JPH05200858A - Syndiotactic polystyrenic film - Google Patents

Abstract

PURPOSE:To provide a base material excellent not only in electric characteristics, transparency and mechanical strength required for industrial products, packing, a magnetic tape or a condenser but also in flatness, printability and heat resistance by optimizing the stretching condition of a polystyrene film having a syndiotactic structure. CONSTITUTION:A film formed by stretching a polystyrenic polymer mainly composed of a syndiotactic structure at least in a uniaxial direction is characterized by that the refractive index Nz in the thickness direction of the film is 1.6200 or more and the heat shrinkage factor thereof at 150 deg.C is below 3%.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is applied to packaging materials, industrial materials, magnetic tapes, capacitors, etc.
The present invention relates to a film made of a styrene resin having a syndiotactic structure, which is excellent in printability and heat resistance.

[0002]

2. Description of the Related Art Recently, a styrene polymer having a syndiotactic structure has been developed (Japanese Patent Laid-Open No. 62-1048).
No. 18), and the development of a stretched film using them (JP-A-1-110122, 1-1).
68709, 1-182346, 2-2797.
No. 31, No. 3-74437, No. 3-109453,
3-99828, 3-124427, 3-1
31644, etc.) These syndiotactic polystyrene-based films have mechanical properties, transparency, chemical resistance,
Due to its excellent electrical characteristics such as dielectric loss and dielectric constant,
It is expected to be applied to various industrial and packaging films. However, conventional syndiotactic polystyrene films have been unsatisfactory in terms of flatness, printability, and heat resistance, so that they have been used for very limited applications.

[0003]

DISCLOSURE OF THE INVENTION The present invention has the above-mentioned drawbacks, namely, excellent flatness, printability, heat resistance and mechanical strength.
An object of the present invention is to provide a base material satisfying electrical characteristics, transparency and chemical resistance.

[0004]

That is, the gist of the present invention as a means for solving these is to stretch at least uniaxially in a polystyrene polymer mainly having a syndiotactic structure, Refractive index Nz is 1.6200 or more and 150 ° C.
And a heat shrinkage ratio of 3% or less. The polystyrene having a syndiotactic structure in the present invention means that the stereoregularity is a syndiotactic structure, that is, a phenyl group or a substituted phenyl group, which is a side chain with respect to the main chain formed of carbon-carbon bonds, alternates. It has a three-dimensional structure located in the opposite direction.

The molecular weight of the styrene polymer in the present invention is not particularly limited, but the weight average molecular weight is preferably 10,000 or more and 3,000,000 or less (JP-A-3-124427). The base material of the present invention includes other resins, inorganic particles, for improving electrostatic adhesion, slipperiness, stretchability, processability, and for other reasons such as roughening, opacifying, hollowing, and weight reduction. A weathering agent, a fluorescent agent, an ultraviolet absorber, an antioxidant, a plasticizer, a compatibilizer, a coloring agent, an antistatic agent, etc. may be added. These are disclosed in Japanese Patent Application Laid-Open No. 3-124427 and by the methods disclosed so far, as long as the characteristics of the syndiotactic polystyrene-based film are not significantly impaired, not only the polystyrene-based film but also polyester, polyolefin, polyamide, The technique used for the thermoplastic resin film such as polyacrylic can be used. The method of adding these additives is not limited as long as the characteristics of the syndiotactic polystyrene film are not significantly impaired. Therefore, it may be added at the time of polymerization, preliminarily kneaded as a masterbatch after polymerization, or added directly at the time of melt extrusion.
The polymer mixture thus obtained can be used to obtain a stretched film by the method illustrated below, but the invention is not limited to the method shown here as long as it satisfies the properties described later.
First, a polymer mixture mainly composed of syndiotactic polystyrene is preferably used for 3 hours or more at 100 to 150 ° C.
And melt-extruded at 290 to 350 ° C., and the resin is cooled by an air knife method, a water cooling method, an electrostatic adhesion method or the like to obtain an unstretched sheet. The extruder used here is not particularly limited, and may be a single-screw extruder, a twin-screw extruder, with or without a vent, and may be a tandem type or a single type.

The unstretched sheet obtained is stretched uniaxially. The method may be stretching between rolls having different speeds (roll stretching), stretching by gripping a clip and expanding (tenter stretching), or stretching by expanding by air pressure (inflation stretching). However, considering the mechanical properties, etc., the film is first stretched in the machine direction (or transverse direction), which corresponds to the flow direction of the film, and then in the transverse direction (or machine direction).
Axial stretching is preferred. The sequential biaxial stretching in which the machine direction and the transverse direction are sequentially stretched will be specifically described. However, the method is not limited to the following method as long as the characteristics of the film to be described later are satisfied.

First, the longitudinal stretching is performed by roll stretching. At this time, the draw ratio is 1.2 to 6.0 times, and the draw temperature is 90 to 1.
It is desirable to carry out in the range of 40 ° C. If the draw ratio is less than 1.2 times, the mechanical strength will be insufficient, and it will be 6.0.
If it exceeds twice, lateral stretching afterward becomes difficult and a film having excellent flatness cannot be obtained. If the stretching temperature is less than 90 ° C, the sheet will not be softened and stretching will be difficult. If it exceeds 140 ° C, the crystallinity will be too high and lateral stretching afterwards will be difficult. The heating method of the sheet at the time of stretching may be a heated roll, infrared heating, or any other method. Further, a guide roll or a nip roll may be used at any place of the preheating and stretching rolls. In the subsequent transverse stretching, tenter stretching is desirable. It is also preferable that the longitudinal stretching is performed twice or more in succession in order to satisfy the characteristics described later. At this time, the draw ratio is 1.2 to 6.0, and the draw temperature is 100.
It is desirable to carry out in the range of ~ 140 ° C. If the draw ratio is less than 1.2 times, the mechanical strength will be insufficient, and it will be 6.0.
If it exceeds twice, fracture tends to occur. Stretching temperature is 100
If the temperature is lower than 0 ° C, the sheet is not softened and is difficult to be stretched.
If it exceeds 40 ° C., the crystallinity becomes too high and breakage easily occurs. It is also possible to increase the mechanical strength in the direction by re-stretching once or more in the machine direction or the transverse direction after the transverse stretching is completed. Further, a method of first performing transverse stretching and then longitudinal stretching (for example, JP-A-64-5819 and JP-A-1-188322) or a method for eliminating the difference in physical properties between the end portion and the central portion of the film (for example, JP-A-3-
No. 158225) can also be used.

In addition to the above-mentioned conditions, a particularly important point in the present invention is that the stretching rate is 10,000% / min, preferably 15000% at least once in the range of 95 to 115 ° C.
/ Min, more preferably 20000% / min or more. When the stretching speed is less than 10000% / min, the refractive index Nz in the thickness direction of the film is 1.62.
It becomes difficult to set it to 00 or more, and it becomes difficult to obtain a film excellent in mechanical strength and particularly flatness. In particular, this syndiotactic polystyrene film has a lower stress applied to the film at the time of stretching as compared with polyethylene terephthalate and the like, so that conditions such as temperature and speed at the time of stretching are important in order to improve flatness. The stretching method is not particularly limited as long as this condition is satisfied, but the stretching speed is high. Therefore, this condition should be satisfied during longitudinal stretching by the roll stretching method, and it is preferable to carry out this longitudinal stretching twice or more in succession. is important.

Further, in the present invention, after the stretching, 17
Heat treatment is performed at 0 to 270 ° C, preferably 200 to 270 ° C. At this time, heat treatment is performed while relaxing 2% or more in the longitudinal direction and / or the transverse direction, whereby a material having a smaller heat shrinkage rate can be obtained. The film thus obtained must have a refractive index in the thickness direction of 1.6200 or more, preferably 1.6210 or more, more preferably 1.6220 or more, and more preferably 1.6230 or more. Since syndiotactic polystyrene has a benzene ring in the side chain, the refractive index in the thickness direction of the film increases as the degree of molecular orientation increases. Therefore, if it is less than 1.6200, the flatness and printability cannot be particularly improved.

The heat shrinkage is preferably 3%, preferably 2%, more preferably less than 1%. When it is 3% or more, it is not preferable because pitch deviation of printing occurs in dry heat transfer, OHP, gravure printing, or the like, and clogging occurs in a copying machine or a transfer machine. The film thus obtained is excellent in flatness, printability, heat resistance, and satisfies mechanical, electrical characteristics, transparency, and chemical resistance. Therefore, it is used for industrial, packaging, magnetic tape, and capacitor tape. It can be applied to various applications such as metallizing films. In particular, by applying the knowledge of polyesters, polyolefins, and other films disclosed so far to expand to these applications, the syndiotactic polystyrene-based film of the present invention also has the features of extremely added value. It was found that a high film was obtained. For example, for industrial use, an antistatic film (for example, Japanese Patent Publication No.
-10136), an ultraviolet absorbing film (for example, JP-A-59-98109 and JP-A-60-54865), and a highly transparent film (for example, JP-A-60-8592).
No. 5), a surface-roughened film (for example, Japanese Patent Publication No. 49-4).
9180, 54-44031), a void-containing film (for example, JP-A-49-134755),
White film (for example, JP-A-62-241928), transparent conductive film (for example, JP-A-2-637)
36) and the like, for packaging, a heat-adhesive film (for example, JP-B-52-30028), a heat-shrinkable film (for example, JP-B-57-31975),
Easy-cutting film (for example, JP-B-55-19167), easy-printing film (for example, JP-A-63-28)
No. 6346), an antifogging film (for example, Japanese Patent Publication No. 1)
No. 14252), a metal vapor deposition film (for example, Japanese Patent Publication No. 62-54671), a twist packaging film (for example, Japanese Patent Publication No. 56-52748), and the like for magnetic tapes (for example, JP-A-61-112629 and 6-62).
1-170518, 62-196121),
For capacitors (for example, Japanese Patent Publication Nos. 1-28493 and 2
No. 39985, etc.) can be applied.

Further, by providing a coating layer on the surface of the film, the wettability and adhesiveness of ink, coating agent and the like are improved (for example, JP-A-60-19522). The compound constituting the coating layer is a compound disclosed as a means for improving the adhesiveness of polyester resin, polyurethane resin, polyester urethane resin, acrylic resin, polystyrene resin, olefin resin, rubber resin, etc. Is applicable. As a method for providing the coating layer, a commonly used method such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, and a reverse roll coating method can be applied. As the step of applying, a method of applying on the surface of the mixed polymer before the orientation treatment,
Any method such as a method of coating on the surface of the void-containing film oriented in the uniaxial direction and further orienting it in the perpendicular direction, a method of coating on the surface of the void-containing film after the orientation treatment, and the like are possible. In the present invention, a so-called composite film in which a surface layer and a center layer are laminated may be used if necessary. The method is not particularly limited. However, from the viewpoint of productivity, it is most preferable to use a so-called co-extrusion method in which the raw materials for the surface layer and the central layer are extruded from different extruders, introduced into one die to obtain an unstretched sheet, and then oriented at least uniaxially. . These may add the additive etc. which were illustrated so far to the surface layer and / or the center layer. It is also possible to change the characteristics of the film by changing the amounts and / or types of additives in the surface layer and the central layer.

[0012]

In the present invention, polystyrene having a syndiotactic structure is mainly used to form a substrate having excellent flatness, printability and heat resistance and satisfying mechanical, electrical characteristics, transparency and chemical resistance. This is to provide it. In the present invention, the polymer is oriented at least uniaxially in order to improve mechanical strength, flatness and heat resistance. Particularly, in the present invention, the refractive index Nz in the thickness direction of the film is set to 1.6200 or more in order to improve flatness and mechanical strength, and the heat shrinkage ratio is set to less than 3% to set heat resistance. This is to make it better. The syndiotactic polystyrene film thus obtained has excellent electrical properties, transparency and mechanical strength required for industrial use, packaging, magnetic tapes, capacitors, etc., and has flatness, printability, and heat resistance. It became excellent in sex.

[0013]

EXAMPLES Examples and comparative examples of the present invention will be described below. The measurement / evaluation methods used in the present invention are shown below. 1) Refractive index Nz of the film in the thickness direction Using an Abbe refractometer manufactured by Atago Optical Co., Ltd., a polarizing plate was attached to an eyepiece, and the refractive index was measured by adjusting the polarizing plate orientation and the film orientation in the thickness direction.

2) Heat shrinkage rate A film having a width of 10 mm and a length of 250 mm is 200 m
Mark at m intervals and fix under a constant tension of 5 g, and mark intervals A
Measure Subsequently, the mark spacing B after being placed in an oven in an atmosphere of 150 ° C. for 30 minutes without load was determined, and the heat shrinkage rate was calculated by the following formula. (A-B) / A x 100 (%)

3) Initial elastic modulus The film was attached to a tensile tester (autograph manufactured by Shimadzu Corporation) at a width of 10 mm and a length interval of 40 mm, and 2
It was pulled at a speed of 00 mm / min, and the strength against elongation at rising was determined in kg / mm @ 2.

4) Light transmittance According to JIS-K6714, the Poick integrating sphere type H. T.
The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.).

5) Haze According to JIS-K6714, the Poick integrating sphere type H. T.
The haze of the film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.).

6) Surface roughness Surfcom 30 according to JIS-B0601-1982
The center line average thickness and maximum roughness were measured using a 0A type surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd.).

7) Film processability When a tape-shaped roll having a narrow slit is rubbed against a metal guide roll and run at high speed for a long time, the tape tension after rubbing the guide roll against a constant supply tension is small or large. And the amount of white powder generated on the surface of the guide roll is evaluated on a scale of 5 and represented by the following rankings. (A) Sliding grade 1 ... Large tension (a lot of scratches) Grade 2 ... A little large tension (a lot of scratches) Grade 3 ... Medium tension (some scratches) Grade 4 ... Slightly small tension ( Class 5: Small tension (no scratches) (b) Abrasion resistance Class 1: Very much white powder is generated Class 2: White powder is frequently generated Class 3: White powder is slightly generated 4 Grade: Almost no white powder generation Grade 5: No white powder generation

8) Durability running performance Using the apparatus shown in FIG. 1, the coefficient of friction between the rough surface of the film and the stainless steel pin is evaluated in an atmosphere of 23 ° C. and relative humidity of 65 ° C.

9) Electromagnetic conversion characteristics After the obtained film was magnetically coated to obtain a video tape having a width of 0.5 inch, S / N was measured by TG-7 / 1 type manufactured by Shibasoku Co., Ltd. Using an NTSC-TV test signal generator and a 925D / 1 type NTSC color television noise measuring instrument, the chroma S / N for the standard tape is evaluated in 3 levels and expressed by the following ranking. Class 1 ... -1 dB or less Class 2 ... -1 dB to +1 dB Class 3 ... +1 dB or more

Example 1 A polystyrene having a weight average molecular weight of 430,000 and having a predominantly syndiotactic structure, to which 1000 ppm of silica having an average particle size of 0.3 μm was added, was used and the screw diameter was 30 mm.
It was extruded from a T-die at 310 ° C. with a twin-screw extruder (1). The melt-extruded sheet is brought into close contact with a cooling roll at 55 ° C. by an electrostatic printing method, and is cooled and solidified to obtain 12
A 0 μm substantially amorphous, non-oriented sheet was obtained. This sheet was preheated at about 95 ° C. by changing the roll peripheral speed, and immediately thereafter, it was continuously stretched 1.4 times in the machine direction at about 103 ° C. and then stretched 2.15 times in the machine direction at about 106 ° C. The stretching speed at this time was about 30,000% / min. Then, preheat at 110 ° C with a tenter and immediately afterwards at 120 ° C in the lateral direction.
The film was stretched 3 times and then heat-treated at 260 ° C. for 10 seconds while relaxing in the longitudinal and transverse directions by 5%, and a film having excellent transparency of 12 μm was obtained. When the obtained film was subjected to gravure printing, it was good without printing blanks, distortions and pitch deviations.

Comparative Example 1 A biaxially stretched film was obtained and gravure printing was carried out in the same manner as in Example 1 except that the stretching speed of longitudinal stretching was set to 5000% / min. Nz is 1.6200
Since the flatness was not satisfied, the flatness was poor, and printing defects were generated, and printability was poor.

Comparative Example 2 A biaxially stretched film was obtained and gravure printing was performed in the same manner as in Example 1 except that the heat treatment temperature was changed to 140 ° C. Since the thermal contraction rate is large, the pitch deviation of printing particularly occurs and the printability is poor.

Example 2 A biaxially stretched film was obtained in the same manner as in Example 1 except that the final film had a thickness of 188 μm. When this film was cut into a size of 5 × 5 m and spread on a flat glass plate, it became a film having excellent flatness that was capable of bringing the entire film into close contact with the glass plate. When this film was cut into A4 size and OHP copied, the film was excellent in flatness and heat resistance and could be copied without clogging in a copying machine.
For example, it has been found that the stretching stress is lower than that of polyethylene terephthalate, and it is easy to improve the flatness by optimizing the conditions.

Comparative Examples 3 and 4 In Comparative Examples 1 and 2, respectively, the final film thickness was 1
A biaxially stretched film was obtained in exactly the same manner except that the thickness was set to 88 μm. When this film was tested in the same manner as in Example 2, Nz in the thickness direction was 1.6.
When it is less than 200, about 5% of the entire surface of the film cannot be brought into close contact with the glass plate due to poor flatness.
Further, in the OHP copy, the film feeding was defective. Further, when the heat treatment temperature was low, a clog was generated in the high temperature portion of the copying machine during OHP copying.

Example 3 A biaxially stretched film was prepared in the same manner as in Example 1 except that 1000 ppm of silicon particles having an average particle size of 0.3 μm was used as an additive and the final film had a thickness of 3 μm. Got When aluminum was vapor-deposited on this film in a vacuum to form a capacitor, the dielectric properties tan δ and dielectric breakdown voltage at room temperature and high temperature were good. Especially, tan δ is lower than that of the polyethylene terephthalate film, which is good. Also, since there was little thickness unevenness, there was almost no difference in dielectric characteristics or dielectric breakdown voltage depending on the location.

Example 4 In Example 1, 2500 globular silica was added as an additive.
A biaxially stretched film was obtained in exactly the same manner except that ppm was used and the final film had a thickness of 9 μm. This film had good slipperiness, abrasion resistance and durability running property. Further, when a magnetic layer was provided on the film with nickel-cobalt and the electromagnetic conversion characteristics were examined, it was satisfactory.

[0029]

INDUSTRIAL APPLICABILITY The syndiotactic polystyrene film of the present invention has excellent electrical properties, transparency and mechanical strength required for industrial use, packaging use, magnetic tape use, capacitor use, etc. Flatness by optimization,
It has excellent printability and heat resistance.

[0030]

[Brief description of drawings]

FIG. 1 is a device for measuring the durability and running property of a film, where 1 is a crank, 2, 4, 6, and 8 are free rolls,
3 and 7 are tension detecting devices, 9 is a load, and 5 is a commercially available VTR guide.

[0031]

[Figure 1]

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

[0035]

[Table 4]

[0036]

[Table 5]

Claims (1)

[Claims] 1. A polystyrene-based polymer mainly composed of a syndiotactic structure, which is stretched in at least one axial direction and has a refractive index Nz in the thickness direction of 1.6.
A syndiotactic polystyrene film having a thermal shrinkage of 200 or more and 150 ° C. of less than 3%.