JPS5817026B2 - Thai Netsuseihousou Thainoseizohouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a package that has excellent heat resistance and can withstand retort processing. More specifically, in a package formed by laminating a polyester film or a printed polyester film on one side of a metal foil, and laminating a film made of a heat-sealable resin mainly composed of polyolefin on the other side of the metal foil, linear The present invention relates to a method for producing a heat-resistant package using an adhesive made of a mixture of thermoplastic copolyester and at least a trifunctional isocyanate compound.

Recently, food hygiene issues have been attracting the attention of many people due to a series of moves accompanying the ban on the use of preservatives.

Against this background, retort processing using pressure sterilization pots has been actively studied and is being implemented for the purpose of extending the preservability and shelf life of foods.

Generally, the time required to kill spore bacteria depends on the time and temperature of the retort treatment, and the higher the temperature, the shorter the time for sterilization.

However, such retort processing is performed under more extreme conditions at higher temperatures than in conventional boiling applications, and in addition, from the viewpoint of long-term storage, a structure in which metal foil is used as an intermediate layer as in the structure of the present invention is required. is suitable and is used by taking advantage of the excellent physical properties of metal foil.

This metal foil has better heat resistance than plastic film.

On the other hand, even if plastic film is usually biaxially stretched, it shrinks when subjected to retort treatment, and when combined with aluminum foil, stress concentration occurs at the adhesive interface, resulting in delamination or adhesive strength during retort treatment. There are many problems such as a decrease in

The inventors of the present invention improved these drawbacks and conducted intensive studies on a method for manufacturing an excellent heat-resistant packaging body, and as a result, they arrived at the present invention.

That is, the first invention produces a heat-resistant package in which a polyester film I is laminated on one side of a metal foil H, and a heat-sealable resin film (I) mainly composed of polyolefin is laminated on the other side of the metal foil H. A method for producing a heat-resistant packaging body, which is characterized in that polyester film I and metal foil ■ and metal foil ■ and heat-sealable resin film ■ are adhered using the following adhesive and cured. .

Adhesive: Linear copolymerized polyester A having a softening point of 200°C or less and composed of dibasic acid (however, 30 mol% or more of the dibasic acid is terephthalic acid) residue and glycol residue. and at least 3 active incyanate groups
The linear copolymerized polyester A100 is composed of an incyanate compound B, which has an incyanate group (NCO)/(OH,l) ratio of 1 to 10 per hydroxyl group, and a linear copolymerized polyester A100.
Adhesion R consists of a range in which the amount of isocyanate compound B does not exceed 50 parts by weight.Furthermore, in the second aspect of the present invention, a printing ink layer (■) is formed on one side of the metal foil (■), and a polyester film 1 is placed on the surface of the printing ink layer. In the method for producing a heat-resistant packaging body by laminating a heat-sealable resin film mainly composed of polyolefin on the other side of the metal foil ■, the printing ink layer ■, the metal foil H, and the metal foil H This is a method for producing a heat-resistant packaging body, which is characterized in that a heat-sealable resin film (1) and a heat-sealable resin film (2) are bonded together using the above-mentioned adhesive and then cured.

Polyester film I in the present invention is a dibasic acid (however, 85 mol% or more of the dibasic acid is terephthalic acid)
The film may be an unstretched film, a uniaxially oriented film, or a biaxially oriented film formed from a polymer consisting of a residue and a glycol residue, and a biaxially oriented film is particularly useful.

Less than 15 mol% of the dibasic acid component of the polyester is
It may be composed of isophthalic acid, biphenyldicarboxylic acid, adipic acid, etc.

The glycol component is composed of ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, etc.

Residues of oxyacids such as p-oxybenzoic acid may be present in place of dibasic acid components other than terephthalic acid.

Polymers particularly useful as polyester film I include, but are not limited to, polyethylene terephthalate, polypropylene terephthalate, polytetramethylene terephthalate, and the like.

However, films made of polyester having a melting point of 200° C. or higher are usually useful.

Its thickness is generally 6-50μ, preferably 12-2μ
A 5μ biaxially stretched film is preferred.

The metal foil ■ used for the center layer is aluminum, copper, etc.
Its thickness is 3-50μ, preferably 6-15μ.

The metal foil may be subjected to any surface treatment such as cleaning with a solvent or the like, application of a coating agent, etc. to the surface of the metal foil in order to improve the adhesion of the package.

The polyolefin film used as the inner layer material is mainly composed of a resin obtained by polymerizing a monomer represented by the general formula: C) I2=CH (R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms). Examples include polyethylene, polypropylene, polybutene-1, poly-4-
Methylpentene-1 etc. can be used.

In addition, to these basic trees and fingers, inorganic substances such as ethylene-propylene copolymer, conjugated diene hydrocarbon resin and polyolefin are added to an extent that does not impair the physical properties, antioxidants,
There is no problem with adding antistatic agents, etc.

Furthermore, the m=component of the adhesive constituting the present invention has a softening point (according to JIS-2531-60 (ring and ball method)) of 222°C or less and a dibasic acid (however, 3 of the dibasic acids
The linear copolymerized polyester A is composed of 0 mol % or more of terephthalic acid residues and glycol residues.

It is particularly preferable that the linear copolymerized polyester A has a softening point of 80 to 180°C.

The linear copolymerized polyester A is preferably a polymer that is soluble at a resin concentration of 10% or more when dissolved in chloroform under reflux at the boiling point.

The linear copolymerized polyester A of the present invention contains a terephthalic acid residue of 30 mol% or more of the dibasic acid component.

Usually, when the dibasic acid component consists of two components, terephthalic acid and another dibasic acid, 95 to 50 mol% of the dibasic acid component is a terephthalic acid residue, and the dibasic acid component is terephthalic acid. , isophthalic acid and other dibasic acids, 95 to 30 mol% of the dibasic acid is terephthalic acid, but this is due to the composition of one or more glycol residues forming the glycol component. The ratio is appropriately determined so as to satisfy the above softening point range.

Generally, 20 to 70 mol% of the glycol component is composed of ethylene glycol residues, but this may be adjusted depending on the composition ratio of the dibasic acid component used to satisfy the above softening point range. determined.

Here, the remaining less than 70 mol% of the dibasic acid component is one or two types of aromatic dibasic acids such as adipic acid, sebacic acid, other aliphatic dibasic acids, isophthalic acid, orthophthalic acid, and diphenyldicarboxylic acid. Consists of more than one species of dibasic acid residues.

In addition to ethylene glycol, glycol components include 1,
2-propylene glycol, ■, 3-propylene glycol, ■, 4-butanediol, diethylene glycol, triethylene glycol, cyfropylene glycol,
It consists of one or more types of glycol residues such as neopentyl glycol.

Furthermore, a residue of an oxyacid such as p-oxybenzoic acid may be present in place of the dibasic acid residue component other than the terephthalic acid residue.

The linear copolymerized polyester A used in the present invention is also typically soluble in organic solvents.

Suitable organic solvents include chloroform, dioxane, tetrahydrofuran, methyl ethyl ketone, ethyl acetate, benzene, toluene, xylene, etc., but it may not be soluble in all of these solvents.

If the terephthalic acid component as an acid component in the linear copolymerized polyester A used in the present invention is less than 30 mol%, the heat resistance as an adhesive for retorts will be low, which is not preferable.

In addition, the ethylene glycol residue of the glycol component is 70
If the amount is more than mol % or less than 20 mol %, the solubility of the copolyester in organic solvents may decrease.

The molecular weight of the linear copolymerized polyester is 3 in reduced viscosity (phenol/tetrachloroethane-60740 (weight ratio)).
It is suitable that the value falls within the range of 0.4 to 1.2 dl/f when measured at 0°C.

The concentration of terminal functional groups (hydroxyl group, carboxyl group) is 10 to 600 equivalents/1σ in terms of hydroxyl group equivalents. It is preferable to use cashier/decorate.

More preferably, it is 30 to 300 equivalents/106f resin.

The isocyanate compound B used in the present invention is a polyvalent isocyanate compound containing at least three active incyanates, such as diisocyanate such as tetramethylene diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, etc., and a terminal group such as trimethylolpropane. There are reaction products with compounds having hydroxyl groups and amine groups, and specifically, the reaction products of 3 moles of trimethylolpropane and 17 moles of tolylene diisocyanate, 3 moles of trimethylolpropane, and hexamethylene. Reaction products with 1 mol of diisocyanate are preferred.

The mixing ratio of the linear copolymerized polyester A and the incyanate compound B is 1 to 10° in terms of the isocyanate group per hydroxyl group (NCO group, l/(OH group); the mixing ratio of B to A is B/A= The adhesive mixture is not more than 50/100.

In the mixing ratio of B to A, (NCO group)/[OH
When the number [group] is less than 1, heat resistance is poor, resulting in delamination during retort processing and a decrease in adhesive strength after retort treatment, and when it exceeds 10, of course, there is a decrease in adhesive strength. After the retort treatment, a phenomenon in which the metal foil becomes colored is observed.

Although the cause of this is not certain, it is presumed to be the influence ν of the isocyanate compound B which does not react with the linear copolymerized polyester A.

The mixing ratio of B to A is within the range of B/A = 50/100, but as the ratio of incyanate compound in the adhesive mixture increases, the adhesive strength decreases as the linear copolymerized polyester component A decreases. Due to the decrease in the hardness of the adhesive and the increase in the hardness of the adhesive as the amount of incyanate compound B increases by 1, this causes stress concentration at the adhesive interface, reducing the adhesive strength or discoloring the metal foil. It is not preferred as an adhesive for the present invention.

The method for obtaining the package of the present invention is to dissolve the adhesive resin mixture in a solvent and apply the polyvarnish film I onto the metal foil H using a conventional coating method such as a gravure roll, a kiss roll, or a reverse roll. A laminated film of polyester film 1 and metal foil H is produced by coating and drying to form an adhesive layer.Next, an adhesive resin layer is similarly formed on the other side of the metal foil laminated with this polyester, and polyolefin is coated and dried to form an adhesive layer. Laminated with other films.

The thickness of the adhesive layer formed between each layer is 1 in solid coating amount.
~1097 m2, preferably 2 to 5 g/m', and can be selected depending on the purpose of the package used, retort conditions, and type of contents.

If the amount of adhesive applied is small, especially when filled with food containing oil, the adhesive strength between the metal foil (2) and the inner layer material (2) may decrease significantly after retort processing.

When melting and applying the adhesive, the resin concentration and application method are set so that the above-mentioned application amount is selected.

A relatively easy method is to use linear copolymerized polyester A
WoI-Luene/Methyl ethyl ketone (4 layers, 1 layer!-ratio)
20 to 30 after mixing with isocyanate compound B.
An adhesive solution of about 100% is prepared and applied with a gravure roll of about 30 to 80μ in 100 to 150 meshes, and the solvent is dried to form an adhesive layer.

So-called dry lamination is suitable for the method of bonding two layers together using the formed adhesive layer.

The conditions for dry lamination also have a significant effect on adhesion and are important requirements.

Specific conditions include nip roll temperature of 70 to 120°C;
The pressure between the nip rolls is 1 to 7 kg/cyrt, which is within the range of normal dry lamination conditions.

If the nip roll temperature is low, sufficient adhesive strength will not be developed, and the laminated films may tunnel after dry lamination.

Also, the higher the temperature, the higher the temperature that will not cause heat shrinkage of the film used.

Preferably, "wrinkles" will not occur at temperatures close to the limit of heat shrinkage.
occurs, which is not very desirable.

Additionally, composite laminates require a curing step to complete adhesive reactivity and impart heat resistance.

Curing conditions are not particularly limited, but generally 30~
It is carried out at 80°C, preferably 40 to 60°C, for 7 to 2 days or more.

Needless to say, insufficient curing impairs the heat resistance of the adhesive and causes delamination during retort.

On the other hand, when curing at high temperatures, if heat is applied before adhesion is fully completed, "slippage" occurs due to the lamination of different materials with different stress relaxation rates, resulting in tunneling.

Further, the humidity in the curing room must be kept low.

It is presumed that under high humidity conditions, the isocyanate compound B in the adhesive reacts with moisture, so that the reaction with the thermoplastic polyester copolymer A does not proceed, and its properties are not exhibited.

If it is desired to print on the bag, printing is performed on the outermost polyester film I using a generally commercially available heat-resistant polyester ink under normal industrial conditions.

The printing ink is Lamipack E1 manufactured by Toyo Ink.
Lamipack EH.

Examples include Lamipack Ny-B, Lamipack RET, Dainippon Ink, NES, CVL-PR, etc. manufactured by Nippon Ink.

The thickness of the printing ink layer (1) varies depending on the printed pattern, but is 0.5 to 5 g/m2, preferably 1 to 3 g/m' in terms of solid coating amount, but is not particularly limited.

An adhesive is applied to the printed surface (2) or an adhesive is formed on the metal foil (2), and the polyester film I and the metal foil (2) are laminated with the printed ff11V as an intermediate layer.

The stacked packages as described above are made into bags of a predetermined size using a bag-making machine such as a three-sided sealer, filled with the desired food, and top-sealed (deaerated and top-sealed if necessary). , can be provided as a test sample,
As a food model substance, it can be filled with water, oil, a mixture of water and oil, vinegar, etc. and used as a sample.

The filled packages are generally retorted.

As the retort treatment method, either the pressurized steam method or the pressurized hot water method can be used without any problems, and the retort treatment can be carried out by a commonly used method.

According to the method of the present invention, a beautiful package with excellent heat resistance and no change in appearance such as delamination can be obtained after retort treatment.

In particular, there is very little decrease in adhesive strength before and after retort treatment.

Furthermore, the heat-sealed portion made of a heat-sealable resin film mainly composed of polyolefin maintains sufficient sealing strength and excellent sealing performance even after retort treatment.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 80 mol% of terephthalic acid and 20 mol% of sebacic acid as dibasic acid components, 60% of ethylene glycol as glycol component (reduced viscosity 0.8 dll?, hydroxyl value 100 equivalents/10
6? Resin, softening point (JISK/2537 ring and ball method) 12
0° C.) and the reaction product of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane were mixed in various proportions to give a 25% strength solution of triene/methyl ethyl ketone (4/1 weight ratio 9).

The above adhesive was applied to a biaxially stretched polyester film (thickness 12μ) using a gravure roll (60μ for 100 meshes) so that the solid content amount was 3.517m2.
The solvent was removed through a 2 m drying oven at 80°C at a speed of m/- to form an adhesive layer.

Next, the coated surface of the polyester film 18 and a soft aluminum foil having a thickness of 9 μm were laminated at a pressure of 4 kg/cvi between a metal roll heated to 90 to 100° C. and a rubber roll for pressure, and then rolled up.

Next, the above-mentioned adhesive layer was formed on the aluminum foil of this laminate, and the corona-treated surface of unstretched polypropylene with a thickness of 50μ, which had been formed in advance from M■-10 polypropylene, was bonded to the polyester film. It was crimped under the same crimping conditions as in the case of , and then rolled up.

The obtained laminate was cured at 40° C. (10% RH) for 5 days.

A three-sided sealed bag with a packaging bag size of 12 crrL in length and 8 crrL in width was prepared using a three-sided seal type bag-making machine manufactured by Tokyo Automatic Co., Ltd. at a sealing temperature of 200° C. and a bag-making speed of 40 bags/min.

This bag contains 80 liters of water or 50 liters of salad oil. was filled, top-sealed, and sealed.

The obtained sample was subjected to retort treatment in a pressurized hot water type retort pot under the following conditions.

Pot internal pressure 2.3 kg/cyrt, air pressure 3.3 kg
/crtt, retort temperature 135°C, time 30 minutes, molecular time 3 minutes, cooling time 6 minutes The adhesiveness of the obtained package was measured.

Figure 1 shows the adhesive strength between the outer layer polyester film and aluminum foil, and Figure 2 shows the adhesive strength between the inner layer unstretched polypropylene film and aluminum foil.

As is clear from FIG. 1, when the (NCO)/(OH) ratio was in the range of 1 to 10, no delamination occurred during retort treatment, no staining, and no coloring of the aluminum foil, which was preferable.

In areas where delamination occurs, cohesive failure of the adhesive occurs during peel strength measurement, suggesting that the adhesive has insufficient heat resistance.

The adhesive strength between aluminum foil and unstretched film is (, NC0
)/(OH) ratio was in the range of 1 to 10, retort treatment was suitable, and the amount of the isocyanate compound added was 23 parts.

If there is a large amount of isocyanate compounds, coloring of the aluminum foil will occur, and if there is a small amount of incyanate compounds, delamination will occur.

Example 2 Samples having the configuration of Example 1 with various amounts of adhesive applied were prepared and filled with 70 cc of water and 10 cc of salad oil to prepare retort samples.

The peel strength after retort treatment at 135° C. for 30 minutes was measured and is shown in FIG.

The composition of the adhesive is as follows.

Linear copolymerized polyester of Example 1 100 parts Trimethylolpropane-tolylene diincyanate reaction product 115 parts (NCO
)/(OH)=5 If the coating amount is small, the strength after retort treatment will be extremely low;
2′? /m2 or more is preferable.

There is no particular problem with a higher coating amount, but if drying problems are taken into consideration, a coating amount of 2 to 51/m2 is preferable.

Example 3 One side of a polyester film (thickness 12μ) was coated with NES (revised) (white) ink manufactured by Dainippon Ink at a solid coating amount of 2.8? / m2 gravure printed 3
Dry at 80 °C and 2 m oven length at a speed of 0 m /mjR,
Next, using the same adhesive as in Example 2, polyester film/printed layer/adhesive/aluminum foil/adhesive/unstretched polypropylene film (thickness 12μ/2-8?/
m2/3-5? / m7 thickness 9μ/3.5? /m
A laminate having a configuration of 2/thickness of 50 μm was created.

A bag was made from this laminate, filled with 30 cc of water, and subjected to retort treatment according to Example 1.

Table 1 shows the physical properties of the obtained package. In the table, Es:
Polyester film printing: Printing layer Al Nialuminum foil Cp: Unstretched polypropylene film Polyester film/Printing layer/
There was no problem with the adhesiveness at the adhesive layer/aluminum foil interface, and no trouble occurred between the printing ink and the adhesive.

[Brief explanation of the drawing]

Figure 1 shows the adhesive strength between polyester film and aluminum foil. FIG. 2 shows the adhesive strength between aluminum foil and unstretched polypropylene film. FIG. 3 shows the relationship between adhesive application amount and adhesive strength.

Claims (1)

[Claims] 1. A heat-resistant package is produced by laminating a polyester film I on one side of a metal foil H, and laminating a heat-sealable resin film (mainly made of polyolefin) on the other side of the metal foil H. A method for producing a heat-resistant packaging body, which comprises bonding polyester film 1 and metal foil (1) and metal foil (2) and heat-sealable resin film (2) using the following adhesive and curing. Adhesive: A linear copolymerized polyester having a softening point of 200° C. or lower and composed of a dibasic acid (however, 30 mol% or more of the dibasic acid is terephthalic acid) residue and a glycol residue; A and an incyanate compound/B having at least three active isocyanate groups, the ratio of incyanate groups (NCO)/(OH,I per hydroxyl group is 1 to 10, and a linear copolymerized polyester A1
The amount of incyanate compound B based on 00 parts by weight is 50 parts by weight.
Adhesive consisting of not more than parts by weight. 2. A printing ink layer (■) and a polyester film (I) are laminated on one side of the metal foil (2), and a polyester film (I) is laminated on the surface of the printing ink layer (2), and a heat-sealable resin film (I) mainly composed of polyolefin is laminated on the other side of the metal foil (2). A method for producing a heat-resistant packaging body characterized by adhering a printing ink layer (■) and a metal foil (■) and a metal foil (■) and a heat-sealable resin film (■) using the following adhesive and curing. Method for manufacturing a package Adhesive: Same as that described in claim 1.