Flexible acrylic resin modified polyvinylidene fluoride film

Abstract

A polymer composition comprising a polyvinylidene fluoride resin and a multi-stage acrylic polymer is provided. The multi-stage acrylic polymer comprises a cross-linked core, at least one intermediate layer, and a shell. Each of the crosslinked core and the shell comprises polymerized units derived from one or more alkyl (meth) acrylate monomers, and the one or more intermediate layers comprise polymerized units derived from one or more alkyl (meth) acrylate monomers, styrene-based monomers, and combinations thereof. Articles comprising the polymer compositions and photovoltaic modules comprising films comprising the polymer compositions are also disclosed.

Description

Technical Field

[0001] The present invention generally relates to flexible acrylic modified polyvinylidene fluoride (PVDF) films. Background Art

[0002] Polyvinylidene fluoride (PVDF) is an important member of the fluoroplastic family. PVDF has excellent properties due to its chemical structure CF bond, which leads to excellent weather resistance, chemical resistance and low moisture vapor transmission rate. PVDF is commonly used as a pipe material, as a lining material for storage tanks and reaction vessels in chemical plants, as interior and exterior plastic parts for buildings and automobiles, and also as a surface protective film for metal plates or an insulating material for electronic and electrical equipment.

[0003] In recent years, PVDF has been used as a weather-resistant film in the backplane of photovoltaic solar panel modules (for example, see Japanese patent application publication No. JP2000294813A). Photovoltaic modules generally include at least one photovoltaic element encapsulated between a front layer and a back layer. The front layer is generally glazed glass, which provides weather resistance, scratch resistance, impact resistance, and heat resistance, while still being able to achieve maximum photoelectric conversion efficiency. The back layer is generally composed of polymer films and laminates to protect photovoltaic cells and wires from environmental influences. It is also desirable that the back layer reflects sunlight to further improve the power generation efficiency of the photovoltaic module. An example of such a backplane is disclosed in Japanese patent application No. JP2009071236A, which discloses a conventional photovoltaic module comprising a polyethylene terephthalate (PET) sheet laminated with a PVDF film containing a white pigment. Titanium dioxide TiO2 is a preferred pigment for reflecting sunlight in photovoltaic modules.

[0004] Challenges associated with using PVDF arise from the poor adhesion of PVDF to other materials. To overcome the poor adhesion, Japanese Patent No. JP H-05-50556 discloses the introduction of polymethyl methacrylate (PMMA) into PVDF to provide better adhesion to PET sheets.

[0005] However, the introduction of PMMA into PVDF leads to a decrease in the toughness of the PVDF film. Generally, PMMA-modified PVDF films become brittle, making the film easily damaged during the lamination process.

[0006] One attempt to solve the problems caused by modifying PVDF membranes with PMMA is disclosed in Chinese registered utility model CN206553441U. In CN206663441U, the PMMA-modified PVDF membrane is further modified by adding a toughening agent to provide the desired toughness.

[0007] There is still the problem of cracks in the protective PVDF film in photovoltaic modules. During the installation and transportation of photovoltaic modules, slight deformation of the module may occur. Deformation of photovoltaic modules can also occur due to temperature changes during use. This deformation can cause cracks in the PVDF film, which in turn can cause moisture or oxygen to enter the photovoltaic module. Moisture and oxygen can cause corrosion of the wires, which can lead to failure or reduced performance of the photovoltaic module.

[0008] Therefore, there is a need for PVDF membranes that can solve the problems that can be solved with existing solutions. Summary of the invention

[0009] One aspect of the present invention provides a polymer composition comprising a polyvinylidene fluoride resin and a multistage polymer. The multistage acrylic polymer comprises a crosslinked core, at least one intermediate layer and a shell. Each of the crosslinked core and the shell comprises polymerized units derived from one or more (meth) alkyl acrylate monomers, and the one or more intermediate layers comprise polymerized units derived from one or more (meth) alkyl acrylate monomers, styrene monomers and combinations thereof.

[0010] Another aspect of the present invention provides an article comprising a polymer composition comprising a polyvinylidene fluoride resin and a multistage acrylic polymer. The multistage acrylic polymer comprises a crosslinked core, at least one intermediate layer and a shell. Each of the crosslinked core and the shell comprises polymerized units derived from one or more (meth) alkyl acrylate monomers, and one or more intermediate layers comprise polymerized units derived from one or more (meth) alkyl acrylate monomers, styrene monomers and combinations thereof.

[0011] Another aspect of the present invention relates to a photovoltaic module, which includes a transparent front layer, a photovoltaic cell and a back layer. The back layer includes a film, which includes a polymer composition, and the polymer composition includes a polyvinylidene fluoride resin and a multi-stage acrylic resin. The multi-stage acrylic polymer includes a cross-linked core, at least one intermediate layer and a shell. Each of the cross-linked core and the shell includes a polymerization unit derived from one or more (meth) alkyl acrylate monomers, and one or more intermediate layers include polymerization units derived from one or more (meth) alkyl acrylate monomers, styrene monomers and combinations thereof. DETAILED DESCRIPTION

[0012] The inventors have now surprisingly found that a polymer composition comprising a polyvinylidene fluoride resin and a multistage acrylic polymer has improved elongation and / or higher tear resistance. The multistage acrylic polymer comprises a crosslinked core, at least one intermediate layer and a shell. Each of the crosslinked core and the shell comprises polymerized units derived from one or more alkyl (meth)acrylate monomers, and the one or more intermediate layers comprise polymerized units derived from one or more alkyl (meth)acrylate monomers, styrenic monomers and combinations thereof.

[0013] 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," "copolymer," "terpolymer," and "resin." As used herein, the term "polymerized units derived from" refers to polymer molecules synthesized according to polymerization techniques, wherein the product polymer contains polymerized units "derived from" the constituent monomers that are the starting materials for the polymerization reaction. As used herein, the term "(meth)acrylate" refers to acrylate or methacrylate or a combination thereof, and the term "(meth)acrylic acid" refers to acrylic acid or methacrylic acid or a combination thereof.

[0014] As used herein, the term "phr" means parts per hundred resin or polymer solids. As used herein, the term "molecular weight" or "weight average molecular weight" or "M w ” refers to the weight average molecular weight of the polymer as measured by gel permeation chromatography (“GPC”) for acrylic polymers according to ASTM D5296-11 (2011) against polystyrene calibration standards and using tetrahydrofuran (“THF”) as the mobile phase and diluent. As used herein, the term “particle size” means the weight average particle size of the emulsion (co)polymer particles as measured using a Brookhaven BI-90 particle size analyzer.

[0015] As used herein, the term "glass transition temperature" or "T g " refers to the temperature at or above which a glassy polymer will undergo segmental motion of the polymer chain. The glass transition temperature of a copolymer can be estimated by the Fox equation (Bulletin of the American Physical Society, 1(3) Page 123 (1956)) as follows:

[0016] 1 / T g =w1 / T g(1) +w2 / T g(2)

[0017] For copolymers, w1 and w2 refer to the weight fractions of the two comonomers, and Tg(1) and T g(2) refers to the glass transition temperature of two corresponding homopolymers prepared from these monomers. For polymers containing three or more monomers, an additional term (w n / T g(n) The glass transition temperature of the homopolymer can be found, for example, in "Polymer Handbook", edited by J. Brandrup and EH Immergut, Interscience Publishers. g It can also be measured by various techniques, including, for example, differential scanning calorimetry ("DSC"). As used herein, the phrase "calculated T g ” shall mean the glass transition temperature calculated by the Fox equation.

[0018] The polymer composition of the present invention preferably comprises the multistage acrylic polymer in an amount ranging from 5 wt% to 40 wt%, based on the total weight of the multistage acrylic polymer and the polyvinylidene fluoride resin in the polymer composition. Preferably, the multistage acrylic polymer is present in an amount ranging from 10 wt% to 35 wt%, more preferably from 15 wt% to 30 wt%, based on the total weight of the multistage acrylic polymer and the polyvinylidene fluoride resin in the polymer composition.

[0019] The multistage acrylic polymer comprises a crosslinked core, one or more intermediate layers and a shell. Each of the crosslinked core and the shell comprises polymerized units derived from one or more (meth) alkyl acrylate monomers, and the one or more intermediate layers comprise polymerized units derived from one or more (meth) alkyl acrylate monomers, styrene monomers and combinations thereof. Preferably, the crosslinked core is present in the multistage polymer in an amount of 25 wt % to 45 wt %, preferably 30 wt % to 40 wt %, more preferably 32 wt % to 38 wt %, based on the total weight of the multistage polymer. The one or more intermediate layers are present in the multistage polymer in an amount of 30 wt % to 70 wt %, preferably 40 wt % to 65 wt %, more preferably 45 wt % to 60 wt %, based on the total weight of the multistage polymer. The shell is present in the multistage polymer in an amount of 5 wt % to 25 wt %, preferably 10 wt % to 20 wt %, more preferably 12 wt % to 18 wt %, based on the total weight of the multistage polymer.

[0020] Preferably, the one or more intermediate layers include a first intermediate layer and a second intermediate layer. When the first intermediate layer and the second intermediate layer are present, the first intermediate layer is present in the multistage polymer in an amount of 25 wt % to 45 wt %, preferably 30 wt % to 40 wt %, more preferably 32 wt % to 38 wt %, based on the total weight of the multistage polymer. In certain embodiments, the second intermediate layer is present in the multistage polymer in an amount of 5 wt % to 25 wt %, preferably 10 wt % to 20 wt %, more preferably 12 wt % to 18 wt %, based on the total weight of the multistage polymer.

[0021] The crosslinked core of the multistage polymer of the present invention comprises polymerized units derived from one or more (meth) alkyl acrylate monomers. (Meth) alkyl acrylate monomers include straight and branched (meth) alkyl acrylates, wherein the alkyl group has 1 to 12 carbon atoms. Suitable (meth) alkyl acrylate monomers include, for example, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, ethylhexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate and isooctyl acrylate. Preferably, the (meth) alkyl acrylate monomer of the crosslinked core comprises butyl acrylate. Based on the total weight of the crosslinked core, the (meth) alkyl acrylate monomer can be present in the crosslinked core in an amount of 95 wt % to 99.9 wt %, preferably 97 wt % to 99.5 wt %, more preferably 98 wt % to 99 wt %.

[0022] The crosslinked core of the multistage polymer of the present invention may also include polymerized units derived from one or more crosslinking monomers, graft-linked monomers, and combinations thereof. Suitable crosslinking and graft-linked monomers include, for example, butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, divinylbenzene, diethylene glycol di(meth)acrylate, diallyl maleate, allyl acrylate, allyl methacrylate, diallyl phthalate, triallyl phthalate, and trimethylolpropane tri(meth)acrylate. The crosslinked monomers and graft-linked monomers of the crosslinked core may include 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, and allyl (meth)acrylate. Based on the total weight of the crosslinked core, the crosslinked monomers and graft-linked monomers may be present in the crosslinked core in an amount of 0.1 wt % to 5 wt %, preferably 0.5 wt % to 3 wt %, and more preferably 1 wt % to 2 wt %.

[0023] The crosslinked core of the multistage polymer of the present invention preferably has a calculated T of -85°C or above, -70°C or above, or -60°C or above. g The crosslinked core of the multistage polymer of the present invention may have a calculated T of -10°C or less, -30°C or less, or -40°C or less.g .

[0024] The one or more intermediate layers of the multistage polymer of the present invention comprise polymerized units derived from one or more alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof. Alkyl (meth)acrylate monomers include linear and branched alkyl (meth)acrylates, wherein the alkyl group has 1 to 12 carbon atoms. Suitable alkyl (meth)acrylate monomers include, for example, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, ethylhexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, and isooctyl acrylate. Suitable styrene monomers include, for example, styrene, alpha-methylstyrene, and vinyltoluene.

[0025] Preferably, the one or more intermediate layers include a first intermediate layer and a second intermediate layer. The first intermediate layer preferably comprises polymerized units derived from one or more (meth) alkyl acrylate monomers. Suitable (meth) alkyl acrylate monomers include, for example, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, ethylhexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate and isooctyl acrylate. The (meth) alkyl acrylate monomer of the first intermediate layer preferably includes butyl acrylate and methyl methacrylate. Based on the total weight of the one or more intermediate layers, the (meth) alkyl acrylate monomer can be present in the first intermediate layer in an amount of 95 wt % to 100 wt %, preferably 97 wt % to 99.9 wt %, more preferably 99 wt % to 99.9 wt %.

[0026] The first intermediate layer of the multistage polymer of the present invention may also include polymerized units derived from one or more crosslinking monomers, graft-linking monomers and combinations thereof. Suitable crosslinking and graft-linking monomers include, for example, butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, divinylbenzene, diethylene glycol di(meth)acrylate, diallyl maleate, allyl methacrylate, allyl acrylate, diallyl phthalate, triallyl phthalate and trimethylolpropane tri(meth)acrylate. The crosslinking monomers and graft-linking monomers of the first intermediate layer may include allyl methacrylate. Based on the total weight of the first intermediate layer, the crosslinking monomers and graft-linking monomers may be present in the first intermediate layer in an amount of 0 wt % to 5 wt %, preferably 0.1 wt % to 3 wt %, more preferably 0.1 wt % to 1 wt %.

[0027] The first intermediate layer may be composed of a plurality of sublayers, each of which independently contains polymerized units derived from the above-mentioned monomer composition for the entire first intermediate layer. The first intermediate layer may contain, for example, one, two, three, four or five sublayers. The first intermediate layer contains a composition gradient between the sublayers, such that Tg Transition from a minimum value to a maximum value across the width of the entire first intermediate layer. In certain embodiments, T is calculated g The composition gradient is achieved by appropriately selecting the manner and timing of adding monomers during the emulsion polymerization process used to prepare the first intermediate layer. A multistage polymerization process may be used during which monomers are added in stages rather than all at once to the emulsion polymerization reactor (or reactor vessel), thereby allowing one layer to penetrate into an adjacent layer, causing a T gradient on the first intermediate layer. g gradient.

[0028] The second intermediate layer of the multistage polymer of the present invention may include one or more of (meth) alkyl acrylate monomers, styrene monomers and combinations thereof. (Meth) alkyl acrylate monomers include linear and branched (meth) alkyl acrylates, wherein the alkyl group has 1 to 12 carbon atoms. Suitable (meth) alkyl acrylate monomers include, for example, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, ethylhexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate and isooctyl acrylate. Suitable styrene monomers include, for example, styrene, α-methylstyrene and vinyltoluene. The (meth) alkyl acrylate monomers of the second intermediate layer preferably include butyl acrylate and methyl methacrylate. Based on the total weight of the second intermediate layer, the (meth) alkyl acrylate monomer can be present in the second intermediate layer in an amount of 98 wt % to 100 wt %, preferably 98.5 wt % to 99.5 wt %, more preferably 98.7 wt % to 99.3 wt %.

[0029] The second intermediate layer of the multistage polymer of the present invention may also include polymerized units derived from one or more chain transfer agents. Suitable chain transfer agents include, for example, 1-dodecanethiol, tert-dodecanethiol, thioethanol, hexyl mercaptan, mercaptopropionic acid, methyl-3-mercaptopropionic ester and butyl-3-mercaptopropionic ester. The chain transfer agent of the second intermediate layer preferably includes 1-dodecanethiol. Based on the total weight of the second intermediate layer, the chain transfer agent can be present in the second intermediate layer in an amount of 0 wt % to 2 wt %, preferably 0.5 wt % to 1.5 wt %, and more preferably 0.7 wt % to 1.3 wt %.

[0030] The second intermediate layer of the multistage polymer of the present invention may have a calculated T of 40°C or more, 45°C or more, or 65°C or more. g The second intermediate layer of the multistage polymer of the present invention may have a calculated T of 110°C or less, 95°C or less, or 80°C or less. g .

[0031] The shell of the multistage polymer of the present invention comprises one or more of (meth) alkyl acrylate monomers, styrene monomers and combinations thereof. (Meth) alkyl acrylate monomers include linear and branched (meth) alkyl acrylates, wherein the alkyl group has 1 to 12 carbon atoms. Suitable (meth) alkyl acrylate monomers include, for example, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, ethylhexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate and isooctyl acrylate. Suitable styrene monomers include, for example, styrene, α-methyl styrene and vinyl toluene. The (meth) alkyl acrylate monomers of the shell preferably include butyl acrylate and methyl methacrylate. Based on the total weight of the shell, the (meth) alkyl acrylate monomer can be present in the shell in an amount of 84 wt % to 98 wt %, preferably 85 wt % to 94 wt %, more preferably 86 wt % to 93 wt %.

[0032] The shell of the multistage polymer of the present invention may also include one or more monomers selected from acid functional monomers, hydroxy functional monomers and combinations thereof. Suitable examples of functional monomers include, for example, acid functional monomers and hydroxy functional monomers. Suitable examples of acid functional monomers include, for example, acrylic monomers with one or more carboxyl groups, such as (meth) acrylic acid, itaconic acid and phthalic acid. Preferably, the one or more acid functional monomers include acrylic acid. Suitable examples of hydroxy functional monomers include, for example, one or more hydroxy substituted C1-C8 (meth) alkyl acrylates. Preferably, the one or more hydroxy functional monomers include hydroxyethyl methacrylate. Based on the total weight of the shell, the one or more monomers selected from acid functional monomers, hydroxy functional monomers and combinations thereof can be present in the shell in an amount of 2 wt % to 16 wt %, preferably 3 wt % to 14 wt %, more preferably 5 wt % to 12 wt %.

[0033] The shell of the multistage polymer of the present invention may also contain polymerized units derived from one or more chain transfer agents. Suitable chain transfer agents include, for example, 1-dodecyl mercaptan, tert-dodecyl mercaptan, thioethanol, hexyl mercaptan, mercaptopropionic acid, methyl-3-mercaptopropionic ester, butyl-3-mercaptopropionic ester. Preferably, the chain transfer agent of the shell includes 1-dodecyl mercaptan. The chain transfer agent may be present in the shell in an amount of 0 wt % to 2 wt %, preferably 0.5 wt % to 1.5 wt %, more preferably 0.7 wt % to 1.3 wt %, based on the total weight of the shell.

[0034] The shell of the multi-stage polymer of the present invention may have a calculated T in the range of 40°C or above, 50°C or above, or 65°C or above. g The shell of the multistage polymer of the present invention may have a calculated T of 100°C or less, 90°C or less, or 80°C or less.g .

[0035] The shell of the multistage polymer of the present invention may have a weight average molecular weight (MW) in the range of 20,000 g / mol to 100,000 g / mol, 30,000 g / mol to 60,000 g / mol, 40,000 g / mol to 60,000 g / mol, or 40,000 g / mol to 50,000 g / mol. w ).

[0036] The multistage polymers of the present invention may have a particle size in the range of 30 nm to 250 nm, preferably 50 nm to 200 nm, more preferably 60 nm to 175 nm, even more preferably 90 nm to 150 nm, as measured by a Brookhaven BI-90 particle size analyzer.

[0037] Suitable polymerization techniques for preparing the polymer contained in the polymer composition of the present invention include, for example, emulsion polymerization and solution polymerization, preferably emulsion polymerization, as disclosed in U.S. Patent No. 6,710,161. Aqueous emulsion polymerization methods are usually carried out in an aqueous reaction mixture containing at least one monomer and a variety of synthetic adjuvants, such as a free radical source, a buffer and a reducing agent in an aqueous reaction medium. Chain transfer agents can be used to limit molecular weight. The aqueous reaction medium is the continuous fluid phase of the aqueous reaction mixture and contains more than 50% by weight of water and optionally one or more water-miscible solvents based on the weight of the aqueous reaction medium. Suitable water-miscible solvents include, for example, methanol, ethanol, propanol, acetone, ethylene glycol ethyl ether, propylene glycol propyl ether and diacetone alcohol. Based on the weight of the aqueous reaction medium, the aqueous reaction medium may contain more than 90% by weight of water, preferably more than 95% by weight of water, more preferably more than 98% by weight of water.

[0038] The polymer composition of the present invention may also contain other optional ingredients, including, for example, plasticizers, antioxidants, UV absorbers and light stabilizers, dyes, pigments, flame retardants, and other additives to prevent, reduce or mask discoloration or deterioration caused by heating, aging or exposure to light or weathering. Those skilled in the art can easily determine the amount of optional ingredients that are effective for achieving the desired properties provided by such ingredients.

[0039] The polymer composition of the present invention has end-use applications including, for example, as sheets and films for photovoltaic modules. The multistage polymer composition of the present invention can be processed into films and / or sheets by extrusion blow molding, extrusion casting, calendering, hot pressing or injection molding. The sheets and films made from the polymer composition of the present invention can have any suitable thickness. In one embodiment, the sheet or film has a thickness of 20 microns to 500 microns.

[0040] According to one aspect of the present invention, the photovoltaic module comprises a transparent front layer, a photovoltaic cell and a back layer comprising a film, the film comprising a polymer composition comprising a polyvinylidene fluoride resin and a multi-stage acrylic polymer. Preferably, the polymer composition further comprises a reflective pigment such as, for example, titanium dioxide (TiO2).

[0041] Some embodiments of the present invention will now be described in detail in the following examples.

[0042] Example

[0043] Example 1

[0044] Preparation of Exemplary Polymer Compositions

[0045] The PVDF compound was prepared by a co-rotating twin-screw extruder at a melt temperature of about 230°C and then by a laboratory hot press to prepare a film at 220°C with a target film thickness of 200 microns. The polymer composition of the present invention comprises a multi-stage acrylic polymer (VERSALOID TM 21308-XP) and polyvinylidene fluoride resin (DongYue DS206), wherein the multistage acrylic polymer is present in an amount of 29.5 phr relative to the weight of the polyvinylidene fluoride resin. In a comparative example, 29.5 phr of toughened polymethyl methacrylate polymer (Evonik 8N PMMA and PARALOID TM EXL-2315 impact modifier blend, from The Dow Chemical Company) instead of multi-stage acrylic polymer. The examples of the present invention and the comparative examples contain the same pigment, processing aid and antioxidant. As shown in Table 1 below, the examples of the present invention show excellent tensile elongation and tear strength compared to the comparative examples. To simulate aging, the film was exposed to a temperature of 121°C, 100% relative humidity, and 2 atm pressure for 96 hours.

[0046] Table 1

[0047] Comparative Example Embodiments of the present invention MFI (g / 10min), 230℃ / 5kg, 4min immersion 9.9 9.7 Tensile elongation (%) 5.15 9.28 Tensile elongation after aging (%) 3.67 6.70 Tear strength(cN) 655.6 725.6 Aged tear strength (cN) 333.5 471.3

Claims

1. A polymer composition, comprising: Polyvinylidene fluoride resin; and A multistage acrylic polymer, wherein the multistage acrylic polymer comprises a crosslinked core, one or more intermediate layers, and a shell, wherein each of the crosslinked core and the shell comprises polymerized units derived from one or more alkyl (meth)acrylate monomers, and the one or more intermediate layers comprise polymerized units derived from one or more alkyl (meth)acrylate monomers, styrenic monomers, and combinations thereof.

2. The polymer composition of claim 1, wherein the multistage acrylic polymer comprises: (a) 25 wt% to 45 wt% of the crosslinked core, based on the total weight of the multistage polymer, the crosslinked core comprising polymerized units derived from: (i) 95 wt% to 99.9 wt% of one or more alkyl (meth)acrylate monomers, and (ii) 0.1 wt% to 5 wt% of one or more crosslinking monomers, graft link monomers, and combinations thereof, based on the total weight of the crosslinked core; (b) 30 wt % to 70 wt % of the one or more intermediate layers, based on the total weight of the multistage polymer, the one or more intermediate layers comprising polymerized units derived from: (i) 95 wt % to 100 wt % of one or more alkyl (meth)acrylate monomers, and (ii) 0 wt % to 5 wt % of a crosslinking monomer, a graft-linking monomer, and combinations thereof, based on the total weight of the one or more intermediate layers; (c) from 5 wt% to 25 wt%, based on the total weight of the multi-stage polymer, of the shell, the shell comprising polymerized units derived from: (i) 84 wt% to 98 wt% of one or more alkyl (meth)acrylate monomers, styrenic monomers, and combinations thereof; (ii) 2 wt% to 16 wt% of one or more monomers selected from acid-functional monomers, hydroxyl-functional monomers, and combinations thereof; and (iii) 0 wt% to 2 wt% of one or more chain transfer agents.

3. The composition of claim 1 or claim 2, wherein the one or more alkyl (meth)acrylate monomers of the crosslinked core, the one or more intermediate layers and the shell are selected from methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, ethylhexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, isooctyl acrylate and combinations thereof.

4. The composition of claim 3, wherein the one or more alkyl (meth)acrylate monomers of the crosslinked core, the one or more intermediate layers, and the shell are selected from butyl acrylate, methyl methacrylate, and combinations thereof.

5. The composition of any one of claims 2 to 4, wherein the one or more monomers selected from acid-functional monomers, hydroxy-functional monomers, and combinations thereof comprise one or more of acrylic acid and hydroxyethyl methacrylate.

6. The composition according to any one of claims 2 to 5, wherein the one or more crosslinking monomers, graft-linking monomers, and combinations thereof of the crosslinked core and the one or more intermediate layers are selected from 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, allyl methacrylate, and combinations thereof.

7. The composition according to any of the preceding claims, wherein the one or more intermediate layers include a first intermediate layer and a second intermediate layer, wherein the first intermediate layer comprises polymerized units derived from (i) 95 wt % to 100 wt % of one or more alkyl (meth)acrylate monomers, and (ii) 0 wt % to 5 wt % of crosslinking monomers, graft-linking monomers, and combinations thereof, based on the total weight of the first intermediate layer, and the second intermediate layer comprises polymerized units derived from (i) 98 wt % to 100 wt % of one or more alkyl (meth)acrylate monomers, styrenic monomers, and combinations thereof, and (ii) 0 wt % to 2 wt % of one or more chain transfer agents, based on the total weight of the second intermediate layer.

8. The composition of any one of the preceding claims, wherein the multistage acrylic polymer is present in an amount ranging from 5 wt% to 40 wt%, based on the total weight of the polyvinylidene fluoride resin and the multistage acrylic polymer.

9. The composition according to any one of the preceding claims, further comprising at least one reflective pigment.

10. An article comprising the polymer composition according to any one of the preceding claims, wherein the article is selected from the group consisting of films and sheets.

11. A photovoltaic module, comprising: Transparent front layer; Photovoltaic cells; as well as A backing layer comprising a film comprising the polymer composition according to any one of claims 1 to 9.