JP3029321B2 - Manufacturing method of laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminate containing a polyethylene resin, and more particularly to a method for producing a laminate having a very high interlayer adhesion and suitable as various packaging materials.

[0002]

2. Description of the Related Art Laminates containing a polyethylene resin have been conventionally used as various packaging materials because of their excellent properties such as cost, handleability, productivity and heat sealability. However, since polyethylene resins are inherently non-polar, lamination with different materials required measures such as graft modification, frame treatment of the substrate, corona discharge treatment, and anchor coating agent treatment.

In order to obtain a laminate containing a polyethylene resin by extrusion lamination molding, a kind of adhesive called an anchor coat agent is applied to a base material,
The technique of extrusion coating a polyethylene resin is often used. The use of anchor coating agent is
In addition to problems in terms of cost, safety, etc., it is difficult to impart sufficient adhesiveness by itself, and the resin is molded at a very high temperature (300 ° C. or higher), and the resin surface is oxidized and laminated. It was often necessary. For this reason, the polyethylene resin has a strong deterioration odor, which may cause a problem when used as a food packaging material. Especially in recent years, smells,
Market requirements regarding taste and the like are becoming more stringent, and there are increasing cases where laminates manufactured by conventional methods cannot be used. Although the problem of odor can be solved to some extent by molding at a low temperature (280 ° C. or lower), it has been difficult to produce a good laminate because the adhesion to the substrate becomes insufficient.

[0004] In order to ensure adhesion to a substrate, the use of a copolymer of ethylene and a polar comonomer as a polyethylene resin has been widely practiced. As the copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, an ethylene-ethyl acrylate-maleic anhydride copolymer, or the like is used. However, these copolymers have strong odors derived from comonomer components, and it is difficult to produce a laminate that can be used for food even if molded at a low temperature. By washing these copolymers with a solvent or the like to remove substances that may cause odor, the range of use of the laminate can be expanded to some extent. However, this method requires a considerably large facility and is not an efficient method because the production cost of the copolymer is greatly increased.

Further, according to the technique proposed by the present inventors, the use of an ethylene-maleic anhydride copolymer makes it possible to form a laminate having low odor and excellent adhesive strength at a low temperature (280 ° C. or lower). Can be obtained. However, the interlayer adhesion strength of the laminate obtained by the technique is 300 to 400 g.
/ 15 mm, and could not be used as a packaging material in some applications due to insufficient adhesive strength in some applications.

[0006] Among the production methods for obtaining a laminate other than the extrusion laminate molding, according to the dry lamination method, a good laminate can be produced. However, this production method is disadvantageous in terms of workability and production cost as compared with the extrusion lamination method, and cannot be said to be an efficient production method.

[0007]

A problem exists in that an efficient method for producing a laminate which has a low odor and a very strong adhesion between layers and can be used as a wide range of packaging material has not been established. It is an object of the present invention to establish such a production method.

[0008]

Means for Solving the Problems The present inventors have studied various production methods to solve the above-mentioned problems, and as a result, the present invention essentially consists of ethylene and a carboxylic anhydride having a radical polymerizable unsaturated bond. , Hydroxyl group or gly
A radical copolymer having no sidyl group or a mixture of the radical copolymer and low-density polyethylene , and
A laminate having an MFR (190 ° C.) of 1 to 80 g / 10 minutes is extrusion-laminated on a substrate or between substrates to form a laminate, and the laminate is subjected to a heat treatment to obtain a desired laminate. Have been found to be able to be manufactured effectively, and the present invention has been completed.

The copolymer consisting essentially of ethylene and a carboxylic anhydride having a radically polymerizable unsaturated bond is:
It is a radical copolymer of ethylene with the acid anhydride and other polymerizable monomers, and does not include a so-called graft copolymer in which polyethylene is radically modified with an acid anhydride.

[0010] The radical polymerizable acid anhydride is one having one or more radically polymerizable unsaturated bonds and one or more acid anhydride groups in a molecule, and capable of introducing an acid anhydride group into a polymer by polymerization. 1 shows a compound. The acid anhydride is preferably a cyclic one, and specific examples of the compound include maleic anhydride, itaconic anhydride, citraconic anhydride, endic acid anhydride, dodecenyl succinic anhydride and the like. Of these, maleic anhydride and itaconic anhydride are particularly preferred. In some cases, two or more of these can be used in combination.

The copolymer according to the present invention may be a multicomponent copolymer composed of three or more components obtained by copolymerizing other comonomers in addition to ethylene and a radical polymerizable test anhydride. Here, examples of the compound that can be used as another comonomer include many compounds such as an ester compound, an amide compound, an acid compound, an ether compound, and a hydrocarbon compound. Specific examples include, as the ester compound, vinyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate,
Hexyl acrylate, octyl acrylate, lauryl acrylate, benzyl acrylate, allyl acrylate, N, N-dimethylaminoethyl acrylate, aminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, Butyl methacrylate, hexyl methacrylate, octyl methacrylate, lauryl methacrylate, benzyl methacrylate, N, N-dimethylaminoethyl methacrylate, allyl methacrylate, dimethyl fumarate, diethyl fumarate, fumarate Dipropyl acrylate, dibutyl fumarate, dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate and the like. Examples of amide compounds include acrylamide, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, N-butylacrylamide, N-hexylacrylamide, N-octylacrylamide,
N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dipropylacrylamide,
N, N-dibutylacrylamide, N, N-dihexylacrylamide, N, N-dioctylacrylamide,
Methacrylamide, N-methylmethacrylamide,
N-ethyl methacrylamide, N-propyl methacrylamide, N-butyl methacrylamide, N-hexyl methacrylamide, N-octyl methacrylamide, N, N-dimethyl methacrylamide, N, N-
Diethyl methacrylamide, N, N-dipropyl methacrylamide, N, N-dibutyl methacrylamide, N, N-dihexyl methacrylamide, N, N-
Examples of dioctyl methacrylamide and ether compounds include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octyl vinyl ether, octadecyl vinyl ether, and phenyl vinyl ether. As the acid compound, acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl fumarate, monoethyl fumarate,
Monobutyl fumarate, monomethyl maleate, monoethyl maleate, monobutyl maleate and the like can be exemplified. Examples of hydrocarbon compounds include styrene, norbornene, butadiene, and the like. In addition, acrylonitrile, methacrylonitrile, acrolein, crotonaldehyde, trimethoxyvinylsilane, vinyl chloride, vinylidene chloride and the like can also be exemplified. If necessary, two or more of these monomers may be used in combination.

From the viewpoint of obtaining a laminate having a low odor, which is one of the objects of the present invention, the unit derived from the comonomer should not exceed 5% by weight in the copolymer. Preferably, the weight ratio is 2% or less, and more preferably, a copolymer obtained from only ethylene and a radical polymerizable acid anhydride without using the comonomer is used. When the unit derived from a comonomer other than the radically polymerizable acid anhydride exceeds 5% by weight, the odor derived from the comonomer becomes remarkable, failing to satisfy the conditions for a good laminate. The comonomer can cause odor because these comonomer easily produce oligomers and the like in the polymerization system, which are difficult to remove in the separation step and have a strong odor. On the other hand, in the case of a radical polymerizable acid anhydride, the copolymerization reactivity is generally high and the homopolymerizability is poor, so that it is difficult to generate an oligomer or the like which may cause an odor, so that the odor of the polymer is hardly deteriorated.

The content of units derived from the radical polymerizable acid anhydride in the copolymer must be in the range of 0.1 to 10% by weight. When the content is less than 0.1% by weight, the adhesion to the substrate is low, and when the content is 10% by weight or more, the production of the copolymer is extremely difficult, and in addition, the copolymer is used by mixing with low density polyethylene. In this case, the compatibility with the resin deteriorates, and a good laminate cannot be obtained. The MFR of the copolymer (JIS-K
(−7210, 190 ° C.) is not particularly limited as long as it is in the range of 0.1 to 500 g / 10 minutes, but the MFR (190 ° C.) of the resin finally used for extrusion lamination molding is 1
Must be in the range of ８０80 g / 10 min. MFR
If (190 ° C.) is less than 1 g / 10 minutes, molding at a low temperature, which is a feature of the present invention, is difficult, and a good laminate cannot be obtained. If the MFR (190 ° C.) exceeds 80 g / 10 minutes, the moldability also deteriorates due to insufficient melt tension.

In producing the copolymer according to the present invention, it is appropriate to utilize equipment for producing high-pressure low-density polyethylene. That is, using a tube-type reaction vessel or a tank-type reaction group, ethylene and a radical polymerizable acid anhydride compressed to 1000 atm or more are injected into the reaction group, and the organic peroxide is injected into the group through a separate pipe. And a copolymer is obtained by a radical initiator represented by After separating the unreacted monomer by a plurality of separators, the copolymer is pelletized by an extruder.

In the present invention, the low-density polyethylene which can be used as a mixture with the copolymer includes a branched low-density polyethylene produced by a high-pressure method, a linear low-density polyethylene produced by a so-called Ziegler catalyst, and a copolymerization ratio of 5% by weight. The following copolymers of ethylene and other vinyl monomers are meant, and in some cases, mixtures thereof may be used.

The mixing ratio of the copolymer and the low-density polyethylene can vary depending on the amount of the acid anhydride in the copolymer. Generally, the proportion of the copolymer in the whole resin is 1% by weight or more, preferably 3% by weight or more. ~ 70% by weight, more preferably 5 ~
It is in the range of 50% by weight. However, the ratio of the unit derived from the radical polymerizable acid anhydride to the whole mixed resin is 0.1%.
It must be at least 1% by weight. If the proportion is less than 0.1% by weight, the adhesiveness between the resin and the substrate may be insufficient when low-temperature molding, which is a feature of the present invention, is performed.

In mixing the copolymer and the low-density polyethylene, various mixing apparatuses conventionally used for mixing thermoplastic resins, that is, various extruders, Banbury mixers, kneaders, rolls, and the like can be used. In some cases, it is also possible to apply directly to a molding machine simply by dry blending without melt-mixing the two.

In the copolymer of the present invention and a mixture of the copolymer and low-density polyethylene, various additives and compounding agents can be used as long as the characteristics of the copolymer are not impaired. is there. Examples of additives and compounding agents include antioxidants (heat stabilizers), ultraviolet absorbers (light stabilizers), antistatic agents, antifogging agents, flame retardants, lubricants (slip agents, antiblocking agents), Inorganic and organic fillers, reinforcing materials, coloring agents (dyes and pigments), foaming agents, cross-linking agents, fragrances and the like can be mentioned.

Further, apart from these additives, it is also possible to mix a compound for activating the acid anhydride group in the copolymer and improving the adhesive strength. Specific examples include metal compounds such as sodium benzoate, sodium stearate, magnesium hydroxide, aluminum hydroxide, and a partially neutralized compound of ethylene and methacrylic acid copolymer (ionomer resin).

In the present invention, extrusion lamination molding means a molding method in which a molten film of a thermoplastic resin is coated on a base material using an extruder and a T-die, sampled while cooling with a chill roll, and sampling. I do. In molding, a plurality of extruders and a co-extrusion T-die can be used to simultaneously coat one or more resins on a substrate. In addition, a method such as sand lamination for extruding a resin between substrates using one or two types of substrates, and tandem lamination for obtaining a multilayer laminate using two or more extruders and a T-die in series are also available. Including.

The substrate that can be used is not particularly limited, and various materials can be used. Specifically, a metal plate such as iron, copper, tin, aluminum, and stainless steel, a foil, a film made of plastic such as polyethylene, polypropylene, polystyrene, nylon, polyester, cellophane, ethylene-vinyl alcohol copolymer, and polyvinylidene chloride ( Various laminates can be manufactured by laminating on a stretched film, a metal-deposited film, a sheet, a nonwoven fabric, and paper such as high-quality paper, kraft paper, and glassine paper.

There is no particular limitation on the thickness of the laminate,
A laminate having a thickness according to the application can be formed. Assuming a general extrusion laminate, a layer containing a copolymer is usually 3 to 50 μm, and a laminate having a total thickness of about 20 to 1000 μm is common. The heat treatment of the laminate, which is the point of the present invention, is performed by conduction heating with a hot roll, a hot plate or the like, infrared or far-infrared irradiation, hot-air blowing, high-frequency induction heating, or the like. The method using a hot roll is preferable from the viewpoint that pressurization is performed at the same time. Especially from the viewpoint of economy and operability,
It is preferable to install a heat roll in the extrusion lamination molding line and perform heat treatment before winding the laminate.

The temperature and time of the heat treatment can vary depending on the type of the substrate, the constitution of the laminate, the type of the copolymer and the low-density polyethylene.
Hereinafter, it is 1 second or more, preferably 200 ° C. or more and 250
By applying a heat treatment at a temperature of 1 ° C. or lower for 1 second or more, the adhesive strength is dramatically improved. If the heat treatment temperature exceeds 280 ° C, molding trouble due to melting of the resin (wrapping around the roll)
Or the appearance of the laminate deteriorates (printing deviation, etc.). When the heat treatment temperature is less than 150 ° C. or the heat treatment time is less than 1 second, the interlayer adhesive strength of the laminate may be insufficient depending on the purpose. When using a heat roll, the winding speed may be limited by the roll diameter in order to perform processing for 1 second or longer. However, if necessary, the winding speed may be reduced by installing multiple heat rolls. It is possible to raise.

The multilayer laminate produced by the above production method has very high interlayer adhesion and low odor, and thus can be suitably used as various packaging materials mainly for food packaging materials. Hereinafter, the present invention will be described specifically with reference to examples.

[0025]

【Example】

(Example 1) A copolymer of ethylene and maleic anhydride was produced using a high-pressure polyethylene production facility having a tank reactor. The obtained copolymer is MFR (190 ° C.)
8.6, 2.2% by weight of units derived from maleic anhydride. A low-density polyethylene having an MFR (190 ° C.) of 7.0 and a density of 0.9165 g / cc;
The mixture was mixed so as to have a weight ratio of 20/80. When mixing, dry blend both with a tumbler, then 5
Using a 0 mmφ single screw extruder, the mixture was melt-kneaded at 170 ° C. and pelletized. The MFR (190 ° C.) of the mixture is 7.
3. The unit derived from maleic anhydride was 0.43% by weight. The polymer composition was measured by an infrared absorption spectrum.

The mixture was laminated on an aluminum foil having a thickness of 30 μm with a laminator having an extruder of 50 mmφ and a die width of 450 mm. The extrusion temperature was 250 ° C., the screw rotation speed of the extruder was 80 rpm, the take-off speed was 80 m / min, and the total thickness of the obtained laminate was 60 μm.
Furthermore, a 200 mm diameter and a roll surface length of 30 mm
Heat treatment was performed using a 0 mm heat roll. The heat transfer oil whose temperature was adjusted was passed through the roll, and care was taken to keep the roll surface temperature constant. Heat treatment at 150 ° C, 180 ° C,
The test was performed at 210 ° C. for three points. The heat treatment time (time in contact with the hot roll) was 2 seconds.

The obtained laminate was subjected to a temperature of 23 ° C. and a relative humidity of 50.
%, And cut into strips having a width of 15 mm, and the 180-degree peel strength between the layers was measured at a peel rate of 300 mm / min. The laminate subjected to the heat treatment at 150 ° C. shows a strength of 650 g / 15 mm width,
900 ℃ / 15mm width, 1150g
/ 15 mm width or more. All of them had very good interlayer adhesive strength, and especially the product treated at 210 ° C. had such an adhesive strength that the laminated film was broken during the peeling test.

Next, the laminate is cut into a suitable size to produce a sealed bag having a resin layer as an inner layer (with an internal volume of about 500).
cc), after heating at 40 ° C. for 30 minutes, the bag was opened and the odor was evaluated organoleptically. In the evaluation, six panelists selected in a preliminary test were used to compare the low-odor low-density polyethylene (Showa Denko, grade name: L156, 310 ° C. extruded laminate product) with a proven track record as a resin for food packaging materials. (210 ° C.)
Comparative evaluation of the odor of the heat-treated product) was performed. Five out of six panelists answered that the laminate obtained by the production method according to the present invention had less odor, and one person evaluated that the laminate was equivalent. From the above results, it can be seen that the laminate obtained by the production method according to the present invention is a good laminate that can be used for various applications.

(Example 2) When laminating according to the method of Example 1, a hot roll is placed in front of a winding roll.
A heat treatment was performed during the molding of the laminated body. The heat roll diameter was 200 mm, the heat treatment time was 1 second, and the heat treatment temperature was 200 ° C. at a take-up speed of 80 m / min.

The interlayer adhesion strength of the obtained laminate was measured in Example 1.
As a result, the laminate was very excellent with a width of 680 g / 15 mm, and was a good laminate usable for various uses. Further, since the heat treatment according to the present embodiment is performed in a laminate molding line, the operation is efficient, and greatly contributes to lowering the manufacturing cost of the laminate.

(Comparative Example 1) Among the laminates manufactured in Example 1, those which were not subjected to any heat treatment were measured for the adhesive strength between the layers by the same method. The adhesive strength is 3
It is 00 g / 15 mm width, and it can be said that it has good adhesive strength. However, it is difficult to apply to fields requiring a high level of adhesive strength, such as packaging of heavy goods and liquid goods. Therefore, this laminate is not a widely usable laminate.

Comparative Example 2 In the mixture of the copolymer and low-density polyethylene used in Example 1, the mixing ratio was 4
A mixture was prepared as / 96. The MFR of the mixture (19
(0 ° C.) is 7.1, and the unit derived from maleic anhydride is 0.1.
08% by weight. Using this mixture, a laminate was produced in the same manner as in Example 1. Heat treatment temperature is 210
° C. The interlayer adhesion strength of the obtained laminate is 120 g /
The width was 15 mm, and the adhesive strength was insufficient.

[0033]

By using the manufacturing method according to the present invention, a laminate that can be used widely as a packaging material can be efficiently manufactured. Since the laminate has an extremely large adhesive strength between layers, it is suitable for various packaging such as heavy objects.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-269516 (JP, A) JP-T2-501643 (JP, A) JP-T2-5021641 (JP, A) (58) Investigated Field (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 B65D 65/40 B29C 47/00-47/96

Claims (3)

(57) [Claims] 1. A consisting essentially carboxylic acid anhydride compound having an ethylenic radical polymer unsaturated bond, hydrin
Radicals without loxyl or glycidyl groups
A polymer or a mixture of the radical copolymer and a low-density polyethylene , and having an MFR (190 ° C.) of 1 to 80.
A method for producing a laminate, comprising extruding a laminate of g / 10 minutes on or between substrates to form a laminate, and then subjecting the laminate to heat treatment. 2. The method for producing a laminate according to claim 1, wherein a heat treatment is performed before winding the extrusion-laminated laminate. 3. The method for producing a laminate according to claim 1, wherein the heat treatment is performed under a condition of 150 ° C. or more and 280 ° C. or less and 1 second or more.