JP2886220B2 - Manufacturing method of laminate - Google Patents

Description

The present invention relates to a method for producing a laminate containing a polyolefin resin, and more particularly to a method for producing a laminate having a low odor suitable for packaging materials such as foods. is there.

[Prior Art] Laminated bodies containing polyolefin-based resins have been used as various types of packaging materials because of their excellent properties as packaging materials such as cost, handleability, productivity and heat sealing properties. However, since polyolefin resins are inherently non-polar, it is necessary to take measures such as modification by graft polymerization, flame treatment of a substrate, corona discharge treatment, treatment with an anchor coat agent, etc., when laminating with a different material.

When a laminate containing a polyolefin resin is to be obtained by extrusion lamination molding, for example, a technique of applying a kind of adhesive called an anchor coat agent to a base material and then extrusion-coating a polyolefin resin is often used. . The use of an anchor coating agent has problems in terms of contamination of the working environment by the solvent and recovery of the solvent, workability, cost, safety, etc. In addition, it is difficult to impart sufficient adhesiveness only by this treatment, It is often necessary to mold polyolefin resins at very high temperatures (300 ° C. or higher) and oxidize the resin surface before laminating.

For this reason, the polyolefin-based resin is deteriorated, and its odor is strong, so that a problem may occur when the obtained laminate is used as a food packaging material.

In particular, in recent years, the demands on the market for packaging materials, which affect odor, flavor, etc., have become more and more severe, and there are increasing cases in which laminates manufactured by conventional methods cannot be used.

To reduce the effect on odor and flavor, the problem can be solved to some extent by lowering the processing temperature of the polyolefin (280 ° C or lower). Was difficult to manufacture.

As another method for securing the adhesiveness to a substrate, the use of a copolymer of ethylene and a polar comonomer as a polyolefin-based 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, although these copolymers have improved low-temperature adhesion, they have a strong odor derived from the comonomer component, and it is not possible to produce a laminate that can be used for food even if molded at low temperature. Have difficulty. 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 considerably large equipment such as solvent cleaning equipment and solvent recovery equipment, and also requires consideration of solvent toxicity and flammability, which significantly increases the production cost of the copolymer. This is not an efficient method.

According to the dry lamination method among the production methods for obtaining a laminate other than the extrusion lamination molding, a favorable laminate can be produced. However, the production method is disadvantageous in terms of workability and production cost as compared with the extrusion lamination method.
It is not an efficient manufacturing method.

[Problems to be Solved by the Invention] There is a problem that an efficient method for producing a laminate suitable as a food packaging material having a low odor and a high adhesive strength between layers has not been sufficiently established. Therefore,
It is an object of the present invention to establish such a production method.

[Means for Solving the Problems] The present inventors have studied various production methods for solving the above problems, and as a result, in extrusion lamination molding,
[1] A random copolymer copolymerized under a pressure of 1000 atm or more, wherein the content of units derived from ethylene and a radical polymerizable acid anhydride is 0.1 to 10% by weight and the content of other comonomer is 2% by weight or less. A method for producing a laminate, wherein the polymer is extrusion-laminated on a substrate at a temperature of 280 ° C. or less, [2] the content of units derived from ethylene and a radical polymerizable acid anhydride is 0.1 to 10; A random copolymer having a weight percent and other comonomer content of 2 weight% or less and copolymerized under a pressure of 1000 atmospheres or more is mixed with a polyolefin resin and
In a ratio of not less than 0.1% by weight, the amount of the unit derived from the radical polymerizable anhydride is 0.1% by weight or more and the MFR is 1 to 80 with respect to the whole mixed resin. By developing a method for producing a laminate characterized by extrusion lamination on a substrate, the present inventors have found that a desired laminate can be produced efficiently, and have completed the present invention.

The thermoplastic resin used in the production method of the present invention is a copolymer consisting essentially of ethylene and a radical polymerizable acid anhydride, or a mixture of the copolymer and a polyolefin resin. The mixture with the copolymer or the polyolefin resin basically has similar properties to ordinary polyolefin resins, but has an adhesive property to a base material such as metal and paper or another synthetic resin base material at the time of low-temperature processing. It is suitable for the production of laminates used for packaging materials and the like which have a problem of flavor because of excellent odor after molding.

In the present invention, a copolymer consisting essentially of ethylene and a radical polymerizable acid anhydride is a radical copolymer obtained by adding ethylene and the acid anhydride or another polymerizable monomer thereto, and is a random copolymer obtained by a high-pressure method. It is a polymer.

In the case of a so-called graft copolymer in which polyethylene is modified together with an acid anhydride and a radical initiator, the graft amount cannot be increased too much.
Poor film appearance. ), Apart from co-extrusion lamination, extrusion lamination molding does not provide sufficient adhesive strength, and is not considered in the present invention.

Radical polymerizable acid anhydride refers to a compound 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. . 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.

This radically polymerizable acid anhydride has a certain degree of copolymerization reactivity, but has poor homopolymerizability, so that it is difficult to generate oligomers and the like that cause odor. Is less.

The content of the unit derived from the radical polymerizable acid anhydride in the copolymer is in the range of 0.1 to 10% by weight. The content is 0.1
If the amount is less than 10% by weight, the adhesion to the base material is low. If the amount is more than 10% by weight, the production of the copolymer is extremely difficult. Deteriorates, and a good laminate cannot be obtained.

The MFR (JIS-K-7210, 190 ° C.) of the copolymer is 0.1 to 50.
There is no particular limitation as long as it is in the range of 0, but the final MFR (190 ° C.) of the resin used for extrusion lamination molding is 1 to
Must be in the range of 80. When the MFR (190 ° C.) is less than 1, molding at a low temperature, which is a feature of the present invention, is difficult, and a good laminate cannot be obtained. When the MFR (190 ° C.) exceeds 80, the moldability also deteriorates due to insufficient melt tension.

The copolymer according to the present invention is obtained by copolymerizing another comonomer in addition to ethylene and a radical polymerizable acid anhydride.
It may be a multi-component copolymer composed of components or more. Here, as the compound that can be used as another comonomer, many compounds such as an ester compound, an amide compound, an acid compound, an ether compound, and a hydrocarbon compound can be given.

Specific examples include, as ester compounds, vinyl acetate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, benzyl acrylate, acrylic acid Allyl, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, N, N-dimethylaminoethyl acrylate, aminoethyl acrylate, butanediol diacrylate, hexanediol diacrylate, triethylene glycol diacrylate, tetraethylene glycol Diacrylate,
Polyethylene glycol diacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, lauryl methacrylate, benzyl methacrylate, 2-hydroxyethyl meth Acrylate, 2-hydroxypropyl methacrylate, N, N-dimethylaminoethyl methacrylate, aminoethyl methacrylate, allyl methacrylate, butanediol dimethacrylate, hexanediol dimethacrylate, triethylene glycol dimethacrylate , Tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, dibutyl fumarate, male Phosphate dimethyl, diethyl maleate, dipropyl maleate, can be mentioned dibutyl maleate.

Examples of the amide compound include acrylamide, N-methylacrylamide, N-ethylacrylamide, N-propylacrylamide, N-butylacrylamide,
-Hexylacrylamide, N-octylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dipropylacrylamide, N, N-dibutylacrylamide, N, N-dihexylacrylamide, N, N-dioctyl Acrylamide, methacrylamide, N-methyl methacrylamide, 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-
Examples include dibutyl methacrylamide, N, N-dihexyl methacrylamide, and N, N-dioctyl methacrylamide.

As ether compounds, methyl vinyl ether,
Examples thereof include 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.

As hydrocarbon compounds, styrene, norbornene,
Butadiene and the like can be exemplified. Other examples include acrylonitrile, methacrylonitrile, acrolein, crotonaldehyde, trimethoxyvinylsilane, vinyl chloride, and vinylidene chloride.

If necessary, two or more of these monomers may be used in combination.

In order to obtain a laminate having a low odor which is an object of the present invention, the unit derived from the comonomer is 2% by weight or less in the copolymer, more preferably the comonomer is not used, and ethylene and radical It is preferable to use a copolymer obtained from only a polymerizable acid anhydride. When the unit derived from a comonomer other than the radically polymerizable acid anhydride exceeds 2% 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 generate oligomers and the like in the polymerization system, which are difficult to remove in the separation step and have a strong odor.

As the radical initiator, a compound generating free radicals, mainly an organic peroxide, is used. For example, diacyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, etc., acetyl peroxide, i-butyl peroxide, octanoyl peroxide, etc .; Peroxy dicarbonates such as propyl peroxy dicarbonate and di-2-ethylhexyl peroxy dicarbonate; peroxy esters such as t-butyl peroxy pivalate and t-butyl peroxy laurate; methyl ethyl ketone peroxide; cyclohexanone peroxide and the like Ketone peroxides, peroxyketals such as 1,1-bis-t-butylperoxycyclohexane, 2,2-bis-t-butylperoxyoctane, and hydrides such as t-butyl hydroperoxide and cumene hydroperoxide. Peroxides, azo compounds such as 2,2-azobisisobutyronitrile, oxygen and the like.

In the production of the copolymer according to the present invention, it is appropriate to utilize equipment for producing high-pressure low-density polyethylene. That is, using a tubular reactor or a tank reactor, 1000
Inject ethylene and radically polymerizable acid anhydride compressed above atmospheric pressure into the reaction group, and polymerize with a radical initiator typified by an organic peroxide injected into the vessel with a separate pipe to obtain a copolymer . After separating the unreacted monomer by a plurality of separators, the copolymer is pelletized by an extruder.

In the present invention, the polyolefin-based resin that can be used by mixing with the copolymer is substantially ethylene, propylene, butene-1, hexene-1, octene-1,3-methylbutene-1,4-methylpentene. -1 such as α-olefin homopolymers and copolymers, specifically, low-density polyethylene, high-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-propylene copolymer, polybutene, ethylene -Butene-1 copolymer,
Represents poly-4-methyl-pentene-1 and the like and mixtures thereof.

The mixing ratio of the copolymer and the polyolefin resin may vary depending on the amount of the acid anhydride in the copolymer. Generally, the ratio of the copolymer in the whole resin is 1% by weight or more, preferably 3 to 70% by weight. %, More preferably 5 to 50% by weight. However, it is preferable that the ratio of the unit derived from the radical polymerizable acid anhydride to the whole mixed resin is 0.1% by weight or more. If the proportion is less than 0.1% by weight,
When the low-temperature molding which is a feature of the present invention is performed, there is a possibility that the adhesiveness between the resin and the base material is insufficient.

In mixing the copolymer and the polyolefin resin, various mixing devices 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.

Various additives and compounding agents can be used in the copolymer according to the present invention and in the mixture of the copolymer and the polyolefin resin, as long as the characteristics of the copolymer are not impaired. Examples of additives and compounding agents include an antioxidant (heat stabilizer), an ultraviolet absorber (light stabilizer), an antistatic agent,
Anti-fogging agents, flame retardants, lubricants (slip agents, anti-blocking agents), inorganic and organic fillers, reinforcing materials, coloring agents (dyes,
Pigments), foaming agents, crosslinking agents, fragrances and the like.

Various materials such as metal, plastic, and paper can be used as the adjacent layer that adheres to the copolymer layer, that is, the substrate. Specifically, iron, copper, tin, aluminum,
Metal plates such as stainless steel, foil, plastic films such as polyethylene, polypropylene, polystyrene, nylon, polyester, cellophane, ethylene-vinyl alcohol copolymer, and polyvinylidene chloride (including stretched films and metallized films), sheets, Laminates can be manufactured by laminating on non-woven fabrics and further on paper such as high quality paper, kraft paper, glassine paper and the like.

In extrusion lamination molding of the copolymer according to the present invention or a mixture of the copolymer and a polyolefin-based resin, various types of molding as described above are possible.

Extrusion lamination molding in the present invention means a molding method in which a molten film of a thermoplastic resin is laminated or coated on a substrate using an extruder and a T-die, and is taken out while cooling. 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.

Further, there is also a method such as sand lamination for extruding a resin between the substrates using one or two types of substrates, tandem lamination for obtaining a multilayer laminate using two or more extruders and a T-die in series. included.

In extrusion lamination molding, molding at a temperature of 280 ° C. (resin temperature immediately below a die) or less is essential.
This is to prevent the odor from deteriorating due to thermal deterioration during molding, and is important for obtaining a laminate suitable for food packaging materials and the like.

The laminate obtained by the above method has a strong adhesive force between layers, and excellent appearance and odor, so that it can be used for various applications as various packaging materials and containers, particularly as a material for packaging materials having a problem of flavor and aroma. It is a laminate that can be used.

Hereinafter, the present invention will be described specifically with reference to Examples.
The present invention is not limited to these examples, and can take various forms.

[Example] (Example 1) A copolymer of ethylene and maleic anhydride was produced using a high-pressure polyethylene production facility having a tank-type reactor. The polymerization pressure is 1850Kg / cm ² , the polymerization temperature is 200 ° C,
Maleic anhydride was dissolved in methyl ethyl ketone, and the solution was pressurized into a suction line of a secondary compressor with a high pressure pump as a solution of about 30% concentration. As the initiator, tertiary butyl peroxypivalate was used.
Unreacted monomers were separated by a low-pressure separator and pelletized by an extrusion granulation equipment. The obtained copolymer was obtained by MFR (190
C) 8.6, and 2.2% by weight of units derived from maleic anhydride. In addition, the copolymer composition was determined by an infrared absorption spectrum. The copolymer was treated with MFR (190 ° C.) 7.0, density 0.9
It was mixed with low-density polyethylene of 165 g / cc so as to have a weight ratio of 20/80. Upon mixing, both were dry-blended with a tumbler, and then melt-kneaded at 170 ° C. using a 50 mmφ single screw extruder to form pellets. M of the mixture
FR (190 ° C) is 7.3 and the unit derived from maleic anhydride is 0.
43% by weight.

The mixture was laminated on an aluminum foil having a thickness of 30 μm with a laminator having an extruder of 90 mmφ and a die width of 750 mm. The extrusion temperature was 250 ° C., the number of revolutions of the screw of the extruder was 60 rpm, the take-off speed was 80 m / min, and the total thickness of the obtained laminate was 60 μm.

The obtained laminate is kept at 23 ° C. and 50% relative humidity for 24 hours.
After adjusting the time condition, cut into strips with a width of 15 mm,
The 180 degree peel strength was measured. When peeled at a speed of 300 mm / min, it showed a strength of 400 g / 15 mm width, indicating that it had excellent interlayer adhesion. Next, the laminate is cut into a suitable size to produce a sealed bag with a resin layer as the inner layer (with an internal volume of about 500 cc). After heating at 40 ° C for 30 minutes, the bag is opened and the odor is evaluated organoleptically. did. In the evaluation, low-odor and low-density polyethylene (Showa Denko,
(L156, molded at 310 ° C.) was made in the same manner and treated in the same manner, and a relative evaluation was made.

Five out of six panelists answered that the laminate 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) MFR (190 ° C) 105 obtained by reacting in the same manner as in Example 1 except that the polymerization temperature was 230 ° C and tertiary butyl peroxy-2-ethylhexanoate was used as an initiator, and anhydrous maleic acid was used. 1.5% by weight of ethylene derived from acid
Maleic anhydride copolymer, MFR (190 ° C) 5.0, density 0.922
0 g / cc linear low density polyethylene and propylene containing 3
A mixture was obtained by blending an ethylene-propylene copolymer of 2% by weight and MFR (230 ° C.) of 1.8 in a weight ratio of 10/70/20 in the same manner as in Example 1. The MFR of the mixture (190
C) was 5.8, and the unit derived from maleic anhydride was 0.16% by weight.

Hereinafter, Example 1 was performed except that the molding temperature was 280 ° C.
Was evaluated for adhesive strength to aluminum foil and odor. This laminate had a peel strength of 380 g / 15 mm width, and was found to have an odor almost equivalent to that of the L156 laminate of Example 1. That is, it is a good laminate that can be used for various applications.

(Example 3) A copolymer of ethylene and itaconic anhydride was prepared in Example 1 except that itaconic anhydride was injected into the system as an acetone solution.
It was manufactured in the same manner as in The MFR (190 ° C) of the copolymer is 1
2. The unit derived from itaconic anhydride was 0.85% by weight.

The copolymer was extrusion-coated at 260 ° C. on a 20 μm polyethylene terephthalate film in the same manner as in Example 1 to obtain a laminate. Further, the adhesive force and odor were evaluated by the method described in Example 1. The laminate had a peel strength of 340 g / 15 mm width and had an odor equivalent to that of the L156 laminate.

Comparative Example 1 A terpolymer of ethylene, maleic anhydride and ethyl acrylate was produced. The MFR (190 ° C.) of the polymer was 32, and units derived from maleic anhydride and ethyl acrylate were 2.9% by weight and 10.6% by weight, respectively. The terpolymer was mixed with the low-density polyethylene shown in Example 1 at a ratio of 20/80, and a laminate was produced under the same conditions as in Example 2 to evaluate the adhesive strength and odor.

Although the interlayer adhesion to the aluminum foil was strong at 370 g / 15 mm width, the smell was extremely strong compared to the L156 laminate, and it could not be used as a food packaging material.

(Comparative Example 2) A laminate with aluminum foil was manufactured using L156 alone. In this case, the adhesive strength to the aluminum foil was not sufficient even at 310 ° C. (140 g / 15 mm width), and it became necessary to use an anchor coating agent. When the molding temperature was raised to 330 ° C., the adhesive strength was improved (300 g / 15 mm width), but the odor based on the thermal deterioration became strong, and it could not be used as a food packaging material. When the molding temperature was 280 ° C., it did not adhere to the aluminum foil at all.

Continuation of the front page (56) References JP-A-56-72033 (JP, A) JP-A-58-152077 (JP, A) JP-A-54-4975 (JP, A) JP-A-60-252673 (JP , A) JP-B 62-36859 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] 1. A random copolymer copolymerized under a pressure of 1000 atm or more, wherein the content of units derived from ethylene and a radical polymerizable acid anhydride is 0.1 to 10% by weight (other comonomer content is (2% by weight or less) on a substrate at a temperature of 280 ° C or less by extrusion lamination. 2. A random copolymer copolymerized under a pressure of 1000 atm or more, wherein the content of units derived from ethylene and a radical polymerizable acid anhydride is from 0.1 to 10% by weight (other comonomer content is 2% by weight or less) and the polyolefin-based resin in a proportion of 1% by weight or more, and the ratio of the unit derived from the radical polymerizable acid anhydride to the whole mixed resin is 0.1% by weight
The above and MFR are mixed in an amount of 1 to 80, and the mixture is
A method for producing a laminate, comprising extruding and laminating on a substrate at a temperature of 80 ° C. or lower.