JPH0531473B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an inner bag for a bag-in-box,
More specifically, by using a laminated film in which both surface layers made of a specific olefin polymer composition and a central layer made of a gas barrier material are laminated using an adhesive, heat resistance and heat sealability at low temperatures are achieved. This invention relates to an inner bag for bag-in boxes with improved strength and blocking resistance. [Prior Art] When storing or transporting various liquids such as foods, medicines, and solvents, it is common practice to use so-called bag-in boxes, in which the liquids are filled into an inner bag made of plastic film and then stored in an outer bag such as a carton. It has been rapidly increasing in recent years. The liquid to be filled can be concentrated juice, ketchup, syrup,
The inner bag is water-resistant, chemical-resistant, oil-resistant, and solvent-resistant because it contains a wide variety of products, including milk, soft drinks, sake, whiskey, wine, chemicals such as acids and alkalis, gasoline, kerosene, toluene, and xylene. It is necessary to have a variety of properties such as water resistance and oxygen barrier properties. Furthermore, these bag-in boxes are used over a relatively wide range of temperatures, usually from 5 to 98 degrees Celsius, so they are required to have excellent heat resistance and low-temperature resistance. It is also necessary to have high impact resistance because it is usually subjected to extremely rough handling during transportation after filling with liquid. In addition, especially in summer, there is a risk that the surfaces of the film may adhere to each other (blocking), causing problems in handling, so it is necessary to consider blocking resistance. The shape of the inner bag used for back-in-boxes is as follows:
There are two types: the blow type, which uses the plastic tube produced by blow molding as is, and the gusset type, which has a gusset so that it can be folded, but the gusset type has a smaller volume for storage and transportation when empty. It is advantageous because it can be small. However, in the case of the gusset type, heat-sealing is required on the peripheral edge when forming the inner bag, so the strength of the heat-sealed part, especially the impact resistance strength of the heat-sealed part at low temperatures (hereinafter referred to as low-temperature heat-sealing strength), is ) is strongly desired. Furthermore, since the gusset type bag is folded during storage, blocking resistance is extremely important. The above heat resistance or blocking resistance and low-temperature heat sealing strength are usually contradictory requirements in the properties of plastics, so it is difficult to satisfy these three in a well-balanced manner. There remained a problem. [Problems to be Solved by the Invention] Conventionally, inner bags for bag-in boxes with excellent pinhole resistance or heat resistance have been disclosed, for example, in 1982-131946, 1982-8257, and 60-198. -120051 etc. However, sufficient studies have not been conducted on techniques for simultaneously improving heat resistance, low-temperature heat-sealing strength, and blocking resistance. An object of the present invention is to solve the above problems by examining the material composition of the inner bag for bag-in boxes, and to provide an inner bag with excellent heat resistance, low-temperature heat seal strength, and blocking resistance. . [Means for Solving the Problems] As a result of intensive studies in line with the above objectives, the present inventors have developed a double surface layer and gas barrier property obtained by combining a specific ethylene/α-olefin copolymer, etc. The inventors have discovered that an inner bag for bag-in-boxes having excellent performance can be obtained by using a laminated film comprising a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having an inner layer of an inner layer having a central layer having a central layer having a central layer having a central layer having a central layer having a central layer having an inner layer of an inner layer of a bag-in-box; That is, the present invention provides an inner bag for a bag-in-box using a laminated film in which both surface layers made of an olefinic polymer composition and a central layer made of a gas barrier material are laminated using an adhesive. The above olefin polymer composition includes (a) ethylene α having a density of 0.910 to 0.940 g/cm ³ ;
- 55 to 90% by weight of an olefin copolymer;
~12 α-olefins, (i) density 0.860 g/cm ³ or more and less than 0.910 g/cm ³ ,
(ii) maximum peak temperature of 100°C or higher as determined by differential scanning calorimetry (DSC), (iii) ethylene α- having the properties of boiling n-hexane insoluble content of 10% by weight or higher
5 to 35% by weight of olefin copolymer, and (c) ethylene/α-olefin copolymer rubber,
The present invention provides an inner bag for a bag-in-box characterized by comprising 5 to 15% by weight of one or more selected from polyisobutylene and ethylene-vinyl acetate copolymer. Hereinafter, the content of the present invention will be explained in detail. (1) Component (a) The ethylene/α-olefin copolymer which is the component (a) of the present invention is a low-density ethylene/α-olefin copolymer.
- Olefin copolymer with a density of 0.910
~0.940g/ ^cm3 , i.e. typically
What is called linear low density polyethylene is used in order to maintain compatibility with the component (b), moldability, flexibility, heat resistance, etc. However, it is always necessary to have a density higher than that of component (b). The melt index (MI) of the ethylene/α-olefin copolymer of component (a) is preferably 0.05 to 50 g/10 min, more preferably, in consideration of the fluidity and strength of the olefin polymer composition. Selected from the range of 0.1 to 20g/10min. (2) Component (b) The ethylene/α-olefin copolymer which is the component (b) of the present invention is a copolymer of ethylene and α-olefin having 3 to 12 carbon atoms. specific α
-Olefins include propylene and butene-
1,4-methylpentene-1, hexene-1,
Octene-1, decene-1, dodecene-1, etc. can be mentioned. Particularly preferred among these are propylene, butene-1, 4-methylpentene-1 and hexene-1, each having 3 to 6 carbon atoms. The α-olefin content in the ethylene/α-olefin copolymer is 5 to 40
Preferably it is mol%. Below, ethylene used as component (b) and α-
A method for producing an olefin copolymer will be explained. The catalyst system used is a combination of a solid catalyst component containing at least magnesium and titanium and an organoaluminum compound. Examples of the solid catalyst component include magnesium salts such as metallic magnesium, magnesium hydroxide, magnesium carbonate, magnesium oxide, and magnesium chloride, and double salts and double oxides containing magnesium atoms and metals selected from silicon, aluminum, and calcium. matter, carbonate,
Titanium compounds are added to magnesium-containing inorganic solid compounds such as chlorides or hydroxides, and those obtained by treating or reacting these inorganic solid compounds with oxygen-containing compounds, sulfur-containing compounds, aromatic hydrocarbons, or halogen-containing substances. Examples include those supported by known methods. Examples of the above oxygen-containing compounds include water,
Alcohol, phenol, ketone, aldehyde, carboxylic acid, ester, polysiloxane,
Examples include organic oxygen-containing compounds such as acid amides, and inorganic oxygen-containing compounds such as metal alkoxides and metal oxychlorides. Examples of the sulfur-containing compound include organic sulfur-containing compounds such as thiol and thioether, and inorganic sulfur-containing compounds such as sulfur dioxide, sulfur trioxide, and sulfuric acid. Examples of aromatic hydrocarbons include various monocyclic and polycyclic aromatic hydrocarbon compounds such as benzene, toluene, xylene, anthracene, and phenanthrene. Examples of halogen-containing substances include compounds such as chlorine, hydrogen chloride, metal chlorides, and organic halides. Titanium compounds include titanium halides, alkoxy halides, alkoxides,
Examples include halogenated oxides. As the titanium compound, a tetravalent titanium compound and a trivalent titanium compound are suitable, and the tetravalent titanium compound specifically has the general formula Ti(OR)n×
Those represented by _4- n (where R represents an alkyl group, aryl group, or aralkyl group having 1 to 20 carbon atoms, X represents a halogen atom, and n satisfies 0≦n≦4) are preferred; Titanium chloride, titanium tetrabromide, titanium tetraiodide, monomethoxytrichlorotitanium, dimethoxydichlorotitanium, trimethoxymonochlorotitanium, tetramethoxytitanium, monoethoxytrichlorotitanium, diethoxydichlorotitanium, triethoxymonochlorotitanium, tetraethoxytitanium, Monoisopropoxytrichlorotitanium, diisopropoxydichlorotitanium, triisopropoxymonochlorotitanium, tetraisopropoxytitanium, monobutoxytrichlorotitanium, dibutoxydichlorotitanium, monopentoxytrichlorotitanium, monophenoxytrichlorotitanium, diphenoxydichlorotitanium , triphenoxymonochlorotitanium, tetraphenoxytitanium, and the like. Examples of trivalent titanium compounds include titanium trihalides obtained by reducing titanium tetrahalides such as titanium tetrachloride and titanium tetrabromide with hydrogen, aluminum, titanium, or organometallic compounds of group metals of the periodic table. Can be mentioned. In addition, the general formula Ti (OR) m × _4- m (where R is 1 carbon number
~20 alkyl group, aryl group or aralkyl group, X represents a halogen atom, m is 0
A trivalent titanium compound obtained by reducing a tetravalent alkoxy titanium halide represented by the formula <m<4) with an organometallic compound of a group metal of the periodic table. Among these titanium compounds, tetravalent titanium compounds are particularly preferred. Another example of a catalyst system is a catalyst system in which a reaction product of an organomagnesium compound such as a so-called Grignard compound and a titanium compound is used as a solid catalyst component, and an organoaluminum compound is combined therewith. Examples of organomagnesium compounds include organomagnesium compounds with the general formulas RMgX, R ₂ Mg, RMg (OR) (where R is an organic residue having 1 to 20 carbon atoms, and X represents a halogen), and ethers thereof. Complexes, or these organomagnesium compounds modified by adding various other organometallic compounds such as organosodium, organolithium, organopotassium, organoboron, organocalcium, organozinc, etc. can be used. can. In addition, as an example of another catalyst system, a solid material obtained by contacting an inorganic oxide such as SiO ₂ or Al ₂ O ₃ with a solid catalyst component containing at least magnesium and titanium is used as a solid catalyst component. , and a combination thereof with an organic aluminum compound can be exemplified. As inorganic oxides, in addition to SiO ₂ and Al ₂ O ₃ , CaO,
Examples include B ₂ O ₃ and SnO ₂ , and double oxides of these oxides can also be used without any problem. Any known method can be used to bring these various inorganic oxides into contact with the solid catalyst component containing magnesium and titanium. That is, at a temperature of 20 to 400°C, preferably 50 to 400°C, in the presence or absence of an inert solvent.
The reaction may be carried out by a method of reacting at 300°C for usually 5 minutes to 20 hours, a method of co-pulverization, or a suitable combination of these methods. In these catalyst systems, a titanium compound can be used as an adduct with an organic carboxylic acid ester, or the above-described magnesium-containing inorganic solid compound can be used after being brought into contact with an organic carboxylic acid ester. Moreover, there is no problem in using an organoaluminum compound as an adduct with an organic carboxylic acid ester. Furthermore, in all cases it is possible to use catalyst systems prepared in the presence of organic carboxylic esters without any problems. Here, various aliphatic, alicyclic, and aromatic carboxylic esters are used as the organic carboxylic ester, and aromatic carboxylic esters having 7 to 12 carbon atoms are preferably used. Specific examples include alkyl esters of benzoic acid, anisic acid, toluic acid, such as methyl and ethyl. Specific examples of organoaluminum compounds to be combined with the above-mentioned solid catalyst components include those with the general formulas R ₃ Al, R ₂ AlX, RAlX ₂ , R ₂ AlOR, and RAl.
(OR) An organoaluminum compound of X and R ₃ Al ₂ X ₃ (where R is an alkyl group having 1 to 20 carbon atoms,
Preferred are compounds represented by an aryl group or an aralkyl group, X represents a halogen atom, and R may be the same or different, and include triethylaluminum, triisobutylaluminum,
Examples include trihexylaluminum, trioctylaluminum, diethylaluminum chloride, diethylaluminum ethoxide, ethylaluminum sesquichloride, and mixtures thereof. The amount of organoaluminum compound used is not particularly limited, but it is usually 0.1 to 0.1 to the amount of titanium compound.
1000 mole times can be used. Furthermore, by bringing the catalyst system into contact with an α-olefin and then using it in the polymerization reaction, the polymerization activity can be greatly improved and the system can be operated more stably than in the case of no treatment. Various α-olefins can be used at this time, but preferably those having 3 to 12 carbon atoms are used.
α-olefins, more preferably α-olefins having 3 to 8 carbon atoms. Examples of these α-olefins include propylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, etc.
1, decene-1, dodecene-1, and mixtures thereof. Catalyst system and α
- The temperature and time during contact with the olefin can be selected within a wide range; for example, the contact treatment can be carried out at 0 to 200°C, preferably 0 to 110°C, for 1 minute to 24 hours. The amount of α-olefin to be contacted can be selected within a wide range, but it is usually 1 to 50,000 g, preferably 5 to 50,000 g per 1 g of the solid catalyst component.
It is preferable to treat with about 30,000 g of α-olefin and react with 1 to 500 g of α-olefin per 1 g of the solid catalyst component. At this time, the pressure at the time of contact can be arbitrarily selected, but it is usually desirable to contact under a pressure of -1 to 100 kg/cm ² ·G. During the α-olefin treatment, the entire amount of the organoaluminum compound used may be combined with the solid catalyst component and then brought into contact with the α-olefin, or a part of the organoaluminum compound used may be combined with the solid catalyst component. After combining with α-olefin, the remaining organoaluminum compound may be added separately during polymerization to carry out the polymerization reaction. In addition, the catalyst system and α-
At the time of contact with olefin, there is no problem even if hydrogen gas coexists, and there is no problem even if other inert gases such as nitrogen, argon, helium, etc. coexist. The polymerization reaction is carried out in the same manner as a typical olefin polymerization reaction using a Ziegler type catalyst. That is, all reactions are carried out in a gas phase or in the presence of an inert solvent, in the absence of oxygen, water, etc.
Alternatively, the monomer itself can be used as a solvent. The polymerization conditions for olefin are a temperature of 20 to 300°C, preferably 40 to 200°C, and a pressure of normal pressure to 70°C.
Kg/cm ²・G, preferably 2Kg/cm ²・G to 60
Kg/cm ²・G. Molecular weight can be adjusted by polymerization temperature,
Although it can be controlled to some extent by changing polymerization conditions such as the molar ratio of catalysts, it is effectively carried out by adding hydrogen to the polymerization system. Of course, a two-stage or more multi-stage polymerization reaction with different polymerization conditions such as hydrogen concentration and polymerization temperature can be carried out without any problem. The ethylene/α-olefin copolymer which is component (b) of the present invention produced in this way has (i) a density of 0.860 g/cm ³ or more and less than 0.910 g/cm ³ , (ii) differential scanning calorimetry It is important that the maximum peak temperature (Tm) shown by method (DSC) is 100°C or higher, and (iii) the content insoluble in boiling n-hexane is 10% by weight or higher. If the above density exceeds 0.910 g/cm ³ , there is a concern that the flexibility of the inner bag for bag-in-box will decrease, and if the density is less than 0.860 g/cm ³ , the tensile strength will decrease and the melting point will decrease. , resulting in poor heat resistance. Furthermore, those having a maximum peak temperature (Tm) measured by differential scanning calorimetry (DSC) of less than 100°C have lower tensile strength and poor heat resistance. Furthermore, if the boiling n-hexane insoluble content of the ethylene/α-olefin copolymer is less than 10% by weight, the amorphous portion and low molecular weight components will increase, resulting in improved blocking resistance, heat resistance, oil resistance, and strength. becomes inferior to MI of the ethylene/α-olefin copolymer
is preferably in the range of 0.05 to 50 g/10 min, more preferably 0.1 to 20 g/10 min. The ethylene/α-olefin copolymer used as component (b) in the present invention is clearly distinguished from the ethylene/α-olefin copolymer obtained by using a vanadium-containing solid catalyst component. That is, conventional ethylene-propylene copolymers and the like using vanadium catalysts have almost no crystallinity, and even if crystal parts exist, they are in very small amounts. For this reason, the maximum peak temperature (Tm) measured by DSC is less than 100°C, and boiling n-hexane insoluble matter does not exist, or even if it exists, it is extremely small. This indicates that it cannot be used in applications that require heat resistance, mechanical strength, etc. In addition, DSC and boiling n-
The method for measuring the hexane-insoluble content is as follows. [Measurement method using DSC] Weigh out approximately 5 mg of a sample from a 100 μm thick hot press-molded film, set it in the DSC device, raise the temperature to 170°C, and hold it at that temperature for 15 minutes.
After the temperature is maintained, it is cooled down to 0°C at a cooling rate of 2.5°C/min. Next, from this state, the temperature increase rate is 10℃/
Measurement is performed by increasing the temperature to 170°C at min. The temperature at the position of the maximum peak that appears during the temperature increase from 0°C to 170°C is defined as Tm. [Measurement method for boiling n-hexane insoluble matter] A sheet with a thickness of 200 μm is formed using a heat press, and three sheets of 20 mm x 30 mm in length and width are cut from it, and the sheets are passed through a double-tube Soxhlet extractor. Extraction is carried out using boiling n-hexane for 5 hours. After taking out the n-hexane insoluble matter and vacuum drying (7 hours under vacuum, 50° C.), the boiling n-hexane insoluble matter is calculated using the following formula. Boiling n-hexane insoluble matter = (extracted sheet weight/unextracted sheet weight) × 100 (wt%) (3) (c) component The (c) component used in the present invention is as follows:
At least one selected from ethylene/α-olefin copolymer rubber, polyisobutylene, and ethylene-vinyl acetate copolymer is used.
Here, the ethylene/α-olefin copolymer rubber refers to ethylene/α-olefin copolymer rubber or ethylene/α-olefin/non-conjugated diene copolymer rubber, the latter of which is ethylene/α-olefin copolymer rubber.
- Olefin/non-conjugated diene copolymer rubber is particularly preferred. These copolymer rubbers are amorphous copolymers and are usually produced using vanadium catalysts. Examples of the α-olefin in the ethylene/α-olefin copolymer rubber component include propylene, 1-butene, 1-pentene, 1-4-methylpentene, 1-hexene, and 1-octene. Particularly preferred is propylene. Examples of the non-conjugated diene include 1,4-hexadiene, 1,6-octadiene, dicyclopentadiene, vinylnorbornene, ethylidenenorbornene, and the like. Preferably 1,4-
These are hexadiene and ethylidene norbornene. The Mooney viscosity (ML ₁₊₄ , 100°C) of the ethylene/α-olefin copolymer rubber used in the present invention is preferably about 10 to 95. If the Mooney viscosity of the ethylene/α-olefin copolymer rubber is less than 10, the tensile strength of the olefin polymer composition will decrease or the surface will become sticky, which is undesirable. If the Mooney viscosity exceeds 95, the heat seal strength of the olefinic polymer composition will decrease, which is not preferable. (4) Method for producing olefin polymer composition The composition of the olefin polymer composition used in the present invention is such that the weight ratio of (a)/(b)/(c) is
55-90/5-35/5-15, preferably 60
~80/13~27/7~13. If the amount of component (a) exceeds 90% by weight, flexibility will be lost and low-temperature heat seal strength will decrease. Also
If it is less than 55% by weight, heat resistance and oil resistance will deteriorate, which is not desirable. If the amount of component (b) exceeds 35% by weight, heat resistance will decrease, while if it is less than 5% by weight, blocking resistance will decrease. Moreover, when component (c) exceeds 15% by weight, blocking resistance and heat resistance tend to decrease, and when it is less than 5% by weight, low-temperature heat sealing strength decreases. In order to produce the olefinic polymer composition used in the present invention, the components (a), (b) and (c) may be uniformly blended. Any known technique can be used as the blending method, and typical examples include dry blending,
This is done by a method such as melt mixing. (5) Gas-barrier material The gas-barrier material used in the present invention includes resin films such as polyamide, polyethylene terephthalate, polyvinyl alcohol, and saponified ethylene-vinyl acetate copolymers, or metal foils such as aluminum foil. Can be mentioned. In particular, a saponified ethylene-vinyl acetate copolymer having low gas permeability and good processability is preferred.
More preferably, the composition has an ethylene content of 20 to 50 mol% and a degree of saponification of the vinyl acetate portion of 90 mol% or more. (6) Adhesive The adhesive for manufacturing the laminated film of the bag-in-box inner bag of the present invention may be a urethane resin, an ionomer resin, that is, a copolymer of ethylene and acrylic acid, etc., cross-linked with metal cations. Examples include modified polyolefins or modified rubbers obtained by reacting polymers or various polyolefins or rubbers with unsaturated carboxylic acids or derivatives thereof. Although not particularly limited, polymers containing modified polyolefins are preferred. The polyolefins used for the above modification include olefin homopolymers such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, or ethylene, propylene, butene-1, and 4-methylpentene-1.
1. Mutual copolymers of hexene-1, octene-1, etc., copolymers of ethylene and vinyl esters such as ethylene and vinyl acetate copolymers and their saponified products, ethylene-acrylic acid copolymers, ethylene-methacrylic Examples include copolymers of ethylene and unsaturated carboxylic acids, unsaturated carboxylic acid esters, etc., such as acid copolymers, ethylene-ethyl acrylate copolymers, and ethylene-ethyl methacrylate copolymers, and mixtures thereof. . Rubbers include polyisobutylene, styrene-butadiene copolymer rubber, and butadiene-butadiene copolymer rubber.
Acrylonitrile copolymer rubber, polybutadiene rubber, chloroprene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene copolymer rubber, natural rubber, ethylene-vinyl acetate copolymer rubber, liquid polybutadiene and mixtures thereof. etc. Examples of the above-mentioned modified products include those obtained by modifying polyolefin or rubber alone, as well as those obtained by modifying a polyolefin composition in which rubber is blended with polyolefin, and the amount of rubber blended is 100 parts by weight of polyolefin. 1 to 40 parts by weight, preferably 2 to 40 parts by weight
It is 30 parts by weight. If the above-mentioned amount is less than 1 part by weight, the effect of improving adhesive strength will not be sufficient, and if it exceeds 40 parts by weight, heat resistance, strength, etc. may deteriorate depending on the use, purpose, etc., which is not preferable. Examples of the unsaturated carboxylic acids used in the present invention include monobasic acids and dibasic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, and citraconic acid. Examples of derivatives of unsaturated carboxylic acids include metal salts, amides, imides, esters, and anhydrides of the unsaturated carboxylic acids, and among these, maleic anhydride is most preferred. The amount of the unsaturated carboxylic acid or derivative thereof (hereinafter simply referred to as unsaturated carboxylic acid) is:
The amount of unsaturated carboxylic acid is 0.05 for the above polyolefin, rubber or polyolefin composition.
-5% by weight, preferably 0.1-3% by weight,
Preferably, the reaction is modified by heating in the presence of an organic peroxide. If the amount of unsaturated carboxylic acid exceeds 5% by weight, there is a risk that decomposition and crosslinking reactions will occur in addition to the addition reaction, and if it is less than 0.05% by weight, the adhesiveness will be insufficient and the purpose will not be achieved. . Examples of organic peroxides include penzoyl peroxide, lauryl peroxide, azobisisobutyronitrile, dicumyl peroxide, t-butyl hydroperoxide, α,
α'-bis(t-butylperoxydiisopropyl)benzene, di-t-butylperoxide,
2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne etc. are preferably used,
0.005 to 2.0 parts by weight per 100 parts by weight of the polyolefin, rubber or polyolefin composition,
It is preferably used in an amount of 0.01 to 1.0 parts by weight. If the amount of organic peroxide added is less than 0.005 parts by weight, the modification effect will not be substantially exhibited;
Even if more than 1 part by weight is added, it is difficult to obtain any further effect, and there is a risk of excessive decomposition or crosslinking reaction. The addition reaction of the unsaturated carboxylic acid can be carried out by melt-mixing in an extruder or a kneader such as a Banbury mixer in the absence of a solvent, or with aromatic hydrocarbons such as benzene, xylene, toluene, hexane, heptane, etc. There are methods such as heating and mixing in a solvent such as an aliphatic hydrocarbon such as octane to cause a reaction, but there are no particular limitations, such as ease of operation, excellent economic efficiency, continuity with subsequent processes, etc. Preferably, this is carried out in an extruder. In the present invention, each modified polyolefin, rubber, or polyolefin composition may be used as an adhesive as is, but these modified products may be diluted with the unmodified polyolefin or unmodified rubber to form an adhesive composition. It can also be used. For example, a method can be used in which the modified polyolefin is an unmodified rubber, and the modified rubber or modified polyolefin composition is diluted with the unmodified polyolefin. When diluting the adhesive composition, the amount of unsaturated carboxylic acid in the adhesive composition may be adjusted to within the range of 0.05 to 5.0% by weight, so that the adhesive composition can be applied without impairing adhesive properties. (7) Manufacturing method of laminated film Methods for manufacturing the laminated film of the present invention include an inflation method in which a multilayer die is used to join resin melted in an extruder at the die tip to form a laminated structure, a multilayer T-die method, etc. In addition to the coextrusion molding method, ordinary molding methods such as a multilayer blow molding method and an injection molding method can be applied, and are not particularly limited. The laminated structure of the film used in the present invention is preferably an olefin polymer composition/adhesive/gas barrier material/adhesive/olefin polymer composition. In addition, the thickness of the entire laminated film is 50 to 500 μm, but especially 70 to 500 μm.
A range of 200 μm is preferred. [Effects of the Invention] As explained above, the bag-in-box inner bag of the present invention has both surface layers made of a composition containing three types of specific ethylene/α-olefin copolymers, and a gas barrier layer. By using a film made by adhering and laminating a central layer made of a durable material, we can meet the basic requirements of inner bags for bag-in-boxes, such as water resistance, chemical resistance, oil resistance, solvent resistance, and oxygen barrier properties. It is possible to maintain the quality of the liquid content for a long time by fully satisfying the physical properties, and
In particular, it has an excellent balance among heat resistance, low-temperature heat-sealing strength, and blocking resistance, all of which are required for inner bags for gusset-type back-in-boxes. Therefore, the bag-in-box inner bag of the present invention can solve all the problems caused by wide temperature conditions, rough transportation conditions, etc., and the problem of mutual adhesion during storage of empty bags. It can be suitably used not only for blow molds but also particularly for gusset molds. [Examples and Comparative Examples] The present invention will be specifically described below based on Examples and Comparative Examples, but the present invention is not limited thereto. In addition, the properties in Examples and Comparative Examples were measured by the following method. (Heat resistance) Inner bag for bag-in-box (capacity 20) 5 pieces
The tubes were filled with hot water at 95°C and left to cool, and the presence or absence of damage such as peeling on the sealing surface was observed, and the number of damaged pieces out of 5 was calculated. (Drop test: low temperature heat seal strength) As a practical test of low temperature heat seal strength,
Bag-in-box inner bag (capacity 20) 5 for 5
The heat-sealed parts were filled with cold water at a temperature of °C and dropped onto the floor from a height of 90 cm to observe whether the heat-sealed parts were damaged or not. (Blocking resistance) Cut the film in the machine direction into short pieces with a width of 20 mm and a length of about 250 mm to use as test pieces.
I prepared a group. The inner surfaces were overlapped by a length of 50 mm, a 10 kg weight was placed on top of the overlapped test pieces, and the pieces were placed in an oven at 50°C for 5 hours, then taken out and subjected to a tensile test. Pulling speed 500mm/min,
The grip spacing was 150 mm, and the average value of the peel strength of 5 sets of test specimens was determined, and this value was classified into the following four levels. : Grade Peeling strength Blocking (Kg/20mm width) A: Less than 2.0 None B: 2.0 or more and less than 2.5 None C: 2.5 or more and less than 3.0, slightly present D: 3.0 or more, present Blocking resistance is indicated using the above grade symbol. Examples 1 to 9 and Comparative Examples 1 to 5 (Production of olefin polymer composition) Components (a), (b), and (c) of the olefin polymer composition used as both surface layers were prepared as follows. did. (a) Components: (A) Ethylene-butene-1 copolymer (density 0.920 g/cm ³ , MI 0.8 g/10 min; trade name: Nisseki Linirex AF1210, manufactured by Nippon Petrochemical Co., Ltd.) (B) Ethylene -Butene-1 copolymer (density 0.935 g/cm ³ , MI 2.0 g/10 min; trade name: Nisseki Linirex AF3710, manufactured by Nippon Petrochemical Co., Ltd.) (b) Components: Substantially anhydrous magnesium chloride, 1,2-
Using a solid catalyst component obtained from dichloroethane and titanium tetrachloride and a catalyst consisting of triethylaluminum, ethylene, butene-1 and propylene were polymerized to obtain a copolymer as shown below. (C) Ethylene-butene-1 copolymer (density 0.869 g/cm ³ , MI 0.9 g/10 min) (D) Ethylene-propylene copolymer (density 0.870 g/cm ³ , MI 0.9 g/10 min) Using a solid catalyst component obtained from anhydrous magnesium chloride, anthracene, and titanium tetrachloride and a catalyst consisting of triethylaluminum, ethylene, propylene, and butene-1 were polymerized to produce a copolymer as shown below. I got it. (E) Ethylene-propylene copolymer (density 0.890g/cm ³ , MI 1.0g/10min) (F) Ethylene-butene-1 copolymer (density 0.905g/cm ³ , MI 1.0g/10min) (c ) Component: (G) Ethylene-propylene-ethylidene norbornene copolymer rubber (EPDM) (density 0.86 g/cm ³ , Mooney viscosity (ML ₁₊₄ ,
100℃) 88; Product name: EP57P, Japan Synthetic Rubber
Co., Ltd.) (H) Ethylene-propylene copolymer rubber (EPR) (density 0.86 g/cm ³ , Mooney viscosity (ML ₁₊₄ ,
100℃) 70; Product name: EP07P, Japan Synthetic Rubber
Co., Ltd.) (I) Ethylene-vinyl acetate copolymer (EVA) (vinyl acetate content 15% by weight, MI 1.0g/
10min) (J) Polyisobutylene (PIB) (Product name: Vistanetx MML-120; manufactured by Etsuo Chemical Co., Ltd.) (K) Ethylene-propylene copolymer (density 0.88g/cm ³ , MI 0.44g/10min; Product name: Tafmar P-0680, Mitsui Petrochemical Industries, Ltd.
Components (a), (b), and (c) were dry-blended to a predetermined weight ratio to prepare an olefinic polymer composition, that is, materials for both surface layers.
Table 1 shows the types, physical properties, and amounts of components (a), (b), and (c) used. In Table 1, the C ₆ insoluble content indicates the boiling n-hexane insoluble content. (Gas barrier material) As a gas barrier material, saponified ethylene-vinyl acetate copolymer (product name: EVAL ED-F,
(manufactured by Kuraray Co., Ltd.) was used. (Adhesive) An adhesive manufactured as follows was used. Linear low-density polyethylene (ethylene-butene-
1 copolymer, density 0.922g/cm ³ , MI2.0g/
100 parts by weight of polyisobutylene (trade name: Vistanex MML-140; manufactured by Etsuo Chemical Co., Ltd.) is made into 100 parts by weight, and to this is added 0.2 parts by weight of maleic anhydride and organic peroxide (2 parts by weight). , 0.02 part by weight of 5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne),
A Banbury mixer was used to knead and react at 200°C for 15 minutes to obtain a modified product. (Manufacture of laminated film) The above-mentioned olefinic polymer composition, gas barrier material, and adhesive are supplied to a multilayer die, and the die temperature is
A five-layer film was produced by an inflation method at 220°C. The thickness of each layer of the laminated film is 60 μm for the olefin polymer composition layer, 10 μm for the adhesive layer, and 10 μm for the adhesive layer.
The gas barrier material layer was 10 μm thick, the adhesive layer was 10 μm thick, and the olefin polymer composition layer was 60 μm thick. (Manufacture of inner bag for bag-in-box) A gusset-type inner bag for bag-in-box with a capacity of 20 was manufactured by heat sealing using the above laminated film. Table 1 shows the evaluation results of the properties of the bag-in-box inner bag thus obtained.

【table】

【table】

[Table] As is clear from Table 1, Examples 1-
All of the bag-in-box inner bags No. 9 are excellent in heat resistance, low-temperature heat seal strength, and blocking resistance. In contrast,
Comparative Examples 1 to 5 in which any one of the components (a), (b), and (c) is outside the scope of the present invention are inferior in at least one of heat resistance, low-temperature heat seal strength, and blocking resistance. Recognize. Examples 10 to 13 The same olefin polymer composition as in Example 2 was used, the same gas barrier material as in Examples 1 to 9 was used, and the adhesive was prepared as follows. (Adhesive) Polyolefin (L) Linear low density polyethylene (LLDPE) (ethylene-butene-1 copolymer, density 0.922
g/ ^cm3 , MI2.0g/10min) Rubber (M) Polyisobutylene (PIB) (Product name: Vistanetx MML-140; manufactured by Etsuo Chemical Co., Ltd.) (N) Ethylene-propylene copolymer rubber (EPR) ( Density 0.860 g/cm ³ , MI 2.0 g/10 min; Product name: EP01P, manufactured by Nihon Gosei Rubber Co., Ltd.) Modification of polyolefin composition A mixture of 100 parts by weight of the above LLDPE and a predetermined amount of PIB or EPR was added to 100 parts by weight. To this, 0.2 parts by weight of maleic anhydride and 0.02 parts by weight of organic peroxide (2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne) were added,
The mixture was kneaded using a Banbury mixer at 200°C for 15 minutes to obtain an adhesive resin. Table 2 shows the composition of each component of the adhesive used. Furthermore, using these adhesives, laminated films were produced in the same manner as in Examples 1 to 9. A test piece with a width of 15 mm was prepared from the above laminated film, and an angle test piece was prepared using a Tensilon tensile tester.
Table 2 shows the interlayer peel strength when stretched at 180° and a tension speed of 50 mm/min. In addition, an inner bag (20) for a gusset type bag-in box was prepared using this laminated film, and the low-temperature heat sealing strength test was conducted. The results are also shown in Table 2.

[Table] As is clear from Table 2, the bag-in-box inner bags of Examples 10 to 13 all exhibited high adhesive interlayer peel strength, and as a result, they had excellent low-temperature heat sealing strength. I understand that.

Claims (1)

[Claims] 1. An inner bag for a bag-in-box using a laminated film formed by laminating both surface layers made of an olefin polymer composition and a central layer made of a gas-barrier material using an adhesive. In the above, the olefin polymer composition is (a) ethylene α having a density of 0.910 to 0.940 g/cm ³ .
- 55 to 90% by weight of an olefin copolymer;
~12 α-olefins, (i) density 0.860 g/cm ³ or more and less than 0.910 g/cm ³ ,
(ii) Maximum peak temperature measured by differential scanning calorimetry (DSC) of 100°C or higher; (iii) Ethylene α- with a boiling n-hexane insoluble content of 10% by weight or higher.
5 to 35% by weight of olefin copolymer, and (c) ethylene/α-olefin copolymer rubber,
An inner bag for a bag-in-box characterized by comprising 5 to 15% by weight of one or more selected from polyisobutylene and ethylene-vinyl acetate copolymer. 2. The bag-in-box inner bag according to claim 1, wherein the component (c) is ethylene-propylene copolymer rubber or ethylene-propylene-nonconjugated diene copolymer rubber. 3. The bag-in-box inner bag according to claim 1 or 2, wherein the gas barrier material is a saponified ethylene-vinyl acetate copolymer. 4. The bag-in-box inner bag according to any one of claims 1 to 3, wherein the adhesive is a polymer containing modified polyolefin. 5. The bag-in-box inner bag according to claim 4, wherein the modified polyolefin is modified with an unsaturated carboxylic acid or a derivative thereof. 6 The unsaturated carboxylic acid or its derivative is
The inner bag for a bag-in-box according to claim 5, which is maleic anhydride.