JPS6189041A - Multilayer film for packaging - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention is flexible, has excellent strength, has excellent transparency and gloss,
Moreover, the present invention relates to a multilayer packaging film with excellent opening properties.

Vinylon film has been used for many years in the packaging film field, especially in the textile packaging film field. This is because vinylon film is flexible, has excellent transparency and gloss, and has excellent mechanical strength, etc., giving textile products a luxurious feel. However, the disadvantages of vinylon film are that it is greatly affected by humidity, and its properties vary widely depending on the season, such as being too soft during the rainy season and becoming hard in winter, and that it is expensive. It will be done. For this reason, in recent years there has been active development of polyolefin-based fiber packaging films that are relatively durable and are hardly affected by seasonal influences.

For example, packaging films that are flexible, transparent, and glossy have been developed by processing linear low-density ethylene (LLDPE) into water-cooled blown film or T-die-cast film. However, the LLDPE film produced by this processing method still has a slightly inferior level of transparency and gloss compared to vinylon film.
Moreover, it has the disadvantage that the strength of the film is considerably low. In addition, by processing a propylene random copolymer copolymerized with about 3 to 5 wt% of ethylene into a T die-cast film or a water-cooled blown film, a packaging film that is flexible, has excellent transparency, and gloss can be obtained. is well known, but it has the drawback that the strength of the film is much lower than that of vinylon film. If this film is subjected to stretching treatment to improve its strength, there is a problem in that the film loses its flexibility. If a propylene random copolymer containing 5 wt% or more of ethylene is used so that the flexibility of the film is not lost even after stretching, there is a problem in that transparency and gloss are lost and the film becomes dull.

Recently, a method has been known in which a cylindrical film is stretched using the Cheebler stretching technique and the cylindrical film is used as a bag (without fusing and sealing as in the past). Only extremely inflexible films are known. This is because, as mentioned above, if a soft copolymer is used that simply increases the comonomer content of the propylene copolymer, transparency and gloss will be lost, and with this processing method, the film This is because opening properties are particularly strictly required, so if a softened propylene copolymer is used, the opening properties will generally deteriorate, making it difficult to put it to practical use.

In view of the above circumstances, the inventors of the present invention have conducted intensive studies to develop a polyolefin packaging film that is flexible, has excellent strength, is transparent and glossy, and has excellent opening properties. As a result, in a multilayer film obtained by further stretching using a propylene-based copolymer containing a specific comonomer in a limited amount as a main component and having a specific cold xylene soluble portion (CXS), the inner layer The present invention has been completed by discovering that a packaging film having all of the above properties can be obtained by increasing the anti-blocking concentration of the copolymer than that of the outer layer. The present invention relates to a packaging multi-layer film in which the inner layer has a higher concentration of anti-blocking agent than the outer layer, and which has been subjected to a stretching process in at least one direction.

A random copolymer of propylene, an α-olefin having 4 or more carbon atoms, or a random copolymer of propylene, an α-olefin having 4 or more carbon atoms, and ethylene, which satisfies the following conditions (1) to (2).

■ The content of α-olefin with carbon number of 4 or more in the copolymer is 7 to 80 mol%, ■ The ethylene content of the copolymer is 3 mol% or less, ■ The cold xylene soluble portion of the copolymer is 15 to 60 wt%. The first feature of the multilayer packaging film obtained by the present invention is that it has a multilayer structure, so while maintaining transparency and gloss,
The film has extremely good opening properties.

The second feature is that although it is flexible, it has excellent mechanical strength, so it can be fastened with hooks, which is often used in textile packaging film bags. The third feature is
It is flexible and has excellent transparency and gloss, giving it a luxurious feel that is far superior to vinylon film.

The present invention will be explained in detail below.

Although the copolymer used in the present invention can be polymerized by solution polymerization (dissolution conditions), it is preferable to produce it by a so-called gas phase polymerization method.

However, the generally widely used slurry polymerization method in which polymerization is carried out in an inert hydrocarbon is not preferred. This is because in the slurry polymerization method, a large amount of polymer dissolves in the inert hydrocarbon solvent, making polymerization extremely difficult. This is because the rate will drop significantly and it will be economically disadvantageous. When performing gas phase polymerization, the polymerization can be carried out using a known fluidized bed reactor, stirred reactor, fluidized bed reactor equipped with a stirrer, or the like. In addition, the polymerization is carried out without the gas liquefying in the reactor, and the polymer particles are
It is essential to conduct the polymerization under conditions of temperature and pressure that do not cause melt agglomeration, and particularly preferred polymerization conditions are 40 to 10
The temperature range is 0°C, and the pressure range is 1 to 59 KgA (hereinafter referred to as G below gauge pressure).

Further, for the purpose of controlling the solution-flowability of the resulting polymer, it is preferable to add a regulator such as hydrogen molecules. Polymerization is
Batch polymerization, continuous polymerization, or a combination of both polymerization methods can be carried out, and the monomers, molecules, and regulators consumed in the polymerization can be continuously or intermittently added to the reactor. can be supplied to

When the copolymer used in the present invention is subjected to gas phase polymerization, it is also possible to wash the copolymer with an alcohol or a hydrocarbon solvent after the polymerization for the purpose of removing catalyst residues or low molecular weight polymers.

In the present invention, the catalyst system used for producing the copolymer is a known catalyst for stereoregular polymerization of α-olefins,
For example 'l'ic1g, TiCl3.

1/(consisting of a solid catalyst component such as a catalyst containing AICIa as the main component or a carrier-supported catalyst in which a Ti compound is supported on magnesium chloride, an organoaluminum catalyst, and optionally a third component such as an electron-donating compound) It is something.

The solid catalyst component may be prepolymerized by treating it with a small amount of olefin in the presence of an organoaluminum compound or an electron-donating compound before polymerization.

The propylene copolymer used in the present invention uses an α-olefin having 4 or more carbon atoms or a very small amount of ethylene as a comonomer. α-olefins having 4 or more carbon atoms include butene-11pentene-1, hexene-1,4-methylpentene-1, etc. alone or in combination, but among these, they are difficult to liquefy when polymerized in the gas phase. Therefore, butene-1 is most preferable because it can maintain a high partial pressure. When the main component of the comonomer is ethylene, there are problems such as poor transparency and deterioration of film transparency over time, which may be due to bleeding of atactic components, which is not preferred in the present invention. The content of α-olefin having 4 or more carbon atoms in the copolymer used is 7 to 80 mol%, and 10 to 25 mol%.
is preferred. If the content of α-olefin having 4 or more carbon atoms is below the lower limit, the copolymer will lose its softness, which is undesirable, and if it exceeds the upper limit, the powder properties during gas phase polymerization will deteriorate and become stable. This makes manufacturing difficult.

Ethylene content of the copolymer used in the present invention is 8 mol%
or less, and more preferably 2.5 mol% or less. If the ethylene content exceeds the upper limit, the transparency of the film will deteriorate over time, which is not preferable. The reason for this is not clear, but it is thought to be caused by bleeding of atactic components.

The cold xylene soluble portion of the copolymer used in the present invention (CX3
) is 15 to 5 Qwt%, more preferably 20 to 5 Qwt%. If CXS is below the lower limit, it is undesirable that it is difficult to achieve softness of the copolymer and there is a disadvantage in terms of polymer yield. If Cx8 exceeds the upper limit, powder properties deteriorate during gas phase polymerization, making polymerization virtually impossible. The copolymer used in the present invention may not be subjected to post-treatment such as a post-polymerization cleaning step, or may be subjected to an appropriate washing step, and in either case, the copolymer used within the above specified range It is good if it is in

The boiling n-heptane insoluble part of the copolymer used in the present invention (
BHIP) is not particularly limited, but is preferably 7 wt% or more.

When BHIP is less than 7 wt%, a large amount of anti-blocking agent is required to be added to the inner layer in order to provide openness, and transparency deteriorates accordingly.

In the present invention, the concentration of the anti-blocking agent in the inner layer is higher than that in the outer layer. By doing so, the opening property can be improved without impairing the transparency and gloss of the film.

The copolymer used in the present invention can be blended with a rubbery ethylene-α olefin random copolymer up to about 20 wt%, and can also be blended with small amounts of other polymeric substances. Additionally, additives such as antistatic agents, stabilizers, and slip agents can be added.

In the multilayer film for packaging of the present invention, regarding the thickness of the inner layer and the outer layer, it is preferable that the number of inner layers is as small as possible. The preferred range is 0.03 to 0.5;
05 to 0.4 is more preferable. If the proportion of the inner layer is below the lower limit, production becomes substantially impossible, which is undesirable; if the proportion of the inner layer exceeds the upper limit, the transparency of the film deteriorates, which is not preferable. Note that it is also possible to perform multilayering of three or more layers without impairing the gist of the present invention.

In the present invention, the multilayer film can be obtained by coextrusion processing methods such as T die casting method and water-cooled inflation method using multilayer dies.

In addition, methods for performing stretching treatment in at least one direction include known uniaxial stretching methods such as roll stretching and roll rolling;
Also, known biaxial stretching methods such as tenter biaxial stretching and tubular biaxial stretching can be employed. Stretching temperature is room temperature ~
Below the melting point of the copolymer, and the stretching ratio is 1.2 to 7.
It is preferably 1.5 to 5 times, more preferably 1.5 to 5 times.

The physical properties of the multilayer film obtained in this way are M
Young's modulus in D and TD directions: 2.000 to 10.0
00V4/crl is preferred, 2.500 to 8,00
More preferably, it is 0 Kg/cpl.

When the Young's modulus of the multilayer film is below the lower limit, it is undesirably too soft compared to vinylon film, and when it exceeds the upper limit, it loses the flexibility of vinylon film, which is undesirable. Also, at least one of the multilayer films
The strength at break in the direction is preferably 400 Kg/Cri or more. If this strength is less than 400 V4/cA, the hook resistance (as the hook of the bag is opened and closed many times, the film stretches in the opening/closing direction and loses its commercial value) is undesirable.

The multilayer packaging film produced as described above has flexibility, transparency, and gloss superior to vinylon film, has excellent opening properties, and can be processed with hooks and bolts. There is almost no change in physical properties depending on the season, which is a disadvantage of the conventional method, and it can be manufactured at a low cost, so it has extremely great practical value.

The data and evaluation in the Examples and Comparative Examples were conducted according to the following method. (1) α-olefin content in the copolymer was determined from the mass balance. Furthermore, the content of butene-1 was determined by a conventional method using an infrared spectrophotometer from characteristic absorption at 770 cm 2 to confirm the mass balance results. In addition, measurements using an infrared spectrophotometer are performed for propylene-butene-1 copolymer.
8 C! -A calibration curve was created and quantified based on the quantitative values obtained by NMR.

(2) Ethylene content in the copolymer was determined from the mass balance. Furthermore, using an infrared spectrophotometer, 7
Quantification was performed using a conventional method from the characteristic absorption of 82crR, 720m to confirm the mass balance results. In addition, in the measurement using an infrared spectrophotometer, a calibration curve was created using quantitative values determined by radiation measurement of an ethylene copolymer labeled with C, and the amount was determined.

(3) Cold xylene soluble portion (CXS) Polymer 51 is dissolved in xylene 500- and then slowly cooled to room temperature.

Then, it is left in a 20°C pass for 4 hours, filtered, and the filtrate is concentrated, dried, dried, and weighed.

(4) Boiling n-hebutane insoluble part (BHIP) So I
Extraction is carried out for 14 hours in a Cousley extractor.

Note that the reflux frequency is once every 5 minutes.

BHIP is determined by drying and weighing the extraction residue.

(5) Intrinsic viscosity ([η]) Tetralin concentration was reduced to 0.4, 0 at normal pressure at 185°C.
．． Measurements were made at four different points: 2, 0.188, and 0.1 f/dt.

(6) Create a press sheet of △Haze copolymer with a thickness of 100μ, and
It was expressed as the difference between the haze after annealing treatment at °C for 9 hours and the haze before treatment.

(7) Young's modulus of film Conforms to ASTM-J) 882.

However, test piece shape: 20 x 120 strips Distance between chucks: 50 cm Tensile speed: 5 cm/min (3) Tensile properties of film conform to ASTM-D882.

However, tensile speed: 200mm/min (9) Haze value (Haze) Compliant with ASTM-DlooI.

(10) Gross Compliant with ASTM-D528.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the embodiments unless it goes beyond the gist thereof.

Example 1 (1) Preparation of a solid catalyst containing titanium trichloride After purging a 1-ton flask equipped with a stirrer and a dropping funnel with argon, a solution consisting of 60 m of titanium tetrachloride and 228 m of n-heptane was mixed with ethylaluminum sesquichloride J. Throat 18
6. A solution consisting of 800 wt of 6- and n-heptane, -
It was added dropwise over 2 hours at 5 to -10"C. After the addition was completed, it was stirred at room temperature for 30 minutes, then the temperature was raised to 80°C and heat treated at 80°C for 1 hour. Then, it was left to stand at room temperature to solidify. After liquid separation, washing was repeated four times with 400 g of n-heptane.

Next, 580 m of n-heptane and 5-diethylaluminum chloride were charged into the flask, and the temperature was kept at 50"C. With stirring, propylene 829 was gradually fed into the suspension at 50 °C for 2 hours. A preliminary polymerization treatment was performed. After the treatment, solid-liquid separation was performed, and washing was repeated twice with n-heptane 400.

Next, add 392 - of toluene to the flask and lower the temperature to 8
It was kept at 5°C. While stirring, add n-butyl ether 1
17- and tri-n-octylamine 3.7- were added and reacted at 85°C for 15 minutes. After reaction, iodine 15.5
A solution of 1 dissolved in 196 toluene was added, and the mixture was further reacted at 85°C for 45 minutes.

After the reaction, solid-liquid separation was performed, washed once with 500 ml of toluene and 8 times with 500 ml of n-heptane, and then dried under reduced pressure to obtain titanium trichloride-containing solid catalyst 90F. Titanium trichloride is 65.2% by weight in the titanium trichloride-containing solid catalyst.
It was contained.

(2) Copolymerization internal volume 1? ? Propylene and butene-1 were copolymerized using a fluidized bed reactor equipped with a stirrer. First, 60% of propylene-butene-1 copolymer particles for catalyst dispersion were fed into the reactor, and then the reactor was purged with nitrogen and then with propylene. 5 KW/cm in propylene
The pressure was increased to 2G and circulating gas was supplied from the bottom of the reactor at a flow rate of 80 m8/hr to keep the polymer particles in a fluidized state, and then the following catalyst was supplied to the reactor. For the catalyst components b) and (C), a solution diluted with hebutane was used.

(a) 21 g of titanium trichloride-containing solid catalyst (
b) Diethylaluminium chloride 11
2g (C) Triethylaluminum l1g (
d) 8 g of methyl methacrylate, hydrogen, propylene, and butene-1 were supplied so that the hydrogen concentration was 1.7 vol. 1% and the butene-1'l Q vol.
The pressure was increased to /cjG, and the temperature of the granular bed was adjusted to 65°C to start polymerization. During the polymerization, hydrogen, propylene, and butene-1 were supplied so as to keep the concentration and pressure of hydrogen and butene-1 constant. When the polymerization amount reached 75Kf,
60 kg of polymer particles were placed in the reactor for catalyst dispersion in the next polymerization.
The remaining polymer particles were transferred to a stirring mixing tank, 210 g of propylene oxide and 100 g of methanol were added, and treated at 80°C for 30 minutes. It was then dried to obtain a white powdery polymer. The same polymerization was repeated three times, and the physical properties of the finally obtained polymer were measured. The result is the first
Shown in the table.

(3) Add anti-blocking agent to the copolymer obtained in film production (2).
A sheet of 270 μm is obtained by a pressing method using a material containing Q, 1 F HR fine powder silica. In addition, fine powdered silica was added as a copolymer anti-fouling agent.
4P HR compounded material was formed into a film and 30μ
A film with a thickness of 270 μm was obtained, and the film was laminated with the above-mentioned 270 μm sheet using an angle press method to obtain a multilayer sheet. Stretching machine that takes a 90 square multilayer sheet and obtains a biaxially stretched film under the following conditions 4) Rem: Tabletop biaxial stretching machine manufactured by Toyo Seiki
Temperature: 180″C Preheating time: 8 minutes Stretching ratio: MD 33x TD 3x Stretching speed:
15? Fl/min The physical properties of the film of approximately Baa thickness obtained above are shown in Table 2. This film is soft, strong, extremely transparent and glossy, and when we checked the opening properties by stacking two films with the inner layer film side facing inside, we found that there was no blocking at all. Met.

Comparative Example 1 A biaxially stretched film was obtained in the same manner as in Example 1, except that the anti-blocking agent content was Q and 4 P HR in both the inner and outer layers.

The physical properties of the film are shown in Table 2. This film is soft and strong, and when we stacked two films with the inner layer film side inside to check the opening properties, there was no blocking at all, but the transparency and gloss were unsatisfactory. It was something.

Comparative Example 2 The copolymer of this comparative example was obtained by slurry polymerization using n-heptane in a solvent, and the multilayered atactic component dissolved in n-heptane was removed. The basic specifications of this copolymer are shown in Table 1. Table 2 shows the physical properties of a multilayer film obtained from this copolymer under the same conditions as those shown in Example 1. Although this film had good strength, it had a high Young's modulus and lacked flexibility, which made it unsuitable for the purpose of the present invention.

Comparative Example 3 A copolymer was obtained under the same polymerization conditions as in Example 1, except for changing the catalyst system used in Example 1 and charging ethylene instead of butene-1. The basic weight of the obtained copolymer is shown in Table 1. A multilayer film was obtained from this copolymer under the same conditions as those shown in Example 1. Although this film had a good degree of softness, components thought to be atactic components bled onto the film surface over time, resulting in poor transparency and the film was difficult to put to practical use.

Comparative Example 4 This copolymer is obtained by a slurry polymerization method using n-heptane as a solvent, and the atactic acid component that dissolves in n-heptane has been removed. The basic specifications of this copolymer are shown in Table 1. A multilayer film was obtained using this copolymer under the same conditions as those shown in Example 1. The physical properties of this film are shown in Table 2. Although this film had good flexibility, strength, and opening properties, it had poor transparency and gloss, which did not interfere with the purpose of the present invention.

Claims (1)

[Scope of Claims] (1) A multilayer packaging material made of the following copolymer, in which the concentration of anti-blocking agent in the inner layer is higher than that in the outer layer, and which has been subjected to stretching treatment in at least one direction. film. A random copolymer of propylene and an α-olefin having 4 or more carbon atoms, or a random copolymer of propylene, an α-olefin having 4 or more carbon atoms, and ethylene, under the following conditions (1) Content of α-olefin having 4 or more carbon atoms in the copolymer. (2) the ethylene content of the copolymer is 3 mol% or less, and (3) the cold xylene soluble portion of the copolymer is 15 to 60 wt%.
A copolymer that satisfies the following. (2) Young's modulus in MD and TD directions is 2,000 to 10
, 000 Kg/cm^2 and a strength at break in at least one direction of 400 Kg/cm^2 or more. (3) The multilayer film for packaging according to claim 1 or 2, wherein the α-olefin having 4 or more carbon atoms is butene-1. (4) The multilayer for packaging according to claim 1, 2, or 3, wherein the copolymer is obtained by polymerizing in a gas phase in the substantial absence of a liquid medium. film. (5) The multilayer film for packaging according to claim 1, 2, 3, or 4, wherein the copolymer has a boiling n-heptane insoluble portion of 7 wt% or more. (6) The multilayer film for packaging according to claim 1, 2, 3, 4, or 5, wherein the stretching method is tubular stretching.