JP2011212989A - Mandrel, device and method for manufacturing resin foamed sheet, and resin foamed sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mandrel that suppresses scars from occurring in a resin foamed sheet and suppresses stress strain occurring in the resin foamed sheet upon forming the resin foamed sheet using the mandrel.SOLUTION: The mandrel is disposed in front in the extruding direction of a circular die upon manufacturing the resin foamed sheet. At an end disposed on the circular die side, a diameter increased region with which a cylindrical body is increased in diameter is formed, and an irregular structure is formed in the diameter increased region by a plurality of minute projections C. Each minute projection C is formed to include a flat surface part C2 and/or a curved surface part C1 each having a radius of 0.2 mm or more at a tip end in the projecting direction. A distance LD between tip ends in the projecting direction of adjacent minute projections C is 0.2-2.0 mm.

Description

  The present invention relates to a mandrel for use in producing a resin foam sheet using a circular die, a resin foam sheet manufacturing apparatus including the mandrel, and a method for producing a resin foam sheet using the mandrel, and also a resin foam sheet The present invention relates to a resin foam sheet formed using a manufacturing apparatus.

  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, while the cylindrical body is pushed forward in the extrusion direction. The inner peripheral surface of the cylindrical body is slidably contacted with the outer peripheral surface of the mandrel disposed in the cylinder to expand the diameter of the cylindrical body, and the obtained cylindrical body is cut along the axial direction into a sheet shape. This is a method of forming a long resin foam sheet (see Patent Document 1).

JP 2005-138508 A

  However, when the above method is used, generally, the long resin foam sheet is continuously wound around the winding roller. At this time, the mandrel and the cylindrical body Due to the strong friction generated between them, there is a possibility that winding will be performed in a state where stress strain is generated in the long resin foam sheet. In such a case, when the long resin foam sheet is processed later, there is a possibility that a problem such as a deviation in the dimensions of the resin foam sheet may occur.

  Then, this invention makes it a subject to provide the mandrel which can suppress the stress distortion which arises in the resin foam sheet obtained when forming a resin foam sheet using a mandrel. Another object of the present invention is to provide a resin foam sheet manufacturing apparatus including the mandrel, a resin foam sheet manufacturing method using the mandrel, and a resin foam sheet formed using the resin foam sheet manufacturing apparatus.

  As a result of studying to solve the above problems, the present inventor has formed a concavo-convex structure in a region in sliding contact with the cylindrical body in the mandrel, thereby reducing friction between the cylindrical body and the mandrel. As a result, it was found that the stress distortion generated in the foam, that is, the resin foam sheet can be suppressed, and the present invention has been completed.

  That is, the mandrel according to the present invention forms a cylindrical body by extruding the foamed resin composition that has been heat-melted when producing a resin foam sheet having a foam layer formed from the foamable resin composition. A mandrel which is used together with a circular die and is disposed in front of the circular die in the extrusion direction and used to cool the cylindrical body while expanding the diameter thereof. The outer peripheral surface slidably contacted with the inner peripheral surface of the cylindrical body is increased in diameter toward the extrusion direction, and an enlarged region is formed in which the cylindrical body is expanded along the outer peripheral surface. A concave-convex structure is formed by a plurality of microprotrusions, and the microprotrusions are provided with a flat surface portion and / or a curved surface portion having a radius of 0.2 mm or more at the tip in the projecting direction, and the protrusions of adjacent microprotrusions The distance between the direction tip is characterized in that it is formed to be 0.2 to 2.0 mm.

According to such a configuration, the concavo-convex structure is formed by a plurality of minute protrusions in the enlarged diameter region, and the minute protrusions have a flat surface portion and / or a curved surface portion having a radius of 0.2 mm or more at the front end portion in the protruding direction. In addition, the contact area between the enlarged diameter region and the cylindrical body can be reduced by forming the distance between the adjacent protrusions in the protruding direction between the minute protrusions to be 0.2 to 2.0 mm. Friction can be reduced when the microprotrusions come into contact with the cylindrical body. As a result, the friction generated between the enlarged diameter region and the cylindrical body is reduced, so that the cylindrical body moves along the moving direction when the cylindrical body moves toward the extrusion direction while being in sliding contact with the enlarged diameter region. It is possible to suppress stress strain generated in the body. For this reason, the stress distortion which arises in a resin foam sheet can be suppressed.
Moreover, since the flat part and / or curved part are formed in the protrusion direction front-end | tip part of a microprotrusion, it can also suppress that a damage | wound generate | occur | produces on the internal peripheral surface of a cylindrical body, and it generate | occur | produces in a resin foam sheet. Scratches can also be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, when forming a resin foam sheet using a mandrel, the stress distortion which arises in a resin foam sheet can be suppressed.

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. (A) is a cross-sectional view showing a concavo-convex structure in which a curved surface portion is formed at the tip of a microprojection, (b) is a cross-sectional view showing a concavo-convex structure in which a flat portion is formed at the tip of a microprojection, (C) is a plan view of one pyramidal microprojection. 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. The side view which shows the structure of the mandrel 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 mandrel according to the present invention is a resin foam sheet comprising only a foam layer formed by foaming a resin composition (hereinafter also referred to as a “foamable resin composition”) that foams by being extruded in a hot melt state. In addition, it is used when producing 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 outer 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 CD is placed in a state in which the central axis (axis line a) of the cylindrical shape passes through the substantial center of the discharge port CDa. It is arranged at the front of the extrusion 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.
Specifically, in the mandrel MD, the edge portion on one end side where the cylindrical body 1 ′ first contacts is the constant diameter portion so that the cylindrical body 1 ′ can be expanded in diameter over some time. It is formed so as to have a smaller diameter, and has an enlarged region R in which the outer diameter is gradually enlarged from the end edge to the constant diameter portion.

  The enlarged-diameter region R is a region formed by chamfering a predetermined radius on the entire circumference of the CD side end, and the radius is preferably 5 to 80 mm.

  In the enlarged diameter region R, a concavo-convex structure is formed on the outer surface in sliding contact with the cylindrical body 1 ′. The concavo-convex structure is formed by a plurality of minute protrusions C. Further, the concave-convex structure has at least the cylindrical body 1 ′ from the position T at which the cylindrical body 1 ′ first comes into contact with the enlarged diameter region R (that is, the position at which the mandrel MD and the cylindrical body 1 ′ first come into contact). It is preferable to form in the area | region of 10-80 mm (length along the surface of the mandrel MD instead of a linear distance) toward the moving direction. Furthermore, it is preferable that the concavo-convex structure is provided so as to extend to a region where the outer diameter does not change substantially on the other end side of the mandrel MD from the enlarged region R, and is preferably 5 mm or more (preferably, It is preferably formed also in a region P of 8 to 12 mm). Moreover, it is preferable that the concavo-convex structure is formed over the entire enlarged diameter region R. Below, the area | region (diameter expansion area | region R and the other area | region P) in which the uneven structure in the mandrel MD is formed is described as the uneven | corrugated area | region E. FIG.

  The microprotrusions C are formed by forming a plurality of grooves on the surface of the uneven area E. In the present embodiment, a plurality of linear grooves (specifically, V-shaped grooves) are formed on the surface of the concavo-convex region E in a twill shape (lattice shape), as shown in FIG. Microscopic projections C having a cross-sectional shape (specifically, a quadrangular pyramid shape) are formed.

The uneven structure can be formed by performing knurling on the surface of the uneven region E. The knurled eyes are preferably in the form of the above-mentioned pattern (squares or rhombuses) from the viewpoint of suppressing friction and scratches with the cylindrical body 1 ', but may also be flat. it can. Further, the angle formed by the linear groove forming the minute protrusion C and the moving direction of the cylindrical body 1 ′ is preferably 0 to 90 °, and more preferably 25 to 65 °.
Further, the width of the groove portion (hereinafter referred to as the groove width) LD is the distance between the minute protrusions C at a height position of about 0.05 mm from the protrusion direction distal end portion to the proximal end portion side of each minute protrusion C. 0.2 to 1.5 mm, more preferably 0.2 to 1.0 mm, and still more preferably 0.2 to 0.7 mm.

The microprotrusions C have a distance (hereinafter referred to as a “protrusion interval”) i between adjacent microprotrusions C in the protruding direction of 0.2 to 2.0 mm, preferably 0.2 to 1.0 mm, and more preferably. The concavo-convex structure is formed by being formed to be 0.4 to 0.7 mm.
The width w between the base ends of each microprojection C is preferably about 0.2 to 2.0 mm, more preferably about 0.2 to 1.0 mm, and 0.4 to 0.7 mm. More preferably, it is about.
Further, the height f of the minute protrusion C is preferably about 0.075 to 1.0 mm, and more preferably about 0.125 to 0.75 mm. Moreover, it is preferable that angle (theta) 2 formed between adjacent quadrangular pyramidal microprotrusions C is about 80-100 degrees.

In addition, a curved surface portion C1 as shown in FIG. 5A or a flat surface portion C2 as shown in FIG. The curved surface portion C1 is preferably formed to have a radius of 0.2 mm or more (preferably 0.2 to 0.4 mm).
Further, as shown in FIG. 5 (c), the curved surface portion C1 and the flat surface portion C2 provided at the front end in the protruding direction of the microprojections C formed in a pyramid shape (specifically, a quadrangular pyramid shape) In a plan view (when the microprojection C is viewed from the protruding direction), the length W ′ of one side is the length W of one side of the base end portion of the microprojection C (that is, between the base end portions of the microprojections C). The width w) is preferably 13 to 98%, more preferably 15 to 95%, and even more preferably 30 to 95%. Moreover, it is preferable that the area ratio of the curved surface part C1 and the plane part C2 with respect to the area of the base end part of the microprotrusion C in planar view is 1.7 to 90%, and it is more preferable that it is 2.3 to 90%. Preferably, it is 9 to 90%.
When such a ratio exceeds the above range, the contact area between the curved part C1 and the flat part C2 and the cylindrical body 1 ′ becomes wider and the friction becomes larger, so that the resin foam sheet 1 has scratches and stress strains. There is a possibility that the effect of suppressing the reduction may be reduced, which is not preferable. On the other hand, when such a ratio is lower than the above range, the tips of the fine protrusions C are pointed, and thus the effect of suppressing scratches generated on the resin foam sheet 1 may be reduced. It is not preferable.

  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.

  The distance between the mandrel MD and the circular die CD is preferably set to a predetermined value. Specifically, the distance along the axis a of the cylindrical body 1 ′ (CD) between the position (cylindrical body contact position) T where the mandrel MD and the cylindrical body 1 ′ first contact each other and the discharge port CDa. -Distance between MD) h is preferably 20 to 100 mm.

  At this time, an angle formed between the cylindrical body 1 ′ between the circular die CD and the mandrel MD and a virtual line L1 extending along the axis a from the discharge port CDa, that is, the cylindrical body 1 ′ contacts the mandrel MD. The angle (cylindrical body contact angle) θ1 at that time is preferably 50 to 85 °, and more preferably 60 to 80 °.

  Moreover, it is preferable that it is 2.0-10.0 m / min as a moving speed (take-off speed) of the cylindrical body 1 'which moves while sliding on the mandrel MD.

Further, on the surface of the mandrel MD, a smooth region F having a smooth surface is formed on the other end side following the uneven region E. In the smooth region F, the entire surface of the cylindrical mandrel MD is formed so as to be smooth, and substantially the entire inner peripheral surface of the cylindrical body 1 ′ after passing through the uneven region E In the region following the concavo-convex region E so as to be in sliding contact with the smooth outer peripheral surface, it is formed to have substantially the same diameter as the other region P of the concavo-convex region E. More specifically, when the substantially entire area of the smooth region F is formed to have a constant diameter, the entire smooth region F is configured to be in sliding contact with the inner peripheral surface of the cylindrical body 1 ′. When the smooth region F is formed on the other end side of the mandrel MD so that the outer diameter dimension gradually decreases toward the other end side, the smooth region F and the cylindrical body are formed on one end side of the mandrel MD. While being in sliding contact with the inner peripheral surface of 1 ′, the smooth region F and the cylindrical body 1 ′ are gradually separated from each other toward the other end side thereafter.
As described above, since the smooth region F and the cylindrical body 1 ′ are in sliding contact, the heat of the cylindrical body 1 ′ further moves to the mandrel MD side, so that the cylindrical body 1 ′ is effectively cooled. be able to.

  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. In addition, as a temperature of pressurized gas, it is preferable that it is 10-90 degreeC.

  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 ′ pushed out from the circular die CD is then sent to the mandrel MD positioned forward in the pushing direction, and moves to the other end side of the mandrel MD while the inner peripheral surface is slidably brought into contact with the uneven region E. 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 (winding speed) is preferably about 1.0 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.

  According to the above structure, when forming a resin foam sheet using a mandrel, the stress distortion which arises in a resin foam sheet can be suppressed.

  That is, a concavo-convex structure is formed in the enlarged-diameter region R by a plurality of microprojections C, and a flat surface portion C2 or a curved surface portion C1 having a radius of 0.2 mm or more is formed at the tip in the projecting direction of the microprojections C. When the distance i is 0.2 to 2.0 mm, the contact area between the enlarged-diameter region R and the cylindrical body 1 ′ can be reduced, and the microprojections C are in contact with the cylindrical body 1 ′. Friction can be reduced.

  Thereby, since the friction which arises between the enlarged diameter area | region R and cylindrical body 1 'is reduced, when cylindrical body 1' moves toward an extrusion direction, cylindrical body 1 'is along a moving direction. Can be suppressed. For this reason, while being able to suppress the stress distortion which arises in the resin foam sheet 1, it can suppress that a damage | wound generate | occur | produces in the resin foam sheet 1. FIG.

  Further, the length W ′ of one side of the flat surface portion C2 or the curved surface portion C1 in a plan view is 13 to 98% with respect to the length W of one side of the base end portion of the minute protrusion C, so that the flat surface portion C2 Alternatively, since the force applied to the cylindrical body 1 ′ by the curved surface portion C1 coming into contact with the cylindrical body 1 ′ is dispersed, it is possible to suppress the occurrence of scratches on the cylindrical body 1 ′ and the cylindrical shape. Stress strain generated in the body 1 'can be suppressed.

  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 description, the resin foam sheet 1 in which the foam layer 10 and the solid layer 20 are laminated one by one has been described. However, the present invention is not limited to this, and the resin foam sheet made only of the foam layer, It may be a resin foam sheet in which a plurality of foam layers or a plurality of solid layers are laminated.

  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.

  Further, the minute protrusion C having the curved surface portion C1 and the minute protrusion C having the flat surface portion C2 may be mixed in the uneven structure, and the curved surface portion C1 and the flat surface portion C2 are formed in one minute protrusion C. May be.

  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 and 2
<Equipment used>
A resin foam sheet was prepared using equipment having an apparatus configuration as shown in FIG. As the confluence mold XH ′, one having the structure shown in FIG. 7 was used.

  As the mandrel MD, the structure shown in FIG. 8 (D1 = 424 mm, D2 = 418 mm, D3 = 500 mm, D4 = 100 mm) was used. The width of the uneven area E of the mandrel MD (distance toward the moving direction of the cylindrical body from the position where it first contacts the cylindrical body), the protrusion interval i and the groove width LD shown in FIG. As shown. A knurling machine was used to form the microprojections. And the front-end | tip part of the protrusion direction of a microprotrusion was grind | polished, and the curved surface part of the radius shown in following Table 1 was formed.

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, homopolypropylene (manufactured by Sun Allomer, “PL500A”, melt flow rate: 3.3 g / 10 min, density: 0.9 g / cm ³ ) 100 parts by weight, 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 mandrel MD is slidably brought into contact with the inside of the extruded cylindrical body 1 'to expand the diameter and cool, and then the cylindrical body 1' is continuously cut along the axial direction to open and expand. Thus, a long resin foam sheet 1 was formed. The long resin foam sheet 1 formed was wound around the winding roller 92 while applying tension along the longitudinal direction. In addition, the winding speed (take-up speed) of the resin foam sheet 1 was set to 3.6 m / min. An electric motor was used as means for driving the take-up roller 92.

The obtained resin foam sheet 1 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 obtained resin foam sheet had a total light reflectance of 98.8%.

<Test method>
The depth of the damage | wound formed in the surface (surface by the side of a foaming layer) slidably contacted with the mandrel MD of the resin foam sheet 1 was measured. Specifically, the obtained resin foam sheet 1 is cut in the longitudinal direction and the width direction, and the depth of scratches in each cross section is measured using a scanning electron microscope (“S-3000N” manufactured by Hitachi, Ltd.). The average value of the measurement results for each cross section is shown in Table 1 below as the measurement results. Moreover, the electrical load (winding load) applied to the electric motor when winding the resin foam sheet 1 was measured. The measurement results are as shown in Table 1 below.

2. 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 foam layer (A) was prepared and tested under the same conditions as in Example 1 except that the test was conducted. The test results are shown in Table 1 below. The obtained resin foam sheet 1 had a total light reflectance of 97.0%.

3. Example 4
A resin foam sheet 1 was prepared under the same conditions as in Example 1 except that a mandrel MD having a curved surface radius, a protrusion interval i, and a groove width LD as shown in Table 1 below was used. I did it. The test results are shown in Table 1 below.

4). Comparative Example 1
A resin foam sheet 1 was prepared and tested under the same conditions as in Example 1 except that a mandrel MD that did not form a curved surface portion on a microprojection was used. The test results are shown in Table 1 below.

5. Comparative Example 2
A resin foam sheet 1 was prepared and tested under the same conditions as in Example 3 except that a mandrel MD that did not form a curved surface portion on a microprojection was used. The test results are shown in Table 1 below.

6). Comparative Example 3
A resin foam sheet 1 was prepared and tested under the same conditions as in Example 4 except that a mandrel MD that did not form a curved surface portion on a microprojection was used. The test results are shown in Table 1 below.

7). Comparative Example 4
A resin foam sheet 1 was produced and tested under the same conditions as in Example 1 except that a mandrel MD having no concavo-convex structure was used. The test results are shown in Table 1 below.

6). Summary When Examples 1 to 4 and Comparative Examples 1 to 3 are compared, it is recognized that the occurrence of scratches in each Example is suppressed more than in each Comparative Example. Further, when Examples 1 to 4 and Comparative Example 4 were compared, scratches were hardly observed under both conditions, but Comparative Example 4 had a higher winding load, and Examples 1 to 4 It is recognized that the tension applied to the resin foam sheet 1 is reduced.
Thus, by using the mandrel MD having the concavo-convex structure formed by the fine protrusions having the curved surface portion, the friction when the cylindrical body 1 ′ and the mandrel MD are in sliding contact is reduced. It is recognized that it is possible to suppress the stress distortion generated in the shape 1 ′, that is, the resin foam sheet 1, and it is possible to suppress the generation of scratches on the resin foam sheet 1.

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 (6)

When producing a resin foam sheet comprising a foam layer formed from a foamable resin composition, the circular die is used together with a circular die that extrudes the melted foamable resin composition to form a cylindrical body. A mandrel that is disposed in front of the extrusion direction and used for cooling while expanding the diameter of the cylindrical body,
At the end arranged on the circular die side, the outer peripheral surface slidably in contact with the inner peripheral surface of the cylindrical body increases in diameter toward the extrusion direction, and the cylindrical body is expanded along the outer peripheral surface. A diameter-expanded region is formed, and a concavo-convex structure is formed in the diameter-expanded region by a plurality of minute projections, and the minute projections are a flat portion and / or a curved surface portion having a radius of 0.2 mm or more at the tip in the protruding direction. The mandrel is characterized in that it is formed so that the distance between the protrusions in the protruding direction between adjacent microprotrusions is 0.2 to 2.0 mm.   The mandrel according to claim 1, wherein the microprotrusions are conical.   The concavo-convex structure is formed in a region of 30 to 80 mm in a moving direction of the cylindrical body from a position where the diameter-enlarged region and the cylindrical body first contact with each other. The described mandrel. In a resin foam sheet manufacturing apparatus for producing a resin foam sheet comprising a foam layer formed from a foamable resin composition,
A resin foam sheet manufacturing apparatus comprising the mandrel according to any one of claims 1 to 3. In a method for producing a resin foam sheet comprising a foam layer formed from a foamable resin composition,
The manufacturing method of the resin foam sheet characterized by using the mandrel of any one of Claim 1 thru | or 3.   The resin foam sheet formed using the resin foam sheet manufacturing apparatus of Claim 4.

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