Graft-modified polypropylene, fiber-reinforced composite material thereof and preparation method of fiber-reinforced composite material

Abstract

The invention belongs to the technical field of modified polypropylene, and provides graft modified polypropylene and a fiber reinforced composite material and a preparation method thereof. The preparation method of the graft modified polypropylene comprises the following steps: blending and granulating polypropylene and an antioxidant to obtain a polypropylene mixture, mixing an initiator and an auxiliary monomer to obtain an auxiliary monomer mixture, blending the polypropylene mixture, the auxiliary monomer mixture and vinyl acetate, and carrying out melt extrusion to obtain the graft modified polypropylene. On one hand, a proper auxiliary monomer is introduced, polypropylene macromolecular free radicals are stabilized through the auxiliary monomer, and the auxiliary monomer and vinyl acetate can be alternately copolymerized, so that degradation of polypropylene is inhibited, the grafting rate of polypropylene is increased, and a polypropylene graft with excellent mechanical properties is obtained; on the other hand, the antioxidant and the polypropylene are blended and granulated, so that the degradation degree of the polypropylene can be effectively reduced, and the melt index of the polypropylene graft is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of modified polypropylene, and in particular to a grafted modified polypropylene and a fiber-reinforced composite material thereof and a preparation method thereof. Background Art

[0002] Polypropylene (PP) is a thermoplastic material obtained by polymerization of propylene. It has excellent chemical resistance, heat resistance, electrical insulation, mechanical properties and processing properties, and has been widely used in many fields such as machinery, automobiles, electronic appliances, construction, textiles, packaging, agriculture, forestry, fishery and food industry. However, PP is a non-polar polymer with inherent disadvantages, such as poor hydrophilicity, adhesion, dyeability, antistatic properties, and even worse compatibility with polar polymers, which seriously restricts the further application of PP.

[0003] By modifying PP in different ways, the polarity of PP can be increased and its application range can be expanded. Common modification methods include additive modification, grafting modification, chemical crosslinking modification, etc. Among them, grafting modification, as an important means of polymer modification, has been widely used in the preparation of modified polypropylene materials. By modifying polypropylene by grafting, polypropylene materials with different functions can be obtained as needed, such as grafting elastic components to improve the brittleness of polypropylene; grafting polar components to improve the hydrophilicity and adhesion of polypropylene. At present, the most common grafting monomer is maleic anhydride. Chinese patent CN104804143A discloses a method for preparing maleic anhydride melt-grafted polypropylene, and styrene is added as an auxiliary monomer during the preparation process. Chinese patent CN101724128A discloses a method for preparing a maleic anhydride-grafted polypropylene resin graft, in which maleic anhydride is grafted onto the molecular chain of polypropylene resin by a melt free radical grafting reaction. In addition to adding maleic anhydride, an organic monomer containing two or more carbon-carbon double bonds is added as an auxiliary monomer. However, the main technical problem of melt grafting polypropylene is that it is difficult to obtain grafted polypropylene with high grafting rate and excellent mechanical properties due to the simultaneous existence of grafting and degradation of polypropylene.

[0004] Based on this, how to obtain grafted polypropylene with high grafting rate and excellent mechanical properties is the key to expanding the application field of PP. Summary of the invention

[0005] The object of the present invention is to provide a graft modified polypropylene and a fiber reinforced composite material thereof and a preparation method thereof in view of the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing graft modified polypropylene, comprising the following steps:

[0008] 1) Blending polypropylene and an antioxidant to form a granulated polypropylene mixture;

[0009] 2) mixing the initiator and the auxiliary monomer to obtain an auxiliary monomer mixture;

[0010] 3) The polypropylene mixture, the auxiliary monomer mixture and vinyl acetate are blended and melt-extruded to obtain graft-modified polypropylene.

[0011] Preferably, the antioxidant in step 1) is one or more of antioxidant 1010, antioxidant CA, diisooctyl phosphite and dilauryl thiodipropionate;

[0012] The mass ratio of the polypropylene to the antioxidant is 100:0.1-1, the temperature of the blending and granulation is 180-220° C., and the particle size of the polypropylene mixture is 0.5-2 mm.

[0013] Preferably, the initiator in step 2) is a peroxide initiator, and the auxiliary monomer is one or more of styrene, acrylonitrile and allyl chloride;

[0014] The mass ratio of the initiator, the auxiliary monomer and the polypropylene in step 1) is 1-3:10-20:100.

[0015] Preferably, the mass ratio of the vinyl acetate in step 3) to the polypropylene in step 1) is 15-25:100, the temperature of the melt extrusion is 180-220° C., and the rotation speed of the melt extrusion is 80-100 rpm.

[0016] The invention also provides graft-modified polypropylene prepared by the preparation method.

[0017] The present invention also provides a fiber-reinforced composite material comprising the graft-modified polypropylene. The fiber-reinforced composite material comprises the following raw materials in mass fractions: 50-70% of recycled fiber and 30-50% of graft-modified polypropylene.

[0018] Preferably, the recycled fiber comprises one or more of polyester fiber, nylon fiber and polypropylene fiber.

[0019] The present invention also provides a method for preparing a fiber-reinforced composite material comprising the graft-modified polypropylene, comprising the following steps:

[0020] Waste clothes or fabrics are defibrated to obtain recycled fibers; the recycled fibers are blended with grafted modified polypropylene and melt-extruded to obtain a fiber-reinforced composite material containing grafted modified polypropylene.

[0021] Preferably, the temperature of the melt extrusion is 130-150° C., and the rotation speed of the melt extrusion is 200-300 rpm.

[0022] Beneficial effects of the present invention:

[0023] On the one hand, the present invention introduces a suitable auxiliary monomer to stabilize the polypropylene macromolecular free radicals through the auxiliary monomer, so that the auxiliary monomer and vinyl acetate can be alternately copolymerized, thereby inhibiting the degradation of polypropylene, improving the grafting rate of polypropylene, and obtaining a polypropylene graft with excellent mechanical properties; on the other hand, the antioxidant is first blended with the polypropylene for granulation, which can also effectively reduce the degradation degree of the polypropylene and reduce the melt index of the polypropylene graft. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing graft modified polypropylene, comprising the following steps:

[0025] 1) Blending polypropylene and an antioxidant to form a granulated polypropylene mixture;

[0026] 2) mixing the initiator and the auxiliary monomer to obtain an auxiliary monomer mixture;

[0027] 3) The polypropylene mixture, the auxiliary monomer mixture and vinyl acetate are blended and melt-extruded to obtain graft-modified polypropylene.

[0028] In the present invention, the polypropylene in step 1) preferably comprises one or more of homopolymer polypropylene, block copolymer polypropylene and random copolymer polypropylene.

[0029] In the present invention, the antioxidant in step 1) is preferably one or more of antioxidant 1010, antioxidant CA, diisooctyl phosphite and dilauryl thiodipropionate;

[0030] The mass ratio of the polypropylene to the antioxidant is preferably 100:0.1-1, more preferably 100:0.3-0.8, and more preferably 100:0.5; the temperature of the blending and granulation is preferably 180-220°C, more preferably 190-210°C, and more preferably 200°C; the particle size of the polypropylene mixture is preferably 0.5-2 mm, and more preferably 1-1.5 mm.

[0031] In the present invention, the initiator in step 2) is preferably a peroxide initiator, and the auxiliary monomer is preferably one or more of styrene, acrylonitrile and allyl chloride;

[0032] The mass ratio of the initiator, the auxiliary monomer and the polypropylene in step 1) is preferably 1-3:10-20:100, more preferably 1.5-2.5:13-18:100, and more preferably 2:15:100.

[0033] In the present invention, the peroxide initiator preferably comprises one or more of di-tert-butyl peroxide diisopropylbenzene, tert-butyl peroxide isopropylbenzene, tert-butyl peroxylaurate, benzoyl peroxide, tert-butyl peroxyacetate, diisopropylbenzene peroxide, tert-butyl peroxybenzoate and di-tert-butyl peroxide.

[0034] In the present invention, the mass ratio of the vinyl acetate in step 3) to the polypropylene in step 1) is preferably 15-25:100, more preferably 18-22:100, and more preferably 20:100; the temperature of the melt extrusion is preferably 180-220°C, more preferably 190-210°C, and more preferably 200°C; the rotation speed of the melt extrusion is preferably 80-100rpm, more preferably 85-95rpm, and more preferably 90rpm.

[0035] The invention also provides graft-modified polypropylene prepared by the preparation method.

[0036] The present invention also provides a fiber-reinforced composite material comprising the graft-modified polypropylene. The fiber-reinforced composite material comprises the following raw materials in mass fractions: 50-70% of recycled fiber and 30-50% of graft-modified polypropylene.

[0037] In the present invention, the recycled fiber preferably comprises one or more of polyester fiber, nylon fiber and polypropylene fiber.

[0038] The present invention also provides a method for preparing a fiber-reinforced composite material comprising the graft-modified polypropylene, comprising the following steps:

[0039] Waste clothes or fabrics are defibrated to obtain recycled fibers; the recycled fibers are blended with grafted modified polypropylene and melt-extruded to obtain a fiber-reinforced composite material containing grafted modified polypropylene.

[0040] In the present invention, it is preferred that the recycled fibers are made into continuous fibers, and then the continuous fibers are blended with the graft-modified polypropylene and melt-extruded.

[0041] In the present invention, the method of converting the recycled fibers into continuous fibers is preferably not limited to blending, twisting, warp knitting, etc.

[0042] In the present invention, the temperature of the melt extrusion is preferably 130-150°C, more preferably 135-145°C, and more preferably 140°C; the rotation speed of the melt extrusion is preferably 200-300 rpm, more preferably 230-280 rpm, and more preferably 250 rpm.

[0043] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0044] Example 1

[0045] 100 kg of homopolymer polypropylene particles (molecular weight of 20,000 Da) and 0.5 kg of antioxidant 1010 were mixed and placed in a twin-screw extruder. They were blended and granulated at 200°C to obtain a polypropylene mixture with a particle size of 0.5 mm. 2 kg of benzoyl peroxide and 15 kg of styrene were mixed to obtain an auxiliary monomer mixture. 20 kg of vinyl acetate, polypropylene mixture and auxiliary monomer mixture were mixed and fed into a twin-screw extruder. They were extruded at 200°C and 90 rpm to obtain grafted modified polypropylene.

[0046] Example 2

[0047] 100 kg of homopolymer polypropylene particles (molecular weight of 20,000 Da) and 0.1 kg of diphenyl isooctyl phosphite were mixed and placed in a twin-screw extruder. The mixture was blended and granulated at 220°C to obtain a polypropylene mixture with a particle size of 1 mm. 3 kg of tert-butyl peroxybenzoate and 20 kg of acrylonitrile were mixed to obtain an auxiliary monomer mixture. 15 kg of vinyl acetate, polypropylene mixture and auxiliary monomer mixture were mixed and fed into a twin-screw extruder. The mixture was extruded at 180°C and 100 rpm to obtain grafted modified polypropylene.

[0048] Example 3

[0049] 100 kg of homopolymer polypropylene particles (molecular weight of 20,000 Da) and 1 kg of dilauryl thiodipropionate were mixed and placed in a twin-screw extruder. The mixture was blended and granulated at 180°C to obtain a polypropylene mixture with a particle size of 2 mm. 1 kg of diisopropylbenzene peroxide and 10 kg of allyl chloride were mixed to obtain an auxiliary monomer mixture. 25 kg of vinyl acetate, polypropylene mixture and auxiliary monomer mixture were mixed and fed into a twin-screw extruder. The mixture was extruded at 220°C and 80 rpm to obtain grafted modified polypropylene.

[0050] Example 4

[0051] 100 kg of homopolymer polypropylene particles (molecular weight of 20,000 Da) and 0.3 kg of antioxidant CA were mixed and placed in a twin-screw extruder. They were blended and granulated at 210°C to obtain a polypropylene mixture with a particle size of 1.5 mm. 1.5 kg of di-tert-butyl peroxide and 13 kg of styrene were mixed to obtain an auxiliary monomer mixture. 18 kg of vinyl acetate, polypropylene mixture and auxiliary monomer mixture were mixed and fed into a twin-screw extruder. They were extruded at 190°C and 95 rpm to obtain grafted modified polypropylene.

[0052] Comparative Example 1

[0053] The styrene in Example 1 is omitted, and the rest is the same as in Example 1.

[0054] Comparative Example 2

[0055] The acrylonitrile in Example 2 is omitted, and the rest is the same as Example 2.

[0056] Comparative Example 3

[0057] The styrene in Example 1 was replaced by methyl acrylate, and the rest was the same as Example 1.

[0058] Comparative Example 4

[0059] The acrylonitrile in Example 2 was replaced by glycidyl acrylate, and the rest was the same as Example 2.

[0060] The grafting rates and melt indices of the graft-modified polypropylenes of Examples 1 to 4 and Comparative Examples 1 to 4 were measured respectively. The test results are shown in Table 1.

[0061] The grafting rate of graft-modified polypropylene was determined by infrared spectroscopy.

[0062] The melt index of grafted modified polypropylene was determined according to GB / T 3682.1-2018.

[0063] Table 1 Grafting rate and melt index of graft-modified polypropylene

[0064]

[0065] Application Example 1

[0066] The waste polyester fabric was washed and dried, and mechanically defibrated to obtain recycled polyester fibers; 60 kg of the recycled polyester fibers and 40 kg of the grafted modified polypropylene prepared in Example 1 were mixed, fed into a twin-screw extruder, and melt-extruded at 140° C. at a rotation speed of 200 rpm to obtain a fiber-reinforced composite material containing the grafted modified polypropylene.

[0067] Application Example 2

[0068] The graft modified polypropylene in Application Example 1 is replaced by the graft modified polypropylene obtained in Example 2, and the rest is the same as Application Example 1.

[0069] Application Example 3

[0070] The graft modified polypropylene in Application Example 1 was replaced by the graft modified polypropylene obtained in Example 3, and the rest was the same as Application Example 1.

[0071] Application Example 4

[0072] The graft modified polypropylene in Application Example 1 is replaced by the graft modified polypropylene obtained in Example 4, and the rest is the same as Application Example 1.

[0073] Application Example 5

[0074] The waste polyester fabric was washed and dried, and mechanically defibrated to obtain recycled polyester fibers; the recycled polyester fibers were twisted to obtain continuous polyester fibers (twist of 80 twists / 10 cm); 60 kg of the continuous polyester fibers and 40 kg of the grafted modified polypropylene obtained in Example 1 were mixed, extruded through an extruder at 140° C. and 250 rpm, and then naturally cooled to room temperature to obtain a fiber-reinforced composite plate containing the grafted modified polypropylene.

[0075] The tensile strength and elongation at break of the fiber reinforced composite materials containing grafted modified polypropylene prepared in Application Examples 1 to 5 were tested in accordance with GB / T 1040.1-2018. The test results are shown in Table 2.

[0076] Table 2 Tensile strength and elongation at break of fiber reinforced composites

[0077] Application Example 1 Application Example 2 Application Example 3 Application Example 4 Application Example 5 Tensile strength / MPa 40.35 42.68 38.96 45.12 44.97 Elongation at break / % 9.72 9.25 10.36 8.78 9.03

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing graft modified polypropylene, characterized in that: The following steps are included: 1) Blending polypropylene and an antioxidant to form a granulated polypropylene mixture; 2) mixing the initiator and the auxiliary monomer to obtain an auxiliary monomer mixture; 3) The polypropylene mixture, the auxiliary monomer mixture and vinyl acetate are blended and melt-extruded to obtain graft-modified polypropylene.

2. The preparation method according to claim 1, characterized in that: Step 1) the antioxidant is one or more of antioxidant 1010, antioxidant CA, diphenyl isooctyl phosphite and dilauryl thiodipropionate; The mass ratio of the polypropylene to the antioxidant is 100:0.1-1, the temperature of the blending and granulation is 180-220° C., and the particle size of the polypropylene mixture is 0.5-2 mm.

3. The preparation method according to claim 1 or 2, characterized in that: Step 2) the initiator is a peroxide initiator, and the auxiliary monomer is one or more of styrene, acrylonitrile and allyl chloride; The mass ratio of the initiator, the auxiliary monomer and the polypropylene in step 1) is 1-3:10-20:

100.

4. The preparation method according to claim 3, characterized in that: The mass ratio of the vinyl acetate in step 3) to the polypropylene in step 1) is 15-25:100, the temperature of the melt extrusion is 180-220° C., and the rotation speed of the melt extrusion is 80-100 rpm.

5. The graft-modified polypropylene prepared by the preparation method according to any one of claims 1 to 4.

6. A fiber-reinforced composite material comprising the graft-modified polypropylene according to claim 5, characterized in that: The fiber-reinforced composite material comprises the following raw materials in mass fractions: 50-70% of recycled fiber and 30-50% of graft-modified polypropylene.

7. The fiber-reinforced composite material according to claim 6, characterized in that: The recycled fiber includes one or more of polyester fiber, nylon fiber and polypropylene fiber.

8. The method for preparing the fiber-reinforced composite material comprising the graft-modified polypropylene according to claim 6 or 7, characterized in that: The following steps are included: Waste clothes or fabrics are defibrated to obtain recycled fibers; the recycled fibers are blended with grafted modified polypropylene and melt-extruded to obtain a fiber-reinforced composite material containing grafted modified polypropylene.

9. The preparation method according to claim 8, characterized in that: The temperature of the melt extrusion is 130-150° C., and the rotation speed of the melt extrusion is 200-300 rpm.

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