KR20190081190A - Film for microwave oven - Google Patents

Abstract

The present invention is a film for a microwave oven. The film is as follows: an upper layer of nylon having a thickness of 11-19μm, a middle layer of polypropylene (PP) having a thickness of 35-45μm and a lower layer of polyethylene (PE) having a thickness of 35-45μm are simultaneously extruded by a three-staged dice to be sequentially stacked, and the upper and middle layers are attached by an epoxy adhesive to form an adhesive layer, and the middle and lower layers are attached to form a heat-resisting adhesive layer by a mixture of a heat-resisting additive comprising an epoxy adhesive and 2-8 parts by weight of ceramic powders having no conductivity and having a particle size of 300-400 mesh with respect to 100 parts by weight of adhesive. An adhesive block on a front of the three-stage dice is placed between first and second discharging ports and discharges the epoxy adhesive, and an adhesive adding supplier has an adhesive adding block which is located between second and third discharging ports on the front of the three-stage dice and discharges the mixture of the epoxy adhesive and the heat-resisting additives. The film is used to manufacture a package such that the package is not stretched when a packaged product is cooked in a microwave oven, the appearance of the package is fine after cooking, there is no scratch when being kept and moved, flexibility and strength are good, and there is no sucking-out phenomenon by a packaged product.

Description

FIELD FOR MICROWAVE OVEN [0002]

The present invention relates to a film for a microwave oven, and more particularly, to a microwave oven film for packaging a frozen food which is warmed and eaten in a microwave oven prior to consumption, in which a nylon, a polypropylene (PP), a polyethylene (PE) Resistant additive, and to a film for a microwave oven having good packaging flexibility, strength and appearance.

Synthetic resins are widely used as food packaging materials, construction materials, electric / electronic / household materials, automobile materials, and fiber materials because they are generally lightweight and have good water resistance, chemical resistance, electrical insulation and mechanical properties, have.

Stretch films excellent in transparency, flexibility and heat-sealing properties are widely used for the packaging of fresh foods packed in the above food packaging, especially meat, fish, vegetables and the like, and the film for food packaging is made of polyvinyl chloride resin, adipinic ester plasticizer And a polyvinyl chloride resin composition in which various antifogging agents are blended are generally used.

The prior art for producing a food packaging film based on polyvinyl chloride described above is disclosed in Patent Document 1, in which 100 parts by mass of a chlorine-containing resin such as a polyvinyl chloride resin is produced by a hydrogen peroxide method and has a peroxide value of 13 or less And an epoxidized soybean oil not containing a phosphorus antioxidant at a ratio of 1 to 50 parts by mass.

The technology disclosed in Patent Document 1 is not suitable for use for packaging foods because epoxidized soybean oil or the like is natural product plasticizer or soybean oil bleed out on the film surface is solidified and the surface of the film is whitened, The appearance of the film may be poor.

As described above, a film that requires not only packaging flexibility but also a good film appearance is desired for a food packaging film.

Japanese Patent Application Laid-Open No. 8-27341

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a microwave oven film for packaging frozen foods warmed and consumed in a microwave oven prior to ingestion, in which a nylon upper layer, a polypropylene (PP) (PP) and polyethylene (PE) are bonded together with an epoxy adhesive and a heat-resistant, non-conductive (non-conductive) And simultaneously adheres to the substrate with an additive to provide a film for a microwave oven having good package flexibility, strength and appearance.

In the present invention, the film is formed by sequentially coextruding a nylon upper layer, a middle layer of polypropylene (PP) and a lower layer of polyethylene (PE) by a three-stage die and sequentially layering the upper and middle layers with an epoxy adhesive And a heat-resistant adhesive layer in which the middle layer and the lower layer are bonded by a mixture of an epoxy adhesive and a heat-resistant additive.

In the present invention, the thickness of the upper layer is 11 to 19 占 퐉, the thickness of the middle layer is 35 to 45 占 퐉, and the thickness of the lower layer is 35 to 45 占 퐉.

In the present invention, the heat-resistant additive is a ceramic powder having no electrical conductivity and is composed of 2 to 8 parts by weight per 100 parts by weight of the adhesive.

Further, the present invention is characterized in that the adhesive supply unit constituted by the adhesive block positioned between the first discharge port and the second discharge port is constituted in front of the three-stage dice, and the adhesive addition block positioned between the second discharge port and the third discharge port The adhesive addition feeder is constituted.

The present invention also provides a hot-air dryer comprising a heater disposed in front of the three-stage die and raising the air inside, and a blower for transferring the heated air by the heater.

A packaging bag made of a nylon upper layer, a middle layer of polypropylene (PP), and a lower layer of polyethylene (PE) according to the present invention was fabricated to prepare a package for a microwave oven, The appearance of the envelope is good.

In addition, the present invention can be applied to packaging of frozen foods by making packaging bags according to the thickness of the upper layer of nylon, the thickness of the middle layer of polypropylene (PP), and the thickness of the lower layer of polyethylene (PE) There is an effect that flexibility and strength are good and a phenomenon of sucking by a package does not occur.

In addition, the present invention has an effect that thermal deformation does not occur when a frozen food is cooked in a microwave oven by the heat resistant additive of ceramics.

In addition, since the thermosensitive additive has no electrical conductivity, the present invention has an effect that it can be used in a microwave oven.

In addition, the present invention has an effect that no problem occurs in the environment generated in the adhesive by the epoxy adhesive.

In addition, the present invention has the effect of removing the moisture of the film by the hot-air dryer in front of the three-stage die.

Figure 1: A partial perspective view of the present invention.
Figure 2: A plan view of an extruder for producing the present invention.
3 is a perspective view of a molding unit of an extrusion molding machine for producing the present invention.
4: sectional view of the forming unit and hot air dryer of the extrusion molding machine producing the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

A typical microwave oven is a kitchen appliance that generates microwaves of 2450 MHz emitted from a magnetron by using electricity in a body to cause molecular motion in the inside of the package by heating the object to be cooked, Can greatly shorten the cooking time of the package and reduce the loss of nutritional value in the process of cooking, defrosting and warming the package, and it is widely used because of the advantage of directly cooking the package while being stored in the container.

Generally, a disposable container used in a microwave oven is made of a container of a certain size capable of accommodating foods made of synthetic resin, that is, a cover made of a transparent synthetic resin, so that food is contained in the inner space of the container and the cover is sealed by heat bonding And is being distributed in the market in general.

In general, the frozen food is circulated in a sealed package in a packaging bag so as not to be in contact with air or oxygen, thereby effectively preventing oxidation and decay of the package contained in the packaging bag, When the frozen food is packed and heated in a microwave oven, the packaging surface is cooked and the surface of the film is stretched, resulting in a poor appearance of the film, which visually reduces the desire for food.

The present invention is characterized in that the upper layer 11 is made of nylon, the middle layer 12 is made of polypropylene and the lower layer 13 is made of a multilayer of polyethylene (PE) A film 10 that can be used for a microwave oven by packaging frozen food adhered with an adhesive mixed with a heat resistance additive of a heat resistant adhesive layer 15

The film 10 of the present invention comprises a first extruder 20 for melting the first molten resin (a), a second extruder 30 for melting the second molten resin (b), a third extruder A nylon, a polypropylene (PP), and a polypropylene (PP) are produced by a three-stage die 60 that forms a synthetic molten resin melted and discharged by a third extruder 40 which melts, And polyethylene (PE) are co-extruded so that the upper layer 11 is made of nylon, the middle layer 12 is made of polypropylene and the lower layer 13 is made of polyethylene (PE) The adhesive of the adhesive layer 14 or the heat-resistant additive of the heat-resistant adhesive layer 15 is adhered by the mixed adhesive to be formed into a single film 10.

The nylon is widely used for climbing clothes, various climbing equipments, industrial parts and the like due to its excellent heat resistance, abrasion resistance, high transparency, high rigidity, high elasticity and physical properties, and being thin, light, For about 20 to 40 minutes to prevent physical properties and dimensional changes due to the moisture absorption effect during use and improve the physical properties such as toughness of the molded article by annealing effect.

The polypropylene (PP) is excellent in chemical resistance, mechanical properties and thermal properties and is used for packaging films, stretch tapes, fibers, pipes, daily necessities, toys, industrial parts and containers. And has a melting point of 150 to 160 ° C and can be continuously used at a temperature of 110 ° C under a load of 4.5 kg.

The polyethylene (PE) is used in a wide range of fields because of its excellent electrical properties, mechanical properties, processability and relatively low cost. The density of the polyethylene varies depending on the polymerization method. Depending on the density, low density polyethylene (LDPE) (MDPE), high density polyethylene (HDPE), cross linking polyethylene (XLPE) and metallocene polyethylene (mPE).

In order to maintain the outer appearance of the film while the film is not stretched when the frozen foods are cooked in a microwave oven as well as the packaging flexibility of the frozen foods during the hermetic packaging and circulation of the frozen foods, The outer surface of the packaging bag is made of nylon of the upper layer 11 and the inner surface of the packaging bag is made of polyethylene of the lower layer 13 and the middle layer 12 of the packaging bag is made of polypropylene .

Since the packaging bag packed with frozen foods is brought into contact with an external object or packages during transportation and storage, damage to the surface of the packaging bag occurs. Therefore, in order to prevent such a phenomenon, the frozen food is packaged and used in a microwave oven The microwave oven film (10) is made of a nylon having abrasion resistance, stiffness, high elasticity, thin and light and strong, and resistant to contamination, and is made of polyethylene (PE) so as to be in direct contact with the package, (PP) having excellent mechanical properties and thermal properties can be applied to the intermediate layer 12 of the film 10 without stretching when the package is cooked in a microwave oven while the package is packaged. , And the packaging and packaging are flexible and the strength of the packaging bag is maintained at the time of storage and transportation, and the appearance of the packaging bag becomes good after cooking.

The film 10 is cut into a predetermined size and thermally fused to form a packaging bag for packaging frozen food or a pouch for packaging a health food or beverage.

The upper layer 11 of the nylon has a thickness of 11 to 19 占 퐉 and the middle layer 12 of polypropylene PP has a thickness of 35 to 45 占 퐉 and the lower layer 13 of polyethylene 35 to 45 탆. When the packaging bag according to the present invention is manufactured, the frozen food is packed so that no scratches are generated during storage and transportation, and flexibility and strength are good and the packaging phenomenon does not occur.

When the packaging bag of the present invention is manufactured, when the thickness of the upper layer 11 of the nylon is 11 μm or less, the frozen food is packed and scratched during storage and transportation. When the frozen food is heated in the microwave oven in a packaged state And when the thickness of the upper layer (11) is 19 μm or more, when the frozen food is packed and heated in a microwave oven while being packed with scratches and frozen foods during storage and transportation, If the thickness of the middle layer 12 of the polypropylene (PP) is 35 탆 or less, the flexibility of the packaging bag is good but the strength is lowered, and the thickness of the middle layer 12 is 45 탆 or more The strength of the packaging bag is good but the flexibility is low. In the case where the thickness of the lower layer 13 of polyethylene (PE) is 35 μm or less, If more than the lower layer (13) having a thickness of 45㎛ there does not occur a draft caused by the packaging.

Nylon, polypropylene (PP) and polyethylene (PE) are simultaneously extruded by the three-stage die 60, nylon and polypropylene (PP) are bonded by epoxy bonding, Propylene (PP) and polyethylene (PE) are bonded simultaneously to a mixture of an epoxy adhesive and a heat resistant additive.

The film is constituted by an adhesive layer 14 for bonding an nylon and a polypropylene (PP) with an epoxy adhesive between the upper layer 11 and the middle layer 12 and between the middle layer 12 and the lower layer 13, That is, a heat-resistant adhesive layer 15 for bonding polypropylene (PP) and polyethylene (PE) with a mixture of an epoxy adhesive and a heat-resistant additive is formed.

The epoxy bonding agent is a liquid thermosetting resin adhesive which bonds the upper layer 11 and the lower layer 13, that is, nylon and polypropylene (PP), without peeling between them, (PP) and polyethylene (PE) are adhered to each other to prevent separation phenomenon between the layers of the film sheet for a microwave oven without peeling.

The epoxy adhesive is a thermosetting resin adhesive made of an epoxy resin and is widely used for bonding steel, copper, wood and various plastics. It has excellent mechanical properties after curing and has strong adhesive force, heat resistance, It is not harmful to the packaging of the frozen food even if it is used as an adhesive for the upper layer 11 and the lower layer 13 of the film 10 because it is excellent and hardens at room temperature and has no byproducts during the reaction.

The microwave oven film must have heat resistance due to heat when cooking frozen foods in a microwave oven, and should not cause thermal deformation, and may cause fire due to generation of sparks due to microwaves. , The heat-resistant additive is made of ceramic.

The ceramic is an additive added to the epoxy adhesive used in the heat-resistant adhesive layer 14, and is a powder having a particle size of 200 to 600 mesh, preferably a powder having a particle size of 300 to 400 mesh and 2 to 8 parts by weight per 100 parts by weight of the adhesive do.

When the heat resistant additive, that is, the ceramic, is 2 parts by weight or less per 100 parts by weight of the epoxy adhesive, thermal deformation is caused by heat when cooking frozen food in a microwave oven. When the heat resistant additive is 5 parts by weight or more, The film has more strength than necessary.

When the ceramic particles have a particle size of 200 mesh or less, the packaging bag for the microwave oven, which is made of the film (10), can be used in a microwave oven for cooking frozen food, Can cause thermal deformation Considering the thickness of the epoxy adhesive, the surface roughness of the film (10) becomes poor due to the large particle size of the powder. When the film is over 600 mesh, heat resistance and workability are good. However, since the ceramic is to be subjected to special precision milling, do.

The ceramic may be selected from the group consisting of phyllite, quartz, muscovite, sericite, biotite, chlorite, ), Chloritoids, garnet, albite, sphene, apatite, zircon, sodium oxide (also known as zircon) sodium oxide, titanium dioxide, zirconia, and silicon nitride.

In general, a synthetic resin film is produced by supplying a synthetic resin chip, which is a raw material of a melting resin, to a hopper of an extrusion molding machine, melting a synthetic resin chip at 160 to 220 ° C by a heater, extruding the melted resin with a cylinder and an extrusion screw, 60, discharged out of the three-stage dies 60, cooled by the blowing air of the air ring, and wound on a winding reel that finally rotates to form a roll film.

The extruder for molding the film 10 comprises an extruder and a molding unit 40. The extruder melts the resin and pressurizes the resin to the molding unit 50. The extruder 20 and the second extruder 20, And a third extruder (30).

When the nylon chips are injected into the hopper 21 of the first extruder 20, the chips are melted by the heat of the heater in the transfer part 22 to become the first molten resin (a) Is fed to the forming unit 50 by the screw of the feeding unit 22 and the chip of polypropylene PP is fed into the hopper 31 of the second extruder 30, The molten resin is melted by the heat and becomes the second molten resin b and is extruded into the molding unit 50 by the screw of the transfer unit 32 and the polyethylene PE is put into the hopper 41 of the third extruder 40 The lower chip is melted by the heat of the heater in the transferring part 42 to be the third molten resin c and is extruded into the molding unit 50 by the screw of the transferring part 42.

The first, second and third molten resins a, b and c melted in the first, second and third extruders 30, 40 and 50 are formed into a molding unit 50, The first molten resin a becomes the upper layer 11 of the film 10 and the second molten resin b becomes the middle layer of the film 10, (12), and the third molten resin (c) becomes the lower layer (13) of the film (10).

An outlet block 51 composed of a three-layer outlet path communicating with the outside is formed in the molding unit 50. The upper melt outlet is connected to the first molten resin (not shown) communicated with the first extruder 20 and extruded from the transfer unit 22 a second molten resin b which is communicated with the second extruder 30 and extruded from the transfer part 32 is introduced into the upper layer 11 of the film 10, And the third molten resin c that is communicated with the third extruder 40 and extruded from the transfer part 42 is introduced into the middle layer 12 of the film 10, So that the upper layer 11 is formed.

The three-stage dice 60 includes a first discharge port 61 for discharging and molding the first molten resin a to be melted and extruded in the first extruder 20, A third discharge port 63 constituting a second discharge port 62 for discharging and molding the molten resin a and constituting a third discharge port 63 for discharging and molding the first molten resin a to be melted and extruded by the third extruder 40 is formed.

The inlet of the upper layer outflow path, the middle layer outflow path and the lower layer outflow path of the forming unit 50 are communicated with the conveyance portions 22, 32 and 42 respectively and the outlet is communicated with the three-stage dice 60, The three-stage dice 60 includes a first discharge port 61, a second discharge port 62 and a third discharge port 63. The first discharge port 61, the second discharge port 62, .

The first discharge port 61 of the three-stage dice 60 is connected to the upper discharge line of the forming unit 50, the second discharge port 62 is connected to the middle discharge line of the forming unit 50, 63 are connected to the lower layer outflow path of the molding unit 50 so that the first discharge port 61 discharges the first molten resin a and the second discharge port 62 discharges the second molten resin b, The third discharge port 63 discharges the third molten resin c so that the first, second and third molten resins a, b and c are laminated on the entire surface of the three-stage dies 60.

An adhesive feeder (70) for feeding an epoxy adhesive to the front of the three-stage dice (60) is constituted, and an adhesive addition feeder (80) for simultaneously supplying a mixture of an epoxy adhesive and a heat resistant additive is constituted.

 The adhesive feeder 70 transfers the epoxy adhesive for bonding the upper layer and the middle layer from the front of the three-stage dice 60 so that nylon and polypropylene (PP) are adhered to each other. And the heat-resistant additive are transferred from the front of the three-stage die 60 to adhere the polypropylene (PP) and the polyethylene (PE).

The adhesive feeder 70 includes a hopper 74 to which an epoxy adhesive is fed and a secondary extruder 71 for conveying the adhesive and a secondary feed pipe 70 for communicating with the secondary extruder 71 and for transferring the epoxy adhesive to the three- And an adhesive block 73 for discharging the transferred epoxy adhesive.

The adhesive addition feeder 80 is connected to a hopper 75 into which a mixture of an epoxy adhesive and a heat resistant additive is fed and a secondary extruder 81 and a secondary extruder 81 which feed the mixture, And an adhesive addition block 83 for discharging the transferred mixture is constituted.

The adhesive block 73 and the adhesive adhering block 83 are formed on the front surface of the three-stage dice 60 while the adhesive block 73 is attached to the first discharge port 61 of the three-stage dice 60 and the second discharge port 62 , And the adhesive addition block 83 is positioned between the second discharge port 62 and the third discharge port 63 of the three-stage dice 60. [

The adhesive block 79 is positioned between the first discharge port 61 and the second discharge port 62 of the three-stage dice 60 so that the epoxy adhesive can be discharged through the transfer pipe 72 when the film 10 is extruded Nylon and polypropylene (PP) are discharged between the nylon and the polypropylene (PP) to bond to form the upper and middle layers.

The adhesive addition feeder 80 is positioned between the second discharge port 62 and the third discharge port 63 of the three-stage dice 60 and the mixture of the epoxy adhesive and the heat resistant additive is transferred through the transfer pipe 82 to the film 10 (PP) and polyethylene (PE) at the time of molding and extrusion, and the polypropylene (PP) and the polyethylene (PE) are adhered to each other to form an intermediate layer and a lower layer.

The nylon, the polypropylene (PP) and the polyethylene (PE) are integrally adhered together by the epoxy adhesive and the mixture of the epoxy adhesive and the heat resistant additive to form the three-layered film 10.

In order to remove the moisture formed on the surface of nylon, polypropylene (PP) and polyethylene (PE) when the film 10 is extrusion-molded, air inside is raised in front of the three- And a hot air dryer 90 constituted by a blower 92 for feeding air heated by the heater 91 is constituted.

The hot air dryer 90 is formed as a hexahedral space and the film 10 extruded by the three-stage die 60 flows out through the inner space of the hot air dryer 90, The indoor air is heated and the heated air is supplied to the film 10 by the blower 91 to remove the moisture formed on the film 10.

The compositions of Examples 1 to 5 of the film of the present invention are shown in Table 1 below.

division Example 1 Example 2 Example 3 Example 4 Example 5 Upper layer thickness (탆) 9 12 15 18 21 Middle layer thickness (탆) 32 36 40 44 48 Lower layer thickness (탆) 32 36 40 44 48 Ceramic (parts by weight) 1.5 3.3 5.0 3.7 8.5

The compositions according to Examples 1 to 5 were mixed and extruded to evaluate the physical properties of the molded film

(1) Bending test

The flexural modulus of the specimen of the KS M3008 standard was measured with an Instron 4400 series Instron 4400 series at a span distance of 50 mm and a crosshead speed of 2.5 m / min.

(2) Tensile test

Tensile strength was measured under the conditions of a load cell of 50 kgf in Instron 4400 series manufactured by INSTRON UTM as a test piece of KS M3006 standard.

(3) Impact strength

Izod impact strength was measured on a rectangular test piece (63 mm x 12 mm x 5 mm) using an impact tester (Model 863, Ueshima Seisakusho Co., Ltd.) according to JIS K7110 standard.

(4) Peeling phenomenon

An adhesive tape having a width of 10 mm and a length of 50 mm was adhered to the upper layer of the film, and then the adhesive tape was pulled and the degree of peeling of the upper layer was visually observed.

The physical properties measured for Examples 1 to 5 are shown in Table 2 below.

Evaluation results of film properties division Example 1 Example 2 Example 3 Example 4 Example 5 Flexural modulus (kgf / cm2) 10,208 10,673 11,120 11,573 12,021 Tensile test (kgf / cm2) 312 320 326 333 341 Impact strength (J / m) 50 54 57 60 65 Peeling phenomenon none none none none none

The flexural modulus of the present invention was measured to be not less than 10,2008 kgf / cm 2, the tensile test was not less than 312 kgf / cm 2, and the impact strength was not less than 50 J / m.

The terms or words used in the specification and claims of the present invention are not to be construed in a conventional or dictionary sense and the inventor can appropriately define the concept of the term in order to explain its invention in the best way And should be construed in light of the meanings and concepts consistent with the technical idea of the present invention.

As described above, the embodiments described in the description of the present invention and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. It is possible to make various modifications within the limit.

It is therefore to be understood that within the scope of the appended claims, the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. .

10: Film 11: Upper layer
12: middle layer 13 : bottom layer
14: Adhesive layer 15: Adhesion heat resistant layer
20: first extruder 21, 31, 41, 74, 84: hopper
22, 32, 42: transfer part 30: second extruder
40: Third extruder 50: Molding unit
51: Outflow block 60: Three-stage die
61: first discharge port 62: second discharge port
63: third discharge port 70: adhesive supply device
71, 81: auxiliary extruder 72, 82: conveying pipe
73: Adhesive block 80: Adhesive additive feeder
83: Adhesive addition block 90: Hot air dryer
91: heater 92: blower
a: first molten resin b: second molten resin
c: third molten resin

Claims (5)

In a microwave oven film,
The film is composed of an upper layer of nylon, a middle layer of polypropylene (PP) and a lower layer of polyethylene (PE) coextruded by a three-stage die and sequentially laminated, and an adhesive layer in which an upper layer and an intermediate layer are bonded with an epoxy adhesive And a heat-resistant adhesive layer in which an intermediate layer and a lower layer are bonded by a mixture of an epoxy adhesive and a heat-resistant additive.
The method according to claim 1,
Wherein the upper layer has a thickness of 11 to 19 占 퐉, the middle layer has a thickness of 35 to 45 占 퐉, and the lower layer has a thickness of 35 to 45 占 퐉.
3. The method of claim 2,
Wherein the heat-resistant additive is a ceramic powder having no electrical conductivity and is composed of 2 to 8 parts by weight per 100 parts by weight of the adhesive.
The method of claim 3,
The front of the three-stage die is positioned between the first discharge port and the second discharge port, and an adhesive block for discharging the epoxy adhesive is constituted to constitute an adhesive supply device for supplying the epoxy adhesive, and the adhesive dispenser is disposed between the second discharge port and the third discharge port An adhesive additive block for discharging a mixture of an epoxy adhesive and a heat resistant additive is constituted to constitute an adhesive addition feeder for supplying a mixture of an epoxy adhesive and a heat resistant additive.
5. The method of claim 4,
The hot air dryer is constituted in front of the three-stage dice and includes a heater for raising the air inside, and a blower for transferring the heated air by the heater. The film extruded by the three- And the moisture is removed by flowing out through the inner space of the microwave oven.

Images