MOLD RELEASE COATINGS FOR GLASS FORMING OR PROCESSING EQUIPMENT AND RELATED METHODS

Abstract

In one aspect, a pressing unit is provided, comprising: a mold and a plunger, and a coating configured on at least one of: the surface of the mold and/or the surface of the plunger, where the coating is configured adjacent to the areas where molten or hot glass or glass ceramic touches; wherein the coating comprises: a mold release coating, configured as the gob-contacting surface, wherein the mold release coating comprises: at least two solid lubricants selected from tungsten disulfide, boron nitride, glassy carbon and graphite; and a thermal barrier coating comprising barrier material components and an organo-silica binder.

Claims

1. A pressing unit, comprising: a mold and a plunger, wherein the mold is configured to receive a gob of glass material or glass ceramic material and process the gob into a product form; and a coating configured on at least one of: the surface of the mold which is configured adjacent to the gob and/or product form, to form a coated mold, and the surface of the plunger which is configured adjacent to the gob and/or product form, to form a coated plunger, wherein the coating comprises: a mold release coating, configured as the gob-contacting surface, wherein the mold release coating comprises: at least two solid lubricants selected from: tungsten disulfide, boron nitride, graphite, and glassy carbon, and an organo-silica binder; and a thermal barrier coating comprising barrier material components and an organo-silica binder, wherein the thermal barrier coating is configured to extend between at least one of: the mold release coating and the portion of the coated mold and the mold release coating and the portion of the coated plunger.

2. The pressing unit of claim 1, wherein the thermal barrier coating comprises: barrier material components retained in an organo-silica binder.

3. The pressing unit of claim 2, wherein the barrier material components are selected from the group consisting of: cerium oxide; zirconium oxide; and silica.

4. The pressing unit of claim 2, wherein the barrier material components are present in an amount of not greater than 80% by weight of the thermal barrier coating.

5. The pressing unit of claim 2, wherein the binder material is present in an amount of not greater 35% by weight in the thermal barrier coating.

6. The pressing unit of claim 1, wherein the mold release coating comprises solid lubricants of: boron nitride and glassy carbon present in a total amount of not greater than 80 percent by weight in the mold release coating.

7. The pressing unit of claim 1, wherein the mold release coating comprises solid lubricants of: boron nitride and tungsten disulfide present in a total amount of not greater than 80 percent by weight in the mold release coating.

8. The pressing unit of claim 1, wherein the mold release coating comprises solid lubricants of: tungsten disulfide, boron nitride, graphite, and glassy carbon present in a total amount of not greater than 50 percent by weight in the mold release coating.

9. The pressing unit of claim 1, further comprising a mold ring mount attached to the mold and configured to mount on a press.

10. The pressing unit of claim 1, wherein one or more of the mold and the plunger is made of cast iron.

11. (canceled)

12. The pressing unit of claim 1, wherein the mold is configured with a mold cavity.

13. The pressing unit of claim 1, further comprising: a melting unit configured to melt a glass or glass ceramic material to form a melt; and a gob forming unit configured to attach to the melting unit to receive the melt and dispense portions of the melt into a plurality of metered gobs into the pressing unit.

14. The pressing unit of claim 1, wherein each gob is configured with: a pre-determined amount of material having an elevated temperature at deposition in the mold in the range of 1350 degrees C. to 1600 degrees C.

15. A glass or glass-ceramic forming equipment, comprising: a melting unit configured to melt a glass or glass ceramic material; a gob forming unit configured to receive the melted glass or glass ceramic material from the melting unit and dispense portions thereof into a plurality of metered gobs, where each of the gobs is configured with: a pre-determined amount of material having an elevated temperature such that the viscosity of each gob at the time of deposition in the mold in the range of 1350 degrees C. to 1600 degrees C.; and the pressing unit of claim 1, the pressing unit configured to receive the gob from the gob forming unit and process the gob into the product form.

16. The glass or glass-ceramic forming equipment of claim 15, wherein the pressing unit further comprises a mold ring mounted on a press.

17. The glass or glass-ceramic forming equipment of claim 15, wherein the mold and the coating have a temperature in the range of at least 250 degrees C. to not greater than 500 degrees C.

18. (canceled)

19. (canceled)

20. A coating, comprising: a mold release composition, comprising: greater than or equal to 20 wt. % and less than or equal to 70 wt. % boron nitride; optionally, greater than or equal to 3 wt. % and less than or equal to 21 wt. % tungsten disulfide; optionally, greater than or equal to 4 wt. % and less than or equal to 11 wt. % glassy carbon; optionally, less than or equal to 5 wt. % graphite, where at least some graphite is present, the remainder, organo-silica solution; and a thermal barrier coating composition, comprising: greater than or equal to 60 wt. % and less than or equal to 85 wt. % of a barrier material component; and greater than or equal to 15 wt. % and less than or equal to 40 wt. % of a binder comprising an organo-silica solution.

21. (canceled)

22. (canceled)

23. (canceled)

24. The coating of claim 20, wherein the barrier material component further comprises: greater than or equal to 12 wt. % and less than or equal to 45 wt. % of a cerium oxide; greater than or equal to 10 wt. % and less than or equal to 30 wt. % of a zirconium oxide comprising an organo-silica solution; and greater than or equal to 5 wt. % and less than or equal to 15 wt. % of silica.

25. A method, comprising: directing a layer of alcohol-based material onto a plurality of glass-contacting surfaces in a glass or glass-ceramic pressing or glass or glass-ceramic processing assembly, wherein the layer is configured as a thermal barrier layer; applying over the thermal barrier layer, a mold release mixture, wherein the mold release mixture comprises: an alcohol-based of a mixture including: (i) a plurality of solid lubricant components; and (ii) an organo-silica binder; removing the alcohol from the thermal barrier layer and the mold release to form a dried thermal barrier layer and a dried mold release mixture; and curing the dried thermal barrier layer and the dried mold release mixture at an elevated temperature for a sufficient duration of time to transform: (i) the dried thermal barrier layer into a thermal barrier coating and (ii) the dried mold release mixture into a mold release coating, wherein the mold release coating is adhered onto the glass contact surfaces of the glass processing assembly via the thermal barrier coating.

26. The method of claim 25, wherein the alcohol-based mixture comprises a dispersion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1A depicts a cross-sectional representation of a bi-layer coating on a portion of a glass forming equipment (e.g., mold), in accordance with one or more embodiments of the present disclosure.

[0060] FIG. 1B depicts a schematic of an embodiment of a pressing assembly, in accordance with one or more aspects of the present disclosure.

[0061] FIG. 2 depicts a schematic drawing of an embodiment of a method for preparing and forming the thermal barrier coating (TBC) on the glass forming equipment (e.g., mold), in accordance with one or more embodiments of the present disclosure.

[0062] FIG. 3 is a schematic drawing of an embodiment of a method for making an organo-silica solution used as binder for preparing the mold release coating, in accordance with one or more embodiments of the present disclosure.

[0063] FIG. 4 depicts a schematic drawing of an embodiment of a method for forming the mold release coating (MRC), in accordance with one or more embodiments of the present disclosure.

[0064] FIG. 5 depicts a flow chart, which illustrates an embodiment of a method of making the coated forming articles of the present disclosure.

DETAILED DESCRIPTION

[0065] Reference will now be made in detail to various embodiments of the present disclosure, which will be described herein with specific reference to the appended drawings.

[0066] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent about, it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0067] Directional terms as used hereinfor example up, down, right, left, front, back, top, bottomare made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0068] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order, nor that with any apparatus specific orientations be required. Accordingly, where a method claim does not actually recite an order to be followed by its steps, or that any apparatus claim does not actually recite an order or orientation to individual components, or it is not otherwise specifically stated in the claims or description that the steps are to be limited to a specific order, or that a specific order or orientation to components of an apparatus is not recited, it is in no way intended that an order or orientation be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps, operational flow, order of components, or orientation of components: plain meaning derived from grammatical organization or punctuation, and; the number or type of embodiments described in the specification.

[0069] As used herein, the singular forms a, an and the include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a component includes aspects having two or more such components, unless the context clearly indicates otherwise.

[0070] FIG. 1A depicts a cross-sectional representation of a bi-layer coating on a portion of a glass forming mold, in accordance with one or more embodiments of the present disclosure.

[0071] Referring to FIG. 1A, a pressing unit component, which is shown as a mold surface composed of cast iron, has a coating applied to its surface, in accordance with one or more embodiments of the present disclosure. As shown in FIG. 1A, the coating includes a thermal barrier coating covering the portion of the mold surface. Over the thermal barrier coating, a mold release coating is applied, in accordance with one or more embodiments of the present disclosure.

[0072] Referring to FIG. 1B, a glass or glass ceramic forming assembly 400 is depicted. The forming assembly 400 includes a melting unit 300; a gob forming unit 200; a pressing unit 100; and optionally, after the forming assembly 400, a product finishing assembly 600. As shown in FIG. 1B, the melt unit 300 forms the melted glass or glass ceramic material, the melt 26. The melt is directed via arrow towards the cob forming unit 200, where the melt 26 is dispensed into gob after gob (i.e., a plurality of gobs, in continuous or semi-continuous frequency), where each gob 28 is directed into the pressing unit 100. In this embodiment of the pressing unit 100, the gob 28 is retained in the mold 10. The mold 10 is configured with a coating 14, which includes a mold release coating 16 which is configured over a thermal barrier coating 18. The mold 10 is configured to actuate with a plunger 12 in order to form a product form 30. In some embodiments, the plunger 12 is also configured with a mold release coating that is configured over a thermal barrier coating 18. When the gob 28 is formed into a product form 30 via actuation of the mold 10 with the plunger 12, the resulting product form 30 is defined with improved product dimensions, improved release from the mold, improved dimensions correlating to the target product form dimensions, etc.) as compared to a pressing assembly 100 coated with previous coatings (non-invention). The product form 30 is then directed out from the glass or glass forming assembly 400.

[0073] Referring to FIG. 2, the thermal barrier coating (TBC) is prepared according the embodied method. A TBC solution is prepared by a 1-step sol-gel reaction. During the sol formulation, a silica source and catalyst are added to a mixture of alcohol and thermal barrier components. In one embodiment, the silica source is colloidal silica, the catalyst is citric acid, the alcohol is ethanol, and the thermal barrier components include both cerium oxide (CeO.sub.2) and zirconium oxide (ZrO.sub.2). After the sol is formed, a binder is added. In this embodiment, the binder is methyltrimethoxysaline (MTMS). Next, the formed sol solution is mixed for a sufficient duration of time to promote mixing and breaking up any localized discontinuities of the thermal barrier components, promoting a mixed and dispersed sol solution. In this embodiment, the sol solution is ball milled for three (3) hours to form the final sol solution. The sol solution of thermal barrier mixture is then directed onto the surface (i.e., glass contacting surface(s)) of the glass forming and/or processing equipment. In this embodiment, the sol solution is directed by spraying via a spray gun over the surface of the tools. The sol solution is allowed to set on the surfaces for a sufficient time before the mold release mixture is applied to the surface of the dried sol solution. In this embodiment, the sol solution was allowed to dry for approximately 30 minutes (e.g., at least 30 minutes).

[0074] Referring to FIG. 3, the mold release coating (MRC) solution was prepared in the same manner as the TBC solution, except that no thermal barrier components (cerium oxide or zirconium oxide) was added to the solution. An MRC solution is prepared by a 1-step sol-gel reaction. During the sol formulation, a silica source and catalyst are added to a mixture of alcohol and thermal barrier components. In one embodiment, the silica source is colloidal silica, the catalyst is citric acid, the alcohol is ethanol. After the sol is formed, a binder is added. In this embodiment, the binder is methyltrimethoxysaline (MTMS) Next, the formed sol solution is mixed for a sufficient duration of time to promote mixing and/or dispersing of the sol solution. In this embodiment, the sol solution is ball milled for three (3) hours to form the final sol solution. The sol solution of thermal barrier mixture is then directed onto the surface (i.e., glass contacting surface(s)) of the glass forming and/or processing equipment. In this embodiment, the sol solution is directed by spraying via a spray gun over the surface of the tools. The sol solution is allowed to set on the surfaces for a sufficient time before the mold release mixture is applied to the surface of the dried sol solution. In this embodiment, the sol solution was allowed to dry for approximately 30 minutes (e.g., at least 30 minutes).

[0075] Referring to FIG. 4, the embodied detailed procedure is summarized as follows: (i) the coating solution is prepared by dispersing the binder and solid lubricants in alcohol (e.g. ethanol) and mixing while dispersing (e.g. ball milling) for a sufficient duration of time (e.g. three (3) hours), (ii) the mixture is directed (e.g. sprayed) over the TBC layer portion(s); and (iii) the stack, including the dried TBC mixture and the mold release coating, is fully dried at room temperature, followed by cured at an elevated temperature (e.g. 600 C.) for a sufficient time to adhere and cure the thermal barrier coating and mold release coating.

[0076] Referring to FIG. 5, the method 500 includes the steps of: directing a layer of alcohol-based material, having thermal barrier materials retained thereon, onto a plurality of glass-contacting surfaces in a pressing unit, wherein the layer is configured as a thermal barrier layer 510; applying over the thermal barrier layer (TBL), a mold release mixture (MRM), comprising: an alcohol-based a mixture including: (i) a plurality of solid lubricant components; and (ii) an organo-silica binder 520; and transforming the thermal barrier mixture and the mold release layer into a thermal barrier layer and a mold release layer 530.

[0077] In some embodiments, the directing step further comprises: removing (e.g., drying) the alcohol from the thermal barrier layer 512.

[0078] In some embodiments, the transforming step further includes: Removing the alcohol from at least one of: the TBL and the MRM to form a dried TBL and a dried MRM 532 and/or Curing at least one of the TBL and MRM to create at least one of a thermal barrier coating (TBC) and a mold release coating (MRC) 534.

EXAMPLES

[0079] In order that various embodiments be more readily understood, reference is made to the following examples, which are intended to illustrate various embodiments of the mold coatings described herein. In the tables that follow, a variety of embodied compositions were made and evaluated according to the embodiments set out herein.

Example 1

[0080] FIG. 1 is a cross-sectional presentation of a bi-layer coating (TBC+MRC) formed on the surface of a glass forming mold. The coatings were prepared as follows. The first step was preparation of the TBC solution by the processing steps shown schematically in FIG. 2. The TBC solution was prepared by mixing 28 parts CeO.sub.2, 8.4 parts yttrium stabilized ZrO.sub.2, 6.72 parts colloidal silica (LUDOX TMA, 34 wt %), 1.82 parts citric acid, 21.52 parts MTMS and 104.36 parts ethanol. The mixture was ball milled at room temperature for 3 hours and was ready for spray coating. The second step was preparation of the organo-silica solution used as bind for forming the WRC film. The binder solution was prepared by mixing 3.5 parts boron nitride, 20.51 parts colloidal silica, 1.5 parts citric acid, 52.71 parts MTMS and 43 parts ethanol. The mixture was stirred at room temperature for 12 hours. The third step was preparation of the MRC solution schematically in FIG. 4. The coating solution was prepared by mixing 22.5 parts boron nitride, 3.38 parts glassy carbon, 7.76 parts of binder and 145.37 parts ethanol. The mixture solution was ball milled for about 3 hours. The final steps were the general cleaning of the mold and plunger, and application of the TBC and MRC solutions which proceeded as follows.

[0081] Conventional cast iron blank mold and plunger were initially cleaned by preheating to 300 C. to remove any residual or organic materials, such as oils, etc. The surfaces of the blank mold and plunder were then lightly sandblasted to remove any residual scale, rust, or other foreign materials on them. Next, the TBC solution was sprayed by a spray gun over the sandblasted surfaces of the mold and plunger. The spray parts were partially dried for 30 min at room temperature.

TABLE-US-00001 TABLE 1 Composition of the thermal barrier coating embodied in the Examples Target Wt. % for this Material Min Wt. % Example Max Wt. % Barrier material CeO.sub.2 12 43.3 45 ZrO.sub.2 10 13 30 Silica 5 10.4 15 Binder Organo-silica solution 15 33.3 40

[0082] After the partial drying, the MRC solution was sprayed coated over the TBC film. The stack was dried at room temperature for 6 hours and then cured at 600 C. for 1 hour under flowing N.sub.2. The composition of the applied WRC coating is shown in Table 2.

TABLE-US-00002 TABLE 2 Composition of mold release coating prepared in Example 1 Target Wt. % for this Material Min Wt. % Example Max Wt. % Solid lubricants Boron nitride 50 67 70 Glassy carbon 5 10 10 Binder Organo-silica solution 15 23 30

Example 2

[0083] Another blank mold and plunger, similar to the one employed in Example I, was coated following the same procedure used in the foregoing example, with the exception that the WRC spray mixture contained 22.5 parts boron nitride, 1.13 parts tungsten disulfide, 7.09 parts binder and 122.94 parts ethanol. The composition of the coating is shown in Table 3.

TABLE-US-00003 TABLE 3 Composition of mold release coating prepared in Example 2 Target Wt. % for this Material Min Wt. % Example Max Wt. % Solid lubricants Boron nitride 50 73 75 Tungsten disulfide 2 4 20 Binder Organo-silica solution 15 23 30

Example 3

[0084] Another blank mold and plunger, similar to the one employed in Example I, was also coated following the same procedure used in the Example 1, with the exception that the WRC spray mixture contained 8.2 parts boron nitride, 8.2 parts tungsten disulfide, 1.64 parts graphite, 1.64 parts glassy carbon and 212.5 parts ethanol. The composition of the applied coating is shown in Table 4.

TABLE-US-00004 TABLE 4 Composition of mold release coating prepared in Example 3 Target Wt. % for this Material Min Wt. % Example Max Wt. % Solid lubricants Boron nitride 10 21 30 Tungsten disulfide 10 21 30 Glassy carbon 2 4 5 Graphite 2 4 5 Binder Organo-silica solution 40 50 60

Example 4

[0085] The durability and glass release performance of the of the mold release coatings were evaluated. The objective of the process is to form molten glass into a 3D shape with variable thickness. The forming device consists of mold, plunger and mold ring. The coating is applied to the mold and plunger. To form a thin 3D part requires a slip layer on the mold with a barrier coating. The slip layer reduces surface friction of the glass to the mold. The heat barrier coating on the mold keeps the mold from acting like a heat sink and cools the glass. Glass temperature is 1350-1600 C. Another function of the slip layer helps prevent the glass from sticking to the mold. The coatings were evaluated with different glass compositions, pressing forces and different mold temperatures. Mold and plunger temperature range was 250-550 C. Pressing force was 10 k-17 k pounds of force. Glass is poured on the mold from a Melter. The mold is indexed into the press and the plunger contacts glass gob to form the part. Plunger is retracted and mold indexes out. The cycle time is 3 sec. The cycle repeats itself every 10-15 sec. In production cycle would repeat itself every 2-3 seconds. The durability of the coating is an important characteristics that contributes to the slip layer and thermal aspects of the coating during utilization. It was observed that the surfaces of the parts remained intact in each of the Examples and none of the molds failed within the available run time for this Example The table below depicts the number of cycles for each coating along with the number of parts made.

TABLE-US-00005 TABLE 5 Glass release performance of mold release coatings during a mold pressing test No. of No. of Coating Description molding cycles parts made EXAMPLE 1 Coating 1 20 EXAMPLE 2 Coating 1 20 EXAMPLE 3 Coating 5 100

REFERENCE NUMBERS

[0086] pressing unit 100 [0087] mold 10 [0088] plunger 12 [0089] coating 14 [0090] mold release coating 16 [0091] thermal barrier coating 18 [0092] mold ring mount 20 [0093] mold cavity 22 [0094] press 24 [0095] melting unit 200 [0096] gob forming unit 300 [0097] glass forming equipment 400 [0098] melt 26 [0099] gob 28 [0100] product form 30 [0101] method of making coated glass forming equipment 500 [0102] directing 510 [0103] removing 512 [0104] applying 520 [0105] transforming 530 [0106] removing 532 [0107] curing 534

[0108] It will be apparent to those skilled in the art that various modifications and variations may be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.