Method for producing an elastomeric article

Abstract

A method for molding silicone elastomer articles from a room-temperature-curable silicone composition that is not suitable for processing using extrusion techniques. This process allows the room-temperature-curable silicone composition to cure in a predefined shape (6) into which it is introduced to form a molded silicone elastomer article. These articles may be suitable for use, for example, as spacers for insulating glass units (IGUs).

Description

Technical Field

[0001] The present disclosure relates to a method for making elastomeric articles from room-temperature curable silicone compositions, which are not actually suitable for being processed using extrusion techniques. These articles can be suitable, for example, for use as spacers for insulating glass units (IGUs).

[0002] Forming transparent units such as insulating glass units (IGUs) consisting of two, three, or more glass plates has been a standard practice for many years, and a suitable combination of a spacer and a sealant applied by an "edge seal" process is used to separate each adjacent pair of plates. The edge seal process provides a means to separate adjacent plates while providing a seal that extends around the perimeter of the surfaces facing the inside of the glass plates to define a substantially sealed insulating space between the glass plates. In such an edge seal system, for example, a spacer is provided to separate the glass plates. The spacer can adhere to the glass by itself, but in most cases, sufficient adhesion of the spacer to the glass plate has conventionally been provided by a primary sealant. The combination of the spacer and the primary sealant is designed to be moisture, vapor, and / or gas impermeable to prevent moisture or water vapor from entering the internal cavity of the unit and condensing, and in the case of a gas-filled unit, to prevent leakage of gas from the unit. The so-called "primary" sealant can be, for example, a "butyl sealant", for example, a polyisobutylene rubber-based material used to bond a non-self-adhesive spacer, for example, a metal spacer, to the glass plate and to use a secondary sealant bonded to the plate around the spacer.

[0003] The aforementioned secondary sealant, often a silicone sealant, is provided around the perimeter of the insulating glass unit between the edges of the glass panes such that the layer of the secondary sealant contacts the outer surface of the spacer. The secondary sealant serves to promote the integrity of the bond of the self - adhering spacer or the primary sealant by minimizing the stresses imposed by external factors such as variations in ambient temperature, air pressure, or wind pressure.

[0004] A wide variety of spacers have been proposed. Currently, non - adhesive spacers are more commonly utilized. These can include foamed plastic materials such as polyolefin foams like silicone foam or ethylene propylene diene terpolymer foam, mastics containing a reinforcing material that helps keep the glass sheets separated by the necessary distance when assembling the insulating glass unit, such as polyisobutylene mastic. Alternatively, the spacer can be made from a rigid material such as a metal like aluminum or stainless steel, or a rigid plastic material such as polycarbonate or polymethyl methacrylate (PMMA). These rigid spacers can be constructed to be hollow to allow the introduction of a desiccant into their hollow regions.

[0005] For example, in one typical form of the insulating glass unit structure, the edge seal comprises a hollow metal or plastic spacer element adhered to the surface facing the inside of the glass pane by a primary sealant to provide a primary airtight seal. The hollow spacer element is filled with a desiccant material that communicates with and absorbs moisture from the insulating space between the glass panes to improve the performance and durability of the insulating glass unit.

[0006] Alternatively, self - adhesive spacers can be utilized. These can include spacers made of thermoplastic materials and self - adhesive silicone spacers such as those described in WO2018 / 160325. During the assembly of an insulating glass unit having a self - adhesive spacer, the spacer is applied as an elongated elastomeric "strand" that adheres to the substrate on which it is intended to be used.

[0007] When used as a self - adhesive spacer for an IGU, the strand is applied to the first of the two glass plates along its edge. The beginning and end of the strand can be joined. Then, the second glass plate is placed directly above the self - adhesive spacer, and the two plates are pressed together until they are at a predetermined distance equal to the width that the spacer has in the insulating glass unit, with the result that the strand of the self - adhesive spacer is pressed against the glass plates, binding the plates together. Then, if necessary, a secondary sealant or alternatively a protective coating etc. can be applied.

[0008] However, heretofore, elongated strands have generally been prepared using an extrusion methodology, but the compositions described in WO2018 / 160325, which are designed to be transparent, are condensation-curing thermosetting materials that cure slowly and do not reach the gel point for at least several minutes from the start of the curing process and, in fact, may not reach the gel point for several hours in some cases, making them unsuitable for extrusion technology. To avoid confusion regarding the gel point, it means the time when tan delta (G” / G’) is 1, i.e., G” (the storage or elastic modulus in shear) and G’ (the loss or viscous modulus in shear) are equal. This represents the transition from a liquid to a solid material. Around this transition point, the material behaves as a viscoelastic material, which deforms differently depending on the level of stress applied to the material. Before the gel point, the material is very sensitive to any stress applied, which can induce its flow. Beyond the gel point, a low applied stress causes a reversible deformation, i.e., the material returns to its initial position after the stress is removed. The gel point of a material can be determined using several alternative methods, such as by testing according to ASTM D4473-08(2016) as an example.

[0009] Most of the non-adhesive spacers, self-adhesive spacers, primary sealants, and / or secondary sealants used in edge seal systems are black, white, or opaque, or otherwise colored, reducing the area of the insulating glass unit through which light can pass.

[0010] Therefore, there is a desire to produce transparent spacers for IGU, especially when vision through the IGU is important currently, such as in the application of commercial refrigerators. In current solutions, in most cases, clear rigid plastics such as polycarbonate or polymethyl methacrylate (PMMA) spacers fixed on glass through the use of clear double-sided tape are used. However, this has certain drawbacks. The plastic materials used are typically hard, so their mobility is limited, and adhesiveness may be lost due to any movement during transportation or use. As a result, moisture can enter the internal cavity of the IGU, leading to condensation and fogging, so there are drawbacks in adhesive durability.

[0011] The transparent silicone spacers described in WO2018 / 160325 have much better adhesive durability than those of the aforementioned rigid plastic spacers due to the fact that they have good flexibility and the chemical adhesion of silicone to glass is maintained even after long-term aging (e.g., high temperature or hot water immersion).

[0012] Therefore, it is desired to produce elongated silicone molded articles suitable for use as spacers from a room-temperature curable silicone composition by a method without the need for extrusion.

[0013] A method for molding a silicone elastomer article molded from a room-temperature curable silicone composition, (i) placing a film over a mold having two or more predefined shapes to establish an evacuable volume between the film and each predefined shape in the mold, (ii) applying suction to the evacuable volume between the first predefined shape of the mold and the film to establish at least a partial vacuum within the evacuable volume of the first predefined shape, such that the film forms a film-like lining conforming to the first predefined shape of the mold, (iii) Further, apply suction to the evacuable volume between the second predefined shape of the mold and the film where the second predefined shape is adjacent to the first predefined shape to establish at least a partial vacuum within the evacuable volume of the second predefined shape, and as a result, also form a film-like liner that conforms to the second predefined shape of the mold. (iv) Sequentially repeat step (iii) until each predefined shape in the mold has at least a partial vacuum within its evacuable volume and the film forms a film-like liner that conforms to each respective predefined shape of the mold. (v) Introduce a room-temperature curable silicone composition into the film-like liners that conform to one or more predefined shapes of the mold, the composition being designed to be sufficiently fluid to conform to the predefined shape in the mold into which it is introduced. (vi) Enabling the room-temperature curable silicone composition to cure in the predefined shape into which it is introduced to form a molded silicone elastomer article. A method is provided herein that includes these steps.

[0014] The above method has a gel point of from a few minutes to several hours and is thus not practical for use with materials such as the room-temperature curable silicone compositions described in WO2018 / 160325 that do not have sufficient structural elasticity during the initial stages of the curing process used to prepare elongated "strands" by extrusion. This is particularly true when the once-mixed composition has a viscosity low enough to be fluid, and is likely to be the case when there is minimal or no filler present in the composition. Further, these compositions cure over a long period of time, for example, from several hours to several days, for example, more than 7 days, typically by a condensation process, via a condensation process.

[0015] To avoid misunderstanding, the room temperature curable silicone composition has a viscosity that is sufficiently low immediately prior to the start of the curing process, is visibly fluid under the influence of gravity, and / or is even self-leveling. Structural elasticity means, for example, the ability to retain its structural form in the absence of a mold or other form of support.

[0016] The above method provides a suitable route for manufacturing shaped silicone elastomer articles, such as elongate silicone elastomer articles from room temperature curable silicone compositions. It is desirable to produce elongate silicone elastomer articles having parallel sides, for example, for use as spacers in insulating glass units (IGUs) that avoid the need to rely on an extrusion process. Thus, the above method provides a means for producing silicone elastomer articles, particularly elongate silicone elastomer articles, such as spacers, formed from a room temperature curable silicone composition that can be fluid at the start of curing. Articles, such as the pre-cured spacers described in WO2018 / 160325, are both self-adhesive and transparent, and thus, this method provides a means for manufacturing self-adhesive transparent spacers when using the compositions described therein or similar compositions, which, when introduced into an insulated glass unit, provide good viewing ability for the viewer.

[0017] The method of the present disclosure utilizes molds and films, which can potentially have adhesion problems between the elastomer and the mold walls, and as a result, can damage the elongate shape of the cured silicone elastomer article when finally removed from the post-cured mold, so it is not desirable to leave one or more pre-defined shapes in the mold filled with the room temperature curable silicone composition throughout the curing period, except when deemed necessary.

[0018] The molds used in this specification have two or more pre-defined shapes. In one embodiment, the two or more pre-defined shapes are two or more elongated parallel channels, or a series of elongated parallel channels in the mold. In such cases, the pre-defined shape can be any suitable cross-section, but a rectangular or square cross-section is preferred to provide a cured or partially cured elongated silicone elastomer article having at least two parallel sides. For example, in one embodiment, if the intended end use for the resulting cured article is as a spacer for an IGU, the parallel channels are formed by walls that are higher than the desired height of the molded article, for example at least 5 mm higher than the molded article. The walls can be of any suitable structure, for example, they can have rounded or sharp edges.

[0019] The formed silicone elastomer articles can be designed to be of any desired shape and size, i.e., suitable for their end use. In the case of elongated silicone elastomer articles such as spacers for IGUs, they can be, for example, 7.5 - 25 mm wide, or 10 mm - 25 mm wide, and 5 - 25 mm deep, or 10 - 25 mm deep, or 10 - 20 mm deep. The length of the elongated silicone elastomer article can be any up to the full length of the channel in which it is molded. In fact, if necessary, after completion of curing, the length of the article can be cut to a predetermined size or cut into a plurality of different lengths. However, for example, the article can be, for example, 0.5 - 3 m long, or 1 - 2.5 m long.

[0020] When each of the pre-defined shapes in the mold or is an elongated channel, the elongated channel can have a rectangular cross-section, or a square cross-section having a substantially horizontal base, or a horizontal base, a first side wall and a second side wall. The first side wall and the second side wall are substantially vertical or vertical, parallel to each other, and disposed substantially perpendicular or alternatively perpendicular to the base.

[0021] Each of two or more pre - defined shapes in the mold contains a series of openings designed to establish at least a partial vacuum by exhausting air and / or other gases from each of the evacuable volumes created by draping the film over the respective pre - defined shape in the mold. The openings can be of any suitable cross - section, but are typically of circular, square, or rectangular cross - section, or can be of circular cross - section. When the holes have a circular cross - section, they can have a diameter of 0.5 - 3 mm, or 0.5 - 2 mm.

[0022] In one embodiment, where two or more pre - defined shapes are a series of elongated parallel channels in the mold, and each parallel channel has a base and first and second parallel side walls at an angle of about 90° to the base, the openings are arranged along one or both side walls and / or at a set distance from the base of the channel. Alternatively, the openings are arranged at a set distance from the corner between the base and the first side wall and at a set distance from the corner between the base and the second side wall. The arrangement of the openings is important as it ensures that when suction is applied to the evacuable volume, the film conforms to the shape of the mold. Thus, in one alternative, the openings can be distributed equidistantly along the length of each channel of the mold, or distributed equidistantly to draw a consistent vacuum along the entire length of each channel.

[0023] By the applied suction, a vacuum is drawn through the openings, gases are exhausted from the evacuable volume of the pre - defined shape (e.g., channel), and as a result, the film is drawn into the pre - defined shape (e.g., channel). The film used is designed to conform to its shape to create a film - lined interior for each pre - defined shape, e.g., a channel. The vacuum drawn in any one pre - defined shape can be drawn independently of the vacuums in each of the other pre - defined shapes in the mold. This can be achieved by having an on / off switch for the vacuum operated for each individual channel.

[0024] Any suitable type of vacuum generator can be used to apply a vacuum to the vacuumable volume between the pre-defined shape of the mold and the film. For example, a Venturi tube (using compressed air or water flow) or a vacuum pump. If a switching mechanism is available that enables suction to be initiated in the pre-defined shape independently of all other pre-defined shapes in the mold, one suitable vacuum generator from the above list can be used per mold. Alternatively, if desired or deemed necessary, an individual vacuum generator can be used for each pre-defined shape.

[0025] In one embodiment, the mold can comprise a single unit having a mold part and a vacuum part, the vacuum part being connected to a suitable vacuum generator as described above and designed to draw in a vacuum through an opening in each respective pre-defined shape. Alternatively, the mold part and the vacuum part can be two interconnected parts, which, during use, allow a vacuum to be applied to the evacuable volume between the film and the pre-defined shape, but which engage to allow the vacuum part to be disconnected when the vacuum is considered unnecessary. Thus, the vacuum part can be detachable, for example, such that during a long curing period while the mold is being used to mold the final article, the vacuum part can be reused with an additional mold that can be fixedly installed above the vacuum part with openings aligned therewith such that it can draw a vacuum as described elsewhere.

[0026] The film utilized herein to form a film lining in the pre-formed shape of the mold can be any suitable film for such purposes. The film is selected based on three main criteria: (i) The ability to conform to the pre-defined shape in the mold via the methods used herein without being damaged or stretched, (ii) Avoidance of the need to heat the film to properly conform it to the pre-defined shape, (iii) Capable of being released from the self - adhesive silicone elastomer product to cause post - curing.

[0027] In one embodiment, the film material used can be selected with respect to its "wettability" by a room - temperature - curable silicone composition that is introduced into a pre - defined shape in that, when the film functions as the inner layer of the mold, i.e., when the composition flows to a position where the composition / air interface is substantially horizontal under gravity, it is desirable for the composition to have a minimum meniscus. Suitable films of this type include, for example, polyethylene (PE), particularly low - density polyethylene (LDPE), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and fluorinated ethylene - propylene (FEP). If necessary, the film can be modified to incorporate additives such as, for example, slip additives and / or antiblocking agents. Wettability means the ability of a liquid to maintain contact with a solid surface, which results from intermolecular interactions when the two come together. These films have been found to be suitable because they did not adversely affect the adhesion properties of the spacer when applied on glass. (i) Their film - surface functional groups, (ii) Different surface species, or (iii) Different orientations of surface species, some films depending on these have been found to possibly affect how the spacer adheres to the post - cured glass. The film can be a release film.

[0028] The film preferably has high flexibility and a film thickness of 10 - 100 μm, or 20 - 70 μm (thin films tend to wrinkle, while thick films do not conform well to the surface).

[0029] The films used in this specification are treated prior to use to enhance adhesion to the mold surface at room temperature or other properties and to maintain their position even in the absence of a vacuum. This may be by application of an adhesive or surface treatment (e.g., corona or plasma activation) such as the NUCREL™ acid copolymer adhesive product from Dow. In one embodiment, the surface of the film that contacts the mold surface is corona or plasma treated prior to use as a means of enhancing the film's conformity to a pre-defined shape in the mold.

[0030] As described above, when each of the pre-defined shapes in the mold is an elongated channel, each channel in the mold has two ends. The two ends can be fixed at a predetermined position, or can be open ends, or one end is fixed at a predetermined position and the second end is an open end. In any case, a slidable guide can be utilized to vary the length of the elongated pre-defined shape (e.g., channel). Also, by curing a room temperature curable silicone composition in a pre-defined shape (e.g., channel), it has been found that it is an important issue to maintain the position of the film in each of the pre-defined shapes of the mold in order to avoid stretching of the film and / or non-conformity to its pre-defined shape that can adversely affect the shape of the elongated silicone elastomer article, so it can also act as a guide to ensure that the film holds its desired position. The film needs to form a film-like liner that conforms to the shape of each of the pre-defined shapes of the mold. The slidable guide has also been found to be able to draw a vacuum more consistently / effectively within its respective evacuable volume during use. If multiple elongated silicone elastomer articles of the same length are required, the slidable guide can be provided in a comb design that acts as a guide for the channel ends and the film in multiple adjacent channels in a single mold. Preferably, the slidable guide fits snugly into each channel and thus acts as a barrier to prevent leakage or escape of the room temperature curable silicone composition, especially when fluid, from its dimensionally unstable initial form until it has fully cured. If the slidable guide is considered not to be sufficiently liquid-tight, a plug of a suitable material can be inserted between the guides when inserting into the mold, and the room temperature curable silicone composition is added once to the mold of the pre-defined shape to avoid leakage of the room temperature curable silicone composition therefrom when it may be fluid during the initial stages of curing. The plug can be made from, for example, a fast-curing one-part silicone sealant, preferably a foam plug with closed cells, and other suitable materials such as putty. The plug is introduced into the film-like liner before introducing the room temperature curable silicone composition.

[0031] In use, the film is first draped over the mold to establish an evacuable volume between the film and each pre - defined shape, such as channels in the mold. The film is then drawn into each pre - defined shape in the mold and conforms to the mold by suction through openings caused by a vacuum generator. As a result, the film becomes a film - like liner for each pre - defined shape in the mold that conforms to the pre - defined shape. By using the film in this way, it prevents the elastomer from adhering to the walls of the mold during curing, and as a result, prevents damage / mechanical failure of the molded silicone elastomer article when removed from the pre - defined shape. The film can also be utilized to remove the resulting molded silicone elastomer article or partially cured molded article from the pre - defined shape in which it was molded.

[0032] In one embodiment, the film first draped over the mold is fixed in place at a predetermined position at one edge of the mold. When the film is clamped, the first channel to which a vacuum is applied is a channel adjacent to the fixing means such that when suction occurs through the openings in the channels discussed above, the film is drawn into the aforementioned channels and forms a film - like liner conforming to its shape. When this is completed for the first channel, suction is applied to each channel and this method is repeated for adjacent channels until the film acts as a film - like liner conforming to the shape of each channel. When this is completed, the room - temperature curable silicone composition can be introduced into each channel. The film can be fixed by clamping the film: a. at one tip of the mold, or b. along the wall of a channel not located near the tip of the mold.

[0033] Preferably, clamping is effected by use of a single clamping means along the entire length of the mold or, in the case of a series of elongated channels, along the entire length of the first channel. Alternatively, a plurality of clamping means may be used spaced along the length of the first elongated channel, with the former being preferred.

[0034] In one embodiment, the film used to mold the elongated elastomeric article can be used as the packaging of the silicone molding part.

[0035] The room temperature curable silicone composition used herein to form the elastomeric article preferably does not contain any inorganic reinforcing filler and can thus be any suitable room temperature curable silicone composition that can be fluid at the start of the curing process. For example, the composition utilized can be the same as or similar to that used to make spacers in WO / 2018 / 160325, which is incorporated herein by reference. The composition is a two-component room temperature curable silicone composition that produces a suitable elastomeric article. The room temperature curable silicone composition (i) at least one condensation curable silyl-terminated polymer having at least one, typically at least two, hydrolyzable and / or hydroxyl functional groups per molecule, (ii) - a silane having at least two hydrolyzable groups per molecular group or at least three hydrolyzable groups, and / or - a crosslinking agent selected from the group of silyl-functional molecules having at least two silyl groups, each silyl group containing at least one hydrolyzable group, (iii) a condensation catalyst selected from the group of titanates and zirconates, may be included, - the molar ratio of hydroxyl groups to hydrolyzable groups is from 0.1:1 to 4:1, - and the molar ratio of M-OR functional groups to hydroxyl groups is from 0.01:1 to 0.6:1, where M is titanium or zirconium, which is characterized.

[0036] The composition is stored in two components before use to avoid premature curing, and then the two components are mixed at a predefined ratio (e.g., weight ratio) immediately before use. Immediately after mixing, the viscosity of the resulting composition can be low enough for the composition to be fluid. In one example of WO2018 / 160325, part A of the composition is simply a silanol-terminated polydimethylsiloxane with a viscosity of 13,500 mPa·s (25 °C), and part B of the composition or the curing package is 100 parts by weight of a trimethoxysilyl-terminated polydimethylsiloxane with a viscosity of 2,000 mPa·s (25 °C) and 0.3 parts by weight of tetra-n-butyl titanate per 100 parts by weight of the trimethoxysilyl-terminated polydimethylsiloxane.

[0037] The cured material was prepared by mixing the two components of the composition four times with a speed mixer at 2300 rpm for 30 seconds and then mixing them together at a weight ratio of 3:1 base:curing agent. In the present disclosure, such a composition once mixed as described is introduced into a predefined shape in a mold lined with a film.

[0038] Room temperature curable silicone compositions can be sprayable, i.e., they can be introduced into each channel manually or by other means, such as by application with a sealant gun. When the composition is introduced by a robot or other automated system, the operator can set the exact amount of composition introduced into each channel to ensure that each molded article is identical or substantially identical. This is particularly true when the composition is fluid and thus flows / settles into the shape of the mold under gravity. Therefore, in this application, it is very important that the film lining is well placed (with no clearance between the film and the mold) so as not to affect the shape of the final molded article. The clearance between the film and the mold can result in a U-shaped cross-section and, importantly, when used as a spacer in an insulated glass unit, can limit the contact between the spacer and the adjacent glass pane, resulting in mechanical failure of the spacer (adhesion failure vs. cohesion failure). To avoid stretching the film by applying tension, the applied film is sucked into the mold by vacuum and placed for each channel. This allows the film to remain in place even if the vacuum is interrupted, and the molded article can retain the intended shape. When the mold is made in two different parts, the upper part of the mold is placed on the lower part (base) and locked so as not to leak. Some molds (e.g., PVC) can be made in one piece with the upper part fixed to the base. In that case, the two parts are always assembled. Before use, the mold is placed on a horizontal plane to ensure the room temperature silicone composition and, once added, is uniformly dispersed to obtain an elastomeric article of standard thickness along the entire length of the channel.

[0039] According to the present disclosure, provided are an alternative method of extrusion, the lack of initial structural elasticity of a room-temperature curable silicone composition used to prepare a formed silicone elastomer article, and the current standard method for preparing an elongated spacer material required for an extended curing process that takes several hours to several days, such as more than 7 days. The methods herein utilize a mold and a film to overcome the problem of preparing an elongated silicone elastomer article from a formed silicone elastomer article, such as a room-temperature curable silicone composition that may be fluid, to form an elastomer having soft mechanical properties. When these are elongated spacers for an insulated glazing unit, they preferably have two substantially parallel or parallel sides of a defined length, width, and depth to match the dimensions and / or combinations thereof required for the spacers in the insulated glazing unit.

[0040] To achieve this, the two or more predefined shapes in the mold are typically in the form of a series of elongated parallel channels. The film initially draped over the series of elongated parallel channels needs to be drawn into each predefined shape to form a film-like lining that conforms to the shape of the channels. The mold is designed such that a vacuum is applied in a manner that avoids damage or stretching of the film that could cause deformation of the elastomer article molded therein. Deformation can occur, for example, if the film does not exactly conform to the predefined shape in the mold before introducing the room-temperature curable silicone composition therein.

[0041] This has been determined to be most preferably achieved by applying the vacuum sequentially as described above, i.e., in the case of a mold having two predefined shapes in the initially predefined shape, then maintaining the vacuum in the first shape and starting the vacuum at the wall of the second defined shape in the mold when the film first conforms to the shape of the first defined shape. This means that the film can be slid / slided to the position of the second defined shape to form a film-like liner conforming to the shape of the second defined shape without damage / stretching of the film conforming to either or both of the defined shapes.

[0042] Thus, if two or more predefined shapes in the mold are a series of elongated parallel channels, for example, in the case of a series of seven channels numbered 1 to 7 sequentially from right to left in the mold, then the vacuum is first drawn to channel 1 or channel 7. For simplicity, assume that the vacuum is first drawn to channel 1. When the vacuum is drawn, the film placed on the mold is drawn into channel 1 to form a film-like liner conforming to the shape of channel 1. When this is satisfactorily completed, the vacuum in channel 1 is maintained and the vacuum in channel 2 adjacent to channel 1 is started, and this method is repeated until the film is satisfactorily placed in channels 1 and 2, then when the vacuum is drawn to channel 7, the vacuum is maintained in the previous six channels, and this method is sequentially repeated for channels 3 to 7 so that the film conforms to the shape of each of the respective channels. When the film conforms to each channel, the selected room temperature curable silicone composition is introduced into each channel in any order in the mold.

[0043] By using this sequential application of vacuum channels by the channel approach, even if the vacuum is cut off after the film has been placed as a film-like liner of each desired shape in the mold, the film is guaranteed to remain in a predetermined position conforming to the predefined shape in the mold.

[0044] In the method described herein, the following steps may be performed: (i) Provide a film of suitable dimensions. It must be of a suitable ratio to easily form a film lining in all predefined shapes in the mold without the need to stretch or damage it so that it can easily conform to all predefined shapes. For example, clamp the film on the side of the first predefined shape to which a vacuum is applied. (ii) A comb-like tool may be utilized to avoid air leakage through the two open ends of the channel when a vacuum is drawn in. If so, it may be installed in close contact with the film at each end of the channel, thereby not only having a dual role as a film guide but also closing any air gaps that may adversely affect the placement of the film and the drawing of the vacuum. (iii) Turn on a vacuum generator, such as a pump or a venturi, and open the valve of the vacuum system so that suction is applied only to the first predefined shape (i.e., the first channel) in the mold. When suction is initiated, the film is drawn into the predefined shape to form a film lining, and then it can be checked for any wrinkles or other defects for the purpose of ensuring that the first predefined shape is ready for the introduction of the room-temperature curable silicone composition. (iv) If satisfied, also open the valve in the vacuum line that opens to the adjacent second predefined shape (e.g., a channel) in the mold, and repeat the above steps. Then, the same is sequentially completed until all predefined shapes (e.g., channels) are evacuated and their respective film linings conform to their shapes. (v) If the aforementioned comb-like tool is considered not to fit well enough in the channel to prevent leakage of the room-temperature curable silicone composition from the channel, plugs of suitable materials, such as fast-curing one-part silicone sealants, foam plugs with closed cells, and other suitable materials such as putties. (vi) Subsequently, the room temperature curable silicone composition can be introduced into a pre-defined shape having a film-like lining in a mold. The room temperature curable silicone composition is usually stored in two components before use to avoid an overly early start of the curing process. Typically, the two components, called Part A and Part B, are mixed in the required weight ratio using a suitable mixer. (vii) When the room temperature curable silicone composition is mixed, it is dispensed into the pre-defined shape in the mold and then the room temperature curable silicone composition is cured.

[0045] The composition is left in the mold to cure until it is considered to have sufficient mechanical strength to maintain its shape without the need for the mold any longer. This period depends on the content of the composition used to produce the elastomeric article. For example, in the case of a composition that cures over about one week, the cured composition is typically left in the mold at room temperature for 1 to 4 days, or 1.5 to 3 days.

[0046] After this period, the partially cured material can be removed from the mold while holding it in the film, and the curing process is continued at room temperature for as long as necessary and / or as long as it is deemed necessary.

[0047] Following the completion of the curing process, the resulting elongated elastomeric article can be packaged and shipped for its end use.

[0048] As previously discussed, the elastomeric articles prepared by the above process are suitable as spacers for insulated glass units. For suitability as a spacer for an insulated glass unit, the elongate article needs to have at least two substantially parallel sides, and thus alternative processes have been developed that are suitable for low viscosity compositions that require long curing times. By providing such clear spacers, a person's visibility can be significantly improved, such as when peering into a display unit such as a refrigerator. Since a misshapen rounded shape does not adhere properly to the glass, it is important that the spacer makes good contact with the glass window.

[0049] Typical spacers are designed to keep two glass plates apart, and in the present disclosure, there is a strong adhesive bond between each glass plate and the spacer. In many warm edge type sealing solutions, a primary sealant is required to adhere the spacer to the glass substrate. In this case, such a sealant may not be necessary.

[0050] If the formed silicone elastomeric article obtained from the method described herein can be sufficiently tacky to the touch, taking into account the presence of excessive hydrolyzable groups, physical adhesion occurs when the substantially cured or fully cured silicone-based material contacts the substrate surface. However, if the level of adhesion is not considered to be sufficiently strong, the substrate can be pretreated to enhance the adhesion between the formed silicone elastomeric articles produced from the process herein.

[0051] Here, the methods described in this specification are described in connection with one or more embodiments, along with the figures attached hereto. To avoid misunderstanding, any consideration of any particular embodiment or related feature is not intended to be limiting. The reader will understand that there are many variations and equivalents that will become apparent from the following considerations. These variations and equivalents are intended to be included within the scope of the invention as if they were described herein.

Brief Description of the Drawings

[0052]

Figure 1A

Figure 1B

Figure 1C

Figure 1D

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0053] For the following description of the figures, each pre-defined shape may be the same or different, but each pre-defined shape is an elongated channel in a mold having a rectangular cross-section. The mold contains a plurality of these channels that are parallel to each other and are designed to produce, for example, an elongated spacer material for use in insulating glazing. It will be understood that such a system is merely an example.

[0054] The figures in this specification relate to the steps and apparatus involved in conforming a film (2) to form a film lining in a series of channels (6) in a mold (4) and then molding a room-temperature curable silicone composition that can be fluid at the start of curing, which has an extended curing time of at least several hours, but typically several days, in the channels (6) previously lined with the film (2).

[0055] First, as seen in Figure 1a, the film (2) is, in this example, draped over a mold (4) having seven channels (6) to establish an evacuable volume (8) between the film and each channel (6) in the mold. The channels can be, for example, 2 m in length, 12.5 mm in width, and 18 mm in depth. A series of holes (not shown) are provided in the sidewalls, corners, and / or base of each channel (6). Each hole is connected to a vacuum system (10) for drawing a vacuum into the respective channel (6), which is intended to draw the film (2) into the channel and form a film lining in the channel (6). The vacuum system (10) is designed such that a vacuum can be drawn into each channel regardless of whether a vacuum is being drawn into one or more other channels. This can be achieved by each channel having an individual vacuum system, but preferably is operated by having a single vacuum system and a switchable valve designed to control the vacuum drawn into each channel independently of the other channels.

[0056] The holes are distributed across each channel in a pattern designed to ensure that the film (2) is made to conform to the walls of a pre-defined shape without damaging the film (2) which, as previously discussed, can lead to hardening of damaged or incorrectly sized spacer units.

[0057] As can be seen in Figures 1b, 1c, and 2, the film (2) is clamped to one edge of the mold (4). Preferably, the bar (13) is fixed along the entire length of the first channel, as shown by the bar (13) which is fixed in place by clamps (12) which are approximately equidistant in Figure 2.

[0058] In use, after the film (2) is placed over the mold (4) and clamped at one edge, suction is initiated in the channel (6a) adjacent to the clamped edge, evacuating the evacuable volume (8) in that channel (6a) and drawing the film into the channel (6a). When the operator is satisfied that the film lines the channel (6a), suction is initiated in the next adjacent channel (6b), i.e., the second channel closest to the clamping means (12, 13) and adjacent to the channel (6a), while maintaining the vacuum in the channel 6a. This process is repeated until the operator is satisfied that the film lines both channels 6a and 6b, after which the vacuum in the next channel is initiated and the process is repeated. This occurs sequentially, for example, in Figures 1b and 2, from right to left in the image for each channel (6), until a vacuum is applied to all channels (6), and the film (2) forms a film-like liner conforming to the shape of its respective channel (6) in each channel (6) until the operator is satisfied (Figure 1c), at which point a room temperature curable silicone composition can be introduced into the mold (4) and cured.

[0059] In one embodiment shown in FIG. 1d, the mold (4) can be in two separable parts, a mold part (4a) and a vacuum part or unit (10), such that one mold (4a) can be detached from the vacuum unit (10) when the application of suction is no longer required while it is being used to mold a room temperature curable silicone composition during a curing process of several hours to several days. Thus, this enables the reuse of the vacuum unit (10) to line a further mold (4a) in the above manner. It has been found that this embodiment is particularly suitable for use when the mold / vacuum unit is made from metal, although when substantially made of plastic, the mold unit was preferably a single unit.

[0060] In one embodiment, as shown herein, it is specific to the method when the mold (4) comprises a series of adjacent parallel channels (6), and as shown in FIG. 3, it has been found that the introduction of the "teeth" (18) from the comb-like tool (16) at both ends of each channel (6) is advantageous. This tool (16) also functioned as a guide for the film (2) to prevent damage to the film (2) during the lining stage, although its teeth (18) also acted as a last resort to ensure that an improved / consistent vacuum was drawn into each channel (6) as required. The comb-like tool (16) can be made from any suitable material, although preferably it is non-stick to the cured silicone elastomer end product and can thus also be made from, for example, polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), low density polyethylene (LDPE), or a metal such as steel or aluminum.

[0061] In use, one tooth (18) from the tool (16) is inserted into the mold (4) at the end of each channel (6) as shown in FIG. 4 before introducing a vacuum into any of the channels (6). For the benefit of the reader, FIG. 4 also shows the vacuum line (20) and depicts one potential vacuum arrangement attached to each channel (6). Such a vacuum line (20) to each channel (6) is operable by turning a switch to apply a vacuum to each respective channel (6). This may be automated or, if desired, manually operated by an operator.

[0062] FIG. 5 shows a partially evacuated mold (4) in which four of the seven channels (6) are lined with film (2), three channels (6) have no vacuum applied yet, and the film remains draped over the top.

[0063] While the comb-shaped tool (16) is beneficial as a guide and / or as the effective end of each end of the channel (6), whereby it has been found that the length of the elongated elastomer is defined as the composition cures, the teeth (18), when removed therefrom, do not fit well enough to prevent leakage of the room temperature curable silicone composition from the mold (4) during the initial stages of the curing process where there is not enough structural elasticity to maintain the shape of the channel. Any suitable means may be utilized to prevent such leakage, but one simple methodology has been found to be to introduce a disposable fast-curing one-part sealant plug (24) between the teeth (18) of the tool (16) and then introduce the room temperature silicone curable composition. A plug (24) of this type is shown in FIG. 6, which shows one end of the mold during the curing process of the room temperature curable silicone composition.

[0064] Subsequently, the room temperature curable silicone composition can be introduced into a pre-defined shape, i.e., the channels (6) in the mold (4). The room temperature curable silicone composition is usually stored in two components before use to avoid an overly early start of the curing process. Typically, the two components, called part A and part B, are usually mixed in the required ratio in a suitable two-part mixer, such as the Conti Flow Vario two-component mixing and dispensing system from Reinhardt-Technik GmbH of Kirchseeon, Germany, or the Graco EFR two-part dispensing pump from Graco Inc. of Minneapolis, Minnesota, which is suitable for mixing low-viscosity liquids (not shown). The selected two-part mixer is suitable for mixing part A and part B in a pre-defined weight ratio through a disposable static or dynamic mixer.

[0065] Once the room temperature curable silicone composition has been added to each channel (6), the vacuum can be stopped and the room temperature curable silicone composition is left in the mold for 1 to 3 days to cure until it has sufficient structural elasticity to maintain its shape without the need for the mold (4). This period depends on the content of the room temperature curable silicone composition used to produce the elastomeric article. For example, in the case of a composition that cures over about one week, the cured composition is typically left in the mold at room temperature for 1 to 4 days, or 1.5 to 3 days. Optionally, the room temperature curable silicone composition can be heated to a temperature of about 80 °C to accelerate the curing process. After this period, the partially cured material can be demolded from the mold (4) while maintaining it on the film (2), and the curing process can continue as long as it is necessary and / or considered necessary to complete the curing process, which is also typically at room temperature, but curing can be accelerated by further heating up to a maximum of about 80 °C.

[0066] Alternatively, a vacuum may be continuously maintained in the mold (4) for 1 to 3 days until the room temperature curable silicone composition cures to an extent that it has sufficient structural elasticity. In a further embodiment, it is also possible to temporarily stop the vacuum (e.g., move the mold to a storage location) and restart the vacuum again during a portion of the curing time. Following completion of the curing process, the resulting elongated silicone elastomer article may be packaged and shipped for end use.

[0067] When the elongated silicone elastomer article is used as a spacer for an IGU, if necessary, in order to obtain a cross-section of the elongated silicone elastomer article, e.g., the spacer, the spacer can be removed from the film and sliced with a blade into + / - 1 mm sections, and the quality of the spacer can be analyzed. The analysis can be performed using an optical microscope. If necessary, clearances in the vertical and horizontal directions can be measured. To avoid misunderstanding, "clearance" is defined as the length of the spacer that does not conform to the shape of the cured channel due to the constraints created by non-conforming film conformations on the surface of each pre-defined shape in the mold. Surface areas that do not conform due to clearance issues may not adhere well to glass, and thus adhesion defects may occur, and the cohesive strength of the spacer on the glass substrate may be further reduced.

[0068] Once the elongated silicone elastomer articles are fully cured, they can be used not only as self-adhesive pre-cured silicone spacers for assembling devices such as transparent units or insulating glass units, but also in electronic displays, weather-resistant seals, optical devices, light-emitting diodes, lenses, and the like.

[0069] Elongated silicone elastomer articles prepared by an encapsulation method using the compositions described in WO2018 / 160325 will provide self - adhesive transparent spacers. In some cases, the final strength of the transparent spacer is sufficient for the application, while in other cases, the use of additional structural adhesives is required at the top and / or bottom to ensure sufficient strength of the IGU. The high transparency of the pre - cured spacers applied using this method will contribute to aesthetically pleasing spacers that are visually clear.

[0070] It should be understood that such transparent spacers can be used to construct transparent internal partitions, transparent windows, and doors, especially for refrigerators where insulation is desired. The resulting pre - cured spacers produced using the aforementioned method can also be useful for assembling cold or hot bent glass units, where the use of a structural spacer is an explicit attribute. If transparent articles can be assembled, opaque articles can also be considered, either in combination with or without the transparent articles. The transparent spacers can have decorative, optical, and / or electronic devices that are fully or partially incorporated into the body of the spacer before curing. The device is then cured in the normal manner as previously discussed. The resulting cured transparent spacers produced using the aforementioned method will have the device visible within or on them, unless hidden from view behind the frame for security reasons, for example.

[0071] The transparent structural spacers produced using the aforementioned method can also be useful for assembling articles sensitive to temperature, ultraviolet light, or liquids. It can be useful for assembling displays made of electronic articles, optical devices, glass, metal, or plastic. It is useful for assembling panels not only for internal partitions in buildings but also for facades and roofs. They can also be useful for assembling appliances, automobiles, or aerospace articles, especially those where transparency is desired.

[0072] Thus, substrates that can be spaced apart by the spacers produced using the foregoing method include glass sheets for flat panel displays (LED, LCD screens), glass panels for facades or automobiles, metals, plastics, woods, construction concrete or slate, automobiles, electronic devices, etc., and concrete fixtures such as metals, plastics, woods, hooks, screws, nuts. If it is necessary to physically strengthen the adhesion level between the spacer and the substrate as required, the substrate can be further primed.

[0073] Insulated glass units can comprise one or more spacers. For example, spacers produced using the foregoing method can be used in articles of the unit where opaque or colored spacers would normally obscure, while other standard spacers can be used in areas where the spacer material does not obscure the user's view through the unit.

[0074] It should be noted that generally the units described are referred to as glass units, but while glass is used as an example, it should be understood that any alternative transparent material can be used depending on the situation. Further, in some cases, insulated glazing units can comprise one or more transparent glass plates, etc. and one plate that is made opaque for patterning, etc.

[0075] The present disclosure also extends to a method of making an insulated glazing unit using an elongated elastomeric article made as described above as a spacer by providing a first glass plate having a first major surface and a second glass plate having a first major surface.

[0076] Apply the elongated elastomeric article prepared using the method described herein as a spacer (optionally transparent), for example, to the first major surface of a first glass panel.

[0077] Place the area of the first major surface of the second glass panel on the spacer and leave the spacer adhered to the glass surface. Then, if necessary, fill the cavity surrounding the perimeter of the glass panel, preferably with a transparent secondary sealant, which can be a moisture-curing hot melt silicone adhesive composition, the cavity being defined by the first major surface of the first glass panel, the outer surface of the transparent spacer, and the first major surface of the second glass panel. Alternatively, instead of a secondary sealant, a protective coating can be applied to the outer surface of the elastomeric article / spacer to form a protective non-stick layer for the purpose of preventing damage to the article / spacer during use.

[0078] In one embodiment, an insert made of plastic, metal, glass, etc. can be added to one or more channels before introducing the room temperature curable silicone composition to provide a transparent spacer with physical support that can protect the resulting elongated silicone elastomeric article, e.g., the spacer in use, from any mechanical damage. Alternatively, such an insert can be introduced into the channel either before or during the curing of the room temperature curable silicone composition. Alternatively, this support can be provided after curing, in which case a primer, etc. may be required to obtain good adhesion between the pre-cured spacer and the insert.

[0079] In one embodiment as described above, a method of making an insulating glass unit is provided that includes the following steps performed in any desired order, i.e., procure two glass plates, provide an endless strip of the spacer prepared in the manner of the method described above between the two glass plates, and press the two glass plates against each other against the spacer to form a spacer adhered to the plates.

Examples

[0080] The cured material was prepared by mixing the two components of the composition together at a weight ratio of base:hardener of 3:1. The base component is · It was a silanol-terminated polydimethylsiloxane with a viscosity of 2,000 mPa·s (at 25 °C). The curing agent component was o 100 parts by weight of a trimethoxysilyl-terminated polydimethylsiloxane with a viscosity of 2,000 mPa·s (at 25 °C) and o 0.2 parts by weight of tetra-n-butyl titanate.

[0081] The materials were mixed 4 times for 30 seconds at a speed of 2300 rpm in a speed mixer, and the resulting mixture was applied to a mold as described above and then cured for 7 days for use. An example of the type of spacer that may be produced using the above method is provided in Figure 7, which shows two glass plates separated by a continuous ribbon of cured material adhered around each glass plate that effectively functions as a spacer between the two glass plates.

[0082] The upper surface of the lower glass plate and the lower surface of the upper glass plate as depicted may be coated with a primer-type material such as DOWSIL (trademark) 1200 OS primer dried for about 30 minutes.

[0083] The pre-measured ribbon of the cured self-adhesive elastomeric article prepared by the aforementioned method was applied to the periphery of the upper surface of the lower glass plate, and subsequently, the lower surface of the upper glass plate was adhered to the cured material in the previously primed area. Almost immediately after construction, the glass unit shown in Figure 7 could be moved and handled without damaging the structure of the construction due to the strength of the bond formed as described herein.

Claims

Claim 1 A method for molding a silicone elastomer article molded from a room temperature curable silicone composition, comprising: (i) applying a film (2) over a mold (4) having two or more predefined shapes (6), establishing an evacuable volume (8) between the film (2) and each predefined shape (6) in the mold (4); (ii) applying suction to the evacuable volume (8) between the first predefined shape (6a) of the mold (4) and the film (2) to establish at least a partial vacuum within the evacuable volume (8) of the first predefined shape (6a), such that the film (2) forms a film-like lining conforming to the first predefined shape (6a) of the mold (4); (iii) further applying suction to the evacuable volume (8) between the second predefined shape (6b) of the mold (4) and the film (2) adjacent to the first predefined shape (6a) by the second predefined shape (6b) to establish at least a partial vacuum also within the evacuable volume of the second predefined shape (6b), such that a film-like lining conforming to the second predefined shape (6b) of the mold (4) is also formed; (iv) sequentially repeating step (iii) until each predefined shape in the mold has at least a partial vacuum within the evacuable volume (8) and the film (2) forms a film-like lining conforming to each respective predefined shape (6) of the mold (4); (v) introducing a room temperature curable silicone composition into the film-like lining conforming to one or more predefined shapes (6) of the mold (4), wherein the composition is designed to conform to the predefined shape (6) in the mold (4) into which it is introduced; (vi) allowing the room temperature curable silicone composition to cure in the predefined shape (6) into which it is introduced, enabling the formation of a molded silicone elastomer article. A method comprising: Claim 2 The method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to claim 1, wherein the pre-defined shape (6) is an elongated channel having a base and first and second walls, and the first and second walls are parallel to each other and perpendicular to the base.

3. The method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to claim 1 or 2, wherein the film (2) is fixed to one edge of the mold (4).

4. The method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to claim 3, wherein the film is clamped along a wall of a channel that is not located at the tip of either one of the molds (12, 13) or near the tip of the mold.

5. The method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to claim 3 or 4, wherein the fixing is achieved by clamping the film using a single clamp along the length of the mold (13) or by using a bar (13) fixed in place by a series of clamps (12) arranged equidistantly from each other along the length of the mold (4).

6. The method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to claim 3, wherein the parallel walls have rounded edges and are designed to be deeper than the depth of the elastomer article cured in the mold (4).

7. The method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to any one of claims 1 to 6, wherein the mold is a one-piece unit (4) or two detachable parts, an upper or mold part (4a) and a lower or vacuum part (10), and in either case is adapted to draw a vacuum through holes in the base and / or the walls of the pre-defined shape (6).

8. A guide (16) is inserted into each tip of the channel to guide the film (2) into its respective channel (6) and / or adjust the length of one or more channels (6) in the mold (4), and / or a plug (24) is inserted into the channel (6) to prevent the room temperature curable silicone composition from leaking out of the channel (6) into which it is introduced. A method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to claim 2 or 4.

9. The insert is (i) before introducing the room temperature curable silicone composition, (ii) after the room temperature curable silicone composition has been introduced either before or during curing, or (iii) after curing, and can be added to one or more channels (6). A method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to any one of claims 1 to 8.

10. The film (2) has a thickness of 20 to 70 μm and / or is selected from polyethylene (PE), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and fluorinated ethylene-propylene (FEP). A method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to any one of claims 1 to 9.

11. The film (2) used for molding the room temperature curable silicone composition can be used as the packaging of the silicone elastomer article and / or is treated by applying a coating surface treatment. A method for molding a silicone elastomer article molded from the room temperature curable silicone composition according to any one of claims 1 to 10.

12. The room temperature curable silicone composition (i) at least one condensation curable silyl-terminated polymer having at least one hydrolyzable and / or hydroxyl functional group per molecule, (ii) - a silane having at least two hydrolyzable groups per molecular group or at least three hydrolyzable groups, and / or - a silyl-functional molecule having at least two silyl groups each containing at least one hydrolyzable group, a crosslinking agent selected from the group of (iii) a condensation catalyst selected from the group of titanates and zirconates, and - The molar ratio of the hydroxyl group to the hydrolyzable group is from 0.1:1 to 4:1, - and the molar ratio of the M-OR functional group to the hydroxyl group is from 0.01:1 to 0.6:1, where M is titanium or zirconium, A method for molding a silicone elastomer article formed from the room-temperature curable silicone composition according to any one of claims 1 to 11.

13. A method for molding a silicone elastomer article formed from the room-temperature curable silicone composition according to any one of claims 1 to 12, wherein the elongated silicone elastomer article is used as a spacer in the manufacture of an insulated glazing unit.

14. A method for manufacturing a spacer in an insulated glass unit, comprising the method according to any one of claims 1 to 12.

Images