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BACKGROUND OF THE INVENTION
This invention relates to laminated films joined by blocking and processes for producing the same.
As the packaging material used for the packaging bags of photographic photosensitive materials, laminated films consisting of a plurality of film layers are used, and the plurality of the film layers are laminated through an adhesive layer or
directly by extrusion laminating. The laminated films are produced through many laminating processes which increase manufacturing cost, and tend to curl. Moreover, tear strength is small.
The inventors disclosed a novel laminated film laminated not by adhesive or extrusion laminating but by blocking in a soft state to a certain degree (U.S. Pat. No. 4,981,734, EP 0,369,447A). The laminated films laminated by blocking have a
great tear strength, Gelbo test strength and impact puncture strength, and curling does not occur. However, the pseudo-adhesion by blocking is unstable, and laminated films were occasionally separated from a cut end at low temperatures. The
pseudo-adhesion was also occasionally separated partially in the laminating process with other flexible sheets or in the bag-making process, resulting in the occurrence of wrinkling, furrowing or blistering troubles. These troubles became a problem in
winter and in strongly air-cooled room.
SUMMARY OF THE INVENTION
An object of the invention is to provide a laminated film laminated by blocking in a suitable strength which does not separate, for example, through the laminating process and the bag-making process, irrespective of seasons, when it is produced
in the normal conditions.
Another object of the invention is to provide a laminated film laminated by blocking wherein the pseudo-adhesion does not vary with film thickness, temperature variation due to seasonal variation, cooling efficiency by air, etc.
The present invention provides laminated films and processes for producing them which have achieved the above objects.
Thus, the present invention provides:
A laminated film comprising an inflation film of which the inner surface is joined by blocking and the cut end is joined by heat fusion.
A process for producing the above laminated film which comprises pressing a tubular film molded by an inflation process by a pressure roll into a flat form to join the inner surface by blocking, and then cutting by fusion.
A process for producing a laminated film which comprises heating the surface of a tubular film molded by an inflation process, and then pressing the tubular film by a pressure roll into a flat form to join the inner surface by blocking.
A laminated film comprising a coextruded multilayer inflation film of which the inner surface is joined by blocking, wherein the Shore hardness (ASTM D-2240) of the thermoplastic resin comprising the inner layer is lower than the thermoplastic
resin comprising the outer layer.
A laminated film comprising a coextruded multilayer inflation film of which the inner surface is joined by blocking, wherein the inner layer comprises an acid-modified polyolefin resin.
A laminated film comprising two thermoplastic resin films of which the inner surfaces are joined by blocking, wherein the joined portion comprises strongly joined portions and weakly joined portions.
A process for producing the above laminated film which comprises pressing two thermoplastic resin films by an embossing roll.
A laminated film which is laminated by blocking, wherein the end portions are joined more strongly than the central portion.
A process for producing the above laminated film which comprises pressing a film laminated by blocking in a linear form with a prescribed width, and then cutting the pressed portion.
DESCRIPTION OF THE DRAWINGS
FIGS. 1 through 15 are partial sectional views of a laminated film embodying the invention.
FIG. 16 is a sectional view illustrating a coextruded double layer film which is deflated and of which the inner layer is joined by blocking.
FIGS. 17 through 21 are partial plan views illustrating various patterns of the strongly joined portions and the weakly joined portions.
FIG. 22 through 28 are partial sectional views of a laminated film of the invention, wherein the end portions are joined strongly more than the central portion.
FIG. 29 is a schematic illustration of an inflation film molding apparatus showing the state of producing a laminated film laminated by blocking.
FIG. 30 is a perspective view illustrating the manufacturing state of the laminated film of the invention wherein the cut end is joined by heat fusion.
FIG. 31 is a schematic sectional view of the laminated film of the invention produced by the apparatus of FIG. 30.
FIG. 32 is a schematic side view of an apparatus for producing the laminated film of the invention having a pattern of the strongly joined portions.
FIG. 33 is a schematic plan view of another apparatus for producing the laminated film of the invention having a pattern of the strongly joined portions.
FIG. 34 is a perspective view illustrating the preparation of a laminated film of the invention of which the end portions are joined more strongly than the central portion.
FIG. 35 is a perspective view of a slitting apparatus applicable to the invention, and FIG. 36 is a partial sectional view of an inflation film slit by this apparatus.
FIG. 37 is a schematic side view of a slitting apparatus also applicable to the invention.
DETAILED DESCRIPTION OF THE INVENTION
To join by blocking means that deflated (in the specification, "deflated" means "rendered flat by passing over a pressure roll") inner surface of inflation film is joined without using an adhesive and heat fusion.
The blocking is allowed to occur by passing the nip roll of an inflation film molding machine with weakening cooling conditions, by passing a pressure roll composed of a heating metal roll and an elastic roll, such as a heat-resistant rubber roll
or a cotton roll before being entirely cooled, or the like. The pressing form includes the entire face pressing, spot pressing, pressing in longitudinal streaks, pressing in lattice pattern, pressing in lateral streaks, pressing in other embossed
patterns. The metal roll may be flat or provided with various embossing, such as spots, streaks, lattice, cloth mark, or other embossed patterns, e.g. more than 210 patterns are disclosed in "BEALON SHIBO (Crimp)" (published by NGK Bealon Corp. Ltd.)
It is preferred to heat the tubular film before blocking by the nip roll or pressure roll. When the inner surface of the inflation film is heated, it can be conducted by heating the mandrel. When the outer surface of the inflation film is
heated, it can be conducted by using a far-infrared heater in a ring form, blowing hot air, using nichrome wire heaters in a ring form, using a heating bar in a ring form, or the like. The above heaters may be composed of a plurality of commercial
linear heaters. A preferred heating temperature renders the inner surface of the inflation film to around the softening point, in view of not degrading the appearance of the film outer surface and obtaining a suitable strength adhesion by blocking. The
heating temperature, therefore, depends upon film molding speed, film thickness, the resin composition, etc. For example, in the case that the inner surface is composed of L-LDPE resin, the heating is conducted so that the temperature of the inner
surface becomes more than 40.degree. C., preferably 50.degree. to 140.degree. C., more preferably 60.degree. to 120.degree. C.
The inflation film may be either of a single layer film or a multilayer film. In the case of a single layer film, it is necessary to provide a temperature difference between the inner surface and the outer surface. The temperature difference
may be formed at the ring die or by air-cooling the outer surface alone.
It is preferred to provide strongly joined portions and weakly joined portions in the jointed portion by blocking. A suitable peel strength of the strongly joined portions is not less than twice, preferably not less than three times,
particularly preferably not less than five times, that of the weakly joined portions. When the peel strength of the strongly joined portions is less than that of the weakly joined portions, not only there is a possibility that the pseudo-adhesion does
not occur at the weakly joined portions in winter and strongly air-cooled room, but also the pseudo-adhesion at the strongly joined portions is reduced. As a result, the separation at the pseudo-adhesion and wrinkling occur in the laminating process of
other flexible sheets or in the bag-making process. In order to induce none of the above problems, to improve physical strength, such as tear strength, to prevent curling and to improve flexibility, a suitable peel strength of the strongly joined
portion, is 2 to 250 g/15 mm width, preferably not more than 100 g/15 mm width, more preferably not more than 50 g/15 mm width. When the peel strength is more than 200 g/15 mm width, at the strongly joined portions, the inner surfaces are joined
substantially in a heat fusion state, and the laminated film tends to tear at the boundary between the strongly joined portion and the weakly joined portion. Moreover, at the strongly joined portion, flexibility and Gelbo test strength decreases, and
pinholes tend to occur. When the peel strength is less than 2 g/15 mm width, the joined portion by blocking tends to be separated similar to the conventional laminated film laminated by blocking. A suitable peel strength of the weakly joined portion is
not more than 150 g/15 mm width, preferably not more than 50/15 mm width, more preferably not more than 20 g/15 mm width. The lower limit is 0.01 g/15 mm width, preferably 0.1 g/15 mm width. A suitable interval between the strongly joined portion and
weakly joined portion is 1 to 100 mm, preferably 2 to 50 mm. When the interval is less than 1 mm, the laminated film is similar to that laminated by the strongly joined portion entirely. As a result, to ensure flexibility and physical strength of the
laminated is difficult, and wrinkling and streaks tend to occur. When the interval exceeds 100 mm, the laminated film is similar to that laminated by the weakly joined portion entirely, and similar problems to the conventional laminated film laminated
by blocking occur. The form of the strongly joined portions may be spots, streaks, lattice, or the like.
The strongly joined portion may be provided at the end portions to form a laminated film wherein the end portions are joined more strongly than the central portion. The end portion to be joined by the strongly joined portion is, for example in
the case of a rectangular film, not necessary to be all of four ends, and it is sufficient to join at least two parallel sides by the strongly joined portion. Besides, when one end is folded, it is sufficient to join the other end in parallel to the
folding end by the strongly joined portion. The peel strength of the strongly joined portion is preferably not less than 20 g/15 mm width, more preferably not less than 50 g/15 mm width, particularly not less than 150 g/15 mm width. The peel strength
of the weakly joined portion is preferably not more than 150 g/15 mm width, more preferably not more than 50 g/15 mm width, particularly preferably not more than 20 g/15 mm width.
The strongly joined portions and weakly joined portions can be formed by the method of indenting the inner surface and/or outer surface of a single layer or multilayer inflation, e.g. by processing the ring die and then pressing by a smooth
surface pressure roll, the method of using a cooling apparatus having ribs at constant intervals in the longitudinal direction, and pressing by a pressure roll having ribs at constant intervals in the lateral direction (see Example 13), the method of
using an embossing roll as the nip roll of a single layer or multilayer inflation film molding machine, the method of joining the inner surface of the deflated single layer or multilayer inflation film entirely by the weakly joined portion by passing a
nip roll, and then forming indentations by passing an embossing roll provided behind the nip roll to form the strongly joined portions (see Examples 11 and 12). A preferred method comprises joining the inner surface of the deflated single layer or
multilayer inflation film by blocking, heating the film laminated by blocking by a heater, such as a hot air heater or a far-infrared heater, and then pressing by an embossing roll. The heating temperature by the heater is lower than the melting point,
preferably the softening point, of the inflation film. When the heating temperature exceeds the melting point, not only the flatness of the inflation film is degraded, but also the outer surface layers facing each other formed by winding the inflation
film are also joined by blocking. As a result, unwinding of the roll of the inflation film is difficult, and breakage of the inflation film occurs.
In the case of the laminated film wherein the end portions are joined more strongly than the central portion, the strongly joined portion can be formed by pressing by a pressure roll or a heating roll, and the strength of the strongly joined
portion is controlled by adjusting pressure, temperature, etc. Cutting of the strongly joined portion may be conducted before or after the formation of the strongly joined portion. For example, a laminated film laminated by blocking is pressed in a
linear form with a prescribed width by a pressure roll to form the strongly joined portion, and then the strongly joined portion is cut to obtain a laminated film having the strongly joined portions at the ends. The laminated film by blocking is
preferably produced from an inflation film by deflating, but may be produced by superimposing two films separately molded and then joining by blocking. The separately molded films may be identical with or different from each other in resin composition,
molding method, such as inflation process, T die method or casting method, thickness, color and layer construction. When packaging bags are made of the above laminated film, the strongly joined portion is preferably utilized as the sealing end.
As the method for joining the cut end of the laminated by heat fusion, laser beam cutting, ultrasonic cutting, flame cutting, electric discharge cutting, heated rotary blade cutting, heated razor blade cutting and the like are usable. Among
them, the heated razor blade cutting is preferred, in view of inexpensive equipment cost and the ease of width change. A suitable temperature is around the Vicat softening point (ASTM D-1525) of the inner layer, actually 50.degree. C. to the melting
point, preferably 70.degree. to 150.degree. C., more preferably 80.degree. to 120.degree. C.
Heretofore, the edge trimming and slitting into a prescribed width of a continuously traveling film web are conducted by slitting the film by a fixed blade at a free traveling portion between conveying rollers, slitting by a combination of a
fixed blade and a rotary blade (e.g. Japanese Patent KOKAI No. 64-58492), slitting by a combination of a rotating roll with channels and fixed blades, slitting by a traveling rotary blade which travels with rotating along a fixed blade, slitting by laser
beam.
The slitting by the fixed blade is cheap and excellent in workability. However, in the case of elevating the traveling speed of the film or slitting a flexible polyolefin resin film containing carbon black which has a great tear strength and
elongation, various troubles occur, such as wrinkling at the free traveling portion, difficulty in slitting or breakage of the film. Particularly, when the film to be slitted is used for a laminated film, unless incision is good, it tends to break the
web. Besides, in the case of slitting a film composed of a linear low density polyethylene (L-LDPE) resin containing carbon black, which is flexible, great in tear strength in the longitudinal direction and liable to elongate, for a long period, the
contact portion of the fixed blade with the film is locally heated resulting in the reduction of sharpness of the blade. Therefore, it is necessary to change the blade about every two days. The degeneration of cuttings in quantity is also a problem.
The cuttings and dust suspended in air adhere to the film, and entrained into the film roll. As a result, they induce indentations or projections by pressing film layers, or remain in a fixed state to the film.
The slitting by the combination of a fixed blade and a rotary blade is excellent in good incision of photographic films magnetic tape films and the like and a small quantity of cuttings. However, the apparatus is expensive and requires a lot of
time for adjusting the upper blade and the lower blade. Moreover, it is not suitable for slitting various films made of various resins which are cheap and different in thickness and molecular orientation, such as packaging films, particularly the films
being flexible, great in tear strength and liable to elongate, such as polyolefin resin films containing carbon black.
The slitting by a combination of a rotating roll with channels and fixed blades is preferred in a wide utilization because of cutting with stretching in the width direction on the surface of the roll with channels. However, the life of the blade
is short similar to the above fixed blade, and it is necessary to change the blade about every two days while the film molding line is stopped. Moreover, means for cleaning cuttings is necessary, because cuttings are generated.
The slitting by a traveling rotary blade is applicable for cutting or slitting papers or the like in a limited length, but it is impractical for slitting a traveling film web.
The slitting by laser beam is restricted in utilization in view of the manufacturing speed, cost, maintenance, safety, etc., although the generation of cuttings is prevented.
However, the aforementioned heated razor blade cutting is excellent, particularly in slitting a film being flexible, great in tear strength and liable to elongate, such as a polyolefin resin film containing carbon black, i.e. few cuttings, long
of blade life, high productivity, incision with a high strength, rare breakage of slit polyolefin resin film, etc. The heated razor blade cutting is also applicable to various films not laminated by blocking. The incision slit by the heated razor blade
is thickened compared with before slitting.
The inflation film of which the inner surface is joined by blocking may be a single layer film or a coextruded multilayer film. In the case of a single layer film, preferred resins composing the film are those suitable for the inner layer of the
coextruded multilayer film.
Preferable inflation films are coextruded multilayer films wherein the resin composing the inner layer which is joined by blocking is different from the resin composing the outer layer wherein blocking does not occur. Preferred resins used for
the inner layer are ethylene copolymer resins, propylene copolymer resins, thermoplastic resin elastomers, such as ethylene-propylene copolymer rubber and ethylene-propylene-diene ternary copolymer rubber, thermoplastic resins containing a tackifier,
modified polyolefin resins (acid-modified polyolefin resins), etc., having a low softening point and excellent physical strength. The thermoplastic resins containing a low polymerization degree, such as polyolefin resin having a mean molecular weight of
300 to 7,000, and the thermoplastic resins containing a tackifier, such as rosin resin, terpenephenol resin, petroleum resin, cumarone-indene resin, styrene resin, phenol resin, etc. are preferable in order to ensure pseudo-adhesion by blocking. It is
preferred that the inner layer contains at least one of the above resins in an amount of more than 50 wt. % in total of the above resins. Particularly preferred resins are polyolefin resins containing more than 50 wt. % in total of the
ethylene-.alpha.-olefin copolymer resin and/or ethylene-vinyl acetate copolymer resin having a Vicat softening point lower than the outer layer by 5.degree. C. or more, because of obtaining a laminated film stable in pseudo-adhesion by blocking and
excellent in physical strength. Other suitable resins include low density homopolyethylene resin and medium.multidot.high density homopolyethylene resin.
Suitable ethylene copolymer resins are ethylene-vinyl acetate copolymer resin, ethylene-propylene copolymer resin, ethylene-1-butene copolymer resin, ethylene-butadiene copolymer resin, ethylene-vinyl chloride copolymer resin,
ethylene-methylmethacrylate copolymer resin, ethylene-methyl acrylate copolymer resin, ethylene-ethyl acrylate copolymer (EEA) resin, ethylene-acrylonitrile copolymer resin, ethylene-acrylic acid copolymer resin, ionomer resin (copolymer of ethylene and
unsaturated acid crosslinked using metal such as zinc), ethylene-.alpha.-olefin copolymer (L-LDPE) resin, ethylene-propylene-butene-1 ternary copolymer resin, and the like. Among the above ethylene copolymer resins, L-LDPE resin and EEA resin are
preferred, because they are excellent in film moldability and heat sealing properties and are great in bag rupture strength, impact puncture strength and tear strength. L-LDPE resin is particularly preferred.
In order to adjust the properties as necessary, it is preferred to blend with other thermoplastic resins, elastomers, rubbers, various additives or modifiers.
The L-LDPE resin is called third polyethylene resin, and it is a low cost high strength resin, having the advantages of both low, medium density polyethylene resin and high density polyethylene resin, which meets the requirements, i.e. resource
conservation and energy conservation, of the times. The L-LDPE resin is a copolymer of ethylene and .alpha.-olefin, and it has a linear structure having short branches. The number of carbon atoms of the .alpha.-olefin is 3 to 13. Preferable
.alpha.-olefins have 4-10 carbon atoms, and examples of the .alpha.-olefin are butene-1, 4-methylpentene-1, hexene-1, heptene-1 and octene-1. The density is usually in the range of 0.87 to 0.95 g/cm.sup.3, and the melt index in usually 0.1 to 50 g/10
minutes. Most of the L-LDPE resin is synthesized by low pressure method, and partly synthesized by modified high pressure method. Examples of commercial L-LDPE resin are "G-Resin" and "TUFLIN" and "NUC-FLX" (UCC), "NUC Polyethylene-LL" and "TUFTHENE"
(Nippon Unicar) "Excelene VL" (Sumitomo Chemical), "Idemitsu Polyethylene-L" and "Moretec" (Idemitsu Petrochemical), "Dowlex" (Dow chemical), "Suclear" (Dupont de Nemour, Canada), "Marlex" (Phillips), "Neozex" and "Ultzex" (Mitsui Petrochemical
Industries), "Nisseki Linirex" (Nippon Petrochemicals), "Mitsubishi Polyethy-LL" (Mitsubishi Petrochemical), "Stamilex" (DSM), and the like. Preferable L-LDPE resins are copolymers of ethylene and .alpha.-olefin of which the number of carbon atoms is 6
to 8 having a melt index (MI) of 0.8 to 10 g/10 minutes (ASTM D-1238) and a density of 0.870 to 0.940 g/cm.sup.3 (ASTM D-1505) manufactured by liquid process or vapor process. Very low density L-LDPE resins having a density of less than 0.910 g/cm.sup.3
are also preferred.
The EEA resin is not restricted, and commercial EEA resins have, for example, a comonomer content of 7 to 41%, a MI of 1.5 to 1500 g/10 minutes (ASTM D-1238), a density of 0.93 to 0.95 g/cm.sup.3 (ASTM D-1505) a brittle temperature of -40.degree. C. to less than -75.degree. C. (ASTM D-746) and a tensile strength of 14 to 160 kg/cm.sup.2 (ASTM D-638).
A preferable coextruded multilayer inflation film has the inner layer containing a thermoplastic resin having a Shore hardness (ASTM D-2240) lower than the thermoplastic resin of the outer layer. A suitable Shore hardness of the thermoplastic
resin having a lower Shore hardness contained in the inner layer is lower than 60 D, preferably 10 to 50 D in view of ensuring pseudo-adhesion by blocking, flexibility and Gelbo test strength. The Shore hardness is preferably lower than the
thermoplastic resin of the outer layer by 2 D or more, particularly 5 D or more. Suitable thermoplastic resins for the inner layer are polyolefin copolymer resins, such as acid-modified polyolefin resin, L-LDPE resin, EEA resin and EVA resin.
Another preferable coextruded multilayer inflation film has the inner layer containing an acid-modified polyolefin resin.
The acid-modified polyolefin resin is an modified polyolefin resin which is a polyolefin resin modified by grafting an unsaturated carboxylic acid compound, and includes graft-modified polyethylene resin, graft-modified polypropylene resin,
graft-modified ethylene copolymer resin and graft-modified poly-.alpha.-olefin resin such as graft-modified ethylene-ethylacrylate copolymer resin, graft-modified ethylene-vinyl acetate copolymer resin, graft-modified polybutene-1 resin and
graft-modified poly-4-methylpentene-1 resin. A preferred grafting rate is 0.01 to 10%.
The unsaturated carboxylic acid compound usable as the modifier of the polyolefin resin is acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, angelic acid,
tetrahydrophthalic acid, sorbic acid, mesaconic acid, end-cis-bicyclo[2,2,1]-hepto-5-en-2,3-dicarboxylic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, aconitic anhydride, methyl acrylate, methyl methacrylate, ethyl methacrylate, ethyl
acrylate, n-butyl acrylate, glycidyl acrylate, glycidyl methacrylate, glycidyl maleate n-butyl methacrylate, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid diethyl ester,
acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N,N-diethylamide, maleic acid-N-monobutylamide, maleic acid-N,N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric
acid-N-monoethylamide, fumaric acid-N,N-diethylamide, fumaric acid-N-monobutylamide, fumaric acid-N,N-dibutylamide maleimide, N-butylmaleimide, N-phenylmaleimide, malonyl chloride, monomethylmaleate, dimethylmaleate, dipropylmaleate, potassium acrylate,
sodium acrylate, zinc acrylate, magnesium acrylate, calcium acrylate, sodium methacrylate, potassium methacrylate, or the like. Two or more unsaturated carboxylic acid compounds may be combined. Preferable unsaturated carboxylic acid compounds are
acrylic acid, maleic acid, maleic anhydride and maleic anhydride is particularly preferred. A suitable amount of the unsaturated carboxylic acid compound is 0.01 to 20 parts by weight, preferably 0.2 to 5 parts by weight, per 100 parts by weight of the
polyolefin base resin in view of securing adhesive strength.
The grafting modification method may be any known method, such as the method of reacting in a melted state disclosed in Japanese Patent KOKOKU No. 43-27421, the method of reacting in a solution state disclosed in Japanese Patent KOKOKU No.
44-15422, the method of reacting in a slurry state disclosed in Japanese Patent KOKOKU No. 43-18144 and the method of reacting in a vapor state disclosed in Japanese Patent KOKAI No. 50-77493. Among them, the melting method using an extruder is
preferred because of simple operation and inexpensiveness.
A peroxide is added in order to accelerate the reaction between the polyolefin base resin and the unsaturated carboxylic acid, Suitable peroxides are organic peroxides such as benzoyl peroxide, lauroyl peroxide, dicumyl peroxide,
.alpha.,.alpha.'-bis(t-butylperoxydiisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne, di-t-butyl peroxide, cumene hydroperoxide, t-butyl-hydroperoxide, t-butylperoxylaurate, t-butylperoxybenzoate,
1,3-bis(t-butylperoxyisopropyl) benzene, di-t-butyl-diperoxyphthalate, t-butylperoxymaleic acid and isopropyl percarbonate, azo compounds such as azobisisobutyronitrile, and inorganic peroxides such as ammonium persulfate. Two or more peroxides may be
combined. Suitable peroxides are di-t-butylperoxide, dicumylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne and 1,3-bis(t-butylperoxyisopropyl) benzene, having a decomposition temperature between 170.degree.
C. and 200.degree. C. A suitable amount of the peroxide is 0.005 to 5 parts by weight, preferably 0.01 to 1 part by weight per 100 parts by weight of the polyolefin base resin.
There are commercial acid-modified polyolefin resins, such as "N polymer" (Nippon Petrochemicals), "Admer" (Mitsui Petrochemical Industries), "ER Resin" (Showa Denko), "Novatec-AP" (Mitsubishi Chemical Industries), "Modic" (Mitsubishi
Petrochemical) and "NUC-Ace" (Nippon Unicar).
The unmodified polyolefin resin is polyethylene resin, polypropylene resin, ethylene copolymer resin, polyvinyl chloride resin, or the like.
A suitable content of the acid-modified polyolefin resin in the inner layer is 5 to 80 wt. %, preferably 10 to 60 wt. %. When the content is less than 5 wt. %, it is difficult to form always the pseudo-adhesion by blocking over the whole inner
surface. Moreover, the effect upon the improvement in the dispersibility of light-shielding material is reduced. In the case of using polyester resin, polyamide resin or ethylene-vinyl alcohol copolymer resin, layer separation can occur at the boundary
between the inner layer and the outer layer. When the content exceeds 80 wt. %, although no problem occurs in the pseudo-adhesion by blocking over the whole surface and on the improvement in the dispersibility of light-shielding material is obtained,
the acid-modified polyolefin adversely affects photographic photosensitive materials. Scrubbability of the mold is also degraded.
As the resin contained in the inner layer other than the acid-modified polyolefin, although there are various resins blendable with the acid-modified resin, such as various thermoplastic resins, various elastomers and tackifier resins, preferred
resins are polyolefin resins, such as various ethylene copolymer resins, various propylene copolymer resins, homopolyethylene resin and homopolyethylene resin, which are inexpensive and excellent in film moldability. Particularly preferred resins are
L-LDPE resin, EEA resin, EVA resin and LDPE resin. Both of the Shore hardness and Vicat softening point of the resin are preferably lower.
As the resin used for the outer layer, there are various thermoplastic resins, various elastomers, and the like, and it is necessary to select the resin having a higher antiblocking ability, wear resistance, Shore hardness and Vicat softening
point than the inner layer. Moreover, in the case of heat sealed uses, such as laminated films for bag, heat sealability is necessary, and in the case of the use for photographic photosensitive materials, it is necessary to select the resin not
affecting photographic properties adversely. In the case of requiring heat sealability, suitable resins for the outer layer are various polyolefin resins having a Shore hardness and Vicat softening point higher than the inner layer, and in the case of
not requiring heat sealability, suitable resins are various polyamide resins, various polyester resins, high molecular weight polyethylene resins and high molecular weight polypropylene resins.
Preferable resins for the outer layer are those having a Vicat softening point higher than the inner layer by 5.degree. C. or more, preferably 10.degree. C. or more, and being excellent in inflation film moldability, physical strength and heat
sealing properties (appearance, prevention of pinholes and rupture, prevention of the decrease in strength, etc.). Such a resin includes ethylene-.alpha.-olefin copolymer resin having a density of more than 0.920 g/cm.sup.3, homopolyethylene resin
having a density of more than 0.920 g/cm.sup.3, homopolypropylene resin, propylene-.alpha.-olefin copolymer resin, polyamide resin, such as nylon 6, nylon 66, nylon 11 and nylon 12, including copolymer resin with another resin, polyester resin,
ethylene-vinyl alcohol copolymer resin. The resin composing the outer layer is preferably the above resin alone or a blend resin containing more than 50 wt. % of the above resin. Particularly preferable resins are homopolyethylene resin and
ethylene-.alpha.-olefin copolymer resin having a density of more than 0.920 g/cm.sup.3, polyamide resin, and polyester resin. In view of heat sealing properties, preferable resins are .alpha.-olefin copolymer resins having 2 to 6 carbon atoms, more
preferably ethylene-.alpha.-olefin copolymer resins, particularly preferably copolymer resins and .alpha.-olefin having 4 to 10 carbon atoms. A suitable content of these resins is more than 3 wt. %, preferably more than 10 wt. %, more preferably more
than 15 wt. %, in view of ensuring heat seal strength with time. By composing the outer layer of an inflation film of a resin composition containing more than 15 wt. % of ethylene-.alpha.-olefin copolymer resin, heat seal strength with time of packaging
bags in ensured, and hot tack properties and physical strength are rendered excellent.
The Shore hardness of the resin used for the outer layer is higher than the inner layer, and higher than 50 D, preferably higher than 60 D, particularly preferably higher than 70 D.
The inflation film may preferably contain carbon black, metal powder (including paste), carbon fiber, conductive polymer, metal fiber, antistatic agent, lubricant, etc., in order to improve antistatic ability.
Carbon blacks, which are the most preferable as the light-shielding material, are divided into gas black, oil furnace black, channel black, anthracene black, acetylene black, Ketjen carbon black, thermal black, lamp black, vegetable black and
animal black according to their origin. Among these, oil furnace carbon black is preferably in terms of light-shielding character, cost and improvement of properties. On the other hand, since acetylene black and Ketjen carbon black have an antistatic
character, they are also preferable, though they are expensive. They may be blended with the oil furnace black in order to improve its character. Though, there are various blending methods, such as dry coloring, liquid coloring, paste coloring,
masterbatch pellets, compound color pellets and gramular color pellets, the masterbatch method using masterbatch pellets is preferred in view of cost and less contamination of the working place. Japanese Patent KOKOKU No. 40-26196 discloses a method of
making a masterbatch of polymer-carbon black by dissolving the polymer in an organic solvent and dispersing the carbon black into the solution. Japanese Patent KOKOKU NO. 43-10362 discloses another method of making a masterbatch by dispersing the carbon
black into polyethylene. The inventor also disclosed a resin composition for color masterbatch (EP 0,277,598A).
Particularly preferable carbon black for the packaging material for photographic photosensitive materials is the oil furnace carbon black having a pH of 6 to 9, a mean particle size of 10 to 120 m.mu., a volatile components content of less than
2% a content of cyanides and sulfur components of less than 1.0%, preferably less than 0.5%, particularly preferably less than 0.1%, and an oil absorption value of more than 50 ml/100 g in view of no occurrence of fogging, rare occurrence of
photosensitivity deviation and great light-shielding ability. Moreover, when it is blended with L-LDPE resin, the lumps of carbon black and fish eyes rarely occur. Channel black is not preferred because of containing components inducing fogging, such
as sulfur component, in quantity as well as expensiveness.
Metal powder includes iron powder, stainless steel powder, copper powder, lead powder, aluminum powder, etc. Carbon fiber includes silicon carbide fiber, as well as pure carbon fiber. Carbon fiber improves conductivity and physical properties,
but it is expensive. Metal fiber is brass fiber, stainless steel fiber, etc. Metal fiber improves conductivity, but it is expensive as well as causing an increase in specific gravity.
In any event, in the case of using as the packaging material for photosensitive materials, particularly used on the photosensitive material side of the packaging material, it is preferred to select a light-shielding material having a content in
total of cyanides and sulfur components of less than 1%, preferably less than 0.5%, more preferably less than 0.1% in order not to degrade photographic properties, such as fogging, sensitivity, tone and color balance. Examples of the light-shielding
material usable for the invention are described below.
Oxides . . . silica, diatomaceous earth, alumina, titanium dioxide, iron oxide, zinc oxide, magnesium oxide, antimony oxide, barium ferrite, strontium ferrite, beryllium oxide, pumice, pumice balloon, alumina fiber, etc.
Hydroxides . . . aluminum hydroxides, magnesium hydroxides, basic magnesium carbonate, etc.
Carbonates . . . calcium carbonate, magnesium carbonate, dolomite, etc.
Sulfates, sulfites . . . calcium sulfate, barium sulfate, ammonium sulfate, calcium sulfite, etc.
Silicates . . . talc, clay, mica, asbestos, glass fiber, glass balloon, glass bead, calcium silicate, montmorillonite, bentonite, etc.
Carbons . . . carbon black, graphite, carbon fiber, carbon hollow bead, etc.
Others . . . iron powder, copper powder, lead powder, aluminum powder, molybdenum sulfide, boron fiber, silicon carbide fiber, brass fiber, potassium titanate, lead titanate zirconate, zinc borate, barium metaborate, calcium borate, sodium
borate, aluminum paste, etc.
Organic Compounds: wood flour such as pine, oak and sawdust, husk fiber such as almond, peanut and chaff, cotton, jute, paper piece, cellophane piece, nylon fiber, polypropylene fiber, starch, aromatic polyamide fiber, etc.
Among them, preferred absorbents provide opacity, and light-absorptive carbon black, titanium nitride and graphite are particularly preferred because of being excellent in heat resistance and light resistance and being relatively inactive.
Antistatic agent applicable to the invention includes:
Nonionic Antistatic Agent:
Alkylamine derivatives:
Polyoxyethylene alkyl amine, tertiary amine e.g. laurylamine, N,N-bis(2-hydroxyethyl cocoamine, N-hydroxyhexadecyl-di-ethanolamine, N-hydroxyoctadecyl-di-ethanolamine, etc.
Fatty amide derivatives:
Oxalic acid-N,N'-distearylamide butyl ester, polyoxyethylene alkyl amide, etc.
Ethers:
Polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, etc.
Polyol esters:
Glycerine fatty acid esters, sorbitan fatty acid esters, 1-hydroxyethyl-2-dodecylglyoxazoline, etc.
Anionic Antistatic Agent:
Sulfonates:
Alkyl sulfonate (RSO.sub.3 Na), alkylbenzene sulfonate, alkyl sulfate (ROSO.sub.3 Na), etc.
Phosphate esters:
Alkyl phosphate, etc.
Cationic Antistatic Agent:
Cationic amides:
Quaternary ammonium salts:
Quaternary ammonium chloride, quaternary ammonium ammonium sulfate, quaternary ammonium nitrate, e.g. stearamide propyl-dimethyl-.beta.-hydroxyethyl ammonium nitrate, etc.
Ampholytic Antistatic Agent:
Alkyl betaines:
Imidaxolines:
Alkyl imidazolines:
Metal salts:
(RNR'CH.sub.2 CH.sub.2 CH.sub.2 NCH.sub.2 COO).sub.2 Mg (R.gtoreq.C, R'.dbd.H or (CH.sub.2).sub.m COO--, etc.
Alkyl alanines:
Conductive resin:
Polyvinylbenzyl cation, polyacrylic acid cation, etc.
Among them, nonionic antistatic agents are particularly preferred, because adverse affect upon photographic properties is small.
As the antistatic agent for the inside, i.e., when the antistatic agent is blended with a thermoplastic resin, whichever of nonionic antistatic agent, anionic antistatic agent or ampholytic antistatic agent. Effective nonionic antistatic agents
are ethylene oxide adducts of higher alcohol, ethylene oxide adducts of alkyl phenol, esters, such as esters of higher fatty acid and polyol, polyethylene glycol esters of higher fatty acid, polyethers, amides, such as higher fatty amides, dialkyl amides
and ethylene oxide adducts of higher fatty amide. Effective anionic antistatic agents are alkyl allylphosphonic acids, adipic acid, glutamic acid, alkyl sulfonic acid salts, alkyl sulfates, polyoxyethylene alkylphosphates, fatty acid salts, alkyl
benzene sulfonates, alkyl naphthalene sulfonates, and sodium dialkyl sulfosuccinates. As to a cationic antistatic agent, amines, such as alkyl amine phosphates, Schiff's base, amide amines, polyethylene imines, complexes of amide amine and metal salt
and alkyl esters of amino acid, imidazolines, amine-ethyleneoxide adducts and quaternary ammonium salts are suitable. As to ampholytic antistatic agent, N-acylsarcosinate, amino carboxylic acid esters, alanine metal salts, imidazoline metal salts,
carboxylic acid metal salts, dicarboxylic acid metal salts, diamine metal salts, metal salts having ethylene oxide groups, and the like are suitable. As to the other antistatic materials, inorganic electrolytes, metal powders, metal oxides, kaolin,
silicates, carbon powder and carbon fiber also exercise the effect of the invention. Besides, graft polymers and polymer blends are also effective.
As to the antistatic agent for the outside, nonionic antistatic agent includes polyols, such as glycerine, sorbitol, polyethylene glycol and polyethylene oxide, polyol esters, higher alcohol-ethylene oxide adducts, alkylphenol-ethylene oxide
adducts, fatty acid-ethylene oxide adducts, amides, amide-ethylene oxide adducts and amine-ethylene oxide adducts. Ampholytic antistatic agent includes carboxylic acids, such as alkylalanines, and sulfonic acids. As anionic antistatic agent, carboxylic
acid salts, sulfuric acid derivatives, such as alkyl sulfonates, phosphoric acid derivatives, such as phosphonic acid, phosphate esters, and polyester derivatives are suitable. As cationic antistatic agent, amines, such as alkylamines, amido amines and
ester amines, vinyl nitrogen derivatives, quaternary ammonium salts, such as ammonium salts containing amide group and ammonium salts containing ethylene oxide, acrylic acid ester derivatives, acrylic amide derivatives, vinyl ether derivatives, and the
like are suitable.
Lubricant applicable to the invention includes: Silicone oil lubricants: silicone oils containing modified
siloxane bond, such as dimethylpolysiloxanes and modified thereof (Shin-Etsu Chemical Co., Ltd., Toray Silicone Co., Ltd.), polymethylphenyl siloxanes, olefin-modified silicones, polyether-modified silicones modified with polyethylene glycol or
polypropylene glycol, olefin/polyether-modified silicones, epoxy-modified silicones, amino-modified silicones and alcohol-modified silicones. Among the above silicone oils, olefin-modified silicones, polyether-modified silicones,
olefin/polyether-modified silicones are excellent.
The silicone oil lubricant makes the basis to obtain a film having good appearance, high sealability and adhesiveness to the article to be packaged without loosening by improving friction coefficient of the film in heated conditions, resulting in
reducing sliding resistance generated during hot plate sealing by an automatic packaging machine and in preventing wrinkling. Besides, reduction of gloss sliding is prevented to obtain a good seal portion. By using the silicone oil lubricant, a high
temperature friction coefficient can be decreased to less than 1.4 during sliding heat sealing. A suitable viscosity is 50 to 100,000 centistokes at ordinary temperature, and a high viscosity lubricant having a viscosity of 5,000 to 30,000 centistokes
at ordinary temperature is preferred. A suitable content varies according to the object of use, and is in the range of 0.01 to 2.5 wt. %, preferably 0.03 to 1 wt. %, more preferably 0.05 to 0.5 wt. %.
The blending effects of the silicone oil lubricant are:
(1) Silicone oil lubricant coats the surface of fiber fillers, non-fiber light-shielding materials and pigments by blending, and improves their dispersibility.
(2) It improves the fluidity of resin resulting in the reduction of screw motor lead and in the prevention of melt fracture.
(3) Fatty amide lubricant, which is liable to bleed out and induces a white powder problem, can be omitted by blending it.
(4) It decreases friction coefficient of a film in heated conditions resulting in the improvement in automatic bag-making ability, in the prevention of wrinkling during heat sealing and of reducing gloss by sliding to obtain a good seal portion.
(5) Light-shielding ability of a light-shielding material is improved by blending together. As a result, the blending amount of the light-shielding material which degrades properties can be reduced.
Saturated fatty amide lubricants
Behenic amide lubricants: "DIAMID KN" (Nippon Kasei Chemical Co., Ltd.)
Stearic amide lubricants: "ARMIDE HT" (Lion), "ALFLOW S-10"(Nippon Oil and Fats Co., Ltd.), "FATTY AMIDE S" (Kao Corp.), "NEWTRON 2" (Nippon Fine Chemical Co., Ltd.), "DIAMID 200" and "DIAMID AP-1" (Nippon Kasei Chemical Co., Ltd.), "AMIDE S" and
"AMIDE T" (Nitto Kagaku K.K.), etc.
Unsaturated fatty amide lubricants
Erucic amide lubricants: "ALFLOW P-10" (Nippon Oil and Fats Co., Ltd.), "NEWTRON-S" (Nippon Fine Chemical Co., Ltd.), "LUBROL" (I.C.I.), "DIAMID L-200" (Nippon Kasei Chemical Co., Ltd.), etc.
Oleic amide lubricants: "ARMOSLIP-CP" (Lion Akzo Co., Ltd.), "NEWTRON" and "NEWTRON E-18" (Nippon Fine Chemical Co., Ltd.), "DIAMIDE O-200" (Nitto Kagaku K.K.), "DIAMID O-200" and "DIAMID G-200" (Nippon Kasei Chemical Co., Ltd.), "ALFLOW E-10"
(Nippon Oil and Fats Co., Ltd.), "FATTY AMIDE O" (Kao Corp.), etc.
Bis fatty amide lubricants
Methylene bis behenic amide lubricants: "DIAMID NK BIS" (Nippon Kasei Chemical Co., Ltd.), etc.
Methylene bis stearic amide lubricants: "DIAMID 200 BIS" (Nippon Kasei Chemical Co., Ltd.), "ARMOWAX" (Lion Akzo Co., Ltd.), "BISAMIDE" (Nitto Kagaku K.K.), etc.
Methylene bis oleic amide lubricants: "LUBRON O" (Nippon Kasei Chemical Co., Ltd.), etc.
Ethylene bis stearic amide lubricants: "ARMOSLIP EBS" (Lion Akzo Co., Ltd.), etc.
Hexamethylene bis stearic amide lubricants: "AMIDE 65" (Kawaken Fine Chemicals Co., Ltd.), etc.
Hexamethylene bis oleic amide lubricants; "AMIDE 60" (Kawaken Fine Chemicals Co., Ltd.), etc.
Monoalkylol amide lubricants
N-(2-Hydroxyethyl)lauric amide lubricants: "TOHOL N 130" (Toho Chemical Ind. Co., Ltd.), etc.
N-(2-Hydroxyethyl)stearic amide lubricants: "AMISOL" (Kawaken Fine Chemicals Co., Ltd.), etc.
N-(2-Hydroxymethyl)stearic amide lubricants: "METHYLOL AMIDE" (Nitto Kagaku K.K.), etc.
Nonionic surfactant lubricant | | |
