JPH0627003A - Analysis of adhesive - Google Patents

Abstract

PURPOSE:To realize quick and highly accurate analysis of trace impurity elements contained in an adhesive mainly composed of polymer by holding liquid ultraviolet ray curable anaerobic adhesive into an adsorbing material and then solidifying them to prepare an analytic sample. CONSTITUTION:An adhesive sample is a liquid substance containing an additive and impurity chloride in addition to polymer, i.e., an acrylic ultraviolet ray curable anaerobic adhesive or main binder containing unsaturated polyester. A small quantity of sample not subjected to chemical treatment is then dripped or applied onto a filter paper made of adsorbing material to prepare an analytic sample 3 which is then set in a vacuum sample chamber 7. The sample 3 is then irradiated with X-ray from an X-ray tube 2 according to X-ray fluorescence analysis and solidified quickly. Existence of impurity element is determined from the wavelength of characteristic X-ray (ClKalpha ray) inherent to the impurity element generated upon irradiation with X-ray. Content of impurity is determined at a data processing section 6 based on the ratio of intensity of characteristic X-ray(ClKalpha ray) of the sample 3 detected through a detector 5 to the intensity of reflected X-ray(e.g. CrKalpha ray).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for analyzing an adhesive, and more particularly to a method for analyzing an impurity element in an adhesive used in a precision motor or the like.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for miniaturization and increase in capacity of hard disk drives (HDD) as computer storage devices. In particular, the production volume of 2.5-inch HDDs has rapidly increased with the spread of notebook computers. Furthermore, the HDD market is 1.8
The development of inch type products has been announced.

In the manufacture of precision motors used for these, an adhesive is used for joining parts. The adhesive must be liquid when applied but must be solid after joining. There are many types, but roughly speaking, solvent type,
There are water-based and solvent-free adhesives. As a basic constituent component of these adhesives, the polymer of the main binder is always blended, and depending on other types, it consists of solvent, inorganic filler, plasticizer, colorant and antiaging agent, catalyst, and accelerator. Is common.

As an adhesive for precision motors, an ultraviolet-curable anaerobic adhesive composed of polyurethane methacrylate, acrylic acid, hydroxyalkyl methacrylate and the like and several kinds of additives has been studied. In addition to adhesiveness, these adhesives have viscosity, vapor pressure, specific gravity, solubility in water,
Physical properties such as boiling point, flash point, and stability are important, but as motors become smaller, corrosive components such as chlorine in the adhesive affect the corrosion of motors and recording media in HDDs. A rapid and highly accurate quantification method is required.

Generally, a standard method for analyzing adhesives is described in "Analytical Chemistry Handbook", Fourth Edition (1991), edited by The Japan Society for Analytical Chemistry. Depending on the adhesive, the main binder polymer and solvent are IR method (infrared spectrum analysis) and GC method.
(Gas chromatograph) can be applied for analysis.

[0006]

However, in the above-mentioned standard method, there is no stipulation of analytical method for impurity elements in the adhesive such as chlorine. Since the adhesive sample is solidified by irradiating it with ultraviolet rays in an anaerobic atmosphere, it is liquid in the atmosphere. Since the adhesive is mainly composed of organic substances, it is generally considered to collect the burned gas in the absorption liquid as a pretreatment of the sample for chlorine analysis and quantify the chlorine ion in the liquid by various detection methods. To be However, as described above, it is difficult to burn a liquid substance, and it is not easy to use a combustion improver. In any case, these methods are time-consuming and lacking in speediness in the analysis operation.

FIG. 5 shows a general procedure for preparing a liquid sample such as an aqueous solution. Sampling (using a syringe),
The process is performed in the order of dropping, management of the dropped sample, drying, sample setting, and analytical measurement. When this method is applied to an ultraviolet curable anaerobic adhesive, the sample cannot be applied as it is because it is a highly viscous liquid. That is, it is necessary to improve the sampling method, sample amount control, and drying operation. In particular, there is a problem that it does not solidify sufficiently even when dried.

Further, the sample is an adhesive, and generally the amount of sample that can be handled is small. For example, there is no analytical method for impurity elements contained in a small amount of less than 0.1 g. The present invention has been made in view of the above points, and an object thereof is to develop a method for preparing an analysis sample to provide a rapid and highly accurate analysis method for trace impurity elements contained in an adhesive mainly composed of a polymer.

[0009]

According to the present invention, the above-mentioned object has an analytical sample preparing step and a quantitative measuring step, wherein the analytical sample preparing step holds a liquid ultraviolet-curable anaerobic adhesive on an adsorbent. Then, solidification is performed, and the quantitative step is to analyze the impurity element in the ultraviolet-curing anaerobic adhesive solidified by the fluorescent X-ray analysis method. Here, the fluorescent X-ray analysis method is the characteristic of the impurity element. It is achieved by measuring the ratio of the X-ray intensity and the intensity of the reflected X-ray from the analysis sample.

As the adsorbent, in addition to a filter paper mainly composed of purified cellulose, a filter material containing a small amount of impurities (filter) can be used. As the adsorbent, filter paper having a size of 10 to 50φ is used, and stable analysis can be performed by keeping the analysis area (X-ray irradiation area) during the fluorescent X-ray analysis constant. More preferably, a 45φ filter paper should be added dropwise to about 20φ in the central portion.

Although the adhesive after dripping and applying is uncured and in a liquid state, it is solidified by irradiating with X-rays in a vacuum atmosphere immediately before measurement of fluorescent X-rays. For fluorescent X-ray analysis, the adsorbent can be used as a standard sample by dropping and applying a solution prepared from a reagent. This aligns the matrices.
The fluorescent X-ray analysis is performed by obtaining the ratio of the characteristic X-ray intensity of the impurity element and the reflected X-ray intensity.

[0012]

[Function] Since the ultraviolet curable anaerobic adhesive is held on the adsorbent and solidified to be an analytical sample, the analytical sample can be rapidly prepared. In particular, solidification by X-ray irradiation in a vacuum atmosphere makes an ultraviolet irradiation device unnecessary. By measuring the ratio of the characteristic X-ray intensity of the impurity element and the reflected X-ray intensity, the influence of the unevenness of the solidified analytical sample surface and the thickness of the adsorbent is corrected,
Increase analysis accuracy.

[0013]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a flow chart showing an analytical sample preparation procedure according to an example of the present invention. The adhesive sample is an acrylic UV-curable anaerobic adhesive containing unsaturated polyester, which is a liquid substance containing an additive in addition to a polymer as a main binder and further containing chlorine as an impurity. After adding or applying a small amount of sample to the filter paper of the adsorbent without chemical treatment,
It can be rapidly solidified by irradiating X-rays in a vacuum atmosphere.

The filter paper of the adsorbent is a clean and uniform filter material mainly composed of purified cellulose, and is used by processing the size of the filter paper so as to make the area to be dropped and applied constant. Usually, JIS P 3801 is used. Use [Chemical analysis filter paper]. The adhesive is an ultraviolet curable anaerobic adhesive, and it is usually cured by using an ultraviolet lamp irradiation device to cure the adhesive, for example, 365 n.
Using a wavelength of m (energy of about 10 (eV) level) and irradiation intensity of 100 mW / cm ² for several minutes level time.
Further, the anaerobic atmosphere does not require molecular oxygen, that is, an atmosphere that blocks air. These operations are required in the previous step of the measurement operation in chlorine analysis, but as a simple alternative to these, a sample applied dropwise to the filter paper of the adsorbent and applied is a high energy X-ray [wavelength 0.1
.About.1 nm, energy about 10 ⁴ (eV) level] was applied to rapidly solidify the sample to make the sample surface in a state where there was little change so that subsequent measurements could be stably performed.

For the quantification of chlorine after the sample preparation, a fluorescent X-ray analysis method is applied. This method is based on the wavelength of characteristic X-rays (ClKα in this case) peculiar to the elements generated by the irradiation of primary X-rays.
The existence of contained elements is known. Further, the content can be obtained from the intensity of the characteristic X-ray. The prepared analytical sample is irradiated with X-rays emitted from a Cr target X-ray tube. At this time, ClKα ray of chlorine attached to the filter paper of the adsorbent is emitted. The intensity of this ClKα ray is slowed down by the intensity of the reflected X-ray of the Cr X-ray irradiated on the sample. This makes it possible to correct the slight unevenness of the filter paper surface of the analysis sample and the influence of the difference in the filter paper thickness on the characteristic X-ray intensity. Examples of the reflected X-rays from the analysis sample include CrKα rays and CrKβ
Lines are used.

By obtaining the ratio of the intensity of ClKα rays from the analytical sample and the intensity of reflected X-rays of CrKα rays, the accuracy can be improved in preparing a calibration curve and measuring the characteristic X-ray intensity of the adhesive sample. The details of the analytical sample preparation procedure are described below. As the sample amount, a liquid adhesive of 0.1 g or less is used. 0.04
Approximately 0.08 g is sampled with a dropper or a glass rod, and is applied dropwise to the center of the filter paper prepared in advance. The filter paper had a diameter of 45φ and was dropped and applied in a circle of about 20φ in the center. The weight of the adhesive in this state is measured by a balance.

Next, the atmosphere of the sample was evacuated and irradiated with X-ray to rapidly solidify. This operation was performed by fixing the sample to the analysis sample holder and mounting the sample holder in the fluorescent X-ray analysis sample chamber. When the adhesive solidifies, the sample is ready for measurement. Next, the method for measuring chlorine in the sample will be described. FIG. 2 is a layout view showing a fluorescent X-ray analysis apparatus according to an embodiment of the present invention. This analyzer comprises an X-ray generator 1, an X-ray tube 2, a dispersive crystal 4, a detector 5, and a data processing unit 6, and a sample chamber 7 in which an analytical sample 3 is set can be evacuated.

FIG. 3 is a diagram showing a ClKα fluorescence X-ray spectrum. Chlorine Cl of the analytical sample is the primary X from the X-ray tube.
Excited emission of ClKα rays when the rays are irradiated. Next, the light is dispersed by the spectroscope, and photoelectric detection is performed by the detector. The primary X-rays emitted in the same manner are emitted from the X-ray tube of the Cr target, and CrKα rays are detected by the detector as reflected X-rays from the sample surface.

Here, it is known that the measured X-ray intensity in the fluorescent X-ray analysis varies depending on the composition of the analysis sample and is affected by the absorption effect, the excitation effect and the difference in the surface state. In this method, the constituent material of the analytical sample is a matrix of filter paper and is a thin sheet as a whole, so that it is a region of sufficient thickness that does not pose a problem for analysis. It can be said that this generally has little influence on the measured X-ray intensity. Further, the ClKα ray intensity is corrected by the intensity ratio using the reflected X-ray in consideration of a slight difference in surface state, and the measurement accuracy is enhanced.

In this way, a calibration curve was prepared by the method of least squares from the relationship between the ClKα ray intensity and the Cl concentration under the following measurement conditions. Measurement conditions Analytical element; Cl spectroscopic crystal; PET [for Cr; LiF] X-ray tube target; Cr X-ray tube voltage; 50 kV X-ray tube current; 50 mA Measurement angle; ClKα line, 2θ = 65.440 deg, CrKα
Line, 2θ = 62.950 deg wave height analyzer; (L−U: 100−300) measurement time; 20 s FIG. 4 is a diagram showing a calibration curve of chlorine. The abscissa is the chlorine concentration (μg), the ordinate is the ratio of ClKα ray intensity / CrKα ray intensity, and is normalized by the X-ray intensity ratio when the chlorine concentration is 50 μg.
A calibration curve with good linearity can be obtained. The empirical formula at this time is as follows.

X (Cl) = 52.29 χ-3.07 Correlation coefficient γ = 0.9998 where χ is the X-ray intensity ratio. It can be seen that the correlation coefficient between the chlorine concentration and the X-ray intensity ratio is 0.9998, which is good. The chlorine concentration was in the range of 1 to 100 μg. Next, Table 1 shows the results of repeated examination of analysis accuracy using the analytical curve prepared above by using the analytical sample having a chlorine concentration of 50 μg prepared by the sample preparation method of the present invention.

[0022]

[Table 1] It can be seen that the repeat analysis accuracy is good when the coefficient of variation is 1% or less.

Next, it was applied to the analysis of an actual sample, and the chlorine of the adhesive was analyzed using the above calibration curve. The results are shown in Table 2.

[0024]

[Table 2] The chlorine amount in the adhesive can be evaluated at the lower limit of quantification (10 μg / g).

According to the method of the present invention, the time required for the analysis is completed within one hour for each sample including the sample preparation, so that it is a rapid analysis method. Thus, according to the present invention, it becomes possible to measure the trace impurity element in the adhesive quickly and with high accuracy.

[0026]

According to the present invention, there are an analytical sample preparing step and a quantitative measuring step, and the analytical sample preparing step holds a liquid ultraviolet-curable anaerobic adhesive on an adsorbent and then solidifies it. Therefore, the analytical sample preparation is quick, and the quantitative step is to analyze the impurity elements in the ultraviolet curable anaerobic adhesive solidified by the fluorescent X-ray analysis method. Since the ratio of the characteristic X-ray intensity of the element and the reflected X-ray intensity from the analytical sample is measured, it is possible to correct the influence of the unevenness of the solidified analytical sample surface and the thickness of the adsorbent, and to improve the analytical accuracy. Can be increased. In this way, a rapid and highly accurate analysis method for trace impurities in the adhesive can be obtained.

[Brief description of drawings]

FIG. 1 is a flow chart showing a procedure for preparing an analytical sample according to an embodiment of the present invention.

FIG. 2 is a layout view showing a fluorescent X-ray analysis apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a fluorescent X-ray spectrum of ClKα rays.

FIG. 4 is a diagram showing a calibration curve according to an example of the present invention.

FIG. 5 is a flowchart showing a conventional analytical sample preparation procedure.

[Explanation of symbols]

 1 X-ray generator 2 X-ray tube 3 Analytical sample 4 Spectroscopic crystal 5 Detector 6 Data processing unit 7 Analytical sample room

Claims (5)

[Claims] 1. An analytical sample preparing step and a quantifying step, wherein the analytical sample preparing step holds a liquid ultraviolet-curable anaerobic adhesive on an adsorbent and then solidifies the quantifying step. The impurity element in the ultraviolet-curable anaerobic adhesive solidified by the X-ray analysis method is analyzed. Here, the fluorescent X-ray analysis method is used to measure the characteristic X-ray intensity of the impurity element and the reflected X-ray intensity of the analysis sample. A method for analyzing an adhesive, which comprises measuring a ratio. 2. The analysis method according to claim 1, wherein the ultraviolet curable anaerobic adhesive is an acrylic adhesive containing unsaturated polyester. 3. The analysis method according to claim 1, wherein the adsorbent is a filter paper. 4. The analysis method according to claim 1, wherein the solidification of the adhesive is performed by irradiating the adhesive with X-rays in a vacuum atmosphere. 5. The analytical method according to claim 1, wherein the impurity element in the adhesive is chlorine.