JP2000135762A - Film for stretch packing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance transparency, cutting properties and cold resistance in addition to the heat sealability and intrusion recovery properties of a conventional film by constituting a heat-resistant layer of a polypropylene resin with a specific m.p. and a hydrogenated vinyl aromatic compd. block/conjugated diene compd. block copolymer in a specific wt. ratio. SOLUTION: A film consists of both surface layers comprising a polypropylene resin with an m.p. of 60-100 deg.C and a heat-resistant layer consisting of 50-95% of a polypropylene resin with an m.p. of 150 deg.C or higher and 5-50 wt.% of a hydrogenated vinyl aromatic compd. block/conjugated diene block copolymer. The hydrogenated copolymer consists of 25 mol% or more of l- butene (a) component and 75 mol% or less of an ethylene (b) component and a styrene monomer component of (a)+(b) >=97 mol% has two or more 90 mol% or more of polystyrene blocks. The resins of both layers are melted and kneaded by separate extruders and made to meet with each other to be laminated and this laminate is extruded into a tubular shape and quenched to be solidified to form a film. By this constitution, the transparency, cutting properties and cold resistance of the film can be enhanced in addition to the heat sealability and intrusion recovery properties of a conventional film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch packaging film used for stretch packaging of foods or the like with a manual operation (hand) or a push-up type or linear type packaging machine.

[0002]

2. Description of the Related Art An ethylene-vinyl acetate copolymer (EV) is used on both surface layers (S layers) as a film having an indentation recovery property and excellent heat sealability for stretch packaging of foods and the like.
A) or propylene-ethylene (and / or α ·
Olefin) copolymer and vinyl aromatic compound block
A film using a composition of a conjugated diene compound block copolymer and a hydrogenated product is already known (JP-A-4-270).
745, JP-A-6-155676, JP-A-6-155678, JP-A-7-177876, JP-A-8-119319, JP-A-9-16
No. 5491, JP-A-10-34835, JP-A-10-86294, etc.).

In these films, both surface layers (S layers) have a relatively low melting point among polyolefin resins and do not block each other.
By using VA or an ethylene-α-olefin copolymer, heat sealing properties and optical properties such as transparency and gloss are provided, and a propylene-ethylene (and / or α-olefin) copolymer and vinyl By using a composition comprising an aromatic compound block-conjugated diene compound block copolymer and a hydrogenated product, heat resistance during heat sealing (melt hole prevention) and indentation recovery have been successfully imparted.

[0004]

However, at present, even the above-mentioned films have not reached a satisfactory level in the market. First of all, the tear strength, especially the tear strength in the machine direction (MD) is as weak as 10 g or less, and the notch generated when the film is cut with a cutting blade in a push-up type packaging machine propagates vertically, and the film is transported by a film transport belt. When the film is transported or when the product is pushed up and the film is stretched, the notch propagates further along the film transport belt, and the notch is cut into a long and thin piece (called a thousand chips), which wraps around the drive system of the packaging machine, causing trouble. Problem has occurred. In order to prevent the generation of the shreds, it is necessary to improve the cutting property. The cutting property is to increase the tear strength of the MD so that the notch does not easily propagate along the conveyor belt and is more lateral than the MD. It is important to prevent the notch from being generated in the MD by making the film easy to propagate the notch in the direction (TD), that is, a film having a tear strength higher than that of the TD.

[0005] Second, the improvement in transparency is still insufficient. HAZE (cloudiness) measured by a method described later is about 1.0 to 1.5% at present, and it looks slightly whitish even when viewed. In particular, when packaging red meat or the like, the whiteness of the film tends to be conspicuous.

Thirdly, there is a plasticized PVC film which is inferior in cold resistance, which is a characteristic of a polyolefin resin film. In the transportation of food, low-temperature distribution is increasing in terms of keeping freshness and hygiene.However, in the case of non-cold-resistant film, the film wrapping the product tears during transportation, or pinholes occur in the film when the products rub against each other. Such a problem easily occurs. Therefore, an object of the present invention is to provide a film having improved transparency, cutability, and cold resistance while maintaining the heat sealing property and the indentation recovery property of a conventional film.

[0007]

The present invention has a melting point of 60 to 60.
Both surface layers of polyolefin resin at 100 ° C (S
Layer) and at least one heat-resistant layer (H layer), the H layer has a melting point of 50 to 95% by weight of a polypropylene resin having a melting point of 150 ° C. or more and a vinyl aromatic compound block-conjugated diene shown below. The present invention relates to a stretch packaging film comprising 5 to 50% by weight of a hydrogenated product of a compound block copolymer.

(1) A polystyrene block (S) comprising at least 90 mol% of a styrene monomer component contains at least 2
The component (2) is mainly composed of a 1-butene (a) component and an ethylene (b) component, and the component ratio of each component is at least 25 mol%, and (b) Ingredient 7
A vinyl aromatic compound block-conjugated diene compound block copolymer consisting of ethylene-1-butene random copolymer block (B) having 5 mol% or less and (a) + (b) ≧ 97 mol%. Hydrogenated products.

Hereinafter, the present invention will be described in detail. The most different point between the present invention and the prior art is that a hydrogenated product of a vinyl aromatic compound block-conjugated diene compound block copolymer (hereinafter abbreviated as “H-SBBC”) used for a heat-resistant layer (H layer) is described above. H-SBB having the following composition characteristics:
C is used.

Therefore, the necessity that the H-SBBC satisfies the above characteristics in the present invention will be described with reference to Table 1 which summarizes the experimental results of Example 1 and Comparative Example 1 described later. In Table 1, Run. No. 1 to 4 correspond to the film of the present invention. No. Nos. 6 to 8 correspond to conventional films. First, H-SBBC used in the present invention
The necessity of “(1) at least two polystyrene blocks (S) composed of 90 mol% or more of styrene monomer components” will be described. Table 1 shows that the films of the present invention were all evaluated as “○” or more, and it was found that the films of the present invention are stretch packaging films having particularly excellent indentation recovery properties.

On the other hand, Run. No. In the film No. 8, the H-SBBC had only one polystyrene block (S), and the indentation recovery was poor. Specifically, the film of the present invention, Run. No. 1 recovered under 11 conditions, whereas Run. No. Film 8 recovered only under 6 conditions. Also, Ru
n. No. The film of No. 6 also has the structure of H-SBBC (S)
A random copolymer of styrene, ethylene and 1-butene containing about 3.5 mol% of a block and styrene connected to the block (styrene increases in concentration toward the terminal). No. Although it was slightly better than 8, the indentation recovery was limited to “Δ” (8 conditions). From the above, it can be concluded that the H-SBBC used in the present invention is "(1) at least two polystyrene blocks (S) composed of 90 mol% or more of a styrene monomer component" in order to impart indentation recovery. You know what you need.

Next, the hydrogenated / conjugated diene compound block copolymer in H-SBBC used in the present invention is composed of “(2) monomer components mainly composed of 1-butene (a) component, ethylene ( the component (b) is composed of 25 mol% or more and the component (b) is 75 mol% or less,
The necessity of “(a) + (b) ≧ 97 mol% of ethylene-1-butene random copolymer block (B)” will be described. From Table 1, all the films of the present invention were evaluated as “○” or more, and especially the transparency and the cold resistance (−
It is understood that the film is a stretch packaging film having excellent dart strength at 30 ° C.).

On the other hand, Run. No. Film No. 7 was inferior in transparency and cold resistance because the hydrogenated / conjugated diene compound block copolymer of H-SBBC was made of hydrogenated polyisoprene. Specifically, in the order of transparency and dart strength at −30 ° C., Ru, which is the film of the present invention, is used.
n. No. 1 is 0.7%, Run. No. 1.3%, 0.02J for film 7
Met. Even if the hydrogenated / conjugated diene compound block copolymer is an ethylene-1-butene / random copolymer, the 1-butene content needs to be 25 mol%.

H-SBBC has a 1-butene content of 25 mol% in Run. No. 2 having the same content as the film of Run. No. 5 in comparison with the film of Run. No. 2 is transparent (HAZE =
0.7%) and cold resistance (dirt strength at −30 ° C. =
0.20 J), whereas Run. No.
Film No. 5 was inferior in transparency (1.2%) and cold resistance (0.17 J). Run. No. As described above, the film No. 6 is a random copolymer of styrene, ethylene and 1-butene having an H-SBBC structure of (S) block and about 6 mol% of styrene connected thereto as described above. .18J).

From the above, the H-SB used in the present invention
The hydrogenated / conjugated diene compound block copolymer in BC is composed of “(2) mainly composed of 1-butene (a).
The component (a) is composed of ethylene (b), and the constituent ratio of each component is 25 mol% or more for component (a), 75 mol% or less for component (b), and (a) + (b) ≧ 97 mol%. It is understood that "ethylene-1-butene random copolymer block (B)" is necessary for imparting transparency and cold resistance. From the above, it is understood that H-SBBC needs to satisfy the above composition characteristics.

Next, the H layer is composed of 50 to 95% by weight of a polypropylene resin having a melting point of 150 ° C. or more and H-SBBC 5 to 5%.
The necessity of comprising 0% by weight will be described. First, the melting point of the polypropylene-based resin needs to be 150 ° C. or higher. If the melting point of the polypropylene-based resin is less than 150 ° C., the film will have low heat resistance and poor heat sealability.

The H layer comprises 50 to 95% by weight of a polypropylene resin at 150 ° C. or higher and 5 to 50% by weight of H-SBBC.
It is necessary to consist of 5 polypropylene resin
If the melting point is less than 0% by weight, the heat resistance at the time of heat sealing is insufficient even if the melting point is high, and if it exceeds 95% by weight, the H-SBBC content is less than 5% as a result, and the indentation recovery property is imparted. Can not. If the H-SBBC is less than 5% by weight, the indentation recovery is inferior. If the H-SBBC is 50% by weight or more, the polypropylene resin becomes less than 50% by weight, and the heat resistance is insufficient, which is not preferable. The H layer has a polyolefin resin, a poly 1-butene resin, a hydrogenated petroleum resin, and a melting point, which are used for a surface layer described below, in a range not exceeding 45% by weight, in addition to the polypropylene resin and H-SBBC. Fifteen
A polypropylene resin having a temperature of less than 0 ° C. and a surfactant such as an antifogging agent and an antistatic agent may be blended.

Next, both surface layers (S layers) have a melting point of 60-1.
The necessity of being made of a polyolefin resin at 00 ° C. (hereinafter abbreviated as PO resin) will be described. If the melting point of the PO-based resin used for the S layer is less than 60 ° C., the film surface is sticky even at about room temperature, and the slipperiness of the film is insufficient.
When packing with a push-up type or linear type packaging machine, the film is difficult to slip with mechanical parts, rubber materials (belts, etc.) and trays, so the film is broken, packaging wrinkles are left, and the tray is crushed. Tends to occur.

On the other hand, when the temperature exceeds 100 ° C., the lower limit temperature at which heat sealing is possible becomes high, resulting in a film having poor heat sealing properties. In the S layer, in addition to a PO resin having a melting point of 60 to 100 ° C, a PO resin having a melting point of less than 50% by weight, for example, a PO resin having a melting point of more than 100 ° C (ethylene-α-olefin copolymer, poly-1- Butene resin, melting point 150 ° C
Less than a polypropylene-based resin), a hydrogenated petroleum resin, and a surfactant such as an anti-fogging agent or an antistatic agent.

Hereinafter, specific examples of the resin used in the present invention will be described. First, the hydrogenated product (H-SBBC) of a vinyl aromatic compound block-conjugated diene compound block copolymer preferably used in the present invention will be described in detail. First, the block (S) mainly comprises a styrene (s) component.
The components are at least 90 mol%, preferably at least 95 mol%. In addition to the (s) component, a 1-butene (a) component, an ethylene (b) component, a 1,4-added butadiene (c) component, and a 1,2-added butadiene (d) component may be contained. The total amount of these is less than 10 mol%, preferably less than 5 mol%. If the styrene (s) component is less than 90 mol%, the cohesive force as a hard block is weakened,
The resulting film has poor indentation recovery.

In the above H-SBBC, the block (S)
Need to exist two or more as described above,
From the productivity of SBBC, the number of blocks (S) is preferably six or less. Next, the block (B) preferably comprises a block (B1) sandwiched between the blocks (S) and a block (B2) for improving the compatibility of the polypropylene resin. Block (B1) is mainly composed of 1-butene (a)
Component and an ethylene (b) component, and is essentially an ethylene-1-butene random copolymer block.
(A) component, styrene (s) component in addition to component (b),
The 1,4-addition butadiene (c) component and the 1,2-addition butadiene (d) component may be contained randomly or in a taper, but the total amount of these components is less than 10 mol%, preferably 5 mol%. Less than mol%. When the content is 10 mol% or more, the low cold resistance tends to decrease.

The 1-butene (a) component in the block (B1) is 20 to 45 mol%, preferably 25 to 45 mol%.
In mole%, the ethylene (b) component is from 80 to 55 mole%, preferably from 75 to 55 mole%. If the 1-butene (a) component is less than 20 mol%, ethylene units are continuous and polyethylene crystallization is likely to occur, and the rubber elasticity of H-SBBC is reduced. As a result, the indentation recovery of the film may be poor. . Also, as the 1-butene (a) component increases, the glass transition point (Tg) of the block (B1) increases, and when the component (a) exceeds 45 mol%, the cold resistance tends to decrease. As the number of blocks (B1) increases, the indentation recovery of the obtained film improves, but the number of blocks (B1) is preferably three or less from the viewpoint of H-SBBC productivity. Since the block (B1) functions as a soft segment in the H-SBBC, the block (B1) exhibits the maximum effect only when it has a structure sandwiched between the blocks (S) which are hard segments.

Next, the block (B2) mainly comprises a 1-butene (a) component and an ethylene (b) component, and is substantially an ethylene-1-butene random copolymer block. Styrene (s) in addition to component (a) and component (b)
Component, 1,4-addition butadiene (c) component and 1,2-
The added butadiene (d) component may be included at random, but the total amount of these components is less than 10 mol%, preferably less than 5 mol%. If the content is 10 mol% or more, the cold resistance tends to be poor.

The 1-butene (a) component in the block (B2) contains 45 to 100 mol%, preferably 55 to 1 mol%.
00 mol%, the ethylene (b) component is 55 to 0 mol%,
Preferably, it is 45 to 0 mol%. If the 1-butene (a) component is less than 45 mol%, the compatibility with the polypropylene resin in the heat-resistant layer (H layer) is poor, and the optical properties of the obtained film tend to be poor. As the number of blocks (B2) increases, the compatibility with the polypropylene-based resin in the heat-resistant layer (H layer) improves, and the resulting film has excellent optical properties.
-The number of blocks (B2) is preferably three or less from the viewpoint of SBBC productivity. Block (B2) is H-SB
The structure existing at the terminal of the block copolymer exerts an effect because it has a function of making the BC compatible with the polypropylene resin in the heat-resistant layer (H layer). The proportion of each block is such that the total content of the block (S) is 5 to 80% by weight (more preferably 5 to 50% by weight) and the block (B)
The total content of 1) is 10 to 70% by weight (more preferably 25 to 60% by weight), and the total content of the block (B2) is 10 to 70% by weight (more preferably 25 to 60% by weight).
(However, (S) + (B1) + (B2) = 100% by weight)
Is preferred.

Next, the H-SBBC has a polystyrene equivalent number average molecular weight (Mn) of preferably 20,000 to 1,000,000 as measured by gel permeation chromatography (GPC), and a molecular weight distribution (Mw / Mn). Is preferably 1 to 5. When Mn is less than 20,000, the obtained film tends to be inferior in tensile elongation characteristics. On the other hand, when Mn exceeds 1,000,000, extrudability tends to be poor. Also, Mw
For those having a large number of low molecular weight components such as / Mn exceeding 5, the low molecular weight components bleeding from the heat-resistant layer (H layer) to the film surface tend to make the film sticky.

The structure of H-SBBC preferably has the structure of (S)-(B1)-(S)-(B2). H-SBBC preferably used in the present invention
Is obtained by hydrogenating an olefinic double bond of a butadiene unit from a base block copolymer shown below in the presence of a hydrogenation catalyst.

(1) Two or more polystyrene blocks (S) each containing 90 mol% or more of a styrene monomer component,
(2) The monomer component is mainly composed of a 1,4-added butadiene (c) component and a 1,2-added butadiene (d) component. 67 mol%, component (d) is 62 to 33 mol%, and (c) +
(D) One or more random polybutadiene blocks (RB1) having ≧ 97 mol% and the same monomer components as in (3) and (2), and the constituent ratio of each component is 0 to 38.
Mol%, component (d) is 100 to 62 mol%, and (c) +
(D) one or more random polybutadiene blocks (RB2) having ≧ 97 mol%, wherein a block (RB1) and / or a block (RB2) exists between two or more blocks (S), and a molecular weight Is a block copolymer whose molecular weight distribution (Mw / Mn) is 1-5.

Here, the block (S) is the same as the block (S) in the H-SBBC preferably used in the present invention. The block (RB1) is a block corresponding to the block (B1) in H-SBBC, and is mainly composed of a 1,4-added butadiene (c) component and a 1,2-added butadiene (d) component, and is composed of styrene ( The component (s) may be contained randomly or in a taper, but the total amount of the component (s) is less than 10 mol%, preferably less than 5 mol%. The 1,2-addition butadiene (d) component in the block (RB1) is 33 to 62 mol%, preferably 40 to 62 mol%.
In mole%, the 1,4-addition butadiene (c) component is 67 to
It is 38 mol%, preferably 60 to 38 mol%.

Further, the block (RB2) is H-SBB
A block corresponding to the block (B2) in C, which is mainly composed of a 1,4-added butadiene (c) component and a 1,2-added butadiene (d) component, and a styrene (s) component is randomly or tapered. (S)
The total amount of the components is less than 10 mol%, preferably less than 5 mol%. The content of the 1,2-addition butadiene (d) component in the block (RB2) is 62 to 100 mol%, preferably 7 to 100 mol%.
The amount of the 1,4-addition butadiene (c) component is 38 to 0 mol%, preferably 29 to 0 mol%.

H-SBBC preferably used in the present invention
The 1-butene structure and the ethylene structure constituting the inner block are structures formed by hydrogenating a 1,2-added butadiene unit and a 1,4-added butadiene unit, respectively. Therefore, when the 1,4-added butadiene unit is hydrogenated, a structure in which two ethylene units are continuous (tetramethylene) is obtained. Therefore, when the base (RB1) before hydrogenation contains 38 mol% of the 1,4-added butadiene (c) component and 62 mol% of the 1,2-added butadiene (d) component, , 10
The block (B1) after 0% hydrogenation contains 45 mol% of the 1-butene structure and 55 mol% of the ethylene structure.

Next, the H--S preferably used in the present invention
The method for producing the block copolymer serving as the base of BBC is described below. As an monomer, 1,3-butadiene and styrene are used in an inert hydrocarbon solvent such as hexane, cyclohexane and benzene, using an anionic polymerization initiator such as an organic lithium compound, and diethyl ether and tetrahydrofuran (THF) as a vinylating agent. , 2,2-bis (2
(Oxolanyl) propane (BOP) and the like, and tertiary amine compounds such as triethylamine, N, N, N ′, N′-tetramethylethylenediamine (TMEDA) and dipiperidinoethane (DPE) are used. If necessary, epoxidized soybean oil as a coupling agent,
Diethyl carbonate, dimethyldichlorosilane, methylphenyldichlorosilane, dimethyldiphenylsilane, using a polyfunctional compound such as silicon tetrachloride, linear, branched,
A radial block copolymer can also be obtained.

In the addition polymerization of 1,3-butadiene, trans 1,4-addition, cis 1,4-addition,
Two types of addition, 2-addition, can occur. This ratio can be controlled by the type, amount and polymerization temperature of the vinylating agent. To increase the 1,2-addition, that is, the vinyl content, it is effective to lower the polymerization temperature or increase the amount of the vinylating agent added. The block copolymer before hydrogenation uses, in addition to the above-mentioned organolithium compound as an initiator, a Ziegler-based system comprising an organometallic compound such as nickel, cobalt and titanium and an organometallic compound such as lithium, magnesium and aluminum. How to use a catalyst,
Alternatively, it may be based on a radical polymerization method.

Next, the reaction and conditions of the hydrogenation reaction may be any methods and conditions as long as a block copolymer having a hydrogenation ratio specified in the present invention can be obtained. Examples of the hydrogenation method include a method using a catalyst containing an organic titanium compound as a main component as a hydrogenation catalyst, and a method using a catalyst composed of an organic compound such as iron, nickel and cobalt and an organic metal compound such as alkylaluminum. , Ruthenium, a method using a catalyst comprising an organometallic compound such as rhodium, palladium,
Examples include a method using a catalyst in which a metal such as platinum, ruthenium, cobalt, and nickel is supported on a carrier such as carbon, silica, alumina, and diatomaceous earth. Among these, a method using a homogeneous catalyst comprising an organometallic compound of titanium alone or an organometallic compound of lithium, magnesium, and aluminum (JP-B-63-4841 and JP-B-1-3797) has been known. It is preferable because it can be industrially hydrogenated under mild conditions at a low temperature, and is also preferable because it has high hydrogenation selectivity to the olefinic double bond of the butadiene unit and does not hydrogenate the aromatic ring in the styrene unit.
A particularly preferred catalyst is a system using a titanocene compound and a reducing agent, which may be separately added to the reaction system, or these reaction products prepared in advance may be added to the reaction system. When the polymer is prepared in advance, an olefinically unsaturated double bond-containing polymer may be allowed to coexist as described in JP-B-7-25811.

The hydrogenation is carried out in a solvent which is inert to the catalyst and in which the copolymer is soluble. Preferred solvents include n-pentane, n-hexane, aliphatic hydrocarbons such as n-octane, cyclohexane, alicyclic hydrocarbons such as cycloheptane, benzene, aromatic hydrocarbons such as toluene, diethyl ether, and the like. Among ethers such as tetrahydrofuran and the like, a single compound or a mixture containing these as a main component is exemplified.
Particularly, it is advantageous in terms of cost to use the copolymer solution obtained when producing the block copolymer as it is.
In this case, it is generally preferable that the active terminal lithium is completely inactivated by a compound having active hydrogen such as alcohol, but it is also possible to leave the active terminal lithium as a part or all of the reducing agent. . Further, an organic compound such as a vinylating agent used during the production of the copolymer may be contained as it is.

In the hydrogenation reaction, a hydrogenation catalyst is generally added under stirring or unstirring while maintaining the copolymer at a predetermined temperature under hydrogen or an inert atmosphere, and then hydrogen gas is introduced. This is performed by applying a predetermined pressure. The term "inert atmosphere" refers to an atmosphere such as helium, neon, or argon that does not hinder the hydrogenation reaction. Nitrogen may be present in the reaction system in a small amount, but is not preferred because it may act as a catalyst poison during the hydrogenation reaction and reduce the hydrogenation activity. In particular, the atmosphere inside the hydrogenation reactor is most preferably an atmosphere containing only hydrogen gas. The hydrogenation reaction process may be any of a batch process, a continuous process, and a combination thereof.

When a titanocene diaryl compound is used as a hydrogenation catalyst, it may be added alone to the reaction solution alone or as a solution dissolved in an inert organic solvent. As the inert organic solvent used when the catalyst is used as a solution, the above-mentioned solvent which does not inhibit the hydrogenation reaction can be used. Preferably, it is the same solvent as the solvent used for the polymerization. The addition amount of the catalyst is 0.02 to 20 mmol per 100 g of the block copolymer before hydrogenation.

The most preferred method of obtaining H-SBBC preferably used in the present invention is to carry out anionic living polymerization of the block copolymer before hydrogenation in a solution using an organolithium initiator and a vinylating agent, and after the polymerization is completed. After adding a coupling agent as necessary or adding a reaction terminator containing active hydrogen such as alcohol, the obtained polymer solution is used as it is in the next hydrogenation reaction. By removing the solvent from the hydrogenated block copolymer solution, H-SBBC can be isolated and obtained. As a method for removing the solvent, after the block copolymer solution is coagulated with methanol or the like, heated or dried under reduced pressure, or the block copolymer solution is poured into boiling water, and the solvent is azeotropically removed. It can be obtained by heating or drying under reduced pressure.

Next, specific examples of preferred propylene resins used for the H layer will be described. The propylene resin may have a melting point of 150 ° C. or more, and may be a propylene homopolymer, a propylene-α-olefin random copolymer (R-PP), a propylene-α-olefin block copolymer (B -PP) and the like. In particular, B-PP having a high heat-resistant temperature and flexibility is preferable. B-
PP is usually obtained by using a reactor having two or more stages, and a propylene homopolymer having a melting point of 150 ° C. or more or R-PP is used in the first stage.
(Referred to as a high melting point component), and propylene and ethylene having little crystallinity, 1-butene, 1
-It is obtained by polymerizing a random copolymer (referred to as a flexible component) with an α-olefin such as hexene and 1-octene. Among them, particularly, a so-called reactor TPO, in which the soft component is finely dispersed in the high melting point component, is preferable, and one in which the soft component is dispersed in a spherical or needle-like shape with an average diameter of 1 μ or less is preferable. Examples of these include "Hifax" and "Adflex" by Montell-JPO, and [Pflex] by Tokuyama.
ER "and" NEWCON "of Chisso.
Among them, soft resins having a relatively high melting point component and high flexibility [Hifax], “Adflex”, “NEWCO”
N "is preferred.

The B-PP melt flow rate (MF
R: Based on JIS-K7210: 230 ° C, 2.16 kg
f) is generally about 0.1 to 100 g / 10 minutes,
0.5 to 50 g / 10 from the viewpoint of stretchability
Minutes. Next, the S layer has a melting point of 60 to
At least one of PO-based resins at 100 ° C. can be used.

For example, a monomer selected from aliphatic unsaturated monocarboxylic acids such as EVA, ethylene-ethyl acrylate copolymer (EEA) and ethylene-methacrylic acid copolymer (EMAA) or an alkyl ester thereof is used. A copolymer with ethylene, or at least a part of a polymer obtained by saponifying at least a part of these copolymers, for example, Na, Z
Polymers ion-bonded with metal ions such as n and Mg are exemplified. Further, ethylene and α such as 1-butene, 1-pentene, 4-methylpentene-1, 1-octene, etc.
-Copolymers with olefins (preferably, α-olefins having 6 or more carbon atoms). According to the strength and heat sealability of the film, the density is 0.905 g / cm ³ or less, and the molecular weight distribution (Mw / M) polymerized with a single-site catalyst such as a Kaminski catalyst or a Brookhart catalyst.
n) is preferably 3 or less. Melt flow rate of the PO resin (MI: based on JIS-K7210: 1)
90 ° C., 2.16 kgf) is generally 0.1 to 20 g /
About 10 minutes, 1-10g from transparency and stretch
It is about / 10 minutes.

The film of the present invention has at least 3 layers comprising both surface layers (S layer) and at least one heat-resistant layer (H layer).
Although it is a layer film, it may further include another layer (M layer). The M layer may have a plurality of layers (M1, M2,...). Examples of the layer configuration in that case include S / H / S,
S / M / H / S, S / H / M / H / S, S / M / H / M
/ S, S / M1 / H / M2 / H / M1 / S, and the like. As an example of the M layer, when it is arranged adjacent to the S layer, EVA or ethylene-α-olefin which is easy to knead and bleed out with an additive such as an anti-fogging agent and is excellent in transparency. And copolymers.

When the film is recovered and reused, it is more transparent to mix and use the M layer, especially the M layer disposed on the core layer of the film, than to mix and use the H layer. Does not decrease. Generally, the thickness ratio of each layer is 5
-40%, H layer 10-90% each, M layer 5-60% each
It is. The H layer is at least 1.5 hours from the film surface.
If it is arranged inside μm, the transparency does not decrease. The thickness of the film is generally about 7 to 20 μm,
Preferably it is 8 to 15 μm.

Next, examples of the method for producing the film of the present invention include a T-die casting method, a direct inflation method (preferably a water-cooled inflation method), a tubular inflation method, and an extrusion laminating method. A preferred method is a tubular inflation method. Hereinafter, a preferred tubular inflation method will be described in detail, but is not limited thereto.

First, both surface layers (S layers) and heat-resistant layers (H
Layer), and if necessary, melt and knead the resin of the M layer by a separate extruder, merge and laminate in a multilayer circular die heated to a temperature of about 170 to 250 ° C. and extrude into a tube. An aqueous solution of an anionic surfactant such as a fatty acid soap or an aqueous solution of a nonionic surfactant such as a polyoxyethylene fatty acid ester is sealed in the tube, and the extruded tube is quenched and solidified with a refrigerant such as water at 40 ° C. or lower. A fold roll is made with a nip roll. The raw material is passed between two pairs of differential nip rolls, heated to about 100 to 150 ° C., blown into the raw material and blown with cold air of about 15 to 30 ° C., and is heated in the longitudinal direction (MD) for about 2 to 2 hours. The tube is stretched 4 times and 2 to 5 times in the transverse direction (TD). The stretched film is folded by a deflator, and if necessary, heat-treated at a temperature equal to or lower than the melting point of the resin of both surface layers (S layers). The heat treatment may be in a strained state or a relaxed state, but preferably about 0 to 10% for MD and 2 to 10 for TD.
% Is preferably carried out in a relaxed state.

The measuring method and the evaluation method are described below. (1) Styrene content The styrene content in H-SBBC was measured by a UV method using characteristic absorption by a phenyl group near 260 mμ. (2) 1,2-microstructure amount of polybutadiene block Calculated by the Hampton method using Fourier transform infrared spectroscopy (FT-IR). By measuring each time polybutadiene is polymerized, the 1,2-microstructure amount of each polybutadiene block was determined from the weight ratio of the charged butadiene monomers. (3) Hydrogenation rate of polybutadiene block Using deuterated chloroform as a solvent, 400 MHz, ¹
It was calculated from the 1 H-NMR spectrum.

(4) Number-average molecular weight of H-SBBC (M
n) Using tetrahydrofuran (THF) as a solvent, gel permeation chromatography (GPC) at a column temperature of 43 ° C. was performed to determine the number average molecular weight (Mn) in terms of polystyrene. (5) The amount of 1-butene and the amount of ethylene in H-SBBC 400 M using tetrahydrofuran (THF) as a solvent
Hz, the sample in which the number of methyl groups was measured in advance by ¹³ C-NMR, the “—CH ₂ —” peak height and the “—CH ₃ ” peak height were determined by FT-IR, and this ratio was taken. NM
Number of methyl groups determined by R and “—CH ₂ —” peak height /
A calibration curve was prepared based on the peak height of “—CH ₃ ”, and the amount of 1-butene and the amount of ethylene were determined based on the calibration curve.

(6) Melting point DS manufactured by Perkin Elmer Co. according to JIS-K7121
It measured using C-7. A sample of about 5 mg is set, and once the temperature is raised from room temperature to 200 ° C. at a rate of 10 ° C./min, the sample is kept at 200 ° C. for 5 minutes to sufficiently dissolve the sample, and then from 200 ° C. to −30 ° C. After cooling at a rate of 10 ° C./min and holding at −30 ° C. for 5 minutes, the temperature was again raised from −30 ° C. to 200 ° C. at a rate of 10 ° C./min, and measured. (7) Density The density was measured using a density gradient tube specific gravity measuring device manufactured by Shibayama Scientific Instruments, in accordance with the method D of JIS-K7112.
The specific gravity liquid used was an isopropyl alcohol / water system.

(8) 200% Elongation Load A film sample was cut into a rectangular shape having a long side of 100 mm and a short side of 10 mm in the machine direction (MD) and the transverse direction (TD). 50 mm between chucks with the long side direction as the measurement direction
Attached to a tensile tester equipped with a strain gauge (connected to an amplifier and a recorder) adjusted at a tension of 200 mm / min in an atmosphere of 23 ° C. and 50% RH and an elongation of 20
When the load reaches 0%, a 200% elongation load (g / cm
Width). (9) Elongation at break The amount of strain when the film was broken was defined as the elongation at break (%) using the same device and under the same conditions as those for measuring the 200% elongation load. (10) Tear strength Measured in an atmosphere of 23 ° C. and 50% RH according to JIS-P8116.

(11) Dart strength Evaluation method Using a thermostated RDT-5000 / DART manufactured by Toyo Seiki Co., Ltd., the breaking energy ENG of the film (unit: J)
I asked. The type of dart is SMALL ALUMINI
UM DART (3.75kg), dirt diameter is 5/8
Inch (15.88 mmφ), maximum cell load is 100
Pounds (45.53 kgf), the inner diameter of the cradle is 2.5 inches (63.5 mmφ), and the dart drop speed is 3.87.
m / sec (fall height is 76 cm). The measurement temperature was 23 ° C (normal temperature) as a measure of impact strength at the time of packaging.
The test was carried out at -30 ° C as a measure of cold resistance.・ Evaluation criteria Scale Symbol Remarks ENG ≧ 0.5 (J) ◎ Excellent impact resistance 0.2 ≦ ENG <0.5 (J) ○ Above, pass level 0.1 ≦ ENG <0.2 (J) △ Film tears by impact ENG <0.1 × Film cracks by impact

(12) Transparency Evaluation method HAZE (%) was measured in accordance with ASTM-D1003.・ Evaluation criteria Scale Symbol Remarks HAZE <0.8 (%) ◎ Excellent transparency 0.8 ≦ HAZE <1.0 (%) ○ Above, pass level 1.0 ≦ HAZE <1.5 (%) △ Film I'm worried about the whiteness of HAZE ≧ 1.5 (%) × unsuitable for practical use

(13) Indentation Recovery Property Evaluation Method The film was attached to a 125 mm × 125 mm frame so that the MD had a stretch ratio of 2%, the TD had a stretch ratio of 2%, 5% and 10%, respectively. . A stainless steel push rod with a 15 mmR tip and a matte finish was set on the compression tester, and the center of the film stretched over the frame was 1000 m.
At a speed of m / min, the indentation depth is 15mm, 20mm, 25mm
mm, 30 mm, and 35 mm, hold the pressed state for 120 seconds, then pull up the push rod at a speed of 1000 mm / min. did. The evaluation was based on the number of conditions out of 15 conditions of stretch conditions (3 conditions) × depth of indentation (5 conditions) in which the indentation trace was completely erased (B).・ Evaluation criteria Scale symbol Remarks B ≧ 12 ◎ Excellent in indentation recovery 10 ≦ B <12 ○ or higher, pass level 8 ≦ B <10 △ Can be used for specific applications B <8 × Not practical

(14) Sealability Evaluation method Polypropylene tray manufactured by Chuo Kagaku Co., Ltd. CH16-10
A weight of 100 g was placed on F (160 × 98 × 33 mm), and this was wrapped with a film cut out to 30 cm × 30 cm. In this case, at the bottom of the tray, there are a portion where the film is overlapped, a portion where the film is overlapped, a portion where the film is overlapped, and a portion where the film is overlapped. After the bottom of the tray was brought into contact with a hot plate heated to a predetermined temperature for 2 seconds, the state of heat sealing was observed. ΔT = T2−T1 is defined as the minimum temperature at which the seal is completely sealed even in the portion where five sheets are overlapped, and the maximum temperature at which no melt hole occurs even in one portion as the maximum seal temperature (T2). The seal range was set.・ Evaluation criteria Scale Symbol Remark ΔT> 60 (℃) ◎ Excellent heat sealability 45 <ΔT ≦ 60 (℃) ○ Above, pass level 30 <ΔT ≦ 45 (℃) △ Available under specific conditions ΔT ≦ 30 (℃) × Not practical

(15) Cutability Evaluation method The cutability of a roll-shaped film sample slit to a width of 400 mm was evaluated using a push-up type packaging machine Wmini-Zero manufactured by Ishida. The cut performance was evaluated by measuring the amount of film chips generated by the propagation of the notch generated during cutting. The cutting blade uses a standard cutting blade, the packaging condition is “poly setting”, the tension conditions are front = 3, rear = 1, left / right = 7, and the overall tension = intermediate. 100 pieces of SK-20F manufactured by Kagaku Co., Ltd. were packed in succession, and the amount of generated debris (W: g) was measured.・ Evaluation criteria Scale Symbol Remarks W <1 (g) ◎ Excellent cutability and less generation of film debris 1 ≦ W <2 (g) ○ Above, pass level 2 ≦ W <5 (g) △ Debris generation Is available, but can be used if frequently cleaned after packaging. W ≧ 5 (g) × Not practical

(16) Wrapping property and evaluation method Except that the tension conditions were adjusted to the optimum conditions for each film,
The same operation as the cutting property was performed, and packaging (100 pieces) was performed. The overall finish was evaluated by observing the finished packaging (wrinkling occurrence), film tear (especially rubbing and tearing at the bottom of the tray), heat sealing, and the like.・ Evaluation criteria Scale symbol 90 or more, no film tearing, complete seal and clean finish ◎ 90 or more, somewhat incomplete seal, no film tear ○, finish Was beautiful (the above, the pass level) 60 or more had no film tearing and was finished neatly △ No film tearing and had beautifully finished less than 60 ×

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <Production Reference Example 1> 60 liters of cyclohexane dried and purified in a 100 liter autoclave purged with nitrogen, tetrahydrofuran (T
A cyclohexane solution containing 605 g (8.40 mol) of HF) and 9.69 g (0.151 mol) of n-butyllithium was charged and heated to 60 ° C. 577 g of styrene was added thereto to carry out polymerization. Subsequently, 4.63 kg of 1,3-butadiene (1,3-BD) and 577 g of styrene were successively added to continue the polymerization. Here the temperature is 40 ° C
And then cooled to tetramethylethylenediamine (TME
35.1 g (0.302 mol) of DA) was added, and 1,3-BD was gradually added so that the polymerization temperature did not exceed 60 ° C. to carry out polymerization. After the completion of the polymerization, 3.8 methanol was added.
3 g (0.120 mol) was added to inactivate the living active terminal.

The obtained block copolymer has a number average molecular weight (Mn) of about 70,000, a styrene content of about 12 wt%,
The 1,2-microstructure of the polybutadiene portion has 37% of the polybutadiene block polymerized first (63% of the 1,4-microstructure) and 72% of the polybutadiene block polymerized later (28% of the 1,4-microstructure). ), The total 1,2-microstructure of the final copolymer was 53% (1,4
-Microstructure was 47%) of S-B1-S-B2 type block copolymer.

Next, 12 liters of the obtained cyclohexane solution of the block copolymer was charged into a 20-liter autoclave purged with nitrogen, and the autoclave was purged with hydrogen. The hydrogen pressure was increased to 0.7 MPa (gauge pressure), and the temperature was raised to 70 MPa. The temperature was raised to ° C. Then, with stirring, 254 mg (1.02 mmol) of dichlorobis (η ⁵ -cyclopentadienyl) titanium and 147 mg (2.
(0.4 mmol) and a hydrogen pressure of 0.7 MPa (gauge pressure).
Was continued to be supplied for 1 hour so as to maintain.

The block copolymer after hydrogenation had a number average molecular weight (Mn) of about 70,000 and a styrene content of about 12 wt.
%, B1 is 22 mol% of 1-butene (a) component, 77 mol% of ethylene (b) component, B2 is 56 mol% of 1-butene (a) component, 43 mol% of ethylene (b) component. ,
The 1-butene (a) component is 3 in the entire conjugated diene hydrogenated portion.
8 mol%, ethylene (b) component 61 mol%, (a)
+ (B) was 99 mol% of S-B1-S-B2 type block copolymer.

Reference Production Example 2 In a 30-liter autoclave purged with nitrogen, 18 liters of dried and purified cyclohexane, 1.76 g (15.1 mmol) of TMEDA and 3 parts of n-butyllithium were used instead of THF. A cyclohexane solution containing 0.73 g (58.3 mmol) was charged and heated to 60 ° C. Therein, 275 g of styrene was added for polymerization. Subsequently, 1.92 kg of 1,3-butadiene and 275 g of styrene were successively added to continue the polymerization. Here, the temperature was cooled to 40 ° C., and 26.8 g (0.146 mol) of BOP was further added.
A block copolymer was produced in the same manner as in Production Reference Example 1 except that 275 g of 1,3-butadiene was added and polymerization was continued.

The obtained block copolymer had Mn of about 6
The styrene content was 20 wt%, the 1,2-vinyl bond content of the polybutadiene portion was 35% for the polybutadiene block polymerized first, 71% for the polybutadiene block polymerized later, and 1,1 in the final copolymer total. 2
-An S-B1-S-B2 type block copolymer having a vinyl bond content of 39% (a 1,4-vinyl bond content of 61%).

Next, 245 mg (0.68 mmol) of di-m-tolyl-bis (η ⁵ -cyclopentadienyl) titanium and 0.82 n-butyllithium were added to a cyclohexane solution of the obtained block copolymer. A hydrogenation reaction was carried out in the same manner as in Production Reference Example 1 except that a cyclohexane solution containing mmol was added (hydrogenation ratio: 99%). The block copolymer after hydrogenation had a number average molecular weight (Mn) of about 60,000 and a styrene content of about 20 wt. %, B1 is 1 mol of 1-butene (a) component, 21 mol% of ethylene (b) component, B1
2, 1-butene (a) component is 54 mol%, ethylene (b) component is 45 mol%, and 1-butene (a) component is 25 mol%, ethylene (b)
The component is 74 mol%, and (a) + (b) is 99 mol% of S
-B1-S-B2 type block copolymer.

<Production Reference Example-3> n- as a polymerization initiator
2.47 g (38.5 mmol) of butyl lithium, T
In the presence of 1.21 g (10.4 mmol) of MEDA, 164 g of styrene and 1.3 of 1,3-butadiene were used.
1 kg and 164 g of styrene were successively polymerized, and 17.7 g (0.096 mol) of BOP was further added.
A block copolymer was produced in the same manner as in Production Reference Example 2, except that 1.09 kg of butadiene was slowly added and polymerization was carried out while controlling the polymerization temperature at 40 ° C to 45 ° C.

The obtained block copolymer had Mn of about 7
The styrene content is 12% by weight, the 1,2-vinyl bond content of the polybutadiene portion is 35% for the polybutadiene block polymerized first, 83% for the polybutadiene block polymerized later, and 1,1 in the final copolymer total. 2
-An S-B1-S-B2 type block copolymer having a vinyl bond content of 57% (1,4-vinyl bond content was 43%).

Next, nickel 2-ethylhexanoate and triethylaluminum (Al / Ni =) were added to a cyclohexane solution of the obtained block copolymer as a hydrogenation catalyst.
2/1) was previously reacted in cyclohexane, Ni was added in an amount corresponding to about 900 ppm, and the hydrogenation reaction was performed at about 80 ° C. at a hydrogen pressure of about 0.65 MPa (water Attachment rate is 98%). The block copolymer after hydrogenation had a number average molecular weight (Mn) of about 70,000, a styrene content of about 12 wt%, and B1 of 1-butene (a) component of 2%.
1 mol%, 77 mol% of ethylene (b) component, 1% of B2
-Butene (a) component is 69 mol%, ethylene (b) component is 29 mol%, and 1-butene (a) component is 43 mol% and ethylene (b) component is 55
Mol%, and (a) + (b) is 98 mol% of S-B1-S
-B2 type block copolymer.

<Production Reference Example-4> n- as a polymerization initiator
7.13 g (0.111 mol) of butyllithium, TM
In the presence of 6.47 g (55.7 mmol) of EDA,
524 g of styrene and 3.76 k of 1,3-butadiene
g and 524 g of styrene were sequentially polymerized, and 12.9 g (0.111 mol) of TMEDA was further added.
A block copolymer was produced in the same manner as in Production Reference Example 1 except that 3.93 kg of butadiene was slowly added and polymerization was carried out while controlling the polymerization temperature at 40 ° C to 45 ° C.

The obtained block copolymer had an Mn of about 1
10,000, styrene content: 13 wt%, 1,2-vinyl bond content of polybutadiene portion: 58% of polybutadiene block polymerized first, 73% of polybutadiene block polymerized later, 1 in total of final copolymer ,
The S-B1-S-B2 type block copolymer had a 2-vinyl bond content of 66% (1,4-vinyl bond content was 34%).

Next, 510 mg (0.141 mol) of di-m-tolyl-bis (η ⁵ -cyclopentadienyl) titanium was added to a cyclohexane solution of the obtained block copolymer.
And a hydrogenation reaction was carried out in the same manner as in Production Reference Example 1 except that a cyclohexane solution containing 1.71 mmol of n-butyllithium was added (hydrogenation ratio: 99%). The block copolymer after hydrogenation had a number average molecular weight (Mn) of about 110,000, a styrene content of about 12 wt%, B1 of 1-butene (a) component of 40 mol%, and ethylene (b) component of 59%. Mol%, B2 is 57 mol% of the 1-butene (a) component, 42 mol% of the ethylene (b) component, and 49 mol% of the 1-butene (a) component and ethylene (b) in the entire hydrogenated portion of the conjugated diene. 5) component
0 mol%, (a) + (b) is 99 mol% of S-B1-
It was an S-B2 type block copolymer.

<Comparative Manufacturing Reference Example-1>
09 g (18.0 mmol), n-butyllithium 4.
A cyclohexane solution containing 12 g (64.3 mmol) was charged and heated to 60 ° C. 275 styrene
g was added to perform polymerization. Subsequently, a block copolymer was polymerized in the same manner as in Production Reference Example 2, except that 2.06 kg of 1,3-butadiene and 275 g of styrene were successively polymerized.

The obtained block copolymer had Mn of about 5
The styrene content is 20% by weight, the 1,2-vinyl bond content of the polybutadiene portion is 36% for the polybutadiene block polymerized first, 36% for the polybutadiene block polymerized later, and 1,1 in the final copolymer total. 2
-An S-B1-S-B2 type block copolymer having a vinyl bond content of 36% (a 1,4-vinyl bond content of 64%).

Next, 228 mg (0.63 mmol) of di-m-tolyl-bis (η ⁵ -cyclopentadienyl) titanium and 0.76 n-butyllithium were added to a cyclohexane solution of the obtained block copolymer. A hydrogenation reaction was carried out in the same manner as in Production Reference Example 1 except that a cyclohexane solution containing mmol was added (hydrogenation ratio: 99%). The block copolymer after hydrogenation had a number average molecular weight (Mn) of about 50,000, a styrene content of about 20 wt%, and B1 and B2 contained 22 mol% of 1-butene (a) component and ethylene (b) component. Is 77 mol%, so that in the whole hydrogenated part of the conjugated diene, 22 mol% of the 1-butene (a) component, 77 mol% of the ethylene (b) component, and (a) + (b) are 99 mol% of S -B1-S-
It was a B2 type block copolymer.

The resins used in the examples of the present invention are shown below. The melt flow rate of each resin shown below is J
In accordance with IS-K7210, MI was measured under condition 4 (190 ° C,
2.16 kgf), the MFR is the condition 14 (230 ° C, 2.
16 kgf). TPS1: hydrogenated S-B1- produced in Production Reference Example 1
S-B2-type block copolymer TPS2: hydrogenated S-B1- produced in Production Reference Example 2
S-B2-type block copolymer TPS3: Hydrogenated S-B1- produced in Production Reference Example 3
S-B2-type block copolymer TPS4: Hydrogenated S-B1- produced in Production Reference Example 4
S-B2 type block copolymer

TPS5: hydrogenated S-B1-SB2 type block copolymer produced in Comparative Production Reference Example 1 TPS6: hydrogenated diene-based random copolymer [density = 0.
89 g / cm ³ , MFR = 3.5 g / 10 min, Tg = −
50 ° C., styrene / 1,2 addition butadiene / 1,4 addition butadiene / unhydrogenated butadiene = 6 mol% / 70 mol% / 23 mol% / 1 mol%, about 5/12 of styrene
Forms a block (S), and 7/12 is a random copolymerized (R) SR structure (DYN manufactured by Nippon Synthetic Rubber Co., Ltd.)
ARON-1320P)] TPS7: hydrogenated styrene-isoprene-styrene-triblock copolymer [density = 0.94 g / cm ³ , M
FR = 6 g / 10 min, Tg = −19 ° C., styrene = 20
% By weight (Kuraray Co., Ltd., Hibler HVS-3)] TPS8: SEBS [density = 0.94 g / cm ³ , MF
R = 9 g / 10 min, styrene = 13% by weight, 30% S
-B diblock type, 70% S-B-S triblock type, the total ratio of 1-butene to ethylene is 26 mol% for the former, 73 mol% for the latter, and the hydrogenation rate Is 99% (KRATON-G manufactured by Shell Japan)
1657 equivalent)]

H1: Propylene-α-olefin block copolymer [density = 0.88 g / cm ³ , MFR =
0.8 g / 10 min, melting point = 165 ° C., heat of fusion = 34.
3J / g (Adflex KS0 manufactured by Montell-JPO)
81P)] h2: Propylene-α-olefin block copolymer [density = 0.88 g / cm ³ , MFR = 30 g / 10
Min, melting point = 165 ° C., heat of fusion = 51.7 J / g (Adflex KS084P manufactured by Montell-JPO)] h3: Propylene-ethylene random copolymer [density = 0.90 g / cm ³ , MFR = 1 g / 10 minutes, melting point =
151 ° C, heat of fusion = 111.7 J / g (J-ALLOMER EG110, manufactured by Nippon Polyolefin Co., Ltd.) h4: Propylene-ethylene random copolymer [density = 0.90 g / cm ³ , MFR = 7 g / 10 minutes, Melting point =
137 ° C, heat of fusion = 89.3 J / g (f8 manufactured by Chisso Corporation)
277)] h5: 1-butene-propylene random copolymer [density = 0.90 g / cm ³ , MI = 2 g / 10 min, melting point =
72 ° C., heat of fusion = 28.2 J / g (Mitsui Chemicals Tuffmer BL2281)]

S1: ethylene-vinyl acetate copolymer [vinyl acetate = 15% by weight, density = 0.94 g / cm ³ , M
I = 2.0 g / 10 min, melting point = 92 ° C. (NUC3758, manufactured by Nippon Unicar)] s2: ethylene-1-octene copolymer [1-octene content = 15% by weight, density = 0.902 g / cm ³ , MI
= 3.3 g / 10 min, melting point = 98 ° C. (The Dow Chemical Co. AFFINITY · PL1850)] s3: ethylene-1-octene copolymer [1- octene content = 22 wt.%, Density = 0.875 g / cm ³ , MI
= 3.0 g / 10 min, melting point = 67 ° C (AFFINITY KC8852 manufactured by Dow Chemical Company)] s4: Ethylene-1-octene copolymer [1-octene content = 24 wt%, density = 0.870 g / cm ³ , MI
= 1.0 g / 10 min, melting point = 57 ° C. (AFFINITY CL8002 manufactured by Dow Chemical Company)] s5: ethylene-1-butene-1-hexene copolymer [density = 0.910 g / cm ³ , MI = 1. 2g / 10
Min, melting point = 103 ° C. (EXACT302 manufactured by EXXON)
5)]

[0075]

Example 1 As both surface layers (S layers), diglycerin laurate (L-71D manufactured by Riken Vitamin) / monoglycerin oleate (OL-100 manufactured by Riken Vitamin) was used for s1.
= 1.5% by weight added to the heat-resistant layer (H
40% by weight of TPS1 and 60% by weight of h1
Using a composition consisting of: S / H / S = 30%
Extruded at a discharge rate of 20 kg / hr from a multilayer circular die (lip diameter = 100 mm, lip opening = 2.0 mm) set at 200 ° C. in a three-layer configuration of / 40% / 30%, and cooled with cold air at 15 ° C. Meanwhile, air was blown in so that the lateral magnification (BUR) became 3.5 times, and the sheet was folded with a roll-type deflator having a take-up speed of 33.7 m / min and an opening of 30 degrees, and taken up with a take-up roll. Incidentally, the distance from the bubble neck to the frost line was about 30 cm. The thickness of the resulting film was about 12 μm (Run. No. 1). Subsequently, the TPS1 of the H layer is changed to TP
No. 2 instead of S2 (Run. No. 2), also TPS
No. 1 was replaced with TPS3 (Run. No. 3), and TPS1 was replaced with TPS4 (Run. No. 3).
4) was formed into a film. The resulting film was evaluated by the method described above.

[0076]

Comparative Example 1 In Example 1, the TPS1 of the H layer was changed to TP
No. 5 (Run. No. 5), also TPS
No. 1 was replaced with TPS6 (Run. No. 6), and TPS1 was replaced with TPS7 (Run. No. 6).
7) Similarly, TPS1 is replaced with TPS8 (Ru
n. No. 8) was formed into a film. The obtained film was evaluated by the method described above. As described in Run. Table 1 shows the physical properties and evaluation results of the films Nos. 1 to 8. The necessity of using a specific H-SBBC, which is the most different point of the present invention from the prior art, will be described below. In Table 1, Run. The films of Nos. 1 to 4 were evaluated as “O” or more in all evaluation items of dart strength at normal temperature, cold resistance (dart strength at −30 ° C.), transparency, indentation recovery property, sealing property, cut property, and packaging property. Met.

On the other hand, Run. The film of No. 5 was inferior in cold resistance, transparency, and cuttability because 1-butene in the hydrogenated / conjugated diene compound block copolymer of H-SBBC was as small as 22 mol%. Run. N
The film of o.6 is a random copolymer of polystyrene block (S), styrene (about 3.5 mol%), ethylene and 1-butene. Inferior in recoverability, and about 3.5 styrene was added to the hydrogenated / conjugated diene compound block copolymer.
It was inferior in cold resistance due to being mol% random copolymerized.

Run. The film of No. 7 is H-SB
The hydrogenated / conjugated diene compound block copolymer of BC was hydrogenated / polyisoprene (Tg = −19 ° C.), and was inferior in cold resistance. Since polyisoprene has a large side chain, it tends to be rigid and have a high Tg, so that it is difficult to provide cold resistance. Run. The film of No. 8 has H in which one polystyrene block (S) and two blocks of the same polystyrene exist at a ratio of 30% and 70%.
-SBBC, and the indentation recovery was poor. In addition, the transparency was inferior to HAZE = 2.5%, possibly due to insufficient compatibility with the polypropylene resin, and the cut property was also inferior. As described above, the necessity of using a specific H-SBBC, which is the most different point of the present invention from the prior art, is understood.

[0079]

[Table 1]

[0080]

Example 2 Example 1 Run. No. In Example 2, the ratio of TPS2 to h1 in the H layer was changed from 40/60 to 5/95 (Run. No. 9), and the ratio was changed to 50/50 (Run. No. 10). . No.
Experiment 2 was repeated.

[0081]

Comparative Example 2 Example 1 Run. No. In Example 2, the ratio of TPS2 to h1 in the H layer was changed from 40/60 to 3/97 (Run. No. 11), and the ratio was also changed to 52/48 (Run. No. 12). . N
o. Experiment 2 was repeated. As described in Run. No. 2 and Run. No. Table 2 shows the physical properties and evaluation results of the films Nos. 9 to 12. Hereinafter, the necessity that the H-SBBC is 5 to 50% by weight and the polypropylene resin having a melting point of 150 ° C. or more in the H layer is 50 to 95% by weight will be described. In Table 2, the film Ru of the present invention is shown.
n. The films of Nos. 2, 9 and 10 had sealability and indentation recovery of “○” or more.

On the other hand, Run. The film of No. 11 was inferior in indentation recovery because the H-SBBC was as small as 3% by weight and as a result, the polypropylene resin was as large as 97% by weight. Run. The film of No. 12 had a high H-SBBC as large as 52% by weight, and as a result, the polypropylene-based resin was as small as 48% by weight. From the above, in the H layer, H-SBBC is 5 to 50% by weight.
The melting point of the polypropylene-based resin with a melting point of 150
The need for 95% by weight can be seen.

[0083]

[Table 2]

[0084]

Embodiment 3 Embodiment 1, Run. No. At 3, H
Example 1 except that the layer h1 was changed to h3. No.
Experiment 3 was repeated (Run. No. 13).

[0085]

Comparative Example 3 Example 1, Run. No. At 3, H
Example 1 except that h1 of the layer was changed to h4. No.
Experiment 3 was repeated (Run. No. 14). that's all,
Run. No. 3 and Run. No. Table 3 shows the evaluation results of the films 13 and 14. The necessity for the melting point of the polypropylene resin in the H layer to be 150 ° C. or higher will be described below. In Table 3, Run. The films of Nos. 3 and 13 had a sealing property of “○”.

On the other hand, Run. In the film of No. 14, the melting point of the polypropylene resin is 137 ° C.,
The film was inferior in sealability due to insufficient heat resistance of the film. From the above, it is understood that the necessity that the melting point of the polypropylene resin in the H layer is 150 ° C. or more. In addition, Run. No. 3 film and Run. No. 1
In comparison of the film No. 3, the former in which the polypropylene-based resin was B-PP was superior to the latter in which the polypropylene-based resin was R-PP in dart strength, tear strength and transparency.

[0087]

[Table 3]

[0088]

Embodiment 4 Embodiment 1, Run. No. At 4, S
S1 of the layer was replaced with s2 (Run. No. 15).
Example 3 and Ru (Run. No. 16)
n. No. Experiment 4 was repeated.

[0089]

Comparative Example 4 Example 1, Run. No. At 4, S
The layer s1 was changed to s4 (Run. No. 17).
Example 5 Ru (Run No. 18)
n. No. Experiment 4 was repeated. As described in Run. N
o. 4 and and Run. No. Table 4 shows the physical properties and evaluation results of the films Nos. 15 to 18. The necessity that the S layer be made of a PO resin having a melting point of 60 to 100 ° C will be described below. In Table 4, the film of the present invention, R
un. No. 4 and Run. The films of Nos. 15 and 16 had sealability and packaging property of “○” or more.

On the other hand, Run. The film of No. 17 has a low melting point of the resin of the S layer as low as 57 ° C., and has a sticky feeling even at room temperature. Removal from the belt was poor, large chips of film were generated, and the tray was crushed. Run. N
The melting point of the resin of the film S layer of o.18 was as high as 103 ° C., the lower limit of the sealable temperature was as high as 130 ° C., and the sealing range was as narrow as 25 ° C. From the above, it is understood that the S layer needs to be made of a PO resin having a melting point of 60 to 100 ° C.

In the case where Run. No.
Run No. 4 using an ethylene-α-olefin copolymer for the film and the S layer. When compared with the films of Nos. 15 and 16, the tear strength, particularly the MD strength, was increased, and as a result, the film was excellent in cutability.

[0092]

[Table 4]

[0093]

Embodiment 5 As S layer, polyoxyethylene (n
= 10) A layer containing 0.5% by weight of oleic acid ester was added to a composition obtained by blending 40% by weight of TPS4 and 60% by weight of h2 as an H layer to obtain monoglycerin / oleate /
Using a layer to which 2.0% by weight of diglycerin oleate = 1/1 was added, each layer was S / H / S = 30% / 40% / 3
Multilayer circular die set at 210 ° C. in a three-layer configuration of 0% (lip diameter = 200 mm, lip opening = 1.2 m)
m), the laminate was extruded at a discharge rate of 15 kg / hr, and the extruded laminate was cooled with 25 ° C. cold water and folded to have a thickness of 10
A raw material of 0 μm was obtained. Here, a 30% aqueous solution of polyoxyethylene (n = 10) oleate was applied to the inner surface of the raw material tube (active ingredient = about 5 mg /
m ² ). Air is blown into the folded web to form a tube, heated to 120 ° C., and cooled with 15 ° C. cold air, while being stretched by a factor of 3.3 to MD and 3.3 to TD, and the degree of opening is increased. Is folded with a 60 degree roll deflator,
It was picked up by a pick-up roll. Finally, the draw ratio was 3.2 times for MD and 3.1 times for TD, and the film thickness was about 10 μm (Run. No. 19). Next, Run. Was changed except that the resin composition of the H layer was changed to a composition having 20% by weight of TPS4, 60% by weight of h2, and 20% by weight of h5. N
o. A film was formed in the same manner as in Example 19 (Run. No. 20). Similarly, except that the resin composition of the H layer was changed to a composition having 5% by weight of TPS4, 60% by weight of h2, and 35% by weight of s3,
un. No. No. 19 (Run. No. 2)
1).

As described above, Run. No. 4 and Run. No.
Table 5 shows the evaluation results of the films 19 to 21. Ru
n. No. The film No. 4 is a film having a thickness of 12 μm formed by the direct inflation method. No. Each of the films 19 to 21 has a thickness of 10 μm formed by the double bubble inflation method.
m film.

As can be seen from Table 5, Run. No. 4 compared to the film of Run. No. The films of Nos. 19 to 21 were excellent in indentation recovery. In the evaluation of packaging,
There were few wrinkles in packaging, and the conditions for tensioning the packaging machine could be taken widely, and it was very excellent as a stretch film for a push-up type packaging machine. As can be seen from Table 5, Run. No. 19-21
The film of Run. No. Although the film was thinner than the film of No. 4, the tear strength was maintained at the same level.
In particular, the 1-butene-propylene random copolymer is H
Run. No. In No. 20, the tear strength was higher in the MD than in the TD, and no chips were generated at all in the evaluation of cutability.

[0096]

[Table 5]

[0097]

Embodiment 6 As S layer, polyoxyethylene (n
= 10) A layer in which 0.7% by weight of lauric acid ester was added, a layer in which diglycerin / laurate was added in 1.6% by weight in s2 as an M layer, and a layer in which TPS1 was 20 as an H layer.
Using a composition layer of 60% by weight of h2, h2 of 20% by weight and h5 of 20% by weight, each layer was S / M / H / M / S = 10% / 25.
% / 30% / 25% / 10%, and the same operation as in Example 5 was repeated (Run. No. 2).
2).

The physical properties of the resulting film were such that the 200% elongation load (g / cm width) was 210/12 in the order of MD / TD.
0, elongation at break (%) is 550/550, tear strength (g)
Was 90/60, and the evaluation results were “◎” for all items. In particular, by using EVA for the S layer, the anti-fog property is excellent,
Moreover, by using the ethylene-α-olefin copolymer for the M layer, a tear strength that cannot be provided by the EVA / H layer / EVA could be provided. It can be seen that increasing the number of layers and functional differentiation is important for obtaining a film that is closer to the best.

[0099]

Embodiment 7 As S layer, polyoxyethylene (n
= 10) A resin in which 0.7% by weight of lauric acid ester is added, a composition layer of 40% by weight of TPS3 and 60% by weight of h2 as an H layer, and a resin obtained by reworking the entire film on s2 as an M layer. Are blended using 50% by weight (h2 is about 9%, TPS3 is about 6%, s1 is about 15%), and each layer is S / H / M / H / S = 15% / 15% / 40.
% / 15% / 15%, and the same operation as in Example 5 was repeated (Run. No. 23) except for a five-layer structure.

The physical properties of the resulting film were such that the 200% elongation load (g / cm width) was 210/12 in the order of MD / TD.
0, elongation at break (%) is 500/550, tear strength (g)
Was 80/60, and the evaluation results were “◎” for all items. Here, Run. No. The film of Run.
No. Although there are some inferior properties such as a slightly lower tear strength than the film No. 22, the HAZ can be obtained by using the rework resin.
E was 0.6%, which was excellent in transparency. Incidentally, Run.
No. When 50% by weight of the rework resin was mixed with the M layer of No. 23, the HAZE was extremely inferior to 3.0%.

[0101]

According to the present invention, for the first time, a film having improved transparency, cutability and cold resistance while maintaining or further improving the heat sealing property and the indentation recovery property of the conventional film can be provided.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 4F071 AA20 AA75 AA84 AH04 BC01 4F100 AK03A AK03B AK04C AK07C AK09C AK11C AK12C AK28C AK65C AK73C AK80C AL02C AL03C BA03 BA06 BA04 J04 J04 JA04 GB04 JA04 GB04 YY00C 4J002 BB111 BP012 GF00 GG02

Claims (1)

[Claims] 1. A stretch packaging film comprising a surface layer (S layer) made of a polyolefin resin having a melting point of 60 to 100 ° C. and at least one heat-resistant layer (H layer), wherein the H layer has a melting point of 150 ° C. 50 to 95% by weight of the above polypropylene resin and hydrogenated product 5 of a vinyl aromatic compound block-conjugated diene compound block copolymer shown below.
A film for stretch packaging, comprising 50% by weight. (1) At least two polystyrene blocks (S) each containing 90 mol% or more of a styrene monomer component. (2) The monomer components are mainly 1-butene (a) component and ethylene (b) component. And the constituent ratio of each component is 25 mol% or more for the component (a) and 75 mol% for the component (b).
Hereinafter, ethylene- (a) + (b) ≧ 97 mol%
A hydrogenated product of a vinyl aromatic compound block-conjugated diene compound block copolymer comprising a 1-butene / random copolymer block (B).