CN111363507B - Coating composition and application thereof - Google Patents

Abstract

The present invention relates to a coating composition comprising: epoxy resin, phenolic resin, oxidized polypropylene wax and solvent, wherein the acid value of the oxidized polypropylene wax is 12-40mg KOH/g. The coating composition according to the present invention can firmly adhere the polypropylene material to a metal such as tin plate. Container closures comprising a metal layer bonded by the above-described coating composition and a polypropylene material liner can withstand handling at higher temperatures and can produce a reliable seal during beverage production and storage.

Description

A kind of coating composition and its application

technical field

The invention belongs to the technical field of coatings. Specifically, the present invention relates to a coating composition and its application.

Background technique

Many food products such as beverages are now packaged in bottles or cans, on which they are sealed by lids. Covers are usually prepared in tinplate, ie chromed or tinned iron, aluminum and a liner which is adhered by paint.

Common coatings currently used for metal caps are polyester amino coatings and coatings containing epoxy and phenolic resins.

There are three main types of gasket materials currently used: polyvinyl chloride (PVC), polyethylene (PE) and polypropylene (PP).

Adhesion between PVC liners and many commonly used paints is good, but because PVC usually contains plasticizers such as dioctyl phthalate, which can cause cancer, it has been gradually abandoned due to health concerns. Use polyvinyl chloride.

Polyethylene liners generally do not contain plasticizers and are therefore considered safety liners. However, due to the low melting point of polyethylene materials, polyethylene liners cannot be used for the packaging of certain beverages such as soy milk and orange juice, because they need to be sterilized at 120-130°C. During this process, polyethylene The gasket will soften and lose its sealing effect.

Polypropylene liners usually do not contain plasticizers, so they are safety liners and can withstand sterilization at 120-130°C, but compared to polyvinyl chloride, polypropylene has few polar groups, and poly Acrylic liners are difficult to attach securely to lids through existing paint.

Therefore, there is a need in the art for a coating composition that can firmly adhere a polypropylene liner to metal such as tinplate.

There is also a need in the art for container closures that can withstand sterilization treatments at 120-130°C.

Contents of the invention

It is an object of the present invention to provide a coating composition capable of firmly adhering polypropylene materials to metals such as tinplate or aluminium.

Another object of the present invention is to provide a container closure comprising a metal layer and a liner of polypropylene material bonded by the above coating composition.

Another object of the present invention is to provide a packaging container comprising the above container cap.

Still another object of the present invention is to provide a metal composite comprising metal and polypropylene material bonded by the above coating composition.

Another object of the present invention is to provide the use of the above coating composition for bonding metal and polypropylene materials.

Therefore, according to the first aspect of the present invention, a coating composition is provided, which comprises: epoxy resin, phenolic resin, oxidized polypropylene wax and solvent, and the acid value of the oxidized polypropylene wax is 12-40 mgKOH/g.

According to a second aspect of the present invention there is provided a container closure comprising a metal layer and a polypropylene material liner bonded by the coating composition described above.

According to a third aspect of the present invention, there is provided a packaging container comprising a container body and the above-mentioned container cover.

According to a fourth aspect of the present invention there is provided a metal composite comprising a metal and a polypropylene material bonded by the coating composition described above.

According to a fifth aspect of the present invention, there is provided the use of the above-mentioned coating composition for bonding metal and polypropylene materials.

The coating composition according to the invention can firmly adhere polypropylene material to metal such as tinplate. A container lid comprising a metal layer bonded by the above-mentioned coating composition and a liner of polypropylene material can withstand processing at higher temperatures and can produce a reliable seal during the production and storage of beverages.

specific implementation plan

The present invention is now described for purposes of illustration and not limitation.

According to the first aspect of the present invention, a coating composition is provided, which comprises: epoxy resin, phenolic resin, oxidized polypropylene wax and solvent, and the acid value of the oxidized polypropylene wax is 12-40 mgKOH/g.

The coating composition according to the present invention has no special requirements on the epoxy resin, and may be an epoxy resin commonly used in this field.

Preferably, the epoxy resin is a bisphenol A epoxy resin, more preferably a bisphenol A epoxy resin with an epoxy value in the range of 0.02-0.07eq/100g.

The epoxy resin may be one type of epoxy resin or a mixture of multiple epoxy resins.

In some embodiments, the epoxy resin is a bisphenol A type epoxy resin with an epoxy value in the range of 0.04-0.07 eq/100 g, such as E-06 type epoxy resin.

In some embodiments, the epoxy resin is a bisphenol A type epoxy resin with an epoxy value in the range of 0.02-0.045 eq/100 g, such as E03 type epoxy resin.

In some embodiments, the epoxy resin is a bisphenol A type epoxy resin with an epoxy value in the range of 0.04-0.07eq/100g and a bisphenol A type epoxy resin with an epoxy value in the range of 0.02-0.045eq/100g Mixture of epoxy resins.

Preferably, the epoxy resin is present in an amount ranging from 20% to 30% by weight, based on the total weight of the coating composition.

The coating composition according to the present invention has no special requirements on the phenolic resin, and may be a commonly used phenolic resin in this field.

Preferably, the phenolic resin is selected from the phenolic resin prepared by polycondensation of phenol, bisphenol A, the phenol homologue of formula (I) or its mixture with formaldehyde:

in:

n is 1 or 2;

R ₁ is C ₁ -C ₁₀ alkyl, preferably C ₁ -C ₆ alkyl, more preferably C ₁ -C ₄ alkyl.

The alkyl includes straight chain alkyl and branched chain alkyl. For example, for _C3 alkyl, n-propyl and isopropyl are included; for _C4 alkyl, n-butyl, isobutyl, tert-butyl and sec-butyl are included.

Examples of phenol homologues include methylphenol, ethylphenol, propylphenol, tert-butylphenol, amylphenol, nonylphenol, xylenol and the like.

The methylphenols include p-cresol, o-cresol and m-cresol.

Depending on storage needs, the phenolic resin can be further etherified with butanol.

In some embodiments, the phenolic resin is selected from phenolic resins prepared by condensation polymerization of bisphenol A, phenol, tert-butylphenol or a mixture thereof with formaldehyde.

As an example of a phenolic resin, one may cite the Phenodur PR285 phenolic resin from the company Allnex.

Preferably, the phenolic resin is present in an amount ranging from 10% to 20% by weight, based on the total weight of the coating composition.

In some embodiments, the Mn molecular weight of the oxidized polypropylene wax is 1500-5000 Daltons, and the Mw molecular weight is 8000-20000 Daltons.

Preferably, the Mn molecular weight of the oxidized polypropylene wax is 2300-2700 Daltons, and the Mw molecular weight is 11000-13000 Daltons.

In some embodiments, the oxidized polypropylene wax has a viscosity at 170°C of 100-700 cps, preferably 100-400 cps, more preferably 120-200 cps, as determined according to ASTM D-1505.

In some embodiments, the oxidized polypropylene wax has a melting point of 150-170°C.

Commercial examples of usable oxidized polypropylene waxes include 2210 oxidized polypropylene wax and 2216 oxidized polypropylene wax available from GMT.

Preferably, the oxidized polypropylene wax is present in an amount ranging from 3% to 15% by weight, based on the total weight of the coating composition.

The solvent is preferably an organic solvent.

Preferably, the solvent is selected from toluene, xylene, tetramethylbenzene, cyclohexanone, propylene glycol methyl ether, ethyl acetate, butyl acetate, ethylene glycol ether alkylate and mixtures thereof.

In some embodiments, the solvent is a mixture of xylene, toluene, butyl acetate, and cyclohexanone.

The coating composition can be prepared by mixing the components together with thorough agitation.

According to a second aspect of the present invention there is provided a container closure comprising a metal layer and a polypropylene material liner bonded by the coating composition described above.

The metal layer is made of metal selected from tinplate, aluminum and the like.

The polypropylene material liner is made of polypropylene material commonly used for sealing.

In the present application, the polypropylene material may be pure polypropylene or a mixture of polypropylene and thermoplastic elastomer.

When a mixture of polypropylene and thermoplastic elastomer is used, the content of polypropylene is not lower than 90% by weight and the content of thermoplastic elastomer is not higher than 10% by weight, based on the total weight of the mixture.

Preferably, the melting point of the thermoplastic elastomer is not lower than 140° C., which can be determined by, for example, DSC method.

Preferably, the thermoplastic elastomer is selected from the group consisting of styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-ethylene/butylene block copolymer (SEBS), styrene-butadiene rubber (SBR), Styrene-isoprene-styrene (SIS).

In some embodiments, the thickness of the metal layer is 0.5-2 mm, and the thickness of the polypropylene material pad is 0.5-1.5 mm.

In some embodiments, the thickness of the metal layer is 1.5 mm, and the thickness of the polypropylene material liner is 1 mm.

The preparation of the container cover can be carried out by methods known in the art, such as first coating the metal sheet or plate with the coating composition, and then forming the cover by stamping the metal sheet or plate coated with the coating composition The blank, such as a crown cap, is then extruded or dropped into the cap blank with molten polypropylene material, and the molten polypropylene material is then extruded to form the liner.

According to a third aspect of the present invention, there is provided a packaging container comprising a container body and the above-mentioned container cover.

The packaging container may be, for example, a wine bottle, a soybean milk bottle, a fruit juice bottle, a seasoning bottle, and the like.

According to a fourth aspect of the present invention there is provided a metal composite comprising a metal and a polypropylene material bonded by the coating composition described above.

Preferably, the metal is selected from tinplate, aluminum and the like.

Preferably, the polypropylene material is prepared from a polypropylene material commonly used for sealing.

For example, the polypropylene material may be pure polypropylene or a blend of polypropylene and a thermoplastic elastomer.

When a mixture of polypropylene and thermoplastic elastomer is used, the content of polypropylene is not lower than 90% by weight and the content of thermoplastic elastomer is not higher than 10% by weight, based on the total weight of the mixture.

Preferably, the melting point of the thermoplastic elastomer is not lower than 140°C, which can be determined by DSC method.

Preferably, the thermoplastic elastomer is selected from the group consisting of styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-ethylene/butylene block copolymer (SEBS), styrene-butadiene rubber (SBR), Styrene-isoprene-styrene (SIS).

According to a fifth aspect of the present invention, there is provided the use of the above coating composition for bonding polypropylene material to metal.

Preferably, the metal is selected from tinplate, aluminum and the like.

Preferably, the polypropylene material is a pure polypropylene material or a mixture of polypropylene and thermoplastic elastomer.

When a mixture of polypropylene and thermoplastic elastomer is used, the content of polypropylene is not lower than 90% by weight and the content of thermoplastic elastomer is not higher than 10% by weight, based on the total weight of the mixture.

Preferably, the melting point of the thermoplastic elastomer is not lower than 140° C., as determined by DSC method.

Preferably, the thermoplastic elastomer is selected from the group consisting of styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-ethylene/butylene block copolymer (SEBS), styrene-butadiene rubber (SBR), Styrene-isoprene-styrene (SIS).

In the description and claims of the present application, descriptions of various technical features on the same subject matter may be combined with each other, as long as such combination does not produce contradictions.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. When the definitions of terms in this specification conflict with the meanings generally understood by those skilled in the art to which the present invention belongs, the definitions stated herein shall prevail.

Except in the working examples or where otherwise indicated, in the specification and claims of this application all numbers expressing amounts, percentages etc. are understood to be modified in all instances by the term "about".

The terms "comprising" and "including" used in the specification of the present application encompass the case of also including or including other elements not explicitly mentioned as well as the case of consisting of the mentioned elements.

Example

The concept and technical effects of the present invention will be further described below in conjunction with the embodiments, so that those skilled in the art can fully understand the purpose, features and effects of the present invention.

Comparative Example 1

Adopt 25g E-06 epoxy resin, 15g PR 285 phenolic resin and 60g solvent (20g xylene, 16g toluene, 16g butyl acetate and 8g cyclohexanone) to prepare coating composition, the gained coating composition is coated on tinplate . The coating was cured at 180°C for 10 minutes to obtain a coating with a dry coat weight of 10-12 g/m ² .

After the tinplate coated with the coating is completely cooled, several polypropylene materials with a diameter of 3-5mm (wherein the content of polypropylene is 93% by weight, the content of thermoplastic elastomer styrene-butadiene rubber is 7% by weight, and the melting point of DSC is 141.4°C) The particles are placed on the coating on the tinplate, and each pile contains 8-10 polypropylene particles. The tinplate and polypropylene particles were transferred together into an oven at 200°C for 3 minutes and then each stack of polypropylene material particles was pressed into a pad using a 200 g weight.

Finally the tinplate with the polypropylene liner on top was removed from the oven and allowed to cool completely before testing the adhesion between the polypropylene liner and the coating.

Adhesion was tested as follows:

First use a blade to cut a 3-5mm incision on the liner, and then perform a stripping operation between the liner and the tinplate. Adhesion was determined and scored according to the difficulty of peeling, where 0 means no adhesion and very easy peeling, and 5 means the adhesion is so good that it cannot be peeled off. When the score is 3 or more, the adhesion is considered to meet the requirements of the art. The test results are shown in Table 1.

Comparative Example 2

Adopt 25g E-06 epoxy resin, 15g PR 285 phenolic resin, 5g oxidized polypropylene wax (2203 oxidized polypropylene wax purchased from GMT company, its acid value is 6.9mgKOH/g, Mn is 5807 daltons, Mw is 26669 Daltons, the viscosity at 170°C is 2205cp, and the melting point is 161.5°C) and 55g solvent (17g xylene, 14g toluene, 16g butyl acetate and 8g cyclohexanone) to prepare the coating composition, and the resulting coating composition Coated on tinplate. The coating was cured at 180°C for 10 minutes to obtain a coating with a dry coat weight of 10-12 g/m ² .

After the tinplate coated with the coating is completely cooled, several polypropylene materials with a diameter of 3-5mm (wherein the content of polypropylene is 93% by weight, the content of thermoplastic elastomer styrene-butadiene rubber is 7% by weight, and the melting point of DSC is 141.4°C) The particles are placed on the coating on the tinplate, and each pile contains 8-10 polypropylene particles. The tinplate and polypropylene particles were transferred together into an oven at 200°C for 3 minutes and then each stack of polypropylene material particles was pressed into a pad using a 200 g weight.

Finally the tinplate with the polypropylene liner on top was removed from the oven and allowed to cool completely before testing the adhesion between the polypropylene liner and the coating.

The adhesion test was carried out and scored as described in Comparative Example 1, and the results are shown in Table 1.

Comparative Example 3

Adopt 25g E-06 epoxy resin, 15g PR 285 phenolic resin, 5g oxidized polypropylene wax (2207 oxidized polypropylene wax purchased from GMT company, its acid value is 10.72mgKOH/g, Mn is 2972 daltons, Mw is 14898 Daltons, the viscosity at 170°C is 847.3cp, and the melting point is 160.6°C) and 55g solvent (17g xylene, 14g toluene, 16g butyl acetate and 8g cyclohexanone) to prepare the coating composition, and the resulting coating composition Coated on tinplate. The coating was cured at 180°C for 10 minutes to obtain a coating with a dry coat weight of 10-12 g/m ² .

After the tinplate coated with the coating is completely cooled, several polypropylene materials with a diameter of 3-5mm (wherein the content of polypropylene is 93% by weight, the content of thermoplastic elastomer styrene-butadiene rubber is 7% by weight, and the melting point of DSC is 141.4°C) The particles are placed on the coating on the tinplate, and each pile contains 8-10 polypropylene particles. The tinplate and polypropylene particles were transferred together into an oven at 200°C for 3 minutes and then each stack of polypropylene material particles was pressed into a pad using a 200 g weight.

Finally the tinplate with the polypropylene liner on top was removed from the oven and allowed to cool completely before testing the adhesion between the polypropylene liner and the coating.

The adhesion test was carried out and scored as described in Comparative Example 1, and the results are shown in Table 1.

Example 1

Adopt 25g E-06 epoxy resin, 15g PR 285 phenolic resin, 5g oxidized polypropylene wax (2210 oxidized polypropylene wax purchased from GMT, its acid value is 12.16mgKOH/g, Mn is 2608 Dalton, Mw is 12965 Dalton, viscosity at 170°C is 181.5cp, melting point is 156.3°C) and 55g solvent (17g xylene, 14g toluene, 16g butyl acetate and 8g cyclohexanone) to prepare the coating composition, the resulting coating composition Coated on tinplate. The coating was cured at 180°C for 10 minutes to obtain a coating with a dry coat weight of 10-12 g/m ² .

After the tinplate coated with paint is completely cooled, some polypropylene materials (wherein the content of polypropylene is 93% by weight, the content of thermoplastic elastomer styrene-butadiene rubber is 7% by weight, and the DSC melting point is 141.4° C. ) particles are placed on the coating on the tinplate, and each pile contains 8-10 polypropylene particles. The tinplate and polypropylene particles are transferred together to an oven at 200 ° C for 3 minutes, and then use a 200g weight to place the Stacks of polypropylene material particles pressed into liners

Finally the tinplate with the polypropylene liner on top was removed from the oven and allowed to cool completely before testing the adhesion between the polypropylene liner and the coating.

The adhesion test was carried out and scored as described in Comparative Example 1, and the results are shown in Table 1.

Example 2

Adopt 25g E-06 epoxy resin, 15g PR 285 phenolic resin, 5g oxidized polypropylene wax (2216 oxidized polypropylene wax purchased from GMT company, its acid value is 17.08mgKOH/g, Mn is 2481 Dalton, Mw is 11740 Dalton, viscosity at 170°C is 126.5cp, melting point is 11°C) and 55g solvent (17g xylene, 14g toluene, 16g butyl acetate and 8g cyclohexanone) to prepare the coating composition, and the resulting coating composition Coated on tinplate. The coating was cured at 180°C for 10 minutes to obtain a coating with a dry coat weight of 10-12 g/m ² .

After the tinplate coated with the coating is completely cooled, several polypropylene materials with a diameter of 3-5mm (wherein the content of polypropylene is 93% by weight, the content of thermoplastic elastomer styrene-butadiene rubber is 7% by weight, and the melting point of DSC is 141.4°C) The particles are placed on the coating on the tinplate, and each pile contains 8-10 polypropylene particles. Transfer the tinplate and polypropylene particles together to an oven at 200°C for 3 minutes, then use a 200g weight to press each pile of polypropylene material particles into a liner

Finally the tinplate with the polypropylene liner on top was removed from the oven and allowed to cool completely before testing the adhesion between the polypropylene liner and the coating.

The adhesion test was carried out and scored as described in Comparative Example 1, and the results are shown in Table 1.

Comparative Example 4

Adopt 25g E-06 epoxy resin, 15g PR 285 phenolic resin, 1g oxidized polypropylene wax (2216 oxidized polypropylene wax purchased from GMT company, its acid value is 17.08mgKOH/g, Mn is 2481 Dalton, Mw is 11740 Dalton, viscosity at 170°C is 126.5cp, melting point is 11°C) and 59g solvent (20g xylene, 14g toluene, 16g butyl acetate and 9g cyclohexanone) to prepare the coating composition, and the resulting coating composition Coated on tinplate. The coating was cured at 180°C for 10 minutes to obtain a coating with a dry coat weight of 10-12 g/m ² .

After the tinplate coated with the coating is completely cooled, several polypropylene materials with a diameter of 3-5mm (wherein the content of polypropylene is 93% by weight, the content of thermoplastic elastomer styrene-butadiene rubber is 7% by weight, and the melting point of DSC is 141.4°C) The particles are placed on the coating on the tinplate, and each pile contains 8-10 polypropylene particles. Transfer the tinplate and polypropylene particles together to an oven at 200°C for 3 minutes, then use a 200g weight to press each pile of polypropylene material particles into a liner

Finally the tinplate with the polypropylene liner on top was removed from the oven and allowed to cool completely before testing the adhesion between the polypropylene liner and the coating.

The adhesion test was carried out and scored as described in Comparative Example 1, and the results are shown in Table 1.

Example 3

Adopt 25g E-06 epoxy resin, 15g PR 285 phenolic resin, 3g oxidized polypropylene wax (2216 oxidized polypropylene wax purchased from GMT company, its acid value is 17.08mgKOH/g, Mn is 2481 daltons, Mw is 11740 Daltons, the viscosity at 170°C is 126.5cp, and the melting point is 11°C) and 57g solvent (18g xylene, 14g toluene, 16g butyl acetate and 9g cyclohexanone) solvent to prepare the coating composition, and the resulting coating The composition is coated on tinplate. The coating was cured at 180°C for 10 minutes to obtain a coating with a dry coat weight of 10-12 g/m ² .

After the tinplate coated with the coating is completely cooled, several polypropylene materials with a diameter of 3-5mm (wherein the content of polypropylene is 93% by weight, the content of thermoplastic elastomer styrene-butadiene rubber is 7% by weight, and the melting point of DSC is 141.4°C) The particles are placed on the coating on the tinplate, and each pile contains 8-10 polypropylene particles. Transfer the tinplate and polypropylene particles together to an oven at 200°C for 3 minutes, then use a 200g weight to press each pile of polypropylene material particles into a liner

Finally the tinplate with the polypropylene liner on top was removed from the oven and allowed to cool completely before testing the adhesion between the polypropylene liner and the coating.

The adhesion test was carried out and scored as described in Comparative Example 1, and the results are shown in Table 1.

Example 4

Adopt 25g E-06 epoxy resin, 15g PR 285 phenolic resin, 8g oxidized polypropylene wax (2216 oxidized polypropylene wax purchased from GMT company, its acid value is 17.08mgKOH/g, Mn is 2481 Dalton, Mw is 11740 Daltons, the viscosity at 170°C is 126.5cp, and the melting point is 11°C) and 52g solvent (16g xylene, 13g toluene, 16g butyl acetate and 7g cyclohexanone) solvent to prepare the coating composition, and the resulting coating The composition is coated on tinplate. The coating was cured at 180°C for 10 minutes to obtain a coating with a dry coat weight of 10-12 g/m ² .

After the tinplate coated with the coating is completely cooled, several polypropylene materials with a diameter of 3-5mm (wherein the content of polypropylene is 93% by weight, the content of thermoplastic elastomer styrene-butadiene rubber is 7% by weight, and the melting point of DSC is 141.4°C) The particles are placed on the coating on the tinplate, and each pile contains 8-10 polypropylene particles. Transfer the tinplate and polypropylene particles together to an oven at 200°C for 3 minutes, then use a 200g weight to press each pile of polypropylene material particles into a liner

Finally the tinplate with the polypropylene liner on top was removed from the oven and allowed to cool completely before testing the adhesion between the polypropylene liner and the coating.

The adhesion test was carried out and scored as described in Comparative Example 1, and the results are shown in Table 1.

Table 1

Although some aspects of the present invention have been shown and discussed, those skilled in the art should appreciate that the above-mentioned aspects can be changed without departing from the principle and spirit of the present invention, so the scope of the present invention will be determined by the claims and equivalent content.

Claims (12)

1. A coating composition characterized in that it comprises: bisphenol a epoxy resin having an epoxy value in the range of 0.02 to 0.07eq/100g, a phenolic resin, an oxidized polypropylene wax having an acid value of 12 to 40mgKOH/g, and a solvent, the oxidized polypropylene wax being present in an amount in the range of 3 wt% to 15 wt%, based on the total weight of the coating composition.

2. The coating composition of claim 1 wherein the oxidized polypropylene wax has a Mn molecular weight of 1500 to 5000 daltons and a Mw molecular weight of 8000 to 20000 daltons.

3. The coating composition of claim 1 or 2, wherein the oxidized polypropylene wax has a viscosity of 100-700cp at 170 ℃, as determined according to ASTM D-1505.

4. The coating composition of claim 1 or 2, wherein the oxidized polypropylene wax has a viscosity of 120-200cp at 170 ℃, as determined according to ASTM D-1505.

5. The coating composition according to claim 1 or 2, characterized in that the epoxy resin has an epoxy value in the range of 0.04-0.07eq/100 g.

6. The coating composition according to claim 1 or 2, characterized in that the phenolic resin is a phenolic resin prepared by polycondensation of a phenol selected from phenol, bisphenol a, phenol homologs of formula (I) or mixtures thereof with formaldehyde:

wherein:

n is 1 or 2;

R ₁ is C ₁ -C ₁₀ An alkyl group.

7. The coating composition according to claim 1 or 2, wherein the solvent is selected from the group consisting of toluene, xylene, tetramethylene, cyclohexanone, propylene glycol methyl ether, ethyl acetate, butyl acetate, ethylene glycol ethyl ether alkyd esters and mixtures thereof.

8. A container lid, characterized in that it comprises a metal layer and a polypropylene material lining bonded by the coating composition according to any one of claims 1 to 7.

9. The container lid of claim 8, wherein the metal layer has a thickness of 0.5-2mm and the polypropylene liner has a thickness of 0.5-1.5mm.

10. A packaging container characterized in that it comprises a container body and a container lid as claimed in claim 8 or 9.

11. A metal composite comprising a metal and a polypropylene material bonded by the coating composition of any one of claims 1-5.

12. Use of the coating composition according to any of claims 1-7 for bonding a polypropylene material to a metal.