JPS6363579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a self-adhesive packaging film made of a polypropylene resin compound, and more specifically, it has improved adhesiveness, transparency, and cuttability, and has improved electronic The present invention relates to a self-adhesive packaging film that also has microwave suitability.

[Prior Art] This type of self-adhesive packaging film is widely used in households, restaurants, hotels, etc. to hermetically package food products, and is used to prevent drying when stored in refrigerators, and to prevent drying when stored in microwave ovens. It exhibits effects such as preventing drying when heated inside, preventing flavor or odor from dissipating or adsorbing odor during storage, and preventing dust from adhering when used for commercial purposes. In particular, with the recent spread of microwave ovens, the demand for this application has increased significantly. In other words, when cooking or heating food in a microwave oven, the container (generally made of ceramic or glass) containing the food is used to prevent water from evaporating and loss of flavor. Used for sealed packaging.

The packaging film used for such purposes has properties such as having low heat shrinkage in a microwave oven and not causing thermal melting or whitening phenomenon (hereinafter referred to as , "Microwave Suitability").

Conventional self-adhesive packaging films are known that are mainly made of polyvinylidene chloride, polyethylene, or polyvinyl chloride. However, films made of polyvinylidene chloride have the disadvantage of large shrinkage when heated, and films made of polyethylene melt if they come into contact with oily foods (e.g. meat, tempura, etc.) and are exposed to high heat. In addition, films made of polyvinyl chloride have the problem of whitening when they come into contact with boiling water. Therefore, all of these conventional self-adhesive films are inadequate in microwave oven suitability.

Furthermore, the cutting mechanism and usage method for the self-adhesive packaging film used for such purposes is, for example, a film with a width of 20 to 45 cm and a thickness of 10 cm wrapped around a core material such as a paper tube.
~20μm film is stored in a case such as a paper tube, and a "saw blade" is attached to this case.
The film is placed against a cutting blade known as a "cutting blade" and cut into appropriate lengths, and the film's adhesive properties seal the openings of food storage containers and the cut ends of the food.

The ``saw blade'' used to cut film is generally a simple blade made by punching out a saw-shaped iron plate approximately 0.2 mm thick, and a saw blade that supports this ``saw blade'' is generally used. Regarding the case,
Paper boxes made of coated cardboard with a weight of about 350 to 700 g/m ² are used, and their rigidity is extremely low.

This type of film is required to be easily cut according to the user's will even with such a simple cutting mechanism, but in reality, the case and "saw blade" are deformed. In addition to this, the film may be deformed or cut at a position that is outside the ``saw blade''. Specifically, when cutting conventional polyvinylidene chloride films, if a tear is created in a part of the film, this tear widens and becomes a "saw blade".
It is cut diagonally instead of along. In addition, conventional polyethylene films are
A considerable tensile force is required during cutting, which not only bends the case but also deforms the film.

For this reason, we proceeded with the development of a packaging film using polypropylene as the main raw material, which had not been tried before, and previously proposed a film obtained by blending a specific amount of polyethylene with polypropylene in JP-A-55-133439. However, the adhesiveness, transparency, cuttability, and suitability for microwave ovens were not satisfactory.

[Object of the Invention] Therefore, an object of the present invention is to provide a self-adhesive packaging film that has superior adhesiveness, transparency, cuttability, and microwave oven suitability.

[Structure of the Invention] The object of the present invention is to contain 2 to 70 parts of polyethylene having a number average molecular weight of 30,000 or less and 500 or more and 0.01 to 1 part of a nucleating agent, and a normal heptane extraction residue per 100 parts of polypropylene. 95% by weight or less
Achieved by a self-adhesive packaging film characterized by forming a polypropylene resin compound containing at least one of atactic polypropylene, petroleum resin, and rosin in an amount of 30% by weight or more. be done.

In addition, in the above resin blend, for 100 parts of polypropylene in the polypropylene resin blend,
A self-adhesive packaging film containing 0.01 to 5 parts of a surfactant is particularly preferred when formed into a film.

The present invention will be explained in detail below.

The polypropylene referred to in the present invention is primarily a propylene polymer. Also, one of other α-olefins (e.g. ethylene, butene, hexene, etc.)
It includes a species or a copolymer with two or more species.

In addition, as for polyethylene having a number average molecular weight of 30,000 or less and 500 or more as defined in the present invention, it does not matter how it is produced; as mentioned above,
Defined only by number average molecular weight [ ].
Current manufacturing methods include reducing the molecular weight by decomposing polyethylene with a molecular weight of 30,000 or more, synthesizing polyethylene with a lower molecular weight, or separating low-molecular-weight products that are by-products during the production of high-molecular-weight polyethylene. Other manufacturing methods are known. In addition, there are also similar products that have some functional groups and can be suspended. No matter which one of these is used, the effects of the present invention can be exhibited as long as the number average molecular weight [ ] is within the scope of the present invention. That is, it contributes to improving cuttability without impeding transparency.

If the number average molecular weight [ ] exceeds 30,000, transparency and adhesiveness will deteriorate, and if it is less than 500,
The effect of the present invention is small.

In the present invention, preferably polyethylene having a number average molecular weight [] of about 1000 to 5000 is used. This generally includes what is called polyethylene wax. Regarding the amount added, if it is less than 2 parts per 100 parts of polypropylene, the effect will be small, and if it exceeds 70 parts, the original performance of polypropylene will be lost, and this will affect its suitability for microwave ovens etc. . Methods for measuring the number average molecular weight include a method using a dilute solution and a method using a spectrophotometer, but the method is not limited to a specific method.

The nucleating agent used in the present invention is polypropylene
It is an additive that can raise the crystallization temperature of polypropylene by 2°C or more when added in an amount of 0.01 to 1 part per 100 parts.

Such nucleating agents include aromatic and saturated aliphatic dicarboxylic acids, benzoic acid, nuclear substituted benzoic acids,
Alicyclic carboxylic acids and metal salts of these various acids, as well as silicic anhydride, thioglycolic anhydride, p-toluenesulfonic acid, talc, sebacic acid, aluminum hydroxide, thiodiglycolic anhydride, and pt-butylbenzoic acid. acid, pt-butylbenzoic acid aluminum salt, dibenzylidene sorbitol, and the like.

If the content of the nucleating agent used in the present invention is less than 0.01 part, the effect of the present invention will not be seen, while if it exceeds 1 part, the nucleating agent will emboss on the film surface, impairing the sense of hygiene.

Generally, the crystallization temperature is determined by measurement using a differential thermal analysis device or a differential scanning calorimetry system. This refers to the temperature measured using the Rigaku Denki Kogyo (manufactured by Rigaku Denki Kogyo) under the following measurement conditions.

[Measurement conditions] Sample pretreatment None Weight of sample Approx. 10mg Heating rate 10℃/min Maximum temperature 250℃ Cooling rate 10℃/min Atmosphere In nitrogen gas flow The crystallization temperature of the sample was measured using the above device and measurement conditions. In this case, a melting peak is observed first,
Then, after increasing the temperature to 250°C, the temperature begins to decrease and a crystallization peak is observed. In the present invention, the temperature at the point where this crystallization curve is farthest from the baseline is defined as the crystallization temperature. The crystallization temperature measured in this way varies slightly depending on various additives.

The above-mentioned nucleating agent that can be used in the present invention is known as a nucleating agent or a crystallization promoter, and is added to a resin composition to make it transparent, for example, in thick molded products manufactured by injection molding. sex,
Used to increase mechanical strength. However, it is currently considered worthless in the field of thin films. However,
Surprisingly, it has been found that when a polypropylene film is formed by adding the above-mentioned nucleating agent to raise the crystallization temperature by 2°C or more, the cutting properties are significantly improved.

In this specification, the normal heptane extraction residue is a numerical value called Isotactic Index, which is commonly used for polypropylene. The film is extracted for 24 hours, the remainder is dried and weighed, and the value is expressed as the ratio to the total weight of the film before extraction.

In the present invention, at least one of actactic polypropylene, petroleum resin, and rosin is added to 100 parts of polypropylene, which contains 2 to 70 parts of polyethylene with a number average molecular weight of 30,000 or less and 500 or more and 0.01 to 1 part of a nucleating agent. The unique feature is that the self-adhesive packaging film produced by blending the seeds has a normal heptane extraction residue of 95% by weight or less and a normal heptane extraction residue of 30% by weight or more, and the normal heptane extraction residue is 95% by weight. or the heptane extraction residue
If it is less than 30% by weight, the adhesiveness or adhesion to ceramic or glass containers and the adhesiveness or adhesion of the film itself to itself will be poor.

To obtain the normal heptane extraction residue used in the present invention of 95% by weight or less and 30% by weight or more, 2 to 70 parts of polyethylene with a number average molecular weight of 30,000 or less and 500 or more per 100 parts of polypropylene; It is obtained from a polypropylene resin compound, which is obtained by adding 0.01 to 1 part of a nucleating agent and usually 1 to 70 parts of at least one selected from atactic polypropylene, petroleum resin, and rosin. In this case, the amount of atactic polypropylene, petroleum resin, and rosin added may be changed depending on the type of polypropylene and polyethylene used. It can be adjusted accordingly.

Atactic polypropylene as used in the present invention is amorphous polypropylene that is produced as a by-product when producing crystalline polypropylene by polymerizing propylene. Petroleum resin is an amorphous resin made directly from petroleum-based unsaturated hydrocarbons, such as cyclopentadiene or higher olefin hydrocarbons, and sulfuric acid, anhydrous aluminum chloride, boron fluoride, etc. as a catalyst. It is made by heating and polymerizing. Rosin is the residue obtained by steam distilling pine resin to remove terpene oils, and has a softening point of 80.
It is a pale yellow to brown brittle solid at temperatures around ℃.

In the present invention, the normal heptane extraction residue is reduced to 30% by adding atactic polypropylene, etc.
If the content is at least 60% by weight, preferably at least 60% by weight,
It is possible to obtain a self-adhesive packaging film that is suitable for microwave ovens (characteristics that have small heat shrinkage in microwave ovens and do not cause thermal melting or whitening phenomena).

In producing a film from the polypropylene resin formulation of the present invention, conventional additives may be included. For example, it is optional to include antioxidants, stabilizers, antiblocking agents, and antistatic agents. Note that the use of lubricants is not preferred since they impair self-adhesion.

Since self-adhesive packaging films require transparency and self-adhesiveness, blocking occurs easily (a phenomenon in which when films are wrapped around a core tube, the films stick to each other and become difficult to peel off).

In the present invention, in order to prevent the occurrence of blocking phenomena, it is preferable to include a surfactant as an additive during the production of the polypropylene resin composition of the present invention or during the film formation of this raw material. The surfactant used in the present invention is selected from one or more of the compounds listed below.

[Compound group]

Glycerin fatty acid ( _C8 - _C22 ) ester, sorbitan fatty acid (C8- _C22 ) ester, propylene glycol fatty acid ( _C8 - _C22 ) ester, sucrose fatty acid ( _{C8 - C22} ) ester, citric acid mono( di- or tri)stearic acid ester, pentaerythritol fatty acid ( _C8 - _C18 ) ester, polyglycerin fatty acid (C8-C18) ester, polyoxyethylene (20) glycerin fatty acid ( _C12 - _C18 ) ester, polyoxyethylene (20) glycerin fatty acid ( _C12 - _C18 ) ester, Oxyethylene (20) sorbitan fatty acid ( _C12 - _C18 ) ester, polyethylene glycol fatty acid ( _C8 - _C22 ) ester, polypropylene glycol fatty acid ( _C8 - _C18 ) ester, polyoxyethylene (9.5) dodecyl ether, poly Oxyethylene (4-14, 30-50) alkyl ( _C4 , ₉ , ₁₂ ) phenyl ether, N,N-bis(2
-Hydroxyethyl) fatty acid ( _C12 - _C18 ) amine, fatty acid ( _C12 - _C18 ) amine, fatty acid (C12 _-C18 )
C ₁₈ ) and diethanolamine condensation product,
Polyoxypropylene polyoxyethylene block polymer, polyethylene glycol (molecular weight
200-9500), polypropylene glycol, alkyl ( _C10 - _C20 ) sulfonate (Na, K,
_NH4 ), alkyl ( _C9 - _C20 ) benzenesulfonic acid (Na, K, _NH4 ), alkylnaphthalenesulfonate (Na), sodium dialkyl ( _C4 , ₅ , ₆ ,
₈ , ₁₃ ) Sulfosuccinate, alkyl (C10 _~
C20 ) sulfate (Na, K, _NH4 ), potassium stearate, N-acyl ( _C8 - _C18 ) sarcosinate.

The amount of surfactant added is preferably 0.01 to 5 parts per 100 parts of polypropylene.

Although it is possible to use a fatty acid amide type compound to reduce the blocking phenomenon, it cannot be used in the present invention because it inhibits self-adhesion.

The amount of surfactant used in the present invention is 0.01
If the amount is less than 5 parts, the effect of improving cutting properties will not be observed, and if it exceeds 5 parts, problems such as a decrease in self-adhesiveness and a decrease in transparency will occur.

It should be noted that the polyethylene, nucleating agent, and surfactant compositions used in the present invention do not necessarily need to be blended at the time of pelletizing the polypropylene resin blend, and may be blended at the time of film formation or other times. good.

For forming a film of the polypropylene resin compound of the present invention, a conventional general film forming method for polypropylene can be adopted. For example, the film may be made using an inflation method or a T-die method, and the extrusion temperature is about 200 to 280°C, and the film is extruded through an annular or flat slit.
It may be cooled and solidified in water or on a cooling roll.
The thickness of the film according to the present invention may be similar to the thickness of conventional wrap films mainly made of polyvinylidene chloride, polyethylene, or polyvinyl chloride,
Generally, it is 7 to 20μ.

[Effects of the Invention] According to the present invention, it is possible to provide a self-adhesive packaging film that has superior adhesiveness, transparency, cuttability, and microwave oven suitability.

[Examples] Hereinafter, the present invention will be illustrated by Examples, but the embodiments of the present invention are not limited thereto.

Example 1 100 parts of polypropylene resin (manufactured by Mitsui Toatsu Chemical Co., Ltd., Mitsui Noblen, EFL-G) had a density of 0.92 g/cm ³ ,
3 parts of polyethylene with a molecular weight of 27000, 0.5 sebacic acid
and 15 parts of atactic polypropylene were added, the crystallization increase temperature ΔTc = 5°C, and the normal heptane extraction residue was 60% by weight,
Pelletization was performed at 210°C using a conventional method.

The above pellets were made into a 10 μm film using an inflation film forming machine with the following specifications.

Diameter 40mm Screw full flight type L/D 22 Die Diameter 20cm Folding diameter 30cm Extrusion temperature 210℃ Screw rotation speed 40rpm Cooling Water cooling This film has a haze of 1.5% and is completely transparent, and has no adhesion to ceramic containers. It was good and warm. Furthermore, the temperature value measured by the microwave oven suitability measurement method described below was 120°C.

[Microwave suitability measurement method] Place paper 2.5 cm above and below a strip of film sample 3 cm wide and 14 cm long, and lower a 10 g weight. 1
The maximum ambient temperature that cannot be broken down by time is displayed in 10°C increments.

Furthermore, the film is wrapped around a core tube, and a case with a conventional "saw blade" (a 0.2 mm thick saw-shaped punched iron plate "saw blade" is attached to a 500 g/m ² coated cardboard case). Store it in the "saw blade"
Attempted amputation by As a result, it was found that the cutting property was good, as it could be cut straight by simply applying it to a "saw blade" and pulling it lightly, without any diagonal cuts.

Further, a film was obtained in the same manner as in Example 1 except that 0.05 part of glycerin monooleate was further added to the resin composition. As a result of evaluating it in the same manner, the following effects were shown in addition to the above effects. That is, the film was wound around a core tube and a storage test was conducted, but even under long-term high temperature storage conditions, no blocking phenomenon was observed and the storage stability was good.

Example 2 100 parts of polypropylene resin (manufactured by Mitsui Toatsu Chemical Co., Ltd., Mitsui Noblen, EFL-G) was added with a density of 0.92 g/
cm ³ , 10 parts of polyethylene with a molecular weight of 27,000, 0.25 parts of sebacic acid, and 10 parts of rosin were added, the temperature of increase in crystallization ΔTc was 2.5°C, and the residue extracted with normal heptane was 70% by weight. A film was made using the same method.

This film had a haze of 1.5%, was completely transparent, and had sufficient self-adhesion. When this was cut in the same manner as in Example 1, it was cut straight with just a slight pull, without any diagonal cuts. In addition, the temperature value according to the microwave oven suitability measurement method is also
The temperature was good at 125℃.

Example 3 100 parts of polypropylene resin (manufactured by Mitsui Toatsu Chemical Co., Ltd., Mitsui Noblen, JHH-G) was added with a density of 0.95 g/
cm ³ , 3 parts of polyethylene with a molecular weight of 5000, 0.25 parts of thiodiglycolic acid anhydride, and 5 parts of petroleum resin were added, the crystallization temperature rise ΔTc = 2.5 °C, and the normal heptane extraction residue was 92% by weight. A film was prepared in the same manner as in Example 1.

This film had a haze of 1.5%, was completely transparent, and had sufficient self-adhesion. When this was cut in the same manner as in Example 1, it was cut straight with just a slight pull, without any diagonal cuts. In addition, the temperature value according to the microwave oven suitability measurement method is also
The temperature was good at 140℃.

Comparative Example 1 100 parts of polypropylene resin (Mitsui Toatsu Chemical Co., Ltd., Mitsui Noblen, EFL-G) was added with a density of 0.92 g/cm ³ ,
10 parts of polyethylene with a molecular weight of 27,000, sebacic acid
A film sample was prepared in the same manner as in Example 1, with the addition of 0.25 parts and 2 parts of atactic polypropylene, a crystallization increase temperature ΔTc = 2.5°C, and a normal heptane extraction residue of 96% by weight. did. As a result, the self-adhesiveness was poor and the product was rejected.

Comparative Example 2 Polypropylene resin (Mitsui Toatsu Chemical, Mitsui Noprene, EFL-G) with a density of 0.95 g/cm ³ and a molecular weight
5000 polyethylene, 0.25 parts of sebacic acid, and 60 parts of atactic polypropylene were added, the crystallization increase temperature ΔTc = 2.5°C, and the normal heptane extraction residue was 27% by weight. A film was prepared in the same manner as in Example 1. A sample was prepared and examined. When the cuttability of this film was examined using the same method as in Example 1, the case with the "saw blade" was deformed and there was a problem with the cuttability.

Claims (1)

[Claims] 1. Contains 2 to 70 parts of polyethylene with a number average molecular weight of 30,000 or less and 500 or more and 0.01 to 1 part of a nucleating agent per 100 parts of polypropylene, and has a normal heptane extraction residue of 95% by weight or less 1. A self-adhesive packaging film, characterized in that it is formed by forming a polypropylene resin compound containing at least one of atactic polypropylene, petroleum resin, and rosin in an amount of 30% by weight or more. 2. The self-adhesive packaging film according to claim 1, wherein the polypropylene resin blend contains 0.01 to 5 parts of a surfactant per 100 parts of polypropylene.