JPH085986B2 - Method for producing thermoplastic 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 thermoplastic polyamide resin foam, and more specifically, it has uniformly fine cells, heat resistance, chemical resistance, heat insulation, light weight, cushioning, The present invention relates to a method for producing a thermoplastic polyamide resin foam excellent in flexibility and gas barrier properties by extrusion foaming.

[0002]

2. Description of the Related Art It is already known to produce a foam by plasticizing a thermoplastic resin containing a foaming agent in a screw type extruder and then extruding it through a suitable die. However, thermoplastic polyamide resins such as nylon have low melt viscosity and tension, even though they are commonly used, and further have nitrogen, carbon dioxide, hydrocarbons,
It was difficult to produce a good foam because of poor compatibility with commonly used foaming agents such as Freon. In addition, it is possible to foam MXD6 nylon using a chemical foaming agent (Engineering Plastic Dictionary, published by Gihodo Publishing,
Although it has been disclosed in Ibo Uchiren, Yasushi Oyanagi, Manabu Senoo), the expansion ratio by such a method is at most about 4 times, which is not sufficient.

Therefore, the inventors of the present invention filed an invention for improving the melt viscosity and tension of polyamide by extrusion-foaming a melt mixture of a thermoplastic polyamide resin containing a cross-linking agent and a foaming agent. (Ganpei 3-9356)
However, even in the present invention, there remains a problem that it is necessary to further increase the expansion ratio.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above problems of the prior art and to provide a thermoplastic polyamide resin foam which can be stably used for a long time, and more specifically, Another object of the present invention is to provide a method for producing a polyamide resin foam which is rich in uniform fine bubbles and which is excellent in heat resistance, chemical resistance, heat insulation, light weight, cushioning, flexibility, and gas barrier properties.

[0005]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above problems, and as a result, when a certain amount of dimethyl ether is used as a foaming agent during extrusion foam molding of a polyamide resin, the foaming agent is contained in the resin. The present invention has been completed by finding that a foamed product having a uniform dispersion, abundant and uniform fine bubbles, a good appearance, and excellent heat resistance can be obtained.

That is, the present invention provides a method for producing a thermoplastic polyamide resin foam, which comprises melt-mixing a thermoplastic polyamide resin and 0.1 to 10% by weight of dimethyl ether and subjecting the mixture to extrusion foaming. Is. Examples of the thermoplastic polyamide resin used in the present invention include ring-opening polymerization of lactam, self-condensation of aminocarboxylic acid,
It is possible to exemplify a linear polymer obtained by condensation of a diamine and an organic dibasic acid and having an amide group in the molecule. Examples of suitable resins include nylon 6 and nylon 6
6, nylon 10, nylon 11, nylon 12, MXD6 nylon, nylon 612, nylon 1212, nylon 46, and the like, among which nylon 6,
Nylon 66 and MXD6 nylon are particularly preferred in the present invention.

The amount of dimethyl ether used as a foaming agent in the present invention is usually 0.2 to 8.0% by weight. Incidentally, together with the dimethyl ether used as a foaming agent, for the purpose of improving the heat insulating property of the foam according to the present invention, trichloromonofluoroethane, dichlorofluoromethane, monochlorodifluoromethane, trichlorotrifluoroethylene, dichlorotetrafluoroethylene. CFCs such as tetrafluoroethane; nitrogen, carbon dioxide gas, etc. for the purpose of improving bubble miniaturization; and propane, butane, pentane, etc. for the purpose of reducing the production cost. The gas species other than the methyl ether may be added alone or a plurality of kinds may be added, but the amount of the gas species added is less than 50% by weight with respect to the methyl ether, preferably 30% by weight. %, And more preferably less than 15% by weight.

In the present invention, it is possible to produce a desired foam only with the thermoplastic polyamide resin and the foaming agent, but in order to produce a foam having a higher expansion ratio, a crosslinking agent is further added. It is preferable to add it. The crosslinking agent used in the present invention is preferably a compound having two carboxylic acid anhydrides in one molecule or a polyfunctional epoxy compound among various crosslinking agents for polyamide resins.

Examples of the compound having two or more carboxylic acid anhydrides in one molecule include pyromellitic acid anhydride, naphthalenetetracarboxylic acid anhydride, benzophenonetetracarboxylic acid anhydride, cyclopentanetetracarboxylic acid anhydride and ethylene glycol. (Anhydro trimellitate)
Alternatively, glycerol (anhydrotrimellitate) is preferably used, and pyromellitic acid anhydride and benzophenonetetracarboxylic acid anhydride are particularly preferable.

As the polyfunctional epoxy compound, diglycidyl terephthalate, diglycidyl orthophthalate, diglycidyl hexahydrophthalate, and 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 or 2,2-dibromoneopentyl glycol diglycidyl ether is preferably used, and diglycidyl terephthalate, diglycidyl orthophthalate, diglycidyl hexahydrophthalate, or functional nitride epoxy is exemplified as particularly preferable. it can.

By adding a cross-linking agent, preferably a compound having two carboxylic acid anhydrides in one molecule or a polyfunctional epoxy compound, a cross-linking structure is introduced into the polyamide resin, thereby melting at the time of melting. It is considered that the viscosity, melt tension and elastic properties are preferably changed and the polyamide resin can be easily foamed. The amount of the polyfunctional epoxy compound added is the polyamide-based resin.
The amount is 0.1 parts by weight or more and 2 parts by weight or less, and more preferably 0.2 parts by weight or more and 1.0 parts by weight or less with respect to 100 parts by weight.

Further, in the present invention, the introduction of the cross-linking or network structure can be promoted by adding a metal or a metal compound to the molten mixture. Examples of the metal or metal compound preferably used include metal carbonates such as sodium carbonate and magnesium carbonate; and fatty acid metal salts such as sodium montanate, zinc stearate and potassium palmitate. When the metal or metal compound is added together with the crosslinking agent, it is generally 10 to 100 parts by weight, preferably 20 to 60 parts by weight, based on 100 parts by weight of the crosslinking agent.

Melt mixing and extrusion foaming in the production of the polyamide resin foam of the present invention are generally carried out by known methods. Preferred among these methods is an extrusion foaming method in which the mixture is melt-mixed in an extruder and the molten mixture is extruded through a die attached to an extrusion port. In this case, the extrusion temperature is appropriately selected depending on the type of thermoplastic resin, but is generally 220 ° C. or higher, preferably
It is 240 ℃ or higher. The shape of the die is not particularly limited, and a sheet-shaped, rod-shaped, or other foam can be obtained according to the shape. The sheet-shaped foam may be manufactured by once manufacturing a rod-shaped foam, forming a hollow body by mandrel molding, and then partially cutting the hollow body.

Dimethyl ether, which is a foaming agent, is injected from one or several points in the middle of the cylinder of the extruder. It can also be injected from both the cylinder and die. In the production of the foam according to the present invention, a stabilizer, a nucleating agent, a pigment, a flame retardant, an antistatic agent, a viscoelasticity modification aid, a cell regulator and other additives may be added.

As the stabilizer, it is possible to use an ultraviolet stabilizer, a heat stabilizer, preferably a phosphorus stabilizer or a tin stabilizer, and the addition amount is 0.1 to 1.0 part by weight. As the crystal nucleating agent, a metal compound or an olefin resin, preferably a metal compound, can be used, and the addition amount thereof is 0.1 to 5 parts by weight.

As the pigment, it is possible to use an inorganic pigment such as carbon black, and the addition amount thereof is 0.5 to 10
Parts by weight. The flame retardant is a brominated flame retardant, a phosphorus flame retardant, or an antimony flame retardant, and the amount added is 0.5.
~ 3 parts by weight. As the antistatic agent, a fatty acid ester-based compound or a sodium sodium alkane-based compound can be used, and the addition amount thereof is 0.1 to 1.0 part by weight.

Isocyanate compounds, peroxides, oxazoline compounds, and oxazine compounds can be used as the viscoelasticity-modifying aid, and the addition amount thereof is 0.
05 to 1.0 parts by weight. As a bubble regulator, talc,
Silica, sodium montanate, fatty acid metal salts such as aluminum stearate, inorganic salts such as sodium carbonate, preferably talc, silica, aluminum stearate, sodium carbonate can be used, the addition amount is 0.1 ~.
It is 5.0 parts by weight.

In the method of the present invention, the desired expansion ratio can be adjusted by changing the polyfunctional epoxy compound, metal compound, amount of foaming agent, extruder structure, temperature and other conditions used. . According to the present invention, a foaming ratio as high as about 20 times can be achieved, and a uniform fine cell structure can be maintained. The foam produced by the present invention can be used in various fields due to its excellent properties, for example, excellent gas barrier properties, heat resistance, food containers making good use of heat insulation, as a building material due to its high strength. It is used as a float for gasoline tanks, an engine head member, etc. that takes advantage of oil resistance, flame resistance, and self-extinguishing property.

[0019]

EXAMPLES The present invention will be described more concretely with reference to the following examples.

[0020]

[Example 1] Nylon 6 resin (UBE nylon 1022B,
100 parts of Ube Industries, Ltd. and 0.6 parts of talc are mixed in a tumbler, and this mixture is uniaxial extruder (caliber: 40 mm, L /
D: 30, nozzle mold was fed into a hopper having a nozzle die diameter of 2 mm) to melt and mix, and 0.7 part of methyl ether (foaming agent) was press-fitted into the melted mixture from the middle of the extruder.

(Operating conditions of single-screw extruder) Temperature of the feeding part of the extruder: 220 ° C Temperature of the compression part of the extruder: 260 ° C Temperature of melting part of the extruder: 230 ° C Temperature of head of the extruder: 230 ℃ Mold temperature: 230 ℃ Extruder screw speed: 25 rpm Discharge rate: 5.0 kg / Hr The obtained foam has rod-like uniform cells and a density of 0.
It was 34.

[0022]

[Example 2] Nylon 6 resin (UBE nylon 1022B,
Ube Industries, Ltd.] 100 parts, diglycidyl terephthalate
(Blenmer DGT, NOF Corporation) 0.30 parts and talc
0.6 part was melt-mixed with a tumbler, and this mixture was uniaxial extruder (bore diameter: 40 mm, L / D: 30, nozzle die diameter:
(2 mm) hopper and melt-mixed. Methyl ether (foaming agent) 2.5 was added to this melt-mixed mixture from the middle of the extruder.
It was press-fitted.

(Operating conditions of the single-screw extruder) Temperature of the feeding part of the extruder: 240 ° C. Temperature of the compression part of the extruder: 265 ° C. Temperature of melting part of the extruder: 250 ° C. Temperature of head of the extruder: 250 ℃ Mold temperature: 250 ℃ Extruder screw speed: 25 rpm Discharge rate: 5.0 kg / Hr The obtained foam has rod-like uniform cells and a density of 0.
It was 081 g / cc.

[0024]

Example 3 100 parts of MXD6 nylon resin (MXD6121, manufactured by Mitsubishi Gas Chemical Co., Inc.) and 0.6 parts of talc were mixed in a tumbler, and this mixture was uniaxial extruder (caliber: 40 mm, L /
D: 30, nozzle diameter: 2 mm), the mixture was melt-mixed by supplying to a hopper, and 0.8 part of methyl ether (foaming agent) was press-fitted into this molten mixture from the middle of the extruder.

(Operating conditions of single-screw extruder) Temperature of the feeding part of the extruder: 250 ° C Temperature of the compression part of the extruder: 275 ° C Temperature of melting part of the extruder: 260 ° C Temperature of extruder head: 265 ℃ Mold temperature: 260 ℃ Extruder screw rotation speed: 25 rpm Discharge rate: 5.2 kg / Hr The obtained foam is rod-shaped with uniform cells and a density of 0.
It was 22 g / cc.

[0026]

[Example 4] MXD6 nylon resin (MXD6121, manufactured by Mitsubishi Gas Chemical Co., Inc.) 100 parts, tetrafunctional nitride epoxy (TETR)
AD-D, Mitsubishi Gas Chemical Co., Ltd.) 0.8 parts and talc 0.6 parts were mixed by a tumbler, and this mixture was single-screw extruder (bore diameter: 40 mm, L / D: 30, nozzle diameter: 3 mm). No. 1 was supplied to the hopper for melt mixing, and 1.8 parts of methyl ether (foaming agent) was pressed into the melt mixture from the middle of the extruder.

(Operating Conditions of Single-Screw Extruder) Temperature of Extruder Supply: 250 ° C. Temperature of Compressor of Extruder: 275 ° C. Temperature of Melt of Extruder: 270 ° C. Temperature of Extruder Head: 275 ℃ Mold temperature: 270 ℃ Extruder screw speed: 25 rpm Discharge rate: 5.4 kg / Hr The obtained foam is rod-shaped with uniform cells and density of 0.
It was 096 g / cc.

[0028]

Example 5 MXD6 nylon resin (MXD6121, manufactured by Mitsubishi Gas Chemical Co., Inc.) 100 parts, diglycidyl terephthalate
(Blenmer DGT, NOF Corporation) 0.30 parts and talc
0.6 part was mixed with a tumbler, and this mixture was supplied to a hopper of a single-screw extruder (caliber: 65 mm, L / D: 35) to be melt-mixed. Ethyl ether was added to the molten mixture from the middle of the extruder. 0.8 parts of (foaming agent) was press-fitted. The mold has a diameter of 60m
A circular mold with m and an annular outlet gap of 0.40 mm was used. Then, the tubular body is extruded into the atmosphere from the die outlet, and the molten resin is taken in while foaming and the cylindrical mandrel (diameter 205 m
m 2 and length 400 mm) was formed into a cylindrical shape, and a part of the cylindrical foam was cut open and wound into a sheet. At that time, cooling water was circulated through the cylindrical mandrel.

(Operating Conditions of Single-Screw Extruder) Temperature of Extruder Supply: 280 ° C Temperature of Compressor of Extruder: 285 ° C Temperature of Melt of Extruder: 260 ° C Temperature of Extruder Head: 260 ℃ Mold temperature: 260 ℃ Extruder screw speed: 25 rpm Discharge rate: 30 kg / Hr The obtained foam has sheet-like uniform cells and a density of
The thickness was 0.28 g / cc and the thickness was 1.1 mm.

[Comparative Example 1] Extrusion was carried out under the same conditions as in Example 1 except that 0.8 part of butane was injected as a blowing agent instead of methyl ether. The obtained foam had a density of 0.50 g / A cavity was found in cc. [Comparative Example 2] Extrusion was carried out under the same conditions as in Example 1 except that 0.8 parts of butane was press-fitted as a foaming agent instead of methyl ether. As a result, the cylindrical foam could not be drawn to the cooling mandrel and was excellent. No foamed sheet was obtained.

[0031]

EFFECT OF THE INVENTION By the production method of the present invention, a thermoplastic polyamide resin foam having uniform fine bubbles and excellent heat resistance, chemical resistance, heat insulating property, light weight property, cushioning property, flexibility and gas barrier property. Can be provided.

Claims (3)

[Claims] 1. A method for producing a thermoplastic polyamide-based resin foam, which comprises melt-mixing a thermoplastic polyamide-based resin and dimethyl ether and extrusion-foaming. 2. A method for producing a thermoplastic polyamide resin foam, which comprises melt-mixing a thermoplastic polyamide resin, dimethyl ether and a cross-linking agent, and extruding and foaming. 3. A method for producing a thermoplastic polyamide resin foam, which comprises melt-mixing a thermoplastic polyamide resin, dimethyl ether, a cross-linking agent, and a metal or a metal compound to perform extrusion foaming.