JPH0449621Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Field of Application] The present invention relates to a packaging film suitable for photographic light-sensitive materials, particularly X-ray films for badges, dentistry, industrial use, etc. [Prior Art] Various types of films for packaging photographic materials have been widely put into practical use, and various performances are required depending on the intended use. A packaging film that completely blocks light is used as a packaging film for photographic materials that loses its quality value when exposed to light. In this case, the properties required are light shielding properties, moisture proofing properties, gas barrier properties, physical strength (breaking strength, tearing strength, impact puncturing strength,
Abrasion strength, etc.) heat sealability (heat seal strength, hot tack property, contaminant sealing property, fusing seal property, etc.), antistatic property, flatness, sliding property, appearance, etc. It is also important that this packaging film is easy to manufacture. It is extremely difficult to achieve all of these properties in a single film, and conventionally, high-pressure branched low-density polyethylene (hereinafter referred to as LDPE) resin light-shielding films mixed with carbon black, paper, and aluminum have been used. Composite laminate films with flexible sheet layers such as foils and cellophane have been used. An example of a typical composite laminate film is shown in FIG. 17, in which a metal foil layer 7 is attached to an LDPE resin light-shielding film layer 4a via an adhesive layer 2.
A is laminated, and a flexible sheet layer 4 is further laminated via an adhesive layer 2. The inventor of the present invention has conducted extensive research to improve packaging materials for photographic materials, and has developed a material with improved physical strength by combining two layers of uniaxially stretched film (Japanese Patent Laid-Open No. 57-6754). It has already been disclosed. In addition, linear low-density polyethylene (hereinafter L-
Regarding packaging materials using resin (labeled as LDPE), at least one layer of a light-shielding film consisting of a polyethylene polymer and a light-shielding substance of 1% or more by weight, with 50% or more by weight of the total ethylene-based polymer being L-LDPE resin is also used. We have already disclosed what we have (Japanese Unexamined Patent Publication No. 132555/1983). However, composite laminate films are expensive and tend to curl, making them particularly unsuitable for packaging films that completely hermetically package individual photographic materials, such as badge, dental, and industrial X-ray films. Not yet. For this reason, when packaging X-ray film for bags, a 200 μm thick LDPE resin light-shielding film mixed with carbon black was melt-sealed on three sides as shown in Figure 8 to ensure the required characteristics. [Problems that the invention aims to solve] Conventional composite laminate films were constructed to improve the properties required for photographic materials, but they were still not sufficient and suffered from tearing and holes during the packaging process. There were drawbacks such as cracking and peeling of the heat seal part. There were also problems with curling and sealing properties. If a large amount of light shielding material such as carbon black is added to LDPE resin, the physical strength and heat sealing strength will be significantly reduced, so the amount added has been kept at around 3%, but there were still problems. In addition, L-LDPE resin film with carbon black added has significantly improved physical strength than LDPE resin film, but because the melt viscosity increases, molding a film of 150 μm or more requires a large motor load, and the film surface This was not possible because it would cause unevenness (skin irritation). Particularly for use in dentistry, X-rays, and radiation exposure for those handling radiation.
It is desired to develop an inexpensive packaging film that satisfies all the necessary properties using just a thermoplastic resin film as a packaging film for vacuum-sealing X-ray film as described in Publication No. 24089. Ta. The present invention improves the above-mentioned problems, and improves packaging film formability, heat sealability (especially fusing sealability), heat seal strength, photographic material insertability,
The object of the present invention is to provide a film for packaging photographic materials that has improved film slitting suitability, moisture resistance, etc. [Means for Solving the Problems] The above object of the present invention is to produce high-pressure branched low-density polyethylene having at least 20 to 70% by weight of linear low-density polyethylene resin and a melt index of 0.2 to 10.0 g/10 min. Resin 25~79.94% by weight and PH5~9,
Carbon black 0.05~ with average particle size 10~50mμ
This is achieved by a film for packaging photographic light-sensitive materials having a thickness of 150 to 250 μm, which is prepared by an inflation molding or deflation molding method containing 10% by weight of a lubricant and 0.01 to 10% by weight of a lubricant. L is the first component essential to the film of the present invention.
-LDPE resin is essential to improve heat sealability and physical strength, which have the greatest influence on the properties of the packaging film of the present invention, and is preferably made of ethylene and 3 to 13 carbon atoms by low pressure method and high pressure modification method. 4
It is a copolymer made by copolymerizing ~10 α-olefins, and is a low-medium density polyethylene resin with an ethylene content of 86 to 99.5 mol% and a linear structure with short branches. It is also called Linear Low Density Polyethylene resin, and is generally referred to as L-
It is called LDPE resin. A specific example of a product name is Unipol (UCC).
), Dowrex (Dow Chemical Company), Sclar (DuPont Canada), Marex (Philips), Neozex and Ultzex (Mitsui Petrochemical), Nippon Liniturex (Japan Petrochemical), Stamilex (DSM), etc. . As α-olefins, butene-1, octene-1, hexene-1, 4-methylpentene-
1, heptene-1, octene-1, etc. are used, and the amount thereof is about 0.5 to 15 mol% of the polymer. The density is generally considered to be about that of low-medium density polyethylene, but many commercially available products have a density within the range of 0.87 to 0.95 g/cm ³ . A typical L-LDPE resin, which is made by copolymerizing ethylene with butene-1, an α-olefin with four carbon atoms, is produced by the presence of a highly active catalyst called the Unipol process developed by Union Carbide in the United States. produced by low pressure, gas phase reaction. This L-LDPE resin is manufactured using the conventional high pressure process (3000
The molecular weight distribution is narrower and more linear than that of LDPE resins produced using LDPE resins (atmospheric pressure, 300°C). Since it is an energy-saving process product, it is inexpensive, has good hot tack properties and impurity sealing properties, and has good cold resistance with little loss of heat seal strength at low temperatures and over time.
There are problems such as poor film formability and physical strength, such as a tendency for molecules to be oriented in the vertical direction due to the molecular structure and a low tear strength in the vertical direction. Manufacturing methods other than the gas phase method include a liquid phase method and a high pressure modification method using ionic polymerization. Specific product names and manufacturing methods: Vapor phase method...G Resin Unipol (UCC), NUC
Polyethylene-LL (Nippon Unicar), etc. Liquid phase method…Idemitsu Polyethylene L (Idemitsu Petrochemical), etc.
Nisseki Linirex (Nippon Petrochemical, etc.), Skrea (DuPont Canada), etc. High-pressure modification method (ionic polymerization)...Rotrex (CDF chimie), etc. L-LDPE copolymerized with ethylene and butene-1
L- is a product made by copolymerizing 4-methylpentene-1, an α-olefin with 6 carbon atoms, with ethylene, which is more expensive than resin but has significantly improved physical strength.
An example of LDPE resin is ULTOSEX, manufactured by Mitsui Petrochemical Co., Ltd., manufactured by a solution method, and an example of L-LDPE resin, in which hexene-1 is copolymerized as an α-olefin, is TUFLIN, manufactured by Union Carbide, manufactured by a gas phase method. DSM is an L-LDPE resin copolymerized with octene, an α-olefin with 8 carbon atoms.
-Stamilex, manufactured by Stamicarbon, using a liquid phase method; and Dowlex, manufactured by Dow Chemical, using a liquid phase method.
Among these L-LDPE resins, the melt index (ASTMD-1238) is 0.4 to 25.0 g/10 minutes,
Preferably, the density (ASTMD-1505) is from 0.870 to 0.940 g/cm ³ . The same L-LDPE resin is made by copolymerizing butene-1 with 4 carbon atoms with ethylene as α-olefin, and 4-methylpentene-1 with 6 or more carbon atoms, hexene-1 as α-olefin.
1. It is cheaper than L-LDPE resin, which is made by copolymerizing octene-1 with 8 carbon atoms and ethylene, but the tear strength is less than 1/2, so the two are completely different resins and should be used as a blend. In case of mixing ratio,
If the grade, etc. is not kept within a limited range, film formability, fusing sealing performance, film slitting performance,
There are cases where physical strength etc. differ greatly and problems arise in practical application. If the content of the L-LDPE resin is less than 20% by weight, the heat seal strength will change significantly over time, and in some cases, the heat seal will peel off, and the quality will deteriorate due to fogging and humidity. In addition, the physical strength decreases, which poses a problem when used as a film for packaging heavy products. If the L-LDPE resin exceeds 70% by weight, the physical strength and heat sealability will be good, but if the film thickness exceeds 150 μm, the motor load during film molding will increase, and not only will skin roughness occur, but the molded film will also be damaged. The thickness variation of the folding diameter becomes large, and the dimensional variation of the fold diameter becomes large. In addition, the film slitting properties are deteriorated, and the cutting properties are poor during fusing and sealing, causing hairs to appear and the appearance to be poor. This is the second component essential to the film of this invention.
Commercially available LDPE resin manufacturers and product names are listed below.

[Effect]

By incorporating L-LDPE resin into the packaging material, the tear strength, breaking strength, impact puncture strength, gelbo test strength, hot peel strength, drop strength, heat sealability, slipperiness, antistatic property, etc. of the packaging material can be improved. Improving. By blending an appropriate amount of carbon black with this L-LDPE resin,
Unlike the case of LDPE resin, these physical strengths are increased. Carbon black also functions as antistatic and light blocking properties. In addition, the effect of adding a lubricant also acts to prevent blocking and improve lubricity. Although LDPE resin is inferior in physical strength to L-LDPE resin, it has excellent bubble stability, has a small motor load on an extruder, and has excellent film formability. In particular, films to which carbon black is added are less likely to cause melt fractures and skin irritation, but their heat sealability and physical strength are reduced. This is due to the fact that the molecular weight distribution of LDPE resin is wider than that of L-LDPE resin and that the molecular structure is branched. In addition, the lubricant not only improves the suitability of the processing machine and makes it easier to insert the product, but also prevents the generation of static electricity during film molding and packaging of photographic materials. Furthermore, it prevents blocking of the film and improves the formability of the film during film forming using the T-die method, inflation method, or the like. [Embodiments] Preferred embodiments of the present invention and their effects will be described below. An example in which the packaging film of the present invention is applied to an X-ray film (in particular, the following specifications are called a badge film) will be shown. Vacuum film is a film that measures the exposure dose of people who handle radiation such as X-rays and gamma rays. Batzi film has a size of 3 x 4 cm and requires two or three layers of different types to be wrapped extremely tightly. 2 pieces for X-ray,
A pack of 3 is called γ-ray use. An example of packaging is shown next. The film is sandwiched between two or three sheets of paper and sealed and packaged with a black polyethylene film that has a light-shielding effect (see Figure 9). As a method for this sealed packaging, a bag as shown in FIG. 10 can be made using a black polyethylene tube. Using this bag, as shown in Figure 9, after inserting a film sandwiched between paper (the inside of the bag may be vacuumed), the area near the opening of the bag is melt-sealed to create a tight package. is obtained. The above-mentioned batch film packaging film is
Using an inflation film molding machine for LDPE resin films, the film was made using the resin formulation shown in the table, and the temperature at which the sealing strength was high even when the fusing sealing conditions were 190 to 230°C was determined based on each resin composition.The pressure was 1Kg/cm. ² (constant) The batch film was sealed and packaged in the processing steps shown in Figure 9 at a time of 1.5 seconds (constant). The inflation film forming conditions were as follows. Screw diameter: 50mmφ Screw L/D: 26/1 Compression ratio: 3.5 Ring die diameter: 100mmφ Ring die lip clearance: 1.0mm Blow ratio: 0.7 (deflation film molding) Set temperature: Cylinder resin temperature at all ring dies at 160℃ Setting Ring Die The above examples show representative examples of preferred embodiments of the film for packaging photographic light-sensitive materials of the present invention, but the present invention is not limited to the above, and other known materials and A combination with a flexible sheet layer is possible. Table 1 shows the layer configurations, resin materials used, and thicknesses of each layer for the products of the present invention, comparative products, and conventional products, and Table 2 shows the results of comparing the properties. As the LDPE resin extrusion adhesive layer 2 in the examples, Mirason 14 manufactured by Mitsui Polychemical Co., Ltd.
(MI5.1g/10min, density 0.919g/ ^cm3 ) As the carbon black, oil furnace black 44B (average particle size 21mmμ, PH7.7) manufactured by Mitsubishi Kasei was used.
LDPE film layer 4 is DFD made by Nippon Unicar.
-0111 (MI 2.4 g/10 min, density 0.923 g/cm ³ ) was used.

【table】

【table】

[Effect of idea]

The packaging material of the present invention, whether it is a single layer film or a laminated film, has good tear strength, weld sealability, impact puncture strength, Gelbo test strength, tensile strength, light shielding property, moisture proofing property, slipperiness, heat sealability, etc. . The packaging material of the present invention not only has greater physical strength and smaller variations in fusing seal strength and heat seal strength than conventional products, but also has almost no decrease in seal strength over time and can permanently ensure complete sealing performance. In addition, the film has good formability, and the motor load during film forming is small and there is no drawdown.
Since the bubble is also stable, the size of the folded diameter is also stable. Even with conventional film molding machines for LDPE resin with a small lip clearance, even if the film molding speed is increased or the film thickness is increased, melt fractures are less likely to occur and skin roughness is less likely to occur, resulting in improved productivity. It is excellent as a film for packaging photographic materials, with almost no blocking and little generation of static electricity.
It also has sufficient moisture resistance and can be used as a single film. Even without the use of a metal foil layer, the film satisfies all the characteristics necessary for a film for packaging photographic materials as described above, so it can be used as a very inexpensive packaging film. As long as the physical strength is guaranteed to be the same, it is possible to make the wall significantly thinner than conventional products, and as a result, costs can be reduced.

[Brief explanation of drawings]

Figures 1 to 6 are all partial cross-sectional views of a packaging film according to an embodiment of the present invention, and Figures 7 and 8 are illustrations of an example of a bag formed using the packaging film of the present invention. FIG. FIG. 9 is a diagram illustrating the process of sealing and packaging X-ray film in a fusing seal bag using the packaging film of the present invention;
The figure shows the process of manufacturing this bag. 1st
Figure 1 is a sectional view of a heater bar used for fusing seals. FIGS. 12 to 15 are partial sectional views of outer paper, and FIGS. 16 to 21 are partial sectional views of conventional packaging films. FIG. 22 is a side cross-sectional view of the end of an embodiment of a packaging bag using the packaging film of the present invention, and FIG. 23 is a partial cross-sectional view of the packaging bag of FIG. 22 cut in the right angle direction. . Second
Figure 4 is a diagram showing the difference in fusing seal strength between the conventional product and the product of the present invention. 1...L-LDPE resin film layer, 1a...L
-LDPE resin light-shielding film layer, 2...Adhesive layer, M
...Metal thin film processed layer, 3...Flexible sheet layer, 3M...Metal thin film processed flexible sheet layer, 4...LDPE resin film layer, 4a...
LDPE resin light-shielding film layer, 5a... Simultaneous multilayer coextruded light-shielding film layer, 6... Intermediate layer of simultaneous multilayer coextrusion light-shielding film layer, 7a... Metal foil layer, 8a... Uniaxial molecular orientation light-shielding film, 9...
X-ray film, 10... black paper, 11... fusing seal bag, 12... opening, 13... folded part, 14...
... Fused seal portion, 15 ... Side edge, 16 ... Heater bar, 17 ... Heater, 18 ... Photosensitive material, 19 ... Packaging bag, 20 ... Outer paper, 21 ...
Inner paper, 22...Center seal portion, 23...Edge heat seal portion, 24...Adhesive, 25...Tape.

Claims (1)

[Scope of claims for utility model registration] (1) At least 20 linear low-density polyethylene resins
~70wt% and melt index 0.2~10.0
g/10 min high pressure branched low density polyethylene resin 25-79.94% by weight, pH 5-9, average particle size 10
A film for packaging photographic light-sensitive materials having a thickness of 150 to 250 μm prepared by an inflation molding or deflation molding method and containing 0.05 to 10% by weight of carbon black of ~50 μm and 0.01 to 10% by weight of a lubricant. (2) The film for packaging photographic materials according to claim 1 or 2, wherein the linear low-density polyethylene resin is a copolymer resin of ethylene and butene-1.