JP4337976B2 - Method for producing thermoplastic aromatic polyester resin foam - Google Patents

Description

  The present invention relates to a method for producing a thermoplastic aromatic polyester resin foam containing layered silicate and the foam.

  Thermoplastic aromatic polyester resins have excellent properties not found in polyethylene or polystyrene. For example, since polyethylene terephthalate has high rigidity, high shape stability, and excellent heat resistance to withstand 200 ° C., it is used in a wide range of applications such as films, fibers, and molded products. Further, in order to further improve mechanical properties and heat resistance, resin compositions obtained by reinforcing these thermoplastic aromatic polyester resins with inorganic fillers such as glass fibers and talc are also widely known. However, in order to sufficiently satisfy the mechanical properties and heat resistance, it is necessary to add a large amount of an inorganic filler, and there is a problem that surface properties are deteriorated, workability is lowered, and specific gravity is increased.

  In recent years, as a means to solve this problem, resin composite materials with improved mechanical strength, thermal stability, gas barrier properties, etc. have been proposed with a small amount of addition by dispersing layered silicate in the resin at the nano level. Has been.

  In a polyester resin, a method of dispersing a layered silicate treated with quaternary ammonium ions in a polymerization stage is disclosed (Patent Document 1).

Japanese Patent Laid-Open No. 3-62846

  However, this ammonium ion is generally poor in heat resistance, and easily decomposes by heat load during polymerization, causing coloration and deterioration of thermophysical properties.

  In addition, a resin having improved color tone and thermophysical properties by dispersing a layered silicate treated with a quaternary phosphonium ion having high heat resistance instead of the ammonium ion has been reported (Patent Document 2). The method is also based on a polymerization method, which is inferior in terms of simplicity and versatility compared to a melt-kneading method using an extruder.

Japanese Patent Laid-Open No. 11-1605

  On the other hand, in order to impart functions such as weight reduction, heat insulation, and buffering properties of the resin, it has been conventionally performed to use the resin as a foam. However, it is very difficult to extrude and foam a thermoplastic aromatic polyester resin because the melt viscosity is too low. This is because the thermoplastic aromatic polyester-based resin is a crystalline resin, and when heated, it has a characteristic of rapidly melting near the crystalline melting point. For this purpose, even if a thermoplastic aromatic polyester resin is melted in an extruder and a foaming agent is added to the resin and extruded as a foamable melt, the melt is too low or too high in viscosity. Does not readily exhibit a suitable viscosity. Therefore, in order to increase the melt viscosity of the thermoplastic aromatic polyester resin and give a viscosity suitable for foaming, it is necessary to add a crosslinking agent to the thermoplastic aromatic polyester resin.

It is known that a diepoxy compound is effective as a crosslinking agent for increasing the melt viscosity of an aromatic polyester resin (Patent Document 3). Further, pyromellitic anhydride is also known as the crosslinking agent (Patent Document 4).
JP-A-53-24364 JP-A-2-150434

  However, the thermoplastic aromatic polyester resin foam in which the layered silicate is uniformly dispersed in the thermoplastic aromatic polyester resin and the mechanical strength and heat resistance are effectively improved with a small amount of addition. Not provided.

  An object of the present invention is to uniformly disperse a layered silicate in a thermoplastic aromatic polyester-based resin, and at the same time, enable extrusion foaming without breaking bubbles, and have improved mechanical strength and heat resistance. The present invention provides an aromatic polyester resin foam and a method for producing the same.

  As a result of diligent research in order to solve the above-mentioned problems, a suitable amount of a polyfunctional epoxy compound is added to a mixture of a layered silicate and a thermoplastic aromatic polyester resin, and a suitable amount of a blowing agent is added. It has been found that a thermoplastic aromatic polyester resin foam can be obtained in which the layered silicate can be uniformly dispersed in the polyester resin and extrusion foaming is possible, and the mechanical strength and heat resistance are improved.

  This is because some residual anions of the organic agent remain in the organically modified layered silicate depending on the degree of cleaning. If it is a generally known cross-linking agent such as pyromellitic anhydride, the ring is opened by the influence of an anion, decomposition of the thermoplastic aromatic polyester-based resin containing the layered silicate by the carboxyl group at the end, and It is thought to cause crosslinking inhibition.

  However, when a polyfunctional epoxy compound is added to a layered silicate, even if it is a thermoplastic aromatic polyester resin containing a layered silicate in which anions remain, a crosslinking reaction occurs while suppressing the decomposition of the resin. Furthermore, since the thickening effect of the epoxy compound is persistent with respect to the thermoplastic aromatic polyester resin, it is easy to obtain a suitable viscosity for obtaining a good foam during extrusion foaming. Moreover, a polyfunctional epoxy compound can improve the compatibility of a thermoplastic polyester resin and a layered silicate, and can improve the dispersibility of a layered silicate.

  The present invention uses, as an extruder, a mixture in which 0.1 to 10 parts by weight of a layered silicate and 0.1 to 3 parts by weight of a polyfunctional epoxy compound are added to 100 parts by weight of a thermoplastic aromatic polyester resin. This is a production method in which 0.5 to 10 parts by weight of a foaming agent is supplied, melted and kneaded, and the resulting foamable thermoplastic aromatic polyester resin composition is extruded and foamed through a die under low pressure.

  In such a production method, in particular, the layered silicate (A) and the polyfunctional epoxy compound (B) have a B / A of at least 0.03 or more, preferably 0.08 or more, particularly preferably 0.15 or more. It is preferable to add to the thermoplastic aromatic polyester-based resin at a ratio of a weight ratio because foaming is easy.

In particular, when a polyfunctional epoxy compound having an aromatic ring is used as the polyfunctional epoxy compound, the compatibility with the thermoplastic aromatic polyester resin is further improved, and the adhesion with the organically modified layered silicate is good. . As a result, the polyfunctional epoxy compound is intercalated between the organically modified layered silicate and the thermoplastic aromatic polyester resin, thereby improving the compatibility between the thermoplastic aromatic polyester resin and the layered silicate. Enhance and improve dispersibility.
Therefore, it is possible to obtain a foam in which the layered silicate is uniformly dispersed in the resin at the same time as obtaining the melt tension necessary for foaming, and the thermoplastic aromatic polyester resin having improved physical properties such as mechanical strength and heat resistance. A foam is obtained.

  According to the present invention, a thermoplastic aromatic polyester-based foam can be continuously produced by extrusion molding, and a fine-bubble thermoplastic aromatic polyester-based resin foam excellent in mechanical strength and heat resistance can be obtained.

  The thermoplastic aromatic polyester resin used in the present invention is a high molecular weight chain ester obtained by reacting an aromatic dicarboxylic acid with a dihydric alcohol. As the dicarboxylic acid, terephthalic acid is most often used, but isophthalic acid and 2,6-naphthalenedicarboxylic acid can also be used. In addition, diphenyl ether carboxylic acid, diphenyl sulfone dicarboxylic acid, and diphenoxy carboxylic acid can also be used. As the dihydric alcohol, ethylene glycol is mainly used, but trimethylene glycol, tetramethylene glycol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2-bis. -(4-β-hydroxyethoxyphenyl) propane, 4,4′-bis- (β-hydroxyethoxy) diphenylsulfone, diethylene glycol can also be used.

Specific thermoplastic aromatic polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and copolymers of terephthalic acid, isophthalic acid, ethylene glycol, and cyclohexanedimethanol. . Of these thermoplastic aromatic polyester resins, polyethylene terephthalate is most preferable.
Since the thermoplastic aromatic polyester resin is generally a resin that is easily hydrolyzed at a high temperature, it is preferably dried in advance when foamed. It is preferable to use a dehumidifying dryer for drying, and in that case, it may be sufficient to dry at 150 ° C. for 4 hours with dry air having a dew point of −30 ° C. or less.

  The layered silicate used in the present invention is a layered silicate having a property of taking water between layers to swell and having cation exchange properties. The cation exchange capacity of these layered silicates is not particularly limited. Specific examples include smectite clay minerals such as montmorillonite, hectorite, saponite, nontronite, stevensite, beidellite, vermiculite, halloysite, and swellable mica. It may be synthesized. These layered silicates are preferably ion-exchanged with a cationic surfactant, and are preferably organically treated with phosphonium ions from the viewpoint of thermal stability.

  The phosphonium ions used above include tetraethylphosphonium, tetrabutylphosphonium, tetraoctylphosphonium, tributyloctylphosphonium, trimethylhexadecylphosphonium, triethylbenzylphosphonium, tetraphenylphosphonium, ethyltriphenylphosphonium, butyltriphenylphosphonium, octyltriphenyl Examples thereof include phosphonium, hexadecyltriphenylphosphonium, and 2-carboxyethyltriphenylphosphonium. Among these, phosphonium having an aromatic ring, particularly butyltriphenylphosphonium, octyltriphenylphosphonium, hexadecyltriphenylphosphonium, and the like are preferable from the viewpoint of compatibility with the thermoplastic aromatic polyester resin.

The insertion of the organic phosphonium ion between the layers of the layered silicate can be performed by an ion exchange reaction in a polar solvent such as water, methanol, ethanol, propanol, or ethylene glycol. The layered silicate prepared in this way is obtained as an organically modified layered silicate in which organic phosphonium ions are ion-bonded between layers, but is washed with a solvent to remove excess anions remaining outside the layer. It is necessary to purify with. If the amount of residual anion is large, it may affect resin degradation, coloring, and crosslinking reaction, so it is desirable to make it 0% or close to 0%, and at most 2% by weight, that is, 2% by weight or less. Is preferably 1% by weight or less, more preferably 0.5% by weight or less, and most preferably 0.2% by weight or less. The amount of residual anions was quantified by ion chromatography (trade name “IC 4000i” manufactured by DIONEX). As a pretreatment, 2.0 g of organic layered silicate was dissolved in 30 ml of ion exchange water and stirred for 30 minutes, followed by filtration with a 0.45 μm chromatodisc, and the resulting solution was used as a measurement sample.
In addition, it is important that the obtained organically modified layered silicate be sufficiently dried to remove moisture that promotes hydrolysis of the thermoplastic aromatic polyester resin.

  The amount of layered silicate added to 100 parts by weight of the thermoplastic aromatic polyester resin is usually 0.1 to 10 parts by weight, preferably 0.5 to 7 parts by weight, more preferably 1 to 5 parts as the amount of inorganic ash. Parts by weight. If it is less than 0.1 parts by weight, the effect of the cell nucleating agent and the reinforcing effect are poor, and if it exceeds 10 parts by weight, the dispersibility of the layered silicate is lowered and the appearance of the foam surface is poor. The inorganic ash content can be determined from the weight fraction of the residue obtained by burning off the organic content in the thermoplastic aromatic polyester resin and the organically modified layered silicate in an electric furnace at 600 ° C.

  When the above layered silicate and thermoplastic aromatic polyester resin are premixed and used as a masterbatch, it is preferable to use a twin-screw extruder with high shear efficiency, in which case a crosslinking agent is added. May be.

  In the present invention, the addition of the polyfunctional epoxy compound increases the viscosity of the thermoplastic aromatic polyester resin at the time of melting, gives a viscosity suitable for foaming, and increases the compatibility between the thermoplastic polyester resin and the layered silicate. This is to increase it. In particular, when the organic layered silicate is contained in the thermoplastic aromatic polyester resin, it is preferable to use a polyfunctional epoxy compound. Polyfunctional epoxy compounds include diglycidyl phthalate, diglycidyl terephthalate, diglycidyl orthophthalate, diglycidyl hexahydrophthalate, 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. In particular, from the viewpoint of compatibility with a thermoplastic aromatic polyester-based resin or an organically modified layered silicate treated with an organic compound having an aromatic ring, a polyfunctional epoxy compound having an aromatic ring, particularly having an aromatic ring Diglycidyl phthalate, diglycidyl terephthalate, and diglycidyl hexahydrophthalate are preferable, and diglycidyl phthalate is particularly preferable. These may be used alone or in combination of two or more.

  The addition amount of the polyfunctional epoxy compound with respect to the thermoplastic aromatic polyester resin is usually 0.1 to 3 parts by weight, preferably 0.2 to 2.4 parts by weight, more preferably 0.4 to 1.8 parts by weight. Part. If it is less than 0.1 part by weight, a viscosity suitable for foaming cannot be obtained sufficiently, and if it exceeds 3 parts by weight, gelation occurs and foaming becomes difficult.

  A foaming agent is used when foaming the thermoplastic aromatic polyester resin. The foaming agent is roughly classified into a physical foaming agent and a chemical foaming agent, and both can be used in the present invention, but it is preferable to use a physical foaming agent. Physical blowing agents are classified into inert gases, saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, ethers, ketones, etc., but any of them is used in the present invention. can do. Specifically, carbon dioxide gas, inert gas such as nitrogen, propane, normal butane, isobutane, normal pentane, isopentane, neopentane, normal hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2 Saturated aliphatic hydrocarbons such as 1,3-dimethylbutane, saturated fats such as methylcyclopropane, cyclopentane, 1,1-dimethylcyclopropane, cyclohexane, methylcyclopentane, ethylcyclobutane, 1,1,2-trimethylcyclopropane Cyclic hydrocarbons, aromatic hydrocarbons such as benzene, halogenated hydrocarbons such as methyl chloride, 1,1,1,2-tetrafluoroethane, 1,1-difluoroethane, ethers such as dimethyl ether and methyl tertiary butyl ether Can be mentioned. Particularly preferred are carbon dioxide, nitrogen, normal butane and isobutane. These foaming agents may be used alone or in combination.

The amount of the foaming agent added to the thermoplastic aromatic polyester resin is 10 parts by weight or less or 0.5 parts by weight with respect to 100 parts by weight of the melt containing the thermoplastic aromatic polyester resin supplied to the extruder and melt-kneaded. Is preferably 10 to 10 parts by weight, and more preferably 1.0 to 5.0 parts by weight.
In particular, a mixture obtained by adding 0.1 to 10 parts by weight of a layered silicate and 0.1 to 3 parts by weight of a polyfunctional epoxy compound to 100 parts by weight of a thermoplastic aromatic polyester resin is supplied to an extruder. It is preferable to melt-knead and add the foaming agent in the above range with respect to 100 parts by weight of the melt.
Usually, the amount of the foaming agent added to the thermoplastic aromatic polyester resin not containing the layered silicate is 2 to 40 parts by weight, but in the case of the thermoplastic aromatic polyester resin containing the layered silicate, It is as follows.
When the addition amount of the foaming agent is less than 0.5 parts by weight, the expansion ratio is hardly increased, and when it exceeds 10 parts by weight, it seems to be caused by the layered silicate, but the bubbles are broken and good. Foam is difficult to obtain.

  As the extruder used in the method for producing the thermoplastic aromatic polyester resin foam of the present invention, any of a single-screw extruder, a twin-screw extruder, and a tandem extruder can be used. The mold may be a flat mold, a circular mold, or a nozzle mold.

  Further, in the method for producing a thermoplastic aromatic polyester resin foam of the present invention, a method of injecting a foaming agent from the middle of an extruder cylinder and mixing with a molten polyester, or a thermoplastic aromatic polyester resin in advance. Any of the methods of mixing polyester and a foaming agent, which are mixed with a chemical foaming agent and melted in an extruder, can be used. In other words, in the method for producing a foam by the extrusion method of the present application using an extruder, mixing of the foaming agent and dispersion of the layered silicate into the thermoplastic aromatic polyester resin can be performed in one stage in advance. A foam can be manufactured simply and continuously. The thermoplastic aromatic polyester-based resin foam is obtained by being extruded from the extruder under a low pressure by the above method. “Extruding under low pressure” as used herein refers to extruding into a pressure zone below the pressure generated at the tip of the screw (hereinafter referred to as extrusion pressure) when extruding the melt from the extruder. The pressure may be higher or lower than atmospheric pressure, may be atmospheric pressure, and may be lower than the extrusion pressure.

  By using the above extruder, the thermoplastic aromatic polyester resin can be impregnated with the foaming agent, and the foam can be continuously produced.

Hereinafter, the present invention will be described in detail in Examples.
(Preparation of organic layered silicate)
500 g of swellable synthetic mica (trade name: ME100, manufactured by Coop Chemical Co., Ltd.) was dispersed in ion-exchanged water, stirred for 3 hours at room temperature with a stirrer, and allowed to swell for 24 hours. The butyl triphenylphosphonium bromide melt | dissolved in methanol there was added so that it might become 120 meq / 100g with respect to swelling synthetic | combination mica, and it stirred at room temperature for 1 hour. The precipitated solid was separated by filtration and washed with a large amount of ion-exchanged water. The obtained solid was dried at 100 ° C., dried under reduced pressure, and pulverized in a mortar to obtain an organically modified layered silicate. The organic stratified silicate had an inorganic ash content of 76% by weight and a residual anion content of 0.17%.

[Example 1]
Diglycidyl terephthalate which is a polyfunctional epoxy compound as a crosslinking agent (trade name: Denacol EX711, manufactured by Nagase ChemteX Corp.) 0 with respect to 100 parts by weight of polyethylene terephthalate (trade name: SA145, manufactured by Mitsui Chemicals, Inc.) .2 parts by weight of the organosilicate prepared above was blended so that the amount of inorganic ash was 3 parts by weight, and melt mixed at a barrel temperature of 270 ° C. with a twin-screw extruder to prepare a master batch.
Single screw extrusion of a composition in which 100 parts by weight of a masterbatch dried at 150 ° C. for 4 hours with dry air having a dew point of −30 ° C. or less and 0.6 parts by weight of diglycidyl terephthalate (total 0.8 parts by weight) Into the machine (caliber: 40 mm, L / D: 30), and liquefied butane gas as a foaming agent is injected from the middle of the extruder cylinder at a ratio of 3.0 parts by weight with respect to 100 parts of the melt. Extrusion foaming was performed from the mold at a discharge rate of 5 kg / hr.
The expansion ratio of the obtained cylindrical foam was 8 times.

(Measurement of heat-resistant temperature)
Next, this cylindrical foam is cut at a length of 50 mm, the length and diameter of the sample are measured, and then the sample is placed in a thermostatic bath for 30 minutes. The temperature in the thermostatic chamber is 9 points from 80 ° C. to 120 ° C. at intervals of 5 ° C., and the number of samples is n = 3 at each temperature. After 30 minutes, the sample is taken out from the thermostat, and after 10 minutes, the length and diameter of the sample are measured. As a result of the measurement, if the dimensional change in both directions was within 1%, it was accepted, and the highest temperature where the dimensional change in both directions was within 1% was defined as the heat resistant temperature.
As a result, the heat resistant temperature of the foam of Example 1 was 115 ° C. In addition, the following each Example and each comparative example performed the same measurement.

[Example 2]
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to diglycidyl phthalate (polyfunctional epoxy compound).

[Example 3]
The same procedure as in Example 1 was performed except that the crosslinking agent was changed to neopentyl glycol diglycidyl ether (polyfunctional epoxy compound).

[Example 4]
The same procedure as in Example 1 was carried out except that the weight ratio B / A between the organic layered silicate (A) 5 parts by weight and the polyfunctional epoxy compound (B) 1.2 parts by weight was 0.24.

[Example 5]
The same as Example 1 except that the weight ratio B / A between the organic layered silicate (A) is 2.0 parts by weight and the polyfunctional epoxy compound (B) is 0.4 parts by weight is 0.2. did.

[Example 6]
The same procedure as in Example 1 was performed except that liquefied butane gas was injected at a ratio of 6.0 parts by weight with respect to 100 parts of the melt.

[Example 7]
The same operation as in Example 1 was performed except that liquefied butane gas was injected at a ratio of 0.5 part by weight with respect to 100 parts of the melt.

[Comparative Example 1]
Except having changed the organosilicate to normal synthetic mica, it carried out similarly to Example 1, the foaming ratio of the obtained foam was 8 times, and the heat-resistant temperature was 100 degreeC.

[Comparative Example 2]
The same procedure as in Example 1 was carried out except that the crosslinking agent was changed to pyromellitic anhydride. As a result, the melt tension did not increase and a good foam was not obtained.

[Comparative Example 3]
The same procedure as in Example 1 was performed except that 0.05 part by weight of the polyfunctional epoxy compound and the weight ratio B / A of the organically modified layered silicate (A) to the polyfunctional epoxy compound (B) were set to 0.02. .

[Comparative Example 4]
The same operation as in Example 1 was performed except that liquefied butane gas was injected at a ratio of 13.0 parts by weight with respect to 100 parts of the melt.

[Comparative Example 5]
The same operation as in Example 1 was conducted except that the polyfunctional epoxy compound was changed to 3.2 parts by weight.

  These results are summarized in Table 1. In the table, the blending amount is expressed in parts by weight.

From Table 1, as compared with Comparative Example 1 using synthetic mica, the aromatic polyester resin foams of the examples can continuously produce thermoplastic aromatic polyester foams by extrusion molding. As a result, a fine-bubble thermoplastic aromatic polyester resin foam excellent in mechanical strength and heat resistance can be obtained.

Claims (5)

For 100 parts by weight of the thermoplastic aromatic polyester resin,
0.1 to 10 parts by weight of an organically modified layered silicate in which anions remain up to 2% by weight;
A mixture added with 0.1 to 3 parts by weight of a polyfunctional epoxy compound is supplied to an extruder and melt-kneaded,
0.5 to 10 parts by weight of a foaming agent is injected into 100 parts by weight of the melt,
A method for producing a thermoplastic aromatic polyester-based resin foam, in which the obtained foamable thermoplastic aromatic polyester-based resin composition is extruded and foamed through a die under low pressure ,
A mixture in which the organically modified layered silicate (A) and the polyfunctional epoxy compound (B) are added to the thermoplastic aromatic polyester resin at a ratio where B / A is at least 0.03 or more. A method for producing a thermoplastic aromatic polyester resin foam, characterized by being supplied to an extruder and melt-kneaded . A mixture in which the organically modified layered silicate (A) and the polyfunctional epoxy compound (B) are added to the thermoplastic aromatic polyester resin in a ratio where B / A is at least 0.15 or more. The method for producing a thermoplastic aromatic polyester resin foam according to claim 1, wherein the thermoplastic aromatic polyester resin foam is supplied to an extruder and melt-kneaded.   The method for producing a thermoplastic aromatic polyester resin foam according to claim 1, wherein the polyfunctional epoxy compound has at least one aromatic ring. The thermoplastic aromatic polyester resin foam according to any one of claims 1 to 3, wherein the organically modified layered silicate is a layered silicate in which an organic phosphonium ion is inserted between layers. Manufacturing method. A thermoplastic aromatic polyester resin foam produced by the production method according to any one of claims 1 to 4.