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 includes a crosslinked core, at least one intermediate layer, and a shell. Each of the crosslinked core and the shell includes polymerization units derived from one or more alkyl (meth)acrylate monomers, and the at least one intermediate layer includes polymerization units derived from one or more alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof. Also disclosed are articles comprising the polymer composition and a photovoltaic module comprising a film comprising the polymer composition.

Description

Technical Field

[0001] The present invention generally relates to a flexible acrylic resin-modified polyvinylidene fluoride (PVDF) film.

Background Art

[0002] Polyvinylidene fluoride (PVDF) is an important member of the fluororesin family. PVDF has excellent performance due to its chemical structure C-F bond, which brings excellent weather resistance, chemical resistance, and low water vapor transmission rate. PVDF is often used as a pipe material and lining material for storage tanks and reaction vessels in chemical plants, plastic parts for interior and exterior decoration of buildings and automobiles, and also as a surface protection film for metal plates or an insulating material for electric and electronic devices.

[0003] In recent years, PVDF has been used as a weather-resistant film in the backsheet of photovoltaic solar modules (see, for example, Japanese Patent Application Laid-Open No. 2000294813 (A)). A photovoltaic module generally includes at least one photovoltaic element encapsulated between a front layer and a back layer. The front layer is often a glass glaze that provides weather resistance, scratch resistance, impact resistance, and heat resistance while still allowing maximum photovoltaic conversion efficiency. The back layer is generally composed of a polymer film and a laminate to protect the photovoltaic cell and electrical wiring from the environment. Also, in some cases, it is desirable for the back layer to reflect sunlight to further increase the power generation efficiency of the photovoltaic module. An example of such a backsheet is disclosed in Japanese Patent Application Laid-Open No. 2009071236 (A), which discloses a conventional photovoltaic module including 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] The problems associated with the use of PVDF are due to the insufficient adhesion of PVDF to other materials. As an attempt to overcome the poor adhesion, Japanese Patent Laid-Open No. 05-50556 discloses introducing polymethyl methacrylate (PMMA) into PVDF to provide better adhesion to a PET sheet.

[0005] However, when PMMA is introduced into PVDF, the toughness of the PVDF film decreases. Generally, PMMA-modified PVDF films become brittle, and the films are easily damaged during lamination.

[0006] One attempt to address the problems caused by modifying PVDF films with PMMA is disclosed in Chinese Registered Utility Model No. 206553441 (U). In Chinese Registered Utility Model No. 206663441 (U), the PMMA-modified PVDF film is further modified by adding a reinforcing agent to provide the desired toughness.

[0007] The problem of cracking still exists in the protective PVDF film in a photovoltaic module. During the installation and transportation of the photovoltaic module, slight deformation of the module may occur. The deformation of the photovoltaic module may also occur during use due to temperature changes. This deformation may cause cracks in the PVDF film, which in turn may lead to the entry of moisture or oxygen into the photovoltaic module. Moisture and oxygen may cause corrosion of the wiring, which may cause failure or performance degradation of the photovoltaic module.

[0008] Therefore, there is a need for PVDF that can address the problems associated 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 multi-stage polymer. The multi-stage acrylic polymer includes a crosslinked core, at least one intermediate layer, and a shell. Each of the crosslinked core and the shell includes polymerized units derived from one or more alkyl (meth)acrylate monomers, and the at least one intermediate layer includes polymerized units derived from one or more alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof.

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

[0011] Yet another aspect of the present invention relates to a photovoltaic module including a transparent front layer, a photovoltaic cell, and a back layer. The back layer includes a film comprising a polymer composition comprising a polyvinylidene fluoride resin and a multi-stage acrylic resin. The multi-stage acrylic polymer includes a crosslinked core, at least one intermediate layer, and a shell. Each of the crosslinked core and the shell includes polymerized units derived from one or more alkyl (meth)acrylate monomers, and the at least one intermediate layer includes polymerized units derived from one or more alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof.

Embodiments for Carrying Out the Invention

[0012] The inventors have surprisingly found a polymer composition comprising a polyvinylidene fluoride resin and a multi-stage acrylic polymer having improved elongation and / or higher tear resistance. The multi-stage 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 at least one intermediate layer comprises polymerized units derived from one or more alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof.

[0013] As used herein, the term "polymer" refers to a polymer compound prepared by polymerizing monomers, whether of the same or different types. The general term "polymer" includes the terms "homopolymer", "copolymer", "terpolymer", and "resin". As used herein, the term "polymerized unit derived from" refers to a polymer molecule synthesized according to polymerization techniques in which the product polymer contains "polymerized units derived from" the constituent monomers that are the starting materials of the polymerization reaction. As used herein, the term "(meth)acrylate" refers to either acrylate or methacrylate or a combination thereof, and the term "(meth)acrylic" refers to either acrylic or methacrylic 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 a polymer measured by gel permeation chromatography ("GPC") of an acrylic polymer against a polystyrene calibration standard in accordance with ASTM D5296-11 (2011) using tetrahydrofuran ("THF") as the mobile phase and diluent. As used herein, the term "particle size" means the weight average particle size of emulsion (co)polymer particles measured using a Brookhaven BI-90 Particle Sizer.

[0015] As used herein, the term "glass transition temperature" or "T g " refers to the temperature at which a glassy polymer undergoes segmental motion of the polymer chains or a temperature higher than that. The glass transition temperature of a copolymer can be estimated as follows by the Fox equation (Bulletin of the American Physical Society, 1(3) page 123 (1956)): 1 / T g = w1 / T g(1) + w2 / T g(2) For a copolymer, w1 and w2 refer to the weight fractions of the two comonomers, and T g(1) and T g(2) refer to the glass transition temperatures of the two corresponding homopolymers made from the monomers. For a polymer containing three or more monomers, additional terms are added (w n / T g(n) ). The glass transition temperature of a homopolymer can be found, for example, in "Polymer Handbook" (Interscience Publishers) edited by J. Brandrup and E. H. Immergut. The T g of a polymer 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 as calculated by the Fox equation.

[0016] The polymer composition of the present invention preferably contains a multi-stage acrylic polymer in an amount in the range of 5 to 40% by weight, based on the total weight of the multi-stage acrylic polymer and the polyvinylidene fluoride resin in the polymer composition. Preferably, the multi-stage acrylic polymer is present in an amount in the range of 10 to 35% by weight, more preferably 15 to 30% by weight, based on the total weight of the multi-stage acrylic polymer and the polyvinylidene fluoride resin in the polymer composition.

[0017] The multi - stage acrylic polymer includes a cross - linked core, one or more intermediate layers, and a shell. Each of the cross - linked core and the shell includes polymerized units derived from one or more alkyl (meth) acrylate monomers, and the one or more intermediate layers include polymerized units derived from one or more alkyl (meth) acrylate monomers, styrene monomers, and combinations thereof. Preferably, the cross - linked core is present in the multi - stage polymer in an amount of 25 - 45 wt%, preferably 30 - 40 wt%, more preferably 32 - 38 wt% based on the total weight of the multi - stage polymer. The one or more intermediate layers are present in the multi - stage polymer in an amount of 30 - 70 wt, preferably 40 - 65 wt%, more preferably 45 - 60 wt% based on the total weight of the multi - stage polymer. The shell is present in the multi - stage polymer in an amount of 5 - 25 wt%, preferably 10 - 20 wt%, more preferably 12 - 18 wt% based on the total weight of the multi - stage polymer.

[0018] 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 multi - stage polymer in an amount of 25 - 45 wt%, preferably 30 - 40 wt%, more preferably 32 - 38 wt% based on the total weight of the multi - stage polymer. In certain embodiments, the second intermediate layer is present in the multi - stage polymer in an amount of 5 - 25 wt%, preferably 10 - 20 wt%, more preferably 12 - 18 wt% based on the total weight of the multi - stage polymer.

[0019] The crosslinked core of the multi-stage polymer of the present invention contains polymerization units derived from one or more alkyl (meth) acrylate monomers. The alkyl (meth) acrylate monomers include linear and branched alkyl (meth) acrylates having an alkyl group with 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. Preferably, the alkyl (meth) acrylate monomer of the crosslinked core contains butyl acrylate. The alkyl (meth) acrylate monomer can be present in the crosslinked core in an amount of 95 to 99.9% by weight, preferably 97 to 99.5% by weight, more preferably 98 to 99% by weight, based on the total weight of the crosslinked core.

[0020] The crosslinked core of the multi-stage polymer of the present invention may further contain polymerization units derived from one or more crosslinkable monomers, graft-bondable monomers, and combinations thereof. Suitable crosslinkable and graft-bondable 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 crosslinkable monomers and graft-bondable 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. The crosslinkable monomers and graft-bondable monomers can be present in the crosslinked core in an amount of 0.1 to 5% by weight, preferably 0.5 to 3% by weight, more preferably 1 to 2% by weight, based on the total weight of the crosslinked core.

[0021] The crosslinked core of the multi-stage polymer of the present invention preferably has a T of -85°C or higher, -70°C or higher, or -60°C or higher. g The crosslinked core of the multi-stage polymer of the present invention may have a calculated T value of -10°C or lower, -30°C or lower, or -40°C or lower. g It may have a calculated value.

[0022] One or more intermediate layers of the multi-stage polymer of the present invention contain polymerization units derived from one or more alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof. The alkyl (meth)acrylate monomers include linear and branched alkyl (meth)acrylates in which 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, α-methylstyrene, and vinyltoluene.

[0023] Preferably, one or more intermediate layers include a first intermediate layer and a second intermediate layer. The first intermediate layer preferably contains polymerization units derived from one or more alkyl (meth)acrylate monomers. 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. The alkyl (meth)acrylate monomers in the first intermediate layer preferably include butyl acrylate and methyl methacrylate. The alkyl (meth)acrylate monomers may be present in the first intermediate layer in an amount of 95 to 100% by weight, preferably 97 to 99.9% by weight, more preferably 99 to 99.9% by weight, based on the total weight of the one or more intermediate layers.

[0024] The first intermediate layer of the multi-stage polymer of the present invention may further contain polymerization units derived from one or more crosslinkable monomers, graft-bondable monomers, and combinations thereof. Suitable crosslinkable and graft-bondable 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 crosslinkable monomer and graft-bondable monomer of the first intermediate layer may include allyl methacrylate. The crosslinkable monomer and graft-bondable monomer may be present in the first intermediate layer in an amount of 0 to 5% by weight, preferably 0.1 to 3% by weight, more preferably 0.1 to 1% by weight, based on the total weight of the first intermediate layer.

[0025] The first intermediate layer may be composed of a plurality of sub-layers, each of which may independently contain polymerization units derived from the monomer composition described above for the entire first intermediate layer. The first intermediate layer can include, for example, 1, 2, 3, 4, or 5 sub-layers. The first intermediate layer has a compositional gradient between sub-layers such that T g transitions from a minimum to a maximum across the width of the entire first intermediate layer. In certain embodiments, the T g calculated value transitions from a lower limit of -30 °C, -25 °C, -15 °C, or 0 °C to an upper limit of 70 °C, 55 °C, 35 °C, or 15 °C. Without wishing to be bound by theory, it is believed that the compositional gradient is achieved by an appropriate selection of monomers and the manner and timing of addition during the emulsion polymerization process used to prepare the first intermediate layer. Instead of adding all the monomers at once, a multi-stage polymerization process can be used in which the monomers are added stepwise to an emulsion polymerization reactor (or reaction vessel) and one layer is interpenetrated with an adjacent layer to create a T g gradient across the first intermediate layer.

[0026] The second intermediate layer of the multi-stage polymer of the present invention may include one or more of alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof. The alkyl (meth)acrylate monomers include linear and branched alkyl (meth)acrylates having an alkyl group with 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-based monomers include, for example, styrene, α-methylstyrene, and vinyltoluene. The alkyl (meth)acrylate monomers in the second intermediate layer preferably include butyl acrylate and methyl methacrylate. The alkyl (meth)acrylate monomers may be present in the second intermediate layer in an amount of 98 to 100% by weight, preferably 98.5 to 99.5% by weight, more preferably 98.7 to 99.3% by weight, based on the total weight of the second intermediate layer.

[0027] The second intermediate of the multi-stage polymer of the present invention may further include polymerization units derived from one or more chain transfer agents. Suitable chain transfer agents include, for example, 1-dodecanethiol, t-dodecanethiol, thioethanol, hexanethiol, mercaptopropionic acid, methyl-3-mercaptopropionate, and butyl-3-mercaptopropionate. The chain transfer agent in the second intermediate layer preferably includes 1-dodecanethiol. The chain transfer agent may be present in the second intermediate layer in an amount of 0 to 2% by weight, preferably 0.5 to 1.5% by weight, more preferably 0.7 to 1.3% by weight, based on the total weight of the second intermediate layer.

[0028] The second intermediate layer of the multi-stage polymer of the present invention may have a T g calculated value of 40 °C or higher, 45 °C or higher, or 65 °C or higher. The second intermediate layer of the multi-stage polymer of the present invention may have a T g calculated value of 110 °C or lower, 95 °C or lower, or 80 °C or lower.

[0029] The shell of the multi-stage polymer of the present invention contains one or more of alkyl (meth)acrylate monomers, styrenic monomers, and combinations thereof. The alkyl (meth)acrylate monomers include linear and branched alkyl (meth)acrylates having an alkyl group with 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 styrenic monomers include, for example, styrene, α-methylstyrene, and vinyltoluene. The alkyl (meth)acrylate monomers of the shell preferably include butyl acrylate and methyl methacrylate. The alkyl (meth)acrylate monomers can be present in the shell in an amount of 84 to 98% by weight, preferably 85 to 94% by weight, more preferably 86 to 93% by weight, based on the total weight of the shell.

[0030] The shell of the multi-stage polymer of the present invention may further include one or more monomers selected from the group consisting of acid-functionalized monomers, hydroxyl-functionalized monomers, and combinations thereof. Suitable examples of the functionalized monomers include, for example, acid-functionalized monomers and hydroxyl-functionalized monomers. Suitable examples of the acid-functionalized monomers include, for example, acrylic monomers having one or more carboxyl groups such as (meth)acrylic acid, itaconic acid, and phthalic acid. Preferably, one or more acid-functionalized monomers include acrylic acid. Suitable examples of the hydroxyl-functional monomers include, for example, one or more hydroxy-substituted C1-C8 alkyl (meth)acrylates. Preferably, one or more hydroxyl-functionalized monomers include hydroxyethyl methacrylate. One or more monomers selected from the group consisting of acid-functionalized monomers, hydroxyl-functionalized monomers, and combinations thereof may be present in the shell in an amount of 2 to 16% by weight, preferably 3 to 14% by weight, more preferably 5 to 12% by weight, based on the total weight of the shell.

[0031] The shell of the multi-stage polymer of the present invention may further include polymerization units derived from one or more chain transfer agents. Suitable chain transfer agents include, for example, 1-dodecanethiol, t-dodecanethiol, thioethanol, hexanethiol, mercaptopropionic acid, methyl-3-mercaptopropionate, butyl-3-mercaptopropionate. Preferably, the chain transfer agent of the shell includes 1-dodecanethiol. The chain transfer agent may be present in the shell in an amount of 0 to 2% by weight, preferably 0.5 to 1.5% by weight, more preferably 0.7 to 1.3% by weight, based on the total weight of the shell.

[0032] The shell of the multi-stage polymer of the present invention may have a T value in the range of 40 °C or higher, 50 °C or higher, or 65 °C or higher. g The shell of the multi-stage polymer of the present invention may have a T value of 100 °C or lower, 90 °C or lower, or 80 °C or lower. g The shell of the multi-stage polymer of the present invention may have a T value in the range of 40 °C or higher, 50 °C or higher, or 65 °C or higher.

[0033] The shell of the multi-stage polymer of the present invention has a weight average molecular weight (M w ) in the range of 20,000 to 100,000 g / mol, 30,000 to 60,000 g / mol, 40,000 to 60,000 g / mol, or 40,000 to 50,000 g / mol.

[0034] The multi-stage polymer of the present invention can have a particle size in the range of 30 to 250 nm, preferably 50 to 200 nm, more preferably 60 to 175 nm, even more preferably 90 to 150 nm, as measured by a Brookhaven BI-90 Particle Sizer.

[0035] Suitable polymerization techniques for preparing the polymers contained in the polymer composition of the present invention include, for example, emulsion polymerization and solution polymerization as disclosed in U.S. Patent No. 6,710,161, preferably emulsion polymerization. The aqueous emulsion polymerization process is typically carried out in an aqueous reaction mixture containing at least one monomer and various synthetic adjuvants, such as a free radical source, a buffer, and a reducing agent, in an aqueous reaction medium. A chain transfer agent can be used to limit the 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. The aqueous reaction medium can 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, based on the weight of the aqueous reaction medium.

[0036] The polymer composition of the present invention may also contain other optional components, such as plasticizers, antioxidants, UV absorbers and light stabilizers, dyes, pigments, flame retardants, and other additives for preventing, reducing, or coating discoloration or deterioration caused by heat, aging, or exposure to light or weathering. The amount of the optional component effective to achieve the desired properties provided by such components can be readily determined by those skilled in the art.

[0037] The polymer composition of the present invention has end uses including, for example, sheets and films for use in photovoltaic modules. The multi-stage 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 produced 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 to 500 microns.

[0038] According to an aspect of the present invention, a photovoltaic module includes a transparent front layer, a photovoltaic cell, and a back layer including a film containing a polymer composition including polyvinylidene fluoride resin and a multi-stage acrylic polymer. Preferably, the polymer composition further includes a reflective pigment such as titanium dioxide (TiO2).

[0039] Some embodiments of the present invention are described in detail in the following examples.

Examples

[0040] Example 1 Preparation of an Exemplary Polymer Composition The PVDF compound was produced through a co-rotating twin-screw extruder at a melting temperature of about 230 °C, and then a film was produced by a laboratory heating compressor at 220 °C, with a target film thickness of 200 microns. The polymer composition of the present invention includes a multi-stage acrylic polymer (VERSALOID™ 21308-XP manufactured by The Dow Chemical Company) and a polyvinylidene fluoride resin (Dong Yue DS206), and the multi-stage acrylic polymer was present in an amount of 29.5 phr based on the weight of the polyvinylidene fluoride resin. In the comparative example, a blend of 29.5 phr of a toughened polymethyl methacrylate polymer (PARALOID™ EXL-2315 impact modifier manufactured by The Dow Chemical Company with Evonik 8N PMMA) was used in place of the multi-stage acrylic polymer. The examples and comparative examples of the present invention contained the same pigments, processing aids, and antioxidants. As shown in Table 1 below, the examples of the present invention showed 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 a pressure of 2 atm for 96 hours.

[0041]

Table 1

Claims

1. 1. A polymer composition comprising: Polyvinylidene fluoride resin, a multi-stage acrylic polymer comprising 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, styrene monomers, and combinations thereof.

2. the multi-stage acrylic polymer (a) 25 to 45 weight percent of said crosslinked core, based on the total weight of said multi-stage polymer, said crosslinked core comprising, based on the total weight of said crosslinked core, polymerized units derived from (i) 95 to 99.9 weight percent of one or more alkyl (meth)acrylate monomers, and (ii) 0.1 to 5 weight percent of one or more crosslinking monomers, graft-linking monomers, and combinations thereof; (b) 30 to 70 weight percent of said one or more intermediate layers, based on the total weight of said multi-stage polymer, said one or more intermediate layers comprising, based on the total weight of said first intermediate layer, (i) 95 to 100 weight percent of one or more alkyl (meth)acrylate monomers, and (ii) 0 to 5 weight percent of polymerized units derived from crosslinking monomers, graft-linking monomers, and combinations thereof; (c) 5 to 25 weight percent of the shell, based on the total weight of the multi-stage polymer, comprising, based on the total weight of the shell, polymerized units derived from: (i) 84 to 98 weight percent of one or more alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof; (ii) 2 to 16 weight percent of one or more monomers selected from the group consisting of acid-functionalized monomers, hydroxyl-functionalized monomers, and combinations thereof; and (iii) 0 to 2 weight percent of one or more chain transfer agents; 10. The polymer composition of claim 1, comprising:

3. 2. The composition of claim 1, 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 the group consisting of methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, ethylhexyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, benzyl acrylate, benzyl methacrylate, isooctyl acrylate, and combinations thereof.

4. 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 the group consisting of butyl acrylate, methyl methacrylate, and combinations thereof.

5. 3. The composition of claim 2, wherein the one or more monomers selected from the group consisting of acid-functionalized monomers, hydroxyl-functionalized monomers, and combinations thereof comprise one or more of acrylic acid and hydroxylethyl methacrylate.

6. 3. The composition of claim 2, 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 the group consisting of 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, allyl methacrylate, and combinations thereof.

7. 2. The composition of claim 1, wherein the one or more intermediate layers comprise a first intermediate layer and a second intermediate layer, the first intermediate layer comprising, based on the total weight of the first intermediate layer, polymerized units derived from (i) 95 to 100 weight % of one or more alkyl (meth)acrylate monomers, and (ii) 0 to 5 weight % of crosslinking monomers, graft-linking monomers, and combinations thereof, and the second intermediate layer comprising, based on the total weight of the second intermediate layer, polymerized units derived from (i) 98 to 100 weight % of one or more alkyl (meth)acrylate monomers, styrene monomers, and combinations thereof, and (ii) 0 to 2 weight % of one or more chain transfer agents.

8. 10. The composition of claim 1, wherein said multi-stage acrylic polymer is present in an amount ranging from 5% to 40% by weight, based on the total weight of said polyvinylidene fluoride resin and said multi-stage acrylic polymer.

9. The composition of claim 1 further comprising at least one reflective pigment.

10. An article comprising the polymer composition of any one of claims 1 to 9, wherein the article is selected from the group consisting of films and sheets.

11. 1. A photovoltaic module comprising: A transparent front layer and a photovoltaic cell; A backing layer comprising a film comprising the polymer composition of any one of claims 1 to 9; 1. A photovoltaic module comprising: