JPS5912936A - Crosslinked polyamide resin composition - Google Patents

Abstract

PURPOSE:To obtain titled composition free from glass fiber but infusible even in a bath of molten solder, thus useful for formed items and heat-resistant electric wire covering materials, by carrying out a crosslinking, using a radiation, of a crosslinking auxiliary-incorporated polyamide resin. CONSTITUTION:The objective composition can be obtained by exposing a radiation (pref. an electron beam) to a polyamide resin (e.g., nylon-12) incomporated with a crosslinking auxiliary such as triallyl (iso)cyanurate to effect crosslinking. The above polyamide resin way further be incorporated with a flame-retardant, filler, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crosslinked polyamide resin composition that can be used as a coating material for molded products and heat-resistant electric wires.

Polyamide resins such as nylon 6 and nylon 12 have excellent heat resistance, mechanical properties, etc., and are therefore used as engineering plastics for various purposes.

For example, it is used as electrical parts such as molded products such as connectors, and mechanical parts such as gears.

However, when looking specifically at the use of these molded products, for example, in the case of connectors, they are often soldered to connect lead wires, etc., and in this case, the
It is required to maintain its shape even when immersed in a high temperature solder bath of 350°C.

However, although polyamide resin has a relatively high melting point of 180 DEG C. to 260 DEG C., it is lower than the aforementioned solder bath temperature, so it melts in the solder bath, and polyamide resin cannot be used as is.

For this reason, glass fiber is generally added to polyamide resin to improve heat resistance and solder resistance. However, although reinforcing with glass fiber or the like can improve defects in the solder bath, there is a problem in that damage to the molding machine screw due to wear increases.

The present inventor did not use glass fiber in polyamide resin,
Moreover, as a result of studies to obtain a resin composition that does not melt in a solder bath, it has been found that the above-mentioned drawbacks can be overcome if a polyamide resin mixed with a crosslinking aid is crosslinked by radiation irradiation.

This invention will be explained in detail below.

Generally known methods for crosslinking polymers include (1) crosslinking using organic peroxides, (2) radiation crosslinking, and (3) organic silane crosslinking. When crosslinking polyamide resin, the melting point of the resin is as high as 160 to 260°C, and the processing temperature (2
00 to 800°C) without decomposition, and the decomposition temperature is 300°C.
Since organic peroxides with a carbon content of C or higher do not generally exist, crosslinking using organic peroxides (1) is not possible.

Further, in the crosslinking using organic silane (3), it is necessary to graft the alkoxysilane onto the polyamide resin, but this method is also impossible at temperatures near 200'C because the alkoxysilane will volatilize.

Therefore, we investigated crosslinking of polyamide resin by radiation irradiation. There are several types of radiation such as electron beams and gamma rays, but from an industrial perspective, it is efficient and advantageous to use electron beams, so we investigated a method using electron beam irradiation.

Nylon 12 was used as the polyamide resin, and nylon 12 alone was first irradiated with an electron beam in air. However, using nylon 12 alone had almost no effect, and when it was immersed in a 350°C solder bath for 5 seconds, it completely melted.

Therefore, we investigated the possibility of incorporating a crosslinking aid into the polyamide resin. A well-known polyfunctional monomer was used as a crosslinking aid. Namely, diacrylates such as diethylene glycol diacrylate, dimethacrylates such as ethylene glycol dimethacrylate and dipropylene glycol dimethacrylate, triacrylates such as trimethylolethane trimecrylate and trimethylolpropane triacrylate, and trimethylol. These include trimethacrylates such as ethane trimethacrylate and trimethylolpropane trimethacrylate, triaccyanurate, triallyl isocyanurate, diallyl maleate, and diallyl fumarate.

After adding these crosslinking aids to the polyamide resin, it was formed into a film and irradiated with an electron beam.

Thereafter, it was immersed in a solder bath at 850°C for 5 seconds. As a result, films using triacucyanurate and triallyl isocyanurate as crosslinking aids retained their shape even when immersed in the solder bath described in 1. However, films using other crosslinking aids was inferior in shape retention.

Furthermore, an electron beam irradiated film made of a polyamide resin composition containing triallyl cyanurate or triallyl isocyanurate as a crosslinking aid and a flame retardant added thereto retains its shape even when immersed in solder at 350°C and has a UL rating.
It also showed a ULV-0 result in the standard (UL-94) combustion test, and was recognized to be flame retardant.

Furthermore, when 60CO gamma ray irradiation was performed instead of electron beam irradiation, it was observed that the material did not dissolve even when immersed in a 350° C. solder bath for 5 seconds, similar to electron beam irradiation.

As described above, the crosslinked polyamide resin composition of the present invention is produced by adding a crosslinking aid such as triallyl cyanurate or triallyl isocyanurate to the polyamide resin and performing radiation crosslinking, so even if the composition is heated above the melting point of the polyamide resin,
This allows it to maintain its shape without melting and deforming.

Next, the present invention will be explained in detail with reference to examples.

Example Polyamide resin (nylon 12) was added with the crosslinking aids listed in Table 1 to form a resin composition, and these were used to form a resin composition with a thickness of 0.
．． It was extruded into a 2B film, and then irradiated with 5 Mrad and 10 Mrad using a 400 KeV electron beam accelerator. Further, 5 Mrad of γ-ray irradiation was performed using a 400,000-Kyu 60CO γ-ray source. These films were then immersed in a solder bath at 350°C for 5 seconds to observe changes in shape, and the results shown in Table 1 were obtained.

That is, all of the films irradiated with radiation retained their shape even when immersed in solder.

In addition, the film made of composition C which also added flame retardant is UL
In the vertical combustion test of -9'4, it was found to have flame retardancy equivalent to V-0.

Comparative Example On the other hand, as a comparative example, a film with a thickness of 0.2 mm was extruded using the composition shown in Table 1 without adding the crosslinking aid, and the film was subjected to a +00 KeV electron beam accelerator in the same manner as in the example. 5 Mrad - and W rays were irradiated using a 60CO source of 5 Mrad, 10 Mrad, and 400,000 Curies. Then, it was immersed in a solder bath at 350°C for 5 seconds.

The results are shown in Table 1, and it was found that all films made of the composition of the comparative example, whether unirradiated or irradiated, melted in the solder bath and could not be put to practical use.

Further, when the irradiated film having composition f in the comparative example was subjected to a UL-94 vertical combustion test, the ignited sample dripped and the cotton spread underneath was burned.

Thus, it has become clear that only the polyamide composition according to the present invention can withstand immersion in a solder bath and has excellent flame retardancy.

Table 1 Table Note (1) 12 Nylon Daicel Chemical Product Name (2) 3
Immersed in 50°C solder bath for 5 seconds ◎: No change at all ×: Completely melted

Claims (4)

[Claims] (1) A crosslinked polyamide resin composition characterized in that a polyamide resin containing a crosslinking aid is crosslinked by radiation irradiation. (2) The crosslinked polyamide resin composition according to claim 1, which uses triallyl cyanurate as a crosslinking aid. (3) The crosslinked polyamide resin composition according to claim 1, which uses triallyl isocyanurate as a crosslinking aid. (4) A polyamide resin composition according to claim 1, characterized in that a flame retardant, a filler, etc. are added to a polyamide resin blended with a crosslinking aid to make the resin flame retardant.