WO2025064389A1

WO2025064389A1 - Methods for separation of multilayer interlayers

Info

Publication number: WO2025064389A1
Application number: PCT/US2024/047020
Authority: WO
Inventors: Sungkyun Sohn; Bert Jozef Campo; Mohammad SABZI; Wenjie Chen
Original assignee: Solutia Inc.
Priority date: 2023-09-19
Filing date: 2024-09-17
Publication date: 2025-03-27

Abstract

Processes are disclosed for separating a soft poly(vinyl butyral) layer from a stiff poly(vinyl butyral) layer of a multilayer interlayer.

Description

METHODS FOR SEPARATION OF MULTILAYER INTERLAYERS

FIELD OF THE INVENTION

[0001] This disclosure is related to the field of recycling polymer interlayers having different poly(vinyl butyral) components.

BACKGROUND OF INVENTION

[0002] Multilayer interlayers have an ever-increasing share in the interlayer market but have limited recyclability in the extrusion process, since the different layers may have different physicochemical properties. Typical of these multilayer interlayers are acoustic trilayers in which two outer skin layers are used, typically having similar properties, with a core layer in which the properties are quite different. When reworked, these acoustic core layers especially do not mix well with the two skin layer materials during extrusion, forming small but discrete domains of core material that cause a certain level of haze, limiting its content in extrusion. The inability to rework this multilayer material is a significant economic loss.

[0003] It is possible to manually peel off a skin layer from a multi-layer sheet to demonstrate the concept of mechanical separation. However, improved processes and mechanical devices would be helpful for a stable, consistent, and cost-efficient mechanical separation operation.

[0004] U.S. Pat. No. 11 ,518,472 discloses a method for recycling an intermediate film for laminated glass, comprising a step of separating a layer comprising an A layer and a layer comprising a B layer from the intermediate film for laminated glass comprising at least the A layer and the B layer.

[0005] U.S. Pat. No. 4,940,187 discloses a set of systematic equipment for recycling raw materials such as: copper, ferrous material, and different plastic materials from waste wires. The equipment includes a classifier for separating the copper and plastic materials, and a wet gravity separator for further separating the different plastic materials having different densities and floating heights in a tank of the gravity separator.

[0006] EP0425800A1 discloses a method of separating synthetic resin foam from rigid articles by subjecting the article to a deformation treatment, after which any synthetic resin foam still bonding to the articles is removed from the articles by means of scraping members. Also disclosed is a device suitable for such use.

[0007] JP7166571 B2 discloses a film-shaped member having a first layer on one side of an adhesive layer, and a second layer on the opposite side, which is separated by cutting along the layer with a blade.

[0008] WO2022250944A2 discloses processes for separating a first layer from a remainder of a multilayer interlayer sheet, in which the multilayer sheet is heated, and thereafter the first layer is separated from the remainder of the multilayer interlayer sheet by pulling the first layer and the remainder of the multilayer interlayer sheet in different directions, in a defined orientation. [0009] Similarly, U.S. Pat. Appln. No. 63/448,707 discloses processes for separating a first layer from a remainder of a tapered multilayer interlayer sheet, in which the tapered multilayer interlayer sheet is heated, and thereafter the first layer is separated from the remainder of the tapered multilayer interlayer sheet by pulling the first layer and the remainder of the tapered multilayer interlayer sheet in different directions, in a defined orientation, without the tapered multilayer interlayer sheet wrinkling or tearing. [0010] In both these cases, when the multilayer sheet is an acoustic interlayer in which the remainder is a core-skin bilayer with the core layer left exposed, it is difficult to mechanically separate the two layers (the core and the remaining skin), since the weak and flimsy core layer easily gets torn, being unable to survive the mechanical peeling force. The core layer can also be quite sticky, making it difficult to work with. Indeed, it sticks to both the skin layer as well as any other material with which it comes in contact. In some cases, it will tend to preferentially adhere to the skin layer, in other cases it may preferentially adhere to the other material. Even worse, this preference may change based on ambient temperature, or in the case of separating the two, under the separation conditions which may change during the separation process. Thus, the differences in properties between these two layers results in their subsequent separation attempts being even more difficult than the step of removing the first skin layer from the core-skin remainder layer.

[0011] In fact, the present inventors have found that manual attempts to peel off the core layer from a 1 -inch wide core-skin bi-layer strip were only partially successful. In addition to the difficulty of handling the weak and flimsy core layer that gets torn very easily, some core layer materials appear crumbly, non-elastic, and strongly adhered to the skin, making it almost impossible to mechanically peel off from the skin layer while remaining substantially intact.

[0012] There remains a need for methods and devices for separating layers of multilayer interlayers to facilitate rework of the material in manufacturing processes, especially multilayer interlayers comprising two layers having significantly different properties.

SUMMARY OF INVENTION

[0013] In one aspect, the invention relates to processes for separating a first soft poly(vinyl butyral) layer from a first stiff poly(vinyl butyral) layer of a first multilayer interlayer, the processes including the steps of: contacting the first soft poly(vinyl butyral) layer of the first multilayer interlayer with a second soft poly(vinyl butyral) layer of a second multilayer interlayer that comprises the second soft poly(vinyl butyral) layer and a second stiff poly(vinyl butyral) layer such that the first soft poly(vinyl butyral) layer of the multilayer interlayer and the second soft poly(vinyl butyral) layer of the second multilayer interlayer adhere to one another and combine; and thereafter separating the combined first soft poly(vinyl butyral) layer of the first multilayer interlayer and the second soft poly(vi ny I butyral) layer of the second multilayer interlayer from at least one of the first stiff poly(vinyl butyral) layer of the first multilayer interlayer and the second stiff poly(vinyl butyral) layer of the second multilayer interlayer.

[0014] In another aspect, the invention relates to apparatuses for carrying out the processes of the invention. [0015] Further aspects of the invention are as disclosed and claimed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 is a schematic of the mechanical separation of a multilayer interlayer by contacting the soft poly(vinyl butyral) layer of the multilayer interlayer with the soft poly(vinyl butyral) layer of a second multilayer interlayer.

DETAILED DESCRIPTION

[0017] The following embodiments and combinations are included within the scope of the invention.

[0018] In a first embodiment, the invention relates to processes for separating a first soft poly(vi nyl butyral) layer from a first stiff poly (vinyl butyral) layer of a first multilayer interlayer, the processes comprising: contacting the first soft poly(vinyl butyral) layer of the first multilayer interlayer with a second soft poly(vinyl butyral) layer of a second multilayer interlayer that comprises the second soft poly(vinyl butyral) layer and a second stiff poly(vinyl butyral) layer such that the first soft poly(vinyl butyral) layer of the multilayer interlayer and the second soft poly(vinyl butyral) layer of the second multilayer interlayer adhere to one another and combine; and thereafter separating the combined first soft poly(vi nyl butyral) layer of the first multilayer interlayer and the second soft poly(vinyl butyral) layer of the second multilayer interlayer from at least one of the first stiff poly(vinyl butyral) layer of the first multilayer interlayer and the second stiff poly(vinyl butyral) layer of the second multilayer interlayer. [0019] In a second embodiment, according to the first embodiment, the invention further comprises applying a solvent to at least one of the first soft poly(vinyl butyral) layer and the second soft poly(vi nyl butyral) layer prior to the step of contacting. [0020] In a further embodiment, according to any of the preceding embodiments, the solvent comprises one or more of alcohols having from 1 to 8 carbon atoms, or a carboxylic acid ester thereof, wherein the acid has from 1 to 8 carbon atoms.

[0021] In a further embodiment, according to any of the preceding embodiments, the contacting includes compressing the first soft poly(vinyl butyral) layer and the second soft poly(vinyl butyral) layer together.

[0022] In a further embodiment, according to any of the preceding embodiments, the solvent comprises one or more of: methanol, ethanol, n- isopropanol, isopropanol, or ethyl acetate.

[0023] In a further embodiment, according to any of the preceding embodiments, a thickness of the first stiff poly(vinyl butyral) layer is at least 1 .0 times, or at least 1 .5 times, a thickness of the second soft poly(vinyl butyral) layer.

[0024] In a further embodiment, according to any of the preceding embodiments, the first stiff poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer which exhibits a 90° peel adhesion value, when laminated to glass, of from about 20 N/cm to about 70 N/cm.

[0025] In a further embodiment, according to any of the preceding embodiments, the first soft poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer which exhibits a 90° peel adhesion value, when laminated to glass, of from about 3 N/cm to about 18 N/cm.

[0026] In a further embodiment, according to any of the preceding embodiments, a difference in a 90° peel adhesion value between the first soft poly(vinyl butyral) layer and the first stiff poly(viny I butyral) layer, when laminated to glass, is at least 10 N/cm, or at least 15 N/cm.

[0027] In a further embodiment, according to any of the preceding embodiments, a difference in a 90° peel adhesion value between the first stiff poly(vinyl butyral) and the first soft poly(vinyl butyral) when in contact is at least about 10 N/cm, at 25 % relative humidity and 21 °C.

[0028] In a further embodiment, according to any of the preceding embodiments, the first soft poly(vinyl butyral) layer comprises poly(vinyl butyral) having a shear storage modulus at 20 °C from about 0.1 MPa to about 18 MPa.

[0029] In a further embodiment, according to any of the preceding embodiments, the first stiff poly(vinyl butyral) layer comprises poly(vinyl butyral) having a shear storage modulus at 20 °C from about 20 MPa to about 600 MPa.

[0030] In a further embodiment, according to any of the preceding embodiments, a difference between a shear storage modulus at 20 °C of the first soft poly(vinyl butyral) layer and the first stiff po ly (vinyl butyral) layer is at least 10 MPa.

[0031] In a further embodiment, according to any of the preceding embodiments, the first soft poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer having a Tg less than about 20 °C.

[0032] In a further embodiment, according to any of the preceding embodiments, the first stiff poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer having a Tg greater than about 25 °C.

[0033] In a further embodiment, according to any of the preceding embodiments, the first soft poly(vinyl butyral) layer comprises a poly(vi nyl butyral) polymer having a residual hydroxyl content from about 8 % to about 13.5 %.

[0034] In a further embodiment, according to any of the preceding embodiments, the first stiff poly(vinyl butyral) layer comprises a poly(vinyl butyral) polymer having a residual hydroxyl content from about 15 % to about 25 %.

[0035] In a further embodiment, according to any of the preceding embodiments, a difference between the residual hydroxyl content of the poly (vinyl butyral) polymer of the first stiff poly(vinyl butyral) layer and the poly (vinyl) butyral polymer of the first soft poly(vinyl butyral) layer is at least 5 weight percent.

[0036] In a further embodiment, according to any of the preceding embodiments, the first stiff poly(vinyl butyral) layer comprises poly(vinyl butyral) having a plasticizer content from about 20 phr to about 50 phr. [0037] In a further embodiment, according to any of the preceding embodiments, the first soft poly(vinyl butyral) layer comprises poly(vinyl butyral) having a plasticizer content from about 45 phr to about 150 phr. [0038] In a further embodiment, according to any of the preceding embodiments, the first stiff poly(vinyl butyral) layer comprises poly(vinyl butyral) having a weight average molecular weight from about 70,000 to 225,000.

[0039] In a further embodiment, according to any of the preceding embodiments, the first soft poly(vinyl butyral) layer comprises poly(vinyl butyral) having a weight average molecular weight from about 150,000 to about 600,000.

[0040] In a further embodiment, according to any of the preceding embodiments, the process includes the use of spreader rollers to ensure the interlayer is flat.

[0041] In a further embodiment, according to any of the preceding embodiments, the process includes the use of annealing to help eliminate wrinkles.

[0042] In a further embodiment, according to any of the preceding embodiments, substantially all of the first soft poly(viny I butyral) layer is removed from the first stiff poly(vinyl butyral) layer such that FT-IR results show substantially no residue of the soft poly(vinyl butyral) layer.

[0043] In an aspect, the invention relates to processes for separating a first soft poly(vinyl butyral) layer from a first stiff poly(vinyl butyral) layer of a first multilayer interlayer, the processes comprising: contacting the first soft poly(vinyl butyral) layer of the first multilayer interlayer with a second soft poly(vinyl butyral) layer of a second multilayer interlayer that comprises the second soft poly(vinyl butyral) layer and a second stiff poly(vinyl butyral) layer such that the first soft poly(vinyl butyral) layer of the multilayer interlayer and the second soft poly(vinyl butyral) layer of the second multilayer interlayer adhere to one another and combine; and thereafter separating the combined first soft poly(vinyl butyral) layer of the first multilayer interlayer and the second soft poly(vi ny I butyral) layer of the second multilayer interlayer from at least one of the first stiff poly(vinyl butyral) layer of the first multilayer interlayer and the second stiff poly(vinyl butyral) layer of the second multilayer interlayer.

[0044] Thus, according to the invention, a soft poly(vinyl butyral) layer may be separated from a stiff poly(vinyl butyral) layer of a multilayer interlayer by using another multilayer interlayer, inverting it, and contacting the soft layer from the first and the second multilayer interlayers so that they adhere. This method takes advantage of the soft, sticky properties of the soft poly(vinyl butyral) layers.

[0045] The processes may optionally include a step of adding a solvent to at least one of the first soft poly(viny I butyral) layer and the second soft poly(vinyl butyral) layer prior to the step of contacting the two together. When we use the term “solvent,” we do not intend to require any minimum amount of dissolution of the soft PVB in the so-called solvent. Rather, without wishing to be bound by any theory, the “solvent” may interact with the core layer PVB in a way that causes the soft layer to better adhere to the other soft layer, easing the separation of the combined core layers to at least one of the two stiff layers. Thus, anything that functions to ease removal of the core layers from the skin layers would be considered a suitable solvent. Thus, according to the invention, methods are provided that include the use of a solvent to better enable separation and recovery of the skin layers for re-use in extrusion.

[0046] A wide range of solvents may be used, for example one or more of alcohols having from 1 to 8 carbon atoms, or a carboxylic acid ester thereof, wherein the acid has from 1 to 8 carbon atoms. Examples include one or more of: methanol, ethanol, n-propanol, isopropanol, or ethyl acetate.

[0047] Likewise, the term “contacting” is not intended to be particularly limited, and optionally includes compressing the two soft poly(vinyl butyral) layers together. It will be appreciated that the soft PVB layers are somewhat sticky, so that avoiding contacting things other than the other soft PVB layer should be avoided. When contacting the two soft PVB layers together, it is important to prevent wrinkles or bubbles, which can affect adhesion, making it difficult to afterward remove the combined soft layers from the skin layer(s). [0048] Thus, according to the invention, the two soft or core layers may be contacted with one another, optionally after application of a solvent, to form a trilayer structure of the two skin layers and the combined core layer in the middle.

[0049] In another aspect, the invention relates to a step of separating the combined core layers from at least one of the skin layers. The method of separation is not especially limited, but may involve peeling.

[0050] The invention thus includes a step of separating the combined soft poly(vinyl butyral) layers from one of the stiff poly(vinyl butyral) layers of the combined multilayer interlayers (skin/combined soft/skin), for example by separating and then pulling a combined soft/stiff layer and the other stiff layer of the multilayer interlayers in different directions. According to this aspect, an angle a defined by the skin layer to be separated and the multilayer sheet (having skin/combined core/skin) at the separation point may be smaller than or equal to an angle defined by the multilayer interlayer and the combined core layers/skin at the separation point, during the process, which may be continuous.

[0051] The invention thus relates also to continuous processes, as just described, for separating a core layer from a skin layer of a multilayer interlayer sheet.

[0052] According to the invention, the orientation described may be maintained during the continuous process.

[0053] According to the invention, multilayer interlayers having at least a soft layer and a stiff layer are separated such that at least a portion of the soft layer is removed from the stiff layer. The multilayer interlayers are typically bilayers, although the invention is not so limited so long as the soft and stiff layers are present, as described herein. The soft and stiff layers are also described herein as the core and skin layers, respectively.

[0054] Those skilled in the art will understand that the layers described comprise poly(vinyl butyral) polymers, which may each be the reaction product of a single reaction, or a blend of reaction products of different reactions. Indeed, when blended, it may be difficult or impossible to distinguish between a single polymer and a blend of polymers. Thus, reference to a poly(vinyl butyral) polymer and its properties may refer to a single polymer which is a single reaction product, a blend of two or more polymers having these properties, or a blend of several polymers in which the resulting blend has the stated properties.

[0055] According to the invention then, a multilayer interlayer, typically a bilayer resulting from a skin layer having been separated from an acoustic trilayer leaving the core layer exposed, is separated into two layers, a soft poly(vinyl butyral) layer and a stiff poly(vinyl butyral) layer.

[0056] The term “stiff poly(vinyl butyral)” refers to a poly(vinyl butyral) resin, or a blend of poly(vinyl butyral) resins, that is demonstrably stiffer than the “soft poly(vinyl butyral),” typically forming a skin or stiff layer of a multilayer poly(vinyl butyral) multilayer sheet, as further described herein.

[0057] The term “soft poly(vinyl butyral)” refers to a poly(vinyl butyral) resin, or a blend of poly(vinyl butyral) resins, that is demonstrably softer than the “stiff poly(vinyl butyral),” typically forming a core or soft layer of a multilayer poly(vinyl butyral) multilayer sheet, as further described herein. The soft or core poly(vinyl butyral) layer is typically sandwiched between two stiff or skin poly(vinyl butyral) layers to form a multilayer poly(viny I butyral) multilayer sheet, from which one skin layer may thereafter be removed prior to the processes of the present invention, or as a precursor step of the present invention.

[0058] The bilayers separated according to the invention may result from processes disclosed and claimed in WO2022250944A2, the relevant disclosure of which is incorporated herein by reference in its entirety, in which a first or skin layer is separated from a remainder of a multilayer interlayer sheet, for example from the core and skin layer of an acoustic trilayer interlayer. According to the processes described, the multilayer sheet may be heated, and thereafter the first (skin) layer separated from the remainder of the multilayer interlayer sheet by pulling the first layer and the remainder of the multilayer interlayer sheet in different directions, resulting in a core-skin bilayer. Any other suitable method may likewise be used to obtain the multilayers (bilayers) that are separated according to the present invention. [0059] As used herein, the terms “multilayer” and “multiple layers” mean an interlayer having more than one layer, and multilayer and multiple-layer may be used interchangeably. The layers of the interlayer are generally produced by mixing a polymer resin such as poly(vinyl butyral) with one or more plasticizers and melt processing the mix into a sheet by any applicable process or method known to one of skill in the art, including, but not limited to, extrusion, with the layers being combined by processes such as co-extrusion or lamination. Other additional ingredients may optionally be added for various other purposes. After the interlayer sheet is formed, it is typically collected and rolled for transportation and storage and for later use in the multiple layer glass panel, as discussed below.

[0060] In various embodiments of the present disclosure, a multilayered interlayer comprises at least two polymer layers, a soft layer and a stiff layer (e.g., a single layer or multiple layers co-extruded and/or laminated together) disposed in direct contact with each other, wherein each layer comprises a polymer resin, as detailed more fully below. As used herein for multilayer interlayers having at least three layers, “skin layer” generally refers to the outer layer(s) of the interlayer and “core layer” generally refers to the inner layer(s). Thus, one exemplary embodiment would be: skin layer//core layer/Zskin layer. In the multilayer interlayers having skin layer//core layer//skin layer configuration, the skin layer is stiffer and the core layer is softer.

[0061] For example, in one trilayer polymer interlayer sheet, the two stiff (or outer or skin) layers may comprise poly(vinyl butyral) (“PVB”) resin with a plasticizer or mixture of plasticizers, while the softer (inner or core) layers may comprise the same or different PVB resin or a different thermoplastic material with the same or different plasticizer and/or mixture of plasticizers. Thus, it is contemplated that the stiff or skin layers and the soft or core layer(s) of the multilayered interlayer sheets may be comprised of the same thermoplastic material or different thermoplastic materials and the same or different plasticizer or plasticizers. Either or both layers may include additional additives as known in the art, as desired. [0062] One type of multiple layer interlayer that utilizes softer inner layers is the multiple layer acoustic type of interlayer. As disclosed herein, acoustic interlayers comprise multiple layers, with a preferred embodiment having a relatively soft layer sandwiched between two relatively stiff layers. The resulting three-layer interlayer can generally be used in lamination processes directly in place of conventional, single layer interlayers, with little or no modification to the lamination process.

[0063] The core or soft layer of the multilayer interlayer is understood to be responsible for the acoustic properties of an acoustic trilayer, and comprises soft poly(vinyl butyral), that is poly(vinyl butyral) (PVB) that is softer than the skin or stiff PVB, which is stiffer than the soft PVB. In one aspect then, the soft poly(vinyl butyral) may have a residual hydroxyl content from about 5 % to about 15 %, or from 8 % to 12 %, or from about 9 % to 11 %, or as described elsewhere herein. In another aspect, the stiff poly(vinyl butyral) may have a residual hydroxyl content of from about 12 % to about 30 %, or from 15 % to about 25 %, or from 18 % to 22 %.

[0064] In some embodiments, the interlayer (e.g., the core layer and the skin layer) will have a generally constant or uniform thickness about the length of the interlayer. However, in alternative embodiments, the interlayer may have at least one region of non-uniform thickness. For example, the interlayer may be wedge-shaped, such that the thickness of the interlayer changes (e.g., linearly or non-linearly) along the length of the interlayer. In some such embodiments, the thickness of the interlayer may change due to a thickness change in the core layer (i.e., with the skin layer(s) having a generally constant thickness). Alternatively, the thickness of the interlayer may change due to a thickness change in the skin layer(s) (i.e., with the core layer having a generally constant thickness). In further alternatives, the thickness of the interlayer may change due to a thickness change in both the core layer and the skin layer(s). [0065] Thus, in one embodiment, the multilayered poly(vinyl butyral) sheets of the invention may comprise interlayers comprising one or more stiff skin layers and a soft core layer(s). In an embodiment, these multilayered interlayer sheets may comprise in order: a polymer layer (skin layer) comprising a stiff plasticized poly(vinyl butyral) resin; a second polymer layer (core layer) comprising a soft plasticized poly(vinyl butyral) resin, or a blend thereof having the same or different residual hydroxyl content; and optionally a third polymer layer (skin layer) comprising stiff plasticized poly(viny I butyral) resin. This optional skin layer is removed prior to the processes of the invention, or incorporated in aspects where a skin layer is removed prior to and such that a core layer is exposed. The core polymer layer is thus disposed adjacent a skin layer. If there are three or more layers, the second polymer layer may be disposed between the first polymer layer and the third polymer layer, resulting in two skin layers and a central core layer.

[0066] In some embodiments wherein the interlayer comprises at least three polymer layers, one or more of the inner layers can be relatively thin, as compared to the other outer layers. For example, in some embodiments wherein the multiple layer interlayer is a three-layer interlayer, the innermost layer can have a thickness of not more than about 12, not more than about 10, not more than about 9, not more than about 8, not more than about 7, not more than about 6, not more than about 5 mils, or it may have a thickness in the range of from about 2 to about 12 mils, about 3 to about 10 mils, or about 4 to about 9 mils. In the same or other embodiments, the thickness of each of the outer layers can be at least about 4, at least about 5, at least about 6, at least about 7 mils and/or not more than about 15, not more than about 13, not more than about 12, not more than about 10, not more than about 9, not more than about 8 mils, or can be in the range of from about 2 to about 15, about 3 to about 13, or about 4 to about 10 mils. When the interlayer includes two outer layers, these layers can have a combined thickness of at least about 9, at least about 13, at least about 15, at least about 16, at least about 18, at least about 20, at least about 23, at least about 25, at least about 26, at least about 28, or at least about 30 mils, and/or not more than about 73, not more than about 60, not more than about 50, not more than about 45, not more than about 40, not more than about 35 mils, or in the range of from about 9 to about 70 mils, about 13 to about 40 mils, or about 25 to about 35 mils. [0067] According to some embodiments, the ratio of the thickness of one of the outer layers to one of the inner layers in a multiple layer interlayer can be at least about 1 .4:1 , at least about 1 .5:1 , at least about 1 .8:1 , at least about 2:1 , at least about 2.5:1 , at least about 2.75:1 , at least about 3:1 , at least about 3.25:1 , at least about 3.5:1 , at least about 3.75:1 , or at least about 4:1 . When the interlayer is a three-layer interlayer having an inner core layer disposed between a pair of outer skin layers, the ratio of the thickness of one of the skin layers to the thickness of the core layer may fall within one or more of the ranges above. In some embodiments, the ratio of the combined thickness of the outer layers to the inner layer can be at least about 2.25:1 , at least about 2.4:1 , at least about 2.5:1 , at least about 2.8:1 , at least about 3:1 , at least about 3.5:1 , at least about 4:1 , at least about 4.5:1 , at least about 5:1 , at least about 5.5:1 , at least about 6:1 , at least about 6.5:1 , or at least about 7:1 and/or not more than about 30:1 , not more than about 20:1 , not more than about 15:1 , not more than about 10:1 , not more than about 9:1 , or not more than about 8:1 .

[0068] Multiple layer interlayers as described herein can comprise generally flat interlayers having substantially the same thickness along the length, or longest dimension, and/or width, or second longest dimension, of the sheet. In some embodiments, however, the multiple layer interlayers of the present invention can be tapered, or wedge-shaped, interlayers that comprise at least one tapered zone having a wedge-shaped profile. Tapered interlayers may have a changing thickness profile along at least a portion of the length and/or width of the sheet, such that, for example, at least one edge of the interlayer has a thickness greater than the other. When the interlayer is a tapered interlayer, at least 1 , at least 2, at least 3, or more of the individual resin layers may include at least one tapered zone. Tapered interlayers may be particularly useful in, for example, heads-up display (HUD) panels in automotive and aircraft applications.

[0069] The term “plasticizer” as used herein refers generally to a molecule or blend of molecules, as further described herein, that plasticizes a polymer at lower plasticizer content, specifically poly(vinyl butyral), thereby softening it. In many embodiments, plasticizers are added to the polymer resin to form polymer layers or interlayers. Plasticizers are generally added to the polymer resin to increase the flexibility and durability of the resultant polymer interlayer. Plasticizers function by embedding themselves between chains of polymers, spacing them apart (increasing the “free volume”) and thus significantly lowering the glass transition temperature (T_g) of the polymer resin, making the material softer. In this regard, the amount of plasticizer in the interlayer can be adjusted to affect the glass transition temperature (T_g). The glass transition temperature (T_g) is the temperature that marks the transition from the glassy state of the interlayer to the rubbery state. In general, higher amounts of plasticizer loading can result in lower T_g. In some embodiments, such as when the interlayer is an acoustic trilayer, the inner core layer (i.e., the soft layer) will have a glass transition temperature less than about 20 °C, while the outer skin layers (e.g., the stiff layer) will have a glass transition temperature greater than about 25 °C.

[0070] Contemplated plasticizers include, but are not limited to, esters of a polybasic acid, a polyhydric alcohol, triethylene glycol di-(2-ethylbutyrate), triethylene glycol di-(2-ethylhexonate) (known as “3-GEH”), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, dioctyl adipate, hexyl cyclohexyladipate, mixtures of heptyl and nonyl adipates, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, and polymeric plasticizers such as oil-modified sebacic alkyds and mixtures of phosphates and adipates, and mixtures and combinations thereof. 3-GEH is particularly preferred. Other examples of suitable plasticizers can include, but are not limited to, tetraethylene glycol di-(2-ethylhexanoate) (“4-GEH”), di(butoxyethyl) adipate, and bis(2-(2-butoxyethoxy)ethyl) adipate, dioctyl sebacate, nonylphenyl tetraethylene glycol, and mixtures thereof.

[0071] Other suitable plasticizers may include blends of two or more distinct plasticizers, including but not limited to those plasticizers described above. Still other suitable plasticizers, or blends of plasticizers, may be formed from aromatic groups, such polyadipates, epoxides, phthalates, terephthalates, benzoates, toluates, mellitates and other specialty plasticizers. Further examples include, but are not limited to, dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycol benzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1 ,3-pentanediol dibenzoate, 2,2,4-trimethyl-1 ,3- pentanediol benzoate isobutyrate, 1 ,3-butanediol dibenzoate, diethylene glycol di-o-toluate, triethylene glycol di-o-toluate, dipropylene glycol di-o-toluate, 1 ,2- octyl dibenzoate, tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bisphenol A bis(2-ethylhexaonate), ethoxylated nonylphenol, and mixtures thereof. In some embodiments, the plasticizer can be selected from the group consisting of dipropylene glycol dibenzoates, tripropylene glycol dibenzoates, and combinations thereof.

[0072] Generally, the plasticizer content of the polymer interlayers of this application are measured in parts per hundred resin parts (“phr”), on a weight per weight basis. For example, if 30 grams of plasticizer is added to 100 grams of polymer resin, the plasticizer content of the resulting plasticized polymer would be 30 phr. When the plasticizer content of a polymer layer is given in this application, the plasticizer content of the particular layer is determined in reference to the phr of the plasticizer in the melt that was used to produce that particular layer. In some embodiments, the high rigidity interlayer comprises a layer having a plasticizer content of less than about 35 phr and less than about 30 phr.

[0073] According to some embodiments of the present invention, one or more polymer layers described herein can have a total plasticizer content of at least about 20 phr, at least about 25 phr, at least about 30 phr, at least about 35 phr, at least about 38 phr, at least about 40 phr, at least about 45 phr, at least about 50 phr, at least about 55 phr, at least about 60 phr, at least about 65 phr, at least about 67 phr, at least about 70 phr, at least about 75 phr of one or more plasticizers. In some embodiments, the polymer layer may also include not more than about 100 phr, not more than about 85 phr, not more than 80 phr, not more than about 75 phr, not more than about 70 phr, not more than about 65 phr, not more than about 60 phr, not more than about 55 phr, not more than about 50 phr, not more than about 45 phr, not more than about 40 phr, not more than about 38 phr, not more than about 35 phr, or not more than about 30 phr of one or more plasticizers. In some embodiments, the total plasticizer content of at least one polymer layer can be in the range of from about 20 to about 40 phr, about 20 to about 38 phr, or about 25 to about 35 phr. In other embodiments, the total plasticizer content of at least one polymer layer can be in the range of from about 38 to about 90 phr, about 40 to about 85 phr, or about 50 to 70 phr.

[0074] When the interlayer includes a multiple layer interlayer, two or more polymer layers within the interlayer may have substantially the same plasticizer content and/or at least one of the polymer layers may have a plasticizer content different from one or more of the other polymer layers. When the interlayer includes two or more polymer layers having different plasticizer contents, the two layers may be adjacent to one another. In some embodiments, the difference in plasticizer content between adjacent polymer layers can be at least about 1 , at least about 2, at least about 5, at least about 7, at least about 10, at least about 20, at least about 30, at least about 35 phr and/or not more than about 80, not more than about 55, not more than about 50, or not more than about 45 phr, or in the range of from about 1 to about 60 phr, about 10 to about 50 phr, or about 30 to 45 phr. When three or more layers are present in the interlayer, at least two of the polymer layers of the interlayer may have similar plasticizer contents falling for example, within 10, within 5, within 2, or within 1 phr of each other, while at least two of the polymer layers may have plasticizer contents differing from one another according to the above ranges.

[0075] In some embodiments, one or more polymer layers or interlayers described herein may include a blend of two or more plasticizers including, for example, two or more of the plasticizers listed above. When the polymer layer includes two or more plasticizers, the total plasticizer content of the polymer layer and the difference in total plasticizer content between adjacent polymer layers may fall within one or more of the ranges above. When the interlayer is a multiple layer interlayer, one or more than one of the polymer layers may include two or more plasticizers. In some embodiments when the interlayer is a multiple layer interlayer, at least one of the polymer layers including a blend of plasticizers may have a glass transition temperature higher than that of conventional plasticized polymer layer. This may provide, in some cases, additional stiffness to layer which can be used, for example, as an outer “skin” layer in a multiple layer interlayer.

[0076] In aspects, the amount of plasticizer in the soft or core poly(vinyl butyral) or a blend of soft poly(vinyl butyral), may be, for example, from about 50 phr to about 150 phr, or from 55 phr to 120 phr, or from 60 to 100 phr.

[0077] In aspects, the stiff poly(vinyl butyral) contained in the plasticized poly (vinyl butyral) multilayer sheet comprises from about 25 phr to about 50 phr plasticizer, or from 30 phr to 45 phr, or from 32 to 42 phr.

[0078] In an embodiment, the plasticized poly(vinyl butyral) multilayer sheet, either an intact acoustic trilayer or a bilayer from which one skin layer has been removed, may comprise triethylene glycol bis(2-ethylhexanoate) present as a plasticizer. In other embodiments, the plasticized poly(vinyl butyral) multilayer sheet may further comprise dihexyladipate or bis(2- ethylhexyl)adipate or another convenient substance such as Benzoflex™ 9-88 benzoate ester as a plasticizer.

[0079] In other embodiments, plasticizer may be selected from one or more of esters of a polybasic acid or a polyhydric alcohol. In further embodiments, the plasticizer may be selected from one or more of: triethylene glycol bis(2-ethylhexanoate), tetraethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, bis(2-ethylhexyl)adipate, bis(2-ethoxyethyl)adipate, dioctyl adipate, hexyl cyclohexyladipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, polymeric adipates, a soybean oil, or an epoxidized soybean oil.

[0080] Additionally, plasticizers that are compatible in high temperatures may be utilized to further increase the flow of the interlayer.

[0081] In various embodiments of interlayers of the present disclosure, the interlayer may comprise about 30 to about 60 phr (parts per hundred parts resin) total plasticizer. While the total plasticizer content is indicated above, the plasticizer content in the stiff layer(s) or soft layer(s) can be different from the total plasticizer content. In addition, the stiff layer(s) and soft layer(s) can have different plasticizer contents, as each respective layer's plasticizer content at the equilibrium state is determined at least in part by its respective residual hydroxyl content. For example, at equilibrium the interlayer could comprise two skin layers, each with 38 phr plasticizer, and a core layer with 75 phr plasticizer, for a total plasticizer amount for the interlayer of about 54.3 phr when the combined skin layer thickness equals that of the core layer. For thicker or thinner skin layers, the total plasticizer amount for the interlayer may change accordingly.

[0082] In other embodiments, the amount of plasticizer in the stiff poly(vinyl butyral) or soft poly(vinyl butyral)s may be from about 20 phr to about 60 phr, or from 25 phr to 50 phr, or from 30 to 45 phr.

[0083] In aspects, the skin or stiff layer of the multilayer interlayer sheet may comprise a PVB polymer having a Tg, for example, from about 20 °C to about 45 °C, or from 25 °C to 40 °C, or from 28 °C to 35 °C. Alternatively, the Tg of the stiff poly(vinyl butyral) may be at least about 20 °C or at least 25 °C, or at least 28 °C, up to about 45 °C, or up to 40 °C, or up to 35 °C.

[0084] In aspects, the soft or core layer of the multilayer interlayer sheet may comprise a PVB polymer having a Tg, for example, from about -15 °C to about 45 °C, or from -10 °C to 30 °C, or from -8 °C to 25 °C.

Alternatively, the Tg of the soft poly(vinyl butyral) may be at least about -15 °C or at least -10 °C, or at least -8 °C, up to about 45 °C, or up to 30 °C, or up to 20 °C.

[0085] In an aspect, the Tg of the core or soft layer may be at least 12 °C lower, or at least 15 °C lower, or at least 20 °C lower, or at least 30 °C lower than the Tg of the stiff layer.

[0086] In embodiments, the polymer interlayer has at least two different glass transition temperatures (T_g) and the difference between the at least two different glass transition temperatures (T_g) is at least 5 -C.

[0087] As a result of the migration of plasticizer within an interlayer, the glass transition temperatures of one or more polymer layers may be different when measured alone or as part of a multiple layer interlayer. In some embodiments, the interlayer can include at least one polymer layer having a glass transition temperature, outside of an interlayer, of at least about 33, at least about 34, at least about 35, at least about 36, at least about 37, at least about 38, at least about 39, at least about 40, at least about 41 , at least about 42, at least about 43, at least about 44, at least about 45, or at least about 46 °C. In some embodiments, the same layer may have a glass transition temperature within the polymer layer of at least about 34, at least about 35, at least about 36, at least about 37, at least about 38, at least about 39, at least about 40, at least about 41 , at least about 42, at least about 43, at least about 44, at least about 45, at least about 46, or at least about 47 °C.

[0088] In the same or other embodiments, at least one other polymer layer of the multiple layer interlayer can have a glass transition temperature less than 30 °C and may, for example, have a glass transition temperature of not more than about 25, not more than about 20, not more than about 15, not more than about 10, not more than about 9, not more than about 8, not more than about 7, not more than about 6, not more than about 5, not more than about 4, not more than about 3, not more than about 2, not more than about 1 , not more than about 0, not more than about -1 , not more than about -2 °C, or not more than about -5 °C, measured when the interlayer is not part of an interlayer. The same polymer layer may have a glass transition temperature of not more than about 25, not more than about 20, not more than about 15, not more than about 10, not more than about 9, not more than about 8, not more than about 7, not more than about 6, not more than about 5, not more than about 4, not more than about 3, not more than about 2, not more than about 1 , or not more than about 0 °C, when measured outside of the interlayer.

[0089] According to some embodiments, the difference between the glass transition temperatures of two polymer layers, typically adjacent polymer layers within an interlayer, can be at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, or at least about 45 °C, while in other embodiments, two or more polymer layers can have a glass transition temperature within about 5, about 3, about 2, or about 1 °C of each other. Generally, the lower glass transition temperature layer has a lower stiffness than the higher glass transition temperature layer or layers in an interlayer and may be located between higher glass transition temperature polymer layers in the final interlayer construction.

[0090] The PVB layers according to the invention are further characterized by their peel adhesion properties, with respect to one another and with respect to other materials they may come in contact with.

[0091] For example, in some embodiments, the stiff PVB as described herein can exhibit a 90° peel adhesion value, when laminated to glass, of at least about 20 N/cm, at least about 25 N/cm, at least about 30 N/cm, at least about 35 N/cm, at least about 40 N/cm, at least about 45 N/cm, or at least about 50 N/cm at 25 % relative humidity and 21 °C. In contrast. Alternatively, the stiff PVB as described herein can exhibit a 90° peel adhesion value, when laminated to glass, of from about 20 N/cm to about 70 N/cm, or from 25 N/cm to 65 N/cm, or from 30 N/cm to 60 N/cm.

[0092] In contrast, in some aspects, the soft PVB as described herein can exhibit a 90° peel adhesion, when laminated to glass, of at least about 2 N/cm, at least about 3 N/cm, at least about 4 N/cm, up to about 20 N/cm, or up to 18 N/cm, or up to 15 N/cm, at 25 % relative humidity and 21 °C. Alternatively, the soft PVB as described herein can exhibit a 90° peel adhesion value, when laminated to glass, of from about 2 N/cm to about 20 N/cm, or from 3 N/cm to 18 N/cm, or from 4 N/cm to 15 N/cm. These values as measured on laminated glass are not intended to suggest that the layers according to the invention have, in fact, been laminated to glass, but rather that the polymers described would exhibit these peel adhesion properties when laminated to glass as described below.

[0093] The peel adhesion properties, with respect to the combined soft and the stiff layers, are as follows: the stiff PVB as described herein can exhibit a 90° peel adhesion to the soft PVB of at least about 8, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30 at least about 35 or at least about 40 N/cm at 25 % relative humidity and 21 °C. [0094] For example, the layers and interlayers according to embodiments of the present invention may exhibit such a peel adhesion while having an average moisture content of at least about 0.2 %, or at least 0.25 %, or at least 0.3 %, or at least 0.35 % or at least 0.4 %, measured by Karl-Fisher Titration according to ASTM E203.

[0095] The 90° peel adhesion to glass values described herein may be determined according to the following procedure, including the lamination/autoclaving described. Similarly, the peel adhesion values of the stiff PVB to the soft PVB (as measured on a three layer stiff/soft/stiff sheet in which a first stiff layer is being removed) are determined according to the following, without of course first laminating/autoclaving the film to glass.

[0096] Peel Adhesion: To measure the bond strength between the plasticized PVB layer and glass, adhesion-coated aluminum foil is initially conditioned at 105 °C for 30 min. Special peel adhesion laminates containing the PVB interlayer to be tested are then prepared using standard laminating techniques by substituting the conditioned aluminum foil for one glass piece of a standard double glass layered laminate. The thickness of the plasticized PVB layer in the laminate being tested is standardized at 30 mils (0.76 mm). More specifically, the coated foil is assembled to one side of the polymeric laminate with the adhesive next to the PVB layer and a test glass layer assembled to the other side of the PVB laminate. After two such laminates are assembled, they are placed with the foil faces in face-to-face contact and passed through deairing rolls. The laminates are then placed singly, with foil down, in a circulating air oven at 100 °C for 5 minutes. The hot laminates are then assembled, rerolled as before and autoclaved at 290 °F (143 °C) at 185 psi (1 ,275k Pa). After autoclaving, a 4 cm wide cut through the foil and polymeric laminate is made using a special double wheeled cutter. The glass at one end of the laminate is then scored and broken. The outside edge of the aluminum foil and polymer laminate on each side of the 4 cm strip is cut at the glass break. At least three samples of a particular common polymeric laminate are tested per reported value. At the time of peel sample lay-up, a standard laminate to be used for moisture analysis is prepared from the same polymeric laminate piece. Prior to conducting the actual peel test, the samples are conditioned at (21 °C) overnight. During peel testing, the sample of glass, foil and polymer laminate are clamped in testing grips of an Instron peel tester (crosshead speed of 5 in (12.7 cm) per min.) and a direct recorded measurement made of the force necessary to separate the polymer laminate from the glass. The average of the various recorded peaks is the value for the sample.

[0097] To measure the bond strength between the stiff plasticized PVB layer and the soft plasticized PVB layer:

[0098] A stiff/soft/stiff trilayer or a stiff/soft bilayer sample are cut to a rectangular strip. The surface layers are adhered to a piece of tape of a corresponding size. The initial separation of the soft/core layers is carried out manually at one end of the strip to facilitate the mounting of the layer to the sample holder of the peel tester. The strip can then be peeled apart at the stiff/soft interface in a 180 degree peel test by a peel testing apparatus.

[0099] The peel adhesion properties described are significant, since the core and skin material both exhibit stickiness to various materials, while the core layer is even stickier than the skin layer. Similarly, the two layers also exhibit a peel adhesion value when in the same film which value affects the ability to neatly separate the two layers.

[00100] The core and skin layers of the multilayers separated according to the invention are further characterized as having a different shear storage modulus.

[00101] Thus, in one aspect, the soft poly(vinyl butyral) layer comprises poly(vinyl butyral) having a shear modulus at 20 °C from about 0.01 MPa to about 20 MPa, or from about 0.1 to about 18 MPa, or from or from about 0.15 to about 15 MPa. Correspondingly, the stiff poly(vinyl butyral) layer comprises poly(vinyl butyral) having a shear modulus at 20 °C from about 20 MPa to about 600 MPa, or from about 28 to about 450 MPa, or from about 30 to about 400 MPa.

[00102] This property is likewise significant, since it indicates among other things the tendency of the layers to remain intact, or put another way, the likelihood the materials will tear. Because of the differences in shear modulus just described, the soft layer is indeed susceptible to tearing, making it difficult to remove the layer intact.

[00103] The glass transition temperature (Tg) and Shear Modulus as described herein can be determined by dynamical mechanical thermal analysis (DMTA) in shear mode. The DMTA measures the storage (elastic) shear modulus (G’) in Pascals, loss (viscous) shear modulus (G”) in Pascals, tan delta (=G”/G’) of the specimen as a function of temperature at a given frequency, and temperature sweep rate. A frequency of 1 Hz and temperature sweep rate of 3 °C/min are used herein. The Tg is then determined by the position of the tan delta peak on the temperature scale in °C and the tan delta peak value is referred as tan delta or peak tan delta. As used herein, “tan delta”, “peak tan delta”, “tan 6” and “peak tan 6” may be used interchangeably.

[00104] One parameter used to describe the polymer resin components of the polymer interlayers of this application is residual hydroxyl content (as vinyl hydroxyl content or poly(vinyl alcohol) (“PVOH”) content). Residual hydroxyl content refers to the amount of hydroxyl groups remaining as side groups on the chains of the polymer after processing is complete. For example, PVB can be manufactured by hydrolyzing poly(vinyl acetate) to poly(vinyl alcohol), and then reacting the poly(vinyl alcohol) with butyraldehyde to form PVB. In the process of hydrolyzing the poly(vinyl acetate), typically not all the acetate side groups are converted to hydroxyl groups. Further, the reaction with butyraldehyde typically will not result in all the hydroxyl groups being converted into acetal groups. Consequently, in any finished PVB, there will typically be residual acetate groups (such as vinyl acetate groups) and residual hydroxyl groups (such as vinyl hydroxyl groups) as side groups on the polymer chain. Generally, the residual hydroxyl content of a polymer can be regulated by controlling the reaction times and reactant concentrations, among other variables in the polymer manufacturing process. When utilized as a parameter herein, the residual hydroxyl content is measured on a wt% basis per ASTM D- 1396.

[00105] In an aspect, the difference between the residual hydroxyl content of the soft poly(vinyl butyral) and the residual hydroxyl content of the stiff poly(vinyl butyral) is at least 6 %, or at least 5 %, or at least 4 %, or from 4 % to 8 %, or from 5 % to 10 %, or as further described herein.

[00106] Thus, in various embodiments, the residual hydroxyl contents of the poly(vinyl butyral) resins for stiff (skin) layer(s) and soft (core) layer(s) may be different. The resin for the core layer(s), for example, can comprise about 9 to about 18 weight percent (wt%) residual hydroxyl groups calculated as PVOH, about 9 to about 16 wt% residual hydroxyl groups calculated as PVOH, or about 9 to about 14 wt% residual hydroxyl groups calculated as PVOH. The resin for the skin layer(s), for example, can comprise about 13 to about 35 weight percent (wt%) residual hydroxyl groups calculated as PVOH, about 13 to about 30 wt% residual hydroxyl groups calculated as PVOH, or about 15 to about 22 wt% residual hydroxyl groups calculated as PVOH; and, for certain embodiments, about 17.25 to about 22.25 wt% residual hydroxyl groups calculated as PVOH, or as described elsewhere herein.

[00107] In various embodiments, the poly(vinyl butyral) resin comprises about 8 to about 35 weight percent (wt%) residual hydroxyl groups calculated as PVOH, about 13 to about 30 wt% residual hydroxyl groups calculated as PVOH, about 8 to about 22 wt% residual hydroxyl groups calculated as PVOH, or about 15 to about 22 wt% residual hydroxyl groups calculated as PVOH; and for some of the high rigidity interlayers disclosed herein, for one or more of the layers, the poly(vinyl butyral) resin comprises greater than about 19 wt% residual hydroxyl groups calculated as PVOH, greater than about 20 wt% residual hydroxyl groups calculated as PVOH, greater than about 20.4 wt% residual hydroxyl groups calculated as PVOH, and greater than about 21 wt% residual hydroxyl groups calculated as PVOH.

[00108] In some embodiments, the poly (vi ny I butyral) resin used in at least one polymer layer of an interlayer may include a poly(vinyl butyral) resin that has a residual hydroxyl content of at least about 18, at least about 18.5, at least about 18.7, at least about 19, at least about 19.5, at least about 20, at least about 20.5, at least about 21 , at least about 21 .5, at least about 22, at least about 22.5 wt% and/or not more than about 30, not more than about 29, not more than about 28, not more than about 27, not more than about 26, not more than about 25, not more than about 24, not more than about 23, or not more than about 22 wt%, measured as described above.

[00109] Additionally, one or more other polymer layers in the interlayers described herein may include another poly(vinyl butyral) resin that has a lower residual hydroxyl content. For example, in some embodiments, at least one polymer layer of the interlayer can include a poly(vinyl butyral) resin having a residual hydroxyl content of at least about 8, at least about 8.5, at least about 9, at least about 9.5, at least about 10, at least about 10.5, at least about 1 1 , at least about 1 1 .5, at least about 12, at least about 13 wt% and/or not more than about 16, not more than about 15, not more than about 14, not more than about 13.5, not more than about 13, not more than about 12, or not more than about 1 1 .5 wt%, measured as described above.

[00110] In one embodiment, the soft or core poly(vinyl butyral) or blend of soft poly(vinyl butyral)s, may have a residual hydroxyl content, as further described herein, from about 5 % to about 15 %. Alternatively, the residual hydroxyl content of the soft poly(vinyl butyral) may be from about 7 % to about 13 %, or from 8 % to 12 %, or as described elsewhere herein.

[00111] In another aspect, the stiff poly(vinyl butyral) or blend of stiff poly(vinyl butyral)s, may have a residual hydroxyl content, as further described herein, from about 12 % to about 28 %. Alternatively, the residual hydroxyl content of the stiff poly(vinyl butyral) may be from about 15 % to about 25 %, or from 18 % to 20 %, or as described elsewhere herein.

[00112] In embodiments, the residual hydroxyl content of the first stiff poly(vinyl butyral resin) is typically the same as the residual hydroxyl content of the second stiff poly (vinyl butyral resin) and typically differs from that in the core poly(vinyl butyral resin). In embodiments, the difference between the core residual hydroxyl content and the skin residual hydroxyl content is at least 4.0 weight percent, or at least 5.0 weight percent, or at least 6.0 weight percent.

[00113] In embodiments, the core poly(vinyl butyral) resin is present in an amount of from about 2 weight percent to about 45 weight percent, or from about 5 weight percent to about 40 weight percent. [00114] In one embodiment, the soft poly(vinyl butyral) or blend of soft poly(vinyl butyral)s, may have a residual acetate content, as further described herein, from about 0 % to about 18 %, or from 0.5 % to 10 %. Alternatively, the residual acetate content may be less than 10 %, or less than 5 %, or less than 2 %, or less than 1 %, or as further described herein.

[00115] In another embodiment, the stiff poly(vinyl butyral) or blend of stiff poly(vinyl butyral)s, may have a residual acetate content, as further described herein, from about 0 % to about 18 %. Alternatively, the residual acetate content of the stiff poly(vinyl butyral) may be less than 10 %, or less than 5 %, or less than 2 %, or less than 1 %, or as further described herein.

[00116] In other embodiments, the residual hydroxyl content of the soft layer can be the same as, greater than, or less than the residual hydroxyl content of the resin in the stiff layer. In various embodiments, the soft resin, or skin resin, or both of these resins, may comprise less than 30 wt% residual ester groups, less than 25 wt% residual ester groups, less than 20 wt%, less than 15 wt%, less than 13 wt%, less than 10 wt%, less than 7 wt%, less than 5 wt%, or less than 1 wt% residual ester groups calculated as polyvinyl ester, e.g., acetate, with the balance being an acetal, such as butyraldehyde acetal, but optionally being other acetal groups, such as an isobutyraldehyde acetal group, a 2-ethyl hexanal acetal group, or a mix of any two of butyraldehyde acetal, isobutyraldehyde acetal, and 2-ethyl hexanal acetal groups, or as discussed elsewhere herein.

[00117] The resin for the core layer(s) or for the skin layer(s) or for both the skin layer(s) and core layer(s) can also comprise less than 20 wt% residual ester groups, less than 15 wt%, less than 13 wt%, less than 1 1 wt%, less than 9 wt%, less than 7 wt%, less than 5 wt%, or less than 1 wt% residual ester groups calculated as polyvinyl ester, e.g., acetate, with the balance being an acetal, preferably butyraldehyde acetal, but optionally including other acetal groups in a minor amount, for example, a 2-ethyl hexanal group (see, for example, U.S. Pat. No. 5,137,954, the entire disclosure of which is incorporated herein by reference). [00118] In an aspect, the multilayered interlayers used in the processes of the invention may comprise: a skin or still polymer layer comprising plasticized poly(vinyl butyral) having a weight average molecular weight (Mw) of less than about 140,000 amu, or less than 150,000 or less than 200,000, or less than 250,000; a core polymer layer comprising plasticized poly(vinyl butyral) having a weight average molecular weight of greater than about 200,000 amu, or greater than 225,000, or greater than 250,000, or greater than 275,000.

[00119] Thus, the skin or stiff polymer layer comprising plasticized poly(vinyl butyral) having a weight average molecular weight (Mw) of from about 60,000 to 250,000, or from 70,000 to 225,000, or from 100,000 to 200,000. The core polymer layer may comprise plasticized poly(vinyl butyral) having a weight average molecular weight of from about 150,000 amu to 600,000, or from 200,000 to 500,000, or from 250,000 to 400,000.

[00120] More generally, as used herein, the term “molecular weight” refers to weight average molecular weight (Mw). The molecular weight of suitable PVB resins will generally be in the range of from about 50,000 to about 600,000, about 70,000 to about 450,000, or about 100,000 to about 425,000 atomic mass units.

[00121] The extruded interlayer formed from plasticized PVB resin can be prepared with systems known to those skilled in the art by extrusion through a conventional sheeting die having cooled die lips, i.e. by forcing molten polymer through a horizontally long, vertically narrow die opening substantially conforming in length and width to that of the sheet being formed therein.

[00122] For example, multiple layer interlayers may be coextruded using a multiple manifold coextrusion device such as that disclosed in U.S. Pat. Publn. No. 2008/0254302, the relevant disclosure of which is incorporated herein by reference. Such a device has a first die manifold, a second die manifold, and a third die manifold. The device operates by simultaneously extruding polymer melts from each manifold toward the extrusion opening, where the multiple layer interlayer is extruded as a composite of three individual polymer layers. Layer thickness can be varied by adjusting the distance between the die lips at the extrusion opening. Melt fracture may be controlled though control of the composition of the melts, the temperature of the die lips or lands at the extrusion opening, or through control of the rate and method of cooling of the extruded interlayer, which can be, for example, immersed in a cooling bath soon after extrusion. According to the invention, the desired film having a rough surface and a smooth surface on opposite sides may be obtained using the separation techniques described herein. [00123] Conventional multilayer interlayers such as a tri-layer acoustic interlayer typically contain a soft core layer consisting of a single poly(vinyl butyral) (“PVB”) resin having a low residual hydroxyl content and a high amount of a conventional plasticizer, and two stiff skin layers having significantly higher residual hydroxyl content (see, for example U.S. Patents 5,340,654, 5,190,826, and 7,510,771 ). Thus, the isolated soft poly(vinyl butyral) may be recycled to form the core layer of a trilayer acoustic interlayer, or the soft poly(vinyl butyral) and plasticizer varnish may be used directly to form a soft poly(vinyl butyral) layer without first separating the two. The residual hydroxyl content in the PVB core resin and the amount of the plasticizer are optimized such that the interlayer provides optimal sound insulation property under ambient conditions for multiple layer glass panels such as windshields and windows installed on vehicles and buildings.

[00124] As noted, in a significant aspect, the multilayer interlayer sheet comprises a multilayer PVB interlayer, for example having a skin/core/skin cross-section. Although a particular PVB interlayer has just been described, a variety of interlayer materials may be used.

[00125] When the interlayers comprise polyvinyl butyral (PVB), the PVB resin may be produced by known acetalization processes by reacting polyvinyl alcohol (“PVOH”) with butyraldehyde in the presence of an acid catalyst, separation, stabilization, and drying of the resin. Such acetalization processes are disclosed, for example, in U.S. Pat. Nos. 2,282,057 and 2,282,026 and Vinyl Acetal Polymers, in Encyclopedia of Polymer Science & Technology, 3rd edition, Volume 8, pages 381 -399, by B.E. Wade (2003), the entire disclosures of which are incorporated herein by reference. The resin is commercially available in various forms, for example, as Butvar® Resin from Solatia Inc., a wholly owned subsidiary of Eastman Chemical Company.

[00126] The PVB resins of the present disclosure typically have a molecular weight of greater than 50,000 Daltons, or less than 500,000 Daltons, or about 50,000 to about 500,000 Daltons, or about 70,000 to about 500,000 Daltons, or about 100,000 to about 425,000 Daltons, as measured by size exclusion chromatography using low angle laser light scattering. As used herein, the term “molecular weight” means the weight average molecular weight.

[00127] In addition to plasticizers, it is also contemplated that adhesion control agents (“ACAs”) can also be added to the polymer resins to form polymer interlayers. ACAs generally function to alter and/or improve the adhesion of the interlayer to the glass panels when forming a laminated panel. Contemplated ACAs include, but are not limited to, magnesium carboxylates/salts. In addition, contemplated ACAs may also include those ACAs disclosed in U.S. Patent 5,728,472, incorporated by reference herein in its entirety, such as residual sodium acetate, potassium acetate, magnesium bis(2-ethyl butyrate), and/or magnesium bis(2-ethylhexanoate).

[00128] Other additives may be incorporated into the interlayer to enhance its performance in a final product and impart certain additional properties to the interlayer. Such additives include, but are not limited to, dyes, pigments, stabilizers (e.g., ultraviolet stabilizers), antioxidants, anti-blocking agents, flame retardants, IR absorbers or blockers (e.g., indium tin oxide, antimony tin oxide, lanthanum hexaboride (LaB₆) and cesium tungsten oxide), processing aides, flow enhancing additives, lubricants, impact modifiers, nucleating agents, thermal stabilizers, UV absorbers, UV stabilizers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcement additives, and fillers, among other additives known to those of ordinary skill in the art.

[00129] Various adhesion control agents (“ACAs”) can be used in the interlayers of the present disclosure to control the adhesion of the interlayer sheet to glass. In various embodiments of interlayers of the present disclosure, the interlayer can comprise about 0.003 to about 0.15 parts ACAs per 100 parts resin; about 0.01 to about 0.10 parts ACAs per 100 parts resin; and about 0.01 to about 0.04 parts ACAs per 100 parts resin. Such ACAs, include, but are not limited to, the ACAs disclosed in U.S. Patent No. 5,728,472 (the entire disclosure of which is incorporated herein by reference), residual sodium acetate, potassium acetate, magnesium bis(2-ethyl butyrate), and/or magnesium bis(2-ethylhexanoate).

[00130] Other additives may be incorporated into the interlayer to enhance its performance in a final product and impart certain additional properties to the interlayer. Such additives include, but are not limited to, dyes, pigments, stabilizers (e.g., ultraviolet stabilizers), antioxidants, antiblocking agents, flame retardants, IR absorbers or blockers (e.g., indium tin oxide, antimony tin oxide, lanthanum hexaboride (LaB₆) and cesium tungsten oxide), processing aides, flow enhancing additives, lubricants, impact modifiers, nucleating agents, thermal stabilizers, UV absorbers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcement additives, and fillers, among other additives known to those of ordinary skill in the art.

[00131] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Further, the ranges stated in this disclosure and the claims are intended to include the entire range specifically and not just the endpoint(s). For example, a range stated to be 0 to 10 is intended to disclose all whole numbers between 0 and 10 such as, for example 1 , 2, 3, 4, etc., all fractional numbers between 0 and 10, for example 1 .5, 2.3, 4.57, 6.1113, etc., and the endpoints 0 and 10.

[00132] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are intended to be reported precisely in view of methods of measurement. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[00133] It is to be understood that the mention of one or more process steps does not preclude the presence of additional process steps before or after the combined recited steps or intervening process steps between those steps expressly identified. Moreover, the denomination of process steps, ingredients, or other aspects of the information disclosed or claimed in the application with letters, numbers, or the like is a convenient means for identifying discrete activities or ingredients and the recited lettering can be arranged in any sequence, unless otherwise indicated.

[00134] As used herein, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. For example, reference to a C_n alcohol equivalent is intended to include multiple types of C_n alcohol equivalents. Thus, even use of language such as “at least one” or “at least some” in one location is not intended to imply that other uses of “a”, “an”, and “the” excludes plural referents unless the context clearly dictates otherwise. Similarly, use of the language such as “at least some” in one location is not intended to imply that the absence of such language in other places implies that “all” is intended, unless the context clearly dictates otherwise.

[00135] As used herein the term “and/or”, when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[00136] This invention can be further illustrated by the following examples of embodiments thereof, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated.

EXAMPLES

Example 1 Prophetic

[00137] A 5” x 10” PVB core-skin bi-layer sample, with the core layer facing down, is placed on top of another PVB core-skin bi-layer sample, with the core layer facing up, 8” x 12” in size. This sample is compressed on the Wabash static press under 5 bar at 80 °C for 10 minutes, followed by cooling down to 25 °C. The sample now appears a tri-layer sheet. The skin layer from the original PVB core-skin bi-layer sample is mechanically separated from the skin-combined core-skin sample at 40 °C. The recovered skin layer can be reused in the skin layer extrusion.

Example 2 Prophetic

[00138] A 5” x 10” PVB core-skin bi-layer sample, with the core layer facing down, is placed on top of another PVB core-skin bi-layer sample, with the core layer facing up, 8” x 12” in size, after squirting 1 gram of methanol on top of the second core-skin bi-layer sample. This sample is compressed on the Wabash static press under 5 bar at 80 °C for 10 minutes, followed by cooling down to 25 °C. The sample now appears a tri-layer sheet. The skin layer from the original PVB core-skin bi-layer sample is mechanically separated from the skin-combined core-skin sample at 40 °C. The recovered skin layer can be reused in the skin layer extrusion. Example 3 Prophetic

[00139] A PVB core-skin bi-layer is continuously unwound from a roll at 1 m/min, with the core layer facing down, is fed to an isochoric double-belt press equipped with steel belts. The bottom steel belt is covered with a PVB core layer. The core-skin bi-layer is combined with the core material on the bottom steel belt at 80 °C. The bi-layer now with the thicker core is cooled down to 25 °C before it is heated again to 45 °C when it exits the double-belt press. At the exit, the skin layer is mechanically separated from the skin-combined core sample. A blade is placed at the end of the bottom steel belt to continuously cut off the extra thickness of core material accumulated on the steel belt. The recovered skin layer can be re-used in the skin layer extrusion. The recovered core layer material can be re-used in the core-layer extrusion.

Claims

CLAIMS:

1 . A process for separating a first soft poly(vinyl butyral) layer from a first stiff poly(vinyl butyral) layer of a first multilayer interlayer, the process comprising: a. contacting the first soft poly(vinyl butyral) layer of the first multilayer interlayer with a second soft poly(vinyl butyral) layer of a second multilayer interlayer that comprises the second soft poly (vinyl butyral) layer and a second stiff poly(vi nyl butyral) layer such that the first soft poly(vinyl butyral) layer of the multilayer interlayer and the second soft poly(vinyl butyral) layer of the second multilayer interlayer adhere to one another and combine; and b. thereafter separating the combined first soft poly(vinyl butyral) layer of the first multilayer interlayer and the second soft poly(vinyl butyral) layer of the second multilayer interlayer from at least one of the first stiff poly(vinyl butyral) layer of the first multilayer interlayer and the second stiff poly(vinyl butyral) layer of the second multilayer interlayer.

2. The process of claim 1 , further comprising applying a solvent to at least one of the first soft poly(vinyl butyral) layer and the second soft poly(vinyl butyral) layer prior to the step of contacting.

3. The process of claim 1 , wherein the solvent comprises one or more of alcohols having from 1 to 8 carbon atoms, or a carboxylic acid ester thereof, wherein the acid has from 1 to 8 carbon atoms.

4. The process of claim 1 , wherein the contacting includes compressing the first soft poly(vinyl butyral) layer and the second soft poly(vinyl butyral) layer together.

5. The process of claim 1 , wherein the solvent comprises one or more of: methanol, ethanol, n-isopropanol, isopropanol, or ethyl acetate.

6. The process of claim 1 , wherein a thickness of the first stiff poly(vinyl butyral) layer is at least 1 .0 times, or at least 1 .5 times, a thickness of the second soft poly(vinyl butyral) layer.

7. The process of claim 1 , wherein the first stiff poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer which exhibits a 90° peel adhesion value, when laminated to glass, of from about 20 N/cm to about 70 N/cm.

8. The process of claim 1 , wherein the first soft poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer which exhibits a 90° peel adhesion value, when laminated to glass, of from about 3 N/cm to about 18 N/cm.

9. The process of claim 1 , wherein a difference in a 90° peel adhesion value between the first soft poly(vinyl butyral) layer and the first stiff poly (vinyl butyral) layer, when laminated to glass, is at least 10 N/cm, or at least 15 N/cm.

10. The process of claim 1 , wherein a difference in a 90° peel adhesion value between the first stiff poly(vinyl butyral) and the first soft poly(vi nyl butyral) when in contact is at least about 10 N/cm, at 25 % relative humidity and 21 °C.

1 1. The process of claim 1 , wherein the first soft poly(vinyl butyral) layer comprises poly(vinyl butyral) having a shear storage modulus at 20 °C from about 0.1 MPa to about 18 MPa.

12. The process of claim 1 , wherein the first stiff poly(vinyl butyral) layer comprises poly(vinyl butyral) having a shear storage modulus at 20 °C from about 20 MPa to about 600 MPa.

13. The process of claim 1 , wherein a difference between a shear storage modulus at 20 °C of the first soft poly(vinyl butyral) layer and the first stiff poly(vinyl butyral) layer is at least 10 MPa.

14. The process of claim 1 , wherein the first soft poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer having a Tg less than about 20 °C.

15. The process of claim 1 , wherein the first stiff poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer having a Tg greater than about 25 °C.

16. The process of claim 1 , wherein the first soft poly(vinyl butyral) layer comprises a poly(vi nyl butyral) polymer having a residual hydroxyl content from about 8 % to about 13.5 %.

17. The process of claim 1 , wherein the first stiff poly(vinyl butyral) layer comprises a poly(vi nyl butyral) polymer having a residual hydroxyl content from about 15 % to about 25 %.

18. The process of claim 1 , wherein a difference between the residual hydroxyl content of the poly(vinyl butyral) polymer of the first stiff poly(vinyl butyral) layer and the poly(vinyl) butyral polymer of the first soft poly(vinyl butyral) layer is at least 5 weight percent.

19. The process of claim 1 , wherein the first stiff poly(vinyl butyral) layer comprises poly(vinyl butyral) having a plasticizer content from about 20 phr to about 50 phr.

20. The process of claim 1 , wherein the first soft poly(vinyl butyral) layer comprises poly(vinyl butyral) having a plasticizer content from about 45 phr to about 150 phr.

21. The process of claim 1 , wherein the first stiff poly(vinyl butyral) layer comprises poly(vinyl butyral) having a weight average molecular weight from about 70,000 to 225,000.

22. The process of claim 1 , wherein the first soft poly(vinyl butyral) layer comprises poly(vinyl butyral) having a weight average molecular weight from about 150,000 to about 600,000.

23. The process of claim 1 , wherein the process includes the use of spreader rollers to ensure the interlayer is flat.

24. The process of claim 1 , wherein the process includes the use of annealing to help eliminate wrinkles.

25. The process of claim 1 , wherein substantially all of the first soft poly(vinyl butyral) layer is removed from the first stiff poly(vinyl butyral) layer such that FT-IR results show substantially no residue of the soft poly(vinyl butyral) layer.