JPH11315156A - Highly heat-resistant crosslinked molded product of noncrystalline polyamide and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a noncrystalline polyamide molded product having excellent heat resistance for a long period of time by irradiating a molded product comprising an uncrosslinked noncrystalline polyamide and a crosslinking agent with radiation. SOLUTION: This molded product is obtained by irradiating, with radiation, a molded product comprising (A) an uncrosslinked noncrystalline polyamide, (B) a crosslinking agent (e.g. triallyl isocyanurate) and, as necessary, (C) e.g. glass fiber, other inorganic fiber, an inorganic powder, a coloring agent, an antioxidant and a plasticizer. Preferably, the component A has a heat of crystal fusion [differential scanning calorimeter(DSC)] of <1 cal/g. Preferably, the component B is compounded at about 1-5 pt(s) wt. per 100 pts.wt. of the component A. The radiation includes electron beams and γ-rays each capable of producing a free radical from the component A. The irradiation dose is preferably 25-300 kGy, more preferably, 50-200 kGy, furthermore preferably, 100-200 kGy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an amorphous polyamide resin, which does not impair the good moldability inherent to amorphous polyamide resin.
The present invention relates to a method for producing a polyamide molded article having improved physical properties such as heat resistance and flame resistance, and a cross-linked molded article having excellent heat resistance of an amorphous polyamide obtained by the method.

[0002]

2. Description of the Related Art Polyamide resins such as nylon 6 and nylon 12 have excellent mechanical properties and the like and are excellent in moldability.
(Abbreviation).

[0003] However, the polyamide resin itself cannot escape the area of general-purpose engineering plastics, and requires special applications, such as heat resistance of coil bobbins, fuse boxes, housings, fans and the like which are used continuously at high temperatures. It cannot be said that it is suitable as a material for molded articles, and some modification is required.

As a first modification means, a composite technique using a reinforcing material such as glass fiber is known. However, if the content of the fiber reinforcing material is increased in order to further improve the strength, the forming is not possible. However, there is a problem that it is difficult to apply to molding of thin parts and products having complicated shapes.

[0005] As a second modification means, from the viewpoint of increasing the heat resistance of the polyamide molded product, a molded product made of a resin composition obtained by blending a crosslinking aid with a polyamide resin (nylon 12) is used. To crosslink (hereinafter,
A method of improving heat resistance by performing "post-crosslinking" (Japanese Patent Application Laid-Open No. 59-12) has been proposed.
935). According to this method, it has been reported that the device can withstand a solder bath at 350 ° C. for 5 seconds, but is insufficient in terms of heat resistance for a long period of time, and is not deformed even under conditions of continuous use at high temperatures. It is desired to establish a technique capable of supplying a polyamide resin molded product that does not occur.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a polyamide molded article exhibiting excellent heat resistance over a long period of time and a method for producing the same. It is in.

[0007]

Means for Solving the Problems A study was conducted on the improvement of the above-mentioned post-crosslinking technique as an immediate task, and a method for remarkably exhibiting the post-crosslinking effect was sought. As a result, between the crystalline polyamide resin composition and the amorphous polyamide resin composition, the degree of dispersion of the added cross-linking agent is different at a stage after the molding process, and the molded article obtained by crosslinking the crystalline polyamide resin composition Then, the inventors first found that the crystal part melted under heating to cause deformation, and completed the present invention.

That is, the method for producing an amorphous polyamide molded article of the present invention includes a step of irradiating a molded article containing an uncrosslinked amorphous polyamide and a crosslinking agent with radiation. . The radiation dose is 25 to 300
It is preferably kGy.

The crosslinked molded article of the present invention, which is obtained from an amorphous polyamide and has excellent heat resistance, is characterized by having a relative viscosity of at least 1.15 times the relative viscosity of the uncrosslinked molded article.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a molded article material used in the method for producing an amorphous polyamide molded article excellent in heat resistance of the present invention, that is, a resin composition containing an uncrosslinked amorphous polyamide and a crosslinking agent Will be described.

The polyamide resin used in the present invention is limited to an amorphous resin. The reason is that, in the case of crystalline polyamide, even if the added cross-linking agent is in a homogeneously dispersed state at the time of melting, it is separated from the crystallized portion by cooling, and the crystallized portion is not cross-linked even when irradiated with a thermoplastic resin. It has the same structure as the part, and the heat resistance becomes insufficient.

The amorphous polyamide used in the present invention is generally referred to as transparent nylon, and nylon 6
A group of polyamide resins that hardly undergo crystallization of the polymer or have a very low crystallization rate, unlike linear aliphatic nylons such as nylon and nylon 66. Specifically, it refers to those having a heat of crystal fusion of less than 1 cal / g measured by a differential scanning calorimeter (DSC). Here, the polyamide resin referred to in the present invention may be a polymer having an amide bond, and may be a polyamide obtained from a dehydration condensation reaction between a carboxylic acid and an amine, and an amide bond obtained from a reaction between a carboxylic acid and an isocyanate. And acyl ureas having the formula (1).

Such an amorphous polyamide has a structure that inhibits crystallization, that is, an aliphatic or alicyclic group having a branched structure, or a monomer component having a functional group at an asymmetric position of the ring structure. It can be synthesized by polymerizing or copolymerizing such monomer components in combination. Specific examples of monomers capable of providing such amorphous nylon include carboxylic acids such as isophthalic acid; and trimethyl-1,6-hexamethylenediamine (which includes 2,2,4-trimethylhexamethylenediamine and 2,4 , 4-trimethylhexamethylenediamine), 4,4'-diamino-3,
3'-dimethyldicyclohexylenemethane (this is equivalent to bis- (3-methyl-4-aminocyclohexyl) methane), 4,4'-diamino-dicyclohexylenepropane (this is bis-p- (aminocyclohexyl) A) propane), amines such as isophorone diamine; isocyanates such as tolylene diisocyanate.

Specific examples of the amorphous polyamide include "Vestamid X 4308" (a monomer component is isophthalic acid, isophoronediamine, laurolactam) from Huls, and "Durethan T40" (a monomer component is adipic acid, isophthalic acid) from Bayer. Acid, 1,6-hexamethylenediamine), “Ultramid KR 4601” from BASF (monomer components are adipic acid, isophthalic acid, 1,6-hexamethylenediamine, 4,4′-diamino-dicyclohexylenemethane), DuPont's "Zytel 330" (monomer components include adipic acid, isophthalic acid, terephthalic acid,
1,6-hexamethylenediamine, 4,4'-diamino-dicyclohexylenemethane), Unitika's "CX100
4,1005 "(monomer components are adipic acid, isophthalic acid, 1,6-hexamethylenediamine, 4,4'-diamino-dicyclohexylenemethane)," PACP9 / 6 "from Philips Petrolium (monomer component is adipine Acid, azelaic acid, 4,4'-diamino-dicyclohexylenepropane), Dow Chemical's "Isonamid"
PA7030 "(monomer components are adipic acid, azelaic acid, 4,4'-diphenylmethane diisocyanate) and the like.

As the crosslinking agent used in the present invention, conventionally known polyfunctional monomers can be used. Specifically, diethylene glycol di (meth)
Acrylates, di (meth) acrylates such as dipropylene glycol di (meth) acrylate; tri (meth) acrylates such as trimethylolethanetri (meth) acrylate and trimethylolpropane tri (meth) acrylate; triallyl cyanurate; Triallyl isocyanurate, diallyl cyanurate, diallyl isocyanurate and the like can be mentioned. Among these, a compound that does not thermally decompose during kneading and molding may be appropriately selected and used according to the type of amorphous polyamide.

The amount of the crosslinking agent is preferably about 1 to 5 parts by weight based on 100 parts by weight of the amorphous polyamide. If the amount is less than 1 part by weight, the crosslinking for improving the heat resistance becomes insufficient. On the other hand, the addition of more than 5 parts by weight saturates the effect of improving heat resistance.

The resin composition which is a molded article material to which the method of the present invention can be applied includes, in addition to the above-mentioned amorphous polyamide resin and a crosslinking agent, if necessary, glass fibers or other inorganic fibers or inorganic powders, A filler such as a coloring agent, an antioxidant, a plasticizer, and a flame retardant may be appropriately contained.

The molded article used in the production method of the present invention is:
A resin composition obtained by adding a predetermined amount of the above-mentioned components and uniformly mixing the same is molded. For preparation and molding of the molding resin composition, a method generally used for a thermoplastic resin composition can be applied.

Specifically, first, a pellet made of the resin composition having the above composition is produced, and a method of molding using the pellet, a resin pellet not containing a filler is first produced, and the resin pellet and the cross-linking are carried out. And other fillers are uniformly mixed using a kneading extruder, mixing roll, Banbury mixer, etc., and appropriately molded using an injection molding machine, extrusion molding machine, etc. A pellet of the resin composition is first produced, and at the time of melting and molding the pellet, an amorphous polyamide is added and mixed so as to have a predetermined ratio, followed by molding. Among these, from the viewpoint of achieving higher uniform dispersibility of the cross-linking agent, it is preferable to mold using an amorphous polyamide resin pellet in which the cross-linking agent is mixed in advance.

Since the resin is not crosslinked at the time of molding, it can be considered in the same manner as molding of an uncrosslinked polyamide. That is, since a general thermoplastic resin manufacturing method can be adopted and the fluidity at the time of molding is good, coil bobbins, housings, fans by injection molding, sheets, films, fibers, etc. by extrusion molding. Large-sized molded product, a molded product having a complicated shape, or a thin-walled molded product can be obtained.

When an uncrosslinked molded article obtained by molding is irradiated with radiation, a molded article having excellent heat resistance according to the present invention (hereinafter referred to as “the molded article”).
A molded article after irradiation is referred to as a "crosslinked molded article", and a molded article before irradiation or a molded article containing no crosslinking agent is referred to as an "uncrosslinked molded article" to thereby obtain a molded article.

The radiation according to the present invention is capable of generating radicals from an amorphous polyamide resin, and includes an electron beam obtained by accelerating electrons by an accelerator, a gamma ray emitted from a radioisotope material, and the like. No. High-energy rays such as high-energy electron beams and γ-rays can penetrate into the molded article and generate radicals even in the polymer inside. It is considered that the higher the radiation irradiation amount, the more radicals can be generated, so that the crosslinking density can be increased. On the other hand, if the irradiation dose is too high, the decomposition of the polyamide starts. Therefore,
The irradiation dose is 25 to 300 kGy, preferably 50 to 2
00 kGy, particularly preferably 100 to 200 kGy. Incidentally, an electron beam is preferably used industrially. This is because, since the γ-ray has a low line density, the irradiation time is prolonged if an attempt is made to irradiate until the energy in the above range is obtained, and various countermeasures are required also from the viewpoint of safety.

The timing of radiation irradiation is not particularly limited, and may be immediately after molding of the uncrosslinked molded article or after cooling of the uncrosslinked molded article. Therefore, after a predetermined number of uncrosslinked molded articles have been produced, radiation irradiation can be performed at once to produce a crosslinked molded article.

As described above, radicals are generated from the polymer by irradiation with radiation such as an electron beam, and react with a crosslinking agent to form a crosslinked structure. Here, the more uniformly the cross-linking agent is dispersed in the resin, the more the cross-linked structure is formed over the details of the molded article. In this regard, in the non-crosslinked molded article of the amorphous polyamide, since the crosslinking agent is satisfactorily and uniformly dispersed as described above, the crosslinked density of the crosslinked molded article obtained after irradiation with radiation is uniform and high. On the other hand, in the case of crystalline polyamide, it is considered that even if the crosslinking agent is uniformly mixed at a temperature equal to or higher than the melting point, the crosslinking agent is expelled from the crystal structure during crystallization at the cooling stage of the uncrosslinked molded article. It is conceivable to reduce the displacement of the crosslinking agent from the crystal structure by irradiating radiation immediately after molding.However, such a method is not suitable for molding methods such as injection molding that take out molded products after curing. Not applicable.

Therefore, the crosslinked molded article of the amorphous polyamide obtained by the method of the present invention is to irradiate an uncrosslinked molded article in which the crosslinking agent is uniformly dispersed, regardless of the type of the molding method. Based on the good uniform dispersion of the cross-linking agent, the cross-linking density is more uniform and higher than that of the cross-linked molded product of the crystalline polyamide, resulting in a cross-linked molded product having excellent properties such as heat resistance and flame resistance. I have.

Specifically, the crosslinked molded article of the amorphous polyamide of the present invention has a relative viscosity of 1.10 compared to the uncrosslinked molded article.
It has increased 15 times or more.

[0027]

[Example] [Production of heat-resistant molded article] Example 1: As an amorphous polyamide, "Sealer PA" (manufactured by DuPont-Mitsui Chemical Co., Ltd.) (glass point shift: 125)
° C) was used. Triallyl isocyanurate was used as a crosslinking agent. Mold clamping force 1 set at 230-260 ° C
A pellet of sealer PA and a crosslinking agent were added to a 30-t injection molding machine and mixed to form a test piece (uncrosslinked molded article) of 120 mm × 12 mm × 4 mm. The crosslinking agent was added in an amount of 3% by weight based on the weight of the uncrosslinked molded article. An electron beam of 50 MeV was applied to this test piece using an electron beam accelerator of 5 MeV.
Irradiation with kGy yielded a crosslinked molded article.

Example 2 A cross-linked molded article was obtained in the same manner as in Example 1 except that the irradiation dose was changed to 100 kGy.

Comparative Example 1 A molded product was obtained in the same manner as in Example 1 except that no crosslinking agent was added. Since the molded article of Comparative Example 1 does not contain a crosslinking agent, it is an uncrosslinked molded article.

Comparative Example 2: Instead of the amorphous polyamide, "Dyamide" (trade name of nylon 12, melting point: 178, manufactured by Daicel Huels Co., Ltd.) which is a crystalline type polyamide is used.
° C), and the set temperature of the molding machine was set to 180 to 220 ° C. Otherwise, the procedure of Example 1 was followed to obtain a crosslinked molded article.

Comparative Example 3 A molded product was obtained in the same manner as in Comparative Example 2 except that no crosslinking agent was added. Similarly to Comparative Example 3, the molded article of Comparative Example 1 is considered to be an uncrosslinked molded article.

[Evaluation] Heat Resistance The heat-resistant molded articles of Example 1 and Comparative Examples 1 to 3 were immersed in an oil bath at 220 ° C. for 10 minutes, and changes in the molded articles were examined. Table 1 shows the results.

[0033]

[Table 1]

As can be seen from Table 1, each of the uncrosslinked polyamide molded products began to melt after one minute (Comparative Examples 1, 3). In Comparative Example 2 using a crystalline polyamide even in the case of a crosslinked molded product, the time until melting was 2 minutes, which was slightly longer than that of a non-crosslinked product, but was insufficient in heat resistance. Was.

On the other hand, although Example 1 was crosslinked in the same manner as Comparative Example 2, it was found that it was softened only, not melted, and was provided with excellent heat resistance.

Flame resistance The test pieces of Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to JI
Flame resistance was tested in accordance with SK6911 5.24.2B method. That is, using a vertical burning test apparatus as shown in FIG. 1, the center of the lower end of the test piece, whose length was held vertically by a clamp, was brought into flame contact, and the time until ignition was measured and the burning time were measured. Table 2 shows the results.

[0037]

[Table 2]

As can be seen from Table 2, when the crystalline polyamide was used, ignition occurred at the early stage of flame contact and combustion continued after ignition regardless of the presence or absence of crosslinking (Comparative Examples 2 and 3). In other words, it can be seen that in the case of crystalline polyamide, even if the heat resistance is improved to some extent by crosslinking, the flame resistance cannot be improved. On the other hand, when the amorphous polyamide was used, regardless of the presence or absence of crosslinking, the flame was extinguished within 10 seconds even if ignited, indicating that the flame was less likely to burn than the crystalline polyamide (Comparative Example 1, Example Examples 1 and 2).

In the order of Comparative Example 1, Example 1, and Example 2, the time until ignition is longer. From this,
In the case of using amorphous polyamide, it can be seen that the higher the crosslink density, the more difficult it is to ignite, that is, the more excellent the flame resistance.

Thermal Decomposition The test pieces of Comparative Example 1 and Example 2 were heated by a differential scanning calorimeter at a rate of 10 ° C./min to 500 ° C., which caused a thermal change of the sample. Was examined. Table 3 shows the results
Shown in

[0041]

[Table 3]

From Table 3, it can be seen that Example 2 having a higher degree of crosslinking has a smaller decomposition endothermic amount and is less likely to be thermally decomposed.
In other words, it is considered that Comparative Example 1 which is an uncrosslinked molded article decomposes by absorbing heat up to 500 ° C., whereas the crosslinked molded article of the present invention is less likely to decompose and thus has a small amount of heat absorption.

Relative Viscosity The molded articles of Comparative Example 1, Examples 1 and 2 were subjected to JIS K
The relative viscosity was measured according to 6810 4.4.1. That is, each sample was completely dissolved with concentrated sulfuric acid to prepare a sample solution, and 15 ml of this sample solution was taken using a viscometer.
At 0 ± 0.1 ° C., the time (sec) of flowing down from the upper time line to the lower time line of the viscometer was measured. The value obtained by dividing the flow time (T) of the sample solution by the flow time (Ts) of the solvent sulfuric acid (T / Ts) is the relative viscosity. The higher the relative viscosity,
It is considered that the apparent molecular weight is large, that is, the degree of crosslinking is high. Table 4 shows the measurement results.

[0044]

[Table 4]

From Table 4, the relative viscosity increased in the order of Comparative Example 1, Example 1, and Example 2. That is, it can be confirmed that the molded article (Example) containing the crosslinking agent is crosslinked. And the one with the larger electron beam irradiation amount (Example 2)
It is considered that the relative viscosity was large and the crosslinking was advanced.

[0046]

The cross-linked molded article of the amorphous polyamide of the present invention is considered to have a high and uniform cross-linking density based on the amorphous nature of the polyamide, and therefore has an excellent heat resistance so as to withstand continuous use at high temperatures. Has heat resistance, flame resistance, and thermal decomposition resistance.

Further, according to the production method of the present invention, since the moldability inherent to the amorphous polyamide can be utilized, a non-crosslinked molded article having a complicated shape, a thin wall or a large size is molded first, and then the heat resistance is reduced. Can be granted. Therefore,
A complex-shaped, thin-walled, or large-sized cross-linked molded article excellent in various physical properties such as heat resistance, flame resistance, and thermal decomposition property can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a flame resistance test.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 77:00

Claims (3)

[Claims] 1. A method for producing an amorphous polyamide molded article, comprising a step of irradiating a molded article containing an uncrosslinked amorphous polyamide and a crosslinking agent with radiation. 2. A radiation dose of 25 to 300 kG.
The method according to claim 1, wherein y is y. 3. A crosslinked molded article of an amorphous polyamide, wherein the relative viscosity of the noncrosslinked molded article of the amorphous polyamide is 1.
A crosslinked molded article of an amorphous polyamide having excellent heat resistance, having a relative viscosity of 15 times or more.