DE2255235C3 - Temperature indicating substance - Google Patents

Description

The invention relates to heat-sensitive mixtures, which are suitable as temperature display substances in disposable thermometers.

The heat-sensitive substances according to the invention have an improved record! .allization ability. The invention particularly relates to the use of certain nucleating agents, preferably on inert supports to significantly accelerate the recrystallization of certain to achieve heat-sensitive mixtures.

In the DT-OS 21 34 314 are disposable thermometers and heat-sensitive substances described so far in the technology for Temperaturmessuni have been used. The heat sensitive substances, also called temperature indicators are called solid solutions of at least two components, which are linear together have settlement melting point curves.

In US-PS 37 04 985 the use of certain organic compounds is described which with the above-mentioned heat-sensitive sub-

ίο punch form eutectic mixtures and use: to be able to visually determine the change in the physical state of the heat-sensitive substances to accelerate. In this way, mar achieves a faster and more precise measurement of the temperature of the patient.

Thermometers of this type make use of the above-mentioned heat-sensitive substances make, the problem often arises that the indicator is sometimes exposed to higher temperatures before it is to be used for temperature measurement. Go through this these heat-sensitive substances change from the solid to the liquid state, and this can lead to a premature temperature display.

Once these heat sensitive substances are melted, they stay for several minutes and sometimes even for several hours until they finally recrystallize. Often they have to However, thermometer was used shortly after exposure to unfavorable temperature conditions will. It is therefore important that the heat-sensitive substances quickly re-solidify. The invention relates to the subject matter specified by claim 1.

Particularly preferred solid solutions (a) for temperature measurements in the clinical field are those made from o-chloronitrobenzene and o-bromonitrobenzene. Preferred nucleating agents are sodium borate (Na ₂ B ₄ O ₇ - 10H ₂ O), cryolite (NaAl ₂ F _4), or Na

trium acetate (CH ₃ COONa · 3 H ₂ O).

It is advantageous if the nucleating agent is on a suitable inert support. Especially preferred inert carriers are talc powder, mixtures of magnesium oxide and silicon dioxide, magnesium silicate, Bismuth trioxide, hygroscopic or hydrophobic produced by high temperature pyrolysis Silica and alumina.

The use of nucleating agents to trigger crystallization is known per se; However not all mixtures respond to nucleating agents in the same way or to the same extent. The addition of nucleating agents eventually leads to recrystallization of the liquid mixture, to which they are added; the invention

however rests on the! Finding that certain nucleating agents significantly accelerate the recrystallization of the above-mentioned heat-sensitive substances so that it is complete in a very short time. This will ensure the effective use of these thermometers, even if they are about to their application for temperature measurement have been exposed to elevated temperatures.

There are many nucleating agents that meet the above requirements and are therefore im Can be used within the meaning of the invention; However, it has been found that certain, in claim 1 defined nucleating agents are particularly advantageous because they accelerate the regeneration

crystallization of the heat-sensitive substances result.

In addition to those already mentioned, further nucleating agents are mentioned below which are according to the invention can be used:

Table \

Copper (H) chloride, CuCl ₂
Potassium pyrosulfate, K ₂ S ₂ O ₇
Hydroxylamine hydrochloride, NH ₂ OH · HCl
Metaboric acid (m.p. 199-200 ° C), HBO.,
Copper (II) bromide, CuBr ₂
Potassium ethyl sulfate, KC ₂ H ₅ SO ₄
Talc powder, USP, Mg ₃ [Si ₄ O ₁₀ (OH)].,
Howlite, Ca ₂ (OH) ₅ B ₅ SiO ₉
Florisil, MgO + SiO ₂
Oxalic acid, (COOH) ₂
Molybdenum dioxide, MoO.,
Magnesium silicate, Mg ₃ [Si ₄ O ₁₀ (OH)],
Titanite, CaTiOSiO ₄
Bauxite, (Guyana) (Gibbsite), Al (OH) ₃
Bauxite, (Arkansas) (gibbsite), Al (OH) ₃
Sepiolite, (Spain), H ₄ Mg ₂ Si ₃ O ₁₀
Lepidolite, purple, KLi ₂ Al (F · OH) ₂
Stilbite, Ca (Al ₂ Si ₇ O ₁₈ ) • 7H ₂ O
Petalite, LiAlSi ₄ O ₁₀
Calcium aluminate, CaAl ₄ O ₇
Datolite, Ca (OH) BSiO ₄
Azurite, Cu (CO ₃ ) ₂ (OH) ₂

To further explain the invention, reference is made to the drawings, in the same Parts are identified by the same reference numerals.

F i g. Fig. 1 is a plan view of a typical thermometer to which the invention is applicable;

Fig. 2 is a vertical section on the line H-II the fig. 1;

Fig. 3 is a graph for explaining accelerated recrystallization (or resolidification) a heat sensitive substance containing sodium borate (borax) as a nucleating agent;

F i g. Fig. 4 is another graph for explaining the accelerated recrystallization of a thermosensitive one Substance containing cryolite as a nucleating agent;

Fig. 5 is a graph showing the beneficial effects of sodium acetate as a nucleating agent.

In Fig. 1, the thermometer 1 has a handle part 3 and an indicator part 5 which z. B. for insertion into the human mouth for temperature measurement can be formed.

The indicator part S contains a number of wells or areas 7 that are at a distance from one another. Each well 7 is provided with a temperature indicating substance 9 filled, which deviates in its melting point from the melting points of the substances in all other areas. The temperature indicating substance 9 is a mixture of heat sensitive substances and a nucleating agent. So each area contains a temperature indicator substance with a melting point (temperature of the beginning melting), which differs from the melting points which distinguishes substances in all other areas. While F i g. I a plurality of Areas 7 shows, there need only be one such area if the temperature indicator should be used to determine only a single specific temperature.

According to FIG. 2, the thermometer I has a carrier film 11, in which the wells 7 are located. For a better understanding there are two such wells shown on an enlarged scale.

The carrier film 11 is a flexible film made of thermally conductive Material like an aluminum foil. This ensures the rapid transfer of heat from the patient is accustomed to the temperature display substances in the depressions. Instead of aluminum foil you can also use flexible, thermally conductive films made of other materials, such as. B. copper, silver, Use gold, stainless steel, etc. The heat-

ao conductive foil 11 must consist of a material which has a high thermal conductivity, a relatively large surface area for contact with the object to be measured and as thin as possible, while still maintaining structural cohesion is retained so that the heat quickly reaches the heat-sensitive materials in the depressions is directed. If aluminum foil is used as the carrier foil, its thickness can be approximately 0.025 to 0.1 μ. The choice of suitable thermally conductive carrier films is within the range of the expert Can s.

There is an indicator layer over the temperature indicating substance and in close contact with it 13, which is covered by a cover layer 15. The one made up of the indicator layer and the cover layer Existing laminate is referred to here as an "indicator system" or "indicator".

A transparent layer 17, e.g. B. made of polypropylene, polyethylene terephthalate, nitrocellulose, Polyvinyl chloride, etc. may exist, is attached to the carrier film 11 as a cover film and has the same Expansion like the carrier film. To ensure the structural cohesion of the thermometer and to prevent contact between the human mouth and the aluminum foil, the Carrier film 11 has a cover layer 19 on its underside (made of a material similar to that of the cover layer 17), which is the same size as the carrier film and follows the outline of the indentations adapts. The lower cover layer is usually glued to the carrier film. The thickness of the bottom Top layer is generally about 0.025 to 0.075 μ to allow rapid heat transfer from the patient to the carrier film 11 and therefore to the heat-sensitive substances in the depressions to facilitate.

If necessary, a thermally conductive metal powder can be added to the lower cover layer 19, to increase their thermal conductivity. Aluminum powder has proven to be special for this purpose proved suitable.

Figures 3, 4 and 5 are discussed in connection with the examples below.

example 1

Twenty individual small aluminum bowls made of embossed aluminum with diameters of each 9.5 mm with portions of a solid solution

of o-chloronitrobenzene and o-bromonitrobenzene From the above examples it can be seen that the

(M.p. 35.23 ° C) charged. For every shell, Na use of nucleating agents becomes a significant one

trium borate (which represents 1.8 percent by weight unbound advantage because it causes recrystallization

nes water) is added in such amounts that it changes from the solid to the liquid state.

that the mixture in each bowl is bombarded with 20% by weight of heat-sensitive substance that has passed

percent sodium borate and 80 percent by weight. The above examples relate

cent consists of the solid solution, and the Gemi- on the use of solid solutions of

The seeds are then stirred thoroughly to produce the germ o-chloronitrobenzene and o-bromonitrobenzene; man

to distribute formers well in the solid solution. But each can also have other heat-sensitive substances

Shell is made with a clear thermoplasti- io zen in just as effective a way, and in

see the foil thermally sealed, and in all cases the most suitable germination

len are half an hour in a to 54.5 ° C ner based on the considerations given above

kept oven inserted until the solid solutions were selected.

but not the nucleating agent, fully molten. The use of nucleating agents in the sense of the zen are. Then the aluminum bowls from 15 invention but has another essential aspect taken out of the oven and the mixtures to advantage. If you z. B. a thermometer like it incipient recrystallization investigated. It was described at the beginning which one heat-observed! that after 5 minutes the contents of all aluminum-sensitive substances contain no nucleating agents, minium shells is completely recrystallized. This for measuring the temperature of a liquid bath, The operation is repeated several times, with each 20 z. B. a temperature of 37.8 ° C is used times the aluminum shells out of the oven reach equilibrium in 15 to 30 seconds, be taken and the recrystallization as above and the thermometer shows a temperature of described, is observed. 37.8 ° C. If the thermometer but before the The above procedure is still in two more measurements for a longer time, z. B. several minutes in which Try repeatedly. In one attempt, a 25 liquid bath has been held, it shows a human natural Sodium borate is used during the higher temperature, although the bath temperature is the second Test (control test) without nucleating agents is still 37.8 ° C. This higher temperature is carried out. Natural sodium borate containing it can be 38.0 ° C, or even 38.3 ° C, and there only 0.5 percent by weight free water. The result is the temperature measurement with this thermometer The details of this example are graphically shown in FIG. 3 represented by a visual display of the change in the unit, in which the percentage of peelings whose state of heat-sensitive substance occurs Contents are completely recrystallized after 5 minutes, and this indication is irreversible, it is important that is plotted against the number of operations. the temperature within about 30 seconds The bottom curve represents the control experiment, which is measured for 2 minutes. It was now over The uppermost, solid curve corresponds to the one found with 35 surprisingly that the addition of a Natural sodium borate attempted to nucleate the heat-sensitive substance and the dashed curve corresponds to the one that prevents prolonged exposure to the Verctwas Sodium borate containing moisture Attempt. higher temperature display leads. If the thermo-like the curves show, the addition of the 40 meter is used to measure the temperature of the Nucleating a significant technical advance to measure the liquid bath described above, achieved, and the presence of a small amount can be seen when the heat-sensitive substance Moisture impairs the effectiveness of a nucleating agent it contains for a relatively long time Nucleating agent not. leave the bath in the bath without affecting the temperature display, example 2 45, which corresponds to the actual temperature of the liquid bath.

The procedure is as in Example 1, but with cryolite. It was also found that one still means as Nucleating agents. In one trial, the cryolite will begin with its improvements in recrystallization Dried to constant weight at the speed of these heat-sensitive substances in the other experiment it contains 0.36% moisture. 50 scored when using the heat-sensitive sub-die Results of this example are shown in FIG. 4 when mixed nucleating agents are found to be suitable placed. The lower curve corresponds to the control carriers located. It is believed that the try the upper, solid curve corresponds to nucleating agents when it is without a carrier of the heat dem the mixture containing the dried cryolite, sensitive substance is added to and the dashed curve corresponds to the mixture, balling and settling at the bottom of the wells which tends to have a moisture content of 0.36, in which the heat-sensitive sub-weight percent containing cryolite. punch located. This leads to the germination This drawing shows that cryolite former presents a smaller surface area, whereby behaves very advantageously as a nucleating agent, especially the rate of recrystallization of the mixture if it contains some moisture. 60 is decreased. But if the nucleator does

B eis ρ ie 1 3 is located ^{on a} blessed "carrier and in this

^v form mixed with the heat-sensitive substance

The procedure is as in Example 1, but with sodium, the recrystallization rates are

acetate as a nucleating agent. The results of these two substances increased significantly because of the nucleating agents

game are shown in FIG. The lower curve 6 ₅ now has a higher effective specific surface

corresponds to the control experiment, the upper curve shows.

corresponds to that carried out with the nucleating agent

Attempt. of the invention into consideration of substances that face each other

behave chemically indifferent to heat-sensitive substances and are insoluble or practically insoluble in them. Furthermore, the carriers must also be chemically indifferent to the nucleating agent. Suitable carriers are talc powder Mg ₃ [Si ₄ O ₁₀ (OH)]. ,, Florisil (a mixture of MgO and SiO *), magnesium silicate, bismuth trioxide, hygroscopic silicon dioxide produced by high temperature pyrolysis, hydrophobic silicon dioxide produced by high temperature pyrolysis, aluminum oxide and mixtures of these substances .

The nucleating agent can be prepared by known methods, e.g. B. by absorption, spraying, coating etc., are deposited on the carrier. The cheapest amount of nucleating agent, regardless of whether he is on or not on a carrier can vary in the range of about 0.1 to 50 weight percent and is preferably in the range of about 1 to 25 percent by weight based on the heat-sensitive Substance. When the nucleating agent is applied to a carrier, the amount of the carrier is usually about 0.1 to 50 percent by weight and preferably about 1 to 25 percent by weight, based on on the heat-sensitive substance.

The following examples illustrate the use of supported nucleating agents.

Example 4

329 g of boric acid (H ₃ BO ₃ ) are dissolved in 1190 ml of boiling water with constant stirring. After addition of 200 bismuth trioxide (Bi ₂ O ₃₎ g at 95 to 100 ⁰ C, the reaction vessel is placed in an ice bath and stirring continued, has dropped to 5 ° C until the temperature of the mixture. The mixture is then allowed to settle for 25 minutes at this temperature and the precipitate is filtered off through glass fiber filter paper. The precipitate is dried in an evaporation dish by heating in a vacuum oven at 140 ° C. for 18 hours. The dried material is removed from the evaporation dish, allowed to cool to room temperature and ground for 2 minutes in a Sears mixer, and the particles with sizes greater than 0.15 mm are sieved out of the ground material. The particles with sizes of less than 0.15 mm are again placed in an evaporation dish and heated ^{to 140 ° C. in a vacuum oven for 18 hours.} The dried material is discharged from the oven and 0.5 percent by weight of Sio ₂ produced by high-temperature pyrolysis, based on the total weight of nucleating agent and carrier, is added in a glass port in order to improve the flowability. The nucleating agent obtained in this way consists essentially of 200 g metaboric acid, 1 g SiO ₂ and 200 g bismuth trioxide.

The advantageous results of the use of nucleating agents located on carriers are demonstrated in a series of experiments in which thermometers of the type described above are used, each of which has 45 temperature measuring ranges and a temperature range of 35.5 to 40.4 ° C. at temperature intervals of each include ^{0.1 ° C.} Solid solutions of o-chloronitrobenzene and o-bromonitrobenzene are found in all wells as heat-sensitive substances. In one series of experiments, the nuclei produced according to this example and located on carriers are added to each temperature measuring range, while in another series of experiments only metaboric acid without carrier is used. The amount of nucleating agent is the same in both series of experiments. In all cases, the thermometers are placed in an oven at 49 ° C and then allowed to cool to room temperature, the time periods required for recrystallization being recorded. The results can be found in Tables II and III.

Table II

Temperature-sensitive substances with the addition of nucleating agents on carriers

Oven treatment at 49 ° C

Time required for recrystallization h

16
21
43
75

2 3 3 5

Table III

Temperature-sensitive substances with the addition of nucleating agents without a carrier

Oven treatment at 49 ° C
H

Time required for recrystallization h

12th
36

8th 8th

A comparison of the results of these two tables shows that the recrystallization of these temperature-sensitive Substances are accelerated considerably when the nucleating agent is on a carrier; this is also still possible noticeable after long-term exposure to elevated temperatures.

Example 5

In this example, copper (II) chloride (CuCl _{2 ) on "hydrophobic SiO 2} " produced by high-temperature pyrolysis is used as the nucleation agent].

det. 1.0 g of copper chloride is dissolved in 50 ml of 95 percent strength ethanol. After adding 9.0 g of SiO ₂ to the solution, the mixture is stirred until a thick paste is formed. The pulp is dried by heating in a vacuum oven to 110 ^° C. for 24 hours, all of the ethanol being driven off. The dried material is turned into a loose powder in a rotating mixer. This nucleating agent located on a carrier is examined according to Example 4 and compared with the same nucleating agent (CuCl.,), But without carrier. _{While the CuCl 2} on the carrier retains its nucleation activity after 34 hours at 54 ° C, the activity of the nucleator without carrier decreases after 6.5 hours of exposure to the same temperature.

For this purpose 2 sheets of drawings

709 636/201

Claims (5)

Patent claims: 1. Temperature indicating substance of improved resolidification ability, consisting of (a) a solid solution
o-chloronitrobenzene and o-bromonitrobenzene, 1-menthol and dl-menthol,
4-chloropropiophenone and 4-bromopropiophenone, 4-chloro-2-methylaniline and 4-bromo-2-methylaniline, n-butyl sulfoxide and n-butyl sulfone or
Λ-chlorocinnamaldehyde and a-bromocinnamaldehyde and (b) G, l to 50 parts by weight ⁰ / ", based on component (a), one with respect to the constituents of component (a) is chemically inert nucleating agent having a melting point which is significantly above the melting point of the component (a) and which has a monoclinic structure and has substantially the same a / b, a / c or c / b unit cell ratios and substantially the same space group as the component (a). 2. Temperature indicating substance according to claim 1, characterized in that the component (a) consists of o-chloronitrobenzene and o-bromonitrobenzene. 3. Temperature display substance according to claim 2, characterized in that the nucleating agent Sodium borate (Na ₀ B ₄ O ₇
Cryolite (NaAl ₂ F ₄ ) or 10H ₂ O),
3H ₂ O) Sodium acetate (CH ₃ COONa is. 4. temperature indicating substance according to claim 3, characterized in that the The nucleating agent is on an inert carrier. 5. temperature indicating substance according to claim 4, characterized in that the inert Carrier talc powder, a mixture of magnesium oxide and silicon dioxide, magnesium silicate, Bismuth trioxide, hygroscopic or hydrophobic produced by high temperature pyrolysis Is silica or alumina.