Multi-layer sheet containing a foam layer suitable for food packaging

Abstract

The present invention relates to a multilayer sheet comprising at least two layers (A) and (B) in close contact with one another, wherein layer (A) is a foamed sheet comprising a high melt strength polypropylene composition and layer (B) is a coated non-foamed layer comprising a polypropylene composition, a process for producing the multilayer sheet, an article comprising the multilayer sheet, and the use of the multilayer sheet for producing an article having improved water vapor and oxygen permeability properties.

Description

[Technical field]

[0001] The present invention relates to a multilayer sheet comprising at least two layers (A) and (B) in close contact with one another, where layer (A) is a foamed sheet comprising a high melt strength polypropylene composition and layer (B) is a coated non-foamed layer comprising a polypropylene composition, a process for producing said multilayer sheet, an article comprising said multilayer sheet, and the use of said multilayer sheet for the manufacture of an article having improved water vapor and oxygen transmission properties. [Background technology]

[0002] In many food packaging applications, especially in dairy packaging such as milk and yogurt cups, excellent barrier properties against oxygen and moisture penetration combined with good thermal insulation properties are required to ensure a long shelf life of the packaged product. In addition to barrier and insulating properties, mono-material solutions are needed for easy and efficient recycling of used packaging using existing recycling streams. The packaging materials used need to also have sufficient mechanical properties to be suitable for the end use. Currently, LDPE-coated paperboard is commonly used for packaging dairy products. However, the barrier properties of LDPE-coated paperboard are usually not optimal, leading to a shorter shelf life of the packaged product. In addition, LDPE-coated paperboard is a multi-component system, which makes the recycling process more cumbersome and costly. Therefore, the recent focus in the development of dairy packaging has been on novel packaging material solutions that meet the above-mentioned requirements, especially improved barrier properties against moisture and oxygen penetration.

[0003] High melt strength polypropylene compositions and foams made therefrom are generally known in the art. However, obtaining homogeneous and improved foam quality remains a challenge. With improved foam quality, the same or even improved mechanical properties can be obtained in articles with a smaller thickness.

[0004] For example, for cups made from polypropylene foam, the wall thickness can be reduced, which allows more cups to be stored in the same volume, thus reducing storage and shipping costs. Additionally, the amount of material undergoing recycling processes or waste disposal is reduced.

[0005] One method for producing high melt strength polypropylene (HMS-PP) is described in European Patent Application Publication No. 0879830, filed by Borealis in 1997. It describes the basis of the Borealis high melt strength (HMS) post-reactor process, which uses peroxides and difunctionally unsaturated monomers and / or polyfunctionally unsaturated low molecular weight polymers to produce long chain branched polypropylene materials.

[0006] WO 2017 / 021292 discloses a foamed sheet of high melt strength polypropylene (HMS-PP) with improved mechanical strength, which, when laminated with a biaxially oriented polypropylene (BOPP) film on the inside, can also be used in applications requiring mechanical stability, such as containers for liquids. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent Application Publication No. 0879830 [Patent Document 2] International Publication No. 2017 / 021292 Brochure Summary of the Invention [Problem to be solved by the invention]

[0008] Although foamed sheets of high melt strength polypropylene (HMS-PP) exhibit good mechanical strength, they are not known for the good barrier properties required for perishable food applications such as dairy products. In the present invention, it has surprisingly been found that a multi-layer sheet comprising a foamed sheet of high melt strength polypropylene (HMS-PP) coated with a coating layer of non-foamed polypropylene exhibits good barrier properties against oxygen and moisture penetration in combination with good thermal insulation properties and mechanical strength, which allows for superior food packaging, especially for perishable foods such as dairy products, compared to prior art means. In addition, this multi-layer sheet is made only from polypropylene and is therefore more easily recyclable compared to composite materials such as LDPE-coated paperboard. [Means for solving the problem]

[0009] The present invention relates to a multilayer sheet comprising at least two layers (A) and (B), Layer (A) is 100-300 kg / m 3 , preferably 125 to 275 kg / m 3 , more preferably 150 to 250 kg / m 3 , and most preferably 175 to 225 kg / m 3 and the foamed sheet comprises a high melt strength polypropylene composition containing 85.0 to 100 wt%, preferably 90.0 to 99.9 wt%, and most preferably 92.0 to 99.8 wt%, of a high melt strength propylene polymer having long chain branches, based on the total weight of layer (A); Layer (B) is a coated non-foamed layer comprising a polypropylene composition comprising 85.0-100 wt.%, preferably 90.0-99.9 wt.%, most preferably 95.0-99.8 wt.% of a linear propylene polymer based on the total weight of layer (B); It concerns a multi-layer sheet in which layers (A) and (B) are in intimate contact with each other.

[0010] In another aspect, the present invention provides a method for producing the above or below described multilayer sheet, comprising the steps of: a) The high melt strength polypropylene composition is mixed with 100 to 300 kg / m 3 , preferably 125 to 275 kg / m 3 , more preferably 150 to 250 kg / m 3 , and most preferably 175 to 225 kg / m 3 to form a foamed sheet having a density of b) coating layer (A) with the polypropylene composition to obtain layer (B) in close contact with layer (A); The present invention relates to a method comprising the steps of:

[0011] In yet another aspect, the present invention relates to an article comprising the above or below described multilayer sheet.

[0012] In yet another aspect, the present invention relates to the use of a multilayer sheet as described above or below for the manufacture of an article having improved water vapor and oxygen transmission properties.

[0013] The article is preferably a food packaging, preferably a dairy packaging such as milk cartons and cups for cream cheese or yogurt.

[0014] definition According to the present invention, the expression "propylene homopolymer" relates to a polypropylene that consists essentially, i.e. at least 99.0% by weight, more preferably at least 99.5% by weight, even more preferably at least 99.8% by weight, for example at least 99.9% by weight, of propylene units. In another embodiment, only propylene units are detectable, i.e. only propylene is polymerized.

[0015] The expression "propylene copolymer" refers to a copolymer of propylene monomer units, and preferably C4 to C6 12The present invention relates to a polypropylene comprising comonomer units selected from α-olefins. The amount of comonomer units in the propylene copolymer is at least 0.1% by weight, preferably at least 0.2% by weight, and even more preferably at least 0.5% by weight. In the present invention, the amount of comonomer units in the propylene copolymer is suitably more than 0.5% by weight.

[0016] Propylene random copolymers are copolymers of propylene monomer units and, for example, C4-C 12 A copolymer with a comonomer unit, such as a comonomer unit selected from an alpha olefin, in which the comonomer unit is randomly distributed along the polymer chain. The propylene random copolymer can include comonomer units from one or more comonomers with different amounts of carbon atoms. The propylene random copolymer does not include an elastomeric phase.

[0017] "In adherent contact" in the sense of the present invention means that layer (A) and layer (B) are in direct contact without any intermediate layer between layer (A) and layer (B). In the process of the present invention, "in adherent contact" means that coating layer (B) is directly coated on one surface of layer (A) without any additional layer between layers (A) and (B).

[0018] The term "linear propylene polymer" indicates that the linear propylene polymer exhibits little or no branching structure.

[0019] Percentages are generally given herein as weight % unless stated differently. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention relates to a multilayer sheet comprising at least two layers (A) and (B), Layer (A) is 100-300 kg / m 3 , preferably 125 to 275 kg / m 3, more preferably 150 to 250 kg / m 3 , and most preferably 175 to 225 kg / m 3 and comprising a high melt strength polypropylene composition comprising 85.0 to 100 wt%, preferably 90.0 to 99.9 wt%, and most preferably 92.0 to 99.8 wt%, of a high melt strength propylene polymer having long chain branching, based on the total weight of the high melt strength polypropylene composition; Layer (B) is a coated non-foamed layer comprising a polypropylene composition comprising 85.0-100 wt. %, preferably 90.0-99.9 wt. %, and most preferably 95.0-99.8 wt. % of a linear propylene polymer based on the total weight of the polypropylene composition; It concerns a multi-layer sheet in which layers (A) and (B) are in intimate contact with each other.

[0021] High Melt Strength Propylene Polymer The major component of the high melt strength polypropylene composition of layer (A) is a high melt strength propylene polymer. The high melt strength propylene polymer is present in the high melt strength polypropylene composition in an amount of from 85.0 to 100 wt%, preferably from 90.0 to 99.9 wt%, and most preferably from 92.0 to 99.8 wt%, based on the total weight of the high melt strength polypropylene composition.

[0022] High melt strength propylene polymers are branched and therefore differ from linear propylene polymers in that the polypropylene backbone extends to the side chains, whereas unbranched propylene polymers, i.e. linear propylene polymers, do not. The side chains have a significant effect on the rheology of the propylene polymer. Thus, linear propylene polymers and high melt strength propylene polymers can be clearly distinguished by their flow behavior under stress.

[0023] Branching can generally be achieved by using specific catalysts, i.e. specific single-site catalysts, or by chemical modification. For the preparation of branched propylene polymers obtained by using specific catalysts, reference is made to EP 1 892 264 A. For branched propylene polymers obtained by chemical modification, reference is made to EP 0 879 830 A1. In such cases, the branched propylene polymer is also called high melt strength propylene polymer. This high melt strength propylene polymer is obtained by chemical modification of propylene polymer as described in more detail below. High melt strength propylene polymers are commercially available from Borealis AG under the trade name Daploy™.

[0024] Therefore, in order to provide a resulting high melt strength polypropylene composition having good shear thinning properties, the high melt strength propylene polymer as the main component of the high melt strength polypropylene composition has an F of greater than 20.0 cN. 30 Melt strength and v > 200mm / sec 30 It has melt extensibility, preferably F of more than 20.0 to 50.0 cN. 30 Melt strength and v of 200 to 300 mm / sec 30 It has melt extensibility. F 30 Melt strength and v 30 Melt extensibility is measured according to ISO 16790:2005.

[0025] Typically, the high melt strength polypropylene composition has a F of greater than 20.0 cN. 30 Melt strength and v > 200mm / sec 30 It also has melt extensibility, preferably F of more than 20.0 to 50.0 cN. 30 Melt strength and v of 200 to 300 mm / sec 30 It has melt extensibility.

[0026] In a preferred embodiment, the high melt strength propylene polymer is (a) F of more than 20.0 cN, for example, more than 20.0 to 50.0 cN, more preferably more than 21.0 cN, even more preferably 21.0 to 50.0 cN, even more preferably 25.0 to 50.0 cN, even more preferably 25.0 to 45.0 cN, and most preferably 30.0 to 45.0 cN, for example, 32.0 to 42.0 cN or 34.0 cN to 42.0 cN. 30 Melt strength, and (b) a v of more than 200 mm / s, for example more than 210 to 300 mm / s, more preferably more than 220 to 300 mm / s, even more preferably more than 225 mm / s, even more preferably 225 to 300 mm / s, even more preferably 230 to 290 mm / s, for example 250 to 290 mm / s or 253 to 290 mm / s 30 Melt Extensibility has.

[0027] In a particularly preferred embodiment, the high melt strength propylene polymer has an F of greater than 20.0 cN. 30 Melt strength and v of 200 to 300 mm / sec 30 Melt extensibility, e.g., F of 20.0 to 50.0 cN 30 Melt strength and v of 220 to 300 mm / sec 30 Melt extensibility, preferably F of more than 21.0 cN 30 Melt strength and v >225mm / sec 30 Melt extensibility, even more preferably F of 21.0 to 50.0 cN 30 Melt strength and v of 225~300mm / sec 30 Melt extensibility, more preferably F of 25.0 to 50.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, even more preferably F of 25.0 to 45.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, most preferably F of 30.0 to 45.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, e.g., F of 32.0 to 42.0 cN 30 Melt strength and v of 230~290mm / sec 30Melt extensibility, or F of 34.0 to 42.0 cN 30 Melt strength and v of 250~290mm / sec 30 Melt extensibility, or F of 34.0 to 42.0 cN 30 Melt strength and v of 253-290 mm / sec 30 It has melt extensibility.

[0028] Further, the high melt strength propylene polymer has a melt flow rate MFR2(230°C), measured according to ISO1133, of 15.0 g / 10 min or less, more preferably in the range of 0.5 to 15.0 g / 10 min, even more preferably in the range of 1.0 to 15.0 g / 10 min, for example in the range of 1.5 to 15.0 g / 10 min.

[0029] In a particularly preferred embodiment, the high melt strength propylene polymer has a melt flow rate MFR2(230°C), measured according to ISO1133, of 7.0 g / 10 min or less, preferably in the range of 0.5 to 7.0 g / 10 min, more preferably in the range of 0.5 to 6.5 g / 10 min, even more preferably in the range of 0.5 to 6.0 g / 10 min, still more preferably in the range of 1.0 to 6.0 g / 10 min, for example in the range of 1.5 to 5.0 g / 10 min.

[0030] Thus, in one particular embodiment, the high melt strength propylene polymer is (a) a melt flow rate MFR2 (230°C) of 15.0 g / 10 min or less, more preferably in the range of 0.5 to 15.0 g / 10 min, even more preferably in the range of 1.0 to 15.0 g / 10 min, for example in the range of 1.5 to 15.0 g / 10 min; (b) F of more than 20.0 cN, for example, more than 20.0 to 50.0 cN, more preferably more than 21.0 cN, even more preferably 21.0 to 50.0 cN, even more preferably 25.0 to 50.0 cN, even more preferably 25.0 to 45.0 cN, and most preferably 30.0 to 45.0 cN, for example, 32.0 to 42.0 cN or 34.0 to 42.0 cN. 30 Melt strength, (c) a v of more than 200 mm / s, preferably more than 210 to 300 mm / s, for example more than 220 to 300 mm / s, more preferably more than 225 mm / s, even more preferably 225 to 300 mm / s, still more preferably 230 to 290 mm / s, for example 250 to 290 mm / s or 253 to 290 mm / s 30 Melt Extensibility has.

[0031] In a particularly preferred variant of this embodiment, said high melt strength propylene polymer has a melt flow rate MFR2(230°C), measured according to ISO 1133, of 7.0 g / 10 min or less, preferably in the range of 0.5 to 7.0 g / 10 min, more preferably in the range of 0.5 to 6.5 g / 10 min, even more preferably in the range of 0.5 to 6.0 g / 10 min, still more preferably in the range of 1.0 to 6.0 g / 10 min, for example in the range of 1.5 to 5.0 g / 10 min.

[0032] Thus, in certain embodiments, the high melt strength propylene polymer has a melt flow rate MFR2(230° C.) of 15.0 g / 10 min or less, a F of 20.0 cN or more, 30 Melt strength and v of 210 to 300 mm / sec 30 Melt extensibility, e.g., melt flow rate MFR2 (230°C) in the range of 0.5 to 15.0 g / 10 min, F of more than 20.0 to 50.0 cN 30 Melt strength and v of 220 to 300 mm / sec 30 Melt extensibility, more preferably a melt flow rate MFR2 (230°C) in the range of 0.5 to 15.0 g / 10 min, F of more than 21.0 cN 30 Melt strength and v >225mm / sec 30 Melt extensibility, even more preferably a melt flow rate MFR2 (230°C) in the range of 1.0 to 15.0 g / 10 min, F of 21.0 to 50.0 cN 30 Melt strength and v of 225~300mm / sec 30 Melt extensibility, more preferably a melt flow rate MFR2 (230°C) in the range of 1.0 to 6.0 g / 10 min, F of 25.0 to 50.0 cN 30 Melt strength and v of 230~290mm / sec 30Melt extensibility, even more preferably a melt flow rate MFR2 (230°C) in the range of 1.0 to 15.0 g / 10 min, F of 25.0 to 45.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, most preferably a melt flow rate MFR2 (230°C) in the range of 1.0 to 15.0 g / 10 min, F of 30.0 to 45.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, e.g., melt flow rate MFR2 (230°C) in the range of 1.0 to 15.0 g / 10 min, F of 32.0 to 42.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, or melt flow rate MFR2 (230°C) in the range of 1.0 to 15.0 g / 10 min, F of 34.0 to 42.0 cN 30 Melt strength and v of 250~290mm / sec 30 Melt extensibility, or melt flow rate MFR2 (230°C) in the range of 1.0 to 15.0 g / 10 min, F of 34.0 to 42.0 cN 30 Melt strength and v of 253-290 mm / sec 30 It has melt extensibility.

[0033] In a particularly preferred variant of this embodiment, said high melt strength propylene polymer has a melt flow rate MFR2(230°C), measured according to ISO1133, of 7.0 g / 10 min or less, preferably in the range of 0.5 to 7.0 g / 10 min, more preferably in the range of 0.5 to 6.5 g / 10 min, even more preferably in the range of 0.5 to 6.0 g / 10 min, still more preferably in the range of 1.0 to 6.0 g / 10 min, such as in the range of 1.5 to 5.0 g / 10 min, or for example in the range of 1.0 to 5.0 g / 10 min.

[0034] Preferably, the high melt strength propylene polymer has a melting temperature of 140-180°C, more preferably 150-175°C, and most preferably 155-170°C.

[0035] In addition, the high melt strength propylene polymer preferably has a crystallization temperature of 110 to 150°C, more preferably 115 to 140°C, and most preferably 120 to 135°C.

[0036] Furthermore, the high melt strength propylene polymer can be a high melt strength random propylene copolymer, or a high melt strength propylene homopolymer, the latter being preferred.

[0037] When the high melt strength propylene polymer is a high melt strength random propylene copolymer, it is a copolymerizable monomer with propylene, such as ethylene and / or C4-C6 12 α-olefins, particularly ethylene and / or C4-C 10 It comprises a comonomer such as an α-olefin, for example 1-butene and / or 1-hexene. Preferably, the high melt strength random propylene copolymer comprises, and in particular consists of, monomers copolymerizable with propylene from the group consisting of ethylene, 1-butene and 1-hexene. More specifically, the high melt strength random propylene copolymer comprises, in addition to propylene, units derivable from ethylene and / or 1-butene. In a preferred embodiment, the high melt strength random propylene copolymer comprises units derivable only from ethylene and propylene. The comonomer content in the high melt strength random propylene copolymer is preferably in the range of more than 0.2 to 10.0 mol%, even more preferably in the range of more than 0.5 to 7.0 mol%.

[0038] In this regard, it should be mentioned that the high melt strength propylene polymer, either a high melt strength propylene homopolymer or a high melt strength random propylene copolymer, may contain additional unsaturated monomers different from the comonomers specified for the high melt strength random propylene copolymer. In other words, the high melt strength propylene homopolymer or high melt strength random propylene copolymer may be a copolymer of propylene, ethylene and other C4-C 12They may contain unsaturated units different from alpha-olefins, such as difunctional unsaturated monomer(s) and / or polyfunctional unsaturated low molecular weight polymer(s), as defined in detail below. Thus, the definitions of homopolymers and copolymers in terms of high melt strength propylene polymers actually refer to unmodified propylene polymers, preferably linear polypropylenes, which are used to obtain the melt strength propylene polymers by chemical modification, as defined in detail below.

[0039] Thus, in one preferred embodiment, the high melt strength propylene polymer is (a) when the high melt strength propylene polymer is a high melt strength propylene homopolymer, (i) Propylene and (ii) Difunctional unsaturated monomer(s) and / or polyfunctional unsaturated low molecular weight polymer(s). A unit derived from or (b) when the high melt strength propylene polymer is a high melt strength random propylene copolymer, (i) Propylene (ii) Ethylene and / or C4-C 12 α-olefins, such as 1-butene and / or 1-hexene, preferably ethylene, and (iii) Difunctional unsaturated monomer(s) and / or polyfunctional unsaturated low molecular weight polymer(s) Includes units derived from.

[0040] "Difunctionally unsaturated" or "polyfunctionally unsaturated" as used above preferably means the presence of two or more non-aromatic double bonds, as for example in divinylbenzene or cyclopentadiene or polybutadiene. Preferably only such difunctional or polyfunctionally unsaturated compounds are used that can be polymerized with the aid of free radicals (see below). The unsaturated sites in the difunctional or polyfunctionally unsaturated compounds are in a chemical bond state that is not actually "unsaturated", since the double bonds are used for covalent bonding to the polymer chain of the unmodified propylene polymer, preferably linear propylene polymer, respectively.

[0041] The reaction of the above difunctional unsaturated monomer(s) and / or polyfunctionally unsaturated low molecular weight polymer(s) synthesized from one and / or more unsaturated monomers, preferably having a number average molecular weight (Mn) of 10000 g / mol or less, with the unmodified propylene polymer, preferably a linear propylene polymer, is carried out in the presence of a thermal free radical former, e.g. a decomposable free radical former such as a thermally decomposable peroxide.

[0042] The difunctional unsaturated monomer is Divinyl compounds such as divinylaniline, m-divinylbenzene, p-divinylbenzene, divinylpentane and divinylpropane, Allyl compounds such as allyl acrylate, allyl methacrylate, allyl methyl maleate and allyl vinyl ether, Dienes such as 1,3-butadiene, chloroprene, cyclohexadiene, cyclopentadiene, 2,3-dimethylbutadiene, heptadiene, hexadiene, isoprene and 1,4-pentadiene, Aromatic and / or aliphatic bis(maleimide) bis(citraconimide) and mixtures of these unsaturated monomers may be also possible.

[0043] Particularly preferred difunctional unsaturated monomers are 1,3-butadiene, isoprene, dimethylbutadiene and divinylbenzene.

[0044] Polyfunctional unsaturated low molecular weight polymers, preferably having a number average molecular weight (Mn) of 10,000 g / mole or less, may be synthesized from one or more unsaturated monomers.

[0045] Examples of such low molecular weight polymers are: Polybutadienes, especially those with different microstructures in the polymer chain, i.e. 1,4-cis, 1,4-trans and 1,2-(vinyl) predominantly in the 1,2-(vinyl) configuration; Copolymer of butadiene and styrene with 1,2-(vinyl) in the polymer chain It is.

[0046] A preferred low molecular weight polymer is polybutadiene, especially polybutadiene having greater than 50.0 weight percent butadiene in the 1,2-(vinyl) configuration.

[0047] The high melt strength propylene polymer may contain a plurality of difunctional unsaturated monomers and / or polyfunctional unsaturated low molecular weight polymers. Even more preferably, the combined amount of difunctional unsaturated monomer(s) and polyfunctional unsaturated low molecular weight polymer(s) in the high melt strength propylene polymer is 0.01 to 10.0 wt % based on the high melt strength propylene polymer.

[0048] In a preferred embodiment, the high melt strength propylene polymer does not contain additives (A), thus, if the polypropylene composition contains additives (A), these additives (A) are not introduced into the high melt strength polypropylene composition during the manufacture of the high melt strength propylene polymer.

[0049] The high melt strength propylene polymers further preferably have a low gel content, typically less than 1.00 wt %, preferably less than 0.80 wt %, more preferably less than 0.50 wt %.

[0050] A suitable high melt strength propylene polymer is WB140HMS™ available from Borealis AG.

[0051] Unmodified Propylene Polymer As mentioned above, said high melt strength propylene polymer is a modified propylene polymer obtained by reacting an unmodified propylene polymer with a thermally decomposable free radical former and, optionally, with difunctionally unsaturated monomer(s) and / or polyfunctionally unsaturated low molecular weight polymer(s), which propylene polymer is preferably a linear propylene polymer.

[0052] The propylene polymer, preferably the linear propylene polymer, preferably has a melt flow rate MFR2, measured according to ISO 1133, in the range of 0.1 to 18.0 g / 10 min, for example 0.1 to 15.0 g / 10 min or 0.2 to 15.0 g / 10 min, more preferably 0.2 to less than 10.0 g / 10 min, even more preferably 0.2 to 9.0 g / 10 min, still more preferably 0.3 to 8.0 g / 10 min.

[0053] The high melt strength propylene polymers are different from the propylene polymers used to prepare the high melt strength propylene polymers in that the main chain of the high melt strength propylene polymer extends into side chains, whereas the starting product, i.e., the propylene polymers, including the preferred linear propylene polymers, do not extend into side chains or are nearly so. Side chains have a significant effect on the rheology of polypropylene. Thus, the starting product, i.e., the propylene polymer, and the resulting high melt strength propylene polymer can be clearly distinguished by their flow behavior under stress.

[0054] Furthermore, as mentioned above, the propylene polymer is preferably a linear polypropylene. This linear propylene polymer is preferably free of branching and therefore has a low v 30 Melt extensibility and / or low F 30 Characterized by melt strength.

[0055] Therefore, the linear propylene polymer is (a) F of more than 1.0 cN, preferably more than 2.0 cN, more preferably in the range of 1.0 to less than 68.0 cN, even more preferably in the range of 1.5 to 65.0 cN, even more preferably in the range of 2.0 to 60.0 cN, even more preferably in the range of 2.5 to 50.0 cN, for example in the range of 2.5 to 45.0 cN 30 Melt strength, and (b) v of less than 200 mm / sec, preferably less than 190 mm / sec, more preferably in the range of 100 to less than 200 mm / sec, even more preferably in the range of 120 to 190 mm / sec, still more preferably in the range of 120 to 175 mm / sec, for example in the range of 125 to 170 mm / sec 30 Melt Extensibility It is preferred that the compound has the formula:

[0056] In other words, the linear propylene polymer has an F of more than 1.0 cN. 30 Melt strength and v less than 200mm / sec 30 Melt extensibility, preferably F > 2.0 cN 30 Melt strength and v less than 190mm / sec 30 Melt extensibility, more preferably F in the range of 1.0 to less than 68.0 cN 30 Melt strength and v in the range of 100 to 200 mm / sec 30 Melt extensibility, more preferably in the range of 1.5 to 65.0 cN 30 Melt strength and F in the range of 120 to 190 mm / sec, and even more preferably in the range of 2.0 to 60.0 cN. 30 Melt strength and F in the range of 120 to 190 mm / sec, e.g., in the range of 2.5 to 50.0 cN 30 Melt strength and v in the range of 120-175 mm / sec 30 It is preferable that the resin has melt extensibility.

[0057] Thus, in one particular embodiment, the propylene polymer is (a) a melt flow rate MFR2 measured according to ISO 1133 in the range of 0.1 to 18.0 g / 10 min, for example 0.1 to 15.0 g / 10 min or 0.2 to 15.0 g / 10 min, more preferably 0.2 to less than 10.0 g / 10 min, even more preferably 0.2 to 9.0 g / 10 min, still more preferably 0.3 to 8.0 g / 10 min; (b) F of more than 1.0 cN, preferably more than 2.0 cN, more preferably in the range of 1.0 to less than 68.0 cN, even more preferably in the range of 1.5 to 65.0 cN, even more preferably in the range of 2.0 to 60.0 cN, even more preferably in the range of 2.5 to 50.0 cN, for example in the range of 2.5 to 45.0 cN 30 Melt strength, (c) v of less than 200 mm / sec, preferably less than 190 mm / sec, more preferably in the range of 100 to less than 200 mm / sec, even more preferably in the range of 120 to 190 mm / sec, still more preferably in the range of 120 to 175 mm / sec, for example in the range of 125 to 170 mm / sec 30 Melt Extensibility has.

[0058] Thus, in one particular embodiment, the propylene polymer has a melt flow rate MFR2 of 0.1 to 18.0 g / 10 min, a F of more than 1.0 cN, 30 Melt strength and v less than 200mm / sec 30 Melt extensibility, preferably a melt flow rate MFR2 (230°C) in the range of 0.2 to 15.0 g / 10 min, F of more than 2.0 cN 30 Melt strength and v less than 190mm / sec 30 Melt extensibility, more preferably a melt flow rate MFR2 in the range of 0.2 to 15.0 g / 10 min, F in the range of 1.0 to 68.0 cN 30 Melt strength and v in the range of 100 to 200 mm / sec 30 Melt extensibility, even more preferably a melt flow rate MFR2 in the range of 0.2 to less than 10.0 g / 10 min, F in the range of 2.0 to 60.0 cN 30 Melt strength and melt flow rate MFR2 in the range of 120 to 190 mm / sec, even more preferably in the range of 0.2 to 9.0 g / 10 min, F in the range of 2.5 to 50.0 cN30 Melt strength and melt flow rate MFR2 in the range of 120 to 190 mm / sec, e.g., 0.3 to 8.0 g / 10 min, F in the range of 2.5 to 45.0 cN 30 Melt strength and v in the range of 120-175 mm / sec 30 It is a linear propylene polymer that has melt extensibility.

[0059] Preferably, said propylene polymer, preferably a linear propylene polymer, has a melting point of at least 140°C, more preferably at least 150°C, even more preferably at least 158°C.

[0060] The propylene polymer, preferably a linear propylene polymer, can be produced in a known manner, for example by using a single-site catalyst or a Ziegler Natta catalyst. The propylene polymer, preferably a linear propylene polymer, can be a propylene homopolymer, preferably a linear propylene homopolymer, or a random propylene copolymer, preferably a linear random propylene copolymer. Regarding the comonomer content and the type of comonomer, see the information provided above for the high melt strength random propylene copolymer. Preferably, the propylene polymer is a linear propylene polymer. Even more preferably, the propylene polymer is a linear propylene homopolymer. Thus, the melt flow rate MFR2 (230°C), the melting point, F 30 Melt strength, v 30 All information provided regarding melt extensibility, and particle size and particle size distribution, respectively, applies specifically to linear propylene homopolymers.

[0061] In a preferred embodiment, the propylene polymer, preferably the linear propylene polymer, is additive-free, thus, if the high melt strength polypropylene composition contains additives, these additives are preferably not introduced into the high melt strength polypropylene composition during the manufacture of the high melt strength propylene polymer.

[0062] Nucleating Agent The high melt strength polypropylene composition may further comprise one or more, preferably one, nucleating agent.

[0063] Nucleating agents are preferably salts of mono- and polycarboxylic acids, such as sodium benzoate; sorbitol compounds, such as diacetals of sorbitol or xylitol, for example 1,3:2,4 bis(3,4-dimethylbenzylidene)sorbitol (CAS number 135861-56-2, e.g. Millad 3988, supplier Milliken); nonitol-based nucleating agents, for example 1,2,3-trideoxy-4,6:5,7-bis-O-((4-propylphenyl)methylene)nonitol (CAS number 882073-43-0, e.g. Millad NX8000, supplier Milliken); phosphorus-based compounds, such as monophenyl, bisphenyl or tetraphenyl phosphates, for example sodium 2,2'-methylenebis-(4,6-di-tert-butylphenyl phosphate (CAS number 85209-91-2, e.g. NA-11, supplier ADEKA Corporation) or hydroxybis(2,4,8,10-tetra-tert-butyl-6-hydroxy-12H-dibenzo(d,g)(1.,3,2)dioxaphoshocin-6-oxidato)aluminum (CAS number 151841-65-5, e.g. ADK STAB NA-21, supplier ADEKA Corporation), or talc or any mixture thereof.

[0064] Talc is especially preferred. In a preferred embodiment, talc is the only nucleating agent present in the high melt strength polypropylene composition.

[0065] The particle size d50 of the nucleating agent, e.g. talc, is preferably in the range of 1 μm to 30 μm, more preferably in the range of 2 μm to 25 μm, even more preferably in the range of 5 μm to 20 μm, and most preferably in the range of 5 μm to 15 μm.

[0066] The nucleating agent, preferably talc, is preferably present in said high melt strength polypropylene composition in an amount of 0 to 15.0 wt.%, more preferably 0.1 to 10.0 wt.%, and most preferably 0.2 to 8.0 wt.%, based on the total weight of the high melt strength polypropylene composition.

[0067] The nucleating agent and optionally additives may be introduced into the high melt strength polypropylene composition in the form of an additive mixture, which comprises, or preferably consists of, a polymer, preferably a further high melt strength propylene polymer, a nucleating agent, and optionally additives. Nucleating agents are not typically considered additives, however, they are part of the additive mixture when present.

[0068] The preferred further high melt strength propylene polymer is preferably prepared as the major high melt strength propylene polymer in a high melt strength polypropylene composition and has the same range of properties as the high melt strength propylene polymers described above. In certain embodiments, the preferred high melt strength propylene polymer of the additive mixture and the high melt strength propylene polymer described above are the same.

[0069] Additives The additives can be any additives useful in the art of high melt strength propylene polymers and their applications.Accordingly, additives used in the high melt strength polypropylene composition, and therefore preferably in the form of additive mixtures, include, but are not limited to, stabilizers, such as antioxidants (e.g., highly hindered phenols, phosphites / phosphonites, sulfur-containing antioxidants, alkyl radical scavengers, aromatic amines, hindered amine stabilizers, or blends thereof), metal deactivators (e.g., Irganox MD 1024), or UV stabilizers (e.g., hindered amine light stabilizers). Other typical additives are modifiers such as antistatic or antifogging agents (e.g. ethoxylated amines and amides, or glycerol esters), acid scavengers, foaming agents, adhesion agents (cling agents, e.g. polyisobutene), lubricants and resins (ionomer waxes, PE waxes and ethylene copolymer waxes, Fischer-Tropsch waxes, montan waxes, fluorine-based compounds, or paraffin waxes), and slip and antiblocking agents (e.g. Ca stearate, erucamide, oleamide, talc, natural and synthetic silica, or zeolites). Preferably, the additive is selected from the group consisting of antioxidants (e.g., highly hindered phenols, phosphites / phosphonites, sulfur-containing antioxidants, alkyl radical scavengers, aromatic amines, hindered amine stabilizers, or blends thereof), metal deactivators (e.g., Irganox MD 1024), UV stabilizers (e.g., hindered amine light stabilizers), antistatic or antifog agents (e.g., ethoxylated amines and amides, or glycerol esters), acid scavengers, foaming agents, adhesion agents (e.g., polyisobutene), lubricants and resins (ionomer waxes, PE waxes and ethylene copolymer waxes, Fischer-Tropsch waxes, montan waxes, fluorine-based compounds, or paraffin waxes), slip agents (e.g., Ca stearate), antiblocking agents (e.g., erucamide, oleamide, talc, natural and synthetic silica, or zeolites), and mixtures thereof. A preferred additive is a slip agent such as calcium stearate.

[0070] As outlined above, additives do not include nucleating agents.

[0071] Typically, the total amount of additives is 15.0 wt% or less, more preferably 10.0 wt% or less, for example in the range of 0.1 to 10.0 wt%, preferably 0.1 to 5.0 wt%, more preferably 0.2 to 1.0 wt%, based on the total weight of the high melt strength polypropylene composition.

[0072] High Melt Strength Polypropylene Composition As mentioned above, the high melt strength polypropylene composition comprises high melt strength propylene polymer in an amount of 85.0-100 wt%, preferably 90.0-99.9 wt%, and most preferably 92.0-99.8 wt%, based on the total weight of the high melt strength polypropylene composition.

[0073] The high melt strength polypropylene composition may further comprise one or more nucleating agents and additives, which are preferably introduced as an additive mixture as described above. The high melt strength polypropylene composition preferably does not contain any additional polymers, except for the polymer of the additive mixture, preferably the high melt strength propylene polymer.

[0074] More preferably, the high melt strength polypropylene composition comprises: (a) 85.00 to 99.90 parts by weight, preferably 87.50 to 99.80 parts by weight, more preferably 90.00 to 99.70 parts by weight, even more preferably 91.00 to 99.60 parts by weight, and even more preferably 92.00 to 99.50 parts by weight of the high melt strength propylene polymer; (b) 0.10 to 15.00 parts by weight, preferably 0.20 to 12.50 parts by weight, more preferably 0.30 to 10.00 parts by weight, and most preferably 0.40 to 8.00 parts by weight of the nucleating agent (NA); (c) optionally up to 20.00 parts by weight, preferably 1.00 to 10.00 parts by weight, more preferably 1.00 to 5.00 parts by weight of a polymer of the additive mixture, preferably a high melt strength propylene polymer; Includes.

[0075] In one preferred embodiment, the preferred high melt strength propylene polymer (c) of the additive mixture is the same as the high melt strength propylene polymer (a).

[0076] More preferably, the total amount of said high melt strength propylene polymer, optional nucleating agent and any polymer of the additive mixture is at least 85 wt.%, more preferably at least 90 wt.%, even more preferably at least 95 wt.%, and most preferably at least 99 wt.%, based on the high melt strength polypropylene composition.

[0077] As mentioned above, the high melt strength propylene polymer is the major part of the high melt strength polypropylene composition, therefore, it is preferred that the high melt strength polypropylene composition exhibits similar rheological behavior as the high melt strength propylene polymer.

[0078] Thus, the high melt strength polypropylene composition preferably comprises: (a) F of more than 20.0 cN, for example, more than 20.0 to 50.0 cN, more preferably more than 21.0 cN, even more preferably 21.0 to 50.0 cN, even more preferably 25.0 to 50.0 cN, even more preferably 25.0 to 45.0 cN, and most preferably 30.0 to 45.0 cN, for example, 32.0 to 42.0 cN or 34.0 cN to 42.0 cN. 30 Melt strength, and (b) a v of more than 200 mm / s, preferably more than 210 to 300 mm / s, for example more than 220 to 300 mm / s, more preferably more than 225 mm / s, even more preferably 225 to 300 mm / s, still more preferably 230 to 290 mm / s, for example 250 to 290 mm / s or 253 to 290 mm / s 30 Melt Extensibility has.

[0079] In an especially preferred embodiment, the high melt strength polypropylene composition has an F of greater than 20.0 cN. 30 Melt strength and v > 200mm / sec 30 Melt extensibility, preferably greater than 210 to 300 mm / sec, e.g., greater than 20.0 to 50.0 cN F 30 Melt strength and v of 220 to 300 mm / sec 30 Melt extensibility, preferably F of more than 21.0 cN 30 Melt strength and v >225mm / sec 30 Melt extensibility, even more preferably F of 21.0 to 50.0 cN 30 Melt strength and v of 225~300mm / sec 30 Melt extensibility, more preferably F of 25.0 to 50.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, even more preferably F of 25.0 to 45.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, most preferably F of 30.0 to 45.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, e.g., F of 32.0 to 42.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, or F of 34.0 to 42.0 cN 30 Melt strength and v of 250~290mm / sec 30 Melt extensibility, or F of 34.0 to 42.0 cN 30 Melt strength and v of 253-290 mm / sec 30 It has melt extensibility.

[0080] Furthermore, the high melt strength polypropylene composition preferably has a melt flow rate MFR2, measured according to ISO1133, of 15.0 g / 10 min or less, more preferably in the range of 0.5 to 15.0 g / 10 min, even more preferably in the range of 0.5 to 15.0 g / 10 min, still more preferably in the range of 1.0 to 15.0 g / 10 min, for example in the range of 1.5 to 15.0 g / 10 min, or for example in the range of 1.0 to 15.0 g / 10 min.

[0081] In a particularly preferred embodiment, the high melt strength polypropylene composition has a melt flow rate MFR2, measured according to ISO 1133, of 7.0 g / 10 min or less, preferably in the range of 0.5 to 7.0 g / 10 min, more preferably in the range of 0.5 to 6.5 g / 10 min, even more preferably in the range of 0.5 to 6.0 g / 10 min, still more preferably in the range of 1.0 to 6.0 g / 10 min, such as in the range of 1.5 to 5.0 g / 10 min, or such as in the range of 1.0 to 5.0 g / 10 min.

[0082] Thus, in one particular embodiment, the high melt strength polypropylene composition comprises: (a) a melt flow rate MFR2 of 15.0 g / 10 min or less, preferably in the range of 0.5 to 15.0 g / 10 min, more preferably in the range of 0.5 to 15.0 g / 10 min, even more preferably in the range of 1.0 to 15.0 g / 10 min, for example in the range of 1.5 to 15.0 g / 10 min, or for example in the range of 1.0 to 15.0 g / 10 min; (b) F of more than 20.0 cN, for example, more than 20.0 to 50.0 cN, more preferably more than 21.0 cN, even more preferably 21.0 to 50.0 cN, even more preferably 25.0 to 50.0 cN, even more preferably 25.0 to 45.0 cN, and most preferably 30.0 to 45.0 cN, for example, 32.0 to 42.0 cN or 34.0 to 42.0 cN. 30 Melt strength, and (c) a v of more than 200 mm / s, preferably more than 210 to 300 mm / s, for example more than 220 to 300 mm / s, more preferably more than 225 mm / s, even more preferably 225 to 300 mm / s, still more preferably 230 to 290 mm / s, for example 250 to 290 mm / s or 253 to 290 mm / s 30 Melt Extensibility has.

[0083] In a preferred variant of this embodiment, the high melt strength polypropylene composition has a melt flow rate MFR2, measured according to ISO 1133, of 7.0 g / 10 min or less, preferably in the range of 0.5 to 7.0 g / 10 min, more preferably in the range of 0.5 to 6.5 g / 10 min, even more preferably in the range of 0.5 to 6.0 g / 10 min, still more preferably in the range of 1.0 to 6.0 g / 10 min, such as in the range of 1.5 to 5.0 g / 10 min, or such as in the range of 1.0 to 5.0 g / 10 min.

[0084] Thus, in certain embodiments, the high melt strength polypropylene composition has a melt flow rate MFR2 of 15.0 g / 10 min or less, a F of 20.0 cN or more, 30 Melt strength and v of 210 to 300 mm / sec 30 Melt extensibility, e.g., melt flow rate MFR2 in the range of 0.5 to 15.0 g / 10 min, F of more than 20.0 to 50.0 cN 30 Melt strength and v of 220 to 300 mm / sec 30 Melt extensibility, preferably a melt flow rate MFR2 in the range of 0.5 to 15.0 g / 10 min, F of more than 21.0 cN 30 Melt strength and v >225mm / sec 30 Melt extensibility, even more preferably a melt flow rate MFR2 in the range of 1.0 to 15.0 g / 10 min, F of 21.0 to 50.0 cN 30 Melt strength and v of 225~300mm / sec 30 Melt extensibility, more preferably a melt flow rate MFR2 in the range of 1.0 to 15.0 g / 10 min, F of 25.0 to 50.0 cN 30 Melt strength and v of 230~290mm / sec 30Melt extensibility, even more preferably a melt flow rate MFR2 in the range of 1.0 to 15.0 g / 10 min, F of 25.0 to 45.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, most preferably a melt flow rate MFR2 in the range of 1.0 to 15.0 g / 10 min, F of 30.0 to 45.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, e.g., melt flow rate MFR2 in the range of 1.0 to 15.0 g / 10 min, F of 32.0 to 42.0 cN 30 Melt strength and v of 230~290mm / sec 30 Melt extensibility, or melt flow rate MFR2 in the range of 1.0 to 15.0 g / 10 min, F of 34.0 to 42.0 cN 30 Melt strength and v of 250~290mm / sec 30 Melt extensibility, or melt flow rate MFR2 in the range of 1.0 to 15.0 g / 10 min, F of 34.0 to 42.0 cN 30 Melt strength and v of 253-290 mm / sec 30 It has melt extensibility.

[0085] In a preferred variant of this embodiment, the high melt strength polypropylene composition has a melt flow rate MFR2, measured according to ISO 1133, of 7.0 g / 10 min or less, preferably in the range of 0.5 to 7.0 g / 10 min, more preferably in the range of 0.5 to 6.5 g / 10 min, even more preferably in the range of 0.5 to 6.0 g / 10 min, still more preferably in the range of 1.0 to 6.0 g / 10 min, such as in the range of 1.5 to 5.0 g / 10 min, or such as in the range of 1.0 to 5.0 g / 10 min.

[0086] The high melt strength polypropylene composition further preferably has a low gel content, typically less than 1.00 wt.%, preferably less than 0.80 wt.%, more preferably less than 0.50 wt.%.

[0087] In a preferred variant of this embodiment, the high melt strength polypropylene composition has a melt flow rate MFR2, measured according to ISO 1133, of 7.0 g / 10 min or less, preferably in the range of 0.5 to 7.0 g / 10 min, more preferably in the range of 0.5 to 6.5 g / 10 min, even more preferably in the range of 0.5 to 6.0 g / 10 min, still more preferably in the range of 1.0 to 6.0 g / 10 min, such as in the range of 1.5 to 5.0 g / 10 min, or such as in the range of 1.0 to 5.0 g / 10 min.

[0088] More preferably, the high melt strength polypropylene composition has a melting temperature of 140-180°C, preferably 150-175°C, and most preferably 155-170°C.

[0089] In addition, the high melt strength polypropylene composition preferably has a crystallization temperature of 110-150°C, preferably 115-140°C, and most preferably 120-135°C.

[0090] Layer (A) Layer (A) is a foamed sheet comprising a high melt strength polypropylene composition as described above or below.

[0091] Layer (A) preferably comprises at least 70% by weight, more preferably at least 80% by weight, more preferably at least 90% by weight, even more preferably at least 95% by weight of said high melt strength polypropylene composition. In a preferred embodiment, the foam consists of the high melt strength polypropylene composition (excluding the blowing agent if still present in the foam after the foaming process).

[0092] The density of the foamed sheet of layer (A) is preferably 100 to 300 kg / m 3 , preferably 125 to 275 kg / m 3 , more preferably 150 to 250 kg / m 3 , and most preferably 175 to 225 kg / m 3 It is.

[0093] This foam has a cell size diameter (air bubble diameter) determined by an optical microscope of preferably 100 to 500 μm, more preferably 125 to 400 μm, and most preferably 170 to 320 μm.

[0094] The foam is further characterized by its surface roughness, which is typically less than 3.5 μm, preferably less than 2.5 μm, and most preferably less than 1.5 μm.

[0095] Layer (B) Layer (B) is a non-foamed layer and preferably comprises the polypropylene composition in an amount of at least 85% by weight, more preferably at least 90% by weight, most preferably at least 95% by weight. In a preferred embodiment, layer (B) consists of the polypropylene composition.

[0096] The polypropylene composition contains 85.0 to 100% by weight, preferably 90.0 to 99.9% by weight, and most preferably 95.0 to 99.8% by weight of a linear propylene polymer based on the total weight of the polypropylene composition.

[0097] The linear propylene polymer can be a linear random propylene copolymer or a linear propylene homopolymer, the latter being preferred.

[0098] When the linear random propylene copolymer is a linear random propylene copolymer, it is a copolymerizable monomer with propylene, such as ethylene and / or C4-C 12 α-olefins, particularly ethylene and / or C4-C 10It comprises a comonomer such as an α-olefin, for example 1-butene and / or 1-hexene. Preferably, the linear random propylene copolymer comprises, and in particular consists of, a monomer copolymerizable with propylene from the group consisting of ethylene, 1-butene and 1-hexene. More specifically, the linear random propylene copolymer comprises, in addition to propylene, units derivable from ethylene and / or 1-butene. In a preferred embodiment, the linear random propylene copolymer comprises units derivable only from ethylene and propylene. The comonomer content in the linear random propylene copolymer is preferably in the range of more than 0.2 to 10.0 mol%, even more preferably in the range of more than 0.5 to 7.0 mol%.

[0099] The polypropylene composition may contain additives in an amount of up to 15.0% by weight, preferably 0.1 to 10.0% by weight, and most preferably 0.2 to 5.0% by weight. Suitable additives are preferably selected from the group comprising antioxidants, stabilizers, fillers, colorants, nucleating agents and antistatic agents. Generally, they are incorporated during granulation of the pulverulent product obtained from the polymerization. The additives can be added to the polypropylene composition in the form of a masterbatch, which typically contains a small amount of a polymer that counts toward the amount of additive in the polypropylene composition, rather than the other polymeric components.

[0100] The polypropylene composition may also contain minor amounts of other polymeric components different from the linear polymer of propylene. However, it is preferred that the linear polymer of propylene is the only polymer component in the propylene polymer composition.

[0101] The polypropylene composition has a melt flow rate MFR2, measured in accordance with ISO 1133, of preferably 5.0 to 50.0 g / 10 min, more preferably 10.0 to 40.0 g / 10 min, even more preferably 15.0 to 35.0 g / 10 min, and most preferably 20.0 to 30.0 g / 10 min.

[0102] The polypropylene composition preferably has a viscosity of 890 to 910 kg / m 3 has a density of

[0103] Multi-layer sheet The present invention is directed to a multilayer sheet comprising as layer (A) a foamed sheet as described above or below, and as layer (B) a coating layer which is a coated non-foamed layer as described above or below, wherein layers (A) and (B) are in intimate contact with each other.

[0104] The multilayer sheet may contain one or more additional layers, provided that layers (A) and (B) are in intimate contact with each other, which may be applied to the multilayer sheet on the surface of either layer (A) and / or (B) in the configuration (X)-(A)-(B), (A)-(B)-(Y) or (X)-(A)-(B)-(Y), where layer (X) is one or more layers in intimate contact with layer (A) on the surface opposite the intimate contact between layer (A) and layer (B) and layer (Y) is one or more layers in intimate contact with layer (B) on the surface opposite the intimate contact between layer (B) and layer (A). This optional additional layer can be of any suitable material, but, when present, is preferably of a polypropylene composition to ensure good recycling characteristics. However, it is preferred that the multilayer sheet consists of layers (A) and (B).

[0105] It is especially preferred that the multi-layer sheet does not include any adhesive layer to improve the adhesion between two layers of the multi-layer sheet.

[0106] The multilayer sheet preferably has a total thickness of 500 to 1000 μm, more preferably 575 to 950 μm, even more preferably 600 to 900 μm, and most preferably 625 to 850 μm.

[0107] Layer (A) preferably has a thickness of 455 to 850 μm, more preferably 525 to 825 μm, more preferably 550 to 800 μm, and most preferably 565 to 765 μm.

[0108] Furthermore, layer (B) preferably has a thickness of 45 to 150 μm, more preferably 50 to 125 μm, even more preferably 55 to 100 μm, and most preferably 60 to 85 μm.

[0109] The multilayer sheet preferably has a thickness of 150 to 300 g / m 2 , more preferably 175 to 280 g / m 2 , and most preferably 200 to 260 g / m 2 The sheet has a basis weight of 1.0 g.

[0110] The multilayer sheet according to the present invention surprisingly exhibits an improved balance of properties in mechanical strength and barrier properties, which allows its use as a packaging material for perishable foods such as dairy products. With layers (A) and (B) both comprising a polypropylene composition, a high recycling rate of the multilayer sheet can be achieved.

[0111] The multilayer sheet has a tensile modulus in the longitudinal direction (machine direction) of preferably 300 to 600 MPa, more preferably 350 to 550 MPa, and most preferably 375 to 500 MPa.

[0112] Furthermore, the multilayer sheet has a tensile modulus in the transverse direction of preferably 300 to 600 MPa, more preferably 350 to 550 MPa, and most preferably 375 to 500 MPa.

[0113] Still further, the multilayer sheet preferably has a longitudinal elongation at break of 10 to 100%, more preferably 15 to 80%, and most preferably 20 to 70%.

[0114] Furthermore, the multilayer sheet preferably has a transverse elongation at break of 10 to 100%, more preferably 15 to 80%, and most preferably 20 to 70%.

[0115] In addition, the multilayer sheet preferably has a longitudinal elongation at yield of 2.0 to 30.0%, preferably 5.0 to 25.0%, and most preferably 10.0 to 20.0%.

[0116] It is further preferred that the multilayer sheet has a nominal longitudinal tensile break strain of 5 to 60%, more preferably 10 to 50%, and most preferably 15 to 40%.

[0117] In addition, the multilayer sheet preferably has a nominal transverse tensile break strain of 5 to 60%, more preferably 10 to 50%, and most preferably 15 to 40%.

[0118] Furthermore, the multilayer sheet preferably has a longitudinal tensile strength of 2.0 to 30.0 MPa, more preferably 3.5 to 25.0 MPa, and most preferably 5.0 to 20.0 MPa.

[0119] In addition, the multilayer sheet preferably has a tensile strength in the transverse direction of 2.0 to 30.0 MPa, more preferably 3.5 to 25.0 MPa, and most preferably 5.0 to 20.0 MPa.

[0120] It is further preferable that the multilayer sheet has a longitudinal tensile breaking stress of 2.0 to 30.0 MPa, more preferably 3.5 to 25.0 MPa, and most preferably 5.0 to 20.0 MPa.

[0121] Furthermore, the multilayer sheet preferably has a tensile stress at break in the transverse direction of 2.0 to 30.0 MPa, more preferably 3.5 to 25.0 MPa, and most preferably 5.0 to 20.0 MPa.

[0122] In addition, the multilayer sheet preferably has a longitudinal tensile yield stress of 2.0 to 30.0 MPa, preferably 3.5 to 25.0 MPa, and most preferably 5.0 to 20.0 MPa.

[0123] In terms of barrier properties, the multilayer sheet preferably has a barrier strength of 1.00 g / (m 2 ·d), more preferably 0.01 to 0.75 g / (m 2 d), and even more preferably 0.10 to 0.60 g / (m 2 d), and even more preferably 0.20 to 0.50 g / (m 2 d), and most preferably 0.30 to 0.40 g / (m 2 ·d) Water vapor transmission rate (WVTR) at 23°C and 85% RH.

[0124] Furthermore, the multilayer sheet is preferably 2000 cm 3 / (m 2 d bar), more preferably 250 to 1500 cm 3 / (m 2 d bar), and even more preferably 350 to 1000 cm 3 / (m 2 d bar), and even more preferably 500 to 900 cm 3 / (m 2 d bar), most preferably 650-800 cm 3 / (m 2 It has an oxygen transmission rate (OTR) of 1.0 MPa (23 °C) and 50% RH (1.0 MPa).

[0125] In addition, the multi-layer sheet is preferably 750 cm 3 / (m 2 d bar), more preferably 100 to 600 cm 3 / (m 2 d bar), and even more preferably 150 to 500 cm 3 / (m 2 d bar), and even more preferably 200 to 400 cm 3 / (m 2d bar), most preferably 250-350 cm 3 / (m 2 It has an oxygen transmission rate (OTR) of 1.0 MPa (1.0 MPa) at 5°C and 0% RH.

[0126] process In another aspect, the present invention provides a process for producing the multilayer sheet described above or below, comprising the steps of: a) The high melt strength polypropylene composition is mixed with 100 to 300 kg / m 3 , preferably 125 to 275 kg / m 3 , more preferably 150 to 250 kg / m 3 , and most preferably 175 to 225 kg / m 3 to form a foamed sheet having a density of b) coating layer (A) with the polypropylene composition to obtain layer (B) in close contact with layer (A); The present invention relates to a process comprising:

[0127] For foaming the foam sheet of layer (A) in process step a), the above or below described high melt strength propylene polymers and high melt strength polypropylene compositions are provided.

[0128] As already outlined above, said high melt strength propylene polymer is preferably produced by using an unmodified propylene polymer, preferably a linear propylene polymer. Preferably, said process further comprises at least a step (i) in which an unmodified propylene polymer is reacted with a thermally decomposable free radical former and optionally with difunctional unsaturated monomer(s) and / or polyfunctional unsaturated low molecular weight polymer(s), thereby obtaining said high melt strength propylene polymer.

[0129] Preferably, the process comprises a further step (ii) after step (i) in which a nucleating agent as described above or below is added to said high melt strength propylene polymer. As already outlined above, the nucleating agent may be added separately or in a mixture with the additional propylene polymer. Optionally, the further additive may be present, usually in a mixture with the additional propylene polymer, if present.

[0130] Even more preferably, the process comprises a further step (ii) after step (i) in which a nucleating agent and optionally further additives, i.e. additives different from the nucleating agent, are added to said high melt strength propylene polymer. This may be achieved using the additive mixtures outlined above. The result of process step (ii) is said high melt strength polypropylene composition.

[0131] The high melt strength polypropylene composition thus produced is subsequently subjected to a foaming process, whereby in process step (a) a foamed sheet comprising the high melt strength polypropylene composition of the present invention is obtained.

[0132] Regarding the definitions and preferred embodiments of the foamed sheet, the high melt strength polypropylene composition, the high melt strength propylene polymer, the unmodified propylene polymer, the nucleating agent, the additive, the additional propylene polymer and the additive mixture, reference is made to the information provided above.

[0133] As mentioned above, in any step (i) of the process, the high melt strength propylene polymer is obtained by treating the unmodified propylene polymer, preferably the linear propylene polymer, with a thermally degradable radical former. However, in such a case there is a high risk that the unmodified propylene polymer, preferably the linear propylene polymer, will degrade, which is detrimental. Therefore, the chemical modification is preferably achieved by the additional use of difunctional unsaturated monomer(s) and / or polyfunctional unsaturated low molecular weight polymer(s) as chemically bonded crosslinking units. Suitable methods for obtaining high melt strength propylene polymers are disclosed, for example, in EP 0787750, EP 0879830A1 and EP 0890612A2. All documents are hereby incorporated by reference. Thereby, the amount of thermally degradable radical former, preferably peroxide, is preferably in the range of 0.05 to 3.00% by weight based on the amount of unmodified propylene polymer. Typically, the thermally decomposable radical former is added to the unmodified propylene polymer, preferably to a linear propylene polymer, together with the difunctional unsaturated monomer and / or the polyfunctional unsaturated low molecular weight polymer. However, it is also possible, but less preferred, to add the difunctional unsaturated monomer and / or the polyfunctional unsaturated low molecular weight polymer first to the unmodified propylene polymer, preferably to a linear propylene polymer, and then add the thermally decomposable radical former, or alternatively, to add the thermally decomposable radical former first to the unmodified propylene polymer, preferably to a linear propylene polymer, and then add the difunctional unsaturated monomer and / or the polyfunctional unsaturated low molecular weight polymer.

[0134] For the difunctional unsaturated monomers and / or polyfunctional unsaturated low molecular weight polymers used to prepare the high melt strength propylene polymers, see the section entitled "Melt Strength Propylene Polymers."

[0135] As mentioned above, the difunctionally unsaturated monomers and / or polyfunctionally unsaturated low molecular weight polymers are preferably used in the presence of a thermally decomposable free radical former.

[0136] Peroxides are the preferred thermally decomposable free radical formers. More preferably, the thermally decomposable free radical formers are selected from the group consisting of acyl peroxides, alkyl peroxides, hydroperoxides, peresters and peroxycarbonates.

[0137] The following peroxides are particularly preferred: Acyl peroxides: benzoyl peroxide, 4-chlorobenzoyl peroxide, 3-methoxybenzoyl peroxide and / or methylbenzoyl peroxide. Alkyl peroxides: allyl t-butyl peroxide, 2,2-bis(t-butylperoxybutane), 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, diisopropylaminomethyl-t-amyl peroxide, dimethylaminomethyl-t-amyl peroxide, diethylaminomethyl-t-butyl peroxide, dimethylaminomethyl-t-butyl peroxide, 1,1-di-(t-amylperoxy)cyclohexane, t-amyl peroxide, t-butylcumyl peroxide, t-butyl peroxide and / or 1-hydroxybutyl n-butyl peroxide. Peresters and peroxycarbonates: butyl peracetate, cumyl peracetate, cumyl perpropionate, cyclohexyl peracetate, di-t-butyl peradipate, di-t-butyl perazelate, di-t-butyl perglutarate, di-t-butyl perphthalate, di-t-butyl persebacate, 4-nitrocumyl perpropionate, 1-phenylethyl perbenzoate, phenylethyl nitroperbenzoate, t-butyl bicyclo-(2,2,1)heptane percarboxylate, t-butyl 4-carbomethoxyperbutyrate, t-butyl cyclobutane percarboxylate, t-butyl cyclohexyl percarboxylate, t-butyl cyclopentyl percarboxylate, t-butyl cyclopropane percarboxylate, t-butyl dimethylpercinnamate, 2-(2,2-diphenylvinyl)perbenzoate. t-butyl, t-butyl 4-methoxyperbenzoate, t-butyl perbenzoate, t-butyl carboxycyclohexane, t-butyl pernaphthoate, t-butyl perisopropylcarboxylate, t-butyl pertoluate, t-butyl 1-phenylcyclopropylpercarboxylate, t-butyl 2-propyl-2-perpentenoate, t-butyl 1-methylcyclopropylpercarboxylate, t-butyl 4-nitrophenylperacetate, t-butyl nitrophenylpercarbamate, t-butyl N-succinimide percarboxylate, t-butyl percrotonate, t-butyl permaleate, t-butyl permethacrylate, t-butyl peroctanoate, t-butyl perisopropylcarboxylate, t-butyl perisobutyrate, t-butyl peracrylate and / or t-butyl perpropionate.

[0138] Mixtures of these above-listed free radical formers are also contemplated.

[0139] In one variant, to obtain said high melt strength propylene polymer, step (ii) is started when at least 70%, preferably at least 80%, even more preferably at least 90%, such as at least 95% or 99% of the reaction between the unmodified propylene polymer and the thermally decomposable free radical former and optionally the difunctional unsaturated monomer has occurred.

[0140] Unless otherwise stated, the following describes a preferred embodiment of this variant.

[0141] In a preferred embodiment, an extruder, such as a twin screw extruder, is used for step (i) and optional step (ii).

[0142] The use of an extruder is particularly advantageous in that it can be used simultaneously to prepare the high melt strength propylene polymer and then to add the nucleating agent to said high melt strength propylene polymer. As outlined above, the nucleating agent may be added separately or together with further additives different from the nucleating agent.

[0143] In a preferred embodiment, the unmodified propylene polymer is added in step (i) to an extruder, as described in detail above, together with a thermally decomposable free radical former, preferably a peroxide, and optionally together with a difunctional unsaturated monomer(s) and / or a polyfunctional unsaturated low molecular weight polymer(s), preferably with a difunctional unsaturated monomer(s) selected from divinyl compounds, allyl compounds or dienes, to provide a high melt strength propylene polymer. It is also possible to use a combination of extruders downstream of a premixing device, in which case the difunctional unsaturated monomer(s) and / or the polyfunctional unsaturated low molecular weight polymer and the thermally decomposable free radical former are added to the polypropylene in the premixing device.

[0144] Subsequently, in step (ii), the nucleating agent, the additional propylene polymer if present, and additives, i.e. additives different from the nucleating agent if present, are preferably added at the downstream end of the extruder screw, as described above, in order not to interfere with the modification reaction to provide the high melt strength propylene polymer.

[0145] In this context, the term "downstream end of the extruder screw" is understood to mean within the last 75% of the length of the extruder screw, preferably within the last 70% of the length of the extruder screw, more preferably within at least 65% of the length of the extruder screw.

[0146] Thus, the extruder (E) used in the process preferably comprises, in the running direction, a feed throat (FT), a first mixing zone (MZ1), a second mixing zone (MZ2) and a die (D), with a side feed throat (SFT) located between the first mixing zone (MZ1) and the second mixing zone (MZ2). Preferably, the extruder is a screw extruder, such as a twin-screw extruder. Thus, the unmodified propylene polymer, the thermally decomposable free radical former, preferably a peroxide, and optionally a difunctional unsaturated monomer and / or a polyfunctional unsaturated low molecular weight polymer monomer, preferably selected from divinyl compounds, allyl compounds or dienes, are fed into the extruder via the feed throat (FT), preferably using a feeder, separately from the nucleating agent, the additional propylene polymer if present, and additives different from the nucleating agent if present, and subsequently pass downstream through the first mixing zone (MZ1). Preferably, the shear stress in the first mixing zone (MZ1) is such that the unmodified propylene polymer melts and initiates a chemical reaction with the radical former and any difunctional unsaturated monomer and / or polyfunctional unsaturated low molecular weight polymer. After the first mixing zone (MZ1), i.e. between the first mixing zone (MZ1) and the second mixing zone (MZ2), the nucleating agent, the additional propylene polymer if present, and additives other than the nucleating agent if present are added, i.e. fed into the extruder. Preferably, the nucleating agent, the additional propylene polymer if present, and additives other than the nucleating agent if present are added via a side feed port (SFT), preferably using a side feeder. Then, all components of the high melt strength polypropylene composition, including the nucleating agent, the additional propylene polymer if present, and additives other than the nucleating agent if present, pass downstream through the second mixing zone (MZ2). Finally, the polypropylene composition is discharged through a die (D).

[0147] Preferably, the first mixing zone (MZ1) is longer than the second mixing zone (MZ2). Preferably, the length ratio between the first mixing zone (MZ1) and the second mixing zone (MZ2) [mm(MZ1) / mm(MZ2)] is at least 2 / 1, more preferably 3 / 1, even more preferably in the range of 2 / 1 to 15 / 1, even more preferably 3 / 1 to 10 / 1.

[0148] In another preferred variant, the high melt strength propylene polymer obtained in step (i) is separated before further processing. Such separation may include storage and transportation of the high melt strength propylene polymer to another facility.

[0149] Unless otherwise stated, the following describes a preferred embodiment of this variant.

[0150] In this variant, in process step (ii) said high melt strength propylene polymer is combined with a nucleating agent, which may be added separately or in admixture with the additional propylene polymer. Further additives different from the nucleating agent, if present, may optionally be present, usually in admixture with the additional propylene polymer.

[0151] In a preferred embodiment, an extruder, such as a twin screw extruder, is used in step (i).

[0152] In a preferred embodiment, the unmodified propylene polymer is added in step (i) to an extruder, as described in detail above, together with a thermally decomposable free radical former, preferably a peroxide, and optionally together with a difunctional unsaturated monomer(s) and / or a polyfunctional unsaturated low molecular weight polymer(s), preferably with a difunctional unsaturated monomer selected from divinyl compounds, allyl compounds or dienes, to provide a high melt strength propylene polymer. It is also possible to use a combination of extruders downstream of a premixing device, in which case the difunctional unsaturated monomer and / or the polyfunctional unsaturated low molecular weight polymer and the thermally decomposable free radical former are added to the polypropylene in the premixing device.

[0153] Thus, the extruder (E) used for preparing the high melt strength propylene polymer preferably comprises, in the direction of operation, a feed throat (FT), a first mixing zone (MZ1), optionally a second mixing zone (MZ2) and a die (D). Preferably, the extruder is a screw extruder, such as a twin-screw extruder. Thus, the unmodified propylene polymer, the thermally decomposable free radical former, preferably a peroxide, and optionally a difunctional unsaturated monomer and / or a polyfunctional unsaturated low molecular weight polymer monomer, preferably selected from divinyl compounds, allyl compounds or dienes, are fed into the extruder via the feed throat (FT), preferably using a feeder, separately from the nucleating agent, the additional propylene polymer if present, and additives different from the nucleating agent if present, and then pass downstream through the first mixing zone (MZ1). Preferably, the shear stress in said first mixing zone (MZ1) is such that the unmodified propylene polymer melts and initiates chemical reactions with the radical formers and with any difunctionally unsaturated monomers and / or polyfunctionally unsaturated low molecular weight polymers.

[0154] After the first mixing zone (MZ1), the resulting product, if present, passes downstream through a second mixing zone (MZ2). Finally, the high melt strength propylene polymer is discharged through a die (D).

[0155] If a second mixing zone is present, the first mixing zone (MZ1) is longer than the second mixing zone (MZ2). Preferably, the length ratio between the first mixing zone (MZ1) and the second mixing zone (MZ2) [mm(MZ1) / mm(MZ2)] is at least 2 / 1, more preferably 3 / 1, even more preferably in the range of 2 / 1 to 15 / 1, even more preferably 3 / 1 to 10 / 1.

[0156] The high melt strength propylene polymer thus obtained is then combined in step (ii) with the nucleating agent, the additional propylene polymer, if present, and additives different from the nucleating agent, if present. In a preferred embodiment, an extruder, such as a twin screw extruder, is used in step (ii).

[0157] In a preferred embodiment, the high melt strength propylene polymer is added to the extruder with the nucleating agent, if present, additional propylene polymer, and additives other than the nucleating agent, if present, as described in detail above, and fed through the feed throat (FT). It is also possible to use a combination of extruders downstream of a premixing device, in which case the nucleating agent, if present, additional propylene polymer, and additives other than the nucleating agent, if present, are added to the high melt strength propylene polymer in the premixing device.

[0158] Thus, the extruder (E) used for preparing the high melt strength propylene composition preferably comprises, in the direction of operation, a feed throat (FT), a first mixing zone (MZ1), optionally a second mixing zone (MZ2) and a die (D). Preferably, the extruder is a screw extruder, such as a twin-screw extruder. Thus, the high melt strength propylene polymer, the nucleating agent, the additional propylene polymer if present and the additives other than the nucleating agent if present are fed into the extruder via the feed throat (FT), preferably using a feeder, and then pass downstream through the first mixing zone (MZ1). Preferably, the shear stress in the first mixing zone (MZ1) is such that the high melt strength propylene polymer melts and starts to mix with the nucleating agent, the additional propylene polymer if present and the additives other than the nucleating agent if present.

[0159] After the first mixing zone (MZ1), the resulting product, if present, passes downstream through a second mixing zone (MZ2). Finally, the high melt strength polypropylene composition is discharged through a die (D).

[0160] If a second mixing zone is present, the first mixing zone (MZ1) is longer than the second mixing zone (MZ2). Preferably, the length ratio between the first mixing zone (MZ1) and the second mixing zone (MZ2) [mm(MZ1) / mm(MZ2)] is at least 2 / 1, more preferably 3 / 1, even more preferably in the range of 2 / 1 to 15 / 1, even more preferably 3 / 1 to 10 / 1.

[0161] Below, preferred features of all embodiments and variations of the process are described, unless expressly stated to the contrary.

[0162] Foaming processes are known to those skilled in the art. In such processes, a melt of a high melt strength polypropylene composition with a gaseous or liquid blowing agent, such as butane, a mixture of butane and propane, HFC or CO2, is suddenly expanded by a pressure drop. Preferably, a liquid blowing agent, such as butane or a mixture of butane and propane, is used. Continuous and discontinuous foaming processes may be applied. In the continuous foaming process, the polypropylene composition is melted and gassed in an extruder under pressure, typically above 20 bar, and then extruded through a die, where a pressure drop causes the formation of a foam. The mechanisms of foaming polypropylene in foaming extrusion are described, for example, in HE Naguib, CBPark, N.Reichelt, Fundamental foaming mechanisms governing the volume expansion of extruded polypropylene foams, Journal of Applied Polymer Science, 91, 2661-2668 (2004). The process for foaming is outlined in STLee, Foam Extrusion, Technomic Publishing (2000). In the discontinuous foaming process, polypropylene composition (micro)pellets are impregnated with a foaming agent under pressure and, after heating below the melting temperature, the pressure in the autoclave is suddenly relieved. The dissolved foaming agent forms bubbles and creates the foam structure. The preparation of discontinuous foam beads is described, for example, in DE-A-3539352.

[0163] The amount of blowing agent is usually less than 10% by weight based on the total weight of the polymer composition and the blowing agent, preferably less than 5% by weight based on the total weight of the polymer composition and the blowing agent.

[0164] The preferred blowing agents are butane and mixtures of butane and propane.

[0165] As outlined above, a foam sheet is preferably formed. The method of forming a foam sheet is generally known in the art, and is described, inter alia, in Taiwan Utility Model No. 463649, which is incorporated herein by reference in its entirety. Preferably, the method and apparatus described in Taiwan Utility Model No. 463649 is used to prepare the above or below foam sheet.

[0166] After obtaining the above or below mentioned foamed sheet as layer (A) in process step (a), layer (B) is coated on one surface of the foamed sheet of layer (A) in process step (b) to obtain the multilayer sheet of the present invention.

[0167] In process step (b), a polypropylene composition containing a linear propylene polymer of layer (B) is melted and coated onto one surface of the foam sheet of layer (A) to form layer (B) in intimate contact with layer (A). Such coating processes are well established in the art.

[0168] The polypropylene composition of layer (B) is commercially available or can be produced by any process suitable for producing polypropylene compositions. Concerning the polypropylene composition and the linear propylene polymer of layer (B), please refer to the descriptions above and below.

[0169] The process for producing the multilayer sheet according to the invention may further comprise the additional step of applying additional layers (X) and / or (Y) to one surface of either or both of layers (A) or (B). To apply the additional layers (X) and / or (Y), any application method known in the art suitable for applying these layers may be applied. Regarding any additional layers (X) and / or (Y), reference is made to the accompanying description above or below.

[0170] However, it is preferred that the process of the present invention does not include a process step in which additional layers (X) and / or (Y) are applied to one surface of either layer (A) or layer (B) or both.

[0171] Goods In yet another aspect, the present invention relates to an article comprising the above or below described multilayer sheet.

[0172] In yet another aspect, the present invention relates to the use of a multilayer sheet as described above or below for the manufacture of an article having improved water vapor and oxygen transmission properties.

[0173] The article is preferably a food package, preferably a food package for perishable food, for example dairy packages such as milk cartons and cups for cream cheese or yogurt.

[0174] In the above article, preferably a food packaging material, the multilayer sheet is preferably formed such that layer (B) is on the inside of the article, preferably in contact with the contents of the article, e.g. a food product, preferably a perishable food product, e.g. a dairy product such as milk, cream cheese or yoghurt. EXAMPLES

[0175] 1.Measurement method Comonomer content in polypropylene Comonomer content can be quantitatively determined by methods well known in the art. 13 The chromaticity is determined by quantitative Fourier transform infrared spectroscopy (FTIR) after fundamental assignments calibrated by C nuclear magnetic resonance (NMR) spectroscopy. Thin films are pressed to a thickness of 250 µm and spectra are recorded in transmission mode. Specifically, the ethylene content of the polypropylene-co-ethylene copolymer is 720-722 and 730-733 cm -1 The propylene-1-butene copolymer is determined using the baseline corrected peak area of ​​the quantitative band found at 767 cm -1 Quantitative results are obtained based on reference to film thickness.

[0176] Melting temperature (T m ) and heat of fusion (H f ), crystallization temperature (T c ) and heat of crystallization (H c ): Melting temperature T m and crystallization temperature T c was measured on a TA Instruments Q2000 Differential Scanning Calorimetry (DSC) according to ISO 11357 / 3 on 5-10 mg samples. Crystallization and melting temperatures were obtained in heat / cool / heat cycles at a scan rate of 10 °C / min between 30 °C and 225 °C. The melting and crystallization temperatures were taken as the endothermic and exothermic peaks in the cooling cycle and the second heating cycle, respectively.

[0177] The melt flow rate MFR2 is measured according to ISO 1133 at a temperature of 230° C. and a load of 2.16 kg.

[0178] F 30 Melt strength and v 30 Melt Extensibility The tests described herein are in accordance with ISO16790:2005. The strain hardening behavior is determined by the method described in the article "Rheotens-Mastercurves and Drawability of Polymer Melts", MH Wagner, Polymer Engineering and Science, Vol. 36, pp. 925-935, the contents of which are incorporated by reference. The strain hardening behavior of polymers is analyzed by a Rheotens apparatus (product of Goettfert, Siemensstr. 2, 74711 Buchen, Germany), in which a strand of melt is elongated by being pulled down with a defined acceleration. Rheotens experiments simulate industrial spinning and extrusion processes. In principle, the melt is squeezed or extruded through a round die and the resulting strand is drawn off. The stress on the extrudate is recorded as a function of the melt properties and the measured parameters (notably the ratio of the power and the drawing speed, practically a measure of the elongation rate). For the results shown below, the material was extruded using a laboratory extruder HAAKE Polylab system and a gear pump with a cylindrical die (L / D=6.0 / 2.0 mm). The gear pump was pre-adjusted to give a strand extrusion speed of 5 mm / s and the melt temperature was set at 200 °C. The spinning (spin) line length between the die and the Rheotens wheel was 80 mm. At the start of the experiment, the winding speed of the Rheotens wheel was adjusted to the speed of the extruded polymer strand (zero pulling force). The experiment was then started by slowly increasing the winding speed of the Rheotens wheel until the polymer filament broke. The acceleration of the wheel was kept small enough so that the pulling force was measured in a quasi-steady state. The acceleration of the pulled melt strand is 120 mm / s 2 The Rheotens was operated in conjunction with the PC program "EXTENS", a real-time data acquisition program that displays and stores the measured data of the pull force and the drawdown speed. The end points of the Rheotens curve (force vs. pulley speed) were determined by the F 30 Melt strength and drawability values ​​were reported.

[0179] Gel Content Approximately 2.0 g of polymer (m p ) was weighed and placed in a weighed metal mesh (m p+m The polymer in the mesh is extracted with boiling xylene in a Soxhlet apparatus for 5 h. The eluent is then replaced with fresh xylene and boiling is continued for another hour. The mesh is then dried and weighed again (m XHU+m ).m XHU+m -m m =m XHU The mass of the hot xylene insoluble matter obtained by the formula (m XHU) to the weight of the polymer (m p ) in relation to the proportion of xylene insolubles m XHU / m p get.

[0180] Foam Density It was measured using a Swiss analytical semi-micro precision balance, specific gravity balance (XS225A) from Switzerland PRECISA Gravimetrics AG, according to ISO 845. Test method: By application of Archimedes the density of the sample is calculated automatically.

[0181] Foam Cell Size Diameter The cell size diameter of the foam was measured using optical microscopy on a Tawain CBS Stereoscopic microscope. The test methods used are as follows: 1. Cut strips of foam material along the cross direction (CD) and machine direction (MD). 2. Hold the foam material in a flat clamp and use a razor blade to cut a thin slice. 3. Focus the microscope at 100x and adjust the illumination onto the foam material. 4. Take measurements of the length and width of each unique cell in the CD and MD orientations and record the values. 5. Count the number of unique cells measured and record the value. 6. Take cell wall thickness measurements across 3-4 tangents to the entire length of each unique cell in the CD and MD orientations and record the values. 7. Take three full strip thickness measurements starting from the bottom of the first measurement cell group, working to the middle of the cell group, and then to the top of the cell group. 8. Take a total length measurement from the lowest full cell to the highest full cell. 9. Move the microscope field so that the bottom of the topmost incomplete cell touches the bottom of the screen. 10. Repeat steps 4-9 for each new unique cell until approximately 0.200 inches (~0.51 cm) to 0.800 inches (~2.0 cm) of the strip has been measured. Be sure to ensure that overall lengths and cell compositions do not overlap. Each overall length measurement after the first is taken from the top of the previous best full cell to the top of the current best full cell.

[0182] Surface roughness of foam This was measured using a Mitutoyo, Japan, portable surface roughness tester, model SJ-310. This surface roughness tester (also known as a surface profilometer) is a contact type surface roughness tester. The roughness determination is fully automated and performed via the included software.

[0183] Basis weight is determined in accordance with ASTM D645.

[0184] Mechanical properties such as nominal strain at break, elongation at break, elongation at yield, tensile modulus, tensile strength, tensile stress at break and tensile stress at yield were measured in the machine and cross directions for the multilayer sheet of Example IE1 and the LDPE laminated paper sheet of Comparative Example CE2 according to ISO 527-3 at 23° C. Tests were performed at a crosshead speed of 1 mm / min.

[0185] The water vapor transmission rate (WVTR) was measured according to standard ISO 15106-3:2003 for the multilayer sheet of Example IE1 and the LDPE laminated paper sheet of Comparative Example CE2. Equipment: Mocon Aquatran Temperature: 38℃±0.3℃ Relative humidity: 0 / 100% Sample area: 5cm 2

[0186] Oxygen transmission rate (OTR) was measured on the multilayer sheet of Example IE1 and the LDPE laminated paper sheet of Comparative Example CE2 as test specimens. The test specimens are mounted as a sealed semi-barrier between two chambers at ambient atmospheric pressure. A slow flow of nitrogen and hydrogen gas mixture (2% H2 in N2) flows through one chamber at a given temperature and relative humidity, and an oxygen flow flows through the other chamber at the same temperature and relative humidity as the N2 flow. As oxygen gas permeates the film into the nitrogen carrier gas, it is carried to a coulometric detector where it produces a current whose magnitude is proportional to the amount of oxygen flowing into the detector per unit time. The oxygen transmission rate test is in accordance with ASTM D3985, using 10 sccm of N2 / H2 gas and O2 (99.999%) gas at 23°C and 50% relative humidity and 5°C and 0% relative humidity, and is performed on a 1 cm2 sheet surface area. 2 This is done as follows.

[0187] 2. Preparation of multilayer sheets The following steps apply: 1. Preparation of a blend of 91 wt. % Daploy™ WB140HMS from Borealis AG with 9 wt. % nucleating agent masterbatch consisting of 77 wt. % talc and 23 wt. % Daploy™ WB140HMS (total amount of talc in this blend: about 7 wt. %). High melt strength polypropylene WB140HMS has a melt flow rate MFR2 (230° C.) of 2.1 g / 10 min, a melt strength F of 36 cN. 30 and melt extensibility v of 255 mm / sec 30 Talc has a particle size d 50 is 7μm, d 95 The commercially available product is HV4 from IMI FABI, which has a diameter of 20 μm. 2. The blend obtained in the first step is fed into a first single screw extruder of Pitac Taiwan (screw diameter 90 mm; L / D ratio 26). The extruder is operated at a temperature of 200°C (five heating zones: 150°C; 200°C; 200°C; 200°C) to melt the polymer. 3. 3 wt. % liquid butane (as a blowing agent) is injected into the last section of the first single screw extruder, thereby obtaining a molten blend. 4. Pass the above molten blend through a second single screw extruder from Pitac Taiwan (screw diameter 120 mm; L / D ratio 34), thereby cooling the molten blend to 160° C. at the end of the second single screw extruder. 5. The melt blend of the fourth step is passed through an extrusion die located at the end of the second extruder. Upon exiting the extruder, the melt blend is subjected to a sudden pressure drop to atmospheric pressure, causing the blowing agent in the melt blend to expand, thereby achieving foaming and resulting in a foam structure. The foam structure is then cooled in a cooling drum at a temperature below 100°C, thereby forming a foam structure of 200 kg / m 3 A foamed sheet having a density of 1.0 μm and a thickness of 667 μm is obtained. 6. Then, the foamed sheet is coated on one surface with commercial polypropylene PC932 from LCY, Taiwan, thereby obtaining a two-layer sheet of 667 μm foamed sheet as layer (A) and 69-78 μm coating layer (B), such that the total thickness of the two-layer sheet is about 0.7 mm.

[0188] The mechanical and barrier properties of the bi-ply sheet prepared as above are compared with those of a double-sided LDPE laminated paper sheet having a thickness of 0.4 mm, the results of which are shown in Table 1 below.

[0189] [Table 1]

Claims

1. A multilayer sheet comprising at least two layers (A) and (B), The layer (A) has a compressive strength of 100 to 300 kg / m ３ and a foamed sheet having a density of from 85.0 to 100 wt. % based on the total weight of the high melt strength polypropylene composition, the high melt strength polypropylene composition comprising a high melt strength propylene polymer having long chain branching, The layer (B) is a coated non-foamed layer comprising a polypropylene composition, the polypropylene composition comprising 85.0 to 100 wt. % of a linear propylene polymer, based on the total weight of the polypropylene composition, and the polypropylene composition has a melt flow rate MFR, measured according to ISO 1133, of 20.0 to 30.0 g / 10 min. ２ having The layers (A) and (B) are in close contact with each other, and the multilayer sheet is composed of two layers, that is, layers (A) and (B).

2. 2. The multilayer sheet of claim 1 having a total thickness of 500 to 1000 μm.

3. 150-300g / m ２ 3. The multilayer sheet of claim 1 or claim 2 having a basis weight of

4. The multilayer sheet according to any one of claims 1 to 3, wherein layer (A) has a thickness of 455 to 850 µm.

5. The multilayer sheet according to any one of claims 1 to 4, wherein layer (B) has a thickness of 45 to 150 µm.

6. The following longitudinal tensile properties: A longitudinal tensile modulus of 300 to 600 MPa; Longitudinal elongation at break of 10-100%; A longitudinal yield elongation of 2.0 to 30.0%; Nominal longitudinal tensile strain at break of 5 to 60%; A longitudinal tensile strength of 2.0 to 30.0 MPa; A longitudinal tensile breaking stress of 2.0 to 30.0 MPa, and / or Longitudinal tensile yield stress of 2.0 to 30.0 MPa 6. The multilayer sheet according to claim 1, further comprising one or more of the following:

7. The following transverse tensile properties: A transverse tensile modulus of 300 to 600 MPa; Transverse elongation at break of 10-100%; Nominal transverse tensile strain at break of 5 to 60%; A transverse tensile strength of 2.0 to 30.0 MPa, and / or Transverse tensile stress at break of 2.0 to 30.0 MPa 7. The multilayer sheet according to claim 1, further comprising one or more of the following:

8. 1.00 g / (m ２ 8. The multilayer sheet according to claim 1, having a water vapor transmission rate (WVTR) at 23° C. and 85% RH of less than d).

9. 2000cm ３ / (m ２ and / or an oxygen transmission rate (OTR) at 23° C. and 50% RH of less than 750 cm ３ / (m ２ 9. The multilayer sheet according to claim 1, having an oxygen transmission rate (OTR) at 5° C. and 0% RH of less than 1.0 MPa (1.0 MPa).

10. The high melt strength polypropylene composition has the following characteristics: Melt flow rate (MFR) at 230°C and 2.16 kg load in the range of 0.5 to 15.0 g / 10 min ２ , F of 20.0 to 50.0cN ３０ Melt strength, V over 200 mm / sec ３０ Melt extensibility, A melting temperature of 140-180°C, Crystallization temperature of 110 to 150°C 10. The multilayer sheet of claim 1, further comprising one or more of the following:

11. 11. The multilayer sheet according to any one of claims 1 to 10, wherein the linear propylene polymer is a linear propylene homopolymer.

12. A method for producing the multilayer sheet according to any one of claims 1 to 11, comprising the steps of: a) The high melt strength polypropylene composition is mixed with a mixture of 100 to 300 kg / m ３ to form a foamed sheet having a density of b) coating layer (A) with said polypropylene composition to obtain layer (B) in close contact with layer (A); The method includes:

13. An article comprising the multilayer sheet of any one of claims 1 to 11.

14. 14. The article of claim 13 which is a food packaging material.

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