JPH0631864A - Co-extruded heat-seal lacquer-coated synthetic resin composite - Google Patents

Abstract

PURPOSE: To provide a coextruded heat-sealable lacquer-coated synthetic resin composite suitable for a lid material. CONSTITUTION: A coextruded heat-sealable lacquer-coated synthetic resin composite as a material for a lid sealable and peelable for a deep packaging container includes a layer 20-300 μm in thickness containing a styrene-based thermoplastic resin, a layer 8-40 μm in thickness containing an ester-based thermoplastic resin, a heat-sealable lacquer 2-15 μm in thickness containing a styrene- butadiene-styrene block copolymer and a vinyl toluene-styrene copolymer, which are arranged from the outside to the inside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coextrusion heat-sealing lacquered synthetic resin composite, use of the composite for packaging, a container cover made of the composite, and a method for closing the container.

[0002]

2. Description of the Prior Art It is known to make container covers, for example lids, of containers intended to be used for containing food and luxury items from lacquered aluminum. Such materials are further processed into lids which generally include an aluminum carrier layer with a sealing lacquer or sealing layer on one side. With this sealing layer, the lid and the container to be closed are hermetically connected and closed.

The disadvantage of aluminum is that so-called monoverpackungs are not always feasible. The single package means a package in which the container and the lid are made of one type of material and are not made of a plurality of different types of materials (for example, metal and synthetic resin). This is an important aspect in view of the simple and pure recycling of packaging and its materials.

For example, the publication "Interterpack 1990,
Valox PKG1530 fuer die Milchwirtschafte
r und fuer Deckelanwendungen, GE Plastics
From Europe, Verpackungen Mai 1990 ", 3
Aluminum substitutes are known which are layered coextruded composites. The structure has a 20 μm thick first layer “Valox.
PKG1530 "(polyester mixture) and 90 μm
It consists of a second layer of thickness "HIPS" (polystyrene) and a third layer which is a sealing layer and is 10 μm thick. This structure has the disadvantage, for example, that it can only be sealed in a narrow temperature and pressure range. In the practical use of such known three-layer composites, decapping of the lid usually occurs during removal of the sealed lid from the container.
That is, the remainder of the lid-synthetic resin layer is left on the edge of the container.
In addition, the delaminated lid is liable to tear,
It can no longer be completely and totally removed from the container. This disadvantage is further enhanced in the case of a lid having a large area.

[0005]

The object of the invention is particularly suitable for container lids, for example removing lids produced therefrom without delamination and tearing from the containers sealed thereby. Like you can
A coextrusion heat sealable lacquered synthetic resin composite is provided. Moreover, the lid material should be easily material recyclable.

[0006]

According to the invention, this means from the outside to the inside the following layers: (a) a styrene-based thermoplastic containing 2
0-300 μm thick layer; (b) Ester-based thermoplastic resin containing 8
A coextrusion heat-sealable lacquer comprising a 2-15 μm-thick heat-sealable lacquer comprising a styrene-butadiene-styrene block copolymer and a copolymer of vinyltoluene and a styrene compound. Achieved by coating synthetic resin composites.

From outside to inside the following layers: (a ₀ ) 8 containing a thermoplastic resin based on ester
˜40 μm thick layer; (a) 2 containing styrene based thermoplastic resin
0-300 μm thick layer; (b) Ester-based thermoplastic resin containing 8
A coextrusion heat-sealable lacquer comprising a 2-15 μm-thick heat-sealable lacquer comprising a styrene-butadiene-styrene block copolymer and a copolymer of vinyltoluene and a styrene compound. Painted synthetic resin composites are particularly preferred.

"Outside" means the synthetic resin composite surface that forms the outside of the container or lid, and "inside" means the synthetic resin composite surface that faces the inside of the container and the packing.

The layer (a ₀ ) is purposely 10 to 30 μm,
It preferably has a thickness of 10 to 20 μm.

Layer (a ₀ ) may comprise an ester-based thermoplastic resin.

Ester-based thermoplastics are, for example, polyalkylenes having 2 to about 10 carbons alkylene radicals or alkylene residues or at least one --O-- interrupted alkylene radical having 2 to 10 carbons. Terephthalate or polyalkylene isophthalate, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate (polytetramethylene terephthalate), polydecamethylene terephthalate or poly-1,4-cyclohexyl dimethylol terephthalate, or isophthalate in the proportion of 1 to Mixed polymer of 10 mol% of polyalkylene terephthalate and polyalkylene isoterephthalate, mixed polymer and terpolymer of the above substances, and block polymer To be grafted modifications.

Other thermoplastics from the series of esters are copolymers of terephthalic acid, other polycarboxylic acids and at least one glycol. In this case, a copolyester of terephthalic acid, ethylene glycol and additional glycol is expedient. Such glycol modified polyesters are known in the art as PETGs.

Ester-based thermoplastic resin having 2 carbon atoms
A polyalkylene terephthalate having 10 to 10 alkylene groups or alkylene residues and a polyalkylene terephthalate having 2 to 10 carbon atoms or alkylene residues interrupted by at least one or two -O- are suitable. Is.

Ester-based thermoplastic resins, polyalkylene terephthalates having alkylene groups or alkylene residues having 2 to 4 carbon atoms are preferred, and polybutylene terephthalate is particularly preferred.

Further, polyalkylene terephthalate having an alkylene group having 2 to 4 carbon atoms or an alkylene residue interrupted by -O- is preferable.

Preferred ester-based thermoplastics are polyalkylene terephthalates having alkylene groups or alkylene residues having 2 to 4 carbon atoms, polyethylene terephthalate being particularly preferred. The polyethylene terephthalate may also include A-PET, PETP and the above PETG or G-PET.

The above substance groups also include, for example, polymer mixtures or mixed copolymers, block copolymers, graft copolymers.

The ester-based thermoplastics, alone or as a mixture with other polymers, can be processed into suitable foils.

In a particularly preferred embodiment, layer (a ₀ ) comprises polybutylene terephthalate, or polybutylene terephthalate with a copolymer of styrene and maleic anhydride. The ratio of polybutylene terephthalate to copolymer can be, for example, from 6: 4 parts by weight to 9: 1 parts by weight, in this case from 8: 2 parts by weight to 8.
A ratio of up to 5: 1.5 parts by weight should be chosen especially, or the polybutylene terephthalate contains, for example, about 25 mol% polystyrene maleic anhydride.

Layers (a) or (a ₀ ) may contain additives customary per se, for example plasticizers, lubricants, fillers, pigments or antioxidants.

Layer (a) expediently has a thickness of 60 to 300 μm.

For example, 60 to 130 μm, particularly 80 to 10 μm
A layer (a) with a thickness of 0 μm can be used, for example, to close the container once (einm
It is particularly advantageously suited for the production of relatively flexible lids and flat lids, such as those suitable for alverschluss).

For example, 130 to 300 μm or preferably 160 to 270 μm or particularly preferably 160 to 220
A layer (a) with a thickness of μm is advantageous for the production of shaped lids, ie for example deep or deep-drawing (getieften oder tiefgezogenen) lids. The lid can be sealed to the container in a manner known per se, thereby forming a unique closure. When opening the packaging container, the lid can be separated from the container within the sealing seam. Then, depending on the molding and material strength, the lid can be reapplied to the container once or several times and optionally fitted, whereby the lid can be reclosed without sealing.

Layer (a) consists of one styrene-based thermoplastic resin or comprises one styrene-based thermoplastic resin. Examples of styrene-based thermoplastics are polystyrene, copolymers and terpolymers of styrene, copolymers with acrylonitrile (SA
N), a copolymer with butadiene (SB) and a terpolymer (ABS) containing synthetic rubber and acrylonitrile.

A purposeful thermoplastic based on styrene is polystyrene and a copolymer of styrene and butadiene. Such copolymers of styrene and butadiene have, for example, a styrene content of 70 to 90 mol%, purposefully 75 to 85 mol%.

Layer (b) suitably has a thickness of 10 to 30 μm, preferably 10 to 20 μm.

Layer (b) consists of or comprises an ester-based thermoplastic resin.

Suitable materials are taught from the above list of ester-based thermoplastics for the foil of layer (a ₀ ).

Suitable and preferred embodiments, such as those mentioned for layer (a ₀ ), also apply to layer (b).

Layer (c) is a heat-sealable lacquer. The layer thickness of the heat-sealable lacquer is expediently 2-10 μm, preferably 3-8 μm.

The layer (c) of the synthetic resin composite not only guarantees sealing, but can also have an advantageous effect on the removal or stripping of the lid from the container during opening. The heat-sealable lacquer can therefore form a suitable release layer [open layer (aufreissschicht)].

Preferred heat-sealable lacquers include styrene-butadiene-styrene block copolymers and copolymers of vinyltoluene and α-methylstyrene.

It is also possible to use heat-sealable lacquers which contain fillers and / or waxes.

Examples of fillers are finely divided aluminum oxide,
Preferred is silicon oxide. Furthermore, talc, mica, calcium carbonate and the like can be used depending on the case. Amorphous, porous synthetic silicon oxide is particularly preferred.

The amount of filler can be, for example, 1 to 5% by weight, in particular 1 to 3% by weight, based on the heat-sealable lacquer layer.

Examples of waxes are polyester waxes, eg olefin waxes such as polyethylene wax, propylene wax, eg microcrystalline waxes and, for example, those of the general formula C ₂₃ H _{48 to} C ₂₉ H ₆₀ , melting points 70 to 2
Petroleum wax, such as paraffin wax having a temperature of 00 ° C.

To use heat-sealable lacquers, the components are dissolved, swelled, dispersed and / or suspended in a solvent or solvent mixture. Suitable solvents or dispersants are of the aliphatic type, for example hydrocarbons of the alkane and cycloalkane series and carbonyl compounds of the ketone or alkyl ester series.

Suitable alkanes are, for example, pentane, hexane, heptane and their isomers or cyclohexane. Suitable carbonyl compounds are, for example, acetone, methyl ethyl ketone or diethyl ketone. Examples of alkyl esters are acetic acid methyl ester, preferably acetic acid ethyl ester or acetic acid butyl ester.

The solvent or dispersant is used in an amount of 60 to 90% by weight, based on the filler content of the heat-sealable lacquer.

Solvent mixtures consisting of 10 to 20% by weight of cycloalkane and 90 to 80% by weight of ketone, such as methyl ethyl ketone, are preferred.

A typical heat sealable lacquer layer is about 50 styrene-butadiene-styrene block copolymers.
Wt%, including the copolymer from about 25 weight percent and a vinyl toluene and α- methyl styrene, for example, fillers about 17 wt%, such as finely divided SiO _2, and about 8 weight percent polyolefin wax polypropylene wax series.

To obtain a typical heat-sealable lacquer layer, the heat-sealable lacquer is applied on a carrier, ie on a synthetic resin composite. For this purpose, the above components are placed in a solvent mixture consisting of 85% by weight of methyl ethyl ketone and 15% by weight of cyclohexane.

The heat-sealable lacquer used according to the invention is in the form of a fluid to a paste and is roller coated, spread, doctor knife coated or sprayed onto layers (a) and (b) or layers (a ₀ ) and (a ₀ ). It is applied on a layer (b) of a prefabricated composite consisting of a) and (b). The solvent from the heat-sealable lacquer evaporates or vaporizes at elevated temperatures and / or reduced pressure. Vaporization at 80 to 160 ° C is preferred. 3 to 30
Within the time of seconds, the solvent is mostly removed, leaving the desired layer of heat sealable lacquer.

In another embodiment, recycled styrene-based thermoplastics can also be used in the production of layer (a). For example, the production of recycled granules or recycled material from polystyrene-containing waste, which is mixed with new material containing styrene-based thermoplastics, optionally in various quantitative ratios, and processed into suitable foils. You can

For example, the foil of layer (a) can be manufactured from recycled thermoplastic resin only. The proportion of recycled material in the styrene-based thermoplastic resin is in particular 0 to 90% by weight, suitably 0 to 60% by weight, preferably 0 to 60% by weight, respectively, based on the total weight of layer (a), respectively. It becomes 0 to 30% by weight.

The lower limit of the proportion of recycled material is not critical, and generally the lower limit is, for example, up to at least 5% by weight, purposefully at least 10% by weight, each based on the total weight of layer (a). %, Preferably at least 20% by weight.

From outside to inside the following layers: (a ₀ ) 10-15 μm thick layer with polybutylene terephthalate as material; (a) 80-100 μm thick with copolymer of styrene and butadiene as material or 180-200
a layer having a thickness of μm; (b) a layer having a thickness of 10 to 15 μm containing polybutylene terephthalate as a material; and (c) containing a styrene-butadiene-styrene block copolymer and a copolymer of vinyltoluene and a styrene compound 2 Particularly preferred is a coextruded synthetic resin composite containing a heat-sealable lacquer with a thickness of .about.15 .mu.m.

The above coextruded synthetic resin composite in which the layer (a ₀ ) is omitted is also preferred.

The synthetic resin composites according to the invention having layers (a ₀ ) and (a) and (b) or layers (a) and (b) are produced by coextrusion.

The coextrusion heat-sealable lacquered synthetic resin composite according to the invention is used as a packaging material.

The synthetic resin composite according to the present invention is preferably used as a lid material for a molded product finished into a container shape.

The lid material can already be present in the shape of a lid, for example as a flat material in the form of arches, rolls or as a die-cut or as a molded lid material, for example deep or deep-drawn.

Molded bodies which are finished in the shape of containers include injection-molded or in particular deep-drawn molded bodies. The shaped bodies have in particular one or more sealing edges or surfaces and have a circular, elliptical, angled or rounded cross section in plan view, for example cups, petri dishes,
It is a bottle or a tube.

If the shaped body is in the form of a tube, the synthetic resin composite according to the invention can likewise be used as a lid material at one or both ends.

The synthetic resin composite according to the present invention is preferably used as a lid for a deep drawing or injection molding container. The synthetic resin composite is placed, for example, in sheet form on a container to be closed, sealed, and then perforated or cut according to essentially the perimeter of the container, or from a sheet-shaped composite laminate the lid is closed. The edges are cut or stamped, optionally shaped and sealed.

Lids made of synthetic resin composites according to the present invention are highly crack and tear stable. Therefore, for example, 1
000cm up to ^2, the purposeful to 500 cm ^2, it is possible in particular to produce a lid suitable for use with large size up to 100 cm ^2, processed. Actually, for example, 1
A lid with an area of 0-100 cm ² is used.

The invention also comprises a container cover made from the coextruded heat-sealable lacquered synthetic resin composite according to the invention.

In particular, layer (a) or (a ₀ ) can be printed and / or pigmented.

For reasons of recyclability and compatibility with the packing, the dyes used here are, for example, halogen-free, in particular chlorine-free, and heavy-metal-free, for example cadmium.

Finally, the invention relates to a coextruded heat-sealable lacquer according to the invention having layers (a ₀ ), (a), (b) and (c) or layers (a), (b) and (c). A method of closing a container using a lid manufactured from a coated synthetic resin composite is included, in which the sealing of the lid to the container is 1
Within a temperature range of 40 to 230 ° C, especially 165 to 230 ° C,
It is performed within 0.2 to 1 second.

It will be appreciated that the temperature range over which sealing of the lid to the container, for example, is possible is very large. Therefore,
It is particularly ensured that the temperature and pressure regulation of the sealing process can be easily controlled and that device-side variations in operating conditions can be accommodated by the material.

With the synthetic resin composite according to the invention, a problem-free adhesion onto the layer (b) of the heat-sealable lacquer, in particular polybutylene terephthalate, is also achieved. Heat-sealable lacquers seal in a very wide temperature range.

Upon removal (stripping) of the synthetic resin composite lid according to the invention, no visible residue is left on the sealing edge, for example the edge of the cup. The synthetic resin composites according to the invention, and in particular the lids produced therefrom, do not impede the recyclability of the container, since the dry heat-sealable lacquer, due to its chemical structure, is largely compatible with the layer (b) forming the carrier. .

Therefore, a recyclable polystyrene-containing synthetic resin lid material having interlayer sealability over a wide range of pressures and temperatures, resulting in an airtight packaging after sealing, for example as punched lids and wound products, is produced. It is possible to This lid has good removability (stripping) and leaves no disturbing sealing layer residue on the container edge. The lid is removed from the container without tearing or delamination.

The compatibility of the materials used in the synthetic resin composites according to the invention guarantees complete recyclability of the materials.

Good economic and ecological results are obtained if a container based on a styrene-containing thermoplastic resin is produced, when using a container which is closed by a lid. In this case, the container and the lid can be recycled together.

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Claims (22)

[Claims] 1. From outside to inside the following layers: (a) 2 containing a styrene-based thermoplastic
0-300 μm thick layer; (b) Ester-based thermoplastic resin containing 8
A coextrusion heat-sealable lacquer comprising a 2-15 μm-thick heat-sealable lacquer comprising a styrene-butadiene-styrene block copolymer and a copolymer of vinyltoluene and a styrene compound. Painted synthetic resin composite. 2. The following layers from the outside to the inside: 8 containing a thermoplastic resin based on (a ₀ ) ester.
˜40 μm thick layer; (a) 2 containing styrene based thermoplastic resin
0-300 μm thick layer; (b) Ester-based thermoplastic resin containing 8
˜40 μm thick layer; and (c) a 2-15 μm thick heat sealable lacquer comprising a styrene-butadiene-styrene block copolymer and a copolymer of vinyltoluene and a styrene compound. Coextrusion heat-sealing lacquered synthetic resin composite. 3. The synthetic resin composite according to claim 2, wherein the layer (a ₀ ) has a thickness of 10 to 30 μm. 4. The synthetic resin composite according to claim 2, wherein the layer (a ₀ ) has a thickness of 10 to 20 μm. 5. The synthetic resin composite according to claim 1, wherein the layer (a) has a thickness of 60 to 300 μm. 6. The synthetic resin composite according to claim 1, wherein the layer (a) has a thickness of 60 to 130 μm or a thickness of 130 to 300 μm. 7. The synthetic resin composite according to claim 1, wherein the layer (b) has a thickness of 10 to 30 μm. 8. The synthetic resin composite according to claim 1, wherein the layer (b) has a thickness of 10 to 20 μm. 9. The synthetic resin composite according to claim 1, wherein the lacquer layer (c) has a thickness of 2 to 10 μm. 10. The thermoplastic resin based on an ester is a polyalkylene terephthalate having an alkyl group having 2 to 10 carbon atoms or an alkyl residue.
The synthetic resin composite described in 1. 11. The synthetic resin composite according to claim 1, wherein the ester-based thermoplastic resin is polybutylene terephthalate. 12. The styrene-based thermoplastic resin is a copolymer of styrene and butadiene.
Or the synthetic resin composite according to 2. 13. The synthetic resin composite according to claim 1, wherein the lacquer layer contains a polystyrene-containing thermoplastic resin, and the thermoplastic resin is a copolymer of styrene and butadiene. 14. The synthetic resin composite according to claim 1, wherein the individual layers are bonded to each other by coextrusion. 15. The synthetic resin composite according to claim 1, wherein the heat-sealable lacquer contains a styrene-butadiene-styrene block copolymer and a copolymer of vinyltoluene and α-methylstyrene. 16. The synthetic resin composite according to claim 15, wherein the heat-sealable lacquer contains a filler. 17. The synthetic resin composite according to claim 15, wherein the heat-sealable lacquer comprises an olefin-based wax. 18. Use of the synthetic resin composite according to claim 1 or 2 as a packaging material. 19. Use of the synthetic resin composite according to claim 18 as a lid material for a molded product finished into a container shape. 20. Use of the synthetic resin composite material according to claim 19 as a lid for a deep container. 21. A container cover made of the synthetic resin composite according to claim 1 or 2. 22. 140-2 sealing of the lid to the container
The method for closing a container using a lid made of a synthetic resin composite according to claim 1 or 2, which is performed in a temperature range of 30 ° C for 0.2 to 1.0 second.