JP3981881B2 - Method for producing thermoplastic elastomer sheet - Google Patents

Description

【００２７】
【発明の効果】
本発明の熱可塑性エラストマーシートの製造方法によれば、ダイの出口幅に沿って均一なポリマー吐出が得られるようになり、成形されたシートの幅方向の厚み精度の向上および有効製品幅の拡大を図ることが可能となる。
【図面の簡単な説明】
【図１】実施例１に使用したダイの概略図
【図２】比較例２に使用したダイの概略図
【符号の説明】
１ 流入口
２ マニホールド部
３ ダイ間隙厚みの傾斜部
４ リップ部
５ リップ部間隙厚み[0001]
[Industrial application fields]
The present invention relates to a method for producing a film or sheet of thermoplastic elastomer (hereinafter referred to as a sheet), and more particularly to a method for producing a sheet from a molten resin laminated in multiple layers with a feed block. In particular, the present invention relates to a manufacturing method in which the thickness accuracy in the width direction of a formed sheet is improved and the effective product width can be increased.
[0002]
[Prior art]
Conventionally, when forming a thermoplastic resin into a sheet using a T-die, especially when forming a sheet from a molten resin laminated in multiple layers with a feed block, the die shape shortens the residence time of the molten resin in the die. In order to reduce the change in physical properties of the molten resin due to temperature, the manifold portion was narrowed. However, in the die for sheet forming, when the manifold part is small, the flow rate at the center part of the die is faster than the flow rate at the end part of the die, and when forming into a sheet-like material, the center part of the sheet becomes thicker than the end part. There is a problem that not only the thickness accuracy in the direction is lowered, but also the effective width that can be used as a product within the full width of the formed sheet is narrowed.
[0003]
The single-layer sheet molding die does not need to consider the disorder of each layer compared to the multilayer sheet molding, so that the resin flows smoothly toward the die end face as an easy-to-process and economical die shape. It was machined with a large radius of curvature. However, since the single-layer sheet molding die is processed with a large radius of curvature so that the resin flows smoothly toward the end surface of the die, the resin residence time in the vicinity of the end surface of the die becomes longer with a high viscosity resin. There is a concern that the resin deteriorates.
[0004]
In JP-A-10-329196, as a die for forming a multilayer sheet, resin flows while contacting the wall surface of the manifold. As a result, friction (shear stress) is generated between the resin and the wall surface. In order to prevent the occurrence of disorder in each layer due to changes in the physical properties of the molten resin, it is smoothly processed with a small radius of curvature from a location closer to the end face of the manifold part than the single-layer sheet molding die, and the outermost part converges to zero. Are disclosed. However, the multi-layer sheet forming die is processed with a smaller radius of curvature smoothly from a position closer to the end face of the manifold portion than the single-layer sheet forming die, and the end portion is processed to converge to zero. When a resin having a large shear rate dependency is flowed, the difference in viscosity between the central portion and the end portion of the die is large, a flow velocity difference is generated, and thickness unevenness occurs in the sheet-like material.
[0005]
In JP-A-7-205252, as a method for producing a multi-layered sheet-like material in which resin thin films are laminated in several hundred to several thousand layers, a multilayer die for discharging one or more types of quantitative molten resins in layers, A multilayer die that folds a plurality of resin layers discharged from a multilayer die while folding, and a widening die that expands the folded and layered resin layer in the width direction are successively connected. A device has been proposed. However, when the feed block method is used in the multilayer sheet molding, a plurality of types of molten resins are joined and laminated, and the multilayer molten resin supplied into the die from the feed block to be laminated has an accuracy such as thickness and width. However, it is discharged from the lip portion that is the outlet as it is determined by the shape of the manifold. The
[0006]
In Japanese Patent No. 1130035, as a method for extruding a laminated sheet, an operation of laminating a plurality of thermoplastic resin flows to obtain a composite resin flow is performed in an adapter capable of adjusting a flow path provided in front of a die. There has been proposed a manufacturing method characterized in that the thickness ratio in the width direction of the laminated flow extruded from the die is adjusted by changing the adapter to one having a merged resin flow path that matches the resin viscosity. However, since an adapter is installed to control the thickness of the sheet, when a highly viscous resin is flowed, shear heat generation occurs between the adapter and the resin, and the resin may be deteriorated.
[0007]
In Japanese Patent Application Laid-Open No. 59-212234, in order to obtain a molded sheet having a small thickness deviation and no bending, the resin temperature is independently operated in a plane perpendicular to the resin flow direction in the die. There has been proposed an extrusion molding method characterized in that the adjusting means is provided in parallel and the temperature adjusting means is individually cooled or heated to control the formability such as uneven thickness and bending of the molded product of the sheet. Unlike the method in which the entire die is controlled at a constant temperature, an expensive apparatus with complicated temperature control is required.
[0008]
Regarding thermoplastic elastomer sheets and films, polyester-based elastomers and polyurethane-based elastomers have already been disclosed, but the manufacturing method by coating and drying is the main, and there is also a manufacturing method by melt extrusion molding. There is no description regarding a simple die shape, and no method has been disclosed in which the thickness is actually uniform and stable production is possible (for example, Japanese Patent Application Laid-Open Nos. 59-111847 and 2001-59028). In the case of thermoplastic elastomers, it is very difficult to obtain a uniform sheet because it has unique rheological properties or is likely to generate surging or drawdown when extruded into a sheet. Met.
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-329196 [Patent Document 2]
Japanese Patent Laid-Open No. 7-205252 [Patent Document 3]
Japanese Patent No. 1130035 [Patent Document 4]
JP 59-212234 [Patent Document 5]
JP 59-111847 A [Patent Document 6]
Japanese Patent Laid-Open No. 2001-59028
[Problems to be solved by the invention]
It is an object of the present invention to improve the thickness accuracy in the width direction and to increase the effective product width by allowing the thermoplastic elastomer molten resin to be uniformly discharged along the die exit width to the die end. An object of the present invention is to provide a method for producing a thermoplastic elastomer sheet that can be expanded.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have intensively studied, and as a result, completed the present invention. That is, the present invention is a method of extrusion molding using a die having a region in which the die gap thickness changes between the manifold portion and the lip portion in the die shape, and includes the following formulas (1) and (2) A thermoplastic elastomer sheet characterized in that a die satisfying the formulas (3) and (3) is installed in an extruder, and a thermoplastic elastomer resin is melt-extruded into a sheet form from the die outlet and then cooled and solidified to obtain a sheet-like material. It is a manufacturing method.
[0012]
(1) W2 / W1 = 1
(2) 5 ° <α <27 °
(3) 7.5 ≦ H / h ≦ 30
[0013]
In the above equations (1), (2), and (3),
W1 is the width on the lip side of the region where the die gap thickness changes between the manifold portion and the lip portion, and W2 is the width on the manifold side of the region where the die gap thickness changes between the manifold portion and the lip portion. Width, α is the divergence angle of the die width in the flow direction from the inlet side of the manifold. The divergence angle when the straight manifold is 0 ° and when there is no divergence is 90 °, and H is the die angle at the manifold section. The average gap thickness, h, represents the average gap thickness of the die at the lip.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Further, embodiments of the present invention will be described in detail.
The present invention is a method for producing a thermoplastic elastomer sheet, characterized in that a die having a specific shape is installed in an extruder, and a thermoplastic elastomer is melt-extruded into a sheet form from a die outlet and then cooled and solidified to obtain a sheet-like product. is there.
[0015]
Examples of the thermoplastic elastomer in the present invention include thermoplastic polyolefin-based elastomers, thermoplastic polyester-based elastomers, thermoplastic polyamide-based elastomers, and thermoplastic polyurethane-based elastomers. In particular, thermoplastic polyolefin elastomers are prone to surging and drawdown, so that the production method of the present invention is effective.
[0016]
In the present invention, by using a specific die described in detail below, if a normal straight manifold type die or a coat hanger type die is used, surging or drawdown occurs and a uniform sheet is generated. Even if it is not obtained, surging does not occur, the thickness accuracy in the width direction is improved, and a thermoplastic elastomer sheet capable of widening the effective width that can be used as a product out of the full width can be obtained.
[0017]
In the die shape of the present invention, a die having a region where the gap thickness of the die changes between the manifold portion and the lip portion is the gap thickness between the manifold portion and the lip portion of the die shown in FIGS. This die has a region (part) 3 that becomes smaller.
[0018]
The expression (1) in claim 1 shows that the width W1 on the lip side and the width W2 on the manifold side of the region where the gap thickness of the die changes between the manifold portion and the lip portion are substantially the same value. Yes. This is to move the molten thermoplastic elastomer filled in the manifold portion with a velocity vector only in the direction of the lip gap.
[0019]
Α in the formula (2) in claim 1 is the die widening angle in the flow direction from the inlet side of the manifold, and is a value when the straight manifold is 0 ° and no spread is 90 °. .
The expression (2) in claim 1 indicates that the die of the present invention has a shape located between the straight die and the coat hanger die having a large spread angle α, and the spread angle α is smaller than 5 °. In this case, there arises a problem that the thermoplastic elastomer resin stays at the end of the manifold. On the other hand, when α is larger than 27 °, the influence of the resin flow rate balance due to the die shape is reduced, the flow rate at the center of the die where the inlet is located is high, the flow rate at the end is low, and the thickness of the thermoplastic elastomer sheet The problem that the spots become larger occurs.
[0020]
The expression (3) in claim 1 shows the average gap thickness ratio between the die of the manifold portion and the lip portion, and when it is smaller than 7.5, the average gap thickness of the lip portion is larger than that of the manifold portion. When the thermoplastic elastomer in a molten state is discharged into the die due to its own weight and cannot be molded as a sheet-like material before being filled in the die, and is larger than 30, The thickness of the lip part is too small compared to the manifold part, so the back pressure of the die becomes high and the discharge of the extruder becomes impossible or the extruder may be damaged, so it cannot be molded as a sheet. .
[0021]
The sheet-like thermoplastic elastomer melt-extruded from the die exit is cast on a moving body such as a roll or an endless belt, and then cooled and solidified.
Since the thermoplastic elastomer sheet obtained by the present invention has a uniform thickness, it can be suitably used for sundries such as cushioning material sheets, electrical insulating sheets, stationery and toys. Moreover, since the part where thickness is uniform in the width direction is wide, the effective width which can be used as a product within the full width can be widened.
[0022]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. In addition, the evaluation method in an Example is as follows.
(1) Evaluation of thickness variation of sheet The surging state and thickness variation (three-stage evaluation) of a sheet obtained by extruding a thermoplastic elastomer from a die and winding it on a roll were evaluated under the following conditions.
○: The difference between the maximum thickness and the minimum thickness of the sheet is 0.25 mm or less. Δ: The difference between the maximum thickness and the minimum thickness of the sheet is 0.25 mm to 0.5 mm.
X: The difference between the maximum thickness and the minimum thickness of the sheet is 0.5 mm or more, and the pellets of polyolefin elastomer Sarlink (3180B) manufactured by Toyobo Co., Ltd., dried at 80 ° C. for 10 hours are used as an extruder. Provided.
The extruder used was a 30 mm single screw extruder manufactured by Pla Giken Co., Ltd., and the number of revolutions was set to 75 rpm, the discharge rate was 5 kg / hour, and the temperature of the cylinder-adapter-die was set to 200 ° C. and controlled.
The thermoplastic elastomer discharged from the die outlet and formed into a sheet was solidified on a 200 mmφ roll and taken off. The gap length between the die and the roll was 100 mm.
[0023]
Example 1
In the die shape used in Example 1, the width W1 on the lip side of the region where the die gap thickness changes between the manifold portion and the lip portion, and the die gap thickness changes between the manifold portion and the lip portion. The width W2 on the manifold side of the region is 200 mm each, that is, W2 / W1 = 1, the die width spread angle α from the inlet side of the manifold to the flow direction is 15 °, the average gap thickness H of the die in the manifold portion is 15 mm, Surging evaluation was performed using a die having an average gap thickness h of 1.5 mm in the lip region. As a result, a surging phenomenon was not observed, and a uniform sheet having a thickness of 1.5 mm and a width of 190 mm was obtained. The evaluation result of thickness spots was ○.
[0024]
(Comparative Example 1)
In contrast to Example 1, a die having a 0 ° spread angle α in the flow direction from the inlet side of the manifold, that is, a so-called straight manifold type die was used. In this case, the thickness unevenness of the center part and the edge part of the sheet was large, and the molten resin did not flow out uniformly in the width direction at the die exit. The evaluation result of thickness spots was Δ.
[0025]
(Comparative Example 2)
For Example 1, a normal coat hanger type die with W2 / W1 = 0.67 and α = 30 ° was used. The thickness unevenness of the center part and the edge part of the discharged sheet was large, and the evaluation result of the thickness unevenness was x.
(Comparative Example 3)
In Example 1, the die having an average gap thickness h of 3 mm was used, and a die with H / h = 5 was used. The thickness unevenness of the center part and the edge part of the discharged sheet was large, and the evaluation result of the thickness unevenness was x.
[0026]
[Table 1]

[0027]
【The invention's effect】
According to the method for producing a thermoplastic elastomer sheet of the present invention, uniform polymer discharge can be obtained along the outlet width of the die, and the thickness accuracy in the width direction of the molded sheet is improved and the effective product width is increased. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a die used in Example 1. FIG. 2 is a schematic diagram of a die used in Comparative Example 2. Description of symbols
1 Inlet 2 Manifold part 3 Die gap thickness inclined part 4 Lip part 5 Lip part gap thickness

Claims (1)

A method of extrusion molding using a die having a region where the gap thickness of the die varies between the manifold portion and the lip portion in the die shape, wherein the equations (1), (2), and (3) A method for producing a thermoplastic elastomer sheet, comprising: installing a satisfactory die in an extruder; melt-extruding a thermoplastic elastomer into a sheet form from a die outlet; and cooling and solidifying to obtain a sheet-like product.
(1) W2 / W1 = 1
(2) 5 ° <α <27 °
(3) 7.5 ≦ H / h ≦ 30
In the above formulas (1), (2), and (3), W1 is the width on the lip side of the region where the gap thickness of the die changes between the manifold portion and the lip portion, and W2 is the manifold portion and lip The width on the manifold side of the region where the gap thickness of the die changes between the part and α is the spread angle of the die width in the flow direction from the inlet side of the manifold, where the straight manifold is 0 ° and there is no spread Is the spread angle when H is 90 °, H is the average gap thickness of the die in the manifold portion, and h is the average gap thickness of the die in the lip portion.

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