JPH10237405A - Adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive compsn. of which the heat seal layer can be easily formed by extrusion and which is excellent esp. in adhesion to polypropylene and is useful as a heat sealant layer for a lid of a polypropylene- made container. SOLUTION: This compsn. contains 5-95wt.% ethylene-α-olefin copolymer having a density of 0.870-0.910g/cm<3> and 5-30wt.% ethylene-vinyl acetate copolymer having a vinyl acetate content of 8-42wt.% and a melt flow rate (at 190 deg.C under a load of 2160g) of 0.1-70g/10min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an adhesive composition comprising an ethylene / α-olefin copolymer and an ethylene / vinyl acetate copolymer. More specifically,
The present invention relates to an adhesive composition in which a heat seal layer can be easily formed by extrusion. This adhesive composition is particularly excellent in adhesiveness to polypropylene and is useful as a heat sealant layer for a lid material of a polypropylene container.

[0002]

2. Description of the Related Art Polypropylene containers are frequently used as containers for enclosing foods such as various dairy products, beverages, and tofu. In the containers, a heat sealant layer is provided on a base material for a lid material. The laminated lid material is used.

The heat sealable heat sealant layer in the above-mentioned lid material includes, for example, 1) a resin layer having a thickness of 10 μm or less made of an ethylene / vinyl acetate copolymer, a vinyl chloride / vinyl acetate copolymer, or the like; 2) a styrene resin or an ethylene / vinyl acetate copolymer resin formed to a thickness of about 20 μ; 3) low crystalline ethylene And those formed of a mixed resin of an α-olefin copolymer and a styrene / butadiene block copolymer.

[0004]

DISCLOSURE OF THE INVENTION The present invention relates to an adhesive composition which is easy to form a heat seal layer by extrusion molding, and particularly has excellent adhesiveness to polypropylene, and has a heat sealant layer for a cover material of a polypropylene container. The purpose of the present invention is to find an adhesive composition useful as an adhesive.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, the density was 0.8
A specific ethylene / α-olefin copolymer (hereinafter referred to as [A]) in the range of 80 to 0.910 g / cm ³ and a vinyl acetate content of 8 to 42% by weight;
A composition containing an ethylene / vinyl acetate copolymer (hereinafter referred to as [B]) having a melt flow rate of 0.1 to 70 g / 10 minutes measured under a load of 2160 g at a temperature of 2 ° C. The inventors have found that the adhesiveness is excellent, and have reached the present invention.

That is, the present invention relates to a composition comprising [A] and [B], wherein [A] contained in the composition is 70 to 95.
%, And 5 to 30% by weight of [B].

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION [A] used in the present invention
Any ethylene / α-olefin copolymer having a density of 0.880 to 0.910 g / cm ³ can be used, and preferably a density of 0.89 to 0.910 g / cm ^3.
An ethylene / α-olefin copolymer having a weight of 5 to 0.905 g / cm ³ . When the density is less than 0.880 g / cm ³ , the heat resistance of the resin composition is poor, and the density is 0.910 g / cm ^3.
If it exceeds g / cm ³ , the resulting resin composition will have poor adhesion. Further, those having a melt flow rate measured at 190 ° C. under a load of 2160 g within a range of 0.1 to 20 g / 10 minutes are preferable. Melt flow rate is 0.1g / 1
If it is less than 0 minutes or more than 20 g / 10 minutes, the moldability of the obtained resin composition will be poor.

Further, the ethylene / α-olefin copolymer has a small amount of low molecular weight components which inhibit the adhesiveness, and therefore, the gel permeation chromatography (GP)
The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured in C) is preferably 3 or less.

Further, since the ethylene / α-olefin copolymer has a uniform composition distribution, and particularly has a good low-temperature sealing property, the endothermic curve obtained from the measurement with a differential scanning calorimeter (DSC) is obtained. Temperature at maximum peak position (Tm
(° C.)) and the number of short-chain branches (SCB) per 1000 carbon atoms determined from the measurement of the ¹³ C-NMR spectrum preferably satisfy the relationship represented by the following formula (1).

Tm <−1.8 × SCB + 138 (1) [A] used in the present invention has a density of 0.880 to
Any ethylene / α-olefin copolymer of 0.910 g / cm ³ can be used. In particular, ethylene / α-
It is preferable to use an olefin copolymer. One or two such ethylene / α-olefin copolymers are used.
Or a metallocene compound in which a ligand having two cyclopentadiniel skeletons is coordinated to a transition metal of the group IVb to VIb of the periodic table, for example, titanium, zirconium or hafnium, or a metallocene compound and a metallocene It can be produced by using a catalyst system containing a compound capable of ionizing a compound to produce a cationic metallocene compound as a basic component.

Examples of the method for producing an ethylene / α-olefin copolymer using the above catalyst system include a gas phase method, a slurry method, a solution method, and a high pressure ionic polymerization method. Among them, it is preferable to produce the ethylene / α-olefin copolymer by a solution method in which polymerization is performed at a temperature from the melting point of the produced ethylene / α-olefin copolymer to 280 ° C., and a high-pressure ionic polymerization method, and particularly the ethylene / α-olefin copolymer used in the present invention. as,
It is preferable to produce by a high pressure ion polymerization method. Incidentally, the high pressure ionic polymerization method means that the pressure as described in JP-A-56-18607 and JP-A-58-225106 is 200 kgf / cm ² or more, preferably 300 to 300 kgf / cm ^2.
2000 kgf / cm ² , temperature of 125 ° C. or higher, preferably 130 to 250 ° C., particularly preferably 150 to 200 ° C.
Is a continuous method for producing an ethylene polymer under the reaction conditions of

The α-olefin copolymerized with ethylene has 3 to 20 carbon atoms. Examples of such α-olefin include 1-butene, 1-pentene, 1-hexene, 1-octene, 1-octene and the like. Heptene, 4-methylpentene-1, 4-methylhexene-1, 4,4-dimethylpentene-1, octadecene, and the like. Among these α-olefins, it is preferable to use 1-hexene, 1-octene, 1-heptene, and 4-methylpentene-1, and particularly preferable is 1-hexene having a high adhesive strength and a stable strength. .

[B] used in the present invention has a vinyl acetate content of 8 to 42% by weight,
The melt flow rate measured under a load of 0 g is 0.1 to
Any ethylene / vinyl acetate copolymer having a weight of 70 g / 10 minutes can be used. Further, an ethylene / vinyl acetate copolymer having a vinyl acetate content of 15 to 25% by weight is preferable, and an ethylene / vinyl acetate copolymer having a melt flow rate of 2 to 25 g / 10 minutes is preferable.

When the vinyl acetate content of the component (B) is less than 8% by weight, the adhesive strength is inferior, and the melt flow rate is less than 0.1%.
If it is less than g / 10 minutes or more than 70 g / 10 minutes, the resin composition obtained will have poor moldability and adhesiveness.

Further, the compounding ratio of [B] is preferably 5 to 30% by weight, and if it is less than 5% by weight, the adhesion to polypropylene is reduced. In addition, if the mixing ratio exceeds 30% by weight,
The melt viscosity of the composition is low, the processability is low, and the boil resistance is also disadvantageous. The adhesive composition of the present invention,
It can be obtained by uniformly kneading [A] and [B] at the above mixing ratio.

The adhesive composition of the present invention may contain commonly used auxiliary additives such as antioxidants, lubricants, anti-blocking agents, antistatic agents, pigments, dyes, etc. without departing from the object of the present invention. It may be added.

The adhesive composition of the present invention can be obtained by a general production method. For example, [A] and [B] are mixed in the above-mentioned mixing ratio with a Henschel mixer, a conical blender, and V.
A method such as dry blending using a blender or the like is employed. In order to knead more uniformly, a method of kneading with a single-screw or multi-screw extruder, a kneader, a Banbury mixer, a roll kneader or the like is preferable.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Synthesis Example Diphenylmethylene (cyclopentadienyl) (fluorenyl) zirconium dichloride: N, N-dimethylaniliumtetrakis (pentafluorophenyl) borate: triisobutylaluminum = 1: 2: 250
(Molar ratio), a polymerization temperature of 150 to 175 ° C. and a polymerization pressure of 900 kgf / cm.
^The copolymerization of ethylene and 1-hexene was performed in ² to obtain an ethylene / 1-hexene copolymer (1).

The obtained ethylene / 1-hexene copolymer (1) was measured by the following method.

Density: JIS K6760 (1981)
The density was measured using a density gradient tube kept at 23 ° C.

Melt flow rate (MFR): JIS
It was measured in accordance with K7210 (1976).

Weight average molecular weight (Mw), number average molecular weight (Mn): Mw and Mn are 150C manufactured by Nippon Millipore Co., Ltd.
ALC / GPC (column: GMHH, manufactured by Tosoh Corporation)
RH (S), three 7.8 mm ID × 30 cm, solvent: 1,2,4-trichlorobenzene, temperature: 140
C., flow rate: 1.0 ml / min, injection concentration 1 mg / ml (injection volume 300 μl)) was measured by gel permeation chromatography (GPC). The column elution volume was calibrated by universal calibration using standard polystyrene manufactured by Tosoh Corporation.

Short chain branch number (SCB): ¹³ C at 100 MHz using a solution containing orthodichlorobenzene as a solvent.
-NMR spectrum (JNM GX manufactured by JEOL Ltd.)
400) Calculated by measurement.

Melting point: Measured using a differential scanning calorimeter (DSC) (DSC-7, manufactured by PerkinElmer). D
After melting the sample at 200 ° C. for 5 minutes in the SC furnace,
Solidification (crystallization) by lowering the temperature to 30 ° C at a rate of ° C / min.
The temperature at the maximum peak position of the endothermic curve obtained by raising the temperature of the sample at a rate of 10 ° C./min (Tm (° C.))
Was measured.

The results obtained are shown in Table 1 (ethylene / 1-hexene copolymer (1)) and Table 2 (ethylene / 1-hexene copolymer (2)).

Reference Example Table 3 shows a commercially available ethylene / vinyl acetate copolymer (3) (trade name: Ultracene 633, manufactured by Tosoh Corporation; density: 0.9).
39 g / cm ³ , melt flow rate 20.0 g / 10
The results obtained by performing the same measurement as in the synthesis example are shown below.

Examples 1 to 3 The ethylene / 1-hexene copolymer (1) obtained in the synthesis example and a commercially available ethylene / vinyl acetate copolymer (3) were obtained by mixing (1) :( 3) = 75: 25. (Example 1), 80:20
(Example 2) As a composition of 90:10 (Example 3),
The mixture was mixed in a V blender, kneaded and granulated with a 40 mm single screw extruder (full flight screw) at a set temperature of 180 ° C. to obtain an adhesive composition.

Next, this adhesive composition was laminated on a polyethylene surface of a composite substrate (oriented polyester / polyethylene = 12/25 (μm)) with a thickness of 30 μm to obtain an evaluation sample film. This film and PP sheet (80 mm long x 100 mm wide x 0.35 mm thick) are heated at a temperature of 1
Heat sealing was performed under the conditions of 60 ° C., a pressure of 2 kgf / cm ² , and a time of 1 second, and the interfacial peel strength when peeling at 90 ° at a peeling speed of 300 mm / min was measured using an autograph (manufactured by Shimadzu Corporation).

The boil resistance test was performed as follows. Injection molded polypropylene cup (volume 1
35 ml), put 105 ml of water into the film, and use this evaluation sample film as a cover material, at a temperature of 160 ° C. and a pressure of 2 kgf / c.
Heat sealing was performed under the conditions of m ² and time of 1 second. Put the thing in this state in a constant temperature water bath at 90 ° C., leave it for 30 minutes, and take it out. By the expansion of air existing in the cup,
It was examined whether or not peeling occurred in the lid material seal portion. It is indicated by the number of samples that are not damaged even after boiling at 90 ° C. for 30 minutes out of 10 measurement samples. Table 4 shows the results. Each of the resin compositions according to the present invention shows good performance as a heat seal material. Also, in the boil resistance test of the laminate, it was confirmed that the laminate lid material did not peel off and had excellent boil resistance.

Comparative Example 1 Synthetic Example Using ethylene / 1-hexene copolymer (2), the same composition as in Example 1 (2) :( 3) = 75: 25
Was measured and evaluated. Table 4 shows the results. This resin composition is inferior in heat seal strength.

Comparative Example 2 Synthesis Example The same measurement and evaluation as in Example 1 were carried out using the ethylene / 1-hexene copolymer (1) alone. Table 4 shows the results. The heat seal strength is sufficiently high and the content is excellent in protecting the contents, but it is difficult to open, and there is a defect that fragments of the sealing layer film of the lid material remain in the opened portion.

Comparative Examples 3 and 4 The ethylene / 1-hexene copolymer (1) obtained in the synthesis example and the commercially available ethylene / vinyl acetate copolymer (3) were obtained by mixing (1) :( 3) = 98: 2. (Comparative Example 3), 65:35
As the composition of (Comparative Example 4), the same measurement and evaluation as in Example 1 were performed. Table 4 shows the results. Comparative Example 3 has a drawback that the heat seal strength is sufficiently large and the content is excellent in protecting the contents, but it is difficult to open, and fragments of the sealing layer film of the lid material remain in the opened portion. Comparative Example 4 is inferior in boil resistance and is not suitable for use requiring boil processing.

Comparative Example 5 The same measurement and evaluation as in Example 1 were carried out using a commercially available ethylene / vinyl acetate copolymer (3) alone. Table 4 shows the results. This resin composition has poor boil resistance and is not suitable for use in applications requiring boil treatment.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

As described above, the adhesive composition of the present invention is an adhesive composition in which a heat seal layer can be easily formed by extrusion molding. It is useful as a heat sealant layer for a lid material.

In addition, a heat seal layer having extremely preferable properties, such as exhibiting so-called peelable property by causing interfacial peeling from the heat seal surface at the time of peeling and also exhibiting boil resistance to enable boil sterilization treatment after heat sealing. Can be provided.

Claims (3)

[Claims] (A) a density of 0.880 to 0.910 g / c
m and ethylene · alpha-olefin copolymer ^3, a (b) a vinyl acetate content of 8 to 42 wt%, 190 ° C., 21
The melt flow rate measured under a load of 60 g is 0.1
Of ethylene-vinyl acetate copolymer having a weight of 70 g / 10 min.
An adhesive composition containing 0 to 95% by weight and 5 to 30% by weight of an ethylene / vinyl acetate copolymer. 2. An ethylene / α-olefin copolymer,
(I) the α-olefin has 3 to 20 carbon atoms, and (i)
The adhesive composition according to claim 1, wherein i) a melt flow rate measured at 190 ° C under a load of 2160 g is in a range of 0.1 to 20 g / 10 minutes. 3. An ethylene / α-olefin copolymer,
(I) Gel permeation chromatography (GP
The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured in C) is 3 or less, and (ii)
Temperature (Tm (° C.)) at the maximum peak position of the endothermic curve obtained from the measurement by the differential scanning calorimeter (DSC) and ¹³ C-NM
The adhesive according to any one of claims 1 to 2, wherein the number of short-chain branches (SCB) per 1000 carbon atoms determined from the measurement of the R spectrum satisfies the relationship represented by the following formula (1). Composition. Tm <−1.8 × SCB + 138 (1)