JPH0776285B2 - Method for producing polyamide resin foam - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyamide resin foam, and more specifically, it has uniform and fine cells, and has excellent heat resistance, chemical resistance, heat insulation, light weight, cushioning and flexibility. The present invention relates to a method for producing an excellent thermoplastic polyamide resin foam by extrusion molding.

[0002]

It is known to produce foams by plasticizing thermoplastic synthetic resins containing a blowing agent in a screw extruder and then extruding through a suitable die. However, this method can only be used for synthetic resins having a high melt viscosity. Since the melt viscosity of a polyamide resin is generally low, air bubbles made from the polyamide resin are crushed before being cured. In order to solve this problem, in JP-A-47-13672, one selected from the group consisting of polyisocyanates, masked isocyanates, and mixtures of mono- and polyisocyanates is disclosed.
A foamable, polymerizable mixture of a seed, a lactam having at least 5 ring members and an alkaline catalyst, was introduced into the inlet of the screw extruder under a pressure of 1.2 atm and a temperature above the melting point of the polyamide obtained. In U.S.A., a method of polymerizing in an extruder cylinder and making a foam through a die heated to a temperature of 210-290 ° C has been proposed.

However, this method is, for example, nylon 6,6
It is not always applicable to general polyamides such as 6, 11, and 12. Further, since the polymerization is carried out in the extruder, there is a problem in that the unreacted material remains in the extruder and stable extrusion is performed for a long time.

[0004]

The object of the present invention is to solve the above-mentioned problems of the prior art and not only to the special polyamide-based resin but also to the widely available polyamide-based resin for a long time. It is to develop a method for producing a polyamide resin foam that can be stably carried out.

Another object of the present invention is to provide a method by which cells having uniform fine and high expansion ratio can be easily obtained, and heat resistance,
It is intended to provide a polyamide resin foam which is excellent in chemical resistance, heat insulation, lightness, cushioning and flexibility.

[0006]

Means for Solving the Problems As a result of earnest research to achieve these objects, the present inventors have found that when a cross-linking agent is added to a melt during extrusion foam molding of a polyamide resin,
Melt viscosity at the time of melting, melt tension and the effect of improving elastic properties are large, and further excellent stability in long-term operation, it is possible to easily obtain a uniform fine polyamide resin foam,
Then, they have found that the obtained foam is excellent in heat resistance, chemical resistance, heat insulation, lightness, cushioning and flexibility.

Accordingly, the present invention provides a molten mixture of a thermoplastic polyamide resin containing a cross-linking agent and a foaming agent,
A method for producing a polyamide resin foam, which comprises extruding and foaming in a low-pressure zone through a die. The thermoplastic polyamide resin used in the present invention is, for example, a linear polymer having an amide group in the molecule obtained by ring-opening polymerization of lactam, self-condensation of aminocarboxylic acid, condensation of diamine and organic dibasic acid. And examples of suitable resins are nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, MXD6 nylon, nylon 612, nylon 12
12, nylon 46, etc., and these resins are used alone or
It can be used as a mixture of two or more species. Further, a modified resin containing 50% by weight or more of these resins can also be used.

As the cross-linking agent used in the present invention, among various cross-linking agents for polyamide resins, compounds having two carboxylic acid anhydrides in one molecule or polyfunctional epoxy compounds are preferable. Examples of the compound having two carboxylic acid anhydrides in one molecule include pyromellitic acid anhydride, naphthalenetetracarboxylic acid anhydride, benzophenonetetracarboxylic acid anhydride, cyclopentanetetracarboxylic acid anhydride, ethylene glycol (anhydrotricarboxylic acid). (Melitate)
And glycerol (anhydrotrimellitate) are preferably used, and pyromellitic anhydride and benzophenonetetracarboxylic anhydride are particularly preferable.

As the polyfunctional epoxy compound, diglycidyl terephthalate, diglycidyl orthophthalate, diglycidyl hexahydrophthalate, tetrafunctional nitride epoxy (for example, TETRAD-D manufactured by Mitsubishi Gas Chemical Co., Inc.)
, Polyethylene glycol diglycidyl ether, polypropylene diglycidyl ether, bisphenol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, hydrogenated BP- A diglycidyl ether and 2,2-dibromoneopentyl glycol diglycidyl ether are preferably used, and diglycidyl terephthalate, diglycidyl orthophthalate, diglycidyl hexahydrophthalate, and tetrafunctional nitride epoxy are particularly preferable.

A cross-linking agent, preferably a compound having two carboxylic acid anhydrides in one molecule or a polyfunctional epoxy compound is added to introduce a cross-linking structure into the polyamide resin, whereby a melt viscosity at the time of melting. It is considered that the melt tension and elastic properties are preferably changed, and the polyamide resin can be easily foamed. For this purpose, it is extruded through the die into the low-pressure zone, generally at a temperature above 220 ° C, preferably above 240 ° C.

In the present invention, crosslinking can be promoted by adding a metal or a metal compound to the molten mixture. Suitable metals or metal compounds include, for example, metal carbonates such as sodium carbonate, calcium carbonate, zinc carbonate and magnesium carbonate, and fatty acid metal salts such as sodium montanate, zinc stearate and potassium palmitate. This is generally used in an amount of 10 to 100 parts by weight, preferably 20 to 60 parts by weight, based on 100 parts by weight of the crosslinking agent.

The blowing agent used in the present invention is an inert gas, a saturated aliphatic hydrocarbon, a saturated alicyclic hydrocarbon, a halogenated hydrocarbon, an ether, a ketone or the like. Specific examples of foaming agents include: Carbon dioxide, nitrogen, methane, normal butane, isobutane, normal pentane, isopentane, neopentane, normal hexane, 2-methylpentane, 2,2-dimethylbutane, 2,3
-Dimethylbutane, methylcyclopropane, cyclopentane, 1,1-dimethylcyclopropane, cyclohexane, methylcyclopentane, ethylcyclobutane, 1,
1,2-trimethylcyclopropane, benzene, trichloromonofluoromethane, dichlorofluoromethane, monochlorodifluoromethane, trichlorotrifluoroethylene, dichlorotetrafluoroethylene, dimethyl ether, 2-ethoxyethanol, acetone, methyl ethyl ketone, acetylacetone and the like.

In the production of the polyamide resin foam of the present invention, the thermoplastic polyamide resin can be mixed with the crosslinking agent by any of the following means. A) A thermoplastic polyamide resin and a cross-linking agent at low temperature (for example,
Mix at a temperature of 150 ° C or lower) (for example, sprinkle a powdered cross-linking agent on a thermoplastic polyamide resin). B) A cross-linking agent is melt-mixed with a thermoplastic resin in advance to form pellets, and the pellets are mixed with a thermoplastic polyamide resin (the thermoplastic resin used here may be the same as or different from the thermoplastic polyamide resin). However, those compatible with the thermoplastic polyamide resin are preferable). C) The thermoplastic polyamide resin is previously supplied to the hopper of the extrusion foam molding machine, and the crosslinking agent is supplied from the supply port provided in the cylinder of the extrusion foam molding machine to mix them.

In any case of mixing by any method, it is particularly advantageous that the water content of the material mixture is as low as possible. The amount of cross-linking agent used is a thermoplastic polyamide resin
Preferably 0.05 to 1.5 parts by weight per 100 parts by weight, especially
1.0 parts by weight. When the amount of the cross-linking agent is less than 0.05 parts by weight, the viscoelastic properties of the material mixture at the time of melting are not improved, and it is difficult to obtain a good foamed molded product in which fine cells are uniformly dispersed. On the other hand, when the amount is more than 2 parts by weight, the melt of the material mixture gels, and it becomes difficult to perform stable extrusion foam molding.

The foamed molded article of the present invention may further contain stabilizers, nucleating agents, pigments, flame retardants, antistatic agents, viscoelasticity modification auxiliaries, bubble control agents and other additives. In the method of the present invention, the desired expansion ratio can be adjusted by changing the types and amounts of the crosslinking agent, metal compound and foaming agent used, the structure of the extruder, the temperature and other conditions. In the conventional method, only about 2 times the expansion ratio was obtained, but according to the present invention, a high expansion ratio of up to about 10 times can be achieved, and even in this case, a uniform fine cell structure is maintained. .

The foam produced according to the present invention can be used in various fields due to its excellent properties. For example, it is used as a building material because of its high strength, and as a gasoline tank because of its oil resistance, flame retardancy and self-extinguishing property. Used as floats and engine head members. Hereinafter, the present invention will be described more specifically with reference to Examples.

The parts in the examples represent parts by weight.

[0018]

[Example 1] Nylon 6 resin (UBE nylon 1022B,
After drying 100 parts of Ube Industries, Ltd. in a dehumidifying dryer at 80 ° C for 4 hours, diglycidyl terephthalate (Blemmer DG)
T, manufactured by NOF CORPORATION) 0.30 parts and talc 0.6 parts were mixed in a tumbler, and the mixture was uniaxial extruder (caliber: 40 mm,
L / D: 30, nozzle die diameter: 3 mm) was fed to a hopper for melt mixing, and 2.5 parts of butane (foaming agent) was pressed into the melt mixture from the middle of the extruder.

(Operating Conditions of Single-screw Extruder) Temperature of Extruder Feeding Section: 240 ° C. Temperature of Compressing Section of Extruder: 265 ° C. Temperature of Melting Section of Extruder: 250 ° C. Temperature of Extruder Head: 255 ℃ Mold temperature: 250 ℃ Extruder screw rotation speed: 25 rpm Discharge rate: 4.9 kg / hr The obtained foam had rod-like uniform fine cells and a density of 0.13 g / cc. .

[0020]

Example 2 100 parts of MXD6 nylon resin (MXD6121, manufactured by Mitsubishi Gas Chemical Co., Inc.) was dried in a dehumidifying dryer at 80 ° C. for 4 hours, and then tetrafunctional nitrogen epoxy (TETRAD-D, manufactured by Mitsubishi Gas Chemical Co., Ltd.) 8 parts and 0.6 parts of talc were mixed with a tumbler, and this mixture was mixed with a single screw extruder (caliber: 40 mm, L / L).
D: 30, Nozzle die diameter: 3 mm) were supplied to a hopper for melt mixing, and 2.5 parts of butane (foaming agent) was pressed into the melt mixture from the middle of the extruder.

(Operational Conditions of Single-screw Extruder) Temperature of Extruder Feeding Section: 250 ° C. Temperature of Compressing Section of Extruder: 275 ° C. Temperature of Melting Section of Extruder: 270 ° C. Temperature of Extruder Head: 275 ℃ Mold temperature: 270 ℃ Extruder screw speed: 25rpm Discharge rate: 5.3kg / hr The obtained foam had rod-like uniform fine cells and a density of 0.12g / cc. .

[0022]

[Example 3] Nylon 12 resin (Grilamid L2
5, 100 parts of MMS Japan Co., Ltd.) was dried in a dehumidifying dryer at 80 ° C. for 4 hours, and then 0.3 parts of diglycidyl orthophthalate (Nippon Yushi Co., Ltd., Bremmer DGP) and talc of 0.6.
Parts were mixed with a tumbler, and this mixture was mixed with a single screw extruder.
(Aperture: 40 mm, L / D: 30, Nozzle die diameter: 3 mm)
Was supplied to the hopper of No. 2 and melt-mixed, but 2.0 parts of butane (foaming agent) was press-fitted into this melt-mixture from the middle of the extruder.

(Operating Conditions of Single-Screw Extruder) Temperature of Extruder Feeding Section: 200 ° C. Temperature of Compressing Section of Extruder: 285 ° C. Temperature of Melting Section of Extruder: 260 ° C. Temperature of Extruder Head: 255 ℃ Mold temperature: 200 ℃ Extruder screw speed: 25rpm Discharge rate: 0.2kg / hr The obtained foam had rod-like uniform fine cells and a density of 0.20g / cc. .

[0024]

[Example 4] Nylon 1212 resin (Zytel CFE3536,
After drying 100 parts of DuPont) in a dehumidifying dryer at 80 ° C for 4 hours, 0.5 part of pyromellitic dianhydride (made by Huls) and 0.6 part of talc were mixed with a tumbler, and this mixture was mixed. It is supplied to the hopper of a shaft extruder (bore diameter: 40 mm, L / D: 30, nozzle die diameter: 3 mm) and melt-mixed. Butane (foaming agent) 2.5 is added to this melted mixture from the middle of the extruder. It was press-fitted.

(Operating Conditions of Single-Screw Extruder) Temperature of Extruder Feeding Section: 200 ° C. Temperature of Compressing Section of Extruder: 285 ° C. Temperature of Melting Section of Extruder: 260 ° C. Temperature of Extruder Head: 270 ℃ Mold temperature: 230 ℃ Extruder screw rotation speed: 25 rpm Discharge rate: 5.1 kg / hr The obtained foam had rod-like uniform fine cells and a density of 0.12 g / cc. .

[0026]

Example 5 Nylon 11 resin (Rilsan BESNOTL, manufactured by Toray Industries, Inc.)
After drying 100 parts by a dehumidifying dryer at 80 ° C. for 4 hours, benzophenone tetracarboxylic acid anhydride (manufactured by Wako Pure Chemical Industries, Ltd.) 0.6
Part and talc 0.6 part are mixed with a tumbler, and this mixture is melt-mixed by being supplied to a hopper of a single-screw extruder (bore diameter: 40 mm, L / D: 30, nozzle die diameter: 3 mm). 2.0% butane (foaming agent) was added to the molten mixture from the middle of the extruder.
It was press-fitted.

(Operating Conditions of Single-Screw Extruder) Temperature of Extruder Feeding Section: 200 ° C. Temperature of Compressing Section of Extruder: 285 ° C. Temperature of Melting Section of Extruder: 260 ° C. Temperature of Extruder Head: 270 ℃ Mold temperature: 230 ℃ Extruder screw speed: 25 rpm Discharge rate: 4.8 kg / hr The obtained foam had rod-like uniform fine cells and a density of 0.22 g / cc. .

[0028]

[Example 6] Extrusion was carried out under the same conditions as in Example 1 except that 0.1 part of sodium carbonate was added as a metal compound and 2.7 parts of butane was injected under pressure. A foam having a density of 0.11 g / cc and having rod-like uniform fine cells was obtained.

[0029]

Comparative Example 1 Extrusion was carried out under the same conditions as in Example 1 except that diglycidyl terephthalate was not added, and the obtained foam contained large bubbles and had a density of 0.47 g / cc.

[0030]

[0031]

According to the present invention, by cross-linking the finished polyamide resin, rather than polymerizing the monomer in the extruder as in the conventional method,
The extruder can be operated stably for a long period of time, and a foam having a foaming ratio several times higher than that of the conventional method can be obtained, and this foam product has a uniform fine cell structure and excellent heat resistance, It has chemical resistance, heat insulation, light weight, cushioning and flexibility.

Claims (3)

[Claims] 1. A method for producing a polyamide-based resin foam, which comprises extruding and foaming a molten mixture of a thermoplastic polyamide-based resin containing a crosslinking agent and a foaming agent through a die into a low-pressure zone. 2. The method according to claim 1, wherein a compound having two carboxylic acid anhydrides in one molecule or a polyfunctional epoxy compound is used as the crosslinking agent. 3. The method according to claim 1, wherein the molten mixture further contains a metal or a metal compound.