JP7323915B2 - Hydrophobic gel-like elastic coupler for ultrasonic flaw detector - Google Patents

Description

The present invention relates to an acoustic coupler interposed between a probe of an ultrasonic flaw detector and an object to be flaw-detected. For example, steel structures, metal welds, plastic structures, concrete structures, glass structures, ceramic structures, semiconductor substrates, etc., can be used as test objects, and interposed between the probe of the ultrasonic tester. It reduces attenuation.

As a flaw detection method for inspecting whether there are scratches on the surface or internal cracks of objects such as steel structures, metal welds, plastic structures, concrete structures, glass structures, ceramic structures, semiconductor substrates, etc. , ultrasonic flaw detectors using ultrasonic imaging means are known. Ultrasonic waves are introduced into the subject, and ultrasonic waves reflected within the subject are received to confirm the ultrasonic waveform, visualize the state of the subject's interior as an image, and detect wounds in the subject. and inspect for the presence of cracks. In this manner, the ultrasonic flaw detection apparatus using the ultrasonic imaging means can visualize and inspect the inside of the object.

Here, if there is air between the probe of the ultrasonic flaw detector that generates ultrasonic waves and the object to be tested, the ultrasonic waves are reflected on the air surface and detected as noise. The problem arises that the surface cannot be imaged correctly.
Therefore, in the prior art, it has been devised to apply water or oil between the probe of the ultrasonic flaw detector and the object to be flaw-detected to remove the presence of air.
However, it is difficult to properly fix the probe of the ultrasonic flaw detector to the object to be flaw-detected while the surface is covered with water or oil, and it takes time to prepare jigs and take measurements.
Therefore, a method of interposing a gel-like elastic coupler (acoustic coupler, acoustic lens) between a probe of an ultrasonic flaw detector and an object to be flaw-detected has attracted attention. The elastic coupler not only eliminates noise caused by air, but also has the effect of effectively suppressing the attenuation of ultrasonic waves by making the acoustic impedance of the gel-like elastic coupler closer to the acoustic impedance of the flaw detection object. Because of these advantages, gel-like elastic couplers are considered important.

Gel-like elastic couplers known in the prior art include those made of a mixture of silicone-based rubber and butadiene-based rubber (for example, Patent Document 1: Japanese Unexamined Patent Publication No. 8-000615). This is a gel-like elastic coupler using hydrophobic gel. In addition, the gel-like elastic coupler includes a hydrophilic gel-like elastic coupler which is flexible.

JP-A-8-000615

However, conventional hydrophilic elastic couplers as described above have problems.
Conventional hydrophilic gel-like elastic couplers are hydrophilic, have good ultrasonic wave permeability, and are flexible and easy to handle. However, in the case of a hydrophilic gel-like elastic coupler, it swells, causing problems such as changes in the essential ultrasonic characteristics and the occurrence of tearing and abrasion due to use.

The gel-like elastic coupler composed of a hydrophobic gel-like substance disclosed in Patent Document 1 has good ultrasonic wave transmission, but since the hydrophobic gel-like substance is generally hard, This makes it unsuitable for detecting flaws in objects that are difficult to deform along the surface and have unevenness.

Therefore, the present invention provides an elastic gel coupler made of a hydrophobic gel material that does not swell even when water is interposed between the gel elastic coupler and the flaw detection target during inspection. A hydrophobic gel-like elastic coupler for ultrasonic flaw detectors that can maintain ultrasonic characteristics in a stable state, has sufficient flexibility, and can be easily deformed along the uneven surface of an object to be tested. intended to provide

In order to achieve the above object, the hydrophobic gel-like elastic coupler of the present invention is a hydrophobic gel-like elastic coupler interposed between a probe of an ultrasonic flaw detector and an object to be flaw-detected. It is obtained from a polyurethane resin composition which is a hydrophobic gel-like elastomer using a polyurethane polyisocyanate prepolymer having a polyol component and an organic polyisocyanate component, and the polyol component has 2 functional groups and a number average molecular weight of 600. A component containing either or both of a polyol of up to 4,000 and a polyol having a number of functional groups of 3 and a number average molecular weight of 1,000 to 6,000; A combination of functional groups of the prepolymer is 2 and 3; A gel-like elastic coupler is used.
The alkylene oxide chains contained in the polyol component and the polyurethane polyisocyanate prepolymer should be mainly composed of hydrophobic alkylene oxide chains, and ethylene alkylene oxide chains (EO), which are hydrophilic alkylene oxide chains, should be kept to a very small amount. is preferred. For example, the ratio of hydrophobic alkylene oxide chain to hydrophilic alkylene oxide chain, hydrophobic alkylene oxide chain:hydrophilic alkylene oxide chain, is 100:0 to 70:30.
In the above configuration, the mixing ratio of the polyol component and the polyurethane polyisocyanate prepolymer is such that the ratio of terminal OH functional groups to NCO functional groups (OH/NCO ratio) is between 0.6 and 1.6. Adjusting is preferred.

Moreover, in the above structure, the hydrophobic alkylene oxide chain in the polyol for polyurethane is preferably either a propylene oxide chain or a butylene oxide chain, or a mixture thereof.
Further, as a plasticizer added during gel formation, propylene carbonate, ethylene carbonate, N-methyl-2-pyrrolidone, diisononylcyclohexane 1,2-dicarboxylate, or glycol ethers (e.g., propylene glycol dimethyl ether, dipropylene glycol dimethyl ether , tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether) is preferably added.
The amount of the plasticizer to be added may be adjusted from 0 to 80 wt %. More preferably, it should be adjusted to 50 to 80 wt%.

For example, the polyol for polyurethane is preferably either polyether polyol or polyester polyol. Here, the present invention is characterized in that the alkylene oxide chains contained therein are hydrophobic alkylene oxide chains that are either propylene oxide chains or butylene oxide chains or mixtures thereof.
For example, as a combination of materials to form a polyurethane polyisocyanate prepolymer, there is a combination in which the polyol for polyurethane is a polyether polyol and the polyisocyanate is a diisocyanate.

The organic polyisocyanate can then be a diisocyanate. It is preferred that the alkylene oxide chains in the diisocyanate be hydrophobic alkylene oxide chains that are either propylene oxide chains or butylene oxide chains or mixtures thereof.
The diisocyanate is preferably any one of hexamethylene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4-toluylene diisocyanate, naphthalene 1,5-diisocyanate and xylylene diisocyanate, or derivatives thereof.
As for the hardness of the hydrophobic polyurethane gel elastic body of the present invention to be provided, it is preferable to adjust the hardness to be in the range of 35 to 80 degrees according to the F-type Asker rubber hardness tester.

With the above configuration, the hydrophobic gel elastic coupler of the present invention is hydrophobic, so that it can be used without swelling even in a state where water is interposed on the surface of the flaw detection target, and ultrasonic waves can be used. It has good permeability, is sufficiently flexible, and deforms according to the unevenness of the surface of the object to be inspected.

Objects to be inspected to which the hydrophobic gel elastic coupler of the present invention can be applied include steel structures, metal welds, plastic structures, concrete structures, glass structures, ceramic structures, semiconductor substrates, and human bodies. It can be applied to a combination of them.

The effect of the hydrophobic gel elastomer coupler of the present invention is that it can be used without swelling even when measuring the surface of an object to be flaw-detected with water interposed therebetween because of its hydrophobic composition. As a gel-like elastic material, it has good ultrasonic wave permeability, is sufficiently flexible, and can be deformed to follow the unevenness of the surface of the object to be inspected.

1 is a diagram showing a structural formula of a polyol for polyurethane, which is a main ingredient. FIG. It is a diagram showing a structural formula of a polyisocyanate that serves as a curing agent. FIG. 4 is a diagram showing the composition of samples used for verification; It is the figure which showed the result of the 24-hour water immersion experiment of each sample. FIG. 4 is a photograph showing changes in sample 1 before and after immersion in water for 24 hours. FIG. 10 is a photographic diagram showing changes in sample 2-1 before and after immersion in water for 24 hours. FIG. 10 is a photograph showing changes in sample 2-2 before and after immersion in water for 24 hours. FIG. 10 is a photograph showing the state of sample 3 after being immersed in water for 24 hours. It is a figure which shows the result of the hardness measurement of each sample. It is a figure which shows the result of ultrasonic sound speed measurement and attenuation measurement of each sample. FIG. 4 is a diagram showing changes in attenuation due to differences in OH/NCO ratio and plasticizer content in a hydrophobic gel-like elastomer coupler;

Examples of the hydrophobic gel-like elastic coupler for the ultrasonic flaw detector of the present invention are described below. However, the present invention is not limited to these examples.
The hydrophobic gel-like elastic coupler for the ultrasonic flaw detector of the present invention will be described with reference to examples.
The hydrophobic gel-like elastic coupler for the ultrasonic flaw detector of the present invention is a polyurethane resin composition that is a hydrophobic gel-like elastic body using a polyurethane polyisocyanate prepolymer having a polyurethane polyol component and an organic polyisocyanate component. It is obtained by things.

A hydrophobic gel-like elastic body is produced by using a polyol for polyurethane as a main component and polyisocyanate or a polyurethane polyisocyanate prepolymer as a curing agent.
The plasticizer is added to reduce the attenuation of the gel elastic body and impart flexibility, and the catalyst is added to promote the urethane reaction.

Here, the polyol component and the polyisocyanate component used in the hydrophobic gel-like elastic coupler of the present invention have the following conditions.
First, the polyol component will be explained.
FIG. 1 is a structural formula of a polyol for polyurethane, which is a main ingredient.
The polyol component contains an alkylene oxide (AO) chain. In the polyol component used in the present invention, the alkylene oxide (AO) chain is mainly composed of "hydrophobic alkylene oxide chain (Hydrophobic AO)", and the hydrophilic alkylene oxide chain It is characterized in that the ethylene alkylene oxide chain (EO) is suppressed to a very small amount.
For example, the ratio of the hydrophobic alkylene oxide chain (Hydrophobic AO) and the ethylene alkylene oxide chain (EO), which is a hydrophilic alkylene oxide chain, is 100:0 to 70:30 for the hydrophobic alkylene oxide chain: the hydrophilic alkylene oxide chain. .

In the present invention, what is described as a "hydrophobic alkylene oxide chain" is mainly propylene oxide (PO), butylene oxide (BO), or a mixture thereof, and ethylene oxide (EO) is suppressed to a very small amount. defined as an alkylene oxide chain with For example, the ratio of EO/PO is set to 0/100 to 30/70.
The polyol component contains an alkylene oxide chain, but the polyol component used in the present invention has a "hydrophobic alkylene oxide chain (Hydrophobic AO)" and does not have a hydrophilic alkylene oxide chain. It is characterized by points.
If the alkylene oxide chain contained in the polyol component is ethylene oxide (EO), the resulting urethane resin will be hydrophilic. , Hydrophobicity is imparted by using propylene oxide (PO), butylene oxide (BO), or a mixture thereof without containing ethylene oxide (EO) as the alkylene oxide chain in the polyol component.
The polyol may be either polyether polyol or polyester polyol. They can be used alone or mixed with other known polyols as long as they do not interfere with the reaction or the final product.

Next, the organic polyisocyanate component will be explained.
FIG. 2(a) is a structural formula of polyisocyanate as a curing agent.
Although the organic polyisocyanate component also contains an alkylene oxide chain, the alkylene oxide chain in the organic polyisocyanate component used in the present invention is mainly propylene oxide (PO), butylene oxide (BO), or a mixture thereof, and ethylene oxide. Hydrophobicity is imparted by suppressing (EO) to a very small amount.
If ethylene oxide (EO) is the main alkylene oxide chain contained in the organic polyisocyanate component, the resulting urethane resin will be hydrophilic, but the gel-like elastomer coupler of the present invention must be hydrophobic. Therefore, it is preferable that the alkylene oxide chain in the organic polyisocyanate component is mainly propylene oxide (PO), butylene oxide (BO), or a mixture thereof, and that ethylene oxide (EO) is suppressed to a very small amount.
Diisocyanate may be used as the organic polyisocyanate, and the diisocyanate may be any of hexamethylene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4-toluylene diisocyanate, naphthalene 1,5-diisocyanate, xylylene diisocyanate, or derivatives thereof. could be.
Note that the organic polyisocyanate may also be prepolymerized.

A polyurethane polyisocyanate prepolymer produced under these conditions is described.
FIG. 2(b) is a structural formula of a bifunctional polyurethane polyisocyanate prepolymer. FIG. 2(c) is a structural formula of a trifunctional polyurethane polyisocyanate prepolymer.
As provided above, the (AO) chains included in the above structural formulas are meant to refer to hydrophobic alkylene oxide chains. Either propylene oxide (PO) or butylene oxide (BO) or a mixture thereof is predominant, and ethylene oxide chains (EO) are suppressed to a very small amount. Thus, the present invention defines an alkylene oxide chain as a "hydrophobic alkylene oxide chain (Hydrophobic AO)".
In general, the alkylene oxide chain also includes an ethylene oxide chain (EO), but since those using the ethylene oxide chain (EO) have hydrophilic properties, the gel-like elastic coupler of the present invention, which is hydrophobic, has very little suppressed to a small amount.

Thus, by making the alkylene oxide chain of the polyurethane polyisocyanate prepolymer a "hydrophobic alkylene oxide chain (hydrophobic AO)", a hydrophobic gel elastic body can be obtained after curing with a curing agent. As will be described later, gel elastic couplers that are actually produced exhibit hydrophobicity.

Next, the number of functional groups and the average molecular weight of the polyol component will be described.
As the polyol component, a polyol having two functional groups and a number average molecular weight of 600 to 4,000 and a polyol having three functional groups and a number average molecular weight of 1,000 to 6,000 are used. More preferably, the number average molecular weight of the 2-functional polyol is in the range of 1,000 to 3,000, and the number average molecular weight of the 3-functional polyol is preferably in the range of 2,000 to 4,500.

Thus, the number of functional groups of the polyol for polyurethane is configured as a three-dimensional network structure of urethane bonds, and the elasticity of the urethane resin formed as a gel-like substance is obtained.
On the other hand, in order to produce the hydrophobic gel-like elastic coupler of the present invention with great flexibility, the molecular weight and OH/NCO ratio should be increased, or the plasticizer content should be increased.

This example is described as an example of a polyether polyol. Bifunctional and trifunctional polyols are mainly used, but even if the number of functional groups of polyurethane polyols is not 100% uniform, bifunctional and trifunctional polyols may be mixed in some parts, or only a small part. may contain a monofunctional one.

Here, regarding a polyol having a functional group number of 2 and a number average molecular weight of 600 to 4,000, the lower the number average molecular weight, the higher the hardness of the resulting polyurethane resin. The hardness of the resulting polyurethane resin is greater than 80 degrees as measured by an Asker rubber hardness tester F type, which is not preferable for the hydrophobic gel-like elastic coupler of the present invention. On the other hand, if the number average molecular weight exceeds 4,000, it is presumed that the chemical reaction does not proceed sufficiently, but it is not preferable because the resulting polyurethane resin lacks shape stability.

Next, regarding polyols with a number of functional groups of 3 and a number average molecular weight of 1,000 to 6,000, when the number average molecular weight is less than 2,000, the hardness of the obtained polyurethane resin is as high as ASKER rubber hardness scale F type. The hardness is greater than 80 degrees, which is not preferable for the hydrophobic gel-like elastic coupler of the present invention. On the other hand, if the number average molecular weight exceeds 6,000, it is presumed that a sufficient crosslink density cannot be obtained, and the resulting polyurethane resin lacks heat resistance, which is not preferable.
The number of functional groups of polyols for polyurethanes is mainly difunctional or trifunctional. may be mixed, or a monofunctional one may be mixed in a very small portion.

Next, polyisocyanate as a curing agent as a material. 5-diisocyanate (NDI), xylylene diisocyanate (XDI) and the like can be used. Other known organic polyisocyanates may be mixed and used as long as they do not interfere with the reaction or the final product.
The alkylene oxide chain (AO) contained therein mainly includes propylene oxide (PO), butylene oxide (BO), and hydrophobic alkylene oxide chain (Hydrophobic AO) which is a mixture thereof, and ethylene oxide (EO). Hydrophobicity is imparted by suppressing to a very small amount.

As the organic polyisocyanate, for example, diisocyanate may be used, and HDI, MDI, TDI, NDI, XDI and the like can be used arbitrarily.
Although the number of functional groups of the polyisocyanate is mainly bifunctional or trifunctional, the polyisocyanate may not have 100% uniformity of functional groups, and bifunctional and trifunctional polyisocyanates may be mixed. When used for forming a network structure of a gel-like elastic body, the number of functional groups of polyisocyanate is mainly bifunctional or trifunctional. The number of functional groups may be monofunctional.
Here, the number of functional groups of the polyisocyanate is adjusted so that the polyol component and the polyisocyanate component do not have two functional groups. In other words, the combinations of the functional groups of the polyol and the polyurethane polyisocyanate prepolymer are 2 and 3, 3 and 2, or 3 and 3, and are adjusted so as not to be a combination of two.
In this way, the functional groups of the polyol component and the polyisocyanate component are configured as a three-dimensional network structure of urethane bonds, and the elasticity of the urethane resin formed as a gel substance is obtained. balance should be adjusted.
On the other hand, in order to produce the hydrophobic gel-like elastic coupler of the present invention with great flexibility, the molecular weight and OH/NCO ratio should be increased, or the plasticizer content should be increased.
For example, the mixing ratio of the polyol component and the polyurethane polyisocyanate prepolymer may be adjusted so that the ratio of terminal OH functional groups to NCO functional groups (OH/NCO ratio) is between 0.6 and 1.6. For example, the produced hydrophobic gel-like elastic coupler is well-balanced as a three-dimensional network structure.

Next, the plasticizer will be explained.
Examples of plasticizers are propylene carbonate, ethylene carbonate, N-methyl-2-pyrrolidone, diisononylcyclohexane 1,2-dicarboxylate, or glycol ethers. Glycol ethers may include propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, and the like.

Most of the conventional urethane resins contain less than 15 wt % of the plasticizer when the total amount of the polyol component and the organic polyisocyanate component is 100 wt %. Since the urethane resin for elastic couplers in the prior art is based on the premise of a hydrophilic composition, it is believed that if the content is 15 wt% or more, the shape stability, mechanical properties, heat resistance, etc. of the polyurethane resin will be impaired. It is from. However, the hydrophobic gel-like elastic coupler of the present invention has a hydrophobic composition, and rather contains a large amount of plasticizer to give flexibility to follow the unevenness of the surface of the flaw detection target. Furthermore, by adding a large amount of plasticizer, a gel elastic body with low damping can be obtained. The amount of plasticizer to be added is preferably 10 to 80 wt %. More preferably, it is 50 to 80 wt%.

The hardness of the hydrophobic polyurethane gel elastic body is preferably adjusted to a range of 35 to 80 degrees according to the F-type Asker hardness tester. With this degree of flexibility, it can be deformed to follow the unevenness of the surface of the object to be inspected, and can provide excellent physical properties as an elastic coupler during ultrasonic measurement.
In addition, although a plasticizer increases flexibility, the inventors of the present invention found that when a specific plasticizer is added to a hydrophobic gel-like elastomer coupler, the resulting hydrophobic gel-like elastomer coupler: It was discovered that it is possible to give physical properties that can suppress the attenuation of ultrasonic waves. This point will be described later in detail.
Hydrophobic gel-like elastomeric couplers are produced using these materials.

Examples of the hydrophobic gel-like elastic coupler for the ultrasonic flaw detector according to the present invention will be described below. The results of examining physical properties of the hydrophobic gel-like elastic couplers using actually produced samples are shown.
FIG. 3 is a diagram showing the composition of samples used for verification.
As shown in FIG. 3, samples 1 and 2 belonging to the hydrophobic gel-like elastic coupler of the present invention were produced, and as a control, a conventional sample 3, which was a hydrophilic elastic coupler, was prepared.
The polyol for polyurethane as the main agent, the polyisocyanate as the curing agent, and the plasticizer are listed in FIG. 4, but differ in the presence or absence of the alkylene oxide chain (AO).

Trifunctional PPG polyether polyol was used as the polyol for polyurethane, which is the main component of Sample 1. That is, the alkylene oxide chain (AO) is a polypropylene glycol (PPG) chain, which is a hydrophobic alkylene oxide chain (hydrophobic AO). As an example, Primepol FF-3320 (manufactured by Sanyo Kasei) was used.
HDI polyisocyanate was used as the polyisocyanate that is the curing agent of sample 1. That is, the alkylene oxide chain (AO) is of the hexamethylene diisocyanate (HDI) type, which is a hydrophobic alkylene oxide chain (hydrophobic AO). As an example, Duranate AE700-100 (manufactured by Asahi Kasei) was used.
As the plasticizer for Sample 1, tripropylene glycol dimethyl ether (TPDM) was used. As an example, Hi-Solv MTPOM (manufactured by Toho Kasei) was used. The content of the plasticizer was set to 50 wt%.
This sample 1 can be used as a hydrophobic gel-like elastic coupler.

The polyol for polyurethane, which is the main component of sample 2, was similarly trifunctional PPG polyether polyol. That is, the alkylene oxide chain (AO) is a polypropylene glycol (PPG) chain, which is a hydrophobic alkylene oxide chain (hydrophobic AO). As an example, Primepol FF-3320 (manufactured by Sanyo Kasei) was used.
Here, two types of Sample 2 were prepared in order to evaluate the difference in performance based on the difference in OH/NCO ratio in the polyol for polyurethane, which is the main component of Sample 2. Sample 2-1 is an example using a polyol with an OH/NCO ratio of 1.0. Sample 2-2 is an example using a polyol with an OH/NCO ratio of 0.8.
HDI polyisocyanate was also used as the polyisocyanate that is the curing agent of sample 2. That is, the alkylene oxide chain (AO) is of the hexamethylene diisocyanate (HDI) type, which is a hydrophobic alkylene oxide chain (hydrophobic AO). As an example, similarly Duranate AE700-100 (manufactured by Asahi Kasei) was used.
As the plasticizer for sample 2, diisononylcyclohexane 1,2-dicarboxylate (DINCH) was used. Hexamol DINCH (manufactured by BASF) was used as an example. The content of the plasticizer was set to 80 wt%.
This sample 2 can be used as a hydrophobic gel-like elastic coupler.

The polyol for polyurethane, which is the main component of Sample 3, is a bifunctional polyether polyol in which the alkylene oxide chain (AO) is of the polyethylene glycol (PEG) type, in which the alkylene oxide chain (AO) is a hydrophilic alkylene oxide chain (AO). That is, it becomes the main ingredient of the hydrophilic urethane gel. As an example, Toho Polyol PB-3050 (manufactured by Toho Chemical Co., Ltd.) is used.
HDI polyisocyanate prepolymer was used as polyisocyanate as a curing agent in sample 3. The alkylene oxide chain (AO) is of the hexamethylene diisocyanate (HDI) type, which is a hydrophobic alkylene oxide chain (hydrophobic AO). As an example, H-6X35-2 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is used.
The plasticizer of sample 3 is tetraethylene glycol dimethyl ether (TG). Tetraglyme (manufactured by Maruzen Yuka Shoji Co., Ltd.) is used as an example. The content of the plasticizer was set to 55 wt%.
This sample 3 can be used as a highly hydrophilic gel-like elastic coupler.

Using Sample 1, Sample 2 (2-1, 2-2), and Sample 3 arranged as described above, physical property comparison tests were conducted.
First, the results of the hydrophobic-hydrophilic property test are shown.
FIG. 4 shows the results of a 24-hour water immersion experiment on sample 1, sample 2 (2-1, 2-2), and sample 3. FIG.
FIG. 4 collectively shows the mass (g) before immersion in water, the mass (g) after immersion in water for 24 hours, and the water absorption (%).

As a result of immersion in water for 24 hours, the weight of the hydrophobic gel-like elastic material of the present invention, Sample 1, decreased as shown in the list of FIG. It was confirmed that the film did not absorb water and had hydrophobic properties. Conversely, the reason why the weight decreased is thought to be that the plasticizer was eluted.
FIG. 5 is a photograph showing changes in sample 1 before and after immersion in water for 24 hours. Due to the outflow of the plasticizer, the overall shrinkage occurred, and cloudiness was also observed. This result shows that TPDM, as a plasticizer, easily dissolves in water.

Sample 2-1, the hydrophobic gel-like elastic material of the present invention, showed almost no change in weight after being immersed in water for 24 hours, as shown in the list of FIG. From this result, it was confirmed that there was no water absorption and that the film had hydrophobicity. Also, there was no elution of the plasticizer as seen in sample 1. From this result, it can be seen that DINCH is a stable plasticizer that does not dissolve in water.
FIG. 6 is a photograph showing changes in sample 2-1 before and after immersion in water for 24 hours. There was no swelling, shrinkage, etc., and there was almost no change in appearance. It was confirmed to have excellent hydrophobicity.
Also, the hydrophobic gel-like elastic body of the present invention, Sample 2-2, showed almost no change in weight after being immersed in water for 24 hours, as shown in the list of FIG. From this result, it was confirmed that there was no water absorption and that the film had hydrophobicity. Also, there was no elution of the plasticizer as seen in sample 1. From this result, it can be seen that DINCH is a stable plasticizer that does not dissolve in water.
FIG. 7 is a photograph showing changes in sample 2-2 before and after being immersed in water for 24 hours. There was no swelling, shrinkage, etc., and there was almost no change in appearance. It was confirmed to have excellent hydrophobicity.

As a result of immersion in water for 24 hours, the weight of the hydrophilic gel-like elastic body of Sample 3 according to the prior art increased significantly as shown in the list of FIG. It has been confirmed that the water absorption is large and the film has hydrophilicity.
FIG. 8 is a photograph showing the state of sample 3 after being immersed in water for 24 hours. It was confirmed that the whole was greatly swollen, the composition was greatly deteriorated, and cracks had already occurred in 24 hours, making it brittle. It can be said that this result clearly shows the factors that make the hydrophilic material of the prior art unsuitable as an elastic coupler for industrial applications in which water is frequently used.

From the above, it was found that the hydrophobic gel-like elastic material of the present invention has hydrophobic physical properties, does not absorb water, and does not swell. It was also found that some plasticizers are easily dissolved in water and some are difficult to dissolve in water.
Due to this hydrophobic physical property, the problem of swelling, which was a problem with conventional hydrophilic gel-like elastic couplers, does not occur. It was confirmed that the points to be done can be prevented.

Next, the flexibility of the elastic body was verified through a hardness test.
FIG. 9 is a diagram showing the hardness measurement results of sample 1, sample 2 (2-1, 2-2), and sample 3. FIG.
For comparison, the same hydrophobic urethane resin material used in the prior art is added as Sample 4 (Aquaren, Olympus).
The hardness was measured with an Asker rubber hardness tester F type. There are various types of durometer (rubber hardness tester) depending on the type of sample to be measured. An Asker rubber hardness tester F-type was used, which was configured to obtain an appropriate indicated value.

The hardness of the hydrophobic polyurethane gel-like elastic body of the present invention, which is sample 1, was 67 degrees according to the F-type Asker hardness tester.
The hardness of the hydrophobic polyurethane gel-like elastomer of the present invention, which is sample 2-1, was 37 degrees according to the F-type Asker hardness tester.
The hardness of the hydrophobic polyurethane gel-like elastic material of the present invention, which is sample 2-2, was 57 degrees according to the F-type Asker hardness tester.
The hardness of the hydrophilic polyurethane gel-like elastic material of the prior art, which is Sample 3, was 53 degrees according to the F-type Asker hardness tester.
The hardness of the hydrophobic polyurethane material of the prior art, which is sample 4, was 90 degrees according to the F-type Asker hardness tester.

From this result, it can be seen that in terms of physical properties such as hardness, that is, flexibility, all of Sample 1, Sample 2-1, and Sample 2-2, which are the hydrophobic polyurethane gel elastic bodies of the present invention, are similar to Sample 3 in terms of the hydrophilic polyurethane gel elasticity of the prior art. It can be seen that sufficient flexibility is ensured even compared to the conventional hydrophobic urethane material of the body and sample 4.
It was confirmed that the hydrophobic polyurethane gel elastic body of the present invention is sufficiently soft and has sufficient flexibility to conform to the unevenness of the surface of the object to be flaw-detected.

As described above, the hydrophobic elastic gel of the present invention has physical properties of softness and flexibility, and does not have the hard physical properties of general hydrophobic elastic gels. It has been confirmed that it is also suitable for flaw detection.

Next, the ultrasonic properties of the hydrophobic polyurethane gel elastic coupler of the present invention were examined.
The ultrasonic wave transmission, which is the ultrasonic wave characteristic of the hydrophobic polyurethane gel elastic coupler, can be verified by the value of the ultrasonic wave attenuation.

In the following, the ultrasonic transmission was verified by measuring the attenuation of ultrasonic waves.
USM35XJE (manufactured by GE Sensing & Inspection Technologies) was used as an ultrasonic flaw detector in ultrasonic attenuation measurement. 5C20N-G (manufactured by Tokyo Keiki Co., Ltd.) was used as an attenuation measuring instrument. The frequency used was 5 MHz. The room temperature at the time of measurement was 20.1°C.

As shown in FIG. 10, the ultrasonic attenuation of sample 1 of the present invention is 4.4 dB/cm, sample 2-1 of the present invention is 5.2 dB/cm, and sample 2-2 of the present invention is 5.6 dB/cm. , the prior art hydrophilic sample 3 was 3.5 dB/cm. Prior art hydrophobic Sample 4 was 5.4 dB/cm.
As a result of measurement, Sample 3, which is a hydrophilic gel-like elastic coupler according to the prior art, has the lowest ultrasonic wave attenuation. It turned out to be excellent. It can be seen that Sample 1 of the present invention has a small attenuation of ultrasonic waves and is superior to Sample 4, which is hydrophobic in the prior art.
From the above, it was verified that the hydrophobic polyurethane gel elastic coupler of the present invention has excellent ultrasonic characteristics.

As described above, the superiority of the ultrasonic properties of the hydrophobic gel-like elastic coupler of the present invention compared to the hydrophilic elastic couplers of the prior art has been verified. The variation of sound velocity as an ultrasonic property with different OH/NCO ratio and plasticizer content in couplers was investigated.

FIG. 11 is a diagram showing changes in attenuation of ultrasonic waves due to differences in OH/NCO ratio and plasticizer content in a hydrophobic gel-like elastic coupler. Samples 1 and 2 of the developed product of the present invention were prepared with an OH/NCO ratio of 1.0 and 0.8, respectively (Sample 1-1 had an OH/NCO ratio of 1.0, Sample 1-2 is 0.8, sample 2-1 is 1.0, and sample 2-2 is 0.8).
As shown in FIG. 11, it was found that the attenuation of ultrasonic waves is also affected by the OH/NCO ratio and the plasticizer content.

First, regarding the content of the plasticizer, it was found that the attenuation of ultrasonic waves decreased as the content of the plasticizer increased in the range of 0 to 80 wt%. For both Samples 1 and 2, ultrasonic attenuation characteristics are obtained when the plasticizer content is 30 wt %.
In Samples 1-1 and 1-2, the ultrasonic attenuation was sufficiently small when the plasticizer was 50 wt %. Samples 2-1 and 2-2, with a plasticizer content of 80 wt %, exhibited ultrasonic attenuation characteristics comparable to those of samples 1-1 and 1-2 with a plasticizer content of 50 wt %.

As for the upper limit, if it exceeds 80 wt%, the shape of the urethane resin may become difficult to stabilize, so up to about 80 wt% is appropriate.
In summary, the content of the plasticizer in the hydrophobic gel-like elastic coupler of the present invention should be in the range of 0 wt % to 80 wt %, preferably 30 wt % to 80 wt %, more preferably 50 wt % to 80 wt %.
The present inventors will continue to develop a hydrophobic gel-like elastic coupler whose composition is stable even if the wt % of the plasticizer is further increased.

Next, regarding the OH/NCO ratio, when the plasticizer content is in the range of 0 to 80 wt%, both Sample 1 and Sample 2 have an overall OH/NCO ratio of 1.0 when the plasticizer content is in the range of 0 to 80 wt%. It was found that the attenuation of ultrasonic waves is smaller when the value is 0.
In summary, the OH/NCO ratio in the hydrophobic gel-like elastic coupler of the present invention is in the range of 0.6 to 1.6, preferably in the range of 0.8 to 1.0, more preferably about 1.0. good.

As described above, the preferred embodiment of the configuration example of the hydrophobic gel-like elastic coupler for the ultrasonic flaw detector of the present invention has been illustrated and described, but various modifications can be made without departing from the technical scope of the present invention. It will be understood that

The hydrophobic gel-like elastic coupler for the ultrasonic flaw detector of the present invention is for detecting flaws on the surfaces of steel structures, metal welds, plastic structures, concrete structures, glass structures, ceramic structures, semiconductor substrates, and the like. It can be widely applied as a hydrophobic gel-like elastic coupler for ultrasonic flaw detectors.

Claims (12)

A hydrophobic gel-like elastic coupler interposed between a probe of an ultrasonic flaw detector and an object to be flaw-detected,
Obtained from a composition for polyurethane resin, which is a hydrophobic gel-like elastic body using a hydrophobic polyurethane polyisocyanate prepolymer having a polyol component for hydrophobic polyurethane as a main ingredient and an organic polyisocyanate component as a curing agent,
The polyol component for hydrophobic polyurethane is a component containing either or both of a polyol having 2 functional groups and a number average molecular weight of 600 to 4,000 or a polyol having 3 functional groups and a number average molecular weight of 1,000 to 6,000. can be,
The combination of the number of functional groups of the polyol component for hydrophobic polyurethane and the number of functional groups of the hydrophobic polyurethane polyisocyanate prepolymer is 2 and 3, 3 and 2, or 3 and 3, and the combination is not two,
Among the alkylene oxide chains contained in the polyol component for hydrophobic polyurethane, the ratio of the hydrophobic alkylene oxide chain to the hydrophilic alkylene oxide chain: hydrophobic alkylene oxide chain:hydrophilic alkylene oxide chain is between 100:0 and 70:30. adjust and
The alkylene oxide chain contained in the organic polyisocyanate component has a hydrophobic alkylene oxide chain as an active ingredient,
A hydrophobic gel-like elastic coupler for an ultrasonic flaw detector, comprising a non-foamed hydrophobic polyurethane gel elastic. A claim characterized in that propylene carbonate, ethylene carbonate, N-methyl-2-pyrrolidone, diisononylcyclohexane 1,2-dicarboxylate, or glycol ethers are added as plasticizers added during gel formation. 2. The hydrophobic gel-like elastic coupler for the ultrasonic flaw detector according to 1. 3. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detector according to claim 2, wherein the amount of said plasticizer added is 30 to 80 wt %. 3. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detector according to claim 2, wherein the amount of said plasticizer added is 50 to 80 wt %. The mixing ratio of the polyol component for polyurethane, which is the main component, and the hydrophobic polyurethane polyisocyanate prepolymer, which is the curing agent, is 0.6 to 1 in terms of the ratio of terminal OH functional groups to NCO functional groups (OH/NCO ratio). 2. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detector according to claim 1, wherein the coupler is adjusted to be between .6. 2. The hydrophobic polymer for ultrasonic flaw detector according to claim 1, wherein the hydrophobic alkylene oxide chain in the polyol for hydrophobic polyurethane is either a propylene oxide chain or a butylene oxide chain or a mixture thereof. gel-like elastic coupler. 7. The hydrophobic gel-like elastic coupler for an ultrasonic flaw detector according to claim 6, wherein said polyol for hydrophobic polyurethane is either polyether polyol or polyester polyol. 2. The hydrophobic gel for ultrasonic flaw detector according to claim 1, wherein the hydrophobic alkylene oxide chain in the organic polyisocyanate is either a propylene oxide chain or a butylene oxide chain or a mixture thereof. shaped elastic coupler. 9. A hydrophobic gel-like elastic coupler for an ultrasonic flaw detector according to claim 8, wherein said organic polyisocyanate is a diisocyanate. The diisocyanate is hexamethylene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4-toluylene diisocyanate, naphthalene 1,5-diisocyanate, xylylene diisocyanate or a derivative thereof, and the alkylene oxide chain contained therein. is a hydrophobic alkylene oxide chain which is either a propylene oxide chain or a butylene oxide chain or a mixture thereof. The hardness of the hydrophobic polyurethane gel elastic body according to any one of claims 1 to 9, wherein the hardness measured by Asker rubber hardness tester F type is adjusted to a range of 35 to 80 degrees. Hydrophobic gel-like elastic coupler for sonic flaw detector. 11. Any one of claims 1 to 10, wherein the flaw detection object is a steel structure, a metal weld, a plastic structure, a concrete structure, a glass structure, a ceramic structure, a semiconductor substrate, or a human body, or a combination thereof. 1. A hydrophobic gel-like elastic coupler for an ultrasonic flaw detector according to claim 1.

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