JP2011212968A - Method of manufacturing resin foamed sheet and reflection sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a resin foamed sheet suppressing variation in thickness of the resin foamed sheet upon forming the resin foamed sheet using a circular die and to provide a reflection sheet comprising the resin foamed sheet manufactured by the manufacturing method.SOLUTION: In the method of manufacturing the resin foamed sheet, the resin foamed sheet is manufactured by extruding a heat-molten foaming resin composition from the circular die and forming a cylindrical body having a foamed layer, increasing the diameter of the cylindrical body by slidingly contacting the outer peripheral face of a mandrel disposed in front in the extruding direction of the cylindrical body from the inner side, and forming the cylindrical body increased in diameter into a sheet shape. The temperature in an inner space of the cylindrical body between the circular die and the mandrel is maintained at 60-110°C.

Description

  The present invention relates to a method for producing a resin foam sheet using a circular die and a reflective sheet comprising the resin foam sheet.

  In recent years, a reflection sheet formed by using a resin foam sheet has been widely used as one of members constituting lighting fixtures, lighting signs, liquid crystal display devices, and the like. The foamed resin sheet that forms the reflective sheet includes a foamed layer obtained by foaming a foamable resin composition into a sheet, a laminate of a plurality of foamed layers, a foamed layer and a solid foamed layer. And the like are used.

  As a general method for producing a resin foam sheet, an extrusion foaming method using a circular die is known. Briefly describing such an extrusion foaming method, a mixture obtained by kneading a resin in a molten state and a foaming agent is extruded from an annular discharge port of a circular die to form a cylindrical body, and the extrusion direction of the cylindrical body The outer peripheral surface of the mandrel arranged in front is slidably contacted with the cylindrical body from the inside to expand the diameter, and the obtained cylindrical body is cut along the axial direction into a sheet shape, thereby forming a long shape. This is a method of forming a resin foam sheet (see Patent Document 1).

JP 2005-138508 A

  However, when the above method is used, the resin extruded from the circular die is three-dimensionally foamed and stretched (expanded) to a cylindrical body having a longer circumference than the annular discharge port. Therefore, due to the influence of the speed at which the diameter is expanded and the speed at which the resin is foamed, the cylindrical body is slackened between the circular die and the mandrel, and thickness unevenness (corrugation) occurs along the circumferential direction of the cylindrical body. There is a case. In such a case, unevenness (thickness unevenness) is also formed along the width direction in the obtained resin foam sheet.

The thickness unevenness as described above is a factor that decreases the performance such as the surface smoothness and rigidity of the resin foam sheet and decreases the reflection performance when used as a reflection sheet. In particular, when used as a reflection sheet of a liquid crystal display device, the light from the light source unit may leak due to the influence of thickness unevenness, or the light amount of the screen may be uneven.
Moreover, when a resin foam sheet is molded, damage may occur in a thin region.

  Then, this invention provides the manufacturing method of the resin foam sheet which can suppress that thickness nonuniformity generate | occur | produces in a resin foam sheet when forming a resin foam sheet using a circular die, and such manufacture It is an object of the present invention to provide a reflective sheet comprising a resin foam sheet manufactured by the method.

  As a result of studying to solve the above problems, the present inventor maintains the temperature of the internal space of the cylindrical body between the circular die and the mandrel at a predetermined temperature, thereby causing uneven thickness of the resin foam sheet. The inventors have found that generation can be suppressed, and have completed the present invention.

  That is, in the method for producing a resin foam sheet according to the present invention, a thermally meltable foamable resin composition is extruded from a circular die to form a cylindrical body having a foam layer, and the cylindrical body is pushed forward in the extrusion direction. A method for producing a resin foam sheet, wherein the outer peripheral surface of the mandrel disposed on the surface is slidably contacted with the tubular body from the inside to expand the diameter, and the expanded tubular body is formed into a sheet shape to produce a resin foam sheet. The temperature of the internal space of the cylindrical body between the circular die and the mandrel is maintained at 60 ° C to 110 ° C.

  According to such a configuration, the tubular body in the region between the circular die and the mandrel is deformed by maintaining the temperature of the internal space of the tubular body between the circular die and the mandrel at 60 ° C to 110 ° C. It can be kept in the soft state possible. For this reason, even when the thickness unevenness occurs in the cylindrical body, the cylindrical body is pressed against the mandrel when the cylindrical body slides against the mandrel, so that the thickness unevenness is smoothed and there is no thickness unevenness. A resin foam sheet can be formed.

  Further, a virtual line connecting the discharge port and the position where the cylindrical body pushed out from the discharge port of the circular die first contacts the mandrel, and a virtual line extending from the discharge port along the axis of the cylindrical body The formed angle is preferably 50 to 85 °.

  According to such a configuration, the cylindrical body pushed out from the discharge port of the circular die and the virtual line connecting the discharge port with the position where the cylindrical body first contacts the mandrel, and the discharge port along the axis of the cylindrical body. When the cylindrical body is in contact with the mandrel when the angle formed with the extending virtual line is 50 to 85 °, friction is applied to the cylindrical body and the cylindrical body is pressed against the outer peripheral surface of the mandrel. Therefore, the thickness unevenness of the cylindrical body can be smoothed more effectively.

  Moreover, it is preferable that the distance along the axial line of the cylindrical body between the position where the cylindrical body extruded from the discharge port of the circular die first contacts the mandrel and the discharge port is 20 to 100 mm.

  According to such a configuration, the distance along the axis of the cylindrical body between the position where the cylindrical body pushed out from the discharge port of the circular die first contacts the mandrel and the discharge port is 20 to 100 mm. Thereby, the temperature of the internal space of the cylindrical body between the circular die and the mandrel can be easily maintained. Specifically, if the distance between the circular die and the mandrel becomes too large, the area of the cylindrical body that comes into contact with the outside air between the circular die and the mandrel increases, and the temperature of the cylindrical body decreases rapidly. Although there is a possibility that the cylindrical body cannot be effectively heated, such a concern can be solved by setting the above range.

  The reflective sheet according to the present invention is characterized by comprising a resin foam sheet formed by any one of the above methods for producing a resin foam sheet.

  According to the manufacturing method of the present invention, when a resin foam sheet is formed using a circular die, it is possible to suppress the occurrence of uneven thickness in the resin foam sheet.

Sectional drawing which shows the structure of the resin foam sheet which concerns on this embodiment. Schematic which shows the apparatus structure used for the manufacturing method of a resin foam sheet. Sectional drawing which shows the structure of a confluence | merging die. Sectional drawing which showed a mode that the cylindrical body was discharged from the circular die | dye and sent to the mandrel. Sectional drawing which showed the vicinity of the internal space of the cylindrical body between a circular die and a mandrel. Schematic which shows the apparatus structure used for manufacture of the resin foam sheet in an Example. Sectional drawing which shows the structure of the confluence | merging die used for manufacture of the resin foam sheet in an Example.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  The method for producing a resin foam sheet according to the present invention is a foam formed by foaming a resin composition (hereinafter also referred to as a “foamable resin composition”) that can cause foaming by performing extrusion in a heated and melted state. It is used when producing a resin foam sheet comprising only a layer, or a resin foam sheet in which a plurality of foam layers are laminated or a foam layer and a non-foam layer (solid layer) are laminated. In the following description, the resin foam sheet 1 formed by laminating a foam layer and a solid layer will be mainly described.

  As shown in FIG. 1, the resin foam sheet 1 has a two-layer structure of a foam layer 10 formed in a foamed state and a solid layer 20 formed in a non-foamed state containing no bubbles. ing.

  The thickness of the resin foam sheet 1 depends on the use of the resin foam sheet, but is preferably 1.5 mm or less when used as a reflective sheet. Moreover, about each thickness of the foaming layer 10 and the solid layer 20, the foaming layer 10 shall be any thickness of 0.5-0.9 mm, and the solid layer 20 is any one of 0.1-0.6 mm Preferably, the thickness is

  The foamable resin composition used for forming the foamed layer 10 usually contains a polyolefin resin (such as polyethylene resin or polypropylene resin) or a thermoplastic resin other than the polyolefin resin (such as polystyrene resin) as a base polymer. Further, a resin composition containing a foaming component can be used. Especially, a polypropylene resin can be used suitably as a base polymer. In addition, you may use resin used as a base polymer in combination of multiple types.

  The polypropylene resin may be a propylene homopolymer (homo PP) or a copolymer with other olefins copolymerizable with propylene (random PP or block PP). In the case of a copolymer, an olefin other than propylene is preferably contained in the copolymer in a proportion of 0.5 to 30% by weight, and particularly preferably in a proportion of 1 to 10% by weight.

  Examples of olefins other than propylene include ethylene or α-olefins having 4 to 10 carbon atoms, and these can be used alone or in combination of two or more.

  As the polypropylene resin as described above, a high melt tension polypropylene resin excellent in foaming property is preferable, and for example, those described in Japanese Patent No. 2521388 and Japanese Patent Application Laid-Open No. 2001-226510 can be used.

  Examples of the component for foaming contained in the foamable resin composition include, for example, a gas component that is in a gaseous state at least at the melting point of the base polymer, a nucleating agent that serves as a nucleus when bubbles are formed by the gas component, and at least Examples thereof include a pyrolytic foaming agent that thermally decomposes at the melting point of the base polymer to generate a gas.

  Examples of the gas component include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, hexane, and heptane, alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane, chlorodifluoromethane, chloroethane, and dichloromethane. Halogenated hydrocarbons such as trifluoroethane, 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), 2-chloro-1,1, Freon-based gas components such as 1,2-tetrafluoroethane (HCFC-124), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), nitrogen, dioxide Carbon, argon, air, etc. are mentioned. Of these, aliphatic hydrocarbons are preferred. These gas components may be used alone or in combination.

  Examples of the nucleating agent include talc, mica, silica, diatomaceous earth, aluminum oxide, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, and sulfuric acid. Examples thereof include inorganic compound particles such as potassium, barium sulfate and glass beads, and organic compound particles such as polytetrafluoroethylene.

  Furthermore, examples of the thermal decomposition type foaming agent include azodicarbonamide, sodium hydrogen carbonate, a mixture of sodium hydrogen carbonate and citric acid, and the like.

In addition, although it does not specifically limit as a foaming ratio of the foaming layer 10, Usually, an apparent density can be made into either in the range of 0.06-2.8 g / cm < ³ >.

The solid layer 20 is not particularly limited as long as it is a resin composition that can be extruded in a non-foamed state (hereinafter referred to as “non-foamable resin composition”). As the non-foamable resin composition, for example, the resin composition used for forming the foamed layer 10 can be suitably used.
The non-foamable resin composition used for forming the solid layer 20 and the foamable resin composition used for forming the foamed layer 10 are the same type of base from the viewpoint of the adhesive strength between the foamed layer 10 and the solid layer 20. A polymer is preferably employed. Specifically, the formation of the foam layer 10 and the solid layer 20 can improve the adhesive strength by adopting a polypropylene resin as the respective base polymer.

  In addition to the base polymer as described above, the non-foamable resin composition used to form the solid layer 20 can contain an additive used as a general polymer film material. Various stabilizers such as weathering agents and anti-aging agents, processing aids such as lubricants, antistatic agents, slip agents, pigments, fillers and the like can be further included as additives.

  Moreover, when using a resin foam sheet as reflection sheets, such as a liquid crystal display device, in order to obtain the reflectance with respect to the light from a light source, an additive is contained in a resin foam sheet. Examples of such additives include rutile type titanium dioxide and anatase type titanium dioxide. In particular, rutile type titanium dioxide is preferably used.

  When the photocatalytic action of such an additive is too strong, there is a possibility of promoting the deterioration of the resin, and therefore it is preferable to subject the additive to a surface treatment. The surface treatment method is not particularly limited, but generally, a method of coating the surface of titanium dioxide particles with a hydrous oxide such as aluminum, silicon, titanium, zirconium, tin or the like is used.

Further, the amount of additives to obtain good reflectance, preferably 50 to 200 g / m ^2, more preferably, 60~170g / m ^2, particularly preferably from 70~150g / m ^2. By setting it as the range of 50-200 g / m < ² >, while being able to obtain sufficient reflectance, it can suppress that the weight of a resin foam sheet (namely, reflection sheet) becomes heavy.

  You may mix | blend another additive with a resin foam sheet. Examples of other additives include copper damage inhibitors (metal deactivators), dispersants (metal stearates), quenchers, antistatic agents, and lactone processing stabilizers.

  Examples of copper damage inhibitors include hydrazine compounds such as N, N-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine, 3- (3,5-di -Tetra-butyl-4-hydroxyphenyl) propionyl dihydride and the like can be used.

  The resin constituting the resin foam sheet may be deteriorated when it comes into contact with a metal such as copper or a heavy metal ion such as copper ion acts on the resin foam sheet. As a result, it is possible to capture copper ions and the like, which are degradation promoting factors, as chelate compounds. For this reason, when a resin foam sheet is used as a reflection sheet incorporated in a liquid crystal display device, a lighting device, or the like, it is possible to prevent the reflection sheet from deteriorating due to contact with a metal such as copper. In order to obtain such an effect, the content of the copper damage inhibitor is set to any one of 0.1 to 1.0 parts by weight with respect to 100 parts by weight of the resin component constituting the resin foam sheet. It is preferable to keep it.

  Moreover, an antistatic agent can also be mix | blended with a resin foam sheet. As the antistatic agent, for example, a surfactant such as glycerin monostearate, an inorganic salt, a polyhydric alcohol, a metal compound, carbon, or the like can be used. When such an antistatic agent is added, charging of the reflection sheet can be prevented, so that dust and dirt can be prevented from adhering to the reflection sheet. In order to obtain such an effect, the content of the antistatic agent is set within the range of 0.1 to 10.0 parts by weight with respect to 100 parts by weight of the resin component constituting the resin foam sheet. It is preferable to keep it.

  The resin foam sheet as described above can be produced as follows.

  FIG. 2 is a configuration diagram illustrating an example of a manufacturing apparatus used in the method for manufacturing a resin foam sheet according to the present invention. As shown in FIG. 2, the resin foam sheet manufacturing method of the present embodiment includes a first extruder 70 that is a tandem extruder and a second extruder 80 that is a single extruder. In addition, an equipment having a merging die XH into which the resin composition melt-kneaded in these extruders is merged and a circular die CD that extrudes the resin composition merged in the merging die XH into a cylindrical shape is used. .

  In addition, the manufacturing apparatus includes a mandrel MD for expanding the cylindrical body 1 ′ discharged from the circular die CD into a cylindrical shape having a predetermined size, and a cylinder after passing through the mandrel MD. A slit device (not shown: FIG. 2 shows only the state of being vertically divided) that slits the body 1 ′ into two sheets to form a long resin foam sheet 1; A winding roller 92 is further provided for winding the scale-shaped resin foam sheet 1 after passing the plurality of rollers 91.

The first extruder 70 is for forming the foamed layer 10, and a material such as a base polymer is charged into the upstream extruder (hereinafter also referred to as “upstream extruder 70 a”). A hopper 71 and a gas introduction part 72 for supplying gas components such as hydrocarbons into the cylinder are provided.
Further, on the downstream side of the upstream side extruder 70a, an extruder for melting and kneading a foamable resin composition containing a base polymer and a gaseous component and discharging the melted resin composition to the confluence mold XH (hereinafter referred to as "downstream side"). Also referred to as an extruder 70b ".

  The second extruder 80 is for forming the solid layer 20. A material such as a base polymer is introduced from the hopper 81, and the non-foamable resin composition is melted and kneaded inside the cylinder. It is configured to be discharged into the mold XH.

  As shown in the schematic cross-sectional view of FIG. 3, the confluence mold XH is a non-foaming resin composition discharged from an annular slit provided in the middle of a flow path through which the foaming resin composition passes. The foamable resin composition is configured to be supplied to the circular die CD in a state where the outer foam of the non-foamable resin composition is coated.

  As shown in FIG. 4, the circular die CD includes an annular discharge port CDa, and the foamed resin composition and the non-foamable resin composition are co-extruded to form the foamed layer 10 and the foamed layer 10. And a cylindrical body 1 ′ having a solid layer 20 positioned on the outer surface. The diameter of the discharge port CDa is preferably about 40 to 300 mm.

As shown in FIG. 4, the mandrel MD has a cylindrical shape, and the circular die is placed in a state where the central axis (axis line a) of the cylindrical shape passes through the approximate center of the discharge port CDa. It is arranged in front of the CD pushing direction.
That is, the mandrel MD is disposed in front of the circular die CD with the openings MDa provided on the circular die CD side (one end side) and the opposite side (the other end side).

  The size of the mandrel MD is not particularly limited as long as the diameter is larger than the outer diameter of the discharge port CDa so that the cylindrical body 1 'can be expanded. However, when the size of the discharge port CDa is as described above, the outer diameter is preferably about 40 to 700 mm, and the ratio of the outer diameter of the mandrel MD to the outer diameter of the discharge port CDa (blow-up ratio). Is preferably 2.5 to 4.0.

  Further, the mandrel MD is limited to the shape illustrated in FIG. 4 in which substantially the entire area excluding the end portion on the circular die CD side (hereinafter referred to as the CD side end portion) and the opposite end portion has a constant diameter. Instead, it may be formed such that a certain area on one end side has a constant diameter and the outer diameter dimension gradually decreases with the other end side facing the edge.

  Further, the mandrel MD is in contact with the cylindrical body 1 ′ extruded from the circular die CD at the CD side end portion, and the outer peripheral surface thereof is slidably contacted with the inner peripheral surface of the cylindrical body 1 ′. After expanding the cylindrical body 1 ′ so as to have substantially the same diameter, the cylindrical body 1 ′ can be cooled while the expanded cylindrical body 1 ′ travels on the constant diameter portion. It is configured.

  As a material for forming the mandrel MD, a metal material such as aluminum having excellent flatness and thermal conductivity can be used. The surface of the mandrel MD may be anodized or hard anodized, and a fluororesin coating layer may be formed thereon.

  In the internal space of the mandrel MD, when the resin foam sheet 1 is manufactured, a gas (pressurized gas) such as air is flowed toward the circular die CD side. As a result, the internal space of the cylindrical body 1 ′ between the circular die CD and the mandrel MD is pressurized, and the cylindrical body 1 ′ between the circular die CD and the mandrel MD is prevented from being slackened. Thus, it is possible to maintain the angle when the cylindrical body 1 ′ is directed from the discharge port CDa to the mandrel MD.

  The procedure for producing the resin foam sheet 1 with such an apparatus will be described in more detail. First, a resin material used for forming the foam layer 10 is introduced from the hopper 71 of the first extruder 70, and the second extruder 80 is used. A resin material used for forming the solid layer 20 is supplied from the hopper 81. Then, the resin material is heated to a temperature equal to or higher than the melting temperature in each extruder, and melt kneading is performed.

  In addition, when additives such as the resin material that becomes the base polymer are included in the foamable resin composition or the non-foamable resin composition, these are also added from the hopper and melt-kneaded in each extruder. To do.

  Among these extruders, in the first extruder 70, a gas component is press-fitted from a gas introduction part 72 provided in the upstream side extruder 70a and mixed with the molten resin.

  The foamable resin composition melt-kneaded by the upstream extruder 70a in the first extruder 70 is adjusted to a temperature suitable for extrusion foaming by the downstream extruder 70b and sent to the confluence mold XH, In the second extruder 80, the non-foamable resin composition is adjusted to a temperature suitable for the formation of the solid layer 20, and is sent to the merge mold XH.

  Then, the respective resin compositions joined in the joining mold XH are co-extruded in a cylindrical shape from the annular discharge port CDa of the circular die CD. At this time, the foamable resin composition is foamed to form the foamed layer 10, and the solid layer 20 is formed from the non-foamable resin composition, whereby the cylindrical body 1 having the solid layer 20 on the outer surface. 'Is formed.

  At this time, the formation of the foam layer 10 and the solid layer 20 can improve compatibility at the interface by using the same kind of resin material, for example, by adopting a polypropylene resin. The peel strength between the layer 10 and the solid layer 20 can be improved.

  The cylindrical body 1 ′ extruded from the circular die CD is then sent to the mandrel MD positioned forward in the extrusion direction, and moved to the other end side of the mandrel MD while sliding the inner peripheral surface against the outer peripheral surface of the mandrel MD. To do. As a result, the cylindrical body 1 ′ is expanded to a temperature at which cutting is easy.

  Then, the cooled cylindrical body 1 ′ is cut in two places by the slit device to form a long resin foam sheet 1. The long resin foam sheet 1 is taken up by a take-up roller 92. The take-up roller 92 is configured to take up (take up) the long resin foam sheet 1 by being rotated by driving means (not shown) such as an electric motor. When winding the long resin foam sheet 1, tension is applied along the longitudinal direction by the winding roller 92. The take-up speed (extrusion speed, take-up speed) is preferably about 1.0 to 10.0 m / min.

In addition, the cylindrical body 1 ′ extruded from the discharge port CDa of the circular die CD is heated at a predetermined temperature before coming into contact with the mandrel MD, whereby uneven thickness is formed in the obtained resin foam sheet 1. Is suppressed. Specifically, as shown in FIG. 5, the temperature of the internal space R of the cylindrical body 1 ′ between the circular die CD and the mandrel MD (hereinafter referred to as the cylindrical body temperature) is maintained at 60 to 110 ° C. By doing so, the cylindrical body 1 'is heated. The cylindrical body temperature is preferably maintained at 60 to 100 ° C, more preferably 70 to 100 ° C.
When measuring the temperature inside the cylindrical body, the cylindrical body 1 ′ pushed out from the discharge port CDa first contacts with the mandrel MD (tubular body contact position) T and the discharge port CDa. It is preferable to measure the temperature at an intermediate point m at a distance perpendicular to the axis a to the cylindrical body 1 ′ from the intermediate point of the distance (CD-MD distance) h along the axis a of the cylindrical body 1 ′. .

  The said cylindrical body temperature can be set to said temperature range by adjusting the air volume of the pressurized gas sent into the internal space of the mandrel MD, and / or making hot air flow in. The temperature of the pressurized gas is preferably 10 to 90 ° C.

  In maintaining the above temperature range, the distance between the circular die CD and the mandrel MD (CD-MD distance h) is preferably set to a predetermined value. Specifically, it is preferably 20 to 100 mm.

  At this time, an angle (cylindrical body contact angle) θ1 formed by a virtual line L1 connecting the cylindrical body contact position T and the discharge port CDa and a virtual line L2 extending from the discharge port CDa along the axis a is 50. It is preferably ˜85 °, more preferably 60˜80 °.

  Moreover, it is preferable that the moving speed (take-off speed) of the cylindrical body 1 ′ between the discharge port CDa and the cylindrical body contact position T is 2.0 to 10.0 m / min.

  The resin foam sheet 1 formed as described above is shaped to have a shape corresponding to the shape of the light source when used as a reflective sheet. As a molding method, a generally used method can be used, and for example, molding using a rod heater or press molding while heating can be used. Further, after the press molding, an annealing treatment or the like may be further performed.

  As mentioned above, according to the manufacturing method of the resin foam sheet which concerns on this invention, when forming a resin foam sheet using a circular die, it can suppress that thickness nonuniformity generate | occur | produces in a resin foam sheet.

  That is, by maintaining the temperature of the internal space R of the cylindrical body 1 ′ between the circular die CD and the mandrel MD at 60 ° C. to 110 ° C., the cylindrical body in the region between the circular die CD and the mandrel MD. 1 'can be kept in a deformable soft state. For this reason, even when the thickness unevenness is generated in the cylindrical body 1 ′, the cylindrical body 1 ′ is pressed against the mandrel MD when being in sliding contact with the mandrel MD. It is possible to form a resin foam sheet 1 having no surface. In particular, at the cylindrical body contact position T, the cylindrical body 1 ′ contacts the corner of the mandrel MD, and the moving direction of the cylindrical body 1 ′ changes toward the mandrel MD by the cylindrical body contact angle θ1. The cylindrical body 1 ′ is pressed against the mandrel MD, and the thickness unevenness is effectively smoothed.

  In addition, an angle formed by a virtual line L1 connecting the cylindrical body contact position T and the discharge port CDa and a virtual line L2 extending from the discharge port CDa along the axis line a is 50 to 85 °, When the body 1 ′ contacts the mandrel MD, friction is applied to the tubular body 1 ′ and the tubular body 1 ′ is pressed against the outer peripheral surface of the mandrel MD. Thickness unevenness generated in 1 ′ can be smoothed.

  In addition, if the distance between the circular die CD and the mandrel MD is too large, the area of the cylindrical body 1 ′ that comes into contact with the outside air between the circular die CD and the mandrel MD becomes large, and the cylindrical body 1 ′. However, when the CD-MD distance h is 20 to 100 mm, such a concern can be solved.

  Further, since the solid layer 20 is formed on the outer surface of the cylindrical body 1 ′ extruded from the circular die CD, the mandrel MD and the solid layer 20 do not come into contact with each other. For this reason, when the mandrel MD is in sliding contact with the inner side of the cylindrical body 1 ′, the solid layer 20 is not rubbed or scratched. When the resin foam sheet 1 is used as a reflection sheet, the solid layer 20 side is It can be suitably used as a reflecting surface.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the summary of this invention.

  For example, in the above, the foamed layer 10 and the solid layer 20 are laminated one by one to form a resin foamed sheet, but a resin foamed sheet consisting only of the foamed layer can also be produced by the production method of the present invention. Is possible.

  In the above, the foamed resin composition and the non-foamable resin composition are coextruded to form a foamed resin sheet in which the foamed layer 10 and the solid layer 20 are laminated. The foamed layer and the solid are formed by a method in which only the foamed layer is formed by the manufacturing method of the invention, and the solid layer is extrusion laminated on the foamed layer, or the solid layer formed by other methods is thermally laminated on the foamed layer. A resin foam sheet in which layers are laminated may be formed.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

1. Examples 1-6, Comparative Examples 1 and 2
<Equipment used>
A resin foam sheet was prepared using equipment having an apparatus configuration as shown in FIG. Further, a confluence mold XH ′ having the structure shown in FIG. 7 was used.

As the first extruder 70, a single-screw extruder having a diameter of 90 mm (upstream extruder 70a) and a single-screw extruder having a diameter of 115 mm connected to the single-screw extruder (downstream extruder 70b). A tandem type extruder was prepared.
In addition, a single screw extruder having a diameter of 90 mm was prepared as the second extruder 80, and a single screw extruder having a diameter of 65 mm was prepared as the third extruder 85.

  Then, the foamable resin composition is introduced from the first extruder 70 into the converging mold XH ′, the outer side thereof is coated with the non-foamable resin composition from the second extruder 80, and the outer side thereof is the third extruder. Each extruder was connected to merging mold XH ′ so that the non-foamable resin composition from machine 85 was coated.

<Procedure of resin foam sheet>

In the first extruder 70, as a base polymer, 60 parts by weight of ethylene-propylene block polypropylene (manufactured by Nippon Polypro Co., Ltd., New Former “FB3312”), 20 parts by weight of homopolypropylene (manufactured by Sun Allomer, “PL500A”), ethylene- Masterbatch containing rutile type titanium oxide in propylene block copolymer (manufactured by Toyo Ink Mfg. Co., Ltd., “PPM 1KB662 WHT FD”, ethylene-propylene block copolymer: 30% by weight, titanium oxide: 70% by weight ) 20 parts by weight of a foaming agent (mixture of sodium bicarbonate and citric acid) 0.5 parts by weight of resin material was supplied.
Then, after the resin material is heated to 200 ° C. and melt-kneaded, 1.0 part by weight of butane (normal butane: 65 wt%, isobutane: 35 wt%) is injected into the upstream side extruder 70 a as a gas component, The foamable resin composition (A) was produced by melt-kneading.
Next, such a foamable resin composition (A) was introduced into the downstream extruder 70b, lowered to 180 ° C., and supplied to the confluence mold XH ′.

In the second extruder 80, 50 parts by weight of homopolypropylene (manufactured by Sun Allomer, “PL500A”), a masterbatch containing rutile titanium oxide in an ethylene-propylene block copolymer (manufactured by Toyo Ink “ PPM 1KB662 WHT FD ”, ethylene-propylene block copolymer: 30% by weight, titanium oxide: 70% by weight) 50 parts by weight of a resin material was supplied.
And after melt-kneading the resin material at 200 degreeC and forming non-foamable resin composition (B), it supplied to the confluence | merging metal mold | die XH '.

Furthermore, in the third extruder 85, 100 parts by weight of homopolypropylene (manufactured by Sun Allomer, “PL500A”, melt flow rate: 3.3 g / 10 min, density: 0.9 g / cm ³ ), ethylene-propylene block A resin material having a composition of 5 parts by weight of polypropylene (“FB3312” manufactured by Nippon Polypro Co., Ltd., melt flow rate: 2.8 g / 10 min, density: 0.9 g / cm ³ ) was supplied.
Then, the resin material was melt-kneaded at 200 ° C. to form a non-foamable resin composition (C), and then supplied to the confluence mold XH ′.

  By extruding one type of foamable resin composition (A) and two types of non-foamable resin compositions (B) and (C) from each extruder into the converging mold XH ′, a foamable resin having a circular cross section. The non-foamable resin composition layer (B) was laminated on the outer peripheral surface of the composition layer (A), and the non-foamable resin composition layer (C) was further laminated on the outside thereof.

And in the state which laminated | stacked each resin composition, it supplies continuously to circular die CD (tip surface diameter: 140mm, clearance of an opening part: 0.7mm) for co-extrusion, and cyclic | annular form of this circular die CD is carried out. Extrusion was carried out from the discharge port and foamed to produce a cylindrical tubular body 1 ′.
In the cylindrical body 1 ', the foamed layer (A) formed of the foamable resin composition (A) is formed on the innermost side, and the solid layer (C) formed of the non-foamable resin composition (C). Is formed on the outermost side, and the solid layer (B) formed of the non-foamable resin composition (B) is formed between the foam layer (A) and the solid layer (C).

The cylindrical body 1 ′ is cooled while being expanded by sliding the outer peripheral surface of a cylindrical mandrel MD having a constant diameter (diameter: 424 mm) on the inner peripheral surface of the extruded cylindrical body 1 ′. 'Was continuously cut along the axial direction and cut open to form a long resin foam sheet 1.
The long resin foam sheet 1 formed was wound around the winding roller 92 while applying tension along the longitudinal direction.

  At this time, as shown in FIG. 5, the temperature of the internal space R (the temperature in the cylindrical body) was maintained at the temperature shown in Table 1 below, and the cylindrical body 1 ′ was heated. Specifically, the temperature of the internal space R is adjusted by adjusting the air volume of the pressurized gas (25 ± 5 ° C.) blown into the cylindrical body 1 ′ (internal space R) through the internal space of the mandrel MD. The cylindrical body 1 ′ was heated.

  In addition, the cylindrical body temperature described in the following Table 1 is an average obtained by measuring the temperature at an intermediate point m at a distance orthogonal to the axis a from the intermediate point of the CD-MD distance h to the cylindrical body 1 ′ at four locations. Value. The temperature was measured using a Digital IN / OUT thermometer (manufactured by DRETEC, “O-215WT”).

  The cylindrical body contact angle θ1, the CD-MD distance h, and the take-up speed (winding speed) were as shown in Table 1 below.

The resin foam sheets of Examples 1 to 5 had a thickness of 0.71 mm and a width of 640 mm. The foam layer (A) has a thickness of 0.4 mm and a density of 0.46 g / cm ³ , and the solid layer (B) has a thickness of 0.3 mm and a density of 1.24 g / cm ³ , and the solid layer (C ) Had a thickness of 0.01 mm and a density of 0.9 g / cm ³ . The total light reflectance was 98.8%.
Moreover, the resin foam sheet of Example 6 was 0.97 mm in thickness and 640 mm in width. Further, the foam layer (A) has a thickness of 0.55 mm, a density of 0.46 g / cm ^3, solid layer (B) has a thickness of 0.40 mm, a density of 1.24 g / cm ^3, solid layer (C ) Had a thickness of 0.02 mm and a density of 0.9 g / cm ³ .

<Test method>
The thickness of the resin foam sheet was measured using “TOF-4R” manufactured by YAMABUN. The measurement location was a 200 mm section (100 measurement points) in the longitudinal direction perpendicular to the width direction at the center of the width direction of 640 mm, the measurement speed was 40 mm / s, and the measurement interval was 2 mm. And from the obtained result, the difference of the maximum thickness and the minimum thickness was calculated, and it was set as the thickness nonuniformity. The test results are shown in Table 1 below.

2. Example 7, Comparative Example 3
The non-foamable resin compositions (B) and (C) are not extruded from the second and third extruders 80 and 85, and the foamable resin composition (A) is joined from the first extruder 70 to the confluence mold XH ′. A resin foam sheet (thickness 0.4 mm, density 0.46 g / cm ³ ) consisting only of the foamed layer (A) under the same conditions as in Examples 1 and 2 and Comparative Examples 1 and 2 except that it was supplied to The test was conducted. The test results are shown in Table 1 below. The obtained resin foam sheet had a total light reflectance of 97.0%.

3. Comparative Examples 4 and 5
Except that the temperature in the cylindrical body was set to 120 ° C., an attempt was made to produce a resin foam sheet under the same conditions as in Examples 1 and 3, but when the diameter was expanded while heading toward the mandrel MD or by contact with the mandrel MD. As a result, the resin foam sheet could not be formed.

3. Summary When each example is compared with each comparative example, it can be seen that each example has less thickness unevenness. This is because the cylindrical body 1 ′ forming the internal space R is heated and maintained in a deformable state by keeping the temperature inside the cylindrical body high, so that the thickness unevenness is smoothed by contact with the mandrel MD. It is thought to be done.
Further, in Comparative Examples 4 and 5, the temperature inside the cylindrical body was too high, and the cylindrical body 1 ′ was too soft, and when the diameter was expanded, it was cut or damaged due to contact with the mandrel MD. However, although the resin foam sheet could not be formed, the resin foam sheet could be formed without cutting and damaging the cylindrical body 1 'by setting the temperature in the cylindrical body as in the example.
Thus, it turns out that the resin foam sheet without a thickness nonuniformity can be obtained by maintaining a cylindrical body temperature in the range of 60-110 degreeC.

DESCRIPTION OF SYMBOLS 1 ... Resin foam sheet, 10 ... Foam layer, 20 ... Solid layer, CD ... Circular die, CDa ... Discharge port, MD ... Mandrel, XH ... Confluence mold

Claims (7)

While extruding the heat-meltable foamable resin composition from a circular die to form a cylindrical body provided with a foam layer, the outer peripheral surface of the mandrel arranged in front of the cylindrical body in the extrusion direction is formed into the cylindrical body. In the manufacturing method of the resin foam sheet, the diameter is increased by sliding contact from the inside, and the expanded cylindrical body is formed into a sheet shape to manufacture the resin foam sheet.
A method for producing a resin foam sheet, characterized in that the temperature of the internal space of the cylindrical body between the circular die and the mandrel is maintained at 60 ° C to 110 ° C.   An angle formed by a virtual line connecting the discharge port and the position where the cylindrical body pushed out from the discharge port of the circular die first contacts the mandrel, and a virtual line extending from the discharge port along the axis of the cylindrical body The manufacturing method of the resin foam sheet of Claim 1 characterized by the above-mentioned.   The distance along the axis of the cylindrical body between the position where the cylindrical body pushed out from the discharge port of the circular die first contacts the mandrel and the discharge port is 20 to 100 mm. The manufacturing method of the resin foam sheet of 1 or 2.   The method for producing a resin foam sheet according to any one of claims 1 to 3, wherein the thickness of the resin foam sheet obtained is 1.5 mm or less.   The other thermoplastic resin composition is coextruded together with the foamable resin composition to form a cylindrical body having a non-foamed layer made of the thermoplastic resin composition on the outer surface. The method for producing a resin foam sheet according to any one of 4.   The method for producing a resin foam sheet according to any one of claims 1 to 5, wherein the base polymer of the foamable resin composition and the thermoplastic resin composition is a polypropylene resin.   A reflective sheet comprising a resin foam sheet formed by the method for producing a resin foam sheet according to claim 1.

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