JPH0714615B2 - Laminated film and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multilayer laminated film obtained by a thermoplastic resin inflation film molding method and a method for producing the same.

[Conventional technology]

In general, high-tech products such as packaging materials for photographic light-sensitive materials, in addition to completely blocking light, have gas barrier properties, moisture resistance, physical strength (breaking strength, tear strength, impact drilling strength, gelbotest strength, wear strength, etc. ), Heat sealing suitability (heat sealing strength, hot tacking property, foreign substance sealing property, etc.), antistatic property, flatness and other properties are required to be satisfied. It is extremely difficult to combine these properties with a single film material, and conventionally, a packaging material having a plurality of layers has been used.

In order to improve the physical strength of the packaging material, the present inventors have laminated two layers of uniaxially molecularly oriented thermoplastic resin films so that the molecular orientation axes cross each other (see JP-A-57-6754 or The foamed sheet bodies were sandwiched and laminated (Japanese Patent Laid-Open No. 59-20184).
No. 8) Proposed a cross-laminated film.

In addition, by conducting intensive research to further improve these packaging materials in terms of quality and cost, and by using a special resin composition for the innermost layer of the multilayer coextrusion inflation film,
Utilizing the blocking phenomenon, which was conventionally considered to be a major failure in blown film production, a packaging material consisting of an inexpensive multilayer laminated film with excellent physical strength by blocking and adhering the innermost layers to each other is provided in Japanese Patent Application No. 62-177303 ( Japanese Patent Publication No. 6-53407), Japanese Patent Application No. 62-268227 (Japanese Patent Publication No. 6-1)
No. 5228), Japanese Patent Application No. 62-291947 (Japanese Patent Publication No. 6-15229)
Japanese Patent Application No. 63-1180 (Japanese Patent Publication No. 1-177537), Japanese Patent Application No. 63-3390 (Japanese Patent Application No. 1-179938), Japanese Patent Application No. 63-6063.
No. (Japanese Patent Publication No. 1-182034).

[Problems to be Solved by the Invention]

However, the conventional co-extruded T-die film and inflation film have a multi-layered structure with an adhesive layer interposed between them. Is reduced,
There was a problem that tear strength and the like also decreased and curling increased.

Further, the cross-laminated film is excellent in bag breaking strength and the like, but is expensive, and when each layer is completely adhered by the adhesive layer, it becomes hard, tear strength and the like are reduced, and curling becomes large. , Various troubles were easy to occur.

On the other hand, a laminated film in which the innermost layers of the inflation film disclosed in Japanese Patent Application No. 62-177303 (Japanese Patent Publication No. 6-53407) are adhered by blocking, does not require an adhesive layer or a laminating step, Since it is not necessary to cut both ends into a sheet film like a film, there is no ear loss, the laminated film cost per unit area can be greatly reduced, and the physical strength can be greatly improved. It is a material. However, when trying to laminate with other flexible sheets using this laminated film, unless the area where the innermost parts of the laminated film are adhered by blocking should be 95% or more, the lamination process by the air of the non-adhesive part As a result, wrinkles and peeling of the blocking part occur, resulting in frequent loss.

In addition, the adhesive strength due to blocking between the innermost layers is likely to fluctuate depending on the cooling conditions and the temperature and humidity in the room at the time of forming the inflation film, and the resin composition of the innermost layer of the multilayer coextrusion blown film is limited. Further, when the resin composition of the innermost layer and the outermost layer are almost the same, not only the blocking of the innermost layers, but also as the laminated film by blocking the outermost layers located on both surfaces when cooled and wound up. If it is made impossible to use or if the outermost layers are not blocked, there is a problem that the innermost layers to be bonded do not block either.

The present invention solves the above problems, physical strength and bag breaking strength in a laminated film due to blocking is large, flexible, and has a small curl, and not only a multilayer coextrusion inflation film but also a single layer inflation film having the innermost layers It is possible to control the adhesive area and adhesive strength by blocking arbitrarily, and it is less affected by cooling conditions at the time of blown film molding, temperature and humidity in the room, and the resin composition of the innermost, inexpensive and excellent laminated film and its It is intended to provide a manufacturing method.

[Means for Solving the Problems]

The present invention has been made to achieve the above object, the laminated film is heated by a locally heated annular heater provided near the inside of the die lip when extruded from the die lip of the annular die of the inflation film molding machine, and extruded. The innermost resin films having a Vicat softening point of 110 ° C. or lower are bonded by blocking.

Further, the method for producing a laminated film is a locally heated annular heater provided near the inside of the die lip of an annular die, the innermost Vicat softening point is 110 ° C. or less and the surface temperature of the outermost resin film is the surface temperature of the resin film. Extruding the resin film from the die lip while heating to a higher level,
After that, the innermost parts are pressure-contacted with a take-up squeeze roll to be bonded by blocking.

The embedding position of the locally heated annular heater is determined by the material and strength of the die lip member and the annular heater capacity, but it is usually set at a distance of 2 to 50 mm from the die lip, preferably 3 to 20 mm at approximately equal intervals from the periphery of the die lip. .

The depth of embedding of the locally heated annular heater is preferably within 50 mm from the surface of the annular die, and beyond this, the locally heated effect is diminished.

This local heating annular heater is used in combination with a general resin heating means provided outside the annular die and optionally inside the annular die. To cool and solidify the outermost side of the cylindrical film discharged from the annular die, conventionally known methods such as air cooling and water cooling are used.

In order to strengthen the blocking or to further strengthen the lamination by welding, pressure embossing rolls and heating rolls of various shapes such as silk, grid, parallel streaks (vertical or horizontal) diagonal streaks, etc. You may press-laminate by.

These embossing rolls and heating rolls are squeeze rolls (nip rolls) for blown film molding machines.
It may be processed during the blown film forming process before and after (online) or offline.

And by controlling the temperature of the local heating annular heater,
A laminated film having desired blocking adhesive strength and blocking adhesive area can be obtained.

Examples of the resin that can be used for the laminated film of the present invention include, for example, high-pressure branched low-density polyethylene (hereinafter LD
PE) resin, linear low density polyethylene (ethylene-α-olefin copolymer resin, hereinafter L-LDPE) resin, medium / low pressure medium density polyethylene resin, medium / low pressure high density polyethylene (hereinafter HDPE Displayed) Resin, ultra low density L
-LDPE resin, homopolypropylene resin, propylene / ethylene random copolymer resin, propylene / ethylene block copolymer resin, polybutene-1 resin, poly-4methylpentene-1 resin, polyisobutylene resin, ethylene-vinyl acetate resin, ethylene -Ethyl acrylate resin,
Ethylene-ethyl methacrylate resin, ethylene-acrylic acid resin, ionomer resin, modified ethylene resin, modified ethylene copolymer resin, modified propylene resin, elastomer resin, various polyester resins (polyethylene terephthalate resin, polyethylene isophthalate resin, etc.),
Examples include various polyamide resins (nylon 6 resin, nylon 66 resin, nylon 11 resin, nylon 12 resin, etc.), polystyrene resin, chlorinated polyethylene resin and the like. These resins can be used alone or as a blend.

Particularly preferred is L-LDPE resin, which is a single layer inflation film or L-LDPE resin on the innermost side,
It is suitable as a laminated film of a multi-layer coextrusion blown film in which a resin obtained by kneading 10% by weight of another thermoplastic resin and an ethylene copolymer resin is the outermost combination.

In this case, the L-LDPE resin preferably has a density of 0.925 g / cm ³ or less. When the density exceeds 0.925 g / cm ³ , the adhesive strength is weak due to blocking and delamination is likely to occur even if the temperature during film formation is increased. Also, L-LD
The PE resin contains 20% by weight or more of the L-LDPE resin, preferably 50% by weight or more of the L-LDPE resin, and the softening point is preferably 110 ° C. or lower.

Further, ethylene acrylate ester resin is also preferable,
A combination of ethylene acrylate ester resin containing 50 wt% or more of ethylene acrylate ester resin having a methyl acrylate and / or ethyl acrylate content of 7 wt% or more and a thermoplastic resin containing 10 wt% or more of ethylene copolymer resin. Is also good.

Similarly, an ethylene vinyl acetate copolymer resin is preferable, and more specifically, an ethylene vinyl acetate copolymer resin having a vinyl acetate content of 5% by weight or more and an ethylene copolymer resin are used.
A combination with a thermoplastic resin containing 10% by weight or more is also preferable.

As the thermoplastic resin used on the outer side, in addition to the resin used on the innermost side, known resins such as polyvinylidene chloride resin, polyvinyl chloride resin and polycarbonate resin and modified resins thereof are used. From the viewpoint of improving heat sealing suitability, it is preferable that the L-LDPE resin, EVA resin, EEA resin, EMA resin, ionomer resin, EAA resin and the like contain 10% by weight or more of an ethylene copolymer resin.

In the laminated film of the present invention, if necessary, a light-shielding substance, a lubricant, an antioxidant, an antiblocking agent and other additives can be used in each layer of the film.

Examples of the light-shielding substance usable in the present invention include various carbon blacks, iron oxides, zinc whites, titanium oxides, titanium nitrides, clays, aluminum powders, aluminum pastes, calcium carbonate, mica, barium sulfate, talc, cadmium pigments, and valves. Examples thereof include patterns, cobalt blue, copper phthalocyanine pigments, monoazo or polyazo pigments, organic pigments such as aniline black, and inorganic pigments.

Among these light-shielding substances, from the viewpoints of quality, cost, light-shielding ability, etc., color pigments that easily absorb or reflect light, especially various carbon blacks of black pigments and titanium nitride, and aluminum powder and aluminum of light-reflecting light-shielding substances. It is preferable to use a paste from which low volatile substances have been removed.

As a method of blending these light-shielding substances in each layer, there are a masterbatch coloring method and a compound coloring method which have been often used conventionally. The light-shielding substance is a powder colorant, a paste colorant, a wet colorant, a masterbatch, a dye / pigment, as a usage pattern depending on the resin used, the machine used, the cost, etc.
There are colored pellets, etc.

Particularly, carbon black is preferable from the viewpoints of securing the light-shielding property, improving the cost and the physical strength.

Carbon black is classified into gas black, furnace black, channel black, anthracene black, acetylene black, oil smoke, pine smoke, animal black, vegetable black, etc. depending on the raw material.

Among these carbon blacks, pH 5-9, especially pH 6
~ 8, average particle size 10 ~ 120mμ is preferred, especially pH
Acetylene carbon black or furnace carbon black having an average particle size of 6 to 9 and an average particle size of 15 to 50 mμ is preferable. By using those having such a pH and particle size, the fog of the photographic light-sensitive material is less likely to occur, the increase or decrease in the photosensitivity is less likely to occur, the light-shielding ability is great, and the spots, fish eyes and pinholes are less likely to occur. It is possible to manufacture a packaging material having a number of advantages.

In the laminated film of the present invention, furnace carbon black is preferable from the viewpoint of improving the light-shielding property, cost and physical properties, and acetylene carbon black and Ketjen carbon black, which are expensive but have an antistatic effect, are also preferable. The content of carbon black is preferably 0.05 to 15.0% by weight.

If it is less than 0.05% by weight, it is necessary to stack another light-shielding layer in order to secure the light-shielding property. If it exceeds 15.0% by weight, the physical strength and heat-sealing property of the film are deteriorated and the cost is increased.

Lubricants mainly improve the fluidity of resin, etc., product insertability,
It is for improving the handling property and film forming processability. Further, it has been proved that it has a peeling antistatic property. The content of this lubricant is preferably 0.01 to 5.0% by weight.

If it is less than 0.01% by weight, there is almost no effect of improving the above properties, and only the kneading cost increases. If it exceeds 5.0% by weight, slippage with the screw of the extruder is increased and it becomes difficult to form a film having a uniform thickness.

Further, bleeding out easily occurs, and when it is used for a photographic light-sensitive material, it adheres to the light-sensitive layer and causes troubles such as development inhibition.

Typical lubricants include paraffin wax, metal soap, etc., (1) silicone lubricant, (2) oleic acid amide lubricant, (3) erucic acid amide lubricant, (4) stearic acid amide lubricant, (5) Bis fatty acid amide lubricant, (6) alkylamine lubricant; electrostripper-TS
-2 (Kao soap) etc.

Dimethyl polysiloxane has a viscosity of 1,000 to 100,000.
It is preferably CPS (measured at 25 ° C). If it is less than 1,000 CPS, it will adversely affect the photographic light-sensitive material (causes fogging and fluctuation of photosensitivity).

This is because if it exceeds 100,000 CPS, it will be difficult to handle, and it will be very expensive and difficult to put into practical use.

Representative examples of antioxidants are shown below.

Phenolic n-octadecyl-3 (3 ', 5'-di-t-butyl 4'
Hydroxyphenyl) propinate, 2,6 di-t-butyl 4-methylphenol, 2,6 di-t-butyl-p-cresol, 2,2'-methylenebis (4-methyl-6-t
-Butylphenol), 4,4'-thiobis (3-methyl6-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), stearyl-β (3,5-di-4) -Butyl 4-hydroxyphenyl) propionate, 1,1,3-tris (2-methyl-4)
-Hydroxy-5-t-butylphenyl) butane, 1,3,
5-Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, octadecyl-
3- (3,5-di-t-butyl-4hydroxyphenyl)
Propionate, tetrakis [methylene-3 (3 ', 5'
-Di-t-butyl-4'-hydroxyphenyl) propionate] methane, etc., sulfur-based dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, laurylstearylthiodipropionate , Distearyl-3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, etc. Phosphorus-based trinonylphenyl phosphite, triphenyl phosphite and the like.

Especially 2,6-di-t-butyl-p-cresol (BHT) and low volatility high molecular weight phenolic antioxidant (trade name)
lreganox1010, lreganox1076, Topano ICA, etc.), dilauryl thiodipropionate, distearyl thiodipropionate, dialkis phosphate, etc., and it is effective to use one or more, especially two or more thereof in combination.

It is preferable to use 0.01 to 2.00% by weight of the antioxidant.
When the amount of the antioxidant is less than 0.01% by weight, the antioxidant effect of the resin becomes small, and the appearance of the resin deteriorates because the resin burns more often to cause lumps. In addition, the generation of the spots also causes the generation of pressure fog when the photographic light-sensitive material is packaged.

On the other hand, if the amount exceeds 2.00% by weight, not only the photographic light-sensitive material utilizing the oxidation / reduction effect is adversely affected, but also bleed out with time and the appearance is deteriorated.

Representative examples of antiblocking agents are shown below.

Silicon oxide (silica), calcium silicate, aluminum silicate, calcium carbonate, talc (magnesium silicate), higher fatty acid polyvinyl ester, n-octadecyl urea, dicarboxylic acid ester amide, N, N'-dioleyl oxamide, N- Ethanol stearamide etc.

In addition to anti-blocking agents, anti-blocking agents include various lubricants, various surfactants, and a density of 0.935 g / c.
Polyethylene resin of m ³ or more is available.

Typical examples of the additives are described below, but the present invention is not limited thereto and can be selected from all known ones.

(Types of Additives) (Representative Examples) (1) Plasticizer; Phthalates, Glycols, Fatty Acids, Phosphates, etc. (2) Stabilizers: Lead-based, cadmium-based, zinc-based, alkaline earth metal-based, Organotin, etc. (3) Antistatic agent; cationic surfactant, anionic surfactant, nonionic surfactant, double-sided surfactant, various carbon black, metal powder, graphite, etc. (4) Flame retardant Phosphoric acid ester, halogenated phosphoric acid,
Esters, halides, inorganic substances, phosphorus-containing polyols, etc. (5) Fillers; alumina, kaolin, clay, calcium carbonate, mica, talc, titanium oxide, barium sulfate, silica, etc. (6) Reinforcing agents; glass roving, metal fibers , Glass fiber, glass milled fiber, carbon fiber, etc. (7) Foaming agent: Inorganic foaming agent (ammonia carbonate, sodium bicarbonate), organic foaming agent (nitroso type, azo type), etc. (8) Vulcanizing agent; Vulcanization accelerator , Accelerating aids, etc. (9) Deterioration inhibitors; UV absorbers, antioxidants, metal deactivators, peroxide decomposers, etc. (10) Coupling agents: Silane-based, titanate-based, chromium-based, aluminum-based Etc.

The laminated film of the present invention may be used as a multilayer laminated film in which innermost parts are adhered by blocking as they are, or as a multilayer laminated film in which various flexible sheets are laminated with or without an adhesive layer. it can.

The laminated film of the present invention is used for packaging various products and the like, but is suitable for packaging photosensitive materials such as photographic light-sensitive materials, foods, pharmaceuticals, and chemical substances.

In particular, silver halide photographic light-sensitive materials, whose quality is destroyed by slight gas, light and humidity, diazo photographic light-sensitive materials, photosensitive resin photographic light-sensitive materials, self-developing photographic light-sensitive materials, diffusion transfer photographic light-sensitive materials, heat-sensitive materials. It is suitable for a photographic light-sensitive material, a photo-fixing type heat-sensitive light-sensitive material, a transfer type heat-developable light-sensitive material, a direct positive type light-sensitive material, an ultraviolet curable light-sensitive material and the like.

When the laminated film of the present invention is applied to the above photographic light-sensitive material, a single flat bag, a double flat bag, a self-supporting bag, a single gusset bag, a double gusset bag, a laminated film, a moisture-proof light-shielding box, and a light chamber load It can be used in all known forms such as an inner sticking of a light-shielding magazine, an inner bag, a leader paper, and the like.

The method used for bag making is a conventionally known plastic film sealing method such as heat sealing, fusing sealing, impulse sealing, ultrasonic sealing, or high frequency sealing depending on the properties of the laminated film. Note that it is also possible to make a bag using an appropriate adhesive or pressure-sensitive adhesive.

[Action]

The present invention, by providing a local heating annular heater inside the die lip of the annular die to heat and extrude the resin inside the die lip, the surface temperature of the resin inside the die lip is higher than the surface temperature of the resin in the outermost layer. Hold at a temperature that facilitates blocking.

Therefore, it is less affected by the innermost resin composition, cooling conditions during film molding, temperature and humidity in the room, etc.
In addition, the adhesive area and adhesive strength are adjusted by adjusting the heating temperature.

Further, since the die lip outlet is locally heated, the resin flow in the die lip portion is made good without deterioration of the resin or melt fracture.

〔Example〕

Examples of the laminated film of the present invention will be described below with reference to FIGS.
It will be described with reference to the drawings.

The laminated film in FIG. 1 is composed of two layers in which the single-layer blown film 1 is pseudo-bonded at the blocking portion B.

The laminated film of FIG. 2 is constructed by pseudo-bonding a two-layer coextruded film 4 of an inner film layer 2 and an outer film layer 3 at a blocking portion B.

The three-layer coextrusion inflation film 6 consisting of the inner film layer 2 and the outer film layer 3 and the intermediate film layer 5 between them in the laminated film of FIG.
It is configured by pseudo-bonding. The laminated film obtained by pseudo-bonding the single-layer and multi-layer coextrusion blown films at the blocking portion is the blocking portion B.
It is characterized by a layered structure with upper and lower symmetry centered on.

The laminated film of FIG. 4 is a four-layer laminated film in which the two-layer coextruded film 4 is pseudo-bonded at the blocking portion B,
A flexible sheet 8 is laminated via an adhesive layer 7.

Next, one embodiment of the method for producing the laminated film of the present invention as described above will be described with reference to FIGS. 5 to 7.

FIG. 5 is a schematic view of an inflation film manufacturing apparatus,
FIG. 6 is a horizontal sectional view of the same annular die, and FIG. 7 is a vertical sectional view of the same annular die.

In FIG. 5, reference numeral 11 is an extruder for heating and kneading resin, reference numeral 12 is an annular die for extruding molten resin into a tube shape from a slit (not shown), reference numeral 13 is a blower tube for feeding compressed air, and reference numeral 14 is An air ring for cooling the molten resin extruded into a tube shape, reference numeral 15 for a guide roller for guiding the tubular resin film 16, reference numeral 7 for a guide plate for guiding the tubular resin film 16 on a flat plate, and a plurality of pass rolls arranged side by side. 18 is a tubular resin film
A squeeze roll (nip roll) for pulling up 16 while sandwiching it, and a reference numeral 19 is a winder for winding the film.

The annular die 12 is, as shown in FIGS. 6 and 7,
A concentric local heating annular heater 22 is embedded near the inside of the die lip 21, heats the inside of the die lip 21, and raises the surface temperature of the resin on the innermost side of the film extruded from the die lip 21 by a compression means such as a nip roll. It facilitates blocking.

In order to manufacture a laminated film composed of the inner film layer 2 made of L-LDPE resin and the outer film layer 3 made of HDPE resin as shown in FIG. The L-LDPE resin and the HDPE resin having a predetermined composition, which are heated and melted in 11 and 11, respectively, are sent to the annular die 12, and the L-LDPE resin inside the die lip 21 is heated by the local heating annular heater 22 of the annular die 12 and the surface thereof. The temperature is higher than the surface temperature of the outer HDPE resin and extruded into a cylinder.

Then, the compressed air is blown from the blower pipe 13 and the cooling air is blown by the air ring 14, (a)
As shown in FIG. 8 which is an enlarged cross-sectional view of a portion, a tubular resin film 16 having a predetermined diameter is formed by an inner film layer 2 made of L-LDPE resin and an outer film layer 3 made of HDPE resin. It

The tubular resin film 16 is cooled to such an extent that the outermost side of the outer film layer 3 does not adhere to the squeeze roll 18, and the innermost side of the inner film layer 2 is guided by the guide rollers 15 ... 15 in a state of having adhesiveness. While rising. Then, after being guided by the guide plate 17 into a flat plate shape, the squeeze roll (nip roll) for pulling 18 · 18 is pressed and adhered by blocking, which is an enlarged cross-sectional view of the (B) part.
It is formed into a four-layer laminated film that is pseudo-bonded at the blocking portion B as shown in the figure, and is wound up by the winding machine 19.

Next, the experimental results comparing the characteristics of the present invention products I and II and the comparative products I and II will be described.

Invention product I The layer structure of the invention product I corresponds to FIG.

The resin composition is a copolymer resin of ethylene and 4-methylpentene-1, with a density of 0.920 g / cm ³ , an MI of 2.1 g / 10 minutes, and a Vicat softening point of 100 ° C. L-LDPE resin 92.4% by weight, blocking. Synthetic silica 0.05% by weight and oleic acid amide 0.05% by weight, furnace carbon black 3% by weight, density 0.923 g / cm ³ , MI 2.4 g / 10 min, Vicat softening point 4.5 ° LDPE resin 4.5% by weight as an inhibitor. % (Used in the form of LDPE resin masterbatch containing 40% of furnace carbon black at 7.5% by weight) as a light-shielding L-LDPE resin.

The molding conditions for the blown film are as follows: screw diameter of resin extruder is 50 mmφ, L / D is 25, diameter of annular die is 100 mmφ, lip clearance is 1 mm, blow-up ratio is 1.76, take-up speed is 12 m / min.

The local heating annular heater was embedded in the annular die lip at a distance of 5 mm from the annular die lip and a depth of 15 mm from the die surface.

The resin surface temperature on the outside of the annular die lip is 180 ° C and the resin surface temperature on the inside is 220 ° C by heating the annular heater locally.
C., extruded to a thickness of 40 .mu.m, and then folded so that the inner sides contact each other to obtain a laminated film having a thickness of 80 .mu.m.

Comparative product I The layer structure of comparative product I corresponds to FIG.

The same light-shielding L-LDPE resin as that of the product I of the present invention was used, and molding was performed under exactly the same molding conditions as the product of the present invention except that the resin surface temperature on both surfaces of the annular die lip was 180 ° C.

Invention product II The layer structure of the invention product II corresponds to FIG.

The resin composition of the inner film layer 2 is the same light-shielding L-LDPE resin as the product I of the present invention.

The resin composition of the outer film layer 3 has a density of 0.954 g / cm ³ , MI
Is 1.1 g / 10 minutes, 20% by weight of HDPE resin having a Vicat softening point of 126 ° C., 72.4% by weight of the same L-LDPE resin as used for the light-shielding L-LDPE resin of the product I of the present invention, 0.05 of oleic acid amide. % By weight, 0.05% by weight of synthetic silica and 3% by weight of furnace carbon black with a density of 0.923 g / cm ³ , MI of 2.4 g / 10
The resin composition is 4.5% by weight of LDPE resin having a Vicat softening point of 92 ° C. (used in the form of LDPE resin masterbatch containing 40% of furnace carbon black 7.5% by weight).

The two-layer coextrusion blown film molding conditions are:
The screw diameter of the extruder is 50 mm for both the outermost layer and the innermost layer
φ, L / D is 20, the diameter of the annular die is 500 mmφ, the blow-up ratio is 1.3, and the take-up speed is 20 m / min.

The film thickness of the inner film layer 2 is 20 μm, and the surface temperature is set to 220 ° C. by heating the local heating annular heater.
Was extruded from an annular die lip at a film thickness of 20 μm and a surface temperature of 180 ° C., and then folded so that the inner resin layers were in contact with each other to obtain a laminated film having a thickness of 80 μm.

Comparative product II The layer structure of comparative product II corresponds to FIG.

The same inner and outer resin compositions as the product II of the present invention were used.

Molding was performed under exactly the same molding conditions as the product II of the present invention except that the resin surface temperature inside and outside the annular die lip was 180 ° C.

The experimental results are shown in Table 1.

[Advantages of the Invention] The present invention uses a locally heated annular heater provided on the inside of the die lip to heat the resin on the innermost side of the die lip, so that blocking occurs due to a resin film that is conventionally difficult to adhere by blocking and a problem in use. A single-layer blown film or the like having a resin composition that does not allow it to be adhered by blocking.

In addition, it is less affected by environmental conditions such as cooling conditions and temperature and humidity, and it is possible to perform an inflation film molding that is adhered by stable blocking. Obtainable.

Furthermore, conventionally, when the temperature of the resin during molding is increased, deterioration and gelation occur in the extruder and annular die, fisheyes and pinholes occur in the film, and valve instability and drawdown occur. Although it was difficult to raise the resin temperature due to defective inflation film molding, the present invention does not cause the above problems due to the local heating of the die lip, and the extruder can be used to improve the flow of the resin in the die lip part. The motor load of can be reduced.

Also, there are no problems caused by cutting of the tubular inflation film, which is caused when it is provided in the vicinity of the squeeze roll, and defective adhesion of blocking due to uneven heating due to uneven spacing between the heater and the tubular inflation film.

[Brief description of drawings]

1 to 4 are partial cross-sectional views showing a layer structure of an embodiment of a laminated film according to the present invention, FIG. 5 is a schematic view of an apparatus for producing a laminated film according to the present invention, and FIG. 6 is an annular die of the same. FIG. 7 is a vertical sectional view, and FIG. 8 is a horizontal sectional view.
FIG. 9 is an enlarged sectional view of part (a) in the figure, and FIG. 9 is an enlarged sectional view of part (b) in FIG. 1 ... Single layer inflation film 2 ... Inner film 3 ... Outer film 4 ... Two-layer co-extrusion inflation film 5 ... Three-layer co-extrusion inflation film 11 ... Extruder 12 ... Annular die 21 ... Die lip 22 ... Local heating Annular heater B is blocking The adhesion site is shown.

Claims (3)

[Claims] 1. When a resin film is extruded from a die lip of an annular die of an inflation film molding machine, it is heated by a locally heated annular heater provided in the vicinity of the inside of the die lip, and the extruded Vicat softening point is 110 ° C. or less. A laminated film characterized by being adhered by blocking, 2. The resin film has an average particle size of 10 to 120 m.
0.05 to 15.0% by weight of carbon black having a pH of 6 to 9
The laminated film according to claim 1, which is used for packaging a photographic light-sensitive material containing the same. 3. A locally heated annular heater provided in the vicinity of the inside of a die lip of an annular die, wherein the innermost Vicat softening point is 11.
The resin film is extruded from the die lip while heating the surface temperature of the resin film at 0 ° C or lower so as to be higher than the surface temperature of the outermost resin film, and then the innermost parts are pressure-contacted with a take-up squeeze roll to be bonded by blocking. A method for producing a laminated film, characterized in that