A PROCESS FOR OBTAINING COMPOSITE MATERIALS FOR USE IN ETHYLENE ADSORPTION

Technical Field of the Invention

The present invention relates to a process for obtaining composite materials according to the preamble of the claim 1.

Background of the Invention

Most fruits and vegetables ripen after they are removed from their associated plants and stalks. Such ripening often changes the characteristics of the produce, including altering sweetness levels, texture, and firmness. Consumption of fruits and vegetables at the optimal point in the ripening process helps maximize not only taste, but also their health benefits.

Ripening is a natural process which is primarily a result of the production of ripening enzymes, many of which are triggered by the release of ethylene by the produce. Ethylene is a simple hydrocarbon gas produced when a fruit ripens, and is known to promote the upregulation of genes that cause the expression of enzymes that foster ripening. These enzymes may change the color of the skin as chlorophyll is degraded, foster the breakdown of acids that make fruit taste sour, convert starches into sweet sugars, and soften pectin.

Maintaining fruits and vegetables in a sufficiently cold state after harvest helps extend shelf life, however it is not enough to eliminate negative effects of the ethylene release. Besides, it is a well-known problem that ethylene release also causes malodors which are captured in the limited air space in a refrigerator. Not only are these malodors unpleasant and offensive to the user of the refrigerator, they can also have a negative impact on the quality of other foods in the refrigerator. For example, it is known that some foods such as fish or onion emit strong odors, and that these odors can transfer to other nearby foods and affect the taste and freshness of those foods. Therefore, the lowest possible content of ethylene in the atmosphere is desired during storage. The better the ethylene content is reduced, the longer the quality of the stored foods can be maintained.

One proposed solution to this problem has been to place an adsorbing filter into the cooling storage units. For example, a prior art publication in the technical field of the invention, which is referred to as US6346143B1, discloses a filter comprising a filter housing which is removably secured within the refrigerator or freezer by suction cups which adhere securely to the smooth surfaces of such units. The filter element comprises a woven or nonwoven fiber material, with the fibers being coated or impregnated with an odor adsorbent material such as baking soda and/or activated carbon in some form. The filter element, or the housing, may also include a pleasant scent which will permeate the air in the cold storage device as unpleasant odors are adsorbed by the filter element. However, this arrangement requires the regular replacement of the filter.

Summary of the Invention

An object of the invention is to provide a process for obtaining composite materials for use in ethylene adsorption, wherein said composite materials have an enhanced porous structure so that it functions throughout the lifetime of the device in which it is incorporated, without the need for periodic replacement.

The present invention proposes a process for obtaining composite materials, comprising the steps of producing an activated carbon component using a physical activation technique from a cellulose-based material containing lignin in an amount of 40-55% by weight (i); preparing a mixture by adding the activated carbon component to polystyrene or acrylonitrile butadiene styrene, wherein the amount of the activated carbon component in the mixture is 0.1-30% by weight (ii); and extruding and molding the mixture (iii).

By step (i), it is ensured that the activated carbon component has a structure with an enhanced porosity, thanks to the synergistic effect arising from the specifically high lignin ratio and the use of physical activation technique. Besides, since the physical activation technique does not contain any chemical treatment, it supports the implementation of the final composite material in cooling devices where food is stored without causing a toxic effect. Thus, safety is provided in terms of food contact issues. By step (ii), the selection of polystyrene or acrylonitrile butadiene styrene as the matrix material provides a final composite material having an enhanced chemical resistance and high flexural strength because of its semi-crystalline nature. By the use of polystyrene or acrylonitrile butadiene styrene, a polymer-based composite material that can be implemented in any plastic part of any household appliance is provided. Additionally, the amount of activated carbon component in the mixture which is defined as 0.1-30% by weight provides an enhanced moisture resistance for the final composite material and increases the chemical resistance of the final composite material which is already ensured by the use of polystyrene or acrylonitrile butadiene styrene. Step (iii) enables the composite material to be designed and shaped according to the device and compartment in which it will be used.

In a possible embodiment, the cellulose-based material is selected from the group comprising oak wood chips and walnut shells. By this selection, the lignin ratio in the cellulose-based material which is specified as 40-55% by weight is provided, thus the production of a highly porous activated carbon component is ensured.

In a possible embodiment, the physical activation technique comprises activating the cellulose-based material with steam application under nitrogen atmosphere. Using steam application for the activation process enables the activated carbon component to have a complex structure providing an adsorptive medium without the use of any chemical compounds. Besides, nitrogen atmosphere creates an oxygen-free and neutral environment in order to provide an accurate activation.

In a possible embodiment, the cellulose-based material is activated at 750°C with a heating rate of 10°C/min in the physical activation technique. These parameters facilitate and increase the formation of pores on the activated carbon component.

In a possible embodiment, the activated carbon component produced by the step (i) is washed with distilled water until pH is neutral. Thus, undesired molecules and water- soluble ash content that stick to the surface of the pores are eliminated. In a possible embodiment, the mixture comprises the activated carbon component in an amount of 1-10% by weight. Thus, it is guaranteed that the final composite material provides an effective ethylene adsorption in any device in which it is used. Besides, this specific range ensures the easy processability and moldability of the mixture comprising the activated carbon component and a polymer selected from polystyrene and acrylonitrile butadiene styrene.

In a possible embodiment, the mixture is prepared by mechanical mixing. Thus, a homogeneous distribution of the activated carbon component in polystyrene or acrylonitrile butadiene styrene is ensured.

In a possible embodiment, the mixture is extruded by using a twin-screw compounder at 210°C to 300°C. By this selection of temperature range and compounder, it is ensured that the mixture coming out of the compounder has a smooth surface. At temperatures below this range, the polymer-based mixture is extruded with an undesirably rough surface. On the other hand, the mixture decomposes over 300°C.

In a possible embodiment, the blending time and screw speed are adjusted as 3 min and 100 rpm respectively during extrusion. These parameters eliminate the risk of decomposition of the mixture and lead to obtain a homogenous final composite material.

In a possible embodiment, molding is carried out by using an injection-molding machine at 210°C to 300°C. By this selection of temperature range and molding machine, the risk of decomposition is eliminated and a composite material having a smooth surface with adsorptive micro pores is obtained.

The present invention also proposes a composite material for use in ethylene adsorption, obtained by a process according to any one of the preceding embodiments. Thus, it is possible to obtain composite materials providing ethylene adsorption and accordingly eliminating malodors caused by ethylene gas. In addition, the use of these composite materials, which are molded according to the desired shape and design, in different environments and devices is provided. The present invention further proposes a use of said composite material in any part of a household appliance. By this arrangement, it is ensured that the composite material subjected to the present invention provides ethylene adsorption in the household appliances in which it is used.

Here, the household appliance can be any kind of appliance such as a cooling device, a cooking device.

Here, the term of "any part of a household appliance" means any components of the household appliance such as drawers, bins, crispers, or any part of those components such as walls, dividers.

In a possible embodiment, the composite material is used in a cooling device. This arrangement allows the composite material to eliminate ethylene release caused by foods stored in cooling devices. Thus, on the one hand, malodors that may occur in the device is prevented, and also, the shelf life of foods is extended.

In a possible embodiment, the composite material is implemented into a drawer of the cooling device in which vegetables and fruits can be preserved. By this arrangement, the ripening process of vegetables and fruits is slowed down and ethylene release specifically caused by them is reduced in the cooling device accordingly. Thus, vegetables and fruits remain fresh longer.

In a possible embodiment, the composite material is embedded into at least a wall of the drawer of the cooling device. Since the composite material of the invention does not need periodic replacement, it can removably or not removably be embedded to any wall of the drawer. Accordingly, it does not require to be reachable by the user.

In a possible embodiment, the composite material is removably placed into the drawer of the cooling device. By this arrangement, the user can remove the composite material, wash and place it back in its position.

In a further possible embodiment, one or more composite materials are used in the drawer of the cooling device as dividers. Thus, the drawer can be divided into multiple compartments, fruits and vegetables can be stored separately according to their ripening speed and their ethylene release amount. Yet, in a further possible embodiment, the composite material can be implemented into a ventilation unit of a cooking device. By this arrangement, the odor arising during a cooking process is eliminated.

Brief description of the figures

The accompanying drawings are given solely for the purpose of exemplifying the invention whose advantages over prior art were outlined above and will be explained in detail hereinafter:

Fig. 1 shows a perspective view of a use of the composite material according to the present invention in a drawer of a cooling device, wherein the composite material is embedded into a side wall of the drawer.

Fig. 2 shows an exploded perspective view of a use of the composite material according to the present invention in a drawer of a cooling device, wherein the composite material is embedded into a side wall of the drawer.

Fig. 3 shows a perspective view of the composite material according to the present invention.

Fig. 4 shows a perspective view of a use of the composite material according to the present invention in a drawer of a cooling device, wherein at least one composite material is removably placed on the bottom inner surface of the drawer.

Fig. 5 shows an exploded perspective view of a use of the composite material according to the present invention in a drawer of a cooling device, wherein at least one composite material is removably placed on the bottom inner surface of the drawer.

Fig. 6 shows a perspective view of a use of the composite material according to the present invention in a drawer of a cooling device, wherein at least one composite material is removably placed into the drawer in such a way that the drawer is divided into more than one compartment. Fig. 7 shows an exploded perspective view of a use of the composite material according to the present invention in a drawer of a cooling device, wherein at least one composite material is removably placed into the drawer in such a way that the vegetable and fruit drawer is divided into more than one compartment.

Fig. 8 shows a perspective view of the cooling device with the drawer comprising the composite material according to the present invention.

Detailed description of the invention and the figures

The present application proposes a process for obtaining composite materials. Said process comprises three steps which essentially are producing an activated carbon component, preparing a mixture comprising said activated carbon component and a polymer selected from polystyrene or acrylonitrile butadiene styrene, and molding this mixture to form a composite material.

More specifically, said steps are as follows: i. producing an activated carbon component using a physical activation technique from a cellulose-based material containing lignin in an amount of 40-55% by weight; ii. preparing a mixture by adding the activated carbon component to polystyrene or acrylonitrile butadiene styrene, wherein the amount of the activated carbon component in the mixture is 0.1-30% by weight; and iii. extruding and molding the mixture

According to the present invention, said cellulose-based material is selected from the group comprising oak wood chips and walnut shells. Oak wood chips and walnut shells are both rich in lignin. As used herein, "rich" refers to a lignin amount of 40-55% by weight of the total weight of the cellulose-based material.

In step (i), the term of "physical activation technique" means carbonization of the cellulose-based material to eliminate the bulk of volatile matter followed by activation of the resulting char in the presence of activating agents selected from the group comprising CO2, steam, air, or combinations thereof. According to the present invention, the physical activation technique comprises activating the cellulose-based material with steam application under nitrogen atmosphere. Here, the term "steam application" refers to a process in which the char created by heating of the cellulose-based material is activated in a furnace with hot steam in the absence of oxygen.

According to step (i), the cellulose-based material is activated at 750-800°C with a heating rate of 10°C/min in the physical activation technique. Further, the mixture comprises the activated carbon component in an amount of 1-10% by weight.

In step (ii), the term "mixture" refers to a composite polymer material in fluid form comprising polystyrene or acrylonitrile butadiene styrene as matrix and said activated carbon component as reinforcing agent.

According to step (ii), the mixture is prepared by mechanical mixing. Following that, according to step (iii), the mixture is extruded by using a twin-screw compounder at 210°C to 300°C. As used herein, "a twin-screw compounder" is a type of blender/mixer which melts and moves the polymer composite material through a cylinder using two co-penetrating and self-cleaning identical screws which are mounted on shafts. Accordingly, they rotate in the same direction in a fixed closed housing called "barrel" and they operate continuously with very short residence times.

According to step (iii), the blending time and screw speed are adjusted as 3 min and 100 rpm respectively during extrusion. Following that, the extruded material is molded by using an injection-molding machine at 210°C to 300°C. As used herein, "an injectionmolding machine" refers to a machine which forces the molten polymer composite material into a mould cavity so that the composite material solidifies into a shape that has conformed to the contour of the mould.

The present application further proposes a composite material (1) obtained by the process subjected to the invention. Said composite material is in the form of a plate having elongated perforations as can be seen in Fig. 3.

According to the present invention, a use of said composite material (1) in any part of a household appliance is also proposed. Referring to Fig.8, said household appliance is a cooling device (C). More specifically the composite material (1) is implemented into a drawer (D) of the cooling device (C) in which vegetables and fruits are preserved as can be seen in Fig 1, Fig. 2, Fig. 4, Fig. 5, Fig. 6 and Fig. 7.

Fig. 1 and Fig. 2 show the use of the composite material (1), wherein the composite material (1) is embedded into at least a wall of the drawer (D) of the cooling device (C). Accordingly, the composite material (1) is removably or fixedly attached to the drawer (D). The composite material (1) can also be produced in one piece with the drawer (D) as can be seen in Fig. 1.

Fig. 4 and Fig. 5 show the use of the composite material (1), wherein the composite material (1) is removably placed into the drawer (D) of the cooling device (C). According to this use, one or more composite materials are removably placed on the bottom wall of the drawer (D).

Referring to Fig. 6 and Fig. 7, the composite material (1) is used as a divider in order to divide the drawer (D) into multiple compartments. Accordingly, one or more composite materials (1) are removably hinged to each other and/or to the drawer (D) walls. Said composite materials (1) can be located in different positions to create compartments of different sizes and different geometric structures in the drawer (D).

Reference list:

1. Composite material

D. Drawer C. Cooling device