JPS621998B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an odorant for fuel gases such as liquefied petroleum gas and city gas that does not contain sulfur and is effective in trace amounts. More specifically, the present invention relates to an odorant for fuel gas containing a norbornene derivative represented by the following formula (1) as an active ingredient, either alone or as an essential ingredient.

[Formula] (In the formula, there is a double bond at one of the positions indicated by the dotted line, and R represents hydrogen or a lower alkyl group.) Currently, fuel gas (city gas or liquefied petroleum gas) is very popular as a household and industrial fuel.
In particular, liquefied petroleum gas as a household fuel is popular throughout the country, partly because it is relatively easy to transport.
On the other hand, the current situation is that there is no end to gas-related disasters in consumer households. Various safety measures are taken to prevent disasters and accidents, and one of them is that it is required by law to add odor components so that in the event of a gas leak, it can be easily detected by the human sense of smell. . The present invention is an odor-imparting material (odorant) for preventing disasters caused by gas leaks.
It is related to. Conventionally, sulfur compounds such as mercaptans and sulfides have been mainly used as odorants for fuel gas. However, recently the sulfur content of fuel gas consumed in Japan has been decreasing, and in order to maintain its characteristics as clean energy, it is desirable to avoid the use of odorants containing sulfur. Various non-sulfur based odorants have recently been developed for this purpose. Examples include triethylamine, n-valeric acid, ethyl acrylate, allyl acrylate, propyl acrylate, vinyl ethyl ether, allyl ethyl ether, fatty acid esters, and aldehydes. However, when used alone, these substances differ in odor quality from gas odor, and when mixed with sulfur-based substances, they are used to modify the odor quality. It is only used as a supplement. Furthermore, it is not completely satisfactory because it is a chemically very active substance and has poor stability. The present inventors obtained as much material as possible that does not contain sulfur and can be used as a gas odorant in terms of physical properties, and conducted a suitability test as an odorant. We have discovered many substances that were previously unknown to be used as odorants, as shown in the figure below.

【table】

【table】

[Table] All of the components in the table have a unique odor, and adding a few ppm to a few percent to the gas can produce a sufficient odor effect. When determining the value of gas odorants, simply determining the detection threshold or low value is not practical. The most important requirement for an odorant is whether its odor quality can be perceived as a so-called "gas odor" that is clearly different from the odors that generally exist. For example, vanillin, which is used as a food additive in ice cream and other products, has an extremely low detection threshold of 3.2×10 ^-8 ppm, but it has a vanilla-like odor and cannot be used as a gas odorant. The substances listed in the table have gas odor properties when used alone or as a mixture, but among these, norbornene derivatives in particular exhibit a surprising odor-adding effect, and the odorless gas to which this substance is added changes completely and becomes extremely sharp. It was discovered that it can become a odorous gas with a warning odor. The results of experiments conducted to clarify the odor-adding effect of norbornene derivatives in the present invention are shown below. In determining the odor effect, a test was conducted using allyl acrylate, which is known to be effective as a non-sulfur compound, as a control. Odorless as a test method
Odorous gas adjusted to contain 50 ppm of odorant per 1 kg of LPG is fed into the odorless room to a gas concentration of 1/200, and after stirring the room air, enter the odorless room to increase the odor intensity. and odor quality tests were conducted. The odor test was scored using the 6-level odor display method shown in Table (2), and the odor quality was marked with an ○ mark if it was detected as a gas odor, and an × mark if it was detected as an odor quality other than gas odor. I decided to ask them to mark it. The judges will be a selected panel of six people. Table (3) shows the results.

【table】

[Table] As can be seen from this judgment result, 30% of all panels detected gas odor with allyl acrylate.
In contrast, 100% of norbornene derivatives are perceived as a gas odor. Also, in terms of odor intensity, allyl acrylate has such an odor that you can almost feel it, but in the case of norbornene derivatives, the odor can be clearly detected, indicating that the odor-adding effect is excellent. Furthermore, the advantage of the norbornene derivative according to the present invention is that acrylic ester-based odorants have the disadvantage of polymerizing when coexisting with acidic substances such as mercaptans, so they cannot be used in combination with mercaptans. However, norbornene derivatives are stable even when mixed with conventional mercaptans and sulfides. On the other hand, in the case of bicyclo(2.2.1)heptane (norbornene), it has no odorizing effect, and is an odorous substance that has an extremely sharp gas-like warning odor only when a double bond group such as vinyl or ethylidene is introduced. becomes. The relationship between chemical structure and odor is not yet clear, but it is generally said that unsaturated compounds have stronger odors than their saturated counterparts. Furthermore, in order to be put to practical use as a gas odorant,
Non-corrosive to metals, rubber, and packing; chemically stable; odor does not disappear or change due to reaction; good diffusivity; low olfactory fatigue; when added to LP gas It is desired that the residual odor level is not strong, that the toxicity is low, that it is difficult to be adsorbed to soil, etc., and the norbornene derivative according to the present invention satisfies these conditions. The norbornene derivatives according to the invention can be used alone or in any other mixture. Experimental examples are shown below, but the present invention is not limited to the examples. Example (1) 0.05g of a mixture of 80 parts of 5-ethylidene-2-norbornene and 20 parts of ethyl acrylate per 1Kg of LPG
When an odor test was conducted with this gas diluted 200 times with air, a clearly strong gas odor was detected. Example (2) A mixture of 50 parts of 5-ethylidene 2-norbornene and 50 parts of 5-vinyl 2-norbornene was added at a ratio of 0.04 g to 1 kg of LPG, and the gas was blown with air.
When an odor test was conducted with the product diluted 200 times, a gas odor was clearly detected.

Claims (1)

[Scope of Claims] 1. An odorant for fuel gas containing a norbornene derivative represented by the following formula (1) as an active ingredient, either alone or as an essential ingredient. [Formula] (In the formula, there is a double bond at one of the positions indicated by the dotted line, and R represents hydrogen or a lower alkyl group.)