DE19754061A1 - Propylene copolymer-based resin composition for forming molded articles of improved surface condition - Google Patents

Abstract

A propylene copolymer-based resin composition for molded articles with improved surface condition includes ethylene/ alpha -olefin copolymers of specific ethylene content and MFR. A resin composition comprises: (a) propylene copolymers, with a 2-4C alpha -olefin(s), of propylene content 70-99.5 (75-90) mol.% and MFI (230 deg C/2.16 kg) 1-25 (3-20) g/10 mins.; (b) ethylene copolymers, with a 5-10C alpha -olefin(s), of ethylene content 80-95 (90-95) mol.% and MFI (230 deg C/2.16 kg) 6-100 g/10 minutes; (c) mineral fillers; and optionally (d) additives. Independent claims are included for the preparation of the above resin composition by mixing the components and a process for improving the surface condition of molded articles involving mixing the above propylene copolymers with ethylene copolymers.

Description

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

When using filled PP resin compounds, especially for large areas Molded parts, for example for use in bumpers or for other injection molding, Pressed or extruded parts, such as. B. for dashboards, center consoles for Motor vehicles etc. have the disadvantage that due to the long flow paths all optical irregularities, especially flow markings ("tiger skin") the surface of the molded parts, but also other impairments of the Surface such as B. roughness, poor uniformity, streaks, etc. occur. According to DE-PS 38 21 075 filled resin masses 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) from 0.1 to 5 g / 10 min. According to EP-A-132,968, the MFI of the ethylene random copolymer phase at 0.1 to 2 g / 10 min. These resin masses however, also have the disadvantage of poor, as described above Surfaces of the molded parts, especially flow marks.

It was therefore the task of resin compositions (resin compositions) find, above all, a good surface quality, especially none Show flow markings, and still good, still tolerable mechanical Show properties, in particular good impact strength and good rigidity.

The task could be solved by using special resin compounds based on propylene copolymers and ethylene copolymers with high MFI being found.

The invention accordingly relates to a resin composition consisting of

• a) polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -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) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min (component A),
• b) ethylene copolymers with one or more α-olefins from the group of the C ₅ - to C ₁₀ -olefins with an MFI (230 ° C / 2.16 kg) from 6 to 100 g / 10 min, preferably from 40 to 80 g / 10 min and an ethylene content of 80 to 95 mol%, preferably 90 to 95 mol% (component B),
• c) mineral fillers (component C),
• d) optionally additives.

In addition to the essential components A, B, C according to the invention, the Resin composition optionally further additives (d), such as. B. stabilizers, for example, heat, UV or processing stabilizers, pigments, for example color pigments or carbon black, lubricants, processing aids, Mold release agents, nucleating agents, antistatic agents or flame retardants.

Another object of the invention is the above-mentioned resin composition for Manufacture of molded parts with improved surface properties, especially with negligible flow marks. Draw the moldings but overall by better surface properties and better optics from such. B. low streakiness, low surface roughness, good Uniformity, little difference in gloss.

The resin compositions according to the invention preferably contain

• a) 65 to 90 wt .-%, particularly preferably 75 to 80 wt .-% polypropylene Copolymers,
• b) 5 to 20% by weight, particularly preferably 8 to 15% by weight, of ethylene copolymers,
• c) 5 to 20% by weight, preferably 8 to 15% by weight, of fillers,
• d) 0 to 10% by weight, preferably 0 to 5% by weight of additives.

Particularly good surface properties are achieved in the case of moldings which are produced from resin compositions whose component A is composed of heterophasic propylene-ethylene copolymers (block copolymers), a PP homopolymer phase or PP random copolymer phase (statistical PP copolymer phase) and one Ethylene propylene rubber (EPR) copolymer phase included. These resin compositions in component A preferably contain 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, for example from Rheometrix RDS-2 at 230 ° C. and a shear rate of 1 s ^-1 ) have proven to be particularly advantageous. 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 further preferred. The ethylene content preferred here 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 / cm ³ .

Mineral fillers include all that can be used in polyolefin technology Fillers in question, for example talc, mica, chalk, wollastonite. Prefers are anisotropic fillers such as B. talc, mica and wollastonite. The fillers have an average particle size of preferably 1 to 60 μm, particularly preferably from 3 to 30 μm.

Another object of the invention is the use of the resin composition according to the invention, which consists essentially of

• a) polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -olefins and a propylene content of 70 to 99.5 mol%, preferably from 75 to 90 mol%,
• b) ethylene copolymers with one or more α-olefins from the group of the C ₅ - to C ₁₀ -olefins with an MFO (230 ° C / 2.16 kg) of 6 to 100 g / 10 min and an ethylene content of 80 up to 95 mol%, preferably from 90 to 95 mol%,
• c) mineral fillers,
• d) optionally additives

exists for the production of molded parts with improved surface properties.

The invention further relates to the use of ethylene copolymers with one or more α-olefins from the group of the C ₅ to C ₁₀ 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 90 to 95 mol%, as an additional component to polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ - 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) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min, which contain mineral fillers and optionally additives, to improve the surface properties of molded parts, and a process for improving the surface properties of molded parts made of polypropylene copolymers with one or more α-olefins from the group of the C ₂ and C ₄ to C ₁₀ 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) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min, which contain mineral fillers and optionally additives, characterized in that these Polypropylenes with ethylene copolymers with one or more α-olefins from the group of the C ₅ to C ₁₀ 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% are mixed.

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

• a) polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -olefins, 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 the C ₅ to C ₁₀ 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% and
• c) mineral fillers,

if necessary with the addition of additives, mixed and then to form parts to be molded.

The molded parts obtained with the resin compositions according to the invention stand out in addition to the improved surface quality, especially from the fact that practically no deterioration in the impact and stiffness properties occur. Another advantage is a lower thermal linear expansion, creating a constant gap between materials with different thermal expansion is retained, for example when using the resins for automotive bumpers where the gap between the bumper and subsequent metallic component even at different temperatures remains practically constant. An additional advantage of the resins of the invention Compared to those according to the prior art lies in an improved paint adhesion.

Examples

As component A, the following were described in Table 1 PP copolymers, analogous to the Daplen® types of PCD polymers, are used. The PP consist of a PP homopolymer and an EPR phase and are preferred manufactured by Himont's Spheripol process (The Global Polyolefins Industry: 1996, Vol 2, Technology and Economics, July 1996, III-141 to III-150, Chem Systems).

Table 1

Component A

As component B, the ethylene-octene (C ₂ -C ₈ ) copolymers of the type Engage® from Du Pont described in Table 2 were used. The type Exxelor® VM 42 from AES with an MFI of 0.5 g / 10 min was used for the comparative example. These PP copolymers are described, for example, in WO 94/06859 as additives for improving the low-temperature impact strength.

Table 2

Component B

As component C.
C1: talc A7 from Naintsch, with d90 of 7 µm (90% of the particles have a diameter of less than 7 µm),
C2: Mica KG40 from Kemira Pigments Oy with d90 of 40 µm used.

Components A, B and C were together with 3 parts by weight each Color masterbatch black from Cabot and 1 part by weight of conventional additives and Processing aids in the amounts listed in Table 3 on a ZSK 40 Twin screw extruders from Werner and Pfleiderer at 225 ° C to form compounds (Resin masses) processed.  

Table 3

Composition of the resin masses (in parts by weight)

The following properties were measured on the compounds:
MFI (melt flow 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 DlN 53453,
Thermal linear expansion (LAK) according to DIN 53 752.

The surface condition was visualized on injection molded plates determined and rated with "+" and "-", with "+" a good, streak-free surface and "-" means an imperfect, streaky surface.

The values are summarized in Table 4.  

Table 4

Properties of the compounds

Claims (15)

1. Resin composition consisting of

• a) polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -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) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min,
• b) ethylene copolymers with one or more α-olefins from the group of the C ₅ to C ₁₀ olefins with an MFI (230 ° C / 2.16 kg) of 6 to 100 g / 10 min and an ethylene content of 80 up to 95 mol%, preferably from 90 to 95 mol%,
• c) mineral fillers
• d) optionally additives.

2. Resin composition consisting of

• a) polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -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) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min,
• b) ethylene copolymers with one or more α-olefins from the group of the C ₅ to C ₁₀ olefins with an MFI (230 ° C / 2.16 kg) of 6 to 100 g / 10 min and an ethylene content of 80 up to 95 mol%, preferably from 90 to 95 mol%,
• c) mineral fillers
• d) optionally additives
  for the production of molded parts with improved surface properties.

3. Resin composition according to claim 1 or 2, consisting of

• a) 65 to 90% by weight, particularly preferably 75 to 80% by weight, of polypropylene copolymers,
• b) 5 to 20% by weight, particularly preferably 8 to 15% by weight, of ethylene copolymers,
• c) 5 to 20% by weight, preferably 8 to 15% by weight, of fillers,
• d) 0 to 10 wt .-%, preferably 0 to 5 wt .-% additives.

4. Resin composition according to one of claims 1 to 3, wherein the ethylene copolymers (b) have an MFI of 40 to 80 g / 10 min. 5. Resin composition according to one of claims 1 to 4, wherein as component (a) heterophasic propylene-ethylene copolymers consisting of one Polypropylene (PP) homopolymer or random copolymer phase and one Ethylene-propylene-rubber (EPR) copolymer phase. 6. The resin composition according to claim 5, wherein component (a) is a EPR copolymer content of 20 to 45 wt .-%, preferably from 25 to 32 wt .-%. 7. Resin composition according to claim 5 or 6, wherein the EPR copolymer portion at a temperature of 230 ° C and a shear rate of 1 s ^{-1 has} a viscosity of less than 2000 Pas. 8. Resin composition according to one of claims 5 to 7, wherein the EPR copolymer content an ethylene content of 30 to 50% by weight, preferably 30 to 45% by weight having. 9. Resin composition according to one of claims 1 to 8, wherein component (b) is an ethylene copolymer with a C ₆ - to C ₈ comonomer. 10. Resin composition according to one of claims 1 to 9, wherein component (b) has a density of 0.86 to 0.88 g / cm ³ . 11. Resin composition according to one of claims 1 to 10, wherein an anisotropic, mineral filler, preferably from the group consisting of talc Mica or wollastonite is used. 12. Use of a resin composition according to one of claims 1 to 11, consisting of

• a) polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -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) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min,
• b) ethylene copolymers with one or more α-olefins from the group of the C ₅ to C ₁₀ olefins with an MFI (230 ° C / 2.16 kg) of 6 to 100 g / 10 min and an ethylene content of 80 up to 95 mol%, preferably from 90 to 95 mol%,
• c) mineral fillers
• d) optionally additives
  for the production of molded parts with improved surface properties.

13. Use of ethylene copolymers with one or more α-olefins from the group of the C ₅ - to C ₁₀ -olefins with an MFI (230 ° C / 2.16 kg) of 6 to 100 g / 10 min and an ethylene content from 80 to 95 mol%, preferably from 90 to 95 mol%, as an additional component to polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -olefins, with a propylene content from 70 to 99.5 mol%, preferably from 75 to 90 mol% and an MFI (230 ° C./2.16 kg) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min, containing mineral fillers and additives, if necessary, to improve the surface properties of molded parts. 14. Process for improving the surface quality of molded parts made of polypropylene copolymers with one or more α-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -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) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min, which contain mineral fillers and optionally additives, characterized in that these polypropylenes with ethylene copolymers with one or more α-olefins from the group of the C ₅ to C ₁₀ 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%, are mixed. 15. A process for the production of moldings with improved surface finish, characterized in that

• a) polypropylene copolymers with one or more (i-olefins from the group of the C ₂ - and C ₄ - to C ₁₀ -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) from 1 to 25 g / 10 min, preferably from 3 to 20 g / 10 min
• b) ethylene copolymers with one or more α-olefins from the group of the C ₅ to C ₁₀ 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% and
• c) mineral fillers
  if necessary with the addition of additives, mixed and then molded into shaped parts.