JPH02130119A - Laminated film and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily control an adhesion area and adhesive strength by making the effect of a resin composition and that of a cooling condition or temperature/ humidity at the time of molding hard to receive by providing an annular heater for local heating to an annular die inside the die lip thereof and heating the resin inside the die lip to extrude the same. CONSTITUTION:In manufacturing a laminated film, for example, an L-LDPE resin and an HDPE resin respectively having predetermined compositions are respectively heated and melted by extruders 11, 11 to be sent into an annular die 12 and the L-LDPE resin inside the die lip 21 is heated by the annular heater 22 for local heating of the annular die 12 so that the surface temp. thereof becomes higher than that of the HDPE resin outside the die lip 21 and both resins are extruded in a cylindrical shape. Compressed air is sent in the die from an air blow pipe 13 and cooled air is sprayed from an air cylinder 14 to form a tubular resin film 16 having a predetermined diameter consisting of an inside film layer 2 composed of the L-LDPE resin and an outside film layer 3 composed of the HDPE resin. This tubular laminated resin film 16 is formed into a four-layer laminated film adhered falsely in a blocking section B in the succeeding process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a multilayer laminated film obtained by a thermoplastic resin blown film molding method and a method for producing the same.

[Prior Art] In general, packaging materials for cutting-edge technology products, such as photosensitive materials, not only completely block light, but also have gas barrier properties, moisture proof properties, physical strength (breaking strength, tear strength, impact puncture strength, gelbo test). It is required to satisfy the following properties: strength, abrasion strength, etc.), heat sealability (heat seal strength, hot tack property, contaminant sealing property, etc.), antistatic property, flatness, etc. It is extremely difficult to combine these characteristics with a single film material, and conventionally, packaging materials consisting of multiple layers have been used.

In order to improve the physical strength of packaging materials, the present inventors also developed a method of laminating two layers of uniaxially oriented thermoplastic resin films so that their molecular orientation axes intersect (Japanese Patent Application Laid-Open No. 57-6754).
, or laminated with a foam sheet sandwiched between them (Japanese Patent Application Laid-open No.
No. 9-201848) proposed a cross-laminated film.

In addition, we have conducted intensive research to further improve these packaging materials in terms of quality and cost, and by making the innermost layer of the multilayer coextruded blown film a special resin composition,
Utilizing the blocking phenomenon, which was conventionally considered to be a serious failure in the production of blown film, a patent application was filed in 17730/1989 for a packaging material made of an inexpensive multilayer laminated film with excellent physical strength, in which the innermost layers are blocked and bonded together.
No. 3, Patent Application No. 1982-268227, Patent Application No. 1982-29
No. 1947, Patent Application No. 1980-1180, Patent Application No. 1983-3
No. 390 and Japanese Patent Application No. 63-6063.

[Problem to be solved by the invention]

However, laminated films made of conventional coextruded T-die films and blown films with a multilayer structure with adhesive layers in between are not only uneconomical due to large trimming losses, but also lose flexibility and have poor bag tear strength. decreases,
There were problems in that the tear strength etc. also decreased and curling increased.

In addition, although cross-laminated films have excellent bag tear strength, they are expensive, and when each layer is completely bonded with an adhesive layer, they become hard, have reduced tear strength, and become curly. , a variety of problems were likely to occur.

On the other hand, the laminated film disclosed in Japanese Patent Application No. 177303/1983, in which the innermost layers of blown films are bonded together by blocking, does not require an adhesive layer or a lamination process, and can be cut at both ends like conventional blown films. It is an excellent packaging material that eliminates the need to form a sheet film, eliminates the occurrence of edge loss, greatly reduces the cost of laminated film per unit area, and greatly improves physical strength. However, when trying to laminate other flexible sheets using this laminated film, the area where the innermost sides of the laminated film are adhered to each other by blocking must be 95% or more, otherwise the lamination process will be affected by the air in the unbonded parts. Wrinkles and peeling of the blocking part occur, resulting in frequent losses.

Furthermore, the adhesive strength due to blocking between the innermost layers tends to fluctuate depending on the cooling conditions and the indoor temperature and humidity during molding of the blown film, and the resin composition of the innermost layer of the multilayer coextruded blown film is limited. In addition, if the resin composition of the innermost layer and the outermost layer is almost the same, not only the innermost layers will block each other, but also the outermost layers on both surfaces will block each other when cooled and rolled up, resulting in a laminated film. If care is taken to prevent the outermost layers from blocking each other, there are problems such as the innermost layers to be bonded also not blocking each other.

The present invention solves the above problems, has high physical strength and bag breakage strength in a laminated film by blocking, is flexible, has little curling, and can be used not only for multilayer coextruded blown films but also for single-layer blown films. By blocking, the adhesive area and adhesive strength can be controlled arbitrarily, and it is less affected by the cooling conditions during blown film molding, indoor temperature and humidity, and the innermost resin composition, and is inexpensive and of excellent quality. The purpose of the present invention is to provide a laminated film and a method for manufacturing the same.

[Means to solve the problem]

The present invention has been made to achieve the above object, and the laminated film is heated by a locally heated annular heater installed near the inside of the die lip when the resin bonded by blocking is extruded from the gui lip of the annular die. It is structured with the following characteristics:

In addition, the laminated film manufacturing method uses a locally heated annular heater installed near the inside of the die lip of the annular die to heat the innermost resin surface temperature to be higher than the outermost resin surface temperature from the die lip. The feature is that the resin is extruded and then the innermost parts are bonded together by blocking.

The embedded position of the local heating annular heater is determined by the material and strength of the die lip and the capacity of the annular heater, but is usually 2 to 50 mm from the die lip, preferably 3 to 20 mm.
They are installed at approximately equal intervals from the periphery of the die lip at a distance of .

The embedded depth of the local heating annular heater is preferably within 50+ nm from the surface of the annular die; if this is exceeded, the local heating effect is reduced.

This local heating annular heater is used in combination with general resin heating means provided outside and, if necessary, inside the annular die. In order to cool and solidify the outermost part of the cylindrical film discharged from the annular die, conventionally known methods such as air cooling or water cooling are used.

In order to strengthen the blocking or to further strengthen the lamination by welding, it is necessary to
Pressure lamination may be performed using a pressurized embossing roll, heating roll, etc. in various shapes such as vertical or horizontal) diagonal stripes.

These embossing rolls, heating rolls, etc. may be used during the blown film forming process (online) before or after the squeeze roll or tube roll of the blown film forming machine, or may be processed offline.

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

Examples of resins that can be used in the laminated film of the present invention include high-pressure branched low-density polyethylene (hereinafter referred to as L
DPE) resin, linear low density polyethylene (ethylene-α olefin copolymer resin, hereinafter referred to as L-LDPE) resin, medium/low pressure medium density polyethylene resin, medium/low pressure process medium density polyethylene resin,
Low pressure high density polyethylene (hereinafter referred to as HDPE) resin, ultra low density L-LDPE resin, homopolypropylene resin, propylene/ethylene random copolymer resin, propylene/ethylene block copolymer resin, polybutene-1 resin , poly(4-methylpentene-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 Combined resin, modified propylene resin, elastomer resin, various polyester resins (polyethylene terephthalate resin, polyethylene isophthalate resin, etc.), various polyamide resins (nylon 6 resin, nylon 66 resin, nylon 11 resin, nylon 12 resin, etc.), polystyrene resin, Examples include chlorinated polyethylene resin. These resins can be used alone or in a blend.

Particularly preferred is L-LDPE resin, with a single-layer blown film or L-LDPE resin placed on the innermost layer, and other thermoplastic resins and ethylene copolymer resin placed on the innermost layer.
It is suitable as a laminated film of a multilayer coextruded blown film having 0% by weight of kneaded resin as the outermost combination.

In this case, this L-LDPE resin has a density of 0.92
It is preferably 5 g/cJ or less. Density is 0.92
If it exceeds 5 g/cffl, even if the temperature during film molding is raised, the adhesive force will be weak due to blocking and delamination will easily occur. In addition, the L-LDPE resin is L-LDPE
It contains at least 20% of resin, preferably at least 50% by weight of L-LDPE resin, and has a softening point of 110°C.
It is preferable that it is below.

Moreover, ethylene acrylic acid ester resin is also preferable,
5% of ethylene acrylate resin with a methyl acrylate and/or ethyl acrylate content of 7% by weight or more
A combination of an ethylene acrylate resin containing 0% by weight or more and a thermoplastic resin containing 10% by weight or more of an ethylene copolymer resin is also good.

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

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

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

Examples of light-shielding substances that can be used in the present invention include various carbon blanks, iron oxide, zinc white, titanium oxide, titanium nitride, clay, aluminum powder, aluminum paste, calcium carbonate, mica, barium sulfate, talc ζ cadmium pigments, and valves. Examples include organic pigments and inorganic pigments such as pattern, cobalt blue, copper phthalocyanine pigments, monoazo or polyazo pigments, and aniline black.

Among these light-shielding substances, colored pigments that easily absorb or reflect light, especially black pigments such as various carbon blacks and titanium nitride, and light-reflecting light-shielding substances such as aluminum powder and aluminum It is preferable to use a paste with lower volatile substances removed than a paste.

Methods for blending these light-shielding substances into each layer include masterbatch coloring, compound coloring, and the like, which have been commonly used in the past. The above-mentioned light-shielding substances may be used in various forms, such as powder colorants, paste colorants, moisturizing colorants, masterbatches, dyes and pigments, and colored pellets, depending on the resin used, the machine used, the cost, etc.

Carbon black is particularly preferred because it ensures light-shielding properties and improves cost and physical strength.

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

Among these carbon blacks, those having a pH of 5 to 9, particularly pH 6 to 8, and an average particle size of 10 to 1201 nμ are preferable, and acetylene carbon black or furnace carbon black with a pH of 6 to 9 and an average particle size of 15 to 50 mμ are particularly preferable. By using such pJI and particle size, the photosensitive material has less capri, less increase and decrease in photosensitivity, has a large light shielding ability, and is less likely to produce bubbles, fish eyes, and pinholes. Packaging materials can be produced that have a number of advantages.

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

If it is less than 0.05% by weight, it is necessary to further laminate another light-shielding layer in order to ensure light-shielding properties. If it exceeds 15.0% by weight, the physical strength and heat sealability of the film will decrease, leading to an increase in cost.

The lubricant mainly improves the fluidity of the resin and improves the ease of product insertion.
This is to improve handling properties and film forming processability. Furthermore, it was found to have antistatic properties against peeling. The content of this lubricant is 0.01 to 5.0% by weight
is preferred.

If it is less than 0.01% by weight, there will be little effect of improving the above-mentioned properties and the kneading cost will only increase.

If it exceeds 5.0% by weight, slippage with the extruder screw will increase, making it difficult to form a film of uniform thickness.

Furthermore, they tend to bleed out, and when used in photographic materials, they adhere to the photosensitive layer and cause problems such as development inhibition.

Typical lubricants include paraffin wax, metal soap, etc., as well as (1) silicone-based lubricants, (2) oleic acid amide-based lubricants, (3) erucic acid amide-based lubricants, (4) stearic acid amide-based lubricants, (5) Bis fatty acid amide lubricant, (6) Alkylamine lubricant; Electro Stripper TS-2 (Kao Soap), etc.

Note that dimethylpolysiloxane has a viscosity of 1,000 to 1
00.0OOCPS (measured at 25°C) is preferable.

If it is less than 1.0OOCPS, it will have an adverse effect on the photographic light-sensitive material (causing capri and sensitivity fluctuations).

If it exceeds 100,000 (1:PS), it becomes difficult to handle.
Moreover, it is very expensive and difficult to put into practical use.

Typical examples of antioxidants are shown below.

Phenolic n-octadecyl-3(3',5'-di-L-butyl4
'Hydroxyphenyl)propinate, 2,6 di-t-
Butyl 4-methylphenol, 2.6-di-L-butyl-
p-cresol, 2,2゛-methylenebis(4-methyl-6-t-butylphenol), 4,4゛-thiobis(
3-methyl-6-tert-butylphenol), 4,4'-butylidenebis(3-methyl-6-butylphenol), stearyl-β(3,5-di4-butyl-4-hydroxyphenyl)propionate, 1,1 .3-Tris (
2-Methyl-4-hydroxy-5-t-butylphenyl)butane, 11315-trimethyl-2,4,6-)lis(3,5-di-butyl-4-hydroxybenzyl)benzene, octadecyl-3- (3,5-di-t-butyl-4hydroxyphenyl)propionate, tetrakis[methylene-3(3',5'-di-t-butyl-4
(Hydroxyphenyl)propionate comethane, etc.
Sulfur-based dilauryl-3,3"-thiodipropionate, similystyl-3,3"-thiodipropionate, laurylstearylthiodipropionate, distearyl-3"-
Examples include thiodipropionate, ditridecyl-3,3'-thiodipropionate, phosphorus trinonylphenyl phosphite, triphenyl phosphite, and the like.

In particular, 2,6-di-t-butyl-p-cresol (BHT)
) and low-recurrence high molecular weight phenolic antioxidants (product name 1reganox 1010+ Ireganox
1076+Topano ICA, etc.), dilauryl thiodipropionate, distearyl thiodipropionate, sialkis phosphate, etc. It is effective to use one or more, especially two or more of them in combination.

It is preferable to use 0.01 to 2.00% by weight of the antioxidant. If the antioxidant content is less than 0.01% by weight, the antioxidant effect of the resin will be reduced, and the appearance will be poor due to the occurrence of lumps due to resin burning. It also causes pressure build-up when packaging photosensitive materials.

Moreover, if it exceeds 2.00% by weight, it not only has an adverse effect on photographic materials that utilize oxidation and reduction effects, but also bleeds out over time, resulting in poor appearance.

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 stearic acid amide, etc.

In addition to anti-blocking agents, substances that have an anti-blocking effect include various lubricants, various surfactants, and density 0.93.
5g/cn! There are the above polyethylene resins, etc.

Representative examples of additives are described below, but the present invention is not limited thereto, and any known additives can be selected.

(Additive types) (Representative examples) (1) Plasticizers: Phthalate esters, glycol esters, fatty acid esters, phosphate esters, etc. (2) Stabilizers: Lead-based, cadmium-based, zinc-based, alkaline earth metal-based , organic tin-based, etc. (3) Antistatic agents; cationic surfactants, anionic surfactants, nonionic surfactants, bifacial active agents, various carbon blacks, metal powders, graphite, etc.; phosphate esters , halogenated phosphate esters, halogens (IJI, aluminium-free, phosphorus-containing polyols, etc.); alumina, kaolin, clay calcium carbonate, mica, talc, titanium oxide, barium sulfate, silica, etc.; glass roving, metal fibers, glass fibers, glass Milled fibers, carbon fibers, etc.; inorganic blowing agents (ammonia carbonate, sodium bicarbonate), organic blowing agents (toroso-based, azo-based), etc. (8) Vulcanizing agents; vulcanization accelerators, accelerators, etc. (9) Deterioration prevention Agent; UV absorber, antioxidant, metal deactivator,
Peroxide decomposer (6) Reinforcing agent (7) Foaming agent (5) Filler (4) Flame retardant (10) Coupling agent; Silane-based, titanate-based, chromium-based, aluminum-based, etc.

The laminated film of the present invention can be used as a multilayer laminated film in which the innermost sides are bonded together by blocking, or as a multilayer laminated film in which various flexible sheets are laminated with or without an adhesive layer. can.

The laminated film of the present invention is used for packaging various products, and is suitable for packaging photosensitive materials such as photographic materials, foodstuffs, pharmaceuticals, and chemical substances.

In particular, silver halide photographic materials, diazo photographic materials, photosensitive resin photographic materials, self-developing photographic materials, diffusion transfer photographic materials, and thermosensitive materials whose quality is destroyed by slight gases, light, and humidity. It is suitable for photosensitive materials, photofixing type thermographic photosensitive materials, transfer type heat developable photosensitive materials, direct positive type photosensitive materials, ultraviolet curing type photosensitive materials, etc.

When the laminated film of the present invention is applied to the above-mentioned photographic materials, - double flat bags, double flat bags, self-standing bags, - heavy gusseted bags, double gusseted bags, laminated films, inner lining of moisture-proof and light-shielding boxes, It can be used for all known forms such as inner lining of room-loading light-shielding magazines, inner bags, and leader paper.

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

[Effect]

In the present invention, a local heating annular heater is provided inside the die lip of the annular die to heat and extrude the resin inside the die lip, so that the surface temperature of the resin on the innermost side of the die lip is higher than the surface temperature of the resin on the outermost side. Maintain temperature at which blocking is easy.

Therefore, it is less affected by the effects of the innermost resin composition, cooling conditions during film molding, indoor temperature and humidity, etc.
Furthermore, the adhesive area and adhesive strength are adjusted by adjusting the heating temperature.

In addition, since the heating is performed locally at the exit of the die lip, the flow of the resin at the die lip is improved without causing resin deterioration or melt fracture.

〔Example〕

Examples of the laminated film of the present invention are shown in Figures 1 to 4 below.
This will be explained based on the diagram.

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

The laminated film shown in FIG. 2 is composed of a two-layer coextruded film 4 consisting of an inner film layer 2 and an outer film layer 3, which are pseudo-adhered at a blocking portion B.

The laminated film shown in FIG. 3 is a 3N coextruded blown film 6 consisting of an inner film layer 2, an outer film layer 3, and an intermediate film layer 5 between them.
It is made up of pseudo-adhesive. The above laminated films in which single-layer and multi-layer coextruded blown films are pseudo-adhered in the blocking part are all in the blocking part B.
It is characterized by a layered structure that is symmetrical upward and downward with .

The laminated film in FIG. 4 is a four-layer laminated film in which a two-layer coextruded film 4 is pseudo-adhered at a blocking part B.
Flexible sheets 8 are laminated with an adhesive layer 7 in between.

Next, an embodiment of the method for manufacturing the laminated film of the present invention as described above will be described based on FIGS. 5 to 7.

Figure 5 is a schematic diagram of the blown film manufacturing equipment;
FIG. 6 is a cross-sectional view of the same annular die, and FIG. 7 is a longitudinal cross-sectional view of the same annular die.

In FIG. 5, reference numeral 11 is an extruder for heating and kneading the resin, reference numeral 12 is an annular die for extruding the molten resin into a tube shape through a slit (not shown), reference numeral 13 is an air pipe for feeding compressed air, and reference numeral 14 is an annular die for extruding the molten resin into a tube shape. An air ring cools the molten resin extruded into a tube, a guide roller 15 guides the tubular resin film 16, a guide plate 7 guides the tubular resin film 16 onto a flat plate, and a plurality of pass rolls are arranged side by side. The reference numeral 18 is a take-up squeeze roll that pinches and pulls up the tubular resin film 16, and the reference numeral 19 is a winder that winds up the film.

As shown in FIGS. 6 and 7, the annular die 12 has a concentric local heating annular heater 22 embedded near the inside of the die lip 21 to heat the inside of the die lip 21 and extrude the die from the die lip 21. This increases the surface temperature of the innermost resin of the film to facilitate blocking by compression means such as nip rolls.

In the above-described blown film manufacturing apparatus, for example, an inner film layer 2 made of L-LDPE resin and an outer film layer 3 made of HDPE resin as shown in FIG.
To produce a laminated film consisting of
L-LDP of a predetermined composition heated and melted in steps 1 and 11, respectively.
Feed the E resin and HDPE resin into the annular die 12,
The L-LDPE resin inside the die lip 21 is heated by the local heating annular heater 22 of the annular die 12 and extruded into a cylindrical shape with its surface temperature being higher than the surface temperature of the HDPE resin outside.

Then, compressed air is sent from the blast pipe 13, and cooling air is blown from the air ring 14, so that the L-LD
A tubular resin film 16 having a predetermined diameter is formed of an inner film layer 2 made of PE resin and an outer film layer 3 made of HDPE resin.

This tubular resin film 16 has an outer film layer 3.
is cooled to such an extent that the outermost side of the inner film layer 2 does not adhere to the squeeze roll 18, and the inner film layer 2 rises while being guided by guide rollers 15 with the innermost side still sticky. After being guided into a flat plate shape by the guide plate 17, it is pressed against the squeeze roll for take-up with tube rolls 18, 18, and adhered by blocking to form the shape shown in FIG. 9, which is an enlarged cross-sectional view of part (B). It is formed into a four-layer laminated film that is pseudo-adhered in the blocking part B, and then the winder 19
It is wound up.

Next, the results of an experiment comparing the characteristics of the invention product I, (1) and the comparative products (2), (2) will be explained.

Invention product■ The layer structure of the product (2) of the present invention corresponds to that shown in FIG.

The resin composition is a copolymer resin of ethylene and 4-methylpentene-1, with a density of 0.920 g/cffl, M I
is 2.1g/10min, and the Vicat softening point is 100'C.
- 92.4% by weight of LDPE resin, 0.05% by weight of synthetic silica as antiblocking agent and 0 oleic acid amide
．． 05% by weight, furnace carbon black 3% by weight,
Density is 0.923g/ad, M I is 2.4g/10
4.5% by weight of LDPE resin with a Vicat softening point of 92°C (LDPE with 40% furnace carbon black)
It is a light-shielding LLDPE resin (used in the form of a resin masterbatch of 7.5% by weight).

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

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

The resin surface temperature on the outside of the annular die lip was set to 180°C, and the resin surface temperature on the inside was set to 220°C by heating with a local heating annular heater, extruded to a thickness of 401M, and then folded so that the inner sides were in contact with each other to a thickness of 80°C. It was made into a laminated film.

Comparison product ■ The layer structure of comparative product I corresponds to that shown in FIG.

Using the same light-shielding L-LDPE resin as inventive product I, the resin surface temperature on both sides of the annular die lip was set at 180°C.
Except for the above, molding was performed under exactly the same molding conditions as the product of the present invention.

Invention product■ The layer structure of the product (2) of the present invention corresponds to that shown in 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 N3 has a density of 0.954 g/
c4SM r: 1.1 g/l, 0 min, Vicat softening point: 126°C HDPE resin 20% by weight, L-LDP same as that used for the light-shielding L-LDPE resin of the invention product I
72.4% by weight of E resin, 0.055% by weight of oleic acid amide, 0.05% by weight of synthetic silica, and 3% by weight of furnace carbon black, and a density of 0.923 g/cd, MI
2.4g/10min, LD with Vicat softening point of 92°C
PE resin 4.5% by weight (furnace carbon black 4
0% LDPE resin masterbatch (used in the form of 7.5% by weight).

The molding conditions for the two-layer coextruded blown film are as follows:
The screw diameter of the extruder is 50 marks for both the outermost layer and the innermost layer, L/D is 20, and the diameter of the annular die is 5001 TII.
llφ, the blow flop ratio was 1.3, and the take-up speed was 20 m/min.

The inner film layer 2 has a thickness of 20 mm and a surface temperature of 220°C by heating with a local heating annular heater, and the outer film layer 3 has a thickness of 20 mm and a surface temperature of 180°C and is extruded from an annular grip, and then the inner resin is heated to 220°C. It was folded so that the layers were in contact with each other to form a laminated film with a thickness of 801M.

Comparison product ■ The layer structure of comparative product (■) corresponds to that shown in FIG.

The same inner and outer resin compositions as in Invention Product (2) were used.

The resin surface temperature on the inside and outside of the annular guilip is 180"
Except for C, molding was performed under exactly the same molding conditions as inventive product (2).

The experimental results are shown in Table 1.

The evaluation is based on the following.

◎...Excellent O...Excellent M...Problems (improvement required) ×...Not practical Because the resin on the innermost side of the Gurilip is heated, it is possible to bond resin films that are difficult to bond with blocking in the past, as well as single-layer blown films, which have a resin composition that does not cause blocking due to problems in use.

In addition, it is less susceptible to the effects of environmental conditions such as cooling conditions and temperature and humidity, and it is possible to form bonded blown films with stable blocking.Moreover, laminated films with different adhesive areas and adhesive strengths can be formed at will. Obtainable.

Furthermore, in the past, when the temperature of the resin during molding was raised, deterioration and gelation occurred in the extruder and annular die, fish eyes and pinholes appeared in the film, unstable bubbles and drawdown occurred, etc. However, in the present invention, since the die lip is heated locally, the above problem does not occur (by improving the flow of the resin at the die lip), it is difficult to control the resin temperature. Extruder motor load can be reduced.

[Brief explanation of drawings]

1 to 4 are partial cross-sectional views showing the layer structure of an embodiment of the laminated film according to the present invention, FIG. 5 is a schematic diagram of an apparatus for manufacturing the laminated film according to the present invention, and FIG. A cross-sectional view, Figure 7 is a cross-sectional view of the same upper edge, and Figure 8 is a cross-sectional view of the same upper edge.
An enlarged sectional view of part (A) in the figure, Figure 9 is (I+) in Figure 5.
FIG. 11... Extruder 12... Annular die 21... Die lip 22... Local heating annular heater B indicates a blocking adhesion site. Patent applicant: Fuji Photo Film Co., Ltd. Agent
Patent attorney Masami Tanaka (1 person)...Single-layer blown film...Inner film...Outer film...Two-layer coextruded blown film...3
N coextrusion blown film Figure 6)

Claims (2)

[Claims] (1) A laminated film characterized in that when it is extruded from the die lip of an annular die, it is heated by a local heating annular heater installed near the inside of the die lip, and the extruded resin is bonded by blocking. (2) A locally heated annular heater installed near the inside of the die lip of the annular die extrudes the resin from the die lip while heating the innermost resin so that the surface temperature is higher than that of the outermost resin, and then extrudes the resin from the die lip. A method for producing a laminated film characterized by adhering the inner sides to each other by blocking.