DYNAMICALLY TEMPERATURE-CONTROLLED IN-MOULD DECORATION

Abstract

The invention relates to an injection-molding process for the production of an injection-molded element, comprising a film element and an in-mold-coating layer directly injected onto said element. The film element occupies only part of the area of the in-mold-coating layer, and therefore at least one portion of the film edges of said film element is located in the middle of the relevant area of the injection-molded element. In order to avoid notching in the boundary region, the process for the production of the injection-molded element utilizes dynamic temperature control for locally restricted heating of the mold in the region where the flow front of the in-mold-coating material encounters the film material. Injection-molded elements are thus obtained in which no optically discernible boundary is present between film element and in-mold-coating layer. Because there are no joints, the injection-molded elements are amenable to successful and durable subsequent coating.

Claims

1. A process for the production of an injection-molded element (1) with a front side and a reverse side, where there is, arranged on the front side of the injection-molded element (1), a film element (2) flush with the surface of an in-mold-coating layer (8), wherein the film element (2) has an edge (2′) and defines an inner edge region which extends from the edge (2′) over a predetermined distance d1 running at right angles to the edge in the direction of the film element (2), where d1 is smaller than half of the width of the film element (2) and wherein the process comprises the following steps in this sequence: providing a mold (3) which in the closed state defines, between a first mold half (4) which replicates the front side of the injection-molded element (1) and a second mold half (5) which replicates the reverse side of the injection-molded element (1), a cavity (6) configured in a manner complementary to the injection-molded element (1), placing the film element (2) into the first mold half (4), closing the mold (3), injecting a plastified thermoplastic material (7) into the cavity (6) in order to configure an in-mold-film coating layer (8), allowing the plastics material (7) to solidify, opening the mold (3) and removing the injection-molded element (1), wherein the thickness of the film element (2) is ≥20 μm to ≤1000 μm, wherein the film element (2) covers only a partial region in the first mold half (4), and wherein at least during one portion of the injection of the plastified thermoplastic material (7) at least the inner edge region of the film element (2) is heated by one or more temperature-controlled elements (9) present in the first mold half (4) at least to a temperature T of 20° C. below the Vicat softening point (determined in accordance with DIN ISO 306:2014 method B at 120 K/h of heating time) of the material of the film element (2).

2. The process of claim 1, wherein locally restricted heating of the mold is achieved by means of dynamic temperature control at the film element/in-mold-coating material boundary.

3. The process of claim 1, wherein regions of the film element (2) that do not belong to the inner edge region are not heated to the temperature T.

4. The process of claim 1, wherein the predetermined distance d1 is ≥1% to ≤40% of the width of the film element (2).

5. The process of claim 1, wherein the film element (2) further defines an outer edge region which extends from the edge (2′) over a predetermined distance d2 running at right angles to the edge in the direction away from the film element (2), wherein d2 is ≥1% to ≤40% of the width of the film element (2), and wherein, in the first mold half (4), sections corresponding to the outer edge region are heated together with the inner edge region to the temperature T.

6. The process of claim 1, wherein the thermoplastic material (7) or the material of the film element (2) comprise a polycarbonate.

7. The process of claim 1, wherein the film element (2) is a heating film, a film with projection function, a film with scattering function, a colored film, a film with optically discernible surface structure, a film comprising functional additives, a film with antireflective function, a film with anti-fingerprint function, a film with antiglare function, a film with antifogging function, a film with increased chemical resistance to the in-mold-coating material, a film with barrier function, an IR-reflective film, a film with absorption properties, a polarizing film, a metallized film or a super retardation film.

8. The process of claim 1, wherein the thickness of the film element (2) is ≥100 μm to ≤700 μm.

9. The process of claim 1, further comprising, after removal of the injection-molded element (1), a subsequent coating of at least the component side on which the film element (2) is present.

10. An injection-molded element (1), produced by the process of claim 1, with a front side and a reverse side, where there is, arranged on the front side of the injection-molded element (1), a film element (2) flush with the surface of an in-mold-coating layer (8), where the film element (2) covers only one portion of the surface of the in-mold-coating layer (8), and where the film element (2) and the in-mold-coating layer (8) respectively comprise a thermoplastic polymer, wherein the bonding of the film element (2) to the in-mold-coating layer (8) is jointless, or in the event that a joint is present between film element (2) and in-mold-coating layer (8), the depth (100) of this joint is ≤12% of the thickness of the film element (2) or the width (200) of said joint is ≤12% of the thickness of the film element (2).

11. The injection-molded element (1) of claim 10, where the film element (2) is a heating film, a film with projection function, a film with scattering function, a colored film, a film with optically discernible surface structure, a film comprising functional additives, a film with antireflective function, a film with anti-fingerprint function, a film with antiglare function, a film with antifogging function, a film with increased chemical resistance to the in-mold-coating material, a film with barrier function, an IR-reflective film, a film with absorption properties, a polarizing film, a metallized film or a super retardation film.

12. The injection-molded element (1) of claim 10, wherein the injection-molded element (1) is a glazing element, a transparent covering or a cladding element, and the film element (2) is a heating film.

13. (canceled)

Description

[0112] The following figures provide more detail of the invention, which however is not restricted thereto. In the figures:

[0113] FIG. 1 shows a cross-sectional view of an injection-molded element of the invention

[0114] FIG. 2 shows a cross-sectional view intended to indicate certain dimensions in injection-molded elements

[0115] FIGS. 3a and 3b show initial phases in the process of the invention

[0116] FIGS. 4a and 4b show second phases in the process of the invention

[0117] FIG. 5 shows a first mold half of a mold

[0118] FIG. 6 shows a micrograph of a comparative sample

[0119] FIG. 7 shows a micrograph of a sample of the invention

[0120] FIG. 1 shows a diagrammatic cross-sectional view of an injection-molded element 1 of the invention with the film element 2 and the in-mold-coating layer 8. That side of the injection-molded element 1 on which the film element 2 is arranged is the front side of the injection-molded element 1 here. Accordingly, the side that is opposite to the film element 2 is the reverse side of the injection-molded element 1.

[0121] The film element 2 is arranged flush with the surface of the in-mold-coating layer 8, i.e. has been let into same in a manner such that on the front side of the injection-molded element 1 there are no height differences between the surfaces of the film element 2 and of the in-mold-coating layer 8 that form the front side of the injection-molded element. The film element has therefore been cut to a size that is smaller than the mold cavity surface. A tolerance range of height differences up to ±1 μm is also included.

[0122] FIG. 1 moreover shows that the film element 2 covers only one portion of the surface of the in-mold-coating layer 8. The in-mold-coating layer 8 therefore also forms one portion of the front side of the injection-molded element 1.

[0123] The invention provides that bonding of the film element 2 to the in-mold-coating layer 8 is jointless, or that any joint present does not exceed certain dimensions. A joint is defined here as a gap where the edges of film element 2 and in-mold-coating layer 8 contact one another.

[0124] FIG. 2 illustrates diagrammatically the dimensions for the description of joint geometries. An enlarged detail of the front side of the injection-molded element is shown, where the film element 2 and the in-mold-coating layer 8 meet one another. The joint depth 100 here is the vertical dimension from the deepest point of the joint to an imaginary continuous of the surfaces of the film element 2 and in-mold-coating layer 8. In the event that the surfaces outside of the joint region are not flush with one another, a surface average is selected as reference plane. The joint width 200 is measured at right angles to the boundary between film element 2 and in-mold-coating layer 8.

[0125] FIGS. 3a and 3b are diagrams of initial phases in the process of the invention. A mold 3 has been provided, having a first mold half 4 and a second mold half 5. The first mold half 4 determines the shape of the front side, and the second mold half 5 determines the shape of the reverse side of the injection-molded element to be produced. As can be discerned from the dimensions of the depression in the first mold half 4 and of the projection in the second mold half 5, a cavity 6 is defined when the mold 3 is closed. A thermoplastic polymer can be introduced into this cavity 6 by way of the injection duct 10.

[0126] The film element 2 intended for in-mold coating has moreover been placed into the first mold half 4. A temperature control element 9, which is equipped for the heating and cooling of the entire back wall of the mold half (FIG. 3a), or of a predetermined edge area of the film element 4 (FIG. 3b), and has been integrated into the first mold half 4. The temperature-control element 9 can take the form of ducts. Running below the mold surface, there can be a plurality of bores through which a fluid is conveyed which ensures that the mold surface is maintained at a predetermined, as far as possible constant, temperature.

[0127] A temperature-control element 9 for dynamic temperature control of a selected film region can optionally likewise have ducts through which a hotter/colder fluid is conveyed in a separate circuit. Alternatively, temperature-control elements in the form of electrical resistance heating systems, or inductive methods, can also be used for local heating of the surface, which in turn can be cooled by way of cooling bores 9a which are close to the surface and through which cold water is conveyed.

[0128] In order to achieve a better appearance of the injection-molded element, it is preferable that this temperature-control element 9 is located below the surface of the first mold half 4. Transport of heat from temperature-control element 9 to film element 2 then takes place through the material present between said elements, which is part of the first mold half. In order to save energy and to increase the precision of heating, the material between said elements is selected to be as thin as possible, its thickness by way of example being ≤15 mm and preferably ≤10 mm.

[0129] FIGS. 4a and 4b are diagrams of a second phase in the process of the invention, starting from the configurations from FIG. 3a and FIG. 3b. The mold 3 is closed, and plastified thermoplastic material 7 has been injected by way of duct 10 into the cavity defined between first mold half 4 and second mold half 5, thus configuring an in-mold-coating layer.

[0130] FIG. 5 is a diagrammatic plan view of a first mold half 4 of a mold of the invention for use in the process of the invention. A film element 2 has been placed into the first mold half. The film element 2 has an edge 2′ and an inner edge region. The inner edge region extends from the edge 2′ over the length of the distance d1 (at right angles from the relevant position on the edge 2) in the direction of the film element 2.

[0131] The film element 2 moreover has an exterior edge region, defined with the aid of the distance d2 in a manner analogous to that for the inner edge region.

[0132] The first mold half 4 moreover has the temperature-control element 9 which, as described above, has preferably been integrated within this mold half. The temperature-control element 9 is not equipped to heat the entire area of the film element. Instead, the temperature-control element 9 follows the edge 2′ of the film element 2 with an additional extent in the direction of the film element 2 (distance d1) and away from the film element (distance d2). The extent of the temperature-control element 9 in the direction of the film element 2 is indicated by the reference sign 9′. In the drawing in FIG. 5, the delimited area of the inner edge of the film element 2 coincides with the extent 9′ of the temperature-control element 9 in the direction of the film element 2.

EXAMPLES

[0133] The invention is illustrated in detail by the examples which follow, but is not restricted thereto.

Materials Used:

[0134] Material for the in-mold-coating layer: Makrolon® 2405 from Covestro Deutschland AG. Aromatic polycarbonate based on bisphenol A with MVR of 19 cm.sup.3/(10 min), determined at 300° C. with 1.2 kg load in accordance with DIN ISO 1133:2012-03, and with Vicat softening point of 145° C., determined with 50 N at 50° C./h in accordance with DIN ISO 306:2014-03. The polycarbonate was pretreated by drying in dry air for 4 hours at 110° C.

Material for the Film Elements:

[0135] Makrofol® DE 1-4 from Covestro Deutschland AG, based on bisphenol A-polycarbonate (MVR 6.0 cm.sup.3/(10 min), determined in accordance with DIN ISO 1133:2012-03, at 300° C. with 1.2 kg load). Vicat softening point, determined in accordance with DIN ISO 306:2014 method B at 120 K/h of heating time, was 150° C. [0136] Makrofol® DE 1-1 from Covestro Deutschland AG, based on bisphenol A polycarbonate (MVR 6.0 cm.sup.3/(10 min), determined in accordance with DIN ISO 1133:2012-03, at 300° C. with 1.2 kg load), single-color-printed with NORIPLAN® HTR N L 67628 ink from Pröll KG, Germany. Vicat softening point, determined in accordance with DIN ISO 306:2014 method B at 120 K/h of heating time, was 150° C. [0137] Bayfol® CR 210 from Covestro Deutschland AG, based on a blend of bisphenol A-polycarbonate (MVR 6.0 cm.sup.3/(10 min), determined in accordance with DIN ISO 1133:2012-03, at 300° C. with 1.2 kg) and polyethylene terephthalate copolyester. Vicat softening point, determined in accordance with DIN ISO 306:2014 method B at 120 K/h of heating time, was 127° C. [0138] Makrofol® DE202 1-4 from Covestro Deutschland AG, based on a copolycarbonate of bisphenol A polycarbonate and bisphenol TMC polycarbonate (MVR 18 cm.sup.3/(10 min), determined in accordance with DIN ISO 1133:2012-03, at 300° C. with 1.2 kg load). Vicat softening point, determined in accordance with DIN ISO 306:2014 method B at 120 K/h of heating time, was 183° C. [0139] Makrofol® UV 503 9-2 from Covestro Deutschland AG, a red-colored coextruded film based on bisphenol A polycarbonate (MVR 12 cm.sup.3/(10 min), determined in accordance with DIN ISO 1133:2012-03, at 300° C. with 1.2 kg load). Vicat softening point, determined in accordance with DIN ISO 306:2014 method B at 120 K/h of heating time, was 145° C. [0140] Makrofol® UV 244 1-1 from Covestro Deutschland AG, a coextruded film based on bisphenol A polycarbonate (MVR 6.0 cm.sup.3/(10 min), determined in accordance with DIN ISO 1133:2012-03, at 300° C. with 1.2 kg load), with a functional layer for protection from UV radiation, and with integrating heating wires. Vicat softening point, determined in accordance with DIN ISO 306:2014 method B at 120 K/h of heating time, was 145° C.

Production of Injection-Molded Elements:

Comparative Examples

[0141] An injection-molded element with dimensions 150×105×4 mm was produced in an Arburg 570C injection-molding machine. For this, a polycarbonate-based film (see table A) as film element with dimensions 70×120 mm was placed into the first mold half of a steel mold in a manner such that in the finished molding it is adjacent to the upper edge and in other respects is placed in the middle with a free edge measuring about 15 mm in relation to the two lateral edges and 40 mm in relation to the lower edge of the molding. The film was fixed by adhesion on the polished surface. The temperature of the mold wall was 100° C. on the ejector side (first mold half) and 80° C. on the opposite nozzle side (second mold half).

[0142] After the two mold halves have been closed to form the mold, the in-mold-coating material Makrolon® 2405 was injected with a maximal injection pressure of about 2500 bar into the mold. The temperature of the polycarbonate melt here was 310° C. Injection time was 3.5 seconds. After a hold-pressure time of 8 seconds (hold pressure: 900 bar) and a cooling time of 25 seconds the mold was opened and the molding was removed.

Inventive Examples

[0143] An injection-molded element with dimensions 150×105×4 mm was produced in an Arburg 570C injection-molding machine. For this, a polycarbonate-based film (see table B) as film element with dimensions 70×120 mm was placed into the first mold half of a steel mold in a manner such that in the finished molding it is adjacent to the upper edge and in other respects is placed in the middle with a free edge measuring about 15 mm in relation to the two lateral edges and 40 mm in relation to the lower edge of the molding. The film was fixed by adhesion on the polished surface, or in the case of films of thickness 500 μm or more was fixed in the cavity with the aid of small piece of double-sided adhesive tape. The temperature of the mold wall was 100° C. on the ejector side (first mold half) and 80° C. on the opposite nozzle side (second mold half).

[0144] After the two mold halves were closed to form the mold, the first mold half was heated to a measured temperature (for data see results table) by means of water-cooling (input temperature 20° C. above the desired temperature) within a heating time, and at the same time the in-mold-coating material Makrolon® 2405 was injected with a maximum injection pressure of 2500 bar into the mold. The temperature of the polycarbonate melt here was 310° C. Injection time was 3.5 seconds. After a hold-pressure time of 8 seconds (hold pressure: 900 bar) the mold wall was cooled within 8 seconds to a measured temperature 100° C. After a cooling time of 25 seconds, the mold was opened and the molding was removed.

Subsequent Coating of the Injection-Molded Elements:

[0145] All of the solvents were purchased as technical-grade products and were used without drying.

Pretreatment/Cleaning of Sample Components

[0146] Ionized air was blown onto the polycarbonate sheets (injected-molded element) in order to remove adhering contaminants before coating.

Method for Subsequent Coating

[0147] Coating took place in a coating chamber under controlled conditions of temperature and humidity, in accordance with the respective instructions of the outer-coating material manufacturer, at 23 to 25° C. and at 40% to 48% relative humidity.

[0148] The sample sheets were cleaned with what are known as iso-wipes (LymSat® from LymTech Scientific; saturated with 70% by weight of isopropanol and 30% by weight of deionized water), rinsed with isopropanol, and dried in air for 30 minutes; ionized air was then blown onto the samples.

[0149] The primers and outer coatings are processed in accordance with manufacturer's instructions. The solids content of the commercially obtainable high-build primer SHP 470 FT 2050 from Momentive Performance Materials was adjusted with a 1:1 solvent mixture of diacetone alcohol and 1-methoxy-2-propanol to 5.2%, measured by the method below.

[0150] The solids content of the outer coatings was determined with the aid of the Mettler Toledo HB43 solids tester, a weighed sample of outer coating being evaporated to constant mass at 140° C. Percentage solids content is then calculated from the ratio of mass after to mass before evaporation. The solids content of the outer coating after curing of the outer coating here in the simplest case is the weight of outer coating minus the weight of solvent.

[0151] This primer was applied by the flow-coating process to one side of the polycarbonate sheets produced by in-mold coating of films.

[0152] A manual coating method was used. This involved pouring the liquid SHP470 primer coating solution over the sheet starting from the upper edge of the injection-molded element in longitudinal direction across the sheet, while the point of application of the primer on the sheet was simultaneously moved from left to right across the width of the sheet. The primed sheet, suspended vertically from a clamp, was air-dried for 30 minutes at 23° C. until dust no longer adhered to the surface, and was then cured for 60 minutes at 130° C.

[0153] After cooling to room temperature, the primed surface was coated with commercially obtainable AS 4700 F from Momentive Performance Materials.

[0154] The solids content of the AS 4700 was adjusted with a 1:1 solvent mixture of isopropanol and n-butanol to 25.0%, measured by the above method.

[0155] Application was likewise by a manual method. This involved pouring the liquid AS 4700 outer coating over the sheet starting from the upper edge of the injection-molded element in longitudinal direction across the sheet, while the point of application of the outer coating on the sheet was simultaneously moved from left to right across the width of the sheet. The outer-coated sheets, suspended vertically from a clamp, were air-dried for 30 minutes at 22° C. and were then cured for 60 minutes at 130° C.

Visual Assessment:

[0156] The sample sheets were visually assessed after coating and evaluated by using a scale of 0 to 6, 0 being the best value and 6 being the worst value. The test investigated whether there is a visible gap at the boundary between film element and in-mold-coating material. The results are shown in the table below.

TABLE-US-00001 Makrofol ® Makrofol ® DE 1-1, DE 1-4, Makrofol ® Makrofol ® printed with Makrofol ® Bayfol ® Makrofol ® Makrofol ® Makrofol ® thickness 250 μm DE 1-4 DE 1-4 NORIPLAN ® DE 1-4 CR 210 DE202 1-4 UV 503 9-2 UV 244 1-1 with double thickness thickness HTR N L 67628 thickness thickness thickness thickness thickness hold-pressure Film element 250 μm 300 μm thickness 250 μm 500 μm 250 μm 125 μm 700 μm 375 μm time Example B1 B2 B3 B4 B5 B6 B7 C D Without 6 6 6 6 6 6 — — — heating Heating temperature [° C.] 153 1 (2) 3 3 2-3 2 4 2 3 — 161 1 (2) 2 2 2 2 2 2 2 — 170 1 2 1 2 2 2 1 (2) 2 1 178 1 1 1 1 2 1 1 1 — 186 1 1 1 1 1 (2) 1 1 1 —

[0157] The grading criteria are as follows: 0: no boundary detectable; 1: film/substrate boundary detectable only with use of mirror techniques; 2: film/substrate boundary only just discernible; 3: film/substrate boundary readily discernible; 4: film/substrate boundary discernible, but no gap visible; 5: visible gap; 6: very clearly visible gap.

[0158] A grade of 3 or better is considered to indicate a pass in the visual assessment. All of the examples without heating are comparative examples.

[0159] The difference between the heating temperatures and the Vicat softening points of the film materials used is shown below:

TABLE-US-00002 Heating temperature [° C.] 153 161 170 178 186 Makrofol/ Difference between heating temperature Bayfol and Vicat softening point [° C.] DE 1-4 3 13 20 28 36 DE 1-1 3 13 20 28 36 CR210 26 34 43 51 59 DE202 1-4 −30 −22 −13 −5 3 UV 503 9-2 8 16 25 33 41 UV 244 1-1 8 16 25 33 41

[0160] Examples with heating are inventive, except for example B6 with 153° C. and 161° C. heating temperature.

[0161] Dynamic temperature control achieved sample sheets which had no discernible gap and almost no discernible boundaries between film element and in-mold-coating material.

[0162] The sample sheets without dynamic temperature control exhibited clear boundaries between film element and in-mold-coating material. Slight blistering was visible in the gap, due to evaporating solvent after film-formation.

Microscopic Studies:

[0163] Microscopic studies were then carried out on microtome sections of the film element/in-mold-coating material boundary regions. For this, a sample including the boundary region is sawn from the sample sheet. A HM 355 S microtome from Microm is used to achieve straight cutting of said sample. This section is then photographed and measured under a DM 2700M microscope from Leica with 500× magnification in incident light in bright-field mode.

[0164] FIG. 6 shows a micrograph of the cross section of a comparative sample not produced by the process of the invention: example B1 without heating. The in-mold-coating layer is in the left-hand half of the image, and the film element is in the right-hand half of the image. With reference to the terminology in FIG. 2, the joint depth is 147 μm and the joint width is 145 μm.

[0165] FIG. 7 shows a micrograph of the cross section of a sample produced by the process of the invention: example B1 with heating to 170° C. The in-mold-coating layer is in the right-hand half of the image, and the film element is in the left-hand half of the image. The bond between them is jointless.

[0166] Dynamic temperature control significantly reduces peripheral gap formation. No coating defects can be seen.

[0167] The sample sheets without dynamic temperature control exhibited a clear gap between the film element and the in-mold-coating material (see table below). The coating filled this notch region to some extent or completely. The critical outer-coating thicknesses were thus exceeded, and this resulted in incomplete evaporation, which leads to blistering during curing. Slight blistering due to evaporating solvent was moreover apparent in the boundary region after film-formation. In addition to the above, excessive thicknesses of outer coating usually signify brittle regions and lead to reduced lifetime.

TABLE-US-00003 Makrofol ® Makrofol ® DE 1-1, DE 1-4, Makrofol ® Makrofol ® printed with Makrofol ® Bayfol ® Makrofol ® Makrofol ® Makrofol ® thickness DE 1-4 DE 1-4 NORIPLAN ® DE 1-4 CR 210 DE202 1-4 UV 503 9-2 UV 244 1-1 250 μm with Film thickness thickness HTR N L 67628 thickness thickness thickness thickness thickness double hold- element 250 μm 300 μm thickness 250 μm 500 μm 250 μm 125 μm 700 μm 375 μm pressure time Example B1 B2 B3 B4 B5 B6 B7 C D Gap uwd Gap uwd Gap uwd Gap uwd Gap uwd Gap uwd Gap uwd Gap uwd Gap uwd Without 147 145 160 115 110 136 >200 201 82 125 125 133 heating Heating temperature [° C.] 153  28   4  <3   5  <3  <3 125  <3  4 <3 161  15  <3 125  <3 170  <3  <3  <3  <3   <3  <3 <3  <3  <3  <3 5 <3 <3 <3 <3 <3 178  <3   4 186  <3  <3  <3  <3 <3 <3 Gap: depth of gap starting from surface; corresponds to dimension with reference sign 100 in FIG. 2 uwd: upper defect width; corresponds to dimension with reference sign 200 in FIG. 2