JPH0885161A - Manufacture of resin film with craze - Google Patents

Abstract

PURPOSE: To form a continuous banded craze by first longitudinally orienting and then laterally orienting a thermoplastic resin film extruded from a molding die by a biaxial orienting machine, bringing the obtained oriented resin film into contact with a craze generator, and locally bending it. CONSTITUTION: In the case of manufacturing a craze film 7, a resin melted and kneaded by an extruder is extruded by a T-die, the obtained film is cooled to be solidified on a casting drum, and then longitudinally oriented 1.3-5 times by a roll group. Then, it is fed to a tenter oven to be heated to a temperature lower by 3-100 deg.C than the melting point of the resin, and laterally oriented to twice or more of the longitudinal orienting magnification by the tenter, thereby obtaining an oriented film 1 having a double refractive index of 0.5×10<-3> or more. Then, a craze generator 3 having an edge 2 of an end angle of 15-135 degrees in parallel with the lateral direction of the film 1 is brought into contact with the film 1, and the film 1 is locally bend to draw a craze film 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin film having crazes. The resin film having this craze is a fresh food packaging material that makes good use of breathability, a leak preventive material for sanitary napkins, a clothing material, a medical material such as a filter, and a building material plate glass that has a viewing directionality that scatters incident light depending on an angle. It is used for overlay film and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a breathable resin film having porosity, a resin film containing an inorganic filler is stretched in a uniaxial or biaxial direction.
It is well known that fine air holes are generated in a film to obtain a breathable resin film (see, for example, JP-A No.
8-149303 and JP-A-58-15538). However, such a porous film causes stress concentration on coarse particles of the dispersed inorganic filler during stretching, which may cause stretch breakage in some cases, or stretches uniformly even if it does not break. Since this does not occur, there are problems in the distribution of film thickness, strength and the like. In addition, there are various defects such as a stiff feeling peculiar to the stretched product. Therefore, in order to improve the flexibility of such a porous film, it has been proposed to add a liquid compound. For example, a liquid hydrocarbon polymer is added to JP-A-60-257221, a liquid polybutadiene is added to JP-A-57-47334, and a liquid polyisobutylene is added to JP-A-58-149925. Is described.

However, since such a liquid compound bleeds to the surface of the porous film, stickiness occurs and there is a problem in using it as a leak preventer or a bag. Further, when a liquid compound is added, interfacial peeling between the filler and the resin is less likely to occur, and there is a problem that the porous performance is lowered, that is, the air permeability is lowered. On the other hand, JP-A-6-82607
The publication discloses a method for producing a craze film in which a transparent oriented resin film is used to generate striped crazes substantially parallel to the molecular orientation direction of the film using a craze generator. There is no description about the manufacturing method.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a method for industrially producing a crazing film having excellent air permeability, moisture permeability, viewing directionality, tensile strength and transparency.

[0005]

According to the present invention, a thermoplastic resin film extruded from a molding die is first stretched 1 to 5 times in the machine direction using a biaxial stretching machine, and then the stretching ratio Stretched in the transverse direction at least 2 times or more to form a stretched resin film having a birefringence of 0.5 × 10 ⁻³ or more, and then the tip angle was set parallel to the stretched resin film in the transverse direction. Of the stretched resin film is brought into contact with a craze generator having an edge of 15 to 135 degrees to locally bend the stretched resin film, and then the stretched resin film is taken out to continuously extend in the transverse direction of the stretched resin film. The present invention provides a method for producing a resin film having crazes, which comprises forming various striped crazes.

[Detailed Description of the Invention] Material for Craze Film The resin used as the material for the craze film is not particularly limited as long as it is a thermoplastic resin capable of forming a film or sheet. Such thermoplastics include polyolefins, polyesters,
Examples thereof include polyamide, styrene resin, polycarbonate, halogen-containing thermoplastic resin, nitrile resin and the like. Among these thermoplastic resins, from the viewpoints of moldability to a film or sheet and economical efficiency, polyolefin,
It is preferable to use polyester, styrene-based resin, and halogen-containing thermoplastic resin, and above all, it is preferable to use polyolefin, styrene-based resin, and halogen-containing thermoplastic resin.

These thermoplastic resins may be used alone, as a composition by mixing two or more kinds, or by blending with another polymer resin, as long as the transparency is not impaired in the resin film. Alternatively, two or more kinds of resins may be used in a multilayer structure. Further, the glass transition temperature of the thermoplastic resin is -45 ° C because of the ease of forming crazes.
Or more, preferably -30 ° C or more, particularly preferably -15
It is desirable to use a resin having a temperature of ℃ or higher. When used as two or more kinds of resin compositions or when used as a multilayer, it is preferable that the thermoplastic resin occupying the main component has a glass transition temperature within the above range. In the case of a thermoplastic resin having a glass transition temperature lower than this, it is difficult to efficiently form crazes because it is too soft.

The polyolefin has a carbon number of 2 to 8
Is a homopolymer of α-olefin, a copolymer of two or more α-olefins, or a copolymer containing α-olefin as a main component and another ethylenically unsaturated monomer. Here, the copolymer may be block, random, graft or the like or a composite thereof. Examples of the ethylenically unsaturated monomer include unsaturated carboxylic acids such as methacrylic acid, methyl methacrylate, and maleic acid, or anhydrides. Specific examples of the polyolefin include low-density branched polyethylene, high-density linear polyethylene, low-density linear polyethylene, isotactic polypropylene, syndiotactic polypropylene, poly (1-butene), poly (4-methyl-1-pentene). ) Etc. can be mentioned.

The polyamide is a condensation product containing a repeating unit having an aromatic or / and an aliphatic amide group as an essential component. Specific examples of polyamides include nylon-4, nylon-6, nylon-6,6,
Examples thereof include nylon-4,6, nylon-12 and amorphous nylon. Among them, preferred polyamides are nylon-6, nylon-6,6 and amorphous nylon.

The polyester is, for example, a thermoplastic polyester produced by condensing a dicarboxylic acid or a lower alkyl ester thereof, an acid halide or an acid anhydride derivative and a glycol or a dihydric phenol according to a conventional method. I can mention. Among these polyesters, saturated polyesters, especially polyethylene terephthalate, polybutylene terephthalate,
Preference is given to using polynaphthalene terephthalate.

The styrene resin is a polymer of a vinyl aromatic compound, and specific examples of the vinyl aromatic compound include styrene, α-methylstyrene, paramethylstyrene, vinyltoluene and vinylxylene. The styrenic resin is a homopolymer or copolymer of these vinyl aromatic compounds. Among these, polystyrene is preferable, and it is more preferable to use rubber graft polystyrene (HIPS), acrylonitrile / butadiene / styrene copolymer, or a water additive thereof.

Examples of the polycarbonate include aromatic polycarbonate, aliphatic polycarbonate, and aliphatic / aromatic polycarbonate. Among these,
It is preferable to use an aromatic polycarbonate composed of 2,2-bis (4-oxyphenyl) alkane type, bis (4-oxyphenyl) ether type, bis (4-oxyphenyl) sulfone, sulfide or sulfoxide type bisphenols. Is.

Examples of the halogen-containing thermoplastic resin include homopolymers and copolymers of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride and the like. In addition to these, homopolymers and copolymers derived from vinylidene chloride can be mentioned. Among these, preferred halogen-containing thermoplastic resins include homopolymers of polyvinylidene fluoride, copolymers of tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene, and vinylidene chloride. The nitrile resin contains 50% by weight or more of α, β-olefin unsaturated mononitrile. Among these unsaturated mononitriles, it is preferable to use acrylonitrile, methacrylonitrile and mixtures thereof. For example, specifically, polyacrylonitrile and acrylonitrile / styrene copolymer can be used.

Formation of Craze A thermoplastic resin film extruded from a molding die is stretched using the above-mentioned thermoplastic resin using a biaxial stretching machine. The stretching temperature of the crystalline resin is 100 to below the melting point.
Range, the amorphous resin has a glass transition point (Tg) ± 100
The stretching range and the stretching speed are 0.5 to 300 m / min. First, the film is stretched 1 to 5 times in the machine direction, and then stretched in the transverse direction at a draw ratio of at least 2 times or more. A stretched resin film having a birefringence of 0.5 × 10 ⁻³ or more, and the stretched resin film is placed in a craze generator having a sharp edge at the tip, which is installed parallel to the transverse direction of the stretched resin film. Abutting, then locally bending the stretched resin film, by moving the bending deformation region relative to the stretched resin film by pulling it, in the lateral direction of the stretched resin film,
Continuous striped crazes can be continuously formed on the film.

The craze film of the present invention is provided with striped craze regions. The striped crazes have a width of generally 0.5 to 100 μm, preferably 1 to 50, substantially parallel to the direction of molecular orientation of the polymer resin film.
μm (see FIG. 4). This striped craze
The ratio of the number of crazes penetrating in the thickness direction of the film is 10% or more, preferably 20, with respect to the total number of crazes.
% Or more, particularly preferably 40 to 100% or more, and if the penetration rate is less than 10%, the air permeability /
It becomes difficult to obtain performance such as polarization. The crazes are formed in a direction substantially parallel to the lateral direction (TD) having a large molecular orientation because the lateral direction having a large molecular chain orientation and the vertical direction (M
This is because the crazes are formed in a fixed array by pulling the stretched resin film in D), and it is difficult to form the crazes in the longitudinal direction perpendicular to the lateral direction in which the molecular chain orientation is large. The craze referred to here includes a surface craze appearing on the surface of the stretched resin film and an inner craze generated inside, and refers to a region having a fine crack-shaped pattern. This craze is composed of molecular bundles (fibrils) and microvoids, and various gases are permeable to this portion.

Thickness The thickness of the stretched resin film is generally 1 to 800 μm, preferably 3 to 500 μm, particularly preferably 8 to 300 μm.
m is used. Orientation The orientation degree of the above stretched resin film is 0.5 in terms of birefringence.
× 10 ^-3 or more, preferably 1 × 10 ^-3 or more, and particularly preferably has a degree of molecular orientation in the 1.5 × 10 ^-3 or more, effective in the formation of crazes. With the stretched resin film having a molecular orientation in which the birefringence is out of the above range, it is difficult to easily form a target craze. Birefringence The birefringence referred to here is expressed as the difference between the main refraction indexes, and is the molding direction of the stretched resin film (longitudinal direction: M
D) refractive index (n2) and the direction perpendicular to it (transverse direction: T
The difference (n1−n2) between the refractive indexes (n1) of D) is one of the indexes that express the degree of molecular orientation. In practice, these birefringences can be measured by using a polarization microscope and a compensator, and the larger this value, the greater the anisotropy and the more likely the craze is. Amount of craze The craze formed on the stretched resin film generally has a thickness of 0.
The amount is an amount that can be recognized as a striped region formed at intervals of 1 to 1,000 μm, preferably 1 to 800 μm. Typical physical properties of craze film As the performance of a stretched resin film having craze, air permeability, moisture permeability, viewing directionality, etc. can be obtained. The air permeability varies depending on the type of resin used. For example, when a vinylidene fluoride homopolymer is used, the gas permeability (JIS-Z1707) of oxygen and nitrogen gas is generally 0.3 to 100,000.
In the range of 0 × 10 ⁴ cm ³ / m ² · 24 hr · atm, the water vapor permeability (JIS-K7129) is generally 10
Transparency (JIS-Z7105) is generally 1-9 in the range of 100,000 × 10 ⁴ g / m ² · 24 hr.
9.5%, preferably 2 to 90%, particularly preferably 5 to
Within 80%, the tensile strength (JIS-Z170
2) is generally 50 to 500 kg / cm both in the vertical and horizontal directions
² , preferably 60 to 500 kg / cm ² , and particularly preferably 75 to 500 kg / cm ² .

Manufacturing Method The craze film of the present invention is manufactured by continuously subjecting a stretched film obtained by using an ordinary biaxial stretching machine to a craze treatment step. That is, the resin melt-kneaded by an extruder is extruded from a T-die to obtain a sheet, which is cooled and solidified on a casting drum, and then the longitudinal velocity of the roll group is utilized to obtain a sheet, preferably 1 Stretching 3 to 5 times (This longitudinal stretching is not always necessary, but for convenience, a film that is not stretched (1 time stretching) is also set to 1 time stretching and is set in the stretching range).

Next, the longitudinally stretched film is fed into a tenter oven and heated to a temperature which is 3 to 100 ° C. lower than the melting point of the resin, and using a tenter, at least twice the longitudinal stretching ratio or in the transverse direction. Stretched 4 to 12 times in the direction, and the thickness is 1 to 800 μm, preferably 3 to 500 μm.
m, more preferably 8 to 300 μm and having a birefringence of 0.5.
A stretched film of x10 ^-3 or more is obtained. Further, a craze generator having an edge having a tip angle of 15 to 135 degrees in a direction parallel to the lateral direction of the film is brought into contact with the film, and then the stretched resin film is locally bent to stretch the bending deformation region. By pulling the resin film and moving it relatively, the craze film having continuous and regular striped craze regions is formed in the lateral direction of the stretched resin film. In order to stabilize the performance of the craze film, it is preferable to provide an annealing step in the transverse stretching step. Further, the stretched resin film may be subjected to corona surface treatment before the craze treatment step.

As the whole production line, as described above, the extrusion process → stretched raw film production process → longitudinal stretching process → horizontal stretching process → (annealing process) → (corona discharge treatment process) → craze treatment process → craze All of the film winding processes are continuously and efficiently manufactured in a continuous line. The layer structure of the film is not limited to a single layer, and may be a multilayer structure with a multilayer coextruder. After the production of the craze film, the craze film may be used as a composite multi-layer with another substrate such as pulp paper, aluminum foil or polyethylene film depending on the application. Further, the craze treatment may be carried out in a step different from the stretching step.

Apparatus for Producing Craze Film An apparatus for producing the craze film of the present invention is, for example, shown in FIG.
As shown in, on the surface of the biaxially stretched resin molecular film 1 having the above-mentioned oriented physical properties produced by a biaxial stretching machine,
The craze generator 3 having the edge 2 at the tip is brought into contact with the stretched resin film in a direction substantially parallel to the lateral direction in which the molecular orientation of the stretched resin film is large, the stretched resin film is locally bent, and the stretched resin film is pulled in the direction of the arrow. By taking this, a band of crazes is formed in the stretched resin film, and the moving direction (M
A film having continuous striped crazes is obtained in the transverse direction substantially perpendicular to D). The proper edge angle 2 of the craze generator 3 is in the range of 15 to 135 degrees, preferably 30.
Is 90 degrees, and the proper radius of curvature of the edge tip is 0.0
The thickness is in the range of 1 to 5 mm, preferably 0.01 to 1 mm. The bending angle 4 of this film is 140 degrees or less,
It is preferably 120 degrees or less, but generally, the smaller the bending angle and the larger the tensile tension, the greater the ratio of the crazes penetrating in the thickness direction of the stretched resin film with respect to all the crazes. A film having good breathability can be obtained.

Two or more craze generators having this edge may be used as shown in FIGS. 2 and 3, and the craze generator may alternately contact the upper surface and the lower surface of the stretched resin film. In that case, the bending angles 4, 10, and 14 need not all be the same. From the viewpoint of efficiency, the ambient temperature for generating the craze is generally 15 to 30 ° C., but in some cases, the temperature may be −40 ° C. to room temperature or lower. The film take-up speed for generating craze is usually 0.5 to 300 m / min, preferably 1 to 100.
m / min. If the take-up speed is too fast or speed unevenness occurs, problems such as cutting of the stretched resin film, scratches on the film surface, and nonuniform craze may be caused.
The degree of air permeability of the craze film can be adjusted by changing the width of the craze formed in the stretched resin film, the distance between the crazes, and the number ratio of the crazes penetrating the film.

Specifically, the degree of molecular orientation of the stretched resin film, the temperature at which the craze is formed, the degree of tension of the stretcher resin film (tension in a tensioned state), the bending angles 4, 10, 14 of the film, etc. By adjusting, the air permeability can be easily controlled, and a craze film can be provided according to the purpose of use. For example, increasing the tension when forming crazes,
The smaller the fold angle, the smaller the spacing of the crazes produced and the greater the proportion of the number of crazes that penetrate the film, resulting in increased breathability. By controlling the width of the crazes, the distance between the crazes, and the ratio of the crazes that penetrate the film, it is possible to control the oxygen gas and nitrogen gas permeability, moisture permeability, transparency, and tensile strength of the craze film. You can

[0023]

EXAMPLES AND COMPARATIVE EXAMPLES The present invention will be described in more detail with reference to the following experimental examples, but the present invention is not limited to these experimental examples. [I] Evaluation Method A birefringence film of the film A small piece was cut out from the film, and a polarizing microscope (X-POL) manufactured by Nippon Kogaku Co., Ltd. and a Senarmont conventor were used to measure the film forming direction and a right angle thereto. The difference in the refractive index in the directions was measured as the birefringence. Confirmation of craze formation A small piece was cut out from the craze-formed film, and the presence or absence of craze formation was confirmed using a biological microscope (XF) manufactured by Nippon Kogaku KK. Oxygen permeability test According to JIS-Z1707, the gas permeability of oxygen gas was determined by a unit of cm ³ / m ² · 24 hr · atm by an isobaric method.

[II] Materials used Polypropylene (indicated as PP in the table; Mitsubishi Polypro FL6CK (trade name) manufactured by Mitsubishi Petrochemical Co., Ltd.) and polyvinylidene fluoride (indicated as PVDF in the table. Mitsubishi Petrochemical Co., Ltd. )
KYNAR720 (trade name) manufactured by Japan, high impact strength polystyrene (indicated as HIPS in the table. HH1 manufactured by Mitsubishi Kasei Co., Ltd.)
02 (trade name), 6 nylon (in the table, written as Ny6).
MC140 (trade name) manufactured by Kanebo Co., Ltd. was used.

[III] Examples Example 1 Polypropylene (Mitsubishi Polychemical FL6CK manufactured by Mitsubishi Petrochemical Co., Ltd.) using a 65 mmφ single screw extruder (L / D = 28).
Melt-extruded at 250 ° C., stretched 3.5 times in the longitudinal direction at 135 ° C., further stretched 10 times in the transverse direction at 160 ° C., and then annealed at 165 ° C. It was created. The film thickness after stretching is 20μ
m, and the birefringence was 21.5 × 10 ⁻³ . Next, using the apparatus shown in FIG. 1, the tip angle is 60 degrees and the tip radius of curvature is 0.2 mm on the surface of the stretched resin film 1.
The craze generator 3 having the edge 2 is abutted in the lateral direction and bent so that the bent angle 4 of the stretched resin film is 140 degrees, and the speed ratio between 5 and 6 is set to 115%. At a speed of 50 m / min to obtain a film 7 in which laterally continuous striped craze regions were generated. Table 1 shows the oxygen transmission rate of this craze film. Also, the film after forming this craze,
The result of observation with a biological microscope (XF) manufactured by Nippon Kogaku Co., Ltd. is shown in FIG.

Examples 2 to 5 Using the resins shown in Table 1, the oxygen permeability of the craze film obtained by carrying out stretching and craze generation treatment in the same manner as in Example 1 under the conditions shown in the table, is shown in the same table. . Comparative Examples 1 to 4 Films were produced with the resins and molding conditions shown in Table 1.
In Comparative Example 1, the molecular orientation of the stretched resin film is the longitudinal direction, and in Comparative Examples 2 to 4, craze formation does not occur because the molecular orientation of the stretched resin film is insufficient, and no improvement in oxygen permeability is observed. It was

[0027]

[Table 1]

[0028]

Industrial Applicability The method for continuously producing a film having crazes according to the present invention utilizes a conventional sequential biaxial stretching machine, and by incorporating a craze generator into the production line, a resin film having uniform crazes can be industrially produced. It can be manufactured on an industrial scale.

[Brief description of drawings]

FIG. 1 shows a craze film manufacturing apparatus.

FIG. 2 shows a craze film manufacturing apparatus.

FIG. 3 shows a craze film manufacturing apparatus.

FIG. 4 is a photograph (200 times) showing a craze structure in polymer crystals of a craze film obtained in Example 1.

[Explanation of symbols]

 1 Stretched resin film 2,8,12 Edge angle 3,9,13 Craze generator 4,10,14 Film bending angle 5,6 Nip roll 7 Craze film 11,15 Guide roll

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fumiyo Ikehata 1 Toho-cho, Yokkaichi-shi, Mie Prefecture Yokkaichi Research Institute, Mitsubishi Petrochemical Co., Ltd. (72) Inventor Mitsuaki Yamahara 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Oil Chemical Company Yokkaichi Research Institute

Claims (1)

[Claims] 1. A thermoplastic resin film extruded from a molding die is first subjected to 1 to 5 in the longitudinal direction by using a biaxial stretching machine.
Double stretching, and then stretching in the transverse direction at a draw ratio of at least 2 times or more to form a stretched resin film having a birefringence of 0.5 × 10 ⁻³ or more, and then in the transverse direction of the stretched resin film. Installed in parallel, the tip angle is 15 to 1
The stretched resin film is brought into contact with a craze generator having an edge of 35 degrees, the stretched resin film is locally bent, and then the stretched resin film is pulled off to continuously extend in the lateral direction of the stretched resin film. A method for producing a resin film having crazes, which comprises forming striped crazes.