JP2010190503A - Gasket for refrigeration storage device and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gasket for a refrigeration storage device having superior adhesiveness with a body part without degrading intrinsic flexibility of olefin elastomer, reducing man-hours in manufacturing by coextrusion of both materials, and further laminating a high-pressure process low-density polyethylene only on an optional position of the olefin elastomer as a base material in a thin film state. <P>SOLUTION: This gasket for the refrigeration storage device is mounted on a body or a door of the refrigeration storage device to form a refrigeration storage space inside of the refrigeration storage device. A molding obtained by extrusion molding is composed of the olefin elastomer, and a part as an outer face including an object closely-contact face where at least opposed flat faces are closely kept into contact with each other to provide a function for blocking the outside air, is coated with low-density polyethylene. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gasket for refrigerated storage equipment and a method for manufacturing a gasket for refrigerated storage equipment. Specifically, it is a gasket for a refrigerated storage device that is used by being fixed to either the main body or the door in order to improve the sealing performance at the fitting portion between the door and the main body of the refrigerated storage device such as a refrigerator or a showcase. The present invention relates to the modification of the surface of a gasket for refrigerated storage equipment in contact with the object plane. Hereinafter, the “gasket for refrigerated storage equipment” may be simply referred to as “gasket”.

  The gasket provided on the contact surface between the door and the body of refrigerated storage equipment such as refrigerators and showcases has a curved structure so that it can be easily expanded and contracted by the elasticity of the side surface. It has a mechanism that jumps to and comes into close contact with the steel plate that comes into contact as the objective surface. For the gasket having this complicated structure, an extruded product of a vinyl chloride elastomer having excellent moldability is suitably used.

  However, PVC elastomers have problems that they are easily impregnated with oil and fat components adhering to the surface and remain as dirt, and mold hyphae can easily enter and stick.

  In addition, there is a problem that scratches are easily generated when wiping off dirt and the like, and darkening is likely to be generated due to dust with a lot of oil.

  In addition, since PVC-based elastomers have a high frictional resistance, when using a shaft-rotating door, the contact position in a non-jumping state when it is struck by the attractive force of the built-in magnet on a steel plate objective contact surface Compared to the rotation, it contacts and adheres to the part shifted to the inside of the rotation. It was brewing.

  As a solution to such a problem, there has been a means of applying fluorine oil or paraffin wax to make it easy to move to a site that relieves the shearing load, but these applied products peel off during use. There was a problem that the effect could not be expected.

  On the other hand, the surface of the gasket molded product in contact with the objective plane has a low density (0.94 or less) polyethylene (high pressure method low density polyethylene) that is excellent in lubricity, difficult to absorb oils and fats, and has excellent lubricity. , LDPE) to solve the above problem.

  However, it is effective to use an olefin-based elastomer (TPO) that can be welded for the lamination of LDPE, but there is a large difference in melt viscosity when laminating these resins by coextrusion. There is a problem that it is difficult to form. For this reason, means for adhering after laminating separately extruded sheets has been used.

  For example, a manufacturing method of a composite high-pressure pipe in which a plurality of resins are laminated is described, and a lamination means by adhesion or fusion is proposed to a reinforcing layer in which a resin sheet subjected to stretch strengthening is spirally wound. (For example, refer to Patent Document 1).

  In addition, a lamination means has been proposed in which adhesive layers are provided on both surfaces of a drawn stretched thermoplastic polyester resin sheet and thermoplastic resins are sequentially extruded (see, for example, Patent Document 2).

  Furthermore, a means for integrating a surface layer of a thermoplastic urethane elastomer and a thermoplastic polyolefin elastomer by co-extrusion has been proposed (for example, see Patent Document 3).

Japanese Patent No. 4076440 JP 2008-105368 A JP 07-009546 A

  However, in order to obtain a laminate obtained by fusing both TPO and LDPE resins using the techniques described in Patent Documents 1 to 3, when coextruding low viscosity TPO onto a high viscosity LDPE extrudate. Therefore, it is difficult to reduce the thickness of the laminated molded product to a thin film by simple coextrusion, and the flexibility of the gasket is impaired. Therefore, before the gasket comes into contact with the object plane, there arises a problem that the certainty of adhesion due to jumping to the steel plate by the built-in magnet is impaired.

  In addition, forming (laminating) a thin film (10 μm) of dissimilar materials according to the prior art includes means for fusing the film. However, the number of manufacturing steps is increased, and uniform adhesion of the thin film is difficult, and bubbles tend to remain on the joint surface. This creates a new problem.

  In order to secure the adhesion with the objective contact surface of the gasket and to ensure the flexibility to mitigate the impact when the door is closed and the jumping performance to the steel plate surface by the built-in magnet, the thin film is coated only on the objective contact surface. It is important that the layers are stacked. However, when extruding gaskets by coextrusion, which is the most effective means for ensuring high adhesion without mixing bubbles, etc., for example, it is possible to laminate in a thin film state only on a limited area such as the objective contact surface It was difficult.

  In particular, when there is a large difference in melt viscosity between the TPO used as the base material and the LDPE used for lamination, when the thin film state of the LDPE to be laminated is secured, the corresponding fluid state is maintained so as not to generate a defective portion where no thin film exists. Thus, only a thick laminate having a thickness of several hundred μm could be obtained because it was necessary to keep the inside of the mold in high pressure.

  This invention was made in order to solve the above-mentioned problems, and provided with excellent adhesion to the main body portion without impairing the original flexibility of the olefin elastomer, and by coextruding both materials. In addition to reducing manufacturing man-hours, we provide high-pressure low-density polyethylene in a thin film state that can be laminated only at any position on the base olefin elastomer and a manufacturing method for refrigerated storage equipment gaskets. The purpose is to do.

  The gasket for refrigerated storage equipment according to the present invention is a gasket for refrigerated storage equipment that is attached to the main body or door of the refrigerated storage equipment so as to form a refrigerated storage space inside the refrigerated storage equipment, and is obtained by extrusion molding. The molded article is made of an olefin-based elastomer, and is formed by coating low density polyethylene on a portion that becomes an outer surface including an objective contact surface that provides a function of shielding the outside air by adhering at least opposite planes.

  The gasket for refrigerated storage equipment according to the present invention is a gasket for refrigerated storage equipment that is attached to the main body or door of the refrigerated storage equipment so as to form a refrigerated storage space inside the refrigerated storage equipment, and is obtained by extrusion molding. The molded product is made of an olefin-based elastomer, and is formed by coating low density polyethylene on a portion that becomes an outer surface including an objective contact surface that provides a function of shielding the outside air by adhering at least the opposed planes. In addition to providing excellent adhesion to the main body without compromising the inherent flexibility of olefin-based elastomers, in addition to reducing manufacturing man-hours by co-extrusion of both materials, high-pressure low-density polyethylene can be used as a substrate in a thin film state. It can be laminated only at an arbitrary position of a certain olefin-based elastomer.

The figure which shows Embodiment 1 and is a figure which shows an example of the gasket for refrigerators. FIG. 5 is a diagram showing the first embodiment, and is a conceptual diagram of a cross section in a portion where both TPO and LDPE resins flow in an extrusion mold (die) used for coextrusion molding in which LDPE is laminated only on an objective adhesion surface.

Embodiment 1 FIG.
First, an outline of the present embodiment will be described. A gasket used for a refrigerator (an example of refrigerated storage equipment) uses a vinyl chloride elastomer and has been characterized by being easy to extrude in addition to being inexpensive. On the other hand, vinyl chloride elastomers are subject to shearing force on revolving doors such as hinges because they are easily impregnated / deposited when oils and fats adhere, mold mycelium enters and contaminates, and because of their high friction coefficient. Since it is easily fixed as it is, there is a problem that a squeak noise at the time of release or a crack accompanied by embrittlement deterioration is likely to occur.

  In the present embodiment, for the purpose of improving low temperature embrittlement and antifouling properties, the surface of a gasket made of an olefin elastomer is coated with a high pressure method low density polyethylene excellent in non-absorbability such as oil and solvent and low friction coefficient. It relates to a gasket dealt with by this.

  The gasket is made of ultra-high molecular weight (over 1.5 million, preferably over 5 million) and low density (0.94 or less) polyethylene (high pressure method low density polyethylene, LDPE) on the surface of a molded product of olefin elastomer (TPO). Are laminated by coextrusion with a thin film of about 10 μm, and then the obtained extruded product is cut to an arbitrary length at an angle of 45 degrees, and these are heat-sealed and processed into a frame shape It is.

  The mold die to be used is one in which a second gate is arranged in the TPO extrusion molding path to provide an LDPE inlet so that both resins can be extruded simultaneously. In the portion where the second gate is disposed, the high-viscosity LDPE is pulled and stretched on the inner wall surface of the mold die to form a thin film state and laminated on the TPO molding surface.

  TPO is excellent in low-temperature brittleness compared to a vinyl chloride elastomer, and is suitable as a gasket (also referred to as packing) for a refrigerator or a showcase that maintains a low-temperature state. In addition, LDPE laminated on TPO is hygienic because it has excellent antifouling properties and is less likely to cause deposits due to dirt and mold adhesion.

  The LDPE laminated on the TPO has a low coefficient of friction on the surface of the molded product that comes into contact with the object surface, so that the load can be reduced even if the gasket is subjected to twisting or shearing distortion (position). Therefore, it is possible to secure a close mode in which stress corrosion cracking is unlikely to occur, and to reduce noise generated by sliding of the contact surface and the gasket at the time of release.

  In addition, LDPE disposed on the surface of the molded product exhibits excellent wear resistance and chemical resistance, and is effective in suppressing the growth of molds and the deposition of oils and fats.

  In addition, LDPE with extremely high viscosity is laminated on the surface of TPO as a thin film by coextrusion with TPO, so that excellent adhesiveness with the main body portion is maintained without impairing the original flexibility of TPO. I can do it.

  At this time, in addition to reducing the number of manufacturing steps by co-extrusion of both materials, LDPE can be laminated in a thin film state on TPO as a base material only at an arbitrary position, so that the sealing performance of the door is ensured. Does not impair important cushioning properties. There is no adverse effect such as reducing the adhesion of the gasket to the objective contact surface (less leakage of cold air).

  Regarding the molding of a gasket for a refrigerator in which LDPE is laminated on the surface of a molded product formed of TPO which is a base material according to the present embodiment, the molding method will be described in detail below.

  1 and 2 are diagrams showing Embodiment 1, FIG. 1 is a diagram showing an example of a gasket 10 for a refrigerator, and FIG. 2 is an extrusion molding metal used for coextrusion molding in which LDPE is laminated only on an object adhesion surface. It is a conceptual diagram of the cross section in the part into which both resin of TPO and LDPE of a type | mold (die) flows.

  In FIG. 1, a gasket 10 (gasket for refrigerated storage equipment) is attached to a heat insulating door of a refrigerator. The base portion 15 of the gasket 10 is fitted into the door sash of the heat insulating door, and the bag-like portion 12 containing the magnet jumps to and contacts the folded portion of the heat insulating box body by magnetic force. The base portion 15 and the bag-like portion 12 containing the magnet are connected by thin flexible portions 17A, 17B, and 17C having sufficient stretchability. The first fin 21 and the second fin 22 are connected to the flexible portion 17C, the first fin 21 abuts on the outer peripheral step portion side wall of the door inner plate, and the second fin 22 is the outer periphery of the door inner plate. It hangs on the flat part of the step part. The second fin 22 has a bag-like portion 23, which improves the heat insulating effect of this portion by contacting the box inside the box.

  The second fin 22 having the bag-like portion 23 attached in this way, however, is expected to fall into the door side due to variations in molding and its own weight, so that the bag-like portion 23 does not hit the box inside the box. The Therefore, the leg part 25 passed from the base part 24A of the bag-like part 23 in the second fin 22 to the first fin 21 is provided to prevent the door from falling down.

  At the same time, the tip of the second fin 22 is hung on the outer peripheral step flat portion of the door inner plate, thereby preventing the door from falling down. At this time, the amount by which the tip of the second fin 22 is hung on the door inner plate is long enough to be applied to the flat portion of the inner plate outer peripheral stepped portion so that the intended operation can be expected even if the inner plate is unevenly mounted. .

  Moreover, when the space | interval of a heat insulation door and a heat insulation box became narrow by dispersion | variation in mass production etc., the 2nd fin 22 bends in the base part 24B of the bag-like part 23 in the 2nd fin 22, and it is with a door inner board. The second fin 22 bends with the point where the contact is made as a fulcrum to prevent the door closing failure from occurring.

  As shown in FIG. 2, the extrusion mold 30 (mold die) is formed by providing an LDPE inlet 2 at an intermediate position of a resin inlet 1 into which TPO as a base material flows. Furthermore, a cooling compressed air injection pipe 3 for shaping and maintaining the shape of the cavity for the purpose of imparting flexibility and heat insulation is provided at an intermediate position of the internal space of the resin inlet 1 through which the resin flows, The structure which arranged the extrusion port 4 previously is comprised. Further, the injection pipe 3 is provided with an injection port 5 and an exhaust pipe 6 through which compressed air is fed for the purpose of preventing the hollow portion of the extruded molded product from contracting due to cooling.

  TPO colored alloyed rubbery polymer of high density PE and EP (ethylene propylene) adjusted to melting point 135 ° C. and MI (melt index) 4.5 g / 10 min is the resin inlet 1 at the tip of the mold. At an extrusion speed of 50 m / min, and an LDPE having a melting point of 130 ° C., MI of 0.8 g / 10 min, and a molecular weight of 3 million from the inlet 2 provided in the middle part of the die die at an extrusion speed of 2 m / min. It was made to flow.

  The olefin elastomer (TPO) is an alloyed product (high density PE) of ethylene propylene and an olefin resin.

  The gasket 10 is formed by arranging a magnet inside the contact portion (bag-like portion 12) that is an object contact surface with the refrigerator housing flange portion on the opposite side, and extends so as to jump to the flange portion of the housing when the door is closed. Need to be flexible. Therefore, the opening thickness of the LDPE inlet 2 provided at the middle position of the mold die (the thickness of the LDPE placed on the TPO (before being stretched)) is for the purpose of shielding the inflow of outside air into the refrigerator. The position (height) of the inflow port 2 was adjusted so that the surface portion disposed on the door and contacting the flange portion of the housing was 500 μm, and the surface portion exposed to the outside was 150 μm. Further, in order to maintain the shape of the gasket, the compressed air is fed into the hollow portion constituting the bag-like portion 12, the flexible portion 17, and the bag-like portion 23 containing the magnet of the gasket 10, thereby contracting due to cooling. Suppressed and promoted solidification of the molten resin.

  As a result, due to the speed difference provided in the extrusion speed of TPO and LDPE, the LDPE is stretched so as to be in close contact with the TPO in the mold, and the contact portion in close contact with the flange portion of the housing is exposed to about 20 μm. Sites corresponding to each of the surface portions could be laminated with a thickness of about 8 μm.

  Here, it is essential that the viscosity of LDPE with respect to TPO is significantly higher. When the viscosity of LDPE with respect to TPO is twice or less, stable stretching can be achieved regardless of the difference in extrusion speed. In addition, the thickness when laminated on the TPO is not uniform, and an appearance in which ripples are formed on the surface of the gasket 10 is not preferable.

  In addition, significantly increasing the extrusion rate ratio of TPO to LDPE can strengthen the tightness of the laminated state, and if the rate ratio is 5 times or less, the presence of bubbles on the contact surfaces of both materials or partial This causes a disadvantage that a suitable layering mode cannot be ensured, for example, it may cause an excessive peeling.

  In order to secure a strong lamination state, it is essential to raise the temperature of LDPE, and when the temperature of TPO is higher, the stretching effect on the contact surface with LDPE cannot be sufficiently achieved. Therefore, there is a problem that it is easy to be deformed at the time of reheating such as when performing edge welding, and a beautiful and smooth welding surface cannot be secured.

  In addition to eliminating the stacking fault caused by the above molding conditions, it is important to dispose LDPE only in a limited part in order to prevent the gasket 10 from jumping to the housing flange of the refrigerator. Thus, according to the present embodiment, it is only necessary to provide the extrusion port 4 at the portion of the die die corresponding to the portion where the LDPE is disposed in the die.

  At this time, if the melting temperature of TPO is lower than that of LDPE, it is difficult to simultaneously melt and maintain a desired shape by simultaneously extruding from the die during molding. For this reason, the amount of compressed air that flows into the injection tube 3 is adjusted, and the TPO is cooled slightly from the melting point so that the shape can be maintained, and a portion that comes into contact with the casing of the gasket 10 is included while being pulled out from the die. It is preferable to discharge and laminate the LDPE from the extrusion port 4 to the arbitrary position from the TPO at a temperature as high as about 30 ° C., for example, because the shape of the gasket 10 is maintained and the shape is not damaged by fusion.

  However, if it is attempted to obtain a thickness of the LDPE laminate of 50 μm or more at this time, the contact surface in the laminated portion excessively increases in temperature, thereby impairing the moldability, and it becomes difficult to maintain the shape described above. It is not preferable. Therefore, the thickness of the LDPE laminate is preferably 50 μm or less.

  The gasket co-extruded product obtained as described above is inserted into a bag-like portion 12 containing a magnet, and then the end is cut at 45 degrees with an arbitrary length through a hot plate. The hot plate is heated to a temperature equal to or higher than the melting point of both materials, and then the hot plate is pulled out, pressed and further cooled and solidified. By performing this operation on four end sides, a refrigerator gasket 10 was obtained.

  As described above, by laminating LDPE on a molded product based on TPO, which is an olefin elastomer, in a mold die, it is simpler than laminating by subsequent fusion that performs heating again. In addition, it is possible to suppress deformation of the base material due to heating, and it is possible to stack even a molded product having a complicated shape as in this embodiment.

  Furthermore, the greatest feature of the present embodiment is that it can be laminated at an arbitrary place. A thin film of 50 μm or less is used in the conventional means for bonding via an adhesive layer and the means for fusing both materials under the same conditions. However, it is difficult to easily stack the layers, but it can be arranged very easily.

  In addition, the LDPE disposed on the surface of the molded product exhibits excellent wear resistance and chemical resistance on the contact surface with the refrigerator housing, where the obtained gasket 10 is the most likely to be soiled. It effectively acts to suppress deposition, and has the characteristics of maintaining excellent antifouling properties.

  DESCRIPTION OF SYMBOLS 1 Resin inlet, 2 Inlet, 3 Injection pipe, 4 Extrusion port, 5 Inlet, 6 Exhaust pipe, 10 Gasket, 12 Bag-like part, 15 base part, 17A flexible part, 17B flexible part, 17C flexible part , 21 1st fin, 22 2nd fin, 23 bag-shaped part, 24A root part, 24B root part, 25 leg part, 30 mold for extrusion molding.

Claims (12)

A gasket for a refrigerated storage device that is attached to the main body or door of the refrigerated storage device so as to form a refrigerated storage space inside the refrigerated storage device,
The molded product obtained by extrusion molding is made of an olefin-based elastomer, and is coated with low-density polyethylene on the outer surface including the objective contact surface that gives the function of shielding the outside air by adhering at least the opposing flat surfaces. A gasket for refrigerated storage equipment.   2. The gasket for refrigerated storage equipment according to claim 1, wherein the olefin elastomer is an alloy of ethylene propylene resin and olefin resin.   The gasket for refrigerated storage equipment according to claim 1 or 2, wherein the low-density polyethylene has a high molecular weight of 1.5 million or more.   The said low density polyethylene is provided with the high molecular weight of 5 million or more, The gasket for refrigerator storage apparatuses of Claim 3 characterized by the above-mentioned.   5. The refrigerated storage device according to claim 1, wherein the low-density polyethylene is laminated on an olefin-based elastomer with a thickness of 50 μm or less in a state of being stretched twice or more. gasket.   Using the extrusion mold provided with a low-density polyethylene extrusion port at the part where the door or main body casing is in close contact with the objective, which forms the sealed structure of the casing, the low-density polyethylene is increased on the surface of the low-viscosity olefin elastomer. A method for producing a gasket for a refrigerator storage device, wherein a frame-shaped shape is formed by thermally fusing the edges of a co-extruded molded product from an extrusion port provided in an intermediate portion of an extrusion path of the extrusion mold in a viscosity state.   The method for producing a gasket for refrigerated storage equipment according to claim 6, wherein the low-density polyethylene has a melt viscosity twice or more that of an olefin elastomer and is subjected to coextrusion.   The refrigeration according to claim 6 or 7, wherein the co-extrusion of the low density polyethylene forms a flow rate relationship in the mold at a speed of 1/5 or less of that of the olefin elastomer forming the base material. Manufacturing method for gaskets for storage equipment.   The method for producing a gasket for refrigerated storage equipment according to claim 6 or 7, wherein the co-extrusion of the low-density polyethylene is performed under conditions that do not lower the extrusion temperature of the olefin-based elastomer near the melting point.   The method for producing a gasket for refrigerated storage equipment according to claim 6, wherein the extrusion port of the low density polyethylene is performed using an extrusion die provided at a portion corresponding to the close contact surface of the objective plane.   The extrusion port of the low density polyethylene is provided at a portion having a state in which an olefin elastomer as a base material is molded into an arbitrary shape in a molten state in a mold. The manufacturing method of the gasket for refrigerator storage apparatuses as described in 2 ..   The four-side heat fusion is performed by cooling and solidifying in a state where the base plate and the surface layer are melted by end-side pressure bonding to the hot plate and then the hot plate is pulled out and pressed. Manufacturing method of gasket for refrigerated storage equipment.

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