JPH0363557A - Measuring method for degree of cure in ultraviolet curing type resin - Google Patents

Abstract

PURPOSE:To quickly, easily and accurately measure the cured state of coating by measuring degree of cure in ultraviolet curing type resin form glass transition temp. which measured by a measuring method for coefficient of cubic expansion. CONSTITUTION:A sample 3 for measurement is encapsulated into a glass vessel 1. The density of the sample 3 is obtained by reading the liquid surface of a glass capillary 2 at constant temp. from graduation. Coefficient of cubic expansion is obtained by calculating rate of change for density correspondent to change in temp. The glass transition temp. for the sample is obtained from a transition point wherein the coefficient of cubic expansion is suddenly changed. The degree of cure for the sample is obtained from glass transition temp.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention relates to a method for measuring the degree of curing of ultraviolet curable resin used for coating optical fibers, etc. It should be done quickly and easily.

[Prior Art] Generally, an ultraviolet curable resin is a crosslinked polymer obtained by curing an ultraviolet curable acrylic monomer such as a urethane acrylate type or an epoxy acrylate type by irradiation with ultraviolet rays. Curing of an ultraviolet curable resin depends on various parameters such as the amount of ultraviolet ray irradiation, the type of curing atmosphere gas, the flow rate, the curing temperature, and the pressure, and the degree of curing is determined by the interaction of these parameters.

Therefore, in order to sufficiently cure the ultraviolet curable resin, it is necessary to optimize each of these parameters, and for this reason, it is important to understand the curing state of the ultraviolet curable resin.

Particularly in the production of optical fibers, there is a process of forming a primary coating made of ultraviolet curable resin on the surface of the optical fiber after spinning, but it is difficult to optimize the above parameters at this time and fully cure the ultraviolet curable resin. , which is very important in obtaining excellent performance of optical fibers.

Conventionally, methods for understanding the curing state of this UV-curable resin include measuring the gel fraction of the UV-curing resin, measuring dynamic viscoelasticity, or determining the glass transition temperature from measuring dynamic viscoelasticity. , or the tensile test method are known.

[Problems to be Solved by the Invention] However, the above-mentioned methods all require a lot of time and effort for measurement, and have the drawback of requiring high accuracy in measurement. In particular, the dynamic viscoelasticity measurement method described above imposes various restrictions on the measurement sample and is prone to measurement errors, and the method of determining the glass transition point from dynamic viscoelasticity has the disadvantage that accurate values are difficult to obtain. There was also.

[Means for Solving the Problems] In the present invention, the degree of curing of an ultraviolet curable resin is determined from the glass transition temperature measured by a volume expansion coefficient measurement method, and the degree of curing of an ultraviolet curable resin is determined from the glass transition temperature measured by a volumetric dilatation measurement method. This makes it easier to manage the manufacturing and quality of products.

The present invention will be described in detail below.

Curing of ultraviolet curable resins usually proceeds by forming a three-dimensional network structure through addition polymerization of acrylic monomers. Therefore, it is known that the number of crosslinking points in the network structure, that is, the gel fraction increases with this curing. As the gel fraction increases, the glass transition temperature of the resin increases. Therefore, the glass transition temperature of an ultraviolet curable resin is a parameter that uniquely determines the progress of curing of the resin, and this glass transition temperature is measured, and if it exceeds a certain value, the curing of the resin is determined. You can see that it has been completed.

In this invention, a volumetric expansion coefficient measurement method is adopted as a method for determining the glass transition temperature.

The volumetric expansion coefficient indicates the rate at which the density of a resin increases with respect to temperature under a constant pressure, and is usually the glass transition temperature at which the molecular chains of the resin begin microscopic molecular movements as the temperature rises. It is known that the free volume in the resin rapidly increases, and the volumetric expansion coefficient suddenly changes accordingly. Therefore, by measuring the temperature at which the volumetric expansion coefficient suddenly changes using the volumetric expansion coefficient measurement method, the desired glass transition temperature can be determined.

The volume expansion coefficient measurement method may be a well-known and commonly used method, and A
A method of measuring using a platometer as defined in STM D864 is preferably employed.

The platometer, as shown in Figures 1 and 2,
It comprises a glass container l and a glass capillary tube 2 of a certain diameter provided on the top of the glass container l,
A scale is provided on the outer wall surface of the glass capillary tube 2.

During measurement, a sample 3 for measurement is sealed in this glass container 1, and a glass capillary tube 2 is placed at a certain temperature.
By reading the liquid level from the scale, the density (d) of sample 3 can be determined.

Furthermore, while changing the temperature of the glass container 1 at an appropriate heating rate using a thermostat or the like, the liquid level of the glass capillary tube 2 is read and the rate of increase in density (,/) accompanying the temperature change is determined. The volumetric expansion coefficient (α) can be determined.

Either a liquid or a solid can be used as the measurement sample. When using a liquid sample, as shown in Fig. Measurement is performed when the conditions are filled up to . However, since the volumetric expansion coefficient of the glass container 1 itself cannot be ignored, the same measurement as above is performed with the container filled with a liquid, such as mercury, that has a known volumetric expansion coefficient and does not react with the sample. It is necessary to determine the volumetric expansion coefficient of the container l itself in advance and use this value to correct each measurement result. When using a solid sample, as shown in Figure 2, fill the glass container 1 with a solid sample 3 of known weight, seal it, and fill the remaining space with mercury or the like 4 up to the scale. Then, perform the same measurements as above.

Once the density (d) of the sample at each measurement temperature (T) is determined by such measurements, the volumetric expansion coefficient (
α) can be known. In addition to such calculations, if the density (d) at each temperature is graphed against the reciprocal of temperature (1/T) as shown in Figure 3, the volume expansion coefficient (α ) can also be found. Also, when graphing like this, as shown in Figure 3, (
It is clear at a glance that there are bending points of 1/T) to (d). This bending point is a transition point where the volume expansion coefficient (α) of the sample suddenly changes, and indicates the glass transition temperature (Tg) of the sample.

If such a volumetric expansion coefficient measurement is performed using each sample prepared according to the progress of curing, the glass transition temperature (Tg) of each sample can be determined corresponding to the progress of the curing state, and it is possible to find a sufficiently high glass transition temperature (Tg). If the transition temperature (Tg) is obtained, it can be known that curing is sufficiently progressing. Furthermore, according to this measurement method, it is possible to use either a liquid or a solid sample, so even samples whose properties change from liquid to solid depending on the progress of curing of the ultraviolet curable resin can be measured. , it is convenient because it can be measured without difficulty using a similar method.

Hereinafter, the present invention will be explained in detail by showing examples.

[Example] A urethane acrylate-based ultraviolet curable resin liquid is applied onto a bare optical fiber wire having an outer diameter of 125 μm which is melt-spun from an optical fiber base material, and then passed through an ultraviolet irradiation furnace to form an ultraviolet curable resin liquid. was cured to form a primary coating layer, and an optical fiber having an outer diameter of 250 μm was prepared.

The primary coating layer after irradiating the optical fiber with an appropriate amount of ultraviolet rays was peeled off and used as a sample, and the density Cd) was measured by the volume expansion coefficient measurement method. The measurements were carried out using the platometer shown in Figure 1.
The density (d) at each measurement temperature was measured while increasing the temperature at a rate of 1° C./min. The density (d) at each of these measurement temperatures (T) is the reciprocal of the measurement temperature (1/T)
and obtained (1/T)~(,/)
The glass transition temperature (Tg) was determined from the bending point of the straight line.

On the other hand, using the same ultraviolet curable resin liquid, ultraviolet rays were irradiated in the same manner, and the respective gel fractions were measured as a function of the amount of ultraviolet irradiation. The results are shown in Figure 4.

From Figure 4, the amount of ultraviolet irradiation is approximately 30 Q rtrJ /
am'' or higher, the gel fraction shows a substantially constant value of 93%, and along with this, the glass transition temperature (T
It can be seen that g) converges to a constant value of about 95°C. That is, if the glass transition temperature (Tg) is in a range equal to or higher than this value, it can be considered that the curing of this coating layer is almost completed.

Therefore, the cured state of the coating could be controlled by sampling the optical fiber at any time during production, peeling off the primary coating layer, and measuring the glass transition temperature using the same method.

[Effects of the Invention] As explained above, the method for measuring the degree of curing of an ultraviolet curable resin of the present invention involves measuring the degree of curing of an ultraviolet curable resin from the glass transition temperature measured by the volumetric expansion coefficient measurement method. Therefore, the cured state of the coating can be determined quickly, easily, and accurately. Further, since the curing conditions may be adjusted appropriately so that the glass transition temperature obtained by measurement falls within a predetermined range, manufacturing control and quality control are facilitated.

[Brief explanation of drawings]

1 and 2 are configuration diagrams showing an example of a platometer used in the present invention, in which FIG. 1 is a schematic sectional view when a liquid sample is used as a measurement sample, and FIG.
The figure is a schematic cross-sectional view when a solid sample is used, FIG. 3 is a graph showing an example of the relationship between the density determined by the dilatometry method and the measurement temperature, and FIG. 2 is a graph showing the relationship between the amount of ultraviolet irradiation and the glass transition temperature and the relationship between the amount of ultraviolet irradiation and the gel fraction of the optical fiber coating in Examples.

Claims (1)

[Claims] A method for measuring the degree of curing of an ultraviolet curable resin, characterized in that the degree of curing of the ultraviolet curable resin is determined from a glass transition temperature measured by a volumetric expansion coefficient measurement method.