Spraying method for separating multilayer intermediate layers

Abstract

A process for separating a flexible poly(vinyl butyral) layer in a multilayer intermediate from a rigid poly(vinyl butyral) layer is disclosed.

Description

Technical Field

[0001] The present disclosure relates to the field of recycling polymer interlayers having different poly(vinyl butyral) components.

Background Art

[0002] Although the market share of multilayer interlayers continues to grow, their recyclability in extrusion processes is limited because different layers may have different physicochemical properties. A typical example of these multilayer interlayers is an acoustic three-layer structure, which typically uses two outer skin layers with similar properties and a core layer with significantly different properties. When reprocessed, these acoustic core layers in particular do not mix well with the two skin layer materials during extrusion, forming small but discrete domains of core material that cause a certain degree of haze, limiting their content in extrusion. The inability to reprocess this multilayer material represents a significant economic loss.

[0003] To demonstrate the concept of mechanical separation, it is possible to manually peel the skin layers from a multilayer sheet. However, improved processes and mechanical apparatus are useful for stable, consistent, and cost-effective mechanical separation operations.

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

[0005] JP2000331384A identifies the easy and complete removal of a protective layer adhered to a substrate without leaving notches, abrasives or the like as the problem to be solved. The described solution is a high-pressure stream of an aqueous working fluid containing an abrasive sprayed onto the protective layer on the substrate, or a swelling agent pre-impregnated into the protective layer to swell the protective layer, and the high-pressure stream is sprayed onto the swollen protective layer. The protective layer is mechanically removed by the impact of the abrasive, and only the substrate is recovered.

[0006] U.S. Patent No. 7,812,061 discloses that used optical discs using PC resin as a base material can be recycled as a raw material for flame-retardant polycarbonate resin compositions through chemical processing.

[0007] U.S. Patent No. 5,278,282 discloses a method for separating polymers from a physically combined solid mixture containing multiple polymers, comprising dissolving a first polymer of the polymers in a solvent at a first low temperature to form a first preferably single-phase solution and the remaining solid component. The solid component contains additional polymers that are not soluble in the solvent at the first temperature but may be soluble at higher temperatures. The method then comprises heating the solvent to dissolve the additional polymers from the solid component to form subsequent solutions. The polymers are then separated from their respective solutions using either a flash evaporation technique when two or more polymers are dissolved at a single temperature, or a conventional technique for extracting polymers from a solvent in a solution.

[0008] U.S. Patent No. 4,940,187 discloses a set of systematic apparatus for recycling raw materials such as copper, iron, and different 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 having different densities and floating heights in a gravity separator tank.

[0009] JP7166571B2 discloses a film-like 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 layers with a blade.

[0010] U.S. Patent No. 4,775,697 discloses a pure polymer, such as polyester used in photographic film and the plastic walls of beverage bottles, or polycarbonate used in high-quality plastic beverage bottles, separated from a thin Saran and similar coating layer of a multilayer film or sheet by a dry polishing process.

[0011] U.S. Patent No. 5,162,383 discloses a pure polymer, such as polyester used in photographic film and the plastic walls of beverage bottles, or polycarbonate used in high-quality plastic beverage bottles, separated from a thin Saran and similar coating layer of a multilayer film or sheet by a wet polishing process.

[0012] WO2005 / 103130 discloses a process for recovering polymers from a polymer coating on a support, thereby removing at least a portion of the polymer coating from the support by subjecting the coated support to a high-pressure water jet, carrying away the polymer compounds in water in the form of an aqueous washing solution, then recovering at least a portion of the polymer compounds from the aqueous washing solution and introducing it into a process of contacting it with a solvent or solvent mixture capable of dissolving the polymer compounds, and subsequently precipitating the polymers from the solvent or solvent mixture in the form of solid polymer particles.

[0013] WO2021 / 237306 discloses a process for recycling laminates and solutions used in such processes. The disclosure is said to be particularly useful in removing bonded overlays from a substrate material, such as plastic. The process involves subjecting the laminate to impact friction and impact forces to substantially separate the substrate layer from one or more surface layers of the overlay, and then cleaning the substrate layer with a cleaning solution to remove the remaining surface layers of the overlay and adhesive from the substrate layer. The cleaning solution may be an aqueous solution containing a surfactant, a solvent, and a base.

[0014] WO2022250944A2 discloses a process for separating a first layer from the rest of a multilayer intersheet, in which the multilayer sheet is heated and then the first layer is separated from the rest of the multilayer intersheet by pulling the first layer and the rest of the multilayer intersheet in different directions with a defined orientation.

[0015] Similarly, U.S. Patent Application No. 63 / 448,707 discloses a process for separating a first layer from the rest of a tapered multilayer intersheet, in which the tapered multilayer intersheet is heated and then the first layer is separated from the rest of the tapered multilayer intersheet by pulling the first layer and the rest of the tapered multilayer intersheet in different directions in a defined orientation without causing wrinkles or tears in the tapered multilayer intersheet.

[0016] In both of these cases, if the multilayer sheet is an acoustic interlayer where the rest is a core-skin bilayer and the core layer remains exposed, then mechanically separating both layers (the core and the rest of the skin) is difficult. This is because the weak and brittle core layer cannot withstand mechanical peeling forces and easily breaks. The core layer can also be very sticky and difficult to work with. In fact, it adheres to both the skin layer and any other material it comes into contact with. In some cases, it tends to adhere preferentially to the skin layer, and in other cases, it may adhere preferentially to the other material. Even worse, this preference tendency can change based on ambient temperature, or, if separating the two, it can change under separation conditions that may change during the separation process. Thus, the difference in properties between these two layers makes subsequent attempts at separation even more difficult than the step of removing the first skin layer from the rest of the core-skin layer.

[0017] In fact, the present 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 of handling the fragile and brittle core layer that tears very easily, some core layer materials are brittle, inelastic, and appear to adhere strongly to the skin, making it almost impossible to mechanically peel them from the skin layer while remaining substantially intact.

[0018] There remains a continuing need for methods and apparatus for separating layers of multilayer interlayers to facilitate reprocessing of materials in manufacturing processes, particularly for separating multilayer interlayers that include two layers having significantly different properties. Summary of the Invention

[0019] In one aspect, the present invention relates to a process for separating a soft poly(vinyl butyral) layer from a hard poly(vinyl butyral) layer in a multilayer interlayer, the process comprising the step of spraying a fluid onto the soft poly(vinyl butyral) layer at a pressure and temperature sufficient to remove at least a portion of the soft poly(vinyl butyral) layer from the hard poly(vinyl butyral) layer.

[0020] In another aspect, the present invention relates to an apparatus for carrying out the method of the present invention.

[0021] Further aspects of the present invention are as disclosed and claimed herein. Brief Description of the Drawings

[0022] [Figure 1] FIG. 2 is a schematic diagram of spray separation of an acoustic trilayer interlayer, including spraying of the core layer of a core-skin bilayer body. [Figure 2] The effective incident angle and nozzle spray angle according to the present invention are shown. Detailed Description of Embodiments for Carrying Out the Invention

[0023] The following embodiments and combinations are included within the scope of the present invention.

[0024] In a first embodiment, the present invention relates to a process for separating a soft poly(vinyl butyral) layer from a hard poly(vinyl butyral) layer in a multilayer interlayer, the process comprising the step of spraying a fluid onto the soft poly(vinyl butyral) layer at a pressure and temperature sufficient to remove at least a portion of the soft poly(vinyl butyral) layer from the hard poly(vinyl butyral) layer.

[0025] In a second embodiment according to the first embodiment, the fluid comprises water.

[0026] In a further embodiment according to any of the preceding embodiments, the temperature of the water is from 10°C to 100°C, or from 24°C to 60°C.

[0027] In a further embodiment according to any of the preceding embodiments, the water is sprayed through at least one nozzle, or through a plurality of nozzles, for example 5 to 25 nozzles.

[0028] In a further embodiment according to any of the preceding embodiments, the fluid is sprayed at a pressure such that the hard poly(vinyl butyral) layer does not tear.

[0029] In a further embodiment according to any of the preceding embodiments, the fluid is sprayed at a pressure such that the fluid is maintained in a flow.

[0030] In a further embodiment according to any of the preceding embodiments, each of the plurality of nozzles comprises a tip, and the distance between at least one of the nozzle tips and the soft poly(vinyl butyral) layer is from about 1 cm to about 10 cm.

[0031] In a further embodiment according to any of the preceding embodiments, each of the plurality of nozzles comprises a tip, and the average distance between the nozzle tips and the soft poly(vinyl butyral) layer is from about 1 cm to about 10 cm.

[0032] In a further embodiment according to any of the embodiments described above, multiple nozzles share a common manifold.

[0033] In further embodiments according to any of the embodiments described above, the portion of the flexible poly(vinyl butyral) layer removed in the first pass is about 10% to about 50% by weight of the flexible poly(vinyl butyral) layer.

[0034] In further embodiments according to any of the embodiments described above, the flexible poly(vinyl butyral) layer is removed in multiple passes.

[0035] In further embodiments according to any of the embodiments described above, the portion of the flexible poly(vinyl butyral) layer to be removed is about 80% to 100% by weight of the flexible poly(vinyl butyral) layer after about 3 to about 5 passes.

[0036] In a further embodiment according to any of the embodiments described above, at least one of the at least one nozzle has a spray angle of about 1 to about 40 degrees.

[0037] In further embodiments according to any of the embodiments described above, the angle of incidence is approximately 20 degrees to approximately 60 degrees.

[0038] In a further embodiment according to any of the embodiments described above, at least one of the at least one nozzle has a spray angle of about 15 to about 30 degrees, and the angle of incidence is about 30 to about 50 degrees.

[0039] In further embodiments according to any of the embodiments described above, the fluid is sprayed through a series of nozzles arranged along the cross-machine direction of the multilayer intermediate layer, the machine direction of the multilayer intermediate layer, or both the cross-machine direction and the machine direction of the multilayer intermediate layer.

[0040] In a further embodiment according to any of the embodiments described above, the thickness of the rigid poly(vinyl butyral) layer is at least 1.5 times the thickness of the flexible poly(vinyl butyral) layer.

[0041] In a further embodiment according to any of the embodiments described above, the rigid poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer that exhibits a 90° peel adhesion strength of approximately 20 N / cm to approximately 70 N / cm, or approximately 3 N / cm to approximately 18 N / cm, when laminated to glass.

[0042] In a further embodiment according to any of the embodiments described above, the difference in 90° peel adhesion strength between the flexible poly(vinyl butyral) layer and the rigid poly(vinyl butyral) layer when laminated to glass is at least 10 N / cm, or at least 15 N / cm.

[0043] In a further embodiment according to any of the embodiments described above, the difference in 90° peel adhesion strength between the hard PVB and the soft PVB at contact is at least about 10 N / cm at a relative humidity of 25% and a temperature of 21°C.

[0044] In further embodiments according to any of the embodiments described above, the 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.

[0045] In further embodiments according to any of the embodiments described above, the 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.

[0046] In a further embodiment according to any of the embodiments described above, the difference in shear storage modulus at 20°C between the flexible poly(vinyl butyral) layer and the rigid poly(vinyl butyral) layer is at least 10 MPa.

[0047] In further embodiments according to any of the embodiments described above, the flexible poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer having a Tg of less than about 20°C.

[0048] In further embodiments according to any of the embodiments described above, the rigid poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer having a Tg greater than approximately 25°C.

[0049] In further embodiments according to any of the embodiments described above, the flexible poly(vinyl butyral) layer comprises a poly(vinyl butyral) polymer having a residual hydroxyl content of about 8% to about 13.5%.

[0050] In further embodiments according to any of the embodiments described above, the rigid poly(vinyl butyral) layer comprises a poly(vinyl butyral) polymer having a residual hydroxyl content of about 15% to about 25%.

[0051] In further embodiments according to any of the embodiments described above, the difference in residual hydroxyl content between the poly(vinyl butyral) polymer of the rigid poly(vinyl butyral) layer and the poly(vinyl) butyral polymer of the flexible poly(vinyl butyral) layer is at least 5% by weight.

[0052] In further embodiments according to any of the embodiments described above, the rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) having a plasticizer content of about 20 phr to about 50 phr.

[0053] In further embodiments according to any of the embodiments described above, the flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) having a plasticizer content of about 45 phr to about 150 phr.

[0054] In further embodiments according to any of the embodiments described above, the rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) having a weight-average molecular weight of approximately 70,000 to 225,000.

[0055] In further embodiments according to any of the embodiments described above, the flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) having a weight-average molecular weight of about 150,000 to about 600,000.

[0056] In further embodiments according to any of the embodiments described above, the process includes the use of annealing, which helps to remove wrinkles.

[0057] Accordingly, in one embodiment, the present invention relates to a means for recovering a skin layer from a core-skin bilayer by spraying or hydroblasting the core layer, wherein pressurized water is sprayed through a nozzle onto the core layer surface to blast and remove the skin layer from the bilayer, for example, about half to all of the core layer, enabling the recovery of the remaining skin layer for reuse in skin layer extrusion. Furthermore, the blasted core layer can also be recovered for reuse in core layer extrusion. Accordingly, the above method may also include "hydroblasting" the core layer from the bilayer, as shown in Figure 1, wherein pressurized water is sprayed through a nozzle onto the core layer surface to blast and remove at least a portion of the core layer from the bilayer, enabling the recovery of the remaining skin layer for reuse in skin layer extrusion. Furthermore, the blasted core layer can also be recovered for reuse in core layer extrusion.

[0058] According to the present invention, the process includes spraying a fluid onto a flexible poly(vinyl butyral) layer at a pressure and temperature sufficient to remove at least a portion of the flexible poly(vinyl butyral) layer from the rigid poly(vinyl butyral) layer.

[0059] The fluid used is not particularly limited. While this invention does not exclude the use of other fluids such as lower alcohols, the inventors have found that water functions adequately from an environmental perspective. To prevent corrosion of metal rollers or other parts that may come into contact with water, water may be provided with a rust inhibitor or the like.

[0060] The spraying method is not particularly limited. Various nozzles can be used. The inventors have found that multiple nozzles are undoubtedly useful when the material moves across the surface in the direction of the machine, but a single nozzle is useful when the material is passed across the surface. Therefore, one or more nozzles may be used. At least two nozzles, for example, 3 to 30 or 5 to 25 nozzles, may be used.

[0061] In one embodiment, the spraying of the fluid is achieved by one or more nozzles having a certain spray angle, as shown in Figure 2. The spray angle is defined as the widest angle of the fluid exiting the nozzle. It has been found that a more linear spray is preferable to a conical spray for the best removal of the material. In the case of a relatively flat spray, the spray angle is reflected in the width of the spray exiting the nozzle, and the "height" of the spray is much smaller than the width. Therefore, according to the present invention, the nozzles may have a spray angle of about 1 to about 40 degrees, or 20 to 60 degrees.

[0062] According to the present invention, the distance between the nozzle and the double layer is not particularly limited. Typically, each of the plurality of nozzles includes a tip, and the distance between at least one of the nozzle tips and the flexible poly(vinyl butyral) layer may be about 1 to about 10 cm, or about 1.5 to about 7.5 cm, or 2 to 5 cm. In other embodiments, each of the plurality of nozzles includes a tip, and the distance between all the nozzle tips and the flexible poly(vinyl butyral) layer is about 1 to about 10 cm, or about 1.5 to about 7.5 cm, or 2 to 5 cm. In various embodiments, the plurality of nozzles may share a common manifold.

[0063] According to the present invention, the angle of incidence of the spray, i.e., the contact angle between the fluid flow and the surface of the multilayer intermediate layer, is not particularly limited, as shown in Figure 2. In various embodiments, the angle of incidence may be, for example, about 20 degrees to about 60 degrees, or about 30 degrees to about 30 degrees.

[0064] In various embodiments, the fluid may be sprayed through a series of nozzles arranged along the cross-machine direction of the multilayer intermediate layer, the machine direction of the multilayer intermediate layer, or both the cross-machine direction and the machine direction of the multilayer intermediate layer.

[0065] The pressure used is also not particularly limited. The inventors found that a pressurized washer set to a pressure of about 3,300 psi is suitable when using water at a temperature of about 25°C. Although it is difficult to specify a numerical range, it was found that a suitable pressure for spraying the fluid is desirable to be such that the rigid poly(vinyl butyral) layer does not rupture. To prevent rupture, multiple passes or multiple steps of spraying the fluid onto the flexible poly(vinyl butyral) layer, for example, at least three or at least five passes, may be advantageous. It was also found that the pressure at which the fluid is sprayed onto the flexible poly(vinyl butyral) layer is desirable to be such that the fluid is not atomized but maintained as a flow.

[0066] Typically, the time required to remove at least a portion of the flexible poly(vinyl butyral) layer from the rigid poly(vinyl butyral) layer can vary depending, for example, on the properties and temperature of the fluid. Similarly, the number of passes required can also vary.

[0067] The temperature may also vary depending on the fluid used and the time used to remove, for example, at least a portion of the flexible poly(vinyl butyral) layer from the rigid poly(vinyl butyral) layer. In one embodiment, the water temperature may be about 10°C to about 100°C, or 24°C to 60°C.

[0068] When multiple passes are used, the portion of the flexible poly(vinyl butyral) layer removed in the first pass may be, for example, about 10% to 50% by weight of the flexible poly(vinyl butyral) layer. Therefore, as described above, the flexible poly(vinyl butyral) layer can be removed by multiple passes.

[0069] Therefore, in one embodiment, the portion of the soft poly(vinyl butyral) layer to be removed may be, for example, about 80% to about 100% by weight of the soft poly(vinyl butyral) layer after about 3 to about 5 passes.

[0070] According to the present invention, a multilayer intermediate 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 intermediate is typically two-layer, but the present invention is not limited as long as soft and hard layers are present, as described herein. The soft layer and hard layer are also described as a core layer and a skin layer, respectively.

[0071] Those skilled in the art will understand that the described layers contain poly(vinyl butyral) polymers. Each poly(vinyl butyral) polymer may be a reaction product of a single reaction or a blend of reaction 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. Thus, references to poly(vinyl butyral) polymers and their properties may refer to a single polymer that is a single reaction product, a blend of two or more polymers having these properties, or a blend of multiple polymers in which the resulting blend has the described properties.

[0072] According to the present invention, as shown in Figure 1, a multilayer intermediate layer, which is a two-layer structure in which the skin layer is separated from a typical three-layer acoustic structure and the core layer is exposed, is separated into two layers: a soft poly(vinyl butyral) layer and a hard poly(vinyl butyral) layer.

[0073] The term “rigid poly(vinyl butyral)” refers to poly(vinyl butyral) resin or blends of poly(vinyl butyral) resin that are significantly harder than “flexible poly(vinyl butyral)” and typically form the skin or rigid layer of multilayer poly(vinyl butyral) sheets, as further described herein.

[0074] The term “flexible poly(vinyl butyral)” refers, as further described herein, to a poly(vinyl butyral) resin or blend of poly(vinyl butyral) resins that is significantly more flexible than “rigid poly(vinyl butyral)” and typically forms a core or flexible layer of a multilayer poly(vinyl butyral) sheet. The flexible or core poly(vinyl butyral) layer is typically sandwiched between two rigid or skin poly(vinyl butyral) layers to form a multilayer poly(vinyl butyral) sheet, from which one skin layer can then be removed prior to or as a preliminary step of the present invention.

[0075] A bilayer separated according to the present invention may result from a process disclosed and claimed in WO2022250944A2. The relevant disclosure is incorporated herein by reference in whole. Here, a first layer or skin layer is separated from the rest of a multilayer intersheet, for example, the core and skin layers of an acoustic three-layer intersheet. According to the described process, a core-skin bilayer can be obtained by heating the multilayer sheet and then pulling the first layer and the rest of the multilayer intersheet in different directions to separate the first (skin) layer from the rest of the multilayer intersheet. Similarly, any other suitable method can be used to obtain a multilayer (bilayer) separated according to the present invention.

[0076] As used herein, the terms “multilayer” and “multiple layers” refer to an intermediate layer having two or more layers, and the terms multilayer and multiple layers may be used interchangeably. Intermediate layers are generally produced by mixing a polymer resin, such as poly(vinyl butyral), with one or more plasticizers, and melt-forming the mixture into a sheet by any applicable process or method known to those skilled in the art, including but not limited to extrusion molding, and the layers are combined by processes such as co-extrusion or lamination. Other additional components may be added at will for various other purposes. After the intermediate sheet is formed, it is typically recovered and rolled for transport and storage and for subsequent use in multilayer glass panels, as described below.

[0077] In various embodiments of this disclosure, a multilayer intermediate includes a soft layer and a hard layer (e.g., a single layer or multiple layers co-extruded and / or laminated together) which are at least two polymer layers arranged in direct contact with each other, and each layer comprises a polymer resin, as will be further described below. Where used herein for a multilayer intermediate having at least three layers, “skin layer” generally refers to the outer layer(s) of the intermediate, and “core layer” generally refers to the inner layer(s). Thus, one exemplary embodiment is skin layer / / core layer / / skin layer. In a multilayer intermediate having a skin layer / / core layer / / skin layer configuration, the skin layer is harder and the core layer is softer.

[0078] For example, in a three-layer polymer intersheet, the two rigid (or outer or skin) layers may contain poly(vinyl butyral) ("PVB") resin with a plasticizer or a mixture of plasticizers, while the softer (inner or core) layer may contain the same or different PVB resin or a different thermoplastic material with the same or different plasticizer and / or a mixture of plasticizers. Thus, it is intended that the rigid or skin layer and the soft or core layer(s) of a multilayer intersheet may consist of the same or different thermoplastic material and the same or different plasticizers or multiple plasticizers. Either or both layers may, as desired, contain additional additives known in the art.

[0079] One type of multilayer interlayer that utilizes a softer inner layer is a multilayer acoustic interlayer. As disclosed herein, the acoustic interlayer comprises multiple layers, and in a preferred embodiment, has a relatively soft layer sandwiched between two relatively hard layers. The resulting three-layer interlayer can generally be used directly in the lamination process in place of conventional single-layer interlayers with little or no modification to the lamination process.

[0080] The core or soft layer of the multilayer intermediate is understood to be involved in the acoustic properties of the acoustic trilayer and comprises soft poly(vinyl butyral), i.e., a skin harder than soft PVB or poly(vinyl butyral) (PVB) softer than hard PVB. In one embodiment, the soft poly(vinyl butyral) may then have a residual hydroxyl content of about 5% to about 15%, or 8% to 12%, or about 9% to 11%, or as otherwise described herein. In another embodiment, the hard poly(vinyl butyral) may have a residual hydroxyl content of about 12% to about 30%, or 15% to about 25%, or 18% to 22%.

[0081] In some embodiments, the intermediate layer (e.g., core layer and skin layer) has a substantially constant or uniform thickness along its longitudinal direction. However, in alternative embodiments, the intermediate layer may have at least one region of non-uniform thickness. For example, the intermediate layer may be wedge-shaped, and its thickness may vary (e.g., linearly or non-linearly) along its longitudinal direction. In some such embodiments, the thickness of the intermediate layer may vary due to a change in the thickness of the core layer (i.e., the thickness of the skin layer(s) is substantially constant). Alternatively, the thickness of the intermediate layer may vary due to a change in the thickness of the skin layer(s) (i.e., the thickness of the core layer is substantially constant). In further alternatives, the thickness of the intermediate layer may vary due to a change in the thickness of both the core layer and the skin layer(s).

[0082] Accordingly, in one embodiment, the multilayer poly(vinyl butyral) sheet of the present invention may include an intermediate layer comprising one or more rigid skin layers and flexible core layers. In one embodiment, these multilayer intermediate sheets may, in order, include a polymer layer (skin layer) comprising a rigid plasticized poly(vinyl butyral) resin; a second polymer layer (core layer) comprising a flexible 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 a rigid plasticized poly(vinyl butyral) resin. This optional skin layer is removed before the process of the present invention or incorporated in an embodiment in which the skin layer is removed beforehand so that the core layer is exposed. Thus, the core polymer layer is positioned adjacent to the skin layer. In the case of three or more layers, the second polymer layer may be positioned between the first polymer layer and the third polymer layer, forming two skin layers and a central core layer.

[0083] In some embodiments, the intermediate layer includes at least three polymer layers, one or more of the inner layers can be made relatively thin compared to the other outer layers. For example, in some embodiments, the multilayer intermediate layer is a three-layer intermediate layer, the thickness of the innermost layer can be about 12 or less, about 10 or less, about 9 or less, about 8 or less, about 7 or less, about 6 or less, or about 5 mils or less, or can be 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 outer layer can be at least about 4, at least about 5, at least about 6, at least about 7 mils, and / or about 15 or less, about 13 or less, about 12 or less, about 10 or less, about 9 or less, or about 8 mils or less, or can be in the range of about 2 to about 15, about 3 to about 13, or about 4 to about 10 mils. If the intermediate layer includes two outer layers, the total thickness of these layers may be 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 exceeding about 73, not exceeding about 60, not exceeding about 50, not exceeding about 45, not exceeding about 40, not exceeding about 35 mils, or in the range of about 9 to about 70 mils, about 13 to about 40 mils, or about 25 to about 35 mils.

[0084] According to some embodiments, the ratio of the thickness of one outer layer to one inner layer in a multilayer 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. If the interlayer is a three-layer interlayer in which an inner core layer is positioned between a pair of outer skin layers, the ratio of the thickness of one skin layer to the thickness of the core layer may fall within one or more of the above ranges. In some embodiments, the ratio of the total thickness of the outer layer 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 less than or equal to about 30:1, less than or equal to about 20:1, less than or equal to about 15:1, less than or equal to about 10:1, less than or equal to about 9:1, or less than or equal to about 8:1.

[0085] Multilayer interlayers as described herein may generally include flat interlayers whose thickness is substantially the same along the length, or longest dimension, and / or width, or second longest dimension of the sheet. On the other hand, in some embodiments, the multilayer interlayers of the present invention may be tapered or wedge-shaped interlayers that include at least one tapered region having a wedge shape. A tapered interlayer has a shape in which the thickness changes along at least a portion of the length and / or width of the sheet, for example, the thickness of at least one edge of the interlayer is greater than that of the other edge. If the interlayer is a tapered interlayer, at least one, at least two, at least three, or more of the individual resin layers may include at least one tapered region. Tapered interlayers may be particularly useful, for example, in head-up display (HUD) panels for automobiles and aircraft.

[0086] As used herein, the term “plasticizer” generally refers to molecules or blends of molecules, as further described herein, which plasticize polymers with low plasticizer content, particularly poly(vinyl butyral), thereby softening the polymer. In many embodiments, plasticizers are added to polymer resins to form polymer layers or intermediates. Generally, the addition of plasticizers to polymer resins improves the flexibility and durability of the resulting polymer intermediates. Plasticizers are incorporated between polymer chains, increasing the spacing between chains ("free volume"), thereby lowering the glass transition temperature (T) of the polymer resin. g It significantly lowers the glass transition temperature (T) and softens the material. Furthermore, by adjusting the amount of plasticizer in the intermediate layer, the glass transition temperature (T) can be changed. g It can also affect the glass transition temperature (T g ) is the temperature at which the intermediate layer transitions from a glassy state to a rubbery state. Generally, the higher the amount of plasticizer added, the higher the temperature. g The temperature becomes lower. In some embodiments, such as when the intermediate layer is an acoustic triple layer, the glass transition temperature of the inner core layer (i.e., the soft layer) is less than approximately 20°C, while the glass transition temperature of the outer skin layer (e.g., the hard layer) is greater than approximately 25°C.

[0087] Possible plasticizers include, but are not limited to, polymeric plasticizers such as polybasic acid esters, polyhydric alcohols, triethylene glycol di-(2-ethyl butyrate), triethylene glycol di-(2-ethylhexanoate) (known as "3-GEH"), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, mixtures of heptyl adipate and nonyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, oil-modified alkyd sebacate, and mixtures of phosphates and adipates, as well as mixtures and combinations thereof. 3-GEH is particularly preferred. Other suitable plasticizers include, but are not limited to, tetraethylene glycol di(2-ethylhexanoate) ("4-GEH"), di(butoxyethyl) adipate, bis(2-(2-butoxyethoxy)ethyl) adipate, dioctyl sebacate, nonylphenyltetraethylene glycol, and mixtures thereof.

[0088] Other suitable plasticizers may include, but are not limited to, blends of two or more different plasticizers, including the plasticizers described above. Further suitable plasticizers, or blends of plasticizers, may be formed from aromatic groups, such as polyadipates, epoxides, phthalates, terephthalates, benzoates, toluates, melitates, 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-ethylhexanoate), ethoxylated nonylphenol, and mixtures thereof. In some embodiments, the plasticizer can be selected from the group consisting of dipropylene glycol dibenzoate, tripylene glycol dibenzoate, and combinations thereof.

[0089] Generally, the plasticizer content of polymer intermediates in this application is measured by weight in parts per 100 parts of resin ("phr"). For example, if 30 grams of plasticizer are added to 100 grams of polymer resin, the plasticizer content of the resulting plasticized polymer is 30 phr. Where the plasticizer content of a polymer layer is indicated in this application, the plasticizer content of a particular layer is determined based on the phr of the plasticizer in the molten material used to produce that particular layer. In some embodiments, high-rigidity intermediates include layers with plasticizer content of less than about 35 phr and less than about 30 phr.

[0090] According to some embodiments of the present invention, one or more polymer layers described herein may contain one or more plasticizers with 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 with a total plasticizer content of about 100 phr or less, about 85 phr or less, 80 phr or less, about 75 phr or less, about 70 phr or less, about 65 phr or less, about 60 phr or less, about 55 phr or less, about 50 phr or less, about 45 phr or less, about 40 phr or less, about 38 phr or less, about 35 phr or less, or about 30 phr or less. In some embodiments, the total plasticizer content of at least one polymer layer can be in the range of 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 about 38 to about 90 phr, about 40 to about 85 phr, or about 50 to about 70 phr.

[0091] If the intermediate layer includes a multilayer intermediate layer, the plasticizer content of two or more polymer layers in the intermediate layer may be substantially the same, and / or the plasticizer content of at least one polymer layer may differ from one or more of the other polymer layers. If the intermediate layer includes two or more polymer layers with different plasticizer content, the two layers may be adjacent to each other. 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 about 80 or less, about 55 or less, about 50 or less, or about 45 phr or less, or in the range of about 1 to about 60 phr, about 10 to about 50 phr, or about 30 to 45 phr. If there are three or more layers in the intermediate layer, the plasticizer content of at least two of the polymer layers in the intermediate layer may be similar, being within 10 phr, 5 phr, 2 phr, or 1 phr, while the plasticizer content of at least two of the polymer layers may differ from each other within the above ranges.

[0092] In some embodiments, one or more polymer layers or intermediate layers described herein may contain a blend of two or more plasticizers, for example, two or more of the plasticizers described above. When a polymer layer contains 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 above-described ranges. When the intermediate layer is a multilayer intermediate layer, one or more polymer layers may contain two or more plasticizers. In some embodiments, when the intermediate layer is a multilayer intermediate layer, at least one of the polymer layers containing the blend of plasticizers may have a higher glass transition temperature than a conventional plasticized polymer layer. This may, in some examples, add further rigidity to a layer that can be used, for example, as an outer "skin" layer of a multilayer intermediate layer.

[0093] In various embodiments, 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.

[0094] In various embodiments, the rigid poly(vinyl butyral) contained in the plasticized poly(vinyl butyral) multilayer sheet contains approximately 25 phr to 50 phr, or 30 phr to 45 phr, or 32 to 42 phr of plasticizer.

[0095] In one embodiment, a plasticized poly(vinyl butyral) multilayer sheet, which is either a complete acoustic triple layer or a double layer from which one skin layer has been removed, may contain triethylene glycol bis(2-ethylhexanoate) as a plasticizer. In other embodiments, the plasticized poly(vinyl butyral) multilayer sheet may further contain, as a plasticizer, dihexyl adipate or bis(2-ethylhexyl) adipate, or another convenient substance, such as Benzoflex® 9-88 benzoate ester.

[0096] In other embodiments, the plasticizer is selected from one or more esters of polybasic acids or polyhydric alcohols. In further embodiments, 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, bis(2-ethylhexyl) adipate, bis(2-ethoxyethyl) adipate, dioctyl adipate, cyclohexyl adipate hexyl, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, polymer adipates, soybean oil, or epoxidized soybean oil.

[0097] Furthermore, by using plasticizers suitable for high temperatures, the fluidity of the intermediate layer can be further increased.

[0098] In various embodiments of the interlayer of this disclosure, the interlayer may contain a total of approximately 30 to approximately 60 phr (parts per 100 parts of resin) of plasticizer. While the total plasticizer content is shown above, the plasticizer content in the hard layer(s) or soft layer(s) may differ from the total plasticizer content. Furthermore, the hard layer(s) and soft layer(s) may have different plasticizer content, as the plasticizer content of each layer in equilibrium is at least partially determined by its respective residual hydroxyl content. For example, in equilibrium, the interlayer may contain two skin layers, each containing 38 phr of plasticizer, and a core layer containing 75 phr of plasticizer, and if the total thickness of the skin layers is equal to the thickness of the core layer, the total amount of plasticizer in the interlayer will be approximately 54.3 phr. For thicker or thinner skin layers, the total amount of plasticizer in the interlayer may vary accordingly.

[0099] In other embodiments, the amount of plasticizer in rigid poly(vinyl butyral) or flexible poly(vinyl butyral) may be about 20 phr to about 60 phr, or 25 phr to 50 phr, or 30 phr to 45 phr.

[0100] In various embodiments, the skin layer or rigid layer of the multilayer intersheet may comprise a PVB polymer having a Tg of, for example, about 20°C to about 45°C, or 25°C to 40°C, or 28°C to 35°C. Alternatively, the Tg of rigid poly(vinyl butyral) may be at least about 20°C, at least 25°C, or at least 28°C, up to about 45°C, up to 40°C, or up to 35°C.

[0101] In various embodiments, the flexible or core layer of the multilayer intersheet may comprise a PVB polymer having a Tg of, for example, about -15°C to about 45°C, or -10°C to 30°C, or -8°C to 25°C. Alternatively, the Tg of flexible 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.

[0102] In some embodiments, the Tg of the core layer or soft layer may be at least 12°C lower, at least 15°C lower, at least 20°C lower, or at least 30°C lower than the Tg of the hard layer.

[0103] In various embodiments, the polymer intermediate layer has at least two different glass transition temperatures (T g ) has at least two different glass transition temperatures (T g The difference between them is at least 5°C.

[0104] As a result of plasticizer migration within the interlayer, the glass transition temperatures of one or more polymer layers may differ when measured individually compared to when measured 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 outside the interlayer. In some embodiments, this same layer may have a glass transition temperature of 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 within the polymer layer.

[0105] In the same or other embodiments, at least one other polymer layer of the multilayer intermediate layer may have a glass transition temperature of less than 30°C, and may have a glass transition temperature of about 25°C or less, about 20°C or less, about 15°C or less, about 10°C or less, about 9°C or less, about 8°C or less, about 7°C or less, about 6°C or less, about 5°C or less, about 4°C or less, about 3°C ​​or less, about 2°C or less, about 1°C or less, about 0°C or less, about -1°C or less, about -2°C or less, or about -5°C or less, measured when the intermediate layer is not part of the intermediate layer. This same polymer layer may have a glass transition temperature of about 25°C or less, about 20°C or less, about 15°C or less, about 10°C or less, about 9°C or less, about 8°C or less, about 7°C or less, about 6°C or less, about 5°C or less, about 4°C or less, about 3°C ​​or less, about 2°C or less, about 1°C or less, or about 0°C or less, measured outside the intermediate layer.

[0106] In some embodiments, the difference in glass transition temperatures between two polymer layers, typically adjacent polymer layers within an intermediate layer, 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, while in other embodiments, two or more polymer layers can have glass transition temperatures of about 5°C, about 3°C, about 2°C, or about 1°C from each other. Generally, layers with lower glass transition temperatures are less rigid than layers with higher glass transition temperatures within the intermediate layer and can be placed between polymer layers with higher glass transition temperatures in the final intermediate layer structure.

[0107] The PVB layers according to the present invention are further characterized by their peel-adhesion properties with respect to each other and to other materials they may come into contact with.

[0108] For example, in some embodiments, when laminated to glass, the rigid PVB described herein may exhibit 90° peel adhesion values ​​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, when laminated to glass, the rigid PVB described herein may exhibit 90° peel adhesion values ​​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.

[0109] In contrast, in some embodiments, the flexible PVB described herein, when laminated to glass, may exhibit 90° peel adhesion values ​​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 flexible PVB described herein, when laminated to glass, may exhibit 90° peel adhesion values ​​of about 2 N / cm to about 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 layer according to the present invention was actually laminated to glass, but rather to suggest that the polymer described exhibits these peel adhesion properties when laminated to glass as described below.

[0110] The peel adhesion properties of the combined soft and hard layers are as follows: The hard PVB described herein may exhibit a 90° peel adhesion strength 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 relative to the soft PVB at a relative humidity of 25% and 21°C.

[0111] For example, layers and intermediate layers according to embodiments of the present invention may exhibit such 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%, as measured by Karl Fischer titration according to ASTM E203.

[0112] The 90° peel adhesion values ​​to glass described herein can be determined by following the procedure described below, including the lamination / autoclave process. Similarly, the peel adhesion values ​​of rigid PVB to flexible PVB (measured with a 3-layer rigid / flexible / rigid sheet with the first rigid layer removed) can be determined as follows, without first laminating / autoclaving the film to the glass.

[0113] Peel-off bonding: To measure the adhesive strength between the plasticized PVB layer and the glass, the bonded coated aluminum foil is first acclimatized at 105°C for 30 minutes. Next, using standard lamination techniques, a special peel-off bonded laminate containing the PVB interlayer to be tested is prepared by replacing one glass piece of a standard double-glass laminate with the acclimatized aluminum foil. The thickness of the plasticized PVB layer in the laminate being tested is standardized to 30 mils (0.76 mm). More specifically, the coated foil is attached to one side of the polymer laminate by adhesive adjacent to the PVB layer, and the glass layer to be tested is attached to the other side of the PVB laminate. After assembling two such laminates, they are positioned so that the foil surfaces face each other and in contact, and passed through a degassing roll. The laminates are then placed one by one in a circulating air oven at 100°C for 5 minutes with the foil side down. The high-temperature laminates are then assembled, re-rolled as described above, and autoclaved at 290°F (143°C) and 185 psi (1,275 kPa). After autoclaving, a special double-wheel cutting machine is used to create a 4 cm wide cut through the foil and polymer laminate. The glass at one end of the laminate is then notched and broken. The outer edges of the aluminum foil and polymer laminate on each side of the 4 cm strip are cut at the glass break point. At least three samples of a specific common polymer laminate are tested according to the reported values. A standard laminate, which will be used for moisture analysis during the layup of the peeled samples, is prepared from the same polymer laminate piece. Before performing the actual peel test, the samples are acclimatized overnight at (21°C). During the peel test, the glass, foil, and polymer laminate samples are clamped with the test grip of the Instron peel tester (crosshead speed 5 in (12.7 cm) / min) and the force required to separate the polymer laminate from the glass is directly recorded. The average of the various peaks recorded is the value for that sample.

[0114] To measure the adhesive strength between a rigid plasticized PVB layer and a flexible plasticized PVB layer:

[0115] A three-layer sample of hard / soft / hard or a two-layer sample of hard / soft is cut into rectangular strips. The surface layers are adhered to tape pieces of the corresponding size. Initial separation of the soft / core layers is performed manually at one end of the strip to facilitate mounting the layers to the sample holder of the peel tester. The strip can then be peeled at the hard / soft interface in a 180-degree peel test using a peel tester.

[0116] The described peel adhesion properties are important because both the core and skin materials exhibit adhesion to various materials, with the core layer being even more adhesive than the skin layer. Similarly, the two layers also exhibit a peel adhesion value when they are in the same film, and this value affects the ability to cleanly separate the two layers.

[0117] The multilayer core and skin layers separated according to the present invention are further characterized as having different shear storage moduli.

[0118] Therefore, in one embodiment, the flexible poly(vinyl butyral) layer includes poly(vinyl butyral) having a shear modulus of approximately 0.01 MPa to approximately 20 MPa, or approximately 0.1 to approximately 18 MPa, or approximately 0.15 to approximately 15 MPa at 20°C. Similarly, the rigid poly(vinyl butyral) layer includes poly(vinyl butyral) having a shear modulus of approximately 20 MPa to approximately 600 MPa, or approximately 28 to approximately 450 MPa, or approximately 30 to approximately 400 MPa at 20°C.

[0119] This property is equally important because it indicates, in particular, the tendency for the layer to remain intact, or in other words, the possibility of the material fracturing. Due to the differences in shear modulus mentioned earlier, the soft layer is indeed prone to fracturing, making it difficult to remove the layer intact.

[0120] 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, the loss (viscous) shear modulus (G") in Pascals, the tan delta of the specimen as a function of temperature at a given frequency (=G'' / G'), and the temperature sweep rate. In this specification, a frequency of 1 Hz and a temperature sweep rate of 3 °C / min are used. Next, Tg is determined by the position of the tan delta peak on a °C temperature scale, and the peak value of the tan delta is referred to as tan delta or peak tan delta. Where used herein, "tan delta," "peak tan delta," "tan δ," and "peak tan δ" may be used interchangeably.

[0121] One of the parameters used to describe the polymer resin components of the polymer intermediate layer 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 remaining as side groups on the polymer chain after the processing is complete. For example, PVB can be produced by hydrolyzing poly(vinyl acetate) to poly(vinyl alcohol), and then reacting this poly(vinyl alcohol) with butyraldehyde to form PVB. In the process of hydrolyzing poly(vinyl acetate), not all acetate side groups are usually converted to hydroxyl groups. Furthermore, in the reaction with butyraldehyde, not all hydroxyl groups are usually converted to acetal groups. As a result, in any completed PVB, residual acetate groups (such as vinyl acetate groups) and residual hydroxyl groups (such as vinyl hydroxyl groups) are usually present as side groups on the polymer chain. In general, among the variables in the polymer manufacturing process, the residual hydroxyl content of the polymer can be adjusted by controlling the reaction time and reactant concentration. When used as a parameter in this specification, the residual hydroxyl content is measured in weight percent according to ASTM D-1396.

[0122] In some embodiments, the difference between the residual hydroxyl content of the flexible poly(vinyl butyral) and the residual hydroxyl content of the rigid 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.

[0123] Therefore, in various embodiments, the residual hydroxyl content of the poly(vinyl butyral) resin in the rigid (skin) layer(s) and flexible (core) layer(s) may differ. The resin for the core layer(s) may contain, for example, about 9 to about 18 weight percent (wt%) of residual hydroxyl groups calculated as PVOH, about 9 to about 16 weight percent (wt%) of residual hydroxyl groups calculated as PVOH, or about 9 to about 14 weight percent (wt%) of residual hydroxyl groups calculated as PVOH. The resin for the skin layer(s) may contain, for example, about 13 to about 35 weight percent (wt%) of residual hydroxyl groups calculated as PVOH, about 13 to about 30 weight percent (wt%) of residual hydroxyl groups calculated as PVOH, or about 15 to about 22 weight percent (wt%) of residual hydroxyl groups calculated as PVOH, and in certain embodiments, it may contain about 17.25 to about 22.25 weight percent (wt%) of residual hydroxyl groups calculated as PVOH, or as otherwise described herein.

[0124] In various embodiments, the poly(vinyl butyral) resin contains about 8 to about 35 weight percent (wt%) of residual hydroxyl groups calculated as PVOH, about 13 to about 30 weight percent of residual hydroxyl groups calculated as PVOH, about 8 to about 22 weight percent of residual hydroxyl groups calculated as PVOH, or about 15 to about 22 weight percent of residual hydroxyl groups calculated as PVOH. With respect to the highly rigid intermediate layers disclosed herein, in one or more layers, the poly(vinyl butyral) resin contains more than about 19 weight percent of residual hydroxyl groups calculated as PVOH, more than about 20 weight percent of residual hydroxyl groups calculated as PVOH, more than about 20.4 weight percent of residual hydroxyl groups calculated as PVOH, and more than about 21 weight percent of residual hydroxyl groups calculated as PVOH.

[0125] In some embodiments, the poly(vinyl butyral) resin used in at least one polymer layer of the intermediate layer may include poly(vinyl butyral) resins having a residual hydroxyl content of at least about 18% by weight, at least about 18.5% by weight, at least about 18.7% by weight, at least about 19% by weight, at least about 19.5% by weight, at least about 20% by weight, at least about 20.5% by weight, at least about 21% by weight, at least about 21.5% by weight, at least about 22% by weight, at least about 22.5 wt%, and / or about 30% by weight or less, about 29% by weight or less, about 28% by weight or less, about 27% by weight or less, about 26% by weight or less, about 25% by weight or less, about 24% by weight or less, about 23% by weight or less, or about 22% by weight or less, as measured above.

[0126] Furthermore, one or more other polymer layers in the intermediate layer described herein may include another poly(vinyl butyral) resin with a low residual hydroxyl content. For example, in some embodiments, at least one polymer layer of the intermediate layer may include a poly(vinyl butyral) resin having a residual hydroxyl content of at least about 8% by weight, at least about 8.5% by weight, at least about 9% by weight, at least about 9.5% by weight, at least about 10% by weight, at least about 10.5% by weight, at least about 11% by weight, at least about 11.5% by weight, at least about 12% by weight, at least about 13% by weight, and / or about 16% by weight or less, about 15% by weight or less, about 14% by weight or less, about 13.5% by weight or less, about 13% by weight or less, about 12% by weight or less, or about 11.5% by weight or less, as measured above.

[0127] In one embodiment, a 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. Alternatively, the residual hydroxyl content of flexible poly(vinyl butyral) may be about 7% to about 13%, or 8% to 12%, or as otherwise described herein.

[0128] In another embodiment, rigid poly(vinyl butyral) or a blend of rigid poly(vinyl butyral) may have a residual hydroxyl content of about 12% to about 28%, as further described herein. Alternatively, 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.

[0129] In various embodiments, the residual hydroxyl content of the first rigid poly(vinyl butyral resin) is typically the same as that of the second rigid poly(vinyl butyral resin) and typically different from that of the core poly(vinyl butyral resin). In various embodiments, the difference between the residual hydroxyl content of the core and the residual hydroxyl content of the skin is at least 4.0 weight percent, or at least 5 weight percent, or at least 6.0 weight percent.

[0130] In various 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.

[0131] In one embodiment, flexible poly(vinyl butyral) or a blend of flexible poly(vinyl butyral) may have a residual acetate content of about 0% to about 18%, or about 0.5% to 10%, as further described herein. 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.

[0132] In another embodiment, rigid poly(vinyl butyral) or a blend of rigid poly(vinyl butyral) may have a residual acetate content of about 0% to about 18%, as further described herein. Alternatively, the residual acetate content of 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.

[0133] In other embodiments, the residual hydroxyl content of the soft layer may be the same as, greater than, or less than the residual hydroxyl content of the resin in the hard layer. In various embodiments, the soft resin, or the skin resin, or both of these resins, calculated as a polyvinyl ester such as acetate, may contain less than 30% by weight of residual ester groups, less than 25% by weight of residual ester groups, 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, with the remainder being an acetal such as butyraldehyde acetal, but optionally other acetal groups such as isobutyraldehyde acetal group, 2-ethylhexanal acetal group, or a mixture of any two of the butyraldehyde acetal group, isobutyraldehyde acetal group, and 2-ethylhexanal acetal group, or as described elsewhere in this specification.

[0134] Resins for core layers(s), skin layers(s), or both skin layers(s) and core layers(s) may also contain less than 20% by weight of residual ester groups, 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, calculated as polyvinyl esters such as acetate, with the remainder being 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).

[0135] In some embodiments, the multilayer intermediate used in the process of the present invention may include a skin or static polymer layer containing plasticized poly(vinyl butyral) having a weight-average molecular weight (Mw) of less than about 140,000 amu, or less than 150,000, less than 200,000, or less than 250,000, and a core polymer layer containing plasticized poly(vinyl butyral) having a weight-average molecular weight of more than about 200,000 amu, or more than 225,000, or more than 250,000, or more than 275,000.

[0136] Therefore, the skin or rigid polymer layer contains plasticized poly(vinyl butyral) having a weight-average molecular weight (Mw) of approximately 60,000 to 250,000, or 70,000 to 225,000, or 100,000 to 200,000. The core polymer layer may contain plasticized poly(vinyl butyral) with a weight-average molecular weight of approximately 150,000 amu to 600,000, or 200,000 to 500,000, or 250,000 to 400,000.

[0137] More generally, as used herein, the term “molecular weight” refers to weight-average molecular weight (Mw). Suitable molecular weights for PVB resins are generally in the range of approximately 50,000 to 600,000, approximately 70,000 to 450,000, or approximately 100,000 to 425,000 atomic mass units.

[0138] Extruded intermediates formed from plasticized PVB resin can be manufactured by extruding them through a conventional sheeting die having a cooled die lip using a system known to those skilled in the art, that is, by pushing a molten polymer through a die opening that is horizontally long and vertically narrow, having a length and width substantially corresponding to the length and width of the sheet formed therein.

[0139] For example, a multilayer intermediate can be co-extruded using a multilayer manifold co-extrusion apparatus such as that disclosed in U.S. Patent Application Publication No. 2008 / 0254302, the relevant disclosure of which is incorporated herein by reference. Such an apparatus has a first die manifold, a second die manifold, and a third die manifold. The apparatus operates to simultaneously extrude a polymer molten material from each manifold toward the extrusion opening, and the multilayer intermediate is extruded as a composite of three separate polymer layers. The thickness of the layers can be varied by adjusting the distance between the die lips in the extrusion opening. Melt fracture can be controlled by controlling the composition of the molten material, the temperature of the die lips or lands in the extrusion opening, or by controlling the cooling rate and method of the extruded intermediate, for example, by immersing it in a cooling bath immediately after extrusion. According to the present invention, a desired film having a rough surface on one side and a smooth surface on the other can be obtained using the separation techniques described herein.

[0140] Conventional multilayer interlayers, such as three-layer acoustic interlayers, typically consist of a flexible core layer made of a single poly(vinyl butyral) ("PVB") resin with a low residual hydroxyl content and a high conventional plasticizer content, and two rigid skin layers with significantly high residual hydroxyl content (see, for example, U.S. Patents 5,340,654, 5,190,826, and 7,510,771). Therefore, isolated flexible poly(vinyl butyral) may be regenerated to form the core layer of a three-layer acoustic interlayer, or the flexible poly(vinyl butyral) layers may be formed by using the flexible poly(vinyl butyral) and plasticizer varnish directly without first separating them. The residual hydroxyl content and the amount of plasticizer in the PVB core resin are optimized so that the interlayer provides optimal sound insulation properties under ambient conditions for multilayer glass panels such as windshields and windows installed in vehicles and buildings.

[0141] As described above, in certain important embodiments, the multilayer intersheet includes, for example, a multilayer PVB interlayer having a skin / core / skin cross-section. While specific PVB interlayers have been described, various interlayer materials can be used.

[0142] When the intermediate layer contains polyvinyl butyral (PVB), PVB resins can be produced by known acetalization processes, which involve reacting polyvinyl alcohol ("PVOH") with butyraldehyde in the presence of an acid catalyst, followed by separation, stabilization, and drying of the resin. Such acetalization processes are described, for example, in U.S. Patents 2,282,057 and 2,282,026, and in Vinyl Acetal Polymers, Encyclopedia of Polymer Science & Technology, 3rd edition, Volume 8, pages 381-399, BEWade (2003), the entirety of which is incorporated herein by reference. Resins are commercially available in various forms, such as Butvar® resin from Solutia Inc., a wholly owned subsidiary of Eastman Chemical Company.

[0143] The PVB resins of this disclosure typically have molecular weights greater than 50,000 daltons, 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 weight-average molecular weight.

[0144] In addition to plasticizers, adhesion control agents ("ACAs") may also be added to the polymer resin to form a polymer intermediate layer. Generally, ACAs have the function of modifying and / or improving the adhesion of the intermediate layer to the glass panel when forming a laminated panel. Possible ACAs include, but are not limited to, magnesium carboxylates / salts. Other possible ACAs include those disclosed in U.S. Patent No. 5,728,472, which is incorporated herein by reference in whole, such as sodium residual acetate, potassium acetate, magnesium bis(2-ethyl butyrate), and / or magnesium bis(2-ethylhexanoate).

[0145] Other additives may be incorporated into the intermediate layer to enhance its performance in the final product and to impart specific additional properties to the intermediate layer. 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-promoting additives, lubricants, impact modifiers, nucleating agents, heat stabilizers, UV absorbers, UV stabilizers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcing additives, and fillers, among others known to those skilled in the art.

[0146] Various adhesion control agents ("ACAs") can be used in the interlayers of this disclosure to control the adhesion of the interlayer to the glass. In various embodiments of the interlayers of this disclosure, the interlayer may contain 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, or 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), sodium residual acetate, potassium acetate, magnesium bis(2-ethyl butyrate), and / or magnesium bis(2-ethylhexanoate).

[0147] Other additives may be incorporated into the intermediate layer to enhance its performance in the final product and to impart specific additional properties to the intermediate layer. 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-promoting additives, lubricants, impact modifiers, nucleating agents, thermal stabilizers, UV absorbers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcing additives, and fillers, among others known to those skilled in the art.

[0148] Unless otherwise indicated, all figures used in this specification and the claims, such as quantities of components, molecular weights, reaction conditions, and other properties, should be understood in all cases to be modified by the term "approximately." Therefore, unless otherwise indicated, the numerical parameters described in the following specification and the appended claims are approximations that may vary depending on the desired properties to be obtained by the invention. At a minimum, each numerical parameter should be interpreted in light of the number of significant figures reported and by applying common rounding techniques. Furthermore, the ranges described in this disclosure and the claims are intended to specifically include the entire range, not just the endpoint(s). For example, a range indicated as 0 to 10 is intended to disclose all integers between 0 and 10, such as 1, 2, 3, 4, etc., all decimals between 0 and 10, such as 1.5, 2.3, 4.57, 6.1113, etc., and the endpoints 0 and 10.

[0149] Although the numerical ranges and parameters describing the broad scope of the present invention are approximations, the numerical values ​​described in specific embodiments are intended to be reported accurately, taking into account the measurement methods. However, every numerical value inherently contains a certain degree of error that inevitably arises from the standard deviation observed during each of those test measurements.

[0150] It should be understood that the reference to one or more process steps does not preclude the existence of additional process steps that precede or follow combined enumerated steps or intervening process steps between these explicitly identified steps. Furthermore, unless otherwise indicated, the names of process steps, components, or other aspects of the information disclosed or claimed in this application, using letters, numbers, or similar symbols, are merely convenient means of identifying distinct activities or components, and the notations described may be arranged in any order.

[0151] As used herein, the singular forms "a," "an," and "the" refer to multiple objects unless the context clearly indicates otherwise. For example, C n References to alcohol equivalents are of multiple types. n It is intended to include the alcohol equivalent. Therefore, even the use of language such as "at least one" or "at least several" in one place is not intended to suggest that other uses of "a," "an," and "the" exclude plural references unless the context clearly indicates otherwise. Similarly, if language such as "at least some" is used in one place, it is not intended to mean "all" simply because such language is not present elsewhere, unless the context clearly indicates a different meaning.

[0152] As used herein, the term "and / or" means that when listing two or more items, any one of the listed items may be taken alone, or any combination of two or more of the listed items may be taken. For example, if a composition is described as containing components A, B, and / or C, the composition may include A alone, B alone, C alone, 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. The present invention can be further illustrated by the following embodiments, but it should be understood that these embodiments are included solely for illustrative purposes and are not intended to limit the scope of the invention unless otherwise specified. [Examples]

[0153] Example 1 Hydroblasting was performed on a 2-inch x 10-inch PVB core skin bilayer sample, core layer facing upwards, using a 3,300 psi Ryobi gas pressure washer powered by a 201cc engine with 5.6 brake horsepower. The water temperature was 25°C. The distance between the nozzle tip and the bilayer was 2.5–5.0 cm. The nozzle spray angle was 25 degrees. The angle of incidence of the hydroblast to the sheet was 45 degrees. Pressurized water from the pressure washer was moved along the direction of the machine to blast the core layer of the core skin bilayer. Judging from cross-sections of the bilayer observed with an optical microscope after hydroblasting, 25% of the core was removed in the first pass, 60% in the second pass, 80% in the third pass, and 100% in the sixth pass. The recovered skin layer could be reused for skin layer extrusion.

[0154] Example 2 Hydroblasting was performed on a 2-inch x 10-inch PVB core skin bilayer sample, core layer facing upwards, placed on a flat stainless steel plate, using a 3,300 psi Ryobi gas pressure washer with a 201cc engine of 5.6 brake horsepower. The water temperature was 35°C. The distance between the nozzle tip and the bilayer was 2.5–5.0 cm. The nozzle water spray angle was 25 degrees. The hydroblast incidence angle was 60 degrees. Pressurized water from the pressure washer was moved along the direction of the machine to blast the core layer of the core skin bilayer. Judging from cross-sections of the bilayer observed with an optical microscope after hydroblasting, 15% of the core was removed in the first pass, 40% in the second pass, 60% in the third pass, and 80% in the sixth pass. The recovered skin layer, containing only 20% of the original core layer volume, was reusable for extruding the skin layer to a level that did not cause optical quality problems.

[0155] Example 3 Hydroblasting was performed on a 2-inch x 10-inch PVB core-skin bilayer sample, core-layer facing upwards, placed on a flat stainless steel plate, using a 3,300 psi Ryobi gas pressure washer with a 201cc engine of 5.6 brake horsepower. The water temperature was 25°C. The distance between the nozzle tip and the bilayer was 2.5–5.0 cm. The nozzle water spray angle was 40 degrees. The hydroblast incidence angle was 45 degrees. Hydroblasting was not very effective, likely due to the wide nozzle spray angle. Judging from cross-sections of the bilayer observed with an optical microscope after hydroblasting, less than 20% of the core was removed after 10 passes.

[0156] Example 4 Hydroblasting was performed on a 2-inch x 10-inch PVB core-skin bilayer specimen, core-layer facing upwards, placed on a flat stainless steel plate, using a 3,300 psi Ryobi gas pressure washer with a 201cc engine of 5.6 brake horsepower. The water temperature was 25°C. The distance between the nozzle tip and the bilayer was 5.0–10.0 cm. The nozzle water spray angle was nearly zero, i.e., the nozzle was set to 0 degrees. The hydroblast incidence angle was 45 degrees. The water penetrated both the core and skin layers, puncturing the entire bilayer and failing to selectively remove the core layer from the bilayer.

[0157] Example 5 Hydroblasting was performed on a 2-inch x 10-inch PVB core-skin bilayer sample, core-layer facing upwards, placed on a flat stainless steel plate, using a 3,300 psi Ryobi gas pressure washer with a 201cc engine of 5.6 brake horsepower. The water temperature was 25°C. The distance between the nozzle tip and the bilayer was 15 cm. The nozzle water spray angle was 25 degrees. The hydroblast incidence angle was 30 degrees. Hydroblasting was not very effective due to the small incidence angle. Judging from cross-sections of the bilayer observed with an optical microscope after hydroblasting, less than 10% of the core was removed after 10 passes.

Claims

1. A process for separating a flexible poly(vinyl butyral) layer from a rigid poly(vinyl butyral) layer of a multilayer intermediate, the process comprising spraying a fluid onto the flexible poly(vinyl butyral) layer at a pressure and temperature sufficient to remove at least a portion of the flexible poly(vinyl butyral) layer from the rigid poly(vinyl butyral) layer.

2. The process according to claim 1, wherein the fluid includes water.

3. The process according to claim 1, wherein the temperature of the water is 10°C to 100°C, or 24°C to 60°C.

4. The process according to claim 2, wherein the water is sprayed through at least one nozzle or through a plurality of nozzles, for example, 5 to 25 nozzles.

5. The process according to claim 1, wherein the fluid is sprayed at a pressure such that the rigid poly(vinyl butyral) layer does not rupture.

6. The process according to claim 1, wherein the fluid is sprayed at a pressure such that the fluid is maintained in flow.

7. The process according to claim 1, wherein each of the plurality of nozzles has a tip, and the distance between at least one of the nozzle tips and the soft poly(vinyl butyral) layer is about 1 to about 10 cm.

8. The process according to claim 1, wherein each of the plurality of nozzles is provided with a tip, and the average distance between the nozzle tip and the soft poly(vinyl butyral) layer is about 1 to about 10 cm.

9. The process according to claim 1, wherein the plurality of nozzles share a common manifold.

10. The process according to claim 1, wherein the portion of the flexible poly(vinyl butyral) layer removed in the first pass is about 10% to about 50% by weight of the flexible poly(vinyl butyral) layer.

11. The process according to claim 1, wherein the soft poly(vinyl butyral) layer is removed by passing it through multiple times.

12. The process according to claim 1, wherein the portion of the flexible poly(vinyl butyral) layer to be removed is about 80% to about 100% by weight of the flexible poly(vinyl butyral) layer after passing through about 3 to about 5 times.

13. The process according to any one of claims 1 to 12, wherein at least one of the at least one nozzle has a spray angle of about 1 to about 40 degrees.

14. The process according to any one of claims 1 to 13, wherein the angle of incidence is approximately 20 degrees to approximately 60 degrees.

15. The process according to any one of claims 1 to 14, wherein at least one of the at least one nozzles has a spray angle of about 15 to about 30 degrees and an incidence angle of about 30 to about 50 degrees.

16. The process according to claim 1, wherein the fluid is sprayed through a series of nozzles arranged along the cross-machining direction of the multilayer intermediate layer, the machine direction of the multilayer intermediate layer, or both the cross-machining direction and the machine direction of the multilayer intermediate layer. The process according to claim 1, wherein the thickness of the rigid poly(vinyl butyral) layer is at least 1.5 times the thickness of the flexible poly(vinyl butyral) layer.

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

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

19. The process according to claim 1, wherein, when laminated on glass, the difference in 90° peel adhesion strength between the flexible poly(vinyl butyral) layer and the rigid poly(vinyl butyral) layer is at least 10 N / cm or at least 15 N / cm.

20. The process according to claim 1, wherein the difference in 90° peel adhesion strength between the rigid PVB and the soft PVB at contact is at least about 10 N / cm at a relative humidity of 25% and a temperature of 21°C.

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

22. The process according to claim 1, wherein the 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.

23. The process according to claim 1, wherein the difference in shear storage modulus at 20°C between the flexible poly(vinyl butyral) layer and the rigid poly(vinyl butyral) layer is at least 10 MPa.

24. The process according to claim 1, wherein the flexible poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer having a Tg of less than about 20°C.

25. The process according to claim 1, wherein the rigid poly(vinyl butyral) layer comprises a plasticized poly(vinyl butyral) polymer having a Tg greater than approximately 25°C.

26. The process according to claim 1, wherein the flexible poly(vinyl butyral) layer comprises a poly(vinyl butyral) polymer having a residual hydroxyl content of about 8% to about 13.5%.

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

28. The process according to claim 1, wherein the difference in residual hydroxyl content between the poly(vinyl butyral) polymer of the rigid poly(vinyl butyral) layer and the poly(vinyl) butyral polymer of the flexible poly(vinyl butyral) layer is at least 5% by weight.

29. The process according to claim 1, wherein the rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) having a plasticizer content of about 20 phr to about 50 phr.

30. The process according to claim 1, wherein the flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) having a plasticizer content of about 45 phr to about 150 phr.

31. The process according to claim 1, wherein the rigid poly(vinyl butyral) layer comprises poly(vinyl butyral) having a weight-average molecular weight of about 70,000 to 225,000.

32. The process according to claim 1, wherein the flexible poly(vinyl butyral) layer comprises poly(vinyl butyral) having a weight-average molecular weight of about 150,000 to about 600,000.

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