Low-water-absorption modified nylon 6 and preparation method thereof

Abstract

The invention belongs to the field of high polymer materials. The invention provides low-water-absorption modified nylon 6 which comprises the following components: nylon 6 resin, an organic fluorosilicone-maleic anhydride copolymer for low-water-absorption modification and an antioxidant, and also provides a preparation method of the low-water-absorption modified nylon 6. The organic fluorosilicone-maleic anhydride copolymer component for low-water-absorption modification of the low-water-absorption modified nylon 6 has a hydrophobic polysiloxane long side chain and a dodecafluoroheptyl methacrylate structural unit with a fluorine-containing side group in structure; the organic fluorosilicone-maleic anhydride copolymer also has an anhydride group brought by a maleic anhydride monomer which chemically reacts with amino of nylon 6, and the organic fluorosilicone-maleic anhydride copolymer and a nylon 6 matrix are connected through chemical bonds to prevent macroscopic phase separation of the system. The low-water-absorption modified nylon 6 is durable and good in low water absorption, the water absorption of nylon 6 is reduced, and the low-water-absorption modified nylon 6 can be applied to the fields of automobiles, household appliances, textiles and the like.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and particularly relates to low water absorption modified nylon 6 and a preparation method thereof. Background Art

[0002] Nylon 6 (PA6), also known as polycaprolactam, is a thermoplastic polyamide made from caprolactam monomers through ring-opening polymerization. Its molecular chain contains amide bonds (-CONH-), which enable hydrogen bonds to form between nylon 6 molecular chains, which is one of the important reasons why nylon 6 has a series of excellent properties. Nylon 6 is one of the most widely used varieties of nylon products. It has the advantages of good thermal stability, good wear resistance, strong corrosion resistance and high strength. It is widely used in home appliances, automobiles, textiles and other fields. However, due to the strong polarity of the amide bonds in the molecular chain of nylon 6, it is easy to form hydrogen bonds with water molecules and has a certain water absorption. It is very easy to absorb a large amount of water in humid air, resulting in strong hydrophilicity and particularly high water absorption. The high water absorption will cause the product size stability to deteriorate, the mechanical properties to decrease, and the electrical insulation performance to decrease, which is very unfavorable for the stability and reprocessing of nylon product performance. The high water absorption of nylon 6 limits its further application.

[0003] Silicone polymers with a polysiloxane structure have excellent hydrophobicity and therefore have low water absorption, and their weather resistance and high and low temperature stability are also very excellent. There have been reports on the blending and modification of silicone polymers with polysiloxane structures with nylon 6 to improve the low water absorption of nylon 6 and reduce its water absorption. However, nylon 6 and polysiloxane silicone polymers have large polarity differences and are incompatible. Such blending will result in large interfacial tension between the two phases and unstable phase morphology, making it difficult to obtain materials with excellent performance.

[0004] There are two ways to modify nylon 6 with silicone polymers with polysiloxane structure: one is to add a compatibilizer to increase the capacity; the other is to embed polysiloxane structure segments into the polymer chain segments of nylon 6 by copolymerization.

[0005] The present invention provides a new technical solution for modifying nylon 6 to have low water absorption to reduce its water absorption, so as to meet the demand of the continuous development of the automobile, electronics, machinery and other industries for high-performance engineering plastics with good dimensional stability, mechanical properties and electrical properties. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a low water absorption modified nylon 6 and a preparation method thereof. The low water absorption modified nylon 6 has a long-lasting and good low water absorption performance, reduces the water absorption of nylon 6, and can be applied to the fields of automobiles, home appliances, textiles, etc.

[0007] The object of the present invention is to provide a low water absorption modified nylon 6, comprising the following components in parts by weight:

[0008] Nylon 6 resin 90-98 parts

[0009] 2-20 parts of organic fluorine silicon-maleic anhydride low water absorption modified copolymer

[0010] Antioxidant 0.2-1.0 part.

[0011] The low water absorption modified nylon 6 organic fluorine silicon-maleic anhydride copolymer component has a hydrophobic long side chain of polysiloxane and a dodecafluoroheptyl methacrylate structural unit with a fluorine-containing side group in structure, and also has an anhydride group that chemically reacts with the amino group of nylon 6. The low water absorption modified nylon 6 organic fluorine silicon-maleic anhydride copolymer is connected to the nylon 6 matrix through chemical bonds to prevent macroscopic phase separation of the system. The modified nylon 6 obtains better and lasting low water absorption performance, and other properties of the nylon 6 substrate are less changed.

[0012] Preferably, in the present invention, the antioxidant is at least one of antioxidant 1010, antioxidant 168, antioxidant 1098, antioxidant 1076, and antioxidant P-EPQ.

[0013] Furthermore, the above-mentioned organic fluorine silicon-maleic anhydride low water absorption modified copolymer comprises the following polymerized monomers in parts by weight:

[0014]

[0015] Preferably, the relative molecular mass of the monovinyl polysiloxane is 1250-5000.

[0016] In the present invention, monovinyl polysiloxane, dodecafluoroheptyl methacrylate, maleic anhydride and styrene are polymerized by free radical solution polymerization to prepare an organic fluorine silicon-maleic anhydride low water absorption modified copolymer.

[0017] Furthermore, the method for preparing the above-mentioned organic fluorine silicon-maleic anhydride low water absorption modified copolymer comprises the following steps:

[0018] (1) adding an organic medium accounting for 60-80% of the total amount of the organic medium into a polymerization reaction device, heating to 60-100° C., adding an initiator accounting for 50-85% of the total amount of the initiator, and mixing uniformly to obtain an initiator-containing solution;

[0019] (2) uniformly mixing the polymerizable monomers monovinyl polysiloxane, dodecafluoroheptyl methacrylate, maleic anhydride, and styrene with an organic medium accounting for 10-20% of the total amount of the organic medium to obtain a mixed solution;

[0020] (3) adding the mixed solution obtained in step (3) dropwise to the initiator-containing solution obtained in step (1) for 2-4 hours, and keeping the mixture warm for 0.5-3 hours after the addition is complete;

[0021] (4) uniformly mixing the remaining amount of initiator and the remaining amount of organic medium to obtain a mixed solution, and adding it dropwise to the system after heat preservation in step (3) for 0.5-1 hour. After the addition is completed, the mixture is reacted at a constant temperature (60-80° C.) for 2.5-4 hours to obtain a resin solution of an organic fluorosilicone-maleic anhydride copolymer for low water absorption modification.

[0022] Preferably, the initiator is at least one of azobisisobutyronitrile, azobisisoheptylnitrile, benzoyl peroxide, diisopropylbenzene peroxide, di-tert-butyl peroxide, dodecyl peroxide, and tert-butyl perbenzoate. The amount of the initiator is 0.1%-2% of the total mass of the polymerized monomers, based on the total mass of the polymerized monomers in the homogeneous solution of the organic fluorosilicone-maleic anhydride low water absorption modified copolymer preparation system.

[0023] Preferably, the organic medium is at least one of toluene, xylene and ethylbenzene, and the amount of the organic medium is 30%-70% of the total mass of the homogeneous solution of the system for preparing the organic fluorosilicone-maleic anhydride low water absorption modified copolymer.

[0024] The present invention also aims to provide a method for preparing modified nylon 6 with low water absorption, comprising the following steps:

[0025] (1) Nylon 6 resin, organic fluorine silicon-maleic anhydride low water absorption modified copolymer, and antioxidant are uniformly mixed according to the above ratio to obtain a mixed material;

[0026] Wherein, the organic fluorosilicone-maleic anhydride low water absorption modified copolymer is added in the form of a polymer solution formed by dissolving in an organic medium;

[0027] (2) The mixed material obtained in step (1) is allowed to stand for 1-2 hours, and then added to a twin-screw extruder for reaction extrusion. The solvent and unreacted residual monomers in the raw material are removed and recovered by a vacuum exhaust device of the twin-screw extruder to obtain modified nylon 6 with low water absorption.

[0028] The present invention adopts the reaction extrusion technology to connect the organic fluorosilicone-maleic anhydride low water absorption modified copolymer with the nylon 6 matrix through chemical bonds to prevent the macroscopic phase separation of the system; compared with the method of introducing polysiloxane blocks into the molecular weight of nylon 6 by copolymerization, the molecular chain movement of the long side chain of polysiloxane introduced into nylon 6 by the present invention is relatively less restricted, the chain activity ability is better, and the long side chain of polysiloxane migrates to the surface of nylon 6 material and is more widely distributed.

[0029] Furthermore, in step (1), the mass ratio of the organic fluorosilicone-maleic anhydride low water absorption modified copolymer to the organic medium is 1:0.3-3.

[0030] Furthermore, in the above step (2), the heating temperature of the twin-screw extruder is set to 180° C.-250° C., and the main screw speed is set to 80-150 rpm.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The present invention uses a free radical solution polymerization method to prepare an organic fluorine silicon-maleic anhydride low water absorption modified copolymer from monovinyl polysiloxane, dodecafluoroheptyl methacrylate, maleic anhydride and styrene. The copolymer component has not only a hydrophobic polysiloxane long side chain and a dodecafluoroheptyl methacrylate structural unit with a fluorine-containing side group, but also an anhydride group introduced by a maleic anhydride monomer that chemically reacts with an amino group of nylon 6. The organic fluorine silicon-maleic anhydride copolymer is connected to the nylon 6 matrix by chemical bonds to prevent the macroscopic phase separation of the system.

[0033] (2) The synergistic effect of the fluorine-containing structural unit and the long silicon-containing organic side chain enables a smaller amount of organic fluorine silicon-maleic anhydride low water absorption modified copolymer to achieve a better modification effect;

[0034] (3) The present invention uses a twin-screw extruder for reaction extrusion, so that the organic fluorosilicone-maleic anhydride low water absorption modified copolymer and the nylon 6 matrix are connected by chemical bonds to prevent the macroscopic phase separation of the system. Compared with the method of introducing polysiloxane blocks into the molecular weight of nylon 6 by copolymerization, the molecular chain movement of the long side chain of polysiloxane introduced into nylon 6 by the present invention is relatively less restricted, the chain activity is better, and the long side chain of polysiloxane migrates to the surface of nylon 6 material and is more widely distributed;

[0035] (4) The process flow of the present invention is simple, the preparation is easy, the cost is low, and it can meet the needs of mass production. The modified nylon 6 obtains better and lasting low water absorption performance, and the other properties of the nylon 6 substrate are less changed. DETAILED DESCRIPTION

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The technical solution adopted by the present invention is:

[0038] The low water absorption nylon 6 (PA6) modified material of the present invention is composed of the following components in parts by weight:

[0039] Nylon 6 (PA6) resin 90-98 parts

[0040] 2-20 parts of organic fluorine silicon-maleic anhydride low water absorption modified copolymer

[0041] Antioxidant 0.2-1.0 parts

[0042] The organic fluorine silicon-maleic anhydride low water absorption modified copolymer is added in the form of a polymer solution, and the amount added is such that the solid content of the organic fluorine silicon-maleic anhydride low water absorption modified copolymer in the polymer solution meets the requirements of the above formula.

[0043] The organic fluorosilicone-maleic anhydride low water absorption modified copolymer is prepared by polymerization of monovinyl polysiloxane, maleic anhydride and styrene, and comprises 50 parts of monovinyl polysiloxane, 2-10 parts of dodecafluoroheptyl methacrylate, 1-4 parts of maleic anhydride and 36-47 parts of styrene in parts by mass.

[0044] The preparation method of the organic fluorine silicon-maleic anhydride low water absorption modified copolymer is as follows: under the protection of inert gas, an organic medium accounting for 60-80wt% of the total amount of the organic medium is added to a polymerization reactor and heated to 60-100°C; an initiator accounting for 50-85% of the total amount of the initiator is added to the polymerization reactor to obtain an initiator-containing solution; then the polymerization monomer and the organic medium accounting for 10-20wt% of the total amount of the organic medium are uniformly mixed to obtain a mixed solution, the mixed solution is dripped into the initiator-containing solution for 2-4 hours, and the temperature is kept for 0.5-3 hours after the dripping is completed; the remaining initiator is uniformly mixed with the remaining organic medium, and dripped into the system for 0.5-1 hour, and the temperature is kept constant for 3 hours. After cooling to room temperature, a resin solution of the organic fluorine silicon-maleic anhydride low water absorption modified copolymer is obtained, which is used for further preparation of low water absorption nylon 6 (PA6) modified material.

[0045] The initiator is at least one of azobisisobutyronitrile, azobisisoheptylnitrile, benzoyl peroxide, diisopropylbenzene peroxide, di-tert-butyl peroxide, dodecyl peroxide, and tert-butyl perbenzoate; based on the total mass of the monomers in the homogeneous solution, the mass concentration of the initiator is 0.1wt%-2wt%.

[0046] The relative molecular mass of the monovinyl polysiloxane is 1250-5000.

[0047] The organic medium of the present invention is at least one of toluene, xylene and ethylbenzene; the mass concentration of the organic medium is 30wt%-70wt% based on the total mass of the homogeneous solution; and the antioxidant is at least one of antioxidant 1010, antioxidant 168, antioxidant 1098, antioxidant 1076 and antioxidant P-EPQ.

[0048] The preparation method of the low water absorption nylon 6 (PA6) modified material of the present invention comprises the following preparation steps:

[0049] S1, prepare a solution of an organic fluorine silicon-maleic anhydride low water absorption modified copolymer for standby use;

[0050] S2, after mixing nylon 6 (PA6) resin, organic fluorine silicon-maleic anhydride low water absorption modified copolymer solution and antioxidant in a proportion, standing for 1-2 hours, and then adding into a twin-screw extruder;

[0051] S3. The heating temperature of the twin-screw extruder is set to 180° C.-250° C., the main screw speed is set to 80-150 rpm, the mixed raw materials are melt-reacted and extruded through the twin-screw extruder, and the solvent and unreacted residual monomers in the raw materials are removed and recovered through a vacuum exhaust device, and finally granulated to obtain the low-water-absorption nylon 6 (PA6) modified material.

[0052] Example 1

[0053] Preparation of solution of organic fluorine silicon-maleic anhydride copolymer for low water absorption modification

[0054] Under nitrogen protection, 1943g of toluene was added to the experimental reactor and heated to 65°C. 10.5g of initiator AIBN was added to the experimental reactor and stirred to dissolve it to obtain an initiator solution; 750.0g of monovinyl polysiloxane (Vi-PDMS, relative molecular weight 2000), 75.0g of methacrylate dodecafluoroheptane, 37.5g of maleic anhydride, 637.5g of styrene, and 555g of toluene were prepared into a uniform mixed solution, which was then added dropwise to the above-mentioned experimental reactor. The addition time was controlled to about 4 hours. After the addition was completed, the temperature was raised to 70°C and kept warm for 3 hours; 4.5g of initiator AIBN and 277g of toluene were prepared into a uniform initiator solution, which was then added dropwise to the above-mentioned experimental reactor. The time was controlled to 1 hour, and finally the temperature was raised to 95°C, and the reaction was carried out at a constant temperature for 3 hours. Finally, the resin solution 1# of the organic fluorine silicon-maleic anhydride low water absorption modified copolymer was obtained for standby use.

[0055] 2. Preparation of low water absorption nylon 6 (PA6) modified material

[0056] 4900g of nylon 6 (PA6) resin, 286g of organic fluorine silicon-maleic anhydride low water absorption modified copolymer solution, 5g of antioxidant 1010, and 10g of antioxidant 168 were fully stirred in a mixer and allowed to stand for 1 hour, and then added into a covered feeding funnel of a twin-screw reaction extruder with a vacuum exhaust device. The twin-screw reaction extruder was a Φ35 type parallel co-rotating meshing twin-screw extruder with a total of thirteen barrel sections and an aspect ratio of 56. The temperature of the extruder barrel is set to 180°C-250°C, the main engine screw speed is set to 100rpm, and a vacuum exhaust chamber and a matching condensation recovery device are opened on the 9th and 12th barrel sections away from the feed port to vacuum remove and recover the solvent and unreacted residual monomers in the raw materials. The blended materials are melt-reacted and extruded through the twin-screw reaction extruder, and then granulated through an air-cooled die face pelletizing device to obtain low-water absorption nylon 6 (PA6) modified material 1#.

[0057] Example 2

[0058] 4785g of nylon 6 (PA6) resin, 571g of the solution of the organic fluorosilicone-maleic anhydride low water absorption modified copolymer prepared in Example 1, 5g of antioxidant 1010 and 10g of antioxidant 168 were prepared through the same preparation process as in Example 1 to obtain low water absorption nylon 6 (PA6) modified material 2#.

[0059] Example 3

[0060] 4585g of nylon 6 (PA6) resin, 1143g of the solution of the organic fluorosilicone-maleic anhydride low water absorption modified copolymer prepared in Example 1, 5g of antioxidant 1010 and 10g of antioxidant 168 were prepared through the same preparation process as in Example 1 to obtain low water absorption nylon 6 (PA6) modified material 3#.

[0061] Water absorption test

[0062] The low water absorption nylon 6 (PA6) modified materials 1#-3# prepared in Examples 1 to 3 were made into samples of 10mm*10mm and 1.0mm±0.1mm thickness, and the water absorption rate of the samples was tested according to Method 1 of GB / T 1034-2008 standard, and the test conditions were soaked in 23℃ water for 24h. Comparative Example 1 uses nylon 6 resin. The test results are shown in Table 1.

[0063] Table 1 Water absorption test results of Examples 1-3 and Comparative Example 1

[0064] Serial number Test sample number Water absorption % 1 Comparative Example 1 9.10 2 Example 1 7.68 3 Example 2 6.35 4 Example 3 5.43

[0065] As can be seen from Table 1, the water absorption of the low water absorption modified nylon 6 modified by the organic fluorosilicone-maleic anhydride low water absorption modified copolymer prepared by the present invention is significantly reduced compared with pure nylon 6. In addition, the preparation method of the low water absorption modified nylon 6 provided by the present invention has a simple preparation process, low cost, and is easy to industrialize.

[0066] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Those skilled in the relevant technical field may make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the scope of the present invention and should be defined by the claims.

Claims

1. A low water absorption modified nylon 6, characterized in that: The composition comprises the following components in parts by weight: Nylon 6 resin 90-98 parts 2-20 parts of organic fluorine silicon-maleic anhydride low water absorption modified copolymer Antioxidant 0.2-1.0 part.

2. The low water absorption modified nylon 6 according to claim 1, characterized in that: The organic fluorine silicon-maleic anhydride low water absorption modified copolymer comprises the following polymerized monomers in parts by weight:

3. The low water absorption modified nylon 6 according to claim 2, characterized in that: The relative molecular mass of the monovinyl polysiloxane is 1250-5000.

4. The low water absorption modified nylon 6 according to claim 2, characterized in that: The preparation method of the organic fluorine silicon-maleic anhydride low water absorption modified copolymer, The following steps are included: (1) adding an organic medium accounting for 60-80% of the total amount of the organic medium into a polymerization reaction device, heating to 60-100° C., adding an initiator accounting for 50-85% of the total amount of the initiator, and mixing uniformly to obtain an initiator-containing solution; (2) uniformly mixing the polymerization monomer and the organic medium accounting for 10-20% of the total amount of the organic medium to obtain a mixed solution; (3) adding the mixed solution obtained in step (3) dropwise to the initiator-containing solution obtained in step (1) for 2-4 hours, and keeping warm for 0.5-3 hours after the addition is complete; (4) uniformly mixing the remaining amount of the initiator and the remaining amount of the organic medium to obtain a mixed solution, and adding it dropwise to the system after the heat preservation in step (3) for 0.5-1 hour. After the addition is completed, the mixture is reacted at a constant temperature for 2.5-4 hours to obtain a resin solution of an organic fluorosilicone-maleic anhydride copolymer for low water absorption modification.

5. The low water absorption modified nylon 6 according to claim 4, characterized in that: The initiator is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, diisopropylbenzene peroxide, di-tert-butyl peroxide, dodecyl peroxide, and tert-butyl perbenzoate. The amount of the initiator is 0.1%-2% of the total mass of the polymerized monomers based on the total mass of the polymerized monomers in the homogeneous solution of the organic fluorosilicone-maleic anhydride low water absorption modified copolymer preparation system.

6. The low water absorption modified nylon 6 according to claim 4, characterized in that: The organic medium is at least one of toluene, xylene and ethylbenzene, and the amount of the organic medium is 30%-70% of the total mass of the homogeneous solution of the system for preparing the organic fluorine silicon-maleic anhydride low water absorption modified copolymer.

7. A method for preparing the modified nylon 6 with low water absorption as claimed in any one of claims 1 to 6, characterized in that: The following steps are included: (1) mixing the nylon 6 resin, the organic fluorine silicon-maleic anhydride low water absorption modified copolymer, and the antioxidant in a uniform ratio to obtain a mixed material; Wherein, the organic fluorosilicone-maleic anhydride low water absorption modification copolymer is added in the form of being dissolved in an organic medium to form a polymer solution; (2) After the mixture obtained in step (1) is allowed to stand for 1-2 hours, it is added to a twin-screw extruder for reaction extrusion, and the solvent and unreacted residual monomers in the raw material are removed and recovered by a vacuum exhaust device to obtain a low water absorption modified nylon 6.

8. The method for preparing modified nylon 6 with low water absorption according to claim 7, characterized in that: In step (2), the heating temperature of the twin-screw extruder is set to 180° C.-250° C., and the main screw speed is set to 80-150 rpm.

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