JP2007224316A - Thermoplastic resin sheet and its formed product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PC/polyester-based sheet scarcely causing lowering of transparency and a bluing phenomenon in heating a substrate, such as drying after printing on the sheet or thermal molding to three-dimensional shapes. <P>SOLUTION: The thermoplastic resin sheet and a thin-wall molded products thereof are composed of (A) 50-80 pts. of a polycarbonate resin and (B) 20-50 pts. of at least one or more kinds of polyester resin, wherein ≥20 pts. of the (B) component is a glycol-modified polyethylene terephthalate, and especially, those containing a specific amount of 1,4-cyclohexanedimethanol unit as the (B) component have great effects. The sheet is suitable for decorative molded products requiring a high level designability, such as a switch panel in the electronic field. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sheet mainly composed of a polycarbonate-based resin and a polyester-based resin, and in particular, a decorative molding substrate sheet, that is, a decoration such as printing on the surface of a molded product at the time of thermoforming such as injection molding or vacuum molding. The present invention relates to a base sheet for a thin molded article used for application, and the molded article. In the present invention, the unit “part” representing the composition of the resin composition is expressed on a mass basis when the total of the resin components is 100 unless otherwise specified.

Sheets (hereinafter abbreviated as “PC / polyester sheet”) composed of a polycarbonate resin and a polyester resin as main components are excellent in transparency, mechanical strength, impact resistance, and the like. For example, as described in Japanese Patent Application Laid-Open No. 9-216998, it is used for food applications, packaging applications, medical product applications, agricultural applications, building material applications, electronic / electrical applications, and applications that make use of the above properties. Many proposals have been made for this purpose.
JP-A-9-216998

On the other hand, for automobile interior parts (panel parts such as speedometers), mobile phones in the electronics field, personal digital assistants, and switch panels for various home appliances, printing and plating were performed for the purpose of enhancing their design. Insert the thin molded body of the sheet into a mold and injection mold the resin, or press-mold a sheet-like material such as polyurethane, so that the thin molded body is integrated and decorated on the surface of the molded body. "Decoration molding" is widely performed. In this decorative molding, the base sheet provided with the decoration such as printing is usually heated and processed into a three-dimensional shape by thermoforming such as vacuum forming. As this base material sheet, PC / polyester sheet is widely used. Especially, it is easy to perform three-dimensional processing of various designs and has excellent printability in terms of chemical resistance. From the point that high expression is possible, as described in JP-A-11-260182, a sheet made of a resin composition using a polybutylene terephthalate resin as a polyester resin (hereinafter referred to as “PC / Abbreviated as “PBT-based sheet”).
JP-A-11-260182

  However, this PC / PBT-based sheet is obtained by crystallization of a polybutylene terephthalate-based resin in a process such as drying after printing on a base sheet for obtaining a decorative molded body or thermoforming into a three-dimensional shape. There is a problem that the transparency is lowered (haze is increased) or the color blurring phenomenon which becomes a bluish hue occurs, particularly in the case where the sheet thickness exceeds about 0.3 mm. . In the present invention, the bluish hue is hereinafter referred to as “blueing”. In addition, “color blur” as used in the present invention means that when the substrate sheet is printed with various hues, the intended hue changes due to the above-described decrease in transparency and bluing. It shows that. Generation | occurrence | production of such color blurring will reduce the designability of the obtained molded object, or it cannot be used depending on a use, The improvement was calculated | required. In addition to the decorative molding sheet, in the above-described other applications, the color blur phenomenon has been desired to be improved in terms of its design properties in the transparent sheet that is subjected to heat treatment such as thermoforming. .

  The present invention is a PC / polyester-based sheet that hardly causes a decrease in transparency or bluing phenomenon in a process of heating the sheet, such as drying after printing on the sheet or thermoforming into a three-dimensional shape. And a three-dimensional thin-walled molded product obtained by thermoforming the same, and particularly a base sheet suitable for a decorative molded product that requires a high degree of design, such as a switch panel in the electronics field, and its heat It is an object to provide a molded body.

  In order to solve this problem, the present inventors examined the composition of the PC / polyester composition that is the raw material of the thermoplastic resin sheet, and by using a specific resin as the polyester resin, thermoforming After receiving a thermal history such as the above, the inventors found that a sheet that hardly causes the above-described decrease in transparency and bluing phenomenon can be obtained, and the present invention has been achieved. That is, the present invention comprises 50 to 80 parts of a polycarbonate resin (A) and 20 to 50 parts of at least one polyester resin (B), and at least 20 parts of the component (B) is glycol-modified polyethylene terephthalate. It is a certain thermoplastic resin sheet. The glycol-modified polyethylene terephthalate preferably has a molar ratio of ethylene glycol unit to 1,4-cyclohexanedimethanol unit in the glycol unit of 80/20 to 60/40. Further, it is preferable to add 0.05 to 0.5 part of a phosphorus compound as a stabilizer for preventing transesterification. Furthermore, the present invention includes these decorative molding base sheets and thin molded bodies for decorative molding obtained by thermoforming them.

  The present invention has excellent mechanical strength, thermoformability, solvent resistance, small change in total light transmittance and haze due to heat treatment such as drying or thermoforming after printing, and “Bluing” Phenomenon hardly occurs and provides a sheet with less color blur, and is particularly suitable for a decorative molding sheet and its thin molded body, and by using the sheet of the present invention or its thin molded body, A decorative molded body having a high height is provided.

  The present invention will be described in detail below.

  The polycarbonate resin (A) used in the present invention is an aromatic homopolycarbonate or copolycarbonate produced by reacting an aromatic dihydroxy compound and a polycarbonate precursor, and a commercially available product can be used. However, considering the impact strength of the sheet, a typical example is a co-polycarbonate containing bisphenol A, carbonyl chloride (phosgene), etc. as a copolymer component, and its viscosity average molecular weight is preferably 2.5 to 30,000. If it is less than 25,000, sufficient strength of the obtained sheet cannot be obtained, and if it exceeds 30,000, the melt viscosity of the resin composition in the extruder becomes too high when the sheet is extruded. For this reason, it is difficult to obtain a sheet having good surface smoothness by extrusion molding.

  In the sheet of the present invention, the compounding composition of the polycarbonate resin (A) is 50 to 80 parts. If the amount is less than 50 parts, sufficient rigidity and impact resistance of the sheet cannot be obtained, and if it exceeds 80 parts, it is difficult to obtain a sheet having good surface smoothness by extrusion molding, and the three-dimensional shape is reduced. The moldability of the is reduced.

  The polyester resin (B) used in the present invention requires at least 20 parts of glycol-modified polyethylene terephthalate. Glycol-modified polyethylene terephthalate is a resin in which a part of ethylene glycol, which is one component of polyethylene terephthalate polycondensation, is replaced with another glycol to suppress crystallinity. As the other glycol component, 1,4-cyclohexanedimethanol is preferable, and the content of 1,4-cyclohexanedimethanol in the glycol unit is 20 to 40 mol%, and particularly excellent transparency reduction and bluing. Even if it is less than this range or exceeds this range, the transparency reduction and the blueing suppression effect are reduced.

  This decrease in transparency and bluing phenomenon occur due to the progress of microcrystallization of the polyester resin component when the sheet is heated for the purpose of drying after printing or thermoforming into a three-dimensional shape as described above. I think that. However, it is conceivable to use other low-crystalline polyester resins as a method for suppressing the microcrystallization, but in both cases, the effect of sufficiently suppressing both the decrease in transparency and bluing is obtained. Absent.

  The sheet of the present invention needs to contain at least 20 parts of these glycol-modified polyethylene terephthalates. If it is less than 20 parts, when the obtained base material sheet is thermoformed, a decrease in transparency and bluing occur.

  The composition of the polyester resin (B) in the sheet is 20 to 50 parts including the glycol-modified polyethylene terephthalate, and other polyester resins in the above range in addition to the resin depending on the use. It can be included. When the total amount of the polyester-based resin (B) in the sheet exceeds 50 parts, a sheet having sufficient rigidity and impact strength cannot be obtained. The polyester-based resin that can be partially contained is, for example, a polybutylene terephthalate-based resin. When these resins are added, the moldability when the base sheet is thermoformed is improved.

  It is preferable to add a phosphorus compound (alkyl phosphite), an amide group-containing polymer, or the like as a stabilizer to the sheet of the present invention in order to prevent coloring due to transesterification. In particular, the phosphorus compound is preferable, and the addition amount is 0.05 to 0.5 part, more preferably 0.1 to 0.3 part. If the amount added is less than 0.05 parts, the effect of preventing coloration due to the transesterification reaction is reduced, and if it exceeds 0.5 parts, the flow characteristics of the molten resin composition increase in film formation of this sheet. The surface smoothness of the resulting sheet tends to decrease.

  Further, if necessary, as long as the effect of the present invention is not impaired, colorants such as pigments and dyes, release agents such as silicone oil and alkyl ester, fibrous reinforcing agents such as glass fibers, talc, clay, Additives such as granular lubricants such as silica, plasticizers such as polyester and polycarbonate oligomers, salt compounds of sulfonic acid and alkali metals, antistatic agents such as polyalkylene glycol, UV absorbers, and antibacterial agents can do.

  Although the thickness of the sheet | seat of this invention is not specifically limited, Usually, it is about 100-1000 micrometers. For example, when used for decorative molding, if it is less than 100 μm, it is difficult to obtain a uniform thin molded body for decorative molding by thermoforming such as vacuum molding, and the thin molded body is installed in a mold. Thus, the strength at the time of injection molding is not sufficient, and it is difficult to obtain a molded product with excellent design. For the surface decoration of molded products, a thickness exceeding 1000 μm is not required.

  The sheet of the present invention is characterized in that, after being subjected to heat treatment such as thermoforming as described above, the transparency is hardly lowered and / or the hue is not changed by bluing. Although the requirement for transparency varies depending on the use of this sheet, in the case of a sheet for decorative molding, the standard value after heat treatment is 85% or more for total light transmittance and 10% for haze. It is about the following. However, even when the haze is 10% or less, when the haze after the heat treatment is clearly higher than that before the heat treatment, this sheet causes a color blurring phenomenon when the sheet is colored by printing or the like. Further, the change in hue in the present invention is difficult to discriminate clearly numerically by measurement with a general color difference meter or the like, and is such that the change can be recognized visually.

  The sheet of the present invention can be obtained by a general method for producing a thermoplastic resin sheet and is not particularly limited. However, in order to obtain a sheet having a smooth surface, melt extrusion molding by a T-die method is desirable. Further, the method of mixing the resin and additive of each component of the raw material composition is not particularly limited as long as each component can be sufficiently mixed. For example, each resin is dehumidified and dried by hot air or the like. In this method, water is sufficiently removed by a generally used method, and the pellets are mixed by a mixer such as a tumbler, then melt-kneaded by an extruder, cooled, solidified, and pelletized. Furthermore, the sheet is manufactured by, for example, supplying the mixed resin composition obtained as described above to the extruder in a sufficiently dried state, melt-extruding by the T-die method, cooling and solidifying it, and taking it out. An inventive sheet is obtained.

  The sheet of the present invention is used as a thin molded body by printing on the surface and thermoforming it into a three-dimensional shape according to the purpose. For example, when used for decorative molding of key top portions of various keyboards, a paint containing metal powder or pearl pigment is screen-printed or spray-coated on the sheet surface. The thermoforming method includes general vacuum forming, pressure forming, and as an application thereof, a plug assist method in which one side of the sheet is brought into contact with the plug, and a pair of male and female dies are brought into contact with both sides of the sheet. A method called so-called “match mold molding” is performed, but the method is not limited to this. Further, as a method for softening the sheet before molding, a known sheet heating method such as radiant heating with an infrared heater or the like which is non-contact heating can be applied.

Hereinafter, the present invention will be described in more detail by way of examples.
In the present invention, the following resins and additives were used.
(A) Polycarbonate Panlite [Trademark: Teijin Chemicals Ltd.]
(B) Polybutylene terephthalate Novaduran [Trademark: Mitsubishi Engineering Plastics Co., Ltd.]
(C) Polyethylene terephthalate 9921 [Eastman Chemical Co., Ltd.]
(D) Glycol-modified polyethylene terephthalate PET-G6763 [same as above]
(E) Phosphorus stabilizer Adekastab [Trademark: Asahi Denka Kogyo Co., Ltd.]

About each resin raw material, before supplying to an extruder, it preliminarily dried on the following conditions so that the water content might be 200-300 ppm or less.
(A) 120 ° C, 5 hours normal pressure
(B) 120 ° C, 5 hours normal pressure
(C) 140 ° C, 4 hours normal pressure
(D) 66 ° C., 6 hours (A) to (E) were blended at a composition ratio shown in each Example or Comparative Example in Table 1 as a normal pressure raw material, and the cylinder temperature was set to 250 to 260 ° C. It was supplied to a 40 mm single screw extruder (manufactured by Nippon Placon Co., Ltd.), melted and kneaded at a screw rotation speed of 80 rpm, and pelletized.

  The raw material pelletized by the above method is dried in advance at 120 ° C. for 5 hours, supplied to a 65 mm single screw extruder (manufactured by Nippon Steel Co., Ltd.), melt-kneaded in a cylinder set at 250 to 260 ° C., Extruded into a sheet form by a T-die having a width of 700 mm and a die lip gap of 0.5 mm, cooled and solidified by a cooling roll set at 60 to 80 ° C., and taken up at a take-up speed of 11.5 m / min to obtain a sheet having a thickness of 300 μm. .

The sheet formed by the above method was vacuum-formed with a molding machine manufactured by Asano Laboratories Co., Ltd. to obtain a three-dimensional thin molded product. At that time, the main molding conditions were as follows.
Sheet surface temperature 100-160 ° C
Heater temperature Upper heater 600 ℃ Lower heater 500 ℃
Mold dimension W120 × L145 × 30

(Sheet tensile test)
The tensile properties of the sheet formed by the above method were measured according to JIS K7127. The measurement results are shown in Table-2. Compared with the numerical value of Comparative Example 1, Examples 1 to 6 to which glycol-modified polyethylene terephthalate was added also showed substantially the same good value.

(Measurement of transparency of sheet before and after heating)
The sheet formed by the above method was heated, and the total light transmittance and haze before and after heating were measured according to JIS K7105. The heat treatment and measurement were performed under the following conditions.
Equipment used Yamato Fine Oven DH62
Heating conditions Unheated, 3 levels of 80 ° C. × 4 hours, 100 ° C. × 30 minutes Measuring instrument used Nippon Denshoku Industries Co., Ltd. Measurement sample thickness 300 μm
The measurement results of Examples and Comparative Examples are shown in Table-3 and Table-4, respectively.

(Hue evaluation of sheets and vacuum thermoformed products)
The state of bluing of the thin molded product obtained by the sheet and vacuum forming was visually observed and evaluated according to the following criteria.
○: Retains hue without bluening
×: Table 5 shows the results of the discoloration evaluation by blueing.

  In Examples 1 to 6, “blueing” was not observed and transparency was maintained. In Comparative Examples 1, 2, 4, and 5 in which polyethylene terephthalate was used as the polyester component, the haze value by the heat treatment was greatly increased. In Comparative Examples 3, 6, 7, and 8, although transparency was maintained, a phenomenon of “blueing” was observed, and in each of the comparative examples, a factor of “color blur” was recognized.

Claims (3)

A thermoplastic resin sheet using a resin composition comprising 50 to 80 parts of a polycarbonate resin (A) and 20 to 50 parts of at least one polyester resin (B), the polyester being a component (B) A thermoplastic resin sheet in which at least 20 parts or more of the system resin is glycol-modified polyethylene terephthalate, and the 1,4-cyclohexanedimethanol unit in the glycol unit in the component (B) is 22 mol% to 33 mol%. A base sheet for decorative molding using the thermoplastic resin sheet according to claim 1. A thin molded article obtained by thermoforming the decorative molding substrate sheet according to claim 2.