A method for preparing polypropylene fiber with low auxiliary agent migration rate

Abstract

The invention relates to a method for preparing polypropylene fiber with low auxiliary agent mobility, wherein the polypropylene containing aliphatic ring secondary amine is blended with an auxiliary agent with an acid anhydride group and then melt-spun to obtain the polypropylene fiber with low auxiliary agent mobility; the auxiliary agent mobility of the polypropylene fiber with low auxiliary agent mobility is not higher than 1%, 5% and 15% respectively when placed in normal hexane at room temperature for 48 hours, 168 hours and 336 hours; the method for preparing polypropylene containing aliphatic ring secondary amine is as follows: polypropylene is reactively blended with dibenzoyl peroxide as an initiator and an olefin monomer containing aliphatic ring secondary amine by twin-screw extrusion granulation to obtain polypropylene containing aliphatic ring secondary amine. The preparation method of the invention is simple, and the polypropylene containing aliphatic ring secondary amine structure can be obtained by a one-step reaction of the melt, and has an excellent effect of reducing the mobility of auxiliary agents containing an acid anhydride group.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene fibers and relates to a method for preparing polypropylene fibers with low auxiliary agent migration rate. Background Art

[0002] Polypropylene (PP) is a polymer obtained by polymerization of propylene. It is widely used in various industries. Thanks to its unique characteristics of light weight, warmth retention, hydrophobicity, moisture conductivity and acid and alkali resistance, its demand in civil and household textiles, sanitary materials, construction engineering, separation and filtration industries is showing an increasing trend. In the face of growing application demand, especially in the engineering field, higher requirements are placed on the long-term reliability of fibers.

[0003] Since the main chain of polypropylene has no polar groups, most small molecule additives containing polar groups have a low degree of interaction with the main chain of polypropylene. Therefore, with the use process, the small molecule additives in the fiber are easy to migrate from the inside of the fiber to the surface, and the various properties of the fiber will decline synchronously over time. For the migration problem inside polypropylene, the most effective solution currently is to introduce functional small molecules into the main chain of the polymer by grafting or copolymerization. However, for the high fluidity requirements of polypropylene fibers, the introduction of the main chain will inevitably reduce the mobility of the main chain, reduce the melt fluidity, and is not conducive to spinning processing. Some polar groups will even cross-link during the high-temperature spinning process, causing gel particles in the melt to clog the spinning assembly and reduce the life of the spinning assembly filtration system. The document "Increasing Polypropylene High Temperature Stability by Blending Polypropylene-Bonded Hindered Phenol Antioxidant [J]. Macromolecules, 2018, 51 (5): 1927-1936." reports a structure in which hindered phenol groups are introduced into the main chain of polypropylene. Since the groups will undergo cross-linking reactions, the structure is processed by solution rather than melt processing, which makes it difficult to adapt to the processing requirements of melt-spun polypropylene fibers.

[0004] Therefore, it is of great significance to study a method for preparing polypropylene fibers with low additive migration rate by melt processing, so as to solve the problem of easy migration of additives in polypropylene fibers. Summary of the invention

[0005] In order to solve the problems in the prior art, the present invention provides a method for preparing polypropylene fiber with low auxiliary agent mobility, by introducing a secondary amine structure into the main chain and directly connecting it with an auxiliary agent containing anhydride structure through hydrogen bonds, thereby ultimately achieving the goal of reducing the mobility of auxiliary agent molecules while ensuring the fluidity of polypropylene, thereby solving the problem of easy migration of auxiliary agents in polypropylene fibers.

[0006] To achieve the above object, the scheme adopted by the present invention is as follows:

[0007] A method for preparing polypropylene fibers with low auxiliary agent mobility, comprising: blending polypropylene containing aliphatic ring secondary amines with an auxiliary agent with anhydride groups and then performing melt spinning to obtain the polypropylene fibers with low auxiliary agent mobility;

[0008] The additive migration rates of the polypropylene fiber with low additive migration rate after being placed in n-hexane at room temperature for 48 hours, 168 hours and 336 hours are not higher than 1%, 5% and 15% respectively.

[0009] As the preferred technical solution:

[0010] The method for preparing a polypropylene fiber with low auxiliary agent mobility as described above is as follows: polypropylene, initiator dibenzoyl peroxide (BPO), and a polyolefin monomer containing a polypropylene ring are reactively blended and extruded by a twin-screw extruder to obtain the polypropylene containing a polypropylene ring containing a polypropylene ring containing a polypropylene ring.

[0011] A method for preparing a polypropylene fiber with low auxiliary agent migration rate as described above, wherein the melt index of the polypropylene is 15 to 50 g / 10 min (tested according to GB / T 3682.1-2018 standard, the test conditions are temperature 230° C., load 2.16 kg);

[0012] The chemical formula of the aliphatic ring secondary amine olefin monomer is Among them, R 1 is 3, R 2 is 4 or 5. The aliphatic ring-containing secondary amine olefin monomer is preferably a six-membered aliphatic ring structure. The six-membered aliphatic ring structure can avoid the effect reduction caused by entanglement, and ensure the melt fluidity as much as possible under the premise of ensuring a certain degree of steric hindrance. The long-chain alkane secondary amine structure is relatively flexible, and it is easy to entangle between the branches, which will reduce the ability of the secondary amine structure and the structure of the auxiliary agent to generate hydrogen bonds; the six-membered aromatic ring has too much steric hindrance, which will significantly increase the melt viscosity and is not suitable for the requirements of melt spinning.

[0013] In the method for preparing polypropylene fiber with low auxiliary agent mobility as described above, the amount of the aliphatic ring secondary amine olefin monomer added is 0.5-5wt% of the polypropylene, and the amount of the initiator dibenzoyl peroxide added is 0.05-0.1wt% of the polypropylene.

[0014] In the method for preparing polypropylene fiber with low auxiliary agent mobility as described above, the temperature of the twin-screw reactive blending is 200-230°C.

[0015] In the method for preparing polypropylene fiber with low auxiliary agent mobility as described above, the addition amount of the auxiliary agent with anhydride group is 0.1-3wt% of the polypropylene containing aliphatic cyclic secondary amine.

[0016] In the method for preparing polypropylene fiber with low auxiliary agent mobility as described above, the content of the anhydride group in the auxiliary agent with anhydride group is not less than 10wt%.

[0017] In the method for preparing polypropylene fiber with low auxiliary agent mobility as described above, the spinning temperature is 220-260° C. and the spinning speed is 1500-2500 m / min.

[0018] The method for preparing polypropylene fiber with low auxiliary agent migration rate as described above comprises the following steps: after melt spinning, the fiber is oiled and bundled, and subjected to hot roller heat stretching treatment, wherein the temperature of one roller is 80-90°C, and the temperature of the second roller is 120-130°C.

[0019] The mechanism of the present invention is as follows:

[0020] Most additives contain strong polar groups. If they are introduced into the main chain of the polymer by grafting or copolymerization, the interaction between these groups will cause the melt fluidity to decrease. The present invention connects the secondary amine structure with a six-membered aliphatic ring on the main chain of polypropylene directly through hydrogen bonds with the additive containing anhydride structure, and finally realizes that the mobility of the additive molecule is reduced while ensuring the fluidity of polypropylene, and the secondary amine group and the anhydride group are only hydrogen bonds of intermolecular force under the conditions of polypropylene melt processing, and no chemical crosslinking will be generated, thereby avoiding the introduction of small molecule additives into the main chain of the polymer in the prior art, and some polar groups will even crosslink during the high-temperature spinning process, so that gel particles are generated in the melt to block the spinning assembly and reduce the life of the spinning assembly filtration system; in addition, the strength of the hydrogen bond will change with the temperature, and the hydrogen bond force will be weakened during high-temperature melt spinning to ensure the normal flow of the melt. After being prepared into fibers, the hydrogen bond force will be enhanced as the temperature decreases, thereby realizing the binding of the additive containing anhydride structure.

[0021] Beneficial Effects

[0022] (1) The method for preparing polypropylene fiber with low auxiliary agent migration rate of the present invention provides a solution to the problem that anhydride auxiliary agents in polypropylene fiber are easy to migrate, and effectively prolongs the service life of the auxiliary agents;

[0023] (2) The present invention provides a method for preparing polypropylene fiber with low auxiliary agent mobility. The polypropylene containing aliphatic ring secondary amine structure can be obtained through a one-step reaction of the melt, and has an excellent effect of reducing the mobility of auxiliary agents containing acid anhydride groups. The preparation method is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the principle of reducing the mobility of additives by secondary amine polypropylene;

[0025] Figure 2 Schematic diagram of the reaction principle of polypropylene and olefin monomer containing aliphatic ring secondary amine. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0027] The present invention adopts the following testing method:

[0028] (1) Breaking strength: GB / T 14344-2022 was used to test the breaking strength of polypropylene fibers with low additive migration rate, with the gauge length controlled at 500 mm and the tensile rate at 500 mm / min;

[0029] (2) Elongation at break: GB / T 14344-2022 was used to test the elongation at break of polypropylene fibers with low additive migration rate, with the gauge length controlled at 500 mm and the tensile rate at 500 mm / min;

[0030] (3) Additive mobility: 1 g of fiber was placed in a sealed container containing 100 mL of n-hexane at room temperature for a specified time. The n-hexane solution was then filtered and concentrated to detect the additive content. The mobility was calculated by comparing it with the amount of fiber added.

[0031] Example 1

[0032] A method for preparing polypropylene fiber with low auxiliary agent migration rate is as follows:

[0033] (1) Material preparation: polypropylene with a melt index of 45 g / 10 min; chemical structure: The secondary amine olefin monomer containing aliphatic ring, wherein R 2 4; anhydride group content of 14wt% of the anhydride group with the auxiliary agent 1 (cas number 5066-71-7); initiator dibenzoyl peroxide;

[0034] (2) Figure 2 As shown, at 210° C., the polypropylene in step (1), the aliphatic ring secondary amine-containing olefin monomer and the initiator dibenzoyl peroxide are reactively blended by a twin-screw extruder, and extruded and granulated to obtain the aliphatic ring secondary amine-containing polypropylene;

[0035] The amount of the aliphatic ring secondary amine olefin monomer added is 1.2 wt% of the polypropylene, and the amount of the initiator dibenzoyl peroxide added is 0.07 wt% of the polypropylene;

[0036] (3) The aliphatic cyclic secondary amine-containing polypropylene obtained in step (2) is blended with the anhydride group-containing additive 1 obtained in step (1), and then melt-spinned at a temperature of 225° C. and a spinning speed of 2000 m / min. After melt-spinning, the fibers are oiled and bundled, and subjected to hot roller heat stretching treatment, with the first roller temperature being 85° C. and the second roller temperature being 125° C., to obtain polypropylene fibers with low additive mobility, such as Figure 1 As shown;

[0037] The amount of the additive with anhydride group is 3wt% of the polypropylene containing aliphatic cyclic secondary amine.

[0038] The breaking strength of the prepared polypropylene fiber with low additive mobility is 3.24 cN / dtex, and the breaking elongation is 27%; the additive mobility of the polypropylene fiber with low additive mobility placed in n-hexane at room temperature for 48h, 168h and 336h is 1%, 5% and 15% respectively.

[0039] Comparative Example 1

[0040] A method for preparing polypropylene fiber is basically the same as that of Example 1, except that step (2) is omitted and "polypropylene containing aliphatic cyclic secondary amine" in step (3) is replaced by "polypropylene".

[0041] The breaking strength of the prepared polypropylene fiber is 3.54 cN / dtex, and the breaking elongation is 28%. The additive migration rates of the polypropylene fiber placed in n-hexane at room temperature for 48h, 168h and 336h are 5%, 15% and 30% respectively.

[0042] By comparing Comparative Example 1 with Example 1, it can be found that the mobility of the additive in Example 1 is significantly lower than that in Comparative Example 1. This is because the secondary amine group in the secondary amine polypropylene in Example 1 has a binding effect on the additive 1 with anhydride groups, thereby effectively reducing the mobility of the additive.

[0043] Example 2

[0044] A method for preparing polypropylene fiber with low auxiliary agent migration rate is as follows:

[0045] (1) Material preparation: polypropylene with a melt index of 35 g / 10 min; chemical structure: The secondary amine olefin monomer containing aliphatic ring, wherein R 1 3; anhydride group-containing auxiliary agent 2 (CAS No. 119568-75-1) with an anhydride group content of 18 wt%; initiator dibenzoyl peroxide;

[0046] (2) Figure 2 As shown, at 220° C., the polypropylene in step (1), the aliphatic ring secondary amine-containing olefin monomer and the initiator dibenzoyl peroxide are reactively blended by a twin-screw extruder, and extruded and granulated to obtain the aliphatic ring secondary amine-containing polypropylene;

[0047] The amount of the aliphatic ring secondary amine olefin monomer added is 0.5wt% of the polypropylene, and the amount of the initiator dibenzoyl peroxide added is 0.05wt% of the polypropylene;

[0048] (3) blending the aliphatic cyclic secondary amine-containing polypropylene obtained in step (2) with the anhydride group-containing additive 2 obtained in step (1), and then melt-spinning the fibers at a temperature of 230° C. and a spinning speed of 1500 m / min. After melt-spinning, the fibers are oiled and bundled, and subjected to hot roller heat stretching treatment, with the first roller temperature at 90° C. and the second roller temperature at 130° C., to obtain polypropylene fibers with low additive mobility;

[0049] The amount of the additive with anhydride group is 1wt% of the polypropylene containing aliphatic cyclic secondary amine.

[0050] The breaking strength of the prepared polypropylene fiber with low additive mobility is 3.56 cN / dtex, and the breaking elongation is 26%; the additive mobility of the polypropylene fiber with low additive mobility placed in n-hexane at room temperature for 48h, 168h and 336h is 0%, 4% and 10% respectively.

[0051] Example 3

[0052] A method for preparing polypropylene fiber with low auxiliary agent migration rate is as follows:

[0053] (1) Material preparation: polypropylene with a melt index of 50 g / 10 min; chemical structure formula: The secondary amine olefin monomer containing aliphatic ring, wherein R 2 5; anhydride group content of 29wt% of anhydride group auxiliary 3 (cas number 4443-40-7); initiator dibenzoyl peroxide;

[0054] (2) at 200° C., the polypropylene in step (1), the aliphatic ring secondary amine-containing olefin monomer and the initiator dibenzoyl peroxide are reactively blended by a twin-screw extruder, and extruded and granulated to obtain the aliphatic ring secondary amine-containing polypropylene;

[0055] The amount of the aliphatic ring secondary amine olefin monomer added is 2.5wt% of the polypropylene, and the amount of the initiator dibenzoyl peroxide added is 0.1wt% of the polypropylene;

[0056] (3) blending the aliphatic cyclic secondary amine-containing polypropylene obtained in step (2) with the anhydride group-containing additive 3 obtained in step (1), and then melt-spinning the fibers at a temperature of 220° C. and a spinning speed of 2500 m / min. After melt-spinning, the fibers are oiled and bundled, and subjected to hot roller heat stretching treatment, with the first roller temperature at 80° C. and the second roller temperature at 120° C., to obtain polypropylene fibers with low additive mobility;

[0057] The amount of the additive with anhydride group is 0.1wt% of the polypropylene containing aliphatic cyclic secondary amine.

[0058] The breaking strength of the prepared polypropylene fiber with low additive mobility is 2.92 cN / dtex, and the breaking elongation is 23%; the additive mobility of the polypropylene fiber with low additive mobility placed in n-hexane at room temperature for 48h, 168h and 336h is 1%, 3% and 12% respectively.

[0059] Example 4

[0060] A method for preparing polypropylene fiber with low auxiliary agent migration rate is as follows:

[0061] (1) Material preparation: polypropylene with a melt index of 15 g / 10 min; chemical structure formula: The secondary amine olefin monomer containing aliphatic ring, wherein R 1 3; an anhydride group-containing auxiliary agent 4 (CAS No. 15781-96-1) with an anhydride group content of 25 wt%; initiator dibenzoyl peroxide;

[0062] (2) at 230° C., the polypropylene in step (1), the aliphatic ring secondary amine-containing olefin monomer and the initiator dibenzoyl peroxide are reactively blended by a twin-screw extruder, and extruded and granulated to obtain the aliphatic ring secondary amine-containing polypropylene;

[0063] The amount of the aliphatic ring secondary amine olefin monomer added is 5wt% of the polypropylene, and the amount of the initiator dibenzoyl peroxide added is 0.1wt% of the polypropylene;

[0064] (3) blending the aliphatic cyclic secondary amine-containing polypropylene obtained in step (2) with the anhydride group-containing additive 4 obtained in step (1), and then melt-spinning the fibers at a temperature of 260° C. and a spinning speed of 2000 m / min. After melt-spinning, the fibers are oiled and bundled, and subjected to hot roller heat stretching treatment, with the first roller temperature at 90° C. and the second roller temperature at 130° C., to obtain polypropylene fibers with low additive mobility;

[0065] The amount of the additive with anhydride group is 0.5wt% of the polypropylene containing aliphatic cyclic secondary amine.

[0066] The breaking strength of the prepared polypropylene fiber with low additive mobility is 3.05 cN / dtex, and the breaking elongation is 22%; the additive mobility of the polypropylene fiber with low additive mobility placed in n-hexane at room temperature for 48h, 168h and 336h is 0%, 3% and 6% respectively.

Claims

1. A method for preparing polypropylene fiber with low auxiliary agent mobility, characterized in that: The polypropylene containing aliphatic cyclic secondary amine and an auxiliary agent with anhydride groups are blended and melt-spinned to obtain the polypropylene fiber with low auxiliary agent mobility; The preparation method of the polypropylene containing aliphatic ring secondary amine is as follows: polypropylene, initiator dibenzoyl peroxide, and aliphatic ring secondary amine olefin monomer are reactively blended and extruded by a twin-screw extruder to prepare the polypropylene containing aliphatic ring secondary amine; The chemical formula of the aliphatic ring secondary amine olefin monomer is Wherein, R1 is 3, and R2 is 4 or 5; The additive migration rates of the polypropylene fiber with low additive migration rate after being placed in n-hexane at room temperature for 48 hours, 168 hours and 336 hours are not higher than 1%, 5% and 15% respectively.

2. The method for preparing a polypropylene fiber with low auxiliary agent mobility according to claim 1, characterized in that: The melt index of polypropylene is 15 to 50 g / 10 min.

3. The method for preparing a polypropylene fiber with low auxiliary agent mobility according to claim 2, characterized in that: The amount of the aliphatic ring secondary amine olefin monomer added is 0.5-5wt% of the polypropylene, and the amount of the initiator dibenzoyl peroxide added is 0.05-0.1wt% of the polypropylene.

4. The method for preparing a polypropylene fiber with low auxiliary agent mobility according to claim 1, characterized in that: The temperature of the twin-screw reactive blending is 200-230°C.

5. The method for preparing a polypropylene fiber with low auxiliary agent mobility according to claim 1, characterized in that: The added amount of the auxiliary agent with anhydride group is 0.1-3wt% of the polypropylene containing aliphatic cyclic secondary amine.

6. The method for preparing a polypropylene fiber with low auxiliary agent mobility according to claim 1, characterized in that: The content of the acid anhydride group in the auxiliary agent with acid anhydride groups is not less than 10 wt %.

7. The method for preparing a polypropylene fiber with low auxiliary agent mobility according to claim 1, characterized in that: The spinning temperature is 220-260°C, and the spinning speed is 1500-2500 m / min.

8. The method for preparing a polypropylene fiber with low auxiliary agent mobility according to claim 7, characterized in that: After melt spinning, the fibers are oiled, bundled, and subjected to hot roller heat stretching treatment. The temperature of the first roller is 80-90°C, and the temperature of the second roller is 120-130°C.

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