Polypropylene resin composition

Resin mass consisting of

a) Polypropylene copolymers with one or more α-olefins from the group of C₂- and C₄- Up to C10 olefins with a propylene content of 70 to 99.5 mol%, preferably 75 to 90 mol% and an MFI (230 ° C / 2.16 kg) of 1 to 25 g / 10 min, preferably 3 to 20 g / 10 min,

b) Ethylene copolymers with one or more α-olefins from the group of C5- to Cio-olefins with an MFI (230 ° C / 2.16 kg) of 6 to 100 g / 10 min and an ethylene content of 80 to 95 Mol%, preferably from 90 to 95 mol%,

c) mineral fillers,

d) optionally additives.

The resin compositions are suitable for the production of

Molded parts with improved surface properties.

DVR 0078018

AT 408 885 B

The invention relates to polypropylene resin compositions containing mineral fillers and based on polypropylene (PP) copolymers and polyethylene (PE) copolymers, and to their use for the production of molded parts with improved surface properties.

When using filled PP resin masses, especially for large-area molded parts, for example for use in bumpers or for other injection-molded, pressed or extrusion parts, such as for dashboards, center consoles for motor vehicles, etc., there is the disadvantage that due to the long flow paths, especially optical irregularities, in particular flow marks (tiger skin) on the surface of the molded parts, but also other impairments of the surface such as Roughness, poor uniformity, streaks, etc. occur. According to DE-PS 3821075 filled resin compositions for bumpers based on propylene-ethylene block copolymers and non-crystalline ethylene-α-olefin random copolymers with a melt viscosity (melt flow index / MFI or melt flow rate / MFR) of 0.1 to 5 g / 10 min used. According to EP-A-132,968, the MFI of the ethylene random copolymer phase is 0.1 to 2 g / 10 min. However, these resin compositions also have the disadvantage described above of inadequate surfaces of the molded parts, in particular of flow marks.

From EP-B 0 603 723 polymer compositions are known which are said to have improved transparency, improved rigidity and improved impact resistance and, moreover, are to be produced by sequential copolymerization. The problem of flow marks or streaks is not addressed. The claimed compositions are made by sequential copolymerization but not by mixing. A limitation of the components that can be used with regard to the required MFI range cannot be found in the document.

In EP 0 593 221 compositions with improved impact resistance are disclosed, but even in this document no mention is made of the problem of flow marks or streaks. Only copolymers containing between 10 and 60 mol% of ethylene are used as the second component for the compositions. Furthermore, mineral fillers are not necessarily provided.

EP 0 677 554 describes polypropylene molding compositions, it being possible for 0.1-3% by weight of an ethylene polymer (monopolymer or with up to 20% by weight of comonomers) to be present in the composition. In addition, the compositions contain carboxamides or mixtures of carboxamides. The problem of surface properties, in particular the problem of flow marks or streaks, is not addressed; only polypropylene molding compounds with good sliding properties are to be provided.

One object of the invention is to find resin masses (resin compositions) which above all have a good surface quality, in particular no flow marks, and which nevertheless show good, still tolerable mechanical properties, in particular good impact strength and good rigidity.

The solution to the problem was found through the use of special resin compositions based on propylene copolymers and ethylene copolymers with a high MFI.

The invention relates in particular to a resin composition consisting of

a) 65 to 90% by weight, particularly preferably 75 to 80% by weight, of polypropylene copolymers with one or more α-olefins from the C group₂- and C₄- to C₁₀-Olefins with a propylene content of 70 to 99.5 mol%, preferably from 75 to 90 mol% and an MFI (230 ° C / 2.16 kg) of 1 to 25 g / 10 min, preferably from 3 to 20 g / 10min,

b) 5 to 20% by weight, particularly preferably 8 to 15% by weight, of ethylene copolymers with one or more α-olefins from the C group₅- to Ci₀-Olefins with an MFI (230 ° C / 2.16 kg) of 40 to 80 g / 10 min and an ethylene content of 80 to 95 mol%, preferably from 90 to 95 mol%,

c) 5 to 20% by weight, preferably 8 to 15% by weight of mineral fillers,

d) optionally 0 to 10% by weight, preferably 0 to 5% by weight of additives.

The resin compound is particularly suitable for the production of molded parts with improved surface properties, in particular with negligible flow marks. The molded parts are, however, characterized overall by better surface properties and better optics, such as, for example, low streakiness, low surface roughness, good uniformity, low differences in gloss.

AT 408 885 B

Particularly good surface properties are achieved with molded parts made from resin compounds whose component a is composed of heterophasic propylene-ethylene copolymers (block copolymers), a PP homopolymer phase or PP random copolymer phase (random PP copolymer phase) and an ethylene -Propylene-Rubber (EPR) -copolymer phase included. These resin compositions in component a contain preferably 20 to 45% by weight, particularly preferably 25 to 32% by weight, of the EPR copolymer phase. Resin compositions in which this EPR copolymer has a viscosity of less than 2000 Pas (measured with a vibration rheometer, e.g. from Rheometrix RDS-2 at 230 ° C. and a shear rate of 1s'¹) prove to be particularly beneficial. Resin compositions in which this EPR copolymer has an ethylene content of 30 to 50% by weight, particularly preferably 30 to 45% by weight, are also preferred. The ethylene content mentioned here as preferred proves to be particularly advantageous when the viscosity of the EPR copolymers is 2000 Pas or greater.

The comonomers of the ethylene copolymers of component b preferably have 6 to 8 carbon atoms in the molecule. The density of component b is preferably 0.86 to 0.88 g / cm³.

An anisotropic mineral filler is advantageously used for the resin composition, preferably from the group consisting of talc, mica or wollastonite. The fillers have an average particle size of preferably 1 to 60 μm, particularly preferably 3 to 30 μm. All of the above-mentioned optional features of the invention lead to particularly advantageous surface properties for the purposes of the task at hand.

Another object of the invention is the use of a resin composition according to the invention, consisting of

a) 65 to 90% by weight, particularly preferably 75 to 80% by weight, of polypropylene copolymers with one or more α-olefins from the C group₂- and C₄- to C₁₀-Olefins with a propylene content of 70 to 99.5 mol%, preferably from 75 to 90 mol% and an MFI (230 ° C / 2.16 kg) of 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min,

b) 5 to 20% by weight, particularly preferably 8 to 15% by weight, of ethylene copolymers with one or more α-olefins from the C group₅- to C₁₀-Olefins with an MFI (230 ° C / 2.16 kg) of 40 to 80 g / 10 min and an ethylene content of 80 to 95 mol%, preferably from 90 to 95 mol%,

c) 5 to 20% by weight, preferably 8 to 15% by weight of mineral fillers,

d) optionally 0 to 10% by weight, preferably 0 to 5% by weight of additives for the production of molded parts with improved surface properties.

Another object of the invention is the use of ethylene copolymers with one or more α-olefins from the group of C.₅- to C₁₀-Olefins with an MFI (230 ° C / 2.16 kg) of 6 to 100 g / 10 min and an ethylene content of 80 to 95 mol%, preferably from 90 to 95 mol%, as an additional component to polypropylene copolymers with an or several α-olefins from the group of the C₂- and C₄- to C₁₀Olefins with a propylene content of 70 to 99.5 mol%, preferably 75 to 90 mol%, and an MFI (230 ° C. / 2.16 kg) of 1 to 25 g / 10 min, preferably 3 to 20 g / 10 min, which contain mineral fillers and possibly additives, to improve the surface quality of molded parts.

Another object of the invention is a process for the production of molded parts with improved surface properties, characterized in that

a) 65 to 90% by weight, particularly preferably 75 to 80% by weight, of polypropylene copolymers with one or more α-olefins from the C group₂- and C₄-to C₁₀-Olefins with a propylene content of 70 to 99.5 mol%, preferably from 75 to 90 mol% and an MFI (230 ° C / 2.16 kg) of 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min,

b) 5 to 20% by weight, particularly preferably 8 to 15% by weight, of ethylene copolymers with one or more α-olefins from the C group₅- to C₁₀-Olefins with an MFI (230 ° C / 2.16 kg) of 40 to 80 g / 10 min and an ethylene content of 80 to 95 mol%, preferably from 90 to 95 mol%,

c) 5 to 20% by weight, preferably 8 to 15% by weight, of mineral fillers, optionally with the addition of 0 to 10% by weight, preferably 0 to 5% by weight of additives, are mixed and then shaped into molded parts.

The moldings obtained with the resin compositions according to the invention are distinguished not only by the improved surface properties but also, above all, by the fact that practically none

AT 408 885 B

Deterioration of the impact strength and rigidity properties occur. Another advantage is a lower thermal expansion, which maintains a constant gap between materials with different thermal expansion, for example when using resins for car bumpers, where the gap between the bumper and the subsequent metallic component remains practically constant even at different temperatures. An additional advantage of the resins according to the invention compared to those according to the prior art is an improved paint adhesion.

Examples

The following PP copolymers described in Table 1, analogous to the Daplen © types of PCD polymers, were used as component A. The PP consist of a PP homopolymer and an EPR phase and are preferably produced by Himont using the Spheripol process (The Global Polyolefins Industry: 1996, Vol 2, Technology and Economics, July 1996, 111-141 to 111-150 , Chem Systems).

Table 1: Component A

<td>component Type designation</td><td>Daplen ©</td><td>A1 C1008</td><td>A2 SVA 393</td><td>A3 SVA 357</td>

<td>MFI (230 / 2.16) - total</td><td>[g / 10min]</td><td> 5</td><td> 9</td><td> 20</td>

<td>Wt% ethylene - total</td><td>[Wt%]</td><td> 16,1</td><td> 10,9</td><td> 17</td>

<td>Mole percent propylene - total</td><td>[Mol%]</td><td> 77,7</td><td> 84,5</td><td> 76,5</td>

<td>Wt% EPR</td><td>[Wt%]</td><td> 32</td><td> 25</td><td> 37</td>

<td>η * / EPR</td><td>Pas</td><td> 3800</td><td> 7000</td><td> 1690</td>

<td>Weight fraction of ethylene / EPR</td><td>[Wt%]</td><td> 50,3</td><td> 43,6</td><td> 46,0</td>

*) dynamic viscosity at a temperature of 230 ° C and a shear rate of 1s'¹

The ethylene-octene (C₂-C₈) Copolymers of the Engage® type from Du Pont are used. For the comparative example, the Exxelor® VM 42 type from AES with an MFI of 0.5 g / 10 min was used. These PP copolymers are described, for example, in WO94 / 06859 as additives for improving the low-temperature impact strength.

Table 2: Component B

<td>Component B type designation</td><td></td><td>B1 Engage 8100</td><td>B2 Engage 8190</td><td>B3 Engage 8400</td><td>B4 Exxelor VM42</td>

<td>MFI (230 / 2.16)</td><td>[g / 10min]</td><td> 2</td><td> 2</td><td> 60</td><td> 0,5</td>

<td>density</td><td>[g / cm3]</td><td> 0,870</td><td> 0,859</td><td> 0,870</td><td> 0,890</td>

<td>Octene content</td><td>[Mol%]</td><td> 8,2</td><td> 10,9</td><td> 8,2</td><td> *)</td>

*) Ethylene-propylene-rubber masterbatch with 65 wt% EPR (contains 60 mol% ethylene)

As component C were

C1: Talc A7 from Naintsch, with d90 of 7 pm (90% of the particles have a diameter of less than 7 pm),

C2: Mica KG40 from Kemira Pigments Oy with d90 of 40 pm used.

Components A, B and C were each mixed with 3 parts by weight of black color masterbatch from Cabot and 1 part by weight of customary additives and processing aids in the amounts listed in Table 3 on a ZSK 40 twin-screw extruder from Werner and Pfleiderer at 225 ° C processed into compounds (resin masses).

AT 408 885 B

Table 3: Composition of the resin masses (in parts by weight)

<td></td><td>Component A</td><td>Component B</td><td>Component C</td>

<td>Ex. 1</td><td>75 A2</td><td>15 B3</td><td>10 C1</td>

<td>Ex. 2</td><td>81 A3</td><td>9B3</td><td>10 C1</td>

<td>Ex. 3</td><td>78 A3</td><td>12 B3</td><td>10 C2</td>

<td>See B.VB 4</td><td>82 A3</td><td>9B1</td><td>9C1</td>

<td>See B.VB 5</td><td>82 A3</td><td>9B2</td><td>9C1</td>

<td>See B.VBO</td><td>80 A1</td><td>10 B4</td><td>10 C1</td>

<td>See B.VB 7</td><td>80 A1</td><td>10 B1</td><td>10 C1</td>

The following properties were measured on the compounds:

MFI (meltflow index) according to DIN 53735 (or ASTM D1238) at 230 ° C / 2.16 kg,

Bending test according to DIN 53452/457,

Charpy U-notch according to DIN 53453,

Thermal linear expansion (LAK) according to DIN 53752.

The surface quality was determined visually on injection-molded plates and rated + and, where + means a good, streak-free surface and a poor, streaky surface.

The values ​​are summarized in Table 4.

Table 4: Properties of the compounds

<td></td><td>Upper area</td><td>LAK * [mm / mK]</td><td>SBV UK-40'C [kJ / m2]</td><td>Flexural modulus of elasticity [Mpa]</td><td>Bending stress [Mpa]</td><td>MFI (230 / 2.16) [g / 10min]</td>

<td>Ex.1</td><td> +</td><td> 90</td><td> 3,6</td><td> 1258</td><td> 26</td><td> 8</td>

<td>Example 2</td><td> +</td><td> 72</td><td> 4,8</td><td> 934</td><td> 20</td><td> 20</td>

<td>Example 3</td><td> +</td><td> 70</td><td> 4,9</td><td> 1173</td><td> 22</td><td> 13</td>

<td>See B.VB 4</td><td> -</td><td> 72</td><td> 6</td><td> 912</td><td> 20</td><td> 17</td>

<td>See B.VB 5</td><td> -</td><td> 72</td><td> 6</td><td> 984</td><td> 20</td><td> 17</td>

<td>See B.VB 6</td><td> -</td><td> 80</td><td> 6,2</td><td> 1017</td><td> 20</td><td> 13</td>

<td>See B.VB 7</td><td> -</td><td> 85</td><td> 6</td><td> 1061</td><td> 22</td><td> 12</td>

*) Coefficient of linear expansion between 23 and 80 ° C