JP4180968B2 - Method and apparatus for producing multilayer sheet or multilayer film - Google Patents

Description

【００５５】
【発明の効果】
本発明によれば、比重差の大きな樹脂の組み合わせであっても幅方向に均一に各層の厚みを制御し多層シートおよび多層フィルムを得ることができる。
【図面の簡単な説明】
【図１】本発明の一つの実施形態を例示した２層シートの押出装置のうち押出機からキャスティングドラムまでを示している。
【図２】本発明の一つの実施形態を例示したフィードブロックと単層ダイの正面図、およびダイの側面図を示している。
【図３】図２のＡ−Ａ断面における２層フィードブロックの断面図である。
【図４】図２のＡ−Ａ断面における３層フィードブロックの断面図である。
【図５】図３のＦ−Ｆ断面における２層フィードブロックの断面図、および表層樹脂流路と層厚調整具の拡大図である。表層側の樹脂の密度が小さい場合に用いる。
【図６】図３のＦ−Ｆ断面における２層フィードブロックの断面図、および表層樹脂流路と層厚調整具の拡大図である。表層側の樹脂の密度が極端に小さい場合に用いる。
【図７】図３のＦ−Ｆ断面における２層フィードブロックの断面図、および表層樹脂流路と層厚調整具の拡大図である。表層側の樹脂の密度が大きい場合に用いる。
【図８】図３のＦ−Ｆ断面における２層フィードブロックの断面図、および表層樹脂流路と層厚調整具の拡大図である。樹脂の密度差が小さい場合に用いる。
【図９】図３のＦ−Ｆ断面における２層フィードブロックの断面図、および表層樹脂流路と層厚調整具の拡大図である。Ｔダイの場合に用いる。
【図１０】図３のＧ−Ｇ、Ｈ−Ｈ断面、および図２のＢ−Ｂ、Ｃ−Ｃ、Ｄ−Ｄ断面における表層樹脂とコア層樹脂の図である。層構成が正常な場合の図である。
【図１１】図２のＢ−Ｂ、Ｃ−Ｃ、Ｄ−Ｄ断面における表層樹脂とコア層樹脂の図である。層構成が異常な場合の図である。
【図１２】図２のＥ−Ｅ断面における２層シートの図であり、（ａ）は層構成が正常な場合、（ｂ）は異常な場合である。
【図１３】図２のＥ−Ｅ断面における３層シートの図であり、（ａ）は層構成が正常な場合、（ｂ）は異常な場合である。
【図１４】図２のＥ−Ｅ断面における９層シートの図であり、（ａ）は層構成が正常な場合、（ｂ）は異常な場合である。
【符号の説明】
１：表層側の押出機
２：表層側のギアポンプ
３：表層側のフィルター
４ａ：表層側のポリマーパイプ
４ｂ：コア層側のポリマーパイプ
５：コア層側の押出機
６：コア層側のギアポンプ
７：コア層側のフィルター
８：キャスティングドラム
９：フィードブロック
９ａ：フィードブロックの表層側の部材
９ｂ：フィードブロックのコア層側の部材
１０：単層ダイ
１１：未延伸シート
１２：ダイへの供給口
１３：マニホールド
１４ａ：表層側の樹脂流路、または表層側の樹脂
１４ｂ：コア層側の樹脂流路、またはコア層側の樹脂
１５：層厚調整具
ｘ：表層流路の高さ方向
Ｈ：表層流路の高さ
Ｌ：異常部の幅
Ｗｂ：表層流路の幅（ダイの反フィード側に対応）
Ｗｃ：ｘ＝Ｈ／２での表層流路の幅（ダイのセンターに対応）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to method and apparatus for manufacturing a multilayer sheet or multilayer film.
[0002]
[Prior art]
One of the methods for producing a thermoplastic resin film as a multilayer film is a co-extrusion method, which includes a multi-manifold method and a feed block method. In the multi-manifold system, a plurality of molten resin flows enter each manifold and are separately developed in the width direction and merged immediately before the die exit. On the other hand, in the feed block system, a plurality of molten resin flows are merged in the feed block and then developed in the width direction by a die manifold.
[0003]
However, this multi-manifold die has a high price per unit due to the complexity of the die structure, and in order to manufacture a wide variety of brands, it is necessary to have dies with different sizes and widths for each product width. There is no versatility.
[0004]
In addition, in the method of co-extrusion of a multilayer film by combining a single layer die and a feed block, it is very difficult to control the distribution of each layer thickness in the film width direction. It is desirable that the thickness of each layer constituting the film can be controlled for each layer. For this reason, in the multilayer film co-extrusion apparatus, it is necessary to control the amount of molten resin in the width direction between the respective layers.
[0005]
Therefore, a method for controlling the thickness of each layer of the multilayer film is proposed in Japanese Patent Application Laid-Open No. 7-241897. That is, by changing the notch shape of the layer thickness adjuster provided in the feed block, the flow path width through which the resin flows is adjusted, and the flow rate is locally changed to make the thickness distribution in the width direction of each layer of the multilayer film uniform. It is an extrusion device to be made.
[0006]
In addition, Reference 1 (POLYMAER ENGNEERING AND SCIENCE, DECEMBER, 1975, vol. 15, No. 12, P825-830) reports a wrapping phenomenon in which the layer structure changes due to a difference in melt viscosity.
[0007]
JP 2002-225107 A discloses a multilayer film extrusion apparatus and a multilayer film in which a layer having a multilayer film is not laminated to the end of the film by defining the cross-sectional shape of the resin flow path at the resin junction of the feed block. Manufacturing methods have been proposed.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-241897
[Patent Document 2]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-225107
[Problems to be solved by the invention]
However, according to the knowledge of the present inventors, in these techniques, an abnormality occurs in the layer structure due to the difference in specific gravity. That is, as shown in the cross-sectional view of the two-layer film in FIG. 12, if it is normal, a two-layer structure is formed over the entire width in the width direction as shown in FIG. 12 (a), but there is a difference in specific gravity between the two molten resins. If so, as shown in FIG. 12 (b), an abnormality in the layer structure occurs in which the portion corresponding to the opposite side of the die in the width direction becomes a single-layer film having only a low specific gravity in the two-layer film.
[0011]
Due to this abnormality, there is a problem that the product width of the multilayer film is reduced, a problem that the film is torn near the boundary between the multilayer part and the single layer part when the film is stretched, and the edge of the film is recovered to form a film again In the case of a brand containing a large amount of pigment when commercialized, there is a problem that the concentration of the pigment in the recovered film changes due to the collapse of the layer structure balance of the edge portion. In addition to the two-layer film, the abnormality shown in FIG. 13B occurs when the film is a three-layer film, and the abnormality shown in FIG. 14B occurs when the film is a nine-layer film.
[0012]
Therefore, in the present invention, when a multilayer film is formed from a multilayer sheet by combining a single layer die and a feed block, by adjusting the flow of each molten resin in the feed block, even a combination of resins having a large specific gravity difference. An object of the present invention is to provide a multilayer sheet or multilayer film production method and production apparatus capable of uniformly controlling the thickness of each layer in the width direction.
[0013]
[Means for Solving the Problems]
That is, the present invention is a method for producing a multilayer sheet in which at least two types of molten resin are merged and extruded from a single-layer die by a feed block provided on the upstream side of a side-feed or central-feed single-layer die. In the method, the feed block includes a flow path for each molten resin, and a flow path width at a position immediately before the molten resin merges in the flow path satisfies at least one of the following formulas (a) and (b): And the melt density of the molten resin satisfies the following formula (c).
[0014]
About the resin flow path with the lowest melt density Wb <Wc (a)
Resin flow path with the highest melt density Wb> Wc (b)
( Wb is the channel width at the position corresponding to the opposite side of the die width direction and Wc is the channel width at the position corresponding to the die center in the die width direction.)
1.05 ≦ ρmax / ρmin ≦ 3.00 (c)
(However, ρmax is the melt density of the resin having the highest melt density among the melted resins, and ρmin is the melt density of the resin having the lowest melt density.)
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an illustration of one embodiment of the present invention. FIG. 2 shows an extruder to a casting drum in a two-layer sheet extrusion apparatus.
[0016]
The extruder for the two-layer sheet is composed of the extruder 1, the gear pump 2, the filter 3, the polymer pipe 4a, and the resin that becomes the core layer of the two-layer sheet in order from the upstream side in the flow direction of the resin that becomes the surface layer of the two-layer sheet. The extruder 5, gear pump 6, filter 7, and polymer pipe 4 b are arranged in this order from the upstream side in the flow direction, and the two molten resins are merged inside the feed block 9 so that the molten resin 11 is formed into a sheet form from the single-layer die 10. It has a structure that is extruded as a two-layer sheet.
[0017]
In the case of using, for example, polyethylene terephthalate as the resin, it can be further cooled by a casting drum 8 to form an unstretched multilayer sheet, and subjected to longitudinal stretching and / or lateral stretching by a stretching apparatus (not shown) to form a multilayer film.
[0018]
FIG. 2 is an illustration of one embodiment of the present invention. A front view of the feed block and the single layer die and a side view of the die are shown. The single-layer die 10 is a side feed type, and has a resin supply port 12 on one side of the die. The BB arrow view, CC arrow view, and DD arrow view respectively show the feed side, center, and counter feed side arrow view positions in the die width direction. Reference numeral 13 denotes a single-layer die manifold.
[0019]
First, an abnormality in the feed block 9 and the layer configuration and a solution method thereof will be described.
[0020]
FIG. 3 is an arrow view of the AA cross section of FIG. 2 and shows a cross section of a two-layer feed block illustrating one embodiment of the present invention. The resin on the surface layer side passes through the flow path 14a connected to 4a, and immediately after being squeezed by the layer thickness adjuster 15, merges with the resin on the core layer side flowing in the flow path 14b, and the supply port 12 to the die Led to.
[0021]
When the resin on the surface layer side and the core layer side are similar and there is not much difference in physical properties, especially when there is no difference in melt density, as shown in FIG. 10, while maintaining the layer structure in each cross section in the width direction A two-layer film having approximately uniform thickness is obtained as shown in FIG. In this case, experience shows that the flow path of the surface layer side flow path 14a narrowed down by the layer thickness adjuster 15 has no problem as a substantially rectangular flow path as shown in FIG. 8 showing the FF cross section of FIG. I understand. However, according to the research by the present researchers, when the film thickness was adjusted with a combination of the layer thickness adjuster of FIG. 8 and the melt density of the resin on the surface layer side was smaller than the melt density on the core layer side, It has been found that the layer configuration changes in each cross section in the width direction of the single-layer die as shown in FIG. 11, and as a result, an abnormality in the layer configuration occurs as shown in FIG. That is, according to FIG. 11, there is no abnormality in the layer structure in the BB cross section corresponding to the feed side in the die, but in the CC cross section and DD cross section corresponding to the cross section on the opposite side from the center of the die. Since the surface layer side resin 14a having a small specific gravity is light, the resin 14a wraps around the die manifold due to the influence of gravity. In other words, since the core layer side resin 14b having a large specific gravity is heavy, it is discharged first to the feed side of the die under the influence of gravity, and does not reach the cross section DD on the opposite side of the die. Therefore, as a result, the resulting two-layer film has a single-layer portion of only the surface layer side resin with almost no core layer resin on the opposite side of the die as shown in FIG.
[0022]
The left figure of FIG. 5 has shown the flow-path shape in the FF cross section of FIG. 3, Furthermore, the right figure is an enlarged view of the surface layer side flow path 14a and the layer thickness adjustment tool 15, and x is the height of the flow path 14a. The vertical direction, Wc is the flow path width at the position of x = H / 2 of the flow path 14a and corresponds to the center in the die width direction, and Wb is the flow path width corresponding to the non-feed side in the die width direction. . If the melt density on the surface layer side is smaller than the melt density on the core layer side, the flow path width should be Wb <Wc as shown in FIG. By narrowing the channel width Wb, the thickness of each layer can be made uniform as a result. When the difference in melt density between the two resins is extremely large, it is necessary to completely close Wb = 0 as shown in FIG. On the other hand, when the melt density on the surface layer side is larger than the melt density on the core layer side, the thickness of each layer can be made uniform by setting the flow path width to Wb> Wc as shown in FIG. In the illustrated diagram, only the flow path shape on the surface layer side is changed, but the flow path shape of the flow path 14b on the core layer side may be adjusted with a layer thickness adjuster, and the flow paths of both resins The shape may be changed.
[0023]
When the thickness of each layer is made uniform in the width direction in the two-layer film, ρmax / ρmin is preferably 1.05 to 3.00, where ρmax is the larger of the melt density of the resin and ρmin is the smaller one. Preferably it is 1.05-2.00. When the ratio is 1.05 or more, the effect of the present invention can be remarkably exhibited. If it is larger than 3.00, the feed block method is not preferable because it is difficult to maintain the layer structure.
[0024]
The flow path width ratio Wb / Wc is a figure in the case of controlling the side with a small melt density with the layer thickness adjuster 15 in FIGS. 5 and 6, preferably 0 to 0.95, and less than 0.95. The case where the effect of the invention can be exhibited remarkably and is substantially blocked with Wb = 0 is also necessary. On the other hand, in FIG. 7 in the case where the higher melt density side is controlled by the layer thickness adjuster, the ratio of Wb / Wc is preferably 1.05 to 5, more preferably 1.05 to 3. The effect of the present invention can be exhibited remarkably at 1.05 or more, and if it exceeds 5, the flow width of Wb is too wide, the change in the flow rate of the resin becomes dull, and the effect of controlling the layer thickness becomes small.
[0025]
5 and 7 exemplify a shape in which the flow path width from Wc to Wb gradually decreases or gradually increases by connecting the flat surfaces, but the curved surface and the flat surface can be obtained even when the curved surface is connected to finely adjust the layer structure. A combination of these may be used. Further, when the shape of the channel width becomes complicated, the minimum width or the maximum width of the channel 14a at x = H / 2 to H in the right diagram of FIG. 5 is defined as Wb.
[0026]
The material of the feed block 9 is generally metal, and stainless steel or hard tool steel is particularly preferable. A known technique can be used for the material and overall shape of the layer thickness adjuster 15. For example, the material is preferably a metal from the viewpoint of pushing and pulling, or electric discharge machining of the notch shape, and further wear resistance and processing. Hard tool steel is preferred to maintain accuracy.
[0027]
The overall shape may be a rectangular parallelepiped as an example, but it may be a cylindrical pin. In the case of a pin, two to three types of notches are applied in advance by changing the machining surface, and fine adjustment of the layer configuration is required. If there is, you can try two or three kinds of notches during film formation by turning the pin. Since the layer thickness adjuster may cause the resin to enter the gap with the surrounding members and generate deteriorated products, use packing for the seal part or use a structure that allows the resin to leak out of the feed block 9 little by little. You can also. Further, in the feed block illustrated in FIG. 3, the flow path 14 a on the surface layer side is narrowed using the layer thickness adjuster 15, but the flow path 14 a itself is processed to be narrowed without using the layer thickness adjuster. However, the shape illustrated in FIGS. 5 to 7 may be used.
[0028]
The extrusion of the two-layer sheet has been mainly described above. However, in the present invention, the extrusion of a sheet having three or more layers can also be performed. For example, in the case of a three-layer sheet, a three-layer feed block may be used as the feed block. As an example, FIG. 4 shows a cross section of the feed block, and FIG. 13 shows a cross section of the sheet. When the melt density of the resin 14a on the surface layer side is small, there is an abnormality in the layer structure as shown in FIG. 13B in the flow path shape of FIG. 8, and if the conditions of the present invention are applied, the thickness of each layer in the width direction Can be made uniform. In the case of a 9-layer sheet, as shown in FIG. 14 (b), it can be seen that there are abnormalities in 2 to 3 layers on both surface layers, and that there are no abnormalities in the layer structure of several layers in the core layer portion. Yes. As the number of layers is increased, the core layer seems to maintain a balance in the die manifold and the layer change of each layer does not easily occur. If adapted, the abnormal part can be eliminated. Further, in the case of a multilayer sheet having three or more layers, the configuration shown in FIG. 1 may be adopted by using three or more extruders. In these cases, if the present invention is applied to the resin having the lowest melt density and / or the resin having the highest melt density, the abnormal portion of the layer structure can be remarkably eliminated.
[0029]
In the present invention, each layer changes due to the difference in specific gravity of the resin. Therefore, as the residence time of the resin in the die is longer, an abnormal portion is more likely to appear at a position on the side opposite to the feed. The average residence time of the resin in the single-layer die 10 is preferably 5 to 200 seconds, more preferably 10 to 150 seconds. If it is less than 5 seconds, the multilayer sheet can be collected with the flow channel shape shown in FIG. 8 without applying the present invention, but the die width is very short and the productivity is extremely poor. The feed block method is not preferable because it is difficult to maintain the layer structure.
[0030]
In FIG. 1 and FIG. 2, the single-layer die 10 is illustrated as a side feed type die in which the resin supply port 12 is on one side of the die, but this method can be used for die assembly and removal from the extrusion apparatus shown in FIG. Although it is easy, the residence time to the antifeed side of the die becomes long. Therefore, although the layer structure is likely to be abnormal on the non-feed side, the effect of the present invention is easily exhibited.
[0031]
As another method, there is a T die or a coat hanger die in which the resin supply port is in the center of the die, and the layer configuration is abnormal at both ends of the die corresponding to the opposite feed side. For example, the flow path shape shown in FIG. It can be solved by using.
[0032]
As the resin constituting the multilayer film in the present invention, a thermoplastic resin mainly composed of a stretchable polymer can be used. For example, an aromatic polyester such as polyethylene terephthalate, polyethylene-2,6-naphthalate, or polybutylene terephthalate. Polyolefins such as polyethylene and polypropylene, polyvinyls such as polystyrene, polyamides such as nylon 6 (polycaprolactam), nylon 66 (poly (hexamethylenediamine-co-adipic acid)), aromatics such as bisphenol A polycarbonate Examples thereof include resins mainly composed of homopolymers such as polycarbonate and polysulfone or copolymers thereof. Examples of the copolymer component include isophthalic acid copolymerized polyethylene terephthalate and 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate. Among the above thermoplastic resins, aromatic polyesters, polyolefins, and polyamides capable of molecular orientation by stretching are preferred, and polyethylene that exhibits excellent optical, mechanical, and thermal properties when the molecules are biaxially oriented. 2,6-naphthalate is also preferred.
[0033]
In the present invention, at least one of the resins constituting the multilayer sheet, for the purpose of causing the sheet or film to wait for whiteness, gloss, concealment, or for improving the winding property of the sheet or film, inert particles Is preferably contained in an amount of 5 to 60% by weight. Also, at this time, an abnormality in the layer structure is likely to occur, and the abnormality can be solved by the present invention. If the inert particles are larger than 60% by weight, they are easily broken when the film is stretched, and an abnormality in the layer structure hardly occurs even if it is smaller than 5% by weight.
[0034]
Examples of the inert particles include rutile type titanium oxide, anatase type titanium oxide, barium sulfate, silica oxide, alumina, calcium carbonate, calcium phosphate, kaolin, talc, inorganic inert particles such as silicone, crosslinked polystyrene, styrene-divinyl. Organic inert particles such as benzene copolymers can be mentioned. The average particle size is preferably 0.01 to 8 μm.
[0035]
The multilayer sheet of the present invention is obtained by stretching a non-stretched multilayer sheet in a longitudinal and / or transverse direction at a predetermined temperature and heat-treating at a predetermined temperature by a conventionally known method. If necessary, the film can be re-longitudinal and / or re-laterally stretched and wound to form a multilayer film. You may provide the process of apply | coating a coating liquid to a film and drying during the manufacturing process of a multilayer film, or after manufacture.
[0036]
【Example】
Hereinafter, the present invention will be further described by way of examples. In addition, the measurement of the physical-property value in an example and evaluation of film forming property were made into the following method.
[0037]
(1) Thickness of each layer An unstretched sample cooled and solidified by the casting drum 8 was cut into a triangle, fixed to an embedding capsule, and then embedded with an epoxy resin. Then, the embedded sample is made into a thin film section having a thickness of about 50 nm in a longitudinal direction with a microtome (ULTRACUT-S), and then observed and projected at 100 kv using a transmission electron microscope. Then, the thickness of each layer was measured from the photograph, and the thickness of each layer was measured.
[0038]
(2) Measurement of the width L of the abnormal portion of the layer structure The width L of the single layer portion shown in FIG. 13B was measured with a metal scale in the unstretched sample cooled and solidified by the casting drum 8.
[0039]
(3) Evaluation of film forming property The following criteria were used.
○: When transversely stretched, the film is broken 0 times / day.
Δ: When transversely stretched, the film breaks once or twice per day.
X ... When transversely stretching, the film breaks 3 times / day or more.
[0040]
(4) Evaluation of width yield Evaluation was made according to the following criteria.
○ ... It was possible to commercialize over 70% of the unstretched film width.
Δ: The product width was less than 70% of the unstretched film width.
× ・ ・ ・ Could not be commercialized.
[0041]
(5) Evaluation of average residence time in the die of the two-layer sheet V (cm ³ ) is the volume of the resin flow path portion of the single-layer die 10, Sa (cm ³ / s) is the volume flow rate of the surface layer side resin, and the core layer When the volume flow rate of the side resin is Sb (cm ³ / s), the following formula is used.
Residence time t (seconds) = V / (Sa + Sb)
[0042]
In addition, resin used by the Example and the comparative example is as follows.
(1) Resin P
Polyethylene terephthalate (PET) having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.65 dl / g. The melt density of the resin at a temperature of 280 ° C. was 1.2 g / cm ³ .
[0043]
(2) Resin Q
Polyethylene terephthalate with an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.64 dl / g and a copolymerization component of 12 mol%. The melt density of the resin at a temperature of 280 ° C. was 1.2 g / cm ³ .
[0044]
(3) Resin P30
Resin P contained 30% by weight of rutile titanium oxide having an average particle size of 0.24 μm and a density of 4.27 g / cm ³ . The melt density at 280 ° C. of the resin containing the pigment can be converted to 1.53 g / cm ³ .
[0045]
(4) Resin Q30
Resin Q contained 30% by weight of rutile titanium oxide having an average particle size of 0.24 μm and a density of 4.27 g / cm ³ . The melt density at 280 ° C. of the resin containing the pigment can be converted to 1.53 g / cm ³ .
[0046]
(5) Resin Q50
Resin Q contained 50% by weight of barium sulfate having an average particle diameter of 0.8 μm and a density of 4.2 g / cm ³ . The melt density at 280 ° C. of the resin containing the pigment can be converted to 1.87 g / cm ³ .
[0047]
[Example 1]
First, a two-layer film was formed using an extrusion apparatus having the configuration shown in FIG. 1, a two-layer feed block shown in FIG. 3, and a layer thickness adjuster having a surface resin flow path shape shown in FIG.
[0048]
The raw material Q on the surface layer side was charged into the extruder 1 and weighed to 180 Kg / hr with the gear pump 2, followed by filtration with the filter 3 and led to the feed block at a temperature of about 280 ° C. On the other hand, the raw material Q30 on the core layer side was put into the extruder 5, weighed to 1250 Kg / hr by the gear pump 6, filtered by the subsequent filter 7, and led to the feed block at a temperature of about 280 ° C. Wb and Wc of the feed block were the channel widths shown in Table 1.
[0049]
Next, the sheet was extruded from a single-layer die 10 having a discharge width of 1200 mm and a resin flow path volume of 3800 cm ³ to form a multilayer sheet, which was longitudinally stretched at 115 ° C. and 3.2 times, and then at 125 ° C. and 3.4 times. The film was transversely stretched and further heat-set at 160 ° C. to obtain a biaxially stretched film without breaking the film for 24 hours. Moreover, when an unstretched film was extract | collected and the layer structure was confirmed, it turned out that the layer structure of 2 layers is formed over the full width. The average residence time of the resin in the die was about 14 seconds.
[0050]
[Example 2]
The resin combination, Wb and Wc were changed as shown in Table 1, and a two-layer film was obtained in the same manner as in Example 1 except that the stretching conditions were changed to PET conditions. The results are shown in Table 1.
[0051]
[Example 3]
A two-layer film was obtained in the same manner as in Example 1 except that the number of layers, the combination of resins, and Wb and Wc were changed as shown in Table 1. The results are shown in Table 1.
[0052]
[Comparative Examples 1-3]
Except for changing Wb and Wc as shown in Table 1, attempts were made to obtain a two-layer film in the same manner as in Examples 1 to 3, but none of them was broken 10 times / day or more when the product was transversely stretched. . The results are shown in Table 1.
[0053]
[Comparative Example 4]
A two-layer film was obtained in the same manner as in Example 1 except that the number of layers, the combination of resins, and Wb and Wc were changed as shown in Table 1, but the width yield was poor.
[0054]
[Table 1]

[0055]
【The invention's effect】
According to the present invention, a multilayer sheet and a multilayer film can be obtained by controlling the thickness of each layer uniformly in the width direction even with a combination of resins having a large specific gravity difference.
[Brief description of the drawings]
FIG. 1 shows an extruder to a casting drum in a two-layer sheet extrusion apparatus exemplifying an embodiment of the present invention.
FIG. 2 shows a front view of a feedblock and a single layer die, and a side view of the die, illustrating one embodiment of the present invention.
FIG. 3 is a cross-sectional view of a two-layer feed block in the AA cross section of FIG. 2;
4 is a cross-sectional view of a three-layer feed block in the AA cross section of FIG. 2. FIG.
5 is a cross-sectional view of a two-layer feed block in the FF cross section of FIG. 3, and an enlarged view of a surface layer resin flow path and a layer thickness adjuster. Used when the density of the resin on the surface layer side is small.
6 is a cross-sectional view of a two-layer feed block in the FF cross section of FIG. 3, and an enlarged view of a surface resin flow path and a layer thickness adjuster. Used when the density of the resin on the surface layer side is extremely small.
7 is a cross-sectional view of a two-layer feed block in the FF cross section of FIG. 3, and an enlarged view of a surface resin flow path and a layer thickness adjuster. Used when the density of the resin on the surface layer side is large.
8 is a cross-sectional view of a two-layer feed block in the FF cross section of FIG. 3, and an enlarged view of a surface layer resin flow path and a layer thickness adjuster. Used when the resin density difference is small.
9 is a cross-sectional view of a two-layer feed block in the FF cross section of FIG. 3, and an enlarged view of a surface layer resin flow path and a layer thickness adjuster. Used for T-die.
10 is a diagram of the surface layer resin and the core layer resin in the GG and HH cross sections in FIG. 3 and the BB, CC, and DD cross sections in FIG. 2; It is a figure in case a layer structure is normal.
11 is a diagram of a surface layer resin and a core layer resin in the BB, CC, and DD cross sections of FIG. 2; It is a figure in case a layer structure is abnormal.
12A and 12B are diagrams of a two-layer sheet in the EE cross section of FIG. 2, in which FIG. 12A shows a case where the layer configuration is normal, and FIG.
13A and 13B are diagrams of a three-layer sheet in the EE cross section of FIG. 2, in which FIG. 13A is a case where the layer configuration is normal, and FIG.
14A and 14B are diagrams of a nine-layer sheet in the EE cross section of FIG. 2, in which FIG. 14A shows a normal layer configuration and FIG. 14B shows an abnormal case.
[Explanation of symbols]
1: Surface layer side extruder 2: Surface layer side gear pump 3: Surface layer side filter 4a: Surface layer side polymer pipe 4b: Core layer side polymer pipe 5: Core layer side extruder 6: Core layer side gear pump 7 : Core layer side filter 8: Casting drum 9: Feed block 9a: Feed block surface layer side member 9b: Feed block core layer side member 10: Single layer die 11: Unstretched sheet 12: Feed port to die 13: Manifold 14a: Resin channel on the surface layer side, or resin 14b on the surface layer side: Resin channel on the core layer side, or resin on the core layer side 15: Layer thickness adjuster x: Height direction of the surface layer channel H: Surface layer flow path height L: Abnormal portion width Wb: Surface layer flow path width (corresponding to the non-feed side of the die)
Wc: Width of surface layer flow path at x = H / 2 (corresponding to die center)

Claims (8)

In the production method of a multilayer sheet, a feed block provided on the upstream side of a side feed type or center feed type single layer die is used to join at least two types of molten resin and extrude from the single layer die to form a multilayer sheet. Includes a flow path for each molten resin, the flow path width at a position immediately before the molten resin merges in the flow path satisfies at least one of the following formulas (a) and (b), and A method for producing a multilayer sheet, wherein the melt density satisfies the following formula (c):
About the resin flow path with the lowest melt density Wb <Wc (a)
Resin flow path with the highest melt density Wb> Wc (b)
( Wb is the channel width at the position corresponding to the opposite side of the die width direction and Wc is the channel width at the position corresponding to the die center in the die width direction.)
1.05 ≦ ρmax / ρmin ≦ 3.00 (c)
(However, ρmax is the melt density of the resin having the highest melt density among the melted resins, and ρmin is the melt density of the resin having the lowest melt density.)   The method for producing a multilayer sheet according to claim 1, wherein the flow path width of the resin having the smallest melt density is Wb <Wc, and the flow path width ratio Wb / Wc is 0 to 0.95.   The method for producing a multilayer sheet according to claim 1, wherein the flow path width of the resin having the highest melt density is Wb> Wc, and the flow path width ratio Wb / Wc is 1.05 to 5. The method for producing a multilayer sheet according to claim 1, wherein the average residence time of the molten resin in the single-layer die is 5 to 200 seconds.   The method for producing a multilayer sheet according to claim 1, wherein the resin having the highest melt density among the molten resins contains 5 to 60% by weight of inert particles. The method for producing a multilayer sheet according to claim 5 , wherein the inert particles are barium sulfate and / or titanium oxide. In a multi-layer sheet manufacturing apparatus, a feed block provided on the upstream side of a side-feed type or center-feed type single-layer die is used to join at least two types of molten resin and extrude from the single-layer die to form a multi-layer sheet. Is provided with a flow path for each molten resin, and the flow path width at a position immediately before the molten resin merges in the flow path satisfies at least one of the following formulas (a) and (b). An apparatus for producing a multilayer sheet, wherein the density satisfies the following formula (c):
The flow path width of the resin with the lowest melt density is Wb <Wc (a)
The flow path width of the resin having the highest melt density is Wb> Wc (b)
( Wb is the channel width at the position corresponding to the opposite side of the die width direction and Wc is the channel width at the position corresponding to the die center in the die width direction.)
1.05 ≦ ρmax / ρmin ≦ 3.00 (c)
(However, ρmax is the melt density of the resin having the highest melt density among the melted resins, and ρmin is the melt density of the resin having the lowest melt density.) With a feed block provided on the upstream side of the side feed type or center feed type single layer die, at least two types of molten resin are merged and extruded from the single layer die to form a multilayer sheet, which is stretched to form a multilayer film In the method for producing a multilayer film, the feed block is provided with a flow path for each molten resin, and the flow path width at a position immediately before each molten resin merges in the flow path is at least one of the following formulas (a) and (b): And the melt density of the molten resin satisfies the following formula (c).
About the resin flow path with the lowest melt density Wb <Wc (a)
Resin flow path with the highest melt density Wb> Wc (b)
( Wb is the channel width at the position corresponding to the opposite side of the die width direction and Wc is the channel width at the position corresponding to the die center in the die width direction.)
1.05 ≦ ρmax / ρmin ≦ 3.00 (c)
(However, ρmax is the melt density of the resin having the highest melt density among the melted resins, and ρmin is the melt density of the resin having the lowest melt density.)

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