MXPA96005837A - Multi-layer multi-layer of bioxial orientation that seals at low temperature, procedure parasu manufacturing and emp - Google Patents

Abstract

The present invention relates to a multilayer polyolefin and sealable sheet, capable of at least B2D, of which D is a polyolefin base layer, Z an intermediate layer and D a finish layer applied over the previous one. The finishing layer contains at least 75% by weight of a sealable polyolefin. The sealable polyolefin of the finishing layer has a minimum sealing temperature of at least 100 ° C. The intermediate layer contains at least 75% by weight of a sealable polyolefin. The minimum sealing temperature of the polyolefin of the finishing layer is greater than the minimum sealing temperature of the polyolefin of the intermediate layer. It's thickness of the finishing layer is less than 0, 4

Description

POLYOLEPHINIC BIOXIAL ORIENTATION SHEET MULTI-FLOOR LETTER OR LOW TEMPERATURE, PROCEDURE FOR ITS MANUFACTURE AND EMPLOYMENT The present invention relates to a multilayer polyolefin sheet formed by at least three BZD layers, of which B is a polyolefin base layer, Z an intermediate layer and D a finishing layer applied over the previous one. The present invention also relates to the use of this sheet and to a process for its manufacture. Packing machines work more and more quickly and, like sensitive packaging products (food, chocolate, bakery), require sheets of low initial sealing temperature in combination with an optimal gear of the machine. In current technology, sheets with initial sealing temperatures of less than 100 ° C / in some cases even lower, up to 74 ° C are known. However, these sheets have great drawbacks in their manufacture. EP-A-C1 114 311 and EP-ft-Q 114 312 describe opaque and transparent polypropylene sheets with an initial sealing temperature (minimum sealing temperature of less than 100 ° C and good machining.) These sheets have a layer of finishing formed by a mixture of terpolymer C2 / C3 / C4 and copolymer C3 / C4 as well as a low molecular weight resin, polypropylene homopolymer and polydiorganosiloxane According to this example, the wide margin of sealing of the sheet and its ba at temperature Initial sealing is achieved by the composition of the olefinic resin starting from copolymer and + erpolymer.The incorporation of resin residues in the drawing rollers during manufacturing.This waste causes the formation of scratches on the sheet. The rollers should be frequently cleaned EP-A-0 184 094 and EP-A-0 187 253 disclose opaque and transparent polypropylene sheets with a sealable surface layer, temperature Seal of less than or equal to 100 ° C is achieved by the olefimca resin composition, starting with C3 / C copolymers and C2 / C3 / C terpolymers. EP-A-0 480 282 discloses a biaxially oriented polyolefin multi-layered sheet which seals at low temperature on both sides, whose base layer contains a propylene homopolymer degraded with peroxide and whose finishing layers contain C2 / C3 terpolymer blends. / C4 and copolymer C2 / C3 as well as a combination of S1O2 and polydialkylsiloxane. The polydialkylsiloxane is very viscous and is added in the nasterbatch form. The initial sealing temperature is 88 ° C. EP-A-0 578 149 discloses a co-extruded and transparent polyolefin laminate sheet with low sealing temperature and defined values of longitudinal and transverse shrinkage, the finishing layers of which have an initial sealing temperature of 124 ° C, preferably 80 at 110 ° C. EP-fl-0 611 647 discloses sheets rnul + icap with at least one finishing layer sealing at low temperature.

The topcoat contains a low crystalline C3 / C4 olefinic ream combination and has an initial sealing temperature of less than T4 ° C. The sheets with the low-temperature sealing layers described above have a high tendency to stick with themselves at high temperature and with the hot parts of the machines, such as, for example, the rollers of the longitudinal stretching or the jaw chains of the transverse stretching. Therefore, the manufacture of such sheets is very problematic. Due to the high tendency to stick to the leaves, the danger of tearing is particularly high. In case of tearing of the sheets during the longitudinal stretching, the gluing of the tape with itself or with the drawing rollers causes them to become entangled in them by twisting them and damaging them. If the sheets tear in the transversal stretch, pieces remain stuck in the chains of jaws and count very much to remove them from the frame. All this leads to long production stops. In addition there is great danger of accidents due to the sticking of the tape still hot with itself. The tape is folded like an accordion formed a kind of large welded skein that can only be removed from the machine with great effort. ThusIt is an object of the present invention to provide a multi-layered sheet with good sealing properties, that is to say an especially low initial sealing temperature, which can be used to package heat-sensitive products in fast-acting wrapping machines. During fabrication, the blade must not stick with itself or with the hot parts of the machine and has to advance without problems. Nor should you stick too much with yourself in the event of a tear. According to the present invention this problem is solved by a ho a of the type mentioned at the beginning, whose characteristic features are that the intermediate layer Z contains 75% by weight, with respect to the same Z layer, of sealable polyolefins and the finishing layer D contains at least 75% by weight, with respect to the same D layer, of sealable polyolefins; so that the minimum sealing temperature (initial sealing temperature) of the finishing layer D is at least 100 ° C and is greater than the minimum sealing temperature of the intermediate layer Z, and the thickness of the layer of finish D is less than 0.4 μrn. Surprisingly, two superposed sealable layers, whose minimum sealing temperatures are adjusted one over the other in the manner indicated, provide an improved sheet with respect to the current technological level. It no longer sticks to itself, nor sticks to the heated rollers, nor to the hot chains of rolling jaws of the transverse drawing frame. In comparison with the current technical level described, the manufacture of this ho a does not present practically problems. Surprisingly, the application of the thin finishing layer, which seals at a higher temperature, on the intermediate layer of sealing at low temperature has not altered the transformation conditions of the sheet of the present invention with respect to the sheet manufactured according to the current technique. The sheet still has a very low initial sealing temperature and can also be used in those applications where the reduced initial sealing temperature of the polyolefin of the intermediate layer can be used and all the advantages that this entails. Surprisingly, it has been shown that in applications where the seal is sealed with fluted jaws, the same temperatures can be chosen as in the case where thin layers of finish are lacking. It is evident that the fluted jaws broke > in the thin finishing layer showing the sealing properties of the lower layer. The base layer of the multilayer sheet according to the present invention contains polyolefins, preferably propylene polymers, and optionally other additives added in effective amounts. In general, the base layer contains at least 50% by weight, preferably from 75 to 100% by weight, especially from 90 to 98% by weight of the propylene polymers with respect to this same layer. The propylene polymer usually contains 90 to 100%, preferably from 95 to 100% by weight, especially from 98 to 100% by weight of propylene units and usually have a melting point of 120 ° C or more preferably from J50 to 170 ° C, and an index of fusion of 0.5 g / 10 rnm. at 8 g / 10 rnin., preferably 2 g / 10 min. at 5 g / 10 rnin., at 230 ° C and a force of 21.6 N (DIN 53 735). Preferred propylene polymers for the base layer are: isopylactic propylene opolymer with an atactic component of 15% by weight or less; copolymers of ethylene and propylene with an ethylene content of 10% by weight or less; propylene copolymer with C, -Ce-α-olefins, with a content of α-olefm of 10% by weight or less; propylene, ethylene and butylene terpolyners having an ethylene content of 10% by weight or less and with a butylene content of 15% by weight or less; especially the isotactic propylene homopolymer. The percentages by weight indicated refer to the corresponding polymers. Also suitable is a mixture of said copolymer and / or copolymer furnaces and / or terpolymers of propylene and other polyolefins, especially of monomers with 2 to 6 volumes of C, containing at least 75% by weight of polymerized propylene. Other polyolefin suitable for this mixture are polyethylenes, especially HDPE, LDPE and LLDPE, so that their proportion in the mixture does not exceed 15% by weight. In the preferred embodiment of the sheet according to the present invention, the propylene polymer of the base layer is degraded with peroxide. The so-called degradation factor A gives a measure of the degradation of the polymer, by means of the relative variation of the melt index, according to DIN 53 735, of the polypropylene with respect to the torque polymer. FI2 A = MFIi MFIi = melt index of the propylene polymer before adding the organic peroxide. HFI2 = melt index of the propylene polymer degraded with peroxide. The degradation factor A of the propylene polymer used usually varies in a range between 3 and 15, preferably between 6 and 10. Co or organic peroxide are especially preferred dialkylperoxides, with alkyl being understood as a saturated radical, linear or branched , of up to six carbon atoms. Especially preferred is 2,5-d? Met? Al-2,5-d? (t-butylperoxy) -hexane or di-t-butyl peroxide. In general, the base layer can contain stabilizers and neutralizers in effective amount and also 1 ubcant, antistatic and / or hydrocarbon resin. In a white or opaque or white-opaque embodiment, the base layer also contains pigments or vacuole-initiating particles, or a combination thereof. Such sheets have a transparency, according to ASTN-D 1033-77, of the 50% maximum, preferably 70% maximum. The pigments include those particles that essentially do not produce vacuoles during stretching. The coloring effect of the pigments is caused by the particles themselves. The term "pigment" is generally linked to a granulornetpa of 0.01 to 1 μm, at most, and encompasses both the so-called "white pigments", which give a white tone to the leaves, and the "colored pigments", which color the leaf to the dye black. The average diameter of the pigment + particles usually varies within the range between 0.01 and 1 μm, preferably between 0.01 and 0.7 μm, especially 0.01 and 0.4 μm. The base layer usually carries from 1 to 25% by weight of pigments, especially 2 to 20% by weight, preferably 5 has + to 15% by weight, based on said layer. The usual pigments are substances such as, for example, aluminum oxide, aluminum sulfate, bench sulphate, calcium carbonate, magnesium carbonate, silicates such as aluminum (kaolin) and magnesium (talc), silicon dioxide and titanium dioxide, the carbonate being Calcium, silicon dioxide, titanium dioxide and sulfate bank the white pigments used with preference. The titanium dioxide particles consistat least 95% by weight of rutile and are preferably used coated with a layer of inorganic oxides, such as the white T1O2 pigments used in papers or paints to improve light fastness. Particularly suitable inorganic oxides include those of aluminum, silicon, zinc or magnesium, or mixtures of two or more of these compounds. They are obtained by precipitating water-soluble compounds, such as for example alkali aluminates, especially sodium, aluminum hydroxide, aluminum sulfate, aluminum nitrate, sodium silicate or silicic acid in aqueous suspension. Coated T1O2 particles are described in EP-A-0 078 633 and EP-A-0 044 515. The coating may also optionally contain organic compounds with polar and apolar groups. The preferred organic compounds are alkandes and fatty acids of 8 to 30 C atoms in the alkyl group, especially fatty acids and primary n-alkanols of 12 to 24 C atoms, as well as polydiorganosiloxanes and / or polyorgano-hydrogenosiloxanes such as polydirnethylsiloxane and polyrne + ilhydrogenosiloxane. The coating of T1O2 particles usually consists of 1 to 12 g. especially from 2 to 6 g of inorganic oxides; optionally it also contains 0.5 to 3 g, in particular 0.7 to 1.5 g of organic compounds, in each case referred to 100 g of T1O2 particles coated with AI2O3 or AIO3 and polydimethylsiloxane. The opaque execution forms of the leaves contain vacuoles-initiating particles, which are incompatible with the poly-epic matrix and during the stretching cause the formation of vacuole-like cavities, whose size, type and quantity depend on the material and size of the particles solid and stretch conditions, as a percentage of elongation and temperature. The vacuoles give the leaves an opaque appearance pearly character due to the scattering of light in the vacuole matrix / polymepca matrix. The average diameter of the vacuole initiator particles is usually from 1 to 6 μm, preferably from 1.5 to 5 μm. The base layer contains between 1 and 25% by weight of vacuole initiator particles, based on the weight of said layer. Vacuole initiator particles in the base layer usually use inorganic and / or organic materials incompatible with polypropylene, for example aluminum oxide, aluminum sulfate, bench sulfate, calcium carbonate, magnesium carbonate, silicates such as aluminum (kaolin) and magnesium (talc), silicon dioxide and titanium dioxide, with calcium carbonate being silicon dioxide and titanium dioxide, which are preferably used as organic fillers, are the common types which are incompatible with the polymer of the base layer; especially HDPE, polyesters, polystyrenes, polyarynnides, organic halogenated polymers, with polyesters being preferred, such as polybutylene or polyethylene terephthalate. According to the present invention, "materials or polymers or incompatible" means that the material or polymer exists in the sheet as separate particles or co or separate phase. The white / opaque sheets of vacuole and pigment initiator particles carry from 1 to 10% by weight, preferably from 1 to 5% by weight, of vacuole starter pieces + and from 1 to 7% by weight, preferably from 1 to 5% by weight of pigments, based on the weight of the basic layer. The density of the opaque or white sheets can vary within wide ranges and depends on the type and amount of the charges. It usually ranges from 0.4 to 1.1 g / cm3. The pigmented sheets have a density of the order of 0.9 g / cm3 or more, preferably between 0.9 and 1.1 g / cm3. The leaves that only contain vacuoles-initiating particles have a density lower than 0.9 g / cm3. Packing sheets containing 2 to 5% by weight of vacuole initiator particles have a density of 0.6 to 0.85 g / cm 3. The sheets containing from 5 to 14% by weight of vacuole initiator particles have a density of 0.4 to 0.8 g / cm3. The sheets carrying pigments and vacuole-initiating particles have a density of 0.5 to 0.85 g / cm3, depending on the ratio between the content of pigments and that of particular vacuole primers. According to the present invention, the multilayer sheet contains at least one intermediate layer, generally applied on at least one layer of the base layer. This intermediate layer contains 75 to 100% by weight, preferably 90 to 100% by weight, especially 95 to 100% based on said layer, of sealable polymers of olefins with 2 to 10 carbon atoms, as well as optionally in an effective amount . The minimum sealing temperature of these polyolefins of the intermediate layer is lower than the minimum temperature of the polyolefin seal of the finishing layer. The minimum temperature of the polymer sealing of the intermediate layer is less than 100 ° C, preferably lower than 90 ° C and above all it is between 65-80 ° C. Examples of such sealable olefinic polymers, with low initial sealing temperature are: a copolymer of ethylene and propylene or ethylene and butylene-1 or propylene and butylene-1 or a terpolymer of ethylene and propylene and butylene-1 or a mixture or a blend of two or more of said copolymers and terpolymersoptionally mixed with one or more of said copolymers and terpolymers, with statistical copolymers of ethylene-propylene having an ethylene content of 1 to 10% by weight, preferably 2.5 to 8% by weight, or copolymers being especially preferred. statistics of propylene and butylene-1 with a content of butylene from 2 to 25% by weight, preferably from 4 to 20% by weight, based respectively on the total weight of the copolymer, or statistical terpolirneros of et? leno-? rop? 1-butylene-1 with an ethylene content of 1 to 10% by weight, preferably 2 to 6% by weight, and a content of butylene-1 of 2 to 20% by weight, preferably from 4 to 20% by weight, respectively referred to the total weight of the terpolymer, or a blend of a terpolymer of ethylene-propylene-butylene-1 and a copolymer of propylene-butylene-1 with a ethylene content of 0.1 to 7% by weight, a propylene content of 50 to 90% by weight and a content of butylene-1 from 10 to 40% by weight, based on the total weight of the polymer blend respectively. The copolymers and terpolymers described above generally have a melt index of 1.5 to 30 g / 10 rnin, preferably 3 to 15 g / 10 min. The blend of copolymer and terpolymers described above generally has a melt flow rate of 5 haeta 9 g / 10 mm. The indicated flow rates are measured at 230 ° C with a force of 21.6 N (DIN 53 735). Of the above-described polyolefins, the sealable propylene polymers containing at least 70% by weight, preferably 75-90% by weight, of propylene relative to the polymer are preferred. The preferred comonomers are ethylene and butylene. Eventually, all the polymers of the intermediate layer described above can be degraded with peroxide in the same way as described above for the base layer, J4 using in principle the same peroxides. The degradation factor for the polymers of the intermediate layer generally ranges from 3 to 15, preferably from 6 to 10. In a preferred embodiment, the intermediate layer contains stabilizers and neutralizers as well as, optionally, anti-adherents, lubricants, resins and hydroon and / or antistatic, in effective amount. The addition of stabilizers, neutralizers and anti-bodies is preferred. The polyolefin sheet of the present invention ies at least one sealable topcoat, applied over the intermediate layer described above. This finishing layer contains from 75 to 100% by weight, preferably from 90 to 100% by weight, especially 100% by weight with respect to said layer, of sealable polymers of olefins with 2 to 10 on atoms and optionally additives in amount effective The minimum sealing temperature of sealable polyolefms is at least 100 ° C and is greater than the minimum sealing temperature of the polyolefm of the intermediate layer. The minimum sealing temperature of the polymer of the finishing layer is at least 100 ° C, preferably 100 to 150 ° C, especially 120 to 140 ° C. Examples of such sealable olefinic polymers are: a copolymer of ethylene and propylene or ethane and butylene-1 or propylene and butylene-1 or a terpolymer of ethylene and propylene and butylene-1 or a mixture or a blend of two or spans of said copolymers and terpolymers, optionally mixed with one or more of said copolymers and terpolymers, with statistical copolymers of ethylene-propylene having an ethylene content of 1 to 10% by weight, preferably 2 or more, being preferred. 5 to 8% by weight, or statistical copolymers of propylene and butylene-1 with a butylene content of 2 to 25% by weight, preferably 4 to 20% by weight, based on the total weight of the copolymer , or statistical terpolirneros of et? leno-? rop? leno-but? leno-1 with an ethylene content of 1 to 10% by weight, preferably 2 to 6% by weight, and a content of butylene -1 from 2 to 20% by weight, preferably from 4 up to 20% in peeo, referred respectively to the total weight of the terpolymer, or a blend of an ethylene-propylene-butylene-1 terpolymer and a copolymer of? ro-leno-butylene-1 with a content in ethylene of 0.1 to 7% by weight, a propylene content of 50 to 90% by weight and a content of butylene-1 of 10 to 40% by weight, based on the total weight of the polymer blend respectively.

The copolymers and terpolymers described above generally have a melt flow rate of 1.5 to 30 g / 10 nm. , preferably from 3 to 15 g / 10 rnin. The blend of copolymers and terpolymers described above generally has a melt flow rate of 5 to 9 g / 10 min. All indicated flow rates are measured at 230 ° C with a force of 21.6 N (DIN 53 735). Of the polyolefins described above, sealable propylene polymers containing at least 70% by weight, preferably 75-98% by weight, of propylene relative to the polymer are preferred. The preferred comonomers are ethylene and butylene. Optionally, all the polymers of the above-described topcoat can be degraded with peroxide in the same way as described above for the basecoat, using in principle the same peroxides. The degradation factor for the topcoat polymers generally varies from one to the other. up to 15, preferably from 6 to 10. In a preferred embodiment, the finishing layer contains stabilizers and neutralizers as well as, optionally, antiadhesives in an effective amount. The multilayer sheet of the present invention comprises the base and intermediate layers described above and a finishing layer as well as, optionally, other layers. The execution forms are preferred in four layers, with a finishing layer on both sides equal or different in thickness and composition.

Also, execution forms are also preferred in five layers, with intermediate layers applied on both sides of a base layer and finishing layer on both sides. These sheets can have sirne + pca structure, that is, with the same intermediate and finishing layers on both sides. In addition, it may be the case that both intermediate or finishing layers are different. Six- and seven-layer sheets are also very useful, with additional intermediate layers on one or both sides of the base. The six-layer ho is an asymmetric structure, while the symmetric structure is favorable for the seven-layer structure. The total thickness of the multi-layered polyolefin of the present invention can vary within wide ranges and depends on the proposed use. Preferably it is from 3 to 150 μm, especially from 5 to 120 μm, and from 30 to 90% of the total thickness of the sheet corresponds to the base layer. The thickness of the sealable top coat, essential in the present invention, is less than 0.4 μm and preferably less than 0.3 μm, especially between 0.05 and 0.2 μm. It has been shown that the good influence of the intermediate layer on the sealing properties is more effective the thinner the applied finishing layer is. With finishing layers of less than 0.4 crm thickness, the sheet has almost the same behavior during the transformation as without this finishing layer. Surprisingly, the thin layer with higher sealing temperature is sufficient to effectively prevent the sheet from sticking to itself, with the rollers or other hot parts of the machine during manufacture. If the thickness of the finishing layer is greater than 0.4 μm, there are also no problems of stickiness of the sheet, but the initial sealing temperature increases, so that the sealing behavior of the intermediate layer is no longer determinative. According to the present invention, the initial sealing temperature of the polyolefin of the finishing layer is greater than the initial sealing temperature of the polyolefin of the intermediate layer. Preferably, the initial sealing temperatures of the polymers differ by more than 15 ° C as a minimum, especially by 20-50 ° C, especially by 25-35 ° C. The initial sealing temperature of a polymer, according to the present invention, is that which is measured with a comparative yarn carrying on both sides a finish layer of 0.7 μm thickness of the polymer to be tested. The base layer and the manufacturing process of this comparative sheet correspond analogously to the embodiment according to the present invention, with intermediate layer and finishing layer formed by both sealable polymers. The optional topcoat on the opposite face may be sealable or non-sealable polyolefins. The most suitable polyolefins are those already described for the base layer. Sealable polymers already described for the intermediate and finishing layers are also very suitable. The thickness of this other finishing layer is usually from 0.1 to 5 μm, preferably from 0.5 to 2 μm. The thickness of the essential intermediate layer in the present invention is usually 0.2 to 10 μm, preferably 0.5 to 5 μm, especially 1 to 2 μm. As already indicated for the corresponding layers, the multilayer sheet of the present invention can carry neutralizing, stabilizing, lubricating, non-sticking, hydrocarbon and / or antistatic resins in one or more layers. The following weight percentage data is referred to the weight of the layer containing the additive. The neutralizers are preferably dihydrotalcite, calcium stearate and / or calcium carbonate, with an average particle size of maximum 0.7 μm, an absolute particle size of less than 10 μ and a specific surface area of at least 40 m / g. The neutralizer is usually added in an amount of 0.02 to 0.1% by weight. As stabilizers, the typical compounds are used for the polymers of ethylene, propylene and other α-olefins. Its dosage ranges from 0, 05 and 2% by weight, phenolic stabilizers, alkaline or alkaline earth stearates and / or alkali metal or alkaline earth metal carbonates are very suitable. Phenolic stabilizers are preferred in an amount from 0.1 to 0.6% by weight, especially from 0.15 to 0.3% by weight, and with a molecular weight greater than 500 g / mmol. Pentaentpil-tetrakis-3- (3,5-d-tert-butyl-4-hydroxyphenyl) -propionate or l, 3,5, -tr? Rnet? L-2, 4, 6- tr? s (3, 5-d? -tert-but? l-4-hydroxybenzyl) benzene are very useful. The lubricants are amidae of higher aliphatic acids, esters of higher aliphatic acids, waxes and metal soaps, as well as polydirnethylsiloxanes. The effective dosage of lubricant is 0.1 to 3% by weight. The addition of 0.15 to 0.25% by weight of aliphatic acid amides higher than the base layer and / or the topcoats is very suitable. An especially appropriate aliphatic amide is erucilarnide. Suitable antiadherents are inorganic additives such as silicon dioxide, calcium carbonate, magnesium silicate, aluminic silicate, calcium phosphate and the like and / or organic polymers incompatible with polyamides, polyesters, polycarbonates and the like. Preferred are benzoguan polymers, aldehyde, silicon dioxide and calcium carbonate. The effective amount of anti-adherent is 0.1 to 2% by weight, preferably 0.1 to 0.5% by weight. The average particle size ee is from 1 to 6 μm, especially from 2 to 5 μm, the particles having a spherical shape, as described in EP-A-0 236 945 and DE-A-38 01 535, especially suitable. The hydrocarbon resins are low molecular weight polymers, whose average molecular weight M-w is usually in the range between 300 and 8,000, preferably between 400 and 5,000, especially between 500 and 2,000. Thus, the average molecular weight fw of the resins is clearly lower than that of the propylene polymers, which constitute the main part of each layer of the sheet and whose average molecular weight Mw is usually greater than 1000,000. The hydrocarbon resins are added with reference to the base layer and / or the intermediate layer (s) (e). The effective amount of low molecular weight resin is from 1 to 20% by weight, preferably from 2 to 10% by weight, based on the layer. As a low molecular weight ream, a natural or synthetic resin with a softening point of 60 to 180 ° C, preferably 80 to 150 ° C, measured according to ASTM E-28 is recommended. Among the numerous resins of ba or molecular weight are preferred hydrocarbon resins, especially those of petroleum (petroleum ream), styrene, cyclopentadiene and terpene (these reams are described in the Ullrnann encyclopedia of industrial chemistry, 4 edition, volume 12 , pages 525 to 555). Suitable petroleum resins are described in numerous works, such as for example in EP-A-0 180 087, which is expressly referred to herein. The preferred unsightly ones are alkaline alkanesulfonates; polydiorganosiloxanes modified with polyether, ie ethoxylated and / or propoxylated (polydialkylsiloxanes, polyalkylphelsiloxanes and the like and / or the tertiary amines, basically linear and saturated aliphatics, with an aliphatic radical of 10 to 20 carbon atoms, substituted with wh? drox groups? - (C? -C < i) -alqu? Lo, N, Nb? S- (2-h? Drox? Et? I) -alk? With 10 to 20 atoms of being particularly suitable. "> carbon, preferably 12 to 18 carbon atoms, in the alkyl radical. The effective amount of unsightly is from 0.05 to 3% by weight. The preferred antistatic is, above all, glycerin monostearate. Furthermore, the present invention relates to a process for manufacturing the multilayer sheet of the present invention by the already known process of coextrusion. In the coextrusion process of this process, the polymer or polymer mixture of each layer is usually compressed by fluidizing in an extrudate, whereby any additives may already be contained in the polymer or polymer mixture, or are added by the masterbatch technique. Then, the molten products corresponding to each layer of the sheet are simultaneously co-extruded through a flat nozzle (wide-slot die), and the extruded sheet is stretched by means of one or more rolls, cooling and solidifying. Then, the sheet thus obtained is usually tensioned longitudinally and transverse to the advance of the extrusion, which produces the orientation of the molecular chains. The longitudinal tension is preferably from 4: 1 to 7: 1 and in the transverse direction from 7: 1 to 11.1. For convenience, the longitudinal tensioning is carried out by means of two rollers of different speed, adapted to the desired stretching ratio and the transversal tensioning with a gripper frame. The biaxial tension of the leaf is followed by its soil (heat treatment), by which the leaf is maintained at a temperature of 100 to 160 ° C for 0.5 to 10 s. The sheet is then rolled up in the usual way by means of the corresponding device. It has been found that it is very advantageous to maintain at a temperature of 20 to 90 ° C the drag rollers or rollers through which the extruded sheet is cooled and solidified. The longitudinal and transversal tensioning temperatures may vary. In general, preferably, the longitudinal tensioning is carried out from 100 to 150 ° C and the transversal tension from 155 to 190 ° C. Eventually, after the biaxial tensioning, one or both faces of the ho can be treated according to one of the known methods, by corona or flamed, as said above. For the corona treatment, we proceed for convenience by passing the ho between two conductive elements that serve as electrodes and applying between them such a high voltage, almost always alternating (from 10 to 20 KV and 20 to 40 KHz), so that can be produced crown deepens. By corona discharge, the air that surrounds the surface of the sheet ionizes and reacts with the molecules of said surface, forming polar inclusions in the polypnepca matrix fundamentally apolar. For the treatment of flaming with polarized flame (see US-A-4,622, 237) a continuous electrical voltage is applied between a burner (negative pole) and a cooling roller. The applied voltage level is from 500 to 3,000 V, preferably from 1,500 to 2,000 V. With the applied voltage, the ionized atoms accelerate more and collide with greater kinetic energy against the surface of the polymer. The chemical bonds of the polymer molecule are broken more easily and radicals are formed quickly. In this case, the thermal overload of the polymer is much lower than in the current flaming treatment and sheets whose sealing properties are better even than those of the untreated sheets can be obtained. The present invention is now explained in more detail by demonstrative examples.

EXAMPLE 1 By co-extrusion and subsequent gradual orientation in the longitudinal and transverse directions, a five-layer sheet with a total thickness of 40 μm and a DZBZD structure was manufactured. Before rolling it, the sheet was subjected to a unilateral crown treatment by the face of the roller. The face of the roller is the side of the wheel that rests on the first drive roller. The surface tension of this side by effect of said treatment was 39 to 40 mN / rn. All layers contained a 0, 13% by weight of pentaeptpt? L-tetrak? S-4- (3,5-d? -terc-but? L-4-hydrox? Phen?) -propionate (Irganox 1010) as a stabilizer and , 06% by weight of calcium stearate as neutralizer. The base layer B was essentially composed of a polypropylene homopolymer with a n-heptane-soluble fraction of 4% by weight and a melting range of 160 to 162 ° C. The flow rate of the polypropylene material was 3.4 g / 10 min. at 230 ° C and 21.6 N load (DIN 53 735). The base layer contained 0.12% by weight of erucilanide with a melting range of 78 to 82 ° C and 0.12% by weight of N, N-b? S-ethox? Alkyl? Nane CArmostat 300). The polyolefin finish layers D were basically formed by an ethylene-propylene-butene-1 terpolymer having a content of 3.5% by weight of ethylene, 88.5% by weight of propylene and 8% by weight of butene-1. . The minimum sealing temperature of this polymer is 106 ° C. The topcoats contained 0.33% by weight of a ceramic spherical particle release with an average diameter of 2 μm. The thickness of the finishing layers was 0.1 μr. The intermediate layers Z were basically formed by a propylene-butene-1 statistical copolymer (RTafmer XR 110T) with a content of 74.3 mol% of propylene and 25.7 mol% of butene-1 with respect to the copolymer, a melting point of 110, 6 ° C and a reclosing temperature of 60 ° C. The minimum sealing temperature of the copolymer is 75 ° C. The thickness of the intermediate layers was 1.5μm.

The properties of the sheets according to the examples and the comparative examples are summarized in the following table with this key: Sheet stickiness during manufacture +: Sheet is not stuck -: Leaf tends to stick Sheet sealing behavior during + transformation: The sheet behaves like the low temperature sealing according to current technology. -: The sheet tends to stick. Behavior of sealing the sheet during the transformation +: The sheet behaves like those of sealing at low temperature according to the current technology. -: Sealing behavior is insufficient. In order to determine the minimum sealing temperature indicated above for the polymers of the intermediate and finishing layers, the following comparative sheets were made: EXAMPLE the By co-extrusion and subsequent gradual orientation in longitudinal and transverse direction, a three-layer sheet with a total thickness of 40 μm, and a DBD structure was manufactured. Before rolling it, the sheet was subjected to a unilateral crown treatment by the face of the roller. The face of the roller is the side of the blade that rests on the first drive roller. The surface tension of this side by effect of said treatment was 39 to 40 rnN / rn. all layers contained 0.13% by weight of pentaeptpt? l-tetrak? s-4- (3,5-d? -tert-but? l-4-hydrox? phen?) -prop-onate (R Irganox 1010) as stabilizer and 0.06% by weight of calcium stearate as neutralizer. The base layer B consisted essentially of a polypropylene homopolymer with a n-heptane-soluble fraction of 4% by weight and a melting range of 160 to 162 ° C. The melt index of the polypropylene homopolymer was 3.4 g / 10 mm. at 230 ° C and 21.6 N load (DIN 53 735). The base layer contained 0.12% by weight of erucilarnide with a melting range of 78 to 82 ° C and 0.12% by weight of N, N-b? S-ethox? Alkamma (RArmostat 300). The polyolefin finishing layers D were basically formed by an ethylene-propylene-butene-1 terpolymer having a content of 3.5% by weight of ethylene, 88.5% by weight of propylene and 8% by weight of butene- 1. The topcoats contained 0.33% by weight of a ceramic spherical particle release with an average diameter of 2 μ. The thickness of the finishing layers was 0.7 μm. The sheet has an initial sealing temperature, D against D, of 106 ° C, which according to the present invention is considered as the minimum sealing temperature of the terpolymer.

EXAMPLE Ib By co-extrusion and subsequent gradual orientation in the longitudinal and transverse direction, a three-layer sheet with an esp > total thickness of 40 μm and a DBD structure. Before rolling it, the sheet was subjected to a unilateral crown treatment by the face of the roller. The face of the roller is the side of the blade that rests on the first drive roller. The surface tension of this side by effect of said treatment was 39 to 40 rnN / rn. All the layers contained 0.13% by weight of pentaerythritil-tetrakis-4- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate (Rgroups 1010) as a stabilizer and 0.06% by weight of stearate Calcium as a neutralizer. Bae B layer essentially comprised a polypropylene homopolymer with a 4 wt% h-heptane soluble fraction and a melting range of 160 to 162 ° C. The melt index of the polypropylene homopolymer was 3.4 g / 10 min. at 230 ° C and 21.6 N load (DIN 53 735). The base layer contained 0.12 wt.% Of erucila ida with a melting range of 78 to 82 ° C and 0.12 wt.% N, N-bis-ethoxyalkylamino (RArmostat 300). The polyolefin topcoats D were basically formed by a statistical copolymer of β-butane-butene-1 (RTafrner XR 1105) with a con um of 45.3% molar of propylene and 25.7% molar of butene-1 with respect to the copolymer, a melting point of 100.6 ° C and a reclosing temperature of 60 ° C. The topcoats contained 0.33% by weight of a ceramic spherical particle release with an average diameter of 2 μm. The thickness of the finishing layers was 0.7 μr. The sheet has an initial sealing temperature, D against D, of 75 ° C, which according to the present invention is considered as the minimum sealing temperature of the terpolymer.

EXAMPLE 2 Compared to Example 1, the base layer additionally contains 5% by weight of calcium carbonate with an average particle size of 1.5 μ and approximately 5% by weight of rutile-type titanium dioxide. The sheet is white / opaque.

EXAMPLE 3 Compared to Example 2, the ho a has on both faces of the base layer other intermediate layers Ul. It is now a seven-layer symmetric sheet with a total thickness of 40 μm and a structure DZUBUZD. For the additional intermediate layers the same polymer was used as in layer B but with an MFI slightly higher than 4.5 g / 10 nm. The thickness of the intermediate layer Ul is 4 μm. The sheet is white / opaque and has a shiny appearance.

COMPARATIVE EXAMPLE 1 In comparison with example i, the thickness of the finishing layer is now 0.5 μm. The behavior of the blade during the transformation is bad.

COMPARATIVE EXAMPLE 2 Compared to Example 1, the finishing layer is now missing. The sheet tends to stick during manufacturing.

COMPARATIVE EXAMPLE 3 Compared to Example 1, the minimum sealing temperature of the finishing layer is now 90 ° C. The sheet tends to stick during manufacturing. To characterize the raw materials and the sheets, the following measurement methods were used: flow rate The flow rate was measured according to DIN 53 735 with 21.6N load and 230 ° C.

Melting point Measurement by DSC, maximum melting curve, heating speed 20 ° C / mm. Determination of the Initial Sealing Temperature of the Polymers To determine the initial sealing temperature of the intermediate and finishing layer polymers, sheets are manufactured analogously to the examples of the present invention p > But only with three layers. The finishing layers are basically formed by the polymer to be tested, that is, once by the polymer of the intermediate layers of the example of the present invention and once by the polymer of the finishing layer of the example of the present invention. The finishing layers have a thickness of about 0.7 μm respectively. The initial sealing temperature of these comparative sheets is considered as the initial polymer sealing temperature. Determination of the minimum sealing temperature (initial sealing temperature) of the sheets. Hot-sealed samples (20 mm x 100 mm seam) are prepared with the HSG / ET sealing device from Brugger, sealed with a sheet at different temperatures with hot jaws at a pressure of 10 N / cm2 for 0.5 s . Test strips are cut out from the sealed panels and are 1/3-inch wide. The resistance T of the seam of the seal, ie the force necessary to detach the strips, is measured by means of a tensile testing machine with a pulling speed of 200 rnrn / min, so that the plane of the seam forms a right angle. with the direction of drag. The minimum sealing temperature is that at which a seam strength of at least 0.5 N / 15 m is reached.

RESISTANCE OF LR COSTURO To make the measurement, two strips of 15 mm width were placed one above the other and sealed at 130 ° C for 0.5 s, with a pressure of 1.5 N / cm2 (Brugger device by NDS with a sealing jaw heated by a only side). The strength of the seam was determined by the T-Peel method (plucked vertically).

FRICTION The friction was determined according to DIN 53 375. The slip friction index was measured after 14 days of production.

SURFACE TENSION The surface tension was determined by the so-called dyeing method (DIN 53 364, moistening with colored liquids of different euphemial tensions).

RUGOSITY The roughness was measured according to DIN 476B at a limit wavelength of 0.25 mrn.

TURBIDITY Leaf Turbidity was measured according to ASTM-D 1003-52. The measurement of Turbidity according to Hólz was made based on ASTM-D 1003-52, but in order to take advantage of the optimum scope of the measurement, it was made with four superposed sheets, using a linear diaphragm of Io instead of a perforated diaphragm of 4o. BRIGHTNESS The brightness was determined according to DIN 67 530, by measuring the reflection value with optical magnitude of the surface of the sheet. Based on the standards ASTM-D 523-78 and ISO 2813, the graduated angle was adjusted on the flat surface of the sample, which reflects or scatters it. The rays of light that reach the photoelectronic receiver are marked as proportional electrical magnitude. The measured value is dimensional and must be indicated with the angle of incidence.

Disc B: Example VB: Comparative example

Claims (15)

NOVELTY OF THE INVENTION CLAIMS

1. - Multilayer polyolefin sheet formed by at least BZD layers, of which B is a base layer of polyolef, Z an intermediate layer and D a topcoat layer applied to the previous layer; further characterized in that the intermediate layer contains at least 75% by weight, relative to the same layer, of sealable polyolefins and the finishing layer D contains at least 75% by weight, relative to the same layer D, of sealable polyolefins; so that the minimum sealing temperature of the polyolefm of the finishing layer D is at least 100 ° C and is greater than the minimum sealing temperature of the polyolefm of the intermediate layer Z, and the thickness of the layer of finishing D ee less than 0.4 μm, 2.- Multilayer sheet according to claim 1, further characterized in that the polyolefin of the finishing layer has a minimum sealing temperature of 102 to 150 ° C and a flow index from 3 to 15 g / 10 rnin. 3. Sheet multiplied according to any of claims 1 and / or 2, further characterized in that the polyolefin of the topcoat is a copolymer of ethylene and propylene or ethylene and butylene or propylene and butylene or a terpolymers of ethylene and propylene and butylene or a mixture or a blend of two or more of said copolymers and terpolymers. 4. Multilayer sheet according to claim 3, further characterized in that the thickness of the finishing layer is less than 0.3 μm, preferably less than 0.2 μrn. 5. Multilayer sheet according to claim 4, further characterized in that the polyolefin of the intermediate layer has a minimum sealing temperature of less than 90 ° C, preferably lower than 90 ° C, and a flow index of 3 to 15 g / 10 min. 6. Multilayer sheet according to claim 5, further characterized in that the polyolefin of the intermediate layer is a copolymer of ethylene and propylene or ethylene and butylene-propylene and butylene-1 or a terpolimer of ethylene and propylene and "leno-1" or a mixture or a blend of two or more of said copolymers and terpolymers. 7. Multilayer sheet according to claim 6, further characterized in that the thickness of the intermediate layer is 0.2 to 10 μm, preferably 0.5 to 2 μin. 8. Sheet according to claim 7, further characterized in that the finishing layer has been subjected to corona treatment or flaming. 9. Multilayer sheet according to claim 8, further characterized in that the base layer has another finishing layer on the opposite side. 10. Multilayer sheet according to claim 9, further characterized in that the finishing layer on the opposite side is basically formed by a sealable or non-sealable polyolefin. 11. Multilayer sheet according to any of claims 9 and 10, further characterized in that the sheet presents another additional intermediate layer. 1

2. Process for manufacturing a minimum three-layer sealable polyolefimca sheet comprising a base layer, an intermediate layer and a topcoat layer applied to the intermediate layer, by which the polymers or the polymer mixture of each layer compressed and fluidized in an extruder, the melted products corresponding to each layer of the ho are simultaneously coextruded through a flat nozzle (wide slot nozzle), the extruded multilayer sheet is stretched and cooled with one or more rollers, solidifying , and the sheet thus obtained is oriented; Characterized because the minimum sealing temperature of the polyolefin of the finishing layer is at least 100 ° C and higher than the temperature of my polyolefin sealing debris of the intermediate layer and the thickness of the finishing layer is less than 0.4 μ. 1

3. Method according to claim 12, further characterized in that the ho is oriented biaxially, tensioned in the longitudinal direction with a ratio of 4: 1 to 7: 1 and in a transverse direction with a ratio of 7: 1 to 11. :1. Method according to any of claims 12 and / or 13, further characterized in that the longitudinal tensioning is carried out at a temperature of 100 to 150 ° C and the cross-tensioning at a temperature of 155 to 190 ° C. 15. Use of sheet p > as packaging material, in accordance with claim 11.