degrees / 1000 carbons.

3. A crosslinkable polyolefin elastomer formulation comprising an organic peroxide and the polyolefin elastomer according to claim 1 or 2.

4. The crosslinkable polyolefin elastomer formulation according to claim 3, wherein the curing package further comprises a silane coupling agent, a crosslinking aid, or both.

5. The crosslinkable polyolefin elastomer formulation according to any one of claims 2 to 4, wherein the formulation comprises 85% to 99.5% by weight of a polyolefin elastomer and 0.1% to 2% by weight of an organic peroxide.

6. The crosslinkable polyolefin elastomer formulation according to any one of claims 2 to 5, wherein the organic peroxide comprises at least one selected from tert-butylperoxycarbonate 2-ethylhexyl ester (TBEC), tert-amylperoxycarbonate 2-ethylhexyl ester (TAEC), 1,1-di(tert-butylperoxy)cyclohexane and 1,1-di-(tert-butylperoxy)-3,3,5-trimethyl-cyclohexane.

7. The crosslinkable polyolefin elastomer formulation according to any one of claims 4 to 6, wherein the crosslinking aid comprises one or more of the following: triallyl cyanurate (TAC), triallyl phosphate (TAP), triallyl isocyanurate (TAIC), 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (vinyl D4), N,N,N',N',N'',N''-hexamyl-1,3,5-triazine-2,4,6-triamine, triallyl trimellitate, trimethylolpropane triacrylate (TMPTA), and trimethylolpropane trimethacrylate (TMPTMA).

8. The crosslinkable polyolefin elastomer formulation according to any one of claims 4 to 7, wherein the silane coupling agent comprises one or more of vinyltrimethoxysilane (VTMS), 3-(trimethoxysilyl)propyl methacrylate, and tetraethoxysilane (TEOS).

9. The crosslinkable polyolefin elastomer formulation according to any one of claims 3 to 8, further comprising a filler.

10. The crosslinkable polyolefin elastomer formulation according to claim 9, wherein the filler comprises TiO2.

11. A crosslinked polyolefin elastomer produced from a crosslinkable polyolefin elastomer formulation according to any one of claims 3 to 10.

12. The crosslinked polyolefin elastomer according to claim 11, wherein the crosslinked polyolefin elastomer is prepared by heat, radiation, electron beam radiation or ultraviolet (UV) radiation.

13. An article comprising the crosslinked polyolefin elastomer according to claim 11 or 12.

14. The article of claim 13, wherein the article is a multilayer film.

15. The article of claim 13, wherein the article is an encapsulant for a photovoltaic module.

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