JP2004025802A - Method of manufacturing thermoplastic resin sheet, and the sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet, which has surface smoothness, is capable of performing a printing excellent in design, and has small internal distortion, and can achieve a thin molded body not to be affected by residual stress during drying after printing and heat molding into a three-dimensional shape, and is suitable for a decorated molded body, etc. <P>SOLUTION: The sheet is manufactured by passing the resin composition containing a polycarbonate resin (A) and a polyester resin (B) as main components through a metal sleeve roll having the surface roughness smaller than 0.5 μm and a mirror surface metal roll under gripping pressure. The metal sleeve roll has a metal thin film layer, which is thinner than 350 μm in thickness, on a base rubber, formed by extrusion, having rubber hardness lower than 65. In the thermoplastic resin sheet, preferably, the average thickness of the metal thin film layer is within the range from 0.05 to 0.3 mm, and the average surface roughness (Ra) is smaller than 0.15 μm. <P>COPYRIGHT: (C)2004,JPO

Description

【００３５】
（特性評価）
実施例及び比較例で得られたシートの特性を、以下の方法で評価した。又、評価結果は表２に纏めて示した。
（１）　透明性測定
シートのヘイズをＪＩＳ　Ｋ７１０５に準拠し測定した。
（２）　シートの外観評価
シートの外観評価を目視観察し、以下の基準で評価した。
○　：　ダイマーク等の表面欠点が全くない
△　：　ダイマーク等の表面欠点がある。
×　：　ダイマーク等の表面欠点が著しい。
（３）　シートの表面粗さの測定
シートの平均表面粗さ（Ｒａ）をＪＩＳ　Ｂ０６０１に準拠して下記の測定器で測定した。
測定器　：　（株）東京精密製　サーフコム１２０Ａ
（４）　シートの加熱収縮率測定
シートの加熱収縮率を以下に示した条件で測定した。
使用機器　：　ヤマト　Ｆｉｎｅ　Ｏｖｅｎ　ＤＨ６２
加熱条件　：　１２０℃×３０ｍｉｎ
試験片　：　幅１００ｍｍ、長さ１００ｍｍ
収縮率計算方法＝［（元の長さ−加熱後の長さ）／（元の長さ）］×１００（％）
（５）　シートの内部歪みの評価
シートを直交する２枚の偏光板の間に挟み、目視にて干渉模様の大小により、以下の基準で内部歪みを評価した。
○　：　干渉模様が殆ど見られない。
△　：　薄い干渉模様が見られる。
×　：　明確な干渉模様が見られる。
（６）　熱成形性
シートを加熱して真空成形する際の成形品の側面の肉厚の均一性を、以下の基準で評価した。
○　：　ほぼ均一に伸びる。
△　：　伸びるが不均一。
×　：　伸びがなく成形できない。
【００３６】
【表２】

【００３７】
【発明の効果】
本発明により、ＰＣ／ポリエステル系樹脂シートで、意匠性の優れた印刷が可能な表面平滑性を有し、更にシートの内部歪みが少なく、印刷後の乾燥や、三次元形状への熱成形で、残留歪みの影響を受けない薄肉成形体を得ることのできるＰＣ／ポリエステル系樹脂シートが得られる。このシートは特にエレクトロニクス分野のスイッチパネル等、高度の意匠性が要求される加飾成形体用として好適である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a sheet containing a polycarbonate-based resin and a polyester-based resin as main components and a sheet thereof, and particularly relates to a base sheet for decorative molding, that is, the surface of a molded article during thermoforming such as injection molding or vacuum molding. The present invention relates to a base material sheet for a thin-walled molded article used when decoration such as printing is applied to a sheet. In the present invention, the units “part” and “%” representing the composition of the resin composition are expressed on a mass basis when the total of the resin components is 100 unless otherwise specified.
[0002]
[Prior art]
A resin composition containing a polycarbonate resin and a polyester resin as main components (hereinafter abbreviated as “PC / polyester resin”) has excellent transparency, mechanical strength, impact resistance, and the like. As described in Japanese Patent Application Laid-Open No. 9-216998, it is intended for use in applications that make use of the above characteristics such as food use, packaging use, medical use use, agricultural use, building material use, electronic and electrical use, and optics. Many suggestions have been made.
[0003]
On the other hand, in order to enhance the design of automotive interior parts (panel parts such as speedometers), as well as switch panels of mobile phones, personal digital assistants and various home appliances in the electronics field, printing and plating were applied to enhance the design. The thin molded body of the sheet is inserted into a mold and resin is injection-molded, or a sheet-shaped material such as polyurethane is press-molded to integrate the thin molded body with the surface of the molded body and decorate the sheet. Decorative molding "is widely performed. In this decorative molding, the substrate sheet on which the above-described decoration such as printing has been performed is usually heated and then formed into a three-dimensional shape by thermoforming such as vacuum forming. As the base sheet, a PC / polyester resin sheet is widely used. In particular, it has excellent printability in terms of easy three-dimensional processing of various designs and chemical resistance. As described in JP-A No. 11-260182, a sheet made of a resin composition using a polybutylene terephthalate-based resin is excellent as a polyester-based resin because a highly designable expression is possible. I have.
[0004]
As a method for producing these sheets, an extrusion molding method using a normal T die is used. In this method, the sheet extruded from the T-die is passed under a narrow pressure between a pair of mirror-finished metal rolls set at a predetermined clearance in advance, thereby reducing the thickness of the sheet and cooling the sheet. However, in the PC / polyester resin sheet formed by this method, a part that has been partially subjected to strong pressure bonding due to the mechanical accuracy of the clearance between the metal rolls and the bias of the thickness distribution causes internal strain in the part, There was a problem that the polyester in the resin component was oriented and crystallized, and a sheet having transparency could not be obtained. Further, in this sheet, the above-described portion of the internal strain caused unevenness in elongation during forming into a three-dimensional shape such as vacuum forming, and a good molded product could not be obtained.
[0005]
On the other hand, instead of the pair of metal rolls, there is a method in which one of the rolls is a rubber roll, but a sheet obtained by using a generally used rubber roll is similar to the above-described method. Although the internal distortion of the sheet was small, the sheet surface roughness was large. Therefore, when this sheet was printed, there was no surface gloss and only the thing lacking its design was produced.
[0006]
In general, as a method of forming a relatively thin high-precision sheet having a thickness of 0.3 mm or less, there is a method in which a sheet extruded from a T-die is pressed against a mirror-finished metal roll using an air knife and uniformly cooled. Although this method is excellent as a means for obtaining a thin sheet having a small thickness distribution, it is extremely difficult to obtain a sheet having no flow pattern of the resin on the sheet surface, and this method is one of the objects of the present invention. It is not suitable for obtaining a certain “sheet having excellent surface smoothness and small internal strain”.
[0007]
[Problems to be solved by the invention]
The present invention is a PC / polyester resin sheet having surface smoothness capable of printing with excellent design properties, further reducing the internal distortion of the sheet, drying after printing, and thermoforming into a three-dimensional shape. It is another object of the present invention to provide a thermoplastic resin sheet capable of obtaining a thin molded body which is not affected by residual strain, and a method for producing the same. In particular, the present invention provides a substrate sheet suitable for a decorative molded body requiring a high degree of design, such as a switch panel in the electronics field.
[0008]
[Means for Solving the Problems]
In order to solve this problem, the present inventors have used the PC / polyester-based resin composition having excellent properties as a raw material and studied the extrusion method thereof, and as a result, have reached the present invention. That is, in the present invention, a resin composition containing a polycarbonate-based resin (A) and a polyester-based resin (B) as main components is melt-kneaded, extruded from a T-die, and subjected to rubber hardness (type A based on JIS K6253-1997). A metal sleeve provided with a metal thin film layer having a thickness of 350 μm or less and an average surface roughness (Ra) (hereinafter simply abbreviated to surface roughness) of 0.5 μm or less on the surface of a lower winding rubber having a durometer of 65 or less. A method for producing a thermoplastic resin sheet, characterized in that the sheet is passed under a narrow pressure between a roll and a mirror-finished metal roll, and a sheet formed by this method. Further, the resin composition of this sheet is preferably such that the polycarbonate resin (A) is 50 to 80 parts and the polyester resin (B) is 20 to 50 parts, and the average thickness thereof is 0.05 to 0.3 mm. And a thermoplastic resin sheet having a surface roughness of 0.15 μm or less is preferable. Further, the sheet of the present invention is excellent as a base sheet for decorative molding, and a good thin molded article for decorative molding can be obtained by thermoforming.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
[0010]
The polycarbonate resin (A) used in the present invention is an aromatic homopolycarbonate or copolycarbonate produced by reacting an aromatic dihydroxy compound with a polycarbonate precursor, and commercially available ones can be used. However, considering the impact strength of the sheet, a copolycarbonate containing bisphenol A, carbonyl chloride (phosgene) or the like as a copolymer component is preferable as a typical example, and the viscosity average molecular weight is desirably 2.5 to 30,000. If it is less than 25,000, it is difficult to obtain a sheet having sufficient strength, and if it exceeds 30,000, the melt viscosity of the resin composition in an extruder when extruding the sheet is high. It is too difficult to obtain a sheet having good surface smoothness by extrusion.
[0011]
In the sheet of the present invention, the composition of the polycarbonate resin (A) is preferably 50 to 80 parts. When it is 50 parts or more, the rigidity and impact resistance of the sheet are good, and when it is 80 parts or less, a sheet having good surface smoothness can be obtained by extrusion molding.
[0012]
The polyester resin (B) used in the present invention is necessary in order to obtain a sheet having good surface smoothness by extrusion molding, and its blending amount is preferably 20 to 50 parts. If the amount is less than 20 parts, sufficient surface smoothness of the sheet may not be obtained by extrusion molding, and if it exceeds 50 parts, the rigidity and impact resistance of the sheet tend to decrease.
[0013]
As the polyester resin (B), generally known polybutylene terephthalate, polyethylene terephthalate, or the like, or a copolymer thereof, or a mixture of one or more of them can be used. In applications where a change in hue is a problem, it is preferable to use a glycol-modified polyethylene terephthalate as the component (B), in part or in its entirety. By including this component, a hue change in a step to which heat is applied such as vacuum forming can be suppressed.
[0014]
It is preferable to add a phosphorus compound (alkyl phosphite) amide group-containing polymer or the like as a stabilizer to the sheet of the present invention in order to prevent coloring due to a transesterification reaction. Particularly, a phosphorus-based compound is preferable, and the addition amount is 0.05 to 0.5 part, more preferably 0.1 to 0.3 part. If the addition amount is less than 0.05 part, the effect of preventing coloring due to the transesterification reaction will be small, and if it exceeds 0.5 part, the flow characteristics of the molten resin composition will increase in the film formation of this sheet. The surface smoothness of the obtained sheet tends to decrease.
[0015]
Also, if necessary, a pigment, a coloring agent such as a dye, a release agent such as a silicone oil or an alkyl ester, a fibrous reinforcing agent such as a glass fiber, a talc, a clay, as long as the effects of the present invention are not impaired. Additives such as a particulate lubricant such as silica, a salt compound of sulfonic acid and an alkali metal, an antistatic agent such as polyalkylene glycol, an ultraviolet absorber, and an antibacterial agent can be added.
[0016]
The sheet of the present invention is obtained by melt extrusion molding by the T-die method. The method of mixing the resin and the additives of the raw material composition is not particularly limited as long as each component can be sufficiently mixed. For example, a general method such as dehumidification drying or hot air drying of each resin is used. After removing water sufficiently by the method used in the above, the pellets are mixed by a mixer such as a tumbler, then melt-kneaded by an extruder, and solidified by cooling to form pellets.
[0017]
Next, in the formation of a sheet, the above-mentioned mixed resin composition is passed under a narrow pressure between a pair of generally used mirror-finished metal rolls by a commonly used extrusion by a T-die method. The distortion remaining in the obtained sheet is large, and when this sheet is heated for drying or thermoforming after printing, unevenness of expansion is caused by the influence of the distortion, and the design property is impaired.
[0018]
In the present invention, a sheet obtained by feeding the mixed resin composition obtained as described above to an extruder in a sufficiently dried state and extruding the sheet by a T-die method is used to form a lower winding having a rubber hardness of 65 or less. Guided between a metal sleeve roll provided with a metal thin film layer on the surface of rubber and a mirror-finished metal roll, passed under a narrow pressure, cooled and solidified, and taken up, a sheet with small residual distortion and excellent surface gloss can be obtained. . The “rubber hardness” in the present invention is a value measured by a type A durometer in accordance with JIS K6253-1997 as described above.
[0019]
If the lower rubber has a rubber hardness of more than 65, a uniform pressure-bonded state cannot be obtained on the sheet, and the residual distortion of the sheet increases. If the rubber hardness is 65 or less, the distortion remaining on the sheet after cooling is reduced. However, if the roll surface is a rubber roll, it is difficult to reduce the surface roughness, and if a roll having a larger surface roughness is used, the resulting sheet also has a large surface roughness and lacks transparency. Met. The present inventors formed a metal thin film layer having a thickness of 350 μm or less on the surface of a lower winding rubber having a rubber hardness of 65 or less, and used a metal sleeve roll having a surface roughness of 0.5 μm or less. By guiding the sheet extruded from the T-die between the sleeve roll and the mirror-finished metal roll, passing it under squeezing pressure, cooling and solidifying it, it is possible to obtain a sheet with excellent residual gloss while keeping the residual distortion small. I found it.
[0020]
From the viewpoint of residual distortion of the sheet, the hardness of the lower winding rubber may be 65 or less as described above, and is not excessively soft. From the viewpoint of the properties and the thickness accuracy of the obtained sheet, it is general to use a sheet of 45 or more. On the other hand, in the sheet forming process, the setting of the squeezing pressure and the roll temperature at the time of taking the sheet are not particularly limited, and can be performed under the conditions used in normal sheet forming.
[0021]
The metal thin film layer on the surface of the rubber has a thickness of 350 μm or less and a surface roughness of 0.5 μm or less. If the thickness exceeds 350 μm, the rubber elasticity of the lower winding rubber cannot be obtained, and the residual distortion of the obtained sheet increases. On the other hand, if the surface roughness exceeds 0.5 μm, the transparency of the obtained sheet is impaired, and the surface gloss is poor when, for example, plating printing is performed on the surface of the sheet. I can't get it.
[0022]
Further, the metal thin film layer used in the present invention is preferably formed by applying a chromium plating having a thickness of about 10 μm on the nickel plating layer from the viewpoint of durability against metal corrosion and the like on the roll surface.
[0023]
In the decorative molding application in which the sheet of the present invention is used, the surface roughness of the sheet is preferably 0.15 μm or less and the transparency is preferably 10% or less in haze value for the above-mentioned reason. This is made possible by using a take-off roll.
[0024]
The average thickness of the sheet obtained by the film forming method of the present invention is usually 0.05 to 1.0 mm, but the effect of the present invention can be clearly obtained only when the thickness is 0.05 to 0.3 mm. It is. If it is less than 0.05, not only is it difficult to obtain a uniform thin molded body for decorative molding by thermoforming such as vacuum molding, but also the strength when the thin molded body is installed in a mold and injection molded. Is not sufficient, and it is difficult to obtain a molded product having excellent design properties. Even if the sheet has a thickness of more than 0.3 mm, the remaining internal strain is sufficiently small, but with a thickness in this range, a sheet having a relatively small internal strain can be obtained even when a film is formed between ordinary mirror-finished metal rolls. The effect of the present invention is small.
[0025]
Further, it is extremely useful as compared with other methods, especially when the thickness of the sheet is 0.05 to 0.2 mm. When a sheet having a thickness of 0.2 mm or less is formed using a pair of ordinary mirror-finished metal rolls, the polyester component is oriented and crystallized due to the above-described residual strain. Is hardly affected by the thickness distribution, so that a sheet having a small internal residual distortion can be obtained.
[0026]
The sheet of the present invention is used as a thin-walled product by printing on the surface and thermoforming into a three-dimensional shape according to the purpose. For example, when used for decorative molding of the key top portion of various keyboards, a paint containing metal powder or pearl pigment is screen-printed or spray-painted on the sheet surface. Thermoforming methods include general vacuum forming, compressed air forming, and plug-assisting methods, in which a plug is brought into contact with one side of a sheet to form the sheet, or a pair of male and female dies on both sides of the sheet. There is a method called so-called match mold molding, in which the molding is performed, but the present invention is not limited to this. As a method for heating and softening the sheet before molding, a known sheet heating method such as radiant heating using an infrared heater or the like which is non-contact heating can be applied.
[0027]
Hereinafter, the present invention will be described in detail with reference to examples.
(Examples 1 to 3)
The following resins and additives were used as resin raw materials for sheets.
(A) Polycarbonate Panlite (manufactured by Teijin Chemicals Limited)
(B) Polybutylene terephthalate Novaduran (Mitsubishi Engineering Plastics Co., Ltd.)
(C) Glycol-modified polyethylene terephthalate PET-G6763 (manufactured by Eastman Chemical Company)
(D) Phosphorus stabilizer ADK STAB (made by Asahi Denka Kogyo Co., Ltd.)
[0028]
Each resin raw material was preliminarily dried under the following conditions before being supplied to the extruder, so that the water content was 200 to 300 ppm or less.
(A) 120 ° C, 5 hours normal pressure (B) 120 ° C, 5 hours normal pressure (C) 66 ° C, 6 hours Tables (A), (B), (C) and (D) as normal pressure resin raw materials The mixture was blended at a ratio of 1 and supplied to a 40 mm single screw extruder (manufactured by Nippon Placon Co., Ltd.) set at a cylinder temperature of 250 to 260 ° C., melt-kneaded at a screw rotation speed of 80 rpm, and pelletized.
[0029]
The raw material pelletized by the above method is dried at 120 ° C. for 5 hours in advance, supplied to a 65 mm single screw extruder (manufactured by Nippon Steel Works), melt-kneaded in a cylinder set at 250 to 260 ° C., and then die-kneaded. Extruded into a sheet shape with a T-die having a width of 700 mm and a die lip interval of 0.5 mm, a mirror surface metal roll set at 60 to 80 ° C., chrome plating 10 μm, nickel 250 μm, a sleeve surface having a surface roughness of 0.3 μm, and a bottom winding The rubber was passed between metal sleeve rolls having a rubber hardness of 60 under narrow pressure to obtain a sheet having the thickness shown in Table 1.
[0030]
(Example 4)
A sheet having a thickness of 0.1 mm was obtained in the same manner as in Examples 1 to 3, except that (A) polycarbonate having the composition shown in Table 1 and (C) glycol-modified polyethylene terephthalate were used as the resin material for the sheet.
[0031]
(Comparative Example 1)
A sheet having a thickness of 0.1 mm was obtained in the same manner as in Examples 1 to 3, except that only polycarbonate was used as the resin material for the sheet.
[0032]
(Comparative Examples 2 to 4)
The sheet extruded from the die lip was held in the same manner as in Examples 1 to 3, except that the sheet was held between a mirror-finished metal roll set at 60 to 80 ° C. and a rubber roll having a surface roughness of 15 μm and a rubber hardness of 60. A sheet having the thickness shown in FIG.
[0033]
(Comparative Examples 5 to 7)
A sheet having a thickness shown in Table 1 was obtained in the same manner as in Examples 1 to 3, except that the sheet extruded from the die lip was nipped between a pair of metal mirror rolls set at 60 to 80 ° C and pulled. Was.
[0034]
[Table 1]

[0035]
(Characteristic evaluation)
The properties of the sheets obtained in Examples and Comparative Examples were evaluated by the following methods. The evaluation results are shown in Table 2.
(1) The haze of the transparency measurement sheet was measured according to JIS K7105.
(2) Evaluation of Appearance of Sheet The appearance of the sheet was visually observed and evaluated according to the following criteria.
: No surface defects such as die marks are present. △: Surface defects such as die marks are present.
×: Surface defects such as die marks are remarkable.
(3) Measurement of Surface Roughness of Sheet The average surface roughness (Ra) of the sheet was measured by the following measuring instrument in accordance with JIS B0601.
Measuring instrument: Surfcom 120A, manufactured by Tokyo Seimitsu Co., Ltd.
(4) Measurement of Heat Shrinkage of Sheet The heat shrinkage of the sheet was measured under the following conditions.
Equipment used: Yamato Fine Open DH62
Heating condition: 120 ℃ × 30min
Test piece: width 100mm, length 100mm
Method of calculating shrinkage = [(original length−length after heating) / (original length)] × 100 (%)
(5) Evaluation of Internal Distortion of Sheet The sheet was sandwiched between two orthogonal polarizing plates, and the internal distortion was evaluated according to the following criteria based on the magnitude of the interference pattern visually.
: Almost no interference pattern is seen.
Δ: A thin interference pattern is observed.
×: A clear interference pattern is observed.
(6) The uniformity of the thickness of the side surface of the molded product when the thermoformable sheet was heated and vacuum formed was evaluated according to the following criteria.
: Almost uniformly stretched.
Δ: Elongated but non-uniform.
×: Molding was not possible due to lack of elongation.
[0036]
[Table 2]

[0037]
【The invention's effect】
According to the present invention, a PC / polyester-based resin sheet has a surface smoothness capable of printing with excellent design properties, furthermore, has a small internal distortion of the sheet, and can be dried after printing or thermoformed into a three-dimensional shape. As a result, a PC / polyester-based resin sheet capable of obtaining a thin-walled molded body which is not affected by residual strain is obtained. This sheet is particularly suitable for decorative molded articles requiring a high degree of design, such as switch panels in the field of electronics.

Claims (7)

A resin composition containing polycarbonate-based resin (A) and polyester-based resin (B) as main components is melt-kneaded and extruded from a T-die. A method for producing a thermoplastic resin sheet, wherein a sheet is passed under a narrow pressure between a metal sleeve roll provided with a metal thin film layer having an average surface roughness (Ra) of 0.5 μm or less and a mirror-finished metal roll. 2. The method for producing a thermoplastic resin sheet according to claim 1, wherein the metal thin film layer uses a metal sleeve roll having two layers of a chromium plating layer and a nickel plating layer from the surface. A thermoplastic resin sheet produced by the method according to claim 1. The thermoplastic resin sheet according to claim 3, wherein the content of the polycarbonate resin (A) is 50 to 80 parts and the content of the polyester resin (B) is 20 to 50 parts. The thermoplastic resin sheet according to claim 3, wherein the average thickness is 0.05 to 0.3 mm and the average surface roughness (Ra) is 0.15 m or less. The decorative molding base sheet according to any one of claims 3 to 5. A thin-walled molded article for decorative molding obtained by thermoforming the base sheet of claim 5.