JPH10329195A - Manufacture of t-die cast film and the film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent low odorousness, low taste transfer, thermal stability and impact resistance by processing a specific ethylene polymer or resin composition containing the polymer via a die gap at specific melting temperature. SOLUTION: Ethylene polymer or resin composition containing the polymer having a density of 0.88 to 0.95 g/cm<3> and melt index of 21.6 kg load at 190 deg.C of 30 to 2000 g/10 min is used. It is processed via a die gap at a melting point of 210 deg.C or lower. And, a lower limit value of the melting temperature is a temperature exceeding a highest crystallizing temperature of copolymer or composition. An antioxidant is used for a small amount for processing at the low temperature or not used at all. And, a small amount of anti-blocking agent or lubricant is added as needed. When a film to be measured has a multilayer, it can be applied to one layer therein. Thus, excellent low odorousness, low taste transfer, thermal stability and impact resistance are realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing a T-die cast film by processing a specific ethylene polymer or a resin composition containing the ethylene polymer at a low temperature.
The present invention relates to a die cast film and a multilayer T die cast film.

[0002]

2. Description of the Related Art In recent years, packaging materials using plastic films have been evaluated for their characteristics such as ease of handling, and the demand for plastic films using polyethylene resins and the like has increased dramatically. As the demand grows, applications are expanding, and packaging films are required to have new performances that have never existed before. For example, the film has low odor and low taste transferability. If the plastic film has an odor component or a component having a taste-transferring property, the odor or taste component of the film is transferred to the food when the food or the like is packaged, and there is a problem that the commercial value is reduced.

[0003] Plastic films are produced by an inflation film molding method or a T-die cast film molding method. However, compared to an inflation film molding method which can be molded at a relatively low temperature (180 ° C to 220 ° C),
In the T-die cast film forming method, pressure loss and the like in a die are large, and therefore, it is general to form at a high temperature of 220 to 260 ° C. For this reason, in particular, in the T-die cast film forming method, there is a problem that the film is easily oxidized and the odor and taste components are largely transferred. Against this background, there has been a strong demand for a film that suppresses the odor and taste transfer components of the film.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a T which is excellent in low odor, low taste transferability, heat stability and impact resistance.
An object of the present invention is to provide a die cast film and a method for producing the same.

[0005]

The inventors of the present invention have long studied the method of producing a T-die cast film by processing an ethylene polymer or a resin composition containing the ethylene polymer. It has been found that the object of the present invention can be achieved by processing a specific ethylene polymer or a resin composition containing the ethylene polymer at a melting temperature of 210 ° C. or lower in a die gap, and has completed the present invention. .

That is, according to the present invention, the density is from 0.88 to 0.88.
An ethylene polymer having a melt index of 0.95 g / cm ³ and a melt index of 30 to 2000 g / 10 minutes at 190 ° C. and a load of 21.6 kg or a resin composition containing the ethylene polymer is heated at 210 ° C. using a die gap. This is a method for producing a T-die cast film, characterized by processing at the following melting temperature. Further, the present invention is a T-die cast film obtained by the above production method. Further, the present invention is a multilayer T-die cast film comprising at least one layer of a T-die cast film obtained by the above-mentioned production method. Hereinafter, the present invention will be described in detail.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ethylene polymer used in the present invention has a density of 0.88 to 0.95 g / cm ³ , preferably 0.890 to 0.94 g / cm ³ , and more preferably 0.1 to 0.94 g / cm ³ .
895-0.935 g / cm ³ , most preferably 0.90
0 to 0.930 g / cm ³ , and a melt index at 190 ° C. under a load of 21.6 kg of 30 to 2000 g / 1.
0 minutes, preferably 45 to 1500 g / 10 minutes, more preferably 50 to 1000 g / 10 minutes, and most preferably 70 minutes.
１０００1000 g / 10 min. Density is
If it is less than 0.88 g / cm ^3, it is not suitable for use as a film. On the other hand, if the density is higher than 0.95 g / cm ³ , the transparency and impact strength decrease, which is not preferable. The density in the present invention refers to JIS K6760-1.
981 measured by the method specified in

If the melt index is less than 30 g / 10 minutes, the extrusion load becomes too high in the T-die cast film processing under the temperature conditions of the present invention, which is not preferable. On the other hand, the melt index is 2
If it exceeds 000 g / 10 minutes, the strength of the film is greatly reduced, which is not preferable. The melt index in the present invention refers to a value measured by a method specified in JIS K6760-1981 under a measurement temperature of 190 ° C. and a load of 21.6 kg.

The ethylene polymer used in the present invention is:
Examples include a homopolymer of ethylene, a copolymer of ethylene and one or more α-olefins having 3 to 20 carbon atoms, or a diolefin having 4 to 20 carbon atoms. These copolymer components include, for example, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-
1, nonene-1, decene-1, hexadecene-1, eicosene-1, 4-methyl-pentene-1, 4-methyl-
Hexene-1, vinylcyclohexane, vinylcyclohexene, styrene, norbornene, butadiene, 1,5
-Hexadiene, isoprene and the like. The content of the above copolymer component is usually 0.05 to 50% by weight.

The ethylene polymer is obtained by a solution polymerization method, a slurry polymerization method, a high pressure ionic polymerization method, or a gas phase polymerization method using the above monomers and comonomers using a Ziegler-Natta catalyst or a metallocene catalyst. Among these, the gas phase polymerization method is preferred.

In the ethylene polymer or the composition containing the ethylene polymer used in the present invention, the weight ratio a (% by weight) of the cold xylene-soluble portion preferably satisfies the following formula (1). And more preferably those satisfying the following formula (2), and most preferably those satisfying the following formula (3). a <4.8 × 10 ⁴ × (0.95-d) ³ + 10 ⁶ × (0.95-d) ⁴ +1 Equation (1) a <4.5 × 10 ⁴ × (0.95-d) ³ + 10 ⁶ × (0.95-d) ⁴ Formula (2) a <4.8 × 10 ⁴ × (0.95-d) ³ Formula (3) (In the above formula, d represents the density of the ethylene polymer or the composition containing the ethylene polymer. )

In the present invention, the cold xylene-soluble portion is defined as the code of federal regulations, Food and Drugs Adm.
It is measured by the method specified in §175.1520 of the inistration.

An ethylene-based polymer or a composition containing the ethylene-based polymer in which the weight ratio a of the cold xylene-soluble portion satisfies the above range is a film having an excellent balance because the film has low odor and excellent strength. give. When a is larger than the range represented by the formula (1), the odor tends to gradually increase and the strength tends to decrease.

The ethylene polymer satisfying such preferable conditions is produced by using a catalyst containing a transition metal compound, particularly produced in the presence of a catalyst containing a transition metal compound having a group having a cyclopentadiene type anion skeleton. Things. The transition metal compound is a so-called metallocene compound, and is generally represented by the general formula MLaXn-a (wherein
M is a transition metal atom belonging to Group 4 of the periodic table of elements or a lanthanide series. L is a group having a cyclopentadiene-type anion skeleton or a group containing a hetero atom, and at least one is a group having a cyclopentadiene-type anion skeleton. A plurality of Ls may be cross-linked to each other.
X is a halogen atom, hydrogen or a hydrocarbon group having 1 to 20 carbon atoms. n represents the valence of the transition metal atom, and a represents 0 <a ≦
n is an integer. ) And can be used alone or in combination of two or more. Further, the catalyst, the metallocene-based compound, an organoaluminum compound containing an alumoxane compound, and / or trityl borate, ionic compounds such as anilinium borate, and /
Alternatively, a particulate carrier including an inorganic carrier such as SiO ₂ and Al ₂ O _{3 and} an organic polymer carrier such as an olefin polymer such as ethylene and styrene may be used in combination.

The ethylene polymer used in the present invention may be a resin composition containing the ethylene polymer and various other resins as required. Other resins, for example, high-pressure low-density polyethylene for improving melt tension and transparency, high-density polyethylene for improving rigidity,
Olefin-based resins such as low-density elastomers for improving impact strength can be mentioned, and these can be used alone or in combination of two or more. The mixing ratio is such that the ethylene polymer is at least 50% by weight, preferably 6% by weight.
0% by weight or more, more preferably 70% by weight or more.

The present invention is a production method characterized in that the ethylene polymer or the resin composition containing the ethylene polymer is processed at a melting temperature of 210 ° C. or less at a die gap. The lower limit of the melting temperature may be any temperature that exceeds the maximum crystallization temperature of the copolymer or the composition. Further, the present invention provides a method for preparing the ethylene-based polymer or the resin composition containing the ethylene-based polymer at a die gap of preferably 180 ° C. or lower and (the maximum crystallization temperature + 5
C.) or higher, more preferably 160 ° C. or lower and (maximum crystallization temperature + 5 ° C.) or higher, most preferably 140 ° C. or lower and (Maximum crystallization temperature + 5 ° C.) or higher. It is a manufacturing method characterized by the following.

If the melting temperature at the die gap exceeds 210 ° C., the odor and taste transferability of the film become remarkable, which is not preferable. The melting temperature at the die gap in the present invention refers to the temperature of at least one point of the molten resin from the portion immediately before the die entrance to immediately after the die exit when the resin is extruded from the extruder. If the melting temperature at the die gap is lower than the maximum crystallization temperature of the ethylene polymer or its composition, crystallization may occur inside the die and the film may not be formed. Here, the maximum crystallization temperature refers to a differential scanning calorimeter DSC manufactured by PerkinElmer.
The highest crystallization peak temperature obtained when a 10 mg sample was packed in an aluminum pan, held at 150 ° C. for 2 minutes, and then cooled at a rate of 10 ° C./min to 40 ° C. using a -7 type apparatus. Say.

An antioxidant may be added to the ethylene polymer used in the present invention or a resin composition containing the ethylene polymer in order to prevent deterioration in quality due to oxidation or the like during processing. Since the present invention processes at a die gap melting temperature of 210 ° C. or less, the occurrence of an oxidation reaction which is a source of odor and taste transfer components is smaller than that of a normal T-die cast film forming method, and the addition of an antioxidant is reduced. be able to.
Since these antioxidants affect the odor of the film, it is better to use as little as possible. The addition amount of the antioxidant is preferably 0 to 0.10% by weight, more preferably 0 to 0.05% by weight. The present invention is particularly preferable because molding can be performed without adding an antioxidant, and when the melting temperature at the die gap is 160 ° C. or less, defective phenomena such as fish eyes do not occur. This antioxidant is preferably used in combination with a primary antioxidant having a phenol skeleton and a secondary antioxidant containing a phosphorus compound or the like.

In the present invention, additives other than the antioxidant, for example, a small amount of an anti-blocking agent or a lubricant for preventing blocking of the film may be added as required.

The resin components such as high-pressure low-density polyethylene, high-density polyethylene, and low-density elastomer, and additives such as antioxidants, anti-blocking agents, and lubricants, which are blended according to various purposes, are melt-kneaded beforehand. The film may be subjected to film processing, or may be individually dry blended or made into one or more master batches and then subjected to film processing after dry blending, and any method may be used.

The T-die cast film produced in the present invention may be a single-layer T-die cast film or a T-die cast film obtained by a method for producing a T-die cast film.
Multi-layer T including at least one layer of die-cast film
It may be a die cast film. When the production method of the present invention is applied to a multilayer T-die cast film, it may be applied to the production of all layers or to at least one layer in a multilayer film. When the production method of the present invention is applied to at least one layer of a multilayer film, it is preferably applied to one surface or both surface layers, but may be applied to a layer inside the surface. Further, the single-layer or multi-layer film thus produced may be used as a raw laminate for dry lamination on a substrate such as another polymer film.

[0022]

As described in detail above, according to the present invention, T is superior in film odor, taste transferability, thermal stability and impact resistance to a film obtained by a conventional method.
A die cast film and a method for producing the film can be provided. In addition, the present invention can provide a T-die cast film which uses less or no antioxidant because it is processed at a low temperature, and a method for producing the film.
Further, the T-die cast film of the present invention has such excellent properties as described above, and thus is suitable for packaging materials, particularly food packaging materials.

[0023]

Hereinafter, the present invention will be described based on examples.
The present invention is not limited to these examples.

The evaluation method was as follows. (1) Melting Temperature at Die Gap The resin temperature at the exit of the die was measured with a thermocouple while extruding the ethylene polymer under the set processing conditions. (2) Odor 4.2 g of the obtained film sample was placed in a 1-liter wide-mouthed glass bottle, heated in an oven at 80 ° C. for 1 hour, and then cooled.
The odor comparison was performed by a sensory test. With Example 1 as a blank, x was given when the odor was stronger than the blank, Δ was given when the odor was the same, Δ was given when the odor was weak, and を was given when the odor was extremely weak. (3) Fish eyes processed diameter per 1000 cm ² of the obtained film
Fish eyes of 0.3 mm or more were detected and counted. 20 or more were evaluated as ×, 10 or more as Δ, and 9 or less as Δ. The smaller the number of fish eyes, the better the thermal stability. (4) Drop weight impact strength According to the method specified in ASTM D1709. (5) Resin pressure (extrusion moldability) No. required for extruding molten resin The resin pressure of one extruder was measured. The higher the value, the higher the extrusion load. In the extruder used in the examples, the lower the value, the better the extrudability, and in the present apparatus, this is 310 kg / c.
If it exceeds m ² , molding becomes impossible.

The metallocene catalyst of the ethylene polymer
Bei thoroughly dried methylalumoxane silica in toluene and bis (1, 3-n-butyl-methylcyclopentadienyl) zirconium dichloride ethylene chloride sequentially reacted solid component and triisobutylaluminum obtained with hexane And prepolymerization was carried out to obtain a prepolymerization catalyst. This prepolymerization catalyst and triisobutylaluminum were allowed to act on a mixed gas of ethylene and hexene-1 in a continuous fluidized-bed gas-phase polymerization apparatus to obtain an ethylene-hexene-1 copolymer. The density of the ethylene-hexene-1 copolymer is adjusted by the concentration ratio of ethylene and hexene-1, and the molecular weight is adjusted by the concentration of hydrogen to be introduced.
Ethylene polymers of the metallocene catalyst shown in Table 1 were obtained.

Ethylenic polymer of Ziegler-Natta catalyst
Preparation of Porous Styrene-divinylbenzene copolymer particles were reacted with tetrabutoxytitanium and tetraethoxysilane in toluene, and subsequently reacted with butylmagnesium chloride to obtain a solid component. Furthermore, butyl ether and titanium tetrachloride were further allowed to act on the solid component obtained by allowing diisobutyl phthalate to act on the solid component in toluene to obtain a solid catalyst component. Preliminary polymerization was carried out by reacting ethylene with the solid catalyst component and triethylaluminum in butane to obtain a prepolymerized catalyst. This prepolymerization catalyst and triethylaluminum were allowed to act on a mixed gas of ethylene and hexene-1 in a continuous fluidized-bed gas-phase polymerization apparatus to obtain an ethylene-hexene-1 copolymer. Ethylene-hexene-
The density of 1 copolymer was adjusted by the concentration ratio of ethylene and hexene-1, and the molecular weight was adjusted by the concentration of hydrogen to be introduced. As a result, ethylene polymers of Ziegler-Natta catalysts shown in Table 1 were obtained. High pressure method Sumikasen F200-0 manufactured by Sumitomo Chemical Co., Ltd. manufactured by LDPE high pressure radical polymerization method was used.

In the following Examples and Comparative Examples, the following T
Die cast film forming conditions were used as common conditions. (1) Extruder: 50 mmφ extruder (No. 1) / 40
mmφ extruder (No. 2) (2) Die: 2 types, 2 layers T die, 600 mm width, gap: 0.9 mm (3) Extrusion amount: No. 1-21 kg / hr, No. 2
-11 kg / hr (4) Film thickness: 50 μm 1 and No. 1 Both extruders extruded the same raw resin to obtain a single-layer film. In Examples 1, 2, 4 to 7, 9, and 10, and Comparative Examples 1 to 3, a predetermined amount of an antioxidant shown in Table 1 was previously mixed with an ethylene polymer, and the mixture was melt-mixed with an extruder. A T-die cast film was formed using the pelletized material.

Examples 1 to 3 and Comparative Examples 1 to 2 Ethylene-hexene-1 copolymers obtained with a Ziegler-Natta catalyst as shown in Table 1 were used as the ethylene-based polymer. A T-die cast film was produced below. Table 1 shows the evaluation results of the obtained films.
Are shown together.

Examples 4 to 9 and Comparative Examples 3 and 4 Ethylene-hexene-1 copolymers obtained with metallocene catalysts as shown in Table 1 were used as ethylene-based polymers. A T-die cast film was produced below. The evaluation results of the obtained film are also shown in Table 1.

Example 10 A so-called high-pressure low-density polyethylene obtained by polymerizing ethylene by a high-pressure radical polymerization method with an ethylene-hexene-1 copolymer obtained with a metallocene catalyst as shown in Table 1 as an ethylene copolymer. (High-pressure LDPE), and a T-die cast film was produced under the processing conditions shown in Table 1. The evaluation results of the obtained film are also shown in Table 1.

[0031]

[Table 1]

* 1) in Table 1 above indicates that 0.06% by weight of Irganox 1076 and 0.02% by weight of Irgafos 168 were used as antioxidants.
4% by weight. * 2) in the above Table 1
It shows that 0.04% by weight of Irganox 1076 and 0.03% by weight of Irgafos 168 were contained as antioxidants.
The above antioxidants are all manufactured by Ciba Specialty Chemical Co., Ltd.

Claims (5)

[Claims] (1) a density of 0.88 to 0.95 g / cm ³ and 1
Processing an ethylene polymer or a resin composition containing the ethylene polymer having a melt index of 30 to 2000 g / 10 minutes at 90 ° C. and a load of 21.6 kg at a melting temperature of 210 ° C. or less in a die gap. A method for producing a T-die cast film, comprising: 2. An ethylene polymer wherein the weight ratio a (% by weight) of the cold xylene-soluble portion of the ethylene polymer satisfies the following formula (1) or a composition containing the ethylene polymer. Item 10. The method for producing a T-die cast film according to Item 1. a <4.8 × 10 ⁴ × (0.95−d) ³ +10 ⁶ × (0.95−d) ⁴ +1 Formula (1) (In the above formula (1), d represents the ethylene polymer or the ethylene polymer. Indicates the density of the composition contained.) 3. The method according to claim 1, wherein the ethylene polymer is produced in the presence of a catalyst containing a transition metal compound having a group having a cyclopentadiene-type anion skeleton. 4. A T-die cast film obtained by the production method according to claim 1. 5. A multilayer T-die cast film comprising at least one layer of a T-die cast film obtained by the production method according to claim 1.