JP2003342387A - Surface decorating sheet and its molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface decorating sheet which is composed of a styrenic resin, has a small internal strain, and can obtain a surface decorative molded product having low warpage when integrated with a thermoplastic resin base material in in-mold decorating or the like, and a molded product using the same. <P>SOLUTION: The decorating styrenic resin sheet is composed of a resin composition mainly having a styrenic copolymer resin which is a polymer to be obtained by anionic polymerization and has a composition ratio [b/(a+b)] of (a) a styrenic monomer to (b) a conjugated diene monomer of 0.20-0.28, and the decorative molded product uses the sheet. A mixture with another styrenic resin having a specified composition is more preferred. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decorative molding sheet containing a styrene-based resin as a main component and a surface decorative molded article formed by in-mold molding using the sheet.
Particularly, the present invention relates to a surface-decorated molded article using a polystyrene resin as a base material. In the present invention, the units "part" and "%" representing the blended composition of the resin composition are expressed on a mass basis when the total of the resin components is 100 unless otherwise specified.

[0002]

2. Description of the Related Art Conventionally, as a method for decorating the surface of a plastic molded body with a design or a photograph, a sheet or film for decorative molding printed with these designs or the like (hereinafter simply referred to as "sheet") The method of integrating the sheet on the surface of the base material of the molded body by in-mold decorative molding is widely used. This method is applied to injection molding, press molding, or thermoforming of a thermoplastic resin sheet. For example, in a method called in-mold label method of injection molding, one gravure printed resin sheet is used. Then, the sheet is stuck in a mold, the mold is closed, and a molten resin is injected to obtain a surface-decorated molded body in which the sheet and the base material are integrated. in this way,
It is also possible to form the decorative molding sheet with the printing surface inside, and in that case, there is an advantage that the printing surface is protected by the sheet.

Further, there is a demand for higher quality of plastic products and a molded product having a high designability. In order to meet the demand, an in-mold transfer molding method, a thermoject method, a CFI
Decorative molding methods such as the (coated film insert) process have been developed.

As a sheet used for such decorative molding, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polyester resin or a resin composition containing these resins as a component is used. It is used properly. For example, polyester resins have good surface gloss and excellent printability.
It is used for panel parts of automobiles, mobile phones, etc. by applying plating or metal-like printing. In addition, the acrylic resin sheet has excellent weather resistance, has moldability that follows a shape with a high deep drawing degree, and has excellent adhesiveness with an acrylonitrile / butadiene / styrene copolymer resin. It is suitable for surface decoration of molded products using this resin as a base material.

On the other hand, styrene resin sheets are rarely used for decorative molding. For example, Japanese Patent Laid-Open No. 2000-35
In 1860, a film made of a rubber-modified polystyrene resin composition having properties such as heat shrinkage in a specific range has been proposed as a film having excellent printing accuracy. The use is not mentioned at all. Further, Japanese Patent Laid-Open No. 10-272652 proposes a composite film for in-mold decoration having a styrene resin layer and a polybutylene terephthalate resin layer. This composite film is a polybutylene terephthalate resin. The layer is essential and does not consist only of styrene resin. The reason why the styrene resin sheet is not used is that it is inferior in weather resistance to the acrylic resin and inferior in printability to the polyester resin, and its use is limited.

However, in recent years, there has been an increasing demand for recycling of plastics due to environmental problems, for example, CDs.
When a pattern or the like is to be provided on the surface of a clear case made of transparent polystyrene such as a case by decorative molding, a sheet made of the same styrene resin as the base material is required as the decorative molding sheet. It was being done. For such applications, these requirements are not a major issue as weatherability requirements are less important and printability has become less of an issue with recent advances in printing technology. However, when a polystyrene resin sheet is used as a sheet for decorative molding and a clear case is obtained by in-mold molding, a molded product with good pattern accuracy cannot be obtained, or "warpage" of the molded product occurs. There is a problem that the value is significantly impaired, and its improvement has been demanded.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a styrene resin sheet which has a small internal strain of the sheet, has a surface smoothness which enables printing, and is integrally formed with a thermoplastic resin substrate by in-mold molding or the like. It is an object of the present invention to provide a sheet capable of obtaining a surface-decorated molded article having less warp of the molded article, good pattern accuracy, and excellent design, and a molded article using the same. In particular, it is possible to provide a decorative molded product such as a clear case based on transparent polystyrene that can be recycled as a polystyrene resin.

[0008]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve this problem, and as a result, anionic polymerization having a chain of a styrene-based monomer and a conjugated diene-based monomer having a specific composition ratio. The inventors have found that the problems can be achieved by using a styrene resin sheet containing a polymer according to (4) as a main component, and have reached the present invention. That is, the present invention is a polymer obtained by anionic polymerization using an organolithium initiator,
Styrene-based monomer (a) and conjugated diene-based monomer (b)
And has a composition ratio b / (a + b) of 0.20 to
It is a styrene-based resin sheet for decorative molding, which is composed of a resin composition containing 0.28 styrene-based copolymer resin (A) as a main component. Furthermore, the styrene-based copolymer (A)
-80%, 20-30% polystyrene resin (B) consisting essentially of chains of styrenic monomers, and 0-10% polystyrene resin (C) containing butadiene chains.
A styrene-based resin sheet for decorative molding composed of the resin composition contained is preferable.

On the other hand, the present invention is a surface-decorated molded article in which the above-mentioned styrene-based resin sheet is subjected to decorative printing to form a decorative sheet, and the sheet and the thermoplastic resin substrate are integrated. The thermoplastic resin base material is preferably a polystyrene resin, more preferably a transparent polystyrene resin, which is used for a clear case or the like having a decorated surface. The present invention also includes a method for producing a surface-decorated molded article, characterized in that the decorative sheet and the thermoplastic resin substrate are integrated by injection molding, press molding or thermoforming of the sheet.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

The styrenic copolymer resin (A) used in the present invention is a polymer obtained by anionic polymerization using an organolithium initiator, and is a styrenic monomer (a).
And a styrene copolymer resin having a chain of a conjugated diene monomer (b) and a composition ratio b / (a + b) of 0.20 to 0.28.

The styrene-based monomer (a) is styrene or α-methylstyrene, and the conjugated diene-based monomer (b) is butadiene or isoprene. To produce the copolymer resin (A) from these monomers,
It is produced by a method of stepwise polymerizing a monomer with an anionic polymerization initiator, a method of copolymerizing a mixture of both monomers in an inert solvent, or a method of appropriately using these in combination. The composition ratio b / (a + b) of the conjugated diene monomer in the copolymer resin is 0.20 to 0.28.
When it is less than 0.20, when used in the sheet of the present invention, not only the flexibility of the sheet becomes insufficient and the adhesion to the mold in decorative molding becomes insufficient, and good pattern accuracy cannot be obtained. Since the residual stress of the obtained molded body is large, the so-called “warpage” of the molded body exceeds the allowable range.

If it exceeds 0.28, the elastic modulus of the sheet is lowered and the heat resistant temperature of the sheet is lowered. Therefore, when heat is applied to the sheet during printing, drying or decorative molding, the sheet The warp, waviness, etc. occur and the printing position accuracy deteriorates, and it is not possible to obtain a molded product with a highly accurate pattern.

The copolymer (A) has a chain of a styrenic monomer (a) and a conjugated diene monomer (b) and has a weight average molecular weight of generally 60,000 to 250,000. It is in the range of. The form of the chain of (a) and (b) is not particularly limited, and not only the copolymer consisting of (a) chain / (b) chain / (a) chain but also, for example, the above-mentioned chain is repeated a plurality of times. It may be a so-called “multi-block copolymer” which is repeated, while the chain composed of (a) and (b) is 3
It may be a so-called “star block copolymer” in which 5 to 5 polyfunctional compounds are bonded. As for the molecular structure, the respective chains are perfect chains, or, as seen in JP-A-48-48456, the transition parts of the (a) chain and the (b) chain are both (a) and (b) random. Any one having a so-called tapered block structure containing a polymer may be used.

The copolymer resin (A) has different weight average molecular chain lengths and compositions of (a) chain and (b) chain, as in the resin described in Japanese Patent Publication No. 1-23857. It may be a mixture of two or more polymers.

The styrene resin sheet of the present invention is preferably a sheet containing a composition containing 60% to 80% of the copolymer resin (A) as a main component. If it is less than 60%, it may be difficult to suppress the "warp" of the above-mentioned molded article within an allowable range when the sheet is subjected to decorative molding. On the other hand, if it exceeds 80%, not only the film formation itself becomes difficult, but also the rigidity of the sheet becomes weak, and it may be difficult to obtain a decorative molded product having a good pattern accuracy in decorative molding. is there.

The polystyrene resin (B) used in the present invention is a resin which substantially consists of the chains of the above-mentioned styrene type monomers, and is generally called GP obtained by bulk polymerization or suspension polymerization. It refers to the resin. The component (B) is not particularly limited, but has a melt flow index (MFI) of JI from the viewpoint of sheet extrudability when melt-mixed with other components during processing into a sheet and extrusion-molded.
S-K7210 0.5 to 15.0 as measured under condition 8
g is preferable, and more preferably in the range of 2.0 to 10.0 g. The proportion of the component (B) in the sheet of the present invention is preferably 20-30%. If it is less than 20%, the pattern accuracy of the decorative molded product may be deteriorated, and if it exceeds 30%, the flexibility of the sheet may be deteriorated, resulting in insufficient adhesion to the mold in decorative molding. The "warpage" of the molded product may exceed the allowable range.

Polystyrene resin (C) used in the present invention
Is a resin generally called high-impact polystyrene (HIPS), which is obtained by bulk polymerization or suspension polymerization of a styrene-based monomer in the presence of butadiene rubber. In the sheet of the present invention, the component (C) can be added as necessary in order to prevent blocking in the film forming process of the sheet, and the composition ratio thereof is in the range of 0 to 10%. If it exceeds 10%, the transparency of the sheet may be remarkably lowered, and it may not be suitable for the intended use of the sheet.

The styrene-based resin sheet of the present invention contains stabilizers, antioxidants, ultraviolet absorbers, colorants such as pigments and dyes, silicone oil and alkyl ester-based release agents within the range that does not impair the effects of the present invention. Molding agents, granular lubricants such as talc, clay and silica, or metal salts of sulfonic acid, antistatic agents such as polyalkylene glycol and the like can be added.

The sheet of the present invention can be obtained by a general method for producing a thermoplastic resin sheet, and the method is not particularly limited, but in order to obtain a sheet having a smooth surface, the T-die method is used. Melt extrusion is preferred.
Further, the method of mixing the resin and the 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 raw material in a mixer such as a tumbler. After the pellets are mixed, melted and kneaded by an extruder, cooled and solidified into pellets, which is fed to an extruder to obtain a sheet by a general T-die method. Alternatively, a part of the raw materials may be melt-kneaded in advance as described above, and may be mixed with other components during sheet extrusion and supplied to the extruder to obtain a sheet.

The thickness of the sheet of the present invention is not particularly limited, but is usually about 75 to 3000 μm.
If it is less than 75 μm, the strength of the sheet may be insufficient and a good design may not be obtained depending on the molding conditions at the time of in-mold decorative molding. Moreover, a thickness of more than 300 μm is not usually required.

As a method for performing decorative printing on the sheet of the present invention, generally used methods (gravure printing, screen printing, offset printing, etc.) can be used.

The surface-decorated molded article of the present invention is injection-molded, press-molded, or thermoformed by using a decorative sheet obtained by printing a design or the like on the above-mentioned styrene resin sheet by a commonly used method. Can be obtained by integrating the decorative sheet and the base resin. In addition, these molding methods are not particularly limited, and any method commonly used as decorative molding can be used. In these moldings, the base resin may be arranged on either the non-printed surface or the printed surface of the decorative sheet, and either one can be selected depending on the intended use of the resulting molded product. In applications where the durability of the printing surface is important, the printing surface can be protected by the decorative sheet by integrating the printing surface with the base resin. On the other hand, in applications such as CD clear cases where the durability of the printed surface does not matter, it is better to integrate the base resin on the non-printed surface side of the decorative sheet to form an adhesive layer between them. It does not need to be provided and is rational.

As the base resin, a resin which can be decoratively molded in the temperature range of 120 to 300 ° C. can be used, and examples thereof include various styrene resins, ABS resins, polycarbonate resins, acrylic resins, Examples include various polyolefin-based resins, various thermoplastic polyester-based resins, vinyl chloride-based resins, and the like. Particularly, a transparent polystyrene resin can be collected and used as a polystyrene resin for recycling. Further, the decorative molded body using this resin as a base material has good transparency and pattern accuracy, and has little warping of the flat surface, so that it is suitable for a clear case whose surface is typified by a CD case, for example. Can be used for.

[0025]

The present invention will be described in detail below with reference to examples. In the present invention, the resin shown below was used as the resin material for the sheet. (A) -1 Styrene-based copolymer resin Clearene 73
0L (made by Denki Kagaku Kogyo Co., Ltd.) Butadiene content
b / (a + b) = 0.25, MFI = 7.2 (A) -2 Styrene-based copolymer resin Clearene 53
0L (made by Denki Kagaku Kogyo Co., Ltd.) Butadiene content
b / (a + b) = 0.16 MFI = 7.3 (B) -1 Polystyrene resin Toyostyrol
G14L (manufactured by Toyo Styrene Co., Ltd.) MFI = 9.3 (B) -2 polystyrene resin Toyostyrol
MW1 (manufactured by Toyo Styrene Co., Ltd.) MFI = 1.8 (C) -1 Polystyrene resin Toyostyrol HIE6 (manufactured by Toyo Styrene Co., Ltd.) Butadiene content 5.5% (C) -2 Polystyrene resin Toyostyrol HISQ301 (manufactured by Toyo Styrene Co., Ltd.) Butadiene content 7.2%

The above raw materials were blended in the composition ratio shown in Table 1 and fed to a 65 mm single-screw extruder at 170 to 210 ° C.
After melt-kneading in the cylinder set to, die width 70
A sheet having a thickness of 0.2 mm was obtained by extruding into a sheet shape by a T-die having 0 mm and a die lip interval of 0.5 mm.

[0027]

[Table 1]

(Measurement of tensile elastic modulus and tensile elongation of sheet)
The tensile elastic modulus and tensile elongation in the MD direction of the sheet formed by the above method were measured according to JIS K7127. The measurement results of Examples and Comparative Examples are shown in Table 2.

(Measurement of DuPont Impact Strength of Sheet) The DuPont impact strength of the sheet formed by the above-mentioned method is measured by JIS.
It measured based on K7124. The measurement results of Examples and Comparative Examples are shown in Table 2.

(Measurement of Heat Shrinkage of Sheet) The heat shrinkage in the MD direction of the sheet formed by the above method was measured in the following manner. Equipment used: Yamato Fine Oven DH62 Heating conditions: 120 ° C. × 20 min Specimen: 120 mm × 120 mm Distance between marked lines: 100 mm Shrinkage calculation method = [(original length-length after heating) / (original length )] × 100 (%) Table 2 shows the measurement results of Examples and Comparative Examples.

[0031]

[Table 2]

(Measurement of Warpage of Molded Article) The sheet formed by the above method is printed by offset printing, and a base resin is applied to the non-printing surface side of the decorative sheet using an apparatus as shown in FIG. It was integrally molded to obtain an upper lid of the CD case. (Molded product dimensions (m
m) W = 124 L = 141 D = 11). The warp amount (21) shown in FIG. 2 of the obtained upper lid of the CD case was measured using a digital caliper. Table 3 shows the measurement results of Examples and Comparative Examples.

(Evaluation of pattern accuracy of molded product) The sheet formed by the above method was printed by offset printing, and integrally molded as a CD case using a device as shown in FIG. 1 (molded product size (mm)). W = 124 L = 141 D = 11).
The pattern accuracy of the obtained molded product was visually observed and evaluated according to the following criteria. The evaluation results are shown in Table 4. ◯: There is no distortion on the printed surface, and the pattern accuracy of the molded product is good. Δ: A slight distortion is observed on the printed surface, and the pattern accuracy of the molded product is not good. X: Many distortions are seen on the printed surface, and the pattern accuracy of the molded product is also poor.

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

EFFECTS OF THE INVENTION According to the present invention, the internal strain of the sheet is small, the surface smoothness that enables printing is obtained, and further, by integrating with the thermoplastic resin substrate by in-mold molding or the like, warpage of the molded body is prevented. It is possible to obtain a styrene-based resin sheet that can obtain a surface-decorated molded article having a small amount of good pattern accuracy and excellent design characteristics, and a decorative molded article using the same. In particular, it becomes possible to provide an excellent surface-decorated molded article such as a clear case based on transparent polystyrene that can be recycled as a polystyrene resin.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an apparatus used for “warpage” evaluation of a surface-decorated molded article of the present invention.

FIG. 2 is a conceptual diagram showing “warpage amount” of the surface-decorated molded article of the present invention.

[Explanation of symbols]

11 injection molding machine 12 mold 13 Thermoplastic resin base material 14 Decorative sheet

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme coat (reference) C08L 25:06) F term (reference) 4F071 AA12 AA22 AA75 AF27 AF32 AF53 AF54 BA01 BB06 4F100 AK01C AK12A AK12C AK12J AK28A AK28J AL01A BA03 BA07 BA10B BA10C GB16 HB31B JB16C JN01C YY00A 4F206 AA13 AD05 AD09 AD20 AF00 AG03 AH56 AM35 JA07 JB19 JF05 4J002 AC081 BC032 BP013 GF00

Claims (6)

[Claims] 1. A polymer obtained by anionic polymerization using an organolithium initiator, which has a chain of a styrene-based monomer (a) and a conjugated diene-based monomer (b) and has a composition ratio thereof. A styrene-based resin sheet for decorative molding, which comprises a resin composition whose main component is a styrene-based copolymer resin (A) having b / (a + b) of 0.20 to 0.28. 2. A styrene-based copolymer resin (A) comprising 60 to 8
0%, 20 to 30% polystyrene resin (B) consisting essentially of styrene monomer chains, and 0 to 10% polystyrene resin (C) containing butadiene chains. The styrene-based resin sheet for decorative molding according to claim 1. 3. A surface-decorated molded article in which one side of the styrene-based resin sheet according to claim 1 or 2 is subjected to decorative printing to form a decorative sheet, and the sheet and the thermoplastic resin substrate are integrated. 4. The surface-decorated molded article according to claim 3, wherein the thermoplastic resin substrate is a polystyrene resin. 5. The clear case according to claim 3, wherein the thermoplastic resin substrate is a transparent polystyrene resin. 6. The method for producing a surface-decorated molded article according to claim 3, wherein the decorative sheet and the thermoplastic resin substrate are integrated by injection molding, press molding or thermoforming of the sheet.