JP4901504B2 - Laminated foam sheet and method for producing the same - Google Patents

Description

  The present invention relates to a laminated foam sheet and a method for producing the same.

  Conventionally, a polypropylene-based resin foam sheet has been widely used as a curing sheet, an assembly box, a partition material, a container for electrical parts and electronic parts. However, because polypropylene resin is highly charged due to friction and the like, dust adheres to the surface of the polypropylene resin foam sheet, dirt is noticeable, or electrical and electronic components are damaged due to charged charges. In view of this, it is generally performed to impart antistatic performance to the polypropylene resin foam sheet.

  In order to impart antistatic performance to the polypropylene resin foam sheet, conventionally, a low molecular weight surfactant such as a monoglycerin ester has been added. The antistatic performance of the sheet is affected by the humidity in the air, changes depending on the season, or has a problem that the antistatic performance is impaired by washing.

  In recent years, in order to solve the above-described problems, a polymer type antistatic agent has been provided, and an antistatic property of a polypropylene resin foam sheet has been achieved using this antistatic agent. Specifically, in Patent Document 1, in a laminated foam in which a synthetic resin layer is laminated on at least one surface of a polyolefin resin foam sheet, one or more layers having a polyolefin resin as the outermost layer of the synthetic resin layer A laminated foam is proposed in which a polymer type antistatic agent is contained in the outermost layer so that the surface resistivity is a predetermined value or less, and this laminated foam is produced by a coextrusion foaming method. It is described that it may be.

  However, in the production using the co-extrusion method, the above laminated foam has a difference between a temperature suitable for extrusion foaming of a polyolefin resin and a temperature suitable for extrusion of a synthetic resin layer. Since the temperature range suitable for foaming of the resin itself is relatively narrow, it is difficult to optimize the extrusion foaming temperature of the polyolefin resin due to the influence of the resin temperature of the synthetic resin layer. There was a problem that it was difficult to increase the expansion ratio of the resulting polyolefin resin foam sheet, and the laminated foam lacked its lightness.

  In addition, it is conceivable to increase the amount of the foaming agent contained in the polyolefin resin, but as the foaming agent increases, the plasticization of the polyolefin resin proceeds and the temperature suitable for foaming the polyolefin resin decreases. The difference between the extrusion temperature of the synthetic resin layer and the temperature suitable for extrusion foaming of the polyolefin resin is further increased, the extrusion foamability of the polyolefin resin is decreased and the expansion ratio of the polyolefin resin foam sheet is increased. There existed a problem that it fell, and the lightweight property of a laminated foam will fall.

  Furthermore, similarly to Patent Documents 2 to 5, a laminated foam in which a polyolefin resin layer containing an antistatic agent is laminated and integrated on at least one surface of a polyolefin resin foam sheet is produced by coextrusion foaming. However, it has the same problems as described above.

JP 2003-136651 A JP 2004-269660 A JP 2004-181933 A JP 2005-74771 A JP 2004-224039 A

  The present invention reduces the difference between the temperature suitable for extrusion foaming of the polypropylene resin and the extrusion temperature of the antistatic resin composition constituting the antistatic layer, and optimizes the extrusion foaming of the polypropylene resin. The present invention provides a laminated foam sheet having a high foaming ratio of a resin foam sheet and excellent in lightness and antistatic performance and a method for producing the same.

  The method for producing a laminated foamed sheet according to the present invention comprises supplying a polypropylene resin to a first extruder and melt-kneading it in the presence of a foaming agent to obtain a foamable polypropylene resin. On the other hand, an ethylene-propylene random copolymer A polyolefin resin containing 50 to 90% by weight, high density polyethylene 10 to 50% by weight, ethylene-propylene block copolymer and / or propylene homopolymer 0 to 20% by weight, and an antistatic agent. The antistatic resin composition is supplied to the second extruder, melted and kneaded, and the foamable polypropylene resin and the antistatic resin composition are supplied to the mold connected to the first and second extruders. A cylindrical foam layer formed by coextrusion foaming from the above mold and foaming a foamable polypropylene resin, and an antistatic layer laminated and integrated on the inner surface of the foam layer To produce a tubular foam body comprising a tubular antistatic layer consisting of fat composition, characterized in that deploying the tubular foam cylindrical on cooling is supplied to the mandrel foam.

  The polypropylene resin supplied to the first extruder is not particularly limited as long as it is used for extrusion foaming. For example, a propylene homopolymer, a copolymer of propylene and another olefin copolymerizable therewith Polypropylene resins containing 20 to 100% by weight of high melt tension polypropylene resins having long chain branches are preferred because of their excellent foamability (for example, Japanese Patent No. 2521388 and Japanese Patent Application No. 11-346797). As described). In addition, a polypropylene resin may be used independently or 2 or more types may be used together, and a polyolefin-type thermoplastic elastomer may be added to a polypropylene resin in order to improve impact resistance.

  Examples of the olefin copolymerizable with propylene include ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, and 1-heptene. And ethylene or an α-olefin having 4 to 10 carbon atoms, such as 3-methyl-1-hexene. The copolymer of propylene and another olefin copolymerizable therewith may be a random copolymer or a block copolymer, and further, not only a binary copolymer but also a ternary. A copolymer may also be used.

  Further, the content of the copolymer of propylene and other olefin copolymerizable with the propylene in the polypropylene resin is preferably 25% by weight or less, more preferably 15% by weight or less. Further, the content of the other olefin in the copolymer of propylene and another olefin copolymerizable therewith is preferably 0.5 to 30% by weight, and more preferably 1 to 10% by weight.

  The foaming agent supplied to the first extruder and melt-kneaded with the polypropylene resin is not particularly limited as long as it is used for extrusion foaming. For example, propane, butane, pentane, etc. Aliphatic hydrocarbons; 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), 2-chloro-1,1,1,2-tetrafluoro Examples include chlorofluorocarbon blowing agents such as ethane (HCFC-124), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), and aliphatic hydrocarbons are preferable. . In addition, a foaming agent may be used independently or may be used together.

  On the other hand, the antistatic resin composition that is supplied to the second extruder and melt-kneaded is an ethylene-propylene random copolymer of 50 to 90% by weight, a high-density polyethylene of 10 to 50% by weight, and an ethylene-propylene block copolymer. A polyolefin resin containing 0 to 20% by weight of a polymer and / or a propylene homopolymer, and an antistatic agent are contained.

  If the content of the ethylene-propylene random copolymer in the polyolefin resin constituting the antistatic resin composition is small, the heat resistance of the antistatic layer is lowered and the residual strain in the laminated foam sheet is removed. During the annealing treatment, the antistatic layer melts or the surface of the antistatic layer is deformed. On the other hand, if it is large, the crystallization rate of the ethylene-propylene random copolymer after being extruded from the mold is lowered, and the mandrel Since the degree of crystallinity of the ethylene-propylene random copolymer at the time when it reaches the point, the stickiness remains in the antistatic layer and the slipperiness on the mandrel is lowered, it is limited to 50 to 90% by weight, 60 to 80% % By weight is preferred.

  If the content of the ethylene component in the ethylene-propylene random copolymer is small, the crystallization speed increases and it may be difficult to lower the extrusion temperature. On the other hand, if the content is large, the crystallization speed decreases. Therefore, the slippage of the mandrel may be reduced, so 1.5 to 6.0% by weight is preferable.

  Further, if the content of the high density polyethylene in the polyolefin resin constituting the antistatic resin composition is small, the crystallization rate of the ethylene-propylene random copolymer after being extruded from the mold is lowered. When the ethylene-propylene random copolymer reaches the mandrel, the degree of crystallinity of the ethylene-propylene random copolymer is insufficient, the stickiness remains in the antistatic layer, and the slipping property on the mandrel decreases. In addition, since the antistatic layer melts or the surface of the antistatic layer is deformed during the annealing process for removing the distortion remaining in the laminated foamed sheet, the amount is limited to 10 to 50% by weight, and 10 to 20% by weight. Is preferred.

  Furthermore, in the polyolefin-type resin which comprises the said antistatic resin composition, either the ethylene-propylene block copolymer or the propylene homopolymer, or both may contain as needed. Therefore, the antistatic resin composition may not contain both the ethylene-propylene block copolymer and the propylene homopolymer.

  When one or both of the ethylene-propylene block copolymer and the propylene homopolymer is contained in the polyolefin resin, the total content of the ethylene-propylene block copolymer and the propylene homopolymer is large. If the extrusion temperature of the antistatic resin composition cannot be lowered and the extrusion temperature is lowered in accordance with the proper extrusion foaming temperature of the expandable polypropylene resin, fine convexes are formed on the surface of the obtained antistatic layer. Part may occur and the appearance may be deteriorated, so 20% by weight or less is preferable, 5 to 20% by weight is more preferable, and 5 to 15% by weight is particularly preferable.

  The antistatic agent constituting the antistatic resin composition is preferably a polymer antistatic agent. Examples of such a polymer antistatic agent include polyethylene oxide, polypropylene oxide, polyethylene glycol, polyesteramide, Polyester ester amide, ionomer such as ethylene-methacrylic acid copolymer, quaternary ammonium salt such as polyethylene glycol methacrylate copolymer, olefin block and hydrophilic block described in JP-A No. 2001-278985 Examples thereof include block copolymers having a structure in which they are alternately and alternately bonded. In the present invention, compatibility with ethylene-propylene random copolymers, dispersibility, and antistatic performance for ethylene-propylene random copolymers. In addition to providing effect, laminated foamed sea In consideration of appearance and thermoformability, polymeric antistatic agent and an olefin based block and a hydrophilic block contains a block copolymer having a structure bonded to repeated alternately more than 50% by weight. For the purpose of further improving the antistatic performance, polyamide is added to a block copolymer having a structure in which olefinic blocks and hydrophilic blocks are alternately and repeatedly bonded, or olefinic blocks and hydrophilic blocks are added. In the block copolymer having a structure in which is repeatedly bonded alternately, a polyamide-based block component may be contained.

  As described above, a polymer type antistatic agent is preferably used as the antistatic agent, but in order to enhance the antistatic effect, an anionic interface such as an alkylbenzene sulfonate such as sodium dodecylbenzenesulfonate is used. An activator, other surfactants or alkali metal salts may be used in combination.

  The polymer type antistatic agent preferably contains 50% by weight or more of a block copolymer having a structure in which olefinic blocks and polyether blocks containing 70 mol% or more of propylene are alternately and repeatedly bonded, The content is more preferably 70% by weight or more, and particularly preferably 80% by weight.

  Furthermore, if the content of the antistatic agent in the antistatic resin composition is small, the antistatic performance of the antistatic layer may be reduced. Since there exists a possibility of having a bad influence on the articles | goods which contact a laminated foam sheet when using it, 5 to 15 weight% is preferable.

  Then, the polypropylene resin is supplied to the first extruder and melt-kneaded, and the foaming agent is injected into the first extruder to mix the polypropylene resin and the foaming agent to produce a foamable polypropylene resin. On the other hand, the antistatic resin composition is supplied to an extruder and melt-kneaded.

  After that, the foamable polypropylene resin from the first extruder and the antistatic resin composition from the second extruder are continuously applied to the same mold to which both the first extruder and the second extruder are connected. In this mold, the foamable polypropylene resin and the antistatic resin composition are merged, and a cylindrical foamable resin layer made of the foamable polypropylene resin is laminated on the inner surface of the foamable resin layer. A cylindrical laminate composed of a cylindrical antistatic layer made of an integrated antistatic resin composition is formed, and the cylindrical laminate is coextruded and foamed from a mold to foam a foamable resin layer. A cylindrical foamed body comprising a cylindrical foamed layer and a cylindrical antistatic layer laminated and integrated on the inner surface of the foamed layer is produced.

  In addition, the antistatic resin composition from the second extruder is branched into two and supplied into the mold, and a cylindrical foam made of the antistatic resin composition is formed on the inner and outer surfaces of the cylindrical foamable resin layer. The antistatic layer is laminated and integrated to form a cylindrical laminate, the cylindrical laminate is coextruded and foamed from a mold, and the foamable resin layer is foamed. You may manufacture the cylindrical foam which consists of a cylindrical antistatic layer laminated | stacked and integrated on the inner and outer surfaces. Further, instead of branching the antistatic resin composition from the second extruder into two, a third extruder is prepared separately, and the antistatic resin composition is supplied to this extruder and melt-kneaded, You may supply an antistatic resin composition in the metal mold | die which the 1st and 2nd extruder is connected.

  At this time, the foamable polypropylene resin and the antistatic resin composition come into contact with each other in the mold, and as described above, the antistatic resin composition contains 50 to 90% by weight of the ethylene-propylene random copolymer. And 10 to 50% by weight of high-density polyethylene, and in particular, by using an ethylene-propylene random copolymer, while maintaining the heat resistance to such an extent that the antistatic layer does not melt in the annealing treatment described later, Even when the extrusion temperature of the antistatic resin composition is brought close to the proper foaming temperature of the expandable polypropylene resin that comes into contact, and the extrusion temperature of the antistatic resin composition is set to be equal to or lower than the extrusion foaming temperature of the expandable polypropylene resin. Easily control coextrusion foaming by expanding the range of coextrusion foaming conditions so that the antistatic resin composition does not crystallize Te are striving to optimize the foaming of the foamable polypropylene resin, and reduce the weight of the laminated foam sheet foamed layer obtained by extrusion foaming of foamable polypropylene resin as a high expansion ratio.

  As described above, since the extrusion temperature of the antistatic resin composition can be brought close to the proper foaming temperature of the expandable polypropylene resin and the foaming polypropylene resin can be extruded and foamed at the proper foaming temperature, the expandable polypropylene type can be used. The resin foams well even at the contact interface with the antistatic resin composition, and the foamed layer obtained by extrusion foaming the foamable polypropylene resin is well foamed and uniform over the entire length in the inner and outer directions. It has become.

  Further, the temperature difference between the expandable polypropylene resin and the antistatic resin composition when supplied into the mold is preferably within 5 ° C., and the temperature of the antistatic resin composition is lower than the temperature of the expandable polypropylene resin and More preferably, the temperature difference between the expandable polypropylene resin and the antistatic resin composition is within 5 ° C.

  And since the ethylene-propylene random copolymer is used for the antistatic resin composition, the foamed layer obtained by foaming the foamable polypropylene resin and the antistatic layer are excellent in heat-fusibility, The resulting laminated foam sheet has excellent mechanical strength.

  Next, the cylindrical foam obtained by coextrusion foaming from the mold as described above is gradually expanded in diameter and then supplied to the mandrel. At this time, the antistatic resin composition is obtained by mixing an ethylene-propylene random copolymer and a high-density polyethylene at a predetermined ratio, and the high-density polyethylene increases the crystallization speed of the ethylene-propylene random copolymer. As a result, after the antistatic resin composition is extruded from the mold and before being supplied to the mandrel, the crystallization of the ethylene-propylene random copolymer is sufficiently advanced. At the time of contact with the mandrel, the viscosity of the ethylene-propylene random copolymer has substantially disappeared, and the antistatic layer that is in direct contact with the mandrel slides smoothly on the mandrel surface. The cylindrical foam is reliably cooled by the mandrel without impairing the surface property of the mandrel. Thereafter, at least at one point, the cylindrical foam is cut and developed continuously along the extrusion direction between the inner and outer peripheral surfaces, and at least a polypropylene-based resin foam sheet formed by developing a cylindrical foam layer. A laminated foam sheet in which an antistatic layer is laminated and integrated on one surface can be obtained.

If the density of the entire laminated foam sheet is low, the mechanical strength of the polypropylene resin foam sheet may be lowered and the strength of the laminated foam sheet may be lowered. On the other hand, if the density is high, the lightweight property of the laminated foam sheet is impaired. Since there exists a possibility, 0.07-0.12 g / cm < ³ > is preferable.

  Since the laminated foam sheet obtained as described above is formed by developing a cylindrical foam, the polypropylene-based resin foam sheet is curved in an arc shape, and further, between both surfaces. Distortion due to the difference in cooling and the difference in inner and outer peripheral lengths of the cylindrical foam remains, and heat treatment, that is, annealing treatment is performed in order to remove the remaining distortion.

  This annealing process is performed in a known manner, and specifically, the annealing process is performed on the laminated foam sheet obtained by developing the cylindrical foam using an annealing apparatus as shown in FIG. The annealing apparatus shown in FIG. 1 includes a pair of endless belts in which a pair of endless belts 1a to 4a and 1b to 4b are opposed to each other in the vertical direction with a space slightly narrower than the thickness of the laminated foam sheet A. A pair of endless belt pairs B1 to B4 are arranged at predetermined intervals in the conveyance direction of the laminated foam sheet A, and a heating zone C is formed by two pairs of endless belt pairs B1 and B2 on the conveyance start point side. A cooling zone D is formed by two endless belt pairs B3 and B4 on the end point side.

  Then, the laminated foam sheet A is successively supplied between the opposed surfaces of the upper and lower endless belts 1a, 1b, 2a and 2b of the endless belt pair B1 and B2 forming the heating zone to obtain the laminated foam sheet A. After removing the distortion remaining in the laminated foam sheet A by pressing while pressing from both sides, preferably at a temperature of 105 to 165 ° C., the upper and lower endless belts 3a, 3b, 4a of the endless belt pairs B3, B4, The laminated foamed sheet A can be annealed by supplying it sequentially between the opposing surfaces of 4b and cooling the laminated foamed sheet A while pressing it from both sides.

  Here, it is preferable to adjust so that the heating temperature of the mandrel contact surface in the laminated foam sheet A is lower than the heating temperature of the other surface, and the conveying speed of the laminated foam sheet A is 2 to 15 m / min. Is preferred. Further, the conveying speed of the laminated foam sheet A in the endless belt pair B3, B4 forming the cooling zone is the same as the conveying speed of the laminated foam sheet A in the endless belt pair B1, B2 forming the heating zone, or A high speed is preferable within 1.03 times.

  The laminated foam sheet A is annealed as described above, but the antistatic layer of the laminated foam sheet A is formed mainly of an ethylene-propylene random copolymer and has excellent heat resistance. Therefore, the laminated foamed sheet can be sufficiently heated without melting its antistatic layer to reliably remove the distortion remaining in the polypropylene resin foamed sheet, and the shape stability of the laminated foamed sheet can be improved.

  The production method of the laminated foam sheet of the present invention is configured as described above, and the antistatic resin composition contains 50 to 90% by weight of an ethylene-propylene random copolymer and 10 to 50% by weight of high density polyethylene. Therefore, in coextrusion foaming, the foaming polypropylene resin can be brought close to the proper foaming temperature without crystallizing the antistatic resin composition in the extruder.

  Therefore, the foamable polypropylene resin foams well on the contact surface side with the antistatic resin composition and foams at a high expansion ratio as a whole, and the antistatic resin composition is smoothly coextruded from the mold. Thus, it is possible to obtain a cylindrical foam obtained by firmly laminating and integrating an antistatic layer excellent in surface properties and thickness accuracy on the inner surface of a foam layer having a high expansion ratio, and deploying this cylindrical foam Thus, a laminated foam sheet excellent in lightness, mechanical strength and thickness accuracy can be easily obtained.

  In addition, the antistatic resin composition comprises a high-density polyethylene added in a predetermined ratio to an ethylene-propylene random copolymer, and the crystallization rate of the ethylene-propylene random copolymer after being coextruded from a mold. Is promoted by high-density polyethylene, and at the time when the cylindrical foam is supplied to the mandrel, the crystallization of the ethylene-propylene random copolymer constituting the antistatic layer surely proceeds to prevent the mandrel from being charged. The antistatic layer that is in direct contact with the mandrel has excellent surface properties, and thus the laminated foam sheet obtained by developing the cylindrical foam has an excellent appearance. .

(Examples 1-6, Comparative Examples 1-4)
A tandem type extruder in which an extruder E2 having a diameter of 115 mm was connected to the tip of an extruder E1 having a diameter of 90 mm was prepared. Then, homopolypropylene (trade name “PF-814” manufactured by Sun Allomer Co., Ltd., melting point: 160 ° C., crystallization temperature: 128 ° C.) 90% by weight and polyolefin-based thermoplastic elastomer (Sun Allomer) were added to the extruder E1 of this tandem type extruder. Product name “Q-100F”, melting point: 142 ° C., density: 0.88 g / cm ³ ) 100 parts by weight of a polypropylene resin consisting of 10% by weight and an air conditioner (trade name “PO- manufactured by Dainichi Seika Co., Ltd.) 410 ") 0.1 parts by weight was supplied and melted and kneaded at 200 to 210 ° C. Butane (normal butane / isobutane (weight ratio) = 65/35) was used as a foaming agent in the extruder E1. After press-fitting a predetermined amount shown in Fig. 1 and further melt-kneading to make a foamable polypropylene resin, the foamable polypropylene resin was continuously supplied to the extruder E2 and cooled. It was continuously supplied at a temperature shown in Table 1 the merging mold which is connected to the extruder E2 at an extrusion amount 88 kg / hour.

  On the other hand, an ethylene-propylene random copolymer 1 (trade name “PF724S”, melting point: 155.5 ° C. manufactured by Sun Allomer Co., Ltd.) and an ethylene-propylene random copolymer 2 (Product manufactured by Sun Allomer Co., Ltd.) were introduced into an extruder E3 having a diameter of 65 mm. Name “PC630A”, melting point: 143.5 ° C., high-density polyethylene (trade name “HJ560W”, melting point: 137.5 ° C., manufactured by Nippon Polyethylene Co., Ltd.), propylene homopolymer (trade name “PF-814” manufactured by Sun Allomer) , Melting point: 160 ° C., crystallization temperature: 128 ° C.) Polyether-polypropylene block copolymer (trade name “Pelestat 230” manufactured by Sanyo Kasei Co., Ltd.) as the polymeric antistatic agent 1 and polymeric antistatic agent 2 Polyether-polypropylene block copolymer (trade name “Pelestat 330” manufactured by Sanyo Chemical Co., Ltd.) The antistatic resin composition mixed at the ratio shown in Table 1 was supplied, melted and kneaded at 220 ° C., cooled, and then the antistatic resin composition in a molten state was branched into two. Above, the same merging mold to which the extruder E2 of the tandem type extruder was connected was continuously fed into the merging mold at the temperature shown in Table 1 at an extrusion rate of 12 kg / hour.

  In the merging mold, the foamable polypropylene resin extruded from the tandem extruder is formed into a cylindrical shape, and the two antistatic resin compositions extruded from the extruder E3 are both formed into a cylindrical shape. Then, after the cylindrical antistatic resin composition is merged and laminated on the inner and outer surfaces of the cylindrical foamable polypropylene resin, the circular gold having a diameter of 120 mm and a slit interval of 1.2 mm connected to the merge mold A cylindrical foam layer formed by co-extrusion foaming from the die of the mold into the atmosphere and foaming a foamable polypropylene resin, and a charge comprising an antistatic resin composition laminated and integrated on the inner and outer surfaces of the foam layer A cylindrical foam composed of a prevention layer was produced.

  After that, the obtained cylindrical foam is gradually expanded in diameter while being cooled by blowing air onto its inner surface, and then the cylindrical foam is supplied to a cooling mandrel having an outer diameter of 418 mm to form a cylindrical foam. The cylindrical foam was cooled by causing the inner antistatic layer of the body to rub against the outer peripheral surface of the cooling mandrel and blowing air to the outer peripheral surface of the cylindrical foam.

  Next, the polypropylene-based resin obtained by expanding the foamed layer of the cylindrical foam by cutting the cylindrical foam continuously between the inner and outer peripheral surfaces in the extruding direction at one point and opening and opening the cylindrical foam. A long laminated foam sheet in which an antistatic layer made of an antistatic resin composition was laminated and integrated on the inner and outer surfaces of the foam sheet was continuously produced, and the laminated foam sheet was wound up in a roll shape. In addition, the winding speed of the laminated foam sheets in Examples 2 to 4 was 1.24 times the winding speed of the laminated foam sheets in Examples 1, 5, 6 and Comparative Examples 1 to 4.

  Next, the laminated foam sheet wound up in a roll shape is successively and continuously supplied between the opposed surfaces of the endless belt pairs 1a, 1b, 2a, 2b constituting the heating zone C of the annealing apparatus shown in FIG. Then, the strain remaining in the laminated foamed sheet was removed by heating. The endless belt in contact with the antistatic layer in contact with the mandrel in the laminated foam sheet was maintained at 128 ° C., and the endless belt in contact with the other antistatic layer was maintained at 148 ° C.

  Thereafter, the laminated foam sheet that has been subjected to the annealing treatment in the heating zone C is successively supplied to the opposed surfaces of the endless belts 3a, 3b, 4a, and 4b constituting the cooling zone D for cooling. Then, the laminated foam sheet was cut into a predetermined length. The temperature of the endless belts 3a, 3b, 4a, 4b was kept at 25 ° C. Also, the conveying speed of the laminated foam sheet by the endless belt pair B3 and B4 constituting the cooling zone D and the conveying speed of the laminated foam sheet by the endless belt pair B1 and B2 constituting the heating zone C are the same speed. It adjusted so that it might become.

The laminated foam sheet of Comparative Example 1 had good appearance but lacked light weight with a density of 0.14 g / cm ³ . The laminated foam sheets of Comparative Examples 2 and 3 have a slow crystallization rate of the antistatic layer of the cylindrical foam, and the antistatic layer is sticky when the cylindrical foam is supplied to the mandrel. The layer partially adhered to the mandrel surface, and a depression was generated on the surface of the antistatic layer in contact with the mandrel in the obtained laminated foamed sheet, resulting in poor appearance. In Comparative Example 4, fine protrusions accompanying crystallization were formed on the surface of the antistatic layer, and the appearance was poor.

  Table 2 shows the thickness, basis weight, and density of the entire laminated foam sheet, and the thicknesses of the polypropylene resin foam sheet and the antistatic layer. Further, the surface resistivity of the obtained laminated foam sheet was measured in the following manner, and the result is shown in Table 2.

(Surface specific resistivity)
The surface specific resistivity ρs of the laminated foamed sheet was measured as described in JIS K6911: 1995 “General Test Method for Thermosetting Plastics”. Specifically, after producing a laminated foamed sheet, it was allowed to stand for 7 days at room temperature and normal pressure, and then cut out 5 pieces of planar square test pieces each having a side of 10 cm from the laminated foamed sheet. After being allowed to stand for 24 hours in an atmosphere of a temperature of 22 ° C. and a relative humidity of 60%, a test apparatus (trade name “Digital Ultra High Resistance / Micro Ammeter R8340” manufactured by Advantest Corporation) and a test apparatus (manufactured by Advantest Corporation) Using “Resistency Chamber R12702A”), the electrodes were crimped to each test piece with a load of about 30 N, a voltage of 500 V was applied, and the resistance value after 1 minute was measured. The surface resistivity of each test piece was calculated, and the arithmetic average value of the surface resistivity of each test piece was used as the surface resistivity of the laminated foam sheet.

Surface resistivity ρs (Ω / □) = π (D + d) × Rs / (D−d)
D: Inner diameter of the annular electrode on the surface (cm) (7 cm for the resiliency chamber R12702A)
d: outer diameter (cm) of inner circle of surface electrode (5 cm for Resistivity Chamber R12702A)
Rs: Surface resistance (Ω)

It is the model side view which showed the annealing apparatus.

Explanation of symbols

1a ~ 4a, 1b ~ 4b Endless belt A Laminated foam sheet
B1 ~ B4 Endless belt pair C Heating zone D Cooling zone

Claims (5)

A polypropylene resin is supplied to the first extruder and melt-kneaded in the presence of a foaming agent to obtain a foamable polypropylene resin. On the other hand, an ethylene-propylene random copolymer 50 to 90% by weight, a high density polyethylene 10 An antistatic resin composition containing 50% by weight and a polyolefin resin containing 0 to 20% by weight of an ethylene-propylene block copolymer and / or a propylene homopolymer and an antistatic agent is used as a second extruder. Supplying, melt-kneading, supplying the foamable polypropylene resin and the antistatic resin composition to the molds connected together to the first and second extruders, coextrusion foaming from the mold, A cylindrical foam layer formed by foaming a foamable polypropylene resin, and a cylindrical antistatic layer comprising an antistatic resin composition laminated and integrated on the inner surface of the foam layer; It manufactures Ranaru cylindrical foam method for producing a laminated foam sheet, characterized in that deploying the tubular foam cylindrical on cooling is supplied to the mandrel foam. Co-extrusion foaming from a mold to produce a cylindrical foam comprising a cylindrical foam layer and a cylindrical antistatic layer made of an antistatic resin composition laminated and integrated on the inner and outer surfaces of the foam layer The manufacturing method of the laminated foam sheet of Claim 1 characterized by the above-mentioned. The method for producing a laminated foam sheet according to claim 1 or 2 , wherein a temperature difference between the expandable polypropylene resin and the antistatic resin composition at the time of supply to the mold is within 5 ° C. An antistatic layer containing a polyolefin resin and an antistatic agent is laminated and integrated on at least one surface of a polypropylene resin foam sheet, and is produced by coextrusion foaming, wherein the antistatic layer comprises: It contains a polyolefin resin containing 50 to 90% by weight of an ethylene-propylene random copolymer and 10 to 50% by weight of high density polyethylene, and an antistatic agent, and has a density of 0.07 to 0.12 g / cm ³ . A laminated foam sheet, characterized by being. The laminated foam sheet according to claim 4, which is heat-treated.

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