JP4032990B2 - Multi-layer foam sheet manufacturing apparatus and multi-layer foam sheet manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for producing a multilayer foam sheet, and a method for producing a multilayer foam sheet using the apparatus. In Related.
[0002]
[Prior art]
Foamed sheets, especially foamed sheets made of propylene-based resins, are used in various applications taking advantage of their light weight and heat insulation properties, etc., and furthermore, a multilayer foamed sheet in which a resin layer is laminated on the foamed sheet according to the purpose of use. Thus, functions such as mechanical properties, heat resistance and gas barrier properties are imparted and used in a wide range of fields such as packaging, boxing, partition plates, food containers, stationery, building materials, and automobile interior materials.
[0003]
Usually, a multilayer foamed sheet is produced by the same method as a multilayer sheet not containing a foamed layer, and as its production method, for example, a method in which each layer of the sheet is pre-formed into a film shape, or a coextrusion method However, the coextrusion method is common from the viewpoint of cost merit.
[0004]
A device combining a feed block and a single manifold die as a device used when a multilayer sheet not including a foam layer is manufactured by a co-extrusion method, wherein the feed block outlet width dimension W and the outlet thickness dimension T are combined. An apparatus in which 20 <W / T <30 is disclosed (see Patent Document 1).
[0005]
[Patent Document 1]
Japanese Unexamined Patent Publication No. Hei 8-192245
[0006]
However, when a multilayer foam sheet including a foam layer is manufactured using the above-described apparatus, there is a problem in that a curtain defect corresponding to the feed block outlet width occurs in the central portion of the multilayer foam sheet. The curtain defect is a phenomenon peculiar to foaming in which the sheet becomes wavy.
[0007]
[Problems to be solved by the invention]
For this reason, as a result of studies to develop a multi-layer foamed sheet manufacturing apparatus capable of manufacturing a multi-layer foam sheet having a beautiful appearance with no curtain defects, the present invention has been achieved.
[0008]
[Means for Solving the Problems]
That is, the present invention provides a multi-layer foamed sheet manufacturing apparatus in which the manufacturing apparatus joins the molten resin compositions supplied from an extruder for melting and kneading the resin composition for forming each layer in a multilayer shape. And a manifold die for manufacturing a multilayer foam sheet connected to the feed block to form a multilayer foam sheet, wherein the manifold has an inlet thickness direction cross section connected to a resin flow path of the feed block in the manifold die When the width dimension of W is W and the thickness dimension is T, the cross section is a quadrilateral foamed sheet having a W / T of 1 to 3, and the multilayer foamed sheet is manufactured using the manufacturing apparatus. Method The It is to provide.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings.
The apparatus for producing a multilayer foamed sheet of the present invention comprises an extruder for melting and kneading a resin composition for forming each layer (an extruder is not shown). When all the layers of the multilayer foam sheet to be produced are made of different resin compositions, it is necessary to provide the same number of extruders as the number of layers, but the multilayer foam containing two or more layers made of the same resin composition In the case of producing a sheet, the number of layers of the multilayer foamed sheet and the number of extruders do not necessarily need to match. For example, the non-foamed layer A and the non-foamed layer C are composed of the same resin composition. In this case, that is, in the case of producing a multilayer foam sheet of two types and three layers such as non-foamed layer A / foamed layer B / non-foamed layer A, the resin composition for forming non-foamed layer A is melt-kneaded. There may be one extruder or two extruders.
[0010]
As such an extruder, an extruder used for single-screw or multi-screw ordinary extrusion molding can be used, and a tandem extruder combining a plurality of extruders can also be used. The extruder used for melt kneading the resin composition for forming the foamed layer is preferably a twin screw extruder, and the extrusion amount per one rotation of the screw is large so that a predetermined extrusion amount can be obtained at a low rotation. More preferably, the extruder has a structure with less shearing heat generated by screw rotation, and more preferably an extruder capable of adjusting the temperature by circulating a cooling medium in the screw body.
[0011]
As shown in FIG. 1, the multilayer foam sheet manufacturing apparatus of the present invention has a feed block and a manifold die connected to the feed block.
[0012]
In the single manifold die 1 of FIG. 1, when the width dimension of the cross section in the thickness direction of the inlet of the manifold 3 connected to the resin flow path 7 of the feed block is W and the thickness dimension is T, the multilayer foam sheet manufacturing apparatus of the present invention In the above, W / T is 1 or more and 3 or less, preferably 1 or more and 2 or less, more preferably 1 or more and 1.5 or less, and its cross-sectional shape is a square shape. As W / T is closer to 1, it is possible to produce a multilayer foam sheet having a beautiful appearance and having no curtain defect.
In the present invention, the inlet thickness direction cross section of the manifold 3 connected to the resin flow path 7 of the feed block is a cross section perpendicular to the resin flow in the die 1. Also, the quadrangular shape does not necessarily mean that all four corners are 90 °, and usually the four corners are arc shapes having a radius of 1 to 3 mm. When the cross-sectional shape is a shape in which the four corners draw a curve as shown in FIG. 6B, W and T are defined by the shortest distance between opposite sides. As shown in FIG. 6 (a), the most preferable cross-sectional shape is W = T, and four corners are arc-shaped quadrangular shapes having a radius of 2 mm, thereby producing a multilayer foam sheet having a very beautiful appearance. Can do.
[0013]
The apparatus for producing a multilayer foamed sheet according to the present invention is not particularly limited except for the cross-sectional shape in the inlet thickness direction of the manifold 3 connected to the resin flow path 7 of the feed block, and the multilayer sheet is usually produced by a coextrusion method. It is a device used at the time.
For example, the resin flow path 7 of the feed block may have the same shape as the inlet shape of the manifold 3 as shown in FIG. 3, and is wider than the inlet width of the manifold 3 as shown in FIGS. Also good.
When the width of the resin flow path 7 of the feed block is wider than the inlet width W of the manifold 3, the width of the resin flow path 7 of the feed block is the same as the inlet width of the manifold 3 as shown in FIG. 4. In this shape, it is preferable to have a structure that is connected to the inlet of the manifold 3 after maintaining the distance of 1 to 5 times W in this shape, and the distance to maintain the shape is 2 to 4 times More preferred. By making the shape of the resin flow path 7 of the feed block as shown in FIG. 4, heat generation due to pressure loss at the inlet of the manifold 3 can be suppressed even when the amount of extrusion is large. A beautiful multilayer foam sheet can be produced.
[0014]
The multi-layer foam sheet manufacturing apparatus of the present invention has the structure as described above as a basic structure. However, according to the layer structure of the target multi-layer foam sheet, an apparatus having a multi-manifold die 8 as shown in FIG. There may be. In particular, when the melt properties of the resin composition constituting each layer and the flow rate ratio of each layer are greatly different, it is preferable to use a multi-manifold die.
[0015]
As an example of the present invention, a method for producing a multilayer foam sheet having a configuration of non-foamed layer C / foamed layer D / non-foamed layer E will be described using the apparatus shown in FIG. FIG. 1 is an example of a multilayer foam sheet manufacturing apparatus using a single manifold die as a manifold die. In this case, the resin composition constituting each layer of the multilayer foamed sheet is joined in a multilayer form in the feed block in a molten state.
[0016]
In the feed block 2, the molten resin composition supplied from the three extruders is the molten resin composition C for forming the non-foamed layer C and the molten foam for forming the foamed layer D. After the resin composition D is joined to the manifold 5 and the molten resin composition E for forming the non-foamed layer E passes through the manifold 6 in the resin flow path 7 of the feed block, the feed block To the single manifold die 1, passes through the manifold 3 in the single manifold die 1, is expanded to the width Wd, and is discharged from the single manifold die 1 to form a multilayer foam sheet. . The multilayer foam sheet is cooled to become a multilayer foam sheet, taken up by a take-up machine (not shown), and then cut into a predetermined size as required.
[0017]
Next, a method for producing a multilayer foam sheet having a configuration of non-foam layer F / non-foam layer C / foam layer D / non-foam layer E / non-foam layer G will be described using the apparatus shown in FIG. FIG. 2 is an example of a multilayer foamed sheet manufacturing apparatus using a multi-manifold die as a manifold die. In this case, the foamable resin composition constituting at least one foamed layer in the multilayer foamed sheet is merged with the resin composition constituting the other layer in a multilayered form in the feed block in a molten state.
[0018]
The non-foamed layer C / foamed layer D / non-foamed layer E are guided to the manifold 3 in the multi-manifold die 8 and expanded to the width Wd in the same manner as described above with reference to FIG. In the resin flow path 11 of the multi-manifold die 8, a molten resin composition D for forming the non-foamed layer D supplied from the extruder and expanded to the width Wd and a molten resin for forming the non-foamed layer E are provided. After being merged with the composition E in a multilayer shape, it is discharged from the multi-manifold die 8 to form a multilayer foamed sheet material. The multilayer foam sheet is cooled to become a multilayer foam sheet, taken up by a take-up machine (not shown), and then cut into a predetermined size as required.
[0019]
The resin constituting the multilayer foamed sheet of the present invention is not particularly limited, but an olefin resin typified by an ethylene resin, a propylene resin or the like is preferably used because it can be recycled. In particular, when the multilayer foamed sheet of the present invention is used for applications requiring rigidity and heat resistance, it is preferable that at least the foamed layer is composed of a resin composition containing 50% by weight or more of a propylene-based resin, and the entire layer is propylene. More preferably, it is composed of a resin composition containing 50% by weight or more of a resin.
As the propylene-based resin, known propylene-based resins such as homopolypropylene, random polypropylene, block polypropylene, and the like can be used, and it is preferable to use a non-branched linear propylene-based resin without branching.
[0020]
As the resin constituting the foamed layer in the multilayer foamed sheet of the present invention, it is preferable to use a propylene-based resin having a high melt strength that hardly breaks when bubbles grow. The propylene-based resin having a high melt strength is a propylene polymer having a melt tension (MT (190)) at 190 ° C. and a melt flow rate (MFR (230)) at 230 ° C. satisfying the following formula A.
MT (190) ≧ 7.52 × MFR (230) ^(-0.576) [Formula A]
[0021]
Examples of the propylene polymer satisfying the formula A include, for example, a propylene polymer (T) introduced with an ultrahigh molecular weight component disclosed in JP-A-11-228629, that is, a crystalline propylene polymer having an intrinsic viscosity of 5 dl / g or more. Obtained by a polymerization method comprising a step of producing part (A) and a step of producing crystalline propylene polymer part (B) having an intrinsic viscosity of less than 3 dl / g, the intrinsic viscosity being less than 3 dl / g, Examples thereof include a propylene polymer (T) in which the proportion of the propylene polymer portion (A) is 0.05% by weight or more and less than 35% by weight.
[0022]
As the foaming agent used for forming the foamed layer in the multilayer foamed sheet of the present invention, physical foaming agents and chemical foaming agents used in ordinary foam molding can be used alone or in combination of several kinds.
Examples of the physical foaming agent used include carbon dioxide, nitrogen gas, air, propane, butane, pentane, hexane, dichloroethane, dichlorodifluoromethane, dichloromonofluoromethane, and trichloromonofluoromethane, preferably The use of safe and environmentally friendly inorganic gases such as nitrogen gas, carbon dioxide gas, and air. In particular, the use of carbon dioxide gas is preferable because a multilayer foam sheet having a foam layer with a high expansion ratio can be produced by using carbon dioxide gas having high solubility in a propylene-based resin as a foaming agent. Since carbon dioxide gas becomes a supercritical state at 7.4 MPa or more and 31 ° C. or more and is in a state excellent in diffusion and solubility in the resin, it is more preferably used under such conditions.
[0023]
When a physical foaming agent is used, it is necessary to press-fit the physical foaming agent into the molten resin composition melt-kneaded in an extruder to obtain a melt-foamable resin composition, which is further melt-kneaded. . The amount of the physical foaming agent to be press-fitted is usually 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin forming the foamed layer.
When a physical foaming agent is used as the foaming agent, it is preferable to add a cell nucleating agent. Cell nucleating agents include talc, silica, diatomaceous earth, calcium carbonate, magnesium carbonate, barium sulfate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, calcium silicate, zeolite, mica, clay, wollastonite, hydrotalcite , Magnesium oxide, zinc oxide, zinc stearate, calcium stearate, PMMA and other polymer beads, synthetic aluminosilicate, and the following chemical foaming agents can be used. 0.1 to 10 parts by weight per part.
[0024]
Chemical foaming agents include baking soda, a mixture of baking soda and an organic acid such as citric acid, sodium citrate, stearic acid, azodicarboxylic acid amide, tolylene diisocyanate, isocyanate compounds such as 4,4′diphenylmethane diisocyanate, azobisbuty Ronitrile, barium azodicarboxylate, azo such as diazoaminobenzene, trihydrazinotriazine, diazo compounds, benzene sulfonyl hydrazide, P, P'-oxybis (benzenesulfonyl hydrazide), toluene sulfonyl hydrazide, etc. Hydrazine derivatives, N, N'-dinitroso-pentamethylene-tetramine, nitroso compounds such as N, N'-dimethyl-N, N'-dinitroso-terephthalamide, P-toluenesulfonyl semicarbazide, 4,4 ' Shi can use other azide compound or a triazole compound such as known compounds of semicarbazide compounds such as bis benzenesulfonyl semicarbazide, in particular, sodium bicarbonate, citric acid, azodicarbonamide is preferably used.
[0025]
When a chemical foaming agent is used, 0.1 to 20 parts by weight is usually added to 100 parts by weight of the resin that forms the foamed layer to produce a multilayer foamed sheet.
When a chemical foaming agent is used as the foaming agent, a foaming aid such as zinc oxide, zinc stearate, or urea may be added in order to adjust the decomposition temperature and speed.
[0026]
The multilayer foamed sheet of the present invention may be formed by appropriately adding various additives such as an antioxidant, a stabilizer, an antistatic agent and a filler to the resin composition forming each layer.
[0027]
The multilayer foamed sheet of the present invention only needs to contain at least one foamed layer, for example, all may be composed of different foamed layers, only one layer is a foamed layer, and the other layers are all non-foamed. It may be a layer. The thickness and expansion ratio of the multilayer foam sheet are not particularly limited, but the total multilayer foam sheet thickness is usually 1 to 7 mm and the expansion ratio is 1.3 to 7 times.
As described above, the multilayer foamed sheet of the present invention is not particularly limited in layer structure, but the core layer is a foamed layer, both outer layers have non-foamed layers, and the foamed layer in the total thickness of the multilayer foamed sheet The thickness ratio is preferably 90 to 99%. The multilayer foam sheet having the above-described structure produced using the production apparatus of the present invention is a multilayer foam sheet having a very beautiful appearance.
[0028]
The multilayer foam sheet of the present invention can be used for packaging, boxing, partition plates, food containers, stationery, building materials, automobile interior materials, etc. even by selecting the layer structure as appropriate according to the purpose of use. It is possible to paste a sheet or film (thin plate) on one or both sides of the multilayer foam sheet of the present invention, or apply a solution such as an antistatic agent solution or a gas barrier resin composition solution. Then, a coating layer may be provided and used as a composite multilayer foam sheet. When a layer is further provided on the surface of the multilayer foamed sheet, it is preferable to perform a surface treatment such as corona treatment or ozone treatment on the surface of the multilayer foamed sheet.
As the thin plate to be bonded, known ones can be used depending on the application, for example, a thin plate made of metal such as aluminum or iron, thermoplastic resin, paper, synthetic paper, hemp, glass wool, etc. And non-woven fabrics and woven fabrics.
[0029]
When the multilayer foamed sheet or composite multilayer foamed sheet of the present invention is used as a food packaging material, at least one surface of the sheet is preferably a propylene-based resin layer or a gas barrier resin layer having a thickness of 10 to 100 μm. As the gas barrier resin, known gas barrier resins such as EVOH (ethylene / vinyl alcohol copolymer), PVDC (polyvinylidene chloride), PVA (polyvinyl alcohol), PA (polyamide) are used.
[0030]
When the multilayer foam sheet or composite multilayer foam sheet of the present invention is used as an automobile interior material, it may be used as a composite multilayer foam sheet in which a nonwoven fabric, woven fabric, hemp, glass wool or the like is bonded to at least one surface of the sheet. preferable.
When the multilayer foamed sheet or the composite multilayer foamed sheet of the present invention is used as a partition plate or the like for a box, it is preferably a sheet having a foamed layer having a high foaming ratio on at least one side in order to protect the contents.
[0031]
The method for laminating the thin plate-like material on the multilayer foamed sheet is not particularly limited. For example, (1) a method of applying an adhesive to the surface of the multilayer foamed sheet and / or the surface of the thin plate-like material, and ▲ 2) A method of laminating an adhesive resin film by heating and melting and laminating the adhesive resin film surface with a multilayer foam sheet, and 3) a surface of the multilayer foam sheet with a heater or hot air, and / or Alternatively, a method of melting and laminating the surface of the thin plate-like material, and a method of (4) extruding and laminating the molten resin between the thin plate-like material and the multilayer foamed sheet are exemplified.
[0032]
The multilayer foamed sheet and the composite multilayer foamed sheet of the present invention can be used as a molded product obtained by thermoforming such as vacuum molding into a desired shape.
A known method can be used as the thermoforming method, and examples thereof include vacuum forming and heat ruled line processing. Since the multilayer foam sheet of the present invention has no curtain defect and a uniform thickness, it has excellent thermoformability.
[0033]
【The invention's effect】
By producing a multilayer foamed sheet using the apparatus of the present invention, it is possible to produce a multilayer foamed sheet having a beautiful appearance with no curtain defects.
[0034]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these examples at all, unless the main point is impaired.
[0035]
(1) Intrinsic viscosity of polymer
The measurement was performed in 135 ° C. tetralin using an Ubbelohde viscometer. The intrinsic viscosity of the crystalline propylene polymer portion (B) was determined from the calculation formula described in JP-A-11-228629 from the intrinsic viscosity of the crystalline propylene polymer portion (A) and the entire propylene polymer (T). .
[0036]
(2) Molecular weight distribution
G. P. C. (Gel permeation chromatography) was measured under the following conditions. The molecular weight distribution was evaluated by the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn).
Model: 150CV type (Millipore Waters)
Column: Shodex M / S 80
Measurement temperature: 145 ° C
Solvent: orthodichlorobenzene
Sample concentration: 5mg / 8mL
A calibration curve was prepared using standard polystyrene. Mw / Mn of standard polystyrene (NBS706: Mw / Mn = 2.0) measured under these conditions was 1.9 to 2.0.
[0037]
(3) MFR
According to JIS K7210, the temperature was 230 ° C. and the load was 2.16 kgf. The unit is g / 10 minutes.
[0038]
(4) Melt tension (MT)
Using a melt tension tester MT-501D3 manufactured by Toyo Seiki Co., Ltd., a strand was extruded from an orifice having a length of 8 mm and a diameter of 2 mm at a sample amount of 5 g, a heating temperature of 190 ° C., a heating time of 5 minutes and an extrusion speed of 5.7 mm / min The tension when the strand was wound at a winding speed of 100 rpm using a roller having a diameter of 50 mm was measured as melt tension (MT) (unit = g).
[0039]
(5) Foaming ratio
In accordance with JIS K7112, the density ρ (total) of the entire multilayer foam sheet was determined using a measurement method based on an underwater substitution method, and the expansion ratio of the entire multilayer foam sheet was calculated according to the following formula. The density ρ (foam) of the foam layer is obtained by using the density ρ (total) and thickness t (total) of the entire multilayer foam sheet, and the thickness (t (non)) and density (ρ (non)) of each non-foamed layer. It calculated from the following formula and calculated | required the expansion ratio of only the foam layer. The density of the propylene resin and ethylene resin used is ρ ₀ (0.9g / cm ³ The thickness of each layer was measured using a normal optical microscope. The unit is ρ (g / cm ³ ), T (cm).
-Overall foaming ratio = ρ ₀ / Ρ (all)
-Density of foam layer ρ (emission) = (t (total) × ρ (total)-t ₁ (Non) × ρ ₁ (Non) -t ₂ (Non) × ρ ₂ (Non))) / (t (all)-(t ₁ (Non) + t ₂ (Non)))
-Foaming ratio of foam layer = ρ ₀ / Ρ (departure)
[0040]
[Reference Example 1] (Production of propylene-based resin PP1)
Propylene polymer powder was produced by the method disclosed in JP-A-11-228629. The propylene polymer powder had a crystalline propylene polymer portion A having an intrinsic viscosity of 7.7 dl / g and a crystalline propylene polymer portion B having an intrinsic viscosity of 1.2 dl / g. The weight ratio of A and B was 11:89, and the intrinsic viscosity of the entire propylene polymer was 1.9 dl / g.
0.1 parts by weight of calcium stearate, 0.05 parts by weight of trade name Irganox 1010 (manufactured by Ciba Geigy), 0.2 parts of trade name Sumilizer BHT (manufactured by Sumitomo Chemical Co., Ltd.) 0.2 with respect to 100 parts by weight of the propylene polymer powder. Part by weight was added and mixed, and melt kneaded at 230 ° C. to obtain pellets (propylene resin PP1) having a melt flow rate MFR of 12 g / 10 minutes and a molecular weight distribution of 8.0. The melt tension MT of the pellet was measured and found to be 4.7 g, and the right side of [Formula A] 7.52 × MFR (230) ^(-0.576) Was 1.80, and [Formula A] was satisfied.
[0041]
[Example 1] (Extrusion Foam Test)
A two-type, three-layer, multi-layer foam sheet having a configuration of non-foamed layer C / foamed layer D / non-foamed layer C was produced by the following method.
As an apparatus for producing a multilayer foamed sheet, a 104 mmΦ co-rotating twin-screw extruder (L / D = 32, L is an effective screw length, D is a screw diameter) provided with a gear pump at the tip as an extruder for the foam layer, A 90 mmφ single-screw extruder (L / D = 32) was used as the non-foamed layer extruder, and these extruders were connected to the feed block 2 of the apparatus shown in FIG.
The shape of the resin flow path 7 in the single manifold die 1 and the feed block 2 is a shape as shown in FIG. 4, the width dimension W of the manifold 3 inlet thickness direction cross section is 30 mm, and the thickness dimension T is 30 mm. The cross-sectional shape was a quadrangular shape having an arc having four corners with a radius of 2 mm as shown in FIG. The manifold diameter was 30 mm.
As the foamable resin composition D for forming the foam layer D, 50 parts by weight of the propylene-based resin PP1 (MFR = 12 g / 10 min) obtained in Reference Example 1 and propylene-based resin PP2 (Sumitomo Chemical ( Co., Ltd., Nobrene AW191A (MFR = 11 g / 10 min)), 40 parts by weight, linear low density polyethylene PE1 (manufactured by Sumitomo Chemical Co., Ltd., Sumikasen E, FV401 (MFR = 4 g / 10 min))) Resin composition for forming non-foamed layer C by using 0.5 PHR blend of cell nucleating agent (manufactured by Nippon Boehringer Ingelheim Co., Ltd., Hydrocerol CF40E) with respect to 10 parts by weight of the composition As C, propylene-based resin PP2 was used.
The foamable resin composition D is introduced into a foam layer extruder through a quantitative feeder, melted and kneaded, and 0.58 PHR of liquefied carbon dioxide gas is supplied as a diaphragm metering pump at a position where melting has progressed (L / D = 20). And then melted and kneaded sufficiently to obtain a melt-foamable resin composition D, then cooled and adjusted to 180 ° C., and adjusted using a gear pump so that the discharge amount becomes 190 kg / h, the feed block 2 It was introduced into the inner manifold 5.
On the other hand, the propylene-based resin PP2 is introduced into a non-foamed layer extruder through a quantitative feeder, melt kneaded, adjusted to 200 ° C., and the manifold 4 in the feed block 2 and the discharge amount 20 kg / h. It was introduced into the manifold 6. The molten foamable resin composition D and the molten resin composition C are joined together in a multilayer shape with a width of 210 mm in the resin flow path 7 and then led to the single manifold die 1 through the resin flow path 7. The multilayer foamed sheet discharged through the single manifold die 1 with the width Wd = 1600 mm extended through the inner manifold 3 is installed immediately after the die discharge port, and is heated to a large number of 210φ rolls adjusted to about 80 ° C. It was made to adhere and cooled, and it took up with the take-up machine provided with the nip roll, and obtained the multilayer foam sheet of the composition of non-foaming layer C / foaming layer D / non-foaming layer C.
The obtained multilayer foamed sheet has a foaming ratio of 3.9 times and a thickness of 5.0 mm in the whole multilayer foamed sheet, the foaming layer D has a foaming ratio of 4.2 times, and the non-foamed layer C has a thickness of 60 μm. there were. The multilayer foamed sheet was a multilayer foamed sheet having a beautiful appearance with no curtain defects.
[0042]
[Comparative Example 1]
Non-foamed layer C / foamed layer D / non-foamed layer C in the same manner as in Example 1 except that a manufacturing apparatus having a width W of 210 mm (W / T = 7) in the cross section in the thickness direction of the inlet of the manifold 3 was used. A multilayer foamed sheet having the following structure was obtained. The obtained multilayer foamed sheet was a multilayer foamed sheet having a very poor appearance, with a curtain defect having a width corresponding to the width dimension W of the cross section in the thickness direction of the inlet of the manifold 3 observed in the center of the sheet.
[0043]
[Comparative Example 2]
Non-foamed layer C / foamed layer D / non-foamed in the same manner as in Example 1 except that a manufacturing apparatus having a width dimension W of the manifold 3 inlet thickness direction cross section of 100 mm (W / T = 3.3) was used. A multilayer foam sheet having the structure of layer C was obtained. In the obtained multilayer foam sheet, a curtain defect having a width corresponding to the width dimension W of the cross section in the thickness direction of the manifold 3 inlet was observed at the center of the sheet. The degree of curtain failure was better than that of the multilayer foamed sheet of Comparative Example 1, but it was not enough for use as a product, and was a multilayer foamed sheet with poor appearance.
[Brief description of the drawings]
FIG. 1 is a drawing of a multi-layer foamed sheet manufacturing apparatus showing an example of the present invention.
FIG. 2 is a drawing of an apparatus for producing a multilayer foam sheet showing an example of the present invention.
FIG. 3 is a drawing showing an example of the AA cross section of FIG. 1 or FIG. 2;
4 is a diagram showing an example of a cross section taken along the line AA of FIG. 1 or FIG. 2;
5 is a drawing showing an example of a cross section taken along the line AA in FIG. 1 or FIG. 2;
6A is a diagram showing an example of a cross section in the inlet thickness direction of the manifold 3; FIG.
(B) The figure which shows one example of the inlet-portion thickness direction cross section of the manifold 3
[Explanation of symbols]
1: Single manifold die
2: Feed block
3: Manifold
4: Manifold
5: Manifold
6: Manifold
7: Resin flow path of feed block
8: Multi-manifold die
9: Manifold
10: Manifold
11: Resin channel

Claims (2)

In the apparatus for producing a multilayer foamed sheet, a feed block for joining the molten resin compositions supplied from an extruder for melting and kneading the resin composition for forming each layer into a multilayer form, and the feed block Is a manufacturing apparatus for a multilayer foam sheet, which is combined with a manifold die for forming a multilayer foam sheet and is connected to a resin flow path of a feed block in the manifold die. An apparatus for producing a multilayer foamed sheet, characterized in that when the thickness dimension is T, the cross section is a square shape having a W / T of 1 or more and 3 or less. In the manufacturing method of a multilayer foamed sheet, the molten resin composition supplied from the extruder which melt-kneads the resin composition for forming each layer is fed using the multilayer foamed sheet manufacturing apparatus according to claim 1. A method for producing a multilayer foamed sheet, comprising: joining a multi-layered form in a block; and extruding from a manifold die connected to the feed block to form a multilayer foamed sheet.

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