CN121138024A - A lightweight, environmentally friendly, flame-retardant automotive sofa leather and its preparation process - Google Patents

Abstract

This invention discloses a lightweight, high-grade environmentally friendly flame-retardant automotive sofa leather and its preparation method, belonging to the field of polymer composite materials and synthetic leather manufacturing technology. This invention aims to solve the technical problems in existing technologies where poor compatibility between flame retardants and the matrix leads to products with a hardened feel, reduced breathability, decreased physical strength, and short-lasting flame-retardant effects. The innovation of this automotive sofa leather lies in the fact that its environmentally friendly flame retardant is contained in microcapsules encapsulated by polymer materials, uniformly and firmly anchored in a three-dimensional microporous framework composed of polyurethane and ultrafine fibers. The key steps of its preparation method include: firstly, independently microencapsulating the environmentally friendly flame retardant as a pretreatment. Through the above-mentioned synergistic design, this invention achieves high-grade, permanent environmentally friendly flame retardancy while perfectly preserving the material's excellent physical properties such as lightness, softness, and breathability, resulting in outstanding overall product performance.

Description

Lightweight environment-friendly flame-retardant automobile sofa leather and preparation process thereof

Technical Field

The invention relates to the technical field of manufacturing of polymer composite materials and synthetic leather, in particular to light-weight environment-friendly flame-retardant automobile sofa leather and a preparation process thereof.

Background

Automobiles are important vehicles in modern society, and the quality of interior decoration materials is directly related to the comfort and safety of driving experience. In recent years, with the increasing strictness of consumer upgrades and safety regulations, there is an increasing market demand for high performance automotive sofa leather and other interior materials that have excellent physical properties, high-grade safety protection, light weight and environmental protection characteristics. Particularly, in the aspect of flame retardant performance, the flame retardant meets the strict industry standard and accords with the environment-friendly trend without halogenation, and the flame retardant has become the necessary requirement for industry development.

The polyurethane superfine fiber synthetic leather has the advantages of being similar to leather in appearance and hand feeling, light in weight, good in air permeability and moisture permeability and the like, and is widely applied to the field of automobile interior trim. In order to provide the polyurethane with flame retardant performance, the common technical means is to add an environment-friendly halogen-free flame retardant, such as a phosphorus-nitrogen system flame retardant, into polyurethane slurry. However, the prior art is often faced with contradictions in performance that are difficult to reconcile in achieving this goal.

The fundamental drawbacks of the prior art stem from the inherent compatibility problems between the flame retardant and the polyurethane matrix. The surface energy of the powdery flame retardant particles and the surface energy of the high-molecular polyurethane resin are greatly different, so that the powdery flame retardant particles are extremely difficult to uniformly disperse in slurry and are easy to agglomerate. This uneven distribution firstly severely deteriorates the physical properties of the product, and agglomerated hard particles exist inside the material as impurities, becoming stress concentration points, making the texture of the final product hard and brittle, and tear and tensile strength decline, severely affecting its reliability as a durable product. Meanwhile, the existence of the particles can also interfere the formation of a polyurethane micropore structure in a wet process to block pores, so that the air permeability and the moisture permeability of the product are greatly reduced, and the due comfortable experience of the synthetic leather is lost. More serious, due to the lack of firm chemical or physical combination between the flame retardant and the matrix, the flame retardant can gradually migrate from the inside to the surface of the material and even fall off in the subsequent cleaning, friction or long-term use process, which not only causes surface appearance defects such as 'frosting', but also causes gradual loss of flame retardant performance, and permanent safety protection cannot be realized.

Therefore, how to fundamentally solve the problems of dispersion stability and compatibility of the environment-friendly flame retardant in a polyurethane system and the combination firmness of the environment-friendly flame retardant and a matrix, develop the automobile sofa leather which can meet the requirements of high-grade, long-acting and environment-friendly flame retardance and keep the light, soft, breathable and excellent physical properties of the material, and the preparation method thereof, and solve the technical problems in the field in the prior art.

Disclosure of Invention

The technical problem to be solved by the invention is to provide the novel automobile sofa leather which can simultaneously meet the requirements of light weight, high-grade environmental protection, flame retardance, excellent comfort and durability in the automobile industry, and provide a stable and reliable preparation process of the novel automobile sofa leather. In the prior art, when high-grade flame retardance is realized, the cost of softness, air permeability or weight increase of materials is often sacrificed, and meanwhile, the dispersibility and stability of the environment-friendly flame retardant in a polyurethane wet system are also a great technical difficulty, so that the product performance is not uniform and the flame retardance effect is not durable easily.

In order to solve the technical problems, the invention provides the following technical scheme.

The first aspect of the invention provides light environment-friendly flame-retardant automobile sofa leather.

This car sofa leather, its structure includes:

(a) A nonwoven fabric substrate composed of ultrafine polyamide-6 fibers;

(b) A microporous polyether polyurethane layer impregnated in and compounded with the nonwoven fabric substrate, and

(C) And the microencapsulated halogen-free environment-friendly flame retardant is dispersed in the microporous polyether polyurethane layer.

In the scheme, the dosage of the microencapsulated halogen-free environment-friendly flame retardant is 15 to 30 parts by weight relative to 100 parts by weight of polyether polyurethane solid, and the unit area mass of the non-woven fabric substrate before compounding is 150 to 250g/m ².

The innovation mechanism and the beneficial effects of the invention are as follows:

The invention creatively combines the superfine fiber technology, the microporous polyurethane technology and the microcapsule flame-retardant technology. The superfine polyamide-6 fiber non-woven fabric substrate gives the product excellent light weight characteristic and soft and plump hand feeling base. The microporous polyether polyurethane layer ensures the air permeability and comfort of the material.

Solves the core contradiction between flame retardance and physical properties, and has the key innovation point that a microencapsulated halogen-free environment-friendly flame retardant is adopted. By microencapsulating the flame retardant, it is allowed to disperse in the polyether polyurethane matrix with a high degree of uniformity in the form of individual minute units, avoiding the agglomeration of the flame retardant powder. The uniform dispersion ensures that each part of the final product has stable and consistent flame retardant performance, and simultaneously reduces the damage of flame retardant aggregates to the micropore structure of polyurethane and the flexibility of a polymer chain to the greatest extent, thereby realizing high flame retardance and simultaneously maintaining the original soft hand feeling and physical properties of the material.

The permanence of the flame-retardant effect is ensured, namely the shell structure of the microcapsule physically anchors the active ingredients of the flame retardant in the polyurethane matrix, so that the washing resistance and migration resistance of the microcapsule are greatly improved, and the flame-retardant effect has excellent durability.

As a preferable scheme, the microcapsule coating layer of the microcapsule halogen-free environment-friendly flame retardant is formed by acrylic ester copolymer, and the material has good compatibility with a polyurethane system.

As a preferable scheme, the superfine polyamide-6 fiber of the non-woven fabric base is formed by splitting sea island fiber taking polyamide-6 as island component and low density polyethylene as sea component after removing the sea component, which is a fundamental way for obtaining superfine fiber structure and realizing soft hand feeling.

The second aspect of the invention provides a preparation process of the lightweight environment-friendly flame-retardant automobile sofa leather.

The preparation process is characterized by comprising the following steps of:

Step one, a microencapsulation pretreatment step, namely microencapsulating halogen-free environment-friendly flame retardant powder to obtain a microencapsulated environment-friendly flame retardant;

Step two, preparing a non-woven fabric base, namely opening, carding, needling and heat setting sea-island short fibers to prepare the non-woven fabric base;

Step three, a wet impregnation and solidification step, namely dispersing the microencapsulated environment-friendly flame retardant obtained in the step one in a dimethylformamide solution of polyether polyurethane to prepare an impregnation liquid, immersing the non-woven fabric substrate obtained in the step two in the impregnation liquid, solidifying in a dimethylformamide aqueous solution, and washing to obtain a wet substrate;

And step four, a deweighting and finishing step, namely performing solvent deweighting treatment on the wet substrate obtained in the step three to remove sea components in the sea-island fiber, and then performing expanding drying, oiling and tentering setting to obtain a finished product.

The process is innovative in that the microencapsulation pretreatment step is introduced into the traditional synthetic leather process as an independent and advanced step, so that the application problem of the environment-friendly flame retardant is solved from the source. The arrangement of the step ensures the high stability and uniformity of the flame retardant in the subsequent wet impregnation liquid, and lays a solid foundation for the smooth proceeding of all subsequent procedures and the high quality of the final product. The steps are buckled and cooperate, and the expected technical effect is finally realized.

As a preferred embodiment:

in the first step, the halogen-free environment-friendly flame retardant powder is suspended in an aqueous medium, and (b) acrylic ester monomers and an initiator are added to perform in-situ polymerization reaction for 3-6 hours at 60-85 ℃.

In the second step, the method concretely comprises (a) adopting sea-island short fibers with the weight ratio of polyamide-6 to low-density polyethylene of (60-80) (40-20), (b) needling with the density of 1200-1800 needles/cm ², and (C) performing heat setting treatment at 100-130 ℃.

In the third step, the preparation of the impregnation liquid comprises the steps of dispersing 15-30 parts by weight of microencapsulated environment-friendly flame retardant into a dimethylformamide solution containing 100 parts by weight of polyether polyurethane solid to form the impregnation liquid with the solid content of 18-30%.

In the third step, the solidification is specifically that the impregnated non-woven fabric is solidified in a dimethylformamide water solution with the mass concentration of 15-25%, and the solidification bath temperature is 20-50 ℃.

In the fourth step, the solvent reduction treatment is specifically that the wet substrate is treated in toluene solution at 70-90 ℃ for 15-30 minutes.

In the fourth step, the expanding and drying is carried out by adopting overfeeding rate of 5-20% to carry out relaxation drying, the drying temperature is 110-150 ℃, and simultaneously, oiling treatment is carried out by adopting oiling agent with concentration of 2.5-3.0%. By this specific post-finishing process, the ultra-fine fibers can be fully relaxed and stretched, thus obtaining a plump and soft final product.

In summary, the present invention includes at least one of the following beneficial technical effects:

1. The invention creatively constructs a functional synergistic composite structure by organically combining the superfine fiber non-woven fabric substrate, the microporous polyurethane and the microencapsulated flame retardant. The structure successfully solves the long-standing performance constraint and technical contradiction between light weight, high-grade environment-friendly flame retardance and excellent comfortableness (softness and ventilation) in the field of automotive interior materials, so that the final product can simultaneously meet a plurality of severe technical indexes.

2. The invention endows the product with excellent and durable environment-friendly flame retardant property. The key point is that the flame retardant active component is physically anchored in the polymer matrix by microencapsulation technology. The structural design greatly enhances the washing resistance and migration resistance of the flame retardant, and ensures that the flame retardant function cannot be attenuated due to daily use, cleaning or time lapse, thereby providing stable and reliable safety guarantee in the whole life cycle of the product.

3. The automobile sofa leather prepared by the invention has excellent soft and plump hand feeling and leather-like comfort. On one hand, the isolation effect of the microcapsule avoids the damage of the flame retardant particles to the polyurethane microporous structure and the flexibility of the polymer chain, and on the other hand, the reduction step in the preparation process and the relaxation after-finishing step are synergistic, so that the fluffy and soft characteristics of the superfine fiber are fully excited, and finally, the high unification of the functionality and the comfort is realized.

4. The preparation process disclosed by the invention has the advantages of high stability, uniform and controllable product quality and feasibility of large-scale industrial production. By arranging independent microencapsulation pretreatment steps, the technical problems of uneven dispersion and easy sedimentation of the environment-friendly flame retardant in a polyurethane wet system are solved from the source, the long-term stability of impregnation liquid is ensured, and a solid foundation is laid for the smooth proceeding of subsequent procedures and the high consistency of the performances of final products.

5. The invention has remarkable environmental protection advantage. Firstly, the halogen-free environment-friendly flame retardant is adopted, so that the problem that the traditional halogen flame retardant generates toxic and corrosive gas during combustion is solved. Secondly, the microencapsulation technique further encapsulates the flame retardant, reducing its potential release to the environment during use. Meanwhile, the overall lightweight design of the product is also beneficial to reducing the energy consumption of the vehicle, and accords with the development trend of energy conservation and emission reduction.

Detailed Description

In order to further illustrate the present invention, the light-weight environment-friendly flame-retardant automotive sofa leather and the preparation process thereof provided by the present invention are described in detail below with reference to examples, but these examples are not intended to limit the present invention in any way.

Example 1

This example was prepared using intermediate parameters within the scope of the claims.

Step one, microencapsulation pretreatment of environment-friendly flame retardant

300 Parts by weight of deionized water and 3 parts by weight of emulsifier are added into a reaction kettle, 100 parts by weight of environment-friendly phosphorus-nitrogen system flame retardant powder is added under stirring, and ultrasonic dispersion is carried out for 45 minutes. Subsequently, 20 parts by weight of an acrylic monomer was added, the system was warmed to 75℃and then 0.3 part by weight of an initiator was added thereto, and the reaction was continued for 4.5 hours with heat preservation. After the reaction is finished, the product is filtered, washed by water and dried in vacuum for 10 hours at 70 ℃ to obtain the microencapsulated environment-friendly flame retardant.

Step two, preparation of superfine denier sea-island fiber non-woven fabric substrate

Sea-island short fibers (fiber specification 3.5D, length 64 mm) with the weight ratio of polyamide-6 to low density polyethylene of 70:30 are adopted as raw materials. After opening and carding to form a net, the net is reinforced by adopting the needling density of 1500 needles/cm ². Subsequently, heat setting was carried out at 115℃to obtain an ironed nonwoven substrate having a mass per unit area of 200g/m ².

Step three, wet impregnation and solidification molding

Dispersing 22 parts by weight of the microencapsulated environment-friendly flame retardant prepared in the step one into a dimethylformamide solution containing 100 parts by weight of polyether polyurethane solid, and regulating the solid content of the final impregnation liquid to be 24%. The nonwoven fabric substrate obtained in the second step was immersed in the solution, rolled under 0.2MPa, and then introduced into a coagulation bath of DMF aqueous solution having a mass concentration of 20% and a temperature of 35℃and allowed to stand for 10 minutes. Finally, the wet-process substrate is obtained by fully washing with warm water at 60 ℃.

Step four, reducing and finishing shaping

The wet substrate obtained in the third step was subjected to a reduction treatment in toluene at 80℃for 22 minutes. After being washed by hot water at 90 ℃, the mixture is sent into a expanding dryer, is subjected to relaxation drying by adopting overfeeding rate of 12 percent, and is subjected to oiling treatment by using oiling agent with concentration of 2.7 percent. And setting the drying temperature to 130 ℃, and finally tentering and shaping to obtain a finished product.

Example 2

This example was prepared using the lower limit parameters within the scope of the claims.

Step one, microencapsulation pretreatment of environment-friendly flame retardant

200 Parts by weight of deionized water and 1 part by weight of emulsifier are added into a reaction kettle, 100 parts by weight of environment-friendly phosphorus-nitrogen system flame retardant powder is added under stirring, and ultrasonic dispersion is carried out for 30 minutes. Subsequently, 10 parts by weight of an acrylic monomer was added, the system was warmed to 60℃and then 0.1 part by weight of an initiator was added thereto, and the reaction was continued for 3 hours with heat preservation. After the reaction is finished, the product is filtered, washed by water and dried for 8 hours in vacuum at 60 ℃ to obtain the microencapsulated environment-friendly flame retardant.

Step two, preparation of superfine denier sea-island fiber non-woven fabric substrate

Sea-island short fibers (fiber specification 2.5D, length 51 mm) with the weight ratio of polyamide-6 to low density polyethylene of 60:40 are adopted as raw materials. After opening and carding to form a net, the net is reinforced by adopting the needling density of 1200 needles/cm ². Subsequently, heat setting was carried out at 100℃to obtain an ironed nonwoven substrate having a mass per unit area of 150g/m ².

Step three, wet impregnation and solidification molding

15 Parts by weight of the microencapsulated environment-friendly flame retardant prepared in the step one are dispersed in a dimethylformamide solution containing 100 parts by weight of polyether polyurethane solids, and the solid content of the final impregnation liquid is regulated to be 18%. The nonwoven fabric substrate obtained in the second step was immersed in the solution, rolled under 0.1MPa, and then introduced into a coagulation bath of DMF aqueous solution having a mass concentration of 15% and a temperature of 20℃and allowed to stand for 5 minutes. Finally, the wet-process substrate is obtained by fully washing with warm water at 50 ℃.

Step four, reducing and finishing shaping

The wet substrate obtained in the third step was subjected to a reduction treatment in toluene at 70℃for 15 minutes. After being washed by hot water at 80 ℃, the mixture is sent into a spreading dryer, is subjected to relaxation drying by adopting overfeeding rate of 5 percent, and is subjected to oiling treatment by using oiling agent with concentration of 2.5 percent. Setting the drying temperature to 110 ℃, and finally tentering and shaping to obtain a finished product.

Example 3

This example was prepared using the upper limit parameters within the scope of the claims.

Step one, microencapsulation pretreatment of environment-friendly flame retardant

400 Parts by weight of deionized water and 5 parts by weight of emulsifier are added into a reaction kettle, 100 parts by weight of environment-friendly phosphorus-nitrogen system flame retardant powder is added under stirring, and ultrasonic dispersion is carried out for 60 minutes. Subsequently, 30 parts by weight of an acrylic monomer was added, the system was warmed to 85℃and then 0.5 part by weight of an initiator was added thereto, and the reaction was continued for 6 hours with heat preservation. After the reaction is finished, the product is filtered, washed by water and dried in vacuum for 12 hours at 80 ℃ to obtain the microencapsulated environment-friendly flame retardant.

Step two, preparation of superfine denier sea-island fiber non-woven fabric substrate

Sea-island short fibers (fiber specification 4.5D, length 76 mm) with the weight ratio of polyamide-6 to low density polyethylene of 80:20 are adopted as raw materials. After opening and carding to form a net, the net is reinforced by adopting the needling density of 1800 needles/cm ². Subsequently, heat setting was carried out at 130℃to obtain an ironed nonwoven substrate having a mass per unit area of 250g/m ².

Step three, wet impregnation and solidification molding

30 Parts by weight of the microencapsulated environment-friendly flame retardant prepared in the step one is dispersed in a dimethylformamide solution containing 100 parts by weight of polyether polyurethane solids, and the solid content of the final impregnation liquid is regulated to be 30%. The nonwoven fabric substrate obtained in the second step was immersed in the solution, rolled under 0.3MPa, and then introduced into a coagulation bath of DMF aqueous solution having a mass concentration of 25% and a temperature of 50℃and allowed to stand for 15 minutes. Finally, the wet-process substrate is obtained by fully washing with warm water at 70 ℃.

Step four, reducing and finishing shaping

The wet substrate obtained in the third step was subjected to a reduction treatment in toluene at 90℃for 30 minutes. After washing with hot water at 95 ℃, the mixture is sent into a spreading dryer, and is subjected to relaxation drying by adopting overfeeding rate of 20 percent, and simultaneously is subjected to oiling treatment by using oiling agent with concentration of 3.0 percent. Setting the drying temperature to 150 ℃, and finally tentering and shaping to obtain a finished product.

Comparative example 1:

The difference from example 1 is that step one was omitted, and 22 parts by weight of the non-microencapsulated flame retardant powder of the environment-friendly phosphorus-nitrogen system was directly added to the preparation of the impregnation liquid in step three, and the remainder was the same.

Comparative example 2:

Compared with the example 1, the difference is that in the preparation of the impregnating solution in the third step, the dosage of the microencapsulated environment-friendly flame retardant prepared in the first step is increased from 22 to 40 parts by weight, and the rest is the same.

Comparative example 3:

Compared with the embodiment 1, the difference is that in the preparation of the impregnating solution in the third step, the dosage of the microencapsulated environment-friendly flame retardant prepared in the first step is reduced from 22 parts by weight to 10 parts by weight, and the rest is the same.

Comparative example 4:

Compared with the embodiment 1, the preparation method is characterized in that the microencapsulated environment-friendly flame retardant is not added in the preparation of the impregnation liquid in the step three, and the rest are the same.

Comparative example 5:

The difference from example1 is that the decrement treatment step in the fourth step is omitted, the wet substrate after the water washing in the third step is directly subjected to post-finishing and shaping, and the rest are the same.

Comparative example 6:

Compared with the embodiment 1, the difference is that in the post-finishing shaping of the step four, a large overfeeding relaxation drying process is not adopted, but a conventional stretching drying process (namely overfeeding rate is 0) is adopted, and the rest is the same.

Test example 1 verification of the microencapsulation technical Effect

1. Description of the experiment

This test was intended to verify the effect of the microencapsulation pretreatment step on the stability of the impregnation liquid, the softness of the product and the durability of the flame retardant properties. The test subjects were samples of example 1 (using microencapsulated flame retardant) and comparative example 1 (using an equivalent amount of uncoated flame retardant powder) and intermediate products thereof.

1. Test of stability of immersion liquid

The experimental steps are as follows:

1000mL of polyurethane infusion was prepared under the same conditions as the formulations of example 1 and comparative example 1, respectively.

The two infusion solutions were placed in two identical 1000mL glass measuring cylinders, respectively, the cylinder mouth was sealed, and allowed to stand at room temperature (25 ℃).

After standing for 24 hours, the state of the slurry in the measuring cylinder was visually observed and recorded, focusing on whether there was delamination, precipitation of a transparent liquid, and the form and amount of bottom precipitate.

2. Flame retardant Performance durability test

The experimental steps are as follows:

From the automobile sofa leathers finally produced in example 1 and comparative example 1, a sufficient number of test pieces were cut out, respectively.

Two sets of coupons were subjected to 10 cycles of home laundering and drying treatment according to ISO 6330 standard.

The washed sample was taken out and conditioned under standard atmospheric conditions (temperature 20.+ -. 2 ℃ C., humidity 65.+ -. 5%) for 24 hours.

And (3) carrying out vertical burning test on the samples subjected to the humidity adjustment according to GB/T5455-2014 'determination of damage length, smoldering and smoldering time of samples in the vertical direction of the burning performance of the textile', and recording the smoldering time and smoldering time of each group of samples.

3. Softness test

The experimental steps are as follows:

Samples of standard sizes were cut from the automotive sofa leathers (not subjected to washing treatment) finally produced in example 1 and comparative example 1, respectively.

Humidity was adjusted for 24 hours under standard atmospheric conditions.

Using a digital softness tester, according to the method of GB/T8942, bending stiffness of the test specimen in the warp and weft directions was measured, and the average value was calculated as the final result

2. Experimental data

Table 1 comparative performance test data for example 1 and comparative example 1

3. Summary of the experiment

The above test data clearly reveals the fundamental technological advances made by the microencapsulation pretreatment step. In example 1, the flame retardant exhibited excellent dispersion stability in the polyurethane slurry thanks to the microencapsulation treatment, and remained in a uniform state after standing for 24 hours. The formation of the microcapsule shell changes the surface property of the flame retardant particles, so that the compatibility of the flame retardant particles with an organic polyurethane system is greatly improved, meanwhile, the agglomeration and rapid sedimentation of high-density inorganic particles due to the action of gravity are prevented through the steric hindrance effect, and the process guarantee is provided for preparing high-quality products with uniform performance.

The sample of example 1 has significantly lower bending stiffness in terms of the physical properties of the final product than comparative example 1, indicating a softer hand. The mechanism is that the uncoated flame retardant powder exists as independent rigid particles in comparative example 1 and tends to agglomerate to form larger aggregates which disrupt the continuity and flexibility of the polyurethane matrix polymer chains and may interfere with the normal formation of the microporous structure, resulting in overall stiffness and poor hand feel of the material. In contrast, the microcapsule flame retardant in example 1 is uniformly distributed in individual tiny units wrapped by a flexible shell, so that the influence on the mechanical properties of the polyurethane matrix is minimized, and the original softness and comfort of the material are successfully maintained while the functionality is introduced.

Most importantly, the results of the flame retardant performance durability test strongly demonstrate the innovation of the present invention in functional durability. The sample of example 1 still maintains excellent flame retardant effect after multiple washings, with very short post and smoldering times. Whereas the sample of comparative example 1 had almost lost flame retardant ability. The physical anchoring mechanism of the microcapsule is deeply revealed, namely, the flame retardant active ingredient is firmly locked in the polyurethane matrix by the polymer shell, so that the loss caused by mechanical force and solvent action in the water washing process is effectively resisted. The innovation on the structure ensures that the flame retardant function is not temporary surface treatment, but becomes the inherent and lasting attribute of the material, and ensures the safety of the product in the whole service life cycle.

Test example 2 verification of flame retardant addition Range

1. Description of the experiment

The test aims to verify the decisive influence of the addition amount range of the microencapsulated flame retardant on the final flame retardant property and the physical strength of the product. The test subjects were samples of example 1 (the addition amount was in the moderate range), comparative example 2 (the addition amount exceeded the upper limit), and comparative example 3 (the addition amount was below the lower limit).

1. Ultimate flame retardant Performance test

The experimental steps are as follows:

Standard size coupons were cut from the automotive sofa leathers finally prepared in example 1, comparative example 2, comparative example 3, respectively.

All coupons were conditioned under standard atmospheric conditions (20.+ -. 2 ℃ C., 65.+ -. 5% humidity) for 24 hours.

And (3) performing vertical burning test on the humidified sample according to the GB/T5455-2014 standard, and recording the continuous burning time and the damage length of each group of sample.

2. Physical Strength test

The experimental steps are as follows:

Samples for tensile and tear tests were cut as required by the standards from the automotive sofa leathers finally prepared in example 1, comparative example 2, comparative example 3, respectively.

Humidity was adjusted for 24 hours under standard atmospheric conditions.

The tensile strength of the test specimens was measured according to GB/T3923.1 and the tear strength of the test specimens was measured according to GB/T3917.3 using a tensile tester, and the data was recorded.

2. Experimental data

Table 2 comparative performance test data for example 1, comparative example 2 and comparative example 3

Test item	Example 1	Comparative example 2	Comparative example 3
				Time to burn(s)	1.8	1.1	32.5
Damage length (mm)	45	38	Burn-through
				Tensile Strength (N)	415	278	435
Tear strength (N)	88	51	92

3. Summary of the experiment

The above test data reveals that the amount of flame retardant added is a critical parameter that is decisive for the final properties of the product and must be controlled within a precise balance. The result of comparative example 3 shows that when the amount of the microcapsule flame retardant added is insufficient, the material exhibits excellent physical strength, but the after-flame time is extremely long in the burning test, and even the burn-through phenomenon occurs. This means that at this level of addition, the number of flame retardant functional units available per unit volume to function is too small to form an effective, dense carbon layer to isolate heat and oxygen upon combustion, and thus the high level safety goals sought by the present invention are not achieved.

In contrast, the results of comparative example 2 demonstrate the negative effects associated with excessive addition of flame retardant. Although the burning test data are excellent, the tensile strength and the tearing strength are greatly attenuated. The intrinsic mechanism is that the microcapsules are used as a functional filler, and when the volume fraction is too high, the continuity and the integrity of the polyether polyurethane matrix are seriously damaged. These excessive, non-reinforcing particles become "defects" or stress concentration points in the polymer network, and when the material is stressed, the generation and expansion of microcracks are easily initiated, so that the macroscopic mechanical properties of the material are rapidly deteriorated, and the basic requirements of the material as a durable product cannot be met.

The overall performance of example 1 perfectly explains the innovativeness of the invention in terms of the component proportions. The addition amount of the flame retardant can ensure that enough functional units migrate to the surface during combustion, an effective protective barrier is rapidly formed through the synergistic effects of melting and dripping, carbon production, incombustible gas release and the like, and excellent flame retardant performance is shown, and meanwhile, the addition amount is accurately controlled within a threshold value which can not cause subversion damage to the mechanical properties of a polyurethane matrix. This demonstrates that the defined component ranges of the present invention do not simply add up, but rather a delicate balance of "functionality" and "structure" is achieved, enabling the final product to combine excellent safety properties with excellent physical durability.

Test example 3 verification of the necessity of flame retardant Components

1. Description of the experiment

The test aims at verifying the decisive effect and the necessity of the component of the microencapsulated halogen-free environment-friendly flame retardant for endowing the product with flame retardant property through direct comparison. The test subjects were samples of example 1 (containing a flame retardant component) and comparative example 4 (not containing a flame retardant component).

1. Basic flame retardant Performance test

The experimental steps are as follows:

Standard size coupons were cut from the automotive sofa leathers finally prepared in example 1 and comparative example 4, respectively.

Both sets of coupons were conditioned for 24 hours under standard atmospheric conditions (20.+ -. 2 ℃ C., 65.+ -. 5% humidity).

And performing vertical burning test on the sample wafer after humidity adjustment according to the GB/T5455-2014 standard. After ignition for 12 seconds, the flame was removed and immediately the specimen was recorded and observed for the time to post-fire, smoldering time, and the length of damage caused by flame spread.

2. Experimental data

Table 3 comparative performance test data for example 1 and comparative example 4.

Test item	Example 1	Comparative example 4
			Time to burn(s)	1.7	Continuously burning to a clamp
Smoldering time(s)	1.3	Inapplicable (complete burning of sample)
			Damage length (mm)	42	Full length of sample

3. Summary of the experiment

The test results show great difference, and the core position of the flame-retardant functional component in the invention is intuitively proved. The sample of example 1 rapidly self-extinguishes after flame removal, and the damage length is effectively controlled within a very small range, exhibiting excellent flame retardant properties. Whereas the sample of comparative example 4, which contained no flame retardant component at all, underwent severe combustion once ignited, and the flame rapidly spread until the entire sample was completely burned out. This clearly shows that the flame retardant properties of the material are not derived from the substrate itself, but are fully conferred by the added microencapsulated halogen-free environmental flame retardant.

The mechanism behind this is that the microcapsule flame retardant in the polyurethane matrix is able to respond rapidly when the composite of example 1 is heated, acting through a phosphorus-nitrogen synergistic effect. The carbon layer is formed on the surface of the material, and is like a solid physical barrier, so that the transmission of external heat source and oxygen to the internal base material is effectively isolated, and meanwhile, the non-combustible gas (such as ammonia gas and water vapor) generated by decomposition of the carbon layer can dilute the concentration of the combustible gas in the combustion area, so that the chain reaction of combustion is inhibited from the gas phase. The dual functions of solid-phase charring and gas-phase flame inhibition jointly construct a high-efficiency flame-retardant system.

In contrast, the sample of comparative example 4 is essentially a mere composite of polyurethane and polyamide fibers, both of which are flammable polymeric materials. Without the intervention of a flame retardant, the combustion process follows a typical high molecular combustion path, i.e. thermal decomposition produces large amounts of combustible small molecular gases which, when mixed with air, sustain and exacerbate combustion, ultimately leading to catastrophic complete destruction. Thus, the test demonstrates indistinctly that the design of the composition comprising specific functional components proposed by the present invention is a fundamental premise and technological innovation of achieving high-grade safety performance of the product.

Test example 4 verification of the synergistic effect of the deweighting step

1. Description of the experiment

This test aims to verify the critical role of the solvent reduction treatment step on the softness, breathability and moisture permeability of the final product and to reveal its synergistic effect with the islands-in-the-sea fiber technology. The test subjects were samples of example 1 (subjected to the decrement treatment) and comparative example 5 (not subjected to the decrement treatment).

1. Softness test

The experimental steps are as follows:

Standard size coupons were cut from the automotive sofa leathers finally prepared in example 1 and comparative example 5, respectively.

After conditioning for 24 hours under standard atmospheric conditions, the average bending stiffness of the plaques was tested according to the method of GB/T8942 using a digital softness tester.

2. Air permeability test

The experimental steps are as follows:

round coupons were cut from the samples of example 1 and comparative example 5, respectively.

After conditioning for 24 hours under standard atmospheric conditions, the air permeability of the plaques was tested under a pressure differential of 100Pa according to GB/T5453 standard using a fully automatic air permeability meter.

3. Moisture permeability test

The experimental steps are as follows:

round coupons were cut from the samples of example 1 and comparative example 5, respectively.

According to the positive cup method of GB/T12704.2-2009, the sample wafer is sealed on a moisture permeable cup containing a desiccant.

The moisture permeable cup was placed in a constant temperature and humidity cabinet at a temperature of 38 ℃ and a relative humidity of 90%.

After 24 hours, the weight gain of the moisture permeable cup was weighed and the moisture permeability of the sample was calculated.

2. Experimental data

Table 4 comparative performance test data for example 1 and comparative example 5.

Test item	Example 1	Comparative example 5
			Bending stiffness (mN)	142	458
Air permeability (L/m 2. S)	1.52	0.09
			Moisture permeability (g/m 2. 24 h)	6850	1120

3. Summary of the experiment

The great difference of the test results strongly proves that the solvent reduction step is an indispensable key link in the preparation process of the invention. The sample of example 1 exhibited superior properties to the cloud of the sample of comparative example 5 in terms of three core comfort indicators of softness, air permeability and moisture permeability. This qualitative leap is entirely due to the fundamental remodelling of the microstructure of the material by the abatement process step.

The sea-island fiber adopted by the invention is a composite fiber precursor, and the soluble sea component (low-density polyethylene) is wrapped by the insoluble island component (superfine polyamide-6 fiber). The solvent reduction step utilizes a specific solvent (e.g., toluene) to completely dissolve and remove the "sea" component. This process causes the individual composite fibers that were otherwise bound together to instantaneously split into a bundle of extremely fine superfine polyamide-6 fibers. It is this structural fission from "one" to "many" that imparts distinct physical properties to the material. The fibres became finer and more free and the sliding resistance between each other was drastically reduced, macroscopically representing a significant reduction in the flexural rigidity of the material, thus obtaining a soft, plump feel characteristic of the sample of example 1.

At the same time, the fiber splitting process creates a three-dimensional network of numerous microscopic channels and pores within the nonwoven substrate. These newly created pores provide an unobstructed path for air and water vapor migration, allowing the breathability and moisture permeability of the material to be improved. In contrast, comparative example 5, in which the "sea" component was still present due to the omission of the reduction step, it was like a dense film filled between the fibers, blocking all potential pores. This results in a final product which is structurally dense, void-free, stiff and almost impermeable to air and moisture. Therefore, the reduction step is a key for activating the sea-island fiber 'superfine' and 'porous' potential, and is a core process support for realizing the innovative aim of combining light weight, high comfort and functionality.

Test example 5 verification of the synergy of the finishing Process

1. Description of the experiment

The test aims to verify the key effect of a relaxation drying process adopting a specific overfeed rate on the improvement of the thickness, the fullness and the elasticity of a product. The test subjects were samples of example 1 (with relaxation oven drying) and comparative example 6 (with conventional stretch oven drying).

1. Product thickness test

The experimental steps are as follows:

from the automobile sofa leathers finally prepared in example 1 and comparative example 6, 5 samples were cut at different positions, respectively.

After conditioning for 24 hours under standard atmospheric conditions, the thickness of each coupon was measured using a digital fabric thickness gauge at a specified pressure.

The average of 5 coupon thicknesses per group was calculated as the final result.

2. Elastic recovery test

The experimental steps are as follows:

standard-sized tensile bars were cut in the warp direction from the samples of example 1 and comparative example 6, respectively.

Humidity was adjusted for 24 hours under standard atmospheric conditions.

On a tensile tester, the bars are stretched to a specified elongation (e.g., 20%) at a constant rate and held for 1 minute.

The load was removed quickly and the bars were allowed to freely recover in a tension-free state for 1 minute.

The length of the bar at this time was measured and its elastic recovery was calculated.

2. Experimental data

Table 5 comparative performance test data for example 1 and comparative example 6

Test item	Example 1	Comparative example 6
			Product thickness (mm)	1.38	0.95
Elastic recovery (%)	97.2	84.6

3. Summary of the experiment

The above test data clearly reveals the decisive influence of the choice of finishing setting process on the morphology and performance of the final product. The sample of example 1, which used the relaxation drying process, had a significantly greater thickness than the sample of comparative example 6, which used conventional stretch drying, and also had a much better elastic recovery than the latter. This suggests that a particular finishing process is a critical synergistic step in stimulating potentially superior properties of the material.

The mechanism behind this is that after the solvent reduction step, innumerable ultrafine fibers have been formed inside the material. During the relaxation drying process, the fabric is in a tension-free, relaxed state as it enters the oven by applying a positive overfeed rate. The high temperature environment not only evaporates water, but also provides energy for the movement of the polymer chains and the superfine fibers. Under the condition of no external force constraint, the 'liberated' ultrafine fibers can spontaneously curl and shrink, and develop from two-dimensional plane arrangement to a three-dimensional space network structure, so that a large number of tiny gaps are generated among the fibers, the whole material becomes fluffy and plump, and the whole material macroscopically shows increased thickness and excellent elasticity.

In contrast, the conventional stretch drying process used in comparative example 6 always places tension on the material during the drying process. The tension forces the superfine fibers which are still in an active state to be forcedly straightened, arranged in parallel and tightly attached along the stretching direction, thereby completely inhibiting the natural trend of stretching the superfine fibers to a three-dimensional space. As a result, a dense, plate-like structure with high internal stress is formed, which is thin and lacks elasticity. When the pre-tensioned structure is stretched again by external force, the fiber has little redundant deformation space, and irreversible slippage is easy to generate, so the elastic recovery rate is low. The comparison strongly proves that the relaxation after-finishing process adopted by the invention is not an isolated step, but is a ring-to-ring and synergistic effect with the prior island fiber reduction technology, and is a necessary guarantee for maximizing the advantages of superfine fibers and realizing soft, plump and high-elasticity hand feeling of the product.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (10)

1. A lightweight environmental protection fire-retardant car sofa leather, characterized by comprising:

(a) A nonwoven fabric substrate composed of ultrafine polyamide-6 fibers;

(b) A microporous polyether polyurethane layer impregnated in and compounded with the nonwoven fabric substrate, and

(C) Microencapsulated halogen-free environment-friendly flame retardant dispersed in the microporous polyether polyurethane layer;

the micro-encapsulated halogen-free environment-friendly flame retardant is 15 to 30 parts by weight relative to 100 parts by weight of polyether polyurethane solid, and the unit area mass of the non-woven fabric substrate before compounding is 150 to 250g/m ².

2. The automotive sofa leather of claim 1, wherein the microcapsule coating of the microencapsulated halogen-free environmentally friendly flame retardant is formed from an acrylic copolymer.

3. The automotive sofa leather according to claim 1 or 2, characterized in that the ultra fine polyamide-6 fibers of the nonwoven fabric substrate are formed by sea-island fibers of polyamide-6 as island component and low density polyethylene as sea component, which are split after removing the sea component.

4. A process for preparing the lightweight environment-friendly flame-retardant automobile sofa leather as claimed in any one of claims 1 to 3, which is characterized by comprising the following steps:

Step one, a microencapsulation pretreatment step, namely microencapsulating halogen-free environment-friendly flame retardant powder to obtain a microencapsulated environment-friendly flame retardant;

Step two, preparing a non-woven fabric base, namely opening, carding, needling and heat setting sea-island short fibers to prepare the non-woven fabric base;

Step three, a wet impregnation and solidification step, namely dispersing the microencapsulated environment-friendly flame retardant obtained in the step one in a dimethylformamide solution of polyether polyurethane to prepare an impregnation liquid, immersing the non-woven fabric substrate obtained in the step two in the impregnation liquid, solidifying in a dimethylformamide aqueous solution, and washing to obtain a wet substrate;

And step four, a deweighting and finishing step, namely performing solvent deweighting treatment on the wet substrate obtained in the step three to remove sea components in the sea-island fiber, and then performing expanding drying, oiling and tentering setting to obtain a finished product.

5. The process of claim 4, wherein the first step comprises:

(a) Suspending halogen-free environment-friendly flame retardant powder in an aqueous medium;

(b) And adding an acrylic monomer and an initiator, and carrying out in-situ polymerization at 60-85 ℃ for 3-6 hours.

6. The preparation process according to claim 4, wherein the second step specifically comprises:

(a) The sea-island short fiber with the weight ratio of polyamide-6 to low density polyethylene of (60-80) to (40-20) is adopted;

(b) Needling with density of 1200-1800 needles/cm ²;

(c) Heat setting at 100-130 deg.c.

7. The process according to claim 4, wherein the impregnating solution in the third step is prepared by dispersing 15-30 parts by weight of microencapsulated environment-friendly flame retardant in a dimethylformamide solution containing 100 parts by weight of polyether polyurethane solids to form an impregnating solution with a solid content of 18-30%.

8. The process according to claim 4, wherein the coagulation in the third step is specifically performed by coagulating the impregnated nonwoven fabric in an aqueous solution of dimethylformamide having a mass concentration of 15 to 25%, and the coagulation bath temperature is 20 to 50 ℃.

9. The process according to claim 4, wherein the solvent reduction treatment in the fourth step is specifically carried out by treating the wet substrate in a toluene solution at 70-90 ℃ for 15-30 minutes.

10. The preparation process according to claim 4, wherein the step four of expanding and drying is specifically performed by adopting an overfeed rate of 5-20% to perform relaxation drying, wherein the drying temperature is 110-150 ℃, and simultaneously, an oiling treatment is performed by adopting an oiling agent with a concentration of 2.5-3.0%.