Method for Recycling Poly(vinyl butyral) from a Multilayer Poly(vinyl butyral) Sheet

Abstract

A process for recovering soft poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet comprising rigid poly(vinyl butyral) and soft poly(vinyl butyral) is disclosed. The multilayer sheet, which can be scrap or recycled material, is first converted to granular form and then treated with a plasticizer. This plasticizer treatment serves to remove the soft poly(vinyl butyral) component from the granules, thereby providing a varnish containing soft poly(vinyl butyral) mixed with an excess of plasticizer. However, this varnish is highly viscous and thus difficult to handle or machine. The present invention provides a solution to this handling problem by adding soft poly(vinyl butyral) having a low plasticizer concentration to the varnish until a product having a plasticizer concentration low enough to be processable, for example pelletized, is obtained. The resulting product can be used to form soft poly(vinyl butyral) sheets, thereby improving the recyclability of scrap multilayer poly(vinyl butyral) materials.

Description

Technical Field

[0001] The present disclosure relates to the field of recycling polymer interlayers for multilayer glass panels having at least one polymer intermediate layer sheet having a plurality of poly(vinyl butyral) components.

Background Art

[0002] Laminated safety glass used in automotive windshields and architectural safety glass typically consists of two sheets of glass laminated together with a plasticized polymer interlayer therebetween. Poly(vinyl butyral) ("PVB") is generally the main component of the polymer interlayer.

[0003] Poly(vinyl butyral) resin is usually combined with a plasticizer prior to melt extrusion into sheets. Poly(vinyl butyral) resin and plasticizer are typically manufactured via a synthetic process that begins with the use of non-renewable raw materials. Poly(vinyl butyral) is obtained by the reaction of poly(vinyl alcohol) and butyraldehyde. The properties of poly(vinyl butyral) are determined by its molecular structure, which is characterized by parameters such as molecular weight and its distribution, residual hydroxyl content, and residual acetate content.

[0004] In recent years, multilayer poly(vinyl butyral) interlayers for laminated glass have been increasingly sold on the market and applied to laminated safety glass. Multilayer interlayers can enhance sound insulation due to the presence of a softer layer ("core layer") in the center of the sheet. Usually, the composition of the core layer differs from that of the outer layer ("skin layer") in terms of the amount of plasticizer relative to the amount of polymer. The plasticizer content is usually higher in the core layer than in the skin layer. To enable such differences in composition between the layers, the PVB compound of the core layer has a different composition from the PVB compound of the skin layer with respect to hydroxyl content and, in some cases, also with respect to residual poly(vinyl acetate) content.

[0005] Conventional multilayer intermediate layers, such as three-layer acoustic intermediate layers, have a low residual hydroxyl content, a soft core layer composed of a single poly(vinyl butyral) ("PVB") resin containing a large amount of conventional plasticizer, and two rigid skin layers with a significantly high residual hydroxyl content (see, for example, U.S. Patent Nos. 5,340,654, 5,190,826, and 7,510,771). An intermediate layer having the reverse configuration, i.e., an intermediate layer having one rigid layer sandwiched between two softer layers, has been found to improve the impact performance of glass panels and can also be designed for sound insulation.

[0006] The following briefly describes how multilayer glass panels are generally manufactured in combination with these intermediate layers. First, at least one polymer intermediate layer sheet (single-layer or multilayer) is placed between two substrates, and the excess intermediate layer is cut off from the edges to create an assembly. It is not unusual to place multiple polymer intermediate layer sheets, or a polymer intermediate layer sheet having multiple layers (or a combination of both) within two substrates to create a multilayer glass panel having multiple polymer intermediate layers. Next, air is removed from the assembly by an applicable process or method known to those skilled in the art, for example, through a nip roller, a vacuum bag, or another degassing mechanism. Further, the intermediate layer is partially adhered to the substrate by any method known to those skilled in the art. In the final step, this preliminary bonding is made more permanent by a high-temperature and high-pressure lamination process, or any other method known to those skilled in the art, such as autoclave treatment (but not limited to this).

[0007] Trim or off-grade homogeneous poly(vinyl butyral) sheet products can be reused in the sheet manufacturing process. After grinding, the chips or flakes can be added back to the feed of the extrusion process. PVB raw materials can also be recovered from laminated glass after they have served their purpose in their actual application. See U.S. Patent Publication No. US2009 / 0209667. However, the presence of a core layer leads to certain visual defects upon re-extrusion when such practices are applied to multi-layer sheets. Due to the compositional differences between the PVB compounds of the skin layer and the core layer, these materials do not mix well in the molten phase. This causes certain types of cloudiness to be visible in laminated glass containing PVB sheets where fragments of multi-layer sheets are used in the raw material feed, resulting in the production of products with poor visual quality that are not suitable for sale in the market.

[0008] Recycling of poly(vinyl butyral) multi-layer sheets derived from off-grade finished sheet products that cannot be reused, and recycling of poly(vinyl butyral) multi-layer sheets derived from laminated glass that has been discarded after fulfilling its main function, can be a step forward both economically and environmentally. Recycling finished sheet products, as compared to manufacturing virgin poly(vinyl butyral) resin, can reduce the environmental footprint of both the poly(vinyl butyral) resin and sheet manufacturing while potentially lowering costs. Therefore, maximizing the reuse of scrap is not only a competitive advantage but also an environmentally sound practice.

[0009] U.S. Patent Publication No. 2003 / 0191202 discloses a method for separating target polymers and their additives from polymer-containing materials, as a result of which the recovery of both target polymers and additives becomes possible. Based on the principle of selective precipitation, the target polymers are precipitated and then separated from the additives and dissolved foreign polymers present in the solution. The separation of the additives from the solution is effected in a further step.

[0010] U.S. Patent Publication No. 2009 / 0209667 discloses a method of recycling poly(vinyl butyral) resin and incorporating the poly(vinyl butyral) resin into laminated glass and other articles. The poly(vinyl butyral) resin is recovered from discarded laminated glass by a well-defined process that includes steps of granulating the laminated glass, solvent extraction of plasticizers and impurities, dissolution of the poly(vinyl butyral), prefiltration of insoluble contaminants, color removal by adsorption or bleaching, postfiltration of carbon particles, precipitation of the poly(vinyl butyral), and washing, stabilization, and drying of the poly(vinyl butyral) resin. In one embodiment, a method for separating two poly(vinyl butyral) resins from a single batch of granules is disclosed. In this embodiment, a solvent is selected that selectively dissolves the first poly(vinyl butyral) resin at an appropriate temperature for the dissolution step and does not dissolve the second poly(vinyl butyral) resin.

[0011] There is still a need for a method of recycling PVB scrap material. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0012] In summary, the present invention provides a process for recovering soft poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet containing rigid poly(vinyl butyral) and soft poly(vinyl butyral). The multilayer sheet, which can be a scrap or recycled material, is first converted into a granular form and then treated with a plasticizer. This plasticizer treatment serves to remove the soft poly(vinyl butyral) component from the granules, thereby providing a varnish containing soft poly(vinyl butyral) mixed with an excess of the plasticizer. However, this varnish is highly viscous and thus difficult to handle or machine. The present invention provides a solution to this handling problem by adding soft poly(vinyl butyral) having a low plasticizer concentration to the varnish until a product having a plasticizer concentration low enough to be machinable, for example pelletized, is obtained. The resulting product can be used to form soft poly(vinyl butyral) sheets, thereby improving the recyclability of scrap multilayer poly(vinyl butyral) materials.

DETAILED DESCRIPTION OF THE INVENTION

[0013] In a first aspect, the present invention provides a process for recovering soft poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet containing rigid poly(vinyl butyral) and soft poly(vinyl butyral), the process comprising a. grinding the plasticized poly(vinyl butyral) multilayer sheet to obtain poly(vinyl butyral) granules; and b. adding additional plasticizer to the poly(vinyl butyral) granules to remove at least a portion of the soft poly(vinyl butyral) from the poly(vinyl butyral) granules to obtain (i) granules rich in rigid poly(vinyl butyral), and (ii) a varnish of the soft poly(vinyl butyral) and the additional plasticizer; and c. physically separating the granules rich in the rigid poly(vinyl butyral) from a varnish of the flexible poly(vinyl butyral) and the additional plasticizer, the varnish having a first concentration of plasticizer, the physically separating; d. adding a low-plasticized poly(vinyl butyral) to the varnish to provide a flexible poly(vinyl butyral) composition having a plasticizer concentration lower than the first concentration.

[0014] In co-pending application PCT / 2022 / 011518, which is hereby incorporated by reference in its entirety, Applicant describes a process for recovering rigid poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet comprising both rigid and flexible poly(vinyl butyral) materials. One of the by-products of this process is a highly viscous varnish composed of an excess of plasticizer in which flexible poly(vinyl butyral) is dissolved, thereby providing a viscous liquid varnish. For example, a varnish containing 10 weight percent flexible poly(vinyl butyral) exhibits a viscosity of greater than 20 Pa-s at 25 °C, and a varnish containing 15 weight percent flexible poly(vinyl butyral) exhibits a viscosity of greater than 150 Pa-s at 25 °C. Due to the challenges in handling such highly viscous varnishes during transportation, storage, use, and clean-up in commercial extrusion processes, most efforts to reuse the varnish in poly(vinyl butyral) sheet extrusion processes become difficult and may not be desirable to implement.

[0015] The present invention provides a solution to the problem of recovering soft poly(vinyl butyral) materials by providing a form that can be more easily processed and recycled. The present invention converts a varnish into a poly(vinyl butyral) composition and blends a soft poly(vinyl butyral) resin with a significantly reduced plasticizer content (hereinafter, "low-plasticized" soft poly(vinyl butyral)) and a varnish, and finally converts it into pellets containing an intermediate level of plasticizer, thereby providing a practical method for reusing the varnish. Generally, such low-plasticized soft poly(vinyl butyral) may contain about 0 to about 45 phr (phr = parts of plasticizer per 100 parts of resin), or in other embodiments, about 0 to about 5 phr, or about 0 to about 2 phr, or about 0 to about 1 phr of plasticizer. In this way, the viscous varnish is converted into a more processable product, which can ultimately be extruded into reusable pellets of soft poly(vinyl butyral). In one embodiment, the low-plasticized soft poly(vinyl butyral) resin added to the varnish is in the form of a powder containing no plasticizer. In this regard, the low-plasticized soft poly(vinyl butyral) may contain some plasticizer, but the overall target level of plasticizer in the isolated soft poly(vinyl butyryl) product is desirably about 20 to 80 phr of plasticizer. Therefore, in the practice of the present invention, there are practical limitations on the amount of plasticizer present in the low-plasticized soft poly(vinyl butyral). In this case (i.e., in step c.), the starting varnish generally ranges from about 300 to 1900 phr of plasticizer.

[0016] In other embodiments, the soft poly(vinyl butyral) composition isolated in step d. above contains about 30 to about 45 phr, or about 35 to about 40 phr of plasticizer.

[0017] In the practice of the present invention, the varnish described in c. above generally contains about 5 to 25 weight percent of soft core poly(vinyl butyral) resin in the plasticizer, based on the total weight of the plasticizer and the soft poly(vinyl butyral), or in other embodiments, about 12 to 18 weight percent of soft core poly(vinyl butyral) resin.

[0018] Using any conventional mixer including, but not limited to, an intermeshing co-rotating twin-screw extruder, the compounding process is carried out at a temperature of about 80 to 200 °C to obtain soft poly(vinyl butyral) pellets. In certain embodiments, these soft poly(vinyl butyral) pellets contain about 20 to 80 phr of a plasticizer.

[0019] The above-mentioned co-pending application PCT / 2022 / 011518 is related to the first three steps described as a. to c. above as a means of separating the rigid poly(vinyl butyral) portion from the multilayer scrap material. In other words, steps a. to c. represent a process of converting a plasticized poly(vinyl butyral) multilayer sheet containing both soft and rigid poly(vinyl butyral) components into granules, and then treating with a plasticizer to wash or remove at least a portion of the soft poly(vinyl butyral) from the granules to obtain granules rich in rigid poly(vinyl butyral).

[0020] If the target plasticizer content in the pellets is less than 20 phr, it becomes extremely difficult to uniformly blend the varnish with the soft poly(vinyl butyral) resin powder without causing thermal decomposition. If the target plasticizer content in the pellets exceeds 80 phr, the glass transition temperature of the pellets is too low, requiring a very low temperature for storage and transportation of the pellets.

[0021] Accordingly, in a further embodiment, the present invention provides the above process further comprising, in step d, converting a soft poly(vinyl butyral) composition in which the concentration of the plasticizer is in the range of about 20 to about 80 phr into pellet form. In one embodiment, the pellets are formed from a soft poly(vinyl butyral) resin in powder form and ground, where the powder has a plasticizer content of about 1 phr or less.

[0022] The soft poly(vinyl butyral) pellets of the present invention, which are the final product of the process of the present invention, can be of any suitable shape and size depending on the given application. In various embodiments of the present invention, the pellets can be at least 1 milligram, at least 10 milligrams, at least 100 milligrams, at least 1 gram, or at least 5 grams. Pellets having lower or higher masses are also within the scope of the present invention. In various embodiments, the pellets of the present invention are 0.1 - 100 milligrams, 3 - 20 milligrams, or 5 - 20 milligrams. In various embodiments of the present invention, the pellets can have a maximum dimension of less than 3 centimeters, less than 2 centimeters, less than 1 centimeter, or less than 0.5 centimeter. In various embodiments, the pellets can have a maximum dimension of 1 - 5 millimeters. The pellet shape can be any of the conventionally used pellet shapes, for example, spherical, oval, linear; shapes such as cylindrical, cubic, and irregular shapes. In other embodiments, the pellets of the present invention are micropellets with a maximum dimension smaller than 10 micrometers and a mass smaller than 4 nanograms. As indicated above, mixtures of pellets of different dimensions are also within the scope of the present invention. The present invention includes batches of pellets, for example, batches having more than 1, more than 100, more than 1,000, or more than 10,000 pellets. The present invention also includes containers containing the pellets of the present invention, which includes containers containing more than 1, more than 100, more than 1,000, or more than 10,000 pellets.

[0023] The soft poly(vinyl butyral) pellets of the present invention can be added to a continuous mixer and mixed with additional plasticizer to match the target plasticizer level and, if necessary, other additives, or added directly to an extruder before injecting the additional plasticizer and other additives.

[0024] As used herein, the term "varnish" is used to describe the resulting flexible poly(vinyl butyral) and additional plasticizer when the use of a plasticizer results in granules rich in rigid poly(vinyl butyral) granules. By using a plasticizer such as those commonly used to plasticize poly(vinyl butyral), the flexible poly(vinyl butyral) can be selectively washed away or extracted from the granular poly(vinyl butyral) mixture to obtain granules rich in rigid poly(vinyl butyral) and varnish, which, since it contains essentially only flexible poly(vinyl butyral), can be used in the production of poly(vinyl butyral) intermediate layers such as acoustic intermediate layers.

[0025] In one embodiment, the flexible poly(vinyl butyral) can have a residual hydroxyl content of about 8% to about 12%. In another embodiment, the rigid poly(vinyl butyral) can have a residual hydroxyl content of about 15% to about 25%.

[0026] In a further embodiment, the plasticized poly(vinyl butyral) multilayer sheet can contain triethylene glycol bis(2-ethylhexanoate) present as a plasticizer. In other embodiments, the plasticized poly(vinyl butyral) multilayer sheet can further contain dihexyl adipate or bis(2-ethylhexyl) adipate, or another convenient substance such as Benzoflax™ 9-88 benzoate, as a plasticizer.

[0027] In other embodiments, the additional plasticizer is selected from one or more of esters of polybasic acids or polyhydric alcohols. In a further embodiment, the additional plasticizer is triethylene glycol bis(2-ethylhexanoate), tetraethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, bis(2-ethylhexyl) adipate, bis(2-ethoxyethyl) adipate, dioctyl adipate, hexyl cyclohexyl adipate, diisononyl adipate, heptyl nonyl adipate, dibutyl sebacate, polymeric adipate, soybean oil, or epoxidized soybean oil.

[0028] In a further embodiment, the difference between the residual hydroxyl content of the rigid poly(vinyl butyral) and the residual hydroxyl content of the flexible poly(vinyl butyral) is at least 4.0 weight percent.

[0029] In a further embodiment, the rigid poly(vinyl butyral) contained in the plasticized poly(vinyl butyral) multilayer sheet contains from about 30 phr to about 45 phr of plasticizer. In one embodiment, the flexible poly(vinyl butyral) is isolated from the mixture of the flexible poly(vinyl butyral) obtained from step b. and the additional plasticizer via one or more of sedimentation, filtration, centrifugation, evaporation, or precipitation to isolate the flexible poly(vinyl butyral).

[0030] The term "rigid poly(vinyl butyral)" is significantly more rigid than "flexible poly(vinyl butyral)" and typically refers to a poly(vinyl butyral) resin or a blend of poly(vinyl butyral) resins that forms the skin layer or the rigid layer of the poly(vinyl butyral) multilayer sheet further described herein.

[0031] The term "soft poly(vinyl butyral)" is significantly softer than "rigid poly(vinyl butyral)" and typically refers to a poly(vinyl butyral) resin or blend of poly(vinyl butyral) resins that forms the core or soft layer of a multilayer poly(vinyl butyral) multilayer sheet, as further described herein. The soft or core poly(vinyl butyral) layer is typically sandwiched between two rigid or skin poly(vinyl butyral) layers to form a multilayer poly(vinyl butyral) multilayer sheet.

[0032] As used herein, the term "plasticizer" generally refers to a molecule or blend of molecules, as further described herein, that plasticizes a polymer with a low plasticizer content, particularly poly(vinyl butyral), thereby softening the polymer. Further, plasticizers useful as additional plasticizers according to the present invention have a high affinity or compatibility for the core layer with respect to the plasticizer, as evidenced in part by a low residual hydroxyl content when present in a greater amount as an additional plasticizer, and thus serve to remove soft poly(vinyl butyral) from a granular poly(vinyl butyral) mixture by selectively washing or partially dissolving the soft poly(vinyl butyral).

[0033] In some embodiments, the additional plasticizer has a hydrocarbon segment having less than 20, less than 15, less than 12, or less than 10 carbon atoms. Suitable additional plasticizers for use in the present invention include, among others, esters of polybasic acids or polyhydric alcohols. Suitable plasticizers include, for example, triethylene glycol bis(2-ethylhexanoate) ("3-GEH"), tetraethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, bis(2-ethylhexyl) adipate, dioctyl adipate, hexyl cyclohexyl adipate, diisononyl adipate, heptyl nonyl adipate, dibutyl sebacate, polymeric adipate, soybean oil, epoxidized soybean oil, and mixtures thereof. In one embodiment, the plasticizer is 3-GEH.

[0034] Furthermore, a plasticizer compatible with high temperatures can be utilized to further increase the flow of the intermediate layer.

[0035] As used herein, the term "poly(vinyl butyral) multilayer sheet" refers to a sheet composed of different layers of poly(vinyl butyral) resin, typically having a soft layer or a core layer, with a rigid layer or a skin layer on each side of the core layer. Thus, the poly(vinyl butyral) multilayer sheet of the present invention comprises at least one soft poly(vinyl butyral) and at least one hard poly(vinyl butyral).

[0036] Reducing the size of a poly(vinyl butyral) multilayer sheet by grinding to obtain a granular poly(vinyl butyral) mixture means reducing the size by any suitable means, such as using a grinder, to obtain granules, chips, flakes, etc., all of which can be considered granules according to the present invention. In this granulation step, granulation can be carried out using any suitable apparatus, which can be, for example, a commercially available granulator such as a Granatec granulator (East Douglas, Mass., USA). Scrap is granulated to reduce the particle size. Granulation of the scrap can result in individual granules having a length dimension of less than 2.6 centimeters, or 0.1 to 1.0 centimeters, or 0.4 to 0.8 centimeters. Granules larger than 2.6 centimeters in size can be used, but generally it is desirable to granulate the sheet to a smaller size, resulting in a larger total granule surface area. At any point during granulation, the granulated flakes can be sieved to remove contaminants released from the poly(vinyl butyral).

[0037] Adding an additional plasticizer to the poly(vinyl butyral) granules means that the plasticizer added in this step is added in addition to the plasticizer contained in the plasticized poly(vinyl butyral) multilayer sheet. In fact, both soft poly(vinyl butyral) and rigid poly(vinyl butyral) already contain a plasticizer. The additional plasticizer may be the same as the plasticizer present in the soft poly(vinyl butyral) and / or rigid poly(vinyl butyral), or it may be different from the plasticizer present in the soft poly(vinyl butyral) and / or rigid poly(vinyl butyral). The amount of additional plasticizer added is sufficient to assist in removing or washing at least a portion of the soft poly(vinyl butyral) from the poly(vinyl butyral) granules to obtain soft poly(vinyl butyral) and a plasticizer varnish.

[0038] Removing at least a portion of the soft poly(vinyl butyral) from the poly(vinyl butyral) granules means washing or dissolving a portion of the soft poly(vinyl butyral) from the granules. Thereafter, the granules can be separated from the soft poly(vinyl butyral) and additional plasticizer according to one or more of the techniques of decantation, filtration, or centrifugation, as further described herein.

[0039] The granules being rich in rigid poly(vinyl butyral) means that the relative amount of rigid poly(vinyl butyral) in the granules is higher than before a portion of the soft poly(vinyl butyral) is washed from the granules.

[0040] In one embodiment, the soft or core poly(vinyl butyral) or blend of soft poly(vinyl butyral) can have a residual hydroxyl content of from about 5% to about 15%, as further described herein. Alternatively, the residual hydroxyl content of the core poly(vinyl butyral) can be from about 7% to about 13%, or 8% to 12%, or as further described herein.

[0041] In one embodiment, the soft or core poly(vinyl butyral) or blend of soft poly(vinyl butyral) can have a residual acetate content of from about 0% to about 18%, as further described herein. Alternatively, the residual acetate content can be less than 10%, or less than 5%, or less than 2%, or less than 1%, or as further described herein.

[0042] The amount of plasticizer in the blend of soft or core poly(vinyl butyral) or soft poly(vinyl butyral) can be from about 50 phr to about 150 phr, or 55 phr to 120 phr, or 60 to 100 phr.

[0043] In another embodiment, the rigid poly(vinyl butyral) or blend of rigid poly(vinyl butyral) may have a residual hydroxyl content of about 12% to about 28%, as further described herein. Alternatively, the residual hydroxyl content of the rigid poly(vinyl butyral) may be about 15% to about 25%, or 18% to 20%, or as further described herein.

[0044] In another embodiment, the rigid poly(vinyl butyral) or blend of rigid poly(vinyl butyral) may have a residual acetate content of about 0% to about 18%, as further described herein. Alternatively, the residual acetate content of the rigid poly(vinyl butyral) may be less than 10%, or less than 5%, or less than 2%, or less than 1%, or as further described herein.

[0045] In other embodiments, the residual hydroxyl content of the core layer may be the same as, more than, or less than the residual hydroxyl content of the resin in the skin layer. In various embodiments, the core resin, or the skin resin, or both of these resins may contain less than 30% by weight, less than 25% by weight, less than 20% by weight, less than 15% by weight, less than 13% by weight, less than 10% by weight, less than 7% by weight, less than 5% by weight, or less than 1% by weight of residual ester groups, calculated as polyvinyl ester. For example, in the case of acetate, the remainder is an acetal such as butyraldehyde acetal, but optionally, it may be an isobutylaldehyde acetal group, a 2-ethylhexanal acetal group, or a mixture of any two of butyraldehyde acetal, isobutylaldehyde acetal, and 2-ethylhexanal acetal groups, or as described elsewhere herein.

[0046] In one embodiment, the multilayer intermediate layer may include a first skin polymer layer containing a plasticized poly(vinyl butyral) having a molecular weight of less than about 140,000 Daltons, a second core polymer layer containing a plasticized poly(vinyl butyral) having a molecular weight of greater than about 140,000 Daltons, and a third skin polymer layer containing a plasticized poly(vinyl butyral) having a molecular weight of less than about 140,000 Daltons. The second polymer layer is disposed between the first polymer layer and the third polymer layer, forming two skin layers and a central core layer.

[0047] In various embodiments of the intermediate layer of the present disclosure, the intermediate layer may contain a plasticizer in an amount of about 30 to about 60 phr (parts per hundred parts of resin). Although the total content of the plasticizer is shown above, the plasticizer content in the skin layer(s) or core layer(s) may differ from the total content of the plasticizer. Further, the skin layer(s) and core layer(s) may have different plasticizer contents because the plasticizer content of each layer in the equilibrium state is at least partially determined by its respective residual hydroxyl content. For example, in the equilibrium state, the intermediate layer may include two skin layers each containing 38 phr of plasticizer and a core layer containing 75 phr of plasticizer. If the total thickness of the skin layers is equal to the thickness of the core layer, the total amount of plasticizer in the intermediate layer will be about 54.3 phr. For thicker or thinner skin layers, the total amount of plasticizer in the intermediate layer may vary accordingly.

[0048] In other embodiments, the amount of plasticizer in the blend of rigid or skin poly(vinyl butyral) or soft poly(vinyl butyral) may be about 20 phr to about 60 phr, or 25 phr to 50 phr, or 30 phr to 45 phr.

[0049] In a further embodiment, the difference between the residual hydroxyl content of the soft poly(vinyl butyral) and the residual hydroxyl content of the rigid poly(vinyl butyral) is at least 6%, or at least 5%, or at least 4%, or 4% to 8%, or 5% to 10%, or as further described herein.

[0050] Accordingly, in various embodiments, the residual hydroxyl content of the poly(vinyl butyral) resin for the skin layer(s) and core layer(s) can vary. The resin for the core layer(s) can include, for example, a residual hydroxyl group of about 9 to about 18 weight percent (wt%), a residual hydroxyl group of about 9 to about 16 wt%, or a residual hydroxyl group of about 9 to about 14 wt% calculated as PVOH. The resin for the skin layer(s) can include, for example, a residual hydroxyl group of about 13 to about 35 weight percent (wt%), a residual hydroxyl group of about 13 to about 30 wt%, or a residual hydroxyl group of about 15 to about 22 wt% calculated as PVOH, and in certain embodiments, can include a residual hydroxyl group of about 17.25 to about 22.25 wt% calculated as PVOH, or a residual hydroxyl group as described elsewhere herein. The resin for the core layer(s), or for the skin layer(s), or for both the skin layer(s) and core layer(s) can also include, calculated as polyvinyl ester, less than 20 wt% of residual ester groups, less than 15 wt%, less than 13 wt%, less than 11 wt%, less than 9 wt%, less than 7 wt%, less than 5 wt%, or less than 1 wt% of residual ester groups, and in the case of acetate, for example, the remainder is acetal, preferably butyraldehyde acetal, and optionally contains small amounts of other acetal groups, such as 2-ethylhexanal groups (see, e.g., U.S. Patent No. 5,137,954, the entire disclosure of which is incorporated herein by reference).

[0051] In one embodiment, the soft poly(vinyl butyral), rigid poly(vinyl butyral), and / or plasticized poly(vinyl butyral) multilayer sheet, or any other poly(vinyl butyral) described herein, may contain a plasticizer selected from one or more of dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycol dibenzoate, butoxyethyl benzoate, butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol benzoate, 2,2,4-trimethyl-1,3-pentanediol isobutyrate benzoate, 1,3-butanediol dibenzoate, diethylene glycol di-o-toluate, triethylene glycol di-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate, tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bisphenol A bis(2-ethylhexanoate), di-(butoxyethyl) terephthalate, di(butoxyethoxyethyl) terephthalate, bis(2-ethoxyethyl) adipate, or one or more of those further described herein.

[0052] In various embodiments, the additional plasticizer added may include dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycol dibenzoate, butoxyethyl benzoate, butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol benzoate, 2,2,4-trimethyl-1,3-pentanediol isobutyrate benzoate, 1,3-butanediol dibenzoate, diethylene glycol di-o-toluate, triethylene glycol di-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate, tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bisphenol A bis(2-ethylhexanoate), di-(butoxyethyl) terephthalate, di(butoxyethoxyethyl) terephthalate, or one or more of those further described herein, and may be the same as or different from the plasticizer in the poly(vinyl butyral) described above, as further described herein. Additional plasticizers suitable as plasticizers in the additional plasticizer or soft poly(vinyl butyral) are described elsewhere herein.

[0053] As described above, the poly(vinyl butyral) multilayer sheet of the present invention typically includes a rigid poly(vinyl butyral) layer and a soft poly(vinyl butyral) layer. As described, the core layer typically includes a soft poly(vinyl butyral) sandwiched between rigid poly(vinyl butyral) skin layers to form the poly(vinyl butyral) multilayer sheet of the present invention.

[0054] In one embodiment, the amount of additional plasticizer added to the poly(vinyl butyral) granules is sufficient to wash, extract, or selectively dissolve a portion of the soft poly(vinyl butyral).

[0055] In another embodiment, the amount of additional plasticizer added to the poly(vinyl butyral) granules is sufficient to suspend the rigid poly(vinyl butyral) granules of the mixture, thus forming a rigid poly(vinyl butyral) suspension.

[0056] In yet another embodiment, the additional plasticizer is added to the poly(vinyl butyral) granules in a continuous process, for example, to form a countercurrent process to remove at least a portion of the soft poly(vinyl butyral) from the poly(vinyl butyral) granules and enrich the granules with rigid poly(vinyl butyral). The granules may then be separated from the resulting varnish mixture of soft poly(vinyl butyral) and additional plasticizer, or the additional plasticizer may be used without separating it from the soft poly(vinyl butyral), or the additional plasticizer may be partially separated from the soft poly(vinyl butyral), or only water may be separated from the mixture.

[0057] In another embodiment, the invention relates to a poly(vinyl butyral) sheet comprising isolated soft poly(vinyl butyral), and to laminated glass comprising this poly(vinyl butyral) sheet.

[0058] In a further embodiment, the invention relates to a poly(vinyl butyral) sheet comprising soft poly(vinyl butyral), and to laminated glass comprising these poly(vinyl butyral) sheets.

[0059] Separating the rigid poly(vinyl butyral) from the poly(vinyl butyral) mixture by decantation or sedimentation means separating the liquid from the rigid poly(vinyl butyral) solid, for example, by allowing the solid to settle to the bottom of the container and removing most of the additional plasticizer from the granules.

[0060] Separating the rigid poly(vinyl butyral) by filtration means filtering the rigid poly(vinyl butyral) solid of the granules from the plasticizer.

[0061] Separating rigid poly(vinyl butyral) from the mixture by centrifugation means separating solids from liquids using a centrifuge.

[0062] The present invention can be further understood in accordance with the following further description.

[0063] Thus, in one embodiment, the multilayer poly(vinyl butyral) sheet of the present invention may include an intermediate layer including one or more rigid skin layers and a soft core layer(s). In one embodiment, these multilayer intermediate sheets include a first polymer layer (skin layer) containing a rigid plasticized poly(vinyl butyral) resin, a second polymer layer (core layer) containing a soft plasticized poly(vinyl butyral) resin, or a blend thereof having the same or different residual hydroxyl content, and optionally, a third polymer layer (skin layer) containing a rigid plasticized poly(vinyl butyral) resin. The second or core polymer layer is disposed adjacent to the first polymer layer. In the case of three or more layers, the second polymer layer can be disposed between the first polymer layer and the third polymer layer, forming two skin layers and a central core layer.

[0064] In embodiments, the second or core poly(vinyl butyral) resin may be present in an amount of about 2 weight percent to about 45 weight percent, or about 5 weight percent to about 40 weight percent.

[0065] In embodiments, the residual hydroxyl content of the third or rigid poly(vinyl butyral resin) is typically the same as the residual hydroxyl content of the first rigid poly(vinyl butyral resin) and is typically different from the residual hydroxyl content of the second or core poly(vinyl butyral resin). In embodiments, the difference between the residual hydroxyl content of the core and the residual hydroxyl content of the skin is at least 4.0 weight percent, or at least 6.0 weight percent.

[0066] In an embodiment, the second poly(vinyl butyral) resin is present in an amount of from about 2 weight percent to about 45 weight percent, or from about 5 weight percent to about 40 weight percent.

[0067] In an embodiment, the polymer intermediate layer has at least two different glass transition temperatures (T g ), and the difference between the at least two different glass transition temperatures (T g ) is at least 5 °C.

[0068] In an embodiment, the residual hydroxyl content of the third, or skin, poly(vinyl butyral resin) is the same as the residual hydroxyl content of the first, or core, poly(vinyl butyral) resin.

[0069] In one embodiment of the invention, a single plasticizer such as triethylene glycol bis(2-ethylhexanoate), or a mixture thereof with dihexyl adipate, can be used.

[0070] Accordingly, the present invention relates to a method of preferentially removing, washing, or partially dissolving a soft poly(vinyl butyral) resin from poly(vinyl butyral) granules by using a plasticizer as an extractant and taking advantage of the difference in solubility of the PVB component in the plasticizer. This is different from the use of conventional solvents. Accordingly, the present invention provides a method of recycling raw materials for reintroduction into the manufacturing process.

[0071] Due to the difference in the cloud points of poly(vinyl butyral) resins of different compositions, specifically when measured by the residual percentage of polyvinyl alcohol (PVOH) in the plasticizer, temperature can be utilized as an important parameter for effectively separating different poly(vinyl butyral) components by the art. In this regard, additional plasticizer can be added to the poly(vinyl butyral) granules at a temperature of at least 25 °C, or at least 30 °C, or from about 25 °C to about 90 °C, or from 30 °C to about 60 °C, or at a temperature as disclosed elsewhere in this specification.

[0072] The poly(vinyl butyral) compound is a component of a multilayer poly(vinyl butyral) sheet, and each layer is composed of poly(vinyl butyral) and a plasticizer having different compositions with respect to the poly(vinyl butyral) composition, that is, having different residual hydroxyl or residual acetate contents, and plasticizer contents. In most cases, the amount of plasticizer relative to the amount of poly(vinyl butyral) is different. Significant extraction of the poly(vinyl butyral) compound from the multilayer sheet granules is typically obtained after grinding the off-grade sheet into smaller flakes, generally in the size range of 3 to 30 mm.

[0073] The degree of separation depends on the plasticizer applied. For example, extraction of the core layer PVB from a poly(vinyl butyral) multilayer sheet using triethylene glycol bis(2-ethylhexanoate) proceeds until 25 to 50% of the core layer PVB is removed in a single fractionation step. Repeating the extraction increases the degree of separation between different poly(vinyl butyral) compounds. Usually, extraction is obtained when the multilayer sheet or a part thereof is exposed to a specific solvent within the temperature range of 25 to 100 °C, and the extraction time is 5 minutes to several days for one extraction cycle.

[0074] Conventional multilayer intermediate layers such as three-layer acoustic intermediate layers usually consist of a soft core layer made of a single poly(vinyl butyral) ("PVB") resin with a low residual hydroxyl content and a high content of conventional plasticizers, and two rigid skin layers with a significantly higher residual hydroxyl content (see, for example, U.S. Patent Nos. 5,340,654, 5,190,826, and 7,510,771). Therefore, the isolated soft poly(vinyl butyral) may be regenerated to form the core layer of the three-layer acoustic intermediate layer, or the soft poly(vinyl butyral) layer may be formed directly without separating the soft poly(vinyl butyral) and the plasticizer varnish. The residual hydroxyl content and the amount of plasticizer in the PVB core resin are optimized so that the intermediate layer provides optimal sound insulation characteristics under ambient conditions for multiple layers of glass panels such as windshields and windows installed in vehicles and buildings.

[0075] PVB resin is produced by a known acetalization process in which polyvinyl alcohol ("PVOH") is reacted with butyraldehyde in the presence of an acid catalyst, and the resin is separated, stabilized, and dried. Such acetalization processes are described, for example, in U.S. Patent Nos. 2,282,057 and 2,282,026, and in Vinylraceal Polymers, Encyclopedia of Polymer Science & Technology, 3rd edition, Volume 8, pages 381 - 399, B.E. Wade (2003), the entire contents of these documents being incorporated herein by reference. The resin is commercially available in various forms, such as, for example, Butvar® resin from Solutia Inc., a wholly owned subsidiary of Eastman Chemical Company.

[0076] As used herein, the residual hydroxyl content in poly(vinyl butyral) (calculated as weight percent of vinyl alcohol or weight percent of PVOH) refers to the amount of hydroxyl groups remaining on the polymer chain after processing is complete. For example, poly(vinyl butyral) can be produced by hydrolyzing poly(vinyl acetate) to poly(vinyl alcohol (PVOH)), and then reacting the PVOH with butyraldehyde. In the process of hydrolyzing poly(vinyl acetate), typically not all of the acetate side groups are converted to hydroxyl groups. Further, the reaction with butyraldehyde typically does not convert all of the hydroxyl groups to acetal groups. As a result, in any completed poly(vinyl butyral) resin, there will typically be residual acetate groups (as vinyl acetate groups) and residual hydroxyl groups (as vinyl hydroxyl groups) present as side groups on the polymer chain. As used herein, the residual hydroxyl content and the residual acetate content are measured on a weight percent (wt%) basis in accordance with ASTM D1396.

[0077] The poly(vinyl butyral) resin of the present disclosure typically has a molecular weight of greater than 50,000 Daltons, or less than 500,000 Daltons, or from about 50,000 to about 500,000 Daltons, or from about 70,000 to about 500,000 Daltons, or from about 100,000 to about 425,000 Daltons as measured by size exclusion chromatography using low angle laser light scattering. As used herein, the term "molecular weight" means weight average molecular weight.

[0078] To control the adhesion of the interlayer sheet to glass, various adhesion control agents ("ACA") can be used in the interlayer of the present disclosure. In various embodiments of the interlayer of the present disclosure, the interlayer can include from about 0.003 to about 0.15 parts of ACA per 100 parts of resin, from about 0.01 to about 0.10 parts of ACA per 100 parts of resin, or from about 0.01 to about 0.04 parts of ACA per 100 parts of resin. Such ACAs include, but are not limited to, the ACAs disclosed in U.S. Patent No. 5,728,472, the entire disclosure of which is incorporated herein by reference, residual sodium acetate, potassium acetate, magnesium bis(2-ethylbutyrate), and / or magnesium bis(2-ethylhexanoate).

[0079] Other additives can be incorporated into the interlayer to enhance its performance in the final product and impart certain additional properties to the interlayer. Such additives include, but are not limited to, dyes, pigments, stabilizers (e.g., UV stabilizers), antioxidants, antiblocking agents, flame retardants, IR absorbers or blockers (e.g., indium tin oxide, antimony tin oxide, lanthanum hexaboride (LaB6) and cesium tungstate), processing aids, flow promoting additives, lubricants, impact modifiers, nucleating agents, heat stabilizers, UV absorbers, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcing additives, and fillers, among others well-known to those skilled in the art. [[ID=IO]]

[0080] In various embodiments of the intermediate layer of the present disclosure, the intermediate layer comprises more than 5 phr, about 5 to about 120 phr, about 10 to about 90 phr, about 20 to about 70 phr, about 30 to about 60 phr, or less than 120 phr, or less than 90 phr, or less than 60 phr, or less than 40 phr, or less than 30 phr of total plasticizer. Although the total plasticizer content is shown above, the plasticizer content in the skin layer(s) or core layer(s) may differ from the total plasticizer content. Further, as disclosed in U.S. Patent No. 7,510,771, the entire disclosure of which is incorporated herein by reference, the skin layer(s) and core layer(s) may have different types and contents of plasticizers within the above ranges, since the plasticizer content of each layer in the equilibrium state is determined by the respective residual hydroxyl content of that layer. For example, in the equilibrium state, the intermediate layer may comprise two skin layers each containing 30 phr of plasticizer and a core layer containing 65 phr of plasticizer. If the total thickness of the skin layers is equal to the thickness of the core layer, the total plasticizer amount in the intermediate layer will be about 45.4 phr. For thicker or thinner skin layers, the total amount of plasticizer in the intermediate layer will vary accordingly. In various embodiments of the present invention, the plasticizer contents of the core layer and the skin layer differ by at least 8 phr, or at least 9 phr, or at least 10 phr, or at least 12 phr, or at least 13 phr, or at least 14 phr, or at least 15 phr, or at least 16 phr, or at least 17 phr, or at least 18 phr, or at least 19 phr, or at least 20 phr, or at least 25 phr. As used herein, the amount of plasticizer, or any other component in the intermediate layer, can be measured as parts per hundred resin (phr) on a weight per weight basis. For example, when 30 grams of plasticizer is added to 100 grams of polymer resin, the plasticizer content of the resulting plasticized polymer is 30 phr. As used herein, when the plasticizer content of the intermediate layer is given, the plasticizer content is determined with reference to the phr of plasticizer in the kneaded material or melt used to produce the intermediate layer.

[0081] The final intermediate layer, whether formed by extrusion or co - extrusion, is generally formed through melt fracture of the polymer melt as it exits the extrusion die and thus generally has a random rough surface topography. Further, it may be embossed on the random rough surface of one or both sides (e.g., skin layers) by any embossing method known to those skilled in the art.

[0082] All methods known to those skilled in the art for manufacturing polymer intermediate layer sheets are contemplated as possible methods for manufacturing the polymer intermediate layer sheets described herein. However, this application focuses on polymer intermediate layer sheets manufactured via extrusion and co - extrusion processes. The final multilayer glass panel laminate of the present invention is formed using lamination processes known in the art.

[0083] Generally, the thickness of the polymer intermediate layer sheet, i.e., the gauge, ranges from about 15 mils to 100 mils (about 0.38 mm to about 2.54 mm), about 15 mils to 60 mils (about 0.38 mm to about 1.52 mm), about 20 mils to about 50 mils (about 0.51 - 1.27 mm), and about 15 mils to about 35 mils (about 0.38 - about 0.89 mm). In various embodiments, each of the layers such as the skin layer and core layer of the multilayer intermediate layer can have a thickness of about 1 mil to 99 mils (about 0.025 - 2.51 mm), about 1 mil to 59 mils (about 0.025 - 1.50 mm), 1 mil to about 29 mils (about 0.025 - 0.74 mm), or about 2 mils to about 28 mils (about 0.05 - 0.71 mm).

[0084] In the embodiments described below, poly(vinyl butyral) PVB is mentioned as the polymer resin, but it will be understood by those skilled in the art that the polymer can be any polymer suitable for use in a multilayer panel. Typical polymers include polyvinyl acetals (PVA) such as PVB or the isomeric poly(vinyl isobutyl) (PVisoB), polyurethanes (PU), poly(ethylene-co-vinyl acetate) (EVA), polyvinyl chloride (PVC), poly(vinyl chloride-co-methacrylate), polyethylene, polyolefins, ethylene acrylic ester copolymers, poly(ethylene-co-butyl acrylate), silicone elastomers, epoxy resins, and acid copolymers such as ethylene / carboxylic acid copolymers and their ionomers derived from any of the aforementioned possible thermoplastic resins, combinations of the foregoing, etc., but are not limited thereto. PVB and its isomeric polymer PVisoB, polyvinyl chloride, and polyurethanes are generally polymers particularly useful for the intermediate layer, and PVB (and its isomeric polymers) are particularly preferred. For example, the multilayer intermediate layer can consist of PVB / / PVisoB / / PVB. Other examples include PVB / / PVC / / PVB or PVB / / PU / / PVB. Further examples include PVC / / PVB / / PVC or PU / / PVB / / PU.

[0085] As used herein, a multilayer panel may include a single substrate such as glass, acrylic, or polycarbonate, on which a polymer interlayer sheet is disposed, and most commonly, a polymer film is further disposed on the polymer interlayer. The combination of the polymer interlayer sheet and the polymer film is generally referred to as a two-layer in the art. A typical multilayer panel having a two-layer structure is (glass) / / (polymer interlayer sheet) / / (polymer film), where the polymer interlayer sheet may include a plurality of interlayers as described above. The polymer film provides a smooth and thin rigid substrate that offers better optical properties than those typically obtained with just the polymer interlayer sheet alone and functions as a performance enhancing layer. Unlike the polymer interlayer sheet used herein, the polymer film does not by itself provide the necessary through-thickness resistance and glass retention properties, but rather improves performance such as infrared absorption properties. Poly(ethylene terephthalate) (“PET”) is the most commonly used polymer film. Generally, as used herein, the polymer film is thinner than the polymer sheet and has a thickness, for example, of about 0.001 to 0.2 mm.

[0086] The interlayers of the present disclosure are most commonly used in multilayer panels that include two substrates such as a pair of glass sheets (or other rigid materials such as polycarbonate or acrylic known in the art), with the interlayer disposed between the two substrates. Examples of such structures include (glass) / / (polymer interlayer sheet) / / (glass), where the polymer interlayer sheet may include a multilayer interlayer as described above. These examples of multilayer panels are in no way intended to be limiting, and those skilled in the art will readily recognize that numerous structures other than those described above can be made using the interlayers of the present disclosure.

[0087] A typical glass lamination process involves the following steps: (1) assembling two substrates (e.g., glass) and an intermediate layer; (2) heating the assembly briefly via IR radiation or convective means; (3) passing the assembly through a pressure nip roll for a first degassing; (4) reheating the assembly to about 60°C to about 120°C to impart a temporary adhesion to the assembly and seal the edges of the intermediate layer; (5) passing the assembly through a second pressure nip roll to further seal the edges of the intermediate layer and enable further handling; and (6) autoclaving the assembly at a temperature of 135°C to 150°C and a pressure of 180 psig to 200 psig for about 30 to 90 minutes. The actual steps, as well as the times and temperatures, may vary as necessary, as is known to those skilled in the art. Other means (steps 2 - 5) known in the art and commercially implemented for degassing the interface between the intermediate layer and the glass include vacuum bag and vacuum ring processes that utilize a vacuum to remove air.

[0088] Unless otherwise specified, all numbers representing amounts of ingredients, properties such as molecular weights, reaction conditions, etc. used in this specification and the claims are to be understood as being modified in all instances by the term "about". Accordingly, unless otherwise indicated, the numerical parameters set forth in the following specification and attached claims are approximations and may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Further, the ranges set forth in this disclosure and the claims are intended to include not only the endpoints (if any), but specifically the entire range. For example, a range described as 0 - 10 is intended to disclose all integers between 0 and 10 (e.g., 1, 2, 3, 4, etc.), all decimals between 0 and 10 (e.g., 1.5, 2.3, 4.57, 6.1113, etc.), and the endpoints 0 and 10.

[0089] Numerical ranges and parameters which may be expressed herein as broad ranges are approximations, even though the numerical values set forth in specific examples are reported as precisely as possible, taking into account the measurement method employed. However, each numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0090] It should be understood that the mention of one or more process steps does not exclude the presence of additional process steps before or after the combined recited steps, or intervening process steps between those expressly identified. Further, the naming of process steps, components, or other aspects of the information disclosed or claimed in this application by letters and numbers, etc. is a convenient means for identifying individual activities or components, and unless otherwise specified, the recited letters can be arranged in any order.

[0091] As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. For example, C n The reference to alcohol equivalent is intended to include multiple types of C n alcohol equivalents. Thus, even if language such as "at least one" or "at least a portion" is used in one place, unless the context clearly indicates otherwise, it is not intended that other uses of "a", "an", and "the" mean to exclude plural referents. Similarly, the use of language such as "at least a portion" in one place is not intended to mean "all" just because such language is not used in other places unless the context clearly indicates otherwise.

[0092] As used herein, the term "and / or" when used in a list of two or more items means that any one of the listed items can be used by itself or any combination of two or more of the listed items can be used. For example, if a composition is described as containing component A, B, and / or C, the composition can include A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

Example

[0093] Comparative Example 1 (Predicted Example) 10 kg of varnish containing 5 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 90.5 phr of plasticizer.

[0094] Example 1 (Predicted Example) 5 kg of varnish containing 5 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 46.3 phr of plasticizer. To reduce adhesiveness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. Next, these pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr and then discharged into an extruder for PVB sheet extrusion.

[0095] Example 2 (Predicted Example) 5 kg of varnish containing 5 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 46.3 phr of plasticizer. To reduce adhesiveness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. Next, these pellets are fed into a twin-screw extruder for PVB sheet extrusion. Then, additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0096] Example 3 (Prediction Example) 4 kg of varnish containing 5 wt% of soft PVB is compounded with 12 kg of soft acoustic PVB resin powder using a twin-screw extruder and then pelletized. The resulting pellets have 31.1 phr of plasticizer. And in order to reduce the adhesiveness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr, and then discharged to an extruder for PVB sheet extrusion.

[0097] Example 4 (Prediction Example) 4 kg of varnish containing 5 wt% of soft PVB is compounded with 12 kg of soft acoustic PVB resin powder using a twin-screw extruder and then pelletized. The resulting pellets have 31.1 phr of plasticizer. And in order to reduce the adhesiveness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a twin-screw extruder for PVB sheet extrusion. And additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0098] Comparative Example 2 (Prediction Example) 10 kg of varnish containing 10 wt% of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder using a twin-screw extruder and then pelletized. The resulting pellets have 81.8 phr of plasticizer.

[0099] Example 5 (Prediction Example) 5 kg of varnish containing 10 wt% of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder using a twin-screw extruder and then pelletized. The resulting pellets have 42.9 phr of plasticizer. And in order to reduce the adhesiveness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr, and then discharged to an extruder for PVB sheet extrusion.

[0100] Example 6 (Prediction Example) 5 kg of varnish containing 10 wt% of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 42.9 phr of plasticizer. And, in order to reduce the adhesiveness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a twin-screw extruder for PVB sheet extrusion. And additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0101] Example 7 (Prediction Example) 4 kg of varnish containing 10 wt% of soft PVB is compounded with 12 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 29.0 phr of plasticizer. And, in order to reduce the adhesiveness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. Next, these pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr, and then discharged into an extruder for PVB sheet extrusion.

[0102] Example 8 (Prediction Example) 4 kg of varnish containing 10 wt% of soft PVB is compounded with 12 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 29.0 phr of plasticizer. And, in order to reduce the adhesiveness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0103] Example 9 10 kg of varnish containing 15 wt% of soft PVB was compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets had 73.9 phr of plasticizer. To reduce the tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder was sprayed onto these pellets. These pellets were fed into a continuous mixer along with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 74 - 80 phr and then discharged into an extruder for PVB sheet extrusion. Therefore, it was found that the obtained PVB was suitable for use as the core of an acoustic intermediate layer.

[0104] Example 10 10 kg of varnish containing 15 wt% of soft PVB was compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets had 73.9 phr of plasticizer. To reduce the tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder was sprayed onto these pellets. These pellets were fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives were injected to reach a target plasticizer composition of 74 - 80 phr. Therefore, it was found that the obtained PVB was suitable for use as the core of an acoustic intermediate layer.

[0105] Example 11 5 kg of varnish containing 15 wt% of soft PVB was compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets had 39.5 phr of plasticizer. To reduce the tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder was sprayed onto these pellets. These pellets were fed into a continuous mixer along with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr and then discharged into an extruder for PVB sheet extrusion. Therefore, it was found that the obtained PVB was suitable for use as the core of an acoustic intermediate layer.

[0106] Example 12 5 kg of varnish containing 15 wt% of soft PVB was compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets had 39.5 phr of plasticizer. To reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder was sprayed onto these pellets. These pellets were fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives were injected to reach a target plasticizer composition of 70 - 80 phr. Thus, it was found that the obtained PVB was suitable for use as the core of an acoustic intermediate layer.

[0107] Example 13 4 kg of varnish containing 15 wt% of soft PVB was compounded with 12 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets had 27.0 phr of plasticizer. To reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder was sprayed onto these pellets. These pellets were fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr and then discharged into an extruder for PVB sheet extrusion. Thus, it was found that the obtained PVB was suitable for use as the core of an acoustic intermediate layer.

[0108] Example 14 4 kg of varnish containing 15 wt% of soft PVB was compounded with 12 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets had 27.0 phr of plasticizer. To reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder was sprayed onto these pellets. These pellets were fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives were injected to reach a target plasticizer composition of 70 - 80 phr. Thus, it was found that the obtained PVB was suitable for use as the core of an acoustic intermediate layer.

[0109] Example 15 (Predictive Example) 10 kg of varnish containing 20 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 66.7 phr of plasticizer. To reduce tackiness, these pellets are sprayed with 0.0 - 1.0 phr of soft acoustic PVB resin powder. Next, these pellets are fed into a continuous mixer with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr and then discharged into an extruder for PVB sheet extrusion.

[0110] Example 16 (Predictive Example) 10 kg of varnish containing 20 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 66.7 phr of plasticizer. To reduce tackiness, these pellets are sprayed with 0.0 - 1.0 phr of soft acoustic PVB resin powder. Next, these pellets are fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0111] Example 17 (Predictive Example) 5 kg of varnish containing 20 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 36.4 phr of plasticizer. To reduce tackiness, these pellets are sprayed with 0.0 - 1.0 phr of soft acoustic PVB resin powder. Next, these pellets are fed into a continuous mixer with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr and then discharged into an extruder for PVB sheet extrusion.

[0112] Example 18 (Predictive Example) 5 kg of varnish containing 20 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 36.4 phr of plasticizer. And, in order to reduce tackiness, 0.0 to 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0113] Example 19 (Predicted Example) 4 kg of varnish containing 20 weight percent of soft PVB is compounded with 12 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 25.0 phr of plasticizer. And, in order to reduce tackiness, 0.0 to 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr, and then discharged into an extruder for PVB sheet extrusion.

[0114] Example 20 (Predicted Example) 4 kg of varnish containing 20 weight percent of soft PVB is compounded with 12 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 25.0 phr of plasticizer. In order to reduce tackiness, 0.0 to 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. Next, these pellets are fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0115] Example 21 (Predicted Example) 10 kg of varnish containing 25 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 60.0 phr of plasticizer. To reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. Next, these pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr, and then discharged into an extruder for PVB sheet extrusion.

[0116] Example 22 (Predictive Example) 10 kg of varnish containing 25 weight percent of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 60.0 phr of plasticizer. To reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. Next, these pellets are fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0117] Example 23 (Predictive Example) 5 kg of varnish containing 25 weight percent of soft acoustic PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 33.3 phr of plasticizer. And to reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr, and then discharged into an extruder for PVB sheet extrusion.

[0118] Example 24 (Predictive Example) 5 kg of varnish containing 25 wt% of soft PVB is compounded with 10 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 33.3 phr of plasticizer. To reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

[0119] Example 25 (Predicted Example) 4 kg of varnish containing 25 wt% of soft PVB is compounded with 12 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 23.1 phr of plasticizer. To reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. These pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70 - 80 phr, and then discharged into an extruder for PVB sheet extrusion.

[0120] Example 26 (Predicted Example) 4 kg of varnish containing 25 wt% of soft PVB is compounded with 12 kg of soft acoustic PVB resin powder in a twin-screw extruder and pelletized. The resulting pellets have 23.1 phr of plasticizer. To reduce tackiness, 0.0 - 1.0 phr of soft acoustic PVB resin powder is sprayed onto these pellets. Next, these pellets are fed into a twin-screw extruder for PVB sheet extrusion. Additional plasticizer and adhesion control additives are injected to reach a target plasticizer composition of 70 - 80 phr.

Table 1

Claims

1. A process for recovering soft poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet comprising rigid poly(vinyl butyral) and soft poly(vinyl butyral), a. pulverizing the plasticized poly(vinyl butyral) multilayer sheet to obtain poly(vinyl butyral) granules; b. adding additional plasticizer to the poly(vinyl butyral) granules to remove at least a portion of the soft poly(vinyl butyral) from the poly(vinyl butyral) granules to obtain (i) granules rich in the rigid poly(vinyl butyral), and (ii) a varnish of the soft poly(vinyl butyral) and the additional plasticizer; c. physically separating the granules rich in the rigid poly(vinyl butyral) from the varnish of the soft poly(vinyl butyral) and the additional plasticizer, the varnish having a first concentration of plasticizer, the physically separating; d. adding low-plasticized poly(vinyl butyral) to the varnish to provide a soft poly(vinyl butyral) composition having a plasticizer concentration lower than the first concentration. The process comprising the above.

2. The process according to claim 1, wherein the low-plasticized poly(vinyl butyral) contains up to about 45 phr of plasticizer.

3. The process according to claim 1, wherein the low-plasticized poly(vinyl butyral) contains from about 0 to about 1 phr.

4. The process according to claim 1, wherein the soft poly(vinyl butyral) composition having a low plasticizer concentration has a plasticizer concentration in the range of about 20 to about 80 phr.

5. The process according to claim 4, further comprising pelletizing the soft poly(vinyl butyral) composition.

6. The process according to claim 4, further comprising forming the soft poly(vinyl butyral) composition into pellets and spraying a powder form of soft poly(vinyl butyral) resin having up to about 1 phr of plasticizer onto the pellets.

7. The process according to claim 1, wherein the plasticizer is selected from one or more of esters of polybasic acids or polyhydric alcohols.

8. The process according to claim 1, wherein the additional plasticizer is selected from one or more of triethylene glycol bis(2-ethylhexanoate), tetraethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, bis(2-ethylhexyl) adipate, bis(2-ethoxyethyl) adipate, dioctyl adipate, hexyl cyclohexyl adipate, diisononyl adipate, heptyl nonyl adipate, dibutyl sebacate, polymeric adipate, soybean oil, or epoxidized soybean oil.

9. The process according to claim 1, wherein the additional plasticizer is added to the poly(vinyl butyral) granules at a temperature of about 25°C to about 90°C.

10. The process according to claim 1, wherein the soft poly(vinyl butyral) has a residual hydroxyl content of about 8% to about 12%.

11. The process according to claim 1, wherein the rigid poly(vinyl butyral) has a residual hydroxyl content of about 15% to about 25%.

12. The process according to claim 1, wherein the soft poly(vinyl butyral) has a residual acetate content of less than about 15%.

13. The process according to claim 1, wherein the soft poly(vinyl butyral) contained in the plasticized poly(vinyl butyral) multilayer sheet initially contains triethylene glycol bis(2-ethylhexanoate) as a plasticizer.

14. The process according to claim 1, wherein the soft poly(vinyl butyral) contained in the plasticized poly(vinyl butyral) multilayer sheet further contains dihexyl adipate as a plasticizer.

15. The process according to claim 1, wherein the triethylene glycol bis(2-ethylhexanoate) is initially present in the soft poly(vinyl butyral) in an amount of about 60 phr to about 100 phr.

16. The process according to claim 1, wherein the additional plasticizer added to the poly(vinyl butyral) granules in step b) contains triethylene glycol bis(2-ethylhexanoate).

17. The process according to claim 1, wherein the difference between the residual hydroxyl content of the soft poly(vinyl butyral) and the residual hydroxyl content of the rigid poly(vinyl butyral) is at least 4.0 weight percent.

18. The process according to any one of claims 1 to 6, further comprising forming the soft poly(vinyl butyral) composition into a sheet.

19. A poly(vinyl butyral) sheet comprising the isolated soft poly(vinyl butyral) composition according to any one of claims 1 to 6.

20. A laminated glass comprising the poly(vinyl butyral) sheet according to claim 20.

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