EP2118186A2

EP2118186A2 - Aminoplastic-based, liquid-impregnated foamed plastic part and uses thereof

Info

Publication number: EP2118186A2
Application number: EP08708699A
Authority: EP
Inventors: Hans-Jürgen QUADBECK-SEEGER; Armin Alteheld; Klaus Hahn; Dietrich Scherzer; Christof MÖCK; Bernhard Vath; Andreas Bode; Ralf Böhling
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2007-02-08
Filing date: 2008-02-05
Publication date: 2009-11-18
Also published as: US20100089551A1; CN101600759A; WO2008095931A2; WO2008095931A3

Abstract

The invention relates to a liquid-impregnated foamed plastic part consisting of a) between 1 and 10 % by volume of an aminoplastic-based, open-pored foamed plastic and b) between 90 and 99 % by volume of a component that is liquid at 25°C, such as aromatic or aliphatic hydrocarbons, alcohols, ketones, water or aqueous dispersions, and to the uses of said part for transporting or metering liquids, for freeze-explosion purposes, for projectile energy absorption or as a latent heat accumulator.

Description

Liquid-soaked foam molding based on an aminoplast and its uses

description

The invention relates to a liquid-soaked foam molding, consisting of a) 1 to 10 vol .-%. an open-celled foam based on an aminoplast and b) 90 to 99% by volume of a component which is liquid at 25 ° C., and also uses thereof.

Open-cell foams based on a melamine / formaldehyde condensation product are known for various heat and sound insulation applications in buildings and vehicles, as well as insulating and shock-absorbing packaging material.

The open-cell structure permits the absorption and storage of suitable cleaning, grinding and polishing agents when used as a cleaning, grinding and polishing sponge (WO 01/94436).

EP-A 1 498 680 describes a cooling and holding battery of melamine / formaldehyde foam, the cell pores of which are completely or partially filled with a flowable heat transfer medium and a jacket, which can consist for example of a polyolefin film.

The use of liquid reservoirs of open-celled foams based on a melamine / formaldehyde condensation product as a fuel tank and for the storage and transport of liquid hazardous substances is described in WO 2007/003608.

For the transport of liquids usually tubes, hoses or open or closed containers such as buckets, bottles, canisters or containers are used. However, these are often rigid, heavy and expensive to fill and empty.

In thermal management, there are various requirements both on a small scale, eg. B. in electronics, as well as on a larger scale, z. B. to meet in vehicles. These requirements include a good insulation effect, heat dissipation and supply by radiation, conduction or convection, damping of temperature fluctuations, avoidance of material fatigue, stable operation of sensors or the intermediate storage of heat. In addition, the materials used for this purpose must be flexible applicable and stable in their thermal, mechanical and magnetic properties. Thermal radiation requires special absorption and emission properties. The object of the invention was to bring a liquid at room temperature component in a solid, easy to transport form, from which it can be converted back into the liquid form at any time easily and reversibly. Furthermore, new applications for liquid components in solid form should be found.

As open-cell foams are preferably elastic foams based on a melamine / formaldehyde condensation product having a specific gravity of 5 to 100 g / l, in particular from 8 to 20 g / l used.

The cell count is usually in the range of 50 to 300 cells / 25 mm. The average cell diameter is generally in the range of 80 .mu.m to 500 .mu.m, preferably in the range of 100 to 250 .mu.m.

The tensile strength is preferably in the range of 100 to 150 kPa and the elongation at break in the range of 8 to 20%.

For the preparation according to EP-A 071 672 or EP-A 037 470, a highly concentrated propellant-containing solution or dispersion of a melamine-formaldehyde precondensate can be foamed and cured with hot air, water vapor or by microwave irradiation. Such foams are commercially available under the name Basotect® from BASF Aktiengesellschaft.

The molar ratio of melamine / formaldehyde is generally in the range of 1: 1 to 1: 5. For the production of particularly low-formaldehyde foams, the molar ratio in the range of 1: 1, 3 to 1: 1, 8 is selected and a sulfite group-free precondensate used, such as. B described in WO 01/94436.

In order to improve the performance properties, the foam materials can then be tempered and pressed. The foams can be cut to the desired shape and thickness and laminated on one or both sides with cover layers. For example, a polymer or metal foil can be applied as a cover layer.

Due to the extensive chemical resistance of the melamine / formaldehyde condensate, the open-cell foam can also come into direct contact with various, even cryogenic liquids. Even at low temperatures, for example below -80 ⁰ C, the foam remains elastic. Damage caused by embrittlement does not occur. The shape and dimensions of the open-cell foam depend on the intended use. In general, the height of the open-cell foam is 1 to 500 mm, preferably in the range of 10 to 100 mm.

The volume of this foam is 0.5 to 10% by volume of the aminoplast resin and 90 to 99.5% by volume of air. This air can be expelled by immersion in a liquid and gives the inventive, liquid-soaked foam molding. A foam molding impregnated with water or another liquid accordingly consists of a liquid of arbitrary dimension.

The liquid components which can be used at 25 ° C. are flowable or pasty substances which are inert toward the aminoplast, for example aromatic or aliphatic hydrocarbons, such as alkanes, benzene, toluene, xylene, alcohols, such as methanol, ethanol, propanol, butanol, hexanol, Ketones, such as acetone or methylethicone, or water, aqueous solutions or dispersions.

The liquid component usually has a density in the range of 800 to 1200 kg / m ³ . There are a particularly wide range of applications for water as a liquid component.

The thermal properties of a material are determined in particular by the thermal conductivity and the heat capacity. These properties can be influenced by a suitable combination of materials largely independently of each other.

Functional liquids, for example an aqueous dispersion of a microencapsulated paraffin mixture, so-called PCM's (phase changing materials) can also be used as the liquid component. The PCM components generally have a melting point T _m in the range of 20 to 40 ⁰ C and have a high

Enthalpy of fusion. They can be processed into composite materials for heat management with the open-cell foam and optionally heat-conductivity-changing additives, such as metallic powders. In general, the proportion of PCM is 10 to 50 wt .-%, based on the composite after removal of the liquid carrier phase. Due to the capillary forces in the open-cell foam, some PCM waxes can also be used without encapsulation.

The mechanical stability and flexibility is ensured by the open-cell foam. The additives are selected according to the requirements of the electrical and magnetic properties. The surface of the composite can be coated to affect the radiation properties. Such composites can be used, for example, for wrapping dishes, for example drinks. or canning or microwave dishes. When filling the hot beverage, a part of the heat energy is used to melt the PCM's, which deliver the heat back to the drink after falling below the crystallization temperature. If there are areas with foam that is not completely filled or a multi-layered composite, this results in additional heat insulation.

It is also possible to combine the heat-insulating and sound-absorbing properties with those of the unfilled open-cell foam. In the case of partial impregnation or by combination of impregnated and non-impregnated layers of the open-cell foam, thermal insulation is possible with which temperature peaks can also be absorbed. Due to their flexibility, open-cell foams impregnated with PCM can be adapted in three dimensions to any shape and used for effective heat management.

A water-soaked foam cube with a height less than 10 cm does not leak. He behaves like an ice cube that does not melt. Since the liquid-impregnated foam molding according to the invention can be excellently cut with a sharp knife, it can also be referred to as a "cut-resistant liquid". From this perspective, there are surprisingly many possible applications.

One application of the liquid-soaked foam molding is the simple and accurate metering of the liquid component.

The dosage of liquid components plays a role especially in medicine or cosmetics. For example, by means of alcohol-impregnated foam moldings, a thin alcohol film for disinfecting the skin surface can be applied evenly. Other medically effective substances can be applied to diseased skin surfaces in a targeted manner. Due to the slightly abrasive effects of melamine resin / IFormaldehyd foams this can be peeled at the same time cornea or dead skin scales.

The foam moldings are also introduced into a commercially available tube thus allow the dropwise dosing of liquid components on light pressure on the tube.

An exact dosage can also be done via the introduction of correspondingly measured cubes from the open-cell foam. For example, a concentrated drug solution can be aspirated into a cube measuring 1cm x 1cm x 1cm and then placed in another fluid. An open-celled foam impregnated with vegetable oil forms a thin oil film on the surface of the water that kills mosquito larvae.

A further possible application for the liquid-soaked foam molding is the simultaneous transport of one or more liquid components without electrical energy. Between two containers with different water levels, a water-soaked foam strip compensates for the level by utilizing the hydrostatic pressure. A filled vessel empties without the need for a hose or suction. At the same time, a cleaning is carried out by the filtration effects of the open-cell foam.

The open-cell foam can also be moistened after application and liquid transport thereby begun. In contrast, a hose used as a fluid lift must first be filled with the fluid, for example by suction. This liquid may leak. Liquid conductors of the open-cell foam can be combined from individual parts and trimmed or connected in three dimensions. Compared to threads or fabrics as a liquid transport medium, the open-cell foam shows easier handling and can be adapted to a variety of spatial structures.

The liquid-soaked foam molding according to the invention can also be used, for example, in solar collectors. In this case, the liquid in the open-cell foam is heated by solar radiation and then removed. Cold fluid can be tracked on the other side. The use of pipes is not necessary. In this application, the combination with radiation-absorbing materials, such as graphite, makes sense to achieve a faster heating of the water.

The foam molding according to the invention is also suitable, for example, for pumping flammable liquids, for example in accidents involving the transport of hazardous substances. Here, a tubular foam molding is soaked in the hazardous substance and can be achieved without suction and without the use of mechanical pumps to transport the spilled liquid in a collecting container provided by gravity. For this application, an antistatic finish of the foam, for example, by applying electrically conductive layers may be beneficial to reduce the risk of sparking.

The liquid flows in the open-cell foam are generally very laminar. If the flow velocity is very high, the lowest mixing is achieved due to the relatively low diffusion rate. This can for example be exploited to promote two or more liquid streams in parallel through the open-cell foam and at the interface any chemical reactions or physical processes, for example, complexations, dye formations, precipitations or polymerizations.

For example, the liquid streams can be fixed in the boundary layer by means of a solid solution. This channeling can create open three-dimensional microfluidic systems or membranes within the foam. The system is expected to work for many different reactions.

While open-cell foams based on an aminoplast resin are used for heat and sound insulation, the liquid-impregnated foam molding according to the invention is also particularly suitable for energy absorption of projectiles. If the transparency is not critical, the liquid-filled foam molding according to the invention is also suitable for examining weft channels as an alternative to gelatin blocks.

The liquid with which the foam is impregnated can have special rheological properties, such as, for example, thixotropy or dilatancy, in order to change the uptake of the liquid into the foam, the outlet capacity or the energy consumption of the impregnated foam. For example, the foam may be impregnated with a dilatant dispersion. The impregnated foam also has a dilatant effect, but is easier to handle than the dispersion outside the foam.

Another use of the liquid-soaked foam molding according to the invention is freeze-blasting. For this purpose, you can put the open-cell foam in crevices or prepared holes and soak with a liquid, such as water. By freezing or cooling, for example by overflowing with liquid nitrogen, the liquid freezes in the open-cell foam and developed by the associated volume unit of pressure that splits the rock. In addition to rocks, other rocks and materials such as concrete, wood, metal or brittle plastics can be split in this way.

The liquid-soaked foam can be advantageously used to protect against fire or to combat fire. For example, flames can be extinguished with soaked foam samples, the liquid can not escape the source of fire by flowing. It can also be a continuous re-wetting of the foam. For example, the application of foam layers to walls of buildings, e.g. in a double cladding, conceivable. This layer is used in the dry state of thermal insulation. at

Risk of fire, the layer is continuously moistened via a supply system and increases the fire protection of the building. Examples:

For the following examples, an open-celled melamine / formaldehyde foam having a density of about 10 kg / m ³ (Basotect® from BASF Aktiengesellschaft) was used.

Example 1 (rise height):

A dry sample of Basotect® was placed in a beaker filled with water. The liquid increased due to capillary forces inside the specimen to a height of about 1 cm above the liquid level. When a Basotect® sample completely soaked with water was placed in the water, the liquid remained at a height of about 8-12 cm above the water level inside the sample. At a higher water column, the supernatant water was up to this value from the sample up to a water column of about 12 cm height, water was kept inside of Basotect®

Example 2 (lifter):

A beaker was filled with water. A second beaker contained no liquid and was positioned next to the first glass at the same height. A Basotect® nonwoven (thickness about 5 mm, width about 7 cm) was first soaked completely in water and then immersed with one end in the liquid-filled glass, while the other end ended in the empty beaker. The height difference between the highest elevation of the foam and the liquid level was less than 12 cm to prevent leakage of the water while draining the foam. Transport of the liquid from the filled beaker to the empty vessel was observed until the level of the water level in both vessels was equal. When one of the beakers was lifted after equilibrium had been established, the transport of the liquid began again until both liquid levels were at the same level.

The transport of the liquid was also observed when a first dry web was used, that after bridging both vessels with the aid of a squeeze bottle was completely moistened until the liquid exchange began.

Instead of using a foam body, it is also possible to use several individual pieces of Basotect®, which are combined to facilitate liquid transport. In the above example, when the fleece was cut at the highest point with scissors, the liquid transport stopped. Were the cut edges using connected to a paper clip, so the compensation of the liquid level began again.

Example 3:

Three rectangular Basotect® blocks are soaked in water. A block was placed in the empty vessel and a block placed in the vessel with water. The third block was placed across the two upright blocks. Upon contact of all three blocks, liquid transport begins at a comparatively high flow rate.

Example 4 (laminarity):

A beaker was filled with blue stained water. A second beaker was filled with redstained water. Both beakers were placed on an approximately 10 cm high pad. In front of this base, ie at a lower level, a third, empty beaker was placed. A Basotect® nonwoven (thickness about 5 mm, width about 10 cm, length about 40 cm) was cut in the middle to a length of about 20 cm. The fleece obtained divided so halfway into two strands with approximately the same width. The fleece was completely soaked in water. The two narrow ends were then each dipped in the blue or red colored water, while the broad end ended in the lower, empty vessel. It was observed that red and blue stained water flowed through the fleece into the lower vessel. Surprisingly, no mixing of the two dye solutions was observed within the impregnated foam. At a sufficiently high flow rate, a blue and a red liquid flow ran side by side through the foam sample and only mixed on leaving the foam in the collecting vessel. Liquid flows in Basotect® are very laminar. If the flow velocity is very high, the lowest mixing was achieved due to the relatively lower diffusion rate.

Example 5:

A jar of water and an empty jar were connected to a Basotect® water-soaked nonwoven fabric for liquid transport. Three small drops of a highly concentrated aqueous solution of a blue dye were added to the nonwoven at a horizontal distance of about 2 cm at the same height with a fine pipette. It was observed that three stained liquid streams formed side by side, which did not mix within the impregnated foam. At the contact surface of the laminar streams, a chemical reaction or a physical process can occur. Example 6:

Example 5 was repeated, but instead of stained water two liquids were used, which showed chemiluminescence on contact. The system started to glow in the contact area of both currents.

Example 7:

Instead of two liquids provided with different dyes, a 0.1 N aqueous sodium hydroxide solution and a 0.1 N aqueous hydrochloric acid containing approximately 5% phenolphthalein were used and the procedure was as in Example 5. From the area of the web, where the two single strands merged, a violet boundary layer was formed by changing the pH indicator from the initially colorless solutions. The color change took place only in the area of the boundary layer. The width depended on the flow rates.

Example 8:

Instead of two liquids provided with different dyes, a 10% strength aqueous solution of a sodium silicate (water glass) and a 10% strength phosphoric acid solution were used and the procedure was analogous to Example 5. From the area of the web, where the two single strands merged, a solid formed. The solids formation took place only in the area of the boundary layer.

Example 9 (water cube):

A cube of Basotect® (7x7x7cm) was dipped in water. The water remained inside the foam and did not leak out. On a plastic plate (e.g., PE), a razor blade was attached so that the sharp sides of the blade were perpendicular to the surface. The surface of the plate was moistened with a soapy water so that it had a low frictional resistance. The water-soaked Basotect® cube was placed on the plastic plate so finished. Now, if one end of the plate was raised so that the cube slipped on the fixed blade, the moving cube was cut by the blade in two parts. In a comparison experiment with dry Basotect the cube could not be cut in this way. Basotect® is wet better, more precise and dust-free cuttable.

Example 10:

A rectangular test specimen made of Basotect® (7x5x20cm) was soaked in water and placed on the base of 7x20cm. Water did not go out. The test piece was raised on the side with a width of 7 cm, so that the height of the entire vertical water column rose over a value of about 10 cm. Water ran out of the foam until it fell below this value. Water uptake and release can be controlled by aligning the soaked specimen

Example 11:

A soaked water cube (2x2x2cm) was cooled in a freezer compartment below 0 ⁰ C. The water inside the cube froze without destroying it. Prolonged storage in the freezer, a roughening of the surface was done by partially occurring sublimation of the ice. The rough ice cubes were easy to handle as they did not slip out of the hands. When the ice cubes were removed from the freezer compartment, the water thawed, leaving the melt water inside the Basotect® block.

Example 12 (lifter bottle):

The bottom of a standard 1, 5 I PET beverage bottle was cut off so that the bottom part consisted of an open cylinder with a diameter of about 7 cm. The bottle cap was preserved. A Basotect® disc with a customized diameter and a height of approximately 1.5 cm was fitted in the opening. The cap of the bottle was opened and the bottle was immersed with the Basotect sealed bottom about 5 cm in a water-filled container. Water penetrated the inside of the bottle through the Basotect® disk, with a corresponding amount of air escaping through the open shutter. When the bottle was lifted with the cap open, the fluid over the Basotect® disc flowed out of the bottle. If the cap of the bottle was closed after the entry of the water, no liquid leaked when removing the bottle from the water, since no gas exchange can take place. If the closure was then opened, the water could drain from the bottle. The water output is controlled by the gas exchange.

Example 13 (Energy Absorption of an Airgun Missile)

With an air rifle (caliber 4.5 mm diabolo, EO <7.5 J, VO <175m / s) was on a block of polystyrene foam (Styropor®, 5x5x5cm), a block of dry Basotect® (5x5x1 cm) and a corresponding Block shot of water-soaked Basotect®. The Styropor® Block flew from its original location after being hit. The bullet hardly penetrated into the material that absorbs the energy as a whole body. Dry Basotect® stopped at the original site during shelling. The projectile pierced the specimen, forming a chaotic, fringed shot channel and behind the specimen powdered Basotect® was. Upon bombardment of soaked Basotect®, this also remained at its place of origin. The firing channel consisted of a clean punched hollow cylinder. Behind the specimen was a completely preserved Basotect® cylinder from the firing channel.

Example 14 (Latent heat storage):

A sample of Basotect® (100 ^* 80 ^* 3 mm, 0.35 g) was impregnated with an aqueous dispersion of a microencapsulated paraffin mixture, which has a melting temperature of 28 ⁰ C (Micronal, BASF AG). After drying the dispersion, the total mass of the impregnated foam fleece was 8.5 g. The material obtained is mechanically flexible, has a pleasant feel and cools when in contact with the body through the melting enthalpy of the paraffin crystallites consumed enthalpy of fusion.

Claims

claims

1. Liquid-soaked foam molding consisting of a) 0.5 to 10% by volume of an open-celled foam based on an aminoplast and b) 90 to 99.5% by volume of a liquid component at 25 ° C.

2. Liquid-soaked foam molding according to claim 1, characterized in that the liquid component is an aromatic or aliphatic hydrocarbon, alcohol, ketone or water.

3. Liquid-soaked foam molding according to claim 1, characterized in that the liquid component is an aqueous dispersion of a microencapsulated paraffin mixture.

4. Liquid-soaked foam molding according to one of claims 1 to 3, characterized in that the open-cell foam has a specific gravity in the range of 5 to 100 kg / m ³ and the liquid component has a density in the range of 800 to 1200 kg / m ³ .

5. Liquid-soaked foam molding according to one of claims 1 to 4, characterized in that the open-cell foam of a MeI- amine / formaldehyde condensation product having a molar ratio MeI- amine / formadehyde in the range of 1: 1 and 1: 5 was prepared.

6. Use of a liquid-soaked foam molding according to any one of claims 1 to 5 for metering the liquid component.

7. Use of a liquid-soaked foam molding according to one of claims 1 to 5 for the simultaneous transport of one or more liquid components without electrical energy.

8. Use of a liquid-soaked foam molding according to any one of claims 1 to 5 for the energy absorption of projectiles.

9. Use of a liquid-soaked foam molding according to any one of claims 1 to 5 for freezing.

10. Use of the liquid-soaked foam molding according to claim 3 as a latent heat storage.

1. A process for producing a latent heat accumulator, characterized in that drying the liquid-impregnated foam molding according to claim 3.