Glass fiber reinforced polymer composition

Abstract

The present invention relates to a glass fiber reinforced polymer composition having excellent stiffness. The invention further relates to a method for obtaining such a composition, and to an article comprising such a composition.

Description

Technical Field

[0001] The present invention relates to glass fiber reinforced polymer compositions, processes for obtaining such compositions, and articles comprising such compositions. Background Art

[0002] Glass fiber reinforced polymer compositions are widely used in the automotive industry due to their processability and mechanical properties. For example, WO2011042364A1 discloses a fiber reinforced composition comprising a heterophasic propylene copolymer, a propylene homopolymer and / or a propylene copolymer and fibers, wherein the propylene copolymer contains not more than 2.0 wt% of C2 to C10 α-olefins other than propylene, the propylene homopolymer and the propylene copolymer have a melt flow rate MFR2 (230°C) of at least 500 g / 10 min, and the composition has a melt flow rate MFR2 (230°C) of at least 10 g / 10 min. The fiber reinforced composition has increased fluidity without sacrificing mechanical properties.

[0003] As the automobile industry develops, there is a greater desire for lightweight automobile parts, and thus a need exists for glass fiber reinforced polymer compositions having excellent stiffness without excessively high density. Summary of the invention

[0004] This need is met by a polymer composition comprising:

[0005] - polypropylene, wherein the polypropylene has a melting enthalpy in the first heating cycle in the range of 80 to 95 J / g, wherein the amount of polypropylene is in the range of 60 to 90 wt.-%, based on the total amount of the polymer composition;

[0006] - glass fibers, wherein the amount of the glass fibers is in the range of 10 to 35 wt. %, based on the total amount of the polymer composition.

[0007] Polypropylene

[0008] The polypropylene according to the present invention can be a propylene random copolymer, or a heterophasic propylene copolymer or a propylene homopolymer, preferably the polypropylene is a polypropylene homopolymer.

[0009] The polypropylene preferably has a melt flow rate (MFR) in the range of 50 to 150 g / 10 min, preferably 60 to 120 g / 10 min, as measured according to ISO 1133-1:2011 (2.16 Kg, 230°C).

[0010] The polypropylene according to this invention has a melting enthalpy in the first heating cycle in the range of 80 to 95 J / g, preferably in the range of 85 to 90 J / g.

[0011] The polypropylene according to this invention preferably has a melting enthalpy in the second heating cycle in the range of 90 to 110 J / g, preferably 95 to 105 J / g.

[0012] The polypropylene according to this invention preferably has a crystallization temperature in the range of 125 to 130 °C.

[0013] The melting enthalpy in the first heating cycle, the melting enthalpy in the second heating cycle and the crystallization temperature were determined in differential scanning calorimetry (DSC) with the following settings:

[0014] At a rate of 10°C / min,

[0015] ○First heating cycle:

[0016] ● Cool to -50℃ and keep isothermal for 1min;

[0017] Heat to 230°C and hold isothermal for 1 min (during heating, the melting enthalpy in the first heating cycle is determined);

[0018] ○ Second heating cycle

[0019] ● Cool to -50°C and hold isothermally for 1 min (during cooling, measure the crystallization temperature);

[0020] • Heat to 230°C and hold isothermally for 1 min (during heating, measure the melting enthalpy in the second heating cycle).

[0021] Surprisingly it was found that a polypropylene having a melting enthalpy in the first heating cycle within a preferred range and / or a melting enthalpy in the second heating cycle within a preferred range and / or a crystallization temperature within a preferred range leads to an even further improvement of the stiffness.

[0022] The polypropylene according to this invention can be produced with conventional polymerization techniques, like Unipol or Spheripol technology.

[0023] Catalysts for preparing polypropylene are also known in the art, such as Ziegler-Natta catalysts, metallocene catalysts. Preferably, the catalyst used to prepare the polypropylene of the present invention is a phthalate-free Ziegler-Natta catalyst, for example, the catalyst comprises a compound of an IUPAC Group 4 to 6 transition metal, a Group 2 metal compound and an internal electron donor, wherein the internal electron donor is a compound selected from the list consisting of substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates and derivatives and / or mixtures thereof, preferably, the internal electron donor is a citraconate.

[0024] Fiberglass

[0025] Glass fibers are widely used to improve the mechanical properties of polypropylene. The cross-section of the glass fibers is typically circular. Preferably, the glass fibers have an average diameter in the range of 11 to 16 μm, more preferably 12 to 14 μm. Surprisingly, it was found that glass fibers with an average diameter in the preferred range lead to an even further improvement in stiffness.

[0026] In a preferred embodiment, the glass fibers comprise up to 2 wt%, preferably in the range of 0.10 to 1 wt%, of a sizing agent based on the weight of the glass fibers. The amount of sizing agent can be determined using ISO 1887:2014.

[0027] Suitable examples of sizing compositions include solvent-based compositions, such as organic materials dissolved in aqueous solutions or dispersed in water, and melt-based or radiation-curable compositions. Preferably, the sizing composition is an aqueous sizing composition.

[0028] As described in the art, for example in documents EP 1 460 166 A1 , EP 0 206 189 A1 or US Pat. No. 4,338,233 , the aqueous sizing composition may comprise a coupling agent and other additional components.

[0029] Coupling agent is usually used to improve the adhesion between the matrix thermoplastic polymer and the fiber reinforcement. Suitable examples of coupling agents used for glass fiber known in the art include organofunctional silanes. More specifically, the coupling agent added to the sizing composition is aminosilane, such as aminomethyl-trimethoxysilane, N-(β-aminoethyl)-γ-aminopropyl-trimethoxysilane, γ-aminopropyl-trimethoxysilane, γ-methylaminopropyl-trimethoxysilane, δ-aminobutyl-triethoxysilane, 1,4-aminophenyl-trimethoxysilane. Preferably, the sizing composition contains aminosilane to achieve good adhesion to the thermoplastic matrix. The sizing composition may additionally include any other additional components suitable for the sizing composition known to those skilled in the art. Suitable examples include but are not limited to lubricants (for preventing damage to strands due to wear), antistatic agents, crosslinking agents, plasticizers, surfactants, nucleating agents, antioxidants, pigments and mixtures thereof.

[0030] The glass fibers preferably have an average length in the range of 0.1 to 1.5 mm, preferably 0.2 to 1.2 mm, more preferably 0.2 to 1.0 mm. The length of the dispersed fibers is reduced during the preparation of the polymer composition according to the present invention. In order to avoid any confusion, the length of the glass fibers in the present invention refers to the length of the glass fibers in the polymer composition.

[0031] The average length of the glass fibers can be obtained, for example, by incinerating the polymer composition, then manually spreading the glass fibers on a scanner using a brush and tweezers, and generating a digital image. A fully automatic image processing algorithm detects all glass fibers without manual input by an operator. 350,000 to 750,000 fiber lengths are detected to calculate the average fiber length.

[0032] Polymer composition

[0033] The polymer composition according to the present invention comprises:

[0034] - polypropylene, wherein the polypropylene has a melting enthalpy in the first heating cycle in the range of 80 to 95 J / g, wherein the amount of polypropylene is in the range of 60 to 90 wt.-%, preferably in the range of 65 to 75 wt.-%, based on the total amount of the polymer composition;

[0035] - glass fibers, wherein the amount of the glass fibers is in the range of 10 to 35 wt. %, preferably in the range of 25 to 34 wt. %, based on the total amount of the polymer composition.

[0036] The polymer composition according to the present invention preferably has a relative humidity of 1.10 to 1.20 g / cm 3 Density within the range as measured according to ISO 1183-1:2019.

[0037] Optionally, the polymer composition further comprises conventional additives, such as antioxidants, nucleating agents, UV stabilizers, etc. Preferably, the amount of additives is at most 5% by weight, preferably at most 3% by weight, based on the total amount of the polymer composition.

[0038] The present invention further relates to a process for preparing the polymer composition according to the invention, comprising the following sequential steps:

[0039] - providing polypropylene and glass fibers according to the present invention;

[0040] - Mixing of polypropylene and glass fibers in an extruder.

[0041] The invention further relates to an article comprising the polymer composition according to the invention, wherein the amount of polymer composition is in the range of 95 to 100 wt.-%, based on the total amount of the article. Preferably, the article is an automotive part, preferably an automotive exterior part.

[0042] Materials and sample preparation

[0043] PP1 is a homopolymer commercially available from SABIC with the grade name PP 595A. PP1 has an MFR of 47 dg / min as measured according to ISO 1133-1:2011 (2.16 Kg, 230°C).

[0044] PP2 is a homopolymer commercially available from Braskem with the grade name F1000HC. PP2 is a polypropylene according to the present invention. PP2 has an MFR of 115 dg / min as measured according to ISO 1133-1:2011 (2.16 Kg, 230°C).

[0045] SGF 1 refers to glass fiber with the grade designation T-480, commercially available from NEG, having an average diameter of 13 μm.

[0046] SGF 2 1 refers to glass fiber with the grade designation T-480H, commercially available from NEG, having an average diameter of 10 μm.

[0047] The additive package consisted of 50 wt% color concentrate, 40 wt% antioxidant, and 10 wt% anti-scratch agent based on the total weight of the additive package.

[0048] Examples were prepared by compounding the compositions in Table 1 in a twin-screw extruder, and then injection-molding them into samples for measurement.

[0049] Measurement

[0050] DSC was measured according to the following protocol:

[0051] - Seal the sample in a Tzero airtight aluminum pan (40 μl);

[0052] - Place the aluminum pan with the sample in a Q2000 DSC machine;

[0053] - Set the heating program on the DSC machine to: at a rate of 10°C / min,

[0054] ○First heating cycle:

[0055] ● Cool to -50℃ and keep isothermal for 1min;

[0056] ●Heat to 230°C and maintain isothermal temperature for 1 min (measure Tm1 and dHm during heating);

[0057] ○ Second heating cycle

[0058] ● Cool to -50°C and maintain isothermal temperature for 1 min (measure Tc1 and dHc during cooling);

[0059] ●Heat to 230°C and maintain isothermal temperature for 1 min (measure Tm2 and dHm2 during heating).

[0060] Density is measured according to ISO 1183-1:2019;

[0061] Flexural modulus was measured according to ISO178:2019(II);

[0062] HDT A is measured according to ISO 75-2:2013 / A flat method (L=1.8 MPa).

[0063] result

[0064] The thermal properties of PP1 and PP2 are shown in Table 1. Tm refers to melting temperature, dHm refers to melting enthalpy, Tc refers to crystallization temperature, dHc refers to crystallization enthalpy, and footnotes 1 and 2 refer to thermal cycles. The thermal properties of PP1 and PP2 are shown in Table 1.

[0065] Table 1

[0066] DSC PP 1 PP 2 Tm1℃ 165.2 167.6 dHm J / g 76.5 87.8 Tc1℃ 122.3 127.6 dHc J / g -95.0 -107.1 Tm2℃ 163.9 166.0 dHm2 J / g 86.3 99.0

[0067] The compositions of the examples and their properties are shown in Table 2.

[0068] Table 2

[0069] Composition / properties unit CE1 IE1 IE2 CE2 CE3 PP1 weight% 66.1 56.1 PP2 weight% 66.1 66.1 56.1 SGF 1 weight% 30 30 40 40 SGF 2 weight% 30 Additive Package weight% 3.9 3.9 3.9 3.9 3.9 density <![CDATA[g / cm 3 ]]> 1.14 1.14 1.14 1.24 1.24 Flexural modulus MPa 6491 7100 7031 9790 9800

[0070] By comparison between CE1 and IE1, it is obvious that the use of PP2 leads to improved flexural modulus, HDT; at higher amounts of glass fibers, CE2, CE3 show too high a density, and in the comparison of CE2 and CE3, there is no surprising effect of using PP2; by comparison between IE1 and IE2 using glass fibers with different average diameters, IE1 shows improved flexural modulus in the case of using glass fibers with high diameters.

Claims

1. A polymer composition comprising: - polypropylene, wherein the polypropylene has a melting enthalpy in the first heating cycle in the range of 80 to 95 J / g, wherein the amount of the polypropylene is in the range of 60 to 90 wt.-%, based on the total amount of the polymer composition; - glass fibers, wherein the amount of the glass fibers is in the range of 10 to 35 wt. %, based on the total amount of the polymer composition.

2. The polymer composition according to claim 1, wherein the polypropylene is a propylene homopolymer.

3. The polymer composition according to claim 1 or 2, wherein the polypropylene has a melt flow rate (MFR) in the range of 50 to 150 g / 10 min, preferably 60 to 120 g / 10 min, measured according to ISO 1133-1:2011 (2.16 Kg, 230°C).

4. The polymer composition according to any of the preceding claims, wherein the glass fibers have an average diameter in the range of 11 to 16 μm, preferably 12 to 14 μm.

5. The polymer composition according to any one of the preceding claims, wherein the amount of the polypropylene is in the range of 65 to 75 wt%, based on the total amount of the polymer composition.

6. The polymer composition according to any one of the preceding claims, wherein the amount of the glass fibers is in the range of 25 to 34 wt. %, based on the total amount of the polymer composition.

7. The polymer composition according to any one of the preceding claims, wherein the polymer composition has a density of 1.10 to 1.20 g / cm 3 Range, measured according to ISO 1183-1:2019.

8. The polymer composition according to any of the preceding claims, wherein the polypropylene has a melting enthalpy in the second heating cycle in the range of 90 to 110 J / g.

9. The polymer composition according to any of the preceding claims, wherein the polypropylene has a crystallization temperature in the range of 125 to 130°C.

10. A process for preparing a polymer composition according to any one of the preceding claims, comprising the following sequential steps: - providing the polypropylene and glass fiber; - Mixing said polypropylene and said glass fibers in an extruder.

11. An article comprising the polymer composition according to any one of claims 1 to 10, wherein the amount of the polymer composition is in the range of 95 to 100 wt. %, based on the total amount of the article.

12. The article according to claim 11, wherein the article is an automotive part, preferably an automotive exterior part.