JPS61227048A - Polypropylene laminated film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a material having both excellent moisture resistance and heat sealability.
This invention relates to a polypropylene laminated film suitable for packaging.

[Prior art]

A laminated film having the following structure is known as a packaging film having moisture resistance and heat sealability.

OPP/AC/PVDC/AC/CPP where OPP
is usually a two-wheel oriented polypropylene film, AC is an anchor coat, e.g. adhesive,
PVDC is polyvinylidene chloride and CPP 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, in order to improve the water vapor permeability of OPP, PVDC is coated on the OF2 to a predetermined thickness, thereby avoiding an increase in manufacturing costs due to complication of the manufacturing process. Moreover, the use of PVDC causes the laminated film itself to turn yellow, making it impossible to obtain clear transparency.
Therefore, the usage of packaging materials is limited, and depending on the type of anchor coat, OPP layer and PVDC layer, CPP layer and P
There were drawbacks such as a risk that the interlayer adhesive strength with the VDC layer would decrease.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned conventional drawbacks, and is a laminated layer that has excellent moisture resistance and heat sealability, can be manufactured at low cost, is colorless and transparent, has excellent glabella adhesive strength, and is suitable for packaging applications. The purpose is to provide films.

[Structure of the invention]

The present invention achieves the above object by adding 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 to 100 parts by weight of polypropylene. Part mixed film (I)
A film (II) 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 is laminated on at least one side of the film, and has a glass transition temperature of 10 to 50°C. At least the polypropylene film (II)
A laminated film in which polypropylene with a thickness of 10 to 50 μm is extruded and laminated on the layer is characterized by a water vapor permeability of 3.5 (g/m 2 days/20 μm) or less.

The polypropylene used for the film layer (I) in the present invention is not particularly limited, but has an isotactic index (II) of 93% or more and an intrinsic viscosity [η] measured in tetralin of 0. 8-4 (di
/g), particularly preferably in the range of 1.0 to 2.2 (dl/g).

A second component other than propylene, such as ethylene, butene,
Random, block or graft copolymerization of hexene, maleic anhydride, etc. may be used, but a homopolymer is preferable in view of the gist of the present invention.

Note that polypropylene contains known additives such as crystal nucleating agents, antioxidants, heat stabilizers, slip agents, antistatic agents,
It is also possible to contain an antiblocking agent, a filler, a viscosity modifier, an anticoloring agent, and the like.

The petroleum resin that is mixed into polypropylene and is substantially free of polar groups includes hydroxyl group (-0H), carboxyl group (-COOH), halogen group (-X), sulfone group (-5o3YSY is HlNa, 1/2Mg etc.) and their modified products, etc. Petroleum resins that do not substantially have polar groups, i.e., cyclopentadiene-based directly from petroleum-based unsaturated hydrocarbons, or higher olefin-based hydrocarbons are the main raw materials. It is resin.

Further, it is desirable for the laminated film of the present invention that the petroleum resin substantially free of such polar groups has a glass transition temperature Tg of 50° C. or higher, preferably 76° C. or higher.

Further, 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.

A typical example of the hydrogenated petroleum resin is a high Tg fully hydrogenated alicyclic petroleum resin such as polydicyclopentadiene, which has a hydrogenation rate of 95% or more at 7g or higher at 76°C.

Terpene resins that do not substantially contain polar groups include hydroxyl groups, aldehyde groups (-CHO), ketone groups (>C-0
), carboxyl group, halogen group, sulfone group, etc.
and terpene resins substantially free of polar groups, such as modified products thereof, ie, carbide ureas having the composition (Cy Hg )n, and modified compounds derived therefrom.

n is a natural number of about 2 to 20.

Terpene resins are sometimes called terpenoids, and representative compounds include pinene, dibenentene, carene, myrcene, ocimene, limonene, tervirune, terpinene, sabinene, tricyclene, bisabolene,
There are zingyperene, santarene, campholene, mylene, totalene, etc. In the case of the laminated film of the present invention, it is desirable to add hydrogen to make the hydrogenation rate 80% or more, preferably 90% or more. , hydrogenated β-pinene, hydrogenated β-dipentene, and the like are preferred.

Thus, the use of hydrogenated petroleum resins substantially free of polar groups and/or hydrogenated terpene resins substantially free of polar groups is important for the present invention, with a bromine number of 10 The number below is preferably 5 or less, more preferably 1 or less.

The film (I) of the present invention includes 100 parts by weight of the polypropylene and one or more resins selected from the petroleum resins that do not substantially contain polar groups and the terpene resins that do not substantially contain polar groups. The film contains 5 to 100 parts by weight, preferably 10 to 29 parts by weight, and has a glass transition temperature of 10 to 20°C to 40°C.

If the mixing amount of the above-mentioned resin that does not substantially contain polar groups exceeds 100 parts by weight, preferably 29 parts by weight, not only the mechanical, thermal and chemical properties of the laminated film of the present invention deteriorate, but also the above-mentioned The resin bleeds out onto the surface of the film (I) layer, and one or more of the above resins is mixed in less than 3 parts by weight of a polypropylene film (n) [through which the film (I) is formed.
Not only does the adhesive strength of the polypropylene extrusion laminated thereon decrease, but also the transparency of the laminated film of the present invention decreases.
Deteriorate appearance.

Furthermore, film (I) has increased permeability to oils such as vegetable oil and mineral oil, causing oil to seep onto the surface of film (I) or (II) or eluting printing ink from the surface of the film, resulting in poor appearance. This results in disadvantages such as: Furthermore, if the amount of the resin mixed is less than 5 parts by weight, preferably 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.

Further, when the Tg value is less than 10°C, the water vapor permeability of the laminated film of the present invention is 3.5 or less, preferably 2 to 2.
3.5, 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 the film (I) may or may not be oriented, but it is possible to increase the Tg by reducing the amount added, and further improve mechanical properties.
From the viewpoint of 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 (N) of birefringence is 0.025 or less, preferably 0.015 or less.
In addition, the difference (D) between the refractive index in the thickness direction and 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, is in the range of 0.006 to 0.012. is preferable in terms of the creases on the surface layer of the film, oil resistance, etc.

Note that the ranges of N and D in film (n) are preferably the same as in film (I).

In addition, the polypropylene layer laminated on the film (]II has an N content of 0.002 or less and a D content of 0.001
It is preferable that it is below.

Further, it is desirable that the crystallinity of the base film is 50% or more, preferably 60% or more, and the base film thickness is 0.
．． A thickness in the range of 5 to 1000 μm, preferably 4 to 250 μm, and more preferably 8 to 60 μm is desirable.

The film (I) 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. If other resins are added to the resin, the amount should be 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 the negative side of the film (I).

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 (II) layer and the polypropylene film (n) layer will decrease, as will be described later. It becomes difficult to extrude and laminate without an anchor such as adhesive.

Furthermore, 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 (n) layer will decrease, and the same problem will occur. The now-anchoring properties of polypropylene extrusion laminates are reduced.

On the other hand, when the thickness exceeds 6 μm, the moisture resistance of the laminated film of the present invention deteriorates when compared at the same thickness.

In addition, in the present invention, printing is performed on this polypropylene (n) layer, or in the presence of carbon dioxide gas or nitrogen gas,
Imino-type and/or amino-type nitrogen atoms can be introduced from the surface to the extreme surface layer of up to 100 layers by corona discharge treatment or plasma treatment in a substantially oxygen-free atmosphere.

The amount of imino-type and/or amino-type nitrogen atoms introduced is usually 1 carbon atom in the surface layer up to 100% from the surface.
00 liimino and/or amino type nitrogen atoms 2
It is more than fl1.

Typical methods for this surface treatment include, for example,
-30.854, etc., a mixed gas of essentially nitrogen and carbon dioxide (N2/COx = 100
/0 to 50150 volume ratio) corona discharge treatment in an atmosphere with an oxygen concentration of 0.1 vol% or less.

Alternatively, a method of chemically modifying the film surface by placing various gases in a plasma state, for example, JP-A-59-98.
140 etc.

Through this surface treatment, polypropylene extrusion laminate film and polypropylene film (I
The adhesive strength with I) can be increased, and the moisture resistance can be improved.

Furthermore, in the present invention, polypropylene is extruded and laminated onto a polypropylene (If) layer containing at least one or more of the above resins in an amount of less than 3 parts by weight, and the resulting laminated film has a water vapor permeability of 3.5 ( g/m2day 720 μm) or less.

This polypropylene extrusion laminate forms a film (I) with an intervening polypropylene (If) layer.
The laminated film of the present invention has good adhesion with the layers, and has excellent transparency and good high-temperature heat resistance after heat sealing.

The thickness of such a polypropylene extrusion laminate is
Normally, the thickness is 10 to 50 μm, preferably 15 to 35 μm, and if the thickness is less than 10 μm, preferably 15 μm, heat sealing properties, moisture proofing properties, and oil resistance to prevent oil from seeping out when packaging curved items are impaired. while the thickness is 5
If the thickness exceeds 0 μm, preferably 35 μm, the hardness and opacity of the laminated film of the present invention will increase, and the moisture resistance will deteriorate.

The polypropylene to be 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 to 100 g/10 minutes and a melting point Tm of 140 to 160°C.

Of course, if the resin to be laminated is polyethylene,
It does not meet the purpose of the present invention because it not only has poor adhesion to the film (If) layer, but also poor transparency and high temperature resistance after heat sealing.

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 (I), and on the other hand, less than 3 parts by weight of one or more of the above resins is mixed into 100 parts by weight of polypropylene. The raw materials are fed to an extruder (n), melted and uniformly mixed at a resin temperature not exceeding 240°C, preferably a maximum temperature of 180 to 220°C, and each melt is (■) / ( f)
/(■) from a composite nozzle and cast onto a cooling drum to obtain a three-layer laminated non-stretched film.

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 the excellent properties aimed at by the present invention, but the resin will thermally decompose or scatter.

Further, the surface temperature of the cooling drum varies depending on the next step, but it is preferably in the range of 60 to 120°C, preferably 95 to 110°C.

Subsequently, a three-layer laminate film can be obtained by uniaxially, biaxially, or multiaxially oriented the cast film, or heat-treated 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, disk stretching,
Belt stretching, combinations thereof, etc. can be used.

At this time, it is necessary to orient so that the Tg value falls within the above-mentioned specific range. For example, in the case of sequential biaxial stretching, the initial longitudinal stretching ratio is preferably 6 to 10 times, and the transverse stretching ratio is preferably about 6 to 12 times. .

Next, polypropylene is extruded and laminated onto at least the polypropylene (II) layer of the three-layer laminate film to obtain the laminate film of the present invention.

〔Effect 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.
Polypropylene (n) mixed with less than 3 parts by weight of a specific resin is laminated on the - side of film (I), which has a T of ~50°C, which is very high compared to ordinary polypropylene. ) layer is extruded and laminated with polypropylene, and the water vapor permeability is 3.5 (g/n 187208 m) or less, so it can produce the following effects.

(I) Water vapor transmission rate is 2 to 4 (g/nf day 7), which is the practical requirement.
20 μm).

In particular, the moisture resistance can be further improved by subjecting the surface of the film (II) 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 purposes, especially for food products.
Suitable for packaging 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 preferable for packaging colorless or white items.

(3) In the present invention, since the surface layer is extruded and laminated with polypropylene, the high temperature heat resistance after heat sealing is extremely excellent.

Therefore, according to the present invention, a laminated film having excellent moisture resistance and heat sealability is provided.

(4) Since polypropylene is extruded and laminated to the film (I) 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, For example, no adhesive is required.

(5) As mentioned above, the laminated film of the present invention exhibits strong interlayer adhesion, so the laminated film does not peel between the eyebrows (and improves reliability when used for packaging). I can do it.

In addition, definitions of terms used in the present invention and measurement methods will be described.

(I) Water vapor transmission rate Measured at 40°C and 90$RH according to JIS Z-0208, and expressed as gird day/day film thickness.

(2) Intrinsic viscosity [η] ^Measured in tetralin according to STM 01601,
Expressed in di/g.

(3) Cut the film of the isotactic index (r I) sample into approximately 1 cm square pieces, place them in a Soxhlet extractor, and extract with boiling methyl alcohol for 6 hours.

The extracted sample is vacuum dried at 60°C for 6 hours.

A sample of weight W (+wg) is taken from this and extracted with boiling n-hebutane for 6 hours. Next, this sample is taken out, washed thoroughly with acetone, dried under vacuum at 60° C. for 6 hours, and then weighed.

If this weight is W' (mg), the isotactic index is calculated by the following formula.

Isotactic index (χ) = 10OXW' /W (4) Glass transition temperature (Tg), melting point (Tm) Sample 10a+g was measured using a scanning calorimeter DSC-■ type (Perk
inE1tser), start from -20°C under a nitrogen flow at a heating rate of 40°C/min, have the students draw a thermograph, and calculate the temperature at which the endothermic peak deviates from the baseline and the temperature at which it returns. The average temperature is defined as Tg.

When the temperature is further increased, the endothermic peak temperature associated with the axis angle of the crystal is defined as Tm.

Of course, even if the sample is a composite film, it may be measured 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) Using a refracting needle with a refractive index Abhe, using Na-D rays as a light source, using methyl salicylate as a mounting liquid, and changing the direction of the polarizing plate of the eyepiece, measure the refractive index N in a specific direction by the total internal reflection method. did.

(7) The imino type and/or amino type nitrogen atom is directly bonded to the carbon atom 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 the types of elements and chemical bonds near the surface of a sample from the spectra of photoelectrons ejected from atoms in sample compounds by soft X-ray irradiation. It is a method of analyzing the state.

In the ESCA method, photoelectron penetration ability is small for hydrocarbon polymer materials, and ESCA measurement of these polymer materials has the characteristic that relatively strong information can be obtained from within 100 layers of the surface, especially in the extreme surface layer. has.

The amino-type and/or imino-type nitrogen referred to in the present invention is a bonded nitrogen identified by ESCA, and is the Is orbital (N is) of the bonded nitrogen measured by ESCA, which is representative of amino groups and imino groups. The binding energy of the fvector is in the range of 397.0 to 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, using an ESCA spectrometer model B5-200 manufactured by Kokusai Denki Co., Ltd., the Nis spectrum and C4s spectrum of the treated surface of the treated film were measured.
The integrated intensity of the peak corresponding to the binding energy of amino-type and/or imino-type nitrogen in the s spectrum, and the C
The ratio i of the integrated intensity of the is spectrum was calculated.

(8) Adhesive strength is determined by depositing A1 on the film to a thickness of about 600 using a belljar type high vacuum evaporation device at a vacuum level of approximately 1 x 10 mmHg, and then applying cellophane adhesive tape to the deposition surface using Chiban Co., Ltd.'s adhesive tape. Cellophane tape (using cellophane tape) is attached, the cellophane tape is rapidly peeled off, and the state of peeling of the AI vapor-deposited film is evaluated.

0: Peeling area of A1 vapor deposited film is 90% or more △:'〃50~
Less than 90%
Measurement was carried out under the condition of a load of 2 kg in accordance with MD1238-73.

〔Example〕

Examples of the present invention will be described below.

Example 1, Comparative Example 1 As polypropylene, Mitsui "Noprene" JS1429 manufactured by Mitsui Toatsu ■ (limiting viscosity measured in tetralin)
η) = 2.25 dl/g, isotactic index II = 98 Value 0.1
% or less) was used.

Raw material (I), which is a uniform blend of 25 parts by weight of "Escolettes" 5320 wt. to 100 parts by weight of this polypropylene resin, is supplied to an extruder and melted at a melting temperature of 220 ° C.
On the other hand, as polypropylene, Mitsui “Noprene” J4H ((η) −1,4, II= also manufactured by Mitsui Toatsu Co., Ltd.
94%) raw material (If) is fed to another extruder and heated at 200°C.
The mixture was melted and coextruded into three layers consisting of (II)/(T)/(If), and then cast onto a casting drum kept at 85°C to obtain a three-layer laminated unstretched film.

This film was immediately introduced into a hot-air oven-heated longitudinal stretching roll kept 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. C. for 10 seconds while allowing 5% relaxation in the lateral direction, followed by corona discharge treatment to obtain a three-layer laminate film with a thickness of 20 μm (I, 5/17/1.5 μm).

The Tg of the obtained film was 30°C.

On this three-layer laminated film, an ethylene-propylene copolymer heated and melted at 280°C (ethylene copolymerization amount: 4 mol%, melt index at 230°C of 40, melting point of 14
(5°C) sheets were extrusion laminated to a thickness of 25 μm.

As a comparative example, low polymerized polyethylene (melt index M at 90°C) was used as a polymer for extrusion lamination.
A laminate film was obtained in exactly the same manner as in Example 1, except that I=7, melting point 121°C) was used.

The properties of the films thus obtained are shown in the following table for comparison.

In the table, the mark 0 indicates that the adhesive property is good and does not peel off, and the mark X indicates that the adhesive property is poor and that it peels off easily.

As described above, when the polymer used in the extrusion laminate 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] A film (I) 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. At least one side is made of polypropylene in which less than 3 parts by weight of one or more of the above resins are mixed with 100 parts by weight of polypropylene, and has a thickness of 1 to 6 μm.
film (II) with a glass transition temperature of 10
In a laminated film in which polypropylene with a thickness of 10 to 50 μm is extruded and laminated on at least the polypropylene film (II) layer to a base film at ~50°C, the water vapor permeability is 3.5 (g/m^2 days/ 20μ
m) A polypropylene laminated film characterized by the following: