Method for producing polymethyl methacrylate sheets and gaskets

Abstract

The invention relates to a method for producing a polymethyl methacrylate sheet, the method comprising the steps of providing a mold comprising at least one gasket enclosed between two substantially parallel mold parts, introducing a liquid comprising a methyl methacrylate prepolymer and / or a methyl methacrylate monomer into the mold, and polymerizing the liquid methyl methacrylate. The invention also relates to a gasket for use in a mold for producing a polymethyl methacrylate sheet.

Description

[0001] This invention relates to a method for producing polymethyl methacrylate (PMMA) sheets. The invention also relates to PMMA sheets produced via said method. Furthermore, the invention relates to a liner used in a mold for producing PMMA sheets, and such a mold.

[0002] Polymethyl methacrylate (PMMA) is a transparent thermoplastic material widely used in a variety of applications, such as optical applications. PMMA is popular for its exceptional (material) properties, such as weather resistance and scratch resistance. Furthermore, the material is known for its good impact strength and good chemical resistance. PMMA is commercially available in granules and sheets or plates. PMMA sheets can be formed into lightweight or shatter-resistant glass alternatives and are also known as acrylic, acrylic glass, or plexiglass. The production of PMMA sheets is typically accomplished using two parallel glass panels separated by a spacer sandwiched between the glass panels via cell casting. Thus, the glass panels and spacer form a casting cell that can contain the casting liquid. A casting liquid, typically methyl methacrylate (MMA) monomer or MMA prepolymer, is poured between the two glass panels, and then subjected to a polymerization step, causing the polymethyl methacrylate sheet to form within the boundaries of the spacer. The glass panels are removed after polymerization. Traditional liners used for casting PMMA are typically made of polyvinyl chloride (PVC). After the PMMA sheet has polymerized, the liner must be removed from the sheet. This is usually done by cutting (or trimming) the edges of the sheet. The liner and any polymer waste that may have adhered to it are then separated from the final PMMA sheet. One disadvantage of PVC is that (P)MMA mixes with PVC material, making it difficult to separate PVC and PMMA waste. Another disadvantage of using PVC is that from an environmental perspective, using this type of plastic is undesirable because it is difficult to recycle. Often, residues or remnants containing PVC still end up in landfills, so it is highly desirable to avoid using PVC altogether.

[0003] Therefore, one object of the present invention is to provide at least one alternative to using PVC as a liner in the mold when producing PMMA sheets.

[0004] The present invention provides a method for producing polymethyl methacrylate (PMMA) sheets, comprising the steps of: providing a mold comprising at least two mold components, each mold component having at least one substantially flat mold surface facing a substantially flat mold surface of an opposing mold component, and wherein the mold comprises at least one gasket sandwiched between the substantially flat mold surfaces of the opposing mold components such that a mold cavity is defined by the mold components and the gasket; at least partially filling the mold cavity by introducing a liquid comprising PMMA prepolymer and / or PMMA monomer; polymerizing the PMMA prepolymer and / or PMMA monomer introduced into the mold cavity to form a PMMA sheet encapsulated by the gasket within the mold cavity; and removing the gasket and the PMMA sheet encapsulated by the gasket from the mold components. Preferably, the gasket comprises at least one hydrocarbon-based copolymer.

[0005] The method according to the invention is specifically a method for manufacturing cast polymethyl methacrylate (PMMA) sheets, i.e., a method for cell casting of PMMA sheets. Where the term sheet is used, it also refers to a sheet material. In the method according to the invention, a liner comprising at least one hydrocarbon-based copolymer is preferably used. The liner according to the invention has several advantages compared to conventional methods that typically utilize PVC liner. A liquid comprising (poly)methyl methacrylate prepolymer and / or methyl methacrylate monomer is introduced into the mold cavity of a mold such that the mold is substantially completely filled with liquid. The mold may also be referred to as a casting cell. It is conceivable that, before introducing the MMA liquid into the mold, the substantially flat mold surfaces facing opposite mold components are partially or completely joined to one another. When the liquid is introduced into the mold, the liquid is in direct contact with at least a portion of the liner. The mold components are removed after the liquid has polymerized. This can be done, for example, by removing the clamping connections between the mold components. A PMMA sheet encapsulated between the liner is obtained. The PMMA sheet may be at least partially bonded or attached to the liner. As mentioned above, the circumferential sides or edges of the cast PMMA sheet are typically removed after casting to obtain a final product in the form of an uncontaminated PMMA sheet. This can be done by cutting or trimming. Specifically, a portion of the edge of the liner and the manufactured PMMA sheet is removed. This removed waste or residue contains a combination of PMMA from the produced sheet and polymers from the liner used in the mold (specifically, a hydrocarbon-based copolymer liner). Because the liner according to the invention contains a hydrocarbon-based copolymer, the waste specifically consists of PMMA and a hydrocarbon-based copolymer. This results in the waste being relatively easily processed for further applications, such as recycling. The waste can, for example, be recycled and / or depolymerized. Several known techniques can be applied to the recycling and / or depolymerization of liners containing at least one hydrocarbon-based copolymer. The application of liners containing at least one hydrocarbon-based copolymer is advantageous because such materials can improve the mechanical properties of the recycling process, as it can, for example, contribute to improved impact resistance. Because hydrocarbon-based copolymers primarily contain hydrogen and carbon atoms, the byproducts are relatively harmless even when chemical recycling and / or incineration of waste or liners are applied. In contrast, recycling PVC can lead to the chemical reaction of chlorine in the polymer, producing harmful byproducts that are environmentally undesirable, compared to conventional PVC liners. It is conceivable that the liner is at least partially made of a hydrocarbon-based copolymer. Preferably, the liner is made of a recyclable polymer. It is also conceivable that the liner contains at least one hydrocarbon-based block copolymer. The hydrocarbon-based copolymer can be in a grafted form. Therefore, the liner may also contain at least one grafted polymer, particularly at least one hydrocarbon-based grafted polymer.The grafted polymer exhibits relatively high compatibility with the base polymer. Non-limiting examples of grafted polymers applicable to the methods according to the invention are grafted SEBS (SEBS-g-GMA) and / or polyethylene grafted with maleic anhydride. When referring to (PMMA) waste, it also means polymer waste, acrylic waste, or residues.

[0006] The method according to the invention can further benefit from the material properties of the gasket. When the MMA liquid is introduced into the mold cavity of the mold such that the mold is substantially completely filled with liquid, the liquid thereby comes into direct contact with at least a portion of the gasket upon introduction into the mold. As a result of this direct contact, the MMA monomers or MMA prepolymers in the liquid may cause a portion of the gasket to dissolve within the liquid. Possibly, during the production of the PMMA sheet, at least a portion of the outer surface of the gasket in direct contact with the MMA liquid will dissolve within the MMA liquid. The degree of dissolution depends particularly on the temperature of the liquid and / or the surface it contacts. Thus, a relatively strong bond can be obtained between the gasket and the sheet. The contact between the MMA monomers or prepolymers and the gasket can also result in a bond between the PMMA of the sheet and the polymer of the gasket. The contact between the MMA monomers or prepolymers and the gasket can further cause at least a portion of the gasket to swell or expand. Due to the swelling of the gasket, an improved seal of the gasket to the mold can be obtained when the method according to the invention is applied. The gasket is encapsulated between two substantially parallel mold components in the mold, which are typically clamped together. Due to the clamping structure, the swelling of at least a portion of the gasket will cause the gasket to press outward against the mold component, resulting in at least partial deformation of the gasket. This swelling and consequent deformation allows the gasket to provide an improved seal, thus preventing leakage of liquid from the mold.

[0007] The method according to the invention is particularly suitable for batch casting of PMMA sheets. However, the method can also be applied to continuous casting processes. The liner is typically used only once, after which it requires further processing, such as recycling and / or depolymerization. The sheets are typically configured for reuse. Polymerization can be carried out via any of the known PMMA polymerization techniques, for example by heating the liquid at a predetermined temperature for a predetermined time interval. An oven may be used for the polymerization step. The required polymerization parameters, such as temperature and / or time, depend on several process factors and are known to those skilled in the art. It is conceivable that the method includes a step of degassing the liquid before introducing it into the mold and / or before initiating polymerization. When referring to MMA liquid, it can also mean a syrup or fluid containing MMA monomers and / or MMA prepolymers. MMA prepolymers can also be referred to as PMMA prepolymers. This prepolymer can be prepared, for example, from an inhibitor, which may be combined with an additive (such as benzoyl peroxide), heated, and then cooled to room temperature. A (liquid) syrup is obtained, which consists of a solution of the polymer in the monomer. Regarding molds or unit castings, each mold component typically includes a flat inner surface that, when clamped together, faces another mold component during mold formation. Such mold components can be, for example, panels or sheets. When the term "shim" is used in the context of this invention, it can also refer to a (peripheral) circumference (hank). Further, for the term "shim," the non-limiting terms profile, strand, cable, wire, or rope may also be used in the context of this invention. More specifically, profiles or ropes, for example, comprising hydrocarbon-based polymers, can be used to form the shims according to the invention.

[0008] In a preferred embodiment, the liner comprises a copolymer of ethylene and methacrylic acid. Such copolymers are known, for example, by the commercial name Surlyn. The use of liners comprising a copolymer of ethylene and methacrylic acid still allows for the recycling and / or depolymerization of PMMA waste.

[0009] In another preferred embodiment of the invention, the liner comprises at least one modified polyolefin. Non-limiting examples of modified polyolefins are, for example, ethylene butyl acrylate (EBA), ethylene-vinyl acetate (EVA), and / or polyethylene (PE) copolymers. In yet another preferred embodiment of the invention, the liner comprises at least one modified polyolefin. Non-limiting examples of modified polystyrene are styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), and / or styrene-ethylene / butene-styrene (SEBS). It is also conceivable that the liner comprises at least one modified polyolefin and / or at least one modified polystyrene. Therefore, the liner may comprise ethylene butyl acrylate (EBA), ethylene-vinyl acetate (EVA), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), and / or styrene-ethylene / butene-styrene (SEBS).

[0010] It is also conceivable that the liner comprises at least one biopolymer and / or the liner is at least partially made of a biopolymer. Therefore, at least a portion of the liner may comprise a natural polymer, such as one or more natural rubbers. Natural polymers can be produced, for example, by the cells of a living organism. Such an implementation would be beneficial from an environmental perspective.

[0011] The gasket is preferably composed substantially of one or more polymers containing carbon and hydrogen atoms. More preferably, the gasket is substantially free of halogens, sulfur, and / or nitrogen. It is advantageous if the gasket is substantially free of halogens such as fluorine and / or chlorine and possibly also free of bromine and / or iodine. If the gasket is substantially free of halogens, sulfur, and / or nitrogen, it is advantageous for further post-use treatment. For mechanical recycling, chemical recycling, and combustion, it is advantageous if the gasket is substantially free of the components mentioned above. The presence of oxygen atoms generally does not negatively affect the recycling process. Therefore, the gasket may contain a small number of oxygen atoms.

[0012] In yet another preferred embodiment, the liner comprises at least one compatibilizer, particularly a non-reactive compatibilizer. Compatibilizers are compatible with many polymers, thus benefiting from their ability to participate in conventional recycling processes. Furthermore, the presence of at least one compatibilizer ensures that impurities typically introduced by other polymers such as polyethylene terephthalate (PET), acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), etc., will not negatively impact conventional recycling processes for, for example, polyolefins and / or polystyrene.

[0013] The gasket may contain at least one additive. The additive is preferably configured to prevent the dissolution of the polymethyl methacrylate (PMMA) of the gasket into the liquid containing PMMA prepolymer and / or PMMA monomer during steps B and / or C). It is also conceivable that the gasket contains a polymer co-extruded with at least one additive. This embodiment allows the acrylic grade of the gasket to be modified to further suit the material properties of the gasket. For example, the additive may affect the melt characteristics of the gasket, such that it can prevent or at least hinder the dissolution of the polymer material of the gasket in MMA. Additives affecting the texture, flexibility, and / or impact resistance of the gasket may also be used. This can have a positive effect on the deformability, sealing ability, and / or processability of the gasket. At least one coloring additive affecting the color of the gasket may also be applied. However, the gasket may also be a substantially transparent gasket. Non-limiting examples of additives that can be used are copolymers, plasticizers, impact modifiers, polymerization primers, and / or resins. For example, it is conceivable to use polybutyl acrylate (PBA) and / or polyvinylidene fluoride (PVDF) as additives. Further non-limiting examples of additives applicable to the method according to the invention are polyethylene (PE) and / or polypropylene (PP). The liner may also contain at least one low-density polyethylene (LDPE). This could be, for example, LDPE containing 2% to 10% EVA. Other possible additives are polytetrafluoroethylene (PTFE), synthetic rubbers, and fluoropolymer elastomers such as Viton, fluoropolymers, and / or silicone- and / or silane-based additives. The use of these possible additives still allows for the recycling and / or depolymerization of PMMA waste. However, additional purification steps may be required to obtain the depolymerization products of the additives from the waste. The amount of additive applied to the liner can, for example, be between 0.5% and 90% by weight. In particular, it is conceivable that the amount of additive applied to the liner is between 5% and 50% by weight, specifically between 10% and 40% by weight, and more specifically between 20% and 30% by weight.

[0014] In a further preferred embodiment of the method, a gasket is used, wherein at least a portion of the gasket is hollow. The gasket used can be, for example, a substantially tubular gasket. This embodiment is advantageous because less material is required, resulting in less residue or waste. The fact that the gasket is at least partially hollow also has the benefit of greater flexibility, allowing the gasket to function better, for example, during mold construction and / or during the introduction of liquid into and / or the distribution of liquid within the mold. Another benefit of the gasket being at least partially hollow is that such a gasket is more easily deformable compared to a solid gasket, resulting in a larger contact area between the gasket and the parallel mold components during use. A larger contact area between the gasket and the mold components will provide a more stable mold construction and may therefore prevent leakage of the liquid MMA prepolymer during sheet production. In fact, the width-to-depth ratio of the gasket can be increased for this embodiment when the gasket is (clampedly) engaged between two substantially parallel mold components. A larger contact area between the gasket and the mold components provides a more stable mold construction, thereby preventing leakage of the liquid MMA prepolymer during sheet production. Furthermore, the gasket can be at least partially flexible. This can positively contribute to the ease of use of the gasket. The gasket can have an elongated, preferably oval or rectangular cross-section. The gasket can also be a substantially annular gasket. Non-limiting examples are shown in the figures.

[0015] In a further embodiment of the gasket according to the invention, at least a portion of the outer surface of the gasket is profiled. This embodiment is relatively easy to manufacture and improves the seal between the gasket and the mold due to the larger contact area between the gasket and the sheet. It can further enhance the adhesion between the PMMA sheet and the gasket. The outer surface of the gasket may, for example, be at least partially roughened.

[0016] It is conceivable that the aspect ratio of the gasket, when enclosed between two substantially parallel mold components of a mold for manufacturing polymethyl methacrylate (PMMA) sheets, is at least 1.5, preferably at least 2, and more preferably at least 2.5. This embodiment provides a relatively stable mold construction. The gasket is preferably made of a polymer with relatively good deformability. For this embodiment, the aspect ratio of the gasket in its initial form is generally lower than that when enclosed between two substantially parallel mold components of a mold for producing PMMA sheets. This is beneficial for the leak-tightness of the mold construction.

[0017] The gasket may be further enclosed by at least one sleeve, particularly a polymer sleeve. The sleeve may, for example, comprise polyethylene, such as, but not limited to, HDPE, LDPE, and / or LLDPE. The sleeve may substantially completely enclose the gasket; thus, the gasket may be completely surrounded by the sleeve. The sleeve may be attached to and / or wound around the gasket. Because the sleeve encloses the gasket, adhesives are generally not required. The sleeve preferably encloses the gasket in a form-fitting manner. In this embodiment, the sleeve will not negatively affect the polymerization process. At least a portion of the outer surface of the sleeve may be irregularly shaped.

[0018] In a preferred embodiment, the liner is at least partially made of recycled material. The liner may also be made substantially entirely of one or more recycled materials. Such embodiments would be beneficial from an environmental perspective. By using recycled materials, such as recycled polymers, the use of virgin plastic can be at least partially eliminated. The liner may also contain both virgin and recycled polymers. The virgin polymer may, for example, contribute to the strength of the liner.

[0019] During the polymerization of methyl methacrylate prepolymer and / or methyl methacrylate monomer, the opposing mold surfaces typically have a substantially parallel orientation. This helps to provide a uniform PMMA sheet. Typically, a liner is bonded to the polymethyl methacrylate sheet during polymerization.

[0020] The gasket can be manufactured via an extrusion process. It is also conceivable that the gasket comprises an extruded polymer. The extrusion process is beneficial for production efficiency and allows for the production of continuous shapes of varying lengths and / or thicknesses. It is also conceivable that the gasket is made from a co-extruded polymer. The preferred thickness of the gasket is typically in the range of 2 to 30 mm, for example, in the range of 2 to 15 mm or in the range of 10 to 30 mm.

[0021] The method may further include the step of cutting at least one edge portion, and preferably each edge portion, of a polymethyl methacrylate (PMMA) sheet such that at least the liner is removed from the sheet. Thus, a cast PMMA sheet is obtained. This can be accomplished by cutting or trimming. Specifically, a portion of the edge of the manufactured PMMA sheet is removed. This removed waste or residue contains a combination of PMMA from the produced sheet and the polymer material of the liner used in the mold. Typically, at least one edge portion, and preferably each edge portion, of the PMMA sheet is cut such that both the liner and the peripheral portion of the PMMA sheet bonded to the liner are removed.

[0022] The present invention also relates to polymethyl methacrylate (PMMA) sheets produced via the method according to the invention. Further, the invention relates to a liner used in a mold for producing PMMA sheets via casting, and preferably via the method according to the invention. The liner can be any of the disclosed liner types. The invention also relates to an assembly of at least a portion of the liner according to the invention and at least a portion of the PMMA sheet. It specifically refers to waste or residue obtained by trimming PMMA sheets produced via the method according to the invention according to any of the above embodiments. This waste can be a valuable product because its composition allows it to undergo recycling and / or depolymerization. This waste can even be recycled and / or depolymerized and subsequently used to produce new liners for similar methods.

[0023] The present invention further relates to a mold for producing polymethyl methacrylate (PMMA) sheets, preferably via the method described above, the mold comprising a liner as described above, wherein the liner is encapsulated between two substantially parallel mold components. The mold may also include at least one clamping element configured to provide clamping engagement between the two parallel mold components. Each mold component may have at least one substantially flat mold surface facing a substantially flat mold surface of an opposing mold component. The liner may be clamped between, or can be clamped onto, the substantially flat mold surfaces of the opposing mold components such that a mold cavity is defined by the mold components and the liner. Preferably, the liner comprises at least one hydrocarbon-based copolymer. The liner may be a liner according to any of the embodiments described.

[0024] The present invention will be further explained based on the following non-limiting provisions.

[0025] 1. A method for producing polymethyl methacrylate (PMMA) sheets, comprising the following steps:

[0026] A) Provides a mold comprising at least two mold components, each mold component having at least one substantially flat mold surface facing a substantially flat mold surface of an opposing mold component, and wherein the mold includes at least one gasket sandwiched between the substantially flat mold surfaces of the opposing mold components such that a mold cavity is defined by the mold components and the gasket.

[0027] B) To at least partially fill the mold cavity by introducing a liquid containing methyl methacrylate prepolymer and / or methyl methacrylate monomer into the mold cavity.

[0028] C) Polymerize the methyl methacrylate prepolymer and / or methyl methacrylate monomer introduced into the mold cavity to form a polymethyl methacrylate sheet encapsulated by the gasket within the mold cavity, and

[0029] D) Remove the gasket and the assembly of the polymethyl methacrylate sheet encapsulated by the gasket from the mold component.

[0030] The method is characterized in that the liner contains at least one hydrocarbon-based copolymer.

[0031] 2. The method according to Clause 1, wherein the liner comprises at least one hydrocarbon-based block copolymer and / or wherein the liner comprises at least one hydrocarbon-based graft copolymer.

[0032] 3. The method according to any one of the preceding clauses, wherein the liner comprises a copolymer of ethylene and methacrylic acid.

[0033] 4. The method according to any one of the preceding clauses, wherein the liner comprises at least one modified polyolefin.

[0034] 5. The method according to any one of the preceding clauses, wherein the liner comprises at least one modified polystyrene.

[0035] 6. The method according to any one of the preceding clauses, wherein the gasket comprises ethylene butyl acrylate (EBA), ethylene-vinyl acetate (EVA), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS) and / or styrene-ethylene / butene-styrene (SEBS).

[0036] 7. The method according to any one of the preceding clauses, wherein the liner comprises at least one biopolymer.

[0037] 8. The method according to any one of the preceding clauses, wherein the liner is substantially free of halogens, sulfur and / or nitrogen.

[0038] 9. The method according to any one of the preceding clauses, wherein the liner comprises at least one compatibilizer, particularly a non-reactive compatibilizer.

[0039] 10. The method according to any one of the preceding clauses, wherein the liner comprises at least one additive configured to prevent the polymeric material of the liner from dissolving into the liquid comprising methyl methacrylate prepolymer and / or methyl methacrylate monomer during step B and / or step C).

[0040] 11. The method according to any one of the preceding clauses, wherein the pad has an elongated cross-section, and preferably an elliptical or rectangular cross-section.

[0041] 12. The method according to any one of the preceding clauses, wherein at least a portion of the pad is hollow.

[0042] 13. The method according to any one of the preceding clauses, wherein the gasket is an annular gasket.

[0043] 14. The method according to any one of the preceding clauses, wherein at least a portion of the outer surface of the pad is irregularly shaped.

[0044] 15. The method according to any one of the preceding clauses, wherein the aspect ratio of the liner when it is clamped between two substantially flat mold component surfaces is at least 1.5, preferably at least 2, more preferably at least 2.5.

[0045] 16. The method according to any one of the preceding clauses, wherein at least one sleeve encloses the gasket.

[0046] 17. The method according to any one of the preceding clauses, wherein the liner is made of recycled material.

[0047] 18. The method according to any one of the preceding clauses, wherein at least during step C), the opposing mold surfaces of the mold have a substantially parallel orientation.

[0048] 19. The method according to any one of the preceding clauses, wherein during step C), the pad is bonded to the polymethyl methacrylate sheet.

[0049] 20. The method according to any one of the preceding clauses, wherein the gasket is prepared via an extrusion process.

[0050] 21. The method according to any one of the preceding clauses, the method further comprising step E), which includes cutting at least one edge portion of the polymethyl methacrylate sheet and preferably each edge portion such that at least the padding is removed from the sheet.

[0051] 22. The method according to Clause 21, wherein during step E), at least one edge portion of the polymethyl methacrylate sheet, and preferably each edge portion, is cut such that both the pad and the peripheral portion of the polymethyl methacrylate sheet bonded to the pad are removed.

[0052] 23. A polymethyl methacrylate sheet produced by any one of the methods described in any one of clauses 1-22.

[0053] 24. A liner for use in a mold for producing polymethyl methacrylate sheets by any one of the methods described in any one of clauses 1-22.

[0054] 25. An assembly comprising at least a portion of the gasket as described in Clause 24 and a polymethyl methacrylate sheet bonded to at least a portion of the gasket.

[0055] 26. A mold for use in a method for producing polymethyl methacrylate sheets, preferably according to any one of claims 1-22, the mold comprising at least two mold components, each mold component having at least one substantially flat mold surface facing a substantially flat mold surface of an opposing mold component, and wherein the mold comprises at least one gasket held or capable of being held between the substantially flat mold surfaces of the opposing mold components such that a mold cavity is defined by the mold components and the gasket, the mold characterized in that the gasket comprises at least one hydrocarbon-based copolymer.

[0056] The present invention will be illustrated based on the non-limiting exemplary embodiments shown in the following figures, in which:

[0057] - Figure 1a and Figure 1b A schematic diagram of a mold used in the method according to the invention for producing polymethyl methacrylate sheets (not shown) according to the invention;

[0058] - Figures 2a to 2f A schematic diagram showing a cross-section of a possible embodiment of the gasket according to the invention; and

[0059] - Figure 3a and Figure 3b A PMMA sheet produced by the method according to the invention is shown.

[0060] In these figures, similar reference numerals correspond to similar or equivalent elements or features.

[0061] Figure 1a and Figure 1b A schematic diagram showing a mold 100 used in the method according to the invention for producing polymethyl methacrylate sheets (not shown) according to the invention; Figure 1a A side view of mold 100 is shown, while Figure 1bA top view is shown. The mold 100 includes two substantially parallel mold components, specifically panels 102a and 102b, preferably glass panel 102, and a gasket 101. The substantially annular gasket 101 is enclosed between the two substantially parallel panels 102a and 102b. The gasket 101 is held between the panels 102a and 102b by a plurality of clamping elements 104. A liquid comprising methyl methacrylate prepolymer and / or methyl methacrylate monomer can be introduced into the mold 100 by conventional methods. This liquid can be introduced, for example, into a receiving space 105 defined by the mold 100, after which the panels 102a and 102b and the gasket 101 are fully clamped and connected via the clamping elements 104.

[0062] Figures 2a to 2f A schematic cross-sectional view of a possible embodiment of the gaskets 201a, 201b, 201c, 201d, 201e, 201f according to the present invention is shown. Each gasket 201a, 201b, 201c, 201d, 201e, 201f is enclosed between two parallel (glass) panels 202a, 202b.

[0063] Figure 2a A gasket 201a according to the invention is shown. The gasket 201a shown is a substantially tubular gasket 201a. The walls of the gasket 201a enclose a hollow space 203a. The wall thickness D of the gasket 201a is substantially constant throughout the gasket 201a. However, it is also conceivable that the wall thickness varies locally, for example, along the length and / or width of the gasket 201a. In the position shown where the gasket 201a is enclosed between panels 202a, 202b, the width-to-depth ratio of the gasket is about 2, so that the width w of the gasket 201a is about twice the length of the depth d of the gasket 201a.

[0064] Figure 2b Pad 201b is shown, wherein the outer surface of pad 201b is irregular. The outer surface of pad 201b includes a (regular) pattern of (small) protrusions.

[0065] Figure 2c Another embodiment of a hollow gasket 201c with a partially irregular outer surface is shown. This irregularity exists in the region of the gasket 201c that contacts the panels 202a, 202b. The gasket 201c includes two hollow spaces 203b, 203c. The wall thickness D1 of the inward-facing wall is greater than the wall thickness D2 of the wall facing parallel panels 202a, 202b. Swelling or expansion of the gasket 201c can cause a reduction in the area of ​​the hollow spaces 203b, 203c.

[0066] Figure 2dAnother embodiment of the gasket 201d according to the invention is shown, the gasket being enclosed between panels 202a, 202b. Gasket 201d is enclosed by sleeve 206d. Thus, in this embodiment, gasket 201d includes a polymer core 207d enclosed by polymer sleeve 206d, wherein core 207d and sleeve 206d are made of a different polymer material. Sleeve 206d form-fits gasket 201d.

[0067] Figure 2e Another possible embodiment of the gasket 201e is shown. The gasket 201e includes an inner layer 207e and an outer layer 206e. The inner layer 207e is formed by the basic structure of the gasket 201e. The outer layer 206e encloses the gasket 201e. The walls of the gasket 201e enclose the hollow space 203e.

[0068] Figure 2f Further possible embodiments of the gasket 201f according to the invention are shown. The gasket 201f is a substantially solid gasket 201f.

[0069] Figure 3a A PMMA sheet 300 produced by the method according to the invention is shown. In the illustrated embodiment, the mold panel is removed, leaving the PMMA sheet 310 enclosed by the gasket 301. To provide the PMMA sheet 310 for various applications, it is necessary to remove the circumferential sides or edges of the sheet 310. The cutting lines in the figure indicate locations where the sheet 310 can be trimmed, for example. The removed gasket 301 and a portion of the PMMA sheet 310 form PMMA waste.

[0070] Figure 3b Show Figure 3a A detailed view of the edge portion of the PMMA sheet 310 shown. Therefore, Figure 3b This figure shows a portion of the waste or residue formed after trimming. The diagram shows that the MMA monomers or MMA prepolymers prior to polymerization have caused a portion of the polymer in the gasket 301 to dissolve in the liquid MMA. Therefore, after polymerization, region M is obtained, which comprises a mixture of the cast PMMA of the sheet 310 and one or more polymers of the gasket 301.

[0071] Therefore, the inventive concepts described above are illustrated by several illustrative embodiments. It is conceivable that individual inventive concepts can be applied without applying the other details of the described examples. It is not necessary to detail all conceivable combinations of the above-described inventive concepts, as those skilled in the art will understand that many inventive concepts can be (re)combined to achieve a particular application. The pads shown in the accompanying drawings can be made of any of the disclosed polymer-based materials.

Claims

1. A method for producing polymethyl methacrylate (PMMA) sheets, comprising the following steps: A) A mold comprising at least two mold components, each mold component having at least one substantially flat mold surface facing a substantially flat mold surface of an opposing mold component, and wherein the mold includes at least one gasket sandwiched between the substantially flat mold surfaces of the opposing mold components such that a mold cavity is defined by the mold components and the gasket. B) The mold cavity is at least partially filled by introducing a liquid containing methyl methacrylate prepolymer and / or methyl methacrylate monomer into the mold cavity. C) Polymerize the methyl methacrylate prepolymer and / or methyl methacrylate monomer introduced into the mold cavity to form a polymethyl methacrylate sheet encapsulated by the gasket within the mold cavity, and D) Remove the gasket and the assembly of the polymethyl methacrylate sheet encapsulated by the gasket from the mold component. The method is characterized in that the liner comprises at least one hydrocarbon-based copolymer; The liner therein comprises a copolymer of ethylene and methacrylic acid.

2. The method of claim 1, wherein the liner comprises at least one hydrocarbon-based block copolymer and / or wherein the liner comprises at least one hydrocarbon-based graft copolymer.

3. The method of claim 1, wherein the liner comprises at least one modified polyolefin.

4. The method of claim 1, wherein the liner comprises at least one modified polystyrene.

5. The method of claim 1, wherein the liner comprises ethylene butyl acrylate (EBA), ethylene vinyl acetate (EVA), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), and / or styrene-ethylene / butene-styrene (SEBS).

6. The method of claim 1, wherein the liner comprises at least one biopolymer.

7. The method of claim 1, wherein the gasket is free of halogens, sulfur and / or nitrogen.

8. The method of claim 1, wherein the liner comprises at least one compatibilizer.

9. The method of claim 1, wherein the liner comprises at least one additive configured to prevent the polymeric material of the liner from dissolving into the liquid comprising methyl methacrylate prepolymer and / or methyl methacrylate monomer during step B and / or step C).

10. The method of claim 1, wherein the liner has an elongated cross-section.

11. The method of claim 1, wherein at least a portion of the gasket is hollow.

12. The method of claim 1, wherein the gasket is an annular gasket.

13. The method of claim 1, wherein at least a portion of the outer surface of the pad is irregularly shaped.

14. The method of claim 1, wherein the aspect ratio of the liner when it is clamped between two substantially flat mold component surfaces is at least 1.

5.

15. The method of claim 1, wherein at least one sleeve encapsulates the gasket.

16. The method of claim 1, wherein the liner is made of recycled material.

17. The method of claim 1, wherein at least during step C), the opposing mold surfaces of the mold have a substantially parallel orientation.

18. The method of claim 1, wherein during step C), the pad is bonded to the polymethyl methacrylate sheet.

19. The method of claim 1, wherein the gasket is prepared via an extrusion process.

20. The method of claim 1, further comprising step E), which includes cutting at least one edge portion of the polymethyl methacrylate sheet to remove at least the padding from the sheet.

21. The method of claim 20, wherein during step E), at least one edge portion of the polymethyl methacrylate sheet is cut such that both the pad and the peripheral portion of the polymethyl methacrylate sheet bonded to the pad are removed.

22. A polymethyl methacrylate sheet produced by the method of any one of claims 1-21.

23. A liner for use in a mold for producing polymethyl methacrylate sheets by any one of claims 1-21.

24. An assembly comprising at least a portion of the gasket according to claim 23 and a polymethyl methacrylate sheet bonded to at least a portion of the gasket.

25. A method for producing polymethyl methacrylate sheets, a mold used in the method according to any one of claims 1-21, the mold comprising at least two mold components, each mold component having at least one substantially flat mold surface facing a substantially flat mold surface of an opposing mold component, and wherein the mold comprises at least one gasket held or capable of being held between the substantially flat mold surfaces of the opposing mold components such that a mold cavity is defined by the mold components and the gasket, the mold characterized in that the gasket comprises at least one hydrocarbon-based copolymer.

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