Method for Recycling Epoxy-Fiber Composites into Polyolefins

Abstract

Fiber-reinforced thermoset composites are recycled by forming them into a particulate and combining the particles with a polyolefin to produce a reinforced polyolefin. A functionalized polyolefin is present in the reinforced material. The presence of the functionalized polyolefin leads to a significant increase in the reinforcing efficacy of the thermoset composite particles.

Claims

1. A filled polyolefin comprising: a) 30 to 90% by weight, based on the total weight of components a)-c), of an unfunctionalized polyolefin resin, the unfunctionalized polyolefin resin having dispersed therein; b) 10 to 60% by weight, based on the total weight of components a)-c), of a particulate fiber-reinforced thermoset composite, the particulate having a maximum particle size of 10 mm; and c) 1 to 50% by weight, based on the total weight of components a)-c), of a functionalized polyolefin.

2. The filled polyolefin of claim 1, wherein the unfunctionalized polyolefin resin is an unfunctionalized polypropylene.

3. The filled polyolefin of claim 1 wherein the functionalized polyolefin contains functional groups selected from carboxylic acid anhydride, imido, amino and hydroxyl groups, or a mixture of two or more thereof.

4. The filled polyolefin of claim 1 wherein the functionalized polyolefin contains functional groups selected from carboxylic acid anhydride, cyclic imido, N-hydroxyalkyl imido or N-aminoalkyl imido groups, or a mixture of two or more thereof.

5. The filled polyolefin of claim 1 wherein the functionalized polyolefin is a functionalized polypropylene.

6. The filled polyolefin of claim 1 wherein the functionalized polyolefin is a functionalized ethylene-alpha-olefin elastomer.

7. The filled polyolefin of claim 1 which contains 30 to 75% component a), 10 to 50% component b) and 5 to 20% of component c).

8. The filled polyolefin of claim 1 wherein the fiber-reinforced thermoset composite is a fiber-reinforced epoxy composite.

9. A method for recycling a fiber-reinforced thermoset composite, comprising the steps of: I. forming the fiber-reinforced thermoset composite into particles having a particle size of at most 10 mm; II. combining the particles from step I with a heat-softened unfunctionalized polyolefin resin and a functionalized polyolefin resin at a weight ratio of 30 to 90% by weight of the unfunctionalized polyolefin resin, 10 to 60% by weight of the particles; and 1 to 50% by weight of the functionalized polyolefin resin, to form a filled polyolefin resin comprising the heat-softened unfunctionalized polyolefin resin having the particles dispersed therein and the functionalized polyolefin resin dispersed or dissolved therein; and III. cooling the filled polyolefin resin from step II to solidify the filled polyolefin resin.

10. The method of claim 9 wherein the fiber-reinforced thermoset composite is a fiber-reinforced epoxy composite.

11. A method for reinforcing a polyolefin, comprising the steps of: A. combining a heat-softened unfunctionalized polyolefin resin with fiber-reinforced thermoset composite particles having a particle size of at most 10 mm and a functionalized polyolefin resin, at a weight ratio of 30 to 90% by weight of the unfunctionalized polyolefin resin, 10 to 60% by weight of the fiber-reinforced thermoset composite particles; and 1 to 50% by weight of the functionalized polyolefin, to form a filled polyolefin resin having the heat-softened polyolefin resin having the fiber-reinforced thermoset composite particles dispersed therein and the functionalized polyolefin dispersed or dissolved therein; and B. cooling the filled polyolefin resin from step A to solidify the filled polyolefin resin.

12. The method of claim 11 wherein the fiber-reinforced thermoset composite is a fiber-reinforced epoxy composite.

Description

EXAMPLES 1-4 AND COMPARATIVE SAMPLES A-C

[0062] A fiber-reinforced epoxy composite made by compression molding a commercially available sheet molding compound is chopped into particles having a size of less than 10 mm. The starting composite and resulting particles contain 33% by weight cured epoxy resin and 67% by weight carbon fibers.

[0063] Filled polyolefin Examples 1-4 and Comparative Sample A are made by combining an injection molding grade, 5 melt index unfunctionalized polypropylene resin and a functionalized polyolefin additive as indicated in Table 1 in a Haake mixer operated at 200° C. and 50 rpm. Once the polypropylene and additive have melted, the foregoing fiber-reinforced epoxy composite particles are added slowly under the same conditions and mixed into the molten materials for 5 minutes.

[0064] Comparative Samples B and C are commercially available glass-filled polypropylene samples containing 30% and 40% by weight, respectively, of long glass fibers. These are sold by Ticona Engineering Polymers as Celestran™ PP-GF30-02 and Celestran PP-GF40-02.

TABLE-US-00001 TABLE 1 Parts By Weight Comp. Ingredient Ex. 1 Ex. 2 Ex. 3 Ex. 4 A* Polypro- 60 60 60 60 70 pylene Composite 30 30 30 30 30 Particles.sup.1 Additive 10 10 10 10 0 Amount Additive MAH- Amine- MAH- Amine- None Type func- func- func- func- tional tional tional tional PP.sup.2 PP.sup.3 PE elas- PE elas- tomer.sup.4 tomer.sup.5 % Carbon 20 20 20 20 20 Fiber *Comparative. .sup.1Particles of the chopped fiber-reinforced epoxy composite. .sup.2A polypropylene copolymer modified with 0.25-0.5 wt.-% maleic anhydride (based on weight of the copolymer), having a density of 0.900 g/m3, melt flow index (190 °C., 2.16 kg) of 22 g/10 minutes, and a peak melting temperature of about 147 °C. .sup.3An amine-functional polypropylene copolymer made by reacting the MAH-functional polypropylene copolymer described in note 2 with diethylene diamine to produce N-substituted maleic imide groups in which the substituent contains a secondary amino group. .sup.4An ethylene/n-octene copolymer elastomer having a density of 0.87 g/cm3 and a melt flow index of 0.5 g/10 min (190 °C./2.16 kg), grafted with maleic anhydride. .sup.5An amine-functional ethylene/n-octene copolymer made by reacting a diamine with the MAH-functional PE elastomer of note 4, to produce N-substituted maleic imide groups in which the substituent contains a secondary amino group.

[0065] Specimens for tensile testing are made from each of Examples 1-4 and Comparative Samples A-C. In each case, the blends are compression molded at 200° C. for 5 minutes to form 1 mm sheets. Tensile strength at break, tensile modulus and elongation at break are measured in each case according to ASTM D638, using a 10 inch (25.4 cm) specimen, a 5 inch (12.7 cm) gauge length, hydraulic grips with a grip strength of about 2200 pounds (9800 N) and a 5 mm/minute head speed. Results are as indicated in Table 2.

TABLE-US-00002 TABLE 2 Tensile Tensile Sample Strength Elongation Modulus Designation (MPa) (%) (GPa) 1 50 1.65 4.65 2 43 1.3 4.45 3 22 1.05 3.1 4 22 1.15 3.0 A* 19 0.8 3.2 B* 19 0.75 2.8 C* 18 0.85 3.0 *Comparative

[0066] Comparative Sample A illustrates the effect of combining the particulate fiber-reinforced epoxy composite particles into polypropylene without the benefit of the functionalized polyolefin additive. Tensile strength, elongation and tensile modulus each are only similar to what is obtained with a glass-reinforced polypropylene (Comparative Samples B and C) despite the presence of stronger carbon fibers in place of the glass fibers of Comparative Samples B and C.

[0067] Examples 1 and 2 of the invention exhibit more than a doubling of tensile strength and nearly a 50% increase in tensile modulus, compared to Comparative Sample A, while simultaneously exhibiting an elongation increase of 50 to 100%. These examples demonstrate the strongly beneficial effect of the functionalized polypropylene additive.

[0068] Examples 3 and 4 show the effect of using a functionalized ethylene-octene copolymer as the additive. In these cases, tensile strength increases by about 15% over the control. This is surprising because of the elastomeric nature of the ethylene-octene copolymer. Ethylene-octene elastomers of this type are rubbery materials that are used as impact modifiers for polypropylene. As such, their inclusion would be expected to result in a decrease in tensile strength and in tensile modulus. Instead, tensile modulus is preserved and an increase in tensile strength is seen, while also obtaining an increase in impact strength. Examples 3 and 4 represent an approach to increasing the impact strength of polypropylene while preserving or even improving tensile properties.