JPH021651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crude film obtained by stretching a film comprising a crystalline polyester having at least 70 mole percent ethylene terephthalate repeating units and crystallized to a specified range of spherulite size. The present invention relates to a polyester film having a planarized surface. The roughened polyester film takes advantage of its excellent properties such as heat resistance, chemical resistance, water resistance, durability, high strength, writability, and moderate transparency, and is used as a tracing film for drafting films and second original drawings. It is widely used as a commercial film. Conventionally, these roughened polyester films are
A method of applying treatments such as sandplast treatment or chemical etching to the surface of a biaxially stretched film, a method of roughening a smooth film surface by coating it with a liquid containing fine particles, and a method of applying a similar or different type of polymer to polyester, or an inorganic material. They were manufactured by a method in which polyester is added and stretched, or a film with unevenness is formed by melt extrusion of polyester and then stretched. However, in the prior art, sandblasting requires special equipment to roughen the surface, chemical etching requires an alkaline treatment bath and attached water washing equipment, and pollution control equipment is required to treat alkaline waste liquid. Additionally, when making a roughened film by adding different polymers or inorganic inert fine particles and stretching, the extruder becomes contaminated with the additives, so cleaning the extruder is necessary when making an additive-free film. Become. Furthermore, when an inorganic substance is added, the transparency of the resulting roughened film is impaired, and when the films are stacked, the underlying pattern cannot be seen, making them unusable as tracing films. The present invention eliminates all of these manufacturing defects, does not use additives, does not require any special equipment, and can easily produce large-area translucent films with uniform, finely roughened surfaces at low cost. It was possible to obtain Normally, a stretched polyester film with a smooth surface is produced by stretching a substantially amorphous film that has been rapidly cooled by melt extrusion in the main dispersion temperature range above the glass transition temperature, and then heat-setting it at a high temperature around 200°C. This increases crystallinity and improves dimensional stability. This film is strong and transparent, and has a very smooth surface.The surface irregularities measured using a stylus meter are peaks with a height of 0.02 to 0.2μ, and 0.1 to 0.2μ.
There are 0 to 2 large peaks per 1 mm of length in any direction. This unevenness is thought to be caused by foreign matter mixed into the polymer, unmelted polymer, gelled matter, catalyst residue, fine stretching unevenness, and scratches on the surface. Usually, a small amount of inorganic inert fine particles are added to the polymer to give the film lubricity, and surface irregularities due to these fine particles are observed. In this case, the height of the peaks is 0.04 to 0.3μ, and there are 1 to 10 large peaks of 0.2 to 0.3μ per 1 mm of length in any direction. However, the film in this case is substantially smooth and is not writable with a pencil.
Moreover, it is transparent and the background can be seen through the film. The present inventors have completed the present invention as a result of intensive research on the stretchability and structure and properties of the stretched film by stretching polyester films having various crystallinity and spherulite size over a wide temperature range. In other words, a polyester film containing spherulites with a spherulite diameter of 0.5 to 5.0μ is heated by 1.5μ in at least one direction in a temperature range above the glass transition temperature of the film and below 140°C without destroying the spherulites.
By stretching the film more than twice as much, the spherulites were allowed to remain and a roughened film having fine spherulite irregularities was successfully obtained. The film of the present invention contains at least 20 peaks with a height of 0.2μ or more per mm of length in any direction on the surface, has a rough surface, is writable with a pencil, is white, translucent, and cloudy. value is 10% or more. The easiest rough surface to create is one containing 50 to 100 peaks of 0.2 to 1 micron per mm of length in any direction. If a film containing small spherulites is stretched, the height of the peaks on the rough surface obtained will be low, and if a film containing large spherulites is stretched, the height of the peaks on the rough surface will be high. The present invention will be explained in more detail. The polymers used in the present invention are crystalline polyesters having at least 70 mole percent ethylene terephthalate repeating units, particularly preferred are polyethylene terephthalate and crystalline copolyesters. Crystalline copolymerized polyester is mainly composed of terephthalic acid and ethylene glycol, and contains isophthalic acid, adipic acid, sebacic acid, naphthalene dicarboxylic acid, diphenoxyethane dicarboxylic acid, and hexahydroterephthalic acid as the third component, i.e., copolymerization component. Acid components such as trimethylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, cyclohexanedimethanol, diethylene glycol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy) Glycol components such as ethoxyphenyl) propane, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, p
- It means a polyester copolymerized with hydroxy acids such as oxybenzoic acid and p-hydroethoxybenzoic acid. Two or more types of the third component may be used in combination. A particularly preferred third component is isophthalic acid and/or
Or neopentyl glycol. Further, the amount of ethylene terephthalate in the copolymerized polyester is 70 mol% or more, preferably 85 mol% or more. If the amount of ethylene terephthalate is less than 70 mol%, the crystallinity of the polymer decreases, making it difficult to form a rough film, and is also unfavorable from the viewpoint of film properties. Furthermore, to these polyethylene terephthalate and copolymerized polyester, other polymers such as polybutylene terephthalate, polybutylene terephthalate,
1,4-Cyclohexane dimethanol polyester, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polystyrene, polyacrylic ester, polymethacrylic ester, polyacrylonitrile, polyolefins such as polyethylene and polypropylene, nylon 6, Polymers such as polyamides such as nylon 66 and nylon 12, polyethers, polyacrylates, polycarbonates, polyacetals, epoxy resins, polyurethanes, fluorine-containing ethylene resins, synthetic rubbers such as styrene-butadiene rubber and silicone rubber, and cellulose esters such as nitrocellulose. , also silicic acid, alumina, barium sulfate,
A small amount of inorganic substances such as calcium carbonate, titanium oxide, and clay may be added as long as they do not inhibit the crystallization of the polyester. Furthermore, there is no problem in adding colorants, pigments, antistatic agents, ultraviolet absorbers, oxidative deterioration inhibitors, lubricants, etc. to the polyester. Furthermore, considering the physical properties of the film and the crystallinity of the polymer, the intrinsic viscosity of polyester is 0.4 or more.
Preferably 0.5 to 1.2 is good. When the intrinsic viscosity is low, crystallization is easy, but the mechanical properties of the film are low; when the intrinsic viscosity is high, the mechanical properties of the film are high, but it is difficult to crystallize. When these polyesters are dried and melt-extruded to form a film, a film containing spherulites can be obtained by slowly cooling the melt film under appropriate cooling conditions. On the other hand, spherulites can be generated by rapidly cooling a melt film to obtain a substantially amorphous film and then heating the film. The latter method of heating an amorphous film is suitable for controlling the spherulite size. In the case of polyethylene terephthalate, in order to grow the spherulite diameter to 0.5 to 5.0μ in a substantially amorphous film, the preferred conditions for heating the amorphous film are a temperature of 90 to 150°C and a time of 5 to 10,000 seconds. . More preferred conditions are a temperature of 100 to 140°C and a time of 20 to 5000 seconds. In order to facilitate the generation of spherulites, inorganic substances such as kaolin, talc, titanium oxide, and silicon oxide, metal salts such as organic carboxylic acids, sulfonic acids, and phosphonic acids, and crystal nucleating agents such as high-melting point polyethylene terephthalate are added to polyester. You can also use In this case, the crystallization conditions are lower and for a shorter time than the above. Furthermore, film crystallization can be performed at lower temperatures and in a shorter time by using not only dry heat but also wet heat and crystallization promoting liquids such as water, methanol, acetone, benzene, nitrobenzene, and nitric acid. . When a film is immersed in acetone or the like, crystallization progresses even at a temperature of 30°C for less than 100 seconds, producing spherulites. The starting material for the film used can be not only the above-mentioned melt-forming film, but also films obtained by dry film-forming or wet film-forming. Spherulite diameter can be directly observed under crossed Nicols using a polarizing microscope. Also, Hν of light scattering
It can also be determined from a scattering image. The light scattering image from a system with a spherulite structure has a four-leaf clover shape.If the position of the maximum intensity of the scattered light is θmax, and the wavelength of the incident light in the system is λ', the spherulite radius R is calculated from the following formula. Seek. (4π/λ') Rsin (θmax/2) = 4.09 The film containing spherulites with a diameter of 0.5 to 5.0μ thus prepared is heated to a temperature above the glass transition temperature of the film and below 140°C. By stretching the film by 1.5 times or more in at least one direction without breaking it, the spherulites remain and unevenness occurs on the film surface. If the stretching ratio is less than 1.5 times, the unevenness will be uneven and the height of the peaks will be small. The stretching temperature range is higher than the glass transition temperature and lower than 140°C, and more preferably 90 to 130°C.
In short, a boundary temperature that changes from the glass transition region to the rubbery region is preferred. In particular, the combination of spherulite size and stretching temperature is delicate; in films that do not contain spherulites or that contain small spherulites with a spherulite diameter of less than 0.5μ, the stretched film may become an oriented film depending on the stretching temperature. The film becomes a film in which the molecular chains flow, and the surface is smooth and does not have any roughness. On the other hand, if the spherulite diameter is too large than 5.0 μm, the film becomes an oriented film when stretched, and the surface is smooth and does not have a rough surface. Particularly in the case of biaxial stretching, breakage is likely to occur during stretching. A rough surface occurs only when a film containing spherulites with a diameter of 0.5 to 5.0 μm is stretched at a temperature at the boundary where the glass transition region changes to the rubbery region. When stretched below the glass transition temperature, the film may break during stretching or become an oriented film with a smooth surface. In addition, at temperatures exceeding 140℃,
Crystallization progresses during the preheating stage and during stretching, and even if the film breaks during stretching or is stretched, the surface remains smooth and transparent. The glass transition temperature of the film can be measured using a direct-reading dynamic viscoelasticity meter from Toyo Baldwin.
It is determined from the change in the dynamic elastic modulus E' of the film using the RHEOVIBRON DDV-form. The glass transition temperature varies slightly depending on the degree of crystallinity in the case of polyethylene terephthalate, ranging from 67 to 80
It is around ℃. As the crystallinity increases, the glass transition temperature increases. For polyesters containing copolymers and plasticizers, the temperature is slightly lower than this. The deformation rate during stretching is not limited in any way, and a wide range of deformation rates can be used, and in reality, a range of 1 to 10 ⁶ %/min is preferred. The stretching may be uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, multiaxial stretching, multistage stretching, etc., and the shape of the film is not limited in any way, such as flat or tube. When stretching the film, it may be laminated with polymer films of the same type or different types, and the laminated film may be stretched. After stretching the film, it may or may not be heat-set. Heat setting may be carried out at a constant length or may be carried out while relaxing. In constant length heat fixing at a temperature of around 200℃,
There is almost no change in the shape of the surface unevenness of the film. Preferred heat fixing conditions are a temperature of 150°C to 230°C;
The time is 1 to 200 seconds. The heat-set film is
Dimensional stability is maintained even at high temperatures of 150-180°C. In particular, the film produced under the conditions of the present invention had good quality with little thickness unevenness and uniform film thickness. The surface roughness of the film can be measured using optical methods (interference microscope, scanning electron microscope, cross-sectional photograph of the film),
Although it can be measured by a mechanical method (stylus type surface roughness meter), the mechanical method using a stylus type surface roughness meter is relatively simple and can express the actual roughness well, so in the present invention, The values determined using a stylus surface roughness meter are adopted in the claims. The stylus type surface roughness meter used was a surface roughness and contour measuring machine Surfcom 300A manufactured by Tokyo Seimitsu Co., Ltd. FIG. 1 shows the measurement results of the film surface roughness of Examples and Comparative Examples. Mountain heights were measured based on the deep valleys of neighboring mountains. In the thus obtained roughened polyester film of the present invention, the surface roughness of the stretched film changes depending on the size of the spherulites contained in the film before stretching. Moreover, the height of the peaks that can be easily obtained on the film surface is in the range of 0.2 to 1.0μ,
As mentioned above, the number of ridges is at least 20 per mm in either direction, preferably 50 to 100.
If the number is less than 20, it is not suitable for the roughened polyester of the present invention. The film of the present invention is matte and white and translucent due to light scattering due to the spherulites contained in the film and the unevenness of the surface. Due to its uneven surface, it has the writing properties of a pencil and is receptive to ink. Furthermore, since the surface is rough, the coefficient of friction is extremely small and the film has excellent lubricity even if the polymer does not contain a lubricant. In addition, because of the rough surface, there is little frictional electrification, and there is little dust adhesion even without the use of antistatic agents. Furthermore, since it is translucent, even if it is stacked on top of printed paper or film, the letters and designs underneath can be clearly read. Furthermore, because of the diffuse reflection of light from the rough surface, the background cannot be seen when the film is removed. Because of its rough surface, it has good adhesion with adhesives and has excellent impregnability with oil. Because the film is stretched, it is strong, and heat-set films have dimensional stability even at high temperatures of 150-180°C. Spherulites are not greatly deformed or completely destroyed even by stretching, so even in stretched films, the tear propagation resistance of the film is improved by the spherulites contained inside the film, and it does not contain normal spherulites. Compared to stretched films that are transparent and have a smooth surface, they are less likely to tear.
This tendency is remarkable in thin films. If metal is further deposited on the fine rough surface, a matte reflective film can be obtained. Since the polymer is polyester, the film is heat resistant, chemical resistant,
It has many advantages, including excellent properties such as water resistance, durability, and high strength. Furthermore, the roughened polyester film of the present invention may be used in a laminated manner with other films, and further value can be added as a laminated film. The roughened polyester film of the present invention utilizes such excellent physical properties to be used as a design drawing film, graph paper, surveying original film, map, second original drawing film, capacitor film, masking film, and mending film. Tapes, adhesive tapes, electrical insulation tapes, light blocking films, reflective films, window covering materials, tents, awning materials, greenhouse films, agricultural films, labels, stickers,
Widely used for printing materials, packaging materials, book covers, calendars, protective films for steel plate coating films, gold and silver thread, printing films, dry electrostatic copying films, base films for magnetic tapes, magnetic commuter passes, magnetic tickets, etc. However, the usage is not limited to the above. Next, the method for measuring the physical properties of the film is shown below. (1) Spherulite diameter: Determined from the Hν scattering image of light scattering.
The sample film is placed between two orthogonal polarizing plates separated by an optical system in which the polarization direction of the incident light is vertical and the polarization direction of the analyzer is horizontal, and the image observed behind the analyzer is the Hν scattering image. be.
The light scattering image from a system with a spherulite structure has a four-leaf clover shape, and if the position of the maximum intensity of the scattered light is θmax and the wavelength of the incident light in the system is λ', the spherulite radius R can be found from the following formula. . (4π/λ′) Rsin (θmax/2) = 4.09 The light source was He manufactured by Nippon Kagaku Engineering Co., Ltd.
-Measured using Ne gas laser NEO-3M type, wavelength 6328 Å. References for measuring spherulite diameter are shown below. (a) Introduction to Polymer Chemistry, 1st edition published by Kagaku Doujin, pages 93-95, published in 1973, (b) RSStein, MBRhodes, J.Appl.Phys.,
31.1873 (1960) (2) Glass transition temperature: Manufactured by Toyo Baldwin Co., Ltd.
When measuring using a RHEO-VIBRON DDV-type at a measurement frequency of 110H ₂ and a heating rate of 2°C/min, the dynamic elastic modulus E' of the film is
The temperature was set to start decreasing rapidly from the order of ¹⁰ dynes/cm ² . (3) Number of peaks with a height of 0.2μ or more: The unevenness of the film surface was measured in accordance with JIS Bo601 using a surface roughness and contour measuring device Surfcom 300A manufactured by Tokyo Seimitsu Co., Ltd. The measurement conditions were a scan speed of 0.03 mm/sec, a cutoff value of 0.08 mm, a roughness (vertical direction) sensitivity on the recording paper of 1 μ/25 mm, and a scan direction (horizontal direction) sensitivity on the recording paper of 90 μ/25 mm. Measure over a length of 0.8mm on the film, count the number of peaks with a height of 0.2μ or more that exist within a range of 0.5mm above the film, and calculate the number of peaks per 1mm of length by averaging three measurements. It was converted into Mountain heights were measured based on the deep valleys of neighboring mountains. (4) Total light transmittance and haze value: Measured using Toyo Seiki haze meter S type according to JIS K6714. (5) Writability of pencil: Items that can be written on the film using Mitsubishi Pencil Uni's HB are marked with an ○, and items that cannot be written are marked with an x. (6) Friction coefficient: Measured according to ASTM D1894. (7) Strength and elongation: Measured at a temperature of 20°C according to JIS C2318. (8) Dry heat shrinkage rate: Temperature 180℃ according to JIS C2318
The film was processed for 20 minutes and determined from the change in dimension of the film before and after processing. (9) Tear strength: Measured according to ASTM D1938. (10) Melting point: Using a differential scanning calorimeter DSC-2 type manufactured by RERKIN-ELMER, the heating rate was 10℃/
The endothermic peak temperature of melting measured at min was taken as the melting point. (11) Crystallinity: Calculated from crystalline and amorphous densities using the density determined by JIS K7112. The present invention will be explained below with reference to Examples, but the present invention is not limited by these Examples unless the gist of the invention is exceeded. Example 1 (and Comparative Example 1) A lubricant-free polyethylene with an intrinsic viscosity of 0.60 measured at a temperature of 30°C using a mixed solvent of phenol/tetrachloroethane (3/2) and using an Ubbelohde capillary viscometer. Using a 60 mm extruder, extrude a melt film from a T-die at a temperature of 290°C, and rapidly cool it on a cooling drum with a surface temperature of 40°C to form a transparent, substantially amorphous film with a width of 250 mm and a thickness of 220 μ. An oriented film was obtained. The crystallinity determined by the density method was 6%. This film was observed using a polarizing microscope and a light scattering method, but no spherulites were observed. This film is manufactured by Tabai Seisakusho, Perfect Oven.
Using P12 type, crystallization treatment was performed at various temperatures of 100 to 200°C for 15 minutes each. These various films were tested in a tensile tester equipped with a heating oven manufactured by Toyo Baldwin.
Uniaxial stretching was carried out using TENSILON UTM-4L type at a temperature of 96°C and a deformation rate of 20%/min to a stretching ratio of 4.0 times. The physical properties of the obtained films are shown in Table 1. Films without spherulites and films with large spherulites did not develop rough surfaces even when stretched, and had smooth surfaces, whereas The crystal-sized one had a rough surface due to stretching and had the writing properties of a pencil. The results are shown in Table 1. [Table] Example 2 (and Comparative Example 2) Using the untreated film of Example 1, a film crystallized at a temperature of 113°C in the same manner was used, and T,
The film was simultaneously biaxially stretched at a deformation rate of 1000%/min and a stretching ratio of 3.5×3.5 using a film stretcher manufactured by M.Long. For heat fixation, the film was attached to a metal fixing frame and treated in a hot air dryer at a temperature of 215°C for 15 seconds.
When a film containing spherulites of appropriate size was stretched, a rough film was obtained. This film had the writing properties of a pencil, had a significantly small film-to-film friction coefficient, and had extremely good lubricity. On the other hand, a film containing no spherulites remained transparent even after stretching, and had a flat surface. This film was not writable with a pencil and had extremely poor slipperiness. In addition, the film containing large spherulites due to excessive crystallization was broken during stretching. The results are shown in Table 2-1 and Table 2-2, and examples of surface roughness measurements are shown in FIGS. 1A and 1D. All figures in Figure 1 are on a scale of 7/10, and the vertical axis is the surface unevenness.
1μ/25mm (1 scale 0.1μ), horizontal axis is scan direction
Indicates 90μ/25mm (1 scale: 9.0μ). [Table] [Table] [Table] Example 3 (and Comparative Example 3) In the same manner as in Example 1, the lubricant SiO ₂ was added at 0.02% by weight.
A film with a thickness of 410μ was obtained by melting and forming a film containing polyethylene terephthalate. This film was crystallized using the same oven as in Example 1 at a temperature of 110°C for different times.The film was then stretched in the same manner as in Example 2 using a film stretcher manufactured by T. It was measured. When an untreated film containing no spherulites was stretched, only a transparent and smooth stretched film was obtained.On the other hand, when a film containing moderately sized spherulites was stretched, it became cloudy and had a rough surface, making it difficult to write with a pencil. gender was recognized. Heat fixation was carried out in the same manner as in Example 2 at a temperature of 215°C.
Processed for seconds. The results are shown in Tables 3-1 and 3-2, and examples of surface roughness measurements are shown in FIGS. 1B, C, and E. [Table] [Table] [Table] Example 4 (and Comparative Example 4) Using the untreated film of Example 3, the temperature was 50°C.
One side of the film was immersed in acetone to crystallize it, and the film was uniaxially stretched 3 times in the transverse direction using a tenter at a temperature of 105° C. at a film running speed of 5 m/min. A moderately crystallized film exhibited a rough surface on only one side after stretching, whereas a non-crystallized film remained transparent and smooth on both surfaces even after stretching. The results are shown in Table 4. [Table] Example 5 (and Comparative Example 5) Melting points of melt polymerization from dimethyl terephthalate, dimethyl isophthalate, and ethylene glycol
Polyethylene terephthalate/isophthalate (9/1) copolymer at 243°C was melt-formed into a film at a temperature of 270°C using a 40° extruder to obtain a transparent unstretched film with a thickness of 300μ. This film was crystallized in an oven at a temperature of 120° C. in the same manner as in Example 1. This film was deformed at 500%/500% at a temperature of 120°C using a film stretcher manufactured by T, M, and Long.
The film was sequentially biaxially stretched at a stretching ratio of 3.5×3.5 times.
The film containing spherulites of appropriate size exhibited a rough surface upon stretching, but the surface of the film containing no spherulites did not become rough even after stretching, and the surface remained smooth. The results are shown in Table 5. [Table] Example 6 (and Comparative Example 6) Melting points of melt polymerization from dimethyl terephthalate, dimethyl isophthalate, and ethylene glycol
Polyethylene terephthalate/isophthalate (8/2) copolymer at 213°C was melt-formed at 250°C using a 40° extruder to obtain a transparent unstretched film with a thickness of 320μ. This film was crystallized in the same manner as in Example 1 using an oven at a temperature of 140°C. This film was simultaneously biaxially stretched at a temperature of 90° C. at a stretching ratio of 3×3 using a film stretcher manufactured by T, M, Long. The film containing a moderate amount of spherulites exhibited a rough surface upon stretching, whereas the film containing no spherulites had a smooth surface. The results are shown in Table 6. 【table】

[Brief explanation of drawings]

FIG. 1 shows a measurement example of the surface roughness of the roughened polyester film obtained according to the present invention and a comparative example used for comparison, on a scale of 7/10, and A is Example 2- 2. B is Example 3-6, C is Example 3-7, D is Comparative Example 2-1, E is Comparative Example 3
-4 film was used.

Claims (1)

[Claims] 1. An amorphous film is prepared from a crystalline polyester having an intrinsic viscosity of 0.4 to 1.2 at 30°C and having at least 70 mol% ethylene terephthalate repeating units; A crystallized film grown to a spherulite diameter of 0.5 to 5.0μ by heating at 90 to 150°C for 5 to 10,000 seconds is heated to a temperature higher than the glass transition temperature of the crystallized film.
The height of the surface of the film obtained by stretching the spherulites by 1.5 times or more in at least one direction without destroying the spherulites in a temperature range of 140°C or lower is 0.2μ or more. A roughened polyester film containing at least 20 peaks per 1 mm of length in any direction and having a haze value of 10% or more.