JPH0331347B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a polypropylene laminated film suitable for packaging as it has both excellent moisture resistance and heat sealability. [Prior Art] A laminated film having the following structure is known as a packaging film having moisture-proofing properties and heat-sealing properties. OPP/AC/PVDC/AC/CPP Here, OPP is usually a biaxially oriented polypropylene film, AC is an anchor coat, such as an adhesive, PVDC is polyvinylidene chloride, and CPP is is extrusion laminated polypropylene. That is, since the oriented polypropylene film and polyvinylidene chloride have poor adhesion, they are bonded together via an anchor coat, and the polyvinylidene chloride and extrusion laminated polypropylene are also bonded together via the anchor coat to form a laminated film. However, in such a laminated film,
To improve the water vapor transmission rate of OPP, OPP
Since PVDC is coated on top to a predetermined thickness, it is impossible to avoid an increase in manufacturing costs due to the complexity of the manufacturing process.
As the laminated film itself becomes yellow due to the use of layer and
There were drawbacks such as the risk of a decrease in interlayer adhesion with the PVDC layer. [Object of the Invention] The present invention has been made to solve the above-mentioned conventional drawbacks, and has excellent moisture proofing and heat sealing properties, can be manufactured at low cost, is colorless and transparent, has excellent interlayer adhesion, and has excellent packaging properties. The purpose is to provide a laminated film suitable for various uses. [Structure of the Invention] The present invention achieves the above object by using polypropylene.
A film () in which 100 parts by weight is mixed with 5 to 100 parts by weight of one or more resins selected from petroleum resins that do not substantially contain polar groups and terpene resins that do not substantially contain polar groups. At least one side is laminated with a film () with a thickness of 1 to 6 μm made of polypropylene mixed with 100 parts by weight of polypropylene and less than 3 parts by weight of one or more of the above resins, and has a glass transition temperature of 10 to 50°C. of the base film,
The thickness of the polypropylene film () layer is 10~
It is characterized by being extruded and laminated with 50μm polypropylene. The polypropylene used for the film layer () in the present invention is not particularly limited, but has an isotactic index () of 93%.
The above is the intrinsic viscosity [η] measured in tetralin.
is preferably in the range of 0.8 to 4 (dl/g), particularly 1.0 to 2.2 (dl/g). A second component other than propylene, such as ethylene,
Random, block or graft copolymerization of butene, hexene, maleic anhydride, etc. may be used, but homopolymers are preferred from the perspective of the present invention. Note that polypropylene can also contain known additives, such as crystal nucleating agents, antioxidants, heat stabilizers, slip agents, antistatic agents, blocking agents, filler viscosity modifiers, and color inhibitors. . The petroleum resin that is mixed with such polypropylene and is substantially free of polar groups includes hydroxyl groups (-OH),
Carboxyl group (-COOH), halogen group (-
X), sulfone group (-SO ₃ Y, Y is H, Na, 1/
2Mg, etc.) and their modified products, which are substantially free of polar groups, i.e., cyclopentadiene-based directly from petroleum-based unsaturated hydrocarbons, or higher olefin-based hydrocarbons as main raw materials. It is a resin that Furthermore, the glass transition temperature Tg of the petroleum resin that does not substantially contain polar groups is 50°C or higher, preferably
A temperature of 76°C or higher is desirable for the laminated film of the present invention. Furthermore, a hydrogenated petroleum resin in which hydrogen is added to such petroleum resin so that the hydrogenation rate is 80% or more, preferably 95% or more is particularly desirable for the laminated film of the present invention. For example, Tg76 is a typical hydrogen petroleum resin.
High Tg fully hydrogenated alicyclic petroleum resins such as polydicyclopentadiene with a hydrogenation rate of 95% or more at temperatures above ℃ can be mentioned. Terpene resins that do not substantially contain polar groups include hydroxyl groups, aldehyde groups (-CHO), ketone groups (>C=O), carboxyl groups, halogen groups,
Terpene resins are substantially free of polar groups such as sulfone groups and modified products thereof, that is, hydrocarbons having a composition of (C ₅ H ₈ )n and modified compounds derived therefrom. n is a natural number of about 2 to 20. Terpene resins are also called terpenoids, and representative compounds include pinene, dipentene, carene, myrcene, ocimene,
Limonene, terpinolene, terpinene, sabinene, tricyclene, bisabolene, zingiperene,
There are santalene, campholene, mylene, totalene, etc. In the case of the laminated film of the present invention, it is desirable to add hydrogen to make the hydrogen percentage 80% or more, preferably 90% or more. In particular, β-pinene, hydrogen β −
Pinene, hydrogenated β-dipentene, etc. are preferred. Thus, the use of hydrogenated petroleum resins that are substantially free of polar groups and/or hydrogenated terpene resins that are substantially free of polar groups is important in the case of the present invention; 10 or less, preferably 5 or less, more preferably 1 or less. The film () in the present invention includes 100 parts by weight of the polypropylene and one or more resins selected from petroleum resins that do not substantially contain polar groups and terpene resins that do not substantially contain polar groups. is mixed in an amount of 5 to 100 parts by weight, preferably 10 to 29 parts by weight, and the glass transition temperature of this film is 10 to 50°C, preferably 20 to 40°C. The mixing amount of the above resin that does not substantially contain polar groups is
If the amount exceeds 100 parts by weight, preferably 29 parts by weight, not only will the mechanical, thermal, and chemical properties of the laminated film of the present invention deteriorate, but the resin will bleed out onto the surface of the film layer, causing the resin to bleed out onto the surface of the film layer. 1
Not only does the adhesion of the polypropylene extruded and laminated onto the film () decrease through the polypropylene film () layer containing less than 3 parts by weight of the above species, but also the transparency and appearance of the laminated film are deteriorated. let Furthermore, film () has increased permeability to oils such as vegetable oil and mineral oil, making film () or ()
This causes disadvantages such as oil seeping onto the surface and printing ink on the film surface eluting, resulting in poor appearance. Further, the mixing amount of the above resin is 5 parts by weight,
Preferably, if the amount is less than 10 parts by weight, the moisture resistance will hardly improve regardless of the glass transition temperature Tg. As described above, the effects of the present invention are particularly significant when the amount of the resin added is as small as 10 to 29 parts by weight. Furthermore, when the Tg value is less than 10°C, the water vapor permeability of the laminated film of the present invention is 3.5 (g/m ² ·
day/sheet) or less, preferably 2 to 3.5 (g/m ²
(day/sheet), and no improvement in mechanical properties was observed. On the other hand, if the Tg value exceeds 50°C, the mechanical properties of the laminated film of the present invention will be significantly inferior. In the present invention, the molecular chains in such a film () may or may not be oriented, but it is possible to increase the Tg by reducing the amount added,
Furthermore, from the viewpoint of mechanical properties, optical properties, thermal properties, etc., it is preferable that the molecular chains are oriented. In particular, the film is biaxial and balanced on the inner surface of the film, that is, the absolute value of birefringence (N) is 0.025 or less, preferably 0.015 or less. Also, the difference (D) between 1/2 of the sum of the refractive index in the vertical direction and the refractive index in the horizontal direction, which is a guideline for film surface orientation, and the refractive index in the thickness direction is
A value in the range of 0.006 to 0.012 is preferable in terms of cleavage of the film surface layer and oil resistance. Furthermore, the range of N and D of the film () is as follows:
Preferably, it is similar to film (). In addition, the polypropylene layer laminated on the film () has N of 0.002 or less and D of
It is preferably 0.001 or less. Further, it is desirable that the crystallinity of the base film is 50% or more, preferably 60% or more, and the base film has a thickness of 4 to 1000 μm, preferably 4 to 250 μm,
More preferably, the thickness is in the range of 8 to 60 μm. The film () in the present invention is made by mixing polypropylene with one or more petroleum resins that do not substantially contain polar groups or terpene resins that do not substantially contain polar groups, as described above. When other resins are added to the resin, the amount is preferably less than 30 parts, preferably less than 20 parts.
Examples of other resins include polyolefins other than polypropylene, petroleum resins containing polar groups, and terpene resins containing polar groups. In the present invention, polypropylene mixed with less than 3 parts by weight of one or more of the above resins is laminated to a thickness of 1 to 6 μm on one side of the film. Here, as the polypropylene in which less than 3 parts by weight of one or more of the above resins are mixed, the above polypropylene is used, and only polypropylene is used at the lower limit of the resin mixing amount. If the amount of the resin mixed exceeds 3 parts by weight, the adhesive strength between the polypropylene extruded and laminated on the polypropylene (2) layer and the polypropylene film (2) decreases, as will be described later, and the polypropylene becomes an adhesive. It becomes difficult to extrude and laminate without such anchors. Additionally, if the thickness of polypropylene containing less than 3 parts by weight of one or more of the above resins is less than 1 μm, the adhesive force between the extrusion laminated polypropylene and the polypropylene film () layer will decrease, and the polypropylene The now anchoring properties of extruded laminates are reduced. On the other hand, if the thickness exceeds 6 μm, the moisture resistance of the laminated film of the present invention deteriorates when compared with the same thickness. In the present invention, this polypropylene layer is printed or subjected to corona discharge treatment or plasma treatment in the presence of carbon dioxide gas or nitrogen gas in an atmosphere substantially free of oxygen to form a layer up to 100 Å from the surface. Imino-type and/or amino-type nitrogen atoms can be introduced into the extreme surface layer of the material. The amount of imino-type and/or amino-type nitrogen atoms introduced is usually 2 or more imino-type and/or amino-type nitrogen atoms per 100 carbon atoms in the surface layer up to 100 Å from the surface. A typical method for this surface treatment is to use a mixed gas of essentially nitrogen and carbon dioxide (N ₂ /CO ₂
= 100/0 to 50/50 volume ratio) Corona discharge treatment is performed in an atmosphere with an oxygen concentration of 0.1 vol% or less. Alternatively, by putting various gases into a plasma state,
There are methods of chemically modifying the film surface, such as Japanese Patent Application Laid-Open No. 59-98140. Such surface treatment can increase the adhesive strength between the polypropylene extruded laminate film and the polypropylene film (2), which will be described later, and can improve moisture resistance. Furthermore, the present invention is characterized in that polypropylene is extruded and laminated on a polypropylene layer containing at least one or more of the above resins in an amount of less than 3 parts by weight. This polypropylene extrusion laminate is
The intervening polypropylene ( ) layer has good adhesion with the film ( ) layer, and provides the laminated film of the present invention with excellent transparency and good high-temperature heat resistance after heat sealing. The thickness of such extruded polypropylene laminates is typically 10-50 μm, preferably 15-50 μm.
35 μm, and this thickness is preferably 10 μm.
If the thickness is less than 15 μm, the heat sealability, moisture proofing property, and oil resistance to prevent oil from seeping out during packaging of oily goods will decrease; on the other hand, the thickness is 50 μm, preferably 35 μm.
If it exceeds this amount, the hardness and opacity of the laminated film of the present invention will increase, and the moisture resistance will deteriorate. The polypropylene extruded and laminated here forms the surface layer of the laminated film of the present invention, and usually has a melt index (MI) of 20.
~100g/10min, melting point Tm = 140~160°C. Of course, if the resin to be laminated is polyethylene, it not only has poor adhesion to the film layer, but also poor transparency and high temperature resistance after heat sealing, which does not meet the purpose of the present invention. Next, a method for manufacturing the laminated film of the present invention will be explained. First, a raw material prepared by adding 5 to 100 parts by weight of a specific petroleum resin or terpene resin to 100 parts by weight of polypropylene is fed into an extruder ().
A raw material in which less than 3 parts by weight of one or more of the above resins is mixed with 100 parts by weight is fed to an extruder (), and the resin temperature is set at a temperature not exceeding 240°C, preferably 180 to 220°C.
After melting and uniformly mixing at the maximum temperature of ℃, each melt is discharged from a composite nozzle ()/()/() and cast onto a cooling drum to form a 3-layer laminated unstretched film. can get. At this time, if the resin temperature exceeds 240° C., preferably 220° C., not only will it not be possible to obtain a laminated film with excellent properties as the object of the present invention, but the resin will thermally decompose or scatter. The surface temperature of the cooling drum also changes depending on the next process, but is preferably 60 to 120 degrees Celsius, preferably 95 to 110 degrees Celsius.
A temperature range of ℃ is good. Subsequently, a three-layer laminated film can be obtained by uniaxially, biaxially, or multiaxially oriented the cast film, or by heat-treating the film to bring the Tg within a specific range. In this case, the method for imparting orientation may be any known method, such as roll stretching, rolling, tenter stretching,
Disc stretching, belt stretching, combinations thereof, and the like can be used. At this time, it is necessary to orient so that the Tg value falls within the above specific range. For example, in the case of sequential biaxial stretching, the initial longitudinal stretching ratio is about 6 to 10 times, and the transverse stretching ratio is about 6 to 12 times. good. Next, polypropylene is extruded and laminated onto at least this polypropylene layer of the three-layer laminated film to obtain the laminated film of the present invention. [Effects of the Invention] The laminated film of the present invention is made by mixing polypropylene and a specific resin as described above, and has a glass transition temperature Tg of 10 to 50°C, which is lower than that of ordinary polypropylene.
On one side of the film (), which is very high compared to
Since polypropylene () mixed with less than 3 parts by weight of a specific resin is laminated, and polypropylene is extruded and laminated on this polypropylene () layer, the following effects can be achieved. (1) Water vapor permeability is 2 to 4 (g/ ^m2・
day/sheet). In particular, the moisture resistance can be further improved by subjecting the surface of the film layer to a corona discharge treatment and introducing imino-type or amino-type nitrogen atoms. Therefore, the laminated film of the present invention can be used for packaging,
It is particularly suitable for packaging foods, medicines, etc. (2) Since the laminated film of the present invention is transparent, the contents of the package can be clearly seen, and it is particularly suitable for packaging colorless or white items. (3) In the present invention, the surface layer is extruded and laminated with polypropylene, so the high temperature heat resistance after heat sealing is extremely excellent.Therefore, according to the present invention, the product has excellent moisture resistance and heat sealability. A laminated film is provided. (4) Since the polypropylene is extruded and laminated onto the film ( ) via polypropylene mixed with less than 3 parts by weight of one or more of the above resins, strong interlayer adhesion is exhibited, and a separate anchor coat, e.g. Does not require adhesive. (5) As mentioned above, the laminated film of the present invention exhibits strong interlayer adhesion, so there is no peeling between the layers of the laminated film, improving reliability when used for packaging purposes. can. In addition, the definition of terms used in the present invention and the measurement method will be described. (1) Water vapor transmission rate Measured at 40°C and 90% RH according to JIS Z-0208, and expressed in g/m ² ·day/sheet. (2) Intrinsic viscosity [η] Measured in tetralin according to ASTM D1601 and expressed in dl/g. (3) Isotactic index () Cut the sample film into approximately 1 cm square pieces, place them in a Soxhlet extractor, and extract with boiling methyl alcohol for 6 hours. Vacuum dry the extracted sample at 60°C for 6 hours Take a sample of weight W (mg) and boil it
- Extract with heptane for 6 hours. Next, take out this sample, wash it thoroughly with acetone, and then
After vacuum drying at 60°C for 6 hours, the weight is measured. If this weight is W' (mg), the isotactic index can be calculated using the following formula. Isotactic index (%) = 100 x W'/W (4) Glass transition temperature (Tg), melting point (Tm) 10 mg of the sample was set in a scanning calorimeter DSC-type (manufactured by PerKin Elmer), and Start a thermograph from -20℃ under an air flow at a heating rate of 40℃/min, and take the arithmetic mean value of the temperature at which the endothermic peak deviates from the baseline and the temperature at which it returns to Tg. do. When the temperature is further increased, the endothermic peak temperature accompanied by the melting angle of the crystal is defined as Tm. Of course, even if the sample is a composite film, the measurement can be performed using this method, and the main peaks are adopted as Tg and Tm, respectively. (5) Bromine number Measured according to JIS K-2543-1979. It is expressed as the number of grams of bromine added to unsaturated components in 100 grams of sample oil. (6) Refractive index Using Abbe's refractometer, using Na-D rays as the light source and methyl salicylate as the mounting liquid, change the direction of the polarizing plate in the eyepiece and measure the refractive index N in a specific direction using the total internal reflection method. did. (7) Imino-type and/or amino-type nitrogen atoms are directly bonded to carbon atoms of the polypropylene polymer chain, and the amount thereof was measured using the ESCA method. ESCA is an abbreviation for soft X-ray excitation photoelectric spectroscopy, which detects elements near the surface of a sample from the spectrum of photoelectrons ejected from atoms in sample compounds by irradiation with difficult X-rays. This is a method to analyze the type and chemical bond state. In the ESCA method, the ability of photoelectrons to pass through hydrocarbon polymer materials is small;
Measurement by ESCA is performed within 100 Å from the surface.
In particular, it has the characteristic that relatively strong information on the extreme surface area can be obtained. The amino-type and/or imino-type nitrogen referred to in the present invention is a bonded nitrogen identified by the ESCA method, and is the 1S orbital (N ₁ s) The binding energy of the spectrum is 397.0 ~
It has a peak in the range of 402.5 eV (however, the main peak of Cis in polypropylene is 28.5 eV) (hereinafter simply referred to as amino-type and/or imino-type nitrogen). Specifically, an ESCA spectrometer ES-200 manufactured by Kokusai Denki Co., Ltd. was used to measure the N ₁ S spectrum and C ₁ s spectrum of the treated surface of the treated _film . The ratio of the integrated intensity of the peak corresponding to the binding energy of amino-type and/or imino-type nitrogen in the spectrum and the integrated intensity of the C ₁ s spectrum was calculated. (8) The adhesion strength is approximately 1 x 10 ^-4 mm when AI is applied to the film to a thickness of approximately 600 Å using a Bergier type high vacuum evaporation device.
Vapor deposition is performed in a vacuum of Hg, and then a cellophane adhesive tape (using "Cello Tape" manufactured by Nichiban) is attached to the vapor-deposited surface, the cellophane tape is rapidly peeled off, and the peeling state of the A1 vapor-deposited film is evaluated. ◎: Peeling area of A-deposited film is 95% or more ○: 〃 90 to less than 95% △: 〃 50 to less than 90% ×: 〃 Less than 50% (9) Melt index (MI) is ASTM
Measurement was carried out in accordance with D1238-73 under the condition of a load of 2 kg. [Examples] Examples of the present invention will be described below. Examples 1 and 2, Comparative Example 1 As the polypropylene, Mitsui "Noprene" JS1429 manufactured by Mitsui Toatsu Co., Ltd. (measured intrinsic viscosity in tetralin [η] = 2.25 dl/g, isotactic index = 98%) ), and as a specific hydrogenated petroleum resin, "Escoretsu" 5320, which is mainly composed of non-polar polydicyclotadiene manufactured by Etsuso Chemical Co., Ltd.
(bromine value 0.1% or less) was used. 100 parts by weight of this polypropylene resin was uniformly blended with 25 parts by weight of "ESCOLETS" 5320 (), which was then fed into an extruder and melted at a melting temperature of 220°C. ) made by Mitsui “Noprene” J4H ([η] = 1.4,
=94%) feed the raw material () to another extruder,
After melting at 200°C and coextruding into a three-layer structure consisting of ()/()/(), the mixture was cast onto a casting drum kept at 85°C to obtain a three-layer laminated non-stretched film. This film was immediately introduced into a hot-air oven-heated longitudinal stretching roll maintained at 135°C, stretched 7 times in the longitudinal direction, and then stretched 10 times in the transverse direction in a tenter heated to 158°C. ℃ for 10 seconds,
After heat treatment while allowing 5% relaxation in the lateral direction, corona discharge treatment was performed to give a thickness of 20μm (1.5/17/
A three-layer laminated film with a thickness of 1.5 μm) was obtained. The Tg of the obtained film was 30°C. On this three-layer laminated film, a sheet of ethylene-propylene copolymer (4 mol% ethylene copolymer, melt index 40 at 230°C, melting point 145°C) heated and melted at 280°C is extruded to a thickness of 25 μm. It was laminated (Example 1). Further, a laminate film was obtained in exactly the same manner as in Example 1 except that the corona discharge treatment was not performed after the heat treatment (Example 2). As a comparative example, a laminate film was obtained in exactly the same manner as in Example 1, except that low polymerized polyethylene (melt index MI = 7 at 190°C, melting point 121°C) was used as the extrusion laminated polymer. The properties of the films thus obtained are shown in the following table for comparison.

[Table] However, the ◎ and ○ marks indicate good adhesion and do not peel off, and the × marks indicate poor adhesion and easy peeling. As described above, when the polymer used for extrusion lamination is polyethylene, it is not only not as transparent as polypropylene, but also cannot be bonded to the base film by non-anchor treatment.

Claims (1)

[Claims] 1 A film in which 100 parts by weight of polypropylene is mixed with 5 to 100 parts by weight of one or more resins selected from petroleum resins that do not substantially contain polar groups and terpene resins that do not substantially contain polar groups ( ) is laminated with a 1-6 μm thick film ( ) made of polypropylene mixed with 100 parts by weight of polypropylene and less than 3 parts by weight of one or more of the above resins, and has a glass transition temperature of 10-50°C.
1. A polypropylene laminated film characterized in that a polypropylene film having a thickness of 10 to 50 μm is extruded and laminated on the polypropylene film ( ) layer of a base film.