JPH0724973A - Laminate with easy layer peeling treatment - Google Patents

Abstract

PURPOSE:To recover and reutilize a resin layer, pulp paper and aluminum foil by separating them by an alkali aq. soln. by integrating a laminate through an adhesive layer having a specific melt flow rate. CONSTITUTION:An ethylene copolymer layer consisting of 80-94mol% of ethylene and 20-6mol% of alpha,beta-unsaturated carboxylic acid and having a melt flow rate of 320-1500g/10min is bonded to the surface of a base material layer. A pulp paper base material and a thermoplastic resin layer with a melt flow rate of 0.05-150g/10-min are integrated through an adhesive layer composed of an ethylene copolymer consisting of 80-94mol% of ethylene and 20-6mol% of alpha,beta-unsaturated carboxylic acid and having a melt flow rate of 320-1500g/10min. This laminate forms a water soluble alkali metal salt of the ethylene/alpha,beta-unsaturated carboxylic acid copolymer and the resin layer is peeled from the base material layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate useful as a packaging material for milk pack containers, fruit drink pack containers, snack confectionery packaging bags, bonito pack bags and the like. After being used, this laminate can be easily separated into a resin layer, pulp paper, aluminum foil, etc. by immersing it in an alkaline aqueous solution, and there is an advantage that these can be collected and reused.

[0002]

2. Description of the Related Art Polyethylene laminated aluminum foil is used as a packaging bag for snacks. Also,
Polyethylene laminated carton paper as a milk container,
As a fruit juice container, a carton paper / polyethylene / aluminum foil / polyethylene laminate is used as a packaging material.

In recent years, the recognition of recycling of packaging materials has been increasing from the viewpoint of environmental protection. However, for laminated packaging materials consisting of a laminate of various dissimilar materials, peeling between the layers is difficult, and in some cases, a low-density polyethylene film is directly melt-extruded and laminated on the surface of the pulp paper base material layer to form a laminated milk package container. Excluding recycling of pulp paper
The current situation is that they are either landfilled or incinerated.

The peeling of the pulp paper and the low-density polyethylene laminate film from the milk pack container for recovering the pulp fiber for waste paper generally uses a chemical treatment (alkali, surfactant, etc.) and a mechanical treatment in combination. However, at present, there is a problem that productivity is poor because mechanical processing requires a long time. On the other hand, in the case of incinerating a laminated packaging material as well, there is a problem in that molten aluminum adheres to the incinerator wall in the case of a laminate using an aluminum foil.

In the former method of separating chemical treatment and mechanical treatment, JP-A-4-211932 discloses a laminated paper comprising a pulp paper base material and a polyethylene film layer, and between the both layers, It is proposed to interpose an adhesion / peel adjustment agent. In this laminated paper, (a) a polyvinyl alcohol, a partially saponified ethylene / vinyl acetate copolymer, a hydrophilic polymer such as polyacrylic acid, etc.
A mixture of (b) a copolymer of an organic silane compound having a hydroxyl group such as polymethylhydrogensiloxane and an α-olefin and (c) a surfactant is mentioned.

This laminated paper is dipped in an aqueous sodium hydroxide solution having a pH of 12, and this is applied to a mechanical mixer for 12 hours.
After peeling by stirring for 1 minute, the pH is adjusted to 9 by adding sulfuric acid, and then 0.7% sodium hypochlorite is used as effective chlorine.
When added and stirred for 3 minutes, the pulp paper and polyethylene film are completely separated. In the laminated paper of this publication, the separation of the pulp paper and the laminated film can be performed in a short time, but the interlayer adhesion strength is low due to the poor water resistance of the adhesion / peelability modifier, and the container formed of this laminated paper When an aqueous solution of milk or the like is stored therein, there is a drawback that it cannot be used for applications in which the adhesive force between layers is further reduced due to the water vapor that permeates the laminated paper and the pressure of the contents rises.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a laminate having a high adhesive force between the respective layers and not peeling between layers in an acidic or neutral aqueous solution, but peeling between layers only in an alkaline aqueous solution. To aim.

[0008]

The first aspect of the present invention is as follows.
An ethylene copolymer of 80 to 94 mol% of ethylene and 20 to 6 mol% of α, β-unsaturated carboxylic acid on the surface of the base material layer (A), and having a melt flow rate of 3
It is intended to provide a laminate having an ethylene copolymer layer of 20 to 1500 g / 10 minutes bonded thereto.

A second aspect of the present invention is a pulp paper base material layer (A).
And a thermoplastic resin layer (C) having a melt flow rate of 0.05 to 100 g / 10 min have an ethylene co-weight of 80 to 94 mol% ethylene and 20 to 6 mol% α, β-unsaturated carboxylic acid. The present invention provides a laminated body which is a united body and is integrated via an adhesive layer (B) having a melt flow rate of 320 to 1500 g / 10 minutes.

[0010]

[Function] When the laminate is dipped in an alkaline aqueous solution and stirred, the carboxyl groups of the ethylene / α, β-unsaturated carboxylic acid copolymer in the adhesive layer react with the alkali to form water-soluble ethylene / α, β. -The alkali metal salt of the unsaturated carboxylic acid copolymer is formed, and the resin layer and the base material layer are easily separated.

[0011]

DETAILED DESCRIPTION OF THE INVENTION Base material layer (A) The base material layer includes pulp paper (kraft paper, high-quality paper, glassine paper, parchment paper, rayon paper, coated paper, etc.),
Aluminum foil, polypropylene biaxially stretched film or polyethylene terephthalate biaxially stretched film with aluminum vapor deposited on the surface, melt flow rate (JIS
K7210) is 0.1 to 150 g / 10 minutes, preferably 5 to 50 g / 10 minutes, as the thermoplastic resin, propylene homopolymer, propylene as a main component, and ethylene, butene-1, hexene-1, Penten-1, 4-
One or two α-olefins such as methylpentene-1
Propylene resin such as copolymer with more than one kind (MFR is 2
Measured at 30 ° C. under a load of 2.16 kg); ethylene homopolymer, mainly composed of ethylene and other vinyl monomers,
For example, propylene, butene-1, hexene-1, octene-1, vinyl acetate, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid One or more ethylene copolymers such as butyl, styrene, acrylamide, acrylonitrile, and maleic acid (MFR is 190
(Measured under conditions of temperature and 2.16 kg load); polyamide, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride and the like. These may be stretched. The thickness of the base material layer is 6
~ 1000 microns (μm), preferably 10-500
μm.

Ethylene Copolymer (B) The ethylene copolymer used in the adhesive layer of the present invention is essentially insoluble in water and becomes water-dispersible only after an alkali treatment. % And an α, β-unsaturated carboxylic acid 20 to 6 mol%, an ethylene copolymer obtained by copolymerizing the melt flow rate (JIS
K7210; 190 ° C, test load 2.16 kgf) is 3
20 to 1500 g / 10 minutes, preferably 340 to 150
It is 0 g / 10 minutes.

Specific examples of α, β-unsaturated carboxylic acids include monobasic acids such as acrylic acid, methacrylic acid and crotonic acid, fumaric acid, maleic acid, and anhydrous dibasic acids such as maleic acid and itaconic acid. Can be mentioned. Among these, acrylic acid and methacrylic acid are preferable. Regarding the α, β-unsaturated carboxylic acid content, when the amount is less than 6 mol%, sufficient releasability between the base material layer and the laminate film layer cannot be obtained when treated with alkali, and conversely 20 When the content is higher than the mol%, the tackiness of the ethylene copolymer increases, and the handling and processability thereof deteriorate. Preferably, the amount of α, β-unsaturated carboxylic acid is 6 to 15 mol%. When the melt flow rate of the ethylene copolymer is lower than 320 g / 10 minutes, when the laminate is treated with alkali, sufficient peeling is not performed, and conversely, when it is higher than 1500 g / 10 minutes,
The melt viscoelasticity becomes too small, the laminating workability is poor, and the tensile strength of the material becomes weak.

The ethylene copolymer used in the adhesive layer (B) of the present invention is, in addition to the above-mentioned ethylene and α, β-unsaturated carboxylic acid, a monomer copolymerizable with these monomers,
For example, other monomers such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, vinyl acetate, and phenylmaleimide can be used in an amount of 12 mol% or less. It may be copolymerized at a ratio.

This copolymer is prepared by mixing these monomers in the presence of a radical polymerization catalyst and a solvent at 150 to 300 ° C. and 1,0.
It is produced by radical polymerization under a pressure of 00 to 3,000 kg / cm ² . As the radical polymerization catalyst, for example, ditertiary butyl peroxide, tertiary butyl cumyl peroxide, dicumyl peroxide, isobutyl peroxide, cyclohexanone peroxide, cumene hydroperoxide, etc. are used.

As the solvent, hexane, heptane, toluene, mineral split, etc. can be used. The thickness of the copolymer adhesive layer is 2 to 200 μm, preferably 10 to 6
It is 0 μm. The laminated body may further include other layers in addition to the two-layer structure of the base material layer (A) and the ethylene copolymer layer (B). For example, a three-layer structure laminate of base material layer (A) / ethylene copolymer layer (B) / resin layer (C), paper base material layer (A) / ethylene copolymer layer (B) / aluminum foil base material It is a laminate having a four-layer structure of layer (A) / ethylene copolymer layer (B).

Resin Layer (C) This resin layer is often used for the purpose of imparting gas barrier property, low temperature heat seal property, gloss to the laminate.
Such a resin has a melt flow rate of 0.01 to
The thermoplastic resin of 150 g / 10 minutes, specifically, the above-mentioned ethylene resin, propylene resin, polyamide, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride and the like can be mentioned.
These may be stretched.

Of these, propylene-based resins and ethylene-based resins are inexpensive and can be heat-sealed at a lower temperature when forming a bag or carton container than a laminate.
It has the advantage of increasing productivity. The thickness of the resin layer (C) is 1
˜500 μm, preferably 2 to 40 μm. Each layer is, if necessary, an antioxidant, a lubricant,
It may contain an antistatic agent, a weather resistance agent, an anti-UV agent, a surfactant, an antifogging agent and the like.

Method for Producing Laminate As a method for producing a laminate, a method of extrusion laminating the ethylene copolymer (B) on the surface of the base material layer, an aqueous dispersion of the ethylene copolymer (B) as a base material A method of coating and drying the layer, a method of coextruding the ethylene copolymer (B) and the resin layer (C) from a die and laminating the layer on the base material layer (A), and a method of forming a molten film of the ethylene copolymer (B) A method of introducing between the material layer (A) and the resin film layer (C) and performing sandwich lamination, using the ethylene copolymer (B) as a hot melt agent, and forming the base material layer (A) or the resin laminate layer (C). ), The other layer is laminated, the ethylene copolymer (B) is treated with an alkali to give an aqueous dispersion, and the aqueous dispersion is applied to the base material layer (A). Method of laminating resin layer (C) It can be applied.

As a laminating method, generally used extrusion laminating, dry laminating, wet laminating, heat laminating, hot melt laminating, non-solvent laminating can be applied. When the extrusion laminating method is applied, an anchor coating agent, flame treatment, corona treatment, plasma treatment, or ozone treatment may be applied to any one layer or two or more layers, if necessary.

Peeling, Separation, and Recovery Method of Each Layer Material As a method of peeling, separation, and recovery of each layer material of the laminated body, for example, the laminated body is required to be immersed in 0.025 wt% sodium hydroxide aqueous solution at a temperature of 50 ° C. According to the method, a method of stirring using a mixer to peel off each layer, and then separating and collecting by the density difference can be applied. Also, as described above, like the conventional peeling of milk container layers, after alkaline treatment, sulfuric acid was added to bring the pH to 9, and then sodium hypochlorite was added as effective chlorine at 0.7%, and the number was adjusted again. Separation of the laminated film layer and pulp paper may be completed by stirring for a minute. The collected layer materials are recycled, incinerated, or landfilled according to the purpose.

[0022]

【Example】

Reference Example 1 (Production of ethylene copolymer) Using a tank reactor with a stirrer, ethylene, acrylic acid,
Polymerization initiator and chain transfer agent are continuously supplied, polymerization pressure is 1800 to 2500 kg / cm ² , polymerization temperature is 190 to ²
Polymerization was carried out at 30 ° C. to obtain various ethylene / acrylic acid copolymers shown in Table 1. Table 1 shows the physical properties of the obtained copolymer.

[0023]

[Table 1]

Reference Example 2 (Production Method of Aqueous Dispersion) 125 g of each of the ethylene copolymers A to E obtained above and acryl of the copolymer were placed in a tank-type reactor equipped with a stirrer and having an inner volume of 1 liter. After adding 25% ammonia water so that the degree of ammonia neutralization of the acid based on the acid constitutional unit becomes 70 mol%, distilled water is added to make 500 g, and the ethylene copolymer is stirred at 100 ° C. for 2 hours. Aqueous dispersions of polymers AE were prepared. The aqueous dispersion prepared from the ethylene copolymer C has a high viscosity at room temperature and has no fluidity, and therefore, distilled water was added to dilute the aqueous dispersion twice.

Production Examples of Laminated Examples Examples 1 to 5 Kraft paper (basis weight: 75 g / m ² ) was used as a base material, and the aqueous dispersions A to E obtained in Reference Example 2 were kraft paper using a bar coater. After being applied to the surface, the kraft paper was dried and wound up to obtain a kraft paper substrate having the ethylene copolymer adhesive layer provided on the paper surface. The thickness of the adhesive layer was 5 μm. Next, after subjecting the adhesive surface of the kraft paper base material to a corona treatment of 50 W / hour, low density polyethylene (melt flow rate 6 g / 10 min, density 0.920 g / cm ³ ) was applied directly under the die at a resin temperature of 325 ° C. Then, extrusion lamination was performed with a thickness of 30 μm to prepare a laminate in which an ethylene copolymer adhesive layer was interposed between the kraft paper substrate and the low density polyethylene film layer.

Comparative Example 1 Polyvinyl alcohol (manufactured by Unitika Ltd., Poval UF0) was placed in a tank reactor similar to that used in Reference Example 2.
50G: Saponification degree 98.5 mol% or more, viscosity 4.5-
6.5 cps (4% -20 ° C) H 100 g, distilled water 4
An aqueous polyvinyl alcohol solution was prepared by adding 00 g and stirring at 100 ° C. for 1 hour. Further, using the aqueous solution, a polyvinyl alcohol layer was formed on the kraft paper under the same conditions as in Example 1 and then subjected to corona treatment, and extrusion laminated with low density polyethylene to laminate polyvinyl alcohol between the paper and polyethylene. Got

Comparative Example 2 Low density polyethylene was extrusion-laminated on kraft paper under the same conditions as in Example 1 without using the aqueous dispersion to obtain a kraft paper / polyethylene film laminate.

Peelability Test Using the laminates of Examples 1 to 5 and Comparative Examples 1 and 2 described above, a peeling test was performed between the kraft pulp paper and the polyethylene film layer by the following method. 15mm x 20 for the laminate
cm sample strips, base layer (kraft paper)
After peeling a little between the resin layer (polyethylene or the ethylene copolymer), it is vertically dipped in a volumetric flask containing 0.025% aqueous sodium hydroxide solution at a temperature of 50 ° C, and the peeled kraft paper surface is placed on top. Fixed on the polyethylene film or ethylene copolymer film surface.
The peelability of the film in the alkaline aqueous solution was evaluated by applying a load of 3 g and measuring the time until peeling by 10 cm. The pH of the alkaline aqueous solution was 11.5. As a comparison, the same evaluation in distilled water was performed.

Water resistance test of packaging When the laminate is actually used as a packaging containing contents such as water, the adhesive layer interposed between the base material layer and the laminate (sealant) layer is a sealant layer. It is important that the water vapor that passes through does not reduce the adhesion. Therefore, the water resistance test method of the packaging material was performed by the following method. 12 cm long and 13 c wide containing 30 ml of distilled water from the laminate
A four-sided sealed package of m was prepared, and the package was left in a gear oven at 50 ° C. for 24 hours and then subjected to a water resistance test. In the water resistance test, a load was applied to the package for 1 minute, and the load when the bag was broken was evaluated as the limit load of the package. The results are shown in Table 2.

[0030]

[Table 2]

Examples 6 to 10 Kraft paper was subjected to corona treatment to obtain ethylene copolymers A to
D and F were extrusion-laminated at a resin temperature directly below the die of 150 ° C. and a thickness of 30 μm to obtain a kraft paper / ethylene copolymer laminate.

Comparative Example 3 Ethylene copolymer G was extrusion laminated onto kraft paper under the same conditions as in Example 6 to obtain a kraft paper / ethylene copolymer laminate. Examples 6 to 10 and Comparative Examples 2 and 3
A peelability test was performed using the laminated body of. The results are shown in Table 3.

[0033]

[Table 3]

[0034]

As is clear from the results of Table 2, in the example of the present invention, the time required for peeling the polyethylene film and the kraft pulp paper in the alkaline aqueous solution was drastically shortened as compared with the comparative example 2. ing. As a result, the time required for the peeling process by mechanical treatment of the pulp paper and the low-density polyethylene laminate film, which is performed when collecting the pulp fiber for used paper, is significantly reduced. In addition, peeling, separation and recovery of each layer material of the laminate of the present invention can be easily performed in an alkaline aqueous solution.

Further, as compared with Comparative Example 1, when the contents such as water are actually stored in the laminated body container, the interfacial adhesive force of the adhesive layer is lowered by the steam passing through the sealant layer film, and the bag is broken. There is nothing. Further, as is clear from the results in Table 3, the lower the ethylene copolymer acrylic acid content and the melt flow rate, the more difficult the peelability is to develop.

As described above, according to the present invention, each layer material of the laminate can be easily peeled off, separated and recovered in an alkaline aqueous solution, and each recovered layer material is regenerated or incinerated depending on the purpose. It becomes possible. Further, the laminate of the present invention can be used without any problem in terms of quality when used in a container whose contents are fruit juice, wine, soy sauce and the like, which are affected by moisture.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C08F 210/02 MJR C09J 123/08 JCB // B32B 7/06 7148-4F (72) Inventor Hashimoto Minori 1st Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute

Claims (2)

[Claims] 1. On the surface of the base material layer (A), ethylene 80-
94 mol% and α, β-unsaturated carboxylic acid 20 to 6 mol%
And an ethylene copolymer layer having a melt flow rate of 320 to 1500 g / 10 minutes. 2. A pulp paper base material layer (A) and a thermoplastic resin layer (C) having a melt flow rate of 0.05 to 150 g / 10 min. An ethylene copolymer with a saturated carboxylic acid of 20 to 6 mol% and a melt flow rate of 320 to 150
A laminated body integrated via an adhesive layer (B) of 0 g / 10 minutes.