CN118176221A

CN118176221A - Recovery of recycled poly (vinyl butyral) polymer

Info

Publication number: CN118176221A
Application number: CN202280072200.0A
Authority: CN
Inventors: 马亦农
Original assignee: Solutia Inc
Current assignee: Solutia Inc
Priority date: 2021-10-28
Filing date: 2022-10-27
Publication date: 2024-06-11

Abstract

A method of recovering poly (vinyl butyral) (PVB). The method includes the step of providing recycled PVB to a recycling system. An additional step includes adding a solvent to the recycled PVB to dissolve the recycled PVB and form a PVB solution. An additional step includes adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture. An additional step includes heating the PVB reaction mixture. An additional step includes filtering the PVB reaction mixture to remove solids. A further step includes removing solvent and butyraldehyde from the PVB reaction mixture to obtain recycled PVB.

Description

Recovery of recycled poly (vinyl butyral) polymer

Technical Field

The present invention relates to the field of poly (vinyl butyral) resin manufacture, and in particular, the present invention is in the field of post-consumer poly (vinyl butyral) recovery and reuse.

Background

Laminated glass panels (e.g., automotive windshields and architectural safety glass) are typically composed of two sheets of glass laminated together with an interposed plasticized polymer layer. Poly (vinyl butyral) ("PVB") is a common polymer that commonly forms the major component in the polymeric interlayers of most automotive windshields and architectural safety glass. Typically, PVB resins are manufactured by synthetic methods that begin with the separation of ethane directly from natural gas or from petroleum refining processes. The ethane is then steam cracked to produce ethylene (ethane/ethylene) which is used with the acetic acid feedstock to produce vinyl acetate monomer. Vinyl acetate monomer is polymerized into poly (vinyl acetate) by free radical polymerization. Poly (vinyl acetate) is hydrolyzed to poly (vinyl alcohol) and then reacted with butyraldehyde to form poly (vinyl butyral).

The above synthetic methods are energy intensive and depend on the use of non-renewable raw materials. Thus, the prospect of recycling PVB from post-consumer recycled (recycle) PVB resins has long been recognized in the art as a potentially valuable source of PVB, which is less costly to produce than virgin PVB resins, and can significantly reduce the environmental footprint of PVB production. Exemplary sources of post-consumer recycled PVB include previously used automotive windshields and architectural safety glasses, as well as other previously used consumer products, such as electrical devices (e.g., solar photovoltaic devices) and electronic display devices.

Although there has long been a need in the art to recycle post-consumer PVB, there are several problems associated with recycling post-consumer PVB. For example, post-consumer PVB typically comprises different mixtures of different PVB compositions, as obtained from various products and/or different manufacturers. Thus, post-consumer PVB blends include PVB having different poly (vinyl butyral) compositions, including different polyvinyl alcohol contents. This compositional difference in the recycled PVB mixture invariably results in unacceptably high haze and/or discoloration of the PVB, despite the removal of other contaminants by the PVB. In particular, when PVB materials having significant compositional differences are mixed together, chemical incompatibility results in hazy or cloudy materials due to the immiscible domains having different refractive indices, which greatly limits their use in recycling.

In view of the foregoing, there is a need for processing post-consumer PVB in a manner that reduces or eliminates compositional differences in recycled PVB material such that the resulting PVB is a transparent polymer having a uniform composition and can be used to prepare new PVB interlayers, e.g., can be incorporated into new laminated glass panels.

Drawings

Fig. 1 is a flow chart of a method of recycling post-consumer PVB according to an embodiment of the present invention;

FIG. 2 is a schematic view of a laminated glass panel comprising a pair of glass sheets opposite a polymer interlayer, wherein the polymer interlayer comprises three layers having a pair of skin layers opposite a core layer; and

FIG. 3 is another schematic view of a laminated glass panel comprising a pair of glass sheets opposite a polymer interlayer, wherein the polymer interlayer has a wedge shape.

Disclosure of Invention

One aspect of the present invention relates to a method of recovering poly (vinyl butyral) (PVB). The method includes the step of providing recycled PVB to the recycling (reclamation) system. Additional steps include adding a solvent to the recycled PVB to dissolve the recycled PVB and form a PVB solution. Additional steps include adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture. An additional step includes heating the PVB reaction mixture. Additional steps include filtering the PVB reaction mixture to remove solids. Further steps include removing solvent and butyraldehyde from the PVB reaction mixture to obtain recycled PVB.

Another aspect of the invention relates to recycled poly (vinyl butyral) (PVB). The recycled PVB is prepared by a process that includes the step of providing recycled PVB to a recycling system. Additional steps include adding a solvent to the recycled PVB to dissolve the recycled PVB and form a PVB solution. Additional steps include adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture. An additional step includes heating the PVB reaction mixture. Additional steps include filtering the PVB reaction mixture to remove solids. Further steps include removing solvent and butyraldehyde from the PVB reaction mixture to obtain recycled PVB.

Another aspect of the invention relates to a laminated glass panel comprising an interlayer comprising recycled poly (vinyl butyral) (PVB). The recycled PVB is prepared by a process that includes the step of providing recycled PVB to a recycling system. Additional steps include adding a solvent to the recycled PVB to dissolve the recycled PVB and form a PVB solution. Additional steps include adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture. An additional step includes heating the PVB reaction mixture. Additional steps include filtering the PVB reaction mixture to remove solids. Further steps include removing solvent and butyraldehyde from the PVB reaction mixture to obtain recycled PVB.

Detailed Description

Embodiments of the present invention relate to methods of recovering, recycling, and/or reusing poly (vinyl butyral) ("PVB"). More particularly, embodiments of the present invention relate to methods of recycling post-consumer recycled PVB to obtain PVB of sufficient quality to form a polymer interlayer and/or a laminated glass panel comprising a polymer interlayer. In more detail, fig. 1 illustrates an exemplary method of recycling PVB according to an embodiment of the present invention. The method includes a step S1 of providing post-consumer recycled PVB material to a recycling system. Post-consumer PVB can include at least some plasticizer. The method can include the additional step S2 of adding a solvent to the recycled PVB material to dissolve the recycled PVB material and form a PVB solution. Additional step S3 can include adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture. During and/or after step S3, the PVB reaction mixture can be heated to allow the different PVB components from the recycled PVB material to rebalance into a uniform composition. Additional step S4 can include adding a base to the PVB reaction mixture to neutralize the mixture. Additional step S5 can include filtering the neutralized PVB reaction mixture to remove salts and other solids. Additional step S6 can include removing solvent and butyraldehyde from the neutralized and filtered PVB mixture to obtain recycled PVB. The recycled PVB can retain a majority of the plasticizer originally contained in the recycled PVB such that the recycled PVB is at least partially plasticized. Additional step S7 can include granulating the recycled PVB. In some embodiments, step S7 can further comprise washing the pelletized PVB to remove other salt impurities. The resulting PVB recovered in the above steps can be of sufficient quality (e.g., sufficient transparency and/or color) for use in commercial products, such as for use in the manufacture of polymer interlayers and/or laminated glass panels comprising the polymer interlayer.

In more detail, the recycled PVB provided to the regeneration system of step S1 can include/or be post-consumer recycled PVB. Such post-consumer recycled PVB can include materials recovered from previously manufactured and/or used automotive windshields and architectural safety glass. Recycled PVB material can also include waste or post-consumer materials from other consumer products, such as electrical devices (e.g., solar photovoltaic devices), electronic display devices, and the like. Recycled PVB materials can have a variety of PVB compositions, such as varying amounts of polyvinyl alcohol ("PVOH"). For example, a first portion of recycled PVB can have an amount of PVOH of about 10 to 15 weight percent (wt%) and a second portion of recycled PVB can have an amount of PVOH of about 15wt% to 20wt%, and a third portion of recycled PVB can have an amount of PVOH of about 20wt% to 25 wt%. If such recycled PVB is mixed together according to the previously used recycling methods, such different amounts of PVOH typically result in hazy, discolored polymers. Other ranges of PVOH amounts (or different PVOH ranges) are also possible, depending on the materials used and the source of the materials.

Recycled PVB can also include an amount of plasticizer that is typically used to soften the PVB and/or reduce the glass transition temperature T _g of the PVB. Contemplated plasticizers include, but are not limited to, polyacids, polyols, triethylene glycol di- (2-ethylbutyrate), triethylene glycol di- (2-ethylhexanoate) (known as "3-GEH"), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, dioctyl adipate, hexyl cyclohexyl adipate, mixtures of heptyl and nonyl adipates, diisononyl adipates, heptyl and dibutyl sebacates, and polymeric plasticizers such as oil-modified sebacate alkyd resins and mixtures of phosphate and adipate esters, as well as mixtures and combinations thereof. In some embodiments, 3-GEH is particularly preferred. Other examples of suitable plasticizers may include, but are not limited to, tetraethyleneglycol di- (2-ethylhexanoate) ("4-GEH"), di (butoxyethyl) adipate, and bis (2- (2-butoxyethoxy) ethyl) adipate, dioctyl sebacate, nonylphenyltetraglycol, and mixtures thereof. Typically, the plasticizer content of a PVB material (e.g., resin or waste) will be measured in parts per hundred parts of resin ("phr") on a weight/weight basis. For example, if 30 grams of plasticizer were added to 100 grams of polymer resin, the plasticizer content of the resulting plasticized polymer would be 30phr. Recycled PVB materials can have various amounts and/or types of plasticizers.

The recycled PVB material can be cut, chopped, and/or shredded to form small diameter (e.g., 2-5 mm) pieces, particles, or flakes of PVB material (referred to herein as "PVB material flakes"). Sheets of PVB material are typically combined together to form a mixed composition sheet (e.g., having a mixed amount of PVOH or other elements). Such sheets of PVB material can be provided to a recycling system, which can be in the form of a single batch reactor recycle system or a continuous recycling recycle system. For example, the single batch reactor may comprise a tank in the form of a continuous stirred tank reactor (CSTR, continuous stirred-tank reactor) or other similar reactor. One or more (or all) of the steps of the methods described herein can be performed in a single batch reactor. Alternatively, a continuous regeneration system may be used, having a plurality of interconnected tanks (e.g., CSTRs). In a continuous regeneration system, each step may be performed independently in one or more of a plurality of tanks. Benefits of a continuous regeneration system may include higher throughput compared to a single batch reactor.

Turning to step S2, the solvent added to the recycled PVB material (e.g., to a single batch reactor recycle system or a continuous regeneration recycle system) can comprise various solvents sufficient to dissolve the recycled PVB material and form a solution. Examples of suitable solvents may include alcohols such as ethanol, methanol or isopropanol. The solvent is configured to dissolve the recycled PVB material to form a PVB solution in the form of a turbid, viscous solution. In some embodiments, an amount of water can also be added to the PVB solution.

Turning to step S3, a catalyst and butyraldehyde can be added to the PVB solution to form a PVB reaction mixture. The catalyst may include various catalysts such as sulfuric acid, sulfonic acid, methanesulfonic acid, or p-toluenesulfonic acid (p-toluenesulfonic acid). Upon addition of catalyst and butyraldehyde, the PVB reaction mixture can comprise about 15wt% to 25wt% recycled PVB material (or 17wt% to 23wt%, or 18wt% to 22wt%, or about 20wt% recycled PVB material), about 75wt% to 85wt% solvent (or 77wt% to 83wt%, or 78wt% to 82wt%, or about 80wt% solvent), about 1wt% butyraldehyde (or 0.25wt% to 2.0wt%, or 0.5wt% to 1.5wt%, or 0.75wt% to 1.25wt% butyraldehyde), about 0.3wt% water (or 0.1wt% to 0.5wt%, or 0.2wt% to 0.4wt% water), and/or about 0.05wt% catalyst. In some specific embodiments, the amount of catalyst can be at least 0.02wt%, at least 0.03wt%, at least 0.04wt%, at least 0.05wt%, at least 0.06wt%, at least 0.07wt%, at least 0.08wt% of the PVB reaction mixture. In other embodiments, the catalyst can comprise from 0.02wt% to 0.08wt%, from 0.03wt% to 0.07wt%, from 0.04wt% to 0.06wt%, or about 0.05wt% of the PVB reaction mixture.

After step S3, the PVB reaction mixture can be heated for a period of time. The mixture may be heated to a temperature of 65 ℃ to 85 ℃, 70 ℃ to 80 ℃, 70 ℃ to 78 ℃, or about 78 ℃. The period of heating may be at least 1 hour, at least 2 hours, at least 3 hours and/or 1 to 5 hours, 2 to 4 hours or about 3 hours. The heat, catalyst, and butyraldehyde allow the PVB reaction mixture to rebalance the various PVB components in the recycled PVB material to a uniform composition. For example, the PVB reaction mixture will rebalance such that the PVB portion of the mixture will reach a uniform PVOH percentage.

Turning to step S4, this step includes cooling the PVB reaction mixture and adding a base to neutralize the mixture. In some embodiments, the PVB reaction mixture can be cooled to a temperature below the temperature heated in step S3. In some embodiments, the base may include potassium hydroxide ("KOH"), sodium hydroxide, and the like. In some embodiments, the amount of base added to the mixture may be about 0.05wt% of the mixture. In some specific embodiments, the amount of base can be at least 0.02 wt.%, at least 0.03 wt.%, at least 0.04 wt.%, at least 0.05 wt.%, at least 0.06 wt.%, at least 0.07 wt.%, at least 0.08 wt.% of the PVB reaction mixture. In other embodiments, the base can comprise from 0.02wt% to 0.08wt%, from 0.03wt% to 0.07wt%, from 0.04wt% to 0.06wt%, or about 0.05wt% of the PVB reaction mixture. Regardless, the embodiments can provide a sufficient amount of base to be added such that the pH of the PVB reaction mixture (about 2.0 to 2.5 prior to neutralization) reaches about 5.0 to about 7.0, or at least about 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.7, 6.8, 6.9, or 7.0, or about 5.1 to about 6.9, or about 5.2 to about 6.8, or about 5.3 to about 6.7, or about 5.4 to about 6.7, or about 5.5 to about 6.7, or about 5.6 to about 6.7, or about 5.7 to about 6.7, or about 5.8 to about 6.7, or about 5.9 to about 6.7.

Turning to step S5, this step includes filtering the neutralized PVB reaction mixture to remove salts and other solids from the mixture. In some embodiments, the filter may include a screen, mesh, cloth, or other similar filter element. With respect to step S6, solvent and butyraldehyde can be removed from the neutralized and filtered PVB mixture to obtain recycled PVB. As will be described in greater detail below, the recycled PVB can be plasticized (i.e., the recycled PVB retains at least some of the primary plasticizer contained as part of the primary recycled PVB). The solvent and butyraldehyde can be removed via evaporative distillation (e.g., via an evaporation column), steam stripping, extrusion evaporation, and the like. In some embodiments, the solvent and butyraldehyde can be recycled and reused (e.g., in additional steps S2-S6) to recover additional PVB from the recycled PVB.

Finally, turning to step S7, the recovered PVB can be pelletized for use in an extrusion process (e.g., via an extruder or co-extruder) to form a PVB interlayer and/or a laminated glass panel comprising the PVB interlayer. The recovered PVB can be pelletized via a pelletizer. In some embodiments, step S7 can also include a further washing step whereby the pelletized recycled PVB is again washed to remove remaining salts or other impurities. Regardless, the resulting recycled PVB can be of sufficient quality and/or clarity for use in commercial products, such as for use in manufacturing polymer interlayers and/or laminated glass panels comprising a polymer interlayer. Notably, recycled PVB can retain substantially all of the plasticizer originally contained in the recycled PVB. For example, in some embodiments, the recycled PVB loses no more than 1-20%, no more than 2-15%, no more than 3-10%, or about 5% of the plasticizer contained in the virgin recycled PVB. For example, the recycled PVB resulting from the above-described recycling methods can have the same or nearly the same amount of plasticizer as originally present in the recycled PVB.

In certain embodiments, steps S1 through S7 described above may be varied, added, and/or subtracted. For example, in some embodiments, deionized water can be added to the neutralized PVB reaction mixture after the PVB reaction mixture is neutralized to effect precipitation of the mixture. Specifically, for example, water can be added to the neutralized PVB reaction mixture in a high intensity mixing tank for precipitation to produce a slurry comprising separated solvent, butyraldehyde, plasticized PVB, and water. A water filling and draining wash process may alternatively be used to facilitate such precipitation. Regardless, the recycled PVB can be filtered and dried to produce a PVB resin having an amount of plasticizer that is initially contained in the recycled PVB (e.g., 3-5 phr).

PVB recovered using the recovery method steps described above can be used to form a polymer interlayer and/or a laminated glass panel comprising a polymer interlayer. As used herein, the terms "polymeric interlayer sheet", "interlayer", "polymeric layer" and "polymeric melt sheet" may refer to a single layer sheet or a multi-layer interlayer. As the name implies, a "monolayer sheet" is a single polymer layer extruded as a layer. In another aspect, the multilayer interlayer may include multiple layers including a single extruded layer, a co-extruded layer, or any combination of single and co-extruded layers. Thus, the multilayer interlayer may include, for example: two or more single layer sheets ("multi-layer sheets") bonded together; two or more layers are coextruded together ("coextruded sheet"); two or more coextruded sheets bonded together; a combination of at least one single layer sheet and at least one coextruded sheet; and a combination of at least one multilayer sheet and at least one coextruded sheet. In various embodiments of the present invention, the multilayer interlayer comprises at least two polymeric layers (e.g., a monolayer or a coextruded multilayer) disposed in direct contact with each other, wherein each layer comprises a polymeric resin. The term "resin" as used herein refers to a polymeric component (e.g., PVB) that is removed from a mixture resulting from acid catalysis and subsequent neutralization of a polymer precursor. Typically, plasticizers, such as those discussed above, are added to the resin to produce a plasticized polymer. Additionally, the resin may have other components in addition to the polymer and plasticizer, including; such as acetates, salts, and alcohols.

While the recycling step described above can be performed to obtain recycled PVB that contains at least some inherent plasticizer (e.g., 3-5phr plasticizer), embodiments can require the addition of additional plasticizer to the PVB prior to the PVB being used to form the polymer interlayer and/or laminated glass panel comprising the polymer interlayer. For example, in some embodiments, additional amounts of 25-50phr, 25-45phr, 30-40phr, or 33-35phr can be added to the resulting PVB prior to manufacturing the polymer interlayer and/or the laminated glass panel. Higher or lower amounts of plasticizer may be added as needed depending on the desired characteristics and application.

Once a sufficient amount of plasticizer is added to the recycled PVB, it is contemplated that the polymeric interlayer sheet can be produced by any suitable method known to one of ordinary skill in the art of producing polymeric interlayer sheets capable of being used in multi-layer panels (e.g., glass laminates). For example, it is contemplated that the polymeric interlayer sheet may be formed by solution casting, compression molding, injection molding, melt extrusion, melt blowing, or any other procedure known to one of ordinary skill in the art for producing and manufacturing polymeric interlayer sheets. Furthermore, in embodiments where multiple polymer interlayers are used, it is contemplated that these multiple polymer interlayers can be formed by coextrusion, blown film, dip coating, solution coating, knife coating, paddle coating, air knife coating, printing, powder coating, spray coating, or other methods known to those of ordinary skill in the art. While all methods of producing polymeric interlayer sheets known to those of ordinary skill in the art are considered possible methods of producing polymeric interlayer sheets described herein, the present application will focus on polymeric interlayer sheets produced by extrusion and/or coextrusion processes.

During extrusion, thermoplastic resins and plasticizers, including any of those described above, are typically pre-mixed and fed into an extruder apparatus. Additives such as colorants and UV inhibitors (in liquid, powder or pellet form) may be used and may be mixed into the thermoplastic resin or plasticizer before it reaches the extruder apparatus. These additives are incorporated into the thermoplastic polymer resin and incorporated into the resulting polymeric interlayer sheet by extension to improve certain properties of the polymeric interlayer sheet and its performance in the final multiple layer glass panel product.

In the extruder apparatus, the pellets of thermoplastic raw material and the plasticizer, including any of those resins, plasticizers, and other additives described above, are further mixed and melted to produce a melt that is substantially uniform in temperature and composition. Embodiments of the present invention may provide a melt temperature of about 200 ℃. Once the melt reaches the end of the extruder device, the melt will be advanced into the extruder die. An extruder die is a component of an extruder apparatus that imparts its profile to the final polymeric interlayer sheet product. The die typically has an opening defined by the die lip that is substantially larger in one dimension than in the vertical dimension. Typically, the mold is designed such that the melt flows uniformly from the cylindrical profile exiting the mold and into the end profile shape of the product. Various shapes can be imparted to the final polymeric interlayer sheet by the mold, provided that a continuous profile is present. In its most basic sense, extrusion is generally a process used to create objects of a fixed cross-sectional profile. This is accomplished by pushing or pulling the material through a die having the desired cross section of the final product.

In some embodiments, a coextrusion process may be used. Coextrusion is a method of simultaneously extruding multiple layers of polymeric material. Typically, this type of extrusion utilizes two or more extruders to melt different thermoplastic melts of different viscosities or other characteristics and deliver them into the desired final form through a coextrusion die at a stable volumetric throughput. For example, the multi-layer interlayers of the present invention (e.g., in the form of a three-layer interlayer) can be preferably coextruded using a multi-manifold coextrusion apparatus comprising a first die manifold, a second die manifold, and a third die manifold. The coextrusion apparatus can be operated by simultaneously extruding the polymer melt from each manifold through a die and out of an opening, wherein the multilayer interlayers are extruded as a composite of three separate polymer layers. The polymer melt may flow through the mold such that the core layer is located between the skin layers, resulting in the fabrication of a three-layer sandwich with the core layer sandwiched between the skin layers. The die opening may include a pair of die lips on either side of the opening. The skin layer may be in contact with the die lip, taking into account the positional orientation of the polymer melt. In any event, by adjusting the distance between the lips at the die opening, the interlayer thickness can be varied.

Typically, a polymer interlayer having three layers will be used to make laminated glass panels. For example, in some embodiments of the present application, the increased acoustic attenuation characteristics of the soft layer combine with the mechanical strength of the hard/rigid layer to create a multi-layer sandwich. In these embodiments, the middle soft layer is sandwiched between two hard/rigid outer layers. This construction of (hard)/(soft)/(hard) results in an easy to handle multilayer interlayer that can be used in conventional lamination processes and can be constructed from relatively thin and light layers. The soft core layer is generally characterized by a lower residual hydroxyl content, a higher plasticizer content, and/or a lower glass transition temperature than the relatively harder skin layer.

The following provides a simplified description of the manner in which a multiple layer glass panel is typically produced in combination with interlayers formed according to the above-described methods. First, as described above, the multi-layer interlayer may be coextruded using a multi-manifold coextrusion apparatus. The apparatus operates by simultaneously extruding the polymer melt from each manifold toward an extrusion opening. The properties of the layer can be varied by adjusting the properties (e.g., temperature and/or opening size) of the die lip at the extrusion opening. Once formed, the interlayer sheet can be placed between two glass substrates and any excess interlayer trimmed from the edges, creating an assembly. It is not uncommon to place multiple polymer interlayer sheets or polymer interlayer sheets with multiple layers (or a combination of both) within two glass substrates, creating a multiple layer glass panel with multiple polymer interlayers. Air is then removed from the assembly by suitable processes or methods known to those skilled in the art; such as by nip rollers, vacuum bags, or other de-gassing mechanisms. Additionally, the interlayer is partially pressed onto the substrate by any method known to one of ordinary skill in the art. In the final step, this pre-bonding is made more durable by a high temperature and high pressure lamination process or any other method known to those of ordinary skill in the art, such as, but not limited to, high pressure steam, in order to form the final overall structure.

In view of the above, a multi-layer panel is composed of two sheets of glass or other suitable substrate with a polymeric interlayer sheet or sheets sandwiched therebetween. Multilayer panels are typically produced by placing at least one polymeric interlayer sheet between two substrates to create an assembly. Fig. 2 shows a multi-layer panel 10 comprising a pair of glass sheets 12 with a multi-layer interlayer sandwiched therebetween. The multi-layer sandwich is constructed as a three-layer sandwich having three separate polymeric sandwich sheets including a soft core layer 14 and two relatively stiff skin layers 16 on either side of the core layer 14. As described above, such a glass panel incorporating such three layers may have excellent acoustic properties due to the sound attenuation provided by the soft core layer.

In some embodiments, the interlayer (e.g., core layer 14 and skin layer 16) has a generally constant or uniform thickness around the length of the interlayer (see, e.g., fig. 2). However, in alternative embodiments, as shown in FIG. 3, the interlayer may have at least one region of non-uniform thickness. For example, the sandwich of core layer 14 and skin layer 16 may be wedge-shaped such that the thickness of the sandwich varies (e.g., linearly) around the length of the sandwich. In some such embodiments, the thickness of the interlayer may vary due to variations in the thickness of the core layer 14 (i.e., the skin layer 16 has a generally constant thickness). Alternatively, the thickness of the interlayer may vary due to variations in the thickness of the skin layer 16 (i.e., the core layer 14 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 14 and the skin layer 16. As described above, such a glass panel incorporating such three layers may have excellent acoustic properties due to the sound attenuation provided by the soft core layer. Furthermore, due to the non-uniformity in thickness of the three layers, the glass panel may provide beneficial characteristics for head-up displays ("HUDs") by reducing unwanted image projection defects (e.g., reducing ghosting).

Advantageously, laminated glass panels formed from at least one polymeric layer/interlayer comprising recycled PVB obtained by the recycling process described above can have excellent optical quality. Clarity is a measure of the optical quality of the laminate. Transparency can be determined by measuring the haze value or percentage of the laminate. Haze is the percentage of scattered light that is directed away from the direction of the incident beam by more than a specified angle. Haze may be measured using a haze meter or spectrophotometer known to those skilled in the art, and using light source C according to ASTM D1003-procedure B, at an observation angle of 2 degrees. In some embodiments, glass panels, polymer layers, and/or interlayers incorporating recycled PVB can have a haze value of less than 5%, less than about 4%, less than about 3%, less than about 2%, less than about 1%, or less than about 0.5%, as described herein.

Color is another measure of the optical quality of the laminate. Significant discoloration or yellowing of the laminate is generally undesirable. Such discoloration is typically measured according to the yellowness index ("YI") using an optical or spectrophotometric meter known to those skilled in the art and according to ASTM D1925. In some embodiments, glass panels, polymer layers, and/or interlayers incorporating recycled PVB can have a YI of less than 12, less than 10, less than 8, less than 6, less than 5, less than about 4, less than about 3, less than about 2, less than about 1, or less than about 0.5, as described herein. In the examples provided below, haze and YI values are measured as described above according to ASTM D1003 and ASTM D1925, respectively.

Examples

Example 1

A one liter three-neck jacketed glass reactor was charged with a mixture of 800 parts SD29 alcohol, 200 parts recycled PVB sheet (composed of 55 parts plasticizer and 145 parts average 19wt% pvoh resin mixture), 15 parts butyraldehyde, 3 parts water and 0.5 parts sulfuric acid. The mixture was stirred and heated to 78 ℃, wherein the mixture was maintained for two to four hours. The resulting mixture was cooled to 65℃and neutralized with 0.46 parts of KOH until the pH of the mixture reached 6. The resulting cloudy mixture was filtered to give a clear, viscous solution. This solution was cast into a PVB film with 35phr of additional plasticizer and allowed to evaporate to give a clear film. The film was pressed into a plasticized PVB sheet having a thickness of 0.772mm and laminated between two sheets of 2.3mm glass. The haze of the laminate was measured as a value below 1.0% and the YI of the laminate was measured as a value below 2.

Example 2

A one liter three-neck jacketed glass reactor was charged with a mixture of 800 parts SD29 alcohol, 200 parts recycled three-layer acoustic PVB sheet (composed of 60 parts plasticizer and 140 parts average 17.4wt% pvoh resin mixture), 15 parts butyraldehyde, 3 parts water and 0.5 parts sulfuric acid. The mixture was stirred and heated to 78 ℃, wherein the mixture was maintained for two to four hours. The resulting mixture was cooled to 65℃and neutralized with 0.46 parts of KOH until the pH of the mixture reached 6. The resulting cloudy mixture was then filtered to give a clear, viscous solution. The solution was cast into PVB film with 35phr of additional plasticizer and allowed to dry to give a clear film. The film was pressed into a plasticized PVB sheet having a thickness of 0.772mm and laminated between two sheets of 2.3mm glass. The haze of the laminate was measured as a value below 1.0% and the YI of the laminate was measured as a value below 2.

Example 3

A mixture of 800 parts SD29 alcohol, 150 parts 18.7wt% PVB resin of pvoh and 20 parts recycled three-layer acoustic PVB sheet (consisting of a resin mixture of 6 parts plasticizer and 14 parts average 17.4wt% pvoh), 15 parts butyraldehyde, 3 parts water and 0.5 parts sulfuric acid was charged to a one liter three-neck jacketed glass reactor. The mixture was stirred and heated to 78 ℃, wherein the mixture was maintained for two to four hours. The resulting mixture was cooled to 65℃and neutralized with 0.46 parts of KOH until the pH of the mixture reached 6. The cloudy mixture was further mixed with 8 equivalents of water in a high intensity mixer to form a PVB slurry. The alcohol and residual butyraldehyde are removed by filling with deionized water and washing with water, and the resulting slurry is filtered. After drying, the PVB was pressed with 35phr of additional plasticizer to a plasticized PVB sheet having a thickness of 0.772 mm. A PVB sheet was laminated between two pieces of 2.3mm glass. The haze of the laminate was measured as a value below 1.0% and the YI of the laminate was measured as a value below 1.

Example 4

A one liter three-necked jacketed glass reactor was charged with a mixture of 800 parts SD29 alcohol, 150 parts PVB resin of 18.7 wt.% pvoh, and 15 parts recycled three-layer acoustic PVB sheet (consisting of a resin mixture of 4.5 parts plasticizer and 10.5 parts average 17.4 wt.% pvoh), 15 parts butyraldehyde, 3 parts water, and 0.5 parts sulfuric acid. The mixture was stirred and heated to 78 ℃, wherein the mixture was maintained for two to four hours. The resulting mixture was cooled to 65℃and neutralized with 0.46 parts of KOH until the pH of the mixture reached 6. The cloudy mixture was further mixed with 8 equivalents of water in a high intensity mixer to form a PVB slurry. The alcohol and residual butyraldehyde are removed by filling with deionized water and washing with water, and the resulting slurry is filtered. After drying, the PVB was pressed with 36phr of additional plasticizer to a plasticized PVB sheet having a thickness of 0.772 mm. A PVB sheet was laminated between two pieces of 2.3mm glass. The haze of the laminate was measured as a value below 1.0% and the YI of the laminate was measured as a value below 1.

Example 5

A one liter three-neck jacketed glass reactor was charged with a mixture of 800 parts SD29 alcohol, 200 parts recycled three-layer acoustic PVB sheet (composed of 60 parts plasticizer and 140 parts average 17.4wt% pvoh resin mixture), 15 parts butyraldehyde, 3 parts water and 0.5 parts sulfuric acid. The mixture was stirred and heated to 78 ℃, wherein the mixture was maintained for two to four hours. The resulting mixture was cooled to 65℃and neutralized with 0.46 parts of KOH until the pH of the mixture reached 6. The cloudy mixture was further mixed with 8 equivalents of water in a high intensity mixer to form a PVB slurry. The alcohol and residual butyraldehyde are removed by filling with deionized water and washing with water, and the resulting slurry is filtered. After drying, the PVB was pressed into a sheet of 0.772mm thickness with 40phr of additional plasticizer. A PVB sheet was laminated between two pieces of 2.3mm glass. The haze of the laminate was measured as a value below 1.0% and the YI of the laminate was measured as a value below 1.

While the invention has been disclosed in connection with certain embodiments, including what is presently considered to be the preferred embodiments, the detailed description is intended to be illustrative, and should not be construed as limiting the scope of the disclosure. As will be appreciated by those of ordinary skill in the art, embodiments other than those described in detail herein are also encompassed by the present invention. Modifications and variations may be made to the described embodiments without departing from the spirit and scope of the invention.

It should also be understood that any range, value, or characteristic given for any single component of the disclosure may be used interchangeably with any range, value, or characteristic given for any other component of the disclosure, where compatible, to form embodiments having defined values for the components, as given throughout this document. For example, a polymer layer may be formed that includes any given range of plasticizer content in addition to any given range of residual hydroxyl content, where appropriate, to form many permutations within the scope of the present invention, but this will be difficult to list.

The invention and its preferred embodiments will now be further described in terms of numbered items 1 to 27.

Item 1. A method of recovering poly (vinyl butyral) (PVB), the method comprising the steps of:

(a) Providing recycled PVB to a recycling system;

(b) Adding a solvent to the recycled PVB to dissolve the recycled PVB and form a PVB solution;

(c) Adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture;

(d) Heating the PVB reaction mixture;

(e) Filtering the PVB reaction mixture to remove solids; and

(F) Solvent and butyraldehyde are removed from the PVB reaction mixture to obtain recycled PVB.

Item 2. The method of item 1, wherein the recycled PVB material provided during step (a) is formed to comprise materials having different polyvinyl alcohol contents.

Item 3. The method of item 1, wherein the regeneration system to which recycled PVB is provided in step (a) comprises a batch reactor system.

Item 4. The method of item 1, wherein the solvent added during step (b) comprises an alcohol.

Item 5. The method of item 4, wherein the alcohol is ethanol, methanol, or isopropanol.

Item 6. The method of item 1, wherein the catalyst added during step (c) comprises sulfuric acid.

Item 7. The method of item 1, wherein the heating of step (d) comprises heating the PVB reaction mixture to a temperature between 70 ℃ and 80 ℃.

The method of item 1, wherein the heating of step (d) comprises heating the PVB reaction mixture for a period of 2-4 hours.

Item 9. The method of item 1, wherein the solids filtered during step (e) comprise salts.

Item 10. The method of item 1, wherein the solvent and butyraldehyde removed during step (f) are further recycled for use in recycling additional PVB.

Item 11. The method of item 1, further comprising the step of neutralizing the PVB reaction mixture by adding a base to the PVB reaction mixture.

The method of clause 11, wherein the base comprises potassium hydroxide.

Item 13. The method of item 1, further comprising the step of granulating the recycled PVB.

Item 14. The method of item 12, further comprising the step of washing the pelletized PVB to remove salt impurities.

Item 15. The method of item 1, wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, wherein the recycled PVB obtained in step (f) comprises a second amount of plasticizer, wherein the second amount of plasticizer differs from the first amount of plasticizer by less than about 10%.

Item 16. A recycled poly (vinyl butyral) (PVB), wherein the PVB is prepared by a method comprising:

(a) Providing recycled PVB to a recycling system;

(d) Heating the PVB reaction mixture;

(e) Filtering the PVB reaction mixture to remove solids; and

The PVB of item 16, wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, wherein the recycled PVB obtained in step (f) comprises a second amount of plasticizer, wherein the second amount of plasticizer differs from the first amount of plasticizer by less than about 10%.

The method of item 16, wherein the solvent added during step (b) comprises an alcohol.

The method of clause 18, wherein the alcohol is ethanol, methanol, or isopropanol.

Item 20. The PVB of item 16, further comprising the step of adding an additional amount of a plasticizer to the recycled PVB.

Item 21. A laminated glass panel comprising an interlayer comprising recycled poly (vinyl butyral) (PVB), wherein the PVB is produced by a method comprising:

(a) Providing recycled PVB to a recycling system;

(d) Heating the PVB reaction mixture;

(e) Filtering the PVB reaction mixture to remove solids; and

The laminated glass panel of item 21, wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, wherein the recycled PVB obtained in step (f) comprises a second amount of plasticizer, wherein the second amount of plasticizer differs from the first amount of plasticizer by less than about 10%.

Item 23. The laminated glass panel of item 21, wherein the solvent added during step (b) comprises an alcohol.

Item 24. The laminated glass panel of item 23, wherein the alcohol is ethanol, methanol, or isopropanol.

Item 25. The laminated glass panel of item 21, wherein the laminated glass panel has a haze value of less than 1% and a yellowness index of less than 2.

Claims

1. A method of recovering poly (vinyl butyral) (PVB), comprising the steps of:

(a) Providing recycled PVB to a recycling system;

(d) Heating the PVB reaction mixture;

(e) Filtering the PVB reaction mixture to remove solids; and

(F) The solvent and the butyraldehyde are removed from the PVB reaction mixture to obtain recycled PVB.

2. The method of claim 1, wherein the recycled PVB material provided during forming step (a) comprises materials having different polyvinyl alcohol contents.

3. The method of claim 1 or 2, wherein the regeneration system to which the recycled PVB is provided in step (a) comprises a batch reactor system.

4. A process according to any one of claims 1 to 3, wherein the catalyst added during step (c) comprises sulfuric acid.

5. The method of any of claims 1-4, wherein the heating of step (d) comprises heating the PVB reaction mixture to a temperature of from 70 ℃ to 80 ℃, or wherein the heating of step (d) comprises heating the PVB reaction mixture for a period of from 2 to 4 hours.

6. The method of any one of claims 1-5, wherein the solids filtered during step (e) comprise salts.

7. The method of any one of claims 1-6, wherein the solvent and butyraldehyde removed during step (f) are further recycled for use in recovering additional PVB.

8. The method of any of claims 1-7, further comprising the step of neutralizing the PVB reaction mixture by adding a base to the PVB reaction mixture, or further comprising the step of washing the pelletized PVB to remove salt impurities.

9. The method of claim 8, wherein the base comprises potassium hydroxide.

10. The method of any of claims 1-9, further comprising the step of granulating the recycled PVB.

11. A recycled poly (vinyl butyral) (PVB), wherein the PVB is prepared by a method comprising:

(a) Providing recycled PVB to a recycling system;

(d) Heating the PVB reaction mixture;

(e) Filtering the PVB reaction mixture to remove solids; and

(F) Removing the solvent and the butyraldehyde from the PVB reaction mixture to obtain the recovered PVB.

12. The PVB of any one of claims 1-11 wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, wherein the recycled PVB obtained in step (f) comprises a second amount of plasticizer, wherein the second amount of plasticizer differs from the first amount of plasticizer by less than about 10%.

13. The method of any one of claims 1-12, wherein the solvent added during step (b) comprises an alcohol.

14. The method of claim 13, wherein the alcohol is ethanol, methanol, or isopropanol.

15. The PVB of any one of claims 11-14 further comprising the step of adding an additional amount of plasticizer to the recycled PVB.

16. A laminated glass panel comprising an interlayer comprising recycled poly (vinyl butyral) (PVB), wherein the PVB is prepared by a method comprising:

(a) Providing recycled PVB to a recycling system;

(d) Heating the PVB reaction mixture;

(e) Filtering the PVB reaction mixture to remove solids; and

17. The laminated glass panel of claim 16, wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, wherein the recycled PVB obtained in step (f) comprises a second amount of plasticizer, wherein the second amount of plasticizer differs from the first amount of plasticizer by less than about 10%.

18. The laminated glass panel of claim 16 or 17, wherein the solvent added during step (b) comprises an alcohol.

19. The laminated glass panel of claim 18, wherein the alcohol is ethanol, methanol, or isopropanol.

20. The laminated glass panel of any of claims 16-19, wherein the laminated glass panel has a haze value of less than 1% and a yellowness index of less than 2.