Modified polyolefin elastomer foam material and preparation method thereof

Abstract

The invention relates to the technical field of polyolefin elastomers, and discloses a modified polyolefin elastomer foam material and a preparation method thereof.After a quaternary ammonium salt antistatic agent and polyolefin macromolecules are subjected to melt grafting, a layer of directional arrangement with outward hydrophilic groups is formed on the surface of the polyolefin macromolecules, and a permeation network with electric conduction capacity is formed; the electrostatic elimination effect is good; the polyolefin elastomer and the diolefin-containing antistatic agent are subjected to melt grafting in a twin-screw extruder by adopting reactive extrusion, so that the crosslinking sites and density are increased, and the strength of the crosslinked melt is obviously improved; the fluorine-containing polymer has the advantages of low surface energy, high thermal stability and the like, and the more fluorine atoms connected to the same carbon atom are, the more stable the fluorine atoms are, so that the thermal deformation temperature of the material is increased; the proportion of the foaming aid is adjusted, so that cells of the polyolefin foaming material have high cell closing property, and the polyolefin foaming material has excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of polyolefin elastomers, and specifically to a modified polyolefin elastomer foaming material and a preparation method thereof. Background Art

[0002] Polyolefin elastomer is a commonly used material produced by random copolymerization of α-olefins, ethylene, etc., and has excellent physical and mechanical properties. There is no carbon-carbon double bond in the polyolefin elastomer molecule, and this special structure endows the foaming material with good resilience, aging resistance and other functions, and is widely used in transportation tools. However, polyolefin elastomer has good electrical insulation, and static electricity is easily generated and accumulated during transportation and use, and static electricity may cause fires or even explosions. Therefore, it is necessary to carry out antistatic treatment on it to eliminate the harm of static electricity.

[0003] The surface of polyolefin foaming material is easily attached with fine particles such as dust due to the action of static electricity, which not only affects the apparent quality of the product but also damages the parts of precision instruments. Therefore, the antistatic modification of polyolefin elastomer foaming material has attracted the attention of many scholars. At present, the methods for antistatic modification of plastics include the surface method, that is, electroplating coating and other methods are used on the surface of plastic products to form a conductive layer on the surface of the products. However, this method has high cost, large pollution, and it is difficult to process products with complex shapes; there is also a method of preparing conductive polyolefin materials by compounding polyolefin with various conductive substances in a certain way, which can improve the conductive performance of the composite material. The way to increase the conductive performance is generally to solve by increasing the amount of conductive substances. However, increasing the amount of conductive materials will reduce the mechanical properties of the composite material on the one hand, and increase the cost on the other hand; there is also a method of fixing an adhesive resin containing an antistatic agent and other modifiers on the surface of polyolefin resin foaming particles to obtain functional polyolefin resin foaming particles. However, it is necessary to melt on the surface of polyolefin resin foaming particles and cover the adhesive resin containing the modifier, resulting in an increase in the cost in terms of productivity and equipment.

[0004] The present invention prepares a modified polyolefin elastomer foaming material with better antistatic effect and excellent foaming performance by synthesizing a bis-olefin-containing trifluoromethyl quaternary ammonium salt antistatic agent, melt-grafting it with polyolefin elastomer, and then carrying out compression molding and foaming. The process is simple and has strong operability. Summary of the Invention

[0005] (1) Technical Problems to be Solved Aiming at the deficiencies of the prior art, the present invention provides a modified polyolefin elastomer foaming material and a preparation method thereof, which solve the problem that static electricity is easily generated during the use of polyolefin elastomer.

[0006] (2) Technical Solutions A preparation method of a modified polyolefin elastomer foaming material, the preparation method comprising the following steps: (1) Dry the polyolefin elastomer at 25 - 35°C for 2 - 4 h, add a bis-olefin-containing trifluoromethyl quaternary ammonium salt antistatic agent and initiator BPO, and stir evenly in a high-speed mixer to obtain a premix. Then add the premix to a twin-screw extruder through a barrel. The temperature of the first zone of the extruder is 70 - 80°C, the second zone is 80 - 90°C, the third zone is 110 - 120°C, the temperature of the fourth zone is 120 - 130°C, the fifth zone is 90 - 100°C, the sixth zone is 130 - 140°C, and the head temperature is 145 - 155°C. At a screw rotation speed of 120 - 140 r / min, a modified polyolefin elastomer material is obtained.

[0007] (2) Add the modified polyolefin elastomer material, foaming agent azodicarbonamide, vulcanizing agent DCP, foaming aid calcium stearate, and zinc stearate to a mixer, mix at high speed for 5 - 25 min, then knead on a two-roll mill with a roll temperature of 120 - 140°C for 5 - 20 min, and then vulcanize on a flat vulcanizer at a vulcanization temperature of 160 - 190°C for 10 - 20 min. Carry out mold pressing and foaming under a mold pressing pressure of 12 - 16 MPa to obtain a modified polyolefin elastomer foamed material.

[0008] Further, the mass ratio of each reactant in step (1) is: polyolefin elastomer : bis-olefin-containing trifluoromethyl quaternary ammonium salt antistatic agent : BPO = 100 : 5 - 25 : 0.1 - 0.3.

[0009] Further, the mass ratio of each foaming component in step (2) is: modified polyolefin elastomer material : azodicarbonamide : DCP : calcium stearate : zinc stearate = 100 : 2 - 6 : 0.6 - 1.5 : 3 - 5 : 1 - 2.

[0010] Further, the preparation method of the bis-olefin-containing trifluoromethyl quaternary ammonium salt antistatic agent includes the following steps: (3) Add 1,4-butanediol diacrylate and ethanol to a three-necked flask, stir and dilute. Weigh dimethylamine and dissolve it in ethanol, stir evenly and then drop it into the three-necked flask, and react at 20 - 35°C for 4 - 8 h. After the reaction, purify by column chromatography with methanol and ethyl acetate to obtain 4-(2-dimethylamino)acetoxybutyl acrylate. The preparation process is as follows:

[0011] (4) Add epichlorohydrin, 2-(trifluoromethyl)acrylic acid, catalyst triphenylphosphine, and inhibitor p-methoxyphenol to a three-necked flask, stir evenly, then raise the temperature for reaction. After the reaction, carry out vacuum distillation to obtain 3-chloro-2-hydroxypropyl trifluoromethyl acrylate. The preparation process is as follows:

[0012] (5) Add 4-(2-dimethylamino)acryloxybutyl acrylate and N,N-dimethylformamide into a three-necked flask, stir evenly, add 3-chloro-2-hydroxypropyl trifluoromethacrylate and p-methoxyphenol, raise the temperature for reaction, cool down after the reaction is completed, add ethyl acetate, precipitate, filter, wash with ether, and dry to obtain a trifluoromethyl quaternary ammonium salt antistatic agent containing diolefins. The preparation process is as follows:

[0013] Further, the mass ratio of each reactant in the step (3) is: 1,4-butanediol diacrylate: dimethylamine = 44-52:100.

[0014] Further, the mass ratio of each reactant in the step (4) is: epichlorohydrin: 2-(trifluoromethyl)acrylic acid: triphenylphosphine: p-methoxyphenol = 85-98:100:9-12:3-7.

[0015] Further, the reaction temperature in the step (4) is 85-105 °C, and the reaction time is 8-12 h.

[0016] Further, the mass ratio of each reactant in the step (5) is: 4-(2-dimethylamino)acryloxybutyl acrylate: 3-chloro-2-hydroxypropyl trifluoromethacrylate: p-methoxyphenol = 100:210-235:2-4.

[0017] Further, the reaction temperature in the step (5) is 70-100 °C, and the reaction time is 10-16 h.

[0018] (III) Beneficial technical effects Using 1,4-butanediol diacrylate and dimethylamine through Michael addition and regulating the reaction ratio between the two to obtain 4-(2-dimethylamino)acryloxybutyl acrylate. Then, epichlorohydrin and 2-(trifluoromethyl)acrylic acid are ring-opened under the action of the catalyst triphenylphosphine and the inhibitor p-methoxyphenol to obtain 3-chloro-2-hydroxypropyl trifluoromethacrylate. Then, the tertiary amine of 4-(2-dimethylamino)acryloxybutyl acrylate and the chlorine of 3-chloro-2-hydroxypropyl trifluoromethacrylate undergo quaternization reaction to obtain a trifluoromethyl quaternary ammonium salt antistatic agent containing diolefins. Then, it is melt-grafted with a polyolefin elastomer and foamed to obtain a modified polyolefin elastomer foamed material.

[0019] Quaternary ammonium salt antistatic agents contain hydrophilic groups and can easily combine with moisture in the air through hydrogen bonds to form a conductive channel, enabling static charges to dissipate and thus achieving the purpose of reducing the surface resistivity of materials. After melt grafting with polyolefin polymers, a dense arrangement is formed on the surface of the quaternary ammonium salt. The hydrophilic groups face the air and are oriented at the interface to form a permeation network with conductive ability, having the advantages of good static elimination effect and strong adsorption ability. By using reactive extrusion, polyolefin elastomers, antistatic agents, and additives are heated and extruded in a twin-screw extruder for melt grafting, which has the characteristics of short reaction time and high grafting efficiency. Fluorine-containing polymers contain a large number of fluorine groups and have advantages such as low surface energy and high thermal stability. The bond energy of the carbon-fluorine bond is large, and the bond distance is short. The more fluorine atoms connected to the same carbon atom, the more stable it is, which improves the heat distortion temperature of the material.

[0020] The diolefins in the trifluoromethyl quaternary ammonium salt antistatic agent containing diolefins increase the crosslinking sites and density with polyolefin elastomers, significantly enhancing the melt strength after crosslinking. By adjusting the proportion of the foaming aid, the cells of the polyolefin foamed material have a high degree of closed-cell property, thus possessing excellent mechanical properties. Specific Embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0022] Example 1 (1) Add 7.2 g of 1,4-butanediol diacrylate and ethanol to a three-necked flask, stir and dilute. Weigh 15 g of dimethylamine and dissolve it in ethanol. After stirring evenly, add it dropwise to the three-necked flask and react at 30 °C for 5 h. After the reaction is completed, purify by column chromatography with methanol and ethyl acetate to obtain 4-(2-dimethylamine) acetoxybutyl acrylate.

[0023] (2) Add 17.1 g of epichlorohydrin, 18 g of 2-(trifluoromethyl) acrylic acid, 1.65 g of the catalyst triphenylphosphine, and 0.9 g of the inhibitor p-methoxyphenol to a three-necked flask, stir evenly, then heat up to react. After reacting at 95 °C for 10 h, perform vacuum distillation to obtain 3-chloro-2-hydroxypropyl trifluoromethyl acrylate.

[0024] (3) Add 5 g of butyl 4-(2-dimethylamino)acetoxyacrylate and N,N-dimethylformamide into a three-necked flask, stir evenly, add 11 g of 3-chloro-2-hydroxypropyl trifluoromethacrylate and 0.15 g of p-methoxyphenol, heat up for reaction, cool after reacting at 80 °C for 12 h, add ethyl acetate, precipitate, filter, wash with ether, and dry to obtain a trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin.

[0025] (4) Dry 100 g of polyolefin elastomer at 30 °C for 3 h, add 5 g of trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin and 0.2 g of initiator BPO, stir evenly in a high-speed mixer to obtain a premix, add the premix into a twin-screw extruder through a barrel. The temperature of the first zone of the extruder is 80 °C, the second zone is 85 °C, the third zone is 110 °C, the temperature of the fourth zone is 125 °C, the fifth zone is 95 °C, the sixth zone is 130 °C, and the head temperature is 150 °C. At a screw speed of 130 r / min, a modified polyolefin elastomer material is obtained.

[0026] (5) Add 100 g of modified polyolefin elastomer material, 2 g of foaming agent azodicarbonamide, 0.9 g of vulcanizing agent DCP, 3 g of foaming aid calcium stearate, and 1 g of zinc stearate into a mixer, mix at high speed for 20 min, then mix on a two-roll mill with a roll temperature of 135 °C for 15 min, and then vulcanize on a flat vulcanizer at a vulcanization temperature of 180 °C for 20 min. Carry out compression molding and foaming under a molding pressure of 15 MPa to obtain a modified polyolefin elastomer foaming material.

[0027] Example 2 The difference between this example and Example 1 is that the dosage of the trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin in step (4) is 10 g, and other conditions remain unchanged.

[0028] Example 3 The difference between this example and Example 1 is that the dosage of the trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin in step (4) is 15 g, and other conditions remain unchanged.

[0029] Example 4 The difference between this example and Example 1 is that the dosage of the trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin in step (4) is 20 g, and other conditions remain unchanged.

[0030] Example 5 The difference between this example and Example 1 is that the dosage of the trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin in step (4) is 25 g, and other conditions remain unchanged.

[0031] Comparative Example 1 Add 100 g of modified polyolefin elastomer material into a mixer, then add 5 g of a diene-containing trifluoromethyl quaternary ammonium salt antistatic agent, 2 g of azodicarbonamide foaming agent, 0.6 g of DCP vulcanizing agent, 4 g of calcium stearate foaming aid and 1.5 g of zinc stearate, and mix at high speed for 20 min. Then, knead on a two-roll mill with a roll temperature of 135 °C for 15 min, and then vulcanize on a flat vulcanizer at a vulcanization temperature of 180 °C for 20 min. Conduct mold pressing foaming under a mold pressing pressure of 15 MPa to obtain a polyolefin elastomer foamed material.

[0032] Comparative Example 2 Add 100 g of modified polyolefin elastomer material into a mixer, 2 g of azodicarbonamide foaming agent, 0.6 g of DCP vulcanizing agent, 4 g of calcium stearate foaming aid and 1.5 g of zinc stearate, and mix at high speed for 20 min. Then, knead on a two-roll mill with a roll temperature of 135 °C for 15 min, and then vulcanize on a flat vulcanizer at a vulcanization temperature of 180 °C for 20 min. Conduct mold pressing foaming under a mold pressing pressure of 15 MPa to obtain a polyolefin elastomer foamed material.

[0033] Antistatic test: Use a high resistance meter to measure the surface resistivity of the material.

[0034] Heat distortion temperature test: Use a heat distortion temperature tester to measure the heat distortion temperature at 0.45 MPa.

[0035] As can be seen from the data in the above table, as the dosage of the diene-containing trifluoromethyl quaternary ammonium salt antistatic agent in the modified polyolefin elastomer foamed material increases, the surface resistivity of the material gradually decreases. When the dosage of the diene-containing trifluoromethyl quaternary ammonium salt antistatic agent is 25 parts, the surface resistivity drops to 1.2×10 4 Ω, and the antistatic effect is excellent. This is because on the one hand, the polar groups of the quaternary ammonium salt antistatic agent can increase the conductivity of the material, and on the other hand, the hydrophilic groups of the quaternary ammonium salt form a conductive channel with water molecules in the environment through hydrogen bonds, conducting away the static charges accumulated inside the material, achieving the effect of reducing the surface resistivity. In Comparative Example 1, the polyolefin elastomer and the diene-containing trifluoromethyl quaternary ammonium salt antistatic agent were not melt grafted, but simply blended, and its surface resistivity was 6.3×10 15 Ω. Comparative Example 2 is a single polyolefin elastomer foamed material, and its surface resistivity is 5.1×10 17 Ω. At this time, the material has high electrical insulation and is prone to generating static electricity.

[0036] The heat distortion temperature of the foaming material increases with the increase of the trifluoromethyl content in the system. The heat distortion temperature of Comparative Example 2 is 101.6 °C, while that of Example 5 reaches 135.2 °C, an increase of 33.6 °C. This is because the fluoropolymer contains a large number of fluorine groups and has advantages such as low surface energy and high thermal stability. The bond energy of the carbon-fluorine bond is large and the bond distance is short. The more fluorine atoms connected to the same carbon atom, the more stable it is, resulting in an increase in the heat distortion temperature of the foaming material.

[0037] Example 6 The difference between this example and Example 1 is that in step (5), the dosage of calcium stearate is 3.5 g and the dosage of zinc stearate is 1.3 g, and other conditions remain unchanged.

[0038] Example 7 The difference between this example and Example 1 is that in step (5), the dosage of calcium stearate is 4 g and the dosage of zinc stearate is 1.5 g, and other conditions remain unchanged.

[0039] Example 8 The difference between this example and Example 1 is that in step (5), the dosage of calcium stearate is 4.5 g and the dosage of zinc stearate is 1.8 g, and other conditions remain unchanged.

[0040] Example 9 The difference between this example and Example 1 is that in step (5), the dosage of calcium stearate is 5 g and the dosage of zinc stearate is 2 g, and other conditions remain unchanged.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that in step (5), the foaming aid calcium stearate is not added, and other conditions remain unchanged.

[0042] Comparative Example 4 The difference between this comparative example and Example 1 is that in step (5), the foaming aid zinc stearate is not added, and other conditions remain unchanged.

[0043] Comparative Example 5 The difference between this comparative example and Example 6 is that in step (5), neither the foaming aid calcium stearate nor zinc stearate is added, and other conditions remain unchanged.

[0044] Density test: Remove the foam skin and test the bulk density of the foaming material.

[0045] Mechanical property test: Use an electronic tensile machine for testing. The thickness of the foaming specimen is 5 mm, the tensile cross-section is 6 mm, and the tensile speed is 500 mm / min to test the tensile strength of the material.

[0046] Hardness test: Test the Shore hardness of the foaming material.

[0047] As can be seen from the above table, as the dosages of foaming aids calcium stearate and zinc stearate increase, the density and hardness of the foamed material gradually decrease, and the tensile strength gradually increases. This is because with the increase in the contents of calcium stearate and zinc stearate, the cross-linking effect of polyolefin is enhanced, which promotes foaming. The melt strength and the bubble expansion force reach a relatively perfect match. The decrease in density is conducive to the formation of an excellent cell structure in the material. The uniformly distributed tiny cells inside the material play a role similar to the toughening of rubber particles, that is, under the action of external force, the possibility of the material being damaged is reduced, and the tensile strength of the material is improved. The density of Comparative Example 3 with only zinc stearate added is 154.7 kg / m 3 , and the density of Comparative Example 4 with only calcium stearate added is 163.2 kg / m 3 , indicating that the addition of a single foaming aid has an insignificant effect on the foaming of polyolefin elastomer. In Comparative Example 5, no foaming aid was added and foaming failed, indicating that it is easier to obtain high-quality foamed materials after the matching of calcium stearate and zinc stearate, making the cells of the polyolefin foamed material have a high degree of closed cells.

[0048] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, not all embodiments. Other embodiments can also be obtained based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A preparation method of a modified polyolefin elastomer foaming material, characterized in that, The preparation method includes the following steps: (1) Dry the polyolefin elastomer at 25 - 35°C for 2 - 4 h, add a trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin and initiator BPO, stir evenly in a high-speed mixer to obtain a premix, and add the premix into a twin-screw extruder through a barrel. The temperature of the first zone of the extruder is 70 - 80°C, the second zone is 80 - 90°C, the third zone is 110 - 120°C, the temperature of the fourth zone is 120 - 130°C, the fifth zone is 90 - 100°C, the sixth zone is 130 - 140°C, and the head temperature is 145 - 155°C. At a screw speed of 120 - 140 r / min, a modified polyolefin elastomer material is obtained; (2) Add the modified polyolefin elastomer material, blowing agent azodicarbonamide, vulcanizing agent DCP, blowing aid calcium stearate and zinc stearate into a mixer, mix at high speed for 5 - 25 min, then knead on a two-roll mill with a roll temperature of 120 - 140°C for 5 - 20 min, and then vulcanize on a flat vulcanizer at a vulcanization temperature of 160 - 190°C for 10 - 20 min, and carry out compression molding and foaming under a molding pressure of 12 - 16 MPa to obtain a modified polyolefin elastomer foaming material.

2. The preparation method of the modified polyolefin elastomer foamed material according to claim 1, characterized in that In the step (1), the mass ratio of each reactant is: polyolefin elastomer: trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin: BPO = 100:5 - 25:0.1 - 0.

3.

3. The preparation method of the modified polyolefin elastomer foaming material according to claim 1, characterized in that, In the step (2), the mass ratio of each foaming component is: modified polyolefin elastomer material: azodicarbonamide: DCP: calcium stearate: zinc stearate = 100:2 - 6:0.6 - 1.5:3 - 5:1 - 2.

4. The preparation method of the modified polyolefin elastomer foaming material according to claim 1, characterized in that, The preparation method of the trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin includes the following steps: (3) Add 1,4-butanediol diacrylate and ethanol into a three-necked flask, stir and dilute. Weigh dimethylamine and dissolve it in ethanol, stir evenly and then drop it into the three-necked flask, react at 20 - 35°C for 4 - 8 h. After the reaction, purify by column chromatography with methanol and ethyl acetate to obtain 4-(2-dimethylamine) acetoxybutyl acrylate; (4) Add epichlorohydrin, 2-(trifluoromethyl) acrylic acid, catalyst triphenylphosphine and inhibitor p-methoxyphenol into a three-necked flask, stir evenly, raise the temperature for reaction. After the reaction, carry out vacuum distillation to obtain 3-chloro-2-hydroxypropyl trifluoromethyl acrylate; (5) Add 4-(2-dimethylamine) acetoxybutyl acrylate and N,N-dimethylformamide into a three-necked flask, stir evenly, add 3-chloro-2-hydroxypropyl trifluoromethyl acrylate and p-methoxyphenol, raise the temperature for reaction. After the reaction, cool, add ethyl acetate, precipitate, filter, wash with ether, and dry to obtain the trifluoromethyl quaternary ammonium salt antistatic agent containing diolefin.

5. The preparation method of the modified polyolefin elastomer foaming material according to claim 4, characterized in that, In the step (3), the mass ratio of each reactant is: 1,4-butanediol diacrylate: dimethylamine = 44 - 52:

100.

6. The preparation method of the modified polyolefin elastomer foaming material according to claim 4, characterized in that In the step (4), the mass ratio of each reactant is: epichlorohydrin: 2-(trifluoromethyl)acrylic acid: triphenylphosphine: p-methoxyphenol = 85-98:100:9-12:3-7.

7. The preparation method of the modified polyolefin elastomer foaming material according to claim 4, characterized in that, In the step (4), the reaction temperature is 85-105 °C and the reaction time is 8-12 h.

8. The preparation method of the modified polyolefin elastomer foaming material according to claim 4, characterized in that, In the step (5), the mass ratio of each reactant is: 4-(2-dimethylamino)acetoxybutyl acrylate: 3-chloro-2-hydroxypropyl trifluoromethylacrylate: p-methoxyphenol = 100:210-235:2-4.

9. The preparation method of the modified polyolefin elastomer foaming material according to claim 4, wherein, In the step (5), the reaction temperature is 70-100 °C and the reaction time is 10-16 h.

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