JPH0280476A - Instantaneous adhesive for strain gauge - Google Patents

Abstract

PURPOSE:To obtain the title adhesive improved in curing speed and low- temperature adhesiveness by using an ethyl alpha-cyanoacylate resin as a base, adding a small amount of a cyanoacetic ester and ethyl 2-cyanopropionate to the base and further adding various esters to the mixture. CONSTITUTION:A strain gauge 9 is composed of a gauge base 1, a grid 3, a gauge tub 4, a gauge lead 5 and a laminated film 6, and this gauge 9 is bonded to the object 8 to be measured with an instantaneous adhesive 7. This adhesive 7 is prepared from 98.0+ or -1% ethyl alpha-cyanoacrylate resin, about 0.1% cyanoacetic ester and ethyl 2-cyanopropionate, and various esters to form a solution which can be cured within a short time by rapidly reacting with a small amount of water. According to the instantaneous adhesive for strain gauge, the curing speed and low-temperature adhesiveness are much better than those of the conventional one, and the properties such as elongation, tensile shear strength, impact strength, fatigue life, moisture resistance and insulation resistance can be markedly improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to so-called instant adhesives, and more specifically,
The above-mentioned gauge base of a strain gauge is formed by integrally attaching a resistive element or a semiconductor element showing a resistance change rate corresponding to strain to one side of the gauge base made of an insulating material, and mechanical quantities such as stress, torque, and displacement. The present invention relates to an instant adhesive for strain gauges that can be used to bond objects to be measured, which are subjected to the following conditions, in an extremely short time.

[Conventional technology]

Conventionally, various organic or inorganic adhesives have been used to bond strain gauges to objects to be measured.For example, nitrocellulose adhesives, phenolic adhesives, epoxy adhesives, polyester adhesives, etc. There are adhesives and cyanoacrylate adhesives. These adhesives are broadly classified into room temperature curing type and heat curing type, but they are suitable for strain measurement near room temperature.

From the viewpoint of saving labor in bonding work, instant adhesives that cure at room temperature and quickly cure are mainly used.

The cyanoacrylate adhesive mentioned above belongs to this type.

As a conventional cyanoacrylate adhesive.

A first conventional example is a methyl-α-cyanoacrylate adhesive, and a second conventional example is an ethyl-α-acrylate adhesive.
The conventional example consists of the following components and blending ratios (% by weight).

[Problem to be solved by the invention]

Characteristics generally required for adhesives for strain gauges.

(b) The shrinkage rate during curing is small. (b) The elastic modulus is large. (c) No cracking, warping, twisting, etc. occur after curing. (d) Adhesive strength varies depending on temperature, humidity, and strain values. (e) No hygroscopicity; (f) High fatigue limit; (g) Maintains high electrical insulation against temperature and humidity.

(k) Chemical resistance.The requirements for such general adhesives are 5a.
However, the requirements that are particularly important for instant adhesives include fast adhesion, good adhesion not only at room temperature but also at low temperatures of around -10°C, as well as fast adhesion. There are many things. This is because bonding of strain gauges is often carried out not only indoors but also outdoors at low temperatures, that is, it is often carried out under various environmental conditions other than room temperature. Because it is easily deteriorated, it must be stored in a dark place (for example, in a refrigerator) at a temperature of 10° C. or lower, and therefore, it must be able to be used for bonding immediately after being taken out of the refrigerator.

However, the methyl-α-cyanoacrylate adhesive, which is the instant adhesive of the first conventional example, has an almost satisfactory curing speed at room temperature of 20 to 30 seconds, but the ethyl-α-cyanoacrylate adhesive of the second conventional example The α-cyanoacrylate adhesive has a problem of poor adhesive workability because it is very slow at 30 to 60 seconds. In both of these first and second conventional examples, the curing speed at 0°C is considerably reduced to about 60 seconds, and furthermore, at -10°C, curing does not proceed and adhesion becomes impossible. There was a serious problem. Therefore, for example, -10℃ in a storage refrigerator.
If the instant adhesive has been stored in the refrigerator, the instant adhesive must reach a temperature of 0°C or higher or close to room temperature before gluing can be performed, resulting in extremely poor workability. It was something.

Further, the first and second adhesives have other characteristics 1
For example, fatigue life, impact strength, and insulation resistance.

It is necessary to improve these points in order to fully utilize the original performance of strain gauges.

The present invention was made in view of the above-mentioned problems of the prior art, and its purpose is to be able to bond in a shorter time than the prior art, and to be able to bond not only at room temperature but also at 0°C to -10°C.
An instant adhesive for strain gauges that can be bonded even at low temperatures of around °C, has particularly good adhesion to various gauge bases, and can also improve various properties when the strain gauge is bonded to the object to be measured. Our goal is to provide the following.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a strain gauge as described above, which comprises a gauge base made of an insulating material, and a resistive element or a semiconductor element that exhibits a rate of change in resistance corresponding to strain is integrally attached to one side of a gauge base made of an insulating material. Ethyl-α-cyanoacrylate resin is used at 98.0 ± 1 in instant adhesives for strain gauges to bond a base and a measured object to which mechanical quantities such as stress, torque, and displacement are applied in an extremely short time.
%, cyanacetic acid ester and dicyanopropionic acid ethyl ester at approximately 0.1%, and various esters are added to make it liquid, and it is structured so that it reacts rapidly with trace amounts of moisture and hardens in an extremely short time. It is characterized by

[For production]

In the instant adhesive for strain gauges according to the present invention, 9
The main component is 8.0±1% ethyl-α-cyanoacrylate resin, which contains about 0.1% cyanacetic acid ester and 2-cyanoacetic acid ethyl ester, and various esters are added. Especially the curing speed,
It works to significantly improve low-temperature adhesion, and also improves elongation rate,
It functions to improve various properties such as tensile shear strength, impact strength, fatigue life, moisture resistance, and insulation resistance.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the composition of an instant adhesive for strain gauges according to the present invention.

As shown in the figure, the instant adhesive of this example.

Contains 98.0±1% ethyl-α-cyanoacrylate, 11g 0.1% of cyanoacetic acid ester and 2-cyanopropionic acid ethyl ester, and contains only a trace amount of methyl-α-cyanoacrylate,
Furthermore, the liquid composition contains approximately 2% of an additive consisting of methoxytetraethylene glycol methanolylate.

FIGS. 2 and 3 are a central vertical cross-sectional view and a plan view, respectively, showing a state in which a strain gauge is adhered to the surface of a measured object using the instant adhesive for strain gauges according to the present invention.

In Figures 2 and 3, 1 is the gauge base;
a and 1b are the upper surface as one surface and the lower surface as the other surface of this gauge base 1. Reference numeral 2 denotes a resistance foil which is separately spread or formed by means such as vapor deposition or sputtering on the upper surface 1a of the gauge base 1, and 3 refers to this resistor 11i2 as a resistance element formed in a meandering shape by photoetching or the like. grid, 4
are gauge tabs formed at both ends of the grid 3 at the same time as the grid 3; 5 is a gauge lead whose one end is connected to the gauge tab 4 by means such as spot welding or soldering; and 6 is a grid for moisture and damage prevention. 3. Gauge tab 4 and gauge base 1 that attaches and supports these
A laminate film 7 that covers the upper surface 1a side is an instant adhesive for strain gauges (hereinafter referred to as "r instant adhesive") according to the above-mentioned embodiment, and is attached to the lower surface 1 of the gauge base 1.
b is adhered to the surface of the object to be measured 8.

Note that the strain gauge 9 is composed of the gauge base 1, the grid 3, the gauge tab 4, the gauge lead 5, and the laminate film 6.

Here, the procedure for bonding the strain gauge 9 to the object to be measured 8 using the present instant adhesive according to the present invention will be specifically explained.

(1) Surface treatment is performed on the surface of the measurement point to make it easier to bond.This surface treatment includes, for example,
First, remove rust, paint, metal, etc. from the area to be measured using a grinder, sandpaper, etc. Next, remove foreign substances such as chips adhering to the surface with a brush, and then apply acetone,
Degrease with clean Silbon paper or wiper paper using Triol, etc.

(2) In order to bond the strain gauge in the correct position, use a scriber, pencil, etc. to draw a scribe line in advance at the location on the object to be measured 8 where the strain gauge is to be attached.

(3) Apply the present instant adhesive to either the surface-treated portion of the object to be measured 8 or the lower surface 1b of the gauge base 1 so as to spread it thinly.

(4) Positioning indicators 10a to 10d for strain gauge 9
The strain gauge 9 is placed in the position where one or two of the marks are to be aligned with the marking line, and the surface is covered with a polyethylene sheet, cellophane tape, etc.
Apply pressure with your fingertips for about 20 seconds at room temperature, about 30 seconds at 0°C, and about 60 seconds at -10°C.

At this time, the present instant adhesive rapidly reacts with a small amount of moisture on the surface of the object to be measured, and hardens by simply pressing lightly with a fingertip for 20 to 60 seconds.

(5) After acupressure, the film such as the above-mentioned polyethylene sheet is peeled off and left in the air for about 1 hour to allow measurement. However, in order to perform highly accurate measurements, at least 4
Leave to stand for a period of time, preferably 24 hours or more.

There are generally two or four strain gauges 9 adhesively fixed to the object to be measured 8 via the instant adhesive 7.
A Wheatstone bridge circuit (hereinafter simply referred to as a ``bridge circuit'') is constructed using the same circuit board. Bridge power is supplied to the input end of this bridge circuit via an appropriate switch box (for example, an automatic multi-point switch). In this state, mechanical force, load, vibration, pressure, etc. are applied to the object to be measured 8.

When stress, torque, or displacement such as tension, compression, bending, or torsion is generated in the object to be measured 8, the strain gauge exhibits a resistance change corresponding to the magnitude of these stresses. This resistance change of the strain gauge appears as a voltage change at the output end of the bridge circuit.
The stress, torque, etc. are measured by a strain measuring device consisting of an A/D converter, a display, etc.

Next, with reference to FIG. 4, the characteristics of this embodiment will be explained while comparing them with the first conventional example and the second conventional example.

In addition, in this example, the composition contains 97.8% ethyl-α-cyanoacrylate, and the other compositions (components) are as follows:
It is blended at the blending ratio (% by weight) shown in FIG.

First, regarding the curing speed of characteristic item (1), in this example, the speed was stably faster than in the first conventional example, and twice as fast as in the second conventional example (within 20 seconds). .

Regarding the low-temperature adhesion between the strain gauge and the steel material (characteristic item ①), the first and second conventional examples required 60 seconds to be bonded and solidified to some extent at 0°C, but this example In this case, the adhesion was well solidified in half the time (30 seconds). Further, at −10° C., both the first and second conventional examples could not be bonded, but the nine embodiments could not bond.

Adhesion was good although the curing time was extended to 60 seconds.

Regarding the elongation of characteristic item (■), a strain gauge was glued to the test piece and a tensile elongation test was conducted.
2.5 times the conventional example, 1.75 times the second conventional example
Improved twice.

Regarding property item ■ tensile shear strength, JISK68
51 R Adhesive Tensile Shear Adhesive Strength Test Method, the steel materials were attached with adhesive and the shear strength was evaluated by applying a force in the tensile direction to both steel materials. The example showed an improvement of about 8% and about 5%, respectively, compared to the first and second conventional examples.

Regarding the impact strength of characteristic item (■), the strength was measured by applying an impact between two sheets of steel bonded with an adhesive. The strength was improved by about 6 times and 2.5 times, respectively, compared to the conventional example.

Regarding the fatigue life of characteristic item (■), the measurement conditions were to apply a strain of ±1500Xlo-' alternately at room temperature, and to determine whether or not the life has been reached, monitor the output of the strain gauge. As a result of using a method that determines that the life has been reached when either a change of 100 × 10-' strain or more or a spike noise appears in the output of the strain gauge, the results of this study were as follows: The fatigue life of the example is 1. It was found that the length was approximately 2.6 times longer than the second conventional example.

Regarding the moisture resistance of characteristic item
As a result of measuring the zero drift of the strain gauge 9 after cyclic exposure in an atmosphere of 5° C. and 90% humidity (RH0) and repeating 20 cycles, the first. The amount of zero drift was reduced by half compared to the second conventional example.

The insulation resistance of characteristic item (■) was measured by applying a DC voltage of 50 V between the object to be measured (conductor) 8 and the gauge lead 5 after the test of characteristic item (2) above.9 In this example,
1st. It was confirmed that each was improved by a factor of 2.times.IO' compared to the second conventional example.

Note that the present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the spirit thereof.

For example, the composition other than the above-mentioned ethyl-α-cyanoacrylate is not limited to the blending ratio (% by weight) shown in FIG. 1, but can be adjusted within a certain range.

Moreover, additives other than the above-mentioned methoxytetraethylene glycol methacrylate may be included, and in short, they may be added as long as they function to improve adhesiveness and curing speed.

In addition, the object to which this instant adhesive strain gauge is attached is not limited to the above-mentioned object to be measured, but also a pressure gauge.

Of course, strain bodies such as load transducers and acceleration transducers are also included.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to significantly improve the curing speed and low-temperature adhesion, which are the most important properties of instant adhesives, compared to conventional adhesives, and also to improve It is possible to provide an instant adhesive for strain gauges that can significantly improve various properties such as elongation, tensile shear strength, impact strength, fatigue life, moisture resistance, and insulation resistance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the composition of one embodiment of the instant adhesive for strain gauges according to the present invention, and FIGS. 2 and 3 are diagrams showing the composition of an instant adhesive for strain gauges according to the present invention. FIG. 4 is a central vertical cross-sectional view and a plan view, respectively, showing the state in which it is adhered to the surface of the body. FIG. 3 is a diagram showing various characteristics of the instant adhesive alone and the combination of the instant adhesive and a strain gauge or a test piece according to the same example. 1... Gauge base, 2... Resistance foil. 3... Grid, 4... Gauge tab, 5... Gauge lead. 6... Laminate film, 7... Adhesive, 8... Measured object, 9... Strain gauge. Patent applicant Kyowa Electric Industry Co., Ltd. Patent applicant Taoka Chemical Industry Co., Ltd. 7! < 4=-chi diagram λ diagram

Claims (1)

[Claims] (1) The above-mentioned gauge base of a strain gauge, in which a resistive element or a semiconductor element showing a resistance change rate corresponding to strain is integrally attached to one side of the gauge base made of an insulating material, and stress, torque, displacement, etc. An instant adhesive for strain gauges is used for bonding objects to be measured in a very short time with a mechanical weight of 98.0±1% ethyl-α-cyanoacrylate resin, cyanacetic ester and
For strain gauges, containing approximately 0.1% of cyanopropionate ethyl ester and adding various esters to form a liquid, which rapidly reacts with trace amounts of moisture and hardens in a very short time. Instant adhesive.