WO2025161267A1 - Methods for preparing softening flame retardant and preparing high-strength flexible flame-retardant polyester industrial yarn - Google Patents

Abstract

The present invention belongs to the field of polyester industrial filaments, and relates to methods for preparing a softening flame retardant and preparing a high-strength flexible flame-retardant polyester industrial yarn. The softening flame retardant is silicon dioxide which is surface grafted with polydimethylsiloxane; a preparation method therefor comprises subjecting silicon dioxide and hydroxyl-terminated polydimethylsiloxane to a grafting reaction to obtain the softening flame retardant; and the use thereof is to use the softening flame retardant and low-viscosity polyester chips as main raw materials to prepare a softening flame-retardant polyester masterbatch, which is then subjected to melt-blending and spinning together with high-viscosity polyester chips, so as to prepare a high-strength flexible flame-retardant polyester industrial yarn, wherein the intrinsic viscosity of the low-viscosity polyester chips is 0.65-0.68 dL/g, and the intrinsic viscosity of the high-viscosity polyester chips is 1.05-1.20 dL/g. The preparation methods of the present invention are simple; the flexibility and flame retardancy of the polyester industrial yarn can both be improved after the prepared softening flame retardant is added to the polyester industrial yarn as an additive; and the obtained high-strength flexible flame-retardant polyester industrial yarn has good performance.

Description

A method for preparing a flexible flame retardant and a high-strength flexible flame-retardant polyester industrial yarn Technical Field

The invention belongs to the field of polyester industrial filaments and relates to a softening flame retardant and a preparation method of high-strength flexible flame retardant polyester industrial filaments.

Background Art

High-strength, coarse-denier polyester industrial yarn is considered a cost-effective high-performance fiber due to its excellent mechanical properties, stable chemical properties, mature processing technology and low cost. It is widely used in engineering fields such as airbags, tire cords, conveyor belts, and outdoor billboards.

However, since polyethylene terephthalate contains benzene rings and its molecular chain is rigid, the polyester industrial yarn that has been fully stretched and heat-set has poor flexibility (high initial modulus and low elongation at break). Poor flexibility is the main reason for the loss of strength during weaving and the fabric's tendency to bend and break. This affects the mechanical properties of the polyester industrial yarn and limits its application in fields such as inflatable rafts that require material flexibility.

With the continuous industrial development of polyester industrial yarns and their products, a series of functional products have been derived. Among them, flame-retardant polyester industrial yarn products are widely used in the field of industrial textiles due to their good resistance to combustion. The flame-retardant modification of polyester industrial yarns needs to achieve the flame-retardant effects such as the industrial yarns and their products can only be charred without open flames when in direct contact with fire, and can extinguish themselves without afterglow or smoldering after the fire source is removed. The main methods to achieve these flame-retardant effects include copolymerization flame-retardant modification, blending flame-retardant modification, and finishing flame-retardant modification. Blending flame-retardant modification is to add flame retardants to polymers through mechanical mixing methods. It is easy to use and has strong operability. It is widely used in polymer modification research. At present, the breaking strength of the blended flame-retardant modified polyester industrial yarn will be lost to a certain extent, which makes it difficult to meet the application of flame-retardant polyester industrial yarn in high-end fire protection and military fields. For example, WO2020/238688A1 uses high molecular weight phosphorus-based flame retardants and high-viscosity polyester chips to blend and melt-spin, with a breaking strength of 6.0~7.5cN/dtex, and LOI value (limiting oxygen index value) ≥32%. For example, CN110528109A thickens the homemade end-epoxy phosphorus-based flame-retardant polyester chips as a functional added component, and uses an online addition process to melt-spin to prepare high-strength polyester industrial yarn with an LOI value ≥28% and a breaking strength of 6.5~7.6cN/dtex.

Therefore, it is necessary to develop an additive that can improve the flexibility and flame retardant properties of polyester industrial yarn while avoiding the loss of mechanical properties of polyester industrial yarn, and then produce polyester industrial yarn with excellent flexibility, flame retardant properties and mechanical properties.

Summary of the Invention

The purpose of the present invention is to solve the problems existing in the prior art and provide a high-strength flexible flame-retardant polyester industrial yarn and a preparation method thereof.

In order to achieve the above object, the technical solution adopted by the present invention is as follows:

A flexible flame retardant, which is silicon dioxide with polydimethylsiloxane grafted on the surface.

The flexible flame retardant of the present invention can be added as an additive to polyester industrial yarn to improve the flexibility and flame retardancy of the polyester industrial yarn, while avoiding adverse effects on the mechanical properties of the polyester industrial yarn.

As the preferred technical solution:

As described above, the degree of polymerization n of the polydimethylsiloxane is 15 to 40, which ensures that the preparation of the flexible flame retardant is low in difficulty, low in energy consumption, narrow in molecular weight distribution, and high in quality. It also ensures that the flexible flame retardant is added as an additive to the polyester industrial yarn to exert its flexible and flame-retardant effects without adversely affecting the mechanical properties of the polyester industrial yarn.

The above-mentioned flexible flame retardant has a grafting rate of polydimethylsiloxane on the surface of silica of 3-10%. This ensures that the flexible flame retardant can play a better role in both flexible and flame retardant performance after being added as an additive to polyester industrial yarn.

The present invention also provides a method for preparing a flexible flame retardant as described in any of the preceding items, wherein silicon dioxide is subjected to a grafting reaction with hydroxyl-terminated polydimethylsiloxane to obtain the flexible flame retardant.

As the preferred technical solution:

The method as described above is specifically as follows: adding a cyclic organosiloxane, a promoter and an alkaline catalyst to a reaction vessel equipped with a condensing reflux device and a stirring device, reacting at 90 to 130° C. for 1 to 3 hours under nitrogen or inert gas protection and stirring (ring-opening polymerization occurs in this step to obtain polydimethylsiloxane), adding water and tetraethyl orthosilicate, and then reacting at 60 to 90° C. for 3 to 6 hours under nitrogen or inert gas protection and stirring (tetraethyl orthosilicate undergoes hydrolysis reaction to produce silicon dioxide, and water reacts with polysiloxane). Dimethylsiloxane reacts to produce hydroxyl-terminated polydimethylsiloxane, which then undergoes a grafting reaction with the surface hydroxyl groups of silica. A flexible flame retardant is obtained by post-treatment (distillation under reduced pressure, stirring until no fraction is distilled out, stopping stirring, cooling to room temperature, washing with water, and centrifugation). The cyclic organosiloxane is dimethylcyclosiloxane (DMC). The flexible flame retardant is prepared in situ under base catalysis in the present invention, which is simpler than the conventional method of preparing silica and then modifying it. The reaction equation is shown in Figure 2.

In the method described above, the mass ratio of cyclic organosiloxane, accelerator, alkaline catalyst, water and tetraethyl orthosilicate is 44-56:1.8-3.3:3.5-7.1:12-16:32-40; the accelerator is one or more of ethylene glycol, triethylamine and dibutyltin dilaurate; and the alkaline catalyst is one or more of sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide.

The present invention also provides an application of a flexible flame retardant as described in any of the preceding items, wherein a flexible flame retardant polyester masterbatch is prepared with the flexible flame retardant and low-viscosity polyester chips as main raw materials, and then the masterbatch is melt-blended with high-viscosity polyester chips to prepare high-strength flexible flame retardant polyester industrial yarn, wherein the intrinsic viscosity of the low-viscosity polyester chips is 0.65-0.68 dL/g, and the intrinsic viscosity of the high-viscosity polyester chips is 1.05-1.20 dL/g; if the flexible flame retardant is directly added to the polyester, the flexible flame retardant is difficult to disperse evenly; if the flexible flame retardant is introduced into the polyester molecular chain to prepare the flexible flame retardant polyester chips, since the main chain structure of the polyester is destroyed, it is difficult to increase the viscosity to the viscosity required for the polyester industrial yarn; the present invention first uses the flexible flame retardant and low-viscosity polyester chips as main raw materials to prepare the flexible flame retardant The softened flame retardant polyester masterbatch is melt-blended and spun with the high-viscosity polyester chips, which effectively solves the above two problems.

As a limited technical solution:

As described above, the preparation process of the flexible flame-retardant polyester masterbatch is as follows: after pre-mixing 70-85% of low-viscosity polyester chips, 15-30% of the flexible flame retardant and the remaining amount of the antioxidant by weight percentage, the mixture is melt-blended and extruded using a twin-screw extruder, and then cooled, granulated and dried to obtain the flexible flame-retardant polyester masterbatch.

For the application described above, the mass ratio of the softened flame-retardant polyester masterbatch to the high-viscosity polyester chips is 5-10:90-95, and the melt-blending spinning adopts a one-step spinning and stretching process. The process parameters of the melt-blending spinning include: screw temperature 280-310°C, post-drawing roller temperature 60-70°C, post-drawing roller speed 500-650m/min, post-drawing roller temperature 90-100°C, post-drawing roller temperature 125-135°C, post-drawing roller temperature 210-240°C, post-drawing roller temperature 140-150°C, and winding speed 3000-3500m/min.

For the above-mentioned applications, the high-strength flexible flame-retardant polyester industrial yarn has a breaking strength of ≥7.6 cN/dtex, an elongation at break of 15-30%, an initial modulus of 40-80 cN/dtex, an LOI value of 32-36%, a smoke density (specific optical density) of 9.42-21.13, and quickly self-extinguishes under flame without any melt droplets, with significantly reduced smoke and gas release;

The elongation at break of the high-strength polyester industrial yarn in the prior art is 14-17%, while the high-strength, flexible, flame-retardant polyester industrial yarn of the present invention has a higher elongation at break than that of the prior art. The initial modulus of the high-strength polyester industrial yarn in the prior art is about 100 cN/dtex, while the initial modulus of the high-strength, flexible, flame-retardant polyester industrial yarn of the present invention is significantly lower than that of the prior art. This is because the polydimethylsiloxane chain segment of the flexible flame retardant of the present invention plays a plasticizing role, thereby improving the flexibility of the polyester industrial yarn. The polyester industrial yarn has a relatively large rigidity due to the presence of benzene rings and a relatively high molecular weight. The addition of the flexible flame retardant destroys the hydrogen bonds between macromolecules and forms random, loose hydrogen bonds with polyester macromolecules, thereby increasing the flexibility of the molecular chain and reducing the ability to resist external deformation, thereby reducing the initial modulus, making the molecular chain easier to stretch, and making it easier for the molecular chain segments to slip relative to each other. The elongation at break is increased, and the flexibility is improved. The present invention solves the problem of poor flexibility and difficulty in bending of the polyester industrial yarn.

The LOI value of the high-strength polyester industrial yarn in the prior art is about 22%. The LOI value of the high-strength, flexible, flame-retardant polyester industrial yarn of the present invention is significantly higher than that of the prior art. This is because the polydimethylsiloxane and silica in the softening flame retardant of the present invention work together to improve the flame retardant properties of the polyester industrial yarn. When the polyester industrial yarn burns, silica migrates to the surface to form a dense and uniform silicon-containing carbon layer, and fills and supports the formed carbon layer, which is beneficial to the densification and stability of the carbon layer, effectively blocking heat radiation and heat conduction, preventing the escape of combustible gases, and isolating oxygen. The migration of silica also accelerates the migration rate of polydimethylsiloxane to the surface. Polydimethylsiloxane has the effect of reducing the thermal decomposition rate and promoting carbonization. During the migration process, it cross-links with the thermal decomposition products of polyester to form a protective carbon layer containing Si-O-C bonds and Si-C bonds. The double carbon layer has the effects of preventing the escape of volatiles from thermal degradation of polyester and preventing molten droplets from dripping.

The high-strength flexible flame-retardant polyester industrial yarn of the present invention has a high breaking strength. On the one hand, due to the polydimethylsiloxane and dioxygen Silicone has a good synergistic flame retardant effect and can achieve a good flame retardant effect with a relatively small addition amount, thus avoiding the adverse effect of excessive addition on the breaking strength of the polyester industrial yarn. On the other hand, since the softened flame retardant polyester masterbatch synthesized by the present invention has good compatibility and migration ability with high-viscosity PET, it can be evenly distributed in the amorphous region, so the breaking strength of the polyester industrial yarn is not affected.

Beneficial effects

(1) The flexible flame retardant prepared by the present invention has a one-step process route that is simple to operate, has low energy consumption, and is suitable for industrial production. The introduction of the flexible polydimethylsiloxane chain segment acts as a plasticizer, thereby improving the activity of the molecular chain and making the molecular chain easy to stretch. After being added to polyester industrial yarn, the flexibility of the polyester industrial yarn can be improved.

(2) The method of the present invention for preparing high-strength flexible flame-retardant polyester industrial yarn overcomes the problem of easy agglomeration and difficult dispersion of silica, and silicone and silica play a synergistic flame retardant role, with excellent flame retardant effect at a small addition amount and less loss of mechanical properties.

(3) The present invention combines hydroxyl-terminated polydimethylsiloxane with hydroxyl-containing silicon dioxide through chemical bonds, thereby improving the compatibility of silicon dioxide with polyester.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an infrared spectrum of silicon dioxide with polydimethylsiloxane grafted on its surface in Example A2 of the present invention;

FIG2 is a reaction equation for preparing a flexible flame retardant;

FIG3 is a cross-sectional SEM image of the softened flame-retardant polyester industrial yarn in Example B1 of the present invention.

DETAILED DESCRIPTION

Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, 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 equally within the scope limited by the appended claims of the application.

The testing methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

Grafting rate (%) = W/(1-W) x 100%, where W is the thermal weight loss rate of silica with polydimethylsiloxane grafted on its surface as measured by TGA.

Breaking strength and breaking elongation: measured with reference to GB/T 14344-2008 Test method for tensile properties of chemical fiber filaments; the mechanical properties of the fiber multifilaments were tested using a 3356 Instron tensiometer; test conditions: temperature (20±5)°C, relative humidity (65±5)%, clamping distance 500mm, tensile rate 500mm/min; each group of samples was tested 20 times in the experiment and the average value was taken.

Breaking strength (cN/dtex) = breaking strength/fineness; breaking strength and breaking elongation are the mechanical property test data obtained simultaneously during the above tensile test; fineness is measured using a YG086 yarn length measuring machine and a FA2004 electronic scale (Max: 200g, Each sample was wound 5 times, 100 m each time, and the fiber was weighed each time. The weight was recorded and the average value was calculated. The result was magnified 100 times to obtain the weight of 10,000 m long fiber, which was recorded as the fiber fineness.

Initial modulus: The slope of the stress-strain curve when the elongation at break is 1% in the above mechanical property test.

LOI value: According to ASTM D2863-2017 Standard Test Method for Minimum Oxygen Concentration Required to Support Candle-Like Combustion of Plastics (Oxygen Index), the LOI value of the prepared polyester industrial yarn was tested using a PX-01-005 oxygen index analyzer.

Smoke density (specific optical density): Determined in accordance with GB/T 8323.2-2008 Plastics—Smoke Generation—Part 2: Single-chamber Test Method for Smoke Density. The prepared polyester industrial yarn was fabricated into a 6mm thick fabric, 75mm in length and width, for testing under an irradiance of 25kW/ ^m² and a pilot flame. A transmittance-time curve was then constructed for the fabric, and the percent transmittance at 10 minutes was measured as _T₁₀ . The specific optical density was calculated as: _D₁₀₀ = _132log₁₀ (100/ _T₁₀ ), where 132 is a factor derived from the expression V/AL for the test chamber. V is the test chamber volume, A is the exposed area of the specimen, and L is the optical path length.

Example A1

A flexible flame retardant is silicon dioxide with polydimethylsiloxane grafted on the surface, with a particle size of 20-100 nm; wherein the polymerization degree n of the polydimethylsiloxane is 15, and the grafting rate of the polydimethylsiloxane on the silicon dioxide surface is 5%.

The method for preparing the above-mentioned flexible flame retardant comprises the following steps:

(1) Preparation of raw materials;

Cyclic organosiloxane: dimethylcyclosiloxane (DMC);

Accelerator: ethylene glycol;

Alkaline catalyst: sodium hydroxide;

water;

Tetraethyl orthosilicate;

Nitrogen or inert gas;

(2) Cyclic organosiloxane, accelerator and alkaline catalyst are added to a reaction vessel equipped with a condensing reflux device and a stirring device, and reacted at 90°C for 3 hours under the protection of nitrogen or inert gas and stirring, and then water and tetraethyl orthosilicate are added, and then reacted at 70°C for 5 hours under the protection of nitrogen or inert gas and stirring. After post-treatment, a flexible flame retardant is obtained; wherein the mass ratio of cyclic organosiloxane, accelerator, alkaline catalyst, water and tetraethyl orthosilicate is 44:2.0:3.0:12:39.

Comparative Example A1

A method for preparing polydimethylsiloxane is basically the same as step (2) of Example A1, except that ethyl orthosilicate is not added.

Comparative Example A2

A method for preparing silicon dioxide is basically the same as step (2) of Example A1, except that no cyclopentane is added. Organosiloxane.

Comparative Example A3

A method for preparing a flexible flame retardant comprises adding a cyclic organosiloxane (same as in Example 1), an accelerator (same as in Example 1), and an alkaline catalyst (same as in Example 1) to a reaction vessel equipped with a condensing reflux device and a stirring device, reacting at 90° C. for 3 hours under nitrogen or inert gas protection and stirring, adding a silica/methyl isobutyl ketone (MIBK) dispersion (wherein silica accounts for 30 wt% of the dispersion), and further reacting at 70° C. for 5 hours under nitrogen or inert gas protection and stirring. After post-treatment, the flexible flame retardant is obtained. The mass ratio of the cyclic organosiloxane, the accelerator, the alkaline catalyst, and the silica/methyl isobutyl ketone dispersion is 44:2.0:3.0:51.

The particle size of the finally prepared flexible flame retardant is 200-400 nm.

Example A2

A flexible flame retardant is silicon dioxide with polydimethylsiloxane grafted on the surface, with a particle size of 20-100 nm; wherein the polymerization degree n of the polydimethylsiloxane is 23, and the grafting rate of the polydimethylsiloxane on the silicon dioxide surface is 7%.

The method for preparing the above-mentioned flexible flame retardant comprises the following steps:

(1) Preparation of raw materials;

Cyclic organosiloxane: dimethylcyclosiloxane (DMC);

Accelerator: triethylamine;

Alkaline catalyst: potassium hydroxide;

water;

Tetraethyl orthosilicate;

Nitrogen or inert gas;

(2) Cyclic organosiloxane, accelerator and alkaline catalyst are added to a reaction vessel equipped with a condensing reflux device and a stirring device, and reacted at 95°C for 2.5 hours under the protection of nitrogen or inert gas and stirring. Water and tetraethyl orthosilicate are then added, and the reaction is continued at 60°C for 6 hours under the protection of nitrogen or inert gas and stirring. After post-treatment, a flexible flame retardant is obtained (according to the infrared spectrum, the Si-O-Si stretching vibration peaks of silica near 1100 cm ^-1 and 800 cm ^-1 are enhanced after grafting, and the asymmetric stretching vibration peak of CH at 2970 cm ^-1 and the symmetric stretching vibration peak of Si- _CH3 at 1260 cm ^-1 are enhanced, indicating that polydimethylsiloxane has been grafted on the _SiO2 surface, as shown in Figure 1); wherein, the mass ratio of cyclic organosiloxane, accelerator, alkaline catalyst, water and tetraethyl orthosilicate is 46:3.3:3.2:14:33.5.

Example A3

A flexible flame retardant is silicon dioxide with polydimethylsiloxane grafted on the surface, with a particle size of 20-100 nm; wherein the polymerization degree n of the polydimethylsiloxane is 32, and the grafting rate of the polydimethylsiloxane on the silicon dioxide surface is 10%.

The method for preparing the above-mentioned flexible flame retardant comprises the following steps:

(1) Preparation of raw materials;

Cyclic organosiloxane: dimethylcyclosiloxane (DMC);

Accelerator: dibutyltin dilaurate;

Basic catalyst: tetramethylammonium hydroxide;

water;

Tetraethyl orthosilicate;

Nitrogen or inert gas;

(2) Adding cyclic organosiloxane, accelerator and alkaline catalyst into a reaction vessel equipped with a condensing reflux device and a stirring device, reacting at 120°C for 1 hour under the protection of nitrogen or inert gas and stirring, adding water and tetraethyl orthosilicate, and then reacting at 85°C for 3.5 hours under the protection of nitrogen or inert gas and stirring, and obtaining a flexible flame retardant after post-treatment; wherein the mass ratio of cyclic organosiloxane, accelerator, alkaline catalyst, water and tetraethyl orthosilicate is 48:1.9:5.1:12:33.

Example A4

A flexible flame retardant is silicon dioxide with polydimethylsiloxane grafted on the surface, with a particle size of 20-100 nm; wherein the polymerization degree n of the polydimethylsiloxane is 40, and the grafting rate of the polydimethylsiloxane on the silicon dioxide surface is 3%.

The method for preparing the above-mentioned flexible flame retardant comprises the following steps:

(1) Preparation of raw materials;

Cyclic organosiloxane: dimethylcyclosiloxane (DMC);

Accelerator: a mixture of ethylene glycol and triethylamine in a mass ratio of 1:1;

Alkaline catalyst: a mixture of sodium hydroxide and potassium hydroxide in a mass ratio of 1:1;

water;

Tetraethyl orthosilicate;

Nitrogen or inert gas;

(2) Adding cyclic organosiloxane, accelerator and alkaline catalyst into a reaction vessel equipped with a condensing reflux device and a stirring device, reacting at 130°C for 1 hour under the protection of nitrogen or inert gas and stirring, adding water and tetraethyl orthosilicate, and then reacting at 90°C for 3 hours under the protection of nitrogen or inert gas and stirring, and post-treating to obtain a flexible flame retardant; wherein the mass ratio of cyclic organosiloxane, accelerator, alkaline catalyst, water and tetraethyl orthosilicate is 50:1.8:3.2:13:32.

Example B1

A method for preparing high-strength flexible flame-retardant polyester industrial yarn, comprising the following steps:

(1) Preparation of raw materials;

Low viscosity polyester chips: intrinsic viscosity is 0.67dL/g;

Softening flame retardant: the softening flame retardant prepared in Example A1;

Antioxidant: Irganox Antioxidant 1010;

High viscosity polyester chips: intrinsic viscosity is 1.05dL/g;

(2) Premixing 70% of low-viscosity polyester chips, 27% of a flexible flame retardant, and the remainder of an antioxidant by weight, melt-blending and extruding the mixture using a twin-screw extruder, followed by cooling, granulation, and drying to obtain a flexible flame retardant polyester masterbatch;

(3) melt-blending the softening flame-retardant polyester masterbatch prepared in step (2) with high-viscosity polyester chips to produce high-strength flexible flame-retardant polyester industrial yarn; wherein the mass ratio of the softening flame-retardant polyester masterbatch to the high-viscosity polyester chips is 5:95;

The melt blending spinning adopts a one-step spinning and stretching process, and its process parameters include: screw temperature 280℃, post-drawing roller temperature 60℃, post-drawing roller speed 500m/min, post-drawing roller temperature 90℃, post-drawing roller temperature 125℃, post-drawing roller temperature 210℃, post-drawing roller temperature 150℃, and winding speed 3000m/min.

The cross-sectional SEM image of the high-strength flexible flame-retardant polyester industrial yarn is shown in Figure 3. It can be seen from the figure that the softening flame retardant is evenly dispersed without agglomeration, no yarn breakage occurs during the spinning process, and there is no effect on the spinnability of the industrial yarn. The post-draft ratio can reach 6 times.

The final high-strength flexible flame-retardant polyester industrial yarn has a breaking strength of 7.6 cN/dtex, a breaking elongation of 20%, an initial modulus of 63 cN/dtex, an LOI value of 35%, and a smoke density (specific optical density) of 12.66.

Comparative Example B1

A method for preparing polyester industrial yarn is basically the same as Example B1, except that the flexibilizing flame retardant used in Example B1 is replaced by an equal mass of polydimethylsiloxane from Comparative Example A1.

The final polyester industrial yarn has a breaking strength of 7.6 cN/dtex, a breaking elongation of 35%, an initial modulus of 38 cN/dtex, an LOI value of 29%, and a smoke density of 24.45.

By comparing Comparative Example B1 and Example B1, it can be seen that since Comparative Example B1 contains only polydimethylsiloxane, the initial modulus is reduced and the elongation at break is increased, but the flame retardant effect is poor. This is because the polydimethylsiloxane content is increased and the flexibility is increased, but the silicon content in polydimethylsiloxane is difficult to achieve a flame retardant effect equivalent to that of silicon dioxide.

Comparative Example B2

A method for preparing polyester industrial yarn is basically the same as that of Example B1, except that the softening flame retardant used in Example B1 is replaced by an equal mass of silica in Comparative Example A2.

The final polyester industrial yarn has a breaking strength of 8.0 cN/dtex, a breaking elongation of 14%, an initial modulus of 98 cN/dtex, an LOI value of 34%, and a smoke density of 10.25.

Comparing Comparative Example 2 with Example B1, it can be seen that since Comparative Example 2 does not contain polydimethylsiloxane for softening, the modulus of the industrial yarn is difficult to reduce, the elongation at break is small, and the flame retardant effect is reduced to a certain extent. This is because the polydimethylsiloxane in the comparative example 2 does not contain polydimethylsiloxane for softening. Silicon oxide has no softening effect and loses the synergistic flame retardant effect of silicon dioxide and polydimethylsiloxane.

Comparative Example B3

A method for preparing polyester industrial yarn is basically the same as that of Example B1, except that the softening flame retardant used in Example B1 is replaced by the softening flame retardant of Comparative Example A3 of equal mass.

The softening flame retardant is unevenly dispersed in the polyester industrial yarn, and the agglomerates cause serious yarn breakage during the spinning process, and the post-drawing ratio is only 3.6 times.

The final polyester industrial yarn has a breaking strength of 5.2 cN/dtex, an elongation at break of 18%, an initial modulus of 45 cN/dtex, an LOI value of 28%, and a smoke density (specific optical density) of 23.25. Comparing Example B1 with Comparative Example B3, it can be seen that the uneven dispersion of the softening flame retardant affects the mechanical properties and flame retardant properties of the industrial yarn.

Example B2

A method for preparing high-strength flexible flame-retardant polyester industrial yarn, comprising the following steps:

(1) Preparation of raw materials;

Low viscosity polyester chips: intrinsic viscosity is 0.67dL/g;

Softening flame retardant: the softening flame retardant prepared in Example A2;

Antioxidant: Irganox Antioxidant 1010;

High viscosity polyester chips: intrinsic viscosity is 1.1dL/g;

(2) Premixing 65% of low-viscosity polyester chips, 30% of a flexible flame retardant, and the remainder of an antioxidant by weight, melt-blending and extruding the mixture using a twin-screw extruder, followed by cooling, granulation, and drying to obtain a flexible flame retardant polyester masterbatch;

(3) melt-blending the softening flame-retardant polyester masterbatch prepared in step (2) with high-viscosity polyester chips to prepare high-strength flexible flame-retardant polyester industrial yarn; wherein the mass ratio of the softening flame-retardant polyester masterbatch to the high-viscosity polyester chips is 10:90;

The melt blending spinning adopts a one-step spinning and stretching process, and its process parameters include: screw temperature 290℃, post-drawing roller temperature 60℃, post-drawing roller speed 500m/min, post-drawing roller temperature 90℃, post-drawing roller temperature 125℃, post-drawing roller temperature 210℃, post-drawing roller temperature 140℃, and winding speed 3200m/min.

The softening flame retardant is evenly dispersed in the polyester industrial yarn, and there is no yarn breakage during the spinning process. It has no effect on the spinnability of the industrial yarn, and the post-drafting ratio can reach 6.4 times.

The final high-strength flexible flame-retardant polyester industrial yarn has a breaking strength of 7.8 cN/dtex, a breaking elongation of 30%, an initial modulus of 40 cN/dtex, an LOI value of 36%, and a smoke density (specific optical density) of 9.42.

Example B3

A method for preparing high-strength flexible flame-retardant polyester industrial yarn, comprising the following steps:

(1) Preparation of raw materials;

Low viscosity polyester chips: intrinsic viscosity is 0.65dL/g;

Softening flame retardant: the softening flame retardant prepared in Example A3;

Antioxidant: Irganox Antioxidant 1010;

High viscosity polyester chips: intrinsic viscosity is 1.05dL/g;

(2) Premixing 65% of low-viscosity polyester chips, 25% of a flexible flame retardant, and the remainder of an antioxidant by weight, melt-blending and extruding the mixture using a twin-screw extruder, followed by cooling, granulation, and drying to obtain a flexible flame retardant polyester masterbatch;

(3) melt-blending the softening flame-retardant polyester masterbatch prepared in step (2) with high-viscosity polyester chips to prepare high-strength flexible flame-retardant polyester industrial yarn; wherein the mass ratio of the softening flame-retardant polyester masterbatch to the high-viscosity polyester chips is 8:92;

The melt blending spinning adopts a one-step spinning and stretching process, and its process parameters include: screw temperature 290℃, post-drawing roller temperature 60℃, post-drawing roller speed 600m/min, post-drawing roller temperature 90℃, post-drawing roller temperature 125℃, post-drawing roller temperature 210℃, post-drawing roller temperature 140℃, and winding speed 3300m/min.

The softening flame retardant is evenly dispersed in the polyester industrial yarn, and there is no yarn breakage during the spinning process. It has no effect on the spinnability of the industrial yarn, and the post-draft ratio can reach 5.5 times.

The final high-strength flexible flame-retardant polyester industrial yarn has a breaking strength of 7.9 cN/dtex, a breaking elongation of 22%, an initial modulus of 70 cN/dtex, an LOI value of 33%, and a smoke density (specific optical density) of 18.29.

Example B4

A method for preparing high-strength flexible flame-retardant polyester industrial yarn, comprising the following steps:

(1) Preparation of raw materials;

Low viscosity polyester chips: intrinsic viscosity is 0.68dL/g;

Softening flame retardant: the softening flame retardant prepared in Example A4;

Antioxidant: Irganox Antioxidant 1010;

High viscosity polyester chips: intrinsic viscosity is 1.15dL/g;

(2) Premixing 73% of low-viscosity polyester chips, 20% of a flexible flame retardant, and the remainder of an antioxidant by weight, melt-blending and extruding the mixture using a twin-screw extruder, followed by cooling, granulation, and drying to obtain a flexible flame retardant polyester masterbatch;

(3) melt-blending the softening flame-retardant polyester masterbatch prepared in step (2) with high-viscosity polyester chips to prepare high-strength flexible flame-retardant polyester industrial yarn; wherein the mass ratio of the softening flame-retardant polyester masterbatch to the high-viscosity polyester chips is 10:90;

The melt blending spinning adopts a one-step spinning and stretching process, and its process parameters include: screw temperature 290℃, post-drawing roller temperature 70℃, post-drawing roller speed 600m/min, post-drawing roller temperature 100℃, post-drawing roller temperature 130℃, post-drawing roller temperature 230℃, post-drawing roller temperature 140℃, and winding speed 3500m/min.

The softening flame retardant is evenly dispersed in the polyester industrial yarn, and there is no yarn breakage during the spinning process. It has no effect on the spinnability of the industrial yarn, and the post-drafting ratio can reach 5.8 times.

The final high-strength flexible flame-retardant polyester industrial yarn has a breaking strength of 8.2 cN/dtex, a breaking elongation of 26%, an initial modulus of 52 cN/dtex, an LOI value of 35%, and a smoke density (specific optical density) of 14.37.

Example B5

A method for preparing high-strength flexible flame-retardant polyester industrial yarn, comprising the following steps:

(1) Preparation of raw materials;

Low viscosity polyester chips: intrinsic viscosity is 0.68dL/g;

Softening flame retardant: the softening flame retardant prepared in Example A1;

Antioxidant: Irganox Antioxidant 1010;

High viscosity polyester chips: intrinsic viscosity is 1.20dL/g;

(2) 82% of low-viscosity polyester chips, 15% of a flexible flame retardant, and the remainder of an antioxidant were pre-mixed by weight, and the mixture was melt-blended and extruded using a twin-screw extruder, followed by cooling, granulation, and drying to obtain a flexible flame retardant polyester masterbatch;

(3) melt-blending the softening flame-retardant polyester masterbatch prepared in step (2) with high-viscosity polyester chips to produce high-strength flexible flame-retardant polyester industrial yarn; wherein the mass ratio of the softening flame-retardant polyester masterbatch to the high-viscosity polyester chips is 5:95;

The melt blending spinning adopts a one-step spinning and stretching process, and its process parameters include: screw temperature 310℃, post-drawing roller temperature 70℃, post-drawing roller speed 650m/min, post-drawing roller temperature 100℃, post-drawing roller temperature 135℃, post-drawing roller temperature 240℃, post-drawing roller temperature 150℃, and winding speed 3500m/min.

The softening flame retardant is evenly dispersed in the polyester industrial yarn, and there is no yarn breakage during the spinning process. It has no effect on the spinnability of the industrial yarn, and the post-drafting ratio can reach 5.4 times.

The final high-strength flexible flame-retardant polyester industrial yarn has a breaking strength of 8.2 cN/dtex, a breaking elongation of 15%, an initial modulus of 80 cN/dtex, an LOI value of 32%, and a smoke density (specific optical density) of 21.13.

Claims (6)

A method for preparing high-strength, flexible, flame-retardant polyester industrial yarn, characterized in that a flexible flame-retardant polyester masterbatch is prepared using a flexible flame retardant and low-viscosity polyester chips as main raw materials, and then the masterbatch is melt-blended with high-viscosity polyester chips to produce the high-strength, flexible, flame-retardant polyester industrial yarn. The low-viscosity polyester chips have an intrinsic viscosity of 0.65 to 0.68 dL/g, and the high-viscosity polyester chips have an intrinsic viscosity of 1.05 to 1.20 dL/g. The high-strength, flexible, flame-retardant polyester industrial yarn has a breaking strength of ≥7.6 cN/dtex, an elongation at break of 15 to 30%, an initial modulus of 40 to 80 cN/dtex, an LOI value of 32 to 36%, and a smoke density of 9.42 to 21.13. The specific process for preparing the flexible flame retardant is as follows: adding cyclic organosiloxane, accelerator and alkaline catalyst to a reaction vessel equipped with a condensation reflux device and a stirring device, reacting at 90-130°C for 1-3 hours under the protection of nitrogen or inert gas and stirring, adding water and ethyl orthosilicate, and then reacting at 60-90°C for 3-6 hours under the protection of nitrogen or inert gas and stirring, and obtaining the flexible flame retardant after post-treatment, wherein the cyclic organosiloxane is dimethylcyclosiloxane, and the flexible flame retardant is silica with polydimethylsiloxane grafted on the surface. The method for preparing a high-strength, flexible, flame-retardant polyester industrial yarn according to claim 1, characterized in that the mass ratio of cyclic organosiloxane, accelerator, alkaline catalyst, water and tetraethyl orthosilicate is 44-50:1.8-3.3:3.0-5.1:12-14:32-39; the accelerator is one or more of ethylene glycol, triethylamine and dibutyltin dilaurate; and the alkaline catalyst is one or more of sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide. The method for preparing a high-strength, flexible, flame-retardant polyester industrial yarn according to claim 1, wherein the degree of polymerization n of the polydimethylsiloxane is 15 to 40. The method for preparing a high-strength, flexible, flame-retardant polyester industrial yarn according to claim 1, wherein the grafting rate of polydimethylsiloxane on the surface of silica is 3-10%. The method for preparing a high-strength, flexible, flame-retardant polyester industrial yarn according to claim 1 is characterized in that the preparation process of the flexible flame-retardant polyester masterbatch is as follows: after premixing 70-82% of low-viscosity polyester chips, 15-30% of a flexible flame retardant, and the remainder of an antioxidant by weight percentage, the mixture is melt-blended and extruded using a twin-screw extruder, and then cooled, granulated, and dried to obtain the flexible flame-retardant polyester masterbatch. The method for preparing a high-strength, flexible, flame-retardant polyester industrial yarn according to claim 5, characterized in that the mass ratio of the softening flame-retardant polyester masterbatch to the high-viscosity polyester chips is 5-10:90-95, the melt blending spinning adopts a one-step spinning and stretching process, and the process parameters of the melt blending spinning include: a screw temperature of 280-310°C, a post-drafting roller temperature of 60-70°C, a post-drafting roller speed of 500-650 m/min, a post-drafting roller temperature of 90-100°C, a post-drafting roller temperature of 125-135°C, a post-drafting roller temperature of 210-240°C, a post-drafting roller temperature of 140-150°C, and a winding speed of 3000-3500 m/min.