JP4939896B2 - POLYOLEFIN RESIN FOAM MOLDED BODY, ITS MANUFACTURING METHOD, AND SERVICE HOLE COVER USING SAME - Google Patents

Description

  The present invention relates to a polyolefin resin foam molded article, a method for producing the same, and a service hole cover using the same. More specifically, at least a portion of the polyolefin resin foam is heated and pressurized to heat and pressurize it to make the foam transparent and its manufacturing method, and to make the body door attached to the inner panel by making it transparent. The present invention relates to a service hole cover using an easy foam.

  Foams using polyolefin resins are used in various industrial fields because they are excellent in flexibility, cushioning properties and heat insulation properties. For example, it is used as a base material of an adhesive tape or as a heat insulating material. When used as a base material for adhesive tape, it is easy to attach to uneven walls using the flexibility of foam, but it has a transparent film-like base material such as cellophane tape. There was a problem that it was difficult to position the mounting position as compared with the tape.

  As such an example, in Patent Document 1, a double-sided pressure-sensitive adhesive sheet based on a soft foam is laminated on one side of a hard synthetic resin sheet, and on one half of the surface of the double-sided pressure-sensitive adhesive sheet on the hard synthetic resin sheet-side pressure-sensitive adhesive layer surface. There has been proposed an adhesive fastener characterized in that a removable adhesive layer is provided. In addition, an adhesive fastener is proposed in which the hard synthetic resin sheet is made of a transparent or translucent material. In this adhesive fastener, although the hard synthetic resin sheet is transparent, since the soft foam layer is not transparent, the transparency as a component is impaired. Therefore, it is necessary to provide a removable adhesive layer on the back surface. It has become. However, if re-peeling is repeated in order to determine the attachment position, there is a concern that dust or the like will adhere and the adhesive force will decrease. Therefore, when it is necessary to use foam for the purpose of heat insulation and buffering, and when it is necessary to install while adjusting the position, a laminated product in which the foam is laminated on the transparent film is used. It has been. In this case, it is necessary to apply an adhesive or cut it in accordance with a desired shape, and the work content is complicated, which may lead to an increase in cost. For this reason, for example, development of a polyolefin resin foam that has been made transparent, for example, entirely or partially has been eagerly desired so that it can be easily manufactured and the attachment position can be easily confirmed.

  However, even when trying to make the foam transparent, the foam generally has bubbles inside, and the resin that makes up the foam and the air in the bubbles have different refractive indexes of light. It is very difficult to do. Some of them have been developed as transparent or translucent foams, such as quartz glass, which is originally transparent within a very low expansion ratio, and foamed acrylic resin, etc. It is limited to. On the other hand, in the case of flexible foams, particularly polyolefin resin foams, foams that have been made entirely or partially transparent have not been proposed, and their development is eagerly desired.

  A plurality of work holes (service holes) are formed in the inner panel of the automobile door, and in order to prevent water from entering into the vehicle interior or the motor part such as a power window from this work hole, intrusion of dust and cold air, A service hole cover made of a synthetic resin film is installed (Patent Document 2). A door trim is disposed on the indoor side of the service hole cover, and the door trim is attached to the inner panel with a clip or a screw. The service hole cover is attached to a sealant such as butyl rubber previously set on the inner panel. At this time, the synthetic resin film constituting the service hole cover needs to be transparent in order to stick at a desired position, and polyolefin resins such as polyethylene and polypropylene are mainly used.

However, since these synthetic resin films have poor moldability, the service hole cover made of synthetic resin film is relatively large and deep in the uneven portions corresponding to the door pockets and speaker portions, so only the uneven portions are It was necessary to attach the one formed by vacuum forming or the like to a predetermined position. As a method for solving this problem, Patent Document 3 proposes a service hole cover manufactured by three-dimensionally molding a foamed plate obtained by molding foamed plastic into a plate shape and forming a convex portion or a concave portion. The service hole cover manufactured in this way has a relatively short manufacturing process and has become a foam from a film, which eliminates the need for sticking felt or the like on the back surface in order to improve hermeticity, and is simple and inexpensive. It is a thing. Moreover, there is a possibility that the chatter noise caused by the wind specific to the film can be reduced. However, when this service hole cover is attached to the inner panel of the vehicle door, since it does not have a transparent part, the installation position is difficult to understand, and installation work may be troublesome. Even if it is a hole cover, it will take time and effort in an attachment stage, and it may not lead to a cost reduction as a whole. As a countermeasure, it may be possible to fit not only the service hall but also the entire inner panel. However, even if it is easy to install, the size will increase, and it will be difficult to obtain cost merit.
Japanese Utility Model Publication No. 03-125037 Japanese Utility Model Publication No. 03-47225 JP-A-11-179797

  As described above, the problem to be solved by the present invention is to provide a foamed molded article that is at least partially transparent so that a desired mounting position becomes clear, and an optimal manufacturing method thereof, It is an object of the present invention to provide a service hole cover that can be easily attached and can prevent intrusion of rainwater, dust, cold air, and the like, using the obtained transparent foamed molded article.

As a result of sincerity studies in view of the above prior art, the present invention has been completed. That is, the present invention has the following configuration.
(1) At least a part of a polyolefin resin foam having a closed cell structure and a gel fraction of 5% or more and having a density of 300 kg / m ³ or less is heated and pressurized to be transparent. A polyolefin resin foam molded article characterized by
( 2 ) The polyolefin resin foam molded article according to (1) , wherein the polyolefin resin foam is cross-linked by ionizing radiation.
( 3 ) The polyolefin resin foam molded article according to (1) or (2) , wherein the total light transmittance of the transparentized part is 30% or more.
( 4 ) Making it transparent by heating and pressurizing at least a part of a polyolefin-based resin foam having a closed cell structure and having a gel fraction of 5% or more and a density of 300 kg / m ³ or less. A method for producing a polyolefin-based resin foam molded article.
( 5 ) The method for producing a polyolefin resin foam molded article according to ( 4 ), wherein the heating temperature is in the range of 50 to 200 ° C.
( 6 ) The method for producing a polyolefin resin foam molded article according to ( 4 ) or ( 5 ), comprising a step of vacuum molding and / or cutting the polyolefin resin foam.
( 7 ) The method for producing a polyolefin resin foam molded article according to any one of ( 4 ) to ( 6 ), wherein the polyolefin resin foam subjected to slice processing is used.
( 8 ) At least part of the polyolefin resin foam having a density of 300 kg / m ³ or less is heated and pressurized to be transparent, and at least part of the transparent part of the polyolefin resin foam is made of an automobile door. Service hole cover, which is bonded to the inner panel.
( 9 ) The service hole cover according to ( 8 ), wherein the polyolefin resin foam is a crosslinked foam having a closed cell structure and a gel fraction of 5% or more.
( 10 ) The service hole cover according to ( 8 ) or ( 9 ), wherein the polyolefin-based resin foam is cross-linked by ionizing radiation.
( 11 ) The service hole cover according to any one of ( 8 ) to ( 10 ), wherein the total light transmittance of the transparent portion is 30% or more.
( 12 ) The service hole cover according to any one of ( 8 ) to ( 11 ), manufactured by the method according to any one of ( 4 ) to (7).

  According to the present invention, since the polyolefin resin foam is partially transparentized, it is easy to attach to a desired mounting position, and it is not necessary to perform bonding with a film or the like. It leads to down. Furthermore, by applying this foamed molded product to the service hole cover, it is possible to prevent rainwater, dust, cold air, and the like from entering without deteriorating workability, to improve soundproofing performance compared to the film, and to be lightweight. Service hole cover can be provided.

Hereinafter, the present invention will be described in detail together with preferred embodiments.
The polyolefin resin foam used to obtain the foamed molded article of the present invention needs to have a density of 300 kg / m ³ or less. When the density of the foam exceeds 300 kg / m ³ , it is not preferable because the film thickness of the bubbles constituting the foam becomes thick, and it is difficult for bubbles to break by heating and compression, resulting in a decrease in transparency. . Further, if the density exceeds 300 kg / m ³ , the flexibility and lightness are remarkably lowered, and the texture as a foam is also impaired. The density of the foam is a value measured according to JIS K6767 (1999).

  Examples of the polyolefin resin used in the present invention include polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), poly-1-butene, 1, 2-polybutadiene and its hydrogenated product, polyisobutylene, random copolymer or block copolymer in any ratio of propylene and ethylene and / or 1-butene, polymethylpentene, cyclopentadiene and ethylene and / or propylene A cyclic polyolefin such as a copolymer of ethylene, and an ethylene-propylene-diene terpolymer having a diene component of 50% by weight or less at any ratio of ethylene and propylene, or ethylene or propylene and 50% by weight or less of, for example, vinyl acetate , Metak Examples thereof include random copolymers, block copolymers, graft copolymers, and the like with vinyl compounds such as alkyl alkyl esters, acrylic acid esters, aromatic alkyl esters, and aromatic vinyl. A mixture of more than one species can be used.

  The polymerization method of these polyolefin resins is not particularly limited, and any of a high pressure method, a slurry method, a solution method, a gas phase method, and the like may be used, and the polymerization catalyst is not particularly limited, such as a Ziegler catalyst or a metallocene catalyst. Absent. These polyolefin-based resins may be used in two or more if necessary, depending on the properties of the target resin composition and foam, or modified with carboxylic acid or the like for the purpose of imparting functions. It may be. However, care should be taken when mixing resins that are not sufficiently compatible, such as when homopolypropylene and polyethylene are mixed, because the heated and pressurized portions may become cloudy and the transparency may be reduced. In this case, the problem may be solved by using a propylene-ethylene copolymer in which a small amount of ethylene is copolymerized instead of homopolypropylene.

  These polyolefin-based resins preferably have a lower crystallinity because they are more transparent after heating and pressurization. For example, when polyethylene is used as the polyolefin-based resin, a low-density polyethylene having a low crystallinity yields a foamed molded product having a higher transparency than a high-density polyethylene having a high crystallinity. A polyethylene resin that is preferably 80% or less, more preferably 70% or less, and still more preferably 65% or less is preferable.

Polyolefin resin foam for use in the present invention, that have a closed cell structure. An open-cell foam is not preferable because the water stoppage may be lowered. For this reason, it is preferable that the closed cell ratio of a foam is 95% or more. The closed cell ratio of the foam is a value measured according to ASTM-D2856.

  The higher the tensile load and the tensile elongation of the polyolefin resin foam used in the present invention, the higher the better, since it is difficult to break when transparentized and the transparent part is difficult to break. On the other hand, if the tensile load is too high, it becomes difficult to make the foam transparent. Further, if the tensile elongation is low, the foam is easily broken, and therefore the tensile elongation is preferably 100% or more. The tensile load and tensile elongation of the foam were measured according to JIS K6767.

Further, the polyolefin resin foam for use in the present invention has a gel fraction of Ru more than 5% of the crosslinked foam der. This is because the use of a crosslinked foam reduces shrinkage and shape change when heated and pressurized during transparency. Gel fraction Ri der 5% or more, preferably 10% or more. The upper limit of the gel fraction is not particularly defined, but if it is too high, the heat resistance of the foam is increased, and it may be difficult to be transparentized by heating and pressurization, so it is preferably 60% or less. The gel fraction of the foam is a value measured as follows. About 50 mg of polyolefin resin foam finely cut to about 1 to 5 mm is precisely weighed and immersed in 25 ml of tetralin at a temperature of 130 ° C. for 3 hours, then filtered through a 200 mesh stainless steel wire mesh, washed with acetone, The insoluble matter on the wire mesh is vacuum dried. Next, the weight of this insoluble matter is precisely measured and calculated according to the following formula.
Gel fraction (%) = {weight of insoluble matter (mg) / weight of weighed polyolefin resin foam (mg)} × 100

  The polyolefin resin foam used in the present invention is preferably one produced by crosslinking using ionizing radiation. Examples of a method for obtaining a crosslinked polyolefin resin foam include a silane crosslinking method, a crosslinking method using an organic peroxide, and a crosslinking method using ionizing radiation, but the surface of the foam is not beautiful in the silane crosslinking method. For this reason, there is a possibility that there is a limit to the application to be used. In the crosslinking method using organic peroxide, the cell membrane thickness of the foam tends to be thick, and the conditions for transparency by heating and pressurization may be restricted. is there. In contrast, when ionizing radiation is used for crosslinking, the crosslinking process and the foaming process are independent, so the appearance of the foam is beautiful and the cell membrane is fine and uniform. It is most preferable because it can be easily made transparent when heated and pressurized, and the appearance of the obtained foamed molded article becomes good.

  Here, the degree of transparency in the present invention will be described. The object of the present invention is to produce a polyolefin-based resin foam molded article in which the attachment position can be easily determined. Therefore, it is necessary to have such transparency that the position to be attached can be seen through the transparent portion. Therefore, in the foamed molded article of the present invention, the total light transmittance of the transparent part is preferably 30% or more and 100% or less, more preferably 40% or more and 100% or less. When the total light transmittance is less than 30%, the transparency is lowered, which may cause a problem in determining the attachment position and the like, which is not preferable. The total light transmittance is measured according to the method A described in JIS K7105 (1981). Further, there may be a plurality of transparent parts, and the position of the transparent part is not particularly limited. When there are a plurality of transparent locations, the total light transmittance may be different depending on each location.

  Moreover, in order to satisfy various required characteristics, various conventionally known additive components may be added to the polyolefin resin foam used in the present invention as long as the effects of the present invention are not impaired. For example, as an additive, a crosslinking aid having a plurality of unsaturated bonds in the molecule to facilitate crosslinking, an organic peroxide, an antioxidant for preventing deterioration of the foam during heating, Lubricant, heat stabilizer, pigment, flame retardant, flame retardant aid, antistatic agent, nucleating agent, plasticizer, antibacterial agent, foaming agent decomposition accelerator, light stabilizer, ultraviolet absorber, You may add an antiblocking agent, a filler, a deodorizer, a thickener, a foam stabilizer, a metal harm prevention agent, etc. individually or in combination of 2 or more types.

  Examples of the shape of the polyolefin-based resin foam used in the present invention include various shapes such as a sheet shape, a block shape, and a particle shape, and a sheet-like foam is most preferable.

  The polyolefin-based resin foam molded article of the present invention may be partially or entirely on a sheet-like material such as a film or a sheet, a fabric-like material such as a knitted fabric or a non-woven fabric, if necessary, or if the transparency is not impaired. What stuck natural leather etc. may be used.

Regarding the polyolefin resin foam used in the present invention, in the polyolefin resin foam molded article according to the present invention, a crosslinked foam is used as described above. However, in the service hole cover according to the present invention, there is no use. It is also possible to use a crosslinked foam. Such a method for producing a polyolefin resin foam used in the present invention can be produced by a conventionally known production method. In the case of non-crosslinked foams, a predetermined amount of a pyrolytic foaming agent such as sodium hydrogen carbonate or azodicarbonamide, or a physical foaming agent such as carbon dioxide gas, chlorofluorocarbon, or volatile hydrocarbon is blended in a polyolefin resin, and a circular die is obtained. It can be manufactured by further extruding and foaming. In the case of a cross-linked foam, for example, a polyolefin resin, a thermally decomposable foaming agent, and various additives are uniformly mixed, melt-kneaded, formed into a long sheet, and then irradiated with ionizing radiation or pre-blended By decomposing organic peroxide such as dicumyl peroxide, the polyolefin resin is cross-linked, and by contacting it with hot air or heat medium, foaming is achieved by decomposing the pyrolytic foaming agent. The body can be manufactured. The cross-linked foam is preferable because the surface is smoother than the non-cross-linked foam. Moreover, the density of a foam can be made into the target value by optimizing the compounding quantity and kind of a foaming agent, the heating temperature at the time of foaming, and a crosslinking degree in a crosslinked foam.

Next, the manufacturing method of the polyolefin-type resin foam molding of this invention is demonstrated.
The polyolefin resin foam molded article of the present invention is a crosslinked foam having a closed cell structure and a gel fraction of 5% or more, and heating at least a part of the polyolefin resin foam having a density of 300 kg / m ³ or less, It is manufactured by making it transparent by pressurizing it.

  The method for heating the polyolefin resin foam may be a conventionally known method, and is not particularly limited, for example, heating with an infrared heater or oven, heating with a heated heating medium, heating with a high frequency welder, or the like. The place to heat may be the whole or only the place which wants to be transparent.

  The temperature at which the polyolefin resin foam is heated needs to be appropriately determined depending on the thickness of the foam, the desired transparency, the resin to be used, the heating time, the pressure at the time of pressurization, etc. It is in the range of ° C. When the temperature is lower than 50 ° C., it is necessary to pressurize at a very high pressure, and only a resin having a relatively low melting point can be used, and the heat resistance of the obtained polyolefin-based resin foam molded article may be lowered, which is not preferable. . On the other hand, if it exceeds 200 ° C., the energy required for heating is increased, and the surface properties of the obtained foamed molded article may be deteriorated.

  As a method for pressurizing the polyolefin resin foam, a conventionally known method may be used, and examples thereof include pressurization using a vertical or horizontal press.

The pressure at the time of pressurizing the polyolefin resin foam also needs to be appropriately determined depending on the thickness of the foam, the desired transparency, the resin to be used, the heating time, the temperature at the time of heating, etc., but 1000 kg / cm ² The following is preferable. If it exceeds 1000 kg / cm ² , damage to the foam is large, and the surface property of the polyolefin resin foam molded article may be deteriorated, or the part to be transparent may be broken, which is not preferable.

  The method for heating and pressurizing the polyolefin-based resin foam is not particularly limited, and may be performed simultaneously using a heated iron plate or the like, or may be rapidly pressurized after being heated once.

  The thickness of the polyolefin resin foam depends on the thickness and shape of the target polyolefin resin foam and the density of the foam, but if it is too thick, it is difficult to make it transparent, and if it is too thin Since the strength of the transparent portion may be insufficient, it is preferably in the range of 0.1 to 10 mm.

  In the process of heating and pressurizing the polyolefin resin foam to produce the polyolefin resin foam molded article, it is a very preferable aspect that a process of cutting such as vacuum molding or trimming is included. As such an example, there is a method in which a foam is heated and vacuum-formed into a desired shape, and at the same time, only a necessary portion is pressurized to be transparent. Instead of vacuum forming, press forming such as plug assist or blow molding may be used. Furthermore, there is a method of heating the foam and pressurizing only the necessary part to make it transparent, and simultaneously cutting the unnecessary part using a Thomson blade or the like. By using these methods, productivity is greatly improved, and a foamed molded product can be produced at a very low cost.

  Moreover, it is one of the preferable aspects to use the polyolefin resin foam by which the slice process was carried out. The polyolefin resin foam has a skin layer on the surface layer, and the surface layer portion is generally higher in density than the inner layer portion. Therefore, even if an attempt is made to make it transparent by heating and pressing under the same conditions, Those having a layer are less transparent. For this reason, when a foam obtained by slicing the foam in advance and removing the skin layer is used, the transparency can be relatively easily achieved. If the conditions may vary depending on the presence or absence of the surface layer, it is preferable to make the foam into half-cut slices because the foam can always have a surface layer on one side, and the conditions can be made constant.

  The higher the tensile load and the tensile elongation of the polyolefin-based resin foam molded article of the present invention, the higher the tensile strength and the tensile elongation, which are preferable because they are less likely to be broken when attached to a car door as a service hole cover. The tensile load and tensile elongation of the foamed molded product have a certain degree of correlation with the tensile load and tensile strength of the foam before molding. Therefore, in order to increase the tensile load of the foamed molded product, It is necessary to increase the load. However, if it is too high, it becomes difficult to make it transparent as described above. Further, if the tensile elongation is low, the foamed molded product tends to be broken. Therefore, the tensile elongation is preferably 70% or more, and more preferably 100% or more.

  Next, a service hole cover using the polyolefin resin foam molded article of the present invention will be described with reference to the drawings.

The service hole cover 1 of the present invention is manufactured from a polyolefin resin foam having a density of 300 kg / m ³ or less. When the density of the foam exceeds 300 kg / m ³ , it is not preferable because the film thickness of the bubbles constituting the foam becomes thick, and it is difficult for bubbles to break by heating and compression, resulting in a decrease in transparency. . Further, if the density exceeds 300 kg / m ³ , the flexibility and lightness are remarkably lowered, and the texture as a foam is also impaired. In addition, the density of a foam is the value measured according to JISK6767 (1999).

  Examples of the polyolefin resin used in the present invention include polypropylene (PP), high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), poly-1-butene, 1, 2-polybutadiene and its hydrogenated product, polyisobutylene, random copolymer or block copolymer in any ratio of propylene and ethylene and / or 1-butene, polymethylpentene, cyclopentadiene and ethylene and / or propylene A cyclic polyolefin such as a copolymer of ethylene, and an ethylene-propylene-diene terpolymer having a diene component of 50% by weight or less at any ratio of ethylene and propylene, or ethylene or propylene and 50% by weight or less of, for example, vinyl acetate , Metak Examples thereof include random copolymers, block copolymers, graft copolymers, and the like with vinyl compounds such as alkyl alkyl esters, acrylic acid esters, aromatic alkyl esters, and aromatic vinyl. A mixture of more than one species can be used.

  The polymerization method of these polyolefin resins is not particularly limited, and any of a high pressure method, a slurry method, a solution method, a gas phase method, and the like may be used, and the polymerization catalyst is not particularly limited, such as a Ziegler catalyst or a metallocene catalyst. Absent. These polyolefin resins may be used in two types if necessary depending on the properties of the target resin composition and foam, or modified with a carboxylic acid or the like for the purpose of imparting a function. It may be. However, care should be taken when mixing resins that are not sufficiently compatible, such as by mixing homopolypropylene and polyethylene, because the heated and pressurized portions may become cloudy and the transparency may be reduced. In this case, the problem may be solved by using a propylene-ethylene copolymer obtained by copolymerizing a small amount of ethylene instead of homopolypropylene.

  These polyolefin-based resins preferably have a lower crystallinity because they are more transparent after heating and pressurization. For example, when polyethylene is used as the polyolefin-based resin, a low-density polyethylene having a low crystallinity yields a foamed molded product having a higher transparency than a high-density polyethylene having a high crystallinity. A polyethylene resin that is preferably 80% or less, more preferably 70% or less, and still more preferably 65% or less is preferable.

  Among these polyolefin-based resins, by using a copolymer such as ethylene or propylene and 50% by weight or less of a vinyl acetate, alkyl methacrylate ester, acrylate ester or the like, the resulting foam has a high tensile elongation. Therefore, since the tensile elongation of the polyolefin resin foamed molded product obtained by making this transparent is also high, this is one of the preferred embodiments.

  The polyolefin resin foam used in the service hole cover 1 of the present invention preferably has a closed cell structure. An open-cell foam is not preferable because the water stoppage may be lowered. For this reason, it is preferable that the closed cell ratio of a foam is 95% or more. The closed cell ratio of the foam is a value measured according to JISK6767.

  In FIG. 1, a service hole cover 1 of the present invention is made transparent by vacuum-forming a polyolefin resin foam and then partially heating and pressurizing it, thereby facilitating attachment to an inner seal of an automobile door. FIG. 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1.

  The method for heating the polyolefin resin foam may be a conventionally known method, and is not particularly limited, for example, heating with an infrared heater or oven, heating with a heated heating medium, heating with a high frequency welder, or the like. The place to heat may be the whole or only the place which wants to be transparent.

  The temperature at which the polyolefin resin foam is heated needs to be appropriately determined depending on the thickness of the foam, the desired transparency, the resin to be used, the heating time, the pressure at the time of pressurization, etc. It is in the range of ° C. When the temperature is lower than 50 ° C., it is necessary to pressurize at a very high pressure, and only a resin having a relatively low melting point can be used, and the heat resistance of the obtained polyolefin-based resin foam molded article may be lowered. More preferably, the temperature is 90 ° C. or higher. On the other hand, when it exceeds 200 ° C., energy required for heating is increased, and the surface property of the obtained foamed molded article may be deteriorated. Therefore, it is not preferable, and it is more preferably 190 ° C. or lower.

  As a method for pressurizing the polyolefin resin foam, a conventionally known method may be used, and examples thereof include pressurization using a vertical or horizontal press.

The pressure at the time of pressurizing the polyolefin resin foam also needs to be appropriately determined depending on the thickness of the foam, the desired transparency, the resin to be used, the heating time, the temperature at the time of heating, etc., but 1000 kg / cm ² The following is preferable. If it exceeds 1000 kg / cm ² , damage to the foam is great, and the surface properties of the polyolefin resin foam molded article may be deteriorated, or the transparent portion may be torn.

  The polyolefin resin foam may be heated and pressurized simultaneously using a heated iron plate or the like, or may be heated quickly after being heated once.

  The thickness of the polyolefin resin foam depends on the thickness and shape of the target polyolefin resin foam and the density of the foam, but if it is too thick, it is difficult to make it transparent, and if it is too thin Since the strength of the transparent portion may be insufficient, it is preferably in the range of 0.1 to 10 mm.

  In order to clarify the attachment position to the inner seal, the part 2 that is partially transparentized by heating and pressurizing the polyolefin resin foam is preferably 30% or more, more preferably 40% or more. When the total light transmittance is less than 30%, the transparency is lowered, which may cause a problem in determining the attachment position and the like, which is not preferable.

  For the above reasons, it is preferable that the polyolefin resin used in the service hole cover 1 of the present invention has a lower crystallinity because it becomes more transparent after heating and pressurization. For example, when polyethylene is used as the polyolefin-based resin, a low-density polyethylene having a low crystallinity yields a foamed molded product having a higher transparency than a high-density polyethylene having a high crystallinity. A polyethylene resin that is preferably 80% or less, more preferably 70% or less, and still more preferably 65% or less is preferable.

  The polyolefin resin foam used in the service hole cover 1 of the present invention is preferably one produced by crosslinking using ionizing radiation. Examples of a method for obtaining a crosslinked polyolefin resin foam include a silane crosslinking method, a crosslinking method using an organic peroxide, and a crosslinking method using ionizing radiation, but the surface of the foam is not beautiful in the silane crosslinking method. For this reason, there is a possibility that there is a limit to the application to be used. In the crosslinking method using organic peroxide, the cell membrane thickness of the foam tends to be thick, and the conditions for transparency by heating and pressurization may be restricted. is there. In contrast, when ionizing radiation is used for crosslinking, the crosslinking process and the foaming process are independent, so the appearance of the foam is beautiful and the cell membrane is fine and uniform. It is most preferable because it can be easily made transparent when heated and pressurized, and the appearance of the obtained foamed molded article becomes good.

  The service hole cover 1 of the present invention is provided with a recessed portion 3 formed by vacuum forming or the like according to the shape of a part attached to a door trim or an inner panel. The recessed portion 3 can be a convex portion depending on the shape of the door trim or the inner panel. By having such a concave (convex) portion 3, the adhesion between the service hole cover and the inner panel can be improved. Moreover, in the service hole cover using the film of the conventional thermoplastic resin, the said part produced the molded product of the film separately, and this was often bonded. For this reason, it took time and effort to manufacture, but the service hole cover of the present invention can be easily formed by vacuum forming it. In addition to vacuum forming, press forming by plug assist or blow molding may be used.

In order to form the recessed portion 3 by vacuum forming or the like, the polyolefin resin foam used in the present invention is preferably a crosslinked foam having a gel fraction of 5% or more. This is because the use of a crosslinked foam reduces shrinkage and shape change when heated. The gel fraction is preferably 5% or more, more preferably 10% or more. The upper limit of the gel fraction is not particularly defined, but if it is too high, the heat resistance of the foam is increased, and it may be difficult to be transparentized by heating and pressurization, so it is preferably 60% or less. The gel fraction of the foam is a value measured as follows. About 50 mg of a polyolefin resin foam finely cut to about 1 to 5 mm is precisely weighed and immersed in 25 ml of tetralin at a temperature of 130 ° C. for 3 hours, then filtered through a 200 mesh stainless steel wire mesh and washed with acetone. The insoluble matter on the wire mesh is vacuum dried. Next, the weight of this insoluble matter is precisely measured and calculated according to the following formula.
Gel fraction (%) = {weight of insoluble matter (mg) / weight of weighed polyolefin resin foam (mg)} × 100

  The service hole cover 1 of the present invention is provided with a hole 4 for passing a harness or the like. The hole 4 can be easily formed by, for example, once forming a cylindrical shape by vacuum forming and then partially cutting it.

The service hole cover of the present invention may be partially or entirely covered with a sheet-like material such as a film or a sheet, a fabric-like material such as a knitted fabric or a non-woven fabric, or natural leather, if necessary. The thing which stuck together etc. may be used. In particular, by laminating a bulky sheet such as a non-woven fabric, the quietness in the passenger compartment can be improved, which is a preferred embodiment. As such a bulky nonwoven fabric, those having a basis weight of 600 g / m ² or less are preferable, and those made of fibers such as polypropylene and polyethylene terephthalate, urethane foams and the like are exemplified.

  Below, it demonstrates based on an Example. In the following examples and comparative examples, the light transmittance of the transparent part is in accordance with the method A described in JIS K7105 (1981), fully automatic direct reading haze computer HGM-2DP (C Measurement was performed using a light source). About the transparent part of the foaming molding, it injected and measured the light beam from the surface and the back surface, respectively, and the average value was made into the total light transmittance of a measuring object.

  The closed cell ratio of the foam was measured by an air pycnometer method described in ASTM-D2856 using an air comparison type hydrometer 1000 model manufactured by Tokyo Science Co., Ltd. The tensile strength and elongation of the foam were measured according to JISK6767. Moreover, the tensile strength and elongation of the foamed molded product were measured according to JISK6767. However, the shape of the sample was a strip shape having a width of 10 mm and a length of 60 mm or more, and the upper and lower two points of the sample were chucked, and the interval was adjusted to 40 mm. Here, adjustment was made so that the transparent portion was between the chucks.

[Production Example 1]
100 kg of low-density polyethylene with a density of 0.923 g / cm ³ (LE602 manufactured by Nippon Polyethylene Co., Ltd.), 11 kg of azodicarbonamide as a pyrolytic foaming agent, and Irganox manufactured by Ciba Specialty Chemicals Co., Ltd. as a thermal stabilizer 0.5 kg of 1010 was mixed uniformly with a Henschel mixer. Using a single screw extruder with a screw diameter of 150 mm, L / D = 34, the front half of the cylinder being set at 160 ° C. and the latter half at 140 ° C., with a discharge rate of 180 kg / h, a sheet thickness of 1.95 mm, A long sheet having a width of 310 mm was prepared. Both surfaces of this sheet are irradiated with an electron beam of 40 kGy at an acceleration voltage of 600 kV to crosslink the resin, and then continuously supplied to a hot air foaming furnace set at 240 ° C. and heated for about 5 minutes, A sheet-like foam was prepared, and the edge of the end was cut off and wound up so as to have a width of 1000 mm. The produced foam was a foam having a good appearance with a thickness of 4 mm, a density of 35 kg / m ³ , and a gel fraction of 23%. The obtained foam was cut in half so that the thickness was halved, and a foam having a skin surface on one side and a thickness of 2 mm was prepared. The obtained foam had a closed cell ratio of 98%, the foam had a breaking strength of 8N, and an elongation at break of 180%.

[Production Example 2]
In Production Example 1, a foam was prepared in the same manner except that the amount of pyrolytic foaming agent added was 0.9 kg, the thickness was 2.2 mm, the density was 350 kg / m ³ , the width was 300 mm, the gel content A foam with a rate of 25% was made. One side of the obtained foam was sliced by 0.2 mm to produce a foam having a skin surface on one side and a thickness of 2 mm. The obtained foam had a closed cell ratio of 99%, the foam had a breaking point load of 65 N, and the elongation at break was 250%.

[Production Example 3]
100 kg of an ethylene-vinyl acetate copolymer having a density of 0.940 g / cm ³ and a vinyl acetate content of about 18% (Ultrasen 3302 manufactured by Tosoh Corporation), 3.5 kg of azodicarbonamide as a pyrolytic foaming agent, As a heat stabilizer, 0.5 kg of Irganox 1010 manufactured by Ciba Specialty Chemicals Co., Ltd. was uniformly mixed with a Henschel mixer. Using a single screw extruder with a screw diameter of 150 mm, L / D = 34, the front half of which is set to 145 ° C. and the latter half to 130 ° C., a discharge thickness of 180 kg / h, a sheet thickness of 1.1 mm, A long sheet having a width of 550 mm was prepared. After irradiating an electron beam of 25 kGy at an acceleration voltage of 600 kV on both surfaces of this sheet to crosslink the resin, it is continuously supplied to a hot-air foaming furnace set at 240 ° C. and heated for about 5 minutes. A sheet-like foam was prepared, and the edge of the end was cut off and wound up so as to have a width of 1000 mm. The produced foam was a foam having a good appearance with a thickness of 2 mm, a density of 125 kg / m ³ , and a gel fraction of 29%. The obtained foam had a closed cell ratio of 99%, the foam had a breaking point load of 45 N, and the elongation at break was 500%.

[Example 1]
The foam prepared in Production Example 1 was cut into a length and a width of 30 cm × 30 cm, sandwiched from both sides by a metal plate having a width of 3 cm and a thickness of 1.5 mm, and fixed with a clip. This is put in an oven set at 125 ° C., heated for 1 minute and then removed from the oven. The tip is set at 125 ° C. using a cylindrical mold with a tip of 10 cm in diameter, and 100 kg / cm ² Was pressed for 30 seconds. After 30 seconds had elapsed, the pressure was released, removed from the press machine, and cooled for 30 seconds to prepare a polyolefin-based resin foam molded article partially transparent in a circular shape having a diameter of 10 cm.

  The produced foamed molded article was not torn, and the total light transmittance of this product was measured. As a result, it was 75% and had good transparency. The thickness of the transparent portion was 0.10 mm, the load at break was 7 N, and the elongation at break was 78%.

[Example 2]
The foam produced in Production Example 3 was cut into a length and width of 30 cm × 30 cm, and the pressure at the time of pressing was set to 20 kg / cm ² and the pressing time was set to 20 using a die heated at a tip portion temperature of 180 ° C. The press was performed in the same manner as in Example 1 except that the second was used. The produced foamed molded article was not broken, and the total light transmittance was measured. As a result, it was 65% and had good transparency. The thickness of the transparent portion was 0.13 mm, the load at break was 35 N, the elongation at break was 140%, and the mechanical strength was excellent.

[Comparative Example 1]
When the same work as in Example 1 was performed using the foam created in Production Example 2, the pressed circular part with a diameter of 10 cm showed a dent with respect to the original thickness of 2 mm, but the part Transparency was not enough. When the total light transmittance of this product was measured, it was 17%, and the transparency was not sufficient.

  According to the present invention, since the polyolefin resin foam is partially transparentized, it is easy to attach to a desired mounting position, and it is not necessary to perform bonding with a film or the like. It leads to down. Furthermore, by applying this foamed molded product to the service hole cover, it is possible to prevent rainwater, dust, cold air, and the like from entering without deteriorating workability, to improve soundproofing performance compared to the film, and to be lightweight. Service hole cover can be provided.

It is a top view of one embodiment of the service hole cover of the present invention. It is A-A 'sectional drawing of FIG.

Explanation of symbols

1 Service hole cover 2 Partially transparent part 3 Recessed part to avoid door trim and parts attached to inner panel 4 Hole for passing harness

Claims (12)

It is characterized in that at least a part of a polyolefin-based resin foam having a closed cell structure and a gel fraction of 5% or more and having a density of 300 kg / m ³ or less is heated and pressurized to be transparent. A polyolefin-based resin foam molding. The polyolefin resin foam molded article according to claim 1 , wherein the polyolefin resin foam is crosslinked with ionizing radiation. The polyolefin resin foam molded article according to claim 1 or 2 , wherein the total light transmittance of the transparent portion is 30% or more. It is made transparent by heating and pressurizing at least a part of a polyolefin resin foam having a closed cell structure and having a gel fraction of 5% or more and a density of 300 kg / m ³ or less. A method for producing a polyolefin resin foam molded article. The manufacturing method of the polyolefin resin foaming molding of Claim 4 whose heating temperature is the range of 50-200 degreeC. The manufacturing method of the polyolefin resin foam molding of Claim 4 or 5 including the process of vacuum-forming and / or cutting a polyolefin resin foam. The manufacturing method of the polyolefin resin foam molding in any one of Claims 4-6 which uses the polyolefin resin foam which carried out the slice process. At least a part of the polyolefin resin foam molded body having a density of 300 kg / m ³ or less is heated and pressurized to make the polyolefin resin foam molded body transparent, and at least a part of the transparent part is made into the inner panel of the automobile door. Service hole cover characterized by being bonded. The service hole cover according to claim 8 , wherein the polyolefin resin foam is a crosslinked foam having a closed cell structure and a gel fraction of 5% or more. The service hole cover according to claim 8 or 9 , wherein the polyolefin-based resin foam is cross-linked by ionizing radiation. The service hole cover according to claim 8 , wherein the total light transmittance of the transparent portion is 30% or more. The service hole cover according to any one of claims 8 to 11 , manufactured by the method according to any one of claims 4 to 7 .

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