WO2006137672A1

WO2006137672A1 - Continuous pressure foaming method

Info

Publication number: WO2006137672A1
Application number: PCT/KR2006/002361
Authority: WO
Inventors: Jang Won Park
Original assignee: Jang Won Park
Priority date: 2005-06-20
Filing date: 2006-06-20
Publication date: 2006-12-28
Also published as: KR100627145B1

Abstract

A method for continuously foaming a forming material comprises the steps of processing a forming material extending in a lengthwise direction thereof while suppressing the forming material from being crosslinked and foamed; inputting the continuous forming material between metal belts of a continuous pressure crosslinking unit comprising a pair of metal belts which are spaced apart from each other by a predetermined distance and conduct orbital motions in opposite directions in order to suppress the forming material from being foamed and heating means for continuously supplying heat to at least one selected from the metal belts; continuously crosslinking the continuous forming material which is interposed between and is moved along with the metal belts, using heat continuously transferred through the metal belts; and con¬ tinuously foaming the forming material continuously moved out of the metal belts in a con¬ tinuously crosslinked state.

Description

CONTINUOUS PRESSURE FOAMING METHOD

Technical Field

[1] The present invention relates, in general, to a method for foaming a forming material, and more particularly, to a continuous pressure foaming method in which a step for pressure crosslinking a forming material and a step for foaming the forming material are separately implemented to produce a continuous foam in a pressurized foaming method. Background Art

[2] As is well known in the art, a forming material is foamed using mechanical facilities selected in consideration of the shape and properties of a foam to be finally produced. In general, foaming methods are divided into a pressure crosslinked foaming method and a normal crosslinked foaming method depending upon whether a forming material processed in a desired shape such as a pellet and a sheet is directly pressurized and heated to produce a foam.

[3] In the pressure crosslinked foaming method, a forming material is placed in a mold and then is heated and pressurized under appropriate conditions to produce a foam. The shape of the finally produced foam can be freely changed depending upon a cavity defined in the mold in which the forming material is placed. Further, since the forming material experiences a crosslinking process in a state in which the forming material is brought into direct contact with the inner surface of the mold defining the cavity, advantages are provided in that the surface of the finally produced foam is smooth, and therefore, the pressure crosslinked foaming method can be widely used for various application products.

[4] However, in the pressure crosslinked foaming method, when producing a foam, a mold defining an internal cavity having the shape corresponding to that of the foam to be finally produced must be necessarily employed. Therefore, even though the shapes of finally produced foams are the same as one another, if the size of the shapes are different, the number of required molds and manufacturing costs cannot but considerably increase.

[5] Also, in the pressure crosslinked foaming method, the foam is produced through a series of processes including opening of a mold, placing of the forming material, closing of the mold, heating of the mold, and re-opening of the mold. In this case where a foam is produced through the processes of opening and closing the mold, the production of the foam cannot but be interrupted to deteriorate productivity.

[6] Moreover, in order to increase the size of a finally produced foam, the size of a press serving as means for pressurizing the mold must be increased. In this regard, when considering the normally heavy weight of a press, limitations necessarily exist in increasing the size of the press, as a result of which the size of a foam to be produced by the pressure crosslinked foaming method is limited to some extent.

[7] On the other hand, in the normal pressure crosslinked foaming method, unlike the pressure crosslinked foaming method, since a mold which has an internal cavity of a desired shape and serves as pressurizing means is not used when heating a forming material, a foam can be continuously produced, and the size of the finally produced foam can be optionally increased.

[8] Nevertheless, since the pressurizing means for controlling the volume of the forming material foamed in a foaming step is not provided, the surface of the finally produced foam is not less smooth than that of the foam produced by the pressure crosslinked foaming method. The fact that the foam is produced to have a somewhat coarse surface means that a process for uniformly re-processing the surface must be added, whereby production efficiency of the normal pressure crosslinked foaming method is deteriorated when compared to the pressure crosslinked foaming method.

[9] In addition, in the normal pressure crosslinked foaming method, because the foam is produced through a crosslinking process with the forming material exposed to the external environment, means for forcing the forming material to undergo a uniform crosslinking process is not provided, unlike the pressure crosslinked foaming method in which the forming material is foamed after being uniformly crosslinked in the closed space defined in the mold. As a consequence, since the properties of the finally produced foam, such as tensile strength and compressive strength, are inferior, the normal pressure crosslinked foaming method cannot be widely used for various application products. Besides, in the normal pressure crosslinked foaming method currently known in the art, it is impossible to produce a continuous foam having an internal cavity structure of an optional shape. Disclosure of Invention Technical Problem

[10] Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a continuous pressure foaming method which can continuously produce a foam and can freely adjust the size of the foam.

[11] Another object of the present invention is to provide a continuous pressure foaming method which can continuously produce a foam in a manner such that the produced foam has excellent inherent properties.

[12] Still another object of the present invention is to provide a method which can con- tinuously produce a continuous foam having therein a cavity structure of an optional sectional shape in a pressurized foaming method.

[13] Further still another object of the present invention is to provide a continuous pressure foaming method which can freely adjust the size of a produced continuous foam and the sectional shape of the cavity structure defined in the produced continuous foam.

Technical Solution

[14] In order to achieve the above objects, according to one aspect of the present invention, there is provided a method for continuously foaming a forming material, comprising the steps of processing a forming material extending in a lengthwise direction thereof while suppressing the forming material from being crosslinked and foamed; inputting the continuous forming material between metal belts of a continuous pressure crosslinking unit comprising a pair of metal belts which are spaced apart from each other by a predetermined distance and conduct orbital motions in opposite directions in order to suppress the forming material from being foamed, and heating means for continuously supplying heat to at least one selected from the metal belts; continuously crosslinking the continuous forming material which is interposed between and is moved along with the metal belts, using heat continuously transferred through the metal belts; and continuously foaming the forming material continuously moved out of the metal belts in a continuously crosslinked state.

[15] In order to achieve the above objects, according to another aspect of the present invention, there is provided a method for continuously foaming a forming material, comprising the steps of processing forming materials extending in a lengthwise direction thereof while suppressing the forming materials from being crosslinked and foamed; preparing at least two processed forming materials, and forming an interface having an optional pattern on a surface of at least one of the prepared forming materials, using at least one interface material, in order to prevent physical and chemical coupling of the forming materials; inputting the forming materials having the interface between metal belts of a continuous pressure crosslinking unit comprising a pair of metal belts which are spaced apart from each other by a predetermined distance and conduct orbital motions in opposite directions in order to suppress the forming materials from being foamed and heating means for continuously supplying heat to at least one selected from the metal belts; continuously pressure crosslinking the continuous forming materials which are interposed between and are moved along with the metal belts, using heat continuously transferred through the metal belts; and continuously foaming the forming materials continuously moved out of the metal belts in a continuously crosslinked state to produce a foam in which cavity structures each having an optional sectional shape are defined due to the presence of the interface.

[16] According to another aspect of the present invention, the continuous pressure crosslinking unit further comprises vertical height adjustment means for adjusting a spacing between the metal belts depending upon a thickness of the inputted forming material.

[17] According to another aspect of the present invention, the continuous pressure crosslinking unit further comprises squeezing means which squeezes at least one of the metal belts in order to suppress the forming material, which is crosslinked while being moved along with the metal belts, from being foamed.

[18] According to another aspect of the present invention, the continuous forming material has the shape of a thin film.

[19] According to another aspect of the present invention, the method further comprises the step of forming a continuous foam to planarize surfaces of the continuous foam by passing the continuous foam between rollers rotated in opposite directions after implementation of the continuous foaming step.

[20] According to another aspect of the present invention, in the forming step, the continuous foam is inputted between the rollers after a surface protective layer is coupled to at least one of upper and lower surfaces of the continuous foam.

[21] According to another aspect of the present invention, the method further comprises the step of passing the continuously produced foam between different rollers which are rotated in opposite directions in a state in which a surface protective layer is coupled to at least one of upper and lower surfaces of the continuously produced foam after implementation of the forming step.

[22] According to still another aspect of the present invention, in the interface forming step, the interface material comprises one selected from a group consisting of liquid or solid substance and a formed product having a predetermined shape.

[23] According to further still another aspect of the present invention, the method further comprises the step of injecting or inserting at least one selected from a group consisting of gas, liquid or solid substance, and a formed product having a predetermined shape, into the internal cavity structure of the continuous foam after implementation of the continuous foaming step.

Advantageous Effects

[24] Thanks to the features of the present invention, since a procedure for crosslinking a forming material is implemented not using a mold having an internal cavity of a predetermined sectional shape but under a constantly pressurized state by the tensioning force of metal belts, a continuous foam having a large size can be produced, whereby the limitations of a pressurized foaming method can be overcome. [25] Also, in the present invention, because the forming material is crosslinked in a state in which the forming material is uniformly pressurized by the metal belts and heat is continuously supplied to the forming material from heating means, the produced foam can have excellent inherent properties, whereby the limitations of an atmospheric foaming method can be overcome. [26] Further, in the present invention, the sectional shape and the properties of the cavity structure defined in the continuous foam can be variously controlled in a manner such that the continuous foam can be positively employed for diverse applications.

Brief Description of the Drawings [27] The above objects, and other features and advantages of the present invention will become more apparent after a reading of the following detailed description when taken in conjunction with the drawings, in which:

[28] FIG. 1 is a schematic constructional view illustrating an entire apparatus for continuously pressure foaming a forming material in accordance with the present invention; [29] FIG. 2 is a constructional view illustrating the step of inputting the forming material in accordance with the present invention; [30] FIG. 3 is a constructional view illustrating the step of continuously pressure cros slinking the forming material in accordance with the present invention; [31] FIG. 4 is a constructional view illustrating the step of continuously foaming the forming material in accordance with the present invention; [32] FIG. 5 is a constructional view illustrating the step of forming a continuous foam in accordance with the present invention; [33] FIG. 6 is a constructional view illustrating the step of applying a surface protective layer on the continuous foam in accordance with the present invention; [34] FIG. 7 is a schematic constructional view illustrating forming materials formed with an interface layer having an optional profile in accordance with the present invention; [35] FIG. 8 is a constructional view illustrating the step of inputting the forming materials formed with the interface layer into a continuous pressure crosslinking unit in accordance with the present invention; [36] FIG. 9 is a constructional view illustrating the step of continuously pressure crosslinking the forming materials formed with the interface layer in accordance with the present invention; [37] FIG. 10 is a constructional view illustrating the step of continuously foaming the forming materials formed with the interface layer and defining cavity structures in the forming materials in accordance with the present invention; [38] FIG. 11 is a perspective view illustrating a continuous foam in which the cavity structures are defined in accordance with the present invention; and [39] FIG. 12 is a cross-sectional view taken along the line A-A' of FIG. 11.

Best Mode for Carrying Out the Invention

[40] A procedure for continuously foaming a forming material in accordance with the present invention comprises the step of processing the forming material, the step of inputting the forming material into a continuous pressure crosslinking unit, the step of continuously pressure crosslinking the forming material, and the step of continuously foaming the crosslinked forming material.

[41] In the step of processing the forming material, a raw material is prepared from a main resinous material selected from various materials, in consideration of the use and the properties of a foam to be produced. The main resinous material and sub-materials are metered to have respective predetermined weights in conformity with a material mixing standard. Then, when a compound is prepared through a mixing step by a proper facility, the compound is processed into a forming material by a calendaring machine or an extruder in a state in which the compound is suppressed from being crosslinked and foamed.

[42] While it is preferred that the forming material use various synthetic resins such as ethylene vinyl acetate (EVA) having various vinyl acetate contents (VA%) and polyethylene (PE) having various densities, as its main raw material, the present invention is not limited to this example, and rather, various forming materials such as natural rubber and synthetic rubber which can be formed into products by various crosslinking methods can be optionally and selectively employed.

[43] It is sufficient that the forming material according to the present invention has a shape which is continuous in the lengthwise direction thereof. In this regard, while a specific limitation is not imposed on the shape of the forming material, it is preferred that the forming material have a uniformly smooth plane. It is more preferable that the forming material comprise a thin film having a fine surface roughness (or a thickness deviation). Therefore, in the event that the surface roughness of the processed forming material corresponds to that of a coarse sheet, it is preferable that the forming material be re-processed to have a surface roughness corresponding to that of a thin film having a fine surface roughness.

[44] If the forming material which is suppressed from being crosslinked and foamed and is continuous in the lengthwise direction thereof is prepared, in order to continuously crosslink the forming material, the forming material 10 is inputted into a continuous pressure crosslinking unit 200. Referring to FIG. 1, the continuous pressure crosslinking unit 200 according to the present invention preferably comprises a pair of metal belts 220 and 270 which are spaced apart from each other by a predetermined distance and which conduct orbital motions in opposite directions, and heating means 290 for continuously supplying heat to the metal belts 220 and 270.

[45] The heating means 290 serve as means for continuously supplying heat to the forming material 10 inputted into the continuous pressure crosslinking unit 200 and for crosslinking the forming material 10. Because it is sufficient that the heating means 290 appropriately supply heat to the metal belts 220 and 270 and appropriately crosslink the forming material 10 moved along with the metal belts 220 and 270 between the metal belts 220 and 270, the construction of the heating means 290 is not limited to a specific one.

[46] The metal belts 220 and 270 simultaneously serve as means for moving the inputted continuous forming material 10, means for appropriately transferring heat supplied from the heating means 290 to the forming material 10 and crosslinking the forming material 10, and means for suppressing the foaming of the continuously crosslinked forming material using the tensioning force of the metal belts 220 and 270. The thickness of the metal belts 220 and 270 is not specifically limited so long as appropriate tensioning force can be applied. Also, since the width of the metal belts 220 and 270 can be adequately changed depending upon the size of the inputted forming material, the width of the metal belts 220 and 270 is also not specifically limited. However, it is preferred that the width of the metal belts 220 and 270 be greater than that of the inputted forming material 10. It is preferred that, as shown in the drawing, the metal belts 220 and 270 be driven by upper rollers 212 and 214 and lower rollers 262 and 264 which are rotated in opposite directions. Since this construction is well known in the art, detailed description thereof will be omitted herein.

[47] Meanwhile, the thickness of the inputted forming material is not specifically limited. The present invention does not exclude the case in which a plurality of forming materials is simultaneously inputted. It is preferred that the continuous pressure crosslinking unit according to the present invention be provided with height adjustment means 230 and 240 for appropriately adjusting the spacing between the metal belts 220 and 270 facing each other.

[48] Also, in the present invention, in addition to the metal belts 220 and 270 serving as means for preventing the forming material from being foamed in the crosslinking process, means for pressing at least one belt selected from the metal belts 220 and 270 may be further provided as means for externally supporting the tensioned state of the metal belts 220 and 270 which is maintained by the tensioning force of the metal belts 220 and 270 themselves. In this regard, FIG. 1 illustrates an example in which squeezing means 280 are provided to both of the metal belts 220 and 270.

[49] In the case where the squeezing means 280 according to the present invention are further provided, it is preferred that the squeezing means 280 be positioned as close as possible to the metal belts 220 and 270 so that the metal belts 220 and 270 can effectively control the foaming phenomenon of the forming material. While the construction of the squeezing means 280 is not specifically limited, it is preferred that the squeezing means 280 be formed in the shape of a plate having a predetermined thickness to uniformly squeeze the metal belts 220 and 270. If the squeezing means 280 is formed in the shape of a plate, when considering heat transfer, it is preferred that the heating means 290 be installed inside the squeezing means 280.

[50] In the continuous pressure crosslinking step, as can be readily seen from FIG. 3, while the continuous forming material 30 inputted between the metal belts 220 and 270 of the continuous pressure crosslinking unit 200 is moved along with the metal belts 220 and 270, the continuous forming material 30 continuously receives heat from the heating means 290 to be continuously crosslinked. That is to say, as the metal belts 220 and 270 are moved, the forming material 30 is also moved in a state in which the forming material 30 is captured in the space defined between the metal belts 220 and 270. While the forming material 30 is moved, the entire forming material 30 is uniformly crosslinked by the heat ΔQ continuously transferred from the heating means 290. Further, foaming of the forming material 30 which is continuously crosslinked is suppressed by the pressure ΔP which is continuously applied by the tensioning force of the metal belts 220 and 270 (and the additionally provided squeezing means 280).

[51] FIG. 3 illustrates the case in which the squeezing means additionally provided to more appropriately suppress the foaming phenomenon of the forming material continuously squeezes the metal belts 220 and 270 toward each other. Unlike this arrangement, in the present invention, it can be envisaged that the crosslinked forming material is pressed only by the tensioning force of the metal belts 220 and 270.

[52] As the forming material continuously crosslinked between the metal belts 220 and

270 which are continuously squeezed by constant pressure is moved out of the metal belts 220 and 270 and is naturally exposed to the external environment, the forming material is continuously foamed as shown in FIG. 4. In other words, as the forming material is continuously moved out of the metal belts 220 and 270 which are maintained in a constantly tensioned state, the pressurized state of the forming material is instantaneously released, and the forming material is continuously produced as a foam 50.

[53] Since the foam produced through the continuous foaming step is naturally formed under the outer circumstances, the surface of the foam may not be smooth but be rough to some extent. In this regard, in the present invention, it can be envisaged that a continuous forming step for planarizing the surface of the continuously produced foam is implemented to obtain a planarized foam as shown in FIG. 5.

[54] Referring to FIGs. 1 and 5, it is preferred that the continuous forming step be im- plemented using a forming roller section 300 composed of a pair of rollers 312 and 314 which are spaced apart from each other by a predetermined distance and are rotated in opposite directions. In this case, it is more preferred that, similarly to the continuous pressure crosslinking unit, the forming roller section 300 be provided with roller spacing adjustment means 330 for adjusting the spacing between the rollers 312 and 314 facing each other in consideration of the thickness of the foam.

[55] Also, in the present invention, as shown in FIG. 6, in order to effectively protect the surface of the continuous foam from the outer circumstances, the step for depositing a surface protective layer 1 on at least one surface of the upper and lower surfaces of the foam can be further implemented. Since the material of the surface protective layer 1 is not specifically limited, a material optionally selected from a variety of materials, such as vinyl, a piece of the forming material, leather, etc. which are widely used for protecting the surface of foam in the art, can be used. Also, an adhesive can be used to appropriately couple the surface protective layer 1 to the surface of the foam.

[56] Since the surface protective layer 1 can be deposited on the surface of the foam at any time after the continuous foam is produced, it is possible to deposit the surface protective layer 1 after implementation of the continuous foaming step or the continuous forming step. Similarly to the forming step, it is preferred that the surface protective layer 1 be deposited using a deposition roller section 400 composed of a pair of rollers 412 and 414 which are spaced apart from each other by a predetermined distance and are rotated in opposite directions. It is more preferred that the deposition roller section 400 be provided with roller spacing adjustment means 430 for adjusting the spacing between the rollers 412 and 414 facing each other.

[57] On the other hand, the present invention provides a method for continuously producing a foam having a cavity structure of an optional sectional shape, which is different from the method for continuously pressure foaming a forming material as described above. The method according to this embodiment comprises the steps of processing forming materials, forming an interface, inputting the forming materials into a continuous pressure crosslinking unit, continuously pressure crosslinking the forming materials, and continuously foaming the resultant crosslinked forming materials. In the method according to this embodiment, the descriptions for the same features as those of the above-mentioned embodiment will be omitted.

[58] In the interface forming step, at least two forming materials which are suppressed from being crosslinked and foamed and are continuous in the lengthwise direction thereof are prepared, and the interface having a desired sectional shape is formed using an interface material on the surface of at least one of the prepared forming materials. The interface material serves to prevent physical and chemical coupling of the forming materials which face each other and sandwich the interface, in the step for con- tinuously pressure crosslinking the forming materials as will be described later. The interface material is not limited in terms of the substance and the shape thereof so long as the interface material can prevent the coupling of the forming materials in the pressure crosslinking step, so that the interface material may be formed of liquid having a predetermined viscosity, powder having a predetermined grain size, a solid substance such as a formed product or a film having a predetermined shape.

[59] The way of forming the interface material is not limited so long as the interface material can be formed on the surface of at least one forming material. For example, the interface material can be formed by printing, copying, coating, depositing, spraying, laminating, inserting, attaching, or a modification thereof. Also, the shape of the interface is completely optional and is not specifically limited. Further, when two or more interfaces are formed, all interfaces can be formed of the same interface material or different interface materials. At least one foaming agent may be selected from foaming agents which are the same as or different from the foaming agent contained in the forming material and be added to the interface material.

[60] FIG. 7 illustrates an example in which the interface is formed between the forming materials according to the present invention. In this example, two forming materials 20 which are processed in the lengthwise direction thereof are prepared, and an interface 120 having an optional shape is formed on the surface of one selected forming material. The following descriptions of manufacturing steps will mainly concentrate on this feature.

[61] If the step, wherein at least two forming materials which are suppressed from being crosslinked and foamed and are continuous in the lengthwise direction thereof are processed and an interface is formed on the surface of at least one forming material selected from the processed forming materials, is completed, in order to continuously crosslink the forming materials, as shown in FIG. 8, the forming materials 20 having the interface 120 are inputted into the continuous pressure crosslinking unit 200 of the device as shown in FIG. 1 to implement the step for continuously pressure crosslinking the forming materials 20.

[62] Referring to FIG. 9, in the forming materials 40 which are crosslinked while being moved along with the metal belts 220 and 270, crosslinking occurs inside the respective forming materials as well as on the surfaces of the forming materials facing each other. However, on the surface portions of the forming materials which are positioned on both surfaces of the interface 120 formed of the interface material, crosslinking of the forming materials does not occur due to the presence of the interface material. Accordingly, in the continuous pressure crosslinking step, except for the surface portions of the forming materials which are positioned on both surfaces of the interface 120, the forming materials 20 which are inputted in a separately processed state are continuously crosslinked to be integrated with each other as shown by the reference numerals 40 and 60, to experience the same process as the crosslinking of a single forming material.

[63] As the forming materials continuously crosslinked between the metal belts 220 and

270 which are continuously squeezed by constant pressure are moved out of the metal belts 220 and 270 and are naturally exposed to the external environment, the forming materials experience the continuous foaming step as shown in FIG. 10. In other words, as the forming materials 60 are continuously moved out of the metal belts 220 and 270 which are maintained in a constantly tensioned state, the pressurized state of the forming materials 60 is instantaneously released, and the forming materials 60 are continuously produced as a foam 80.

[64] When forming the foam, the portions of the forming materials, which are not coupled to each other due to the presence of the interface formed between the forming materials before the foaming step starts, are foamed while being expanded in volume at the same rate as the other portions of the foaming materials. However, since the portions of the forming materials which are not coupled to each other are foamed in a state in which they are separated from each other by the presence of the interface, three dimensional spaces each having a predetermined sectional shape are defined in the foam. Each space defined in the foam represents an internal cavity structure 160.

[65] FIG. 11 is a constructional view illustrating a continuous foam produced in accordance with the manufacturing procedure of this embodiment, and FIG. 12 is a cross-sectional view taken along the line A-A' of FIG. 11. The internal cavity structure 160 which is defined by an internal forming surface 162 is filled with a predetermined amount of gas (for example, N₂ or CO₂), which is produced by the resolving action of the foaming agent when foaming the forming materials and is not discharged out of the foam, whereby the internal space is maintained at predetermined pressure. The sectional shape and the construction of the inner cavity structure have no relation with the constructions and shapes of various manufacturing devices or facilities associated with foaming of the materials, such as molds and the likes. In the present invention, the sectional shape and the construction of the inner cavity structure can be controlled by variously changing the shape of the interface or the interface material.

[66] Meanwhile, since the foam produced through the continuous foaming step is naturally formed under the outer circumstances, the surface of the foam may not be smooth but be rough to some extent. In the present invention, it can be envisaged that a continuous forming step for planarizing the surface of the continuously produced foam is additionally implemented, and/or a surface protective layer is additionally formed. For these additional embodiments, the construction of the aforementioned embodiment can be applied as it is. [67] Moreover, this embodiment may further include the step of injecting or inserting gas containing air, liquid having a predetermined viscosity, powder, or solid substance having a predetermined shape into at least one selected from or all of the internal cavity structures of the foam produced through the continuous foaming step. In this regard, the solid substance having a predetermined shape includes a formed product. The introduction or insertion of a specific substance into the internal cavity structures is always possible after the continuous foaming step for defining the internal cavity structures is completed.

[68] In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.

Claims

[1] A method for continuously foaming a forming material, comprising the steps of: processing a forming material extending in a lengthwise direction thereof while suppressing the forming material from being crosslinked and foamed; inputting the continuous forming material between metal belts of a continuous pressure crosslinking unit comprising a pair of metal belts which are spaced apart from each other by a predetermined distance and conduct orbital motions in opposite directions in order to suppress the forming material from being foamed and heating means for continuously supplying heat to at least one selected from the metal belts; continuously crosslinking the continuous forming material which is interposed between and is moved along with the metal belts, using heat continuously transferred through the metal belts; and continuously foaming the forming material continuously moved out of the metal belts in a continuously crosslinked state.

[2] A method for continuously foaming a forming material, comprising the steps of: processing forming materials extending in a lengthwise direction thereof while suppressing the forming materials from being crosslinked and foamed; preparing at least two processed forming materials, and forming an interface having an optional pattern on a surface of at least one of the prepared forming materials, using at least one interface material, in order to prevent physical and chemical coupling of the forming materials; inputting the forming materials having the interface between metal belts of a continuous pressure crosslinking unit comprising a pair of metal belts which are spaced apart from each other by a predetermined distance and conduct orbital motions in opposite directions in order to suppress the forming materials from being foamed and heating means for continuously supplying heat to at least one selected from the metal belts; continuously pressure crosslinking the continuous forming materials which are interposed between and are moved along with the metal belts, using heat continuously transferred through the metal belts; and continuously foaming the forming materials continuously moved out of the metal belts in a continuously crosslinked state to produce a foam in which cavity structures each having an optional sectional shape are defined due to the presence of the interface.

[3] The method as set forth in claims 1 or 2, wherein the continuous pressure crosslinking unit further comprises vertical height adjustment means for adjusting a spacing between the metal belts depending upon a thickness of the inputted forming material.

[4] The method as set forth in claims 1 or 2, wherein the continuous pressure crosslinking unit further comprises squeezing means which squeezes at least one of the metal belts in order to suppress the forming material, which is crosslinked while being moved along with the metal belts, from being foamed.

[5] The method as set forth in claims 1 or 2, wherein the continuous forming material has the shape of a thin film.

[6] The method as set forth in claims 1 or 2, further comprising the step of: forming a continuous foam to planarize surfaces of the continuous foam by passing the continuous foam between rollers rotated in opposite directions after implementation of the continuous foaming step.

[7] The method as set forth in claim 6, wherein, in the forming step, the continuous foam is inputted between the rollers after a surface protective layer is coupled to at least one of upper and lower surfaces of the continuous foam.

[8] The method as set forth in claim 6, further comprising the step of: passing the continuously produced foam between different rollers which are rotated in opposite directions in a state in which a surface protective layer is coupled to at least one of upper and lower surfaces of the continuously produced foam after implementation of the forming step.

[9] The method as set forth in claim 2, wherein, in the interface forming step, the interface material comprises one selected from a group consisting of liquid or solid substance and a formed product having a predetermined shape.

[10] The method as set forth in claim 2, further comprising the step of: injecting or inserting at least one selected from a group consisting of gas, liquid or solid substance, and a formed product having a predetermined shape, into the internal cavity structure of the continuous foam after implementation of the continuous foaming step.