Method for separating multilayer interlayer

Abstract

A process for separating a soft poly (vinyl butyral) layer from a hard poly (vinyl butyral) layer of a multilayer interlayer is disclosed.

Description

Technical Field

[0001] This disclosure relates to the field of recycling polymer sandwiches with different poly(vinyl butyral) components. Background Technology

[0002] Multilayer sandwich structures are gaining an increasingly large share of the sandwich market, but they have limited recyclability in extrusion processes because different layers may have different physicochemical properties. A typical example of these multilayer sandwich structures is the acoustic triplet sandwich, which uses two outer skin layers that typically have similar properties with a core layer that has significantly different properties. When reprocessed, these acoustic core layers, in particular, tend to mismix with the two skin layer materials during extrusion, forming small but discrete core material domains that contribute to a degree of haze, thus limiting their content in extrusion. The inability to reprocess such multilayer materials represents a significant economic loss.

[0003] The skin can be manually peeled from multi-layered sheets to demonstrate the concept of mechanical separation. However, improved processes and machinery will facilitate stable, consistent, and cost-effective mechanical separation operations.

[0004] U.S. Patent No. 11,518,472 discloses a method for recycling an interlayer for laminated glass, the method comprising the step of separating the layers comprising layer A and layer B of laminated glass from the interlayer.

[0005] U.S. Patent No. 4,940,187 discloses a systematic apparatus for recovering raw materials such as copper, ferrous materials, and various plastic materials from waste wire. The apparatus includes: a classifier for separating copper and plastic materials; and a wet gravity separator for further separating different plastic materials with different densities and buoyancy heights within the separator's tank.

[0006] EP0425800A1 discloses a method for separating synthetic resin foam from a rigid article, wherein the method involves subjecting the article to deformation treatment, after which any synthetic resin foam still adhering to the article is removed from the article by a scraping member. An apparatus suitable for this purpose is also disclosed.

[0007] JP7166571B2 discloses a membrane member having a first layer on one side of an adhesive layer and a second layer on the opposite side, the membrane member being separated by cutting along the layers with a blade.

[0008] WO2022250944A2 discloses a process for separating the first layer of a multilayer sandwich sheet from the remaining portion, wherein the multilayer sheet is heated and then the first layer of the multilayer sandwich sheet is separated from the remaining portion by pulling the first layer of the multilayer sandwich sheet in a defined orientation in different directions.

[0009] Similarly, U.S. Patent Application No. 63 / 448,707 discloses a process for separating the first layer of a tapered multilayer sandwich sheet from the remaining portion, wherein the tapered multilayer sandwich sheet is heated, and then the first layer of the tapered multilayer sandwich sheet is separated from the remaining portion by pulling the first layer and the remaining portion of the tapered multilayer sandwich sheet in defined orientations in different directions without causing the tapered multilayer sandwich sheet to wrinkle or tear.

[0010] In both cases, when the multilayer sheet is an acoustic sandwich with the remaining portion being a core-skin bilayer and the core layer exposed, it is difficult to mechanically separate the two layers (core and remaining skin) because the fragile and vulnerable core layer is easily torn due to its inability to withstand mechanical peeling forces. The core layer may also be very sticky, making it difficult to process. In fact, it will stick to both the skin and any other material it comes into contact with. In some cases, it tends to preferentially adhere to the skin; in others, it may preferentially adhere to other materials. Worse still, this preference may vary based on ambient temperature, or, in the case of separating the two, may vary under the separation conditions that may change during the separation process. Therefore, the differences in the properties between the two layers make subsequent separation attempts even more difficult than the step of removing the first skin layer from the remaining core-skin layer.

[0011] In fact, the inventors have found that manual attempts to peel the core layer from a 1-inch-wide core-skin bilayer strip have only been partially successful. In addition to the difficulty in handling the fragile and vulnerable core layer, which is very easy to tear, some core layer materials also exhibit brittleness, inelasticity, and a strong adhesion to the outer skin, making it almost impossible to mechanically peel the core layer from the skin while keeping it substantially intact.

[0012] There is still a need for methods and apparatus for separating layers of multilayer sandwiches (especially multilayer sandwiches comprising two layers with significantly different properties) so as to facilitate the reprocessing of materials during manufacturing. Summary of the Invention

[0013] In one aspect, the present invention relates to a method for separating a first soft poly(vinyl butyral) layer from a first hard poly(vinyl butyral) layer of a first multilayer sandwich, the method comprising the steps of: contacting the first soft poly(vinyl butyral) layer of the first multilayer sandwich with a second soft poly(vinyl butyral) layer of a second multilayer sandwich, the second multilayer sandwich comprising the second soft poly(vinyl butyral) layer and the second hard poly(vinyl butyral) layer, such that the first soft poly(vinyl butyral) layer of the multilayer sandwich and the second soft poly(vinyl butyral) layer of the second multilayer sandwich adhere to and bond together; and subsequently separating the bonded first soft poly(vinyl butyral) layer of the first multilayer sandwich and the second soft poly(vinyl butyral) layer of the second multilayer sandwich from at least one of the first hard poly(vinyl butyral) layer of the first multilayer sandwich and the second hard poly(vinyl butyral) layer of the second multilayer sandwich.

[0014] In another respect, the present invention relates to apparatus for performing the method of the present invention.

[0015] Further aspects of the invention are as disclosed and claimed herein. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the mechanical separation of the multilayer sandwich structure by bringing the soft poly(vinyl butyral) layer of the multilayer sandwich structure into contact with the soft poly(vinyl butyral) layer of the second multilayer sandwich structure. Detailed Implementation

[0017] The following implementation schemes and combinations are included within the scope of this invention.

[0018] In a first embodiment, the present invention relates to a method for separating a first soft poly(vinyl butyral) layer from a first hard poly(vinyl butyral) layer of a first multilayer sandwich, the method comprising: The first soft poly(vinyl butyral) layer of the first multilayer sandwich is brought into contact with the second soft poly(vinyl butyral) layer of the second multilayer sandwich, wherein the second multilayer sandwich includes the second soft poly(vinyl butyral) layer and the second hard poly(vinyl butyral) layer, such that the first soft poly(vinyl butyral) layer of the multilayer sandwich and the second soft poly(vinyl butyral) layer of the second multilayer sandwich adhere to and bond to each other; and Subsequently, the first soft poly(vinyl butyral) layer of the first multilayer sandwich and the second soft poly(vinyl butyral) layer of the second multilayer sandwich are separated from at least one of the first hard poly(vinyl butyral) layer of the first multilayer sandwich and the second hard poly(vinyl butyral) layer of the second multilayer sandwich.

[0019] In a second embodiment, according to the first embodiment, the invention further includes applying a solvent to at least one of the first flexible poly(vinyl butyral) layer and the second flexible poly(vinyl butyral) layer prior to the contact step.

[0020] In a further embodiment, according to any of the foregoing embodiments, the solvent comprises one or more of the following: an alcohol having 1 to 8 carbon atoms; or a carboxylic acid ester thereof, wherein the acid has 1 to 8 carbon atoms.

[0021] In a further embodiment, according to any of the foregoing embodiments, the contact includes pressing the first flexible poly(vinyl butyral) layer and the second flexible poly(vinyl butyral) layer together.

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

[0023] In a further embodiment, according to any of the foregoing embodiments, the thickness of the first rigid poly(vinyl butyral) layer is at least 1.0 times or at least 1.5 times the thickness of the second flexible poly(vinyl butyral) layer.

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

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

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

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

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

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

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

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

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

[0033] In a further embodiment, according to any of the foregoing embodiments, the first flexible poly(vinyl butyral) layer comprises a poly(vinyl butyral) polymer with a residual hydroxyl content of about 8% to about 13.5%.

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

[0035] In a further embodiment, according to any of the foregoing embodiments, the difference between the residual hydroxyl content of the poly(vinyl butyral) polymer in the first rigid poly(vinyl butyral) layer and the poly(vinyl butyral) polymer in the first flexible poly(vinyl butyral) layer is at least 5 by weight.

[0036] In a further embodiment, according to any of the foregoing embodiments, the first rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) with a plasticizer content of about 20 phr to about 50 phr.

[0037] In a further embodiment, according to any of the foregoing embodiments, the first flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) with a plasticizer content of about 45 phr to about 150 phr.

[0038] In a further embodiment, according to any of the foregoing embodiments, the first rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) with a weight-average molecular weight of about 70,000 to 225,000.

[0039] In a further embodiment, according to any of the foregoing embodiments, the first flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) with a weight-average molecular weight of about 150,000 to about 600,000.

[0040] In a further embodiment, according to any of the foregoing embodiments, the method includes using a flattening roller to ensure the interlayer is flat.

[0041] In a further embodiment, according to any of the foregoing embodiments, the method includes using annealing to help eliminate wrinkles.

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

[0043] In one aspect, the present invention relates to a method for separating a first soft poly(vinyl butyral) layer from a first hard poly(vinyl butyral) layer of a first multilayer sandwich, the method comprising: contacting the first soft poly(vinyl butyral) layer of the first multilayer sandwich with a second soft poly(vinyl butyral) layer of a second multilayer sandwich, the second multilayer sandwich comprising the second soft poly(vinyl butyral) layer and the second hard poly(vinyl butyral) layer, such that the first soft poly(vinyl butyral) layer of the multilayer sandwich and the second soft poly(vinyl butyral) layer of the second multilayer sandwich adhere to and bond together; and subsequently separating the bonded first soft poly(vinyl butyral) layer of the first multilayer sandwich and the second soft poly(vinyl butyral) layer of the second multilayer sandwich from at least one of the first hard poly(vinyl butyral) layer of the first multilayer sandwich and the second hard poly(vinyl butyral) layer of the second multilayer sandwich.

[0044] Therefore, according to the present invention, by using another multilayer sandwich, flipping it over, and bringing the soft layers from the first and second multilayer sandwich into contact so that they adhere, the soft poly(vinyl butyral) layer of the multilayer sandwich can be separated from the hard poly(vinyl butyral) layer. This method utilizes the soft, adhesive properties of the soft poly(vinyl butyral) layer.

[0045] The method may optionally include the step of adding 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 both together. When we use the term "solvent," we do not intend to require that the soft PVB achieve any minimum amount of dissolution in the so-called solvent. Rather, without wanting to be bound by any theory, the "solvent" interacts with the core PVB in a way that allows the soft layer to better adhere to the other soft layer, thereby simplifying the separation of the bonded core layer from at least one of the two hard layers. Therefore, any substance that acts to simplify the removal of the core layer from the skin layer will be considered a suitable solvent. Therefore, according to the invention, a method is provided that includes using a solvent to enable better separation and recovery of the skin layer for reuse in extrusion.

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

[0047] Similarly, the term "contact" is not intended to be particularly restrictive and optionally includes pressing two soft poly(vinyl butyral) layers together. It should be understood that the soft PVB layers are somewhat sticky, so contact with anything other than another soft PVB layer should be avoided. When two soft PVB layers are brought together, it is important to prevent wrinkles or bubbles, as these can affect adhesion and make it difficult to remove the bonded soft layer from the skin afterwards.

[0048] Therefore, according to the present invention, the two soft layers or core layers may optionally be brought into contact with each other after the application of a solvent to form a three-layer structure having two skin layers and an intermediate bonded core layer.

[0049] In another aspect, the present invention relates to a step of separating at least one of the bonded core layer and skin layer. The separation method is not particularly limited, but may involve peeling.

[0050] Therefore, the present invention includes the following steps: separating one of the bonded soft poly(vinyl butyral) layer and the hard poly(vinyl butyral) layer of a bonded multilayer sandwich (outer skin / bonded soft / outer skin), for example by first separating the bonded soft / hard layer of the multilayer sandwich from another hard layer, and then pulling in different directions. According to this aspect, during this process, the angle α defined at the separation point by the skin to be separated and the multilayer sheet (having an outer skin / bonded core / outer skin) can be less than or equal to the angle β defined at the separation point by the multilayer sandwich and the bonded core / outer skin, and the process can be continuous.

[0051] Therefore, as just described, the present invention also relates to a continuous method for separating the core layer from the skin layer of a multilayer sandwich sheet.

[0052] According to the present invention, the described orientation can be maintained during the continuous method.

[0053] According to the present invention, a multilayer sandwich having at least a soft layer and a hard layer is separated such that at least a portion of the soft layer is removed from the hard layer. The multilayer sandwich is typically a double layer, but the invention is not limited to this, as long as a soft layer and a hard layer are present as described herein. The soft layer and the hard layer are also described herein as a core layer and a skin layer, respectively.

[0054] Those skilled in the art will understand that the described layer comprises a poly(vinyl butyral) polymer, each of which may be a product of a single reaction or a blend of products of different reactions. In fact, when blended, it may be difficult or impossible to distinguish between a single polymer and a blend of polymers. Therefore, references to poly(vinyl butyral) polymers and their properties may refer to a single polymer as a single reaction product, a blend of two or more polymers having these properties, or a blend of several polymers, wherein the resulting blend possesses the aforementioned properties.

[0055] According to the present invention, the multilayer sandwich (usually a double layer resulting from the separation of the skin layer from the acoustic three layers, thereby exposing the core layer) is separated into two layers, namely a soft poly(vinyl butyral) layer and a hard poly(vinyl butyral) layer.

[0056] The term "rigid poly(vinyl butyral)" refers to poly(vinyl butyral) resin or mixtures of poly(vinyl butyral) resins that are significantly harder than "soft poly(vinyl butyral)" and are typically formed as the skin or hard layer of multilayer poly(vinyl butyral) sheets, as further described herein.

[0057] The term "soft poly(vinyl butyral)" refers to poly(vinyl butyral) resin or mixtures of poly(vinyl butyral) resins that are significantly softer than "rigid poly(vinyl butyral)" and typically form the core or soft layer of a multilayer poly(vinyl butyral) sheet, as further described herein. A soft or core poly(vinyl butyral) layer is typically sandwiched between two rigid or outer poly(vinyl butyral) layers to form a multilayer poly(vinyl butyral) sheet, thereafter, either prior to or as a preliminary step of the method of the invention, a skin layer may be removed.

[0058] The separated double layer according to the present invention can be derived from the process disclosed and claimed in WO2022250944A2, the relevant disclosure of which is incorporated herein by reference in its entirety, in which the first layer or skin layer of a multilayer sandwich sheet is separated from the remaining portion (e.g., the core and skin layers of an acoustic triple sandwich). According to the described process, the multilayer sheet can be heated, and then the first (skin) layer of the multilayer sandwich sheet can be separated from the remaining portion by pulling the first layer and the remaining portion of the multilayer sandwich sheet in different directions, thereby producing a core-skin double layer. Any other suitable method can also be used to obtain the separated multilayer (double layer) according to the present invention.

[0059] As used herein, the terms "multilayer" and "multiple layer" refer to a sandwich structure having more than one layer, and the terms multilayer and multi-layer are used interchangeably. The layers of a sandwich structure are typically produced by mixing a polymeric resin (such as poly(vinyl butyral)) with one or more plasticizers and then melting the mixture into a sheet using any suitable process or method known to those skilled in the art (including, but not limited to, extrusion), wherein the layers are combined by processes such as co-extrusion or lamination. Additional components may optionally be added for various other purposes. After the sandwich sheet is formed, it is typically collected and rolled up for transport and storage, and for later use in multilayer glass panels, as discussed below.

[0060] In various embodiments of this disclosure, the multilayer sandwich comprises at least two polymer layers disposed in direct contact with each other, namely a soft layer and a hard layer (e.g., a single layer or multiple layers co-extruded and / or laminated together), wherein each layer comprises a polymer resin, as described more fully below. As used herein, for a multilayer sandwich having at least three layers, "skin" generally refers to the outer layer of the sandwich, while "core" generally refers to the inner layer. Thus, an exemplary embodiment would be: skin / / core / / skin. In a multilayer sandwich having a skin / / core / / skin configuration, the skin is harder, while the core is softer.

[0061] For example, in a three-layer polymer sandwich sheet, the two hard layers (or outer or skin layers) may comprise poly(vinyl butyral) (“PVB”) resin having a plasticizer or a mixture of plasticizers, while the soft layer (inner or core layer) may comprise the same or different PVB resins, or different thermoplastic materials having the same or different plasticizers and / or mixtures of plasticizers. Therefore, it is conceivable that the hard or skin layers and soft or core layers of a multilayer sandwich sheet may comprise the same or different thermoplastic materials and the same or different one or more plasticizers. Depending on the requirements, any one or both layers may include additional additives as known in the art.

[0062] One type of multilayer sandwich utilizing a relatively soft inner layer is a multilayer acoustic sandwich. As disclosed herein, the acoustic sandwich comprises multiple layers, wherein a preferred embodiment has a relatively soft layer sandwiched between two relatively hard layers. The resulting three-layer sandwich can typically be used directly in the lamination process with little or no modification to the lamination process, replacing conventional single-layer sandwiches.

[0063] The core or soft layer of the multilayer sandwich should be understood to play a decisive role in the acoustic properties of the acoustic trilayer and to include a soft poly(vinyl butyral) (PVB) that is softer than the outer skin or rigid PVB, which is harder than the soft PVB. In one aspect, the soft PVB may have a residual hydroxyl content of about 5% to about 15%, or 8% to 12%, or about 9% to 11%, or as described elsewhere herein. In another aspect, the rigid PVB may have a residual hydroxyl content of about 12% to about 30%, or 15% to about 25%, or 18% to 22%.

[0064] In some embodiments, the interlayer (e.g., core and skin) will have a substantially constant or uniform thickness around its length. However, in alternative embodiments, the interlayer may have at least one region with non-uniform thickness. For example, the interlayer may be wedge-shaped, such that the thickness of the interlayer varies along its length (e.g., linearly or non-linearly). In some such embodiments, the thickness of the interlayer may vary due to variations in the thickness of the core layer (i.e., the skin layer has a substantially constant thickness). Optionally, the thickness of the interlayer may vary due to variations in the thickness of the skin layer (i.e., the core layer has a substantially constant thickness). In a further alternative, the thickness of the interlayer may vary due to variations in the thickness of both the core layer and the skin layer.

[0065] Therefore, in one embodiment, the multilayer poly(vinyl butyral) sheet of the present invention may include a sandwich layer comprising one or more rigid skin layers and a flexible core layer. In embodiments, these multilayer sandwich sheets may sequentially include: a polymer layer (skin layer) comprising rigid plasticized poly(vinyl butyral) resin; a second polymer layer (core layer) comprising flexible plasticized poly(vinyl butyral) resin, or a blend of flexible plasticized poly(vinyl butyral) resins having the same or different residual hydroxyl content; and optionally a third polymer layer (skin layer) comprising rigid plasticized poly(vinyl butyral) resin. This optional skin layer is removed prior to the method of the present invention, or introduced in the aspect of removing the skin layer and subsequently exposing the core layer. Thus, the core polymer layer is disposed adjacent to the skin layer. If three or more layers are present, a second polymer layer may be disposed between the first polymer layer and the third polymer layer, thereby creating two skin layers and a central core layer.

[0066] In some embodiments where the interlayer comprises at least three polymer layers, one or more of the inner layers may be relatively thin compared to the other outer layers. For example, in some embodiments where the multilayer interlayer is a three-layer interlayer, the innermost layer may have a thickness of no more than about 12, no more than about 10, no more than about 9, no more than about 8, no more than about 7, no more than about 6, or no more than about 5 mils, or it may have a thickness in the range of 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 may be at least about 4, at least about 5, at least about 6, at least about 7 mils and / or no more than about 15, no more than about 13, no more than about 12, no more than about 10, no more than about 9, or no more than about 8 mils, or may be in the range of about 2 to about 15, about 3 to about 13, or about 4 to about 10 mils. When the interlayer comprises two outer layers, these layers may have a 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 no more than about 73, no more than about 60, no more than about 50, no more than about 45, no more than about 40, no more than about 35 mils, or a combination of thicknesses in the range of about 9 to about 70 mils, about 13 to about 40 mils, or about 25 to about 35 mils.

[0067] According to some implementation schemes, the thickness ratio of one of the outer layers to one of the inner layers in a multilayer sandwich 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 sandwich is a three-layer sandwich with an inner core layer disposed between one outer skin layer, the thickness ratio of one skin layer to the core layer can fall within one or more of the above ranges. In some implementations, the combined thickness ratio of the outer layer to the inner layer may 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 no more than about 30:1, no more than about 20:1, no more than about 15:1, no more than about 10:1, no more than about 9:1, or no more than about 8:1.

[0068] The multilayer sandwich as described herein may comprise a generally flat sandwich having substantially the same thickness along the length or longest dimension and / or width or second longest dimension of the sheet. However, in some embodiments, the multilayer sandwich of the present invention may be a tapered or wedge-shaped sandwich comprising at least one tapered region having a wedge-shaped profile. A tapered sandwich may have a thickness profile that varies along at least a portion of the length and / or width of the sheet, such that, for example, at least one edge of the sandwich has a thickness greater than that of another edge. When the sandwich is a tapered sandwich, at least one, at least two, at least three, or more of the individual resin layers may comprise at least one tapered region. Tapered sandwiches may be particularly useful in head-up display (HUD) panels, for example, in automotive and aircraft applications.

[0069] As used herein, the term "plasticizer" generally refers to a molecule or blend of molecules that, as further described herein, plasticizes a polymer, particularly poly(vinyl butyral), at low plasticizer contents, thereby softening it. In many embodiments, plasticizers are added to a polymer resin to form a polymer layer or interlayer. Plasticizers are typically added to polymer resins to increase the flexibility and durability of the resulting polymer interlayer. Plasticizers space the polymer chains by embedding themselves between them (increasing "free volume") and thereby significantly lower the glass transition temperature (Tg) of the polymer resin. g This is achieved by adjusting the amount of plasticizer in the interlayer to influence the glass transition temperature (T0). g Glass transition temperature (T) gT0 is the temperature that marks the transition from the glassy state to the rubbery state of the interlayer. Generally, a higher plasticizer loading will result in a lower T0. g In some implementations, such as when the interlayer is an acoustic trilayer, the inner core layer (i.e., the soft layer) will have a glass transition temperature of less than about 20°C, while the outer skin layer (e.g., the hard layer) will have a glass transition temperature of greater than about 25°C.

[0070] Contemplated plasticizers include, but are not limited to, polyesters, polyol esters, triethylene glycol di(2-ethylbutyrate), triethylene glycol di(2-ethylhexanoate) (referred to as 3-GEH), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, dioctyl adipate, cyclohexylhexyl adipate, mixtures of heptyl and nonyl adipate, diisononyl adipate, heptenoyl adipate, dibutyl sebacate, and polymeric plasticizers such as oil-modified sebacate alkyd resins, mixtures of phosphate esters and adipates, and mixtures and combinations thereof. 3-GEH is particularly preferred. Other examples of suitable plasticizers may 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 different plasticizers, including but not limited to those described above. Still other suitable plasticizers or blends of plasticizers may be formed from aromatic groups, such as polyadipate, epoxides, phthalates, terephthalates, benzoates, toluene esters, hexabenzoates, and other specialty plasticizers. Other examples include, but are not limited to, dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycol dibenzoate, isodecanyl 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 triphenylhexacarboxylate, di-2-ethylhexyl terephthalate, bisphenol A bis(2-ethylhexanoate), ethoxylated nonylphenol, and mixtures thereof. In some embodiments, the plasticizer may be selected from dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, and combinations thereof.

[0072] Typically, the plasticizer content of the polymer interlayer in this application is measured by weight / weight in parts per hundred parts of resin (“phr”). For example, if 30 grams of plasticizer are added to 100 grams of polymer resin, the resulting plasticized polymer will have a plasticizer content of 30 phr. When the plasticizer content of a polymer layer is given in this application, the plasticizer content of a particular layer is determined with reference to the phr of the plasticizer used in the melt to produce that particular layer. In some embodiments, the high-rigidity interlayer comprises layers having plasticizer contents 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 may 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, or at least about 75 phr. In some embodiments, the polymer layer may also contain one or more plasticizers of no more than about 100 phr, no more than about 85 phr, no more than about 80 phr, no more than about 75 phr, no more than about 70 phr, no more than about 65 phr, no more than about 60 phr, no more than about 55 phr, no more than about 50 phr, no more than about 45 phr, no more than about 40 phr, no more than about 38 phr, no more than about 35 phr, or no more than about 30 phr. In some embodiments, the total plasticizer content of at least one polymer layer may be in the range of about 20 phr to about 40 phr, about 20 phr to about 38 phr, or about 25 phr to about 35 phr. In other embodiments, the total plasticizer content of at least one polymer layer may be in the range of about 38 phr to about 90 phr, about 40 phr to about 85 phr, or about 50 phr to 70 phr.

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

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

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

[0077] In all respects, the rigid poly(vinyl butyral) contained in plasticized poly(vinyl butyral) multilayer sheets contains about 25 phr to about 50 phr of plasticizer, or 30 phr to 45 phr, or 32 to 42 phr of plasticizer.

[0078] In one embodiment, the plasticized poly(vinyl butyral) multilayer sheet (either a complete acoustic triple layer or a double layer with one of the skin layers removed) may contain triethylene glycol bis(2-ethylhexanoate) as a plasticizer. In other embodiments, the plasticized poly(vinyl butyral) multilayer sheet may also contain dihexyl adipate or di(2-ethylhexyl) adipate or another convenient substance (such as Benzoflex™ 9-88 benzoate) as a plasticizer.

[0079] In other embodiments, the plasticizer may be selected from one or more esters of polybasic acids or polyols. In a further embodiment, the plasticizer may be selected from one or more of the following: triethylene glycol bis(2-ethylhexanoate), tetraethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, di(2-ethylhexyl) adipate, di(2-ethoxyhexyl) adipate, dioctyl adipate, cyclohexylhexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, polymeric adipate, soybean oil, or epoxidized soybean oil.

[0080] In addition, plasticizers that are compatible at high temperatures can be used to further increase the fluidity of the interlayer.

[0081] In various embodiments of the sandwich structure disclosed herein, the sandwich structure may contain about 30 to about 60 phr (per 100 parts of resin) of total plasticizer. Although the total plasticizer content is indicated above, the plasticizer content in the rigid or flexible layer may differ from the total plasticizer content. Furthermore, the rigid and flexible layers may have different plasticizer contents because, at equilibrium, the plasticizer content of each respective layer is at least partially determined by its corresponding residual hydroxyl content. For example, when the combined skin thickness is equal to the core thickness, for a total plasticizer dosage of about 54.3 phr for the sandwich structure, at equilibrium, the sandwich structure may comprise two skin layers (each with 38 phr of plasticizer) and a core layer (with 75 phr of plasticizer). For thicker or thinner skin layers, the total plasticizer dosage of the sandwich structure may vary accordingly.

[0082] In other embodiments, the amount of plasticizer in rigid poly(vinyl butyral) or flexible poly(vinyl butyral) 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 all respects, the skin or rigid layer of the multilayer sandwich sheet may contain a PVB polymer with a Tg of, for example, about 20°C to about 45°C, or 25°C to 40°C, or 28°C to 35°C. Optionally, the rigid poly(vinyl butyral) may have a Tg of 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 all respects, the soft layer or core layer of the multilayer sandwich sheet may contain a PVB polymer with a Tg of, for example, about -15°C to about 45°C, or -10°C to 30°C, or -8°C to 25°C. Optionally, 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] On the one hand, the Tg of the core layer 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 hard layer.

[0086] In the implementation scheme, the polymer interlayer has at least two different glass transition temperatures (T0). g And at least two different glass transition temperatures (T) g The difference between them is at least 5°C.

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

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

[0089] According to some embodiments, the difference in glass transition temperatures between two polymer layers (typically adjacent polymer layers within a sandwich structure) can be at least about 5°C, at least about 10°C, at least about 15°C, at least about 20°C, at least about 25°C, at least about 30°C, at least about 35°C, at least about 40°C, or at least about 45°C. In other embodiments, the glass transition temperatures of two or more polymer layers can differ from each other by about 5°C, about 3°C, about 2°C, or about 1°C. Typically, the layer with the lower glass transition temperature has lower stiffness than the layer with the higher glass transition temperature in the sandwich structure and can be located between the polymer layers with the higher glass transition temperature in the final sandwich structure.

[0090] The PVB layer according to the invention is further characterized by its peel-adhesion properties relative to each other and to other materials that may come into contact with it.

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

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

[0093] The peel adhesion properties relative to the bonded soft and hard layers are as follows: at 25% relative humidity and 21°C, the hard PVB as described herein exhibits a 90° peel adhesion 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 to the soft PVB.

[0094] For example, layers and interlayers according to embodiments of the invention may exhibit this 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%, which is measured by Karl-Fisher titration according to ASTM E203.

[0095] The 90° peel adhesion value to glass described herein can be determined according to the following procedure, including the lamination / autoclave treatment described. Similarly, the peel adhesion value of rigid PVB to flexible PVB (measured on three layers of rigid / flexible / rigid sheets, wherein the first hard layer has been removed) can be determined in a manner that, of course, does not require prior lamination / autoclave treatment to the glass.

[0096] Peel-off Adhesion: To measure the adhesion strength between the plasticized PVB layer and the glass, the adhesive-coated aluminum foil was first pretreated at 105°C for 30 minutes. Then, using standard lamination techniques, a special peel-off adhesion laminate containing a PVB interlayer was prepared by replacing one glass pane in a standard double-glazed laminate with the pretreated aluminum foil. The thickness of the plasticized PVB layer in the laminate was normalized to 30 mils (0.76 mm). More specifically, the coated foil was assembled onto one side of the polymer laminate with the adhesive immediately adjacent to the PVB layer, and the test glass layer was assembled onto the other side of the PVB laminate. After assembling two such laminates, they were placed with the foil sides facing each other and passed through a degassing roller. The laminates were then individually placed foil-side down in a circulating air oven at 100°C for 5 minutes. The heat-laminated components were then assembled, re-rolled as before, and autoclaved at 290℉ (143°C) and 185psi (1,275kPa). After autoclaving, a 4 cm wide cut was made in the foil and polymer laminate using a special dual-wheel cutter. The glass at one end of the laminate was then scratched and broken. At the glass break, a 4 cm strip was cut along the outer edge of the foil and polymer laminate on each side. At least three samples of a specific commonly used polymer laminate were tested for each reported value. Standard laminates for moisture analysis were prepared from the same polymer laminate during the peeling of the sample layup. The samples were pretreated overnight at (21°C) before the actual peel test. During the peel test, the glass, foil, and polymer laminate samples were clamped in the test fixture of the Instron peel tester (beam speed 5 inches (12.7 cm) per minute), and the force required to separate the polymer laminate from the glass was directly recorded and measured. The average of the peak values ​​recorded is the value of the sample.

[0097] To measure the bond strength between the rigid plasticized PVB layer and the flexible plasticized PVB layer: Cut the hard / soft / hard three-layer or hard / soft two-layer sample into rectangular strips. Adhere the surface layer to a piece of tape of the corresponding size. Manually perform initial separation of the soft / core layer at one end of the strip to facilitate mounting the layer onto the sample holder of the peel tester. Then, the strip can be peeled apart at the hard / soft interface using a peel tester with a 180-degree peel test.

[0098] The described peel adhesion properties are significant because both the core and outer skin materials exhibit adhesion to a variety of materials, with the core layer being even more adhesive than the skin layer. Similarly, when within the same membrane, the two layers also exhibit peel adhesion values ​​that affect the ability to neatly separate the two layers.

[0099] The multilayered core and skin layers separated according to the present invention are further characterized by having different shear storage moduli.

[0100] Therefore, in one aspect, the flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) with a shear modulus of about 0.01 MPa to about 20 MPa, or about 0.1 to about 18 MPa, or about 0.15 to about 15 MPa at 20°C. Correspondingly, the rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) with a shear modulus of about 20 MPa to about 600 MPa, or about 28 to about 450 MPa, or about 30 to about 400 MPa at 20°C.

[0101] This property is also significant because it (among other things) indicates the tendency of the layer to remain intact, or in other words, the likelihood that the material will tear. Due to the difference in shear modulus just described, soft layers are indeed prone to tearing, making it difficult to remove the layer completely.

[0102] The glass transition temperature (Tg) and shear modulus described herein can be determined by dynamic mechanical-thermal analysis (DMTA) in shear mode. DMTA measures the storage (elastic) shear modulus (G') (in Pascals), loss (viscous) shear modulus (G'') (in Pascals), and tan delta (=G'' / G') as a function of temperature for a given frequency and temperature scan rate. A frequency of 1 Hz and a temperature scan rate of 3 °C / min were used in this paper. Tg was then determined by the position of the tan delta peak on the temperature scale (in °C), and the tan delta peak is referred to as tan delta or peak tan delta. As used herein, “tan delta,” “peak tan delta,” “tan δ,” and “peak tan δ” are used interchangeably.

[0103] One parameter used to describe the polymer resin composition of the polymer interlayer of this application is the residual hydroxyl content (as vinyl hydroxyl content or poly(vinyl alcohol) (“PVOH”) content). Residual hydroxyl content refers to the amount of hydroxyl groups that remain as side groups on the polymer chain after processing. For example, PVB can be prepared by hydrolyzing poly(vinyl acetate) to poly(vinyl alcohol), and then reacting the poly(vinyl alcohol) with butyraldehyde to form PVB. During the hydrolysis of poly(vinyl acetate), not all acetate side groups are typically converted to hydroxyl groups. Furthermore, the reaction with butyraldehyde typically does not result in all hydroxyl groups being converted to acetal groups. Therefore, in any finished PVB, residual acetate groups (such as vinyl acetate groups) and residual hydroxyl groups (such as vinyl hydroxyl groups) will typically be present on the polymer chain as side groups. Generally, the residual hydroxyl content of the polymer can be adjusted by controlling the reaction time, reactant concentration, and other variables in the polymer manufacturing process. When used as a parameter herein, residual hydroxyl content is measured according to ASTM D-1396 on a weight % basis.

[0104] In one respect, the difference between the residual hydroxyl content of the soft poly(vinyl butyral) and the residual hydroxyl content of the hard poly(vinyl butyral) is at least 6%, or at least 5%, or at least 4%, or 4% to 8%, or 5% to 10%, or as further described herein.

[0105] Therefore, in various embodiments, the residual hydroxyl content of the poly(vinyl butyral) resin used for the hard (skin) layer and the soft (core) layer may differ. For example, the resin used for the core layer may contain about 9 to about 18 wt% of residual hydroxyl groups, about 9 to about 16 wt% of residual hydroxyl groups, or about 9 to about 14 wt% of residual hydroxyl groups calculated by PVOH. For example, the resin used for the skin layer may contain about 13 to about 35 wt% of residual hydroxyl groups, about 13 to about 30 wt% of residual hydroxyl groups, or about 15 to about 22 wt% of residual hydroxyl groups calculated by PVOH; and for some embodiments, about 17.25 to about 22.25 wt% of residual hydroxyl groups, or as described elsewhere herein.

[0106] In various embodiments, the poly(vinyl butyral) resin comprises about 8 to about 35 wt% of residual hydroxyl groups, about 13 to about 30 wt% of residual hydroxyl groups, about 8 to about 22 wt% of residual hydroxyl groups, or about 15 to about 22 wt% of residual hydroxyl groups, calculated as PVOH; and for some of the high-rigidity interlayers disclosed herein, in one or more of the layers, the poly(vinyl butyral) resin comprises more than about 19 wt% of residual hydroxyl groups, more than about 20 wt% of residual hydroxyl groups, more than about 20.4 wt% of residual hydroxyl groups, and more than about 21 wt% of residual hydroxyl groups, calculated as PVOH.

[0107] In some embodiments, the poly(vinyl butyral) resin in at least one polymer layer for the interlayer may comprise a poly(vinyl butyral) resin with a residual hydroxyl content measured as described above of at least about 18 wt%, at least about 18.5 wt%, at least about 18.7 wt%, at least about 19 wt%, at least about 19.5 wt%, at least about 20 wt%, at least about 20.5 wt%, at least about 21 wt%, at least about 21.5 wt%, at least about 22 wt%, at least about 22.5 wt%, and / or not exceeding about 30 wt%, not exceeding about 29 wt%, not exceeding about 28 wt%, not exceeding about 27 wt%, not exceeding about 26 wt%, not exceeding about 25 wt%, not exceeding about 24 wt%, not exceeding about 23 wt%, or not exceeding about 22 wt%.

[0108] Additionally, one or more other polymer layers in the interlayer described herein may comprise another poly(vinyl butyral) resin having a lower residual hydroxyl content. For example, in some embodiments, at least one polymer layer of the interlayer may comprise a poly(vinyl butyral) resin having a residual hydroxyl content measured as described above of at least about 8 wt%, at least about 8.5 wt%, at least about 9 wt%, at least about 9.5 wt%, at least about 10 wt%, at least about 10.5 wt%, at least about 11 wt%, at least about 11.5 wt%, at least about 12 wt%, at least about 13 wt%, and / or not exceeding about 16 wt%, not exceeding about 15 wt%, not exceeding about 14 wt%, not exceeding about 13.5 wt%, not exceeding about 13 wt%, not exceeding about 12 wt%, or not exceeding about 11.5 wt%.

[0109] In one embodiment, the blend of flexible or core poly(vinyl butyral) or flexible poly(vinyl butyral) may have a residual hydroxyl content of about 5% to about 15%, as further described herein. Optionally, the residual hydroxyl content of the flexible poly(vinyl butyral) may be about 7% to about 13%, or 8% to 12%, or as described elsewhere herein.

[0110] On the other hand, rigid poly(vinyl butyral) or blends of rigid poly(vinyl butyral) may have a residual hydroxyl content of about 12% to about 28%, as further described herein. Optionally, the residual hydroxyl content of rigid poly(vinyl butyral) may be about 15% to about 25%, or 18% to 20%, or as described elsewhere herein.

[0111] In the embodiments, the residual hydroxyl content of the first rigid poly(vinyl butyral) is generally the same as that of the second rigid poly(vinyl butyral), and generally different from that of the core poly(vinyl butyral). In the embodiments, the difference between the residual hydroxyl content of the core and the residual hydroxyl content of the outer sheath is at least 4.0% by weight, or at least 5.0% by weight, or at least 6.0% by weight.

[0112] In the embodiments, the core poly(vinyl butyral) resin is present in an amount of about 2% to about 45% by weight, or about 5% to about 40% by weight.

[0113] In one embodiment, the flexible poly(vinyl butyral) or blend of flexible poly(vinyl butyral) may have a residual acetate content of about 0% to about 18%, or 0.5% to 10%, as further described herein. Optionally, 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.

[0114] In another embodiment, the rigid poly(vinyl butyral) or blend of rigid poly(vinyl butyral) may have a residual acetate content of about 0% to about 18%, as further described herein. Optionally, the residual acetate content of the rigid 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.

[0115] In other embodiments, the residual hydroxyl content of the soft layer may be equal to, greater than, or less than the residual hydroxyl content of the resin in the hard layer. In various embodiments, the soft resin or the outer resin, or both, may contain less than 30% by weight, less than 25% by weight, less than 20% by weight, less than 15% by weight, less than 13% by weight, less than 10% by weight, less than 7% by weight, less than 5% by weight, or less than 1% by weight of residual ester groups, wherein the balance is acetal (such as butyraldehyde acetal), but optionally other acetal groups (such as isobutyraldehyde acetal groups, 2-ethylhexaldehyde acetal groups, or a mixture of any two of butyraldehyde acetal, isobutyraldehyde acetal, and 2-ethylhexaldehyde acetal groups), or as discussed elsewhere herein.

[0116] Based on polyethylene ester (e.g., acetate), the resin used for the core layer or for the skin layer or for both the skin layer and the core layer may also contain less than 20% by weight, less than 15% by weight, less than 13% by weight, less than 11% by weight, less than 9% by weight, less than 7% by weight, less than 5% by weight, or less than 1% by weight of residual ester groups, wherein the balance is acetal, preferably butyraldehyde acetal, but optionally containing small amounts of other acetal groups, such as 2-ethylhexanal groups (see, for example, U.S. Patent No. 5,137,954, the entire disclosure of which is incorporated herein by reference).

[0117] In one aspect, the multilayer sandwich used in the method of the present invention may include: an outer skin or rigid polymer layer comprising plasticized poly(vinyl butyral) with 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 amu; and a core polymer layer comprising plasticized poly(vinyl butyral) with a weight-average molecular weight greater than about 200,000 amu, or greater than 225,000, or greater than 250,000 or greater than 275,000 amu.

[0118] Therefore, the outer skin or rigid polymer layer comprises plasticized poly(vinyl butyral) with a weight-average molecular weight (Mw) of about 60,000 to 250,000, or 70,000 to 225,000, or 100,000 to 200,000. The core polymer layer may comprise plasticized poly(vinyl butyral) with a weight-average molecular weight of about 150,000 amu to 600,000, or 200,000 to 500,000, or 250,000 to 400,000 amu.

[0119] More generally, as used herein, the term “molecular weight” refers to weight-average molecular weight (Mw). Suitable PVB resins typically have molecular weights in the range of 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.

[0120] The extruded sandwich formed from plasticized PVB resin can be prepared using a system known to those skilled in the art by extrusion through a conventional sheet die with a cooling die lip, i.e. by forcing the molten polymer through a die that is long in the horizontal direction and narrow in the vertical direction, the die being substantially in length and width to the length and width of the sheet being formed therein.

[0121] For example, multi-manifold co-extrusion apparatuses (such as the multi-manifold co-extrusion apparatus disclosed in U.S. Patent Publication No. 2008 / 0254302, the relevant disclosure of which is incorporated herein by reference) can be used to co-extrude multilayer sandwiches. Such apparatuses have a first die manifold, a second die manifold, and a third die manifold. The apparatus operates by simultaneously extruding polymer melt from each manifold toward the extrusion opening, wherein the multilayer sandwich is extruded as a composite of three separate polymer layers. The layer thickness can be varied by adjusting the distance between the die lips at the extrusion opening. Melt breakage can be controlled by controlling the melt composition, the temperature of the die lips or land at the extrusion opening, or by controlling the cooling rate and cooling method of the extruded sandwich, for example, by immersing the extruded sandwich in a cooling bath shortly after extrusion. According to the invention, the separation techniques described herein can be used to obtain a desired film having rough and smooth surfaces on opposite sides.

[0122] Conventional multilayer sandwich structures (such as three-layer acoustic sandwich structures) typically contain a soft core layer of a single poly(vinyl butyral) (“PVB”) resin with a low residual hydroxyl content and a large amount of conventional plasticizer, and two hard skin layers with significantly higher residual hydroxyl content (see, for example, U.S. Patents 5,340,654, 5,190,826, and 7,510,771). Therefore, the separated soft PVB can be recycled to form the core layer of a three-layer acoustic sandwich structure, or the soft PVB and plasticizer varnish can be used directly to form the soft PVB layer without prior separation. The residual hydroxyl content and amount of plasticizer in the PVB core resin are optimized to provide optimal sound insulation properties for multilayer glass panels (such as windshields and windows) installed in vehicles and buildings under ambient conditions.

[0123] As mentioned above, in an important aspect, multilayer sandwich sheets include multiple layers of PVB sandwich, for example, having an outer skin / core / outer skin cross-section. Although a specific PVB sandwich has just been described, a variety of sandwich materials can also be used.

[0124] When the interlayer contains polyvinyl butyral (PVB), PVB resin can be prepared using a known acetalization process by reacting polyvinyl alcohol (“PVOH”) with butyral in the presence of an acid catalyst, separating, stabilizing, and drying the resin. Such acetalization processes are disclosed, for example, in U.S. Patent Nos. 2,282,057 and 2,282,026 and in BE Wade (2003), Vinyl Acetal Polymers, in Encyclopedia of Polymer Science & Technology, 3rd Edition, Vol. 8, pp. 381-399, the entire disclosure of which is incorporated herein by reference. This resin is commercially available in various forms, such as as Butvar® resin manufactured by Solutia Inc., a wholly owned subsidiary of Eastman Chemical Company.

[0125] The PVB resins disclosed herein 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 scattering. As used herein, the term "molecular weight" refers to weight-average molecular weight.

[0126] In addition to plasticizers, it is conceivable that adhesion control agents (“ACAs”) may also be added to the polymer resin to form a polymer interlayer. ACAs are commonly used to alter and / or improve the adhesion of the interlayer to the glass panel during the formation of laminated panels. Contemplated ACAs include, but are not limited to, magnesium carboxylate / salts. Furthermore, contemplated ACAs may also include those disclosed in U.S. Patent 5,728,472, such as residual sodium acetate, potassium acetate, magnesium bis(2-ethylbutyrate), and / or magnesium bis(2-ethylhexanoate), which is incorporated herein by reference in its entirety.

[0127] Other additives may be introduced into the interlayer to enhance its performance in the final product and to impart certain additional properties to the interlayer. Such additives include, but are not limited to, dyes, pigments, stabilizers (e.g., UV 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 aids, flow-enhancing additives, lubricants, impact modifiers, nucleating agents, heat stabilizers, UV absorbers, UV stabilizers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcing additives, and fillers, as well as other additives known to those skilled in the art.

[0128] Various adhesion control agents (“ACAs”) can be used in the interlayers of this disclosure to control the adhesion of the interlayer sheet to the glass. In various embodiments of the interlayers of this disclosure, the interlayer may comprise about 0.003 to about 0.15 parts ACA per 100 parts of resin; about 0.01 to about 0.10 parts ACA per 100 parts of resin; and about 0.01 to about 0.04 parts ACA per 100 parts of resin. Such ACAs include, but are not limited to, the ACA 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-ethylbutyrate), and / or magnesium bis(2-ethylhexanoate).

[0129] Other additives may be introduced into the interlayer to enhance its performance in the final product and to impart certain additional properties to the interlayer. Such additives include, but are not limited to, dyes, pigments, stabilizers (e.g., UV 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 aids, flow-enhancing additives, lubricants, impact modifiers, nucleating agents, heat stabilizers, UV absorbers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcing additives, and fillers, as well as other additives known to those skilled in the art.

[0130] Unless otherwise specified, all numerical values ​​used in the specification and claims to indicate the quantity of components, properties (such as molecular weight), reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​that may vary according to the desired properties sought to be obtained according to the invention. At a minimum, each numerical parameter should be interpreted based on at least the number of significant figures reported and by applying ordinary rounding techniques. Furthermore, the ranges stated in this disclosure and claims are intended to specifically include the entire range, not just the endpoints. For example, a range stated as 0 to 10 is intended to disclose all integers between 0 and 10 (such as, for example, 1, 2, 3, 4, etc.), all fractions between 0 and 10 (such as 1.5, 2.3, 4.57, 6.1113, etc.), and the endpoints 0 and 10.

[0131] Although the numerical ranges and parameters illustrating the broad scope of the invention are approximate, the numerical values ​​described in specific embodiments are intended to be reported precisely according to the measurement methods. However, any numerical value inherently includes some error that must be caused by the standard deviation found in its corresponding test measurement.

[0132] It should be understood that mentioning one or more process steps does not preclude the existence of additional process steps before or after the combined steps, or the insertion of process steps between those explicitly identified steps. Furthermore, using letters, numbers, etc., to name the process steps, ingredients, or other information disclosed or claimed in this application is a convenient means of identifying discrete activities or components, and the letters may be arranged in any order unless otherwise specified.

[0133] As used herein, the singular forms “a,” “an,” and “the” include plural indicators unless the context clearly specifies otherwise. For example, referring to C n The alcohol equivalent is intended to include multiple types of C n Alcohol equivalent. Therefore, even if language such as “at least one” or “at least some” is used in one place, it is not intended to imply that other uses of “a,” “an,” and “the” exclude multiple indicators unless the context clearly specifies otherwise. Similarly, the use of language such as “at least some” in one place is not intended to imply that the absence of such language elsewhere implies an intent to mean “all,” unless the context clearly specifies otherwise.

[0134] 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 may be used alone, or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B and / or C, then the composition may contain only A; only B; only C; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B and C.

[0135] The present invention can be further illustrated by the following embodiments thereof, but it should be understood that, unless otherwise specifically stated, these embodiments are included for illustrative purposes only and are not intended to limit the scope of the invention.

[0136] Example Example 1 Prediction A 5” x 10” PVB core-skin bilayer sample was placed core-down on top of another 8” x 12” PVB core-skin bilayer sample, core-up. The sample was then pressed for 10 minutes at 80°C and 5 bar on a Wabash static press, followed by cooling to 25°C. The sample now appears as a three-layer sheet. At 40°C, the skin layer of the original PVB core-skin bilayer sample was mechanically separated from the core-skin sample with the outer skin attached. The recovered skin layer can be reused in skin extrusion.

[0137] Example 2 Prediction After spraying 1 gram of methanol onto the top of another 8” x 12” PVB core-skin bilayer sample with the core layer facing upwards, a 5” x 10” PVB core-skin bilayer sample was placed on top of the second core-skin bilayer sample with the core layer facing downwards. The sample was then compressed at 80°C and 5 bar for 10 minutes on a Wabash static press, followed by cooling to 25°C. The sample now appears as a three-layer sheet. At 40°C, the skin layer of the original PVB core-skin bilayer sample was mechanically separated from the core-skin sample with the outer skin attached. The recovered skin layer can be reused in skin extrusion.

[0138] Example 3 Prediction The PVB core-skin bilayer is continuously unwound from the roll at 1 m / min and fed with the core facing down into an isochoric twin-belt press equipped with steel belts. The bottom steel belt covers the PVB core layer. The core-skin bilayer is bonded to the core material on the bottom steel belt at 80°C. The bilayer, now with a thicker core, is cooled to 25°C before leaving the twin-belt press and then reheated to 45°C. At the exit, the skin layer is mechanically separated from the core sample bonded to the skin. Blades are placed at the end of the bottom steel belt to continuously remove the excess core material accumulated on the steel belt. The recycled skin layer can be reused in skin layer extrusion. The recycled core layer material can be reused in core layer extrusion.

Claims

1. A method for separating a first soft poly(vinyl butyral) layer from a first hard poly(vinyl butyral) layer of a first multilayer sandwich, the method comprising: a. The first soft poly(vinyl butyral) layer of the first multilayer sandwich is brought into contact with the second soft poly(vinyl butyral) layer of the second multilayer sandwich, wherein the second multilayer sandwich includes the second soft poly(vinyl butyral) layer and the second hard poly(vinyl butyral) layer, such that the first soft poly(vinyl butyral) layer of the multilayer sandwich and the second soft poly(vinyl butyral) layer of the second multilayer sandwich adhere to and bond with each other; and b. Thereafter, the first soft poly(vinyl butyral) layer of the first multilayer sandwich and the second soft poly(vinyl butyral) layer of the second multilayer sandwich are separated from at least one of the first hard poly(vinyl butyral) layer of the first multilayer sandwich and the second hard poly(vinyl butyral) layer of the second multilayer sandwich.

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

3. The method of claim 1, wherein the solvent comprises one or more of the following: an alcohol having 1 to 8 carbon atoms; or a carboxylic acid ester thereof, wherein the acid has 1 to 8 carbon atoms.

4. The method of claim 1, wherein the contact comprises pressing the first flexible poly(vinyl butyral) layer and the second flexible poly(vinyl butyral) layer together.

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

6. The method according to claim 1, wherein the thickness of the first rigid poly(vinyl butyral) layer is at least 1.0 times or at least 1.5 times the thickness of the second flexible poly(vinyl butyral) layer.

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

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

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

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

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

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

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

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

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

16. The method of claim 1, wherein the first flexible poly(vinyl butyral) layer comprises a poly(vinyl butyral) polymer with a residual hydroxyl content of about 8% to about 13.5%.

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

18. The method of claim 1, wherein the difference in the residual hydroxyl content between the poly(vinyl butyral) polymer of the first rigid poly(vinyl butyral) layer and the poly(vinyl butyral) polymer of the first flexible poly(vinyl butyral) layer is at least 5 by weight.

19. The method of claim 1, wherein the first rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) with a plasticizer content of about 20 phr to about 50 phr.

20. The method of claim 1, wherein the first flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) with a plasticizer content of about 45 phr to about 150 phr.

21. The method of claim 1, wherein the first rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) with a weight-average molecular weight of about 70,000 to 225,000.

22. The method of claim 1, wherein the first flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) with a weight-average molecular weight of about 150,000 to about 600,000.

23. The method of claim 1, wherein the method includes using a flattening roller to ensure the interlayer is flat.

24. The method of claim 1, wherein the method includes using annealing to help eliminate wrinkles.

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

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