JPS5847043A - Self-adhesive packaging film - Google Patents

Abstract

PURPOSE:To provide the titled film useful for the packaging of foods and having excellent cutting properties, tackiness, blocking resistance and microwave oven applicability, by molding into a film a resin compsn. consisting of PP, PE having a specified MW and a nucleating agent and having an n-heptane-extraction residue content within a specified range. CONSTITUTION:2-70pts.wt. PE having a number-average MW of 500-30,000 and 0.01-1pt.wt. nucleating agent such as silicic anhydride or p-toluene-sulfonic acid are blended with 100pts.wt. PP to obtain a compsn. having an n-heptane- extraction content of 30-95wt%. If necessary, 0.01-5pts.wt. surfactant such as a 12-18C aliph. amine or potassium stearate is added thereto. The mixture is kneaded and pelletized. The pellets are extruded at 200-280 deg.C through an inflation die or a T-die. The extrudate is cooled with water or a cooling roll to obtain a self-adhesive packaging film of 7-20mu in thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a self-adhesive packaging film made of a polypropylene resin composition, and more specifically, has significantly improved cuttability, viscosity, anti-blocking properties, and microwave oven suitability. This invention relates to a self-adhesive packaging film.

This Dan's self-adhesive packaging film is widely used in general households, restaurants, hotels, etc. to hermetically package foods. It exhibits effects such as preventing drying when heated, preventing flavor or odor from dissipating or absorbing odor during storage, and preventing dust from accumulating when used for commercial purposes. In particular, with the recent spread of microwave ovens, is it possible to use this for this purpose? J-san is joining the party.

In other words, when cooking or heating food in a microwave oven, the container in which the food is placed (generally made of ceramic or glass ψ) is used to prevent water from evaporating and losing flavor. Used for sealed packaging.

The cutting mechanism and usage method for self-adhesive packaging films used in such applications include, for example, cutting a film with 20 to 45 microorganisms and a thickness of 10 to 20 μm wrapped around a paper tube with a terminal core material into a case such as a paper box. The film is placed on a cutting blade called a 71c "saw blade" attached to this case, and the film is pulled out and cut to an appropriate length. It is used to seal the cut ends of foods.

The above-mentioned "saw blade" used for cutting film is
Generally, a simple blade is used, which is simply a saw-shaped blade punched out of an iron plate with a thickness of about α2-thickness, and the case supporting this "saw blade" is made of coated cardboard with a weight of about 350 to 700 g/d. A paper box made of paper is used, and its 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, there are cases where the case or the "saw blade" is deformed. Instead of υ, the film may be deformed or
There are cases where the saw blade comes off and the cut occurs at the 9 position. Specifically, when conventional polyvinylidene chloride films are cut, cracks form in part of the film, and these cracks widen and are cut along the "saw blade". It is dangerous to cut diagonally. Also, conventional polyethylene films undergo considerable tensile force when cut, resulting in not only the case being bent but also the film being deformed.

On the other hand, the demand for self-adhesive packaging films for this purpose has increased significantly with the recent spread of microwave ovens. In other words, when cooking or warming food in a microwave oven, a container (generally made of ceramic or glass) containing the food is used to prevent the moisture in the food from evaporating and causing the food to lose its flavor. Used for sealed packaging.

Packaging films used for such purposes are required to have a property (hereinafter referred to as microwave suitability) that has little heat shrinkage in a microwave oven and does not cause thermal melting or whitening phenomena.

However, conventional films made of polyvinylidene chloride have the disadvantage of large shrinkage when heated, and conventional films made of polyethylene have the disadvantage that when they come into contact with oil parts (e.g. meat, tempura, etc.) and become highly heated, In addition to the drawback that the film melts in the bath, films made of conventional polyvinyl chloride undergo a whitening phenomenon when exposed to boiling water, making them unsuitable for use.Therefore, these conventional self-adhesive packaging films There is no doubt that all of them have sufficient microwave oven suitability.

The present inventors have proceeded with the development of a packaging film based on polypropylene, which has not been tried before, and has achieved
As a result of intensive research and efforts to improve transparency, cuttability, storage stability, and suitability for microwave ovens, we have completed the present invention.

An object of the present invention is to provide a self-adhesive packaging film that has excellent adhesiveness and transparency, and has improved cutting properties, anti-blocking properties, and microwave oven suitability.

The above object of the present invention is to provide 100 parts of polypropylene,
Polyethylene 2 with a number average molecular weight of 30,000 or less and 500 or more
-70 parts of a nucleating agent and 0.01 to 1 part of a nucleating agent, and a self-adhesive film formed from a polypropylene resin composition whose normal heptane extraction residue is 95% by weight or less and 30% by weight or more. This is achieved through flexible packaging films.

According to a preferred embodiment of the present invention, 2 to 70 parts of polyethylene having a number average molecular weight of 30,000 or less and 500 or more and 1 to 1 part of a nucleating agent α are contained per 100 parts of polypropylene, and the crystallization temperature of the polypropylene is A polypropylene resin composition which is allowed to rise by 2°C or more and has a normal hebutane extraction residue of 95% by weight or less and 30% by weight or more, and contains 0.01 to 5 parts of a surfactant. A self-adhesive packaging film is produced by forming a film using the following as a main component.

The present invention will be described below.

In the present invention, "part" means "part by weight."

The polypropylene resin composition referred to in the present invention is primarily a propylene polymer. In addition, other α-olefins (
For example, it contains a copolymer with one or more of the following: ethylene, butene, hexacene, etc.).

The number average molecular weight 0-] specified in the present invention is 30,000 or less and 50
Regarding polyethylene having a molecular weight of 0 or more, the number average molecular weight (Mn
).

Current manufacturing methods include polyethylene with a molecular weight of 30,000 or more that is decomposed to lower its molecular weight, synthesis of polyethylene with a lower molecular weight, or low molecular weight polyethylene that is a by-product during the production of high-molecular-weight polyethylene. Manufacturing methods such as separation of lid products are known. In addition, there are similar products that have some functional groups and can be suspended. No matter which one of these, if the number average molecular weight (Mn) is within the scope of the present invention,
The effects of the present invention are exhibited. That is, it contributes to improved cutting performance without impairing transparency.

When the number average molecular weight (Mn) exceeds 30,000, transparency and adhesiveness deteriorate, and when it is less than 500.

The effect of the present invention is small.

In the present invention, preferably the number average molecular weight (Mn) is 1
000 to about 5000 polyethylene is used. This generally includes what is called polyethylene wax. Regarding the amount added, polypropylene 10
If the amount is less than 2 parts compared to 0 parts, the effect will be small, and if it exceeds 70 parts, the inherent performance of polypropylene will be lost, which will further impede its suitability for microwave ovens.

Methods for measuring the number average molecular weight (Mn) include a method using a dilute solution and a method using a spectrophotometric needle, but the method is not limited to a specific method.

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

Such nucleating agents include aromatic and saturated aliphatic dicarboxylic acids, benzoic acid, nuclear-substituted benzoic acids, alicyclic carboxylic acids, and gold salts of these various acids, as well as silicic anhydride, thioglycolic anhydride, and paratoluene. Sulfonic acid, talc,
Furthermore, sebacic acid, aluminum decide, thiodiglycolic anhydride, p-1-butylbenzoic acid sp-'-
Examples include 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; on the other hand, if it exceeds 1 part,
This creates a dusty appearance on the film surface, impairing the sense of hygiene.

Generally, the crystallization temperature is measured using a differential thermal analyzer (Differ).
-nential Thermal Analysis)
, Differential Scanning Calorie Needle (Differ- ential Sc
The crystallization temperature in the present invention refers to the temperature measured using a differential scanning calorimeter (manufactured by Rigaku Denki Kogyo) under the following measurement conditions.

〔Measurement condition〕

When the crystallization temperature of the sample was measured using the above device and measurement conditions, a melting peak was observed first, then 250°C
When the temperature is raised to 6, 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. used to increase strength and mechanical strength. However, it is currently considered worthless in the field of thin films. However, surprisingly, it was found that when a film was formed from a polypropylene resin composition in which the crystallization temperature was increased by 2°C or more by adding the above-mentioned nucleating agent as an additive, the cutting performance was significantly improved. .

In particular, in the present invention, sufficient tackiness can be achieved by combining the nucleating agent of the present invention with 2 to 70 parts of the polyethylene of the present invention described above and polypropylene with normal heptane extraction residual electricity within the scope of the present invention. In addition, the cutting properties can be significantly improved, and the suitability for microwave ovens, transparency, and anti-blocking properties can be significantly improved.

In this specification, the normal heptane extraction residue refers to
It is a numerical value measured by a method substantially the same as the method for measuring ctic index, and a film made of the polypropylene resin composition of the present invention is extracted with boiling normal heptane using a Soxhlet extractor for 24 hours, and the remainder is dried. This value is expressed as a ratio to the total weight of the film before extraction. The extraction valve is mainly made of atactic polypropylene, but is not limited to this, and may contain other hydrocarbons, rosin, petroleum resin, etc.

In the present invention, if the normal hebutane extraction residue exceeds 95% by weight, that is, if the extraction valve is less than 5% by weight, the adhesiveness or adhesion of the film to ceramic or glass containers, and the adhesion of the film itself to each other, may be reduced. The quality or adhesion will deteriorate. On the other hand, if the normal heptane extraction residue is less than 30% by weight, that is, if the extraction valve exceeds 70% by weight,
The film itself is too flexible, and if the value measured by the microwave suitability measurement method described below is 100°C or less, it will not be suitable for microwave ovens. In the present invention, in order to obtain sufficient microwave oven suitability, a polypropylene resin composition having a normal hebutane extraction residue of 90 to 60% by weight is formed into a film.

The normal hebutane extraction residue used in the present invention is 95%
~30% by weight of the polypropylene resin composition is selected from the group consisting of atactic polypropylene, petroleum resins, rosin, and other hydrocarbons during the production of polypropylene resin compositions with conventional polypropylene homopolymers and/l or random copolymers. At least one type of normal heptane extracted component may be added or not added, and the residual amount of this normal heptane extraction may be 30 to 95% by weight.

In the present invention, by incorporating 0.001 to 5 parts of a surfactant during production of the polypropylene resin composition raw material of the present invention or during film formation of this raw material, in addition to the above-mentioned cutting properties, blocking phenomenon prevention performance is achieved. Particularly effective surfactants in the present invention that can impart 0 include the following.

Glycerin fatty acid (C8-C2□) ester, norbitan fatty acid (Co-CD) ester, propylene gel 17:
j-le fatty acid (C8-C2 ester, sucrose m fat x<
C, ~ CD) ester, citric acid mono(di or tri)stearate, pentaerythritol fatty acid (・
C8~C1,) ester, polyglycerin fat @(C8
~Cpg) ester, polyoxyethylene (20) glycerin fatty acid (C12~Cx8)-n stel, polyoxyethylene (20) norbitane fat 1m (C8~C2□
) ester, polyethylene/IJ:ff-rumu
Acid (Cm~C2□) ester, polypropylene glycol fatty acid (08~C88) ester, polyoxyethylene (9,5) dodecyl ether, polyoxyethylene (
4-14.30-50) Alkyl (Ca, s, ss) phenyl ether, N, N-bis(2-hydroxyethyl) fatty (C8-C2□) amine, fatty acid (C, □-C,
@) Amine, condensation product of fatty acid (C12 to C1,) and jetanolamine, polyoxypropylene polyoxyethylene block polymer, polyethylene glycol (molecules 1200 to 500), polypropylene glycol, alkyl (C10"Cm.) Sulfonate (N
a, N1(4), alkyl (C0-C2°)benzenesulfonate (Na, K, NHL) alkylnaphthalenesulfonate ('Na), sodium dialkyl (C4, s0g'1.la) sulfonate Succinate, alkyl (C>o-Czo) sulfate (Na,
NH4), potassium stearate, N-acyl (C8~
C2□) Sarcosinate, etc. are effective. Conventionally, rounded fatty acid amide-based compounds have been used to reduce the blocking phenomenon, but they cannot be used in the present invention because they inhibit self-adhesion.

If the amount of the surfactant used in the present invention is less than 0.01 part, no improvement in cutting properties will be observed, and if it exceeds 5 parts, problems such as a decrease in self-adhesiveness and a decrease in transparency will occur. It turns out.

In the present invention, general additives may be included in addition to the additives of the present invention described above. 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.

The method for producing the film according to the present invention is arbitrary.

For example, the polyethylene of the present invention, a nucleating agent (and surfactant), or atactic polypropylene, etc. are added to a polypropylene resin composition along with other additives such as an antioxidant, a stabilizer, and an antistatic agent using an extruder. Knead it,
It may be formed into pellets and used as a raw material for film formation described below.

For forming a film of the polypropylene resin composition whose crystallization temperature has been raised by 2° C. or more and which contains various additives according to the present invention, conventional general film forming methods for polypropylene can be employed. For example, the film may be made using the inflatable blowing method or the -T die method. The extrusion temperature is about 200 to 280°C, extruded through an annular or flat slit, and cooled with water or on a cooling roll. Just let it solidify. The thickness of the film according to the present invention may be the same as that of conventional so-called laminate films, and is generally 7 to 20 μm.

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

The present invention will be illustrated below with reference to Examples, but the embodiments of the present invention are not limited thereto.

Example 1 100 parts of a polypropylene resin composition (Sankata Noprene, GFL-G, manufactured by Sankata Noryo Kagaku Co., Ltd.) was added with a density of 0.9 part M/c.
d, 10 parts of polyethylene with a molecular weight of 5000 and 0.2 parts of sepacic acid as a nucleating agent were added to increase the crystallization temperature Δ
Tc = 2.5°C, and the normal heptan extraction residue was 90% by weight with glycerin monoole) 0
．． After mixing with a mixer and pelletizing in a usual manner at 220°C, a film was formed to a thickness of 12μ using a T-die film forming machine with the following specifications to obtain sample size 1 of the present invention. Ta.

The film of this sample Nal had a haze of 15%, was completely transparent, and had excellent adhesion to ceramic containers. In addition, the temperature value according to the microwave oven suitability measurement method below is also 1.
The temperature was 40°C, which was good.

Microwave Oven Suitability Measurement Method] Place paper on the top and bottom 255I of a strip-shaped film sample piece with a width of 3Z and a length of 1451, and then lower a 10g weight.

Displays the maximum ambient temperature that does not expire in 1 hour in 10°C increments. (Refer to Tokyo Metropolitan Ordinance No. 1072 “Quality Labeling of Wrap Films”) In addition, the film of sample size 1 above was wrapped around a core tube, and a case with a conventional general “saw blade” (0.2 mm thick saw-shaped punched An iron plate ``saw blade'' was attached to a 500 g/j coated cardboard case and stored in ψ, and an attempt was made to cut with the ``saw blade''. (The cuttability was very good, as it cut straight with just a light pull and did not cut diagonally. Also, a 1'hl sample of film was similarly wrapped around a core tube and a storage test was conducted. Even under long-term high-temperature storage conditions, no blocking phenomenon was observed and the storage stability was good.

Example 2 100 parts of a polypropylene resin composition (Sankata Noprene, EFL-G, manufactured by Sankata Noryo Kagaku Co., Ltd.) was added with a density of 0.92 f.
/- 3 parts of polyethylene with a molecular weight of 27,000 was added, 0.5 parts of mono(sinic acid) was added as a nucleating agent, the crystallization increase temperature ΔTcx was 5°C, and 15 parts of atactic polypropylene was added, followed by normal heptane extraction. The remaining amount is 6
Extruded pellets were obtained from those with zero heavy charge.

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

The haze of this film is 1.2% and it is completely transparent.
Moreover, the self-adhesiveness was also sufficient. When this was cut in the same manner as in Example-1, it was found that although the film in Example-1 was also slightly stronger, it was cut straight with just a very light pull compared to the conventional product, and there were no diagonal cuts. There wasn't.

Further, no blocking phenomenon was observed, and the storage stability was good. Furthermore, the temperature value determined by the microwave oven measurement method is also 1
The temperature was good at 20°C.

Comparative Example 1 100 parts of polypropylene resin composition (Sankata Noprene, GFL-G, manufactured by Sankata Noryo Kagaku Co., Ltd.) had a density of 0.959/-
Containing 10 parts of polyethylene with a molecular weight of 400, 0.005 parts of thioglycolic anhydride was added as a nucleating agent, the crystallization temperature increased Δ'I'c = 1°C, and the normal hebutane extraction residue was 96% by weight. Example 1. A film was obtained in the same manner as above.

The cuttability of this film was measured in Example 1. When we investigated using the same method as above, we found that not only was a strong tensile force required when cutting with a saw blade, but the adhesiveness was also insufficient.

Comparative Example 2 100 parts of a polypropylene resin composition (Sankata Noprene, EFL-G, manufactured by Sankata Noryo Kagaku Co., Ltd.) had a density of 0.93 f/
- Contains 10 parts of polyethylene with a molecular weight of 35,000, to which 1 part of thiodiglycolic anhydride is added as a nucleating agent, at a crystallization increase temperature ΔTc = 1'C, with 27% by weight of normal hebutane extraction residue. A film sample was prepared and examined in the same manner as in Example 2.

The results showed that not only was the microwave oven suitability value poor at 100℃, but the transparency was 3.0, the tackiness was poor, and the cutting performance was also found to be unstable, so it was rejected. .

Patent applicant: Mitsui Toatsu Chemical Co., Ltd. Representative Patent Attorney Nobuaki Sakaguchi (1 other person)

Claims (2)

[Claims] (1) Contains 2 to 70 parts of polyethylene with a linear 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% or less 1. A film for packaging made from a thick, sticky material, characterized by being formed from a polypropylene resin composition having a weight and density of 30% or more. (2) Contains 0.01 to 5 parts of "Kaikou Tsuki wo Shushu Oki" per 100 parts of polypropylene.
+J'i. 7. A self-adhesive packaging film according to Item 1, characterized in that it is made by forming a film from a watch U+.