JPH0480056B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention has excellent heat resistance, flame resistance, and abrasion resistance.
The present invention also relates to a thermoplastic polyimide foam with good secondary processability.

[Conventional technology]

Conventionally, foams made from polymer materials can be roughly divided into (1) foams made from thermoplastic resins such as polystyrene, polyvinyl chloride, polypropylene, polyethylene, etc.; and (2) thermosetting resins. For example, polyurethane resin, phenolic resin, urea,
Foams made from melamine resin, imide resin, etc. have been developed.

The former foam has excellent wear resistance and secondary processability, so it can be used in automobiles, architecture, electronics, etc. by taking advantage of the properties of foam such as heat resistance and light weight.
Although it is widely used in the electrical field, it has problems with heat resistance, especially flame resistance. That is, at high temperatures such as 150° C. or higher, the shape of the foam is significantly deformed and the foam loses its function. In addition, when it comes into contact with flame, the surface of the foam burns, and even if it is made flame retardant with flame retardants, it immediately melts from the part that comes in contact with the flame, and as it flows down, the foam melts one after another, and finally results in most of the foam disappearing. Due to these drawbacks, it cannot be applied to fields where flame resistance is a problem, such as building materials and aircraft materials.

In addition, foams made from the latter thermosetting resin,
For example, even in polyurethane resin foams, the above-mentioned problem regarding flames has not been solved. In addition, foams made from phenolic resin, urea, and melamine resin do not melt in flames and have excellent flame resistance, but they have poor abrasion resistance as foams, easily crack, and There were problems such as the impossibility of processing, and there were restrictions in terms of use.

Foams made from polyimide resins have also been developed. For polyimide resin, after esterifying aromatic carboxylic dianhydride manufactured by International Harvester Co., Ltd. with alcohol, diamines are added to create a prepolymer, and foam A or ether bonding is made based on the prepolymer. Foam B is representative, which is based on polyetherimide (manufactured by General Electric Company, USA, trademark ULTEM 1000, etc.) which is made from tetracarboxylic dianhydride contained in the molecule.

Foam A is an excellent material because its shape does not change particularly at temperatures below 200° C., has excellent heat resistance, and does not melt even when exposed to flame. However, it has insufficient wear resistance and cannot be subjected to secondary processing, so once it is made into a foam, it cannot be processed and used for a variety of purposes, and there are limitations in this respect. It was hot.

Furthermore, although foam B has improved flame resistance, abrasion resistance, and secondary processability, its heat resistance is still not sufficient.

[Problem to be solved by the invention]

The purpose of the present invention is to achieve the advantages of foams made from thermoplastic resins, such as wear resistance and secondary processability.
The object of the present invention is to obtain a new polyimide foam that provides the advantages of foams made from thermosetting resins, flame resistance and heat resistance.

[Means to solve the problem]

As a result of various studies regarding the provision of a new thermoplastic polyimide foam, the present inventors have found that by selecting a specific polyimide, the drawbacks of conventional products as described above can be overcome and extremely superior performance can be achieved. The present invention was completed based on the discovery that a polyimide foam having the following properties can be obtained.

That is, the present invention is a thermoplastic polyimide foam having the following repeating structural unit () and an apparent density of 0.02 to 0.2 g/cc.

(wherein, X is a direct bond, a divalent hydrocarbon group having 1 to 10 carbon atoms, a hexafluorinated isopropylidene group,
A carbonyl group, a thio group, or a sulfonyl group, and R is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a fused polycyclic aromatic group, and an aromatic group. It represents a tetravalent group selected from the group consisting of non-fused polycyclic aromatic groups interconnected directly or through a bridge member. ) The thermoplastic polyimide of the present invention described above comprises an ether diamine represented by the formula (), (In the formula, X is the same as before) A polyimide obtained by reacting with one or more tetracarboxylic dianhydrides shown in the formula (), (In the formula, R is the same as before) It is characterized by using a diamine having an ether bond as a raw material. Specifically, JP-A-61-
143478, 62-68817, 62-86021 (U.S. Patent No.
4847349), etc., and all thermoplastic polyimides produced by these methods can be used in the present invention.

A particularly preferred polyimide for producing the thermoplastic polyimide foam of the present invention can be produced using the following raw materials. That is, as ether diamine, 4,4'-bis[4-(3-aminophenoxy)
phenyl]sulfide, 4,4'-bis(3-aminophenoxy)phenyl]sulfone, 4,4'-bis(3-aminophenoxy)benzophenone,
4,4'-bis(3-aminophenoxy)biphenyl, 2,2-bis[4-(3-aminophenoxy)
phenyl]propane or 2,2-bis[4-
(3-aminophenoxy)phenyl]-1,1,
1,3,3,3-hexafluoropropane, a compound selected from these alone or a mixture of two or more, and as a tetracarboxylic dianhydride, pyromellitic dianhydride,
3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenyl dianhydride These are enyl ether tetracarboxylic dianhydride and p-phenyleneoxydi(4-phthalic acid) dianhydride, and a compound selected from these may be used alone or in a mixture of two or more.

The thermoplastic polyimide that can be used in the present invention described above was dissolved by heating in a mixed solvent of parachlorophenol/phenol (weight ratio 90/10) at a concentration of 0.5 g/100 ml, and then cooled to 35°C and measured. Number viscosity: 0.35 to 0.65 dl/g, preferably 0.40 to
It is in the range of 0.60 dl/g.

The apparent density of the foam made from the above thermoplastic polyimide is preferably in the range of 0.02 to 0.2 g/cc,
If it exceeds 0.2 g/cc, it not only impairs the economic efficiency of weight reduction, but also reduces the advantages of the foam, such as cushioning properties, heat insulation properties, and sound insulation properties.

If it is less than 0.02 g/cc, it is not preferable because not only the mechanical strength of the foam decreases, but also flame resistance, abrasion resistance, and secondary processability deteriorate.

The apparent density in this case is calculated by submerging the foam in a certain amount of water in a graduated cylinder, measuring the volume, and dividing the previously measured weight of the foam by its volume.

Furthermore, among the thermoplastic polyimide foams having an apparent density of 0.02 to 0.2 g/cc, the structure of the foam is particularly important, and the average diameter of the cells is 0.1 to 1 mm, and the proportion of closed cells in the cells is 50%. The above are more preferred.

Note that the average diameter of the bubbles and the ratio of closed cells are calculated as follows.

Average diameter of bubbles: The average diameter of 10 large, medium, and small bubbles extracted from a cross-sectional photograph of the foam in the thickness direction.

Proportion of closed cells: A sample of a specified size (40 x 40 mm) is placed under the water surface, and the pressure is reduced to -400 mmHg for 1 minute. After that, the weight before being left under water and the weight after being left under reduced pressure were measured, and the amount of water (V _W ) sucked into the foam was calculated using the following formula. .

V _F −V _W /V _F ×100 V _F ; Volume of foam To obtain the thermoplastic polyimide foam of the present invention, it is possible to employ a conventional thermoplastic resin foam extrusion device.

Examples of blowing agents include sublimable substances with a boiling point exceeding 200°C, such as phthalic anhydride; chemical blowing agents that decompose at around 200°C, such as trihydrazinotriazine, barium azodicarboxylate, dinitrosopentamethylenetetramine; Boiling point organic compounds such as dichlorotrifluoroethane,
There are hydrates such as monochlorotetrafluoroethane, dichlorofluoromethane, monochlorodifluoromethane, and acetone that dissociate water at temperatures exceeding 200°C, such as oxalic acid dihydrate. Among them, sublimable substances are good.

The amount of blowing agent used is selected depending on the apparent density of the resulting foam. Specifically, in the case of sublimable substances, 0.025 to 100g of thermoplastic polyimide
0.3 mol, in the case of a chemical blowing agent, 0.2 to 10 parts by weight per 100 parts by weight of polyimide, preferably 0.2 to 2 parts by weight, in the case of a low boiling point organic compound, 100 g of polyimide
0.05 to 0.5 mol, or in the case of hydrates, the dissociated water is 0.025 to 0.025 to 100 g of polyimide.
The amount can be adjusted to 0.3 mol and produced by a normal foaming method.

For example, when the blowing agent is solid, the blowing agent and thermoplastic polyimide are both fed through the hopper of the extruder, the cylinder temperature of the extruder is set to 360 to 400°C, the polyimide and the blowing agent are uniformly kneaded, and then gradually The temperature is lowered, the temperature of the nozzle attached to the tip of the extruder is set at 250-370°C, and the extruder is discharged into the atmosphere to form a foam. The foam released from the mouthpiece slit is cooled by air or by a sizing device.
A layer of fine bubbles can also be formed on the surface by cooling to 150-250°C.

When the blowing agent is a liquid, the heated thermoplastic polyimide blowing agent is forced into the extruder from the middle, and then a foam can be produced in the same manner as described above.

Further, the size of the bubbles is controlled by the amount of an inorganic nucleating agent such as talc, silica gel, or a surfactant added. For foams with an average cell diameter of 0.1 to 1 mm, when the blowing agent is a sublimable substance, a low-boiling organic compound, or a hydrate, the above-mentioned nucleating agent is used in an amount of 0.1 to 3 parts by weight per 100 parts by weight of polyimide. When the foaming agent is a chemical foaming agent, it is preferable to use 0.1 to 1 part by weight of the above-mentioned nucleating agent per 100 parts by weight of polyimide for foaming.

Furthermore, the closed cell ratio is adjusted appropriately depending on the temperature of the mixture in the extruder, the cooling conditions after being discharged from the nozzle slit, etc., and is made to be 50% or more.

There is no problem in using the above blowing agents together,
In addition, antistatic agents, colorants, etc. may be added as necessary.

〔Example〕

Further, the present invention will be explained in detail by way of examples.

Example 1 Pyromellitic dianhydride was converted into 4,4-bis(3-
A polyimide powder having a logarithmic viscosity of 0.45 dl/g obtained using aminophenoxy)biphenyl as a raw material was extruded into pellets using an extruder at a cylinder temperature of 400°C. Here, the logarithmic viscosity is in a mixed solvent of parachlorophenol/phenol (weight ratio 90/10).
Concentration 0.5g/100ml - After heating and dissolving with solvent, 35℃
This is the value measured after cooling.

After mixing 0.05 mol of phthalic anhydride with 100 g of the polyimide pellets and 0.7 parts by weight of talc with 100 parts by weight of the polyimide pellets, 30 mmφ
It was supplied from the hopper of the extruder. After melting and kneading the extruder cylinder temperature at 380 to 410°C, the temperature was gradually lowered and the temperature of the nozzle attached to the tip of the extruder was controlled at 355°C. The resin pressure measured by the pressure gauge attached to the inlet of the cap was 110 Kg/cm ² .
The foam was discharged from the die into a sizing mold under reduced pressure to obtain a foam with a thickness of 5 mm and a width of 100 mm. The resulting foam had an apparent density of 0.09 g/cc, an average cell diameter of 0.5 mm, and a closed cell ratio of 78%.

Cut this foam into a sample of 25 mm x 120 mm, place it horizontally on the fulcrum of a 100 mm span, and place 100 g on the sample in the center between the spans.
I put a weight on it. In this state, it was left in a constant temperature bath at a temperature of 200° C. for 1 hour, but there was almost no change, indicating that it was a foam with excellent heat resistance. In addition, even if a 25 mm x 120 mm sample was held horizontally and exposed to indirect flame for 10 seconds with a burner, it would not burn.
There were no drips.

On the other hand, a sample punched into a 100 mm disk was subjected to a Taber abrasion test (according to JIS K-7204). CS-10 was used as the wear wheel, and the test was carried out under a load of 250g.
The amount of wear sample after 1000 consecutive repetitions was 95 mg.

This foam was reheated by leaving it in an atmosphere at 380° C. for 1 minute, and then molded in a U-shaped mold with a clearance of 4 mm between the male and female molds. By setting the mold temperature to 180°C, a good molded product was obtained without any cracks on the surface.

Example 2 Bis[4-(3-aminophenoxy)phenyl]
Polyimide powder obtained from sulfide and pyromellitic dianhydride (logarithmic viscosity 0.46 dl/g)
was pelletized in the same manner as in Example 1.

This polyimide and phthalic anhydride were mixed in an amount of 0.03 mol per 100 g of polyimide pellets, and 0.3 parts by weight of talc was mixed with respect to 100 parts by weight of polyimide pellets.
Extrusion was carried out in the same manner as in Example 1. The resulting foam had an apparent density of 0.15 g/cc, an average cell diameter of 0.8 mm, and a closed cell ratio of 75%.

No deformation was observed in a test at 200°C, indicating excellent heat resistance and no dripping even when exposed to flame. It also showed an excellent Taber abrasion test of 135mg, and even when this foam was laminated with an epoxy adhesive, sufficient strength was obtained without destroying the base material at the interface.

Comparative Example 1 In Example 1, the amount of phthalic anhydride mixed was
A foam was obtained in the same manner except that the amount was changed to 0.4 mol.
The resulting foam had an apparent density of 0.018 g/cc, a cell diameter of 0.5 mm, and a closed cell ratio of 66%.

In addition, in the Taber abrasion test of foam, repeated continuous
When conducted 1000 times, the value was equivalent to 2500 mg. Although this foam was laminated using an epoxy adhesive, the base material at the interface was easily destroyed, and sufficient strength of the laminated board could not be obtained.

Comparative Example 2 A foam was extruded in the same manner as in Example 1, except that the temperature of the nozzle attached to the tip of the extruder was set to 410°C. The apparent density of the foam obtained is
It was 0.11 g/cc, and the closed cell ratio was 45%.
This foam was second-molded in the same manner as in Example 1, but
It broke at the U-shaped corner.

Example 3 0.7 to 100 parts by weight of polyimide used in Example 1
Parts by weight of talc were supplied from a hopper of a 30 mmgφ extruder. Extruder cylinder temperature 380~410
After melting the polyimide at ℃, add acetone from the middle of the extruder to 100g of polyimide.
Mix by press-fitting at a ratio of 0.2 mol, gradually lower the temperature of the resin, and insert the nozzle attached to the tip of the extruder.
The temperature was set to 320℃. The foam was discharged from the die into a sizing mold under reduced pressure to obtain a foam with a thickness of 5 mm and a width of 100 mm. The apparent density of the obtained foam is 0.05g/cc
The average diameter of the bubbles is 0.8 mm, and the closed cell ratio is
It was 62%.

In the heat resistance test shown in Example 1, there was no deformation at 200°C, and there was no dripping even in the combustion test.
The result of the abrasion test was 537 mg, and Example 1
A good molded product was obtained by heat molding in the same manner as above.

Comparative Example 3 Same as Example 3 except that polyetherimide obtained from 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride and m-phenylenediamine was used. A foam with a thickness of 5 mm and a width of 100 mm was obtained. The resulting foam had an apparent density of 0.09 g/cc, an average cell diameter of 0.5 mm, and a closed cell ratio of 85%.

When this foam was cut into pieces of 25 x 120 mm and subjected to the same heat resistance test as in Example 1, it began to sag from the center of the fulcrum.

Example 4 A foam was obtained in the same manner as in Example 1 except that 1.8 parts by weight of trihydrazinotriazine was added to 100 parts by weight of polyimide instead of phthalic anhydride. The apparent density of the foam obtained is
0.15g/cc, average bubble diameter 0.3mm, closed cell ratio
It was 86%.

There was no deformation when this foam was subjected to the heat resistance test shown in Example 1, and no dripping occurred during the combustion test. The result of the abrasion resistance test was 57 mg. This foam was laminated using an epoxy adhesive, but the base material at the interface did not break and sufficient strength of the laminate was obtained.

The foam was reheated by leaving it in an atmosphere at 380° C. for 1 minute, and then molded in a U-shaped mold with a clearance of 4 mm between the male and female molds. By setting the mold temperature to 180°C, a good molded product was obtained without any cracks on the surface.

〔Effect of the invention〕

According to the present invention, it has excellent not only chemical resistance and heat insulation properties, but also heat resistance, flame resistance, and abrasion resistance, as well as excellent secondary processability such as formability, lamination, adhesion, and surface treatment such as painting. A thermoplastic polyimide foam is provided.

Claims (1)

[Claims] 1. A thermoplastic polyimide foam having a repeating structural unit of formula () and having an apparent density of 0.02 to 0.2 g/cc. (wherein, X is a direct bond, a divalent hydrocarbon group having 1 to 10 carbon atoms, a hexafluorinated isopropylidene group,
A carbonyl group, a thio group, or a sulfonyl group, and R is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a fused polycyclic aromatic group, and an aromatic group. It represents a tetravalent group selected from the group consisting of non-fused polycyclic aromatic groups interconnected directly or through a bridge member. 2. The polyimide foam according to claim 1, wherein the foam has an apparent density of 0.02 to 0.2 g/cc, the average diameter of the cells in the foam is 0.1 to 1 mm, and the closed cell ratio in the cells is 50% or more. 3 A thermoplastic polyimide having a repeating unit of general formula (1) is selected from the group consisting of a sublimable substance, a chemical blowing agent that decomposes at around 200°C, a low boiling point organic compound, and a compound that dissociates water at a temperature of 200°C or higher. A method for producing a thermoplastic polyimide foam, which comprises extrusion foaming in the presence of a foaming agent. (wherein, X is a direct bond, a divalent hydrocarbon group having 1 to 10 carbon atoms, a hexafluorinated isopropylidene group,
A carbonyl group, a thio group, or a sulfonyl group, and R is an aliphatic group having 2 or more carbon atoms, a cycloaliphatic group, a monocyclic aromatic group, a fused polycyclic aromatic group, and an aromatic group. It represents a tetravalent group selected from the group consisting of non-fused polycyclic aromatic groups interconnected directly or through a bridge member. )