JPS63113033A - Foaming agent composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition capable of increasing the volume of emitted gas in thermal decomposition with a small amount of the unreacted residual nitrite in foams, by wetting an azodicarbonamide with an aqueous solution of a nitride, drying and pulverizing the resultant azodicarbonamide. CONSTITUTION:A composition obtained by wetting an azodicarbonamide with an aqueous solution of a nitride, preferably sodium nitrite or potassium nitrite, drying and pulverizing the resultant azodiacarbonamide. The amount of the nitrite used is preferably 5-50pts.wt. based on 100pts.wt. azodicarbonamide in a dry state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a foaming agent composition suitably used for foaming thermoplastic resins, rubbers, and the like.

[Conventional technology]

Chemical blowing agents that decompose to generate gas when heated are used in the production of foamed materials such as thermoplastic resins and rubbers, among which azodicarbonamide is particularly widely used.

This azodicarbonamide (hereinafter referred to as ADCA) has excellent properties as a blowing agent, such as rapid generation of nitrogen gas when heated, non-flammable decomposition products, and non-toxicity. Ru.

By the way, it is being considered to add other compounds to ADCA to increase the amount of gas generated and thereby use ADCA economically.

For example, ADCA with chromium alum, dichromate,
Dry mixing of chromate or chromium dioxide (Japanese Patent Publication No. 54-16547); using hydrothermally synthesized calcium silicate with ADCA (Japanese Patent Publication No. 52-2
No. 936), adding a magnesium compound to ADCA (Japanese Unexamined Patent Publication No. 52-40577), ADC
For example, mixing nitrite with A (Japanese Unexamined Patent Publication No. 49-369).

[Problem that the invention seeks to solve]

The method disclosed in Japanese Patent Publication No. 54-16547 has the disadvantage that the chromium compound added is toxic and, although the amount of gas generated increases, the decomposition residue is colored, resulting in colored foam.

In addition, the Special Publication Corporation of Showa 5, which uses hydrothermally synthesized calcium silicate,
The method described in Publication No. 2-2936 requires the addition of a large amount of this hydrothermally synthesized calcium silicate, and has the disadvantage that the physical properties deteriorate, especially when attempting to obtain a highly foamed product.

Furthermore, the method of adding a magnesium compound described in JP-A-52-40577 has little effect on increasing the amount of gas generated.

Furthermore, in the method described in Japanese Unexamined Patent Publication No. 49-3695, experiments conducted by the inventor revealed that unless the nitrite has a particle size of 10 μm or less, the effect of increasing the amount of gas generated is poor. However, it is difficult to grind nitrite into particles of 10 μm or less because the particles tend to stick to each other. Even if it can be crushed, unreacted nitrite remains in the resulting foam, which is a hygiene problem, especially when used for applications that come into contact with food.

In view of the above points, the present invention provides a blowing agent composition that increases the amount of generated gas and does not cause coloring of the decomposition residue (and is also free from safety and hygiene concerns) when ADCA is used as a blowing agent. The purpose is to

[Means for solving problems]

The blowing agent composition of this invention is characterized in that azodicarbonamide is wetted with an aqueous nitrite solution, then dried and pulverized.

Examples of the nitrite in this invention include sodium nitrite, potassium nitrite, silver nitrite, and barium nitrite. Among these, sodium nitrite and potassium nitrite are more preferably used from the viewpoint of non-coloring of the decomposition residue and safety and hygiene of the foam.

The amount of nitrite used is not particularly limited, but in a dry state, it is 2 to 2 to 00 parts by weight of ADCAl.
The amount is 100 parts by weight, preferably 5 to 50 parts by weight. If it is less than 2 parts by weight, the effect of increasing the amount of gas generated is poor;
If it exceeds 0, the amount of gas generated will not change much and the physical properties of the foam may be impaired, which is not preferable.

In addition, by wetting ADCA in a nitrite aqueous solution and then drying and pulverizing it, the nitrite adheres to the ADCA surface, resulting in a foam that has an excellent effect of increasing the amount of gas generated and has dense cells. It will be done.

Note that conventionally known auxiliary agents used for adjusting the decomposition temperature, such as zinc stearate and zinc oxide, can be used in combination without departing from the spirit of the present invention.

[Effect]

In the foaming agent composition of the present invention, by wetting ADCA in a nitrite aqueous solution, drying and pulverizing it, the amount of gas generated during thermal decomposition increases, the foaming effect is remarkable, and The residual amount of unreacted nitrite is significantly reduced.

〔Example〕

Examples 1-4 (Sample) ADCAloog was dissolved in 20% sodium nitrite (NaN
O□) 100 g each of aqueous solution (Example 1), 20
0g (Example 2), 300g (Example 3), 5
00g (Example 4) was dried under vacuum, and then ground in a ball mill to obtain a foaming agent composition with an average size of 10μ.

In addition, ADCA and sodium nitrite (
The blending ratio with NaNOz) is as shown in Table 1.

0.1 g of each of these compositions was taken, accurately weighed, and used as a sample for measuring the amount of gas generated.

Note that Comparative Example 1 was prepared using only ADCA without adding sodium nitrite.

Table 1 (Measurement and results of amount of gas generated) Approximately 0.1 g of the sample was placed in a 18 mmφ x 105 am glass test tube, and 10 cc of liquid paraffin was added.
While immersing this in a heat bath kept at 230°C, the gas generated is introduced from the top of a 50cc buret filled with water, while the bottom of the burette and the glass funnel are connected with a hose. While adjusting both water levels so that they were always the same, the apparent amount of gas generated was measured using a liquid volume change automatic recording device (manufactured by Rigaku Denshi Co., Ltd., model LCT-1).

This apparent gas generation amount was converted to the standard state using the following formula (atmospheric pressure is assumed to be latm).

V”VA X (273/(273+T))÷W+C
/100V: Generated gas il (cc/ADCA1g
)VA Double apparent amount of generated gas (c c) T: Temperature of generated gas (''C) W: Sample weight (g) C: ADCA content of sample (%) The measurement results are as shown in Table 1. However, by adding sodium nitrite, the amount of gas generated per gram of ADCA increases.

In addition, the decomposition residue floating or precipitating in the liquid paraffin in the test tube was white.

(Molding of foam and measurement of residual nitrite amount) Each blowing agent composition shown in Table 1 and a simple mixture of ADCA and sodium nitrite ground to an average particle size of lOμ (Example 2 shown in Table 2) - 5) were each mixed into 100 parts by weight of low density polyethylene to form a foamable resin composition in which ADCA was blended in an amount of 10 parts by weight. A sheet with a thickness of 1 mm was produced using a press.

Table 2 Each sheet was irradiated with 3 Mr ad of electron beam to crosslink the resin, and then heated and foamed in hot air at 260°C to obtain a foam.

Each of these foams was extracted with Han distilled water, and JISKO10
Sodium nitrite was quantitatively measured according to the measurement method according to 2.

The density, cell state, and IJ content of each foam were as shown in Table 3.

Table 3 [Effects of the Invention] In the blowing agent composition of the present invention, the amount of gas generated during thermal decomposition increases, the foaming effect is remarkable, and the amount of ADCA used can be reduced or a highly foamed product can be obtained. It is economical because it can be

In addition, the amount of unreacted nitrite remaining in the foam is significantly reduced, and the resulting foam is sanitary and safe.

Furthermore, since the decomposition residue is white and uncolored, it does not stain the foam.

Claims (1)

[Claims] 1. A blowing agent composition characterized in that azodicarbonamide is wetted with an aqueous nitrite solution, then dried and ground.