A semi-finished light-foam core of multilayered polypropylene boards and a method of its manufacture

Abstract

A semi-finished light-foam core of multilayered polypropylene boards, in particular sandwiches, comprises a base layer of the light-foam polypropylene core with a thickness of 1 to 100 mm, with a bulk density of 20 to 250 kg / m3, which has a thermoadhesive layer attached on one or both sides with a thickness of 5 to 500 μm based on a polypropylene copolymer with a specific Vicat melting temperature T v in the range of 70 to 150 °C, and / or a seal initiation temperature T SIT in the range of 70 to 140 °C, and / or a melting temperature T m in the range of 100 to 155 °C. The invention further relates to a method of manufacture of this semi-finished product and a sandwich-type polypropylene laminate based on this semi-finished product, which is overlaid on one or both sides thereof with a reinforcing composite layer or layers with a thickness of 0.1 to 10.0 mm and a density of 900 to 2000 kg / m3 based on a polypropylene with a fibrous or particulate filler.

Description

[0001] A semi-finished light-foam core of multilayered polypropylene boards and a method of its manufacture

[0002] Technical Field

[0003] The invention relates to a semi-finished light-foam core of multilayered polypropylene boards and a method of its manufacture, and further to a sandwich-type polypropylene laminate manufactured using this semi-finished light-foam core.

[0004] Background of the Invention

[0005] Various solutions are currently known with respect to multilayered laminates with a light-foam core in general. For example, U.S. patent US4167431 discloses a method for producing a laminate in which a closed-cell light-foam PVC layer with a heat-sealable coating of a high-molecular-weight polymethyl methacrylate thereon and at ambient temperature is bonded to an extruded PVC film without the risk of damaging said light- foam layer. The produced laminate is cooled immediately afterwards to prevent subsequent damage to the light-foam layer. The problem is that the polymethyl methacrylate bonding layer disclosed in the patent is effective for PVC materials but is not suitable for PP laminates.

[0006] Chinese patent CN110216958 relates to a multilayered laminated film that contains light-foam layers and has a low thermal conductivity and good tensile and compressive strength. The multilayered film laminate is formed by alternately laminating a light-foam layer and a compact layer, wherein the compact layer is made of a separate polyolefin material and the foam layer is formed by mixing and foaming two polyolefin materials. The preparation method comprises the steps of: dosing polypropylene and a mixture of ethylene-octene copolymer and low-density polyethylene separately into two extruders, mixing the melts from the two extruders in a co-extrusion head; subsequently guiding through a multiplier to achieve multilayered stacking, modifying the resulting multilayered melt in a calibration device to obtain a PP / (POE / LDPE) alternately laminated microlayer, in which the light-foam layer and the compact layer are alternately laminated by utilizing the difference in melting temperatures of PP and the POE / LDPE mixture during intermittent foaming. The resulting multilayered material has good thermal insulation and mechanical properties and the manufacturing costs are low. The multilayered film is designed for thermal and acoustic insulation packaging applications. However, the method of manufacture of the multilayered laminated film is only intended for materials within the thickness range of films. Its use for sandwich laminates of larger thicknesses (boards) is not technically possible.

[0007] Korean patent KR101830688 relates to a sandwich laminate panel that contains a light-foam core and a covering protective layers made of a non-combustible material attached to the core by means of adhesive layers. The covering protective layers are special, impact-resistant nylon layers, e.g., based on aluminum thin-film foil, PP films vapor-deposited or coated with aluminum oxide. The adhesive layers are foils or films based on a polymer containing a polar functional group on the main polyolefin chain, which may be a hydroxyl group, a carboxylic acid group, an acid anhydride group, an amino group, an epoxide group, an isocyanate group, an oxazoline group, and a maleimide group. These are sandwich laminates with special covering layers, which is reflected in the specific composition of the adhesive layers. Such adhesive layers are not suitable for PP sandwich laminates with composite PP covering layers.

[0008] The object of the U.S. patent US6287678 is a composite structural panel with a thermoplastic light-foam core and composite covering layers containing natural fibers in a polymer matrix. Preferably, the thermoplastic material of all layers is polypropylene - the core consists of expanded polypropylene rigid foam. In the method of manufacture of the composite structural panel, a first preheated outer layer is laminated and pressed onto the foam core in a first pressing step followed by a second preheated outer layer in a second step. There is a suitable delay with cooling of the laminate between the two forming steps. In addition to the natural fibers in the polyolefin matrix, the covering layers contain polyolefin (PP) fibers, which are used to bond the covering layers to the core during thermal lamination. This lamination method is driven by the desire to prevent unwanted overheating of the light-foam core, but at the cost of introducing cooling of the laminate between the first and second steps, resulting in the associated thermal energy loss. Also, the bonding of the laminated layers via PP fibers contained in the polymer matrix of composite layers may not be optimal in terms of the resulting properties of the laminate.

[0009] Cyclic presses (see fig. 1 ) or continuous belt presses (see fig. 2) are used during the manufacture of the polypropylene sandwiches by thermal lamination of reinforcing composite layers based on polypropylene (PP) on the foam extruded polypropylene (XPP) core. In the first phase of the lamination, the contact surfaces of the bond are activated at the temperature T1with simultaneous bonding by pressing at the pressure P-1, in the second phase the hot bond is cooled to the temperature T2, under the constant exposure to the pressure P2, or pressure P3, for the time t1and t2 or speed v, to achieve the final strength of the bond.

[0010] A major problem of this lamination is the narrow lamination temperature range defined by the melting temperature or the material seal initiation temperature of the PP- based reinforcing composite layer with a melting temperature in the range of 155 to 173 °C and the XPP core material with a melting temperature in the range of 155 to 165 °C.

[0011] On the one hand, it is desirable to achieve a sufficiently high lamination temperature in order to activate the contact surfaces of the bond to the necessary extent and for the PP-based reinforcing composite layers to sufficiently bond to the XPP core.

[0012] On the other hand, a lamination temperature is desired that is not so high as to cause damage to the PP-based reinforcing composite layer by melting leading to a poor quality PP sandwich surface or damage to the XPP core by melting leading to a loss of thickness of the XPP core and thus an undesirable reduction of the thickness of the final PP sandwich, or in a worse case, the formation of areas on the finished PP sandwich where the PP-based reinforcing composite layer is not perfectly bonded to the XPP core.

[0013] The process window of the lamination temperature T1is very narrow due to the above-mentioned reasons and is only in a range of 5 °C, usually in the range of 160 to 165 °C.

[0014] The lamination by the above-mentioned method is further complicated by the use of a larger thickness of the PP-based reinforcing composite layer. The lamination of a reinforcing composite layer with a thickness greater than 1 mm is indeed complicated, it is associated with a significant increase in the heating time and with limited quality of the resulting PP sandwiches.

[0015] The lamination by said method is further complicated when XPP cores with a lower bulk density are used, which are sensitive to high temperatures and deteriorate quickly. The use of an XPP core with a bulk density lower than 80 kg / m3is practically impossible for this lamination method.

[0016] Summary of the Technical Solution

[0017] A semi-finished light-foam core of multilayered polypropylene boards, in particular sandwiches according to the invention, contributes to a large extent to the elimination of the above problems. The summary of the invention lies in the fact that the base layer of the light-foam polypropylene core (XPP) with a thickness of 1 to 100 mm, with a bulk density of 20 to 250 kg / m3has a thermoadhesive layer attached on one or both sides with a thickness of 5 to 500 pm based on a polypropylene copolymer with a specific Vicat melting temperature Tvin the range of 70 to 150 °C, and / or a seal initiation temperature TSIT in the range of 70 to 140 °C, and / or a melting temperature Tmin the range of 100 to 155 °C.

[0018] The polypropylene copolymer of the thermoadhesive layer having a specific lower melting temperature in the range of 100 to 155 °C and / or a seal initiation temperature in the range of 80 to 140 °C may be, in particular, a copolymer selected from a group comprising polypropylene C2 / C4 terpolymers having a seal initiation temperature TSIT in the range of 70 to 130CC, propylene ethylene random copolymers with a Vicat melting temperature Tvin the range of 100 to 150 °C and random copolymers of isotactic propylene units with a random distribution of ethylene units polymerized using metallocene catalysts with a Vicat melting temperature Tvin the range of 70 to 110 °C.

[0019] The essence of the method of manufacture of the semi-finished light-foam core according to the invention lies in the fact that on the base layer of the extruded polypropylene core with a thickness of 1 to 100 mm, a thermoadhesive layer or layers is / are applied on one or both sides thereof with a thickness of 5 to 500 pm based on polypropylene copolymer with a specific Vicat melting temperature Tvin the range of 70 to 155 °C and / or a seal initiation temperature TSIT in the range of 70 to 140 °C and / or a melting temperature Tmin the range of 100 to 155 °C by extrusion coating or thermal lamination of the thermoadhesive layer in the form of a film, fabric, mesh, or web. The sandwich-type polypropylene laminate comprises a light-foam core according to the invention overlaid on one or both sides thereof with a reinforcing composite layer or layers with a thickness of 0.1 to 10.0 mm and a density of 900 to 2000 kg / m3based on polypropylene with a fibrous or particulate filler. The reinforcing composite layer or layers may also have a thermoadhesive layer attached on the side adjacent to the light-foam core with a thickness of 5 to 500 pm of the same composition as the thermoadhesive layers attached to the core.

[0020] The main advantage of the semi-finished light-foam core of multilayered polypropylene boards according to the invention, and in particular the polypropylene sandwiches according to the invention, lies in the fact that the application of the thermoadhesive layer or layers based on polypropylene copolymers with a specific lower Vicat melting temperature Tvin the range of 70 to 150 °C and / or seal initiation temperature TSIT in the range of 70 to 140 °C and / or melting temperature Tmin the range of 100 to 155 °C allows the temperature process window of the lamination temperature T1to be extended to a range of 20 to 45 °C, wherein it is not necessary for the maximum lamination temperature T1to exceed the temperature of 155 °C. The semi-finished core or also the PP-based reinforcing composite layers modified in this way then allow the use of the lamination temperature T1defined by the range of the melting temperature of the used thermoadhesive layer. Alternatively, the lamination temperature T1may be defined by the parameter of the seal initiation temperature (SIT) of the used thermoadhesive layer, where the minimum lamination temperature T1should be above this temperature.

[0021] Due to the very small thickness of the thermoadhesive layer of 5 to 500 pm and thus its low thermal capacity, this layer can be applied at higher temperatures without damaging the XPP core. The application at high temperature results in a perfect bonding of the PP-based adhesive layer to the XPP core or the PP-based reinforcing composite layer.

[0022] When applying the PP-based thermoadhesive layer to the XPP core by extrusion coating or thermal lamination of the thermoadhesive layer in the form of a film, fabric, mesh, or web, the application temperature varies according to the chosen method and taking into account possible damage to the XPP core, generally in the range of 155 to 180 °C. The pressing of the adhesive layer is carried out at a pressure up to 100 kPa. The temperature and pressure exposure time is in a range of up to 10 s. The thermoadhesive layer is usually applied from both sides of the XPP core. The semi-finished light-foam core of multilayered polypropylene boards and the method of its manufacture as well as the use of this semi-finished product for the sandwich-type polypropylene laminate according to the invention provides the following advantages and improvements over the current methods of manufacture of polypropylene boards and sandwiches:

[0023] - The possibility of using XPP cores with a very low bulk density of up to 20 kg / m3

[0024] - Increased maximum thickness of the applicable PP-based reinforcing composite layers, up to 10 mm.

[0025] - Increased productivity of sandwich lamination by shortening the pressing time t1and t2 or increasing the speed v.

[0026] - Reduced risk of damage to the PP-based reinforcing composite layers by partial or complete melting.

[0027] - Reduced risk of poor bonding of the PP-based composite layers and the XPP core due to insufficient activation of the contact surfaces at a low temperature T1or short exposure time to the temperature T1.

[0028] - Reduced risk of poor bonding of the PP-based composite layers and the XPP core due to a disproportionate damage to the XPP core by a too high temperature T1.

[0029] Description of Drawings

[0030] The summary of the technical solution is further clarified using exemplary embodiments thereof, which are described with reference to the accompanying drawings, in which: fig. 1 schematically shows the lamination of the reinforcing composite layers to the foam core used in cyclic presses - the current method, fig. 2 schematically shows the continuous lamination of the reinforcing composite layers to the foam core used in belt presses - the current method, fig. 3 schematically shows the application of thermoadhesive layers to the foam core, fig. 4 schematically shows the application of thermoadhesive layers to the foam core as well as the reinforcing composite layers, fig. 5 schematically shows the lamination of the reinforcing composite layers to the foam core in cyclic presses using the thermoadhesive layers of fig. 4, fig. 6 schematically shows the continuous lamination of the reinforcing composite layers to the foam core in belt presses using the thermoadhesive layers of fig. 3.

[0031] Exemplary Embodiments of the Technical Solution

[0032] The technical solution will be further clarified using exemplary embodiments with reference to the respective drawings.

[0033] Example 1

[0034] In an exemplary embodiment (see fig. 3), the semi-finished light-foam core of multilayered polypropylene boards comprises a base layer 2 of an extruded polypropylene core (XPP) with a thickness of 26 mm and bulk density of 200 kg / m3, which has a thermoadhesive layer 3 attached on one or both sides with a thickness of 400 pm based on a polypropylene C2 / C4 terpolymer with a seal initiation temperature TSIT= 112 °C and a Vicat melting temperature Tv= 137 °C. Specifically, copolymer Adsyl 3 C 30 F HP.

[0035] The method of manufacture of the semi-finished light-foam core according to the invention involves applying the thermoadhesive layer 3 or layers based on polypropylene C2 / C4 terpolymer to the base layer 2 of the light-foam polypropylene core on one or both sides thereof by extrusion coating.

[0036] Example 2 In an exemplary embodiment, the semi-finished light-foam core of multilayered polypropylene boards is identical to Example 1 , however, the particular material of the thermoadhesive layer 3 is a polypropylene C2 / C4 terpolymer with a seal initiation temperature TSIT in the range of 70 to 130 °C and a Vicat melting temperature Tvin the range of 70 to 155 °C selected from a group comprising Adsyl 7410 XCP, C yrell RR213M, Borseal™ TD115BF, Borealis PP TD320BF, Topilene C600HF PP, Hanwha TotalEnergies PP TF412, ELTEX® P KV359, and SABIC®PP 827L

[0037] Example 3

[0038] In an exemplary embodiment (see fig. 3), the semi-finished light-foam core of multilayered polypropylene boards comprises the base layer 2 of the extruded polypropylene core (XPP) with a thickness of 80 mm and bulk density of 40 kg / m3, which has the thermoadhesive layer 3 attached on one or both sides with a thickness of 70 pm based on propylene ethylene random copolymer with a Vicat melting temperature Tv= 130 °C and peak melting temperature Tm= 145 °C. Specifically, Total PPR 6288.

[0039] The method of manufacture of the semi-finished light-foam core 2 according to the invention lies involves applying the thermoadhesive layer 3 or layers based on propylene ethylene random copolymer to the base layer 2 of the light-foam polypropylene core on one or both sides thereof by thermal lamination of the thermoadhesive layer 3 in the form of a film.

[0040] Example 4

[0041] In an exemplary embodiment, the semi-finished light-foam core of multilayered polypropylene boards is identical to Example 3, however, the particular material of the thermoadhesive layer 3 is a propylene ethylene random copolymer with a Vicat melting temperature Tvin the range of 100 to 150 °C selected from a group comprising Borealis RB707CF, Borealis RD265CF, SABIC®PP 622L, Moplen RP225M, ExxonMobil™ PP9513, Total 6571 BB, and Moplen RP220M.

[0042] Example 5

[0043] In an exemplary embodiment (see fig. 3), the semi-finished light-foam core of multilayered polypropylene boards comprises the base layer 2 of the extruded polypropylene core (XPP) with a thickness of 9.2 mm and bulk density of 80 kg / m3, which has the thermoadhesive layer 3 attached on one or both sides with a thickness of 40 pm based on a random copolymer of isotactic propylene units with a random distribution of ethylene units polymerized using metallocene catalysts with a Vicat melting temperature Tv= 77.3 °C in a mixture with a propylene ethylene random copolymer with a Vicat melting temperature Tv= 125 °C. Specifically, 40% Vistamaxx 3588FL + 60 % Moplen RP220M.

[0044] The method of manufacture of the semi-finished light-foam core according to the invention involves applying the thermoadhesive layer 3 or layers based on a random copolymer of isotactic propylene units with a random distribution of ethylene units polymerized using metallocene catalysts to the base layer 2 of the light-foam polypropylene core on one or both sides thereof.

[0045] Example 6

[0046] In an exemplary embodiment, the semi-finished light-foam core of multilayered polypropylene boards is identical to Example 3, however, the particular material of the thermoadhesive layer 3 is a random copolymer of isotactic propylene units with a random distribution of ethylene units polymerized using metallocene catalysts with a Vicat melting temperature Tvin the range of 70 to 110 °C in a mixture with 0 to 80 wt% propylene ethylene random copolymer with a Vicat melting temperature in the range of 100 to 150 °C. Specifically, a mixture of Vistamaxx 3980FL + Moplen RP220M, or alternatively pure Vistamaxx 3588FL.

[0047] Example 7

[0048] In an exemplary embodiment, the PP-based reinforcing composite layer 1_ is prepared from four partial layers of polypropylene film with a total weight of 400 g / m2reinforced with hemp fibers oriented in one direction at a content of 40%. The films are oriented with respect to each other alternately at 0° and 90°. In accordance with fig. 4, the thermoadhesive layer 3 is added as the fifth layer in the form of a film with a thickness of 50 pm manufactured by extrusion casting from a propylene ethylene random copolymer specified in more detail in example 2 with a Vicat melting temperature Tvof 130 °C, with a peak melting temperature of 145 °C. All five layers are laminated together in a hot cyclic press at a temperature of 180 °C, a pressure of 0.5 MPa, for a time of 1 min and cooled in the cyclic press at a temperature of 70 °C, a pressure of 0.8 MPa, for a time of 1 min. The length and width of the reinforcing composite layer so prepared are 2500 mm and 1250 mm respectively. The thermoadhesive layer 3 is laminated onto the foam polypropylene (XPP) core with a bulk density of 40 kg / m3and a thickness 80 mm on both sides (in accordance with fig. 4) in the form of a film with a thickness of 70 pm manufactured by extrusion casting from a polymer based on propylene ethylene random copolymer specified in more detail in Example 2 with a Vicat melting temperature T / = 130 °C, with a peak melting temperature Tm= 145 °C. The lamination is carried out in a hot cyclic press at a temperature of 165 °C, a pressure of 0.1 MPa for a time of 5 s, and after the lamination the laminate is cooled by air blowing. The length and width of the core so prepared are 2500 mm and 1250 mm respectively.

[0049] The two PP-based reinforcing composite layers 1. and the foam polypropylene (XPP) core prepared in this way with the thermoadhesive layers 3 on all contact surfaces are laminated in a polypropylene sandwich in a continuous belt press (similar to fig. 6) under conditions of heating at the temperature T1= 155 °C, pressure P1= 0.03 MPa, slot size of 20.5 mm, length of the heating zone of the press of 3 meters and under conditions of cooling at the temperature T2 = 50 °C, pressure P2 = 0.1 MPa, slot size of 20.1 mm, and length of the cooling zone of the press of 2 meters. The lamination speed is set to 6 m / min. The length and width of the polypropylene sandwich manufactured in this way, after trimming the edges, are 2440 mm and 1220 mm respectively. The resulting thickness thereof is 20.0 mm.

[0050] Example 8

[0051] The PP-based reinforcing composite layer 1. is prepared by consolidating a layer of a hybrid fabric composed of 40% polypropylene fibers and 60% glass fibers, in a twill weave, with a weight of 5.0 kg / m2, and the thermoadhesive layer 3 applied in the form of a powder in an amount of 70 g / m2, from a polymer based on polypropylene C2 / C4 terpolymer as specified in more detail in example 1 with the seal initiation temperature TSIT = 112 °C and Vicat melting temperature Tv= 137 °C. The consolidation takes place in a continuous belt press under conditions of heating at the temperature T1 = 180 °C, pressure P1= 0.1 MPa, length of the heating zone of the press of 2 meters and under conditions of cooling at the temperature T2 = 70 °C, pressure P2 = 0.2 MPa, length of the cooling zone of the press of 1 meter. The consolidation speed is set to 0.5 m / min. The resulting reinforcing composite layer with the thermoadhesive layer 3 is manufactured in a width of 3050 mm and is wound into rolls.

[0052] The thermoadhesive layer 3 with a thickness of 400 pm, from a polymer based on polypropylene C2 / C4 terpolymer specified in more detail in Example 1 with the seal initiation temperature (SIT) TSIT = 112 °C and Vicat melting temperature Tv= 137 °C is coated onto the foam polypropylene (XPP) core with a bulk density of 200 kg / m3and thickness of 26 mm from both sides by extrusion.

[0053] The two PP-based reinforcing composite layers 1. and one foam polypropylene (XPP) core prepared in this way with the thermoadhesive layers 3 on all contact surfaces (in the assembly of fig. 4) are laminated in a polypropylene sandwich in a continuous belt press (similar to fig. 6) under conditions of heating at the temperature T1= 155 °C, pressure P1= 0.05 MPa, slot size of 31 .5 mm, length of the heating zone of the press of 3 meters and under conditions of cooling at the temperature 72 = 50 °C, pressure P2 = 0.06 MPa, slot size of 31.1 mm, length of the cooling zone of the press of 2 meters. The lamination speed is set to 2 m / min. The length and width of the polypropylene sandwich manufactured in this way, after trimming the edges, are 20,000 mm and 3000 mm respectively. The resulting thickness thereof is then 31 mm.

[0054] Example 9

[0055] The PP-based reinforcing composite layer 1. is prepared by coextrusion casting of an 0.75 mm thick film of a recycled polypropylene compound filled with a 40% content of talc and the thermoadhesive layer 3 with a thickness of 30 pm from a polymer based on polypropylene C2 / C4 terpolymer specified in more detail in Example 1 with the seal initiation temperature (SIT) TSIT = 95 °C and Vicat melting temperature Tv= 126 °C. The resulting reinforcing composite layer with the thermoadhesive layer 3 is manufactured in a width of 1250 mm and is wound into rolls.

[0056] The thermoadhesive layer 3 in the form of a film with a thickness of 40 pm manufactured by extrusion casting from a polymer based on polypropylene C2 / C4 terpolymer specified in more detail in Example 1 with the seal initiation temperature (SIT) TSIT = 95 °C and Vicat melting temperature Tv= 126 °C is laminated onto the foam polypropylene (XPP) core with a bulk density of 80 kg / m3and thickness of 9.2 mm from both sides. The lamination takes place in a continuous belt press under conditions of heating at the temperature T1= 155 °C, pressure P1= 0.005 MPa, length of the heating zone of the press of 2 meters, slot size of 9.0 mm, and under conditions of cooling at the temperature 72 = 20 °C, pressure P2 = 0.02 MPa, length of the cooling zone of the press of 1 meter, slot size of 8.8 mm. The lamination speed is set to 20 m / min. The length and width of the foam core prepared in this way are 1220 mm and 2050 mm respectively.

[0057] The two PP-based reinforcing composite layers 1. and one foam polypropylene (XPP) core, with the thermoadhesive layers 3 on all contact surfaces, are laminated in a polypropylene sandwich by pressing in a hot cyclic press (in accordance with fig. 5) at the temperature T1= 130 °C, pressure P1= 0.1 MPa, for the time t1= 30 s, with a slot size of 10.2 mm, and subsequently in a cold cyclic press at the temperature T2 = 40 °C, pressure P2 = 0.2 MPa, for the time t2 = 30 s, with a slot size of 10.0 mm. The length and width of the polypropylene sandwich manufactured in this way, after trimming the edges, are 2000 mm and 1000 mm respectively. The resulting thickness thereof is then 10 mm.

[0058] List of Reference Signs

[0059] 1 - reinforcing composite layer

[0060] 2 - base layer

[0061] 3 - thermoadhesive layer

Claims

CLAIMS1. A semi-finished light-foam core of multilayered polypropylene boards, particularly sandwiches, characterized in that a base layer (2) of the light-foam polypropylene core with a thickness of 1 to 100 mm, with a bulk density of 20 to 250 kg / m3has a thermoadhesive layer (3) with a thickness of 5 to 500 pm attached on one or both sides based on a polypropylene copolymer with a specific Vicat melting temperature Tvin the range of 70 to 150 °C and / or a seal initiation temperature TSIT in the range of 70 to 140 °C and / or a melting temperature Tmin the range of 100 to 155 °C, wherein said polypropylene copolymer of the thermoadhesive layer (3) is a copolymer selected from a group comprising polypropylene C2 / C4 terpolymers with a seal initiation temperature TSIT in the range of 70 to 130 °C, propylene ethylene random copolymers with a Vicat melting temperature Tvin the range of 100 to 150 °C, and random copolymers of isotactic propylene units with a random distribution of ethylene units polymerized using metallocene catalysts with a Vicat melting temperature Tvin the range of 70 to 110 °C.

2. A method of manufacture of the semi-finished light-foam core according to claim 1 , characterized in that on the base layer (2) of the extruded polypropylene core with a thickness of 1 to 100 mm, the thermoadhesive layer (3) or layers is / are applied on one or both sides thereof with a thickness of 5 to 500 pm based on a polypropylene copolymer with a specific lower Vicat melting temperature Tvin the range of 70 to 150 °C and / or a seal initiation temperature TSIT in the range of 70 to 140 °C and / or a melting temperature Tmin the range of 100 to 155 °C by extrusion coating or thermal lamination of the thermoadhesive layer (3) in the form of a film, fabric, mesh, or web.

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