Homogeneous mixed medicament of micro gas generator for safety belt and preparation method of homogeneous mixed medicament

Abstract

The invention discloses a micro gas generator homogeneous mixed medicament for a safety belt and a preparation method of the micro gas generator homogeneous mixed medicament, the micro gas generator homogeneous mixed medicament is prepared from the following components in percentage by mass: 90-97% of green gas generating medicament particles and 3-10% of nitrocellulose medicament particles uniformly dispersed in gaps of the green gas generating medicament particles, and the sum of the mass percentages of the components is 100%. By utilizing the advantages of high combustion speed and low ignition threshold of the nitrocellulose agent, the ignition delay and the combustion period of the mixed agent are shortened, the exposure time of the safety belt elbow in a high-temperature environment is shortened, the structural strength of the safety belt elbow is ensured, the problem of elbow explosion in a bonfire test is finally solved, and meanwhile, the environment-friendly characteristic of a green gas-producing agent is reserved; in addition, through the two-time charging process of the automatic production line, the mixed charging efficiency is high, and the product consistency is good.

Description

Technical Field

[0001] This invention belongs to the technical field of micro gas generators, specifically relating to a homogeneous mixing agent for a micro gas generator used in seat belts. This invention also relates to a method for preparing the homogeneous mixing agent for a micro gas generator used in seat belts. Background Technology

[0002] In automotive passive safety systems, miniature gas generators are a crucial component of pre-tensioned seat belts. Their function is to rapidly generate gas upon a collision, tightening the seat belt to restrain occupants and reduce injury. With increasing environmental regulations, green propellants are widely used in miniature gas generators. However, green propellants suffer from slow combustion rates and long ignition delays, a deficiency particularly evident in campfire tests (simulating the extreme environment of a vehicle fire). When a vehicle catches fire, the high temperature environment continuously heats the seat belt bend (the metal tube connecting the gas generator and the seat belt tightening mechanism). Because the green propellant ignites late, the bend's strength significantly decreases under prolonged high temperatures. At this point, the high-pressure gas generated by the miniature gas generator can easily cause the insufficiently strong bend to burst, creating a safety hazard.

[0003] In existing technologies, improving the combustion performance of green propellants typically involves optimizing the propellant formulation or increasing ignition energy. However, optimizing the formulation often sacrifices some environmental performance and may introduce new pollutants. Increasing ignition energy leads to increased generator energy consumption and costs, and since the ignition tube's detonation temperature is higher than the propellant's combustion temperature, its effect on improving combustion delay is limited. Furthermore, some solutions achieve staged combustion of the propellant by dividing the combustion chamber into zones, but this structural design increases the generator's manufacturing complexity and assembly difficulty, hindering mass production. Therefore, there is an urgent need for a propellant assembly method that does not require changes to the combustion chamber structure, retains the environmentally friendly characteristics of green propellants, and effectively shortens combustion delay. Summary of the Invention

[0004] The purpose of this invention is to provide a homogeneous mixing agent for a miniature gas generator used in seat belts, which solves the problem of seat belt bends cracking due to delayed combustion of the agent when a vehicle catches fire.

[0005] Another object of the present invention is to provide a method for preparing a homogeneous mixture of agents for a miniature gas generator for seat belts.

[0006] The first technical solution adopted in this invention is: a homogeneous mixing agent for a micro gas generator for seat belts, which is composed of the following components by mass percentage: 90% to 97% green gas-generating agent particles, 3% to 10% nitrocellulose agent particles uniformly dispersed in the gaps between the green gas-generating agent particles, and the sum of the mass percentages of the above components is 100%.

[0007] The first technical solution of the present invention is further characterized in that, The nitrocellulose agent granules are composed of the following components by mass percentage: 0.5% to 2% stabilizer, with the balance being the nitrocellulose agent granule body, and the sum of the mass percentages of the above components is 100%; wherein, the nitrocellulose agent granule body is selected as columnar nitrocellulose agent granules with a nitrogen content of 11.5wt% to 12.5wt%, a single-pore tubular structure, and an average thickness of 0.8 to 1.4 mm for the combustion structure layer.

[0008] The stabilizer used is diphenylamine or dibutyl phthalate.

[0009] Green gas-generating granules are composed of the following components by mass percentage: 40%–55% combustible agent, 40%–50% oxidant, 5%–7% binder, and 0%–4% auxiliary components, with the sum of the mass percentages of the above components being 100%.

[0010] The combustible agent is selected from at least one of guanidine nitrate, nitroguanidine, and 5-aminotetrazolium; the oxidant is selected from one or a mixture of two of potassium nitrate, strontium nitrate, potassium perchlorate, copper oxide, and basic copper nitrate; the binder is selected from one of hydroxypropyl methylcellulose, polyvinyl alcohol, and phenolic resin; and the auxiliary component is selected from at least one of iron oxide, lithium carbonate, carbon powder, and silicon powder.

[0011] The green gas-producing drug particles have a diameter of 0.9–2.2 mm and a length of 0.6–3.0 mm.

[0012] The second technical solution adopted in this invention is: a method for preparing a homogeneous mixing agent for a seat belt micro gas generator, comprising the following steps: Step 1: Select nitrocellulose granules; Step 2: Prepare green gas-generating drug particles with a particle size larger than nitrocellulose drug particles using a wet molding process; Step 3: Using an automated drug loading production line equipped with independent dual silos and two metering devices, the green gas-generating drug particles obtained in Step 2 are fed into the shell of a micro gas generator through the first metering device to form a bottom drug bed; then the nitrocellulose drug particles obtained in Step 1 are fed into the shell of a micro gas generator that already contains green gas-generating drug particles through the second metering device, naturally filling the gaps between the green gas-generating drug particles to form a homogeneous mixed drug.

[0013] The second technical solution of the present invention is further characterized in that, The independent dual-compartment system stores the nitrocellulose granules obtained in step 1 and the green gas-generating granules obtained in step 2, respectively; both metering devices are driven by servo motors with a metering accuracy of ±30mg.

[0014] The beneficial effects of this invention are as follows: The homogeneous mixing agent for the seat belt micro gas generator and its preparation method utilize the advantages of nitrocellulose agent, such as fast combustion speed and low ignition threshold, to shorten the ignition delay and combustion cycle of the mixed agent, reduce the exposure time of the seat belt bend in a high-temperature environment, ensure its structural strength, and ultimately solve the problem of bend cracking in campfire tests, while retaining the environmentally friendly characteristics of green gas-generating agents; in addition, the automated production line with a two-stage loading process results in high mixing efficiency and good product consistency. Attached Figure Description

[0015] Figure 1 This is a Pt function test curve of various examples of the present invention and a single-pack green gas-generating agent. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] This invention provides a homogenized mixing agent for a miniature gas generator used in seat belts, comprising the following steps: Step 1: Selection of NC (Nitrocellulose) Particles Its core physicochemical parameters must meet the following requirements: nitrogen content of 11.5wt% to 12.5wt% (to ensure a balance between combustion rate and chemical stability), single-pore tubular structure, average thickness of combustion structure layer of 0.8 to 1.4 mm (to ensure uniform dispersion in green gas-generating agents, and this structural characteristic ensures that it can serve as an efficient and reliable ignition core in green gas-generating agents, achieving uniform ignition), 0.5wt% to 2wt% of stabilizer (diphenylamine or dibutyl phthalate, directly meeting the storage life requirements), and columnar particle shape (matching the particle shape of green gas-generating agents, avoiding mixed loading and segregation, ensuring the uniformity of agent mixing, and thus improving the consistency of product performance).

[0018] Step 2: Preparation of green gas-generating drug granules The core components are a combustible agent, an oxidizer, and a binder. The combustible agent is selected from at least one of guanidine nitrate, nitroguanidine, and 5-aminotetrazole (40%–55% by mass), providing the main material basis for gas production. The oxidizer is selected from one or a mixture of two of potassium nitrate, strontium nitrate, potassium perchlorate, copper oxide, and basic copper nitrate (40%–50% by mass), which can effectively regulate the combustion rate. The binder is selected from hydroxypropyl methylcellulose, polyvinyl alcohol, phenolic resin, etc. (5%–7% by mass), ensuring stable particle formation. 0–4% auxiliary components (such as iron oxide, lithium carbonate, carbon powder, silicon powder, etc.) can be added as needed to optimize gas production performance or reduce hygroscopicity. A wet molding process is used to produce green gas-generating particles with a diameter of 0.9 mm–2.2 mm and a length of 0.6 mm–3.0 mm. These particles are larger than NC (non-nitrogenous) particles, forming a gradation structure of "fine NC particles + coarse green gas-generating particles," laying the foundation for homogeneous mixing after two loading processes.

[0019] Step 3: Automated production line performs two-stage drug loading and mixing. An automated drug filling production line equipped with dual hoppers and high-precision metering devices completes the drug filling and mixing in two separate metering processes, eliminating the need for vibration compaction. The specific process is as follows: ① First loading: Green gas-generating granules are precisely loaded into the integrated combustion chamber (micro gas generator shell) through the first automated metering device. The loading mass is 90% to 97% of the total loading mass, directly forming the bottom bed of granules, which provides basic support for the gap filling of the second NC agent.

[0020] ② Second loading: NC (non-toxic) propellant particles are added to the combustion chamber already containing the green gas-producing propellant via a second automated metering device. The loading mass is 3%–10% of the total propellant mass. The NC particles naturally fill the gaps between the green gas-producing propellant particles without additional compaction, ultimately forming a homogeneous mixture. This two-loading process requires no additional mixing equipment or vibration program. Natural mixing is achieved through precise feeding via two metering devices, shortening the single mixing cycle to less than 5 seconds. This significantly improves production efficiency compared to traditional mixing processes, and the uniformity of the mixture is highly accurate thanks to automated metering control.

[0021] ③ Production line compatibility design: The dual silos of the automated production line independently store green gas-generating drugs and NC agents to avoid cross-contamination; both metering devices are driven by servo motors with a metering accuracy of ±30mg, ensuring that the drug ratio is accurate and controllable each time; the production line can be adapted to different specifications of micro gas generator shells (inner diameter 10~15mm, length 18~35mm) through parameter adjustment, with strong compatibility.

[0022] The homogeneous mixture of the micro gas generator for seat belts obtained by this invention, when a vehicle fire triggers a campfire test scenario, receives a trigger signal and the energy released by the ignition part of the electric igniter directly acts on the homogeneous mixture, which has been mixed through two loading processes. Because the NC (nitrogenous charge) particles are uniformly dispersed in the gaps between the green gas-generating particles and have a low ignition threshold and fast combustion speed, they are rapidly ignited under the action of ignition energy, forming a large number of dispersed "ignition cores." These ignition cores simultaneously release high-temperature flames and heat, rapidly heating the surrounding green gas-generating particles, overcoming the ignition delay defect of pure green gas-generating agents. Under the action of multi-point synchronous ignition, the green gas-generating agent quickly enters the stable combustion stage. Throughout the combustion process, the uniform dispersion of the NC agent enables rapid propagation of the combustion wave, significantly shortening the total time from ignition triggering to complete combustion of the mixture, reducing the exposure time of the seat belt bend in the high-temperature environment, effectively avoiding the risk of explosion under high-pressure gas generation, and ensuring successful completion of the campfire test. Simultaneously, the green gas-generating agent accounts for 90%–97%, ensuring the environmental friendliness of the gas generation process.

[0023] Meanwhile, the optimization effect of NC reagent on the breaking performance of the micro gas generator was verified by plate heating test: after adding NC reagent, the breaking temperature of the micro gas generator dropped from 270℃ to 200℃, which effectively improved the thermal response characteristics of the generator, enhanced its safety and adaptability in practical applications, and further proved its reliability in campfire test.

[0024] In addition to the above methods, the present invention also possesses the following features: 1) Automated two-stage drug filling and efficient mixing: The two drugs are filled sequentially through an automated production line to achieve mixing without the need for additional mixing equipment. The single mixing cycle is less than 5 seconds, which has a significant advantage in production efficiency compared to the traditional "preparation + mixing". In addition, the uniformity of mixing is controlled by automation, resulting in a high product consistency qualification rate and reducing quality fluctuations caused by human intervention.

[0025] 2) Successfully passed the campfire test, and the plate test verified its reliability: Utilizing the rapid ignition characteristics of the NC agent to create a multi-point combustion effect significantly shortened the ignition delay time of the mixed agent and the overall combustion cycle, greatly reducing the exposure time of the seatbelt bend at high temperatures, ensuring its structural strength, and completely solving the problem of bend cracking. In the plate test, the breaking temperature of the micro gas generator provided data support for the successful completion of the campfire test.

[0026] 3) Retaining environmental protection characteristics: Green gas-producing agents account for 90% to 97%, no toxic or harmful components are introduced, and environmental protection regulations are met.

[0027] 4) Strong production line compatibility: The automated production line can be adapted to different specifications of micro gas generators by adjusting the metering parameters, without the need to modify the equipment, and is suitable for the production needs of multiple micro gas generators.

[0028] Example 1 (Comparative Example 1 - without NC) Step 1: Using 55% guanidine nitrate, 10% potassium nitrate, 30% potassium perchlorate, and 5% hydroxypropyl methylcellulose (by mass) as raw materials, columnar green gas-generating drug particles with an average particle size of 1.6 mm and a length of 1.6 mm are prepared by wet molding.

[0029] Step 2: Using an automated drug loading production line, a miniature gas generator shell with an inner diameter of 13mm and a length of 24mm is used to feed in 1180mg of green gas-generating drug granules.

[0030] Example 2 (Example 1 - Add NC) Step 1: Select columnar NC agent particles with a nitrogen content of 11.5wt% to 12.5wt%, a single-hole tubular structure, an average thickness of 1.1±0.3mm for the combustion structure layer, and 0.5wt% to 2wt% of stabilizer added.

[0031] Step 2: Using 55% guanidine nitrate, 10% potassium nitrate, 30% potassium perchlorate, and 5% hydroxypropyl methylcellulose (by mass) as raw materials, columnar green gas-generating drug particles with an average particle size of 1.6 mm and a length of 1.6 mm are prepared by wet molding.

[0032] Step 3: Automated two-stage drug filling and mixing: A dual-hopper automated drug filling production line is used, with a micro gas generator shell with an inner diameter of 13mm and a length of 24mm. First filling: 1130mg of green gas-generating drug granules are added (95.8% of the total drug mass); Second filling: 50mg of NC drug granules are added (4.2% of the total drug mass).

[0033] Step 4: ① Campfire Test: In the campfire test, the time from ignition to complete combustion of the agent was 3 minutes, which is 46% shorter than that of the pure green gas-generating agent (4.48 minutes); the high-temperature exposure time of the seat belt bend was 3 minutes, and there was no explosion upon ignition, thus successfully passing the campfire test. ② Plate Test: The miniature gas generator was installed in a steel plate. The break temperature of the miniature gas generator corresponding to the pure green gas-generating agent was 267℃. After adding the NC agent, the break temperature dropped to 213℃, which is 54℃ lower than that of the pure green gas-generating agent, verifying that the combustion temperature of the miniature gas generator decreased significantly after adding the NC agent.

[0034] Example 3 (Comparative Example 2 - without NC) Step 1: Using 50% potassium nitrate, 40% guanidine nitrate, 6% hydroxypropyl methylcellulose, 2.5% lithium carbonate, and 1.5% silica powder (by mass) as raw materials, columnar green gas-generating drug particles with an average particle size of 1.2 mm and a length of 1.2 mm are prepared by wet molding.

[0035] Step 2: Using an automated drug loading production line, a miniature gas generator shell with an inner diameter of 13mm and a length of 24mm is used to feed 1000mg of green gas-generating drug granules.

[0036] Example 4 (Example 2 - Add NC) Step 1: Select columnar NC agent particles with a nitrogen content of 11.5wt% to 12.5wt%, a single-pore tubular structure, an average thickness of 1.1±0.3mm for the combustion layer structure, and 0.5wt% to 2wt% of stabilizer added.

[0037] Step 2: Using 50% potassium nitrate, 40% guanidine nitrate, 6% hydroxypropyl methylcellulose, 2.5% lithium carbonate, and 1.5% silica powder (by mass) as raw materials, columnar green gas-generating drug particles with an average particle size of 2.0 mm and a length of 2.0 mm are prepared by wet molding.

[0038] Step 3: Automated two-stage drug filling and mixing: A dual-hopper automated drug filling production line is used, with a micro gas generator shell with an inner diameter of 13mm and a length of 24mm. First filling: 950mg of green gas-generating drug granules (95% of the total drug mass) are added; Second filling: 50mg of NC drug granules (5% of the total drug mass) are added.

[0039] Step 4: ① Campfire Test: In the campfire test, the time from ignition to complete combustion of the agent was 3.5 minutes, which is 32.7% shorter than that of the pure green gas-generating agent (5.2 minutes); the high-temperature exposure time of the seat belt bend was 3.5 minutes, and there was no explosion upon ignition, thus successfully passing the campfire test. ② Plate Test: The miniature gas generator was installed in a steel plate. The break temperature of the miniature gas generator corresponding to the pure green gas-generating agent was 289℃. After adding the NC agent, the break temperature dropped to 202℃, which is 87℃ lower than that of the pure green gas-generating agent, verifying that the combustion temperature of the miniature gas generator decreased significantly after adding the NC agent.

[0040] Example 5 (Comparative Example 3 - without NC) Step 1: Using 45% potassium perchlorate, 35% nitroguanidine, 10% 5-aminotetrazolium, 7% hydroxypropyl methylcellulose, and 3% potassium carbonate (by mass) as raw materials, columnar green gas-generating drug particles with an average particle size of 2.0 mm and a length of 2.0 mm are prepared by wet molding.

[0041] Step 2: Using an automated drug loading production line, a miniature gas generator shell with an inner diameter of 13mm and a length of 22mm is used to feed in 860mg of green gas-generating drug granules.

[0042] Example 6 (Example 3 - Add NC) Step 1: Select columnar NC agent particles with a nitrogen content of 11.5wt% to 12.5wt%, a single-pore tubular structure, an average thickness of 1.1±0.3mm for the combustion layer structure, and 0.5wt% to 2wt% of stabilizer added.

[0043] Step 2: Using 45% potassium perchlorate, 35% nitroguanidine, 10% 5-aminotetrazolium, 7% hydroxypropyl methylcellulose, and 3% potassium carbonate (by mass) as raw materials, columnar green gas-generating drug particles with an average particle size of 1.2 mm and a length of 1.2 mm are prepared by wet molding.

[0044] Step 3: Automated two-stage drug filling and mixing: A dual-hopper automated drug filling production line is used, with a micro gas generator shell with an inner diameter of 13mm and a length of 22mm. First filling: 810mg of green gas-generating drug granules are added (94% of the total drug mass); Second filling: 50mg of NC drug granules are added (6% of the total drug mass).

[0045] Step 4: ① Campfire Test: In the campfire test, the time from ignition to complete combustion of the agent was 2.6 minutes, which is 36.6% shorter than that of pure green gas-generating agent (4.1 minutes); the high-temperature exposure time of the seat belt bend was 2.6 minutes, and there was no explosion upon ignition, successfully passing the campfire test. ② Plate Test: The miniature gas generator was installed in a steel plate. The break temperature of the miniature gas generator corresponding to pure green gas-generating agent was 249℃. After adding NC agent, the break temperature dropped to 191℃, which is 58℃ lower than that of pure green gas-generating agent, verifying that the combustion temperature of the miniature gas generator decreased significantly after adding NC agent.

[0046] like Figure 1 As shown, there is no significant difference in product performance before and after adding NC reagent. Therefore, this invention achieves multiple technical advantages without changing the core function of the product: directly purchasing NC reagent eliminates the preparation process, reduces investment and cost of special equipment, avoids dust and static electricity risks, and improves production safety; the two reagent mixing processes are completed through an automated production line, eliminating the need for additional mixing equipment, with a single mixing cycle of <5s, which is more efficient than traditional processes, and automated control ensures mixing uniformity, reduces quality fluctuations, and achieves a high product consistency pass rate; relying on the rapid ignition characteristics of NC reagent to form multi-point combustion, shortens ignition delay and combustion cycle, reduces the high-temperature exposure time of the safety belt bend, ensures structural strength, and completely solves the problem of bend cracking, which has been verified as reliable by campfire and plate tests; the proportion of green gas-producing reagent is 90% to 97%, with no toxic or harmful components, meeting environmental protection requirements, and the procurement cost of NC reagent is low; the production line can be adapted to different specifications of products by only adjusting the metering parameters, without the need for equipment modification, and has strong compatibility.

Claims

1. A miniature gas generator for seat belts for homogenizing and mixing pharmaceuticals, characterized in that, It consists of the following components by mass percentage: 90%–97% green gas-generating drug particles, 3%–10% nitrocellulose agent particles uniformly dispersed in the gaps between the green gas-generating drug particles, and the sum of the mass percentages of the above components is 100%.

2. The homogeneous mixing agent for the miniature gas generator used in seat belts as described in claim 1, characterized in that, The nitrocellulose agent particles are composed of the following components by mass percentage: 0.5% to 2% stabilizer, with the balance being the nitrocellulose agent particle body, and the sum of the mass percentages of the above components is 100%; wherein, the nitrocellulose agent particle body is selected as columnar nitrocellulose agent particles with a nitrogen content of 11.5wt% to 12.5wt%, a single-pore tubular structure, and an average thickness of 0.8 to 1.4 mm for the combustion structure layer.

3. The homogeneous mixing agent for the miniature gas generator used in seat belts as described in claim 2, characterized in that, The stabilizer is selected from diphenylamine or dibutyl phthalate.

4. The homogeneous mixing agent for the miniature gas generator used in seat belts as described in claim 1, characterized in that, The green gas-generating granules are composed of the following components by mass percentage: 40%–55% combustible agent, 40%–50% oxidant, 5%–7% binder, and 0%–4% auxiliary components, with the sum of the mass percentages of the above components being 100%.

5. The homogeneous mixing agent for the miniature gas generator used in seat belts as described in claim 4, characterized in that, The combustible agent is selected from at least one of guanidine nitrate, nitroguanidine, and 5-aminotetrazolium; the oxidant is selected from one or a mixture of two of potassium nitrate, strontium nitrate, potassium perchlorate, copper oxide, and basic copper nitrate; the binder is selected from one of hydroxypropyl methylcellulose, polyvinyl alcohol, and phenolic resin; and the auxiliary component is selected from at least one of iron oxide, lithium carbonate, carbon powder, and silicon powder.

6. The miniature gas generator for seat belts as described in claim 4, characterized in that, The green gas-producing drug particles have a diameter of 0.9–2.2 mm and a length of 0.6–3.0 mm.

7. The method for preparing the homogeneous mixing agent for the miniature gas generator used in seat belts as described in claim 1, characterized in that, Includes the following steps: Step 1: Select nitrocellulose granules; Step 2: Prepare green gas-generating drug particles with a particle size larger than nitrocellulose drug particles using a wet molding process; Step 3: Using an automated drug loading production line equipped with independent dual silos and two metering devices, the green gas-generating drug particles obtained in Step 2 are fed into the shell of a micro gas generator through the first metering device to form a bottom drug bed; then the nitrocellulose drug particles obtained in Step 1 are fed into the shell of a micro gas generator that already contains green gas-generating drug particles through the second metering device, naturally filling the gaps between the green gas-generating drug particles to form a homogeneous mixed drug.

8. The method for preparing the homogeneous mixing agent for the miniature gas generator for seat belts as described in claim 7, characterized in that, The independent dual silos store the nitrocellulose granules obtained in step 1 and the green gas-producing granules obtained in step 2, respectively; both metering devices are driven by servo motors with a metering accuracy of ±30mg.

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