Recovery of poly(vinyl butyral) polymer

Abstract

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

Description

[Technical field]

[0001]

[0001] This invention relates to the field of poly(vinyl butyral) resin production, and more particularly, this invention is in the field of recovery and reuse of post-consumer poly(vinyl butyral). [Background technology]

[0002]

[0002] Laminated glass panels, such as automobile windshields and architectural safety glass, are typically composed of two sheets of glass laminated together with a layer of plasticized polymer sandwiched between them. Poly(vinyl butyral) ("PVB") is a common polymer that typically constitutes the major component in the majority of polymer interlayers in automobile windshields and architectural safety glass. Generally, PVB resins are produced by a synthetic process that begins with the separation of ethane from natural gas or directly from an oil refining process. The ethane is then steam cracked to produce ethene (ethylene), which is used with an acetic acid feedstock to obtain vinyl acetate monomer. The vinyl acetate monomer is polymerized by free radical polymerization to poly(vinyl acetate). The poly(vinyl acetate) is hydrolyzed to poly(vinyl alcohol), which is then reacted with butyraldehyde to obtain poly(vinyl butyral).

[0003]

[0003] The above synthesis processes are energy intensive and depend on the use of non-renewable raw materials. Therefore, the prospect of recycled PVB resin derived from post-consumer recycled PVB has long been considered in the art as a potentially valuable source of PVB, which is less costly to produce than virgin PVB resin and can significantly reduce the environmental footprint of PVB production. Exemplary sources of post-consumer recycled PVB include post-consumer automobile windshields and architectural safety glass, as well as other post-consumer consumer products, such as power devices (e.g., photovoltaic devices) and electronic display devices.

[0004]

[0004] Despite the long-felt need in the art, there are several problems associated with recycling post-consumer PVB. For example, post-consumer PVB generally includes various mixtures of different PVB compositions as obtained from various products and / or different manufacturers. As a result, post-consumer PVB mixtures may include PVB of various poly(vinyl butyral) compositions with various polyvinyl alcohol contents. Such compositional differences within the recycled PVB mixtures always result in unacceptable high haze and / or discoloration of the PVB, even though other impurities have been removed from the PVB. Specifically, when PVB materials of significantly different compositions are mixed together, chemical incompatibility results in a cloudy or hazy material due to immiscible microdomains with different refractive indices, which greatly limits its utilization in recycling.

[0005]

[0005] In view of the above, a need exists to process post-consumer PVB in a manner that can reduce or eliminate compositional differences in recycled PVB material, such that the resulting PVB is a transparent polymer with a uniform composition that can be used to make new PVB interlayers, such as those that may be incorporated into new laminated glass panels. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a flowchart of a method for recovering post-consumer PVBs according to an embodiment of the present invention. [Diagram 2]

[0007] FIG. 1 is a schematic diagram of a laminated glass panel including a pair of glass sheets facing a polymer interlayer, the polymer interlayer including three layers having a pair of skin layers facing a core layer. [Diagram 3]

[0008] FIG. 2 is another schematic diagram of a laminated glass panel including a pair of glass sheets facing a polymer interlayer, the polymer interlayer having a wedge shape. Summary of the Invention [Means for solving the problem]

[0007]

[0009] One aspect of the invention relates to a method for recovering poly(vinyl butyral) (PVB). The method includes providing recycled PVB to a regeneration system. A further step includes adding a solvent to the recycled PVB to dissolve the recycled PVB and form a PVB solution. A further step includes adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture. A further step includes heating the PVB reaction mixture. A further step includes filtering the PVB reaction mixture to remove solids. A further step includes removing the solvent and butyraldehyde from the PVB reaction mixture to obtain recovered PVB.

[0008]

[0010] Another aspect of the invention relates to recovered poly(vinyl butyral) (PVB). The recovered PVB is produced by a process that includes providing recycled PVB to a regeneration system. A further step includes adding a solvent to the recycled PVB to dissolve the recycled PVB and form a PVB solution. A further step includes adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture. A further step includes heating the PVB reaction mixture. A further step includes filtering the PVB reaction mixture to remove solids. A further step includes removing the solvent and butyraldehyde from the PVB reaction mixture to obtain recovered PVB.

[0009]

[0011] Another aspect of the invention relates to a laminated glass panel including an interlayer including recycled poly(vinyl butyral) (PVB). The recycled PVB is produced by a process including the step of providing recycled PVB to a reclamation system. A further step includes adding a solvent to the recycled PVB to dissolve the recycled PVB and form a PVB solution. A further step includes adding a catalyst and butyraldehyde to the PVB solution to form a PVB reaction mixture. A further step includes heating the PVB reaction mixture. A further step includes filtering the PVB reaction mixture to remove solids. A further step includes removing the solvent and butyraldehyde from the PVB reaction mixture to obtain the recovered PVB. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010]

[0012] An embodiment of the present invention is directed to a method of recovering, recycling, and / or reusing poly(vinyl butyral) ("PVB"). More particularly, an embodiment of the present invention is directed to a method of recycling post-consumer recycled PVB to obtain a sufficient amount of PVB for forming a polymer interlayer and / or a laminated glass panel including a polymer interlayer. More particularly, FIG. 1 shows an exemplary method of recycling PVB according to an embodiment of the present invention. The method includes a step S1 of providing a post-consumer recycled PVB material to a regeneration system. The post-consumer PVB may include at least some plasticizer. The method may include a further step S2 of adding a solvent to the recycled PVB material to dissolve the recycled PVB material and form a PVB solution. A further step S3 may 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 may be heated to re-equilibrate the various PVB components derived from the recycled PVB material to a uniform composition. A further step S4 may include adding a base to the PVB reaction mixture to neutralize the mixture. A further step S5 may include filtering the neutralized PVB reaction mixture to remove salts and other solids. A further step S6 may include removing the solvent and butyraldehyde from the neutralized and filtered PVB mixture to obtain recovered PVB. The recovered PVB may retain a significant portion of the plasticizer originally contained in the recycled PVB, such that the recovered PVB is at least partially plasticized. A further step S7 may include pelletizing the recovered PVB. In some embodiments, step S7 may also include washing the pelletized PVB to remove other salt impurities. The resulting PVB recovered during the above steps may be of sufficient quality (e.g., sufficient transparency and / or color) to be used in commercial products, such as the manufacture of polymer interlayers and / or laminated glass panels containing polymer interlayers.

[0011]

[0013] More specifically, the recycled PVB provided to the regeneration system in step S1 may include post-consumer recycled PVB. Such post-consumer recycled PVB may include materials recovered from previously manufactured and / or used automobile windshields and architectural safety glass. The recycled PVB material may also include scrap or post-consumer materials from other consumer products such as power devices (e.g., photovoltaic devices), electronic display devices, and the like. The recycled PVB material may have various PVB compositions, such as various amounts of polyvinyl alcohol ("PVOH"). For example, a first portion of the recycled PVB may have a PVOH amount of about 10-15 weight percent (wt.%), a second portion of the recycled PVB may have a PVOH amount of about 15-20 wt.%, and a third portion of the recycled PVB may have a PVOH amount of about 20-25 wt.%. When such recycled PVB is mixed together according to previously used recovery methods, such various PVOH amounts will generally result in a cloudy, discolored polymer. Other ranges of PVOH amounts (or different PVOH ranges) are possible, depending on the materials used and the source of the materials.

[0012]

[0014] Recycled PVB may contain a certain amount of plasticizer, which is generally used to soften the PVB and / or lower the glass transition temperature T gContemplated plasticizers include, but are not limited to, esters of polybasic acids, polyhydric alcohols, triethylene glycol di-(2-ethylbutyrate), 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, and polymeric plasticizers such as oil-modified sebacic acid alkyds, and mixtures of phosphates and adipates, and mixtures and combinations thereof. In some embodiments, 3-GEH is particularly preferred. Other examples of suitable plasticizers include, but are not limited to, tetraethylene glycol di(2-ethylhexanoate) ("4-GEH"), di(butoxyethyl)adipate, and bis(2-(2-butoxyethoxy)ethyl)adipate, dioctyl sebacate, nonylphenyl tetraethylene glycol, and mixtures thereof. Generally, the plasticizer content of a PVB material (e.g., resin or scrap) will be measured on a weight / weight basis as parts per hundred 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 will be 30 phr. Recycled PVB materials may have various amounts and / or types of plasticizers.

[0013]

[0015] The recycled PVB material may be cut, chopped, and / or shredded to form small diameter (e.g., 2-5 mm, etc.) chips, granules, or flakes of PVB material (referred to herein as "flakes of PVB material"). The flakes of PVB material are generally combined with each other to form flakes of mixed composition (e.g., having mixed amounts of PVOH or other elements). Such flakes of PVB material may be fed into a regeneration system, which may be in the form of a single batch reactor recycle system or a continuous regeneration recycle system. For example, the single batch reactor may include a vessel in the form of a continuous stirred tank reactor (CSTR) or another similar reactor. One or more (or all) of the steps of the methods described herein may be carried out in a single batch reactor. Alternatively, a continuous regeneration system may be used, which includes multiple interconnected vessels (e.g., CSTRs). In a continuous regeneration system, each of the steps may be carried out independently in one or more of the multiple vessels. Advantages of a continuous regeneration system include higher throughput compared to a single batch reactor.

[0014]

[0016] Referring 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) may include a variety of solvents sufficient to dissolve the recycled PVB material and form a solution. Examples of suitable solvents may include alcohol, such as ethanol, methanol, or isopropanol. The solvent is configured to dissolve the recycled PVB material and form a PVB solution having the form of a cloudy, viscous solution. In some embodiments, an amount of water may also be added to the PVB solution.

[0015]

[0017] Referring to step S3, a catalyst and butyraldehyde may 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-tolylsulfonic acid (p-toluenesulfonic acid). When the catalyst and butyraldehyde are added, the PVB reaction mixture may contain about 15-25 wt.% recycled PVB material (or 17 wt.%-23 wt.%, or 18 wt.%-22 wt.%, or about 20 wt.% recycled PVB material), about 75-85 wt.% solvent (or 77 wt.%-83 wt.%, or 78 wt.%-82 wt.%, or about 80 wt.% recycled PVB material). solvent), about 1 wt.% butyraldehyde (or 0.25 wt.% to 2.0 wt.%, or 0.5 wt.% to 1.5 wt.%, or 0.75 wt.% to 1.25 wt.% butyraldehyde), about 0.3 wt.% water (or 0.1 wt.% to 0.5 wt.%, or 0.2 wt.% to 0.4 wt.% water), and / or about 0.05 wt.% catalyst. In some particular embodiments, the amount of catalyst may 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.%, or at least 0.08 wt.% of the PVB reaction mixture. In other embodiments, the catalyst may comprise 0.02 wt.% to 0.08 wt.%, 0.03 wt.% to 0.07 wt.%, 0.04 wt.% to 0.06 wt.%, or about 0.05 wt.% of the PVB reaction mixture.

[0016]

[0018] With continued reference to step S3, the PVB reaction mixture may be heated for a period of time. The mixture may be heated to a temperature of 65° C. to 85° C., 70° C. to 80° C., 70° C. to 78° C., or about 78° C. The time 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 re-equilibrate the various PVB components of the recycled PVB material to a uniform composition. For example, the PVB reaction mixture may re-equilibrate such that the PVB portion of the mixture reaches a uniform PVOH percentage.

[0017]

[0019] Referring 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 may be cooled to a temperature below the temperature to which it was heated in step S3. In some embodiments, the base may include potassium hydroxide ("KOH"), sodium hydroxide, or the like. In some embodiments, the amount of base added to the mixture may comprise about 0.05 wt.% of the mixture. In some specific embodiments, the amount of base may 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.%, or at least 0.08 wt.% of the PVB reaction mixture. In other embodiments, the base may comprise 0.02 wt.% to 0.08 wt.%, 0.03 wt.% to 0.07 wt.%, 0.04 wt.% to 0.06 wt.%, or about 0.05 wt.% of the PVB reaction mixture. In any event, embodiments may provide for a sufficient amount of base to be added such that the pH of the PVB reaction mixture (which is about 2.0-2.5 before 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, 6.5, 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.

[0018]

[0020] With reference 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 filtering element. With reference to step S6, the solvent and butyraldehyde may be removed from the neutralized and filtered PVB mixture to obtain recovered PVB. As described in more detail below, the recovered PVB may be plasticized (i.e., the recovered PVB retains at least a portion of the original plasticizer included as part of the original recycled PVB). The solvent and butyraldehyde may be removed by evaporative distillation (e.g., by an evaporation column), water-steam stripping, extrusion evaporation, and the like. In some embodiments, the solvent and butyraldehyde may be recycled and reused (e.g., in further steps S2-S6) to recover additional PVB from the recycled PVB.

[0019]

[0021] Finally, referring to step S7, the recovered PVB may be pelletized for use in an extrusion process (e.g., by an extruder or co-extruder) to form a PVB interlayer and / or a laminated glass panel including a PVB interlayer. The recovered PVB may be pelletized by a pelletizer. In some embodiments, step S7 may include a further washing step, whereby the pelletized recovered PVB is washed again to remove residual salts or other impurities. Regardless, the recovered PVB obtained may be of sufficient quality and / or transparency to be used in commercial products, such as in the manufacture of polymer interlayers and / or laminated glass panels including polymer interlayers. In particular, the recovered PVB may retain almost all of the plasticizers originally included in the PVB. For example, in some embodiments, the recovered PVB may lose 1-20% or less, 2-15% or less, 3-10% or less, or about 5% of the plasticizers included in the original recycled PVB. For example, the recovered PVB obtained from the above recovery methods may have the same or about the same amount of plasticizers originally present in the recycled PVB.

[0020]

[0022] In certain embodiments, modifications, additions, and / or omissions may be made to steps S1-S7 above. For example, in some embodiments, after the PVB reaction mixture is neutralized, deionized water may be added to the neutralized PVB reaction mixture to cause precipitation of the mixture. Specifically, precipitation may be caused by adding water to the neutralized PVB reaction mixture in, for example, a high intensity mixing tank, thereby resulting in a slurry containing the separated solvent, butyraldehyde, plasticized PVB, and water. A water flushing process may instead be used to facilitate such precipitation. In any event, the recovered PVB may be filtered and dried to obtain a PVB resin having some of the amount of plasticizer (e.g., 3-5 phr) originally contained in the recycled PVB.

[0021]

[0023] The PVB recovered using the above recovery method steps can be used to form a polymer interlayer and / or a laminated glass panel that includes a polymer interlayer. As used herein, the terms "polymer interlayer sheet", "interlayer", "polymer layer" and "polymer melt sheet" may refer to a monolayer sheet or a multilayer interlayer. A "monolayer sheet", as the name implies, is a single polymer layer that is extruded as one layer. A multilayer interlayer, on the other hand, may include multiple layers, including separately extruded layers, coextruded layers, or any combination of separately extruded layers and coextruded layers. Thus, a multilayer interlayer may include, for example, two or more monolayer sheets combined with each other ("multilayer sheet"); two or more layers coextruded together ("coextruded sheet"); two or more coextruded sheets combined with each other; a combination of at least one monolayer 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 polymer layers (e.g., monolayer or coextruded multilayer) disposed in direct contact with each other, each layer comprising a polymer resin. As used herein, the term "resin" refers to the polymer component (e.g., PVB) removed from the mixture resulting from the acid-catalyzed reaction and subsequent neutralization of the polymer precursor. Generally, a plasticizer, such as those discussed further above, is added to the resin to obtain a plasticized polymer. Furthermore, the resin may have other components in addition to the polymer and plasticizer, including, for example, acetates, salts, and alcohols.

[0022]

[0024] Although the above recycling steps can be performed to obtain a recovered PVB having at least some inherent plasticizer (e.g., 3-5 phr of plasticizer), embodiments may require adding additional plasticizer to the PVB before the PVB is used to form a polymer interlayer and / or a laminated glass panel including a polymer interlayer. For example, in some embodiments, an additional amount of 25-50 phr, 25-45 phr, 30-40 phr, or 33-35 phr may be added to the resulting PVB before the polymer interlayer and / or laminated glass panel is produced. Higher or lower amounts of plasticizer may be added as desired, depending on the desired properties and application.

[0023]

[0025] Once a sufficient amount of plasticizer has been added to the recycled PVB, it is believed that the polymer interlayer sheet can be manufactured by any suitable process known to those skilled in the art of manufacturing polymer interlayer sheets that can be used in multi-layer panels (such as glass laminates). For example, it is believed that the polymer interlayer sheet can be formed by solution casting, compression molding, injection molding, melt extrusion, melt blowing, or any other means for producing and manufacturing polymer interlayer sheets known to those skilled in the art. Furthermore, in embodiments in which multiple polymer interlayers are utilized, it is believed that these multiple polymer interlayers can be formed by coextrusion, blown film, dip coating, solution coating, blade, paddle, air knife, printing, powder coating, spray coating, or other methods known to those skilled in the art. While any method for producing a polymer interlayer sheet known to those skilled in the art is considered a possible method for producing the polymer interlayer sheets described herein, this application will focus on polymer interlayer sheets produced by extrusion and / or coextrusion processes.

[0024]

[0026] In the extrusion process, the thermoplastic resin and plasticizer, including any of the resins and plasticizers described above, are typically premixed and fed into the extrusion device. Additives such as colorants and UV inhibitors (in liquid, powder, or pellet form) may be used and can be mixed into the thermoplastic resin or plasticizer before reaching the extrusion device. These additives are incorporated into the thermoplastic polymer resin, and thus the resulting polymer interlayer sheet, to enhance certain properties of the polymer interlayer sheet and its performance in the final multilayer glass panel product.

[0025]

[0027] In the extrusion device, the particles of thermoplastic raw materials and plasticizers, including resins, plasticizers, and any of the other additives mentioned above, are further mixed and melted to obtain a melt that is generally uniform in temperature and composition. An embodiment of the present invention may provide a melt temperature that is approximately 200°C. When the melt reaches the end of the extrusion device, it is forced into an extrusion die. The extrusion die is the part of the extrusion device that gives the final polymer interlayer sheet product its profile. The die generally has an opening defined by a lip, which has one dimension substantially larger than the perpendicular dimension. The die is generally designed so that the melt flows uniformly from a cylindrical profile emerging from the die to the final profile shape of the product. Multiple shapes can be imparted to the final polymer interlayer sheet by the die, as long as there is a continuous profile. Generally, in the most basic sense, extrusion is a method used to make objects of a fixed cross-sectional profile. This is achieved by pushing or pulling a material through a die of the desired cross-section for the final product.

[0026]

[0028] In some embodiments, a coextrusion method may be utilized. Coextrusion is a method in which multiple layers of polymeric materials are extruded simultaneously. Generally, this type of extrusion utilizes two or more extruders to melt and pump a fixed volume of different thermoplastic melts of different viscosities or other properties through a coextrusion die into a desired final form. For example, the multilayer interlayer of the present invention (e.g., in the form of a three-layer interlayer) may be preferably coextruded using a multi-manifold coextrusion device including a first die manifold, a second die manifold, and a third die manifold. The coextrusion device may be operated by simultaneously extruding the polymer melt from each manifold through the die and out of the opening, and the multilayer interlayer is extruded as a composite of three individual polymer layers. To result in the production of a three-layer interlayer in which the core layer is sandwiched between the skin layers, the polymer melt may flow through the die such that the core layer is disposed between the skin layers. The opening of the die may include a pair of lips located on either side of the opening. Given the placement of the polymer melt, the skin layers may contact the lips. Regardless, the interlayer thickness may be varied by adjusting the distance between the die lips located at the die opening.

[0027]

[0029] In many cases, polymer interlayers having three layers will be used in the manufacture of laminated glass panels. For example, in some embodiments of this application, the improved acoustic damping properties of the soft layer are combined with the mechanical strength of the hard / rigid layer to create a multi-layer interlayer. In these embodiments, a central soft layer is sandwiched between two hard / rigid outer layers. This (hard) / / (soft) / / (rigid) configuration creates a multi-layer interlayer that is easy to handle, can be used in conventional lamination methods, and can be constructed with 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 hard skin layers.

[0028]

[0030] The following presents a simplified description of how a multi-layer glass panel is typically produced in combination with an interlayer formed according to the above process. First, a multi-manifold coextrusion device can be used to coextrude the multi-layer interlayer as described above. The device operates by simultaneously extruding the polymer melt from each manifold toward the extrusion orifice. The properties of the layers can be varied by adjusting the die lip properties of the extrusion orifice (e.g., temperature and / or orifice dimensions). Once formed, the interlayer sheet can be placed between two glass substrates, and the excess interlayer is trimmed off from the edges to create an assembly. It is unusual for multiple polymer interlayer sheets or a polymer interlayer sheet with multiple layers (or a combination of both) to be placed inside two glass substrates to create a multi-layer glass panel with multiple polymer interlayers. Air is then removed from the assembly by any applicable process or method known to those skilled in the art; for example, by nip rollers, vacuum bags, or another degassing mechanism. Furthermore, the interlayer is partially pressed to the substrate by any method known to those skilled in the art. In a final step, this preliminary bond is made more permanent by a high temperature and pressure lamination process or any other method known to those skilled in the art, such as, but not limited to, autoclaving, to form the final integral structure.

[0029]

[0031] In view of the above, a multilayer panel includes two sheets of glass, or other applicable substrate, with a polymer interlayer sheet(s) sandwiched therebetween. Multilayer panels are generally produced by placing at least one polymer interlayer sheet between two substrates to create an assembly. FIG. 2 shows a multilayer panel 10 including a pair of glass sheets 12 with a multilayer interlayer sandwiched therebetween. The multilayer interlayer is configured as a three-layer interlayer having three individual polymer interlayer sheets, including a soft core layer 14 and two relatively hard skin layers 16 disposed on either side of the core layer 14. Such glass panels incorporating such a three-layer structure may have better acoustic properties due to the sound reduction provided by the soft core layer, as discussed above.

[0030]

[0032] In some embodiments, the interlayer (e.g., the core layer 14 and the skin layer 16) have a generally constant or uniform thickness over the length of the interlayer (see, e.g., FIG. 2). However, in alternative embodiments, the interlayer may have at least one region of non-uniform thickness, as shown in FIG. 3. For example, the interlayer, including the core layer 14 and the skin layer 16, may be wedge-shaped such that the thickness of the interlayer varies over the length of the interlayer (e.g., linearly). In some such embodiments, the thickness of the interlayer may vary due to a change 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 a change in the thickness of the skin layer 16 (i.e., the core layer 14 has a generally constant thickness). In a further alternative form, the thickness of the interlayer may vary due to a change in the thickness of both the core layer 14 and the skin layer 16. Such glass panels incorporating such three layers may have better acoustic properties due to the sound reduction provided by the soft core layer, as discussed above. Additionally, due to the non-uniform thickness of the three layers, the glass panel can provide beneficial properties for use in head-up displays ("HUDs") by reducing undesirable image projection defects (e.g., reducing ghost images).

[0031]

[0033] Advantageously, laminated glass panels formed with at least one polymer layer / interlayer containing recovered PVB resulting from the above recovery methods may have excellent optical quality. Transparency is one indicator of the optical quality of a laminate. Transparency can be determined by measuring the haze value or percentage of a laminate. Haze is the percentage of transmitted light that is scattered so that its direction deviates from the direction of the incident beam by more than a specified angle. Haze can be measured using a haze meter or spectrophotometer known to those skilled in the art according to ASTM D1003-Procedure B at an observation angle of 2 degrees using Illuminant C. In some embodiments, glass panels, polymer layers, and / or interlayers incorporating recovered PVB described herein may have a haze value of less than 5 percent, less than about 4 percent, less than about 3 percent, less than about 2 percent, less than about 1 percent, or less than about 0.5 percent.

[0032]

[0034] Color is another indicator of the optical quality of the laminate. Significant discoloration or yellowing of the laminate is often undesirable. Such discoloration is generally measured according to the Yellowness Index ("YI") using optical instruments or spectrophotometers known to those skilled in the art and in accordance with ASTM D1925. In some embodiments, glass panels, polymer layers, and / or interlayers incorporating the recycled PVB described herein may 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. In the examples shown below, haze and YI values ​​were measured as described above in accordance with ASTM D1003 and ASTM D1925, respectively. EXAMPLES

[0033] Example 1

[0035] A mixture of 800 parts SD29 alcohol, 200 parts recycled PVB flake (consisting of 55 parts plasticizer and 145 parts resin blend with an average of 19 wt.% PVOH), 15 parts butyraldehyde, 3 parts water, and 0.5 parts sulfuric acid was charged to a 1 liter three-neck jacketed glass reactor. The mixture was stirred and heated to 78°C, at which temperature the mixture was maintained for 2-4 hours. The resulting mixture was cooled to 65°C and neutralized with 0.46 parts KOH until the mixture reached a pH of 6. The resulting hazy mixture was filtered to obtain a clear viscous solution. With 35 phr of additional plasticizer, the solution was cast into a PVB film and evaporated to obtain a clear film. The film was pressed into a plasticized PVB sheet having a thickness of 0.772 mm and laminated between two pieces of 2.3 mm glass. The haze of the laminate was measured to a value of less than 1.0% and the YI of the laminate was measured to a value of less than 2.

[0034] Example 2

[0036] A mixture of 800 parts SD29 alcohol, 200 parts recycled triple layer acoustic PVB flake (consisting of 60 parts plasticizer and 140 parts resin blend with an average of 17.4 wt.% PVOH), 15 parts butyraldehyde, 3 parts water, and 0.5 parts sulfuric acid was charged to a 1 liter three-neck jacketed glass reactor. The mixture was stirred and heated to 78°C, at which temperature the mixture was maintained for 2-4 hours. The resulting mixture was cooled to 65°C and neutralized with 0.46 parts KOH until the mixture reached a pH of 6. The resulting hazy mixture was then filtered to obtain a clear viscous solution. With 35 phr of additional plasticizer, the solution was cast into a PVB film and dried to obtain a clear film. The film was pressed into a plasticized PVB sheet having a thickness of 0.772 mm and laminated between two pieces of 2.3 mm glass. The haze of the laminate was measured to a value of less than 1.0% and the YI of the laminate was measured to a value of less than 2.

[0035] Example 3

[0037] A mixture of 800 parts SD29 alcohol, 150 parts PVB resin at 18.7 wt.% PVOH, and 20 parts recycled triple layer acoustic PVB flake (consisting of 6 parts plasticizer and 14 parts resin blend at an average of 17.4 wt.% PVOH), 15 parts butyraldehyde, 3 parts water, and 0.5 parts sulfuric acid was charged to a 1 liter three-neck jacketed glass reactor. The mixture was stirred and heated to 78°C, and the mixture was maintained at that temperature for 2-4 hours. The resulting mixture was cooled to 65°C and neutralized with 0.46 parts KOH until the mixture reached a pH of 6. The cloudy mixture was further mixed in a high intensity mixer with 8 equivalents of water to form a PVB slurry. The alcohol and residual butyraldehyde were removed by flood washing with deionized water, and the resulting slurry was filtered. After drying, the PVB was pressed into a plasticized PVB sheet having a thickness of 0.772 mm with 35 phr of additional plasticizer. The PVB sheet was laminated between two pieces of 2.3 mm glass. The haze of the laminate was measured to be less than 1.0% and the YI of the laminate was measured to be less than 1.

[0036] Example 4

[0038] A mixture of 800 parts SD29 alcohol, 150 parts PVB resin at 18.7 wt.% PVOH, and 15 parts recycled triple layer acoustic PVB flake (consisting of 4.5 parts plasticizer and 10.5 parts resin blend at an average of 17.4 wt.% PVOH), 15 parts butyraldehyde, 3 parts water, and 0.5 parts sulfuric acid was charged to a 1 liter three-neck jacketed glass reactor. The mixture was stirred and heated to 78°C, at which temperature the mixture was maintained for 2-4 hours. The resulting mixture was cooled to 65°C and neutralized with 0.46 parts KOH until the mixture reached a pH of 6. The cloudy mixture was further mixed in a high intensity mixer with 8 equivalents of water to form a PVB slurry. The alcohol and residual butyraldehyde were removed by flood washing with deionized water, and the resulting slurry was filtered. After drying, the PVB was pressed with 36 phr of additional plasticizer into a plasticized PVB sheet having a thickness of 0.772 mm. The PVB sheet was laminated between two pieces of 2.3 mm glass. The haze of the laminate was measured to be less than 1.0% and the YI of the laminate was measured to be less than 1.

[0037] Example 5

[0039] A mixture of 800 parts SD29 alcohol, 200 parts recycled triple layer acoustic PVB flake (consisting of 60 parts plasticizer and 140 parts resin blend with an average of 17.4 wt.% PVOH), 15 parts butyraldehyde, 3 parts water, and 0.5 parts sulfuric acid was charged to a 1 liter three-neck jacketed glass reactor. The mixture was stirred and heated to 78°C, and the mixture was maintained at that temperature for 2-4 hours. The resulting mixture was cooled to 65°C and neutralized with 0.46 parts KOH until the mixture reached a pH of 6. The cloudy mixture was further mixed in a high intensity mixer with 8 equivalents of water to form a PVB slurry. The alcohol and residual butyraldehyde were removed by flood washing with deionized water, and the resulting slurry was filtered. After drying, the PVB was pressed into a sheet having a thickness of 0.772 mm along with 40 phr of additional plasticizer. The PVB sheet was laminated between two pieces of 2.3 mm glass. The haze of the laminate was measured to be less than 1.0% and the YI of the laminate was measured to be less than 1.

[0038]

[0040] Although disclosed in conjunction with the description of specific embodiments, including what are presently considered to be preferred embodiments, the detailed description is intended to be illustrative and should not be understood as limiting the scope of the disclosure. As will be appreciated by those skilled in the art, embodiments other than those specifically described herein are encompassed by the present invention. Modifications and variations of the described embodiments can be made without departing from the spirit and scope of the present invention.

[0039]

[0041] It will be further understood that any of the ranges, values, or properties set forth for any single component of the present disclosure can be used interchangeably with any of the ranges, values, or properties set forth for any of the other components of the disclosure, where applicable, to make embodiments having the stated values ​​for each of the components as set forth throughout this specification. For example, a polymer layer can be formed that includes a plasticizer content in any of the ranges set forth for residual hydroxyl content in addition to any of the ranges set forth, and many variations can be made, as needed, that are within the scope of the present invention but would be burdensome to list.

[0040]

[0042] The present invention and its preferred embodiments will now be further described with reference to numbered items 1-27.

[0041]

[0043] Item 1. A method for recovering poly(vinyl butyral) (PVB), comprising: (a) feeding recycled PVB to a regeneration 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; (f) removing the solvent and butyraldehyde from the PVB reaction mixture to obtain recovered PVB. A method comprising:

[0042]

[0044] Item 2. The method of item 1, wherein the PVB materials constituting the recycled PVB provided in step (a) include materials having various polyvinyl alcohol contents.

[0043]

[0045] Item 3. The method of item 1, wherein the regeneration system to which the recycled PVB is supplied in step (a) comprises a batch reactor system.

[0044]

[0046] Item 4. The method of item 1, wherein the solvent added in step (a) comprises an alcohol.

[0045]

[0047] Item 5. The method according to item 4, wherein the alcohol is ethanol, methanol, or isopropanol.

[0046]

[0048] Item 6. The method of item 1, wherein the catalyst added in step (c) comprises sulfuric acid.

[0047]

[0049] Item 7. The method of item 1, wherein the heating in step (d) comprises heating the PVB reaction mixture to a temperature of 70°C to 80°C.

[0048]

[0050] Item 8. The method of item 1, wherein the heating of step (d) comprises heating the PVB reaction mixture for 2 to 4 hours.

[0049]

[0051] Item 9. The method of item 1, wherein the solids filtered in step (e) comprise salts.

[0050]

[0052] Item 10. The process of item 1, wherein the solvent and butyraldehyde removed in step (f) are further recycled for use in the recovery of additional PVB.

[0051]

[0053] 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.

[0052]

[0054] Item 12. The method of item 11, wherein the base comprises potassium hydroxide.

[0053]

[0055] Item 13. The method of item 1, further comprising the step of pelletizing the recovered PVB.

[0054]

[0056] Item 14. The method of item 12, further comprising washing the pelletized PVB to remove salt impurities.

[0055]

[0057] Item 15. The method of item 1, wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, and the recovered PVB obtained in step (f) comprises a second amount of plasticizer, the second amount of plasticizer differing from the first amount of plasticizer by less than about 10 percent.

[0056]

[0058] Item 16. (a) feeding recycled PVB to a regeneration 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; (f) removing the solvent and butyraldehyde from the PVB reaction mixture to obtain recovered PVB. 2. Recovered poly(vinyl butyral) (PVB) produced by a process comprising:

[0057]

[0059] Item 17. The PVB of item 16, wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, and the recovered PVB obtained in step (f) comprises a second amount of plasticizer, the second amount of plasticizer differing from the first amount of plasticizer by less than about 10 percent.

[0058]

[0060] Item 18. The method of item 16, wherein the solvent added in step (b) comprises an alcohol.

[0059]

[0061] Item 19. The method of item 18, wherein the alcohol is ethanol, methanol, or isopropanol.

[0060]

[0062] Item 20. The PVB of item 16, further comprising the step of adding an additional amount of plasticizer to the recovered PVB.

[0061]

[0063] Item 21. A laminated glass panel comprising an interlayer comprising recycled poly(vinyl butyral) (PVB), the PVB comprising: (a) feeding recycled PVB to a regeneration 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; (f) removing the solvent and butyraldehyde from the PVB reaction mixture to obtain recovered PVB. 2. A laminated glass panel produced by a method comprising:

[0062]

[0064] Item 22. The laminated glass panel of item 21, wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, and the recovered PVB obtained in step (f) comprises a second amount of plasticizer, the second amount of plasticizer differing from the first amount of plasticizer by less than about 10 percent.

[0063]

[0065] Item 23. The laminated glass panel of item 21, wherein the solvent added in step (b) comprises an alcohol.

[0064]

[0066] Item 24. The laminated glass panel of item 23, wherein the alcohol is ethanol, methanol, or isopropanol.

[0065]

[0067] Item 25. The laminated glass panel of item 21 having a haze value of less than 1 percent and a yellowness index of less than 2.

Claims

1. 1. A method for recovering poly(vinyl butyral) (PVB), comprising: (a) feeding recycled PVB to a regeneration 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; (f) removing the solvent and butyraldehyde from the PVB reaction mixture to obtain recovered PVB; A method comprising:

2. 10. The method of claim 1, wherein the PVB materials comprising the recycled PVB provided in step (a) include materials having varying polyvinyl alcohol contents.

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

4. 10. The method of claim 1, wherein the catalyst added in step (c) comprises sulfuric acid.

5. 10. The method of claim 1, wherein the heating in step (d) comprises heating the PVB reaction mixture to a temperature of 70°C to 80°C, or wherein the heating in step (d) comprises heating the PVB reaction mixture for 2 to 4 hours.

6. 10. The method of claim 1, wherein the solids filtered in step (e) comprise salts.

7. 10. The method of claim 1, wherein the solvent and butyraldehyde removed in step (f) are further recycled for use in the recovery of additional PVB.

8. 10. The method of claim 1, 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. 9. The method of claim 8, wherein the base comprises potassium hydroxide.

10. 10. The method of claim 1, further comprising pelletizing the recovered PVB.

11. (a) feeding recycled PVB to a regeneration 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; (f) removing the solvent and butyraldehyde from the PVB reaction mixture to obtain recovered PVB; 1. Recycled poly(vinyl butyral) (PVB) produced by a process comprising:

12. 12. The PVB of claim 11, wherein the recycled PVB provided in step (a) comprises a first amount of plasticizer, and the recovered PVB obtained in step (f) comprises a second amount of plasticizer, the second amount of plasticizer differing from the first amount of plasticizer by less than about 10 percent.

13. 10. The method of claim 1, wherein the solvent added in step (b) comprises an alcohol.

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

15. 13. The PVB of claim 11 or 12, further comprising the step of adding an additional amount of plasticizer to the recycled PVB.

16. 1. A laminated glass panel comprising an interlayer comprising recycled poly(vinyl butyral) (PVB), the PVB comprising: (a) feeding recycled PVB to a regeneration 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; (f) removing the solvent and butyraldehyde from the PVB reaction mixture to obtain recovered PVB; 1. A laminated glass panel manufactured by a method comprising:

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

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

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

20. 20. The laminated glass panel of any one of claims 16 to 19 having a haze value of less than 1 percent and a yellowness index of less than 2.

Images