GAS-GENERATING AGENT COMPOSITION

Description

TECHNICAL FIELD

The present disclosure relates to a gas-generating agent composition.

BACKGROUND ART

For an inflator that uses a gas-generating agent composition and that is used in a vehicle safety device, such as an airbag device, installed in a vehicle, attempts have been made to ensure reliability of a product. For example, attempts have been made to make a pressure index smaller while the combustion temperature of a gas-generating agent composition is decreased and ignition ability is improved (Patent Document 1). The invention described in Patent Document 1 solves a problem by means of setting the ratio of melamine cyanurate to nitroguanidine to fall within a specific range.

CITATION LIST

Patent Document

• • Patent Document 1: JP 2012-211064 A

SUMMARY OF INVENTION

Technical Problem

One of the properties of a gas-generating agent composition is a combustion temperature. In the related art, in a case where the combustion temperature of a gas-generating agent composition is high, it has been considered that measures need to be taken to decrease the temperature of the gas at the time of gas generation, thereby protecting an airbag. Thus, there has been a demand for reducing the combustion temperature of a gas-generating agent composition as much as possible. Meanwhile, there is a problem that when the combustion temperature of the gas-generating agent composition is decreased, the ignition ability of the gas-generating agent composition is deteriorated.

Furthermore, there is also a demand for reducing the value of a pressure index, which is a property of the gas-generating agent composition, as much as possible to prevent a variation in combustion rate associated with a change in pressure.

Furthermore, the gas-generating agent composition is required to have an appropriate combustion rate depending on the intended use.

In view of these, an object of the present disclosure is to provide a gas-generating agent composition having a high combustion temperature, a small pressure index, excellent ignition ability, and an appropriate combustion rate.

Solution to Problem

As a result of diligent research to solve the problems described above, the present inventors have found that the problems described above can be solved by adding melamine cyanurate to guanidine nitrate and basic copper nitrate to form a three-component system, and setting the combustion temperature of the three-component system to 1680 K or higher.

In particular, it has been found that, in a case where melamine cyanurate is added in a gas-generating agent composition containing guanidine nitrate as a fuel and basic copper nitrate as an oxidant, the pressure index of the gas-generating agent composition can be reduced and the combustion rate can be adjusted to a desired value.

Furthermore, when the combustion temperature is 1680 K or higher, excellent ignition ability is achieved. In the present description, excellent ignition ability is synonymous with a short ignition time.

The present disclosure relates to the following items.

• • [1] A gas-generating agent composition containing components (a) to (c) below, wherein a combustion temperature calculated based on a composition containing the components (a) to (c) below is 1680 K or higher:
  • (a) guanidine nitrate;
  • (b) basic copper nitrate; and
  • (c) melamine cyanurate.
  • [2] The gas-generating agent composition according to [1], wherein a content of (a) guanidine nitrate is 30 wt. % or greater and 60 wt. % or less; a content of (b) basic copper nitrate is 40 wt. % or greater and 65 wt. % or less; and
  • a content of (c) melamine cyanurate is 0.5 wt. % or greater and 12 wt. % or less.
  • [3] The gas-generating agent composition according to [2], wherein the content of (a) guanidine nitrate is 32 wt. % or greater and 55 wt. % or less.
  • [4] The gas-generating agent composition according to [2], wherein the content of (b) basic copper nitrate is 43 wt. % or greater and 60 wt. % or less.
  • [5] The gas-generating agent composition according to [2], wherein the content of (c) melamine cyanurate is 1 wt. % or greater and 11 wt. % or less.
  • [6] The gas-generating agent composition according to any one of [1] to [5], wherein the combustion temperature calculated based on the composition containing the components (a) to (c) is 1700 K or higher.
  • [7] The gas-generating agent composition according to any one of [1] to [6], wherein the combustion temperature calculated based on the composition containing the components (a) to (c) is 2000 K or lower.
  • [8] The gas-generating agent composition according to any one of [1] to [7], wherein a pressure index is 0.35 or less.
  • [9] The gas-generating agent composition according to [8], wherein the pressure index is 0.23 or less.
  • [10] The gas-generating agent composition according to [8], wherein the pressure index is 0.01 or greater.
  • [11] The gas-generating agent composition according to any one of [1] to [10], wherein a weight ratio of a total amount of the component (a) and the component (b) to an amount of the component (c) (((a)+(b))/(c)) is in a range of 8 or greater and 150 or less.
  • [12] The gas-generating agent composition according to [11], wherein the weight ratio of the total amount of the component (a) and the component (b) to the amount of the component (c) (((a)+(b))/(c)) is in a range of 11.6 or greater and 125 or less.
  • [13] An inflator containing the gas-generating agent composition described in any one of [1] to [12].

Advantageous Effects of Invention

An embodiment of the present disclosure can provide a gas-generating agent composition having a high combustion temperature, a small pressure index, excellent ignition ability, and an appropriate combustion rate.

DESCRIPTION OF EMBODIMENTS

The present disclosure will be described below with reference to specific embodiments. In the present specification, when a lower limit value and an upper limit value of a numerical range are separately indicated, the numerical range can be a combination of any lower limit value and any upper limit value among the range.

(a) Guanidine Nitrate

The component (a) according to an embodiment of the present disclosure is guanidine nitrate. Because guanidine nitrate contains oxygen in a molecule, the blended amount of an oxidant component can be reduced, and guanidine nitrate has advantages such that it has good thermal stability and is expected to achieve cost reduction and a high gasification rate at the time of combustion.

The lower limit of the content of guanidine nitrate in the gas-generating agent composition according to an embodiment of the present disclosure is typically 30 wt. % or greater and 60 wt. % or less, and is 32 wt. % or greater and 55 wt. % or less in a preferred aspect. When the content (blending proportion) of guanidine nitrate is less than 30 wt. %, the molar amount of generated gas per 100 g of the gas-generating agent composition decreases, and a large amount of nitrogen oxide tends to be generated due to oxygen excess. Meanwhile, when the content (blending proportion) of guanidine nitrate is greater than 60 wt. %, a large amount of carbon monoxide tends to be generated due to lack of the oxidant component.

Furthermore, a known additional fuel can be contained as long as the object of the present disclosure can be achieved.

Examples of the known additional fuel include one or more selected from the group consisting of tetrazole compounds such as 5-aminotetrazole and bitetrazole ammonium salt; guanidine compounds such as dicyandiamide; and triazine compounds such as melamine, trimethylolmelamine, alkylated methylolmelamine, ammeline, ammelide, nitrate of melamine, perchlorate of melamine, trihydrazinotriazine, and nitrated compounds of melamine.

(b) Basic Copper Nitrate

The component (b) according to an embodiment of the present disclosure is basic copper nitrate. By using basic copper nitrate, the combustion temperature of the gas-generating agent composition can be adjusted to a desired range. Specifically, the combustion temperature of the gas-generating agent composition can be set to a non-excessively high degree.

The content of basic copper nitrate is typically in a range of 40 wt. % or greater and 65 wt. % or less with respect to the amount of the gas-generating agent composition in a preferred aspect. In particular, to reduce carbon monoxide and nitrogen oxide concentrations in the generated gas, the content of basic copper nitrate is more preferably in a range of 43 wt. % or greater and 60 wt. % or less in another preferred aspect.

The gas-generating agent composition according to an embodiment of the present disclosure may contain an additional oxidant as long as the effects of the gas-generating agent composition are not impaired. Examples of the additional oxidant include one or more selected from basic cobalt nitrate, basic zinc nitrate, and basic manganese nitrate. Other examples of the additional oxidant include ammonium nitrate, metal perchlorates, ammonium perchlorate, metal nitrites, and metal chlorates.

(c) Melamine Cyanurate

The component (c) according to an embodiment of the present disclosure is melamine cyanurate. In a case where melamine cyanurate is contained in the gas-generating agent composition containing (a) guanidine nitrate and (b) basic copper nitrate, the pressure index of the gas-generating agent composition can be decreased. By decreasing the pressure index, a variation in combustion temperature associated with a change in pressure can be prevented.

The content of melamine cyanurate as the component (c) in the gas-generating agent composition according to an embodiment of the present disclosure is typically 0.5 wt. % or greater and 12 wt. % or less, 1 wt. % or greater and 11 wt. % or less in a preferred aspect, and 1 wt. % or greater and 6.5 wt. % or less in a more preferred aspect.

The weight ratio of the total amount of the component (a) and the component (b) to the amount of the component (c) (((a)+(b))/(c)) in the gas-generating agent composition according to an embodiment of the present disclosure is typically 8 or greater, can be 11.6 or greater, and is preferably 14.5 or greater, more preferably 20 or greater, and even more preferably 21 or greater, from the viewpoint of decreasing the pressure index. Meanwhile, the upper limit of this ratio may be 150 or less, 125 or less, and 100 or less. That is, the ratio is typically 8 or greater and 150 or less, 11.6 or greater and 125 or less in another aspect, 14.5 or greater and 125 or less in yet another aspect, and 20 or greater and 100 or less in yet another aspect. From the viewpoint of decreasing the pressure index, this ratio is preferably as large as possible.

To adjust this ratio, the contents of guanidine nitrate, basic copper nitrate, and melamine cyanurate are only required to be adjusted in such a range that the combustion temperature is adjusted to 1680 K or higher.

To decrease the pressure index of the gas-generating agent composition, the component (c) is required to be added to the gas-generating agent composition in addition to the component (a) and the component (b). Meanwhile, the weight ratio of the total amount of the component (a) and the component (b) to the amount of the component (c) (((a)+(b))/(c)) is preferably as large as possible. That is, the weight proportion of the component (c) with respect to the total amount of the component (a) and the component (c) is preferably small.

Combustion Temperature of Gas-Generating Agent Composition

The combustion temperature of the gas-generating agent composition according to an embodiment of the present disclosure is calculated by using a program known as “NEWPEP”. “NEWPEP” is based on PEP programs described in Naval Weapons Center Report titled “Theoretical Computation of Equilibrium Composition, Thermodynamic Properties, and Performance Characteristics of Propellant System” published in 1960, 1979, and 1990. This program is a public property and can be easily utilized by a person skilled in the art.

The combustion temperature of the gas-generating agent composition is determined based on the types of the constituents contained in the gas-generating agent composition and the compositional proportions thereof. In the present disclosure, the combustion temperature of the gas-generating agent composition is calculated based on the composition containing guanidine nitrate, basic copper nitrate, and melamine cyanurate, and the combustion temperature is 1680 K or higher. Thus, even in a case where the gas-generating agent composition according to an embodiment of the present disclosure contains another optional component, the combustion temperature is calculated based on the composition containing guanidine nitrate, basic copper nitrate, and melamine cyanurate. To set the combustion temperature of the gas-generating agent composition to 1680 K, the composition of guanidine nitrate, basic copper nitrate, and melamine cyanurate can be appropriately changed.

The combustion temperature of the gas-generating agent composition according to an embodiment of the present disclosure is 1680 K or higher, and may be 1700 K or higher, 1750 K or higher, 1800 K or higher, or 1850 K or higher. The upper limit of the combustion temperature may be, for example, 2000 K or lower, 1950 K or lower, or 1900 K or lower. The lower limit and upper limit of the combustion temperature can be appropriately combined. For example, in a case where the lower limit is 1680 K or higher, the upper limit may be 200 K or less or 1950 or less. Alternatively, the lower limit may be changed to another numerical value, and the upper limit may be set to 200 K or less or 1950 or less. As described above, in the known art, common general technical knowledge involves lowering of the combustion temperature of the gas-generating agent composition. In contrast, the combustion temperature is increased in the gas-generating agent composition according to an embodiment of the present disclosure.

The gas generation efficiency of the gas-generating agent composition is also calculated by a program of NEWPEP similarly with the combustion temperature. The gas generation efficiency of the gas-generating agent composition according to an embodiment of the present disclosure is not particularly limited, and, for example, 2.5 mol/100 g or greater and 3.5 mol/100 g or less, or 2.7 mol/100 g or greater and 3.2 mol/100 g or less.

Furthermore, the oxygen balance calculated based on the composition containing guanidine nitrate, basic copper nitrate, and melamine cyanurate in the gas-generating agent composition according to an embodiment of the present disclosure is preferably −2.5 or greater and −0.1 or less. The oxygen balance is calculated based on the compositional proportions of guanidine nitrate, basic copper nitrate, and melamine cyanurate contained in the gas-generating agent composition.

Pressure Index

The combustion rate of the gas-generating agent composition is known to fluctuate with an amplitude of powers of the pressure index n due to pressure variation in an inflator.

rb=αPⁿ (in the formula, rb: combustion rate, α: combustion coefficient, P: pressure, n: pressure index)

In the present disclosure, the pressure index and the combustion coefficient of the gas-generating agent composition are calculated from combustion rates measured under pressures of 5 MPa, 7 MPa, and 9 MPa based on the formula described above.

The pressure index of the gas-generating agent composition according to an embodiment of the present disclosure is desirably as small as possible to prevent a variation in ignition speed associated with a change in pressure. For example, the pressure index is preferably 0.35 or less, more preferably 0.31 or less, even more preferably 0.23 or less, and particularly preferably less than 0.2. Meanwhile, the lower limit of the pressure index of the gas-generating agent composition can be, for example, 0.01 or greater and may be 0.05 or greater. The upper limit and the lower limit of the pressure index can be appropriately combined. For example, in a case where the upper limit is 0.35 or less, the lower limit may be 0.01 or greater or 0.05 or greater. Alternatively, the upper limit may be changed to another numerical value, and the lower limit may be set to 0.01 or greater or 0.05 or greater.

Because the gas-generating agent composition according to an embodiment of the present disclosure contains melamine cyanurate in addition to guanidine nitrate and basic copper nitrate, the pressure index can be decreased as compared with the case of a gas-generating agent composition containing no melamine cyanurate.

Additional Optional Component

As long as the object of the present disclosure can be achieved, the gas-generating agent composition according to an embodiment of the present disclosure can contain any known additive for the purposes of adjusting the combustion rate of the gas-generating agent composition, and cleaning combustion gas. Examples of the known additive include metal oxides such as copper (II) oxide, iron oxide, zinc oxide, cobalt oxide, manganese oxide, molybdenum oxide, nickel oxide, bismuth oxide, silica, and alumina; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, cobalt hydroxide, and iron hydroxide; cobalt carbonate, calcium carbonate; composite compounds of metal oxides or hydroxides, such as acid clay, kaolin, talc, bentonite, and diatomaceous earth; metallic acid salts such as sodium silicate, mica molybdate, cobalt molybdate, and ammonium molybdate; and molybdenum disulfide, calcium stearate, silicon nitride, silicon carbide, metaboric acid, boric acid, and boric anhydride.

In the gas-generating agent composition according to an embodiment of the present disclosure, the content of an optional component other than the components (a) to (c) may be, for example, 5 wt. % or less, 3 wt. % or less, 1 wt. % or less, or 0 wt. %. The gas-generating agent composition according to an embodiment of the present disclosure may be in a form wherein the content of the optional component other than the components (a) to (c) is 0 wt. %, that is, may be formed only of the components (a) to (c).

The gas-generating agent composition according to an embodiment of the present disclosure can be formed into a desired shape and may be formed into a single-hole cylindrical, multi-hole cylindrical, or pellet-like molded article. The molded article can be produced by adding and mixing water or an organic solvent into the gas-generating agent composition and then subjecting the mixture to extrusion molding (a single-hole cylindrical or multi-hole cylindrical molded article) or subjecting the mixture to compression molding using a tableting machine or the like (a pellet-like molded article).

Because the gas-generating agent composition according to an embodiment of the present disclosure has a high combustion rate, the molded article does not need to be made small, and a complicated production process is not required.

The gas-generating agent composition according to an embodiment of the present disclosure or a molded article produced therefrom can be applied to, for example, an airbag inflator for a driver's seat, an airbag inflator for a front passenger seat, a side airbag inflator, an inflator for an inflatable curtain, an inflator for a knee bolster, an inflator for an inflatable seat belt, an inflator for a tubular system, and an inflator for a pretensioner in various vehicles. The gas-generating agent composition according to an embodiment of the present disclosure or a molded article produced therefrom can be suitably used for, among these, a side airbag inflator that requires rapid deployment.

The gas-generating agent composition according to an embodiment of the present disclosure or an inflator containing a molded article produced from the composition may be of a pyro-type in which a gas is supplied only from the gas-generating agent or of a hybrid-type in which a gas is supplied from both compressed gas, such as argon, and the gas-generating agent.

The gas-generating agent composition according to an embodiment of the present disclosure or a molded article produced therefrom can also be used as an igniting agent called an enhancer (or a booster), which serves to transmit an energy of a detonator or a squib to the gas-generating agent.

The configurations, combinations thereof, and the like in each embodiment are an example, and various additions, omissions, substitutions, and other changes may be made as appropriate without departing from the spirit of the present invention. The present disclosure is not limited by the embodiments and is limited only by the claims.

Examples

Hereinafter, the present disclosure will be specifically described with reference to Examples. However, the present disclosure is not limited to the following Examples.

Preparation of Gas-Generating Agent Composition

A pre-molded gas-generating agent composition having a composition shown in Table 1 was prepared.

	TABLE 1
	Raw material proportions		Performance

				Guanidine	Basic copper	Melamine	Gas	Combustion
		Oxygen	Combustion	nitrate	nitrate	cyanurate	generation	rate	Pressure
		balance	temperature	(GN)	(BCN)	(MC)	efficiency	7 MPa	index
Classification		g/100 g	K	wt. %	wt. %	wt. %	mol/100 g	mm/sec	—

Examples	Experimental	−2.0	1700	40.76	51.31	7.93	2.90	11.5	0.26
	Example 1
	Experimental	−1.3	1700	37.84	53.41	8.75	2.82	10.9	0.20
	Example 2
	Experimental	−0.9	1700	36.14	54.63	9.23	2.77	11.3	0.23
	Example 3
	Experimental	−0.5	1700	34.38	55.87	9.75	2.73	11.6	0.20
	Example 4
	Experimental	−0.1	1700	32.68	57.09	10.23	2.68	12.0	0.21
	Example 5
	Experimental	−0.9	1700	36.14	54.63	9.23	2.77	11.8	0.26
	Example 6
	Experimental	−2.0	1750	45.41	48.94	5.65	2.97	11.4	0.28
	Example 7
	Experimental	−1.3	1750	42.49	51.04	6.47	2.89	11.5	0.10
	Example 8
	Experimental	−0.9	1750	40.80	52.25	6.95	2.85	11.3	0.27
	Example 9
	Experimental	−0.9	1750	40.80	52.25	6.95	2.85	11.5	0.23
	Example 10
	Experimental	−0.5	1750	39.03	53.50	7.47	2.80	11.8	0.27
	Example 11
	Experimental	−0.1	1750	37.34	54.71	7.95	2.76	12.4	0.15
	Example 12
	Experimental	−2.0	1800	50.20	46.50	3.30	3.05	11.2	0.11
	Example 13
	Experimental	−1.3	1800	47.29	48.59	4.12	2.97	10.5	0.10
	Example 14
	Experimental	−0.9	1800	45.59	49.81	4.60	2.93	11.5	0.21
	Example 15
	Experimental	−0.9	1800	45.59	49.81	4.60	2.93	11.4	0.15
	Example 16
	Experimental	−0.5	1800	43.82	51.06	5.12	2.88	11.5	0.31
	Example 17
	Experimental	−0.1	1800	42.13	52.27	5.60	2.84	11.5	0.25
	Example 18
	Experimental	−0.9	1833	48.86	48.14	3.00	2.98	11.0	0.09
	Example 19
	Experimental	−0.9	1853	50.90	47.10	2.00	3.01	10.1	0.07
	Example 20
	Experimental	−0.9	1872	52.94	46.06	1.00	3.04	9.6	0.14
	Example 21
	Experimental	−2.4	1813	53.57	44.43	2.00	3.12	10.4	0.17
	Example 22
	Experimental	−1.6	1834	52.15	45.85	2.00	3.06	9.9	0.13
	Example 23
Comparative	Experimental	−0.9	1892	54.98	45.02	0.00	3.08	8.4	0.32
Examples	Example 24
	Experimental	−0.9	1892	54.98	45.02	0.00	3.08	9.3	0.28
	Example 25
	Experimental	−2.4	1853	57.63	42.37	0.00	3.18	9.5	0.24
	Example 26
	Experimental	−1.6	1872	56.30	43.70	0.00	3.13	9.7	0.33
	Example 27
* The combustion temperature and the gas generation efficiency are numerical values calculated based on NEWPEP.
** The oxygen balance is a calculated value determined from the composition.

Molding into Cylindrical Strand

Each of the gas-generating agent compositions of Examples and Comparative Examples shown in Table 1 was weighed, and then mixed raw materials were subjected to compression molding, to produce a molded article.

The produced molded article was pulverized with an agate mortar, and a powder passed through a wire mesh having a mesh size of 500 μm was charged in a mortar side of a predetermined mold.

Subsequently, compression was held for 5 seconds at a pressure of 14.7 MPa applied by a hydraulic pump from a pestle-side end surface, and the resultant product was removed and molded into a cylindrical strand having an outer diameter of 9.6±0.1 mm and a length of 12.7±1.0 mm, to thereby produce a post-molded gas-generating agent composition.

Measurement Methods of Combustion Rate and Pressure Index

The cylindrical strand serving as a sample was placed in an SUS sealed bomb having an internal volume of 1 L and pressurized and stabilized at 5 MPa, 7 MPa, or 9 MPa while the inside of the bomb was completely purged with nitrogen. Thereafter, a predetermined electric current was passed through a nichrome wire brought into contact with the end surface of the strand, and the strand was ignited and combusted by the fusion energy from the nichrome wire. The behavior of pressure inside the bomb with time was checked by a recorder chart, a period of time from the start of the combustion until the peak of pressure rise was checked from the scale of the chart, and the numerical value determined by dividing the length of the strand before combustion by this period of time was defined as the combustion rate. Table 1 shows the test results under application of a pressure of 7 MPa in Examples and Comparative Examples. Furthermore, the pressure index was determined by using the numerical value of the combustion rate determined under application of each of the pressures. The results are shown in Table 1.

As is clear from comparison between the results of Examples and Comparative Examples shown in Table 1, when a gas-generating agent composition containing guanidine nitrate and basic copper nitrate further contains melamine cyanurate, the pressure index of the gas-generating agent composition can be decreased, and the combustion rate under application of a pressure of 7 MPa can be improved.

INDUSTRIAL APPLICABILITY

According to the present disclosure, there can be provided a gas-generating agent composition having a high combustion temperature, a small pressure index, and a desired combustion rate.