RU2378169C2 - Transparent polypropylene containers for shoe packing - Google Patents

Abstract

FIELD: packing industry. ^ SUBSTANCE: present invention is related to containers intended for packaging and storage of clothes, sports items, toys or items for do-it-yourselfer, preferably, shoes. Transparent polypropylene container is manufactured from heterophase copolymer of propylene including 50-98 wt % of crystalline homopolymer of propylene or crystalline static copolymer of propylene with ethylene and/or C4-C10-1-alkenes, containing 0.5-15 wt % of ethylene and/or C4-C10-1-alkene; or 2-50 wt % (i) of elastomer copolymer of ethylene with one or higher number of C4-C10-1-alkenes (coplymer (a)), containing 60-85 wt % of ethylene, or (ii) mixture of copolymer (a) with copolymer of propylene, containing 15-40 % of ethylene (copolymer (b)). Weight ratio (a)/(b) preferably makes from 1/4 to 4/1. Copolymer has cloud factor equal to ëñ 40%, module of elasticity in stretching equal to ëÑ 700 MPa, Charpy impact strength with cut at 0 C equal to ëÑ 3 kJ/m2, whitening value in stressing that equals 0-8 mm. Transparent polypropylene container has thickness of walls of at least 0.8 mm. ^ EFFECT: suggested transparent polypropylene containers have proper mechanical characteristics, which make it possible to handle packaging easily, are efficient in manufacturing. ^ 6 cl, 1 dwg

Description

The present invention relates to the use of containers made of transparent polypropylene for packaging or storage of products such as clothing, sports products, toys and products for the home craftsman, and in particular shoes, more specifically, transparent polypropylene containers suitable for packaging shoes as well as systems including containers made of a transparent polymer that are suitable for packaging or storing products such as clothing, sports products or toys.

Two-component cardboard boxes consisting of a box and a lid are often used for packaging products, such as clothing, sports products or toys, and especially for packaging shoes. The disadvantage of this type of packaging is often its poor mechanical strength, especially when many such cardboard boxes are stacked on top of each other, which is common in many shoe stores. In addition, the packaging, and in particular the lid, is often damaged when the lower boxes are pulled out of the stack of cardboard boxes, since the box is usually pulled by the lid.

Another disadvantage of cardboard packaging is that the contents of the cardboard box are not visible. This means that it is either necessary to remove the goods from the cardboard box in order to display them in the store, or customers or store personnel can only get information about the contents on the inscriptions on the outside of the cardboard box. This is also a drawback in cases where the shoes need to be often removed from the cardboard box and then put back in, since the shoes that are incorrectly laid are not easy to find, and if errors are found, restoring the original order is a difficult task.

Another drawback of such carton packaging is the limited reusability. Thus, this package is essentially a one-time package that must be thrown away either by the buyer or seller of the goods, which is associated with significant costs.

Reusable packaging made of plastic, in particular for shoes, is known, for example, from European patent application EP-A659649. The described containers have a folding frame and side sections made of flexible material that can be folded.

Shoe boxes made of transparent or translucent plastic are described in international application WO 86/07576. However, no plastic has been disclosed which is particularly suitable for the manufacture of such boxes.

Polypropylene belongs to the class of plastics, which are very suitable for use in packaging. They usually have excellent mechanical properties, such as satisfactory hardness, rigidity and dimensional stability. In addition, they are attractive from an economic point of view. However, strength, especially at low temperatures, whitening under the influence of stress, deformation and, in particular, transparency, often leave much to be desired.

The present invention is to overcome the above disadvantages of the prior art and to obtain containers that are suitable for packaging products, such as clothing, sports products or toys, and have good mechanical characteristics that allow easy handling of the packaging, and which can be economically manufactured, and which are characterized by slight deformation.

We found that this problem is easily solved by using containers made of transparent polypropylene for packaging or storage of products such as clothing, sports products, toys or products for the home craftsman, and these containers have a wall thickness of at least 0.8 mm, and the transparent polypropylene is a propylene homopolymer or propylene copolymer, which has a cloud point of ≤40% based on the thickness of the polypropylene equal to 1 mm, and measured using test sam ples manufactured by injection molding, and has a tensile modulus integral ≥700 MPa and a Charpy impact strength with notch at 0 ° C, part of ≥3 kJ / m ^2.

In addition, we found containers made of transparent polypropylene that are suitable for use as packaging, as well as systems including containers made of transparent polymer that are suitable for packaging or storing products such as clothing, sports products, toys or products for the home master.

In accordance with the present invention, transparent polypropylene is used to make containers. In the present invention, the term polypropylene means a polymer derived from monomers comprising at least 50% by weight of propylene. Possible comonomers are, in particular, α-olefins, i.e. hydrocarbons containing terminal double bonds. Preferred α-olefins are linear or branched C ₂ -C ₂₀ -1-alkenes that are not propylene, preferably linear C ₂ -C ₁₀ -1-alkenes or branched C ₂ -C ₁₀ -1-alkenes, such as 4- methyl 1-pentene, conjugated and non-conjugated dienes, such as 1,3-butadiene, 1,4-hexadiene or 1,7-octadiene, or vinyl aromatic compounds, such as styrene or substituted styrene. Other suitable olefins are those in which the double bond is part of a cyclic structure, which may include one or more ring systems. Examples are cyclopentene, norbornene, tetracyclododecene and methylnorbornene and dienes such as 5-ethylidene-2-norbornene, norbornadiene and ethylnorbornadiene. Mixtures of two or more olefins can also be copolymerized with propylene. Particularly preferred olefins are ethylene and linear C ₄ -C ₁₀ -1-alkenes, such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene and preferably ethylene and / or 1 -butene.

The transparent polypropylene used in the manufacture of containers in accordance with the present invention has a haze value based on a polypropylene thickness of 1 mm and measured using injection molded test pieces in accordance with ASTM D 1003 of ≤40% , preferably ≤25%, more preferably ≤15%, and particularly preferably ≤12%. The cloud point is a measure of the opacity of the material and, thus, a parameter that characterizes the transparency of the material. The lower the haze value, the higher the transparency.

Transparent polypropylene also has a favorable combination of stiffness and strength. For polypropylene, the tensile modulus is ≥700 MPa, and preferably ≥800 MPa when measured in accordance with ISO 527-2: 1993. To determine the tensile modulus of elasticity, preference is given to a type 1 test piece obtained by injection molding having a total length of 150 mm and a constant cross section of 80 mm, with a melting point of 250 ° C and a surface temperature of 30 ° C. To ensure additional crystallization, the test sample is then stored for 7 days under standard conditions: 23 ° C / atmospheric humidity 50%. When determining the modulus, the strain rate should be 1 mm / min. The strength of transparent polypropylene, defined as notched Charpy impact strength at 0 ° C., is ≥3 kJ / m ² , preferably ≥4 kJ / m ^2, and particularly preferably ≥6 kJ / m ² . Charpy notched impact strength measured in accordance with standard

ISO 179-2 / 1 eU.

Transparent polypropylene also has good whitening characteristics when exposed to stress. For the objectives of the present invention, whitening under the influence of stress is the appearance of a white color in the exposed area when the polymer is subjected to mechanical stress. It is generally believed that whitening is caused by small voids formed in the polymer under the action of mechanical stress. Good whitening characteristics upon exposure to stress mean that, under the influence of mechanical stress, white-colored areas are not formed or very small such areas are formed.

One technique for quantifying whitening under stress is to expose certain test samples to a given shock stress and then measure the size of the resulting white spots. For this, a domed indenter technique is used in which a falling pointed load is allowed to fall onto a specimen in a device for determining impact strength using a falling pointed load in accordance with DIN 53443 part 1. In this invention, a falling pointed load weighing 250 g and a height of with which the load falls, is equal to 50 cm. As test samples, round discs obtained with injection molding having a diameter of 60 mm and a thickness of 2 mm are used, and each test sample is subjected only to about a single shock test. The whitening under the influence of stress is represented as the diameter of the whitening section expressed in millimeters under the influence of stress and the average value is calculated, in each case calculated for 5 test samples, and the values for each sample are determined on the side of the circular disk opposite to the side affected by the shock, as the average value of the measurement results in the direction of injection molding and in the perpendicular direction.

Transparent polypropylene detects the absence or very slight whitening when exposed to voltage at 23 ° C, determined by the dome-shaped indenter method. In the case of preferred transparent polypropylenes, the domed indenter method at 23 ° C. results in a value of 0 to 8 mm, preferably 0 to 5 mm, and most preferably 0 to 2.5 mm.

Suitable transparent polypropylene are propylene homopolymers or, preferably, propylene copolymers obtained using catalyst systems based on metallocene compounds.

Heterophasic propylene copolymers, also known as multiphase propylene copolymers or propylene block copolymers, may also be suitable transparent polypropylenes. Such compositions typically contain layered phases in which a polyolefin having relatively low stiffness is typically dispersed in a matrix of a propylene polymer having greater stiffness.

Heterophasic propylene copolymers suitable for use as transparent polypropylenes are, for example, those which include a copolymer of ethylene with 1-butene as a soft phase.

Particularly suitable heterophasic propylene copolymers are copolymers comprising a propylene polymer A forming a matrix and a propylene polymer B dispersed therein, the heterophasic propylene copolymers being prepared using catalyst systems based on metallocene compounds.

The propylene polymer A may be a propylene homopolymer or copolymer containing up to 15 wt.%, And preferably up to 10 wt.%, Of non-propylene olefins, and preferred propylene copolymers contain from 1.5 to 7 wt.%, Preferably from 2 5 to 5 wt.%, Non-propylene olefins. As a comonomer, preference is given to using ethylene or linear C ₄ -C ₁₀ -1-alkenes and mixtures thereof, preferably ethylene and / or 1-butene.

Propylene B copolymers typically contain 5 to 40% by weight of non-propylene olefins. As component B, it is also possible to use two or more different propylene copolymers, which can vary both in the content of comonomers and in the type of olefin (s), which is not propylene. Preferred comonomers are ethylene and linear C ₄ -C ₁₀ -1-alkenes and mixtures thereof, preferably ethylene and / or 1-butene. In another preferred embodiment, monomers containing at least two double bonds, for example 1,7-octadiene or 1,9-decadiene, are additionally used. The content of non-propylene olefins in propylene copolymers is usually from 7 to 25 wt.%, Preferably from 10 to 20 wt.%, Particularly preferably from 12 to 18 wt.% And most preferably from 14 wt.% To 17 wt.% Based on propylene copolymer B.

The mass ratio of the amount of propylene polymer A to the number of propylene copolymers B can vary. Preferably, it is from 90:10 to 60:40, more preferably from 80:20 to 60:40, and particularly preferably from 70:30 to 60:40, wherein propylene copolymers B can be all propylene copolymers constituting component B.

Preferably, such a transparent polypropylene has a narrow molar mass distribution M _w / M _n . For the purposes of the present invention, the molar mass distribution M _w / M _n is the ratio of the weight average molar mass M _w to the number average molar mass M _n . Preferably, the molar mass distribution M _w / M _n is in the range from 1.5 to 3.5, more preferably in the range from 1.8 to 2.5, and particularly preferably in the range from 2 to 2.3.

Preferably, if the average molar mass M _{n of} such a preferred transparent polypropylene is in the range from 20,000 g / mol to 500,000 g / mol, more preferably in the range from 50,000 g / mol to 200,000 g / mol, and particularly preferably in the range from 80,000 g / mol to 150,000 g / mol.

To obtain such preferred transparent polypropylenes, preference is given to the use of catalytic systems based on metallocene compounds of transition metals of groups 3, 4, 5 or 6 of the periodic system of elements.

Particular preference is given to catalyst systems based on metallocene compounds having the formula (I),

wherein

M means zirconium, hafnium or titanium, preferably zirconium,

X are the same or different and independently from each other mean hydrogen, halogen or a group -R, -OR, -OSO ₂ CF ₃ , -OCOR, -SR, -NR ₂ or -PR ₂ , where R means a linear or branched C ₁ -C ₂₀ -alkyl, C ₃ -C ₂₀ -alkaloalkyl, which may contain one or more C ₁ -C ₁₀ -alkyl radicals, C ₆ -C ₂₀ -aryl, C ₇ -C ₂₀ -alkylaryl or C C ₇ -C ₂₀ arylalkyl and may contain one or more heteroatoms, which are atoms of groups 13-17 of the periodic Table of the elements or one or more unsaturated linkages and pref titelno means C ₁ -C ₁₀ -alkyl such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl or n-octyl or C ₃ -C ₂₀ -pialoalkyl, such as cyclopentyl or cyclohexyl, where X radicals can also be linked to each other and preferably form a C ₄ -C ₄₀ dienyl ligand, more preferably a 1,3-dienyl ligand or a group -OR'O- wherein R ′ is a divalent group selected from the group consisting of C ₁ -C ₄₀ alkylidene, C ₆ -C ₄₀ arylidene, C ₇ -C ₄₀ alkylarylidene and C ₇ -C ₄₀ arylalk ylidene, where X preferably represents a halogen atom or a group —R or —OR or the two radicals X form a group —OR′O—, and it is particularly preferred that X represents chlorine or methyl,

L is a divalent bridging group selected from the group consisting of C ₁ -C ₂₀ alkylidene, C ₃ -C ₂₀ cycloalkylidene, C ₆ -C ₂₀ arylidene, C ₇ -C ₂₀ alkylarylidene and C ₇ -C ₂₀ arylalkylidene radicals that may contain heteroatoms that are atoms of groups 13-17 of the periodic system of elements, or means a silylidene group containing up to 5 silicon atoms, for example, -SiMe ₂ - or -SiPh ₂ -, where L preferably means a radical selected from the group including -SiMe ₂ -, -SiPh ₂ -, -SiPhMe-, -SiMe (SiMe ₃ ) -, -CH ₂ -, - (СН ₂ ) ₂ -, - (CH ₂ ) ₃ - and -С (СН ₃ ) ₂ ,

R ¹ means a linear or branched C ₁ -C ₂₀ -alkyl, C ₃ -C ₂₀ -cyaloalkyl, which may contain one or more C ₁ -C ₁₀ -alkyl radicals, C ₆ -C ₂₀ -aryl, C ₇ -C ₂₀ -alkylaryl or C ₇ -C ₂₀ -arylalkyl and may contain one or more heteroatoms that are atoms of groups 13-17 of the periodic system of elements, or one or more unsaturated bonds, where R ¹ preferably means unbranched in α- position and preferably means a linear or branched C ₁ -C ₁₀ -alkyl group, which is unbranched at the α-position, preferably a linear C ₁ -C ₄ alkyl group such as methyl, ethyl, n-propyl or n-butyl,

R ² means a group of the formula -C (R ³ ) ₂ R ⁴ in which

R ³ are the same or different and independently from each other mean linear or branched C ₁ -C ₂₀ -alkyl, C ₃ -C ₂₀ -cycloalkyl, which may contain one or more C ₁ -C ₁₀ -alkyl radicals as substituents, C ₆ -C ₂₀ aryl, C ₇ -C ₂₀ alkylaryl or C ₇ -C ₂₀ arylalkyl and may contain one or more heteroatoms that are atoms of groups 13-17 of the periodic system of elements, or one or more unsaturated bonds, or two radicals R ³ may be bonded to form a saturated or unsaturated on ring C ₃ -C _20, preferably wherein R ³ is a linear or branched C ₁ -C ₁₀ alkyl group and

R ⁴ means hydrogen or a linear or branched C ₁ -C ₂₀ alkyl, C ₃ -C ₂₀ -alkaloalkyl, which may contain one or more C ₁ -C ₁₀ -alkyl radicals, C ₆ -C ₂₀ -aryl as substituents , C ₇ -C ₂₀ -alkylaryl or C ₇ -C ₂₀ -arylalkyl and may contain one or more heteroatoms that are atoms of groups 13-17 of the periodic system of elements, or one or more unsaturated bonds, where R ⁴ preferably means hydrogen,

T and T 'mean divalent groups of formulas (II), (III), (IV), (V) or (VI),

in which

the atoms marked with ^* and ^** are in all cases bonded to the atoms of the compounds of formula (I) that are marked with the same symbol, and

R ⁵ are the same or different and independently from each other mean hydrogen or halogen or linear or branched C ₁ -C ₂₀ -alkyl, C ₃ -C ₂₀ -cycloalkyl, which may contain one or more C ₁ -C ₁₀ as substituents -alkyl radicals, C ₆ -C ₂₀ -aryl, C ₇ -C ₂₀ -alkylaryl or C ₇ -C ₂₀ -arylalkyl and may contain one or more heteroatoms that are atoms of groups 13-17 of the periodic system of elements, or one or more the number of unsaturated bonds, where R ⁵ preferably means hydrogen or linear or a branched C ₁ -C ₁₀ alkyl group, preferably a linear C ₁ -C ₄ alkyl group, such as methyl, ethyl, n-propyl or n-butyl, and

R ⁶ are the same or different and independently from each other mean halogen or linear or branched C ₁ -C ₂₀ -alkyl, C ₃ -C ₂₀ -cycloalkyl, which may contain one or more C ₁ -C ₁₀ -alkyl as substituents radicals, C ₆ -C ₂₀ aryl, C ₇ -C ₂₀ alkylaryl or C ₇ -C ₂₀ arylalkyl and may contain one or more heteroatoms that are atoms of groups 13-17 of the periodic system of elements, or one or more unsaturated bonds, where R ⁶ preferably means an aryl group of the formula (VII),

wherein

R ⁷ are the same or different and independently from each other mean hydrogen or halogen or linear or branched C ₁ -C ₂₀ -alkyl, C ₃ -C ₂₀ -cycloalkyl, which may contain one or more C ₁ -C ₁₀ as substituents -alkyl radicals, C ₆ -C ₂₀ -aryl, C ₇ -C ₂₀ -alkylaryl or C ₇ -C ₂₀ -arylalkyl and may contain one or more heteroatoms that are atoms of groups 13-17 of the periodic system of elements, or one or more the number of unsaturated bonds, or two radicals R ⁷ may be bonded to form nasy ennogo or unsaturated ring C ₃ -C _20, preferably wherein R ⁷ represents a hydrogen atom, and

R ⁸ means hydrogen or halogen or a linear or branched C ₁ -C ₂₀ alkyl, C ₃ -C ₂₀ -alkaloalkyl, which may contain one or more C ₁ -C ₁₀ -alkyl radicals, C ₆ -C ₃₀ as substituents -aryl, C ₇ -C ₂₀ -alkylaryl or C ₇ -C ₂₀ -arylalkyl and may contain one or more heteroatoms that are atoms of groups 13-17 of the periodic system of elements or one or more unsaturated bonds, where R ⁸ preferably means branched an alkyl group of the formula —C (R ⁹ ) ₃ in which

R ⁹ are the same or different and independently from each other mean a linear or branched C ₁ -C ₆ -alkyl group or 2 or 3 R ⁹ radicals are associated with the formation of one or more ring systems.

Preference is given to the case when at least one of the groups T and T 'is substituted by the radical R ^{6 of the} formula (VII), and particular preference is given to the case when both groups are substituted by such a radical. Particular preference is given to the case when at least one of the groups T and T 'is a group of the formula (IV), which is substituted by the radical R ^{6 of the} formula (VII), and the other has the formula (II) or (IV) and is also substituted by the radical R ⁶ formulas (VII).

Particular preference is given to catalyst systems based on metallocene compounds of the formula (VIII),

Particularly useful metallocene compounds and methods for their preparation are described, for example, in WO 01/48034 and international patent application No. PCT / EP02 / 13552.

Mixtures of various metallocene compounds or mixtures of various catalyst systems may also be used. However, preference is given to using only one catalyst system comprising one metallocene compound, which is used for polymerization to produce propylene polymer A and propylene copolymer B.

Examples of suitable metallocene compounds are

dimethylsilanediyl- (2-ethyl-4- (4'-tert-butylphenyl) indenyl) - (2-isopropyl-4- (4'-tert-butylphenyl) indenyl) zirconium dichloride,

dimethylsilanediyl- (2-methyl-4- (4'-tert-butylphenyl) indenyl) -2-isopropyl-4- (1-naphthyl) indenyl) zirconium dichloride,

dimethylsilanediyl- (2-methyl-4-phenyl) -1-indenyl) - (2-isopropyl-4- (4'-tert-butylphenyl) -1-indenyl) zirconium dichloride,

dimethylsilanediyl- (2-methylthiapentenyl) - (2-isopropyl-4- (4'-tert-butylphenyl) indenyl) zirconium dichloride,

dimethylsilanediyl- (2-isopropyl-4- (4'-tert-butylphenyl) indenyl) - (2-methyl-4,5-benzindenyl) zirconium dichloride,

dimethylsilanediyl- (2-methyl-4- (4'-tert-butylphenyl) indenyl) - (2-isopropyl-4- (4'-tert-butylphenyl) indenyl) zirconium dichloride,

dimethylsilanediyl- (2-methyl-4- (4'-tert-butylphenyl) indenyl) - (2-isopropyl-4-phenylindenyl) zirconium dichloride,

dimethylsilanediyl- (2-ethyl-4- (4'-tert-butylphenyl) indenyl) - (2-isopropyl-4-phenyl) indenyl) zirconium dichloride and

dimethylsilanediyl- (2-isopropyl-4- (4'-tert-butylphenyl) indenyl) - (2-methyl-4- (1-naphthyl) indenyl) zirconium dichloride

or mixtures thereof.

In addition, preferred catalyst systems based on metallocene compounds typically additionally include compounds capable of forming metallocene ions as cocatalysts. Suitable cocatalysts include strong, uncharged Lewis acids, ionic compounds containing cations of Lewis acids, and ionic compounds containing Bronsted acids as cations. Examples are tris (pentafluorophenyl) borane, tetrakis (pentafluorophenyl) borate, and N, N-dimethylanilinium salts. Other compounds that are suitable for use as compounds capable of forming metallocenium ions and thereby act as cocatalysts are open-chain and cyclic aluminoxane compounds. They are usually obtained by the reaction of trialkylaluminum with water, and they are usually contained as mixtures of linear and cyclic chain molecules or cell-like molecules of various sizes. Preferred catalyst systems based on metallocene compounds are typically used on substrates. Suitable substrates are, for example, porous organic or inorganic inert solids, such as micronized powdered polymers and inorganic oxides, for example silica gel. Metallocene systems may additionally contain organometallic compounds of metals of groups 1, 2 and 13 of the periodic system of elements, for example n-butyllithium and aluminum alkyl derivatives.

In the preparation of particularly preferred heterophase compositions, it is preferable to first polymerize the propylene polymer A in the first step by polymerizing from 90 to 100 wt.% Propylene, based on the total polymerization weight, from 90 to 100 wt.% Propylene, based on the total weight of the mixture, if necessary in the presence of additional olefins, usually at temperatures from 40 to 120 ° C and pressures in the range from 0.5 to 200 bar. In the second stage, a mixture containing from 2 to 95 wt.% Propylene and from 5 to 98 wt.% Additional olefins is polymerized onto the polymer obtained by the reaction of the first stage, usually at temperatures from 40 to 120 ° C and pressures in the range from 0 , 5 to 200 bar. The polymerization of propylene polymer A is preferably carried out at a temperature of from 60 to 80 ° C, particularly preferably from 65 to 75 ° C, and a pressure of from 5 to 100 bar, particularly preferably from 10 to 50 bar. The polymerization of propylene copolymer B is preferably carried out at a temperature of from 60 to 80 ° C, particularly preferably from 65 to 75 ° C, and a pressure of from 5 to 100 bar, particularly preferably from 10 to 50 bar.

In the polymerization, various additives can be used, for example, molar mass regulators, such as hydrogen, or inert gases, such as nitrogen and argon.

Preferably, if the composition of the propylene copolymers in such preferred transparent polypropylene obtained using catalytic systems based on metallocene compounds is homogeneous. These include few copolymers incorporated into blocks. The expression “included in blocks” is used to indicate that two or more comonomer units follow one after another. For preferred propylene B copolymers derived from propylene and ethylene, the structure can be determined using ¹³ C-NMR (nuclear magnetic resonance) spectroscopy. The interpretation of the spectrum relates to the prior art and can be performed by a person skilled in the art, for example, by the method described in HNCheng, Macromolecules 17 (1984), pp.1950-1955, or in L. Abis et al., Makromol. Chemie 187 (1986), pp. 1877-1886. The structure can then be described using the relative contents of “PE _x ” and “PEP”, where PE _x means the content of propylene-ethylene units including ≥2 consecutive ethylene units, and PEP means the content of propylene-ethylene units including an isolated ethylene unit located between two propylene units. Preferred propylene copolymer compositions derived from propylene and ethylene have a PEP / PE _x ratio in the range of 0.75 to ≥1, preferably in the range of 0.85 to ≥1.4, more preferably in the range of 0 , 85 to 1.2, and particularly preferably in the range of 0.9 to 1.1.

In the case of the preferred use of ethylene as a comonomer, it is particularly preferable if the ethylene content in propylene copolymers B is from 10 to 20 wt.%, More preferably from 12 to 18 wt.% And even more preferably about 16 wt.%. The transparency of the propylene copolymer compositions used in accordance with the present invention is practically independent of the content of propylene copolymer B.

Particularly preferred heterophasic propylene copolymers suitable for use as transparent polypropylenes are also those which include

A) from 50 to 98, preferably from 60 to 95 wt.% Crystalline propylene homopolymer or crystalline random copolymer of propylene with ethylene and / or C ₄ -C ₁₀ -1-alkenes containing from 0.5 to 15 wt.% Ethylene and / or C ₄ -C ₁₀ -1-alkene; and

B) from 2 to 50, preferably from 5 to 40 wt.% (I) of an elastomeric copolymer of ethylene with one or more C ₄ -C ₁₀ -1-alkenes (copolymer (a)) containing from 60 to 85 wt. % ethylene, or (ii) a mixture of copolymer (a) with a propylene copolymer containing from more than 15% to 40% ethylene (copolymer (b)), where the mass ratio (a) / (b) is preferably from 1/4 to 4 /one.

Examples of C ₄ -C ₁₀ -1-alkenes that can be used as comonomers in fractions A and B are 1-butene, 1-pentene, 1-hexene and 4-methyl-1-pentene. Particularly preferred is 1-butene.

The melt flow rate of such heterophasic propylene copolymers (230 ° C / 2.16 kg), determined in accordance with ISO 1133, is preferably from 0.1 to 100 g / 10 min.

Such useful heterophasic propylene copolymers are usually prepared by sequential copolymerization of monomers in the presence of stereospecific Ziegler-Natta catalysts supported on a magnesium dihalide support. The polymerization is carried out in at least two stages: in the first stage, the polymer of fraction A is synthesized, in the second stage, the polymer of fraction B is synthesized. The synthesis of the latter is carried out in the presence of the polymer and catalyst used in the previous stage. The duration and temperature of the reactions for these two stages are not critical and are preferably in the range from 0.5 to 5 hours and from 50 to 90 ° C, respectively. Molecular weight control is carried out using commonly used molecular weight regulators, for example hydrogen and ZnEt ₂ .

Suitable stereospecific catalysts include a reaction product between:

1) a solid-phase component containing a titanium compound and an electron-donating compound (internal electron donor) on a magnesium chloride substrate;

ii) an aluminum alkyl derivative (cocatalyst); and optional

iii) electron donor compound (external electron donor).

Preferably, if such catalysts make it possible to obtain a propylene homopolymer having an isotactic index in excess of 90%.

Catalysts having the above characteristics are known from the patent literature; particularly preferred are the catalysts described in patent application US-A 4399054 and EP-A 45977.

The solid-phase component of the catalyst (i) as an electron donor contains a compound usually selected from ethers, ketones, lactones, compounds containing N, P and / or S atoms, and mono- and dicarboxylic acid esters.

Particularly suitable are phthalic acid esters and succinic acid esters. Other particularly suitable electron donors are 1,3-diesters, as shown in European patent applications EP-A361493 and EP-A728769.

As cocatalysts (ii), it is preferable to use trialkyl derivatives of aluminum such as Al-triethyl, Al-triisobutyl and Al-tri-n-butyl.

Electron-donor compounds (iii) that can be used as external electron donors (added to Al-alkyl compounds) include aromatic acid esters (such as alkyl benzoates), heterocyclic compounds (such as 2,2,6,6-tetramethylpiperidine and 2 , 6-diisopropylpiperidine) and preferably silicon compounds containing at least one Si-OR bond (where R is a hydrocarbon radical). The above 1,3-diethers are also suitable for use as external donors. If the external donor is one of these simple 1,3-diesters, the internal donor can not be used.

Particularly preferred transparent polypropylenes obtained using catalytic systems based on metallocene compounds or using stereospecific Ziegler-Natta catalysts supported on magnesium dihalides are preferably prepared using a multistage polymerization process comprising at least two polymerization steps carried out sequentially, usually with using a cascade of reactors. Conventional reactors used for the polymerization of propylene can be used. The polymerization can be carried out in a known manner in bulk, in suspension, in the gas phase or in a supercritical medium. It can be carried out in batch or, preferably, in continuous mode. Possible methods are those performed in a solvent, suspension methods, gas phase mixing methods, and gas phase methods using a fluidized bed. Inert hydrocarbons, for example isobutane, or even the monomers themselves can be used as a solvent or suspending medium. In addition, one or more stages of the process used in accordance with the present invention can be carried out in two or more reactors. The size of the reactors is not critical to the process used in accordance with the present invention. It depends on the required performance in the reaction zone or in individual reaction zones.

Preference is given to methods in which the polymerization in the second stage, which produces propylene copolymer (s) B or fraction B, is carried out in the gas phase. The preliminary polymerization of propylene A polymers or fraction A can be carried out either in bulk, i.e. in liquid propylene as a suspending medium, or, similarly, in the gas phase. If all polymerization is carried out in the gas phase, the method is preferably carried out in a cascade of stirred gas phase reactors, which are connected in series and in which the powdery reaction layer is driven by a vertical mixer. The reaction layer typically includes a polymer that is polymerized in an appropriate reactor. If the initial polymerization of propylene polymers A is carried out in bulk, it is preferable to carry out the process in a cascade consisting of one or more loop reactors and one or more gas phase fluidized bed reactors. Obtaining can also be carried out in a multi-zone reactor.

The amounts of monomers added in the individual steps and the conditions of the process, such as pressure, temperature or the addition of molar mass regulators, such as hydrogen, are selected so that the polymer formed possesses the necessary characteristics.

Conventional additives, for example molar mass regulators, such as hydrogen or inert gases, such as nitrogen or argon, can also be used in the polymerization.

Transparent polypropylene typically further includes additives known to those skilled in the art, for example, stabilizers, lubricants and mold release agents, fillers, nucleating agents, antistatic agents, plasticizers, colorants, pigments or flame retardants in conventional amounts. They are usually included during the granulation of the powdered product obtained by polymerization.

Conventional stabilizers are antioxidants such as spatially hindered phenols, treatment stabilizers such as phosphites or phosphonites, acid scavengers such as calcium stearate or zinc stearate or dihydrotalcite, spatially hindered amines or stabilizers with respect to the effects of UV radiation. Typically, propylene copolymer compositions used in accordance with the present invention contain one or more stabilizers in an amount of up to 2 wt.%.

Suitable lubricants and mold release agents are, for example, fatty acids, calcium or zinc salts of fatty acids, fatty acid amides or low molecular weight polyolefin waxes, which are usually used in concentrations of up to 2% by weight.

Possible fillers are, for example, talc, chalk and fiberglass, which can usually be used in amounts of up to 50 wt.%.

Suitable nucleating agents are, for example, inorganic additives such as talc, silicon dioxide and kaolin, salts of mono- or polybasic carboxylic acids, for example sodium benzoate or aluminum tert-butyl benzoate, dibenzylidene sorbitol and its C ₁ -C ₈ alkyl substituted derivatives, such as methyldibenzylidene sensorbit ethyl dibenzylidene sorbitol and dimethyldibenzylidene sorbitol and salts of phosphoric acid diesters, for example 2,2'-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate. The content of nucleating substances in the propylene polymer composition is usually up to 5 wt.%.

Such additives are usually commercially available and are described, for example, in Gächter / Müller, Plastics Additives Handbook, 4th Edition, Hansa Publishers, Munich, 1993.

In a preferred embodiment, the transparent polypropylenes contain from 0.1 to 1 wt.%, Preferably from 0.15 to 0.25 wt.% Of a nucleating agent, preferably dibenzylidene sorbite or a dibenzylidene sorbite derivative, more preferably dimethyldibenzylidene sorbite.

Containers are used for packaging or storing products, such as clothing, sports products, toys or products for the home craftsman. For example, they are suitable for packaging or storing any type of shoe, such as shoes, sandals, boots, sports shoes, roller skates and ski shoes, underwear, tennis accessories, toys such as toy cars and designers, and homemade products such as tools, screws and nails. In particular, containers are used for packaging or storing shoes.

The containers have a wall thickness of at least 0.8, and preferably at least 1.0 mm. The wall thickness of the containers is usually approximately the same in all areas of the container. However, they may also have hardened sections or ribs. Typically, containers are dimensioned so that products can be easily packaged, preferably shoes.

Preferred containers are made in two parts and consist of a box in the form of a box and a lid. The box and the lid can be connected to each other, preferably with a flexible joint. The box-shaped box and the lid are preferably shaped so that when the containers are closed, the lid is put on the box.

In addition, the boxes are preferably shaped so that the empty boxes can be inserted into each other. This is usually done by giving the box a conical shape. It is also preferable that the upper reinforcing rib of the box is located outside, giving it rigidity. In addition, it makes it easy to put the lid on the box to close the container.

A possible construction of a preferred container consisting of a box in the form of a box and a lid is shown in the attached drawing.

Preferably, the caps have short sides, the height of which is usually from 10 to 20 mm. It is also preferable that the lower reinforcing rib of the lid is located inside, giving it rigidity. In addition, it makes it easy to put the lid on the box to close the container.

It is preferable to make containers by injection molding. However, containers can be made by molding, for example folding, extruded sheets, preferably extruded corrugated sheets.

The present invention also relates to containers made of transparent polypropylene, and these containers have a wall thickness of at least 0.8 mm, the transparent polypropylene being a propylene homopolymer or a propylene copolymer that has a cloud point of ≤40% based on a thickness of polypropylene equal to 1 mm, and measured using test specimens made by injection molding, and has a tensile modulus of ≥700 MPa and impact strength in Charlie with an incision at 0 ° C, component ≥3 kJ / m ² , and at the bottom of the container is a material that has a sliding friction coefficient that is greater than that of transparent polypropylene. This material prevents or at least reduces the sliding of packaged or stored items such as shoes. Examples of suitable materials having a sliding friction coefficient that is greater than that of transparent polypropylene are elastomers and plastic elastomers such as thermoplastic polyolefins and block copolymers of styrene oligomers. Suitable thermoplastic polyolefins are sold, in particular, by Basell under the name Adflex. Usually, only some parts of the bottom of the containers are coated with material that has an increased coefficient of sliding friction. These sections can be, for example, oval, have the shape of rectangular stripes or the shape of protrusions. The manufacture can be carried out, for example, using two-component injection molding. However, containers and castings of a material having a high coefficient of sliding friction can be manufactured individually and then the castings are attached to the container, for example using an adhesive joint.

The present invention also relates to systems for packaging or storing products, such as clothing, sports products, toys or products for a home craftsman, such that at least two items are in the package, the items being in a container made of a transparent polymer and having a wall thickness equal to at least 0.8 mm, and at least two objects are separated from each other by a transparent elastic film. Such systems make it easy to see products that consist of at least two items, and are packed in a way that excludes impact of objects against each other and against the walls of the package when transporting packaging systems.

Examples of suitable transparent polymers that can be used to make containers for systems are polystyrene, polycarbonate, block copolymers of styrene with butadiene and polypropylene, the transparent polypropylenes described above being particularly suitable.

Preferred transparencies are flexible and have low stiffness. In addition, preferred transparent films are made of a material that has a sliding friction coefficient that is greater than that of the transparent polymer. Suitable clear films can be made, for example, from thermoplastic polyolefins, for example from thermoplastic polyolefins sold by Basell under the name Adflex.

The present invention also relates to reusable packaging systems for packaging clothing, sports products, toys or products for the home craftsman, and in particular shoes, in which containers made of a transparent polymer and having a wall thickness of at least 0, 8 mm, used for packing clothes, sports products, toys or products for the home craftsman, and for the reuse of containers there are smaller containers that can be neatly inserted or put into these containers. These liners are preferably made from the same transparent polymer from which the containers are made. The liners can also be shaped into containers for layout, which contain many compartments, for example from 2 to 10, preferably from 4 to 8 compartments.

Suitable liners can be sold empty as accessories for the subsequent use of containers originally used as packaging material. However, these inserts can also be sold filled, i.e. as reusable packaging for other products. Suitable products that can be sold packaged in such inserts are, for example, shoe care products such as cream tubes, cleaning products or cleaning cloth, or sewing accessories such as needles, threads or buttons.

Suitable transparent polymers that can be used to make containers for systems are, for example, polystyrene, polycarbonate, styrene-butadiene block copolymers and polypropylene, the transparent polypropylene described above being particularly suitable.

Claims (6)

1. A container for packaging or storing products, such as clothing, shoes, sports products, toys or homemade products, including transparent polypropylene and having a wall thickness of at least 0.8 mm, in which the transparent polypropylene is a heterophasic propylene copolymer comprising a) from 50 to 98, preferably from 60 to 95 wt.%, crystalline propylene homopolymer or crystalline random copolymer of propylene with ethylene and / or C ₄ -C ₁₀ -1-alkenes containing from 0.5 to 15 wt. % ethylene and / or C ₄ -C ₁₀ -1 alkene; and
C) from 2 to 50, preferably from 5 to 40, wt.% (i) an elastomeric copolymer of ethylene with one or more C ₄ -C ₁₀ -1-alkenes (copolymer (a)) containing from 60 to 85 wt. % ethylene, or (ii) a mixture of copolymer (a) with a propylene copolymer containing from more than 15 to 40% ethylene (copolymer (b)), and the mass ratio a) / b) is preferably from 1/4 to 4/1;
however, the copolymer has a cloud point of ≤40% based on a polypropylene thickness of 1 mm and measured using injection molded test pieces, tensile modulus of ≥700 MPa, and notched Charpy impact strength at 0 ° С, component ≥3 kJ / m ² , and the whitening value at a voltage of 0-8 mm, determined by the dome-shaped indenter method using round discs with a diameter of 60 mm and a thickness of 2 mm, obtained by injection molding. 2. The container according to claim 1, characterized in that it is a box in the form of a box, separated by at least one transparent elastic film so as to separate at least two objects. 3. The container according to claim 1, characterized in that it consists of two parts and consists of a box in the form of a box and a lid, and the box and the lid can be connected to each other. 4. The container according to claim 3, characterized in that the box in the form of a box and the lid is shaped so that when the container is closed, the lid is put on the box. 5. The container according to claim 3, characterized in that the box is shaped so that it can be inserted into another empty container. 6. The container according to claim 1, characterized in that it is made by injection molding.

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