JPH01195042A - Multilayer co-extrusion inflation film - Google Patents

Abstract

PURPOSE:To mold a film having excellent quality free from a press flaw, rupture, a scratch, wrinkles or stripes, by setting a polyolefin resin film layer to an inner layer and adding a polyethylene resin having specific density to said inner layer in a specific amount. CONSTITUTION:A polyolefin resin to which 0.5-70wt.% of a polyethylene resin having density of 0.936g/cm<3> or more is added is charged in an extruder 1a while an L-LDPE resin is charged in an extruder 1b and both resins are respectively melted under heating. Next, a polyolefin resin film layer 11 is extruded from the inside slit of a ring die 2 and an L-LDPE resin film layer 12 is extruded from the outside slit of said die 2. At this time, a tubular resin film 6 wherein the film layer 11 is positioned inside and the film layer 12 is positioned outside is molded by the compressed air from a blow pipe 3 and the cooling air from an air ring 4 and rises through a take-over squeeze roll 8, a guide roller 5 and a guide plate 7, and taken up by a take-up roll 9 in such a state that the film layer 11 is brought into contact with said roll 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for forming a multilayer coextruded blown film for use in packaging materials for photosensitive substances.

[Conventional technology]

Conventionally, films used for packaging materials for photosensitive materials are blown films made of high-pressure branched low-density polyethylene (hereinafter referred to as LDPE) resin, or -axially stretched high-density polyethylene (hereinafter referred to as HDPE) resin film layers. There was a cross-laminated film that was pasted together so that the two sides intersected.

In addition, as a film that improves the physical strength such as impact puncture strength of the above film, the present inventor proposed a linear low density polyethylene (hereinafter referred to as L-LDPE) resin film layer and a polyolefin resin film layer. There is a multilayer coextruded blown film including a film layer (Japanese Patent Application Laid-open No. 18548/1983).

Such multilayer coextrusion blown film is
Generally, it is molded using a blown film manufacturing apparatus as shown in FIG.

In this figure, numeral 1 is an extruder that heats and kneads the resin, numeral 2 is a ring die that extrudes the molten resin into a tube shape through a slit (not shown), numeral 3 is a blow pipe that sends compressed air, and numeral 4 is a tube. An air ring that cools the extruded molten resin, 5 is a tubular resin film J, a guide roller that guides 6, 7 is a guide plate that guides the tubular resin film onto a flat plate, 8 is a tube A take-up squeeze roll that pinches and pulls up the resin film 6, and a tube roll), and numeral 9 is a winder that winds up the film.

In this blown film manufacturing apparatus, the L-
To form a multilayer coextruded blown film consisting of two layers, an LDPE resin film layer and an HDPE resin film layer, L-LDPE resin and HDPE resin of a predetermined composition, which are heated and melted in extruders 1 and 1, respectively, are placed in a ring die. 2 and extrude it from the circular slit of the ring die 2 with the L-LDPE resin on the inside and the HDPE resin on the outside. At this time, compressed air is sent from the blast pipe 3 and cooling air is blown from the air ring 4, thereby forming a tubular resin film 6 having a predetermined diameter. This tubular resin film 6 rises while being guided by guide rollers 5...5, is guided into a flat plate by a guide plate 7, and is transferred to a squeeze roll for take-up.
After being taken up and made into a flat plate by nip rolls 8.8, it is wound up by a winder 9.

[Problem to be solved by the invention]

However, in the above-described method of extruding a blown film with the L-LDPE resin film layer on the inside and the HDPE resin film layer on the outside, when the L-LDPE resin film layer is rolled up with the take-up roll 9, the L-LDPE
There was a problem in that the resin film layers came into contact with each other and caused blocking. Furthermore, when fatty acids or fatty acid compounds such as fatty acid amides, paraffin wax, fatty acid metal salts, etc. are added to the HDPE resin film layer to improve film formability or to render halogen compounds harmless, these additives They are exposed from the resin film and deposited on the guide roller, causing pressure scratches and abrasions on the film.Furthermore, these deposits peel off from the guide roller and become white lumps that adhere to the film, causing the film to deteriorate. When wound up, there was a problem in that not only pressure scratches but also fill 1 and tearing occurred.

On the other hand, when extruding with the L-LDPE resin film layer on the outside and the HDPE resin film layer on the inside, there was a problem in that wrinkles, streaks, etc. occurred and the yield rate decreased. .

The present invention solves the above problems and prevents pressure scratches on the film.
An object of the present invention is to provide a method for forming a multilayer coextruded blown film that can form a film of excellent quality without tears, scratches, wrinkles, streaks, etc.

[Means to solve the problem]

The present invention has been made to achieve the above objects,
A specific polyolefin resin film layer is extruded with an internal layer I.

That is, the multilayer coextruded blown film of the present invention has a polyolefin resin film layer as an inner layer,
The inner layer has a density of 0.936g/c+f1 or more (JIS
K6760 measurement method) polyethylene resin from 0.5 to 70
It is structured with the addition of a heavy view%.

In the present invention, a polyolefin resin film layer is extruded as an inner layer. This polyolefin resin film layer does not need to be made only of polyethylene resin with a density of 0.936 g/cm3 or more; as long as it contains a polyethylene resin with a density of 0.936 g/cffl, other resins such as L-
It may contain LDPE resin, LDPE resin, etc.

This resin has a melt index (JISK6760)
(hereinafter referred to as MI) is 0.3g/10min or more, density (J
ISK9690) is 0.936g/crf1 or more, especially Ml is 0.5g/10min or more and the density is 0.941g/c
nt or more is preferable.

When Ml is less than 0.3 g/10 minutes, film formability is poor and molecules are easily oriented in the longitudinal direction, making it difficult to obtain a film with a good balance of longitudinal and transverse physical strength. Also, lump-like failures occur frequently, damaging the photosensitive material.

If the density is less than 0.941 g/cff1, it is difficult to obtain a polyethylene resin film with excellent anti-blocking properties and a high Young's modulus.

Further, the polyolefin resin film layer contains at least one of a light-shielding substance, a fatty acid, and a fatty acid compound in order to prevent blocking and prevent charging.

This light-shielding substance can be kneaded or dispersed in each layer, and is not transparent to visible light, ultraviolet rays, etc. Light-shielding substances that can be used in the present invention include various carbon blacks, grubite, iron oxide, zinc white, titanium oxide, clay, aluminum powder, aluminum paste, calcium carbonate, mica, barium sulfate, talc, and cadmium pigments. , Bengara, Kohar 1 to Blue, copper phthalocyanine pigments, monoazo or boriazu pigments, and organic pigments such as aniline black.

Preferably, the light shielding substance is contained in an amount of 0.1 to 20.0% by weight.

If it is less than 0.1% by weight, the effect of adding the light-shielding substance (ensuring light-shielding properties, preventing static electricity, etc.) cannot be expected, and the cost increases by the kneading cost.

If it exceeds 20.0% by weight, the physical strength of the film, especially tearing strength and impact puncturing strength, will decrease and heat sealability will deteriorate.

Furthermore, failures often occur in which the photosensitive material is contaminated by the light blocking material on the film surface, or the light blocking material is detached from the film and adheres to the photosensitive material.

It is also preferable to mix two or more types of light shielding substances according to the required characteristics. In this case, the unit area (m2) of packaging material is carbon black with an average particle diameter of 200 mμ or less.
0.5g/M to 50g/rr (it is preferable for packaging materials for photosensitive materials to contain carbon blacks with a pH of 5 to 9 and an average particle size of 10 to 120).
Preferably, furnace carbon black has a pH of 6 to 9 and an average particle diameter of 50 mμ or less. By using a material with such pH and particle size, there is less fogging (there is less increase or decrease in photosensitivity, there is a large light shielding ability, and there is no problem with pins caused by carbon black lumps, fins, etc.). It is possible to obtain a packaging material that has a number of advantages, such as improved physical strength and improved heat-sealing properties, in which holes are less likely to occur.

As mentioned above, there are various forms in which light-blocking substances are blended, but
The master patch method is preferable in terms of cost reduction and prevention of workplace contamination.

Next to carbon black', metal powder which is preferable as a light-shielding substance will be explained. This metal powder is a light-reflecting shade material that gives a silvery appearance with high commercial value, and is also moisture-proof and
It has excellent light shielding properties, antistatic properties, heat insulation properties under sunlight, gas barrier properties, etc.

As the metal powder, it is particularly preferable to use aluminum powder or a substance obtained by removing lower volatile substances from aluminum paste and kneading it into a thermoplastic resin.

Aluminum paste here refers to the aluminum paste that is produced when aluminum powder is made by known methods such as ball milling, stamp milling, or atomization in the presence of mineral spirit and a small amount of higher fatty acids such as stearic acid or oleic acid. It is made into a paste. In the present invention, this aluminum paste and polyolefin thermoplastic resin (various polypropylene resins, various polyethylene resins, EVA
resin, EEA resin, EAA resin, etc.) are heated and kneaded, and low volatile substances (mainly mineral spirits with a strong odor) are removed by heating or a vacuum pump, etc., and the resulting product is used as aluminum paste compound resin and aluminum paste master patch resin.

In particular, it is preferable to use it as an aluminum paste master hatch resin in order to eliminate adverse effects on photographic materials and odor. For example, even if the mineral spirit content in a master patch resin with an aluminum paste content of 40% by weight is 1.0% by weight, if you try to make the aluminum paste concentration in the film layer 2% by weight, the aluminum paste 19 parts by weight of natural resin is kneaded with 1 part by weight of master hatch, and some mineral spirit is removed as gas during film forming in the film layer, so the mineral spirit content is 0.05 parts by weight. % or less. As a result, there is no adverse effect on the photographic material, and odor is also reduced.

Aluminum powder is made by pulverizing molten aluminum into powder by atomizing, granulating, rotating disk dropping, evaporating, etc., or by crushing aluminum foil into flakes by ball milling, stamp milling, etc. Contains short aluminum fibers (filler). Since aluminum powder alone is unstable, various known treatments such as surface treatment with a binder, higher fatty acid, or higher fatty acid are performed to make the surface of the aluminum powder inactive.

The fatty acids include oleic acid, stearic acid, lauric acid, ricinoleic acid, naphthenic acid, octylic acid, phthalic acid,
Saturated and unsaturated fatty acids such as adipic acid, cehatic acid, acetyl ricinoleic acid, and maleic acid.

The fatty acid compounds include oleic acid amide, erucic acid amide, stearic acid amide, bis fatty acid amide F, magnesium stearate, calcium stearate, zinc stearate, aluminum stearate, barium stearate, calcium laurate, zinc octylate, and oleic acid. Butyl, butyl stearate, etc.

The amount of polyethylene resin having a density of 0.936 g/crf1 or more contained in the polyolefin resin film layer is limited to 0.5 to 70% by weight. 0.5g/cf
If it is less than f1, blocking will occur, and if it exceeds 70% by weight, the physical strength will decrease, the inner layers will become slippery, and wrinkles and streaks will occur frequently, which is not practical.

Also, the L-L l) PE resin-based film layer is extruded as an outer layer. If this L-LDPE resin film layer is configured to contain 30% by weight or more of L-LDPE resin, LDPE resin, HDPE resin, ethylene copolymer resin, polypropylene resin, etc. It may also be a mixture of one or more kinds of base resins.

This L-LDPE resin is called the third polyethylene resin, and is a low-cost, high-strength resin that meets the demands of the times for energy and resource conservation, and has the advantages of medium-low pressure and high-pressure polyethylene resins. be. This resin is produced by a low pressure method with ethylene and 3 to 13 carbon atoms, preferably 4 to 13 carbon atoms.
It is a copolymer made by copolymerizing eight α-olefins, and is a low-medium density polyethylene resin with an ethylene content of 85 to 99.5 mol% and a linear structure with short branches.

α-olefins include butene-1, octene-1, hexene-1,4-methylpentene-1, heptene-1,
etc., and the amount thereof is about 0.5 to 15 mol% of the polymer. The density is generally considered to be about low = 11-medium density polyethylene resin, but commercially available products often have a density within the range of 0.87 to 0.95 g/cffl.

Specific examples of L-LDPE resins by trade name include G Resin (UCC), Dowlex (Dow Chemical), Sflair (DuPont Canada), Marlex (Philips), Neozex and Ultzex (Mitsui Oil). Chemicals), Kuchimasu Nix (Japan Petrochemical), and Stamilex (DSM).

Among these L-LDPE resins, those with an ethylene content of 9 are particularly preferable from the viewpoint of physical strength and heat seal strength.
0-99.5 mol%, α-olefin content 0.5-99.5 mol%
10 mol%, melt index (hereinafter referred to as Ml) is 0.8 to 30 g/10 min (J l5K6760), density is 0.870 to 0.940 g/crfl (JISK
6760), and is obtained by a liquid phase process of an α-olefin having 6 to 8 carbon atoms.

Particularly preferable representative examples include Urtozex and Mitsui Petrochemical ■, which are made by artificially introducing 4-methylpentene-1 having 6 carbon atoms into polyethylene as an α-olefin side chain. DSM with 8-carbon octene-1 introduced as an α-olefin side chain
There are SUMILEX manufactured by the company and DOWLEX manufactured by the Dow Chemical Company.
It is PE resin. ).

This L-LDPE resin film layer contains one or more of a light-shielding substance, a fatty acid compound, and an antiblocking agent to prevent bronking, oxidation, moldability, and antistatic properties.

Antiblocking agents include silica, diatomaceous earth, calcium silicate, aluminum silicate, talc, magnesium silicate, calcium carbonate, higher fatty acid polyvinyl ester, n-occudecyl urea, dicarboxylic acid ester amide, and the like.

Note that the light-shielding substance and fatty acid compound are the same as in the case of the polyolefin resin film layer.

Furthermore, the polyolefin resin film layer and L-L
Various additives can be added to the DPE resin film layer.

Typical examples of additives are described below, but the present invention is not limited thereto (although they can be selected from all known additives).

(Additive type) (Representative example) (1) Plasticizer
; Phthalate ester, glycol ester, fatty acid ester, phosphate ester, etc. (2) Stabilizer; Lead-based, cadmium-based, zinc-based, alkaline earth metal-based, organotin-based, etc. (3) Antistatic agent; Cationic type Surfactants, anionic surfactants, nonionic surfactants, double-sided active agents, various carbon blacks, metal powders, graphite, etc. (4) Flame retardants; phosphate esters, halogenated phosphate esters, halides, inorganic substances, Phosphorus-containing polyol, etc. (5) Filler; alumina, kaolin, crew, calcium carbonate, mica, talc, titanium oxide, silica, etc. (6) Reinforcement agent; glass roving, metal fiber, glass fiber, glass milled fiber, carbon fiber, etc. (7) Colorant; Inorganic pigment (AI, Fe2O3, T
ioz, ZnO.

CdS, etc.), organic pigments (carbon black, dyes, etc.) (8) Foaming agents; inorganic foaming agents, (ammonium carbonate, sodium bicarbonate) organic foaming agents, thoron-based, ab-based), etc. (9) Anti-degradation agents; ultraviolet absorbers, Antioxidants Metal deactivators, peroxide decomposers, etc. (10) Lubricants; paraffin, wax, fatty,
Fatty acid amide type, silicone type, ester type, higher alcohol, etc. (12) Coupling agents; silane type, titanate type, chromium type, aluminum type, etc. (13) Various thermoplastic resins, deodorants, oxygen absorbers, absorption agent, rubber, etc.Also, an intermediate layer is laminated between the polyolefin resin film layer and the L--15=LDPE resin film layer,
It may be a laminated film with three or more layers.

The method of the present invention can be carried out in any apparatus for producing multilayer coextruded blown films.

The multilayer coextruded blown film formed by the method of the present invention can be used for packaging various products, and is particularly suitable for packaging photosensitive materials such as photographic materials, foodstuffs, pharmaceuticals, and chemicals.

When the multilayer coextruded blown film according to the method of the present invention is applied to, for example, the above-mentioned photographic materials, it can be applied to - vertical bags, double flat bags, self-supporting bags, - heavy gusset bags, double gusset bags, laminated films, moisture-proof and light-shielding boxes. It can be used for inner lining, inner lining of a light-shielding magazine loaded in a bright room, inner layer bag, and all known forms of leader paper.

゛ Depending on the properties of the laminated film, 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. Note that it is also possible to make bags using an appropriate adhesive, adhesive, or the like.

[Effect]

In the method for forming a multilayer coextruded blown film of the present invention, a polyolefin resin film layer is extruded as an inner layer, so when the film is wound up with a winder, the polyolefin resin film layers overlap each other to prevent blocking. Furthermore, since the L-LDPE resin film layer is extruded as the outer layer, additives are not exposed from the outer layer and do not adhere to guide rollers or the like.

〔Example〕

An embodiment of the method for forming a multilayer coextruded blown film of the present invention will be described with reference to FIGS. 2 and 3.

In FIG. 3, the resin constituting the polyolefin resin film layer is charged into an extruder 1a, and the resin constituting the L-LDPE resin film layer is charged into an extruder 1b, and each is heated and melted. Next, the polyolefin resin film layer 11 is extruded from the inner slit of the ring die 2, and the LDPE resin film layer 12 is extruded from the outer slit. At this time, the compressed air from the blast pipe 3 and the cooling air from the air ring 4 cause the polyolefin resin film layer 11 to form on the inside, as shown in FIG. A tubular resin film 6 with an L-LDPE resin film layer 12 located on the outside is molded.

This tubular resin film 6 is lifted up via the guide rollers 5...5 and the guide plates 7, 7 to the collecting roll.
Since the E-resin film layer 12 is in contact with these, additives will not adhere to the guide rollers 5, etc.

Then, it is folded into a flat plate shape with take-up squeeze rolls 8, and as shown in FIG. taken. Therefore, no blocking occurs between the inner layers.

Next, present invention products ■, ■, comparative products I, ■, ■, and conventional products ■
We will explain the experimental results comparing the characteristics of .

Invention product I Inner layer has a density of 0.954 g/cyfl, M 11.1
g/10 min polyolefin resin 20% by weight, ethylene and 4-methylpentene-1 copolymer resin with density 0°920 g/c[, Ml 2.0 g/10 min L-
This is a polyolefin resin film layer having a thickness of 35 μm and consisting of 76.9% by weight of 1-D PE resin, 3% by weight of furnace carbon black, and 0.1% by weight of oleic acid amide.

The outer layer has a density of 0.920 g/cJ and Ml of 2.1 g/cJ.
96.75% by weight of L-LDPE resin, which is a copolymer resin of 10-minute ethylene and 4-methylpentene-1, 3% by weight of furnace carbon blank, and 0 oleic acid amide.
．． 05% by weight and 0 synthetic silica as a prolagging inhibitor.
．． It is a 35 μm thick L-L DPE resin film layer consisting of 2% by weight.

Invention product ■ Inner layer has a density of 0.954 g/c tonne M 11.1 g/10
It is a copolymer resin of ethylene and 4-methylpentene with a density of 0.920g/cf and 2% by weight of HDPE resin.
fl, M I 2.0g/10min L-LDPE resin 9
3% by weight, 3% by weight of furnace carbon blank,
It is a 35 μm thick polyolefin resin film layer containing 0.1% by weight of oleic acid amide, and is otherwise the same as product I of the present invention.

Comparative product■ Inner layer has a density of 0.920g/cffl and Ml of 2.0
A 35-μm-thick L was made of 97% by weight of L-LDPE resin, which is a copolymer resin of ethylene and octene-1, and 3% by weight of furnace carbon black.
-LDPE resin film layer.

The outer layer has a density of 0.920 g/afl and Ml of 2.1 g.
96.75% by weight of L-LDPE resin, which is a copolymer resin of ethylene and 4-methylpentene-1, 3% by weight of furnace carbon black, 0.05% by weight of oleic acid amide, and synthetic silica. This is a 35 μm thick L-LDPE resin film layer containing 0.2% by weight.

Comparative product■ Inner layer has a density of 0.964g/c+fl, and MI is 0
．． It is a 25 μm thick HDPE resin film layer consisting of 95% by weight of HDPE resin of 4g/10min, 3% by weight of furnace carbon black, and 2% by weight of calcium stearate.

The outer layer has a density of 0.920 g/c and an MI of 2.1 g/c.
96.95% by weight of L-LDPE resin, which is a copolymer resin of 10-minute ethylene and 4-methylpentene-1, 3% by weight of furnace carbon black, 0.05% by weight of oleic acid amide, and as a prolagging inhibitor. This is a 45 μm thick T--LDPE resin film layer containing 0.2% by weight of synthetic silica.

Comparison product ■ This is a layer structure in which the inner layer and outer layer of the product (2) of the present invention are completely reversed.

Conventional product■ Density is 0.923g/c+fl, MI is 2.4g/10
It is a single blown film with a thickness of 70 μm consisting of 96.95% by weight of high-pressure branched low-density polyethylene resin, 3% by weight of furnace carbon black, and 0.05% by weight of oleic acid amide.

The experimental results are shown in Table 1.

The evaluation is based on the following.

◎; Very good ○; Excellent; Within practical limits; Problems, improvement required ×; Not practical , folding iZ330mm
It was cut to 220 mm with a razor, and judgment was made based on the ease with which the cut opening was made.

*B film moldability Motor load (current value), bubble stability, frost line position, fish eyes, bumps, film wrinkles, and film thickness unevenness when molding the blown film of the present invention using a blown film molding machine Evaluation is made based on the suitability for manufacturing a monotal blown film.

*C White powder generation prevention properties Each sample was tested with a die cap of 1 mm and a blow ratio of 2.
Determine by visual inspection the degree to which the white powder adhering to the pass roll and wound film and the amount of white powder clumps are small when produced using a blown film forming machine in step 1. *D Physical strength Required for packaging materials for photosensitive materials. tear strength (JIS
P8116), impact hole L strength, bursting strength (
JIS P 8112) and total physical strength such as heat seal strength.

*E Wrinkle and streak prevention characteristics Each sample was tested with a die cap of 1 mm and a blow ratio of 2.
Judging by visual inspection of the appearance of the film, the degree of difficulty in generating wrinkles and streaks when produced using a blown film forming machine in step 1 *F Bag-making suitability A sealed bag is produced using the packaging material of the present invention. It has excellent properties such as the difference in melting temperature between the inner and outer layers, low-temperature heat-sealing properties, heat-sealing strength, hot tack properties, contaminant sealing properties, heat-sealing strength over time, curling, etc., which are sometimes required, and does not generate pinholes. The evaluation is based on the ease of manufacturing a packaging bag for photosensitive materials that is difficult to tear during distribution and can be sealed even at low temperatures.

〔Effect of the invention〕

In the present invention, by extruding a predetermined polyolefin resin film layer as an inner layer and a predetermined >LDPE resin film layer as an outer layer, the polyolefin resin film layers come into contact with each other, so blocking does not occur and L - Since the LDPE resin film layer is in contact with external guide rollers, etc., additives do not adhere to the guide rollers, etc., and the film is not adversely affected by adhering substances. Therefore, it is possible to consistently form a multilayer coextruded blown film of excellent quality.

[Brief explanation of the drawing]

FIG. 1 is an enlarged cross-sectional view showing the layer structure during molding of the blown film of the present invention, FIG. 2 is an enlarged cross-sectional view of section A in FIG. 3, and FIG. 3 is a schematic diagram of a blown film manufacturing apparatus. 1...Extruder 2...Dice 5...Guide roller 6...Double-shaped resin film 7...Guide plate 8...Squeeze roll) 11...
Polyolefin resin film layer 12...L-LDP
E-resin film layer patent applicant Fuji Photo Film Co., Ltd. agent Patent attorney Japan-China political situation Haka 1 person Figure 2 Figure 1

Claims (1)

[Claims] In a multilayer coextruded blown film including a linear low-density polyethylene resin film layer and a polyolefin resin film layer, the polyolefin resin film layer is an inner layer, and the inner layer has a density of 0.936 g/c.
A multilayer coextruded blown film characterized by adding 0.5 to 70% by weight of a polyethylene resin of m^3 or more.