CN1678456A - Polypropylene packaging film - Google Patents

Abstract

The present invention provides a polypropylene-based multilayer packaging film, the properties of which undergo little change over time, which is composed of a surface layer made of a material comprising 100 parts by weight of a composition comprising 50 to 80% by weight of a crystalline polypropylene-based resin and 20 to 50% by weight of at least one softening agent selected from amorphous or low-crystalline propylene- α -olefin copolymers and 1-butene polymers, 5 to 15 parts by weight of a hydrogenated terpene resin and 10 to 20 parts by weight of an aliphatic hydrocarbon which is liquid at ordinary temperature, and a core layer (B) made of a material comprising 80 to 98% by weight of a crystalline polypropylene-based resin and 2 to 20% by weight of an aliphatic hydrocarbon which is liquid at ordinary temperature.

Description

Polypropylene packaging film

field of invention

The present invention relates to films for packaging articles, such as films for food packaging. Specifically, the present invention relates to a polypropylene-based packaging film having the quality of maintaining clinging property and pulling-out ease after a certain period of time.

Background technique

Thin thermoplastic resin films are already used in restaurants, food stores or homes for storing food or for heating in microwave ovens. Among them, packaging films made of 1,1-dichloroethylene are generally used for food packaging due to their excellent properties, including moisture resistance, oxygen permeation resistance, heat resistance, adhesion to containers, and transparency. wrap.

In recent years, various packaging films for food packaging mainly composed of polyolefin-based resins have been proposed. Examples of such films include polyethylene-based resins, polypropylene-based resins, and poly-4-methyl-1-pentene resins. The surfaces of these films have little adhesion, so when they are used as films for food packaging, for example, they cannot sufficiently adhere to containers, which is a fatal defect for them. In order to satisfy such expected properties, various polyolefin-based films mixed with various additives or another resin, or polyolefin films laminated with another resin have been proposed. However, their practical usability remains poor, not only because of poor adhesion to the container, but also because of increased film-to-film adhesion, which results in poor pull-out from the dispensing cassette.

In order to overcome the various problems described above, there are various proposals for packaging films. JP-A-10-202806 proposes a self-adhesive packaging film comprising a core layer of a polypropylene-based resin and a skin layer containing a surfactant as an adhesive. However, it is difficult to achieve high adhesion by this technique. In addition, when food with a high water content is packaged with a packaging film and heated in a microwave oven, the problem of bubbling of the surfactant on the surface of the packaging film occurs under the action of water.

Enhancing the adhesion will inevitably increase the pull-out force, while reducing the pull-out force will make the adhesion worse. An increase in elastic modulus, which is an index of rigidity, deteriorates tensile properties. Thus, the features required for packaging films conflict with each other. Therefore, maintaining a balance between these features is a difficult problem to solve.

For example, JP-A-2002-46238 proposes a multilayer film composed of a core layer comprising a resin having impermeability and a skin layer comprising a resin composition containing an additive having adhesiveness, and a skin layer. However, since additives for achieving adhesion have low molecular weight or low glass transition temperature, they exhibit a phenomenon called "bleed in" and migrate in the film. Therefore, even if such a film exhibits a good balance of adhesion and pull-out properties immediately after the film is formed, the adhesion and pull-out properties deteriorate with time due to transfer of additives into the surface layer.

Since poly(4-methyl-1-pentene) resin has excellent heat resistance, packaging films using this resin have been proposed many times as in JP-A-2001-121660. Because poly(4-methyl-1-pentene) resin is a high-hardness material, a large amount of plasticizer must be added to meet the level of flexibility required by the packaging film. However, if a large amount of plasticizer is added, the resin's inherent heat resistance or low tensile elongation at break is impaired.

It is an object of the present invention to provide a packaging film which does not require much force to be pulled out from a dispensing box, although it contains a polypropylene-based resin excellent in adhesiveness, and whose characteristics vary little with time and storage temperature.

Summary of the invention

In order to achieve the above objects, the present inventors conducted extensive studies and completed the present invention. The present invention mainly relates to the following:

Polypropylene-based multilayer packaging film, which has:

(A) Surface layer comprising the first composition, 5-15 parts by weight of (S3) hydrogenated terpene resin and 10-20 parts by weight of (S4) at normal temperature relative to 100 parts by weight of the first composition It is a liquid aliphatic hydrocarbon, the first composition includes 50-80% by weight of (S1) crystalline polypropylene resin and 20-50% by weight of (S2) selected from amorphous or low crystalline propylene-α-olefins at least one softening agent in the copolymer and 1-butene polymer; and

(B) a core layer comprising 80-98% by weight of (C1) a crystalline polypropylene-based resin and 2-20% by weight of (C2) an aliphatic hydrocarbon that is liquid at normal temperature;

The above-mentioned polypropylene-based multilayer packaging film, wherein the change in adhesion energy is in the range of -20% to +50% before and after the packaging film wound on the paper tube is left for 3 weeks under the conditions of 40°C and 20%RH, Variations in pull-out force in the range of -50% to +20%; and

When the film surface of the above-mentioned polypropylene-based multilayer packaging film is observed at a magnification of 40,000 times as a phase image of an atomic force microscope, the film has a structure formed by a fibril network and a matrix (matrix) exists between the fibril networks, and the fibrils The average width is not less than 1 nm and not more than 100 nm, and the average pore diameter is not less than 3 nm and not more than 1 μm.

By specifying the above-mentioned packaging film of the present invention, it exhibits the following advantages. Specifically, for the surface layer of a packaging film, using a resin composition containing a predetermined amount of a specific softener, a hydrogenated terpene resin, and an aliphatic hydrocarbon that is liquid at normal temperature, it is possible to properly plasticize the resin, thereby simultaneously achieving adhesion. sex and pull.

Addition of an aliphatic hydrocarbon which is liquid at normal temperature to the core layer (B) adjacent to the surface layer (A) may suppress deterioration of adhesion and pull-out properties over time.

Brief description of the drawings

Fig. 1 is a photograph of the packaging film of the present invention observed at a magnification of 40,000 times as a phase diagram of an atomic force microscope.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is specifically described below.

The polypropylene-based resin used in the present invention may be a homopolymer having only polypropylene units in its molecular chain or a binary or terpolymer additionally having ethylene or 1-butene in its molecular chain. Among these copolymers, those obtained by random copolymerization are preferred from the viewpoint of transparency. For stereoregularity, isotactic or syndiotactic structures, or mixtures thereof, may be used. Although there are no other specific limitations, it is preferable to comply with food packaging standards in view of being safely used for packaging food. In addition, it is preferable that the melt flow rate measured at 230° C. under a load of 2.16 kg according to the method of ASTM D1238 is 1 to 20 g/10 minutes.

The component contained in the surface layer (A) as a softener is selected from amorphous or low crystalline propylene-α-olefin copolymers and 1-butene polymers. From the viewpoint of safety, it is preferable to conform to food packaging standards.

The term "amorphous or low crystalline propylene-α-olefin copolymer" used herein refers to a copolymer of propylene and an α-olefin having at least 4 carbon atoms such as 1-butene or 1-pentene. The preferred propylene ratio is 65-85% by weight. Preferably it has a melt flow rate of 1 to 10 g/10 minutes measured at 230° C. under a load of 2.16 kg according to the method of ASTM D1238. Its density is preferably 0.85-0.89 g/cm ³ as determined according to ASTM D1505. It is flexible in itself, and when a crystalline polypropylene-based resin is combined therein, it does not lose transparency and produces a softening effect. Examples of amorphous or low-crystalline polypropylene α-olefin copolymers include "TAFMER XR" (trade name, product of Mitsui Chemicals, Inc.).

The term "1-butene polymer" refers to a homopolymer obtained by catalytic polymerization of liquid 1-butene monomer. Its melt flow rate is preferably 0.1 to 5 g/10 minutes as measured at 190° C. under a load of 2.16 kg according to the method of ASTM D1238. It preferably has a density of 0.904-0.920 g/cm ³ as measured according to ASTM D1505.

The above-mentioned softener has good compatibility with the crystalline polypropylene-based resin. Adding an appropriate amount of the above-mentioned softening agent can effectively reduce the tensile modulus or flexural modulus, in other words, can effectively impart flexibility without greatly impairing the original transparency of the crystalline polypropylene-based resin. , Moisture resistance and heat resistance.

Assuming that the total amount of the crystalline polypropylene-based resin and the softener is 100% by weight, the amount of the softener to be added is 20% by weight or more from the standpoint of flexibility, feel, and ability to follow the contours of the packaged product. The amount of the softener added is 50% by weight or less from the viewpoint of film-forming performance, processability, appearance or performance of film products, hardness feeling as a packaging film, and ease of processing. More preferably, the softening agent is used in an amount of 20-40% by weight, more preferably 20-30% by weight.

A hydrogenated terpene resin as another component of the surface layer (A) was used as a binder.

The hydrogenated terpene resin is obtained by hydrogenating a homopolymer using α-pinene, β-pinene, limonene or dipentene obtained from pine bark or citrus peel as a raw material, or a copolymer thereof. From the viewpoint of obtaining the tackiness of the film, the softening point of the hydrogenated terpene resin is preferably 120° C. or higher, and from the viewpoint of the flexibility and adhesiveness of the surface layer (A) portion containing the hydrogenated terpene resin, the hydrogenated terpene resin is preferably The softening point is below 135°C. Assuming that the amount of the resin composition containing the crystalline polypropylene resin and the softener is 100 parts by weight, from the viewpoint of adhesion, the amount of the hydrogenated terpene resin added is 5 parts by weight or more, in order to suppress film-film adhesion, Therefore, from the viewpoint of reducing the pull-out force, the amount of the hydrogenated terpene resin added is 15 parts by weight or less. The hydrogenated terpene resin is preferably added in an amount of 5-10 parts by weight, more preferably 5-8 parts by weight.

An aliphatic hydrocarbon which is liquid at normal temperature contained in the surface layer (A) is used as an adhesion aid. For the adhesion aid, added are saturated hydrocarbons obtained by purifying crude oil such as liquid paraffin, mineral oil, and white mineral oil; polyisobutylene obtained by homopolymerizing isobutylene; and polybutene obtained by copolymerizing isobutylene and n-butene At least one of alkenes. Among them, mineral oil is most preferable. Assuming that the amount of the composition comprising the crystalline polypropylene resin and the softener is 100 parts by weight, the amount of the adhesion aid to be added is 10 parts by weight or more and 20 parts by weight or less from the viewpoint of feel and stable adhesion . More preferably, it is 15 parts by weight or more.

The packaging film of the present invention has high adhesiveness and excellent pull-out property by using in combination a hydrogenated terpene resin as a binder and an aliphatic hydrocarbon as an adhesion assistant which is liquid at normal temperature. When the packaging film contains an excess of the hydrogenated terpene resin contained in the conventional packaging film, it can be made to have adhesion by pressing the films against each other firmly, but the adhesion and pull-out of the film cannot be achieved when pressing with a small pressure. Poor sex. On the other hand, when the film contains an excessive amount of aliphatic hydrocarbon which is liquid at normal temperature, the film produces an excessively plasticized surface, failing to achieve desired high adhesion.

When the addition amounts of the hydrogenated terpene resin and the aliphatic hydrocarbon which are liquid at normal temperature respectively as the components of the surface layer (A) are respectively c parts by weight and d parts by weight, if they satisfy the following equation, then better Adhesion and pull-out:

d≥0.75×c+3.8

In other words, by mixing a specific ratio of hydrogenated terpene resin (S3) with aliphatic hydrocarbon (S4), which is liquid at normal temperature, the resulting film is able to create a properly plasticized surface and exhibit better adhesion and pull out.

Known additives such as antioxidants may be added to the surface layer (A) comprising the polypropylene-based resin composition without departing from the object of the present invention. However, it is preferred that the additive does not comprise fatty acid esters of aliphatic polyols such as fatty acid glycerides. Additives are used for anti-fogging, plasticizing, improving processability or antistatic purposes. As described above, when wet food is packaged with a film containing such aliphatic ester and heated in a microwave oven, bubbles are formed on the packaging surface, causing user's inconvenience.

The film of the present invention has a core layer (B) adjacent to the skin layer (A). This structure makes it possible to prevent aliphatic hydrocarbons which are liquid at normal temperature in the skin layer (A) from being transferred to the core layer (B) by exudation to form a density gradient, thereby retaining a sufficient amount of aliphatic hydrocarbons in the skin layer. The crystalline polypropylene-based resin forming the core layer (B) may be similar to those used in the skin layer (A). Preferably it complies with food packaging standards.

The aliphatic hydrocarbon (C2) which is liquid at normal temperature used in the core layer (B) of the present invention is a saturated hydrocarbon such as liquid paraffin, mineral oil, or white mineral oil. Although there is no particular limitation on its physical properties, it is generally preferred that the aliphatic hydrocarbon has a kinematic viscosity at 40°C of 10 to 80 cSt, more preferably 10 to 40 cSt.

Assuming that the total amount of the crystalline polypropylene-based resin (C1) and the liquid aliphatic hydrocarbon (C2) at normal temperature is 100% by weight, in order to suppress bleeding and maintain adhesion even after time passes, Pull-out property, the amount of the aliphatic hydrocarbon (C2) that is liquid at normal temperature is more than 2% by weight, from the viewpoint of hardness and stable film-forming performance, the aliphatic hydrocarbon (C2) that is liquid at normal temperature ) in an amount of 20% by weight or less. The added amount is preferably 2-15% by weight, more preferably 2-12% by weight.

Due to the exudation phenomenon, the aliphatic hydrocarbons that are liquid at normal temperature in the surface layer (A) are transferred from the surface layer (A) to the core layer (B), so that the percentage of aliphatic hydrocarbons in the surface layer (A) relative to the hydrogenated terpene resin reduce. This causes changes in the adhesion and pull-out properties obtained at the initial stage. Increasing the composition ratio of the surface layer (A) can be easily considered as a countermeasure against the bleeding phenomenon, but in order to express high adhesion, the surface layer (A) needs to have a soft composition. Therefore, this countermeasure lowers the modulus of elasticity of the entire film, thereby causing a significant deterioration in hardness. Therefore, in the present invention, the bleeding phenomenon can be prevented by adding a specific amount of low-viscosity aliphatic hydrocarbon to the core layer (B) adjacent to the surface layer (A), thereby maintaining adhesion and pull-out without causing the entire film to Significant deterioration in modulus of elasticity.

The exudation of aliphatic hydrocarbons in the surface layer (A) can be well controlled according to the following method. Assuming that the amount of aliphatic hydrocarbons that are liquid at normal temperatures in the surface layer (A) is d parts by weight, the amount of aliphatic hydrocarbons that are liquid at normal temperatures in the core layer (B) is e weight %, and the surface layer (A) is The volume ratio of the core layer (B) (if skin layers are provided on both sides of the core layer (B), the volume ratio is the total) is f, and when the respective amounts satisfy the following equation, the film has satisfactory hardness while maintaining good Adhesion and pull-out

0.13×d/(3√f)≤e≤0.66×d.

It is preferable that the core layer (B) does not contain a resin having a melting peak temperature of 200° C. or higher. Adding a resin having a high melting peak temperature such as poly(4-methyl-1-pentene) resin achieves high heat resistance up to 170° C. or higher while increasing the elastic modulus of the resulting film. Therefore, not only the desired confidentiality cannot be achieved, but also the ease of workability including hardness deteriorates.

In order to maintain molding processability or easy moldability, known additives such as antioxidants may be added to the composition of the core layer (B) to the extent that it does not depart from the object of the present invention.

Regarding the composition ratio of the layers, assuming that the volume ratio of the surface layer (A) to the core layer (B) is f, f is preferably 0.2-2.7. When the volume ratio of the surface layer (A) is less than 0.2, adhesion cannot be exhibited over the entire range of the film. On the other hand, when the volume ratio is greater than 2.7, the ease of processability of the film becomes poor due to softening of the film and decrease in hardness. .

Although there is no specific limitation on the ratio of the skin layer (A) when it is located on both sides of the core layer, it is preferable that both are in an almost equal ratio because it is not necessary to distinguish the two sides.

In addition to the skin layer (A) and the core layer (B), the multilayer film may, to the extent that does not inhibit the object of the present invention, have further layers, such as rework layers including, for example, trimmed edges formed during manufacture. Considering the balance of adhesion and pull-out properties, the other layer is preferably 5% by weight or less of the entire layer and 5% or less of the entire volume ratio. It is necessary to stack other layers so as not to interfere with the adjacent state of the surface layer (A) and the core layer (B).

As an index related to the adhesion of the packaging film of the present invention, the term "adhesion energy" is used. The term "adhesion energy" is an index for evaluating film-film adhesion or film-container adhesion when a container or food is covered with a packaging film. As mentioned above, this adhesiveness and pull-out property are important properties of a packaging film. The above-mentioned adhesion energy is determined in terms of the energy required to separate films adhered to each other. A detailed measurement method is described later. From the viewpoint of proper adhesion, the adhesion energy is preferably 1.0-3.0 mJ, more preferably 1.5-2.5 mJ.

The "pull-out force" of the packaging film used in the present invention is a property as important as adhesion, and the pull-out property of the film from the film roll in the dispensing cassette is evaluated by the pull-out force. The pull-out force is measured according to the method described later. From the viewpoint of good pull-out properties, the pull-out force is preferably 200-1000 mN, more preferably 200-800 mN, and still more preferably 200-600 mN.

Packaging films are often stored under conditions of high temperature and humidity, such as in domestic kitchens or commercial cook-offs. Preferably, the adhesion energy and pull-out force do not undergo large changes during storage. As an index of change, the rate of change in adhesion energy and pull-out force before and after wrapping a paper tube with a wrapping film and leaving it to stand at 40° C. and a relative humidity of 20% for 3 weeks was used. It is preferable that the rate of change of adhesion energy is -20% to +50%, and the rate of change of pull-out force is -50% to +20%. Within these ranges, a good balance between adhesion energy and pull-out force does not disappear until the packaging film is sold and consumed as a product.

When imaging phase information generated by stimulation of an atomic force microscope (AFM) cantilever, it is preferred that the surface of the membrane of the present invention has a predetermined structure. When the phase information produced by the stimulation of the cantilever is observed at a magnification of 40,000 times, the part with a small delay, in other words, the hard part is represented by a bright phase map, while the part with a large delay, in other words, Soft parts are represented by dark phase maps. When the desired surface of the packaging film of the present invention is observed by the method described above, there is a fibrous network structure with a matrix in between. The image thus observed is represented in FIG. 1 . A "network structure" is a seemingly bright continuous image portion, and a "matrix" is a seemingly dark discontinuous portion surrounded by such a network structure. The observable continuous fibrous bright parts are called "fibril network structure", and the discontinuous dark parts are called "matrix". In the area of 10 mm x 10 mm, 50 images with dimensions of 2 microns x 2 microns were randomly selected. Take the section with the most uniform fibril width and fibril-fibril distance. From the images thus taken out, 100 fibril widths and 100 fibril-fibril distances were selected, and the mean values of all but the highest 10 and lowest 10 were calculated as the subsequently described fibril width and Matrix size.

Preferably, the average fibril width is 1 nm or more and 100 nm or less. Within this range, the smoothness of the film surface can be maintained and the adhesion can be further improved. More preferably, the average width is 10 nm or more and 50 nm or less.

It is preferable that the size of the matrix (ie, the average value of the fibril-fibril distance) is 3 nm or more and 1 μm or less. Within this range, the adhesive component constituting the matrix remains in the network structure on the surface of the film, no excess adhesive component appears on the surface, and the balance between adhesion and pull-out can be maintained. More preferably, the matrix size is 10 nm or more and 50 nm or less.

In the network structure of the present invention, the crystalline part of the propylene-based resin mainly forms fibrils, and the amorphous part of the propylene-based resin, softener, hydrogenated terpene resin and aliphatic hydrocarbon which is liquid at normal temperature form a matrix. As described above, since the fibrils have a network structure of a predetermined size, the softening component of the matrix part, which has a great influence on the adhesion, is retained by the fibrils in the minimum amount required to exhibit the adhesion on the surface. amount, making it possible to exhibit both good adhesion and pull-out.

When the softening component exists locally on the surface of the membrane without a network structure, or when the softening part exists as a sea-island structure with a larger pore size than the network structure described in the present invention, the component imparting adhesion properties is present on the surface It does not exist uniformly, and the balance between adhesion and pull-out property deteriorates.

It is preferred that the film of the present invention has a predetermined flexibility. More specifically, it is preferred that it has a tensile modulus of 200-1000 MPa. Films were measured in the machine direction (MD direction) and transverse direction (perpendicular to the MD direction) under 2% tension using a tensile tester (Shinko Tsushin Kogyosha's Universal Tensile Compression Tester) according to the method described in ASTM-D-882. The tensile modulus is determined by the mean value of the tensile modulus in the TD direction). From the viewpoint of film flexibility, hardness and ease of processing, the tensile modulus is preferably 200 Mpa or more, and from the viewpoint of flexibility, adhesiveness and ease of processing, it is preferably 1000 Mpa or less. More preferably, it is 400 MPa or more and 700 MPa or less.

From the viewpoint of the strength and hardness of the packaging film and the ease of processing during packaging, the thickness of the film of the present invention is preferably 3 μm or more. From the viewpoint of size and ease of processing during use, it is 25 μm or less. In particular, a convenient, adhesive and pull-out film for household food packaging is required to have a thickness of 6 μm to 15 μm.

Known film-forming techniques can be used to prepare the films of the present invention. The polypropylene-based resin composition of the skin layer (A) was prepared by melting and kneading in an extruder. Together with commercially available polypropylene-based resin pellets, predetermined amounts of a softener and a hydrogenated terpene resin that are solid at normal temperature were fed into the mixer. After thorough and homogeneous mixing, the mixture thus obtained is fed into an extruder for the skin layer. The aliphatic hydrocarbons of the skin (A) and core (B) are liquid at normal temperature, so a liquid injector is installed in the middle of the screw of each skin and core extruder to add them to the melted and plasticized resin . The compositions are homogenized by kneading under appropriate extrusion conditions, and they are extruded from a multilayer die or the like into a multilayer film having skin and core layers and optionally a rework layer. It is also possible to fully melt and knead the compositions of the skin layer (A) and the core layer (B) separately in a known device such as a twin-screw extruder that allows mid-feeding, granulate the resulting materials, and then separately Feed to extruder for skin and core.

A film having a multilayer structure such as a three-layer structure can be prepared according to the following method. In the above-mentioned extruders for the skin layer and the core layer connected in parallel, predetermined resins are respectively charged and then sufficiently melted and kneaded. Downstream from them, the resins from these extruders are combined so that they have three layers and then extruded in the form of flakes using annular dies or through T-die with slit-like discharge opening. The resin thus extruded is cooled and solidified by known methods such as passing it through a cooling water tank or exposing it to cold air or cooling rolls. From the viewpoint of surface smoothness and appearance, the cooling temperature of the surface of the extruded sheet is preferably 10° C. or higher, and from the viewpoint of preventing bleeding of the adhesive bonded to the surface layer (A) on the surface, or adhesion , the cooling temperature is below 50°C.

Stretching of the film is preferably performed by a commonly used known method, such as uniaxial or biaxial stretching by a roll method (roll method) or a tenter method (tenter method); The ease of cutting of packaging films for food packaging is multiaxially stretched in the longitudinal direction and/or transverse direction at a stretch ratio of at least 2 by a tubular method. The stretch ratios in the longitudinal and transverse directions are not necessarily the same. More preferably, it is stretched at a stretch ratio of at least 2 in the longitudinal direction and the transverse direction by multiaxial stretching using a tubular stretching method. After stretching is completed, the film is formed into a predetermined shape by trimming the ends of the film, cutting the film to a desired size, or winding it on a paper tube.

A film obtained by multiaxial stretching using a tubular stretching method can be heat-set in a known manner to adjust the heat shrinkage rate of the film. Examples of methods usable for this purpose include indirect heating by contact with rolls or by infrared rays while suppressing movement of the film in the MD direction; heating by hot air or radiant heat while suppressing movement of the film in the transverse direction by a tenter; and using hot air Or radiant heat heating while bubbling again.

The film of the present invention not only has the balance between the excellent adhesion and pull-out properties required for packaging films, but also has excellent transparency, heat resistance, moderate flexibility, good hand feeling, easy cutting and safety properties, making it suitable for use as a film for household food packaging.

Example

Embodiments for carrying out the present invention are described below. Each of them is an embodiment of the present invention, and the present invention is not limited by these Examples. The properties of the films obtained in the present invention and Comparative Examples were evaluated according to the following methods.

(adhesion energy)

Film-to-film adhesion when covering a container such as a plate or food with a packaging film was evaluated and measured according to the following method.

Two cylinders having a base area of 25 cm ² and a weight of 400 g were prepared. Filter papers of the same area are bonded to their bottom surfaces respectively in advance. Secure wrapping film to each bottom surface to which filter paper is bonded, holding under tension to prevent wrinkling of the film. After the two cylinders were closely fitted and contacted with their film surfaces, they were bonded under an environment of 23° C. and 50% RH for 1 minute under a load of 500 g. Then, the overlapped films were separated at a rate of 5 mm/min in a direction perpendicular to the surface using a tensile tester (Shinko Tsushin Kogyosha's Universal Tensile Compression Tester), and the energy (mJ) generated at this time was called adhesion energy.

(adhesion energy changes)

The stability of the adhesion energy over time was evaluated. The adhesion energy of the packaging film after 24 hours in an environment of 23° C. and 50% RH after forming the packaging film and the adhesion energy of the packaging film after storage in an environment of 40° C. and 20% RH for 21 days were measured by the above-mentioned method.

Adhesion energy before storage was evaluated according to the following criteria:

◎: Greater than or equal to 1.5mJ and less than 2.5mJ

○: Greater than or equal to 0.5mJ and less than 1.5mJ, or greater than or equal to 2.5mJ and less than 3.5mJ

△: Greater than or equal to 3.5mJ and less than 4.0mJ

×: less than 0.5mJ, or greater than or equal to 4.0mJ

According to the following criteria, the change of the adhesion energy of the packaging film before and after storage at 40°C and 20%RH for 21 days was evaluated:

◎: -20%≤(change)＜+50%

○: -50% ≤ (change) < -20%, or +50% ≤ (change) < +75%

△: (change) <-50%, or +75% ≤ (change)

×: Cannot be measured because the film cannot be pulled out

(pull force)

The pull-out property of the packaging film from the film roll was evaluated according to the following method.

A film with a width of 300 mm was wound on a paper tube with an outer diameter of 41 mm, an inner diameter of 38 mm and a width of 308 mm under a tension of 20 N at a rate of 100 m/min to prepare a film roll with a film length of 20 m.

Both ends of the paper tube of the above-mentioned film roll are clamped and fixed by a special jig capable of rotating under a very light load, and the jig is fixed on the lower part of a tensile testing machine (Shinko Tsushin Kogyosha's general-purpose tensile and compression testing machine) . The end of the film was adhered and fixed to a 330 mm wide upper fixing tool, and the force obtained when the film was unrolled at a rate of 1000 mm/min was measured. The maximum load at this time is called pull-out force.

In order to measure the change in pull-out force with time, the pull-out force of the sample after being formed for 24 hours and the sample after being stored in an environment of 40° C. and 20% RH for 21 days were measured.

The pull-out force prior to storage was evaluated according to the following criteria:

◎: greater than or equal to 50mN and less than 600mN

○: greater than or equal to 600mN and less than 1200mN

△: greater than or equal to 1200mN and less than 1500mN

×: less than 50mN, or greater than or equal to 1500mN

The pull-out force of the sample after being stored in an environment of 40° C. and 20% RH for 21 days compared with the pull-out force of the sample before storage was evaluated according to the following criteria:

◎: -50%≤(change)＜+20%

○: -80% ≤ (change) < -50%, or +20% ≤ (change) < +50%

△: (change) <-80%, or +50% ≤ (change)

×: Cannot be measured because the film cannot be pulled out

(transparency)

The haze of the film was measured using "NDH-300A" (NipponDenshoku Industries, Ltd.) according to the method described in ASTM-D-103, and the transparency was evaluated according to the following criteria:

◎: Less than 1.0

○: Greater than or equal to 1.0 and less than 2.0

△: Greater than or equal to 2.0 and less than 3.0

×: greater than or equal to 3.0

(heat resistance)

In order to evaluate the heat resistance, the heat resistance temperature was measured in accordance with Tokyo Consumer Life Ordinance Article 11. Films with a heat-resistant temperature of 140°C or higher were evaluated as ◎, films with a heat-resistant temperature of 130°C or 135°C were evaluated as ○, and films with a heat-resistant temperature of 125°C or less were evaluated as △.

(flexibility)

To evaluate flexibility, the tensile strength of the film in the machine direction (MD) and transverse direction (TD) under a tension of 2% was measured using a tensile tester (Shinko Tsushin Kogyosh Tensile Compression Tester) according to the method described in ASTM D882. Elongation modulus. Evaluation according to the following criteria:

The average value of the tensile modulus of the film in the MD and TD directions,

◎: greater than or equal to 400MPa and less than 700MPa

○: greater than or equal to 200MPa and less than 400MPa, or greater than or equal to 700MPa and less than 1000MPa

△: greater than or equal to 100MPa and less than 200MPa

×: less than 100MPa, or greater than or equal to 1000MPa

(feel)

In order to evaluate the hand feel, 50 housewives were randomly selected to perform sensory evaluation, evaluate the hand feel of the film and evaluate according to the following criteria:

◎: At least 45 housewives judged that the film has a good hand feeling

○: More than or equal to 40 and less than 45 housewives judged that the film has a good hand feeling

△: More than or equal to 30 and less than 40 housewives judged that the film has a good hand feeling

×: Fewer than 30 housewives judged that the film has good hand feeling

(cutting)

The film was wound on a paper tube having a width of 300 mm and a winding length of 20 m, and the resulting film roll was put into a dispensing box of "Saran Wrap" (trade name, product of Asahi Kasei Corporation). Cut the membrane with the blade attached to the dispenser box. Cuttability of the film was evaluated from the state when the film was cut according to the following criteria.

◎: The film can be cut with light force

○: A little force is required to cut the film, but it can be cut

△: The film can be cut, but cannot be easily cut

×: The film could not be smoothly cut. Sometimes the film is not cut, but stretched or broken in the transverse direction, or the dispensing box is broken due to excessive load applied when cutting the film.

(Observation of membrane surface)

The film surface was observed as a phase map obtained by an atomic force microscope. The film was glued and fixed on glass, and the phase map was obtained by observing the surface of the film in tapping mode with "Nano Scope lila" (trade name, product of Digital Instrument). Measurements were performed using a silicon single crystal cantilever (spring constant: 0.70-0.58 N/m) under the conditions of a scan rate of 0.5 to 1 Hz, a scan range of 2 μm, a Z limit of 440 V, and a sampling point of 512512. The contact pressure of the cantilever is controlled according to the membrane, the set point is 0.8-1.4V when the target amplitude is 2V, and the set point is 2.0 when the target amplitude is 4V -3.5V. Within a 10 mm x 10 mm area of the sample, 50 images of 2 μm x 2 μm were randomly selected and observed. Of these images, the portion with the most uniform fibril width and fibril-fibril distance was taken. The 2 µm x 2 µm area thus taken out was magnified 40,000 times, and 100 fibril widths and 100 fibril-fibril distances were selected from the resulting 80 mm x 80 mm image. After excluding the largest 10 and smallest 10, an average of 80 widths or 80 distances is used. The surface structure was evaluated by the average fibril width value according to the following criteria:

◎: greater than or equal to 1nm and less than 50nm

○: greater than or equal to 50nm and less than 100nm

×: greater than or equal to 100nm

The average fibril-fibril distance was evaluated according to the following criteria:

◎: greater than or equal to 10nm and less than 50nm

○: greater than or equal to 3nm and less than 10nm, or greater than or equal to 50nm and less than 100nm

×: less than 3nm, or greater than or equal to 100nm

The films were comprehensively evaluated based on the above results. Films with ◎ evaluations in each item were judged to be excellent, films with only ◎ or ○ evaluations were judged to be practical, and films with ○ or X evaluations were judged to be unsuitable for practical use.

Example 1

A crystalline polypropylene-based resin ("Grand PolyproF327", trade name, product of Grand Polymer Co., Ltd., a terpolymer of propylene, ethylene, and 1-butene) was mixed at a weight ratio of 75:25 and as Low-crystalline propylene-α-olefin copolymer resin ("TAFMER XR110T", trade name, product of Mitsui Chemicals, Inc.) of softener. 5 parts by weight of a hydrogenated terpene resin ("Clearon P125", trade name, product of Yasuhara Chemical Co., Ltd.) was charged to the mixer with respect to 100 parts by weight of the obtained mixture, and then thoroughly mixed at normal temperature for 5 minute. The resulting mixture was kneaded in a molten state in a co-rotating twin-screw extruder ("TEM-35BS", trade name, product of Toshiba Machine) with a screw diameter of 37 mm and an L/D of 42 to prepare a small ball. As an aliphatic hydrocarbon that is liquid at normal temperature, mineral oil ("MORESCO white P70", trade name, product of Matsumura Oil Research / (kinematic viscosity at 40°C: 9.6 cSt)) was added from the middle of the column with a syringe pump . The amount added was 15 parts by weight relative to 100 parts by weight of the total amount of the crystalline polypropylene resin and the softener. The resulting mixture is the resin for the skin.

The same crystalline polypropylene-based resin as used above was melted in a co-rotating twin-screw extruder ("TEM-35BS", trade name, product of Toshiba Machine) with a screw diameter of 37 mm and an L/D of 30 and 20 parts by weight of mineral oil ("MORESCO white P70", trade name, product of Matsumura Oil Research) was added to the middle of the extruder through a syringe pump. The amount used was adjusted so that the weight ratio of the crystalline polypropylene resin to the mineral oil was 90:10. The resulting composition was uniformly mixed and the pellets thus obtained were prepared as a core resin. The volume ratio etc. of each layer are shown in Table 1.

A multilayer stretched film was formed using the resin thus obtained. First, the resin mixture is separately fed into the surface layer extrusion unit and the core layer extrusion unit of a multi-layer extruder capable of extruding symmetrical two- and three-layer pairs of resin layers. After sufficient molding in each extrusion unit, the raw film was extruded through a multi-layer annular die at 220°C, followed by water cooling.

The obtained raw material film was stretched at 120° C. with a tubular directional stretcher at a stretch ratio of 5 in the longitudinal direction and 4 in the transverse direction. Then, the end portion of the cylindrical film is trimmed and the films are rolled up one by one. The film was heat-set by holding a tenter at a predetermined width in the longitudinal direction of the film by holding a tenter in hot air at 130° C. for a period of 20 seconds. This resulted in an approximately uniform film with a thickness of 10 μm, a skin layer of 0.25 μm in thickness, a core layer of 0.5 μm in thickness and another skin layer of 0.25 μm in thickness. By measuring the physical properties of the film, it was found to exhibit good performance as shown in Table 2. When the film thus obtained was observed at magnification of 40,000 times as a phase image of an atomic force microscope, a structure formed of network fibrils and a matrix existing therebetween was observed.

Example 2

Except that the crystalline polypropylene resin and the low crystalline propylene-α-olefin copolymer resin are mixed in a weight ratio of 65:35 as the surface resin; the mineral oil addition amount of the core layer is 7% by weight; the surface layer, the core layer and another A film having a thickness of 10 μm was formed in the same manner as in Example 1 except that the thickness ratio of the surface layer was changed to 0.20:0.60:0.20. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 3

Except that the crystalline polypropylene-based resin and the low-crystalline propylene-α-olefin copolymer resin are mixed in a weight ratio of 55:45 as the surface resin composition; the thickness ratio of the surface layer, the core layer, and the other surface layer becomes 0.15:0.70: Except for 0.15, a film having a thickness of 10 μm was formed in the same manner as in Example 1. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 4

Except by adding 15 parts by weight and 10 parts by weight of hydrogenated terpene resin and mineral oil to 100 parts by weight of the surface layer resin composition formed of crystalline polypropylene-based resin and low-crystalline propylene-α-olefin copolymer resin A film having a thickness of 10 μm was formed in the same manner as in Example 1 except that the obtained resin was used as the surface layer resin. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 5

In addition to mixing the crystalline polypropylene-based resin and the low-crystalline propylene-α-olefin copolymer resin in a weight ratio of 55:45; adding the crystalline polypropylene-based resin and the low-crystalline propylene-α-olefin relative to 100 parts by weight The total amount of the copolymer resin is 10 parts by weight and 20 parts by weight of hydrogenated terpene resin and mineral oil; the composition ratio of the polypropylene resin of the core layer to the mineral oil becomes 97:3; and the surface layer, the core layer and another surface layer A film having a thickness of 10 μm was formed in the same manner as in Example 1 except that the thickness ratio was changed to 0.15:0.70:0.15. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 6

In addition to using 15 parts by weight of "MORESCO White P40" (trade name, product of Matsumura Oil Research Corp., kinematic viscosity at 40°C: 4.4cSt) as mineral oil in the resin composition of the surface layer, and using "MORESCO White P40 " (trade name, product of Matsumura Oil Research Corp.) was used as the mineral oil in the resin composition of the core layer, and a film with a thickness of 10 μm was formed in the same manner as in Example 1. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 7

In addition to adding 15 parts by weight of polybutene ("NissanPolybutene 06SH" (kinematic viscosity at 40°C: 95cSt), trade name, product of NOFCORPRATION) to the resin composition of the surface layer as an aliphatic hydrocarbon that is liquid at normal temperature Except for mineral oil, a film having a thickness of 10 μm was formed in the same manner as in Example 1. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 8

A film having a thickness of 10 μm was formed in the same manner as in Example 1, except that 30% by weight of a 1-butene polymer (“TAFMER BL4000”, a product of Mitsui Chemicals, Inc.) was used as a softener for the resin composition of the surface layer . The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 9

Except for using 70% by weight of ethylene-propylene random copolymer ("PC630A", trade name, product of Sun Allomer) as the crystalline polypropylene-based resin of the surface layer resin composition, it was formed in the same manner as in Example 1. Membranes with a thickness of 10 μm. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 10

In addition to using 75% by weight of ethylene-propylene block copolymer ("Grand Polypro J705", trade name, product of Grand Polymer Co., Ltd.) A film with a thickness of 10 µm was formed in the same manner as in Example 1. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 11

A film having a thickness of 10 μm was formed in the same manner as in Example 1 except that the extruded raw material film was stretched at a stretch ratio of 2.5 in the longitudinal direction and 2.5 in the transverse direction. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Example 12

Formed in the same manner as in Example 1, except that the extruded raw film was stretched at 60° C. at a stretch ratio of 4 in the longitudinal direction and 3 in the transverse direction, and no heat-setting treatment was performed after stretching. Membranes with a thickness of 10 μm. The physical properties of the resulting film were measured and found to exhibit good performance as shown in Table 2.

Comparative example 1

Except that a resin composition obtained by mixing a crystalline polypropylene-based resin and a low-crystalline propylene-α-olefin copolymer resin in a weight ratio of 40:60 is used as a surface resin; and the thickness ratio of the surface layer, the core layer, and the other surface layer becomes Except for 0.15:0.70:0.15, a film having a thickness of 10 μm was formed in the same manner as in Example 1. The volume ratios etc. of the three layers are shown in Table 3. The physical properties of the resulting film were measured and found to exhibit initial adhesion and excess pull-out force as shown in Table 4.

Comparative example 2

Except that the resin composition obtained by mixing the crystalline polypropylene-based resin and the low-crystalline propylene-α-olefin copolymer resin in a weight ratio of 85:15 was used as the surface resin, the same method as in Example 1 was used to form a 10 μm film. The physical properties of the resulting film were measured and found to exhibit low adhesion at the initial stage as shown in Table 4.

Comparative example 3

In addition to adding thereto a resin composition obtained by adding 20 parts by weight of a hydrogenated terpene resin with respect to a total amount of 100 parts by weight of a crystalline polypropylene-based resin and a low-crystalline propylene-α-olefin copolymer resin as a surface layer, A film having a thickness of 10 μm was formed in the same manner as in Example 1. The physical properties of the obtained film were measured and found to exhibit low adhesion energy in the initial stage as shown in Table 4.

Comparative example 4

In addition to adding thereto a resin composition obtained by adding 2 parts by weight of a hydrogenated terpene resin with respect to a total amount of 100 parts by weight of a crystalline polypropylene-based resin and a low-crystalline propylene-α-olefin copolymer resin as a surface layer, A film having a thickness of 10 μm was formed in the same manner as in Example 1. The physical properties of the resulting film were measured and found to exhibit low initial adhesion energy in the initial stage as shown in Table 4.

Comparative Example 5

Resin obtained except adding thereto 10 parts by weight of hydrogenated terpene resin and 5 parts by weight of mineral oil relative to 100 parts by weight of the total amount of crystalline polypropylene-based resin and low-crystalline propylene-α-olefin copolymer resin A film having a thickness of 10 μm was formed in the same manner as in Example 1 except that the composition was used as the surface layer. The physical properties of the resulting film were measured and found to exhibit low adhesion energy and high pull-out force as shown in Table 4.

Comparative example 6

Resin obtained except adding thereto 10 parts by weight of hydrogenated terpene resin and 25 parts by weight of mineral oil relative to 100 parts by weight of the total amount of crystalline polypropylene-based resin and low-crystalline propylene-α-olefin copolymer resin A film having a thickness of 10 μm was formed in the same manner as in Example 1 except that the composition was used as the surface layer. The physical properties of the obtained film were measured, and it was found to exhibit poor properties as shown in Table 4, such as low hardness and poor hand feeling, due to being too soft.

Comparative Example 7

A film having a thickness of 10 μm was formed in the same manner as in Example 1, except that the weight ratio of the crystalline polypropylene resin constituting the core layer and the mineral oil was changed to 99:1. The physical properties of the obtained film were measured, and it was found that it exhibited good adhesion and pull-out force as shown in Table 4 at the initial stage, however, the adhesion and pull-out force increased when it was left at 40° C. for 21 days.

Comparative Example 8

Except that the weight ratio of crystalline polypropylene-based resin to mineral oil ("MORESCO WHITE P70", trade name, product of Matsumura Oil Research Corp.) which is an aliphatic hydrocarbon which is liquid at normal temperature was changed to 60:40 , An attempt was made to form a film in the same manner as in Example 1. However, no film could be formed due to poor film-forming properties.

Comparative Example 9

Except that the resin composition of the core layer was changed to 75:25 of crystalline polypropylene-based resin to low-crystalline propylene-α-olefin copolymer resin ("TAFMER XR110T", trade name, product of Mitsui Chemicals, Inc.) Except that, a film having a thickness of 10 μm was obtained in the same manner as in Example 1. The physical properties of the obtained film were measured, and it was found that it exhibited the same level of adhesion and pull-out force as the film obtained in Example 1 of Table 4 at the initial stage, but when it was left at 40° C. for 21 days, the adhesion was not and pull-out force increase.

Comparative Example 10

A single-layer film having a thickness of 10 μm was formed in the same manner as in Example 1 except that the film was changed to a single-layer film having the surface layer composition of Example 1. The physical properties of the obtained film were measured, and it was found that its adhesion and pull-out were stable, as shown in Table 4, but its hardness was poor due to being too soft.

Table 1 Polypropylene in skin softener in the surface layer Hydrogenated terpene resins in skin aliphatic hydrocarbons in the surface layer Polypropylene in inner layer Aliphatic hydrocarbons in inner layer The thickness of all layers The volume ratio of the surface layer to all layers Volume ratio of inner layer to all layers The volume ratio of the surface layer to the inner layer weight% weight% parts by weight parts by weight weight% weight% Micron - - - example 1 F32775 110T25 P1255 P7015 F32790 P7010 10 0.5 0.5 1.0 Example 2 F32765 110T35 P1255 P7015 F32793 P707 10 0.4 0.6 0.67 Example 3 F32755 110T45 P1255 P7015 F32790 P7010 10 0.3 0.7 0.43 Example 4 F32775 110T25 P12515 P7010 F32790 P7010 10 0.5 0.5 1.0 Example 5 F32755 110T45 P12510 P7020 F32797 P703 10 0.3 0.7 0.43 Example 6 F32775 110T25 P1255 P7015 F32790 P7010 10 0.5 0.5 1.0 Example 7 F32775 110T25 P1255 06 SH15 F32790 P7010 10 0.5 0.5 1.0 Example 8 F32770 BL400030 P1255 P7015 F32790 P7010 10 0.5 0.5 1.0 Example 9 PC63070 110T30 P1255 P7015 F32790 P7010 10 0.5 0.5 1.0 Example 10 J70575 110T25 P1255 P7015 F32790 P7010 10 0.5 0.5 1.0 Example 11 F32775 110T25 P1255 P7015 F32790 P7010 10 0.5 0.5 1.0 Example 12 F32775 110T25 P1255 P7015 F32790 P7010 10 0.5 0.5 1.0

Table 2 Adhesion energy after 24 hours of film formation Pull-out force after 24 hours of film formation The change of adhesion energy of the film after being placed at 40℃ for 21 days Changes in the pull-out force of the film after being placed at 40°C for 21 days heat resistance transparency flexibility feel Ease of cutting With or without network structure average fibril width Average size of matrix unit - - - - - - - - - - nm nm example 1 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ Example 2 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ Example 3 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ○ Example 4 ○ ○ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ Example 5 ◎ ◎ ○ ○ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ Example 6 ○ ○ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ Example 7 ○ ○ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ Example 8 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ Example 9 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ Example 10 ◎ ◎ ◎ ◎ ◎ ○ ○ ◎ ◎ have ◎ ◎ Example 11 ○ ○ ◎ ◎ ◎ ◎ ○ ○ ○ none - - Example 12 ○ ○ ◎ ◎ ◎ ◎ ◎ ◎ ◎ have x x

table 3 Polypropylene in skin softener in the surface layer Hydrogenated terpene resins in skin aliphatic hydrocarbons in the surface layer Polypropylene in inner layer Aliphatic hydrocarbons in inner layer Other resins in the inner layer The thickness of all layers The volume ratio of the surface layer to all layers Volume ratio of inner layer to all layers The volume ratio of the surface layer to the inner layer unit weight% weight% parts by weight parts by weight weight% weight% weight% Micron - - - than 1 F32740 110T60 P1255 P7015 F32790 P7010 - 10 0.3 0.7 0.43 than 2 F32785 110T15 P1255 P7015 F32790 P7010 - 10 0.5 0.5 1.0 than 3 F32775 110T25 P12520 P7015 F32790 P7010 - 10 0.5 0.5 1.0 than 4 F32775 110T25 P1252 P7015 F32790 P7010 - 10 0.5 0.5 1.0 than 5 F32775 110T25 P12510 P705 F32790 P7010 - 10 0.5 0.5 1.0 than 6 F32775 110T25 P12510 P7025 F32790 P7010 - 10 0.5 0.5 1.0 than 7 F32775 110T25 P1255 06SH15 F32799 P701 - 10 0.5 0.5 1.0 than 8 F32775 110T25 P1255 P7015 F32760 P7040 - 10 0.5 0.5 1.0 than 9 F32775 110T25 P1255 P7015 F32775 - 110T25 10 0.5 0.5 1.0 than 10 F32775 110T25 P1255 P7015 - - - 10 1.0 0.0 -

Table 4 Adhesion energy after 24 hours of film formation Pull-out force after 24 hours of film formation The change of adhesion energy of the film after being placed at 40℃ for 21 days Changes in the pull-out force of the film after being placed at 40°C for 21 days heat resistance transparency flexibility feel Ease of cutting With or without network structure average fibril width Average size of matrix unit - - - - - - - - - - nm nm than 1 △ △ △ △ △ ○ x △ △ have ◎ x than 2 △ ○ △ △ ◎ ○ x △ ◎ have ◎ ◎ than 3 △ △ x x ◎ ◎ ◎ ◎ ◎ have ◎ ◎ than 4 △ ○ △ ◎ ◎ ◎ ◎ ◎ ◎ have ◎ ○ than 5 x x x x ◎ ◎ ◎ ◎ ◎ have ◎ ◎ than 6 ○ ○ ○ ○ ◎ ◎ x x ◎ have ◎ ◎ than 7 ○ ○ △ △ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ than 8 failed to form a film than 9 ○ ○ △ △ ◎ ◎ ◎ ◎ ◎ have ◎ ◎ than 10 ○ ○ ◎ ◎ ○ ◎ x x ○ have ◎ ◎

The meaning of the abbreviations in the table:

Real=embodiment; Ratio=comparative example

F327: Crystalline polypropylene resin ("Grand Polypro F327", trade name, product of Grand Polymer Co., Ltd., MFR=7.0g/10min)

PC630: Homopolypropylene resin ("PC630A", trade name, product of Sun Allomer Co., Ltd., MFR=7.5g/10min)

J705 = crystalline block polypropylene resin ("Grand Polypro J705", trade name, product of Grand Polymer Co., Ltd., MFR = 10g/10min)

110T = low crystallinity propylene-α-olefin copolymer resin ("TAFMER XR110T", trade name, product of Mitsui Chemicals, Inc., MFI=6.0g/10min (230°C), density: 0.890g/cc)

BL4000=1-butene copolymer (“TAFMER BL4000”, trade name, product of Mitsui Chemicals, Inc., MFR=1.8g/10min, density: 0.915g/cc)

P125 = Hydrogenated terpene resin ("Clearon P125", trade name, product of Yasuhara Chemical Co., Ltd.)

P70 = mineral oil ("Smoil P70", trade name, product of Mtsumura Oil Research, kinematic viscosity: 12.35 (40°C cSt)

P40 = mineral oil (“MORESCO WHITE P-40”, trade name, product of Matsumura OilResearch, kinematic viscosity: 4.3 (40°C cSt)

06SH = aliphatic hydrocarbon that is liquid at normal temperature ("Nissan Polybutene 065H", trade name, product of NOF CORPORATION, kinematic viscosity: 95 (40°CcSt)

Although the invention has been described in detail with reference to the specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

This application claims priority from Japanese Patent Application No. 2002-250192 filed on August 29, 2002, the contents of which are incorporated herein by reference.

Industrial Applicability

The present invention provides a polypropylene-based multilayer film which has an excellent balance between adhesion and pull-out properties, which undergo little change over time, and which has excellent transparency, heat resistance, flexibility, Feel, and ease of cutting. Such a film can be suitably used as a packaging film for food packaging.

Claims (6)

1. polypropylene-based multilayer packaging film, it comprises:

(A) top layer, it comprises first composition and is that (S3) hydrogenated terpene resin of 5-15 weight portion and (S4) of 10-20 weight portion are the aliphatic hydrocarbon of liquid at normal temperatures with respect to first composition of 100 weight portions, and first composition comprises that (S1) crystalline polypropylene of 50-80 weight % is that (S2) of resin and 20-50 weight % is selected from least a softening agent in amorphous or low-crystalline propylene-alpha olefin copolymer and the 1-butene polymers; With

(B) with the sandwich layer of top layer adjacency, (C2) that its (C1) crystalline polypropylene that comprises 80-98 weight % is resin and 2-20 weight % is the aliphatic hydrocarbon of liquid at normal temperatures.

2. the polypropylene-based multilayer packaging film of claim 1, wherein under the condition of 23 ℃ and 50%RH, adherence can be 1.0-3.0mJ, pullout forces is 200-1000mN.

3. claim 1 or 2 polypropylene-based multilayer packaging film, the packaging film that wherein will be wrapped on the paper tube was placed under the condition of 40 ℃ and 20%RH before and after 3 weeks, the variation of adherence energy is in-20% to+50% scope, and the variation of pullout forces is in-50% to+20% scope.

4. the polypropylene-based multilayer packaging film of claim 3, when amplifying 40,000 times when observing the film surface as the phase diagram of AFM, has the substrate formed structure that exists by the fibrillation network with between the fibrillation network, and fibriilar mean breadth is that 1nm is above with below the 100nm, and fibrillation-interfibrillar average distance is that 3nm is above with below the 1 μ m.

5. claim 1 or 2 polypropylene-based multilayer packaging film, it is at longitudinal direction and/or stretch with the draw ratio more than 2 times in a lateral direction.

6. claim 1 or 2 polypropylene-based multilayer packaging film, its total thickness is 3-25 μ m.

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