Apparatus and method for freezing premixed two-component sealant compositions

Abstract

The present invention relates to a method of freezing a premixed processable two-component sealant, the method comprising the steps of: providing a premixed processable two-component sealant (S) in a sealed container (6); subsequently cooling the premixed processable two-component sealant (S) in the container (6) with a coolant; the coolant is not in direct contact with a sealed container (6) containing the premixed processable two-component sealant (S); and the cooling is performed at a cooling rate that allows the premixed processable two-component sealant (S) to cool to a temperature at which the reaction between the components of the premixed processable two-component sealant (S) is suppressed and any premature cure of the sealant has not progressed to form a non-processable two-component sealant. The invention further relates to a device for freezing premixed processable two-component sealants (S), comprising a base plate (2); the device comprises one or more cylindrical tubes (3) having a top end (3.1), a bottom end (3.2), a lateral wall having an inner wall surface (3.3i) and an outer wall surface (3.3 o); one or more cylindrical tubes (3) are arranged with their bottom ends (3.2) vertically on the base plate (2); the one or more cylindrical tubes (3) have one or more spacer elements (4) at an inner wall surface (3.3i) of a lateral wall of the cylindrical tube (3) and / or one or more spacer elements (4.5) attached to the base plate (2). The apparatus may be suitable for use in methods of freezing premixed processable two-component sealants.

Description

[0001] The present invention relates to a method for freezing a two-component composition for premixing and an apparatus for use in this method. The method and the apparatus are particularly useful for freezing two-component sealant compositions, preferably two-component sealant compositions containing hollow spheres. Such sealants are particularly useful when sealing aircraft components. Background Art

[0002] In the sealant industry, so-called two-component compositions are typically used for sealing. As used herein, a "two-component composition" is a composition typically comprising a base component containing a curable resin and another crosslinking component (also referred to as a hardener) containing a curing agent. The two components are stored separately to avoid premature curing during storage, and each of the two components typically does not meet the conditions of a sealant when present alone. After the two components are mixed, the curing reaction begins and the processing time starts. The processing time during which the mixture can be processed is also referred to as the "pot life" of the composition.

[0003] In some cases, it is not suitable or even impossible to mix the components at the application site. In such cases, alternatively, storage-stable one-component compositions can be used, which can contain a curable resin and a curing agent in the same component. This can be achieved by selecting the curable resin and the curing agent in such a way that no significant reaction occurs between the curable resin and the curing agent during storage, and a significant reaction only occurs after the composition is heated to an elevated temperature. However, heating also limits the field of application to those applications where heat can be applied at the use location and the substrate and the composition to be cured and its components are compatible with the heat application. For example, large substrates (such as substrates in the aircraft industry) are typically not suitable for curing by heating in an oven; or, a sealant composition containing hollow filler particles filled with air and / or gas may not be suitable for use at high temperatures due to the expansion of the air or gas in the hollow filler particles.

[0004] Another type of one-component sealant is a moisture-curing one-component composition, which can cure after contacting moisture in the air at ambient temperature.

[0005] Therefore, in cases where it is impossible or not desirable to mix the components or perform heat curing at the application site; or in cases where a moisture-curable composition cannot provide the desired properties, it may be inevitable to use two-component compositions such as two-component sealants to achieve the desired purpose.

[0006] To achieve this, state-of-the-art methods include forming a homogeneous premix of the components of the two-component system and slowing down the curing reaction of the premix by immediately freezing the premix in a container after formation.

[0007] Common regulations (such as those of Bombardier specifically for polysulfide sealants and polysulfide ether sealants (BAERD Gen-015)) require freezing storage containers filled with sealant in a cold bath to ensure a rapid temperature drop. In all cases, direct heat dissipation is required through the contact of a refrigerant with the outer wall of the storage container containing the sealant.

[0008] However, this procedure is still suitable for sealant compounds without hollow fillers. Sealant compositions containing hollow fillers (such as hollow microspheres) are not suitable for freezing by prior art freezing methods because the hollow fillers (hollow fillings) are typically damaged, resulting in the sealant composition no longer meeting the specification requirements.

[0009] In addition, since most sealant compounds containing hollow fillings have a low specific gravity, they are also prone to significant volume changes when the temperature drops. If such a sealant is filled into a cartridge that is closed on one side with a closure (such as a screw cap or a plug cap) and on the other side with a movable piston, in the case of a sharp temperature drop, the sealant will shrink, which means that the piston must also adapt to the shrinking sealant. However, in the case of a sealant that is cryogenically frozen by direct contact with a cold bath, the piston must be pressed against the cartridge wall, which means that the piston cannot adapt to the changing sealant volume. In this case, due to the resulting vacuum, air enters the cartridge and even the cold bath may be sucked in.

[0010] In addition, modern sealant compounds often contain microspheres filled with air and / or gas, which are very sensitive to pressure or pressure changes. Excessive pressure or even very rapid pressure changes usually cause these microspheres to expand or even contract, which may lead to complete failure of this type of filling. In this case, the air and / or gas used in the microspheres is expected to escape. The air and / or gas is then released into the product surrounding the microspheres, resulting in a foamy texture.

[0011] In addition, since sealants in the aerospace industry are increasingly processed using automated application methods and in order to fully utilize the potential of such automated application processes, the sealants used must be applied without defects (such as defects caused by the inclusion of air or gas bubbles).

[0012] Accordingly, there is a need to provide a method for freezing a two-component sealant that is more gentle and allows the problems of the prior art to be overcome, in particular with respect to the following situation: air or coolant enters the cartridge during freezing, resulting in non-uniformity due to the formation of bubbles from the trapped air or coolant. Even more particularly, the problems associated with sealants containing hollow fillers should be solved. The method should be more gentle to ensure that the hollow fillers are not damaged during the process. However, the method should be applicable to any two-component sealant, whether or not filled with hollow fillers. In addition, a device for use in the method of the present invention should be provided. Summary of the Invention

[0013] The above problems are solved by providing a method for freezing a premixed processable two-component sealant, the method comprising the steps of:

[0014] a. providing a premixed processable two-component sealant (S) in a sealed container (6); and

[0015] b. cooling the premixed processable two-component sealant (S) in the container (6) with a coolant;

[0016] i. the coolant does not come into direct contact with the sealed container (6) containing the premixed processable two-component sealant (S),

[0017] ii. the cooling is carried out at a cooling rate that allows the premixed processable two-component sealant (S) to be cooled to a temperature at which the reaction between the components of the premixed processable two-component sealant (S) is inhibited and any premature curing of the sealant has not progressed to form a non-processable two-component sealant.

[0018] This method is also referred to hereinafter as "the method of the present invention", "the method according to the present invention" or "the method of the invention".

[0019] As used herein, the term "sealant" is equivalent to the terms "sealing composition" and "sealant compound" which are also widely used in the art.

[0020] The term "freezing" in the "freezing method" should be understood as cooling a premixed processable two-component sealant from a fluid state, semi-fluid state or paste state to a solid state.

[0021] "Two-component sealant" or "two-component sealant composition" typically refers to a composition that contains a base component containing a curable resin and another crosslinking component (also known as a hardener) containing a curing agent, where these two components are typically stored separately to avoid premature curing during storage, and where each of the two components typically does not meet the conditions of a sealant when present alone. After mixing the two components, the curing reaction begins and the processing time starts. The period during which the sealant can be processed is also referred to as the "pot life" of the composition.

[0022] The term "premixed" with respect to a "two-component sealant" means that the components that are typically stored separately have been mixed, preferably to a homogeneous state.

[0023] The term "processable" with respect to a "premixed two-component sealant" mainly means that the premixed two-component composition has not fully cured. This does not exclude some "premature curing" that may have occurred during the formation of the premix or when cooling the premix. Thus, the term "processable" specifically means that the sealant composition is in a state within its "pot life" under processing conditions (i.e., the conditions under which the sealant is used as a ready-to-use sealant).

[0024] "Inhibiting" the reaction between the components of a premixed processable two-component sealant means slowing down the reaction, typically to an extent where the reaction between the components of the premixed processable two-component sealant is inhibited. This is typically due to the solid state of the premixed two-component sealant after cooling, where the components that react with each other cannot significantly cure.

[0025] The term "coolant" refers to a solid or liquid cooling material whose temperature is lower than the temperature at which the premixed processable two-component sealant reaches a solid state. This term specifically does not cover gaseous cooling media such as cold air.

[0026] Another subject matter claimed in the present invention is a device for freezing a premixed processable two-component sealant, which device can be suitable for use in the method according to the present invention. The freezing device is characterized in that the device comprises

[0027] - a bottom plate (2),

[0028] - one or more cylindrical tubes (3), which one or more cylindrical tubes have

[0029] - a top end (3.1),

[0030] - a bottom end (3.2),

[0031] - a lateral wall having an inner wall surface (3.3i) and an outer wall surface (3.3o),

[0032] One or more cylindrical tubes (3) are vertically arranged on the bottom plate (2) with their bottom ends (3.2).

[0033] - One or more cylindrical tubes (3) have one or more spacer elements (4) at the inner wall surface (3.3i) of the lateral wall of the cylindrical tube (3) and / or one or more spacer elements (4.5) attached to the bottom plate (2).

[0034] The device is also hereinafter referred to as "the device of the present invention", "the device according to the present invention" or "the device of the invention". Detailed description

[0035] Hereinafter, the method and device according to the present invention will be described in more detail.

[0036] Method for freezing a processable two-component sealant (S) in premix

[0037] Step a.

[0038] The method according to the present invention includes a first step a., which is to provide a premixed processable two-component sealant (S) in a sealed container (6).

[0039] In order to provide such a premixed processable two-component sealant (S) in the sealed container (6), the premixed processable two-component sealant (S) will be formed.

[0040] The method of the present invention is not particularly limited to freezing a specific two-component sealant (S), but is suitable for use with any type of two-component sealant (S). Such a sealant (S) preferably but not necessarily contains fillers. However, the present invention is particularly suitable and advantageous if the sealant (S) contains one or more types of hollow fillers (such as hollow microspheres) that can be filled with air and / or gas. Particularly preferred are hollow glass microspheres filled with air and / or gas.

[0041] The most preferred sealant (S) for use in the method of the present invention is a sealant used in the aviation industry, such as airframe and fuel tank sealants. Typical sealants (S) used in the aviation industry, particularly for the above purposes, contain one or more polysulfide polymers and / or one or more polysulfide ether polymers in the base component, and one or more oxidative crosslinking agents (such as manganese-(IV)-oxide) or one or more crosslinking agents that react by an addition reaction (such as polyisocyanate compounds or epoxy compounds) in the crosslinking component; and contain one or more hollow fillers filled with air and / or gas.

[0042] The mixing of the two components can be carried out in a specially designed two-component cartridge equipped with a dedicated mixer, i.e., the container (6) itself containing the finally pre-mixed processable two-component sealant (S) can contain the mixing means; or the mixing can be carried out continuously or sequentially in a two-component unit, which allows the subsequently pre-mixed product to be filled into a commercially available container (6) such as a cartridge, cup or syringe. The present invention is particularly suitable if the mixing is carried out outside the sealed container (6) to be filled and the pre-mixture is immediately filled into the container after the mixing procedure.

[0043] The sealed container (6) is preferably a cartridge (6) which is closed on one side with a closure (C) such as a screw cap or a plug cap, and on the other side of the cartridge (6) a movable piston (P) is inserted, thus sealing the cartridge on both sides. Furthermore, it is highly preferred that the piston (P) which seals the cartridge (6) is located near the top (3.1) of the cylindrical tube (3), at a height above the filling height of the coolant which is in the region (7) around the cylindrical tube (3) and contacts the outer wall surface (3.3o) of the cylindrical tube (3), thus preventing any thermal stress at the level of the piston (P) (see Figure 1I ).

[0044] Step b.

[0045] In step b., the pre-mixed processable two-component sealant (S) in the sealed container (C) is cooled with a coolant.

[0046] The purpose of this step is to gently but still rapidly cool the pre-mixed processable two-component sealant (S) to slow down the reaction between the components of the pre-mixed sealant (S). In practice, this can be achieved when the sealant is in a frozen solid state and the temperature reached by the entire sealed container (6) is in the range of -10 °C to -60 °C. Although the reaction between the components cannot be completely prevented, it will be inhibited to a certain extent such that the pre-mixed two-component sealant (S) can be stored until it is used at the processing site under processing conditions without excessive premature curing. Therefore, after the frozen pre-mixed two-component sealant (S) has reached the processing temperature again, i.e., the temperature at which the sealant is used for its intended purpose, the sealant must still be processable. As already explained above, "processable" means that the sealant is in a state within its typical "pot life" under processing conditions (i.e., under ready-to-use conditions).

[0047] It must be taken into account that the target temperature to which the pre-mixed processable two-component sealant (S) must be cooled depends on the sealant components and their reactivity with each other.

[0048] Typically, the target freezing temperature is the equilibrium temperature reached inside the sealed container (6). For a typical pre - mixed processable two - component sealant, the target temperature to be achieved for the entire sealed container (6) is preferably in the range of - 30°C to - 60°C, more preferably in the range of - 35°C to - 55°C, and even more preferably in the range of - 40°C to - 50°C, such as - 40°C to - 45°C. However, in many cases, it is sufficient to perform the initial freezing process within a time sufficient to cool the pre - mixed processable two - component sealant until the reaction between the components is effectively prevented.

[0049] It has been observed that a substantially pre - mixed two - component sealant (S) as used in the method according to the invention generally follows the temperature dependence of the reaction rate according to the Arrhenius equation. This means that reducing the temperature by approximately 10°C will reduce the reaction rate by approximately 50%. As an example, reducing the temperature from ambient temperature (20°C) to 0°C will reduce the reaction rate by a factor of 50% twice, such that the pot life is extended by approximately four times. In the fully frozen state, the reaction rate between the sealant components is even lower. Typically, it is sufficient to leave the sealed container (6) in the freezing device for a time sufficient to reach approximately - 10°C to - 15°C, after which the sealed container (6), preferably the cartridge (6), can be removed and stored preferably at a lower temperature. As shown in Table 1 in the experimental section of this specification, using a standard cartridge (6), this temperature can be reached in about 10 minutes starting from room temperature (20°C). However, preferably, before storage or transportation, the sealed container (6) is cooled for about 15 to 30 minutes using a freezing device optimized for the standard cartridge.

[0050] The object of the present invention is to rapidly reduce the temperature so as to significantly slow down the reaction rate to prevent excessive premature curing until the frozen state is reached, while maintaining the integrity of the sealant (S), in particular avoiding air entering the sealed container (6) and avoiding damage to the hollow fillers, which are preferably included in the sealant.

[0051] The inventors have also observed that the rapid cooling methods of the prior art are unable to accomplish this task. The rapid cooling methods of the prior art cool such a container by bringing the outer wall of the sealed container (6) containing the pre - mixed processable two - component sealant (S) into direct contact with a coolant (i.e., a cooling medium); for example, as Figure 3B shown by X - ray photographs. The cartridge (6) containing the pre - mixed processable two - component sealant (S) shows a significant amount of trapped air that enters the cartridge (6) during the freezing procedure, and the texture of the contents of the cartridge is non - uniform.

[0052] To accomplish the task of rapid cooling without damaging the sealant and its properties, it is achieved by providing a gentle freezing method according to the present invention.

[0053] In the method of the present invention, the sealant is cooled in a sealed container at a cooling rate preferably of 1.8 °C / min to 3.8 °C / min, more preferably of 2.0 °C / min to 3.6 °C / min, and even more preferably of 2.2 °C / min to 3.5 °C / min. This allows reaching the frozen state within an acceptable time range without causing excessive premature curing of the premixed sealant (S).

[0054] According to the method of the present invention, the premixed processable two-component sealant (S) in the container (6) is cooled by a coolant, however, the coolant does not come into direct contact with the container (6) containing the premixed processable two-component sealant (S). Thus, the coolant of the present invention indirectly cools the premixed processable two-component sealant (S). This can be achieved as follows: there is a coolant-free space (A) between the coolant and the container (6) containing the premixed processable two-component sealant (S).

[0055] Such a coolant-free space (A) between the coolant and the sealed container to be cooled containing the premixed processable two-component sealant can be achieved, for example, by placing the sealed container (6) containing the premixed processable two-component sealant into a cylindrical tube (3) having an inner wall surface (3.3i), which inner wall surface does not come into direct contact with the outer wall of the sealed container (6) to be cooled containing the premixed processable two-component sealant (S). Thus, there is a coolant-free, air-filled space (A) between the inner wall surface (3.3i) of the cylindrical tube (3) and the outer wall of the sealed container (6) to be cooled containing the premixed processable two-component sealant (6). The coolant is placed outside the cylindrical tube (3) and comes into direct contact with the outer wall surface (3.3o) of the cylindrical tube (3), thereby cooling the cylindrical tube (3). In this embodiment, the cold cylindrical tube (3) cools the air in the air-filled space (A) between the inner wall surface (3.3i) of the cylindrical tube (3) and the outer wall surface of the sealed container containing the premixed processable two-component sealant. Thus, heat transfer and cooling occur indirectly through the air-filled space (A). By varying the size of this air-filled space (A) and selecting a specific coolant with a suitable cooling temperature, the cooling rate of the sealant can be adjusted, thereby allowing the object of the present invention to be achieved for different premixed two-component sealants (S) and the geometries of the sealed containers (6) containing these different premixed two-component sealants.

[0056] The coolant suitable for the purposes of the method according to the invention is dry ice, which has a temperature of approximately 78.4 °C (sublimation temperature) and is the most preferred coolant; however, other coolants, in particular mixtures of dry ice with one or more organic solvents such as ketones (e.g., cyclohexanone), hydrocarbons (especially aromatic hydrocarbons such as m-xylene), alcohols (e.g., ethanol) or acetonitrile, can also be used in the method according to the invention. The use of dry ice is particularly preferred because storage in a deep freezer and transport of the frozen sealant after freezing can be easily achieved with dry ice, while the presence of additional organic solvents would require higher precautions.

[0057] In addition to gently freezing the premixed processable two-component sealant and thus avoiding air ingress into the sealed container (6) containing the sealant (S) and maintaining the integrity of the hollow filler, a key objective of the method according to the invention is of course to inhibit the reaction between the components of the sealant and to avoid premature curing of the sealant to the extent of obtaining an unprocessable (i.e., over-crosslinked) two-component sealant. After thawing the frozen sealant and bringing it to the processing temperature, sufficient processability and pot life are to be ensured. Following the above method according to the invention and its preferred embodiments ensures the processability of the thawed sealant, making it ready for use under processing conditions.

[0058] In the following, a device and its preferred embodiments are described, each of which can be suitably used in the method according to the invention.

[0059] Device for freezing a processable two-component sealant in premix

[0060] The freezing device according to the invention is characterized in that the device comprises a bottom plate (2); the device comprises one or more cylindrical tubes (3), the one or more cylindrical tubes having a top end (3.1), a bottom end (3.2), and a lateral wall having an inner wall surface (3.3i) and an outer wall surface (3.3o); the one or more cylindrical tubes (3) are vertically arranged on the bottom plate (2) with their bottom ends (3.2); and the one or more cylindrical tubes (3) have one or more spacer elements (4) at the inner wall surface (3.3i) of the lateral wall of the cylindrical tube (3) and / or one or more spacer elements (4.5) attached to the bottom plate (2). The bottom plate (2) is preferably a perforated bottom plate.

[0061] The following will refer to Figures 1A to 1I and Figures 2A to 2C describe the freezing device in more detail.

[0062] Figure 1A A schematic top view of the freezing device according to the invention is shown, while Figure 1B A schematic side view of the freezing device according to the invention is shown.

[0063] AsFigure 1A and Figure 1B The freezing devices shown each comprise a base plate (2) on which a cylindrical tube (3) with an inner diameter (d) is arranged vertically (i.e. in an upright position). The bottom end (3.2) is mounted on the base plate (2) and the open top end (3.1) is ready to receive a sealed container containing a premixed processable two-component sealant. The cylindrical tubes (3) are spaced apart from each other by a distance (s) which is large enough so that a coolant (such as dry ice) can be easily placed in the area (7) between and around the cylindrical tubes (3). The coolant will come into contact with the outer wall surface (3.3o) of the lateral wall of the cylindrical tube (3). In Figure 1A and Figure 1B In both, the spacer elements (4) are shown attached to the inner wall surface (3.3i) of the lateral wall of the cylindrical tube (2). In order to hold the coolant in place, it is preferred that the base plate (2) with the cylindrical tube (3) attached thereto is placed in an open container (1) such as a tray, the side walls of which hold the coolant in place.

[0064] exist Figure 1C In the Figure 1B An alternative schematic side view of a freezing device is shown. Figure 1C In the embodiment, no open container (1) is required, as the base plate (2) comprises one or more side walls (2.1) which hold the coolant in place.

[0065] Figure 1D A schematic top view of a single cylindrical tube (3) is shown. A spacer element (4) preventing the outer wall surface of the sealed container containing the premixed processable two-component sealant from coming into direct contact with the inner wall surface (3.3i) of the cylindrical tube defines an air-filled space (A) through which heat transfer occurs. Figure 1D In the embodiment, the receiving area (R) defines the area where the sealed container containing the pre-mixed processable two-component sealant (S) is placed.

[0066] Figure 1E A perspective view of the inner wall surface (3.3.i) of a cylindrical tube (3) having an inner circumference (U) and a height (h) is shown. For better presentation, the cylindrical tube is presented in an "unfolded" form, thereby showing the inner wall surface (3.3i) as a rectangular surface. The spacer element (4) attached to the inner wall surface (3.3i) is also exemplarily in the form of a tube or strand, thereby attempting to minimize contact with the outer wall surface of the sealing container (6) containing the pre-mixed processable two-component sealant (S).

[0067] However, the form and size of such a spacing element is not critical, as long as it is suitable for acting as a spacing element (4). Figure 1FIn addition to the spacer element (4.1) as in Figure 1E similar spacer elements in the form of a segmented form (4.2) or even in the form of a simple dot-like elevation (4.3) are also shown. Figure 1G Another arrangement of the spacer element (4) is shown, that is, the spacer element of Figure 1E can be arranged to rotate by 90° to form a ring (4.4) in the cylindrical tube (3).

[0068] In Figure 1H yet another possibility of arranging the spacer element (4) is shown. In addition to the possibility of the dot-like spacer element (4.3), as an alternative or addition to such spacer elements existing on the inner wall surface (3.3i) of the cylindrical tube (3), spacer elements (4.5) can also be attached to the bottom plate (2) of the freezing device, thus preventing the sealed container containing the pre-mixed processable two-component sealant from contacting the inner wall surface (3.3i) of the cylindrical tube (3). Such spacer elements (4.5) can extend from the bottom plate as, for example, a circular ring to receive the sealed container (6) containing the pre-mixed processable two-component sealant (S) in the receiving area (R) and form an air-filled space (A).

[0069] Figure 1I A schematic view of a freezing device is shown. The freezing device is exemplarily equipped with a cylindrical tube (3) attached to the bottom plate (2). The freezing device is placed in an open container (1), and the open container is filled with a coolant (such as dry ice) in the area (7) around the cylindrical tube (3). The cylindrical tube (3) is equipped with spacer elements (4) and contains a sealed container (6), which is typically a cartridge (6) here and contains a pre-mixed processable two-component sealant (S). The part of the cartridge (6) facing the bottom plate (2) is sealed with a closure (C) (such as a screw cap or a plug-in cap), and the opposite part of the cartridge (6) is sealed with a movable piston (P). Preferably, the filling height of the coolant in the area (7) is not higher than the height required to cool the sealed container (6) through the air-filled space (A) until the filling height of the sealant (S) in the sealed container (6), that is, the piston (P) is at a level higher than the filling height of the coolant in the area (7).

[0070] Figure 2A A perspective view of a freezing device according to the present invention as used in the example is shown, while Figure 2B shows a top view of the freezing device.

[0071] Figure 2CA top view photograph of an open container (1) is shown, in which the refrigeration device of the present invention is placed. The area (7) between the cylindrical tubes (3) is filled with dry ice as a coolant. Seven of the twelve cylindrical tubes (3) are empty, so the bottom plate (2), which is a perforated plate (2) in this embodiment, can be seen downwards. Spacer elements (4) in the form of tubes are also shown, which extend from the top end (3.1) to the bottom end (3.2) of the cylindrical tubes (3) along the inner wall surface (3.3i) of the lateral wall of the cylindrical tubes (3). Five cylindrical tubes (3) containing sealed containers (6) are also shown, and the sealed containers contain a premixed processable two-component sealant (S), wherein the wall (5) of the sealed container does not touch the inner wall surface (3.3i) of the cylindrical tube (3).

[0072] It is obvious from the present invention that the arrangement of the components of the refrigeration device can deviate from the specific embodiment shown in the above figure. In particular, the shape of the spacer elements (4) is not critical as long as they are used to create an air-filled space (A), however, this air-filled space should preferably ensure a constant distance between the outer wall surface of the sealed container (6) containing the premixed processable two-component sealant and the inner wall surface (3.3i) of the cylindrical tube (3) to allow uniform cooling of the premixed processable two-component sealant (S). Therefore, it is also preferred that the shape of the sealed container (6) containing the premixed processable two-component sealant (S) is the same as that of the cylindrical tube (3), only with a smaller diameter, so as to fit in the receiving area (R) and allow the existence of the air-filled space (A).

[0073] Although the sizes of the refrigeration device and the sealed container (6) containing the premixed processable two-component sealant can vary, it should be noted that the sealed container (6) does have a suitable diameter to allow the premixed processable two-component sealant contained in the sealed container to be cooled within a sufficiently short time by heat transfer through the air-filled space (A) to prevent premature curing of the sealant resulting in the formation of a non-processable two-component sealant.

[0074] The material forming the device is preferably thermally stable, even during long-term use. In particular, the cylindrical tubes (3) should allow excellent heat transfer. Preferred materials for the bottom plate (2), the cylindrical tubes (3), and the open container (1) are metals or alloys, such as aluminum and stainless steel. In the present invention, the sealed container (6) containing the premixed processable two-component sealant is preferably a cylinder. The sealed container (6) is preferably composed of a plastic material (such as many soft plastic materials known to those skilled in the art, such as low-density polyethylene (LDPE)) having properties that do not interfere with the refrigeration process.

[0075] For standard cartridges with an outer diameter of 40 mm to 55 mm and a height of 70 mm to 250 mm and made of LPDE, it has been found particularly suitable that the cylindrical tube (3) has an inner diameter of approximately 55 mm to 60 mm, and the spacer element (4) creates an air-filled space (A) that spaces the outer surface of the cartridge from the inner wall surface (3.3i) of the lateral wall of the cylindrical tube (3) by the difference between the inner diameter of the cylindrical tube (3) and the outer diameter of the cartridge (6). Thus, the air-filled gap has a width of approximately 5 mm to 10 mm. Further preferably, the distance (s) between adjacent cylindrical tubes is at least 30 mm, preferably at least 35 mm and most preferably in the range of 35 mm to 50 mm or 60 mm, the upper limit being set only for practical reasons to allow the use of multiple cylindrical tubes (3) without wasting too much space on the base plate (2).

[0076] In the following, the invention is further illustrated by working examples and the results are compared with prior art freezing methods.

[0077] Examples

[0078] Inventive Examples I-I to I-III and Comparative Examples C-I to C-VIII

[0079] Eleven standard cartridges were filled with a premixed two-component manganese dioxide-cured polysulfide polymer system with a low density ( type MC-780B, commercially available from Chemetall GmbH, Frankfurt, Germany). The sealant has excellent resistance to aviation gasoline and jet fuel as well as to chemicals and petroleum products used in the aircraft industry and is thus suitable for sealing aircraft components.

[0080] The base component containing the polysulfide polymer and hollow microspheres (plastic microbubbles, "Holospheres", 5 wt.-%) was premixed with the crosslinking component containing manganese oxide as the oxidative crosslinking agent (i.e., the hardener component). The premixing was carried out using a static / dynamic mixing device. The mixing ratio of the base component to the crosslinking component used in the inventive examples was 100 parts by weight of the base component to 10 parts by weight of the crosslinking component, such that the approximate pot life time (application time, processing time) at 23 °C was approximately 2 hours.

[0081] After premixing, the cartridges were immediately filled and sealed with pistons. Three of the thus-prepared cartridges (for Inventive Examples I-I to I-III) were immediately placed into Figure 2A 、 Figure 2B and Figure 2CIn the refrigeration device shown, the distance between the cylindrical tubes is 38 mm, the inner diameter of the cylindrical tubes is 56 mm, and the three spacer elements are in the form of hollow plastic tubes with a diameter of 6 mm and extend from the top end to the bottom end of the cylindrical tubes along the inner wall surface of the lateral wall of the cylindrical tubes. The area between the cylindrical tubes is filled with dry ice, and the level of the piston of the cylinder is slightly higher than the level of the dry ice outside the cylindrical tubes. The cylinder is placed in the refrigeration device for 20 minutes until a temperature equilibrium is reached between the temperature of the sealant and the temperature of the air in the air gap between the inner wall surface of the cylindrical tube and the outer surface of the cylinder.

[0082] In a separate experiment, temperature sensors were used in the air gap and at the center of the cylinder containing the sealant to determine the appropriate minimum refrigeration time. Using the above MC-780B type premix and using dry ice as the coolant, a typical temperature curve of the temperature at the center of the cylinder is shown in Table 1 below:

[0083] Table 1

[0084] Cooling time [minutes] Temperature at the center of the cartridge containing the sealant [°C] 0 21 5 3 10 -15 15 -25 20 -33 25 -38 30 -45

[0085] For the above series, the temperature equilibrium between the air gap and the temperature of the sealant at the center of the cylinder is in the range of -40 °C to -45 °C, which is reached after approximately 25 minutes to 30 minutes.

[0086] The cylinders containing the premixed two-component sealant thus refrigerated were subjected to X-ray examination. Figure 3A (Cylinders of Invention Examples I-I, I-II, and I-III) showed that no air was trapped in the sealant and the cylinder and no foam formation occurred. Instead, the refrigerated sealant was in a completely uniform state.

[0087] After thawing the sealant in the cylinder that has undergone the method of the present invention, the premixed sealant is still completely processable under processing conditions, that is, the sealant is in a state within its typical pot life.

[0088] For comparison, eight cylinders prepared in the same manner as the cylinders prepared according to the method of the present invention were not subjected to the refrigeration method of the present invention, but were subjected to conventional refrigeration in a refrigeration bath containing a mixture of dry ice and ethanol for 20 minutes. In this case, the cylinder was in direct contact with the coolant.

[0089] The cylinders containing the premixed two-component sealant thus conventionally refrigerated were also subjected to X-ray examination. Figure 3B (Cylinders of Comparative Examples C-I to C-VIII) showed that air entrapment was observed near the closure (C) and / or near the movable piston (P), but in some cases, there was also non-uniformity in the entire sealant composition, which was particularly evident in the cylinder of Comparative Example C-IV.

[0090] In particular, for sealants used in the aircraft industry, such as for aircraft fuselage and fuel tank sealants, this non-uniformity and air entrapment are unacceptable.

Claims

1. A method for freezing a premixed processable two-component sealant, the method comprising the following steps: a. Providing a premixed processable two-component sealant (S) in a sealed container (6); and b. Cooling the premixed processable two-component sealant (S) in the container (6) with a coolant; i. The coolant does not come into direct contact with the sealed container (6) containing the premixed processable two-component sealant (S), ii. The cooling is carried out at a cooling rate that allows the premixed processable two-component sealant (S) to be cooled to a temperature at which the reaction between the components of the premixed processable two-component sealant (S) is inhibited and any premature curing of the sealant has not progressed to form an unprocessable two-component sealant.

2. The method according to claim 1, characterized in that The two-component sealant (S) comprises: A base component comprising one or more polysulfide polymers and / or one or more polysulfide ether polymers; and A crosslinking component comprising one or more crosslinking agents selected from the group consisting of oxidation crosslinking agents and crosslinking agents that react by an addition reaction.

3. The method according to any one of claims 1 or 2, characterized in that The oxidation crosslinking agent is manganese-(IV)-oxide, and the crosslinking agents that react by an addition reaction are selected from polyisocyanate compounds and epoxy compounds.

4. The method according to any one of claims 2 or 3, characterized in that The base component comprises a polysulfide polymer, and the crosslinking component comprises manganese-(IV)-oxide.

5. The method according to any one or more of claims 1 to 4, characterized in that The sealed container (6) is a cartridge, cup or syringe filled with the premixed processable two-component sealant (S).

6. The method according to claim 5, characterized in that, The cartridge (6) is closed on one side with a closure (C) such as a screw cap or a plug-in cap and on the other side with a movable piston (P), thus sealing the cartridge (6) from both sides.

7. The method according to any one or more of claims 1 to 6, characterized in that The coolant is dry ice or a mixture of dry ice and one or more organic solvents.

8. The method according to any one or more of claims 1 to 7, characterized in that, The cooling rate at which the premixed processable two-component sealant (S) is cooled in the sealed container (6) is in the range of 1.8 °C / minute to 3.8 °C / minute.

9. The method according to any one or more of claims 1 to 8, characterized in that, Cooling is carried out until the premixed processable two-component sealant (S) is in a solid state and the temperature reached by the entire sealed container (6) is in the range of -10 °C to -60 °C.

10. The method according to any one or more of claims 1 to 9, characterized in that, The method is carried out by using a device for freezing a premixed processable two-component sealant (S) as described in any one or more of claims 11 to 15.

11. A device for freezing a premixed processable two-component sealant (S), the device comprising: - A bottom plate (2), - One or more cylindrical tubes (3) having: - A top end (3.1), - A bottom end (3.2), - A lateral wall having an inner wall surface (3.3i) and an outer wall surface (3.3o), The one or more cylindrical tubes (3) are vertically arranged on the bottom plate (2) with their bottom ends (3.2), - The one or more cylindrical tubes (3) have one or more spacer elements (4) at the inner wall surface (3.3i) of the lateral wall of these cylindrical tubes (3) and / or one or more spacer elements (4.5) attached to the bottom plate (2).

12. The device according to claim 10, characterized in that, The device is placed in an open container (1), or the base plate (2) includes one or more side walls (2.1), and the open container (1) and the base plate (2) including one or more side walls (2.1) hold the coolant in place.

13. The device according to any one of claims 11 or 12, characterized in that, The area (7) around these cylindrical tubes (3) is filled with the coolant, and the filling height of the coolant is lower than the height (h) of these cylindrical tubes (3).

14. The device according to any one or more of claims 11 to 13, characterized in that The base plate (2) is a perforated base plate.

15. The device according to any one or more of claims 11 to 14, characterized in that, The device is used to cool sealant cartridges (6) which have an outer diameter in the range of 45 mm to 55 mm and a height in the range of 70 mm to 250 mm, these cylindrical tubes (3) have an inner diameter in the range of 55 mm to 60 mm, these spacer elements (4) form an air-filled space (A) with a width in the range of 5 mm to 10 mm, and the distance (s) between adjacent cylindrical tubes is at least 30 mm.

Images