Thermoformable polymer sheet based on pseudo-amorphous polyaryl ether ketone

Abstract

Sheets having a thickness of 1000 to 10,000 microns, which are useful for the production of thermoformed semi-crystalline articles, have a 100 sec. -1 The thermoformable sheet is based on a polyaryletherketone having a viscosity of at least about 400 Pa·s at 360° C. The polyaryletherketone is in a quasi-amorphous state in the thermoformable sheet.

Description

Technical Field

[0001] The present invention relates to a polymer sheet suitable for use in thermoforming applications, the polymer sheet being based on a pseudo-amorphous poly(aryl ether ketone) (PAEK) polymer having certain melt viscosity characteristics.

Background Art

[0002] High-temperature thermoplastic polymers, such as poly(aryl ether ketone) (PAEK), continue to be evaluated as an option in a number of applications, including those in the aerospace and integrated circuit industries. Generally, PAEK has exceptional characteristics including high temperature and chemical resistance, very good mechanical properties, excellent wear resistance, and natural flame retardancy. PAEK parts can be produced by a number of methods including thermoforming methods. However, PAEK parts formed by conventional thermoforming methods may not exhibit the desired resistance to deformation at high temperatures, among other properties.

[0003] The process of thermoforming is a routine manufacturing method. In conventional thermoforming, a plastic sheet is heated to a high temperature and placed in contact with a cold (or room temperature) mold to form the desired shape. When a pseudo-amorphous sheet is thermoformed by such a conventional thermoforming method, the thermoformed part remains amorphous because it is rapidly cooled and retains the properties of the thermoformed amorphous sheet. However, in certain applications, it may be desirable to form semi-crystalline parts having the desired mold shape. There remains a need for a thermoforming method that can produce semi-crystalline parts from pseudo-amorphous sheets and thus produce molded parts that exhibit improved heat resistance, improved chemical resistance, and improved mechanical properties compared to pseudo-amorphous parts formed by conventional thermoforming methods.

[0004] International Publication No. 2018 / 232119 describes such a method, the entire disclosure of which is incorporated herein by reference for all purposes. This method comprises the following steps: As a softening step, heating a sheet containing at least one pseudo-amorphous polymer to a temperature exceeding the glass transition temperature of the pseudo-amorphous polymer to soften the pseudo-amorphous polymer. As a crystallization step, heating a sheet containing a pseudo-amorphous polymer to a temperature that exceeds the glass transition temperature of the pseudo-amorphous polymer and is less than the melting temperature of the pseudo-amorphous polymer for a time sufficient to crystallize the pseudo-amorphous polymer. During the softening step or during the crystallization step before crystallization occurs, placing a sheet containing a pseudo-amorphous polymer on a mold, and Forming a semi-crystalline molded article comprising The pseudo-amorphous polymer is a polyaryl ether ketone (PAEK) selected from the group consisting of polyether ketone ketone (PEKK), polyether ketone (PEK), polyether ketone ether ketone ketone (PEKEKK), and mixtures thereof.

[0005] Thermally formable polyaryletherketone sheets in which the polyaryletherketone is amorphous or only slightly crystalline (crystallinity 5 wt% or less) are known in the art, as exemplified by the disclosure of U.S. Patent No. 4,996,287. However, the procedures described in U.S. Patent No. 4,996,287 for the preparation of such PAEK sheets have significant limitations. Notably, this patent teaches that when the T:I ratio of the PEKK used to prepare such sheets is relatively high (e.g., 70:30 or 80:20), the maximum achievable sheet thickness is only 625 microns (see Table 1). Thus, prior to the present invention, neither thick (e.g., at least 1000 microns) and high T:I ratio pseudo-amorphous PEKK sheets nor any method of obtaining such sheets was known. However, since the properties of thermally formed PEKK sheets are significantly affected by both sheet thickness and T:I ratio, it is highly desirable to develop methods and compositions capable of producing relatively thick, thermally formable pseudo-amorphous sheets containing PEKK with a high T:I ratio (e.g., 70:30).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Means for Solving the Problem

[0008] One aspect of the present invention is a sheet containing a polymer, the sheet having a thickness of from about 1000 microns to about 10,000 microns (e.g., from 1000 microns to 10,000 microns), and the polymer having a viscosity at 360 °C of at least about 400 Pa·s (e.g., at least 400 Pa·s) measured by a parallel plate rheometer at 100 seconds -1 and being a pseudo-amorphous polyaryletherketone (PAEK). It has been found here that using a PAEK that meets such viscosity requirements (i.e., a viscosity at 360 °C of at least about 400 Pa·s measured by a parallel plate rheometer at 100 seconds -1 is the key to enabling the extrusion of a relatively thick polymer sheet containing PAEK, which is suitable for use in a thermoforming process involving a mold because the properties are pseudo-amorphous, to produce a semi-crystalline molded article. It is desirable to have a pseudo-amorphous polyaryletherketone in the sheet for thermoforming because PAEK sheets with a higher degree of crystallinity tend to be too rigid to be easily used in the molding step of the thermoforming process.

[0009] A further aspect of the present invention provides a method for manufacturing a semi-crystalline article by thermoforming the sheet as described above using a mold. This method comprises the steps of: a) As a softening step, heating the sheet as described above to a temperature above the glass transition temperature of the polymer to soften the polymer; b) As a crystallization step, heating the sheet to a temperature above the glass transition temperature of the polymer and below the melting temperature of the polymer for a time sufficient to crystallize the polymer; c) Placing the sheet on the mold during the softening step or during the crystallization step before crystallization occurs; and d) Forming a semi-crystalline molded article may be included.

[0010] The semi-crystalline article thus obtained may exhibit a dimensional change of less than about 5%, less than about 4%, less than about 3%, less than about 2%, or less than about 1% compared to the mold.

[0011] Also provided by the present invention is a method for producing a sheet comprising a polymer, wherein the sheet has a thickness of from about 1000 microns to about 10,000 microns (e.g., from 1000 microns to 10,000 microns), and the polymer is a pseudo-amorphous polyaryletherketone (PAEK) having a viscosity at 360° C. of at least about 400 Pa·s (or at least 400 Pa·s) as measured by a parallel plate rheometer, and the method comprises -1 a) heating a resin composition comprising the polymer to a suitable processing temperature above the melting point of the polymer to obtain a molten resin composition, b) shaping the molten resin composition into a sheet (e.g., by melt extrusion through a die of suitable size), and c) rapidly cooling the sheet at a rate effective to obtain a pseudo-amorphous polymer is also provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0012]

Figure 1

Figure 2

Figure 3

[0013] As used herein, the term "article" may be used interchangeably with "part" or "object". Representative articles of the present invention include, for example, speaker cones, speaker spiders, back-end / burn-in integrated circuit (IC) test sockets, IC wafer carriers, IC wafer handling tools, IC handling trays, electronic packaging, blister packaging, 3D electronic circuits, bearings, backing plates, bushings, sensors, switches, electronic enclosures, tubing, cylinders, cups, containers, lids for containers, satellite panels, mirrors, pump components (e.g., impellers, stators, housings), aerospace industry components (e.g., cabinets, cabinet doors, sinks, control panels, toilets, seat components including backs and bottoms), compressed natural gas (CNG) or compressed liquefied petroleum gas (CLPG) composite tank forms, composite tooling forms, laminate protective cover films (e.g., FFF / FDM / RFF tooling), and chemical storage containers (or their components). Representative articles of the present invention may include complex-shaped special parts having promising applications, particularly including, but not limited to, aerospace, aircraft, oil and gas, electronics, architecture and construction, ducting, and high-temperature containers.

[0014] "Thermoforming" (including "vacuum forming"), as used herein and in the art, involves heating a sheet of material to a temperature at which it is malleable (e.g., in an oven), and forming the heated sheet over a mold. Depending on the thermoforming method selected, the mold may be relatively cool or relatively warm (as will be described in more detail below). For example, the mold may be at about room temperature, however, in other embodiments, it may be at a temperature higher than room temperature, such as a temperature below the glass transition temperature of the polymer contained in the sheet being thermoformed. The heated sheet may be stretched over or covering the mold using a vacuum, where it can then be cooled to form a molded article. Conventional thermoforming methods involve heating a sheet of material, such as a plastic sheet (e.g., in an oven), to a high temperature, such as a temperature above the glass transition temperature of the material, and placing the heated sheet in contact with a cold (e.g., room temperature) mold to form the desired shape. The sheet may be stretched into or onto the mold, for example, using a vacuum. When a sheet of a pseudo-amorphous material undergoes such a conventional thermoforming method, the thermoformed part is rapidly cooled on the mold, and as a result, takes the shape of the mold. The thermoformed part that is rapidly cooled retains the properties of the pseudo-amorphous sheet that was thermoformed.

[0015] As used herein, the term "sheet" refers to a three-dimensional article that is typically flat or substantially planar and has a thickness that is significantly thinner than the length and width of the article (as opposed to pellets, tablets, or cylinders). For example, the sheet may have a thickness of less than 10% or less than 5% of both the length and width. The sheet is distinguished from a film by having a greater thickness. The sheet has a thickness of 500 microns or more, whereas a film has a thickness of less than 500 microns. The sheet may be attached to a substrate or may be completely independent of the substrate. The sheet may be non-porous, porous, microporous, etc., depending on the application and use. The sheet thickness can be measured, for example, using a standard micrometer.

[0016] As used herein, the term "pseudo-amorphous" polymer refers to a polymer having a crystallinity from 0 weight percent to 5 weight percent, as measured by X-ray diffraction. Thus, the term "pseudo-amorphous" includes both completely amorphous polymers (0 weight percent crystallinity, also may be referred to as amorphous polymers) and polymers containing a limited degree of crystallinity (up to 5 wt%). For example, the pseudo-amorphous polymers contemplated herein may have a crystallinity of less than 5 weight percent, preferably less than 3 weight percent, or less than 2 weight percent. As used herein, the term "semi-crystalline" polymer refers to a polymer having a crystallinity greater than 5 weight percent as measured by X-ray diffraction. The semi-crystalline polymers contemplated herein may have a crystallinity of at least 6 weight percent or at least 7 weight percent as measured by X-ray diffraction.

[0017] As used herein, the term "about" includes the exact value specified. For example, the range "about X to about Y" is understood to include the range "X to Y". Further, any range presented is understood to include its endpoints (e.g., "X to Y" includes the values of both X and Y).

[0018] As used herein, each compound can be considered interchangeably with respect to its chemical formula, chemical name, abbreviation, etc. For example, PAEK may be used interchangeably with polyaryl ether ketone, and PEKK may be used interchangeably with polyether ketone ketone. Further, each compound described herein includes homopolymers and copolymers unless otherwise specified. The term "copolymer" means including polymers containing two or more different monomers, for example, polymers containing 2, 3, or 4 different repeating monomer units can be included.

[0019] As used in this specification and the claims, the terms "comprising" and "including" are inclusive or open-ended and do not exclude additional, unrecited elements, compositional components, or method steps. Thus, the terms "comprising" and "including" encompass the more restrictive terms "consisting essentially of" and "consisting of".

[0020] The term polyaryl ether ketone ("PAEK") is intended to encompass all homopolymers and copolymers (including, for example, terpolymers). In one embodiment, the polyaryl ether ketone is selected from the group consisting of polyether ketone ketone (PEKK), polyether ether ketone (PEEK), polyether ketone (PEK), polyether ketone ether ketone ketone (PEKEKK), and mixtures thereof. At least one polyaryl ether ketone may optionally include a plurality of polyaryl ether ketones. In an embodiment, the "at least one polymer" may include, consist essentially of, or consist of at least one PAEK, particularly at least one PEKK.

[0021] As already mentioned, the inventors have found that the melt viscosity of a polymer or combination of polymers used to produce a thermoformable sheet is an important variable for successfully obtaining a sheet containing a thick (at least about 1000 microns thick), pseudo-amorphous (i.e., not semi-crystalline) polymer. In particular, a polyaryl ether ketone (PAEK) or a combination of polymers containing at least one PAEK should have a viscosity at 360 °C of at least about 600 Pa·s at 100 seconds -1 as measured by a parallel plate rheometer. The viscosity may be measured using ASTM D4440-15. The viscosity at 360 °C is at 100 seconds as measured by a parallel plate rheometer -1If it is less than about 600 Pa·s at, the melt strength of the polymer is likely to be insufficient to enable the extrusion of a thick sheet (≧1000 microns) having a desired substantially uniform thickness (i.e., the thickness of the extruded sheet is likely to be uneven). Preferably, a polyaryletherketone (PAEK) or a combination of polymers containing at least one PAEK has a viscosity at 360° C. of at least about 700 Pa·s at 100 seconds -1 measured by a parallel plate rheometer. More preferably, a polyaryletherketone (PAEK) or a combination of polymers containing at least one PAEK has a viscosity at 360° C. of at least about 800 Pa·s at 100 seconds -1 measured by a parallel plate rheometer. According to certain embodiments, the viscosity at 360° C. of a PAEK or a combination of polymers containing at least one PAEK is at 100 seconds -1 not exceeding about 5000 Pa·s measured by a parallel plate rheometer.

[0022] In representative embodiments, the polyaryletherketone comprises, consists essentially of, or consists of polyetherketoneketone (PEKK). Suitable polyetherketoneketones for use in the present invention may comprise, consist essentially of, or consist of repeating units represented by the following Formulas I and II. -A-C(=0)-B-C(=0)- I -A-C(=0)-D-C(=0)- II A is a ρ,ρ'-Ph-O-Ph group, Ph is a phenylene group, B is p-phenylene, and D is m-phenylene. The isomer ratio of Formula I: Formula II (T:I) in the polyether ketone ketone can be in the range from 100:0 to 0:100. However, in various embodiments of the present invention, it may be 50:50 to 90:10, or 65:35 to 75:25, or 68:32 to 72:28, or about 70:30, or 70:30. The isomer ratio can be easily varied, for example, by changing the relative amounts of the different monomers used to prepare the polyether ketone ketone, as desired to obtain a certain set of properties. Generally speaking, a polyether ketone ketone having a relatively high Formula I: Formula II ratio will have a faster crystallization rate compared to a polyether ketone ketone having a lower Formula I: Formula II ratio. As is known in the art, it is possible to prepare samples containing high T:I ratio PEKK that are pseudo-amorphous (i.e., PEKK exhibits a crystallinity of 5 wt% or less and is in a pseudo-amorphous state), yet can be converted to samples with semi-crystalline properties by certain heat treatments or processing of the sample.

[0023] Therefore, the T:I ratio may be adjusted, among other parameters, to control the rate of crystallization in PEKK. Generally speaking, a lower T:I ratio will result in a slower crystallization rate in an extruded sheet containing PEKK, and thus a longer processing window. Conversely, a higher T:I ratio will result in a faster rate of crystallization, and thus a shorter processing window. In one embodiment, a polyether ketone ketone having a T:I isomer ratio of about 50:50 to about 90:10 may be used.

[0024] For example, the chemical structure [PEKK(T)] for the repeating unit of a polyether ketone ketone with all para-phenylene bonds may be represented by the following Formula III.

[0025]

Chemical formula

[0026] The chemical structure for the repeating unit of a polyetherketoneketone having one metaphenylene bond in the main chain [PEKK(I)] may be represented by the following formula IV.

[0027]

Chem.

[0028] The chemical structure for the repeating unit of a polyetherketoneketone in which the isomers of T and I appear completely alternately, for example, a homopolymer [PEKK(T / I), that is, PEKK having a 50:50 T:I ratio] having 50% of both the isomers of T and I can be represented by the following formula V.

[0029]

Chem.

[0030] Polyaryletherketones can be prepared by any suitable method, and many such methods exist and are well known in the art. For example, polyaryletherketones may be formed by heating a substantially equimolar mixture of at least one bisphenol and at least one dihalobenzoid compound or at least one halophenol compound. As another example, polyaryletherketones may be formed by contacting at least one aromatic acid chloride and at least one aromatic ether in the presence of a Lewis acid. The polymer may be pseudo-amorphous (including amorphous) or semi-crystalline, which can be controlled through the synthesis and processing of the polymer. The polymers used in the embodiments disclosed herein are preferably pseudo-amorphous (including amorphous). Further, the polymer may also be of any suitable molecular weight (under conditions where the minimum melt viscosity requirement is met) and may be functionalized or sulfonated if desired. In one embodiment, the polymer undergoes sulfonation or any exemplary surface modification known to those skilled in the art.

[0031] Suitable polyetherketoneketones (PEKK) are available from several commercial suppliers under a variety of trade names. For example, polyetherketoneketone is sold by Arkema Inc. under the trade name KEPSTAN®. A plurality of different polyetherketoneketone polymers are manufactured and supplied by Arkema Inc.

[0032] In the embodiments disclosed herein, the pseudo-amorphous polymer used may include other polymers in addition to one or more polyaryl ether ketones. In one embodiment, the other polymers are compatible by sharing similar melting points, melt stabilities, etc. and exhibiting complete or partial miscibility with each other. In particular, other polymers that exhibit mechanical compatibility with polyaryl ether ketones may be added to the composition. However, it is also contemplated that the polymers need not be compatible with polyaryl ether ketones. The other polymers may include, for example, polyamides (e.g., polyamide 11 and polyamide 12 commercially available from Arkema under the name Rilsan®, poly(hexamethylene adipamide), or poly(8-caprolactam)); fluorinated polymers (e.g., PVDF, PTFE, and FEP); polyimides (e.g., polyetherimide (PEI), thermoplastic polyimide (TPI), and polybenzimidazole (PBI)); polysulfones / sulfides (e.g., polyphenylene sulfide (PPS), polyphenylene sulfone (PPSO2), polyether sulfone (PES), and polyphenyl sulfone (PPSU)); poly(aryl ether); and polyacrylonitrile (PAN). In one embodiment, the other polymers include polyamide polymers and copolymers, polyimide polymers and copolymers, etc. Polyamide polymers may be particularly suitable for high-temperature applications. The additional polymers may be mixed with the polyaryl ether ketones by conventional methods.

[0033] In the embodiments disclosed herein, the pseudo-amorphous polymers used may also contain additional components such as fillers or additives, for example, core-shell impact modifiers; fillers or reinforcing agents such as glass fibers, carbon fibers, etc.; plasticizers; pigments or dyes; heat stabilizers; ultraviolet stabilizers or absorbers; antioxidants; processing aids or lubricants; flame retardant synergists such as Sb2O3, zinc borate, etc.; or mixtures thereof, in order to obtain specific properties desirable for particular applications. These components may, in some cases, be present in an amount of, for example, from about 0.05 weight percent to about 70 weight percent, based on the total weight of the composition from which the polymer sheet or article (used to form the semi-crystalline articles of the disclosed embodiments, where the article contains a polymer in a semi-crystalline state, particularly PAEK) is formed. Preferably, any such fillers or additives are non-nucleating.

[0034] Suitable fillers may include fibers, powders, flakes, etc. Reinforcing fillers may be used. For example, suitable fillers may include at least one of carbon nanotubes, carbon fibers, glass fibers, polyamide fibers, hydroxyapatite, aluminum oxide, titanium oxide, aluminum nitride, silica, alumina, barium sulfate, graphene, graphite, etc. The size and shape of the filler are also not particularly limited. Such fillers may, in some cases, be present in an amount of from about 0.1 weight percent to about 70 weight percent, or from about 10 weight percent to about 70 weight percent, based on the total weight of the composition from which the polymer sheet or article used in the disclosed embodiments is formed.

[0035] A resin composition comprising one or more polyaryl ether ketones and optionally in combination with one or more of the other polymers, fillers, and / or other additives described above can be formed into a sheet using the following general procedure, which can be adapted or modified to best suit the particular resin composition being processed and the desired characteristics (such as thickness, degree of crystallization) of the thermoformable sheet obtained therefrom.

[0036] The sheet of the present invention is relatively thick (i.e., the sheet has a thickness of at least about 500 microns, for example, from about 1000 microns to about 10,000 microns, preferably from about 1000 to about 3500 microns) and contains at least one polyaryl ether ketone in a pseudo - amorphous state, such as polyether ketone ketone. Generally speaking, such sheet thickness is substantially uniform. The length and width of the sheet may be varied as desired for a particular end - use application, depending on the dimensions of the molded article, including semi - crystalline molded articles that can be prepared by thermoforming the pseudo - amorphous sheet.

[0037] The thermoformable sheet according to the present invention is preferably made by melt extrusion. Conventional single - screw or twin - screw extruders, sheet extrusion dies, and take - off devices designed to extrude a thermoplastic resin into a sheet may be used. The extrusion temperature will depend on the polymer melt temperature (affected by the T:I ratio in the case of PEKK) and the molecular weight or melt viscosity. For example, when the T:I isomer ratio in PEKK is 70:30 or 50:50, the preferred extrusion temperature is between about 360°C and about 380°C. As a further example, when the T:I isomer ratio is 60:40, the preferred extrusion temperature is between about 325°C and about 360°C. Generally, an extrusion temperature from about 5°C to about 70°C or from about 10°C to about 50°C above the melting point of the polyaryl ether ketone is sufficient. An extrusion temperature close to the lower limit of the above range is preferred and should preferably be less than 400°C. Lower extrusion temperatures may be preferred because the extruded resin composition has a viscosity that promotes the extrusion of a sheet having a uniform thickness and acceptable structural integrity, and to reduce the crystallization window time. Also, as the sheet thickness is increased, it is usually preferred to operate at the lower limit of the usable temperature range. Higher extrusion temperatures are possible but can cause undesirably longer times in the crystallization stage of the thermoforming process.

[0038] An extruded sheet containing polyaryl ether ketone is conveyed directly from the die onto a smooth metal or textured roll, commonly referred to as a "cooling roll", because the surface temperature of these rolls is maintained at a level below the melting temperature of the polymer. A flow of air or other gas may also be directed at the extruded sheet to facilitate cooling. The rate at which the sheet is cooled (termed the quench rate) and solidified is an important aspect in achieving a pseudo-amorphous sheet structure. The quench rate is primarily determined by the temperature of the cooling roll, the sheet thickness, and the line speed, and should not be so fast as to cause a warped, wrinkled, or curled sheet, nor should it be so slow that it does not achieve the desired pseudo-amorphous characteristics of the sheet. Typically, it is desirable for the extruded sheet to be cooled as quickly as possible to approximately room temperature while avoiding any warping, wrinkling, or curling of the sheet. The dependence of physical properties and thermoformability on the quench rate is thought to be related to the inherent polymer properties, such as the crystallization rate and the rate of polymer solidification, since cooling occurs by the glass transition temperature. Following extrusion and quenching, the extruded sheet may be cut or divided to provide individual sheets having dimensions appropriate for use in a particular desired thermoforming operation.

[0039] According to certain embodiments, the sheet according to the present invention may be reheated to a softened state (without significant crystallization), and then formed into an article, and then the polymer (e.g., PAEK) present in the formed article is crystallized (e.g., by heating to a temperature higher than where crystallization would occur).

[0040] The sheet according to the present invention can be used in any type of molding method to produce a finished molded article, but is particularly well-suited for use in thermoforming. As described in more detail hereinafter, such sheets are particularly useful in the production of semi-crystalline molded articles in which the polymer component of the sheet is converted from a pseudo-amorphous state to a semi-crystalline state.

[0041] The shaped article can be prepared from the sheet according to the invention using a thermoforming method. Thermoforming is a method of heating a thermoplastic sheet to its processing temperature and bringing it into contact with a mold surface using a differential pressure and / or pressure created by mechanical means or vacuum, and cooling while pressing it against the contour of the mold until the shape of the mold is maintained. The thermoformed semi-crystalline molded article thus obtained can have dimensions very close to the dimensions of the mold used to create such an article, so the sheet of the present invention is particularly useful in such a method. For example, the semi-crystalline molded article can exhibit a dimensional change compared to the mold of less than about 5%, less than about 4%, less than about 3%, less than about 2%, or even less than about 1%. Thus, the sheet of the present invention enables the production of thermoformed articles that exhibit less deformation, less shrinkage, and / or better dimensional tolerances compared to other PAEK-based sheets known in the art. The sheet before thermoforming may be transparent. As a result of thermoforming the sheet and increasing the crystallinity of the polyaryl ether ketone, the molded article obtained from the sheet that was initially transparent may become opaque.

[0042] The sheet of the present invention can be easily thermoformed by standard methods using standard equipment such as vacuum, pressure, mechanical, or twin-sheet thermoforming. The optimal thermoforming conditions will vary depending on the specific type of thermoforming machine and the mold used, but such conditions can be readily determined by techniques commonly and conventionally used in the art. When the polyaryl ether ketone is polyether ketone ketone (PEKK), for example, the thermoforming temperature range for the sheet (i.e., the temperature of the sheet during thermoforming) is typically within the range of 160°C to 300°C. However, a sheet temperature above 220°C can result in too rapid a crystallization rate, so a sheet temperature of from about 160°C to about 220°C is generally preferred.

[0043] The time required to heat the sheet to the thermoforming temperature range prior to the forming phenomenon can be an important variable in the method of thermoforming the sheet of the present invention. Generally speaking, in certain types of thermoforming procedures, it is desirable to minimize the preheating time while maintaining a uniform heat distribution in the sheet in order to achieve a uniform draw in the forming process. The residence time depends on process variables such as the dimensions of the sheet (especially sheet thickness), the characteristics of the heat of a particular oven, and the desired forming temperature range, so the ideal forming conditions must be determined experimentally, but can be readily determined by a plastic thermoforming technician. The residence time for PEKK-based sheets is typically short, for example 1 to 5 minutes.

[0044] Either a radiant or a convective oven is suitable for preheating, but radiant heaters are generally preferred because of their good efficiency. The surface temperature of a radiant heater is usually maintained between 500 °C and 1100 °C, preferably between 600 °C and 900 °C. Excessively high sheet temperatures or oven residence times can result in poor forming characteristics of the pseudo-amorphous polyaryletherketone-containing sheet, such as insufficient draw or molding defects, and brittleness in the formed article.

[0045] Thermoforming of the sheet can be achieved by vacuum forming, with or without pressure or plug assist. The vacuum level is typically at least 68 kPa. The forming pressure can range from atmospheric pressure to 690 kPa. The mold temperature can range, for example, from room temperature to 290 °C. According to certain embodiments of the present invention, a mold temperature of about 160 °C to about 280 °C may be used. By increasing the mold temperature and / or adding pressure, generally the internal stress is minimized and better detail and material distribution are achieved, resulting in a more uniform part.

[0046] The sheet according to the present invention is particularly suitable for use in the thermoforming procedure described in International Publication No. 2018 / 232119, the entire disclosure of which is incorporated herein by reference for all purposes. The procedure described in the above-mentioned published patent specification enables the production of thermoformed parts that are semi-crystalline from a pseudo-amorphous polymer sheet such as the sheet according to the present invention. According to an embodiment of the present invention, a method of producing a molded part includes thermoforming a sheet according to the present invention under conditions effective to produce a semi-crystalline molded article.

[0047] According to an embodiment, a method of manufacturing a semi-crystalline article from a sheet comprising at least one pseudo-amorphous polymer includes a softening step of heating the sheet to a temperature above the glass transition temperature of the pseudo-amorphous polymer to soften the pseudo-amorphous polymer without substantially crystallizing the pseudo-amorphous polymer, and a crystallization step of heating the at least one pseudo-amorphous polymer to a temperature above the glass transition temperature of the pseudo-amorphous polymer and below the melting temperature of the pseudo-amorphous polymer for a time sufficient to crystallize the pseudo-amorphous polymer (thereby forming a semi-crystalline polymer). Some crystallization may occur during the softening step, however, preferably, if crystallization occurs during the softening step, such crystallization is considered to be less than about 10 wt%, less than about 5 wt%, less than about 2 wt%, less than about 0.5 wt%, less than about 0.1 wt%, or less than about 0.01 wt%. In some embodiments, the sheet comprising the pseudo-amorphous polymer may be placed on a mold during the softening step. In some embodiments, the sheet comprising the pseudo-amorphous polymer may be placed on a mold during the crystallization step before crystallization occurs at least to some extent. The semi-crystalline molded article may be formed on a mold. The semi-crystalline molded article may be opaque. However, in certain embodiments, the semi-crystalline article may be substantially semi-transparent or semi-transparent.

[0048] The sheet may be maintained on the mold during the crystallization process for a time ranging from several seconds to several minutes, depending on factors such as sheet thickness. For example, if the sheet has a thickness of from about 1000 microns to about 2000 microns, the sheet may be maintained on the mold for a time of from about 30 seconds to about 1 minute. As another example, if the sheet has a thickness of about 3000 microns, the sheet may be maintained on the mold for up to 4 minutes (e.g., up to about 6 to 7 minutes).

[0049] In some embodiments, the mold may be heated on at least one surface. In some embodiments, a sheet comprising a pseudo - amorphous polymer may be heated to a temperature above the glass transition temperature (Tg) of the pseudo - amorphous polymer during the softening process, e.g., to a temperature in the range of from about 160°C to about 220°C or from about 190°C to about 215°C during the softening process. During the softening process, in some embodiments, the temperature of the sheet may be measured using a non - contact method, e.g., by using a non - contact infrared gun. In some embodiments, the mold and the sheet comprising the pseudo - amorphous polymer may be heated to a temperature in the range of from about 210°C to about 280°C, from about 230°C to 260°C, or up to about 250°C during the crystallization process. In some embodiments, the temperature of the sheet comprising the pseudo - amorphous polymer may be measured by using a probe within the mold.

[0050] In some embodiments, a sheet comprising a pseudo - amorphous polymer is placed on the mold during or immediately before the crystallization process. In some embodiments, a sheet comprising a pseudo - amorphous polymer may be placed on the mold using a vacuum after the softening process. In other embodiments, a sheet comprising a pseudo - amorphous polymer is maintained on the mold during both the softening process and the crystallization process.

[0051] In some embodiments, the produced molded article may exhibit a crystallinity (in absolute value) that is at least 1 wt% higher, at least 5 wt% higher, at least 10 wt% higher, at least 15 wt% higher, at least 20 wt% higher, or at least 25 wt% higher than that of a sheet containing a pseudo - amorphous polymer, or a crystallinity that is about 10 to about 30 wt% or about 10 to about 25 wt% higher than that of a sheet containing a pseudo - amorphous polymer. For example, a molded article having a crystallinity of 25 wt% may be produced from a sheet containing a pseudo - amorphous form of PEKK having a crystallinity of 2 wt% (a 23 wt% increase in crystallinity, i.e., the molded article has a crystallinity 23 wt% higher than the starting pseudo - amorphous PEKK - based sheet).

[0052] Exemplary embodiments of the present invention can be summarized as follows. Aspect 1: A sheet containing a polymer, wherein the sheet has a thickness of about 1000 to about 10,000 microns (or 1000 microns to 10,000 microns), and the polymer is a pseudo - amorphous polyaryletherketone (PAEK) having a viscosity at 360 °C of at least about 400 Pa·s (or at least 400 Pa·s) measured by a parallel - plate rheometer at 100 seconds -1

[0053] Aspect 2: The sheet of Aspect 1, wherein the polymer has a viscosity at 360 °C of at least about 600 Pa·s (or at least 600 Pa·s) measured by a parallel - plate rheometer at 100 seconds -1

[0054] Aspect 3: The sheet of Aspect 1, wherein the polymer has a viscosity at 360 °C of at least about 800 Pa·s (or at least 800 Pa·s) measured by a parallel - plate rheometer at 100 seconds -1

[0055] Aspect 4: The polymer has a viscosity at 360 °C of at least about 1000 Pa·s (or at least 1000 Pa·s) measured by a parallel - plate rheometer at 100 seconds -1 ​​​The sheet of Aspect 1 having a viscosity at 360 °C of about 5000 Pa·s or less (or 5000 Pa·s or less).

[0056] Aspect 5: The sheet of any one of Aspects 1 to 4, wherein the polyaryl ether ketone (PAEK) is selected from the group consisting of polyether ketone ketone (PEKK), polyether ketone (PEK), polyether ketone ether ketone ketone (PEKEKK), and combinations thereof.

[0057] Aspect 6: The sheet of any one of Aspects 1 to 5, wherein the polyaryl ether ketone (PAEK) is polyether ketone ketone (PEKK).

[0058] Aspect 7: The sheet of Aspect 6, wherein the polyether ketone ketone (PEKK) has a T:I isomer ratio of about 50:50 to about 90:10 (or 50:50 to 90:10).

[0059] Aspect 8: The sheet of Aspect 6, wherein the polyether ketone ketone (PEKK) has a T:I isomer ratio of about 65:35 to about 75:25 (or 65:35 to 75:25).

[0060] Aspect 9: The sheet of Aspect 6, wherein the polyether ketone ketone (PEKK) has a T:I isomer ratio of about 68:32 to about 72:28 (or 68:32 to 72:28).

[0061] Aspect 10: The sheet of Aspect 6, wherein the polyether ketone ketone (PEKK) has a T:I isomer ratio of about 70:30 (or 70:30).

[0062] Aspect 11: The sheet of any one of Aspects 1 to 10, further comprising one or more non-nucleating fillers.

[0063] Aspect 12: The sheet of any one of Aspects 1 to 11, further comprising one or more non-nucleating fillers selected from the group consisting of reinforcing fibers, pigments, heat stabilizers, antioxidants, glass spheres, silica, and talc.

[0064] Aspect 13: A sheet according to any one of Aspects 1 to 12, which is transparent.

[0065] Aspect 14: A method for manufacturing a semi-crystalline article, including a step of thermoforming a sheet according to any one of Aspects 1 to 13 using a mold.

[0066] Aspect 15: a) As a softening step, heating a sheet according to any one of Aspects 1 to 13 to a temperature exceeding the glass transition temperature of the polymer to soften the polymer; b) As a crystallization step, heating the sheet to a temperature that exceeds the glass transition temperature of the polymer and is less than the melting temperature of the polymer for a time sufficient to crystallize the polymer; c) Placing the sheet on the mold during the softening step or during the crystallization step before crystallization occurs; and d) A step of forming a semi-crystalline molded article A method for manufacturing a semi-crystalline article, including these steps.

[0067] Aspect 16: A semi-crystalline article obtained according to Aspect 14 or Aspect 15, showing a dimensional change of less than about 3% (or less than 3%) compared to the mold.

[0068] Aspect 17: A method for producing a sheet according to any one of Aspects 1 to 13, including: a) Heating a resin composition containing a polymer to an appropriate processing temperature exceeding the melting point of the polymer to obtain a molten resin composition; b) A step of shaping the molten resin composition into a sheet; and c) A step of rapidly cooling the sheet at a rate effective to obtain a polymer in a pseudo-amorphous state A method including these steps.

[0069] Throughout this specification, embodiments have been described in a way that enables a clear and concise specification to be written, but it will be appreciated and recognized that the embodiments can be variously combined or separated without departing from the invention. For example, it will be recognized that all the preferred features described herein are applicable to all aspects of the invention described herein.

[0070] In some embodiments, the invention herein can be construed to exclude any element or method step that does not materially affect the basic and novel features of the composition or method. Further, in some embodiments, the invention can be construed to exclude any element or method step not specified herein.

[0071] The invention has been described and illustrated herein with reference to specific embodiments, but the invention is not intended to be limited to the details shown. Rather, various modifications may be made within the realm and scope of equivalents of the claims without departing from the invention.

Examples

[0072] (Example 1) A pseudo-amorphous sheet with a thickness of 3 mm was produced from a PEKK copolymer having a viscosity of 850 Pa·s at 360 °C measured by a parallel plate rheometer with a T:I ratio of 70:30 using a single-screw extruder and a two-cooling roll system. The extrusion temperature was set at 375 °C, the line speed was 0.5 m / min, and cooling was performed only by the cooling rolls and ambient air. -1

[0073] ​The sheet was thermoformed using a shuttle-type thermoforming machine equipped with a female mold for vacuum forming. The sheet was placed in a heating oven and withdrawn when the surface temperature of the sheet reached 210 °C. Next, the sheet was quickly placed on the mold and heated to 250 °C by an electric cartridge heater. After vacuum forming, the part was removed after being in contact with the mold for 4 minutes so that crystallization could occur. In the obtained object, the area in contact with the mold was opaque and crystalline, and the area not in contact with the mold was transparent. Wide-angle X-ray diffraction was performed on the sheet before and after thermoforming, indicating that the crystallinity increased from <1 wt% before thermoforming to approximately 29 wt% after thermoforming.

[0074] WAXD conditions The WAXD diffraction pattern of the polymer sheet was obtained using the following procedure. The X-ray diffraction experiment was performed with a Rigaku Corporation SmartLab diffractometer. All data acquisitions were performed in 1D mode. Acquisition conditions for the experiment: WAXS: 2θ range of 1.0° to 80.0°. Step = 0.03°. Scan speed = 1.0° / min. IS = 1.0 mm, RS1 = 3.0 mm, RS2 = 3.1 mm. Cross-beam optics.

[0075] (Example 2) In this example, a computer study was conducted to measure the crystallinity of an extruded PEKK sheet with a T:I ratio between 68:32 and 74:26 and a thickness between 1 mm and 10 mm using a finite element model. The model included the density, thermal conductivity, and heat capacity of each PEKK grade, an extruder temperature of 380 °C, an extrusion speed of 10 cm / min, and a heat transfer coefficient of 65 W / m 2Use / K for convective cooling in ambient air at 25 °C (assuming some air circulation), and specify a sheet thickness between 1 mm and 10 mm. The model adjusts the parameters to match the measured crystallinity half-time of each grade and uses the crystallization rate based on the isothermal and non-isothermal crystallization equations of Choupin, "Mechanical performances of PEKK thermoplastic composites linked to their processing parameters" (2017). Table 1 lists the estimated maximum thickness of the extruded PEKK sheet for each grade (T:I ratio) required to maintain a crystallinity of 5 wt% or less in any part of the sheet.

[0076]

Table 1

[0077] Comparative Example 1 A pseudo-amorphous sheet with a thickness of 3 mm was produced from a PEKK copolymer having a viscosity of 850 Pa·s at 360 °C measured by a T:I ratio of 70:30 and a parallel plate rheometer using a single-screw extruder and a two-roll cooling system. The extrusion temperature was set at 375 °C, the line speed was 0.5 m / min, and cooling was performed only by the cooling roll and ambient air. -1 The sheet was thermoformed using a shuttle-type thermoforming machine equipped with a female mold for vacuum forming. The sheet was placed in a heating oven and withdrawn when the surface temperature of the sheet reached 210 °C. Next, the sheet was quickly placed on the mold and heated only up to 120 °C by an electric cartridge heater. After vacuum forming, the part was removed after being in contact with the mold for 4 minutes. The resulting object was transparent. Wide-angle X-ray diffraction was performed on the sheet before and after thermoforming, showing that the crystallinity remained <1 wt% before and after thermoforming.

[0078] The sheet was thermoformed using a shuttle-type thermoforming machine equipped with a female mold for vacuum forming. The sheet was placed in a heating oven and withdrawn when the surface temperature of the sheet reached 210 °C. Next, the sheet was quickly placed on the mold and heated only up to 120 °C by an electric cartridge heater. After vacuum forming, the part was removed after being in contact with the mold for 4 minutes. The resulting object was transparent. Wide-angle X-ray diffraction was performed on the sheet before and after thermoforming, showing that the crystallinity remained <1 wt% before and after thermoforming.

Claims

**Claim 1**: A method for manufacturing a semi-crystalline article, comprising: - preparing a polyaryl ether ketone (PAEK) having a viscosity at 360 °C of at least 600 Pa·s at 100 s-1, as measured by a parallel plate rheometer; - extruding the polyaryl ether ketone (PAEK) into a pseudo-amorphous polymer sheet having a thickness of 1000 to 10,000 microns; - thermoforming the obtained aryl ether ketone polymer (PAEK) sheet into a semi-crystalline article ; wherein the thermoforming step comprises: a) as a softening step, heating the aryl ether ketone polymer (PAEK) sheet to a temperature above the glass transition temperature of the polyaryl ether ketone (PAEK) to soften it; b) as a crystallization step, heating the aryl ether ketone polymer (PAEK) sheet for a time sufficient to crystallize the aryl ether ketone polymer (PAEK) sheet to a temperature above the glass transition temperature of the polyaryl ether ketone (PAEK), below the melting temperature of the polyaryl ether ketone (PAEK), and within the range of 210 °C to 280 °C; c) placing the aryl ether ketone polymer (PAEK) sheet on a mold during the softening step or during the crystallization step before crystallization occurs; and d) forming a semi-crystalline molded article . **Claim 2** The polyaryl ether ketone (PAEK) has a viscosity at 360 °C of at least 800 Pa·s at 100 seconds, measured by a parallel plate rheometer. -1 The method according to claim 1, wherein the polyaryl ether ketone (PAEK) has a viscosity at 360 °C of at least 800 Pa·s at 100 seconds, measured by a parallel plate rheometer. **Claim 3** The method according to claim 1, wherein the polyaryl ether ketone (PAEK) has a viscosity at 360 °C of 5000 Pa·s or less at 100 seconds, measured by a parallel plate rheometer. -1 ​ **Claim 4** The method according to claim 1, wherein the polyaryl ether ketone (PAEK) is selected from the group consisting of polyether ketone ketone (PEKK), polyether ketone (PEK), polyether ketone ether ketone ketone (PEKEKK), and combinations thereof. **Claim 5** The method according to claim 1, wherein the polyaryl ether ketone (PAEK) is polyether ketone ketone (PEKK). **Claim 6** The method according to claim 5, wherein the polyether ketone ketone (PEKK) has a T:I isomer ratio of 50:50 to 90:

10. **Claim 7** The method according to claim 5, wherein the polyether ketone ketone (PEKK) has a T:I isomer ratio of 65:35 to 75:

25. **Claim 8** The method according to claim 5, wherein the polyether ketone ketone (PEKK) has a T:I isomer ratio of 68:32 to 72:

28. **Claim 9** The method according to claim 5, wherein the polyetherketoneketone (PEKK) has a T:I isomer ratio of 70:

30. **Claim 10**: The method according to claim 1, wherein the aryl ether ketone polymer (PAEK) sheet further comprises one or more non-nucleating fillers. **Claim 11**: The method according to claim 1, wherein the aryl ether ketone polymer (PAEK) sheet further comprises one or more non-nucleating additives selected from the group consisting of reinforcing fibers, pigments, heat stabilizers, antioxidants, glass spheres, silica, and talc. **Claim 12**: The method according to claim 5, wherein the ether ketone ketone (PEKK) polymer sheet has a thickness of 2000 to 10,000 microns. **Claim 13** The method according to any one of claims 1 to 12, wherein the semi-crystalline article exhibits a dimensional change of less than 3% compared to the mold.

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