Recovery of poly(vinyl butyral) polymer

Abstract

A method for recovering poly(vinyl butyral) (PVB). The method includes providing a solvent to a regeneration system. A further step includes adding recycled PVB to the solvent and stirring at a specified temperature for a specified time to dissolve the recycled PVB to form a PVB mixture. A further step includes filtering the PVB mixture to remove PVB solids. A further step includes applying heat to the PVB solids obtained from the PVB mixture to obtain recovered PVB polymer.

Description

[Technical field]

[0001] FIELD OF THEINVENTION This invention relates to the field of poly(vinyl butyral) resin production, and more particularly, this invention is in the field of post-industrial and post-consumer poly(vinyl butyral) recovery and reuse. [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-industrial and 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 post-industrial raw materials include PVB derived from PVB rolls that are out of specification, damaged, or otherwise unusable. Exemplary post-consumer recycled PVB raw materials include post-used automobile windshields and architectural safety glass, as well as other post-used consumer products, such as power devices (e.g., photovoltaic devices) and electronic display devices.

[0004]

[0004] Despite the long-standing and urgent need in the art, there are several problems associated with recycling PVB. For example, both post-industrial and post-consumer PVB generally contain various mixtures of different PVB compositions as obtained from various products and / or different manufacturers, as well as additives such as plasticizers, UV absorbers, solar absorbers, etc. As a result, post-industrial and / or post-consumer PVB mixtures may contain PVB of various poly(vinyl butyral) compositions with various polyvinyl alcohol contents. Such compositional differences within the mixture of recycled PVB 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] Furthermore, the presence of plasticizers in recovered PVB makes it more difficult to reuse or recycle. By first separating or removing the plasticizers from the PVB, it is possible to return the important components of PVB to their respective raw material state for recycling or reprocessing. The regenerated PVB resin obtained after separation can then be converted to a single PVB composition, for example by reacetalization in an ethanol solution.

[0006] In view of the above, a need exists to process post-industrial and / or post-consumer PVB in a manner that can remove plasticizers from recycled PVB material so that the resulting PVB is a clear polymer that can be used to make new PVB resins and interlayers, such as those that may be incorporated into new laminated glass panels. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a flow chart of a method for recovering PVB, according to an embodiment of the present invention. [Diagram 2]

[0008] 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]

[0009] 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. [Figure 4]

[0010] FIG. 2 is a graph showing two examples of multi-stage extraction at two different temperatures using an ethanol / water mixture with a water content of 40%. [Diagram 5]

[0011] FIG. 1 is a graph showing yield of plasticizer removal versus various numbers of extraction cycles. [Figure 6]

[0012] FIG. 1 is a graph showing various numbers of extraction cycles at higher initial polymer loadings. [Figure 7]

[0013] FIG. 2 is a graph showing plasticizer extraction as a function of time and water percentage. [Figure 8]

[0014] FIG. 1 is a GPEC chromatogram of the extract, showing no detectable resin between 16 and 23 minutes. [Figure 9]

[0015] FIG. 1 is a GPEC chromatogram of an extracted sheet showing two resins at 16-23 min and elution of less than 2 phr of plasticizer at 8-10 min. Summary of the Invention [Means for solving the problem]

[0008]

[0016] One aspect of the invention relates to a method for recovering poly(vinyl butyral) (PVB). The method includes feeding a solvent to a regeneration system. A further step includes adding recycled PVB to the solvent and stirring at a specific temperature for a specified time to form a PVB mixture. The PVB mixture is stirred to extract or remove the plasticizer from the recycled PVB. A further step includes filtering the PVB mixture to remove the PVB solids. The PVB solids may be analyzed to determine the amount of residual plasticizer in the PVB solids. If necessary, the PVB solids may be fed to a regeneration system and the preceding steps may be repeated one or more times. The steps may be repeated multiple times, such as until the plasticizer is completely removed (or below a desired level) from the PVB solids. A further step includes subjecting the PVB solids resulting from the PVB mixture to further processing, such as evaporation, vacuum and / or heat, or other processes known to those skilled in the art, to obtain a recovered PVB polymer.

[0009]

[0017] Another aspect of the invention relates to a recovered poly(vinyl butyral) (PVB) polymer. The recovered PVB polymer is produced by a method that includes feeding a solvent to a regeneration system. A further step includes adding recycled PVB to the solvent and stirring at a specific temperature for a specified time to form a PVB mixture. The PVB mixture is stirred to extract or remove the plasticizer from the recycled PVB. A further step includes filtering the PVB mixture to remove the PVB solids. The PVB solids may be analyzed to determine the amount of residual plasticizer in the PVB solids. If necessary, the PVB solids may be fed to a regeneration system and the preceding steps may be repeated one or more times. The steps may be repeated multiple times, such as until the plasticizer is completely removed (or below a desired level) from the PVB solids. A further step includes subjecting the PVB solids resulting from the PVB mixture to further processing, such as evaporation, vacuum and / or heat, or other processes known to those skilled in the art, to obtain a recovered PVB polymer.

[0010]

[0018] Another aspect of the invention relates to a laminated glass panel comprising an interlayer comprising recycled poly(vinyl butyral) (PVB). The recycled PVB is produced by a method comprising feeding a solvent to a reclamation system. A further step comprises adding recycled PVB to the solvent and stirring at a specific temperature for a specified time to form a PVB mixture. The PVB mixture is stirred to extract or remove the plasticizer from the recycled PVB. A further step comprises filtering the PVB mixture to remove the PVB solids. The PVB solids may be analyzed to determine the amount of residual plasticizer in the PVB solids. If necessary, the PVB solids may be fed to a reclamation system and the preceding steps repeated one or more times. The steps may be repeated multiple times, such as until the plasticizer is completely removed (or below a desired level) from the PVB solids. A further step comprises subjecting the PVB solids resulting from the PVB mixture to further processing, such as evaporation, vacuum and / or heat, or other processes known to those skilled in the art, to obtain a recovered PVB polymer.

[0011]

[0019] Another aspect includes further processing the recovered PVB polymer, such as in a reacetalization process. Further processing of the recovered PVB may include adding the recovered PVB polymer to a solvent, such as an alcohol, and stirring with a specific amount of catalyst and a specific amount of butyraldehyde at a specific temperature for a specified time to dissolve and equilibrate the recovered PVB polymer into a PVB solution. A further step includes filtering the PVB solution to remove undissolved solids. A further step includes neutralizing the PVB solution with a base, such as potassium hydroxide (KOH). A further step includes precipitating the neutralized PVB solution and washing with water to remove the solvent to obtain a PVB solid. A further step includes filtering the resulting PVB solid and drying the filtered PVB solid to obtain the recovered PVB polymer. In an embodiment, the PVB polymer may be of a single composition (i.e., a known or uniform composition, such as one derived from a single source and having the same or similar properties, such as the same residual hydroxyl level). In other embodiments, the PVB polymer may be of a heterogeneous composition derived from multiple or unknown sources.

[0012]

[0020] Another embodiment includes further processing the recovered PVB polymer, which is of a single polymer composition. When the PVB polymer is of a single (i.e., known or uniform) composition, the recovered PVB polymer can be directly processed. Further processing of the recovered PVB may include a further step of adding the recovered PVB polymer to a solvent, such as alcohol, and stirring at a specific temperature until the recovered PVB polymer is completely dissolved to form a PVB solution. A further step includes filtering the PVB solution to remove undissolved solids. A further step includes precipitation of the PVB solution and washing with water to remove the solvent to obtain a PVB solid. A further step includes filtering the resulting PVB solid and drying the filtered PVB solid to obtain a recovered PVB polymer, which is of a single or uniform composition. Alternatively, instead of precipitation, a further step after filtration includes evaporating the solvent to obtain a recovered PVB polymer, which is of a single or uniform composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013]

[0021] 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-industrial and / or post-consumer recycled PVB to obtain a sufficient amount of PVB polymer that can be used to form polymer interlayers and / or laminated glass panels that include polymer interlayers, or can be used in other processing steps. 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 solvent to a regeneration system. The solvent may be a mixture of alcohol and water containing a certain amount of water such that the recycled PVB is not soluble in the alcohol. The solvent mixture is stirred. The method may include a further step S2 of adding recycled PVB material to the solvent to form a PVB mixture. The recycled PVB may include at least some plasticizer. A further step S3 may include stirring the PVB mixture for a specified time at a specified temperature to allow the plasticizer to be extracted from the recycled PVB to form a mixture of liquid and PVB solids. A further step S4 may include filtering the PVB mixture to remove the PVB solids. A further step S5 may include determining the level of plasticizer remaining in the PVB solids to determine whether further reclamation is required. If plasticizer is present in the PVB solids (above a desired level), the process may be repeated by returning the PVB solids to step S1. A further step S6 may include processing or treating the removed PVB polymer, such as by heat, evaporation, and / or vacuum, to form a dried PVB polymer or a dissolved PVB solution. Step S6 may optionally include further processing of the dried PVB polymer or the dissolved PVB solution. The recovered PVB polymer will not retain a significant portion of the plasticizer originally contained in the recycled PVB and may not contain detectable levels of plasticizer.The resulting PVB polymer recovered during the above steps may be further processed or 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, or to be used in resin manufacturing processes and reacetalized to form PVB resins. The recovered PVB can also be used in other applications, such as adhesives that can be formed with the recovered PVB, as well as flooring, ceramic compositions, binders, coatings, inks, dispersions, and other applications.

[0014]

[0022] Alcohols such as ethanol, methanol, and isopropanol are good solvents for both PVB and plasticizers when the alcohol, such as ethanol, is pure or has a relatively low water content. The inventors have found that when water is present in certain amounts or levels (as described below), a solvent containing a mixture of alcohol and water can be used to regenerate or recycle the PVB polymer, and that the solvent mixture dissolves only the plasticizer during the process, with minimal dissolution of the PVB resin. This allows the plasticizer to be extracted and separated from the PVB polymer (resin).

[0015]

[0023] PVB becomes insoluble in solvent mixtures of alcohol and water when the water content exceeds a certain amount by weight, while plasticizers (such as triethylene glycol di-(2-ethylhexanoate)) have significant solubility in solvent mixtures of alcohol and water. If there is too little water in the solvent mixture, the recycled PVB will dissolve in the solvent, and therefore the solvent must be formulated and selected to have a certain optimum amount of water to remove or extract the plasticizer from the recycled PVB.

[0016]

[0024] Table 1 shows the extracts of PVB obtained using various solvent mixtures (with various levels of alcohol in water), which were analyzed using gradient polymer elution chromatography (GPEC).

[0017] [Table 1]

[0018]

[0025] As shown in Table 1, when the alcohol is ethanol, the optimum range of weight percent water in the alcohol / water solvent mixture for extraction of plasticizer from interlayer product is about 30 to about 40%. When the amount of water in the ethanol / water mixture exceeds about 40% water by weight, the solubility of the plasticizer in the alcohol / water mixture becomes very limited. As shown in Table 1, when the water content in the solvent mixture is too low, the resin becomes increasingly soluble in ethanol, and when the water content is too high, the extraction efficiency decreases.

[0019]

[0026] Similarly, when using a solvent mixture of methanol and water, the optimum range of water is about 15 to about 25% water by weight. If the amount of water in the methanol / water mixture exceeds about 25% water by weight, the solubility of the plasticizer in the alcohol / water mixture becomes very limited. As shown in Table 1, if the water content in the solvent mixture is too low, the resin becomes increasingly soluble in methanol, and if the water content is too high, the extraction efficiency decreases.

[0020]

[0027] Finally, when using a solvent mixture of isopropanol and water, the optimum range of water is about 40 to about 48% water by weight. If the amount of water in the isopropanol / water mixture exceeds about 48% water by weight, the solubility of the plasticizer in the alcohol / water mixture becomes very limited. As shown in Table 1, if the water content is too low, the resin becomes increasingly soluble in isopropanol, and if the water content is too high, the extraction efficiency decreases.

[0021]

[0028] Table 2 compares the efficiency of various alcohol / water solvent mixtures on extracted sheets at 22° C. The amounts shown in Table 2 represent the starting amount of plasticizer (at time 0) for three different alcohol / water solvent mixtures, as well as the resulting levels of plasticizer in the PVB after one extraction cycle, with extraction times of 1 hour and 4 hours, respectively.

[0022] [Table 2]

[0023]

[0029] As shown by the data in Table 2, methanol with 20% water, ethanol with 29% water, and isopropanol with 48% water have comparable extraction efficiencies, however, the solvent mixture containing ethanol with 29% water will result in greater resin loss than methanol with 20% water and isopropanol with 48% water, i.e., 1.9, 0.4, and 0% resin loss, respectively (see Table 1). This indicates that if similar efficiencies are expected, solvent systems with less resin loss or leaching may be preferred, depending on the desired effect and the solvents available.

[0024]

[0030] Figure 4 shows two examples of multi-stage extraction at two different temperatures using an ethanol / water mixture with 40% water content and 11.8 weight percent (wt.%) polymer loading. As shown by Figure 4, higher temperatures are advantageous in the early iterations of the extraction, but the advantage of high temperatures decreases in later stages. This suggests that a temperature gradient method can be applied in the multi-stage extraction process, using higher temperatures in early iterations and lower temperatures in later stages.

[0025]

[0031] FIG. 5 shows that shorter and more frequent extraction cycles result in more plasticizer removal, 50% for 4 cycles and 4 hours compared to 30% for 1 cycle of the same extraction time. This shows that the extraction rate is also a function of the plasticizer concentration in the extract and the polymer loading, as further demonstrated in FIG. 6. FIG. 6 shows the extraction of plasticizer starting with a higher polymer loading of 28.5 wt.%. After each extraction, the amount of plasticizer remaining decreases. Although the amount of plasticizer remaining decreases, comparing FIG. 6 with FIG. 4, the amount of plasticizer extracted is much higher, especially at shorter times, when starting with a lower polymer loading (about 11.8 wt.% compared to about 28.5 wt.%). The extraction efficiency of the process is higher when starting with a lower polymer loading.

[0026]

[0032] Figure 7 shows the difference in extraction rate for different mixtures of water and ethanol. As shown in Figure 7, water reduces the extraction rate, but to limit the solubility of PVB resin, a minimum of about 30% water in the ethanol / water mixture achieves less resin loss. As shown, it is necessary to select an optimal balance or ratio of water and alcohol in the solvent mixture. Using more water in the solvent mixture results in less resin leaching but lower extraction efficiency and extraction rate.

[0027]

[0033] The recycled PVB fed to the regeneration system in step S2 may include post-industrial and / or post-consumer recycled PVB. Such post-industrial recycled PVB may include PVB rolls that are out of specification, damaged, or otherwise unusable, while such post-consumer recycled PVB may include materials recovered from previously manufactured and / or used automotive windshields and architectural safety glass, as well as end or other off-cut materials. Recycled PVB materials may also include other consumer products, such as power devices (e.g., photovoltaic devices), electronic display devices, and scrap or post-consumer materials from other sources. Recycled PVB materials may have various PVB compositions, such as various amounts of polyvinyl alcohol ("PVOH"), as well as various amounts and types of plasticizers and other additives. For example, a first portion of the recycled PVB may have a PVOH amount of about 9-15 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.%. These PVOH amounts are for illustrative purposes only, and other ranges of PVOH amounts (or different PVOH ranges) are possible depending on the materials used and the source of the materials. Generally, the recycled PVB may have a PVOH amount of about 9 to about 25 wt.%, or more, although other amounts are possible depending on the starting materials.

[0028]

[0034] Recycled PVB may contain an amount of plasticizer (or a different amount of plasticizer depending on the starting recycled PVB), which is generally used to soften the PVB and / or to increase 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.

[0029]

[0035] The recycled PVB material may be cut, chopped, and / or shredded to form small diameter (e.g., 2-20 mm, although other sizes including up to 1 cm may be used depending on the equipment and other factors) chips, granules, pellets, or flakes of PVB material (chips, granules, pellets, flakes, etc. are referred to herein as "ground PVB material"). Ground PVB material, such as flakes, chips, and / or pellets of PVB material, may be combined with one another to form a mixed composition (e.g., having mixed amounts of PVOH or other elements), or ground PVB from one source (such as PVB rolls having a known composition) may be used alone. Such ground 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 tank in the form of a continuous stirred tank reactor (CSTR) or another similar reactor, such as a countercurrent screw press extractor or other equipment known to those skilled in the art. 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 regenerative system may be used, which includes multiple interconnected vessels (e.g., CSTRs) or multiple compartments in a tubular arrangement. In a continuous regenerative system, each of the steps may be carried out independently in one or more of the multiple vessels or multiple compartments in a tubular arrangement. Benefits of a continuous regenerative system may include higher throughput and higher efficiency compared to a single batch reactor.

[0030]

[0036] Referring to step S1, the solvent added to the regeneration system (e.g., a single batch reactor recycle system or a continuous regeneration recycle system) may include a variety of solvents sufficient to selectively dissolve the components of the recycled PVB material to form a solution or mixture. Examples of suitable solvents may include a mixture of one or more alcohols, such as ethanol, methanol, or isopropanol, with a sufficient amount of water to selectively dissolve one or more components of the recycled PVB (e.g., plasticizers and other additives, such as UV absorbers, solar or infrared absorbers, antioxidants, etc.). The solvent mixture is configured to selectively dissolve the components of the recycled PVB material to form a PVB mixture that can be filtered to separate the PVB polymer from the solvent and other materials and impurities, such as plasticizers. Other alcohols, such as alcohols with more than three carbon atoms, such as n-butanol, or alcohols with more than one hydroxyl group (i.e., diols and triols), may also be used as long as the alcohol is miscible in water.

[0031]

[0037] Referring to step S2, recycled PVB is added to the regeneration system (and solvent) and stirred to form a PVB mixture.

[0032]

[0038] Referring to step S3, the PVB mixture may be stirred for a period of time. The time of stirring may be at least 1 hour, at least 2 hours, at least 3 hours, at least 4 hours, at least 5 hours or more, although other times may be appropriate. The mixture may be stirred at room temperature (about 22-23° C.), or the mixture may be heated to a temperature above room temperature, such as at least about 25° C., at least 30° C., at least 35° C., at least 40° C., at least 45° C., or at least about 50° C. or more. The time and temperature of stirring are selected to be effective to extract the plasticizer from the recycled PVB.

[0033]

[0039] Referring to step S4, this step involves filtering the PVB mixture to remove PVB polymer solids from the mixture. In some embodiments, the filter may include a screen, mesh, cloth, or other similar filtering element. With reference to step S4, the solvent and plasticizer (and other impurities) can be removed from the PVB mixture to obtain a recovered PVB polymer. As described in more detail below, after the initial filtering step, the recovered PVB may retain significant levels of the original plasticizer present in the recycled PVB. It may be necessary to return the recovered PVB to steps S1 or S2 of the regeneration process to further dissolve (and extract) the plasticizer. The return to the beginning of the process may be performed one or more times, and in embodiments, the return to the beginning of the process is repeated until the plasticizer is completely removed or removed to undetectable levels. The recovered PVB may have some residual plasticizer (if desired), or after multiple cycles (discussed further below), there may be no detectable levels of plasticizer or very small amounts of plasticizer present (i.e., the recovered PVB may retain low levels of the original plasticizer included as part of the original recycled PVB).

[0034]

[0040] Referring to step S5, the recovered PVB solids can be analyzed to determine the amount of plasticizer remaining in the recovered PVB solids, and if the level of plasticizer is too high (i.e., above an undetectable level or above a desired level), the recovered PVB solids may be returned to the regeneration system after step S1 (where fresh solvent is added or present in the regeneration system).

[0035]

[0041] Referring to step S6, the filtered mixture (i.e., recovered PVB polymer) may have the alcohol and water removed, such as by drying, evaporating, or vacuuming off the alcohol and water. For example, the recovered PVB solids may be dried, such as in an oven, at a certain temperature for a period of time to form a dried PVB polymer. The drying time may be at least 1 hour, at least 2 hours, at least 3 hours, at least 4 hours, at least 5 hours, at least 6 hours, at least 7 hours, at least 8 hours, at least 9 hours, at least 10 hours, at least 11 hours, at least 12 hours or more. The drying temperature may be at least about 20° C., at least about 25° C., at least about 30° C., at least about 35° C., at least about 40° C., at least about 45° C., at least about 50° C., at least about 55° C., at least about 60° C., at least about 65° C., at least about 70° C. or more. The time and temperature for drying may vary depending on the method used to dry or remove the water and alcohol.

[0036]

[0042] In another embodiment, the recovered PVB solids may be dissolved in a solvent, such as alcohol, for further processing without the need for drying or solvent removal. If the recovered PVB polymer is a known or homogeneous polymer, the recovered PVB polymer can be further processed directly. Further processing of the recovered PVB may include a further step of adding the recovered PVB polymer to a solvent, such as alcohol, and stirring at a certain temperature until the recovered PVB polymer is completely dissolved to form a PVB solution. A further step includes filtering the PVB solution to remove undissolved solids. A further step includes causing precipitation in the PVB solution and washing with water to remove the solvent to obtain a PVB solid. A further step includes filtering the resulting PVB solids and drying the filtered PVB solids to obtain a recovered PVB polymer, the recovered PVB polymer being of a single or homogeneous composition. Alternatively, instead of precipitation, a further step after filtration includes evaporating the solvent to obtain a recovered PVB polymer, the recovered PVB polymer being of a single or homogeneous composition.

[0037]

[0043] If the recovered PVB is mixed or of heterogeneous composition, further processing of the recovered PVB may include adding the recovered PVB polymer to a solvent such as alcohol and stirring with a specific amount of catalyst and a specific amount of butyraldehyde at a specific temperature for a specified time to dissolve and equilibrate the recovered PVB polymer into a PVB solution. A further step includes filtering the PVB solution to remove undissolved solids. A further step includes neutralizing the PVB solution with a base such as potassium hydroxide (KOH) to form a neutralized PVB solution. A further step includes precipitating the neutralized PVB solution and washing with water to remove the solvent to obtain a PVB solid. A further step includes filtering the resulting PVB solid and drying the filtered PVB solid to obtain the recovered PVB polymer.

[0038]

[0044] Alternatively, the recovered PVB polymer may optionally be further processed, such as in an acetalization process, 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 resulting recovered PVB polymer, especially in the case of post-industrial recycled materials, may be of sufficient quality and / or transparency to be used in commercial applications, such as the manufacture of a polymer interlayer and / or a laminated glass panel including a polymer interlayer. In particular, the recovered PVB polymer may retain very little or even none of the plasticizer originally included in the recycled PVB. For example, in some embodiments, the recovered PVB polymer may retain about 5% or less, about 4% or less, about 3% or less, about 2% or less, about 1.5% or less, about 0.5% or less, or about 0% (or a level that is undetectable) of the plasticizer included in the original recycled PVB.

[0039]

[0045] In certain embodiments, steps S1-S6 above may be modified, added, and / or removed. Additionally, the recovered PVB polymer may be subjected to further processing, as previously described.

[0040]

[0046] The PVB recovered using the above recovery method steps can be used to form resins, resin layers, polymer interlayers, and / or laminated glass panels that include polymer interlayers. 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.

[0041]

[0047] While the above recycling steps can result in 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. In other embodiments, an additional amount of less than 25 phr, or less than 20 phr, or less, or more than 50 phr, or more than 55 phr, or more than 60 phr, or more than 65 phr, or more than 70 phr, or more 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.

[0042]

[0048] The recovered PVB resin(s) typically have a molecular weight of greater than 30,000, or less than 500,000, or from about 30,000 to about 500,000 daltons, or from about 500,000 to about 500,000 daltons, or from 100,000 to about 425,000 daltons, as measured by size exclusion chromatography using low angle laser light scattering. As used herein, the term "molecular weight" refers to weight average molecular weight.

[0043]

[0049] 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.

[0044]

[0050] 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.

[0045]

[0051] 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.

[0046]

[0052] 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.

[0047]

[0053] 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.

[0048]

[0054] 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.

[0049]

[0055] 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.

[0050]

[0056] In some embodiments, the intermediate layer (e.g., the core layer 14 and the skin layer 16) have a generally constant or uniform thickness over the length of the intermediate layer (see, e.g., FIG. 2). However, in alternative embodiments, the intermediate layer may have at least one region of non-uniform thickness, as shown in FIG. 3. For example, the intermediate layer, including the core layer 14 and the skin layer 16, may be wedge-shaped such that the thickness of the intermediate layer varies (e.g., linearly) over the length of the intermediate layer. In some such embodiments, the thickness of the intermediate layer 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 intermediate layer 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, the thickness of the intermediate layer may vary due to a change in the thickness of both the core layer 14 and the skin layer 16. In a further embodiment (not shown), one or more layers may increase in thickness across the width of the interlayer while one or more layers simultaneously decrease in thickness while maintaining an interlayer having at least one region of non-uniform thickness, such as a wedge-shaped interlayer. 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. Furthermore, due to the non-uniform thickness of the three layers, the glass panels may provide properties beneficial for use in head-up displays ("HUDs") by reducing undesirable image projection defects (e.g., reducing ghost images).

[0051]

[0057] 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.

[0052]

[0058] 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

[0053] Example 1

[0059] A solvent mixture of 100 parts ethanol (SD29 alcohol) and 50 parts deionized water was charged to a 1 liter three-neck jacketed glass reactor and stirred. To the stirred mixture, 20 parts recycled tri-layer PVB (consisting of 6 parts plasticizer and 14 parts resin mixture with an average of 17.4 wt.% PVOH) was added and stirred at room temperature (22°C) for 1 hour. The resulting mixture was then filtered and dried in an oven at 50°C for 12 hours. The dried polymer weighed 18.89 parts.

[0054] Example 2

[0060] A solvent mixture of 100 parts ethanol (SD29 alcohol) and 50 parts deionized water was charged to a 1 liter three-neck jacketed glass reactor and stirred. To the stirred mixture, 20 parts recycled tri-layer PVB (consisting of 6 parts plasticizer and 14 parts resin mixture with an average of 17.4 wt.% PVOH) was added and stirred at room temperature (22°C) for 4 hours. The resulting mixture was then filtered and dried in an oven at 50°C for 12 hours. The dried polymer weighed 18.12 parts.

[0055] Example 3

[0061] A solvent mixture of 100 parts ethanol (SD29 alcohol) and 30 parts deionized water was charged to a 1 liter three-neck jacketed glass reactor and stirred. To the stirred mixture, 20 parts recycled tri-layer PVB (consisting of 6 parts plasticizer and 14 parts resin mixture with an average of 17.4 wt.% PVOH) was added and stirred at room temperature (22°C) for 4 hours. The resulting mixture was then filtered and dried in an oven at 50°C for 12 hours. The dried polymer weighed 18.28 parts.

[0056] Example 4

[0062] A solvent mixture of 100 parts ethanol (SD29 alcohol) and 30 parts deionized water was charged to a 1 liter three-neck jacketed glass reactor and stirred. To the stirred mixture, 20 parts recycled tri-layer PVB (consisting of 6 parts plasticizer and 14 parts resin mixture with an average of 17.4 wt.% PVOH) was added and stirred at room temperature (22°C) for 4 hours. The resulting mixture was then filtered and dried in an oven at 50°C for 12 hours. The dried polymer weighed 16.84 parts.

[0057] Example 5

[0063] A solvent mixture of 100 parts ethanol (SD29 alcohol) and 50 parts deionized water was charged to a 1 liter three-neck jacketed glass reactor and stirred. To the stirred mixture was added 20 parts recycled tri-layer PVB (consisting of 6 parts plasticizer and 14 parts resin mixture with an average of 17.4 wt.% PVOH) and stirred at 40° C. for 4 hours. The resulting mixture was then filtered and dried in an oven at 50° C. for 12 hours. The dried polymer weighed 17.32 parts.

[0058] Example 6

[0064] A mixture of 100 parts ethanol (SD29 alcohol) and 50 parts deionized water was charged to a 1 liter three-neck jacketed glass reactor and stirred. To the stirred mixture, 60 parts recycled tri-layer PVB (consisting of 18 parts plasticizer, and 42 parts resin blend with an average of 17.4 wt.% PVOH) was added and stirred at room temperature (22° C.) for 4 hours. The resulting mixture was then filtered and dried in an oven at 50° C. for 12 hours. The dried polymer weighed 57.99 parts. The process was repeated multiple times by taking the resulting dried (recovered) polymer and adding it to the same proportions of alcohol / water solvent mixture, stirring, filtering, and drying, and repeating until the weight of the dried polymer remained constant at 44 parts.

[0059] Example 7

[0065] A mixture of 800 parts ethanol (SD29 alcohol), 150 parts recycled PVB resin mixture obtained using the process of Example 6 (average 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 about 4 hours. The resulting mixture was cooled to 65°C and neutralized with 0.46 parts KOH until the mixture reached a pH of 6.7. The resulting 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 recovered PVB was pressed into a plasticized PVB sheet having a thickness of 0.772 mm (containing 38 phr of plasticizer (3GEH)). 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.

[0060] Example 8

[0066] A mixture of 80 parts methyl alcohol and 20 parts deionized water was charged to a 1 liter three-neck jacketed glass reactor and stirred. To the stirred mixture, 20 parts recycled tri-layer PVB (consisting of 6 parts plasticizer and 14 parts resin blend with an average of 17.4 wt.% PVOH) was added and stirred at room temperature (22° C.) for 1 hour. The resulting mixture was then filtered and dried in an oven at 50° C. for 12 hours. The dried polymer weighed 18.03 parts.

[0061] Example 9

[0067] A mixture of 80 parts methyl alcohol and 20 parts deionized water was charged to a 1 liter three-neck jacketed glass reactor and stirred. To the stirred mixture, 20 parts recycled tri-layer PVB (consisting of 6 parts plasticizer and 14 parts resin blend with an average of 17.4 wt.% PVOH) was added and stirred at room temperature (22°C) for 4 hours. The resulting mixture was then filtered and dried in an oven at 50°C for 12 hours. The dried polymer weighed 16.63 parts.

[0062]

[0068] Gradient polymer elution chromatography (GPEC) is a technique that can provide information about the composition of copolymers or terpolymers and the concentration of the polymer components, including the amount of plasticizer. The GPEC method involves first dissolving the polymer (i.e., PVB) in a good solvent, or using an extractant if the concentration of the extracted component is of interest. The dissolved sample or solution is injected onto the column under solvent conditions that cause the polymer to precipitate. The mobile phase is then changed to a gradient, which causes the polymer to elute as it redissolves. In the case of PVB, the main separation mechanism is believed to be the solubility of the PVB fraction in the mobile phase, so that the plasticizer elutes first due to its high solubility and low molecular weight in the solvent. There is also a separation mechanism due to the interaction of PVB with the column packing. There can be multiple factors that affect the separation, but the composition of the copolymer is believed to be the largest factor. The GPEC method can be used to determine the composition of the polymer, or in this case, the concentration of the resin and plasticizer in the sample.

[0063]

[0069] Experimental conditions and equipment used for GPEC testing:

[0070] Equipment and conditions: i.Thermo Scientific Dionex Ultimate 3000 Series HPLC ii. Corona Veo Charged Aerosol Detector-Evaporator (low setting) iii. Column: Supelco Discovery C18, 150mm, 4.6mm, 5 micron, 180A.

[0064] iv. Column temperature: 30°C v. Injection volume: 10 microliters vi. Gradient (flow rate: 1 ml / min)

[0065] [Table 3]

[0066]

[0071] GPEC sample preparation: PVB interlayer solid samples were dissolved in glacial acetic acid and the extract was used as is (approximately 0.05-0.5 g in 10 ml acetic acid). The solution was left to dissolve overnight at room temperature. Sample types included extracts in alcohol / water mixtures, plasticizer solutions, plasticizer / resin gels, and pellet, resin, or sheet samples.

[0067]

[0072] GPEC Quantification: Estimate the relative concentrations of resin (R) and plasticizer (Pz) based on relative area percentages using the following formula:

[0068]

[0073] Pz / R=(a*area of ​​plasticizer) / (area of ​​resin) (where a is the response factor).

[0074] The weight percent of resin in a sample is determined by analysis of a solution of known resin concentration and by determining a single point response factor or by linear calibration.

[0069]

[0075] Figure 8 is a GPEC chromatogram of the extract, showing no detectable resins from 16-23 minutes. Figure 9 is a GPEC chromatogram of the extracted sheet, showing two resins from 16-23 minutes and less than 2 phr of plasticizer eluting from 8-10 minutes.

[0070]

[0076] The above examples show that recycled PVB can be processed using certain steps to recover or regenerate PVB polymer, as described hereinbefore. Using the processes described herein, recycled PVB can be processed to recover PVB polymer that contains only low levels of plasticizers or no detectable levels of plasticizers. As described above, the recovered PVB polymer can then be used in further processes.

[0071]

[0077] 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.

[0072]

[0078] 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.

[0073]

[0079] The present invention and its preferred embodiments will now be further described with reference to numbered items 1-23.

[0074]

[0080] Item 1. A method for recovering poly(vinyl butyral) (PVB), comprising: (a) providing a solvent to a regeneration system; (b) adding recycled PVB to a solvent and stirring to form a PVB mixture including PVB solids and a plasticizer; (c) filtering the PVB mixture to remove PVB solids; A method comprising:

[0075]

[0081] Item 2. The method of item 1, further comprising the step (d) of measuring the level of plasticizer in the PVB solids.

[0076]

[0082] Item 3. The method of item 2, further comprising the step (e) of applying heat to the PVB solids to obtain recovered PVB polymer.

[0077]

[0083] Item 4. The method of item 2, further comprising repeating steps (a) to (d).

[0078]

[0084] Item 5. The method of item 1, wherein the regeneration system to which the recycled PVB is supplied in step (a) comprises a batch reactor system.

[0079]

[0085] Item 6. The method of item 1, wherein the solvent added in step (a) comprises a mixture of water and an alcohol.

[0080]

[0086] Item 7. The method of item 6, wherein the alcohol is ethanol, methanol, or isopropanol, or a mixture of two or more alcohols.

[0081]

[0087] Item 8. The method of item 6, wherein water is present in an amount of about 15 to about 48 wt.%.

[0082]

[0088] Item 9. The method of item 8, wherein the alcohol is ethanol and water is present in an amount of about 30 to about 40 wt.%.

[0083]

[0089] Item 10. The method of item 8, wherein the alcohol is methanol and water is present in an amount of about 15 to about 25 wt.%.

[0084]

[0090] Item 11. The method of item 8, wherein the alcohol is isopropanol and the water is present in an amount of about 40 to about 48 wt.%.

[0085]

[0091] Item 12. The method of item 1, wherein the recycled PVB has a diameter of about 2 to about 20 millimeters.

[0086]

[0092] Item 13. The method of item 1, wherein the regeneration system to which the recycled PVB is supplied in step (a) comprises a continuous regeneration system.

[0087]

[0093] Item 14. The method of item 13, wherein the continuous regeneration system is a continuous stirred tank reactor.

[0088]

[0094] Item 15. The method of item 1, wherein the recycled PVB is added to the solvent in an amount of at least 1 wt.% (5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, or more).

[0089]

[0095] Item 16. Recycled PVB formed by any of the methods described in Items 1 to 15.

[0090]

[0096] Item 17. Resin layer containing recycled PVB from Item 16.

[0091]

[0097] Item 18. An intermediate layer comprising the resin layer of Item 17.

[0092]

[0098] Item 19. The intermediate layer of item 18, further comprising a second resin layer.

[0093]

[0099] Item 20. The intermediate layer of item 18, wherein the resin layer is a core layer, and the intermediate layer further comprises a second resin layer and a third resin layer, the core layer being between the second resin layer and the third resin layer.

[0094]

[0100] Item 21. A composition comprising the recycled PVB of item 16.

[0095]

[0101] Item 22. A laminate comprising a first substrate, the intermediate layer of item 18, and a second substrate, wherein the intermediate layer is between the first substrate and the second substrate.

[0096]

[0102] Item 23. The method of item 1, wherein step (b) comprises stirring at a temperature of about 22° C. to about 60° C. (22° C. to about 50° C., 22° C. to about 40° C., 22° C. to about 30° C.).

Claims

1. 1. A method for recovering poly(vinyl butyral) (PVB), comprising: (a) providing a solvent to a regeneration system; (b) adding recycled PVB to a solvent and stirring to form a PVB mixture containing PVB solids and a plasticizer; (c) filtering the PVB mixture to remove PVB solids; A method comprising:

2. 10. The method of claim 1, further comprising the step (d) of measuring the level of plasticizer in the PVB solids.

3. 3. The method of claim 2, further comprising the step (e) of applying heat to the PVB solids to obtain recovered PVB polymer.

4. The method of claim 2 further comprising repeating steps (a) through (d).

5. 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.

6. 10. The method of claim 1, wherein the solvent added in step (a) comprises a mixture of water and an alcohol.

7. 7. The method of claim 6, wherein the alcohol is ethanol, methanol, or isopropanol, or a mixture of two or more alcohols.

8. 7. The method of claim 6, wherein water is present in an amount of about 15 to about 48 wt.%, or wherein the alcohol is ethanol and water is present in an amount of about 30 to about 40 wt.%, or wherein the alcohol is methanol and water is present in an amount of about 15 to about 25 wt.%, or wherein the alcohol is isopropanol and water is present in an amount of about 40 to about 48 wt.%.

9. The method of claim 1, wherein the recycled PVB has a diameter of about 2 to about 20 millimeters.

10. 10. The method of claim 1, wherein the recycling system to which the recycled PVB is supplied in step (a) comprises a continuous recycling system.

11. 11. The method of claim 10, wherein the continuous regeneration system is a continuous stirred tank reactor.

12. 10. The method of claim 1, wherein the recycled PVB is added to the solvent in an amount of at least 1 wt. % (5 wt. %, 10 wt. %, 15 wt. %, 20 wt. %, or more).

13. 13. Recycled PVB formed by the method of any one of claims 1 to 12.

14. A resin layer comprising the recycled PVB of claim 13.

15. An intermediate layer comprising the resin layer according to claim 14.

16. 16. The interlayer of claim 15, further comprising a second resin layer.

17. 16. The intermediate layer of claim 15, wherein the resin layer is a core layer, and the intermediate layer further comprises a second resin layer and a third resin layer, the core layer being between the second resin layer and the third resin layer.

18. A composition comprising the recycled PVB of claim 13.

19. 16. A laminate comprising a first substrate, the intermediate layer of claim 15, and a second substrate, wherein the intermediate layer is between the first substrate and the second substrate.

20. 13. The method of any one of claims 1 to 12, wherein step (b) comprises stirring at a temperature of from about 22°C to about 60°C (22°C to about 50°C, 22°C to about 40°C, 22°C to about 30°C).

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