JPH11166067A - Thermoplastic polyester-based resin foamed product and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject foamed product having a high foaming ratio, having uniform and fine pores and capable of exhibiting an excellent mechanical strength, etc., by using a thermoplastic polyester-based resin having a shoulder in the high mol.wt. region of a mol.wt. distribution and having a high melting viscoelasticity. SOLUTION: This foamed product is obtained by extruding and foaming a thermoplastic polyester-based resin (preferably a branched aromatic polyester- based resin) having a Z-average mol.wt. (hereinafter referred to as Mz) of >=1×10<6> and a branching parameter (g) of <=0.8. The Mz is measured by dissolving a thermoplastic polyester-based resin in a suitable solvent, injecting the obtained solution into a high performance liquid chromatograph to subject the solution to a gel permeation chromatography, and subsequently determining the Mz from the obtained mol.wt. distribution. The (g) is determined from the ratio of the square of the inertial radius of a branched polyester resin in a diluted solution to that of a linear polyester resin having the same mol.wt. in the diluted solution. The foamed product is useful for heat-resistant containers, shock-absorbing package materials and so on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermoplastic polyester resin foam and a method for producing the same. More specifically, it has a high expansion ratio, has uniform and fine cells, and is excellent in mechanical strength, heat resistance, cushioning property, heat insulation property and chemical resistance. For example, it is preferably used for heat-resistant containers and cushioning packaging materials. The present invention relates to a thermoplastic polyester resin foam and a method for producing the same.

[0002]

2. Description of the Related Art Linear aromatic polyester resins such as polyethylene terephthalate have excellent mechanical properties, heat resistance, chemical resistance and dimensional stability. And has a wide range of uses such as fibers. However, when the linear aromatic polyester resin is used for extrusion foaming, the elasticity at the time of melting is insufficient, and the viscosity is low. There is a problem that it is extremely difficult to obtain a foam.

As a method for solving the above problem, a method of mixing a compound having two or more acid anhydride groups in one molecule into a linear aromatic polyester resin when the resin is subjected to extrusion foam molding (particularly, the method). Japanese Patent Publication No. H5-15736) and a method in which the same acid anhydride as described above is combined with a specific metal compound and mixed with the resin (Japanese Patent Publication No. H5-47575). In addition to the above method, the molecular weight distribution (weight average molecular weight / number average molecular weight) is 5.0 to 21.0.
A method of extruding and foaming the above polyester has been proposed (JP-A-7-33899).

[0004]

According to the method of the prior art described above, the melt viscosity required for extrusion foaming can be increased, but the melt viscosity decreases remarkably when kneading is continued, and the melt viscosity decreases. There is a problem that the resin is not stable, the molten resin and the foaming agent are not uniformly dispersed at the time of extrusion foaming, and an extruded foam cannot be manufactured in a stable state.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention has a high expansion ratio, uniform and fine cells, mechanical strength, heat resistance, cushioning property, heat insulation property and chemical resistance. The present invention has been made in order to provide a foam having excellent heat resistance and a method for stably producing the foam.

That is, according to the present invention, the Z-average molecular weight is 1 ×
In at ¹⁰⁶ or higher, branching parameter a thermoplastic polyester resin foam comprising by extrusion foaming of thermoplastic polyester resin is 0.8 or less (claim 1) and Z average molecular weight of 1 × 10 ⁶ or more, the branch The present invention relates to a method for producing a thermoplastic polyester resin foam obtained by extruding a thermoplastic polyester resin having a parameter of 0.8 or less (claim 2).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The major feature of the present invention is that a thermoplastic polyester resin having a specific Z-average molecular weight (hereinafter referred to as Mz) and a specific branching parameter g is used.

The inventors of the present invention have conducted intensive studies in view of the above prior art, and as a result, have found that a thermoplastic polyester resin extruded having a uniform closed cell structure of fine cells and a high closed cell ratio and high expansion ratio. In order to obtain a foam in a stable manner, it is not sufficient to use a resin having a large molecular weight distribution of about 5.0 to 21.0 as in the prior art, and it is not sufficient. It has been clarified that it is necessary to use a thermoplastic polyester resin having a shoulder and a property of exhibiting high melt viscoelasticity.

Accordingly, the present inventors have found Mz as an element for characterizing the shoulder in the high molecular weight region of the molecular weight distribution curve, and a branching parameter g as an element for characterizing the development of high melt viscoelasticity. . In the present invention, since a thermoplastic polyester resin having a specific Mz and a specific branching parameter g is used, in addition to the excellent mechanical properties of the thermoplastic polyester resin itself, heat resistance, etc., it is uniform. A thermoplastic polyester resin foam having fine cells, a high closed cell ratio and a high expansion ratio can be stably obtained.

The thermoplastic polyester resin foam of the present invention is obtained by extrusion foaming a thermoplastic polyester resin having a Mz of 1 × 10 ⁶ or more and a branching parameter g of 0.8 or less.

The Mz is 1 × 10 ⁶ or more, preferably 1.05 × 10 ⁶ or more, and more preferably 1.1 × 10 ^6.
1.0 × 10 ⁷ or less, and further 8.0 × 1
0 to ^6, particularly preferably at 6.0 × 10 ⁶ or less. If the Mz is less than 1.0 × 10 ⁶ , the melt viscoelasticity suitable for extrusion foaming cannot be obtained,
If it exceeds × 10 ⁷ , the melt viscosity of the resin may be too high, and extrusion foaming may be difficult.

The Mz can be measured by the following method.

A solution obtained by dissolving a thermoplastic polyester resin in an appropriate solvent is injected into a high performance liquid chromatograph to perform gel permeation chromatography (GPC). Then, Mz is determined from the obtained molecular weight distribution curve. The large Mz thus obtained is an indicator that a large amount of high molecular weight components are present, and an increase in melt viscoelasticity can be expected.

The branch parameter g is an index of the number of branch points per molecule of the polymer having a long-chain branched structure.

The branch parameter g is 0.8 or less, preferably 0.75 or less, more preferably 0.7 or less.
It is preferably at least 2, more preferably at least 0.3, particularly preferably at least 0.35. If the branch parameter g exceeds 0.8, untangling that is difficult to unravel does not occur, and stable development of melt viscoelasticity during extrusion foam molding cannot be maintained. If the ratio is less than 0.2, gelation tends to occur, and stable development of melt viscoelasticity tends not to be expected.

The branching parameter g is defined as follows from the ratio of the square of the radius of gyration of a dilute solution of a branched polyester resin and a linear polyester resin having the same molecular weight. g = (square of radius of inertia of branched polyester resin) /
(Square of radius of inertia of linear polyester resin)

The branching parameter g of the linear polyester resin is 1, and the smaller the branching parameter g is, the more the branching parameter g becomes 1.
The number of branch points per molecule is large.

Due to the long-chain branched structure, entanglement that is difficult to unravel is generated, which stably develops the high melt viscoelasticity of the resin, and is resistant to the pressure of the foaming agent during extrusion foam molding, so that it is difficult to break bubbles. And a suitable foam. That is, a good foam can be stably obtained by using a branched polyester resin having a large number of branch points.

The branch parameter g can be measured by the following method.

A solution obtained by dissolving a linear polyester resin in an appropriate solvent is injected into a GPC device equipped with a polygonal laser light scattering device (MALLS) and a refractometer (RI) to obtain a relationship curve between molecular weight and radius of gyration. . This curve is

[0021]

(Equation 1)

And a and b are obtained. here,

[0023]

(Equation 2)

Is the radius of gyration, M is the molecular weight, and a and b are constants. Similarly, a solution obtained by dissolving a branched polyester resin in an appropriate solvent is used for a polygonal laser light scattering device (MALL).
S) and injected into a GPC device equipped with a refractometer (RI) to obtain a relationship curve between molecular weight and radius of gyration. The branching parameter g of the component having a molecular weight M of the branched polyester resin is determined according to the above equation,

[0025]

(Equation 3)

Is calculated. The branch parameter at the molecular weight corresponding to the peak position of the MALLS chromatogram is defined as the branch parameter g of the sample.

The intrinsic viscosity of the thermoplastic polyester resin (the value measured at 23 ° C. in a mixed solvent of phenol and tetrachloroethane (phenol / tetrachloroethane (volume ratio) = 1/1), hereinafter the same) In order to sufficiently exhibit the effect of formation, the content is usually 0.4 dl / g or more, preferably 0.5 dl / g or more, and 1.1 dl / g or less in order to easily perform melt molding. More preferably, it is 1.0 dl / g or less.

The thermoplastic polyester resin of the above-mentioned thermoplastic polyester resin may include not only ordinary thermoplastic polyester but also those having an ether, imide, amide bond or the like in a molecular chain. In that case,
The number is preferably 1 to 10 units per 100 unit ester bonds so as not to significantly reduce the heat resistance characteristic of polyester.

As the thermoplastic polyester resin, for example, a branched aromatic polyester resin can be preferably used.

Examples of the branched aromatic polyester resin include terephthalic acid units as main components.
It can be obtained by polymerizing a divalent carboxylic acid, a dihydric alcohol having an ethylene glycol unit as a main component, and a branch-forming compound having at least three ester-forming groups.

The term "terephthalic acid as the main component" means that the divalent carboxylic acid contains at least 70% (% by weight, hereinafter the same) of terephthalic acid (including dialkyl terephthalate such as dimethyl terephthalate). The term "ethylene glycol as the main component" means that the dihydric alcohol contains 70% or more of ethylene glycol. When terephthalic acid and ethylene glycol are each less than 70%, the foam of the present invention provides a balance utilizing the excellent mechanical properties, heat resistance, chemical resistance, and dimensional stability of thermoplastic polyesters such as polyethylene terephthalate. The effect of easily giving good physical properties tends to decrease.

The amount of the branching compound used is as follows:
It is preferable to adjust the amount of the unit derived from the branch-forming compound to be 0.01 to 5 mol per 100 mol of the total number of divalent carboxylic acid units in the objective branched aromatic polyester resin. . The amount of the branch-forming compound used is preferably 0.1 mol or more, more preferably 0.5 mol or more, per 100 mol of the total number of divalent carboxylic acid units in order to sufficiently exhibit the effect of forming a branch bond. It is more preferably at least 3 mol, and in order to make it easier to control the degree of polymerization of the branched aromatic polyester-based resin, it is at most 3 mol relative to 100 mol of the total number of divalent carboxylic acid units. Is more preferable.

Specific examples of the divalent carboxylic acid include, in addition to terephthalic acid, dialkyl terephthalate such as dimethyl terephthalate, dialkyl terephthalate such as isophthalic acid and dimethyl isophthalate, and the like.
Naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, and the like. These may be used alone or in combination of two or more.

Specific examples of the dihydric alcohol include, in addition to ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol,
2-bis (4-β-hydroxyethoxyphenyl) propane, 4,4′-bis (β-hydroxyethoxy) diphenyl sulfone and the like. These may be used alone or in combination of two or more.

Specific examples of the branch-forming compound include:
For example, tri- or tetracarboxylic acids such as trimellitic acid, pyromellitic acid, naphthalene tricarboxylic acid, and naphthalene tetracarboxylic acid and lower alkyl (alkyl having 1 to 6 carbon atoms) esters thereof, glycerin,
And tri- or tetraols such as trimethylolpropane, trimethylolethane, and pentaerythritol, dihydroxycarboxylic acid, hydroxydicarboxylic acid, and derivatives thereof. These may be used alone or in combination of two or more. Among the branch-forming compounds, pyromellitic acid and glycerin are preferable because the degree of polymerization of the branched aromatic polyester resin can be easily controlled.

Specific examples of the branched aromatic polyester-based resin include polyethylene terephthalate and polybutylene terephthalate using trimellitic acid and pyromellitic acid as branch-forming compounds, and glycerin, trimethylo-butyl branch-generating compounds. Examples include polyethylene terephthalate and polybutylene terephthalate using lupropane and pentaerythritol.

The branched aromatic polyester resin preferably has an intrinsic viscosity of 0.4 to 1.1 dl / g.

The branched aromatic polyester resin is, for example, a linear aromatic polyester obtained by polycondensing a dihydric carboxylic acid having terephthalic acid as a main component and a dihydric alcohol having ethylene glycol as a main component. It can also be obtained by copolymerizing a group-forming polyester-based resin with a branch-forming compound having at least three ester-forming groups.

In order to adjust the content of the unit from the branch-forming compound in the branched aromatic polyester resin to a desired degree according to the purpose, the branched aromatic polyester resin may be used. A group polyester resin may be contained.

The content of the linear aromatic polyester-based resin in the branched aromatic polyester-based resin is determined by the total amount of the divalent carboxylic acid units contained in the branched aromatic polyester-based resin and the linear aromatic polyester-based resin. It may be adjusted in consideration of the number of moles of the unit from the branch-forming compound with respect to the number of moles. For example, in order to further improve the stability of the melt elasticity of a branched aromatic polyester resin containing a linear aromatic polyester resin, it is necessary to prepare the branched aromatic polyester resin based on 100 moles of the divalent carboxylic acid unit. It is preferable to adjust the amount of the linear aromatic polyester-based resin so that the unit from the hydrophilic compound is at least 0.01 mol, more preferably at least 0.1 mol. Further, in order to make it difficult for the gelation of the branched aromatic polyester resin containing the linear aromatic polyester resin to progress, the branched aromatic polyester resin is preferably branched with respect to 100 moles in total of the aromatic divalent carboxylic acid units. It is preferable to adjust the amount of the linear aromatic polyester-based resin so that the amount of the productive component unit is 5 mol or less, and more preferably 3 mol or less.

The above-mentioned linear aromatic polyester resin is
It can be obtained by polycondensing a polyvalent carboxylic acid component and a dihydric alcohol component.

The linear aromatic polyester resin has a number average molecular weight of 10,000 to 50,000 and an intrinsic viscosity of 0.4.
It is preferably about 1.1 dl / g.

The linear aromatic polyester resin can be obtained by a known method of melt polycondensation or solid phase polymerization used for producing a polyester resin. In general, high molecular weight compounds tend not to be obtained by the melt polycondensation method, so there is a case where the molecular weight is increased by solid-phase polymerization. Tend to be high.

On the other hand, in the present invention, a polyester resin having a relatively small molecular weight obtained by melt polycondensation can be used. Therefore, when simplicity and low cost are required, the polyester resin obtained by melt polycondensation can be used. In some cases, it is preferable to use a resin.

Examples of the divalent carboxylic acid component include the same compounds as those used for obtaining the branched aromatic polyester resin. These may be used alone or in combination of two or more.

Further, as the dihydric alcohol component,
For example, the same compounds as those used for obtaining the branched aromatic polyester resin can be used. These may be used alone or in combination of two or more.

Specific examples of the linear aromatic polyester resin include polyethylene terephthalate, polybutylene terephthalate, poly-1,4-cyclohexane dimethylene terephthalate, polyethylene isophthalate,
Examples include polybutylene isophthalate and polyethylene naphthalate. These may be used alone or in combination of two or more. Among them, polyethylene terephthalate, polybutylene terephthalate, and poly-1,4-cyclohexane dimethylene terephthalate are preferred from the viewpoint of high industrial value and ease of handling.

Examples of the thermoplastic polyester resin other than those described above include, for example, the branched aromatic polyester resin containing a compound having two or more acid anhydride groups in one molecule, A branched aromatic polyester resin containing a compound having two or more oxazoline groups in one molecule, a branched aromatic polyester resin containing a compound having two or more epoxy groups in one molecule, or the like is also used. be able to.

The compound having two or more acid anhydride groups, oxazoline groups, epoxy groups and the like in one molecule functions so that the branched aromatic polyester resin has a more complicated branched structure. . For example, 2 in one molecule
In the case of a compound having two or more acid anhydride groups, a hydroxyl group present in the molecular chain of the branched aromatic polyester-based resin and a compound having two or more acid anhydride groups in one molecule are included. It is thought to be due to binding by reaction with the acid anhydride present. Therefore, when a compound having two or more acid anhydride groups in one molecule is used, the Mz of the branched aromatic polyester-based resin and the thermoplastic polyester-based resin comprising the compound must be further increased. Can be.

The compound having two or more acid anhydride groups in one molecule is not particularly limited, but is considered in view of the fact that the reactivity between a hydroxyl group and an acid anhydride group as described above is good. Then, pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, ethylene glycol-bis (anhydrotrimellitate), glycerol-tris ( Anhydrotrimellitate) and the like, and these may be used alone.
It may be used in combination of more than one kind. Of these, pyromellitic dianhydride and benzophenonetetracarboxylic dianhydride are preferred because they are easy to handle.

The amount of the compound having two or more acid anhydride groups in one molecule depends on the amount of the branched aromatic polyester resin.
Further, in order to impart melt elasticity suitable for extrusion foaming, it is preferably at least 0.1 part, and more preferably at least 0.2 part based on 100 parts of the branched aromatic polyester resin. Further, in order to eliminate the possibility that the gelling of the branched aromatic polyester resin proceeds excessively and make it difficult to extrude and foam in a good state, 5 parts or less per 100 parts of the branched aromatic polyester resin, Is preferably 2 parts or less.

The thermoplastic polyester resin foam of the present invention is obtained by melting a thermoplastic polyester resin having Mz of 1 × 10 ⁶ or more and a branching parameter g of 0.8 or less in an extruder. , A foaming agent, and the obtained foamed composition is extruded to a low pressure region and foamed.

As the foaming agent, any of a liquid volatile foaming agent which is vaporized by heating and a gaseous foaming agent which can be dissolved in a resin under pressure can be used.

Specific examples of the liquid volatile foaming agent include, for example, saturated aliphatic hydrocarbons such as butane, pentane and hexane, saturated alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene and xylene. Examples include hydrogen, halogenated hydrocarbons such as methyl chloride, and fluorochloro-substituted hydrocarbons such as Freon (trade name, manufactured by DuPont).

Specific examples of the gas type foaming agent include nitrogen and carbon dioxide.

The foaming agents may be used alone or in combination of two or more.

The foaming agent can be used without particular limitation as long as it has the property of being vaporized or expanded by heating.

The amount of the foaming agent used is not particularly limited, and may be appropriately adjusted according to the desired expansion ratio of the obtained foam. Usually, the amount of the foaming agent used is preferably about 1 to 30 parts with respect to 100 parts (parts by weight, hereinafter the same) of the thermoplastic polyester resin.

Further, in the present invention, a stabilizer, a nucleating agent such as talc, a pigment, a filler, a flame retardant, an antistatic agent and the like may be used as required.

When producing a thermoplastic polyester resin foam using the thermoplastic polyester resin,
For example, a single-screw extruder, a multi-screw extruder, a tandem-type extruder, or the like can be used.

From the viewpoint that the properties of the obtained foam can be easily adjusted, extrusion foaming is performed using a tandem type extruder in which a twin-screw extruder is used as a first-stage extruder and a single-screw extruder is used as a second-stage extruder. Is preferably performed.

In this method, the thermoplastic polyester resin and other necessary additives are preferably melt-mixed in a first-stage extruder.

The method of adding a stabilizer, a nucleating agent such as talc, a pigment, a filler, a flame retardant, an antistatic agent and the like to the thermoplastic polyester resin at the time of carrying out the extrusion foaming molding is carried out in advance by melting before melting. A method in which the above-mentioned additives and the like are mixed with the above-mentioned thermoplastic polyester-based resin and supplied to a twin-screw extruder from a quantitative feeder, or the thermoplastic polyester-based resin and a stabilizer, a nucleating agent such as talc, a pigment, and a filler. , A flame retardant, an antistatic agent, etc., from separate quantitative feeders to a twin-screw extruder.

The foaming agent can be injected from a first-stage extruder, a conveying pipe connecting the first-stage extruder and the second-stage extruder, or any part of the second-stage extruder. In order to improve the dispersion and mixing of the foaming agent, it is preferable to inject the foaming agent from the first extruder.

The foamable composition containing a foaming agent is transferred to a second-stage extruder through a transport pipe, and while continuing to be kneaded by the second-stage extruder, the resin structure and the temperature are adjusted so as to be suitable for forming a foam. And the pressure is maintained. A die is attached to the tip of the second-stage extruder, and the foamable resin composition is extruded from the die into a low-pressure region. The extruded foamable resin composition is foamed by moving from the inside of the extruder under high pressure to a low pressure region to be foamed.

The twin-screw extruder preferably has a screw configuration in which a kneading disc or an element for kneading is arranged.

Although the kneading disk or the kneading element can be arranged at a plurality of positions, in order to stably inject the foaming agent, at least one kneading disk or a kneading element is provided at a portion upstream of the foaming agent injection port in the extrusion direction. It is preferable to arrange them in places.

By kneading with a twin-screw extruder having such a screw configuration, a sufficient kneading force can be applied to the thermoplastic polyester resin and additives, and the molten composition can be further homogenized. In addition, the injection amount and the dispersion state of the foaming agent can be stabilized.

Further, when particles such as talc are used as the cell regulator, the particles can be uniformly mixed and dispersed by using a twin-screw extruder, and the particles can be converted into fine particles without agglomeration. Since it is present, the function as a bubble regulator can be effectively exhibited.

The foam produced by the above method has an apparent density of not more than 500 kg / m ³ ,
It is preferably at most kg / m ³ . Since the apparent density is 500 kg / m ³ or less, it is possible to realize a lightweight property which is an advantage of the foam.

Further, by setting the closed cell ratio of the bubbles existing in the foam to 70% or more, preferably 80% or more, the heat insulating property of the obtained foam can be enhanced.

Further, the size of the bubbles in the foam is 500 μm or less in diameter, and 10 μm or less in 300 μm or less.
It is preferable that this is the case. By setting the size of the cells in the foam within the above range, the heat insulation of the obtained foam can be enhanced.

The expansion ratio is 3 to 30 times, and more preferably 5 to 30 times.
~ 15 times is preferred. When the magnification is less than 3 times, the lightness tends to decrease, and when the magnification is 30 times or more, the strength of the foam tends to decrease.

The thermoplastic polyester resin foam thus obtained has a beautiful appearance and a uniform and fine cell structure, and is preferably used, for example, in heat-resistant containers, heat-insulated containers, buffer packaging materials and the like.

[0075]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The z-average molecular weight of the resin, the branching parameter g, the apparent density of the foam, the size of the cells, the closed cell ratio, the melt viscosity of the resin, and the melt tension were measured by the following methods.

(Z-average molecular weight (Mz)) The thermoplastic polyester-based resin pellets are freeze-pulverized and then dried with a vacuum dryer.
After drying at 0 ° C. for 4 hours, 5 mg of the resin sample was added to hexafluoroisopropanol / chloroform (each 0.1 m).
l) After dissolving with a solution, further add a total of 1 with chloroform.
Diluted to 0 ml.

The diluted sample was subjected to GPC to obtain Mz
Was measured.

The GPC measurement conditions are shown below. Measuring device: GPC manufactured by Japan Waters Limited
(Type 600 HPLC) Complete column: Shodex (K-8, manufactured by Showa Denko KK)
00P, K-802 (2), K-80M (2) Column temperature: 40 ° C Solvent: chloroform (for liquid chromatography) Flow rate: 1.0 ml / min Detector: UV 254 nm Injection amount: 0. 05ml

(Branching parameter g) After the resin pellets were freeze-pulverized, an eluent was added so as to have a concentration of 0.2%, and the mixture was filtered with a filter having an average pore diameter of 0.5 μm to obtain a sample. First, a linear polyester resin (Kanebo Co., Ltd.)
Product name: Bellpet EFS-7, Kuraray Co., Ltd.
(Trade name: Clappet KZ-700R) was injected into GPC to obtain a relationship curve between the radius of gyration of the linear polyester resin and the absolute molecular weight. This curve is calculated by the least square method.

[0081]

(Equation 4)

Then, a and b were obtained. In the formula

[0083]

(Equation 5)

Is the radius of gyration, M is the absolute molecular weight, and a and b are constants. Next, a sample prepared from the obtained branched polyester resin was injected into GPC, and a relation curve between the radius of gyration of the molecule and the absolute molecular weight was obtained.

The branching parameter g at the molecular weight M _p corresponding to the position of the peak in the MALLS chromatogram of the branched polyester resin is represented by

[0086]

(Equation 6)

Was calculated.

The GPC measurement conditions are shown below. Measurement device: Tosoh Corporation, CCP & 8020 system Column: Showa Denko Corporation, Shodex HFIP-800P, HFIP 805, HFIP-803 Column temperature: 40 ° C. Eluent: 5 mM sodium trifluoroacetate / hexafluoroisopropanol flow Speed: 1 ml / min Detector: RI detector RI-8020 MALLS detector manufactured by Tosoh Corporation Wyatt Technology DAWN DSP Injection volume: 500 μl

(Apparent Density) The apparent density was measured according to the method A (measurement method by underwater displacement method) of JIS K 7112 “Measurement method of plastic density and specific gravity”.

(Size of Bubble) The cross-section of the foam was measured for the number average cell diameter in the width direction of the foam using a transmission electron microscope (Hitachi Scanning Electron Microscope S-450) according to ASTM D 3576. did.

(Closed cell rate) Using a multi-pycnometer (manufactured by Yuasa Ionics Co., Ltd.), ASTM D285
The measurement was performed according to the method described in No. 6.

(Melt viscosity, melt tension)
It refers to a viscosity measured in accordance with IS K 7199 "Testing method for flow characteristics of thermoplastics using capillary rheometer". The melt viscosity of the thermoplastic polyester resin obtained without injection of a foaming agent during extrusion foam molding was measured under the following conditions.

Measurement device: Capillary rheometer (Capillograph manufactured by Toyo Seiki Co., Ltd.) Measurement resin amount: 20 g Measurement temperature: 280 ° C. Measurement shear rate: 122 sec ⁻¹ orifice: 1 × 10 mm, entrance angle 90 °

The melt tension of the thermoplastic polyester resin was determined by measuring the stress when the filamentous resin extruded from the capillary rheometer as in the measurement of the melt viscosity was pulled out, and the pulling speed was set at 11.1 mm / sec.
The stress at the time when the filament was broken was increased by ² to obtain the stress.

(Overall evaluation) Apparent density, bubble size,
Regarding the evaluation items of the closed cell rate, there are four grades (◎, ○, △,
×) was evaluated. The evaluation criteria are shown below. ◎: Apparent density is less than 200 kg / m ³ , and change in apparent density is 20 minutes and 80 minutes after the start of extrusion foaming.
Less than Kg / m ^{3 The} bubble diameter is less than 200 μm, and the change in the bubble diameter after 20 minutes and 80 minutes from the start of extrusion foaming is less than 25 μm The closed cell ratio is 85% or more, and the time after 20 minutes from the start of extrusion foaming is 80 minutes Subsequent changes in the closed cell rate satisfy all three evaluation items of less than 5%. ：: The apparent density is less than 300 kg / m ³ , and the change in apparent density is 40 minutes after 20 minutes and 80 minutes from the start of extrusion foaming.
Less than Kg / m ^{3 The} bubble diameter is less than 400 μm, and the change in the bubble diameter after 20 minutes and 80 minutes from the start of extrusion foaming is less than 50 μm. Subsequent changes in the closed cell rate satisfy all three evaluation items of less than 8%. Δ: The apparent density was less than 500 kg / m ³ , and the change in the apparent density was 20 minutes and 80 minutes after the start of extrusion foaming.
Less than Kg / m ^{3 The} cell diameter is less than 500 μm, and the change in cell diameter after 20 minutes and 80 minutes from the start of extrusion foaming is less than 10 μm The closed cell ratio is 80% or more, and the time after 20 minutes from the start of extrusion foaming is 80 minutes Subsequent change in the closed cell rate satisfies all three evaluation items of less than 10%. ×: Other than the above-mentioned ◎, ○, Δ.

Example 1 An ethylene terephthalate oligomer prepared by preparing 15.0 mol of dimethyl terephthalate and 30.0 mol of ethylene glycol using antimony trioxide as a catalyst and glycerin 0.1 g were prepared.
45 moles and melt kneading at 280 ° C. under a reduced pressure of 1 mmHg for 20 minutes, and a branched aromatic polyester-based resin containing 3 moles of glycerin unit with respect to 100 moles of terephthalic acid unit (intrinsic viscosity: 0. 73 dl / g).

The obtained branched aromatic polyester resin and a polyethylene terephthalate resin (intrinsic viscosity: 0.65 dl / g), which is a linear aromatic polyester resin, are mixed in a dehumidifying dryer set at 140 ° C. After drying for a period of time, the weight ratio of the branched aromatic polyester resin to the polyethylene terephthalate resin is adjusted to 1: 2 (at this time, the total number of moles of terephthalic acid units from the two resins) The glycerin unit is 1 mol per 100 mol), and this is co-rotating meshing twin-screw extruder with a cylinder diameter of 30 mm (Ikegai Iron Works Co., Ltd. PCM-30)
(Extruder) from a vibrating quantitative feeder, and extruded under the following conditions to obtain pellets.

Extruder cylinder temperature 260-275 ° C. Extruder head temperature 280 ° C. Extruder cap temperature 280 ° C. Discharge rate 16.5 kg / h

M of the obtained thermoplastic polyester resin
z is 1396000, and the branch parameter g is 0.5
41.

To 100 parts of the thermoplastic polyester resin obtained above, 0.5 parts of pyromellitic acid and talc (Microace K1 manufactured by Nippon Talc Co., Ltd., average particle size: 3.2 μm)
0.25 parts, blended oil (Koshigaya Chemical Industry Co., Ltd.)
Super Ease) A composition obtained by mixing 0.05 part was used as a first-stage extruder using a co-rotating intermeshing twin-screw extruder (Pla Giken PG extruder) with a cylinder diameter of 45 mm and L / D32. 16 kg from a vibratory quantitative feeder to a tandem type extruder in which a single screw extruder (extruder 350 type manufactured by Tanabe Plastic Machinery Co., Ltd.) having a cylinder diameter of 50 mm and L / D27 is connected by a conveying pipe as a second stage extruder.
/ H, and liquefied butane gas as a foaming agent is injected from the foaming agent inlet at a ratio of 2.0 parts to 100 parts of the melt, and continuously extruded under the following conditions to form a cylindrical sheet-like foam. I got a body. By adding 0.5 parts of the pyromellitic acid, Mz is further reduced to 1567000 and the branch parameter g is set to 0.522. An annular base having a diameter of 50 mm is attached to the tip of the second stage extruder.

First-stage extruder cylinder temperature: 265 to 290 ° C. Conveyor tube temperature: 280 to 285 ° C. Second-stage extruder cylinder temperature: 270 to 280 ° C. Second-stage extruder head temperature: 270 to 280 ° C. Second-stage extruder base temperature 270-280 ° C

20 minutes after the start of the extrusion foam molding, and 8
With respect to the foam obtained after 0 minutes, the apparent density, the size of cells, and the closed cell ratio were measured.

The melt properties of the obtained thermoplastic polyester resin composition were measured in the same manner as described above except that no foaming agent was injected.

Table 1 shows the results.

From Table 1, it can be seen that the melt properties of the resin after 20 minutes and 80 minutes are stable, and that a foam of a thermoplastic polyester resin composition having uniform and fine cells can be stably produced. We can see that we can do it.

Example 2 Z-average molecular weight: 103255, intrinsic viscosity: 0.65 dl
/ G and 100 parts of polyethylene terephthalate resin having a branching parameter of 1.0 were mixed at a ratio of 0.24 parts of glycerin with a twin-screw extruder under the same conditions as in Example 1 to obtain pellets.

Next, 0.75 parts of pyromellitic dianhydride was added to 100 parts of the obtained pellets, and the mixture was melt-kneaded with the twin-screw extruder to obtain a thermoplastic polyester resin.

M of the obtained thermoplastic polyester resin
z is 1182000, and the branch parameter g is 0.5
94.

A composition obtained by mixing 0.25 part of talc and 0.05 part of a blended oil in 100 parts of the above-mentioned thermoplastic polyester resin was continuously subjected to a twin-screw single-screw tandem extruder in the same manner as in Example 1. To obtain a cylindrical sheet-like foam.

As in Example 1, the foam obtained at 20 minutes and 80 minutes after the start of extrusion foaming was measured for apparent density, cell size and closed cell ratio. In the same manner as described above, the melt properties of the obtained thermoplastic polyester-based resin composition were measured.

The results are shown in Table 1.

From Table 1, it can be seen that the melt properties of the resin after 20 minutes and 80 minutes are stable, and that a foam of a thermoplastic polyester resin composition having uniform and fine cells can be stably produced. You can see that it was done.

Example 3 Z-average molecular weight: 103255, intrinsic viscosity: 0.65 dl
/ G, 100 parts of polyethylene terephthalate resin having a branching parameter of 1.0, mixed with 0.6 parts of pyromellitic acid and 0.2 parts of triphenylphosphite under the same conditions as in Example 1 The mixture was melt-kneaded with an extruder to obtain pellets.

Next, 1.24 parts of 1,3-phenylenebisoxazoline was added to 100 parts of the obtained pellets, and the mixture was melt-kneaded by the twin-screw extruder to obtain a thermoplastic polyester resin.

M of the obtained thermoplastic polyester resin
z is 1003500, and the branch parameter g is 0.7
38.

A composition obtained by mixing 0.25 part of talc and 0.05 part of a blended oil in 100 parts of the thermoplastic polyester resin was continuously used in a twin-screw single-screw tandem extruder in the same manner as in Example 1. To obtain a cylindrical sheet-like foam.

The foam obtained at 20 minutes and 80 minutes after the start of the extrusion foaming was measured for the apparent density, the size of the cells and the closed cell ratio in the same manner as in Example 1, and no foaming agent was injected. In the same manner as described above, the melt properties of the obtained thermoplastic polyester-based resin composition were measured.

Table 1 shows the results.

From Table 1, it can be seen that the melt properties of the resin after 20 minutes and 80 minutes were stable and the closed cell ratio was slightly reduced, but the thermoplastic polyester resin composition having uniform and fine cells was found. It can be seen that the foam of the product could be manufactured stably.

Example 4 Z-average molecular weight: 103255, intrinsic viscosity: 0.65 dl
/ G, 100 parts of polyethylene terephthalate resin having a branching parameter of 1.0, and 0.6 parts of pyromellitic acid,
What was mixed at a ratio of 0.2 parts of triphenyl phosphite was melt-kneaded with a twin screw extruder under the same conditions as in Example 1,
The pellet was obtained.

Next, 1.30 parts of diglycidyl benzoate was added to 100 parts of the obtained pellets, and the mixture was melt-kneaded with the twin-screw extruder to obtain a thermoplastic polyester resin.

M of the obtained thermoplastic polyester resin
z is 1023500, and the branch parameter g is 0.6
99.

A composition in which 0.25 part of talc and 0.05 part of a blended oil were mixed with 100 parts of the thermoplastic polyester resin in the same manner as in Example 1 was continuously used in a twin-screw tandem extruder. Extruded to give a cylindrical sheet-like foam.

In the same manner as in Example 1, the apparent density, cell size and closed cell ratio of the foam obtained 20 minutes and 80 minutes after the start of extrusion foaming were measured. In the same manner as described above, the melt properties of the obtained thermoplastic polyester-based resin composition were measured.

Table 1 shows the results.

From Table 1, it can be seen that the melt properties of the resin after 20 minutes and 80 minutes were stable, and the cell diameter was slightly increased, but the foam of the thermoplastic polyester resin composition was stabilized. It turns out that it was able to be manufactured.

Comparative Example 1 Z-average molecular weight: 103255, intrinsic viscosity: 0.65 dl
/ G, 100 parts of linear polyethylene terephthalate resin having a branching parameter of 1.0, and a mixture of 0.25 parts of talc and 0.05 parts of blended oil mixed in a ratio of biaxial-uniaxial tandem as in Example 1. Although extrusion foaming was performed continuously by an extruder, the foaming agent and the molten resin were intermittently released from the mold, and a foamed sheet could not be obtained.

The melt properties of the obtained thermoplastic polyester resin composition were measured in the same manner as in Example 1 except that the foaming agent was not injected.

Table 1 shows the results.

Comparative Example 2 Z-average molecular weight: 103255, intrinsic viscosity: 0.65 dl
/ G, a mixture of 100 parts of linear polyethylene terephthalate resin having a branching parameter of 1.0 at a ratio of 0.4 parts of pyromellitic acid and 0.2 parts of triphenyl phosphite under the same conditions as in Example 1 The mixture was melt-kneaded with a screw extruder to obtain pellets.

Next, 0.72 parts of 1,3-phenylenebisoxazoline was added to 100 parts of the obtained pellets, and the mixture was melt-kneaded by the twin-screw extruder to obtain a thermoplastic polyester resin.

M of the obtained thermoplastic polyester resin
z is 653500, and the branch parameter g is 0.89.
Met.

A mixture of 100 parts of the thermoplastic polyester resin and 0.25 part of talc and 0.05 part of blended oil was continuously mixed with a twin-screw single-screw tandem extruder in the same manner as in Example 1. Extrusion foaming was performed, but only a foamed sheet whose appearance was broken could be obtained.

The melt properties of the obtained thermoplastic polyester resin composition were measured in the same manner as in Example 1 except that the blowing agent was not injected.

Table 1 shows the results.

Comparative Example 3 Z-average molecular weight: 103255, intrinsic viscosity: 0.65 dl
/ G, 100 parts of a linear polyethylene terephthalate resin having a branching parameter of 1.0 and a mixture of 0.5 parts of pyromellitic acid, 0.25 parts of talc, and 0.05 parts of a blended oil were mixed with Example 1. Similarly, it was continuously extruded by a twin-screw single-screw tandem extruder to obtain a cylindrical sheet-like foam.

In the same manner as in Example 1, the foam obtained at 20 minutes and 80 minutes after the start of extrusion foaming was measured for apparent density, cell size and closed cell ratio.

The melt properties of the obtained thermoplastic polyester resin composition were measured in the same manner as in Example 1 except that the foaming agent was not injected.

Table 1 shows the results.

From Table 1, it can be seen that the melt properties of the resin after 20 minutes and 80 minutes are significantly lower than the melt properties after 20 minutes, and accordingly, the obtained foam has large bubbles and foam breakage. Is observed, which indicates that the foam could not be produced stably.

[0141]

[Table 1]

[0142]

According to the present invention, a foam of a thermoplastic polyester resin composition having uniform and fine cells can be stably produced by a simple method. The foam obtained by the present invention can be used as an extruded foam sheet, an extruded foam board, a foam blow-molded product, and further can be used as a material for secondary molding.

Claims (2)

[Claims] 1. A thermoplastic polyester resin foam obtained by extrusion foaming a thermoplastic polyester resin having a Z-average molecular weight of 1 × 10 ⁶ or more and a branching parameter of 0.8 or less. 2. A method for producing a thermoplastic polyester resin foam obtained by extrusion-foaming a thermoplastic polyester resin having a Z-average molecular weight of 1 × 10 ⁶ or more and a branching parameter of 0.8 or less.