Process for recovering poly (vinyl butyral) from multilayer poly (vinyl butyral) sheets

Abstract

A process for recovering a soft poly (vinyl butyral) from a plasticized poly (vinyl butyral) multilayer sheet comprising a hard poly (vinyl butyral) and a soft poly (vinyl butyral) is disclosed. The multi-layer sheet, which may be a leftover material or a recycled material, is first converted into particulate form and then treated with a plasticizer. The plasticizer treatment is used to remove the soft poly (vinyl butyral) component from the particles, but thereby provide a varnish comprising the soft poly (vinyl butyral) mixed with an excess of plasticizer. However, the varnish is very high in viscosity and thus difficult to handle or machine. The invention provides a solution to this problem by adding to the varnish a soft poly (vinyl butyral) having a lower concentration of plasticizer until a product having a sufficiently low concentration of plasticizer is obtained, enabling the product to be mechanically processed, such as pelletized. The resulting product may then be utilized to form a soft poly (vinyl butyral) sheet, thereby improving the recoverability of the multi-layer poly (vinyl butyral) leftover.

Description

Technical Field

[0001] The present disclosure relates to the field of recycling polymer interlayers for multiple layer glass panels having at least one polymer interlayer sheet with multiple poly(vinyl butyral) components. Background Art

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

[0003] Poly(vinyl butyral) resins are usually mixed with plasticizers before melt extrusion into sheets. Poly(vinyl butyral) resins and plasticizers are usually manufactured by synthetic processes using 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 can be characterized by parameters such as molecular weight and its distribution, residual hydroxyl content, residual acetate content, etc.

[0004] In recent years, multilayer poly(vinyl butyral) interlayers for laminated glass have been increasingly marketed and have been applied to laminated safety glass. Multilayer interlayers can provide enhanced sound insulation by the presence of a softer layer in the center of the sheet (the "core layer"). Typically, the composition of the core layer differs from the composition of the outer layers (the "skin layers") with respect to the amount of plasticizer relative to the polymer. The plasticizer content in the core layer is typically higher than the plasticizer content in the skin layer. In order to achieve such a difference in composition between the layers, the composition of the PVB compound in the core layer differs from that of the PVB compound in the skin layer with respect to the hydroxyl content and possibly also the residual poly(vinyl acetate) content.

[0005] Conventional multilayer interlayers, such as three-layer acoustic interlayers, contain a soft core layer composed of a single poly(vinyl butyral) ("PVB") resin having a low residual hydroxyl content and a high amount of traditional plasticizers, and two hard skin layers having significantly higher residual hydroxyl content (see, e.g., U.S. Patents 5,340,654, 5,190,826, and 7,510,771). Interlayers having the opposite configuration, i.e., a hard layer sandwiched between two softer layers, have been found to improve the impact performance of glass panels and can also be designed for sound insulation.

[0006] The manner in which multilayer glass panels are generally produced with these interlayer combinations is briefly described below. First, at least one layer of polymer interlayer sheet (single or multiple layers) is placed between two substrates and the excess interlayer is trimmed off the edges to form an assembly. It is not uncommon to place multiple layers of polymer interlayer sheets or polymer interlayer sheets having multiple layers (or a combination of the two) within two substrates to form a multilayer glass panel having multiple layers of polymer interlayers. Then, air is removed from the assembly by an applicable process or method known to those skilled in the art, such as by pressure rollers, vacuum bags, or other degassing mechanisms. In addition, the interlayer is partially laminated to the substrate by any method known to those of ordinary skill in the art. In the final step, in order to form the final single structure, the preliminary bond is made more durable by a high temperature and high pressure lamination process or any other method known to those of ordinary skill in the art (such as but not limited to high temperature and high pressure treatment).

[0007] Scraps or unqualified homogeneous poly(vinyl butyral) sheet products can be reused in the sheet manufacturing process. After grinding, the fragments or flakes can be added again to the feed of the extrusion process. When the laminated glass has served its purpose in practical application, the PVB raw material can also be recovered from it. See U.S. Patent Publication No. US2009 / 0209667. However, when such practices are applied to multilayer sheets, the presence of the core layer will lead to certain visual defects when re-extruded. Due to the difference in the composition of the PVB compounds in the skin layer and the core layer, these materials cannot be mixed well in the melting stage. This will lead to a specific type of haze in laminated glass containing PVB sheets, in which fragments of multilayer sheets are used in the raw material feed, which makes the product have poor appearance quality and is not suitable for sale on the market.

[0008] Recycling poly(vinyl butyral) multilayer sheets from off-spec finished sheet products that cannot be reused and from laminated glass that has served its primary function and is being discarded can provide both economic and ecological advances. For example, the cost of recycling finished sheet products can be lower than producing fresh poly(vinyl butyral) resin, while also reducing the environmental footprint of poly(vinyl butyral) resin and sheet production. Therefore, maximizing the reuse of waste materials 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 a target polymer and its additive from a polymer-containing material, thereby enabling the recovery of both the target polymer and the additive. Based on the principle of selective precipitation, the target polymer is precipitated and subsequently separated from the additives and dissolved foreign polymers present in the solution. In a further step, the separation of the additive from the solution is achieved.

[0010] U.S. Patent Publication No. US2009 / 0209667 discloses a method for recovering 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 waste laminated glass by a well-defined process, which includes the steps of laminated glass pelletization, solvent extraction of plasticizers and impurities, dissolution of the poly(vinyl butyral), pre-filtration of insoluble contaminants, removal of color by adsorption or bleaching, post-filtration 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 particles is disclosed. For this embodiment, a solvent is selected for the dissolving step that selectively dissolves a first poly(vinyl butyral) resin and does not dissolve a second poly(vinyl butyral) resin at a suitable temperature.

[0011] There remains a need for methods of recycling PVB scrap. Summary of the invention

[0012] In summary, the present invention provides a process for recovering soft poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet comprising hard poly(vinyl butyral) and soft poly(vinyl butyral). The multilayer sheet, which may be scrap or recycled material, is first converted into a granular form and then treated with a plasticizer. The plasticizer treatment is used to remove the soft poly(vinyl butyral) component from the granules, thereby providing a varnish comprising soft poly(vinyl butyral) mixed with an excess of plasticizer. However, the varnish is very viscous and therefore difficult to handle or machine. The present invention provides a solution to this processing problem, namely by adding soft poly(vinyl butyral) having a relatively low concentration of plasticizer to the varnish until a product having a sufficiently low concentration of plasticizer is obtained to enable the product to be machined, such as granulated. The resulting product can then be used to form a soft poly(vinyl butyral) sheet, thereby improving the recyclability of the multilayer poly(vinyl butyral) scrap. DETAILED DESCRIPTION

[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 comprising hard poly(vinyl butyral) and soft poly(vinyl butyral), the process comprising:

[0014] a. grinding the plasticized poly (vinyl butyral) multilayer sheet to obtain poly (vinyl butyral) particles;

[0015] b. adding an additional plasticizer to the poly(vinyl butyral) particles, thereby removing at least a portion of the soft poly(vinyl butyral) in the poly(vinyl butyral) particles to obtain (i) particles rich in the hard poly(vinyl butyral) and (ii) a varnish of the soft poly(vinyl butyral) and the additional plasticizer;

[0016] c. physically separating the particles rich in the hard poly(vinyl butyral) from the varnish of the soft poly(vinyl butyral) and the additional plasticizer, wherein the varnish has a first concentration of plasticizer; and

[0017] d. adding under-plasticized poly(vinyl butyral) to the varnish to provide a soft poly(vinyl butyral) composition having a plasticizer concentration lower than the first concentration.

[0018] In co-pending application PCT / 2022 / 011518 (incorporated herein in its entirety by reference), applicants describe a process for recovering hard poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet containing both hard and soft poly(vinyl butyral) materials. A byproduct of the process is a high viscosity varnish consisting of an excess plasticizer in which the soft poly(vinyl butyral) is dissolved, thereby providing a viscous liquid varnish. For example, a varnish containing 10 wt % soft poly(vinyl butyral) exhibits a viscosity of more than 20 Pa-sec at 25°C, and a varnish containing 15 wt % soft poly(vinyl butyral) exhibits a viscosity of more than 150 Pa-sec at 25°C. The challenges of handling such high viscosity varnishes during shipping, storage, use, and cleanup in commercial extrusion processes make most efforts to reuse the varnish in poly(vinyl butyral) sheet extrusion processes challenging and potentially prohibitive.

[0019] The present invention provides a solution to this problem of recycling soft poly(vinyl butyral) materials by providing a form that is more easily processed and recycled. The present invention provides a practical method for reusing varnishes by converting the varnishes into poly(vinyl butyral) compositions and ultimately into pellets having a moderate level of plasticizer by mixing the varnishes with soft poly(vinyl butyral) resins having a significantly reduced plasticizer content (hereinafter referred to as "underplasticized" soft poly(vinyl butyral)). Generally speaking, such underplasticized soft poly(vinyl butyral)s may contain from about 0 to about 45 phr (phr = parts of plasticizer per hundred parts of resin) of plasticizer, or in other embodiments from about 0 to about 5, or from about 0 to about 2, or from about 0 to about 1 phr of plasticizer. In this way, the viscous varnish is converted into a more easily processable product that can ultimately be extruded into reusable soft poly(vinyl butyral) pellets. In one embodiment, the under-plasticized soft poly(vinyl butyral) resin to be added to the varnish is in the form of a powder that does not contain a plasticizer. In this regard, the under-plasticized soft poly(vinyl butyral) may contain some plasticizer, but since the total target level of plasticizer in the soft poly(vinyl butyral) product to be isolated ideally contains about 20 to 80 phr of plasticizer, in the practice of the present invention, there is a practical limit to the amount of plasticizer present in the under-plasticized soft poly(vinyl butyral), as long as the starting material varnish in this case (i.e., in step c) is generally in the range of from about 300 to 1900 phr of plasticizer.

[0020] In other embodiments, the soft poly(vinyl butyral) composition to be isolated in step d. above comprises from about 30 to about 45, or from about 35 to about 40 phr of a plasticizer.

[0021] In the practice of the present invention, the varnish described in c. above generally comprises about 5 to 25 weight percent of a soft core poly(vinyl butyral) resin in a plasticizer, or in other embodiments, about 12 to 18 weight percent of a soft core poly(vinyl butyral) resin, based on the total weight of the plasticizer and the soft poly(vinyl butyral).

[0022] Any conventional mixer, including but not limited to an intermeshing co-rotating twin-screw extruder, may be used to carry out the compounding process at a temperature between about 80-200° C. to provide soft poly(vinyl butyral) pellets, which in certain embodiments contain about 20 to 80 phr of a plasticizer.

[0023] The above-mentioned co-pending application PCT / 2022 / 011518 relates to the above-mentioned first three steps a. to c. as a means of separating the hard poly(vinyl butyral) portion from the multilayer scrap. In other words, steps a. to c. describe a process in which a plasticized poly(vinyl butyral) multilayer sheet containing soft and hard poly(vinyl butyral) components is converted into particles, which are then treated with a plasticizer to wash or remove at least a portion of the soft poly(vinyl butyral) from the particles, thereby obtaining particles rich in hard poly(vinyl butyral).

[0024] If the target plasticizer content in the pellets is less than 20 phr, it is extremely difficult to uniformly mix the varnish with the soft poly(vinyl butyral) resin powder without causing thermal degradation. If the target plasticizer content in the pellets is more than 80 phr, the glass transition temperature of the pellets becomes too low, requiring the pellets to be stored and transported at extremely low temperatures.

[0025] Thus, in a further embodiment, the present invention provides the above process, further comprising the step of converting the soft poly(vinyl butyral) composition having a plasticizer concentration in the range of about 20 to about 80 phr in step d. into pellet form. In one embodiment, a soft poly(vinyl butyral) resin in powder form is sprinkled on the pellets, wherein the powder has less than or equal to about 1 phr of plasticizer.

[0026] The soft poly (vinyl butyral) pellets of the present invention are the final product of the process of the present invention, and they can be of any suitable shape and size, depending on a given application. In various embodiments of the present invention, the pellets can be at least 1 mg, at least 10 mg, at least 100 mg, at least 1 gram, or at least 5 grams. Pellets with lower or higher mass are also within the scope of the present invention. In various embodiments, the pellets of the present invention are between 0.1 and 100 mg, 3 and 20 mg, or 5 and 20 mg. In various embodiments of the present invention, the maximum dimension of the pellets can be less than 3 cm, less than 2 cm, less than 1 cm, or less than 0.5 cm. In various embodiments, the maximum dimension of the pellets can be from 1 to 5 mm. The pellet shape can be any conventionally used pellet shape, such as spherical, oval, linear, cylindrical, cubic, etc., as well as irregular shapes. In other embodiments, the pellets of the present invention are microgranules with a maximum dimension as small as 10 microns and a mass as small as 4 nanograms. As described above, mixtures of pellets of different sizes are also within the scope of the present invention. The invention includes individual batches of pellets, such as batches having more than 1, more than 100, more than 1,000, or more than 10,000 pellets. The invention also includes containers containing pellets of the invention, including containers containing more than 1, more than 100, more than 1,000, or more than 10,000 pellets.

[0027] The soft poly(vinyl butyral) pellets of the invention can be added to a continuous mixer where they are mixed with additional plasticizer to match the target plasticizer level and other additives as needed, or directly to an extruder where additional plasticizer and other additives are injected.

[0028] As used herein, the term "varnish" is used to describe the soft poly(vinyl butyral) and additional plasticizer obtained when the particles have been enriched with hard poly(vinyl butyral) particles using a plasticizer. The soft poly(vinyl butyral) can be selectively washed or extracted from the pelletized poly(vinyl butyral) mixture using a plasticizer, such as a plasticizer commonly used to plasticize poly(vinyl butyral), to obtain particles enriched with hard poly(vinyl butyral) and a varnish that can be used to produce poly(vinyl butyral) interlayers, such as acoustic interlayers, because it contains essentially only soft poly(vinyl butyral).

[0029] In one embodiment, the soft poly(vinyl butyral) may have a residual hydroxyl content of from about 8% to about 12%. In another embodiment, the rigid poly(vinyl butyral) may have a residual hydroxyl content of from about 15% to about 25%.

[0030] In further embodiments, the plasticized poly(vinyl butyral) multilayer sheet may include triethylene glycol bis(2-ethylhexanoate) as a plasticizer. In other embodiments, the plasticized poly(vinyl butyral) multilayer sheet may also include dihexyl adipate or bis(2-ethylhexyl) adipate or another convenient substance such as Benzoflex TM 9-88 benzoate) as a plasticizer.

[0031] In other embodiments, the additional plasticizer is selected from one or more esters of polyacids or polyols. In further embodiments, the additional plasticizer may be selected from one or more of the following: triethylene glycol bis(2-ethylhexanoate), tetraethylene glycol bis(2-ethylhexanoate), triethylene glycol bis(2-ethylbutyrate), triethylene glycol diheptanoate, tetraethylene glycol diheptanoate, dihexyl adipate, bis(2-ethylhexyl) adipate, bis(2-ethoxyethyl) adipate, dioctyl adipate, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, polymerized adipate, soybean oil, or epoxidized soybean oil.

[0032] In further embodiments, 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.

[0033] In a further embodiment, the hard poly(vinyl butyral) contained in the plasticized poly(vinyl butyral) multilayer sheet comprises from about 30 phr to about 45 phr of plasticizer. In one embodiment, the soft poly(vinyl butyral) can be separated from the mixture of the soft poly(vinyl butyral) and the additional plasticizer obtained in step b. by one or more of sedimentation, filtration, centrifugation, evaporation or precipitation to separate the soft poly(vinyl butyral).

[0034] The term "rigid poly(vinyl butyral)" refers to a poly(vinyl butyral) resin or a mixture of poly(vinyl butyral) resins that is significantly harder than a "soft poly(vinyl butyral)" and typically forms the skin or hard layer of a multilayer poly(vinyl butyral) multilayer sheet, as further described herein.

[0035] The term "soft poly(vinyl butyral)" refers to a poly(vinyl butyral) resin or a mixture of poly(vinyl butyral) resins that is significantly softer than a "hard poly(vinyl butyral)" and typically forms the core or soft layer of a multilayer poly(vinyl butyral) multilayer sheet, as further described herein. The poly(vinyl butyral) soft layer or core layer is typically sandwiched between two poly(vinyl butyral) hard layers or skin layers to form a multilayer poly(vinyl butyral) multilayer sheet.

[0036] As used herein, the term "plasticizer" generally refers to a molecule or mixture of molecules that, as further described herein, plasticizes a polymer, particularly poly(vinyl butyral), at relatively low levels of the plasticizer, thereby softening it. In addition, the plasticizers useful as additional plasticizers according to the present invention, when present in relatively high amounts as additional plasticizers, aid in the removal of the soft poly(vinyl butyral) from the pelletized poly(vinyl butyral) mixture by selectively washing away or partially dissolving the soft poly(vinyl butyral), due to the core layer having a higher affinity or compatibility for the plasticizer, as evidenced in part by its lower residual hydroxyl content.

[0037] In some embodiments, the additional plasticizer has a hydrocarbon segment of less than 20, less than 15, less than 12, or less than 10 carbon atoms. Suitable additional plasticizers for use in accordance with the present invention include esters of polyacids or polyols, etc. 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, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, polymerized adipates, soybean oil, and epoxidized soybean oil, and mixtures thereof. In one embodiment, the plasticizer is 3-GEH.

[0038] Additionally, plasticizers that are compatible at high temperatures may be used to further increase the fluidity of the interlayer.

[0039] As used herein, the term "poly(vinyl butyral) multilayer sheet" refers to a sheet composed of different layers of poly(vinyl butyral) resin, typically a soft layer or core layer with a hard layer or 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).

[0040] When we say that the poly(vinyl butyral) multilayer sheet is ground to obtain a granulated poly(vinyl butyral) mixture, we mean that it is reduced in size by any suitable tool (e.g., grinder) to obtain particles, fragments, thin slices, etc., all of which can be considered as particles of the present invention. In this granulation step, granulation can be carried out using any suitable equipment, which can be, for example, a commercial granulator, such as a Granutec granulator (East Douglas, Mass., USA). The scraps are granulated to reduce the particle size. The granulation of the scraps can produce a single particle with a long dimension less than 2.6 centimeters, or 0.1 to 1.0 centimeters, or 0.4 to 0.8 centimeters. Although particles with a size greater than 2.6 centimeters can be used, it is generally desired that the sheet be granulated to a smaller size, thereby producing a larger total particle surface area. At any time during the granulation process, the granulated thin slices can be sieved to remove the pollutants released in the poly(vinyl butyral).

[0041] When we say that additional plasticizer is added to the poly(vinyl butyral) particles, we mean that the plasticizer added in this step is in addition to the plasticizer contained in the plasticized poly(vinyl butyral) multilayer sheet. In fact, both the soft poly(vinyl butyral) and the rigid poly(vinyl butyral) already contain plasticizer. The additional plasticizer can be the same plasticizer present in the soft poly(vinyl butyral) and / or the rigid poly(vinyl butyral), or it can be different from the plasticizer present in the soft poly(vinyl butyral) and / or the rigid poly(vinyl butyral). The amount of additional plasticizer added is sufficient to help remove or wash away at least a portion of the soft poly(vinyl butyral) from the poly(vinyl butyral) particles to obtain the soft poly(vinyl butyral) and plasticizer varnish.

[0042] When we say that at least a portion of the soft poly(vinyl butyral) is removed from the poly(vinyl butyral) particles, we mean that a portion of the soft poly(vinyl butyral) is washed or dissolved from the particles. The particles can then be separated from the soft poly(vinyl butyral) and additional plasticizer according to one or more of the following techniques: decantation, filtration, or centrifugation as further described herein.

[0043] When we say that the particles are enriched in hard poly(vinyl butyral), we mean that the relative amount of hard poly(vinyl butyral) in the particles is higher than it was before a portion of the soft poly(vinyl butyral) was washed from the particles.

[0044] In one embodiment, the soft or core poly(vinyl butyral) or blend of soft poly(vinyl butyral) may 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) may be from about 7% to about 13, or from 8% to 12%, or as further described herein.

[0045] In one embodiment, the soft or core poly(vinyl butyral) or blend of soft poly(vinyl butyral) can have a residual acetate content 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.

[0046] The amount of plasticizer in the soft or core poly(vinyl butyral) or blend of soft poly(vinyl butyral) may be from about 50 phr to about 150 phr, or from 55 phr to 120 phr, or from 60 to 100 phr.

[0047] In another embodiment, the rigid poly(vinyl butyral) or blend of rigid poly(vinyl butyral) can have a residual hydroxyl content from about 12% to about 28%, as further described herein. Alternatively, the rigid poly(vinyl butyral) can have a residual hydroxyl content from about 15% to about 25%, or from 18% to 20%, or as further described herein.

[0048] In another embodiment, the rigid poly(vinyl butyral) or blend of rigid poly(vinyl butyral) can have a residual acetate content from about 0% to about 18%, as further described herein. Alternatively, the rigid poly(vinyl butyral) can have a residual acetate content of less than 10%, or less than 5%, or less than 2%, or less than 1%, or as further described herein.

[0049] In other embodiments, the residual hydroxyl content of the core layer can be equal to, greater than, or less than the residual hydroxyl content of the resin in the skin layer. In various embodiments, the core resin or the skin layer resin or both resins can contain less than 30% residual ester groups, less than 25% residual ester groups, less than 20%, less than 15%, less than 13%, less than 10%, less than 7%, less than 5%, or less than 1% residual ester groups by weight, calculated as polyvinyl ester (e.g., acetate), with the balance being acetals (such as butyraldehyde acetals), but optionally other acetal groups (such as isobutyraldehyde acetal groups, 2-ethylhexanal acetal groups, or a mixture of any two of butyraldehyde acetals, isobutyraldehyde acetals, and 2-ethylhexanal acetal groups), or as discussed elsewhere herein.

[0050] In one embodiment, the multilayer interlayer may include: a first skin polymer layer including plasticized poly(vinyl butyral) having a molecular weight of less than about 140,000 Daltons; a second core polymer layer including plasticized poly(vinyl butyral) having a molecular weight greater than about 140,000 Daltons; and a third skin polymer layer including plasticized poly(vinyl butyral) having a molecular weight less than about 140,000 Daltons. The second polymer layer is disposed between the first polymer layer and the third polymer layer, thereby forming two skin layers and a central core layer.

[0051] In various embodiments of the interlayer of the present disclosure, the interlayer may contain about 30 to about 60 phr (parts per hundred parts of resin) of total plasticizer. Although the total plasticizer content is indicated above, the plasticizer content in one or more cortexes or one or more core layers may be different from the total plasticizer content. In addition, one or more cortexes and one or more core layers may have different plasticizer contents because the plasticizer content of each corresponding layer is at least partially determined by its corresponding residual hydroxyl content under equilibrium conditions. For example, when the total cortex thickness is equal to the core layer thickness, for a total plasticizer amount of about 54.3 phr of the interlayer, the interlayer may include two cortexes (each cortex contains 38 phr of plasticizer) and one core layer (the core layer contains 75 phr of plasticizer) under equilibrium. For thicker or thinner cortexes, the total plasticizer amount of the interlayer may change accordingly.

[0052] In other embodiments, the amount of plasticizer in the hard or skin poly(vinyl butyral) or soft poly(vinyl butyral) blend may be from about 20 phr to about 60 phr, or from 25 phr to 50 phr, or from 30 to 45 phr.

[0053] In further embodiments, 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 from 4% to 8%, or from 5% to 10%, or as further described herein.

[0054] Thus, in various embodiments, the residual hydroxyl content of the poly(vinyl butyral) resin of one or more skin layers and one or more core layers may be different. For example, the resin used in one or more core layers may contain from about 9 to about 18 weight percent (wt%) residual hydroxyl groups (calculated as PVOH), from about 9 to about 16 weight percent residual hydroxyl groups (calculated as PVOH), or from about 9 to about 14 weight percent residual hydroxyl groups (calculated as PVOH). For example, the resin used in one or more batches may contain from about 13 to about 35 weight percent (wt%) residual hydroxyl groups (calculated as PVOH), from about 13 to about 30 weight percent residual hydroxyl groups (calculated as PVOH), or from about 15 to about 22 weight percent residual hydroxyl groups (calculated as PVOH); and, for certain embodiments, from about 17.25 to about 22.25 weight percent residual hydroxyl groups (calculated as PVOH), or as described elsewhere herein. The resin used for the core layer or for the skin layer or for both the skin layer and the core layer may also contain less than 20 wt % 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 % residual ester groups (calculated as polyvinyl ester (e.g., acetate)), the balance being acetal, preferably butyraldehyde acetal, but optionally including small amounts of other acetal groups, such as 2-ethylhexanal groups (see, e.g., U.S. Pat. No. 5,137,954, the entire disclosure of which is incorporated herein by reference).

[0055] 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 include a plasticizer selected from one or more of the following: dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycol benzoate, butoxyethyl benzoate, butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1-benzoate. ,3-pentanediol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3-butanediol dibenzoate, diethylene glycol di-o-toluate, triethylene glycol di-o-toluate, dipropylene glycol di-o-toluate, 1,2-octyl dibenzoate, tri-2-ethylhexyl trimellitate, di-2-ethylhexyl terephthalate, bisphenol A bis(2-ethylhexanoate), di-(butoxyethyl) terephthalate, di(butoxyethoxyethyl) terephthalate, bis(2-ethoxyethyl) adipate, or as further described herein.

[0056] In various embodiments, the additional plasticizer added may include one or more of the following: dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, polypropylene glycol dibenzoate, isodecyl benzoate, 2-ethylhexyl benzoate, diethylene glycol benzoate, butoxyethyl benzoate, butoxyethoxyethyl benzoate, butoxyethoxyethoxyethyl benzoate, propylene glycol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol dibenzoate, 2,2,4-trimethyl-1,3-pentanediol benzoate isobutyrate, 1,3 -butylene glycol 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 as further described herein, and may be the same as or different from the plasticizer in the poly(vinyl butyral) just described, as further described herein. Further plasticizers suitable as additional plasticizers or plasticizers in the soft poly(vinyl butyral) are described elsewhere herein.

[0057] As described above, the poly(vinyl butyral) multilayer sheet of the present invention generally comprises a hard poly(vinyl butyral) layer and a soft poly(vinyl butyral) layer. As described above, the core layer generally comprises a soft poly(vinyl butyral) sandwiched between hard poly(vinyl butyral) skin layers to form the poly(vinyl butyral) multilayer sheet of the present invention.

[0058] In one embodiment, the amount of additional plasticizer added to the poly(vinyl butyral) particles is sufficient to wash away, extract, or selectively dissolve a portion of the soft poly(vinyl butyral).

[0059] In another embodiment, the amount of additional plasticizer added to the poly(vinyl butyral) particles is sufficient to suspend the rigid poly(vinyl butyral) particles of the mixture to form a rigid poly(vinyl butyral) suspension.

[0060] In yet another embodiment, additional plasticizer is added to the poly(vinyl butyral) particles 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) particles so that the particles are enriched in hard poly(vinyl butyral). The particles can then be separated from the resulting varnish mixture of soft poly(vinyl butyral) and additional plasticizer, or the varnish can be used without separating the additional plasticizer from the soft poly(vinyl butyral), or without only partially separating the additional plasticizer from the soft poly(vinyl butyral), or without separating water from the mixture.

[0061] In another embodiment, the present invention is directed to a poly(vinyl butyral) sheet comprising a separate soft poly(vinyl butyral), and a laminated glass comprising the poly(vinyl butyral) sheet.

[0062] In further embodiments, the present invention is directed to poly(vinyl butyral) sheets comprising soft poly(vinyl butyral), and laminated glasses comprising these poly(vinyl butyral) sheets.

[0063] When we say that the rigid poly(vinyl butyral) is separated from the poly(vinyl butyral) mixture by decantation or sedimentation, we mean that the liquid is separated from the rigid poly(vinyl butyral) solids, for example, by allowing the solids to settle to the bottom of a container and removing most of the additional plasticizer from the particles.

[0064] When we say that the rigid poly(vinyl butyral) is separated by filtration, we mean that the rigid poly(vinyl butyral) solids in the pellets are filtered away from the plasticizer.

[0065] When we say that the rigid poly(vinyl butyral) is separated from the mixture by centrifugation, we mean that a centrifuge is used to separate the solid from the liquid.

[0066] The present invention can be further understood based on the following further description.

[0067] Thus, in one embodiment, the multilayer poly(vinyl butyral) sheets of the present invention may include an interlayer comprising one or more rigid skin layers and one or more soft core layers. In one embodiment, these multilayer interlayer sheets may include: a first polymer layer (skin layer) comprising a rigid plasticized poly(vinyl butyral) resin; a second polymer layer (core layer) comprising a soft plasticized poly(vinyl butyral) resin, or a blend of soft plasticized poly(vinyl butyral) resins having the same or different residual hydroxyl content; and an optional third polymer layer (skin layer) comprising a rigid plasticized poly(vinyl butyral) resin. The second or core polymer layer is disposed adjacent to the first polymer layer. If there are three or more layers, the second polymer layer may be disposed between the first polymer layer and the third polymer layer, thereby forming two skin layers and a central core layer.

[0068] In embodiments, the second or core poly(vinyl butyral) resin may be present in an amount from about 2 weight percent to about 45 weight percent, or about 5 weight percent to about 40 weight percent.

[0069] 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.

[0070] In embodiments, the second poly(vinyl butyral) resin is present in an amount from about 2 weight percent to about 45 weight percent, or about 5 weight percent to about 40 weight percent.

[0071] In an embodiment, the polymer interlayer has at least two different glass transition temperatures (T g ), and at least two different glass transition temperatures (T g ) is at least 5°C.

[0072] In embodiments, the third or skin poly(vinyl butyral) resin has the same residual hydroxyl content as the first or core poly(vinyl butyral) resin.

[0073] In one embodiment of the present invention, a single plasticizer such as triethylene glycol bis(2-ethylhexanoate) or a mixture thereof with dihexyl adipate may be used.

[0074] Thus, the present invention relates to a method of preferentially removing, washing away or partially dissolving soft poly(vinyl butyral) resin from poly(vinyl butyral) particles using a plasticizer as an extractant, taking advantage of the solubility differences of the PVB component in the plasticizer. This is different from using conventional solvents. Thus, the present invention provides a method of recovering raw materials for reintroduction into the manufacturing process.

[0075] Due to the differences in cloud points of poly(vinyl butyral) resins of different compositions, specifically measured as the percentage of residual polyvinyl alcohol (PVOH) in the plasticizer, this technique allows the use of temperature as a key parameter for effectively separating the different poly(vinyl butyral) components. In this regard, additional plasticizer can be added to the poly(vinyl butyral) particles at a temperature of at least 25°C, or at least 30°C, or from about 25°C to about 90°C, or 30°C to about 60°C, or as disclosed elsewhere herein.

[0076] The poly(vinyl butyral) compound is a component of a multilayer poly(vinyl butyral) sheet, wherein each layer is composed of poly(vinyl butyral) and a plasticizer, wherein the composition is different from the composition of the poly(vinyl butyral) (i.e., different residual hydroxyl or residual acetate content) and the plasticizer content. In most cases, the amount of plasticizer is different relative to the amount of poly(vinyl butyral). The rejected sheet is ground into smaller flakes (usually ground to a size ranging from 3 to 30 mm), and a large amount of the poly(vinyl butyral) compound is generally extracted from the multilayer sheet particles.

[0077] The degree of separation depends on the plasticizer used, for example, the extraction of the core layer PVB from the poly(vinyl butyral) multilayer sheet using triethylene glycol bis(2-ethylhexanoate) can be carried out to the extent that 25% to 50% of the core layer PVB is removed in a single fractionation step. Repeated extraction will increase the degree of separation between the different poly(vinyl butyral) compounds. Generally, the extraction can be achieved when the multilayer sheet or a portion thereof is exposed to a specific solvent at a temperature ranging from 25 to 100° C., and the extraction time for one extraction cycle is between 5 minutes and several days.

[0078] Conventional multilayer interlayers, such as three-layer acoustic interlayers, typically contain a soft core layer composed of a single poly(vinyl butyral) ("PVB") resin having a low residual hydroxyl content and a high amount of traditional plasticizer, and two hard skin layers having significantly higher residual hydroxyl contents (see, e.g., U.S. Patents 5,340,654, 5,190,826, and 7,510,771). Thus, the separated soft poly(vinyl butyral) can be recycled to form the core layer of a three-layer acoustic interlayer, or the soft poly(vinyl butyral) and plasticizer varnish can be used directly to form the soft poly(vinyl butyral) layers without first separating the two. The residual hydroxyl content and the amount of plasticizer in the PVB core resin are optimized so that the interlayer provides optimal sound insulation performance under ambient conditions for multilayer glass panels installed on vehicles and buildings, such as windshields and windows.

[0079] PVB resins are prepared by reacting polyvinyl alcohol ("PVOH") with butyraldehyde in the presence of an acid catalyst by a known acetalization process, followed by resin isolation, stabilization, and drying. Such acetalization processes are disclosed, for example, in U.S. Pat. Nos. 2,282,057 and 2,282,026 and Vinyl Acetal Polymers, in Encyclopedia of Polymer Science & Technology, 3rd Edition, Vol. 8, pp. 381-399, by BE Wade (2003), the entire disclosures of which are incorporated herein by reference. The resins are commercially available in a variety of forms, such as those produced by Solutia Inc., a wholly owned subsidiary of Eastman Chemical Company. Resin.

[0080] As used herein, the residual hydroxyl content (calculated as weight percent vinyl alcohol or weight percent PVOH) in poly(vinyl butyral) refers to the amount of hydroxyl groups remaining on the polymer chain after processing is completed. For example, poly(vinyl butyral) can be made by hydrolyzing polyvinyl acetate to polyvinyl alcohol (PVOH) and then reacting the PVOH with butyraldehyde. In the process of hydrolyzing polyvinyl acetate, generally not all of the pendant acetate groups are converted to hydroxyl groups. Further, the reaction with butyraldehyde generally does not result in all of the hydroxyl groups being converted to acetal groups. Therefore, in any finished poly(vinyl butyral) resin, there will generally be residual acetate groups (in the form of vinyl acetate groups) and residual hydroxyl groups (in the form of vinyl hydroxyl groups) as pendant groups on the polymer chain. As used herein, the residual hydroxyl content and the residual acetate content are measured in weight percent (weight percent) according to ASTM D1396.

[0081] As measured by molecular exclusion chromatography using small angle laser light scattering, the poly(vinyl butyral) resins of the present disclosure typically have 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 used herein, the term "molecular weight" means weight average molecular weight.

[0082] Various adhesion control agents ("ACAs") may be used in the interlayers of the present disclosure to control the adhesion of the interlayer sheets to the glass. In various embodiments of the interlayers of the present disclosure, the interlayer may include about 0.003 to about 0.15 parts of ACA per 100 parts of resin; about 0.01 to about 0.10 parts of ACA per 100 parts of resin; and about 0.01 to about 0.04 parts of ACA per 100 parts of resin. Such ACAs include, but are not limited to, ACAs disclosed in U.S. Pat. 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).

[0083] Other additives may be incorporated into the interlayer to enhance its performance in the final product and to 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 tungsten oxide), processing aids, flow enhancing additives, lubricants, impact modifiers, nucleating agents, thermal stabilizers, UV absorbers, dispersants, surfactants, chelating agents, coupling agents, adhesives, initiators, reinforcing additives and fillers, and other additives known to those of ordinary skill in the art.

[0084] In various embodiments of the interlayer of the present disclosure, the interlayer comprises a total plasticizer of greater 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. Although the total plasticizer content is indicated above, the plasticizer content in one or more cortexes or one or more core layers may be different from the total plasticizer content. In addition, one or more cortexes and one or more core layers may have different plasticizer types and plasticizer contents, within the scope discussed above, because the plasticizer content of each corresponding layer is determined by the residual hydroxyl content of the layer in equilibrium, as disclosed in U.S. Patent No. 7,510,771 (the entire disclosure of which is incorporated herein by reference). For example, when the total skin thickness is equal to the core layer thickness, for a total plasticizer amount of about 45.4 phr of the interlayer, the interlayer can include two skin layers (each containing 30 phr of plasticizer) and a core layer (the core layer contains 65 phr of plasticizer) under balance. For thicker or thinner skin layers, the total plasticizer amount of the interlayer will change accordingly. In various embodiments of the present invention, the plasticizer content of the core layer and the skin layer differs 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 or more. As used herein, the amount of plasticizer or any other component in the interlayer can be measured in parts per hundred of resin (phr), based on weight / weight. For example, if 30 grams of plasticizer are added to 100 grams of polymer resin, the plasticizer content of the resulting plasticized polymer is 30 phr. As used herein, when the plasticizer content of an interlayer is given, the plasticizer content is determined by reference to the phr of the plasticizer in the mixture or melt used to produce the interlayer.

[0085] The final interlayer, whether formed by extrusion or coextrusion, generally has a random rough surface morphology because it is formed by melt fracture of the polymer melt as it leaves the extrusion die, and can also be embossed on a random rough surface on one or both sides (e.g., the skin layer) by any embossing method known to a person of ordinary skill in the art.

[0086] Although all methods of producing polymer interlayer sheets known to those of ordinary skill in the art are considered possible methods of producing the polymer interlayer sheets described herein, this application will focus on polymer interlayer sheets produced by extrusion and coextrusion processes. The final multilayer glass panel laminate of the present invention is formed using a lamination process known in the art.

[0087] Generally speaking, the thickness or gauge of the polymer interlayer sheet will be in the range of 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 to 1.27 mm), and about 15 mils to about 35 mils (about 0.38 to about 0.89 mm). In various embodiments, the thickness of each layer of the multilayer interlayer (such as the skin layer and the core layer) can be about 1 mil to 99 mils (about 0.025 to 2.51 mm), about 1 mil to 59 mils (about 0.025 to 1.50 mm), 1 mil to about 29 mils (about 0.025 to 0.74 mm), or about 2 mils to about 28 mils (about 0.05 to 0.71 mm).

[0088] Although the following embodiments refer to the polymer resin as poly(vinyl butyral) PVB, one of ordinary skill in the art will appreciate that the polymer may be any polymer suitable for use in a multilayer panel. Typical polymers include, but are not limited to, polyvinyl acetal (PVA) (such as PVB or isomeric poly(vinyl isobutyral) (PVisoB), polyurethane (PU), poly(ethylene-co-vinyl acetate) (EVA), polyvinyl chloride (PVC), poly(vinyl chloride-co-methacrylate), polyethylene, polyolefins, ethylene acrylate copolymers, poly(ethylene-co-butyl acrylate), silicone elastomers, epoxy resins, and acid copolymers (such as ethylene / carboxylic acid copolymers and ionic polymers thereof, which are derived from any of the above possible thermoplastic resins, combinations of the above substances, etc.). PVB and its isomeric polymers PVisoB, polyvinyl chloride, and polyurethane are particularly useful polymers for interlayers in general; PVB (and its isomeric polymers) are particularly preferred. For example, a multilayer interlayer may 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.

[0089] As used herein, a multilayer panel may comprise a single substrate, such as glass, acrylic or polycarbonate, on which a polymer interlayer sheet is disposed, and most commonly, a polymer film is also disposed on the polymer interlayer. The combination of a polymer interlayer sheet and a polymer film is generally referred to as a double layer in the art. A typical multilayer panel having a double layer structure is: (glass) / / (polymer interlayer sheet) / / (polymer film), wherein the polymer interlayer sheet may include a plurality of interlayers, as described above. The polymer film provides a smooth, thin and hard substrate that provides better optical properties than those typically obtained using a polymer interlayer sheet alone, and may serve as a performance enhancement layer. The polymer film differs from the polymer interlayer sheet as used herein in that the polymer film itself does not provide the necessary penetration resistance and glass retention properties, but rather provides performance improvements, 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, such as having a thickness from about 0.001 to 0.2 mm.

[0090] The interlayers of the present disclosure are most commonly used in multilayer panels comprising two substrates, such as a pair of glass sheets (or other rigid materials known in the art, such as polycarbonate or acrylic resins), wherein the interlayer is disposed between the two substrates. An example of such a construction is: (glass) / / (polymer interlayer sheet) / / (glass), wherein the polymer interlayer sheet may include multiple layers of interlayers, as described above. These examples of multilayer panels are in no way intended to be limiting, as one of ordinary skill in the art will readily recognize that a variety of constructs other than those described above may be fabricated utilizing the interlayers of the present disclosure.

[0091] A typical glass lamination process includes the following steps: (1) assembling two substrates (e.g., glass) and an interlayer; (2) heating the assembly for a short time by infrared radiation or convection; (3) passing the assembly through a pressure roller for a first degassing; (4) heating the assembly for a second time to about 60° C. to 120° C. so that the assembly has sufficient temporary adhesion to seal the edges of the interlayer; (5) passing the assembly through a second pressure roller to further seal the edges of the interlayer and allow further processing; and (6) subjecting the assembly to a high temperature and high pressure treatment at a temperature between 135° C. and 150° C. and a pressure between 180 psig and 200 psig for about 30 to 90 minutes. As known to those skilled in the art, the actual steps as well as the time and temperature can vary as desired. Other methods known in the art and commercially practiced for interlayer-glass interface degassing (steps 2-5) include vacuum bag and vacuum ring processes, in which a vacuum is used to remove air.

[0092] Unless otherwise indicated, all numerals representing the number of components, characteristics (such as molecular weight, reaction conditions, etc.) used in the specification and claims are to be understood as being modified by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters set forth in the following specification and the appended claims are approximate values, which can be varied according to the desired characteristics to be sought to be obtained by the present invention. At a minimum, each numerical parameter should be interpreted at least according to the numerical value of the significant figures reported and by applying common rounding techniques. In addition, the scope described in the disclosure and claims is intended to specifically include the entire scope, rather than just one or more endpoints. For example, the scope defined as 0 to 10 is intended to disclose all integers between 0 to 10 (such as, for example, 1, 2, 3, 4, etc.), all fractions between 0 to 10 (such as 1.5, 2.3, 4.57, 6.1113, etc.) and endpoints 0 and 10.

[0093] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are intended to be reported precisely as measured. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0094] It should be understood that the reference to one or more process steps does not exclude the presence of additional process steps before or after the steps in the combination or the insertion of process steps between those steps explicitly identified. In addition, the use of letters, numbers or the like to represent process steps, components or other aspects of information disclosed or claimed in the application is a convenient way to identify discrete activities or components, and the listed letters may be arranged in any order unless otherwise indicated.

[0095] As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to C n Alcohol equivalents are intended to include various types of C n Alcohol equivalents. Thus, even if language such as "at least one" or "at least some" is used in one place, it does not mean that the use of "a", "an", and "the" elsewhere excludes plural referents unless the context clearly dictates otherwise. Similarly, the use of language such as "at least some" in one place does not mean that "all" is meant to be used without the use of such language elsewhere, unless the context clearly dictates otherwise.

[0096] 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 may be used alone, or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B, and / or C, the composition may contain only A; only B; only C; 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.

[0097] Example

[0098] Comparative Example 1 (predict)

[0099] 10 kg of varnish containing 5 weight percent of soft PVB and 10 kg of soft acoustic PVB resin powder were put into a twin-screw extruder for mixing and then pelletized. The pellets obtained contained 90.5 phr of plasticizer.

[0100] Example 1 (predict)

[0101] 5kg of varnish containing 5 weight percent soft PVB and 10kg of soft acoustic PVB resin powder were mixed in a twin-screw extruder and then granulated. The resulting pellets contained 46.3phr of plasticizer. These pellets were sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were then fed into a continuous mixer with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80phr, and then discharged into an extruder for PVB sheet extrusion.

[0102] Example 2 (predict)

[0103] 5kg of varnish containing 5 weight percent soft PVB and 10kg of soft acoustic PVB resin powder were mixed in a twin screw extruder and then granulated. The resulting pellets contained 46.3phr of plasticizer. These pellets were sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were then fed into a twin screw extruder to extrude PVB sheets. Additional plasticizers and adhesion control additives were then injected to reach a target plasticizer composition of 70-80phr.

[0104] Example 3 (predict)

[0105] 4 kg of varnish containing 5 weight percent soft PVB and 12 kg of soft acoustic PVB resin powder were mixed in a twin screw extruder and then granulated. The resulting pellets contained 31.1 phr of plasticizer. These pellets were then sprinkled with 0.0-1.0 phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80 phr, and then discharged into an extruder for PVB sheet extrusion.

[0106] Example 4 (predict)

[0107] 4kg of varnish containing 5 weight percent soft PVB and 12kg of soft acoustic PVB resin powder were mixed in a twin screw extruder and then granulated. The resulting pellets contained 31.1phr of plasticizer. These pellets were then sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were fed into a twin screw extruder to extrude PVB sheets. Additional plasticizers and adhesion control additives were then injected to reach a target plasticizer composition of 70-80phr.

[0108] Comparative Example 2 (predict)

[0109] 10 kg of varnish containing 10 weight percent of soft PVB and 10 kg of soft acoustic PVB resin powder were mixed in a twin-screw extruder and then granulated. The obtained pellets contained 81.8 phr of plasticizer.

[0110] Example 5 (predict)

[0111] 5kg of varnish containing 10 weight percent soft PVB and 10kg of soft acoustic PVB resin powder were mixed in a twin-screw extruder and then granulated. The resulting pellets contained 42.9phr of plasticizer. These pellets were then sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80phr, and then discharged into an extruder for PVB sheet extrusion.

[0112] Example 6 (predict)

[0113] 5kg of varnish containing 10 weight percent soft PVB and 10kg of soft acoustic PVB resin powder are put into a twin screw extruder for mixing and then granulated. The resulting pellets contain 42.9phr of plasticizer. These pellets are then sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are fed into a twin screw extruder to extrude PVB sheets. Additional plasticizers and adhesion control additives are then injected to reach a target plasticizer composition of 70-80phr.

[0114] Example 7 (predict)

[0115] 4 kg of varnish containing 10 weight percent soft PVB

[0116] Mixed with 12kg soft acoustic PVB resin powder in a twin screw extruder and then granulated. The resulting pellets contain 29.0phr of plasticizer. These pellets are then sprinkled with 0.0-1.0phr soft acoustic PVB resin powder to reduce viscosity. These pellets are then fed into a continuous mixer with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80phr and then discharged into an extruder for PVB sheet extrusion.

[0117] Example 8 (predict)

[0118] 4 kg of varnish containing 10 weight percent soft PVB and 12 kg of soft acoustic PVB resin powder were mixed in a twin screw extruder and then granulated. The resulting pellets contained 29.0 phr of plasticizer. These pellets were then sprinkled with 0.0-1.0 phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were fed into a twin screw extruder for extruding PVB sheets. Additional plasticizers and adhesion control additives were injected to reach a target plasticizer composition of 70-80 phr.

[0119] Example 9

[0120] 10kg of varnish containing 15 weight percent soft PVB is put into a twin-screw extruder and mixed with 10kg of soft acoustic PVB resin powder, and then granulated. The resulting pellets have 73.9phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 74-80phr, and then discharged into an extruder for PVB sheet extrusion. Therefore, it is found that the resulting PVB is suitable for use as the core of an acoustic interlayer.

[0121] Example 10

[0122] 10kg of varnish containing 15 weight percent soft PVB is mixed with 10kg of soft acoustic PVB resin powder in a twin screw extruder and then granulated. The resulting pellets have 73.9phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are fed into a twin screw extruder for extruding PVB sheets. Additional plasticizers and adhesion control additives are injected to reach a target plasticizer composition of 74-80phr. Therefore, it is found that the resulting PVB is suitable for use as the core of an acoustic interlayer.

[0123] Embodiment 11

[0124] 5kg of varnish containing 15 weight percent soft PVB is put into a twin-screw extruder and mixed with 10kg of soft acoustic PVB resin powder, and then granulated. The resulting pellets have 39.5phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80phr, and then discharged into an extruder for PVB sheet extrusion. Therefore, it is found that the resulting PVB is suitable for use as the core of an acoustic interlayer.

[0125] Example 12

[0126] 5kg of varnish containing 15 weight percent soft PVB is mixed with 10kg of soft acoustic PVB resin powder in a twin screw extruder and then granulated. The resulting pellets have 39.5phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are fed into a twin screw extruder for extruding PVB sheets. Additional plasticizers and adhesion control additives are injected to reach a target plasticizer composition of 70-80phr. Therefore, it is found that the resulting PVB is suitable for use as the core of an acoustic interlayer.

[0127] Embodiment 13

[0128] 4kg of varnish containing 15 weight percent soft PVB is put into a twin-screw extruder and mixed with 12kg soft acoustic PVB resin powder, and then granulated. The resulting pellets have 27.0phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr soft acoustic PVB resin powder to reduce viscosity. These pellets are fed into a continuous mixer together with additional plasticizer and adhesion control additives to reach a target plasticizer composition of 70-80phr, and then discharged into an extruder for PVB sheet extrusion. Therefore, it is found that the resulting PVB is suitable for use as the core of an acoustic interlayer.

[0129] Embodiment 14

[0130] 4kg of varnish containing 15 weight percent soft PVB is mixed with 12kg of soft acoustic PVB resin powder in a twin screw extruder and then granulated. The resulting pellets have 27.0phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are fed into a twin screw extruder for extruding PVB sheets. Additional plasticizers and adhesion control additives are injected to reach a target plasticizer composition of 70-80phr. Therefore, it is found that the resulting PVB is suitable for use as the core of an acoustic interlayer.

[0131] Embodiment 15 (predict)

[0132] 10kg of varnish containing 20 weight percent soft PVB and 10kg of soft acoustic PVB resin powder are mixed in a twin-screw extruder and then granulated. The resulting pellets contain 66.7phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are then fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80phr, and then discharged into an extruder for PVB sheet extrusion.

[0133] Example 16 (predict)

[0134] 10kg of varnish containing 20 weight percent soft PVB and 10kg of soft acoustic PVB resin powder are mixed in a twin screw extruder and then granulated. The resulting pellets contain 66.7phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are then fed into a twin screw extruder to extrude PVB sheets. Additional plasticizers and adhesion control additives are injected to reach a target plasticizer composition of 70-80phr.

[0135] Embodiment 17 (predict)

[0136] 5kg of varnish containing 20 weight percent soft PVB and 10kg of soft acoustic PVB resin powder were mixed in a twin-screw extruder and then granulated. The resulting pellets contained 36.4phr of plasticizer. These pellets were sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were then fed into a continuous mixer with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80phr, and then discharged into an extruder for PVB sheet extrusion.

[0137] Embodiment 18 (prophecy)

[0138] 5kg of varnish containing 20 weight percent soft PVB and 10kg of soft acoustic PVB resin powder are put into a twin screw extruder for mixing and then granulated. The resulting pellets contain 36.4phr of plasticizer. These pellets are then sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are fed into a twin screw extruder to extrude PVB sheets. Additional plasticizers and adhesion control additives are injected to reach a target plasticizer composition of 70-80phr.

[0139] Embodiment 19 (predict)

[0140] 4 kg of varnish containing 20 weight percent soft PVB and 12 kg of soft acoustic PVB resin powder were mixed in a twin screw extruder and then granulated. The resulting pellets contained 25.0 phr of plasticizer. These pellets were then sprinkled with 0.0-1.0 phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80 phr, and then discharged into an extruder for PVB sheet extrusion.

[0141] Embodiment 20 (predict)

[0142] 4kg of varnish containing 20 weight percent soft PVB and 12kg of soft acoustic PVB resin powder were mixed in a twin screw extruder and then granulated. The resulting pellets contained 25.0phr of plasticizer. These pellets were sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were then fed into a twin screw extruder to extrude PVB sheets. Additional plasticizer and adhesion control additives were injected to reach a target plasticizer composition of 70-80phr.

[0143] Embodiment 21 (predict)

[0144] 10kg of varnish containing 25 weight percent soft PVB and 10kg of soft acoustic PVB resin powder are put into a twin-screw extruder for mixing and then granulated. The resulting pellets contain 60.0phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are then fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80phr, and then discharged into an extruder for PVB sheet extrusion.

[0145] Embodiment 22 (predict)

[0146] 10kg of varnish containing 25 weight percent soft PVB and 10kg of soft acoustic PVB resin powder are put into a twin screw extruder for mixing and then granulated. The resulting pellets contain 60.0phr of plasticizer. These pellets are sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets are then fed into a twin screw extruder to extrude PVB sheets. Additional plasticizers and adhesion control additives are injected to reach a target plasticizer composition of 70-80phr.

[0147] Embodiment 23 (predict)

[0148] 5kg of varnish containing 25 weight percent soft PVB and 10kg of soft acoustic PVB resin powder were mixed in a twin-screw extruder and then granulated. The resulting pellets contained 33.3phr of plasticizer. These pellets were then sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80phr, and then discharged into an extruder for PVB sheet extrusion.

[0149] Embodiment 24 (predict)

[0150] 5kg of varnish containing 25 weight percent soft PVB was mixed with 10kg of soft acoustic PVB resin powder in a twin screw extruder and then granulated. The resulting pellets contained 33.3phr of plasticizer. These pellets were sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were fed into a twin screw extruder to extrude PVB sheets. Additional plasticizers and adhesion control additives were injected to reach a target plasticizer composition of 70-80phr.

[0151] Embodiment 25 (predict)

[0152] 4 kg of varnish containing 25 weight percent soft PVB and 12 kg of soft acoustic PVB resin powder were mixed in a twin-screw extruder and then granulated. The resulting pellets contained 23.1 phr of plasticizer. These pellets were sprinkled with 0.0-1.0 phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were fed into a continuous mixer together with additional plasticizer and adhesion control additives to achieve a target plasticizer composition of 70-80 phr, and then discharged into an extruder for PVB sheet extrusion.

[0153] Embodiment 26 (predict)

[0154] 4kg of varnish containing 25 weight percent soft PVB and 12kg of soft acoustic PVB resin powder were mixed in a twin screw extruder and then granulated. The resulting pellets contained 23.1phr of plasticizer. These pellets were sprinkled with 0.0-1.0phr of soft acoustic PVB resin powder to reduce viscosity. These pellets were then fed into a twin screw extruder to extrude PVB sheets. Additional plasticizer and adhesion control additives were injected to reach a target plasticizer composition of 70-80phr.

[0155] Table 1. Summary of Examples.

[0156]

[0157]

Claims

1. A process for recovering soft poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet comprising hard 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) particles; b. adding an additional plasticizer to the poly(vinyl butyral) particles, thereby removing at least a portion of the soft poly(vinyl butyral) in the poly(vinyl butyral) particles to obtain (i) particles rich in the hard poly(vinyl butyral) and (ii) a varnish of the soft poly(vinyl butyral) and the additional plasticizer; c. physically separating the particles rich in the hard poly(vinyl butyral) from the varnish of the soft poly(vinyl butyral) and the additional plasticizer, wherein the varnish has a first concentration of plasticizer; as well as d. adding under-plasticized poly(vinyl butyral) to the varnish to provide a soft poly(vinyl butyral) composition having a plasticizer concentration lower than the first concentration.

2. The process of claim 1 wherein the underplasticized poly(vinyl butyral) comprises up to about 45 phr of plasticizer.

3. The process of claim 1 wherein the underplasticized poly(vinyl butyral) comprises from about 0 to about 1 phr.

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

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

6. The process of claim 4 further comprising the step of forming the soft poly(vinyl butyral) composition into pellets and sprinkling a soft poly(vinyl butyral) resin in powder form having less than or equal to about 1 phr of plasticizer on the pellets.

7. The process according to claim 1, wherein the plasticizer is selected from one or more of esters of polyacids or polyols.

8. The process of 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, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, dibutyl sebacate, polymerized adipate, soybean oil or epoxidized soybean oil.

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

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

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

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

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

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

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

16. The process of claim 1 wherein the additional plasticizer added to the poly(vinyl butyral) particles in step b) comprises triethylene glycol bis(2-ethylhexanoate).

17. The process of 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 of 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 of any one of claims 1 to 6.

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

Images