JP5345509B2 - Polypropylene resin composition for packaging film of heat sterilized food, and film for packaging of heat sterilized food obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the packaging film of a heat-sterilized food, improved in heat resistance, low temperature shock resistance, resistance to bag fracture by dropping, transparency, and moreover, food sanitation and the like, all in a good balance. <P>SOLUTION: There is provided a propylene resin composition for the packaging film, which is formed of a propylene-ethylene block copolymer obtained by sequentially polymerizing a propylene polymer component (A) in a first step and a propylene-ethylene random copolymer component (B) in a second step, and satisfying the following conditions (i) to (iv). The conditions are: (i) the soluble content of the propylene polymer component (A) at -15&deg;C by TREF (temperature rising elution fractionation) is not more than 0.8 wt.%; (ii) molecular weight distribution of the propylene-ethylene block copolymer ranges from 3.5 to 6.0; (iii) the proportion of the propylene-ethylene random copolymer component (B) to the whole propylene ethylene block copolymer is 10 to 40 wt.%; and (iv) the ethylene content of the copolymer component (B) is 10 to 50 wt.%. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a polypropylene resin composition for packaging films of heat-sterilized foods, and more specifically, heat-sterilized foods that are excellent in transparency, low-temperature impact resistance, bag-breaking resistance, heat resistance, food hygiene, and the like. This relates to a packaging film resin film composition and a heat sterilized food packaging film.

With the recent diversification of eating habits and the universal use of the restaurant industry, the food and food industry has changed and developed in various ways, and simple cooked foods and retort foods are increasingly used. The demand for foods that have been heat sterilized, such as boiled and retorted, has increased significantly.
Polypropylene-based materials have been widely used as packaging materials due to their heat resistance, packaging suitability, economic efficiency, and environmental problem adaptability. However, they meet the demand for packaging films for the above-mentioned heat-sterilized foods. Requests are also high.

In addition to essential performance such as heat sealability and heat resistance so that the inner surface of the film does not melt during heat sterilization, the packaging film has low temperature resistance because the packaging film does not break during transportation and handling at low temperatures. From the viewpoints of impact resistance, drop bag resistance, transparency for visually recognizing the contents, and food hygiene, it is required that the exudation transfer of the film-derived components to the food contents is extremely small.
Thus, various improvement techniques have been studied for polypropylene-based packaging materials so as to satisfy these various requirements, but they have not yet fully met the high and severe market requirements.

Conventionally, for example, a propylene-ethylene block copolymer produced with a Ziegler-based catalyst and whose intrinsic viscosity is specified is used, and it has excellent balance of heat resistance and low temperature impact resistance, and food hygiene is also good. The xylene-soluble part of the film for retort food packaging (see Patent Document 1) and the propylene-ethylene copolymer film produced by two-stage polymerization, its intrinsic viscosity, etc. A retort food packaging film (see Patent Document 2), which is considered to be excellent in heat sealability, etc. has been proposed, but all of these films were insufficient in transparency and other performances.
In addition, a polypropylene film for retort, which is said to have improved transparency, anti-blocking property, slipperiness, etc. by blending a specific neutralizing agent and specific inorganic inert fine particles into crystalline polypropylene, is also presented ( However, there was no description regarding heat resistance, heat sealability, impact resistance, and food hygiene, and it did not satisfy the suitability as a polypropylene film for retort.

  Furthermore, a crystalline propylene / α-olefin random copolymer which is polymerized using a metallocene catalyst and defines MFR, melting peak temperature and elution characteristics to orthodichlorobenzene solvent, and ethylene whose density and MFR are specified・ Films for heat sterilized food packaging that are made into a film with a propylene-based resin composition comprising an α-olefin random copolymer, and are excellent in transparency, impact resistance, food hygiene, heat sealability, and heat resistance. (See Patent Document 4), and these performances are balanced and improved, but further improvements such as low temperature impact resistance and drop bag breakage resistance are desired.

Japanese Patent Laid-Open No. 6-93062 (see summary on page 1) JP 2000-186159 A (refer to the summary on page 1) Japanese Patent Laid-Open No. 9-20846 (see the summary on page 1) JP 2004-359711 A (see the summary on page 1 and Tables 1 and 2 of paragraphs 0055 to 0056)

  In view of the situation in the background art described above, the present invention, in addition to the essential performance such as heat sealability and heat resistance, in order to cope with the demand for the polypropylene material to meet the demand as a packaging film for heat sterilized food, A packaging film for heat-sterilized foods made from polypropylene-based materials that has improved low-temperature impact resistance, drop-proof bag resistance, transparency for visually observing the contents, and food hygiene. Development is a problem to be solved by the invention.

The present inventors aim to solve the above problems, as a heat sterilized food packaging film, in addition to essential performance such as heat sealability and heat resistance, low temperature impact resistance and drop bag resistance, In addition, in order to improve the physical properties of polypropylene materials and improve the physical properties of polypropylene materials, transparency, and food hygiene, etc. in a well-balanced manner, the properties of polypropylene materials, copolymers with olefinic monomers such as ethylene, and the composition of these and polypropylene Considering the property modification of the product, various properties of the propylene-based resin composition and the correlation of the performances of the packaging film, etc., they were examined experimentally.
As a result of the process, the above-mentioned various performances have been improved in a balanced manner, and it is optimal for packaging films for heat-sterilized foods, and it is possible to find a new polypropylene packaging material that has not been known so far. The present invention has been realized.

The present invention is basically a block copolymer obtained by two-stage polymerization of propylene and ethylene using a single site polymerization catalyst such as a metallocene catalyst, and a propylene-based crystalline polymer component and an amorphous ( Alternatively, a propylene resin composition comprising a propylene-ethylene random copolymer component having low crystallinity) is used.
And although it is an important requirement in the present invention (a specific matter of the invention), since various performances as packaging films for heat-sterilized foods are improved in a well-balanced manner, the temperature rise of the propylene-based crystalline polymer component is increased. The elution characteristics in the elution fractionation method (hereinafter sometimes abbreviated as “TREF”) are defined, the molecular weight distribution of the propylene-ethylene block copolymer which is the sole or main component of the resin composition is specified, The composition ratio of the propylene-ethylene random copolymer and the ethylene content are set, and these requirements are the main features of the present invention.

Specifically, the present invention provides, as a first basic invention, “sequentially polymerizing a propylene-based polymer component (A) in the first step and a propylene-ethylene random copolymer component (B) in the second step. And a propylene-based resin for a packaging film of heat-sterilized food, characterized in that it is formed from a propylene-ethylene block copolymer (X1) that satisfies the following conditions (i) to (iv): Composition.
(I) The soluble content of the propylene-based polymer component (A) at −15 ° C. by temperature-temperature elution fractionation (TREF) is 0.8% by weight or less.
(Ii) The molecular weight distribution (Mw / Mn) of the propylene-ethylene block copolymer (X1) is 3.5 to 6.0.
(Iii) The ratio of the propylene-ethylene random copolymer component (B) to the total amount of the propylene-ethylene block copolymer (X1) is 10 to 40% by weight.
(Iv) The ethylene content of the copolymer component (B) is 10 to 50% by weight. Is a configuration of the invention.

  Then, the present invention is an invention of addition or embodiment to the basic invention described above or an invention of utilization, embodying a polymerization catalyst and a polymerization step, adding a killer compound to the polymerization step, and propylene-ethylene random copolymer. For retort foods that improve the particle properties of the polymer, form a packaging film for heat sterilized food obtained by melt extrusion film formation of a propylene resin composition, and further use a packaging film for heat sterilized food Packaging material.

In accordance with the basic invention described in paragraph 0010, the present invention is a packaging film for heat sterilized food, in addition to essential performance such as heat sealability and heat resistance, low temperature impact resistance, drop bag resistance, and transparency. This is a special feature that has not been seen in the past.
Such actions and effects are demonstrated by the data of each example described later and the comparison of each example and each comparative example.

  In the above, since the background of the creation of the present invention and the basic components and features of the present invention have been described in overview, the present invention can be summarized as a unit group of the following invention. The invention of [1] is a basic invention, and the following is a more specific or embodiment or utilization of the basic invention. The entire invention group is collectively referred to as “the present invention”.

[1] Obtained by sequentially polymerizing the propylene-based polymer component (A) in the first step and the propylene-ethylene random copolymer component (B) in the second step, and the following (i) to (iv) A propylene-based resin composition for packaging films of heat-sterilized foods, characterized in that it is formed from a propylene-ethylene block copolymer (X1) that satisfies the following conditions.
(I) The soluble content of the propylene-based polymer component (A) at −15 ° C. by temperature-temperature elution fractionation (TREF) is 0.8% by weight or less.
(Ii) The molecular weight distribution (Mw / Mn) of the propylene-ethylene block copolymer (X1) is 3.5 to 6.0.
(Iii) The ratio of the propylene-ethylene random copolymer component (B) to the total amount of the propylene-ethylene block copolymer (X1) is 10 to 40% by weight.
(Iv) The ethylene content of the copolymer component (B) is 10 to 50% by weight.

[2] Propylene-ethylene block copolymer (X1) was produced by gas phase polymerization or bulk polymerization in the first presentation and gas phase polymerization in the second step using a metallocene catalyst as a polymerization catalyst. The propylene-based resin composition for packaging films of heat-sterilized foods according to [1], which is a product.
[3] A propylene-based food packaging film for heat-sterilized foods according to [2], wherein a killer compound as a polymerization catalyst is added to the second step to improve the particle properties of the propylene-ethylene random copolymer. Resin composition.

[4] A film for packaging heat-sterilized food, obtained by melt extrusion film-forming the propylene-based resin composition according to any one of [1] to [3].
[5] A packaging material for retort food, wherein the packaging film for heat-sterilized food according to [4] is used.

  In propylene resin packaging materials, as a packaging film for heat-sterilized foods, in addition to essential performances such as heat sealability and heat resistance, low temperature impact resistance, drop bag resistance, transparency, and food hygiene Etc. can be improved in a well-balanced manner, and can meet the conventional demand for packaging films for heat-sterilized foods.

It is a graph which shows the base line and area of a chromatogram in the gel permeation chromatography of this invention.

1. Propylene-ethylene block copolymer of the present invention (1) Propylene-ethylene block copolymer The propylene-ethylene block copolymer of the present invention (hereinafter also referred to as copolymer (X1)) is a crystalline propylene-based copolymer. It is a block copolymer obtained by sequentially polymerizing a polymer component (A) and a low crystalline or amorphous propylene-ethylene random copolymer component (B). Sequential polymerization means continuous multistage polymerization of two or more stages.
This copolymer (X1) is commonly called a block copolymer and is obtained by continuous polymerization. However, the copolymer (X1) is substantially composed of a propylene-based polymer component (A) and a propylene-ethylene random copolymer. It is a composition with a union component (B). However, since the copolymer (X1) is obtained by sequential polymerization, each of these (co) polymers is produced in an independent reactor, and then each of the obtained (co) polymers is mechanically processed. Compared to the composition mixed in the above, it has a micro phase separation structure or a co-continuous structure.

  On the other hand, a conventional crystalline propylene polymer component (A) and a low crystalline or amorphous propylene-ethylene random copolymer component (B) are produced separately and mechanically mixed. In the case where the ratio of the copolymer component (B) is relatively large, the copolymer component (B) is not sufficiently dispersed and easily appears on the surface of the product by forming a large continuous phase. During the melt-kneading, the copolymer component (B) often melts first to form a matrix, so that not only stickiness and bleed-out are easily exhibited, but also the heat resistance is lowered.

Here, the crystallinity means that a lamella can be formed because the copolymer has a high stereoregularity and a relatively small comonomer content. That is, the propylene-based polymer component (A) is crystalline, exhibits heat resistance, and suppresses stickiness and bleed out.
On the other hand, low crystallinity or non-crystallinity means that the crystallinity is lower than the crystallinity of the propylene polymer component (A) in various methods for evaluating crystallinity such as TREF, or the crystallinity cannot be observed. Means that.

(2) Molecular weight distribution Regarding the molecular weight distribution (Mw / Mn) of the copolymer (X1), the condition (ii) in claim 1, that is, the molecular weight distribution (Mw / Mn) of the propylene-ethylene block copolymer (X1). ) Must be 3.5 to 6.0.
Copolymers having a molecular weight distribution (Mw / Mn) of more than 6.0 have low crystallinity and low molecular weight components, which may cause stickiness and bleed-out that may lead to problems with blocking of molded products and poor appearance. . When the molecular weight distribution is less than 3.5, the workability during film forming tends to be deteriorated, and the low-temperature impact resistance may be lowered.

(3) MFR
The propylene-ethylene block copolymer (X1) has an MFR of 0.1 to 60 dg / min, more preferably 0.5 to 30 dg / min, under measurement conditions described later. If the MFR is too low, the viscosity resistance during kneading or molding increases, which puts a heavy load on the apparatus, and the high-speed film-forming suitability is extremely lowered, which is not preferable.

2. Propylene polymer component (1) Propylene polymer component obtained in the first step In the present invention, the polymer component (A) polymerized in the first step mainly refers to a crystalline propylene homopolymer. However, as long as it does not depart from the spirit of the invention, it may be a copolymer of propylene and a small amount of another α-olefin having 2 to 20 carbon atoms. Here, examples of other α-olefins include ethylene, 1-butene, 1-hexene, and 1-octene.
Crystalline polypropylene is a propylene homopolymer component because it is a component contributing to rigidity and heat resistance in the propylene-ethylene copolymer.

The comonomer content of the polymer component (A) is preferably 0 to 15% by weight, more preferably 0 to 5% by weight, and particularly preferably 0 to 2% by weight.
Increasing the comonomer content improves impact resistance and significantly increases the polymerization activity during production and lowers the production cost. However, if the comonomer content exceeds 15% by weight, the heat resistance decreases and the stickiness is increased. It becomes difficult to suppress bleed out. In addition, the particle properties may deteriorate during the first step and polymerization may not be possible.
Such a polymer component (A) is preferably produced by using a single-site catalyst metallocene catalyst in order to narrow the molecular weight distribution, among others, a special metallocene complex (such as an azulene ring or an indenyl ring). In the case of polymerizing using a complex contained in a ligand, the molecular weight is also improved, and a high molecular weight polymer that cannot be produced by a normal metallocene catalyst can be produced.

(2) Regulation by TREF The polymer component (A) has a condition of (i) in claim 1, that is, a -15 ° C. soluble content by TREF of 0.8% by weight or less, preferably 0.5% by weight or less. It is important that the content is particularly preferably 0.3% by weight or less.
If this soluble content is too much, stickiness and bleed out are likely to occur, adversely affecting the quality of the molded product, and particle properties and particle flowability deteriorate due to particle agglomeration and reactor adhesion. There is a risk that production will become impossible.

In the present invention, the TREF measurement method is specifically performed as follows.
A sample to be measured is dissolved in o-dichlorobenzene (containing 0.5 mg / ml BHT) at 140 ° C. to obtain a solution. After this was introduced into a 140 ° C. TREF column packed with glass beads, etc., it was cooled to 100 ° C. at a rate of 8 ° C./min and subsequently cooled to −15 ° C. at a rate of 4 ° C./min for 60 minutes. Hold. Thereafter, -15 ° C o-dichlorobenzene (containing 0.5 mg / ml BHT), which is a solvent, flows through the column at a flow rate of 1 ml / min, and is dissolved in -15 ° C o-dichlorobenzene in the TREF column. The components are eluted for 10 minutes, and then the column is linearly heated to 140 ° C. at a rate of temperature increase of 100 ° C./hour to obtain an elution curve.

(3) Melting peak temperature Furthermore, the polymer component (A) has a melting peak temperature Tm (A) measured by a differential scanning calorimeter (DSC), which is a measure of crystallinity, in the range of 149 to 165 ° C. Practically preferred.
Tm (A) is measured as a melting peak temperature obtained by a differential scanning calorimeter (DSC) in a conventional manner with respect to the polymer component (A) sampled in a small amount after the first step. When Tm (A) becomes too low, the heat resistance is deteriorated, and the film is softened during the retort treatment, or fusion of both films is seen by the retort treatment, which is not preferable. In addition, problems such as being easily taken on a roll during film formation also arise.
The adjustment (control) of the melting peak temperature Tm (A) can be performed according to the α-olefin content used for copolymerization.

3. Propylene-ethylene random copolymer component (1) obtained in the second step (1) Propylene-ethylene random copolymer component The propylene-ethylene random copolymer component (B) is low crystalline or amorphous, It is a component that contributes to the flexibility and impact resistance of the copolymer. This component is polymerized mainly as a propylene-ethylene random copolymer after the second stage of the multistage polymerization method.
Here, unless departing from the spirit of the present invention, it may be further copolymerized with other α-olefins such as 1-butene, 1-hexene, 1-octene and the like.

(2) Ratio of copolymer component (B) Regarding the copolymer component (B), the condition (iii) in claim 1, that is, the ratio W (B) in the total amount of the block copolymer (X1) is 10 It should be ˜40% by weight.
When W (B) exceeds 40% by weight, the aggregation of the polymer particles increases, the heat resistance of the copolymer (X1) decreases, and stickiness and bleedout are difficult to suppress, and W (B ) Is less than 10% by weight, the amount of the copolymer component (B) contributing to flexibility and impact resistance becomes insufficient, and flexibility and impact resistance are lowered.

The ratio W (B) of the copolymer component (B) to the total amount of the copolymer (X1) can be obtained by dividing the polymerization amount in the second step by the polymerization amount of the entire copolymer (X1). Specifically, since the polymerization amount in the second step can be calculated from the monomer consumption amount, the reaction heat, the increased mass of the reactor itself, and the like, this may be divided by the total polymerization amount of the copolymer (X1). Further, in the case of continuous polymerization in which reactors are connected in series, calculation can be performed from the production amount per hour in the first and second steps.
As a simple method, the polymer component (A) obtained in the first step and the copolymer component (B) obtained in the second step are separated by solvent fractionation (for example, cold xylene soluble fractionation method). It can also be sorted and calculated from each mass. Furthermore, the mass ratio of the polymer component (A) obtained in the first step and the copolymer component (B) obtained in the second step can also be determined by instrumental analysis such as TREF and CFCIR.

The technique for evaluating the crystallinity distribution of the copolymer component (B) by the temperature rising elution fractionation method (TREF) is well known to those skilled in the art. For example, a detailed measurement method is described in the following document: It is shown.
G. Glockner, J. et al. Appl. Polym. Sci. : Appl. Polym. Symp. 45, 1-24 (1990)
L. Wild, Adv. Polym. Sci. 98, 1-47 (1990)
J. et al. B. P. Soares, A .; E. Hamielec, Polymer; 36, 8, 1639-1654 (1995)

The copolymer (X1) used in the present invention has a great difference in crystallinity between the polymer component (A) and the copolymer component (B), and each copolymer is produced by using a metallocene catalyst. Since the crystallinity distribution is narrow, there are very few intermediate components between the two, and both can be accurately separated by TREF.
W (B) can be controlled by changing the ratio of the production amount of the first step for producing the polymer component (A) and the production amount of the second step for producing the copolymer component (B). it can. For example, in order to increase W (A) and decrease W (B), the production amount of the second step may be reduced while maintaining the production amount of the first step, which shortens the residence time of the second step. It can be easily controlled by lowering the polymerization temperature or increasing the amount of the polymerization inhibitor. The reverse is also true.

(3) Ethylene content of copolymer component (B) The copolymer component (B) has a condition of (iv) in claim 1, that is, an ethylene content E (B) of 10 to 50% by weight, preferably 15 to It is 45% by weight, particularly preferably 20 to 40% by weight.
When E (B) exceeds 50% by weight, the copolymer (B) component is not sufficiently compatible with the propylene-based polymer component (A), and the impact resistance of the block copolymer is reduced. In particular, the impact resistance at low temperatures is reduced. Moreover, the transparency at the time of film forming also deteriorates. Even when E (B) is less than 10% by weight, the impact resistance is lowered.

The ethylene content E (AB) of the entire copolymer (X1) can be determined from a ¹³ C-NMR spectrum by a proton complete decoupling method. For the assignment of the spectrum, for example, “Macromolecules; 17, 1950 (1984)” can be referred to. In addition, a standard sample of several copolymers with different ethylene contents is prepared in advance, its ¹³ C-NMR spectrum and infrared absorption spectrum are measured, and then a calibration curve for determining the ethylene content is prepared and used. May be converted. Alternatively, a calibration curve in CFC-IR (a combination of a cross fractionator and a Fourier transform infrared absorption spectrum analysis) may be created and used.

The ethylene content E (B) in the copolymer component (B) in the second step is expressed by the following formula from the ethylene content E (X1) of the entire copolymer and the above E (A) and W (B). 1 can be calculated.
E (B) = {E (X1) −E (A) × (1−E (B))} / W (B) (Formula 1)

  The MFR of the copolymer (X1) is desirably 0.1 to 60 dg / min. If it is below the lower limit MFR, the viscosity of the block copolymer of the product when melted is too high and the moldability deteriorates. On the other hand, if the upper limit MFR is exceeded, the melt tension at the time of melting decreases and the moldability deteriorates, such being undesirable. A preferred lower limit of this range is 0.5 dg / min, and a preferred upper limit of this range is 30 dg / min.

The mass average molecular weight of the copolymer component (B) in the copolymer (X1) is 10,000 to
It is preferably 5,000,000. A mass molecular weight of less than 10,000 is not preferable because the impact resistance of the product formed from the copolymer (X1) is lowered. Moreover, since the external appearance of a product will deteriorate when mass molecular weight exceeds 5,000,000, it is unpreferable. A preferred lower limit of this range is 50,000, and a more preferred lower limit is 100,000. A preferable upper limit of this range is 3,000,000, and a more preferable upper limit is 1,000,000. Measurement is by CFC-IR.

The MFR of the copolymer component (B) is not particularly limited, but is preferably 5 dg / min or less when impact resistance at low temperature is required.
The MFR of the copolymer component B is obtained by converting the mass average molecular weight Mw _EPR of the copolymer component (B) obtained by the cross fractionator from a correlation formula between the MFR and the mass average molecular weight. Simply, using the fact that the natural logarithm of MFR is proportional to the mass average molecular weight, it can be easily calculated from the total MFR of W (B), MFR (A), and copolymer (X1). There is essentially no difference in the calculation method.
The MFR of the copolymer component (B) can be adjusted by adjusting the amount of hydrogen supplied in the polymerization step or the polymerization temperature.

4). Production method of propylene-ethylene block copolymer (X1) (1) Production conditions The propylene-ethylene block copolymer (X1) used in the present invention satisfies the following conditions (i) to (iv): It is obtained by sequentially polymerizing the propylene-based polymer component (A) in the first step and the propylene-ethylene random copolymer component (B) in the second step.

(I) The -15 ° C soluble content of the propylene-based polymer component (A) by TREF is 0.8% by weight or less.
(Ii) The molecular weight distribution (Mw / Mn) of the propylene-ethylene block copolymer (X1) is 3.5 to 6.0.
(Iii) The ratio of the propylene-ethylene random copolymer component (B) relative to the total amount of the propylene-ethylene block copolymer (X1) is 10 to 40% by weight.
(Iv) The ethylene content E (B) of the copolymer component (B) is 10 to 50% by weight.

(2) Polymerization catalyst In producing the propylene-ethylene block copolymer (X1) used in the present invention, it is usually preferable to use an improved or new generation polymerization catalyst, particularly a metallocene catalyst.
In the traditional Ziegler-based catalyst, since there are multiple types of active sites for the catalytic reaction, the crystallinity and molecular weight distribution of the produced propylene-ethylene block copolymer are wide, and by producing many low crystals and low molecular weight components, Product stickiness and bleed-out are strongly seen, and there are drawbacks that problems such as bleed-out and poor appearance tend to occur.
In addition, since the formation of low crystalline components is difficult to suppress even if the molecular weight is increased, the stickiness and bleed-out are not sufficiently reduced, and the appearance of so-called butts and fish eyes due to the high molecular weight of the elastomer Defects are also likely to occur, and the extrusion moldability deteriorates, so there are many problems such as the need to use an organic peroxide in the granulation step.

On the other hand, single-site catalysts such as metallocene catalysts have higher catalytic activity than Ziegler-based catalysts, the molecular weight distribution of the produced polymer is narrow, and the copolymer has a uniform composition distribution. It is a catalyst superior to a Ziegler catalyst for producing a polymer.
Therefore, in the present invention, in order to eliminate the above-mentioned drawbacks caused by the Ziegler-Natta catalyst, it is preferable to select a polymerization method using a metallocene catalyst as a single site catalyst.

(3) Polymerization method The propylene-ethylene block copolymer (X1) used in the present invention is produced by producing a crystalline propylene polymer component (A) as the first step and at the first step as the second step. Further, a low crystalline or amorphous propylene-ethylene random copolymer component (B) is continuously produced in the presence of the obtained polymerization reaction mixture.

As the polymerization method, solution polymerization, slurry polymerization, gas phase polymerization, and bulk polymerization are possible. The polymerization in the first step is a polymerization of the crystalline propylene polymer component (A), and usually a slurry polymerization or a gas phase polymerization in which each monomer is kept in a gaseous state without substantially using a liquid solvent is employed. Is done. In addition, as a polymerization mode in the first step, bulk polymerization using propylene as a solvent without substantially using an inert solvent can be employed as long as the catalyst component and each monomer come into efficient contact.
There is no particular limitation on the polymerization method, but bulk polymerization and gas phase polymerization are preferred. A preferable gas phase polymerization method is a method in which polymerization is performed in a gaseous monomer without using a medium, for example, a method in which the generated polymer particles are flowed in a monomer stream to form a fluidized bed or the generated polymer particles are stirred by a stirrer. It is a system which stirs in a reaction tank. The bulk polymerization and the gas phase polymerization are preferable because a high boiling point solvent does not exist in the system, and thus a removal step is not necessary.

In the polymerization step of the second step, the propylene-ethylene random copolymer component (B) having a high ethylene content is polymerized in the presence of the catalyst-containing propylene polymer component (A) obtained by the polymerization of the first step. It is a process.
The polymerization method is not particularly limited but is preferably gas phase polymerization. Vapor phase polymerization is preferred because the propylene-ethylene random copolymer component (B) has a high ethylene content, so in a polymerization process other than the gas phase process, propylene--into the liquid (solvent or liquid propylene) present in the polymerization system. This is because the ethylene random copolymer component (B) is easily dissolved and stickiness between the polymer particles is easily generated.
This is further promoted when the content W (B) of the propylene-ethylene random copolymer component (B) in the copolymer is high.
Therefore, using the continuous method, first, the propylene polymer component (A) is polymerized by the bulk method or the gas phase method, and then the propylene-ethylene random copolymer component (B) is polymerized by the gas phase method. Is particularly preferred.

(4) Polymerization conditions The polymerization temperature is usually 0 to 150 ° C. The lower limit is preferably 50 ° C., more preferably 60 ° C., and the upper limit is preferably 90 ° C., more preferably 80 ° C.
When the temperature is lower than the lower limit, there is a problem that the polymerization activity is lowered or the heat removal efficiency of the reaction heat is deteriorated, and when the temperature exceeds the upper limit, the generated polymer is sticky. This upper limit temperature is also related to the melting point Tm (A) of the propylene-based polymer component (A), and in particular, is not more than a temperature of Tm (A) -40 ° C., particularly not more than a temperature of Tm (A) -50 ° C. preferable.

The polymerization pressure is generally greater than 0 kg / cm ² G, or less 2,000kg / cm ² G. The lower limit of the pressure is preferably 5 kg / cm ² G, more preferably 10 kg / cm ² G, and particularly preferably 15 kg / cm ² G.
When the amount is less than the preferred lower limit, problems such as a decrease in polymerization activity or a decrease in molecular weight occur. A preferable upper limit is 60 kg / cm ² G.
Vapor phase polymerization is performed under temperature and pressure conditions where propylene or a mixed monomer of propylene and ethylene is introduced to maintain a gas phase state. The bulk polymerization is preferably performed under temperature and pressure conditions that can maintain propylene or a mixed monomer of propylene and ethylene in a liquid state.
The polymerization time is usually 5 minutes to 10 hours, preferably 15 minutes to 7 hours, more preferably 30 minutes to 5 hours.

  In the case of continuous copolymerization, the amount ratio of each monomer in the reaction system does not need to be constant over time, and each monomer can be supplied at a constant mixing ratio. It is also possible to change. Further, hydrogen can be used as an auxiliary as a molecular weight regulator of the produced polymer.

In the present invention, it is desirable to carry out copolymerization at a molar ratio of propylene / ethylene in the reaction system in the polymerization in the first step of 100/0 to 80/20.
If the lower limit molar ratio is less than 80/20, the rigidity decreases, which is not preferable. These values are measured with a gas chromatograph.

It is desirable to carry out the copolymerization at a molar ratio of propylene / ethylene in the reaction system in the polymerization in the second step of 10/90 to 90/10.
When the lower limit molar ratio is less than 10/90, impact resistance is lowered, which is not preferable. On the contrary, the same inconvenience arises even if the upper limit molar ratio of 90/10 is exceeded. These values are measured with a gas chromatograph.
An inert gas such as nitrogen, propane, or isobutane can be allowed to coexist in the polymerization system, but if it is present in a large amount, the monomer partial pressure is lowered and the activity becomes low. The ratio of these inert gases is 20 mol% or less, preferably 10 mol% or less.

The polymerization reaction is preferably performed by multistage polymerization. As an example of multistage polymerization, there is a mode in which a catalyst is continuously supplied to the most upstream reactor of a plurality of reactors connected in series, and the polymer is continuously extracted and transferred to a subsequent polymerization tank. As another example, the catalyst is continuously supplied to one polymerization tank and the first stage polymerization is performed, and then the monomer is purged, without deactivating the catalyst present in the polymerization tank, A method of performing the second stage polymerization can also be exemplified.
In any case, since the influence of the monomer and hydrogen brought from the previous process (previous polymerization) on the next process is reduced, the purge amount of the monomer and the like is increased before the process is transferred, or an inert gas such as nitrogen. It is also possible to dilute or replace with, rather it is preferable to do so.

  The polymerization reaction in the second step in the present invention refers to a polymerization reaction performed after the polymerization reaction under at least one condition, for example, a copolymer component that is performed after the polymerization of the propylene-based polymer component (A) is performed in multiple steps. The polymerization of (B) is also included. Each of the first step and the second step can be divided into several stages. Specifically, a method in which a plurality of reactors are connected in series and each step is performed in several stages, and a method in which each step is performed in a plurality of batches using a single reactor can be mentioned.

The killer compound is a compound that lowers and deactivates the activity of the polymerization catalyst (particularly the activity of the second step). The killer compound selectively captures and deactivates short path particles smaller than normal catalyst particles. Thereby, the production | generation of the particle | grains with which the content of a copolymer component (B) is excess is suppressed.
As the killer compound, a compound having polarity such as oxygen, ethanol, and acetone is usually used. Also, when using a metallocene catalyst, it has no active hydrogen that reacts or interacts with the aluminum compound (scavenger), while it has a polar group that interacts with the single site active site of the metallocene catalyst. Also good. Examples of such compounds include alkyl halides, ethers, and vinyl ethers.

In multi-stage continuous polymerization, the killer compound may be supplied to any polymerization reactor. Preferably, it supplies to the reactor which performs a 2nd process. When the second step is carried out in a plurality of reactors, it is preferably supplied to the most upstream reactor. If particles with an excessive amount of W (B) are present, the copolymer component (B) is not sufficiently dispersed in the molded body during melting or molding of the copolymer, resulting in poor appearance due to the generation of bright spots or gels. As a result, the impact resistance of the copolymer is lowered.
In addition, since many killer compounds act on the surface of the polymer particles in the reactor, only the active sites on the surface are selectively deactivated, the amount of surface sticky components is reduced, and the stickiness between the particles is reduced. Adhesion to the wall is also suppressed.
Furthermore, the addition of a killer compound is also used as a means for controlling the polymerization activity in the second step. This makes it possible to control the amount of component B relative to the total amount of the copolymer.

In the present invention, the second step is carried out after completion of the first step. However, it is an important matter how to stably produce the copolymer component (B) having a high ethylene content and being sticky in the second step. For stable production, it is necessary to prevent adhesion of polymer particles that are easily sticky. For that purpose, it is important to increase the particle size of the polymer particles after the first step, that is, the particle size of the polymer particles before the start of the second step.
When the particle size of the polymer particle is large, the effect of the killer compound is easily exhibited as described above, and the specific surface area of the polymer particle is small, so that the contact area of the polymer particle per unit mass is small and the cohesion that is easy to stick is obtained. The rate at which the coalesced component (B) bleeds out to the surface (moves to the polymer particle surface) can be reduced.
Therefore, there is a preferable range for the average particle size of the polymer particles after the first step, and the lower limit thereof is usually 800 μm, preferably 1,000 μm, more preferably 1,100 μm.

In addition to the above conditions, polymer particle fines also affect the operational stability of the reactor. If this amount is large, the operation stability such as adhesion to the reactor wall, clogging in the transfer pipe, scattering to the gas pipe, and clogging of the filter will be adversely affected.
The amount of fine powder is represented by the amount of fine powder having a particle size of 212 μm or less in the particle size distribution measurement, and can be quantified by passing the polymer particles through a sieve having a mesh size of 212 μm. The amount of fine powder is preferably 2.0% by weight or less, more preferably 1.0% by weight or less, particularly preferably 0.5% by weight or less, and especially 0.1% by weight or less.

5. Polymerization catalyst suitable for production of propylene-ethylene block copolymer (1) Metallocene catalyst As described above, a metallocene catalyst is used to produce the propylene-ethylene block copolymer (X1) in the present invention. Is preferred.
In the propylene-ethylene block copolymer, it is well known to those skilled in the art that stickiness and bleedout deteriorate when the molecular weight and crystallinity distribution are wide. In order to suppress it, it is desirable to carry out polymerization by using a metallocene catalyst that can narrow the molecular weight and crystallinity distribution.
In the conventional Ziegler-based catalyst, an excellent propylene-based polymer component (A) that can be a sticky and bleed-out component and that has a soluble content of −15 ° C. in TREF of 0.8% by weight or less cannot be obtained.

  The metallocene-based catalyst generally has (I) a metallocene complex composed of a transition metal compound of Group 4-6 of the periodic table (short-period type) having a conjugated five-membered ring ligand, and activates it (II) It is composed of a cocatalyst and (III) an organoaluminum compound used as necessary. Depending on the characteristics of the olefin polymerization process, particle formation is essential, and (IV) the carrier may be a further constituent.

(2) Metallocene complex (I)
As the metallocene complex used in the present invention, representative examples include metallocene bridged complexes of transition metal compounds of Groups 4 to 6 of the periodic table having a conjugated five-membered ring ligand. What is represented by a formula, and especially an azulene type thing are preferable.

(In the formula, M is Ti, Zr or Hf. X and Y are auxiliary ligands which react with the cocatalyst of component (II) to produce an active metallocene having olefin polymerization ability. Z and Z ′ are an optionally substituted cyclopentadienyl group, indenyl group, fluorenyl group, or azulenyl group, and Q is a group that bridges Z and Z ′. And Z ′ may further have a substituent on the side ring.)

As Z and Z ′, an indenyl group or an azulenyl group is preferable, and an azulenyl group is particularly preferable.
Q represents a binding group that crosslinks between ligands such as two conjugated five-membered rings at an arbitrary position, and specifically, is preferably an alkylene group, a silylene group, or a germylene group.
M is a metal atom of a transition metal selected from Groups 4 to 6 of the periodic table, preferably titanium, zirconium, hafnium or the like. Zirconium or hafnium is particularly preferable.
X and Y are auxiliary ligands that react with the cocatalyst of component (II) to produce an active metallocene having olefin polymerization ability. Therefore, as long as this object is achieved, X and Y are not limited in the kind of ligand, and each may be a hydrogen atom, a halogen atom, a hydrocarbon group, or a hydrocarbon group optionally having a heteroatom. Etc. can be exemplified. Among these, a hydrocarbon group having 1 to 10 carbon atoms or a halogen atom is preferable.

  The following can be illustrated as a specific compound of a metallocene complex. In a metallocene complex having a structure in which a substituent has two cyclopentadienyl ligands constituting a ring and they are bridged, as an azulene-based one, dimethylsilylene bis {1- (2- Methyl-4-isopropyl-4H-azurenyl)} zirconium dichloride, dimethylsilylenebis {1- (2-methyl-4-phenyl-4H-azurenyl)} zirconium dichloride, dimethylsilylenebis [1- {2-methyl-4- (4-Chlorophenyl) -4H-azurenyl}] zirconium dichloride, dimethylsilylenebis [1- {2-methyl-4- (4-fluorophenyl) -4H-azurenyl}] zirconium dichloride, dimethylsilylenebis [1- {2 -Methyl-4- (3-chlorophenyl) -4H-azurenyl}] zirconium Chloride, dimethylsilylenebis [1- {2-methyl-4- (2,6-dimethylphenyl) -4H-azurenyl}] zirconium dichloride, dimethylsilylenebis {1- (2-methyl-4,6-diisopropyl-4H) -Azurenyl)} zirconium dichloride, diphenylsilylenebis {1- (2-methyl-4-phenyl-4H-azurenyl)} zirconium dichloride, methylphenylsilylenebis {1- (2-methyl-4-phenyl-4H-azurenyl) } Zirconium dichloride, methylphenylsilylenebis [1- {2-methyl-4- (1-naphthyl) -4H-azulenyl}] zirconium dichloride, dimethylsilylenebis {1- (2-ethyl-4-phenyl-4H-azurenyl) )} Zirconium dichloride, dimethylsilyl Bis [1- {2-ethyl-4- (1-anthracenyl) -4H-azurenyl}] zirconium dichloride, dimethylsilylenebis [1- {2-ethyl-4- (2-anthracenyl) -4H-azurenyl}] zirconium Dichloride, dimethylsilylenebis [1- {2-ethyl-4- (9-phenanthryl) -4H-azulenyl}] zirconium dichloride, dimethylmethylenebis [1- {2-methyl-4- (4-biphenylyl) -4H- Azulenyl}] zirconium dichloride, dimethylgermylenebis [1- {2-methyl-4- (4-biphenylyl) -4H-azurenyl}] zirconium dichloride, dimethylsilylenebis {1- (2-ethyl-4- (3 5-dimethyl-4-trimethylsilylphenyl-4H-azurenyl)} zirconium And mujichloride.

  Examples of the azulene-based compound having different conjugated multi-membered ring ligands include dimethylsilylene [1- {2-methyl-4- (4-biphenylyl) -4H-azurenyl}] [1- {2-methyl -4- (4-biphenylyl) indenyl}] zirconium dichloride, dimethylsilylene {1- (2-ethyl-4-phenyl-4H-azurenyl)} {1- (2-methyl-4,5-benzoindenyl)} Examples include zirconium dichloride.

  Examples of the metallocene complex having a structure in which two indenyl ligands are bridged include dimethylsilylene bis {1- (2-methyl-4-phenylindenyl)} zirconium dichloride, dimethylsilylene bis {1- (2-Methyl-4,5-benzoindenyl)} zirconium dichloride, dimethylsilylenebis [1- {2-methyl-4- (1-naphthyl) indenyl}] zirconium dichloride, diphenylsilylenebis {1- (2- Methyl-4-phenylindenyl)} zirconium dichloride, methylphenylsilylenebis {1- (2-methyl-4-phenylindenyl)} zirconium dichloride, dimethylsilylenebis {1- (2-ethyl-4-phenylindenyl) )} Zirconium dichloride, dimethylgermylenebis {1- 2-ethyl-4-phenylindenyl)} zirconium dichloride, methylaluminum bis {1- (2-ethyl-4-phenylindenyl)} zirconium dichloride, phenylphosphinobis {1- (2-ethyl-4-phenyl) Indenyl)} zirconium dichloride, phenylaminobis {1- (2-methyl-4-phenylindenyl)} zirconium dichloride, dimethylsilanediylbis (tetrahydroindenyl) zirconium dichloride, diethylsilanediylbis (tetrahydroindenyl) zirconium Examples include dichloride.

  Examples of the metallocene complex having one substituted fluorenyl ligand and one substituted cyclopentadienyl group, which are bridged, include isopropylidene (cyclopentadienyl-9-fluorenyl) titanium dichloride, isopropyl chloride. Liden (cyclopentadienyl-9-fluorenyl) zirconium dichloride, isopropylidene (cyclopentadienyl-9-fluorenyl) hafnium dichloride, isopropylidene (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) titanium dichloride, Isopropylidene (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) zirconium dichloride, isopropylidene (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) hafnium dichlorine Isopropylidene (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) titanium dichloride, isopropylidene (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) zirconium dichloride Isopropylidene (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) hafnium dichloride, diphenylmethylene (cyclopentadienyl-9-fluorenyl) titanium dichloride, diphenylmethylene (cyclopentadienyl-9 -Fluorenyl) zirconium dichloride, diphenylmethylene (cyclopentadienyl-9-fluorenyl) hafnium dichloride, diphenylmethylene (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) titanium Chloride, diphenylmethylene (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) zirconium dichloride, diphenylmethylene (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) hafnium dichloride, diphenylmethylene (cyclopentadi) Enyl-2,7-di-t-butyl-9-fluorenyl) titanium dichloride, diphenylmethylene (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) zirconium dichloride, diphenylmethylene (cyclopentadi) Enyl-2,7-di-t-butyl-9-fluorenyl) hafnium dichloride, dimethylsilanediyl (cyclopentadienyl-9-fluorenyl) titanium dichloride, dimethylsilanediyl (cyclopentadi) Enyl-2,7-dimethyl-9-fluorenyl) titanium dichloride, dimethylsilanediyl (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) titanium dichloride, dimethylsilanediyl (cyclopentadienyl-) 9-fluorenyl) zirconium dichloride, dimethylsilanediyl (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) zirconium dichloride, dimethylsilanediyl (cyclopentadienyl-2,7-di-t-butyl-9-) Fluorenyl) zirconium dichloride, dimethylsilanediyl (cyclopentadienyl-9-fluorenyl) hafnium dichloride, dimethylsilanediyl (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) hafnium dichloride Dimethylsilanediyl (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) hafnium dichloride, diethylsilanediyl (cyclopentadienyl-9-fluorenyl) titanium dichloride, diethylsilanediyl (cyclopenta) Dienyl-2,7-dimethyl-9-fluorenyl) titanium dichloride, diethylsilanediyl (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) titanium dichloride, diethylsilanediyl (cyclopentadienyl) -9-fluorenyl) zirconium dichloride, diethylsilanediyl (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) zirconium dichloride, diethylsilanediyl (cyclopentadienyl-2,7-di) t-butyl-9-fluorenyl) zirconium dichloride, diethylsilanediyl (cyclopentadienyl-9-fluorenyl) hafnium dichloride, diethylsilanediyl (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) hafnium dichloride, diethyl Silanediyl (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) hafnium dichloride, diphenylsilanediyl (cyclopentadienyl-9-fluorenyl) titanium dichloride, diphenylsilanediyl (cyclopentadienyl- 2,7-dimethyl-9-fluorenyl) titanium dichloride, diphenylsilanediyl (cyclopentadienyl-2,7-di-t-butyl-9-fluorenyl) titanium dichloride, diph Phenylsilanediyl (cyclopentadienyl-9-fluorenyl) zirconium dichloride, diphenylsilanediyl (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) zirconium dichloride, diphenylsilanediyl (cyclopentadienyl-2,7) -Di-t-butyl-9-fluorenyl) zirconium dichloride, diphenylsilanediyl (cyclopentadienyl-9-fluorenyl) hafnium dichloride, diphenylsilanediyl (cyclopentadienyl-2,7-dimethyl-9-fluorenyl) hafnium Dichlorides such as dichloride, diphenylsilanediyl (cyclopentadienyl 2,7-di-t-butyl-9-fluorenyl) hafnium dichloride, and dimetals of group 4 transition metals in the periodic table Chill body, diethyl body, dihydro derivative, diphenyl body, and the like can be exemplified dibenzyl body.

A compound in which the silylene group of the compounds of these specific examples is replaced with a germylene group and zirconium is replaced with hafnium, or vice versa, is also exemplified as a suitable example. A hafnium compound is preferred when the desired copolymer has a high molecular weight.
The component (I) is preferably a compound having a substituted cyclopentadienyl group, a substituted indenyl group, a substituted fluorenyl group, or a substituted azulenyl group that is crosslinked with a silylene group, a germylene group, or an alkylene group having a hydrocarbon substituent. Transition metal compounds composed of ligands, particularly those composed of ligands having a substituted indenyl group or a substituted azulenyl group, which are crosslinked with a silylene group having a hydrocarbon substituent or a germylene group, are particularly preferred. Or what has a substituent in 2nd-position and 4th-position is preferable.

(3) Cocatalyst (activator component) (II)
The co-catalyst is a component that activates the metallocene complex, and is a compound that can react with the auxiliary ligand of the metallocene complex to convert the complex into an active species having olefin polymerization ability. -1) to (II-4).
(II-1) Aluminum oxy compound (II-2) An ionic compound or Lewis acid (II-3) solid acid (II-) capable of reacting with component (I) to convert component (I) into a cation 4) Ion exchange layered silicate

It is well-known that the aluminum oxy compound of (II-1) can activate a metallocene complex, and specific examples of such a compound include compounds represented by the following general formulas.

In each of the above general formulas, R ¹ represents a hydrogen atom or a hydrocarbon group, preferably a hydrocarbon group having 1 to 10 carbon atoms, especially 1 to 6 carbon atoms. Moreover, several R < ¹ > may be same or different, respectively. P represents an integer of 0 to 40, preferably 2 to 30.
Among the general formulas, the compounds represented by the first and second formulas are compounds also referred to as aluminoxanes. Among these, methylaluminoxane or methylisobutylaluminoxane is preferable. The above aluminoxanes can be used in combination within a group and between groups. And said aluminoxane can be prepared on well-known various conditions.
The compound represented by the third general formula is 10: 1 to 1 type of trialkylaluminum or two or more types of trialkylaluminum and an alkylboronic acid represented by the general formula R ² B (OH) ₂ . It can be obtained by a 1: 1 (molar ratio) reaction.
In the general formula, R ¹ and R ² represent a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms.

  The compound (II-2) is an ionic compound or Lewis acid capable of reacting with the component (I) to convert the component (I) into a cation, and examples of such an ionic compound include carbonium. Examples thereof include complexes of cations such as cations and ammonium cations with organic boron compounds such as triphenylboron, tris (3,5-difluorophenyl) boron and tris (pentafluorophenyl) boron. Examples of the Lewis acid as described above include various organic boron compounds such as tris (pentafluorophenyl) boron. Alternatively, metal halides such as aluminum chloride and magnesium chloride are exemplified.

In addition, a certain thing of said Lewis acid can also be grasped | ascertained as an ionic compound which can react with a component (I) and can convert a component (I) into a cation.
Here, as the particulate carrier carrying component (II-1) and component (II-2), inorganic oxides such as silica, alumina, magnesia, silica alumina, silica magnesia, magnesium chloride, magnesium oxychloride, chloride Examples thereof include inorganic halides such as aluminum and lanthanum chloride, and porous organic carriers such as polypropylene, polyethylene, polystyrene, styrenedivinylbenzene copolymer, and acrylic acid copolymer.

Examples of the solid acid (II-3) include alumina, silica-alumina, and silica-magnesia.

The ion-exchangeable layered compound (II-4) occupies most of the clay mineral, and is preferably an ion-exchangeable layered silicate.
An ion-exchange layered silicate (hereinafter, sometimes simply abbreviated as “silicate”) has a crystal structure in which surfaces formed by ionic bonds and the like are stacked in parallel with each other by a binding force, and contains Refers to a silicate compound in which the ions to be exchanged are exchangeable. Most silicates are naturally produced mainly as a main component of clay minerals, and therefore often contain impurities (quartz, cristobalite, etc.) other than ion-exchangeable layered silicates. You may go out.

Various known silicates can be used, and specific examples include layered silicates described in Haruo Shiramizu, “Clay Mineralogy”, Asakura Shoten (1995). A silicate having a type 1 structure is preferred, a smectite group is more preferred, and montmorillonite is particularly preferred. As for silicates, those obtained as natural products or industrial raw materials can be used as they are without any particular treatment, but it is preferable to carry out chemical treatment. Specific examples include acid treatment, alkali treatment, salt treatment, organic matter treatment, and the like. These processes may be used in combination with each other. These processing conditions are not particularly limited, and known conditions can be used.
Moreover, since these ion-exchange layered silicates usually contain adsorbed water and interlayer water, it is preferable to use them after removing the water by heating and dehydrating under an inert gas flow. Depending on the degree of these chemical treatments, the ion exchange properties may be small, but there is no particular problem if the raw material before the chemical treatment is an ion exchangeable layered silicate.
As the component (II) which is a promoter, the ion-exchangeable layered compound II-4 is stable and excellent in performance, and is preferable because it does not react vigorously with air or water.

(4) Organoaluminum compound (III)
As the organoaluminum compound used as needed in the metallocene catalyst system, those containing no halogen are used, and specifically, compounds represented by the following general formula are used.
AlR _3-i X _i
(In the formula, R represents a hydrocarbon group having 1 to 20 carbon atoms, X represents hydrogen, an alkoxy group, and i represents a number of 0 ≦ i ≦ 3. However, when X is hydrogen, i represents 0 ≦ i <. 3)

Specifically, trialkylaluminum such as trimethylaluminum, triethylaluminum, tripropylaluminum, triisobutylaluminum, and trioctylaluminum, or dimethylaluminum methoxide, diethylaluminum methoxide, diisobutylaluminum methoxide, diisobutylaluminum ethoxide, etc. Alkyl-containing alkylaluminums, and further halide-containing alkylaluminums such as diethylaluminum halides are mentioned.
Of these, trialkylaluminum, particularly triisobutylaluminum and trioctylaluminum are particularly preferable.

(5) Carrier (IV)
Examples of the carrier appropriately used in the metallocene catalyst system include various known inorganic or organic fine particle solids. The average particle size of the carrier is usually 5 to 300 μm, preferably 30 to 300 μm, more preferably 40 to 250 μm, and particularly preferably 46 to 200 μm. The specific surface area of the carrier is usually 50~1,000m ² / g, preferably from 100 to 500 m ² / g, pore volume of the support is usually 0.1~2.5cm ³ / g, preferably 0 .2 to 0.5 cm ³ / g.

Examples of inorganic solids include porous oxides, and 100 to 1,000 as necessary.
Baked at a temperature of 150 ° C, preferably 150 to 700 ° C.
Specifically, SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , TiO ₂ , B ₂ O ₃ , CaO, ZnO, BaO, ThO _2, etc., or a mixture thereof such as SiO ₂ —MgO, SiO ₂ —Al ₂ O ₃ , SiO ₂ —TiO ₂ , SiO ₂ —V ₂ O ₅ , SiO ₂ —Cr ₂ O ₃ , SiO ₂ —TiO ₂ —MgO, and the like can be given. Of these, those containing SiO ₂ or Al ₂ O ₃ as the main component are preferred.
Moreover, if it is a solid thing among the said (II) promoters, it can be used as a support | carrier and promoter, and it is preferable. Specific examples include (B-3) solid acid and (B-4) ion-exchange layered silicate. In order to improve the particle properties of the block copolymer, various known granulations are preferably performed.

  As the organic solid, a (co) polymer produced mainly from an α-olefin having 2 to 14 carbon atoms such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, or vinylcyclohexane, An example is a (co) polymer solid produced mainly from styrene.

  In the above examples of the components (I) to (IV) of the catalyst, each component of the catalyst does not constitute the essence of the present invention. . In the present invention, it is a matter of course that equivalent components other than those exemplified are included, and there is no reason for eliminating them.

(6) Prepolymerization The catalyst of the present invention is preferably subjected to a prepolymerization treatment in which a small amount of polymer is brought into contact with an olefin in advance to improve particle properties. The olefin to be used is not particularly limited, but ethylene, propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, 3-methyl-1-butene, vinylcycloalkane, styrene and the like can be used. It is possible to use it, and it is particularly preferable to use propylene. As an olefin supply method, an arbitrary method such as a supply method for maintaining the olefin at a constant speed or a constant pressure in the reaction tank, a combination thereof, or a stepwise change is adopted.

The prepolymerization time is not particularly limited, but is preferably in the range of 5 minutes to 24 hours. The prepolymerization amount is preferably 0.01 to 100 parts by mass, more preferably 0.1 to 50 parts by mass with respect to 1 part by mass of the catalyst component. After completion of the prepolymerization, the catalyst can be used as it is, depending on the usage form of the catalyst, but may be dried if necessary.
The prepolymerization temperature is not particularly limited, but is usually 0 ° C to 100 ° C, preferably 10 to 70 ° C, more preferably 20 to 60 ° C, and particularly preferably 30 to 50 ° C. Below this range, the reaction rate may decrease or the activation reaction may not proceed, and if it exceeds this range, the prepolymerized polymer may be dissolved, or the prepolymerization rate may be too high and the particle properties may deteriorate. There is a possibility that the active point may be deactivated due to a side reaction.
The preliminary polymerization can be carried out in a liquid such as an organic solvent, and it is preferable to do so. The concentration of the solid catalyst during the prepolymerization is not particularly limited, but is preferably 50 g / L or more, more preferably 60 g / L or more, and particularly preferably 70 g / L or more. The higher the concentration, the more active the metallocene and the higher the activity of the catalyst.
Further, a polymer such as polyethylene, polypropylene or polystyrene, or an inorganic oxide solid such as silica or titania can be allowed to coexist during or after the contact of the above components.

6). Others (1) Additive In the resin composition for packaging film of heat-sterilized food of the present invention, an antioxidant, an ultraviolet absorber, a neutralizing agent, a nucleating agent, within the range not impairing the effects of the present invention, Known additives such as light stabilizers, antistatic agents, lubricants, antiblocking agents, odor adsorbents, antibacterial agents, pigments, inorganic and organic fillers and various synthetic resins may be added as needed. it can.

(2) Film molding The packaging film for heat-sterilized food of the present invention is excellent in transparency, heat resistance, low-temperature impact resistance and food hygiene, and its effect is sufficiently exerted when used mainly as an unstretched film. The
The film can be obtained by melt extrusion film formation, and can be produced by a casting method, an inflation method or the like that is generally performed industrially.
In addition, the film of the present invention can be used as a single layer film or a laminated film using the above resin composition. In the case of a laminated film, the layer made of the resin composition of the present invention is preferably 50% or more of the total film thickness. The film thickness is preferably 5 to 200 μm, and more preferably 10 to 100 μm.
The surface of the film can be subjected to corona discharge treatment, flame treatment, ozone treatment, etc. in order to improve the wettability of the surface.

  In producing the packaging film for heat-sterilized food of the present invention, propylene-ethylene block copolymer (X1), and, if necessary, ethylene-propylene random copolymer and / or ethylene-butene-1 random copolymer Propylene-ethylene block copolymer (X1) consisting of separate pellets and, if necessary, ethylene-propylene random copolymer, even if the blend is premixed and pelletized with an extruder, etc., as a film The coalescence and / or ethylene-butene-1 random copolymer may be supplied to a film forming machine to form a film.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The rationality and significance of the configuration of the present invention and the prior art will be described based on the data of each Example and the comparison between each Example and each Comparative Example. Demonstrate excellence. In addition, physical property measurement and analysis in the following examples are according to the following methods.

(1) Calculation of ethylene content E (A) in propylene polymer component (A) Based on the ethylene content of a standard sample calculated by the ethylene content measurement method by ¹³ C-NMR described in JP-A-2003-73426. In addition, a relational expression (the following formula (2)) between the peak height I [absorbance] in the range of 700 to 760 cm ⁻¹ in the infrared absorption spectrum and the ethylene content E (A) (wt%) is calculated. It calculated using.
At the end of the first step, 5 g of the propylene polymer component (A) was extracted in advance, a 0.5 mm sheet was prepared by 190 ° C. press molding, and the infrared absorption spectrum was measured. D (mm) in the following formula (2) is a sheet thickness, and a numerical value accurately measured to a unit of 10 μm was used.
E (A) = 5 × I / D + 0.0613 Formula (2)

(2) Measurement of rubber content, ethylene content and molecular weight Rubber content (ethylene-propylene copolymer (B): EPR in the second step) in propylene-ethylene block copolymer (X1) (= W (B) ), The method for measuring the ethylene content (E (B)) in EPR and the mass average molecular weight (Mw _EPR ) of _EPR are as follows.
A cross fractionator (CFC T-100 manufactured by Dia Instruments), Fourier transform infrared absorption spectrum analysis (FT-IR Perkin Elmer 1760X), and gel permeation chromatography (GPC) are the same as in JP-A-2005-220235. They were combined by the method (this is abbreviated as CFC-IR), measured in the same manner and analyzed.
W (B) was determined from the amount of CFC-IR soluble at 40 ° C., and E (B) was determined from the ethylene content of the CFC-IR soluble at 40 ° C.

(3) Measurement of melting peak temperature Tm (A) The propylene polymer component (A) was pressed at 190 ° C. to prepare a sheet, which was weighed to 5 mg. This was put in an aluminum pan and covered, and then set in a DSC measuring apparatus (DSC-6200 manufactured by Seiko Denshi Kogyo). The temperature was raised from room temperature to 200 ° C. at a rate of 100 ° C./min, held for 5 minutes, and the crystallization temperature was determined by lowering the temperature from 230 ° C. to 40 ° C. at a rate of 5 ° C./min. Further, the melting point and the heat of crystal fusion were determined by raising the temperature from 40 ° C. to 200 ° C. at a rate of 10 ° C./min.

(4) Measurement by TREF A sample is dissolved in o-dichlorobenzene (containing 0.5 mg / ml BHT) at 140 ° C. to obtain a solution. After this is introduced into a TREF column at 140 ° C., it is cooled to 100 ° C. at a temperature decreasing rate of 8 ° C./min, subsequently cooled to −15 ° C. at a temperature decreasing rate of 4 ° C./min, and held for 60 minutes. Thereafter, -15 ° C o-dichlorobenzene (containing 0.5 mg / ml BHT), which is a solvent, flows through the column at a flow rate of 1 ml / min, and is dissolved in -15 ° C o-dichlorobenzene in the TREF column. Elute the components for 10 minutes. Next, the column is linearly heated to 140 ° C. at a temperature increase rate of 100 ° C./hour to obtain an elution curve.

(5) Mw / Mn measurement In the present invention, the mass average molecular weight (Mw) and the number average molecular weight (Mn) are those measured by gel permeation chromatography (GPC). Conversion from the retention volume to the molecular weight is performed using a calibration curve prepared in advance with standard polystyrene. Standard polystyrenes used are the following brands manufactured by Tosoh Corporation. (F380, F288, F128, F80, F40, F20, F10, F4, F1, A500
0, A2500, A1000)
A calibration curve is created by injecting 0.2 mL of a solution dissolved in ODCB (containing 0.5 mg / mL BHT) so that each is 0.5 mg / mL. The calibration curve uses a cubic equation obtained by approximation by the least square method. The viscosity equation [η] = K × Mα used for conversion to molecular weight uses the following numerical values.
PS: K = 1.38 × 10 ⁻⁴ α = 0.7
PP: K = 1.03 × 10 ⁻⁴ α = 0.78
The measurement conditions for GPC are as follows.
Apparatus: Waters GPC (ALC / GPC 150C) Detector: FOVBORD MIRAN 1A 1R detector (measurement wavelength: 3.42 μm) Column: Showa Denko AD806M / S (3) Mobile phase solvent: o- Dichlorobenzene Measurement temperature: 140 ° C. Flow rate: 1.0 ml / min Injection volume: 0.2 ml
Sample preparation: Prepare a 1 mg / mL solution using ODCB (containing 0.5 mg / mL BHT) and dissolve at 140 ° C. for about 1 hour. The baseline and section of the obtained chromatogram are performed as shown in FIG.

(6) Measurement of particle size distribution Using a laser diffraction / scattering type particle size distribution measuring apparatus LA-920 manufactured by Horiba, Ltd., the dispersion solvent was measured under the conditions of ethanol, refractive index 1.0, and shape factor 1.0.

(7) Measurement of average particle size of polymer particles and carrier The particle size of 20 g of each of the sample polymer particles and the carrier was determined using a particle size distribution measuring device cam sizer manufactured by Lecce Technology. The particle diameter of DIN 66141 Q3 (0.5) (the value of X = 0.5 in the cumulative distribution Q3 (x) based on mass) was defined as the average particle diameter.

(8) Polymer bulk density (BD)
Measured according to ASTM D1895-69.

(9) MFR
According to JIS K7210A method and condition M, measurement was performed under the following conditions. The unit is g / 10 minutes. In addition, MFR (X1) shows MFR of a propylene-ethylene block copolymer (X1).
Test temperature: 230 ° C. Nominal load: 2.16 kg Die shape: 2.095 mm in diameter and 8.000 mm in length

(10) Film stiffness The tensile modulus of the film was measured under the following conditions, and the obtained value was used as a measure of stiffness. The calculation method of the tensile elastic modulus was based on JIS K-7127. Sampling was performed so that the long side of the sample was MD.
Sample length: 150 mm Sample width: 15 mm Distance between chucks: 100 mm Crosshead speed: 1 mm / min

(11) Odor of film The obtained film was sealed in a clean Erlenmeyer flask with a capacity of 300 mL so as to be about 1/2 of the volume of the container, and kept heated in a thermostatic bath at 80 ° C. for 2 hours. The odor sensory evaluation was performed according to the following criteria within 10 minutes.
○: Odorless or slightly odor △: Slightly odor ×: Smelly odor ××: Smelly odor

(12) Heat resistance test of film The obtained film is cut into two pieces of MD · 120 mm × TD · 100 mm, MD is aligned and arranged so that the chill roll faces are outside, MD2 side, TD1 side Was thermocompression-bonded at a width of 10 mm (conditions: 200 ° C. · 2 kg / cm ² · 1.0 seconds) to obtain a food packaging bag. Subsequently, it sealed in the state which extracted the air which does not contain any content, and retort sterilization was implemented for 135 degreeC x 30 minutes.
After performing retort sterilization, cut the thermocompression bonding part of MD2 side and TD1 side, pick and open the paired film with both fingers, and melt the film between the inner surfaces of the package after retort sterilization according to the following criteria. The presence or absence of wearing was confirmed.
○: Can be opened without resistance, and no fusion is seen between the films.
Δ: There is a partial resistance when opening, but the film can be easily opened.
X: Although partial fusion | bonding is seen, a film can be opened.
XX: Fusion is observed and the film cannot be opened.

(13) Dropping bag impact test of the film after retort sterilization Cut out two films of the obtained size into a size of MD140 mm × TD170 mm, arrange the MD so that the chill roll surface is on the outside, MD2 side, TD1 side Was thermocompression-bonded at a width of 10 mm (conditions: 200 ° C. · 2 kg / cm ² · 1.0 seconds) to obtain a food packaging bag. Next, 250 ml of tap water was filled and retort sterilization was performed at 121 ° C. for 30 minutes.
After retort sterilization, the sample was stored frozen at 3 ° C. for 1 week. The sample after frozen storage was subjected to 20 vertical drops continuously from a height of 120 cm on the concrete floor so that the final seal part (the last sealed side) was up, and then the presence or absence of broken bags was confirmed. . The experiment is performed on a plurality of samples, and the evaluation result is expressed as “number of broken bags / n (n: the number of bags used in the bag drop test)”.

(14) Transparency deterioration confirmation test of film after retort sterilization The obtained film was cut into a size of MD140 mm × TD170 mm, and arranged so that the chill roll surface was on the outside with MD aligned, MD2 side, TD1 The side was subjected to thermocompression bonding with a width of 10 mm (conditions: 200 ° C. · 2 kg / cm ² · 1.0 seconds) to obtain a food packaging bag. Next, 250 ml of tap water was filled and retort sterilization was performed at 121 ° C. for 30 minutes.
After carrying out retort sterilization, the film was incised inside each of the four sealing surfaces of the food packaging bag to remove the contents, and a film after heat treatment was obtained. The film was measured for HAZE according to ASTM D-1003 (after HAZE / treatment). In addition, the unheated film was similarly measured for HAZE (before HAZE / treatment), and the difference was ΔHAZE (= HAZE / after treatment−Haze / before treatment), which was used as an indicator of the effect of preventing transparency deterioration after heating. . The smaller the value of ΔHAZE, the better the effect of preventing the transparency after heating.

(15) Impact resistance of film after retort sterilization Using a film compliant with JIS P8134 at an atmospheric temperature of 0 ° C. and −10 ° C., using a film subjected to retort sterilization by the above method, a film specimen having a diameter of 50 mm is used. The sample was fixed to a holder and struck with a 25.4 mm hemispherical metal penetrating portion, and the amount of work (J) required for penetrating fracture was measured and obtained by dividing by the film thickness.

[Production Example 1 / Catalyst synthesis]
(1) Solid catalyst synthesis a. Chemical treatment of ion-exchange layered silicate Into a 3 L separable flask equipped with a stirring blade and a reflux apparatus, 2,250 g of pure water was added, 665 g of 98% sulfuric acid was added dropwise, and the internal temperature was set to 90 ° C. Further, 400 g of commercially available granulated montmorillonite (Mizusawa Chemical Co., Ltd., Benclay SL, average particle size: 47 μm) was added and stirred. Thereafter, the reaction was carried out at 90 ° C. for 3 hours. This slurry was filtered with a Nutsche and a suction bottle connected to an aspirator, and washed 5 times with 2 L of pure water.
The cake collected in this manner was added to an aqueous solution in which 432 g of lithium sulfate monohydrate was dissolved in 1,924 ml of pure water in a 5 L beaker and reacted at room temperature for 2 hours. The slurry was filtered using a device in which an aspirator was connected to Nutsche and a suction bottle. After 2 L of pure water was added to the cake for washing, the resulting cake was added to 4 L of pure water to make a slurry, which was stirred for 5 minutes. It put into Nutsche and suction-filtered. After repeating this a total of 5 times, the cake was recovered and dried at 120 ° C. overnight. This was sieved with a sieve having an aperture of 74 μm to remove coarse particles to obtain 220 g of chemically treated montmorillonite.
b. Drying step a. The chemically treated montmorillonite obtained in 1 above was placed in a 1 L flask and dried under reduced pressure at 200 ° C. for 3 hours. Thereafter, it was further dried under reduced pressure for 2 hours to obtain a treated montmorillonite.
c. Treatment of montmorillonite to be treated with organoaluminum 20.16 g of the treated montmorillonite obtained in the above was weighed, 72 ml of heptane and 128.0 ml (49.6 mmol) of a heptane solution of tri-normal octylaluminum were added, and the mixture was stirred at room temperature for 1 hour. Then, after washing with heptane to a residual liquid ratio of 1/100, a slurry adjusted to an amount of 100 ml was obtained.

(2) Prepolymerization with propylene c. 6.10 ml (2,360 μmol) of a tri-normal octylaluminum heptane solution was added to the slurry obtained in (1). In a separate flask (volume 200 ml), (r) -dichloro [1,1′-dimethylsilylenebis {2-methyl-4- (4-chlorophenyl) -4H-azurenyl}] hafnium 480 mg (590 μmol) The slurry which added heptane (60 ml) to was added, and it stirred at 60 degreeC for 60 minutes.
To the slurry thus obtained, 340 ml of heptane was further added to adjust the total amount to 500 ml, and the mixture was introduced into a stirring autoclave having an internal volume of 1 L that had been sufficiently purged with nitrogen. When the temperature in the autoclave was stabilized at 40 ° C., propylene was supplied at a rate of 10 g / hour to maintain the temperature. After 4 hours, the supply of propylene was stopped, and the temperature was maintained at 40 ° C. for 1 hour.
Thereafter, the residual monomer was purged and the prepolymerized catalyst slurry was recovered from the autoclave. The recovered prepolymerized catalyst slurry was allowed to stand, and 310 ml of the supernatant was extracted. Subsequently, 16.72 ml (12.01 mmol) of a heptane solution of triisobutylaluminum was added at room temperature, and then dried under reduced pressure to recover 63.5 g of a solid catalyst. The prepolymerization ratio (a value obtained by dividing the amount of the prepolymerized polymer by the amount of the solid catalyst) was 2.08.

[Production Example 1 / Polymerization]
As the polymerization apparatus, an apparatus described in JP-A-2006-316158 was used.
First Step: Polymerization of Propylene Polymer Component (A) In the raw material supply system, 30 kg / hr of liquefied propylene, 0.50 NL / hr of hydrogen, 50 ml of triisobutylaluminum / n-heptane solution (concentration 144 g / L) / Hr. At this time, the hot water temperature of the reactor jacket was adjusted so that the internal temperature would be 70 ° C. When the liquid is fully filled and the flow state is stabilized, the prepolymerized catalyst produced in the above (Catalyst synthesis of Production Example 1) is slurried in normal heptane, and 169 mg of high-pressure nitrogen is added as a solid catalyst (excluding the weight of the prepolymerized polymer). The polymerization was started by press-fitting. After about 4 minutes, the temperature in the tank reached 75 ° C. due to the heat of polymerization, and the polymerization was continued for 2.5 hours while maintaining it. After that, the unreacted monomer in the reactor was purged to complete the first polymerization. I let you. A part of the powder was sampled from the reactor just before the polymerization was completed. As a result, MFR (A) = 1.77 (dg / min).

Second Step: Polymerization of Propylene-Ethylene Random Copolymer Component (B) After purging unreacted monomers in the reactor, propylene becomes 3 kg / hr, ethylene 2.3 kg / hr, and hydrogen becomes 0.68 NL / hr. Distributed. At this time, the hot water temperature of the jacket of the reactor was adjusted so that the internal temperature was 75 ° C. Furthermore, the pressure control valve opening was automatically adjusted so that the internal pressure was 2.8 MPaG. The time when the reactor internal temperature and internal pressure reached predetermined values was defined as the polymerization start time of the second step. Two hours later, 0.25 NL of a mixed gas of carbon monoxide / nitrogen (carbon monoxide concentration 5%) was added to stop the reaction. The polymer obtained by purging the residual monomer was dried. As a result, 3,950 g of a polymer was obtained.

[Production Example 2]
The ethylene feed amount and the hydrogen feed amount in the second step are 5.2 kg / hr, respectively.
Polymerization was carried out under the same conditions as in Production Example 1, except that the pressure was 71 NL / hr, the internal pressure was changed to 3.5 MPaG, and the polymerization time was 3 hours. As a result, 4,275 g of a polymer was obtained.
[Production Example 3]
Production Example 1 except that the amount of catalyst was 300 mg, the polymerization temperature in the first step was 65 ° C., the hydrogen feed amount was 0.40 NL / hr, the internal pressure in the second step was 3.5 MPaG, and the polymerization time was 2.5 hours. Polymerization was carried out under the same conditions as described above. As a result, 3,500 g of a polymer was obtained.
[Production Example 4]
Production Example except that the catalyst amount was 370 mg, the hydrogen feed amounts of the first step and the second step were 0.60 NL / hr and 2.29 NL / hr, respectively, and the polymerization time of the second step was 2 hours. Polymerization was carried out under the same conditions as in 2. As a result, 4,850 g of a polymer was obtained.

[Production Example 5 / Catalyst synthesis]
(1) Solid catalyst synthesis In the same manner as in Production Example 1, chemical treatment of the ion-exchangeable layered silicate and its drying step were performed. 19.97 g of this was weighed into a 1 L flask, and 212 ml of heptane and 10.22 g (51.5 mmol) of triisobutylaluminum were added as a heptane solution (141.9 mg / mL), followed by stirring at room temperature for 1 hour. Then, after washing with heptane to a residual liquid ratio of 1/100, a slurry adjusted to an amount of 100 ml was obtained.
(2) Prepolymerization with propylene 3.14 ml (2,430 μmol) of a triisobutylaluminum heptane solution was added to the slurry obtained in (1) above. In another flask (volume 200 ml), (r) dichloro [1,1′-silafluorenylbis {2-ethyl-4- (4-trimethylsilyl-3,5-dichlorophenyl) -4H-azurenyl} The slurry which added heptane (60 ml) to 722 mg (614 micromol) of hafnium was added, and it stirred at 60 degreeC for 60 minutes.
To the slurry thus obtained, 340 ml of heptane was further added to adjust the total amount to 500 ml, and the mixture was introduced into a stirring autoclave having an internal volume of 1 L that had been sufficiently purged with nitrogen. When the temperature in the autoclave was stabilized at 40 ° C., propylene was supplied at a rate of 10 g / hour to maintain the temperature. After 4 hours, the supply of propylene was stopped and maintained at 40 ° C. for 2 hours.
Thereafter, the residual monomer was purged and the prepolymerized catalyst slurry was recovered from the autoclave. The recovered prepolymerized catalyst slurry was allowed to stand, and 340 ml of the supernatant was extracted. Subsequently, 16.7 ml (12.0 mmol) of a heptane solution of triisobutylaluminum was added at room temperature, and then dried under reduced pressure to recover 65.4 g of a solid catalyst. The prepolymerization ratio (a value obtained by dividing the amount of the prepolymerized polymer by the amount of the solid catalyst) was 2.16.

(Production Example 5 / Polymerization)
First step: Polymerization of propylene-based polymer component (A) In the raw material supply system, 30 kg / hr of liquefied propylene, 0.40 NL / hr of hydrogen, 50 ml of triisobutylaluminum / n-heptane solution (concentration 144 g / L) / Hr. At this time, the hot water temperature of the reactor jacket was adjusted so that the internal temperature would be 60 ° C. When the liquid was fully filled and the distribution state was stabilized, the prepolymerized catalyst produced above was slurried in normal heptane, and 200 mg of solid catalyst (excluding the weight of the prepolymerized polymer) was injected using high-pressure nitrogen to initiate polymerization. . About 4 minutes later, the temperature in the tank reached 65 ° C. due to the heat of polymerization, so that the polymerization was continued for 1.5 hours, and then the unreacted monomer in the reactor was purged to complete the polymerization in the first step. I let you. A part of the powder was sampled from the reactor just before the polymerization was completed. As a result, MFR (A) = 2.21 (dg / min).
Second Step: Polymerization of Propylene-Ethylene Random Copolymer Component (B) After purging unreacted monomers in the reactor, propylene becomes 3 kg / hr, ethylene 5.2 kg / hr, and hydrogen becomes 1.71 NL / hr. Distributed. At this time, the hot water temperature of the jacket of the reactor was adjusted so that the internal temperature was 75 ° C. Furthermore, the pressure control valve opening was automatically adjusted so that the internal pressure was 3.5 MPaG. The time when the reactor internal temperature and internal pressure reached predetermined values was defined as the polymerization start time of the second step. Two hours later, 0.25 NL of a mixed gas of carbon monoxide / nitrogen (carbon monoxide concentration 5%) was added to stop the reaction. The polymer obtained by purging the residual monomer was dried. As a result, 3,600 g of a polymer was obtained.

[Comparative Production Example 1]
The amount of catalyst is 500 mg, the polymerization temperature in the first step is 65 ° C., the hydrogen feed amount is 0.40 NL / hr, the ethylene feed amount and the hydrogen feed amount in the second step are 11.3 kg / hr and 1.60 NL / hr, respectively. The polymerization was carried out under the same conditions as in Production Example 1 except that the internal pressure was changed to 3.5 MPaG and the polymerization time was 3 hours. As a result, 3,900 g of polymer was obtained.

[Comparative Production Example 2]
Polymerization was carried out using the catalyst of Production Example 5.
Step 1: Production of propylene-ethylene random copolymer component (A) by bulk polymerization method After fully replacing the interior of an autoclave with a stirrer with a volume of 3 L with propylene, heptane solution of triisobutylaluminum (140 mg / ml) 2 .86 ml was added, 135 ml of hydrogen in a standard state volume was introduced, followed by 750 g of liquid propylene, and the temperature was raised to 70 ° C. The prepolymerized catalyst obtained in the above (2) was slurried in heptane, and 38 mg (the amount of the net solid catalyst excluding the prepolymerized polymer) as a solid catalyst was injected together with 5 ml of heptane to initiate polymerization. The temperature inside the tank was maintained at 70 ° C. for 60 minutes after the catalyst was charged. The residual monomer was purged and the inside of the tank was replaced with argon five times. Stirring was stopped, and while flowing argon, a Teflon (registered trademark) tube was inserted, and a small amount of polypropylene was extracted. The extracted amount was 16.3 g.
Second step: Propylene-ethylene random copolymer component (B) produced by vapor phase polymerization method After restarting the stirring of the polymerization tank, ethylene and propylene were supplied at a molar ratio of 52:48 to a pressure of 1.33 MPa at 40 ° C. . Thereafter, the internal temperature was maintained at 80 ° C. for 67 minutes, and ethylene and propylene were supplied at a molar ratio of 27:73 so as to maintain the pressure at 1.5 MPa, and gas phase copolymerization was carried out. After completion of the polymerization, the recovered polymer was dried at 75 ° C. under reduced pressure for 60 minutes.

[Comparative Production Example 3]
(1) Production of solid catalyst component 20 L of dehydrated and deoxygenated n-heptane was introduced into a tank equipped with a stirrer with an internal volume of 50 L purged with nitrogen, and then 10 mol of magnesium chloride and 20 mol of tetrabutoxy titanium were introduced. After reacting at 95 ° C. for 2 hours, the temperature is lowered to 40 ° C., 12 L of methyl hydropolysiloxane (viscosity 20 centistokes) is introduced, and further reacted for 3 hours. Washed with n-heptane. Subsequently, 5 L of dehydrated and deoxygenated n-heptane was introduced into the tank using the tank with a stirrer, and then 3 mol of the solid component synthesized above was introduced in terms of magnesium atoms. Thereafter, 5 mol of silicon tetrachloride was mixed with 2.5 L of n-heptane and introduced at 30 ° C. over 30 minutes, the temperature was raised to 70 ° C., and the reaction was performed for 3 hours. The solid component was washed with n-heptane.
Subsequently, 2.5 L of dehydrated and deoxygenated n-heptane was introduced into the tank using the tank equipped with a stirrer, and 0.3 mol of phthalic acid chloride was mixed and introduced at 90 ° C. for 30 minutes. , Reacted at 95 ° C for 1 hour. After completion of the reaction, washing with n-heptane was performed. Next, 2 L of titanium tetrachloride was added at room temperature, and the mixture was heated to 100 ° C. and reacted for 2 hours. After completion of the reaction, washing with n-heptane was performed. Further, 0.6 L of silicon tetrachloride and 8 L of n-heptane were introduced, reacted at 90 ° C. for 1 hour, and sufficiently washed with n-heptane to obtain a solid component. This solid component contained 1.30% by weight of titanium.
Next, 8 L of n-heptane, 400 g of the solid component obtained above, 0.27 mol of t-butyl-methyl-dimethoxysilane and 0.27 mol of vinyltrimethylsilane were introduced into the tank equipped with a stirrer substituted with nitrogen. And contact at 30 ° C. for 1 hour. Next, the mixture was cooled to 15 ° C., 1.5 mol of triethylaluminum diluted in n-heptane was introduced over 15 minutes under 15 ° C., and after the introduction, the temperature was raised to 30 ° C. and reacted for 2 hours. The solid catalyst component (a) (390 g) was obtained by washing with heptane. The obtained solid catalyst component (a) contained 1.22% by weight of titanium.
Further, 6 L of n-heptane and 1 mol of triisobutylaluminum diluted in n-heptane were introduced over 30 minutes under 15 ° C., and then about 0.4 kg / hour while controlling propylene to not exceed 20 ° C. At 1 hour for prepolymerization. As a result, a polypropylene-containing solid catalyst component (a) in which 0.9 g of propylene was polymerized per 1 g of solid was obtained.

(2) Production of propylene-based block copolymer (pre-stage polymerization step: production of crystalline propylene polymer component)
Polymerization was performed using a continuous reaction apparatus in which two fluidized bed reactors having an internal volume of 230 L were connected. First, in the first reactor, the polymerization temperature is maintained at 75 ° C. and the propylene partial pressure is 1.8 MPa, and hydrogen as a molecular weight control agent is further added to hydrogen / propylene so that ethylene is 0.013 in ethylene / propylene molar ratio. As a solid catalyst component (a), the polymer polymerization rate of the above-described catalyst is 20 kg / hr as a solid catalyst component (a) at a continuous feed of 0.0036 molar ratio. To prepare a crystalline propylene polymer component. The powder polymerized in the first reactor (crystalline propylene polymer component) was continuously withdrawn so that the amount of powder held in the reactor was 60 kg, and transferred to the second reactor.
(Second-stage polymerization step: production of propylene-ethylene random copolymer component)
Subsequently, propylene and ethylene are continuously fed so that the molar ratio of ethylene / propylene is 0.25 so that the inside of the second reactor has a polymerization temperature of 80 ° C. and a pressure of 2.0 MPa, Hydrogen as a molecular weight control agent is continuously supplied so that the molar ratio of hydrogen / (propylene + ethylene) is 0.0010, and ethyl alcohol as an active hydrogen compound is 1.2 times that of triethylaluminum. The propylene / ethylene random copolymer component was produced by supplying the solution so as to have a molar ratio. The powder that has been polymerized in the second reactor (a propylene-based block copolymer comprising a crystalline propylene polymer component and a propylene / ethylene random copolymer component) has a powder holding amount of 40 kg in the reactor. To the vessel continuously. Nitrogen gas containing water was supplied to stop the reaction to obtain a propylene-based block copolymer. The above results are listed in Table 1.

[Examples 1 to 5, Comparative Examples 1 to 4]
Tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4-) is added to 100 parts by weight of the propylene-ethylene block copolymer obtained in Production Examples 1 to 5 and Comparative Production Examples 1 to 3. Hydroxyphenyl) propionate] methane 0.05 parts by weight, tris- (2,4-di-t-butylphenyl) phosphite 0.05 parts by weight, calcium stearate 0.0
5 parts by weight were mixed with a tumbler to obtain a propylene resin composition for a packaging film of heat-sterilized food.
They were melt-kneaded at 230 ° C. by a 35 mm diameter twin screw extruder and pelletized. Using this pellet, it was melt extruded at 250 ° C. with a 35 mm diameter extruder having a T-shaped die having a width of 330 mm, and then cooled and solidified while being wound around a chill roll having a diameter of 300 mm adjusted to 50 ° C. A film for packaging of stretched and heat-sterilized food was obtained. The physical properties of the obtained film were measured according to the measurement method. Table 2 shows the evaluation results.

[Kneading conditions]
Kneading machine: TOSHIBA MACHINE Co., Ltd. 35 mm diameter same direction biaxial kneader Kneading temperature: 230 ° C. Screw rotation speed: 250 rpm Feeder rotation speed: 50 rpm
[Film forming]
T-die molding machine: 35 mm diameter uniaxial molding machine manufactured by Plako Corporation Extrusion temperature: 250 ° C. Chill roll temperature: 30 ° C. Take-off speed: 10.0 to 12.0 m / min Film thickness: around 60 μm

[Consideration of results of Examples and Comparative Examples]
As is clear from Examples 1 to 5 in Table 2, the packaging film for heat-sterilized foods comprising the propylene-ethylene block copolymer (X1) according to the present invention is odorless, heat resistant, and drop-proof bag-breaking resistance. It has excellent balance in impact resistance after retorting and transparency maintenance after heating.
On the other hand, the film having a large ethylene content in the copolymer component (B) of Comparative Example 1 is slightly inferior in impact resistance after retorting and inferior in transparency. The film having a small molecular weight distribution Mw / Mn in Comparative Example 2 is inferior in bag breaking resistance and impact resistance. In the film of Comparative Example 3 having a large molecular weight distribution Mw / Mn, odor is confirmed, which is not preferable from the viewpoint of food hygiene, is inferior in heat resistance, and the transparency deterioration after retort treatment is remarkable.
From the above results, in each example which is the invention of claim 1 of the present application, each performance of the packaging film for heat sterilized food is significantly superior in comparison with each comparative example, It can be said that the rationality and significance of the composition of the invention and the superiority to the prior art are clearly shown.

The polypropylene resin composition for packaging film of heat-sterilized food of the present invention has little odor and good food hygiene, and is excellent in transparency, impact resistance, heat resistance, and drop bag breaking resistance. Therefore, in the field of packaging materials, it can be effectively used for applications such as packaging films for retort foods that are heat-treated at high temperatures.

Claims (5)

Obtained by sequentially polymerizing the propylene-based polymer component (A) in the first step and the propylene-ethylene random copolymer component (B) in the second step, the following conditions (i) to (v) are satisfied. A propylene-based resin composition for a packaging film of a heat sterilized food, which is formed from a propylene-ethylene block copolymer (X1) to be filled.
(I) The soluble content of the propylene-based polymer component (A) at −15 ° C. by temperature-temperature elution fractionation (TREF) is 0.8% by weight or less.
(Ii) The molecular weight distribution (Mw / Mn) of the propylene-ethylene block copolymer (X1) is 3.5 to 6.0.
(Iii) The ratio of the propylene-ethylene random copolymer component (B) to the total amount of the propylene-ethylene block copolymer (X1) is 10 to 40% by weight.
(Iv) The ethylene content of the copolymer component (B) is 10 to 50% by weight.
(V) The melting peak temperature Tm (A) of the propylene-based polymer component (A) is 149 to 165 ° C. The propylene-ethylene block copolymer (X1) is produced by gas phase polymerization or bulk polymerization in the first step and gas phase polymerization in the second step, using a metallocene catalyst as a polymerization catalyst. The propylene-based resin composition for packaging films of heat-sterilized foods according to claim 1, wherein A propylene-based film for a heat-sterilized food packaging film according to claim 2, wherein the killer compound of the polymerization catalyst is added to the second step to improve the particle properties of the propylene-ethylene random copolymer. Resin composition. A film for packaging heat-sterilized food, which is obtained by melt-extrusion film formation of the propylene-based resin composition according to any one of claims 1 to 3. A packaging material for retort food, wherein the packaging film for heat-sterilized food according to claim 4 is used.

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