JP2000065771A - Method for measuring deterioration degree of polypropylene resin molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make measurable a deterioration degree within a shorter time without using a special apparatus by replacing a nitrogen atmosphere having a sample allowed to stand therein and raised to a predetermined holding temperature with an oxygen atmosphere to isothermally hold the sample at the holding temp. and measuring the oxidation induction period up to the appearance of the heat generating peak of the sample. SOLUTION: A predetermined amt. of a sample formed into a powdery matter by finely grinding a polypropylene resin molded product being an object to be measured is allowed to stand in a nitrogen atmosphere and this nitrogen atmosphere is heated to a predetermined temperature at a constant speed. Thereafter, the nitrogen atmosphere is replaced with an oxygen atmosphere to isothermally hold the oxygen atmosphere to the holding temp. and, after while, the sample is oxidized to generate exothermic reaction. When a time is further elapsed, oxidation becomes violent to generate the peak of exothermic reaction. The time up to the appearance of the exothermic peak is measured as an oxidation induction period and this oxidation induction period is used as the measure of a deterioration degree. The holding temperature is set so that the oxidation induction period becomes 60-100 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring the degree of deterioration of a molded polypropylene resin article for measuring the degree of deterioration of the molded polypropylene resin article having a predetermined shape.

[0002]

2. Description of the Related Art A molded article of a polypropylene resin such as a corrugate is deteriorated by heat or the like to cause deterioration in physical properties. Therefore,
In order to ensure the long-term reliability of the resin molded product, it is necessary to grasp the degree of deterioration of the resin molded product that has once been on the market.

As a method for measuring the degree of deterioration of a resin molded product, a method using a physical property test and a method using a SEC (Si
ze Exclusion Chromatography).

The former method is a method of measuring the tensile strength, tensile elongation, and the like of a resin molded product, and using the measured values as a measure of the degree of deterioration.

The latter method is a method of measuring the molecular weight of a resin in a resin molded product and using the molecular weight as a measure of the degree of deterioration.

That is, when a resin molded product is deteriorated, the molecules of the resin are cut and the molecular weight is reduced. Therefore, the degree of deterioration can be measured by separating the polypropylene resin component from the compound forming the polypropylene resin molded product, dissolving the polypropylene resin in a solvent, and measuring the molecular weight by SEC.

[0007]

However, the above-described method of measuring the degree of deterioration has the following problems.

First, in the case of a method based on a physical property test, when measuring the tensile strength and tensile elongation of a resin molded product, it is necessary to form an object to be measured into a dumbbell-shaped test piece. However, there is a problem in that it is often difficult to prepare a resin molded product which has once been marketed and molded into another shape into the shape of the dumbbell-shaped test piece.

Next, in the case of molecular weight measurement by SEC, since polypropylene resin is a resin which is soluble only in an aromatic solvent at a high temperature (about 130 ° C.), it can be measured at a high temperature when measuring the molecular weight. There is a problem that a special SEC device is required, and that it takes a long time to perform such a molecular weight measurement.

Accordingly, the present invention has been made to solve the above-described problems, and has been made to solve the above problem without using a special measuring device for a polypropylene resin molded product once molded into a predetermined shape. An object of the present invention is to provide a method for measuring the degree of deterioration of a molded polypropylene resin article, which can measure the degree of deterioration in a short time.

[0011]

In order to solve the above-mentioned problems, in the method for measuring the degree of deterioration of a molded polypropylene resin article of the present invention, a sample of a deteriorated polypropylene resin molded article is left in a nitrogen atmosphere, After raising the temperature to a predetermined holding temperature at a constant speed, the nitrogen atmosphere is replaced with an oxygen atmosphere, and the temperature is kept isothermally at the holding temperature, and an oxidation induction period until an exothermic peak of the sample appears is measured. I have.

When the degree of deterioration of the molded polypropylene resin product is small, the amount of the antioxidant remaining in the molded polypropylene resin product is large. And the oxidation induction period becomes longer.

On the other hand, when the degree of deterioration of the molded polypropylene resin product is large, the amount of the antioxidant remaining in the molded polypropylene resin product is small, so that the antioxidant effect is small and the oxidization immediately occurs at the holding temperature in an oxygen atmosphere. Have done
The oxidation induction period is shortened.

Therefore, when the degree of deterioration of the molded polypropylene resin product is small, the measured oxidation induction period becomes longer,
Conversely, when the degree of deterioration is large, the oxidation induction period is shortened, so that the degree of deterioration of the polypropylene resin can be known using the oxidation induction period as a scale.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for measuring the degree of deterioration of a molded polypropylene resin product according to one embodiment of the present invention will be described.

First, an OIT method for measuring an oxidation induced time (OIT) used as a measure of the degree of deterioration will be described.

The OIT method is a method for measuring a time until an exothermic peak due to oxidation of a resin in a high-temperature oxygen atmosphere appears, and is specifically performed as follows.

First, a polypropylene resin molded product to be measured is frozen and pulverized to a powder, which is used as a sample.

This sample is left in a predetermined amount (for example, about 5 mg) in a nitrogen atmosphere, and the temperature of the nitrogen atmosphere is raised to a predetermined holding temperature at a constant speed (for example, 20 ° C./min). Thereafter, the nitrogen atmosphere is replaced with an oxygen atmosphere, and the temperature is kept isothermally at the holding temperature. Then, after a while, the sample is oxidized to cause an exothermic reaction, and after a lapse of time, the oxidation reaction becomes violent and a peak of the exothermic reaction occurs. At this time, the time until the exothermic peak appears is measured as the oxidation induction period.

The holding time needs to be appropriately changed depending on the heat resistance of the resin to be tested. This is because if the holding temperature is high, the oxidation induction period is short and a significant difference is unlikely to appear, and if the holding temperature is low, the oxidation induction period is long and the measurement takes too much time. Therefore, depending on the heat resistance of the resin, the oxidation induction period is 60 to 100.
Set the holding temperature in minutes.

FIG. 1 is a diagram showing the relationship between the amount of heat and heat absorbed and the time and the relationship between the ambient temperature and the time when the OIT of a predetermined resin is measured.

As shown in FIG.
When the temperature is raised at a constant rate of ° C./min, the sample is completely melted and a peak of the endothermic reaction occurs after about 7 to 8 minutes have passed. After that, when replacing the nitrogen atmosphere with the oxygen atmosphere,
After the exothermic reaction with a constant calorific value has continued for about 60 minutes,
About 70 minutes after the start of the measurement, the oxidation reaction becomes intense and a peak of heat generation occurs. The time until this exothermic peak appears, that is, 69.600 minutes, is the oxidation induction period.

In this measurement, the time at which the peak of heat generation appears was determined by the line of constant heat generation until 60 minutes elapse after the start of the experiment and the rising line of heat generation after the peak of heat generation appeared. The time of the oxidation is called the oxidation induction period.

The method for measuring the degree of deterioration of a molded polypropylene resin article is a method in which the oxidation induction period measured as described above is used as a measure of the degree of deterioration of the molded polypropylene resin article.

Next, how to use the oxidation induction period measured as described above as a measure of the degree of deterioration of a molded polypropylene resin product will be described.

First, the oxidation induction period measured as described above depends on the antioxidant effect of the resin to be measured. The antioxidant effect of a resin is greatly affected by the amount of the antioxidant contained in the resin.

For example, with respect to a resin composed of the same main component, as the amount of the antioxidant increases, the antioxidant effect increases, so that it becomes difficult to oxidize in a high-temperature oxygen atmosphere.
Oxidation induction period is prolonged. On the other hand, the smaller the amount of the antioxidant, the smaller the antioxidant effect. Therefore, the antioxidant is more likely to be oxidized in a high-temperature oxygen atmosphere, and the oxidation induction period is shortened.

Considering the case where the above is applied to a deteriorated polypropylene resin molded product, the following will be explained.

For example, in the case of a molded polypropylene resin product containing a certain amount of an antioxidant, if the degree of deterioration of the molded polypropylene resin product is small, as shown in FIG. The amount of antioxidant that is not consumed much and remains in the molded polypropylene resin is relatively large. In this case, the measured oxidation induction period is relatively long because the polypropylene resin molded article has a large antioxidant effect.

On the other hand, when a similar degree of deterioration of the molded polypropylene resin product is large, as shown in FIG. 2B, a large amount of the antioxidant is consumed, and the antioxidant remaining in the molded polypropylene resin product is consumed. The dosage is relatively small. In this case, the measured oxidation induction period becomes relatively short because the polypropylene resin molded article has a small antioxidant effect.

Therefore, when the degree of deterioration of the molded polypropylene resin product is small, the measured oxidation induction period becomes longer,
Conversely, when the degree of deterioration is large, the oxidation induction period becomes short, so that it is possible to know the degree of deterioration of the polypropylene resin molded product using the oxidation induction period as a scale.

<Examples> Samples A and B having different heat resistances were deteriorated in an aging tank, and the oxidation induction period was measured for each.

The deterioration condition was such that each of Sample A and Sample B was allowed to stand at 120 ° C. for 24 hours, 48 hours, 120 hours, 240 hours, and 500 hours.

Table 1 below shows the oxidation induction period for each case.

The holding temperature is 185 ° C.

[0036]

[Table 1]

As shown in Table 1, in each of the samples A and B, it can be seen that the longer the deterioration time, the easier the oxidation is, and the shorter the oxidation induction period.

FIG. 3 is a graph showing the logarithmic coordinates of the oxidation induction period and the deterioration time for each of Sample A and Sample B.

As shown in the figure, it can be seen that the deterioration time and the oxidation induction period are almost inversely proportional.

[0040]

As described above, in the method for measuring the degree of deterioration of a molded polypropylene resin article of the present invention, the oxidation induction period of the deteriorated molded polypropylene resin article is used as a measure of the degree of deterioration of the molded polypropylene resin article. When measuring the degree of deterioration, there is no need to prepare a special shape such as the shape of a dumbbell-shaped test piece, and the degree of deterioration can be measured for a polypropylene resin molded product once molded into a predetermined shape.

Since the molecular weight is not measured by SEC when measuring the degree of deterioration, the degree of deterioration can be measured in a shorter time without using a special measuring device.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the amount of heat and heat absorbed by a resin and time, and the relationship between ambient temperature and time.

FIG. 2 is a diagram showing the relationship between the amount of consumed antioxidant and the amount of remaining antioxidant.

FIG. 3 is a diagram showing a relationship between a deterioration time and an oxidation induction period.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsuya Hase 1-14 Nishisuehirocho, Yokkaichi-shi, Mie Sumitomo Wiring Systems, Ltd. (72) Inventor Yoshimitsu Yokota 1-14 Nishisuehirocho, Yokkaichi-shi, Mie Sumitomo (72) Inventor Masato Otsuka 1-114 Nishisuehiro-cho, Yokkaichi-shi, Mie F-term (reference) 2G040 AB15 BA02 BA29 CA02 CB03 DA02 DA14 EA02 EB02 EC09 GA04 GC01 HA11 ZA05

Claims (1)

[Claims] 1. A sample of a deteriorated polypropylene resin molded product is left in a nitrogen atmosphere, and the temperature of the nitrogen atmosphere is raised to a predetermined holding temperature at a constant speed. Then, the nitrogen atmosphere is replaced with an oxygen atmosphere. Hold isothermally at the holding temperature,
A method for measuring the degree of deterioration of a molded polypropylene resin product, wherein an oxidation induction period until the exothermic peak of the sample appears is measured, and the oxidation induction period is used as a measure of the degree of deterioration of the molded polypropylene resin product.