CN1070447C - Strippable film and strippable packing material - Google Patents

Abstract

The present invention provides an easy-peelable film having low-temperature sealability, heat resistance, and impact resistance, and an easy-peelable sealing material made of the easy-peelable film and a substrate.

The easy-peelable film and the easy-peelable sealing material formed by the easy-peelable film and the base material are characterized in that the content of α-olefin is 7-20% by weight, the density is 0.892-0.925g/cm ³ , at 190°C, 2.16 kg An ethylene-alpha-olefin copolymer having a melt flow rate (MFR) measured under load in the range of 0.1 to 40 g/10 minutes is made.

Description

Easy-peel film and easy-peel sealant

The present invention relates to an easy-peelable film and an easy-peelable sealing material using the easy-peelable film.

Polypropylene has excellent heat resistance, moldability, mechanical properties, and appearance, and is easy to dispose of waste, and has the advantages of having little influence on food.

By making effective use of the above characteristics, polypropylene can be widely used as packaging materials for various foods, or simple food containers that double as packaging materials. Therefore, easy-pull lids that can be opened without resistance with an appropriate force are widely used as lids for these containers. At the same time, it is desired to develop an easy-peel lid material that is most suitable for polypropylene.

Previously, it has been known that special resins such as ionomers and modified ethylene-vinyl acetate copolymers are used directly or in the form of a mixture as a sealant layer, exhibiting properties that can be easily peeled off from polypropylene, that is, have easy peeling properties. Non-volatile materials, or low-molecular-weight ethylene-vinyl acetate copolymer (EVA) and other adhesives are coated on the substrate film to make it exhibit moderate adhesive strength.

However, in the case of using an adhesive, there are problems such as deterioration of the working environment due to the use of an organic solvent in the coating process and leakage of contents due to lowering of mechanical strength at low temperatures. Moreover, these cover materials are easily deteriorated by heat and moisture due to the characteristics of sealing materials, and have poor heat resistance, which greatly limits their application range. In addition, ethylene-vinyl acetate copolymers and ionomers are prone to odor and are not suitable for food.

Also, a technique is known in which a raw material blank formed on a polypropylene basis is used as a sealant.

For example, in Japanese Patent Publication No. 61-246061, it is described that a resin composition formed of 40-80% by weight of polypropylene and 60-20% by weight of ethylene-α-olefin copolymer with low crystallinity is used as the heat-sealing part. Technology. On the other hand, Japanese Patent Publication No. Hei 6-328639 describes a technique in which a resin composition containing polybutene, polyethylene, and polypropylene is used as a heat-sealing portion, and polypropylene is used as a base material layer.

However, both resin compositions have problems of insufficient low-temperature sealability due to polypropylene being an essential component and a narrow temperature range suitable for heat sealing.

The object of the present invention is to provide an easy-peelable film having suitable easy-peelability, necessary and sufficient heat resistance, impact resistance and low-temperature heat-sealability when used as a packaging material, and the film and substrate Made of easy-peel sealing material.

The inventors of the present invention conducted research on an easy-peelable film having easy-peelability, heat resistance, impact resistance, and low-temperature heat-sealability, and an easy-peelable sealing material made of the film and a substrate, and as a result, unexpectedly The present invention has been accomplished by finding that a film using only a specific ethylene-α-olefin copolymer as a sealing material achieves the object of the present invention without using polypropylene.

That is, the present invention relates to an easy-peeling film characterized by containing 7-20% by weight of α-olefin, having a density of 0.892-0.925 g/cm ³ , and a melting point measured at 190°C under a load of 2.16 kg. The flow rate (MFR) is in the range of 0.1-40 g/10 minutes, formed from ethylene-alpha-olefin copolymer.

Furthermore, the present invention relates to an easily peelable sealing material characterized by comprising the aforementioned easily peelable film and a substrate.

The present invention will be described in detail below.

The term "easily peelable" in the present invention refers to the property that the sealability for actual use is ensured and the seal can be easily opened by human hands. Specifically, for the heat sealing of easy-peeling sealing materials and polypropylene resin containers, when the peeling speed is 300 mm/min, the results of the 180° or 90° peeling test are carried out, and the peeling strength is between 600- 2500g/15mm width or 400-2000g/15mm width range where the applicable sealing temperature is above 30°C is called easy peeling. If the 180°peel strength is lower than 600g/15mm width, or the 90°peel strength is lower than 400g/15mm width, the sealing of the contents will be reduced, and the impact during transportation will cause the peeling of the sealing part. On the other hand, if the 180° peel strength exceeds 2500 g/15 mm width, or the 90° peel strength exceeds 2000 g/15 mm width, it does not have easy peelability and is difficult to use for peeling.

The ethylene-α-olefin copolymer in the present invention contains 7-20% by weight of α-olefin, ideally 8-18% by weight, and has a density of 0.892-0.925g/cm ³ , preferably 0.895-0.920g/cm 3 . cm ³ , and the best is 0.895-0.912g/cm ³ . The density is measured in accordance with JIS-K6760.

When the content of α-olefin is less than 7% by weight, or the density exceeds 0.925 g/cm ³ , sufficient heat-sealing strength with polypropylene cannot be obtained, and the sealability of the contents is poor. Whereas, in the case where the α-olefin content exceeds 20% by weight, or the density is less than 0.892 g/cm ³ , the film becomes softer than necessary and becomes difficult to handle.

Examples of the α-olefin of the copolymer include α-olefins having 3 to 12 carbon atoms such as propylene, butene-1, hexene-1, and octene-1.

Moreover, in the present invention, the density of the ethylene-α-olefin copolymer is 0.895-0.920 g/cm ³ , and the α-olefin is an ethylene-α-olefin copolymer of an α-olefin having 3 to 12 carbon atoms An easy-peel film is ideal.

The melting flow rate (MFR) of the ethylene-α-olefin copolymer in the present invention is in the range of 0.1-40g/10min, ideally 0.1-25g/10min at 190°C and 2.16kg load.

When the MFR of the above-mentioned ethylene-α-olefin copolymer is less than 0.1 g/10 min, the processability of the film is poor and unfavorable. On the other hand, when the MFR exceeds 40 g/10 minutes, a stable molten film cannot be obtained, making it difficult to form a film, and if it is used as a cover material, the sealing layer will be severely deformed, which is not ideal due to poor heat-sealing strength and appearance.

When the ethylene-α-olefin copolymer of the present invention is made into a sheet with a thickness of 0.3 mm, the exudation on the surface of the sheet (but not including the exudation of additives) after a period of 7 days at 60° C. is low. An ethylene-α-olefin copolymer at 0.25 mg/cm ² is ideal.

The preparation method of the ethylene-α-olefin copolymer of the present invention can use ethylene and α-olefins, in the presence of Ziegler catalysts or metallocene catalysts, usually at 0-300°C, normal pressure-3000kg/ cm ² , in the presence or absence of solvent, in the form of gas-solid, gas-liquid, liquid-solid or homogeneous liquid phase. Furthermore, the polymerization may be carried out by any method of a batch type, a semi-continuous type, or a continuous type. It is even possible to carry out the polymerization under different reaction conditions divided into two or more steps. The molecular weight can be adjusted by adjusting the polymerization temperature, catalyst concentration, comonomer amount, etc., but it is more effective to add hydrogen to the polymerization system.

The Ziegler type catalyst is formed by a solid catalyst component containing a transition metal, a cocatalyst component formed of an organoaluminum compound, and a support as required.

Metallocene catalysts are one or more compounds with stable anions formed by reacting with reactants of organoaluminum hydrocarbon compounds, organoaluminum compounds, transition metal compounds, and organometallic compounds, and belong to group IVB of the periodic table of elements. A transition metal compound and, if necessary, a carrier are formed.

Although the ethylene-α-olefin copolymer of the present invention can be used alone, if the conditions of the final composition are within the scope of the present invention, the ethylene-α-olefin copolymer can also be ethylene-α-olefin One or more types of copolymers and/or ethylene homopolymers are used in combination.

For example, after mixing the above-mentioned mixture with a Henshire mixer (Henshiel Mikisa-), a tumble mixer, etc., the film can be directly formed into a film, or the above-mentioned mixture can be mixed by using an extruder, a mixer, a sealed mixer, etc. After mixing, granulate to form a thin film.

There is no particular limitation on the film-making method of the easy-peelable film of the present invention, generally, an air-filled film-forming film-making device, a T-die film-making device, etc. can be used.

The ethylene-α-olefin copolymer involved in the present invention may contain within the range that does not affect the purpose of the present invention: metal soap bases such as calcium stearate as required; neutralizing agents such as hydrotalcite; Butyl-p-cresol (BHT), tetrakis(methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)methane (IRGANOX1010), n-octadecyl -3-(4'-hydroxy-3,5'-di-tert-butyl-phenyl)propionate (IRGANOX1076) is a heat-resistant stabilizer of phenolic resins; bis(2,4-di- Phosphide heat-resistant stabilizers represented by tert-butylphenyl) pentaerythritol diphosphide and tris(2,4-di-tert-butylphenyl) phosphide; higher fatty acid amides and higher fatty acid esters Representative lubricants; antistatic agents such as aliphatic glycerol esters, sorbitol esters, and polyethylene glycol esters with a carbon number of 8-22; anti-blocking agents represented by silicon dioxide, calcium carbonate, and talc ; Weather-resistant stabilizers, anti-fogging agents, pigments, dyes, dripping agents, nucleating agents, etc. are usually used to add various mixtures to polypropylene resins.

The ethylene-α-olefin copolymer of the present invention may, if necessary, contain high-pressure polypropylene within a range generally used as a processability modifier and within a range that does not affect the object of the present invention.

The easily peelable sealing material of the present invention is composed of an easily peelable film formed of the above-mentioned ethylene-α-olefin copolymer and a substrate.

The easy-peelable film may use the ethylene-α-olefin copolymer of the present invention in a single layer, or the ethylene-α-olefin copolymer may be used as at least one surface layer in a multilayer film.

The method for forming the multilayer film is not particularly limited, and methods such as co-extrusion molding and sandwich molding may be mentioned.

Examples of materials for the multilayer film include polypropylene-based resins having a higher density than the above-mentioned ethylene-α-olefin light copolymers.

The method for producing the easily peelable sealing material of the present invention is not particularly limited, and examples thereof include various known methods such as dry lamination, extrusion lamination, sandwich lamination, and extrusion.

As the substrate of the present invention, for example, any polymer capable of forming a film or paper, aluminum foil, adhesive film, etc. can be used. Polymers capable of forming thin films include, for example, polyamide resins such as nylon 6, nylon 66, nylon 11, and nylon 12; polyethylene terephthalate, polybutylene terephthalate, and the like; Polyester resins; polyolefin resins such as polypropylene, poly-1-butene, and poly-4-methyl-1-pentene; polyvinylidene chloride, polyvinyl chloride, polystyrene, polyvinyl alcohol, ethylene · Vinyl alcohol copolymer, polycarbonate, etc., among them, gas barrier properties, printability, transparency, rigidity, adhesiveness, etc., can be appropriately selected. Furthermore, the base material can be used by laminating a plurality of raw materials as needed. Furthermore, in the case where the base material can be stretched, uniaxial stretching or biaxial stretching can be performed.

Among these raw materials, polyamide resins, polyester resins, aluminum foils, and the like are desirable base materials.

The polypropylene-based resin to be bonded to the easy-peelable film and the easy-peelable sealing material of the present invention is not particularly limited, and examples thereof include propylene homopolymer, propylene-ethylene random copolymer, and propylene-ethylene block copolymer things. The ethylene content of these copolymers is not particularly limited, and is, for example, 0.1 to 15% by weight.

As described above, according to the present invention, it is possible to provide an easy-peelable film having excellent low-temperature sealability, a wide heat-sealing temperature range, and heat resistance and impact resistance, and an easy-peelable sealing material composed of the easy-peelable film and a substrate.

Furthermore, the present invention is most suitable as an easy-peelable film and an easy-peelable sealing material for polypropylene-based resin containers and the like.

Example

The present invention will be described below based on examples, but these examples do not limit the present invention in any way.

First, methods of measuring physical parameters in the following Examples and Comparative Examples will be described. (1) Density (d)

According to the method stipulated in JIS K6760. Density was measured after annealing in water at 100° C. for 1 hour. However, when the density of the sample is less than 0.905g/cm ³ , annealing cannot be performed. (2) Melting flow rate (MFR)

According to the condition 4 of Table 1 of JIS K6760, the measurement was carried out under the conditions of 190°C and 2.16 kg load. (3) Surface exudation

Using a hot stamping machine at 150°C, several required sheets of 150mm×150mm×0.3mm were produced, and adjusted for 7 days in a 60°C oven without contacting each other. These slices, equivalent to each slice, are cleaned with about 300 ml of heptane, the solution is recovered, and weighed dry. Surface exudation was obtained by dividing the measured weight by the surface area of the tablet.

When measuring the amount of exudation on the surface, the samples used should be as additive-free as possible. Furthermore, when it is difficult to prepare an additive-free sample, the washed and recovered surface exuded components are measured by high-speed liquid chromatography and gas chromatography, and the concentrations of various additives are calculated and corrected based on the results. (4) α-olefin content

The characteristic absorption of α-olefins can be obtained by infrared spectrophotometer. (5) Sealing strength

The easy-peelable film side of the easy-peelable sealing material made of the base material and the easy-peelable film is laminated with the sheet formed of the polypropylene resin to be bonded. Under the pressure of 4kg/cm ² , after heat sealing on a 10mm silverware, fully cool. Take a test piece with a width of 15 mm from the obtained sample, and the strength when peeling off the sealed portion at a crosshead speed of 300 mm/min at a peeling angle of 180° and 90° is called the sealing strength (g/15mm) .

In Examples and Comparative Examples, the substrate layer and the easily peelable film could not be peeled off, but the sheet made of polypropylene resin as an adherend could be peeled off from the easily peelable film. (6) Impact strength

Measured according to ASTM D1822-61T.

Example 1

The ethylene-1-hexene copolymer with a density of 0.912g/cm ³ and an MFR of 2g/10min was formed by blown film at a processing temperature of 170°C, and passed on the stretched polyamide film Dry the sandwich for gluing. After heat-sealing it with a 500-micron tablet formed of a bonded propylene-ethylene random copolymer (MFR (measured at 230° C.) of 7.5 g/10 min, ethylene content of 4.5% by weight) under the above conditions, For others, the density strength was measured under the same conditions as above. The results are listed in Table 1.

Example 2

Except that the ethylene-1-hexene copolymer in Example 1 was replaced by an ethylene-1-butene copolymer with a density of 0.905 g/cm ³ and an MFR of 2 g/10 minutes, the procedure was the same as in Example 1.

The measurement results are listed in Table 1.

Example 3

Except that the ethylene-1-hexene copolymer with a density of 0.908 g/cm ³ and an MFR of 2 g/10 minutes was used instead of the ethylene-1-hexene copolymer in Example 1, the procedure was the same as in Example 1.

The measurement results are listed in Table 1.

Example 4

Except that the ethylene-1-hexene copolymer with a density of 0.921 g/cm ³ and an MFR of 2 g/10 minutes was used instead of the ethylene-1-hexene copolymer in Example 1, the procedure was the same as in Example 1.

The measurement results are listed in Table 1. Comparative example 1

Except that the ethylene-1-hexene copolymer with a density of 0.932 g/cm ³ and an MFR of 2 g/10 minutes was used instead of the ethylene-1-hexene copolymer in Example 1, the procedure was the same as in Example 1.

The measurement results are listed in Table 1.

Example 5

Except that the ethylene-1-hexene copolymer with a density of 0.908g/cm ³ and an MFR of 2g/10min was used instead of the ethylene-1-hexene copolymer in Example 1, the MFR of the adherend (measured at 230°C ) was 8.5 g/10 minutes of propylene homopolymer, the others were carried out in the same manner as in Example 1.

The measurement results are listed in Table 2.

Example 6

Except that the ethylene-1-hexene copolymer in Example 5 was replaced by an ethylene-1-butene copolymer with a density of 0.905 g/cm ³ and an MFR of 2 g/10 minutes, the procedure was the same as in Example 5.

The measurement results are listed in Table 2. Comparative example 2

Except that the ethylene-1-hexene copolymer with a density of 0.932 g/cm ³ and an MFR of 2 g/10 minutes was used instead of the ethylene-1-hexene copolymer in Example 5, the procedure was the same as in Example 5.

The measurement results are listed in Table 2.

Example 7

In addition to using the ethylene-1-butene copolymer with a density of 0.905g/cm ³ and an MFR of 2g/10min instead of the ethylene-1-hexene copolymer in Example 1, and using a propylene-ethylene interlayer as the adherend Except for the segment copolymer (MFR (measured at 230° C.) of 9 g/10 minutes, and ethylene content of 2% by weight), the same procedures as in Example 1 were carried out.

The measurement results are listed in Table 3.

Example 8

Except that the ethylene-1-butene copolymer in Example 7 was replaced by an ethylene-1-hexene copolymer with a density of 0.908 g/cm ³ and an MFR of 2 g/10 minutes, the procedure was the same as in Example 7.

The measurement results are listed in Table 3. Comparative example 3

Except that the ethylene-1-butene copolymer in Example 7 was replaced by an ethylene-1-hexene copolymer with a density of 0.932 g/cm ³ and an MFR of 2 g/10 minutes, the procedure was the same as in Example 7.

The measurement results are listed in Table 3.

Example 9

In addition to using an ethylene-1-butene copolymer with a density of 0.900 g/cm ³ and an MFR of 2 g/10 minutes instead of the ethylene-1-hexene copolymer of Example 1, MFR (at 230° C. Measurement) was carried out in the same manner as in Example 1 except that the propylene homopolymer was 60 g/10 minutes and contained 2.5% by weight of titanium dioxide.

The measurement results are listed in Table 4.

Example 10

The same procedure as in Example 9 was carried out except that the ethylene-1-butene copolymer in Example 9 was replaced with an ethylene-1-butene copolymer having a density of 0.895 g/cm ³ and an MFR of 2 g/10 minutes.

The measurement results are listed in Table 4. Comparative example 4

The same procedure as in Example 9 was carried out except that the ethylene-1-butene copolymer in Example 9 was replaced by an ethylene-1-butene copolymer with a density of 0.890 g/cm ³ and an MFR of 1 g/10 minutes.

The measurement results are listed in Table 4.

No peel strength was exhibited after heat sealing due to excessive exudation on the surface. Table 1

Example 1 Example 2 Example 3 Example 4 Comparative example 1 adherend Propylene-ethylene random copolymer α-olefin containing C’6 C’4 C’6 C’6 C’6

Weight% 13.0 11.2 13.3 10.8 5.4 Surface exudation 0 0 0.02 0 0mg/cm ² MFRg/10min 2 2 2 2 2 Density g/cm ³ 0.912 0.905 0.908 0.921 0.932 Impact strength 1500 1300 1770 1360.cm/6 cm ²密封强度g/15mm180°剥离160℃ 880 1730 1580 950 820190℃ 1070 2280 2150 1020 900220℃ 990 2050 2130 1030 82090°剥离60℃ 410 2280 1570 340 310190℃ 440 2100 1830 440 300220℃ 540 1830 1760 470 310表2

Example 5 Example 6 Comparative example 2 adherend Propylene homopolymer α-olefin containing C’6 C’4 C’6

Weight % 13.3 11.2 5.4 Surface exudation 0.02 0 0mg/cm ² MFRg/10 minutes 2 2 2 Density g/cm ³ 0.908 0.905 0.932 Impact strength 1770 1300 650kg.cm/cm ² Sealing strength g/15mm 180°peel 160 ℃ 1560 1400 510190℃ 1670 1650 650220℃ 1820 1620 92090°Peel 160℃ 570 1150 150190℃ 1200 1410 390220℃ 1200 1860 350Table 3

Example 7 Example 8 Comparative example 3 adherend Propylene-ethylene block copolymer α-olefin containing C’4 C’6 C’6

Weight % 11.2 13.3 5.4 Surface exudation 0 0.02 0mg/cm ² MFRg/10 minutes 2 2 2 Density g/cm ³ 0.905 0.908 0.932 Impact strength 1300 1770 650kg.cm/cm ² Sealing strength g/15mm 180°peel 160 ℃ 1730 1730 550190℃ 1760 1990 1010220℃ 1900 1870 91090°Peel 160℃ 1570 630 170190℃ 1490 960 390220℃ 1750 1150 380Table 4

Example 9 Example 10 Comparative example 4 adherend Propylene homopolymer α-olefin containing C’4 C’4 C’4

Weight % 13.6 14.0 16.0 Surface Exudation 0.18 0 0.30mg/cm ² MFRg/10min 2 2 1 Density g/cm ³ 0.900 0.895 0.890 Impact Strength 800 1350 1000kg.cm/cm ² Sealing Strength g/15mm180°Peel 160°C 800 1790 Peel 190°C 1490 1680 Peel 220°C 1550 1770 Peel 90°Peel 160°C 440 1730 Peel 190°C 1520 1550 Peel 220°C 1500 1530 Peel

Claims (5)

1. An easy-peelable film, characterized in that it contains 7-20% by weight of α-olefin, has a density of 0.892-0.925g/cm ³ , and has a melt flow rate measured at 190°C under a load of 2.16kg. 0.1-40g/10min range of ethylene-alpha-olefin copolymer. 2. The easily peelable film according to claim 1, characterized in that the density of the ethylene-α-olefin copolymer is 0.895-0.920 g/cm ³ , and the α-olefin is an α-olefin with 3-12 carbon atoms. olefins. 3. The easy-peelable film according to claim 1, wherein when the ethylene-α-olefin copolymer is made into a sheet with a thickness of 0.3 mm, after 7 days at 60° C., the surface of the sheet Among the exudates, the amount of exudates other than additive exudates is below 0.25 mg/cm ² . 4. An easy-peelable film, characterized in that it is composed of a multi-layer film, at least one surface layer of the multi-layer film is the easy-peelable film according to any one of claims 1-3. 5. An easy-peelable sealing material, characterized in that it consists of the easy-peelable film and substrate according to any one of claims 1-4.