EP0578455A1 - Polyolefin solid plate - Google Patents

Abstract

A solid plate based on polyolefin for inserts or packages. More precisely, this plate is made up of at least one layer and comprises at least one polyolefin and talc. The invention finds application in the packaging field.

Description

The present invention generally relates to solid plates based on polyolefin.

These plates are used in particular as palletizing inserts or for packaging intended for the transport or storage of containers. They are used, for example, to separate several layers of glass or metal containers or bottles.

The Applicant has already developed an intermediate plate having anti-slip properties. This non-slip plate is based on polyolefin and is formed of a core layer and on at least one of the faces thereof, of an outer non-slip layer. Such a plate is described in the French patent application filed under the number 91 13978.

However, although having good non-slip properties, these plates do not provide the sufficient mechanical properties required for the transport and storage of containers. In fact, when pallets of bottles are stacked on several heights, the plates forming spacers are no longer rigid enough, at ambient temperature and more particularly at higher temperature. Good stability of the containers placed between these plates is no longer ensured. In addition, if the packages or pallets containing these plates are stored at high temperatures, such as in hangars overheated to 70 ° C, the plates are deformed under heat. Finally, for winter storage at low temperatures, impact resistance is poor.

The subject of the invention is solid plates which overcome all the drawbacks mentioned above. More specifically, the invention consists of a solid plate based on polyolefin for spacers or packaging, characterized in that it is formed of at least one layer and in that it comprises at least one polyolefin and talc.

According to an advantageous characteristic of the invention, the aforementioned polyolefin is a polypropylene, homopolymer or copolymer, or their mixtures.

According to another advantageous characteristic of the invention, the talc content of the plate is at least equal to 5% by weight.

It has in fact been discovered that the introduction of talc as a filler for the polyolefin, confers on the plate surprisingly improved mechanical properties, such as rigidity and heat resistance, in particular creep.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows.

The plate according to the invention is a full, calendered plate.

This plate is formed of a layer comprising a polyolefin loaded with talc.

Talc has been chosen from different mineral substances such as chalk, mica, fiberglass or others, as providing very advantageous results in mechanical properties.

The talc content of the plate must be at least 5% by weight. There is no upper limit by weight but this content often remains less than 25% for a simple reason of cost of the raw material.

The preferred talc content, meeting both the required mechanical characteristics and the cost requirements, varies between approximately 5 and approximately 20% by weight. More preferably, the talc content varies between about 9 and about 15% talc. In addition, a plate too loaded with talc will become brittle and difficult to transform, in particular as regards the cutting of the plates.

Those skilled in the art will be able to adjust the talc content as well as the total thickness of the plate as a function of the desired mechanical properties of rigidity and heat resistance, while retaining good impact resistance. Indeed, the plate must have a minimum thickness of about 3 millimeters to maintain good impact resistance and avoid breakage.

The polyolefin may be polypropylene in the form of a homopolymer or of an ethylene-based copolymer, or mixtures thereof.

Polypropylene homopolymer is preferably used, such as for example HOMOPOLYMER HY 6100 sold by SHELL Chimie, the properties of which are presented in Table I below. TABLE I PROPERTY TEST METHOD UNIT VALUE Fluidity index ISO 1133 dg / min 1.5 Volumic mass ISO 1183 g / cm³ 0.903 Tensile strength ISO 527 MPa 35 Flexural modulus ISO 178 MPa 1350 IZOD impact resistance (notched) at 20 ° C ISO 180 kJ / m² 5.2 Heat deformation temperature at 1.80 MN / m² (A) ISO 75 ° C 60 at 0.45 MN / m² (B) ° C 108 Vicat softening temperature ISO 306 ° C 153 Hardness ISO 868 Shore D 73

However, this product has a modulus of rigidity in bending and an impact resistance insufficient for use in the plates for dividers or packaging. Similarly, the heat deformation temperature under two different constraints: one of 1.80 MN / m² (A) and the other of 0.45 MN / m² (B), is low.

The mixture of polypropylene homopolymer and talc makes it possible to provide the plate with a rigidity, a Vicat softening point and a temperature of heat distortion under load significantly improved, compared to the other types of polypropylene, homopolymer or copolymer, conventionally used, as is moreover illustrated in the examples which follow.

Polypropylene can also be used in the form of a copolymer, preferably a block copolymer such as, for example, Moplen EPYS 30RE sold by Himont, and the characteristics of which are developed in Table II below. TABLE II PROPERTY TEST METHOD UNIT VALUE Fluidity index ASTM 1238 / L dg / min 1.5 Specific weight ASTM D1505 g / cm³ 0.9 Elastic flexural modulus ASTM D790 MPa 1200 IZOD impact resistance (notched) at 23 ° C ASTM D256 J / m 350 Vicat softening point ASTM D1525 ° C 50 Heat deformation temperature (0.46 MN / m²) ASTM D648 ° C 85

Also for this Moplen copolymer, the elastic flexural modulus and the impact resistance are insufficient. In addition, the Vicat softening point and the heat distortion temperature are very low.

According to another preferred embodiment of the invention, the plate comprises on the one hand, a layer as described above, that is to say based on polyolefin and talc, which corresponds to the core layer forming the core of the plate and on the other hand, on at least one of the faces thereof, an external non-slip layer.

The non-slip outer layer is arranged on at least one of the faces of the core layer, and is, for its part, made of a product which confers the non-slip property to the plate. This is for example a thermoplastic based on very soft polyolefin and having a very low modulus of elasticity. The concentration of non-slip thermoplastic in the outer layer is at least about 5% by weight and is preferably between about 20 and about 100% by weight.

The thickness of the non-slip outer layer can vary between approximately 5 and approximately 150 μm and preferably between approximately 30 and approximately 70 μm.

A thermoplastic rubber can be used, such as Santoprene 201-55 sold by Advanced from Elastomer Systems or HIFAX FX 7036 XCP sold by Himont, the properties of which are given in Table III below. TABLE III PROPERTY TEST METHOD UNIT VALUE Fluidity index "L" ASTM D1238 g / 10 ' 0.8 Specific weight ASTM D 792 g / cm³ 0.89 Flexural modulus ASTM D 790 MPa 100 Stress at flow threshold ASTM D 638 MPa 5 at the breakup MPa > 8 Elongation at flow threshold % 60 at the breakup % > 350 Vicat softening point (10N) ASTM D1525 ° C 55 Shore D hardness ASTM D2240 - 30

The process for manufacturing solid plates is known per se and consists, for example, of non-slip solid plates. in a process of coextrusion of a flow in two layers in which the external layer is deposited on the core layer by means of a coextrusion block or else by using a multilayer die. The plate formed from the above layers is then calendered.

An example of a process is described in Kunstoff-Extrusions-technik, Tome II: Extrusionsanlagen page 200 by Hanser-Knappe-Potente, Editions Hanser.

Different embodiments of the plates are possible depending on the use of these. According to the embodiment used in the following examples, the manufactured plate is without housing.

In another embodiment. one can manufacture a rigid plate provided with housings whose outline corresponds to the projection on a horizontal plane of the articles or containers in front be arranged between the plates.

The mechanical properties of the plates manufactured in the tests illustrating the invention are measured by two tests: the first which is a 3-point bending test, relating to the rigidity and the second which is a test for measuring the creep on the full plates.

Rigidity measurement

The 3-point bending stiffness test consists of measuring the slope of the deformation curve of a rectangular plate resting on two supports.

The plate is deformed by means of a fault applied at equal distance from the supports and moving at constant speed.

The diameter of the supports is 10 millimeters. The two supports are 10 cm apart and the tip is 5 cm away from the projection of each of the supports on the upper face of the plate.

We use a traction machine model INSTRON 4301 equipped with a force sensor 100 kgf.

The measurement protocol is as follows:

Two measurements are carried out: one in the running direction (SM) and the other in the transverse direction (ST) on specimens of determined dimensions.

5 samples 4 x 20 cm² are taken from each plate to be tested for the SM measurement and 5 samples are 4 x 20 cm² for the ST measurement. The measurement is carried out as follows.

First, lower the crosshead at a constant speed of 5 mm / min, determine the optimal conditions for calculating the slope (speed of the paper and choice of the scale of forces for the recorder), note the conditions chosen for each sample, then measure the slope (in kgf / mm) which is plotted for each curve.

   F (en kgf) et X (en mm) sont mesurées sur la courbe.
   Vp est la vitesse du papier (en mm/min) et
   Vt est la vitesse de la traverse (en mm/min)The slope is calculated as follows: $$\text{Slope P =}\frac{\text{F x Vp}}{\text{X x Vt}}\text{in kgf / mm}$$

F (in kgf) and X (in mm) are measured on the curve.
Vp is the speed of the paper (in mm / min) and
Vt is the speed of the sleeper (in mm / min)

The results are calculated as the mean value of the 5 SM and ST measurements of the samples tested.

These measurements are carried out on the one hand at 20 ° C. and on the other hand at 60 ° C.

Creep measurement

This test consists in measuring the deformation of the plate under the effect of a force corresponding to the weight exerted by a load of approximately 50 kg simulating a storage of pallets.

An INSTRON 4301 dynamometer is used for the measurements on which an oven is installed, the temperature of which is fixed at 70 ° C. 15 cm by 15 cm plate samples are prepared and these samples are conditioned at 75 ° C., 2 to 3 hours before the test.

A sample is placed in the oven and the temperature of the oven is stabilized at 70 ° C. Then a force of 50 kgf ± 0.1 is exerted by means of an aluminum piece having the shape of a bottom of the bottle.

To achieve this force, the machine cyclically weighs between 49.9 and 50.1 kg and the speed of movement of the crosspiece on which the above-mentioned part is arranged is 1 mm / min.

As soon as a load of 50 kg is applied to the sample (on reading), the stopwatch is started and the deformation values of the sample are noted after 1 minute, 3 minutes and then 15 minutes.

Creep values are thus obtained at 70 ° C in millimeters for 1.3 and 15 minutes.

Example 1 .

On the one hand, a control plate is prepared comprising a layer based on polypropylene homopolymer only, more precisely based on homopolymer HY 6100 described above. This article therefore does not include talc.

On the other hand, two plates are prepared, each formed of a layer which comprises polypropylene homopolymer and talc.

For convenience in the preparation of this layer, a product is used as a starting component which is a mixture of polypropylene and talc, a mixture which exists on the market.

More specifically, this mixture is Stamylan P 13T1040 manufactured by DSM. It contains 60% polypropylene homopolymer and 40% talc. Its properties are presented in Table IV below. TABLE IV PROPERTY TEST METHOD UNIT VALUE Fluidity index ISO R1133 dg / min 1.7 Flexural modulus ISO R 178 MPa 3640 IZOD impact resistance (notched) + 23 ° C ISO R 180 kJ / m² 2.7 Heat deformation temperature ISO R 75 at 1.80 MN / m² (A) ° C 74 at 0.45 MN / m² (B) ° C 129 Vicat softening temperature ISO R 306 ° C 93 Hardness ISO R 868 Shore D 74

By comparing the homopolymer HY 6100 (Table I) with the Stamylan P containing talc (Table IV), we will note a much higher flexural modulus for the mixture containing talc and a heat deformation temperature under two constraints different (A) and (B), also higher in the case of mixing.

The effect of talc on the rigidity and the heat resistance of the product in mixture is therefore clearly observed on the mixture as such.

The layer is obtained by mixing 25 to 30% of Stamylan P with 70 to 75% by weight of polypropylene homopolymer HY 6100.

Two plates are made from these products.

For all the plates, control and plates according to the invention, the stiffness is measured at 20 ° C then at 60 ° C and the creep at 70 ° C according to the tests described above.

The results are summarized in Table V below.

The desired rigidity is at least 1 kgf / min at 20 ° C and at least 0.5 kgf / min at 60 ° C and the creep deformation at 70 ° C must not exceed 3 millimeters after 1 minute, 3.2 millimeters after 3 minutes and 3.4 millimeters after 15 minutes.

It is clear from Table V that the plates containing talc have mechanical characteristics far superior to those of the control and quite satisfactory. Rigidity has largely doubled its value. It should be noted that the rigidity of the control at 60 ° C was not measured because of its low value at 20 ° C which is already lower than the desired value at 60 ° C.

Creep deformation at 70 ° C decreased by at least 40% for plates containing talc.

Example 2

Seven plates are prepared formed from a layer prepared from homopolymer polypropylene and talc. For convenience. a blend of 60% homopolymer polypropylene and 40% talc is also used here as a raw material: Vestolen P manufactured by HÜLS.

The properties of this product are presented in Table VI below. TABLE VI PROPERTY TEST METHOD UNIT VALUE Fluidity index ISO 1133 dg / min 2.8 Flexural modulus ISO 527 MPa 4500 Impact resistance at room temperature IZOD (notched) ISO 180 kJ / m² 3.2 Heat deformation temperature at 1.80 MN / m² (A) ° C 100 at 0.45 MN / m² (B) ° C 140 Vicat softening temperature ISO 306 ° C 110

By comparing the homopolymer HY 6100 (Table I) with the Vestolen P containing talc (Table VI), it is noted that the flexural modulus of flexion of the mixture containing talc (Vestolen P) is three times that of polypropylene homopolymer alone and the heat deformation temperature under two different stresses (A) and (B), is much higher in the case of the mixture containing talc (Vestolen P) than for polypropylene homopolymer alone.

Talc therefore provides the mixture with improved properties.

The layer is obtained by mixing Vestolen P with polypropylene homopolymer in proportions of 25-30% and 70-75% by weight respectively.

Seven plates are made from these products.

The stiffness is measured at 20 ° C then at 60 ° C and the creep at 70 ° C according to the same tests as in Example 1.

The results are given in Table VII below.

In general, it is concluded from the results of Table VII that the rigidity required at 20 ° C is always greater than 1 and that at 60 ° C is always greater than 0.5. Likewise, the creep properties are entirely satisfactory, the deformation remaining well below 3, 3.2 and 3.4 millimeters respectively after 1, 3 and 15 minutes.

Compared to the control plate not containing talc, the rigidity at 20 ° C and 60 ° C of the plates according to the invention is at least twice that of the control plate and the heat deformation at 70 ° C plates according to the invention decreased by about 40% and up to about 60% compared to the control plate.

It can be observed that the rigidity increases in proportion to the talc content (see plates 4, 5, 8 and 9). Likewise, the creep deformation at 70 ° C generally decreases when the talc content increases (see plates 4, 6, 8 and 9).

We also note that the thickness of the plate parameter is involved in the mechanical properties.

For plates n ° 7 to 9, the thickness of the plate increases to compensate for the brittle nature that can be encountered with higher talc contents.

In the practice of the invention, it is more advantageous to choose talc contents situated between 9 and 12% by weight which provide entirely satisfactory mechanical properties and which do not entail excessive cost as regards the purchase of raw material. Finally, it should be noted that when the thickness of the plate is considerably increased to 3.7 millimeters for a talc content of 9% by weight (plate No. 3), the mechanical property of rigidity is significantly improved.

Claims (9)

1) Solid plate based on polyolefin for spacers or packaging, characterized in that it is formed of at least one layer and in that it comprises at least one polyolefin and talc. 2) Plate according to claim 1, characterized in that the aforementioned polyolefin is a polypropylene, homopolymer or copolymer, or mixtures thereof. 3) Plate according to claim 2, characterized in that the polyolefin is preferably polypropylene homopolymer. 4) Plate according to one of claims 1 to 3, characterized in that the talc content is at least equal to 5% by weight. 5) Plate according to one of claims 1 to 4, characterized in that the talc content is preferably between about 5 and about 20% by weight. 6) Plate according to one of the preceding claims, characterized in that it comprises a core layer based on polyolefin and talc and on at least one of the faces of the above-mentioned layer, an external non-slip layer. 7) Plate according to claim 6, characterized in that the above-mentioned non-slip outer layer comprises a thermoplastic product compatible with polyolefins and having non-slip properties. 8) Plate according to claim 7, characterized in that the above product is a polyolefin-based thermoplastic. 9) Plate according to one of claims 1 to 8, characterized in that the thickness of the plate is at least equal to 3 millimeters.