JPH1044215A - Production of thermoplastic polyester resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quantitatively and uniformly mix and disperse a modifier by melting and mixing thermoplastic polyester resin and a modifier for melt properties in a tandem extruder constituted of a biaxial extruder at the front stage and a monoaxial extruder at the rear stage and mixing a foaming agent, and extruding the mixture from the metal mouth to a low pressure zone. SOLUTION: A composition in which thermoplastic polyester resin and a modifier for melt properties are mixed is supplied in a tandem extruder in which a biaxial extruder of rotational meshing in the same direction, and having kneading disc parts as the first stage extruder at the upstream side at the injection opening for the foaming agent of the later half part of the cylinder, and a monoaxial extruder as the second stage extruder, are connected with each other by a conveying pipe, and further a foaming agent is injected to extrude and foam the mixture in a specified condition. That is, the foaming resin composite material melted and kneaded in the first stage biaxial extruder is transferred to the second stage monoaxial extruder. While the material is continuously melted and kneaded by the monoaxial extruder to homogenization of the resin structure and temperature is effected. The foamable resin composition is extruded from the metal mouth attached to the front end of the second stage extruder to the low pressure zone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a thermoplastic polyester resin foam. More specifically, a method for producing a thermoplastic polyester resin foam which has uniform and fine cells by extrusion molding, and is capable of stably obtaining a foam having excellent heat resistance, chemical resistance, heat insulation, and cushioning properties. About.

[0002]

2. Description of the Related Art It is already known that an extrusion foaming method can be used as a method for obtaining a foam of a thermoplastic polyester resin. The extrusion foaming method is a method of melting a thermoplastic resin in an extruder, mixing a foaming agent into the melted resin, and extruding the resin from a die attached to the tip of the extruder to a low-pressure region to produce a foam, For example, it is already widely used in the production of foams such as polystyrene and polyethylene.

[0003] On the other hand, thermoplastic polyester resins are used as various molding materials, but even if they are used as they are for extrusion foaming, it is extremely difficult to obtain uniform foaming due to low viscosity at the time of melting. To overcome these drawbacks, it is difficult to overcome these drawbacks by using a variety of modifiers to increase the melt viscosity of the thermoplastic polyester resin, and to provide a suitable viscosity for foaming by extrusion foaming. Attempts have been made to apply to

In the production method described in JP-B-61-48409, it has been proposed to mix a diglycidyl ester compound with a thermoplastic polyester resin, and the production method described in JP-B-3-16977 has been proposed. Has proposed that a thermoplastic polyester resin be mixed with a polyfunctional glycidyl ester compound and a polyfunctional carboxylic anhydride, and further disclosed in JP-A-2-150434.
In the production method described in Japanese Patent Application Laid-Open No. H11-264, a method is proposed in which a compound having two or more acid anhydride groups in one molecule is added to a thermoplastic polyester resin to produce a foam having no colored foreign matter.

[0005]

SUMMARY OF THE INVENTION These prior arts are:
This method involves extrusion foaming by mixing a modifier with a thermoplastic polyester resin.In either case, it is necessary to quantitatively and uniformly mix and disperse the modifier into the thermoplastic polyester resin. In the method of extrusion foaming using a single screw extruder, which is commonly used for extrusion foaming of polystyrene and polyethylene, the accuracy of quantitative measurement and the uniformity of mixing and dispersion are insufficient, and the quality of the extruded foam tends to fluctuate. There were disadvantages. Further, since the thermoplastic polyester resin is likely to be hydrolyzed and degraded in properties when it absorbs moisture during heating and melting, it is necessary to strictly control the moisture management and the elapsed time during extrusion foaming in order to suppress such adverse effects. However, in the conventional method, these tend to fluctuate due to disturbance factors, and the quality of the foam tends to fluctuate.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention melts and mixes a thermoplastic polyester resin and a melting property modifier in an extruder, and mixes a blowing agent into the molten resin. In a method of producing a foam by foaming a resin by extruding a resin into a low-pressure region from a die attached to a tip of an extruder, a twin-screw extruder is arranged in a former extruder, and a single-screw extruder is arranged in a latter extruder. A method for producing a thermoplastic polyester-based resin foam characterized by using a tandem extruder is described.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As the thermoplastic polyester resin used in the present invention, those exhibiting thermoplasticity in the range of 230 to 300 ° C. are preferable. The melt viscosity at a temperature when the polyester resin exhibits thermoplasticity is 100 Pa · s or more, preferably 300 Pa · s or more, and 100000 Pa · s or less.
Preferably, the pressure is 8000 Pa · s or less. The above-mentioned melt viscosity is a shear rate of 60. measured in accordance with JIS K 7199 “Method of testing flow characteristics of thermoplastics using capillary rheometer”.
It refers to the viscosity at 8 s ^-1 . As the thermoplastic polyester resin, for example, a resin mainly containing a polyester obtained by polycondensing a polyvalent carboxylic acid and a polyhydric alcohol is preferably used.

[0008] The main component of the polyester obtained by polycondensation of the polyvalent carboxylic acid and the polyhydric alcohol is that the polyester resin is a polyester component comprising a polyvalent carboxylic acid and a polyhydric alcohol.
0% by weight or more, and more preferably 85% by weight or more. Representative examples of the polyester include, for example, a linear polyester obtained by polycondensing an aromatic dicarboxylic acid and a diol, and a branched polyester having at least 3, preferably 3 to 6, ester-forming groups. Examples include a branched polyester obtained by copolymerizing with a producing component. The linear polyester and the branched polyester can be used alone or in combination of two or more.

Representative examples of the aromatic dicarboxylic acids include, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid and the like. These aromatic dicarboxylic acids can be used alone or in combination of two or more.

Representative examples of the diols include, for example, ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2-bis (4 -Β-hydroxyethoxyphenyl) propane,
4,4-bis (β-hydroxyethoxy) diphenyl sulfone and the like. These diols can be used alone or in combination of two or more.

Preferred specific examples of the linear polyester include polyethylene terephthalate, polybutylene terephthalate, poly-1,4-cyclohexane dimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polyethylene isophthalate. These are used alone or in combination of two or more. Among them, polyethylene terephthalate, polybutylene terephthalate and poly-1,4-cyclohexane dimethylene terephthalate are more preferably used from the viewpoint of high industrial value and easy handling.

The intrinsic viscosity of the linear polyester is preferably 0.4 to 1.1 dl / g, particularly preferably 0.1 to 0.1 to obtain melt viscoelasticity that enables easy melt molding.
It is preferably from 5 to 1.0 dl / g. In addition, the intrinsic viscosity in the present invention means that a mixture of phenol and tetrachloroethane (weight ratio 1/1) is used as a solvent,
It refers to the value measured at 3 ° C.

[0013] The branched polyester is obtained by copolymerizing the linear polyester with a branch-forming component. When the branched polyester is used, there is an advantage that the melt viscosity and the melt viscoelasticity are increased, and it is easy to produce a foam sheet having fine cells. The branch-forming component is a component used to generate a branched structure in the main chain of the polyester. The branch-forming component has at least 3, preferably 3 to 6, ester-forming groups. Examples of the ester-forming group include a hydroxyl group and a carboxyl group, and these groups can be used alone or in combination.

Representative examples of the branch-forming component include tri- or tetracarboxylic acids such as trimellitic acid and pyromellitic acid, and lower alkyl esters thereof;
Tri- or tetraols such as glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol; dihydroxycarboxylic acids, hydroxycarboxylic acids, and derivatives thereof. These branch-forming components can be used alone or in combination of two or more. Among these branch-forming components, glycerin is preferred from the viewpoint that the degree of polymerization of the branched polyester is easily adjusted.

In preparing the above-mentioned branched polyester, in order to sufficiently improve the retention stability of the melt viscoelasticity imparted by the reaction between the branched polyester and the melting property modifier, it is necessary to form the branched polyester. The amount of the component is 0.1 mol or more per 100 mol of the aromatic dicarboxylic acid unit,
In particular, it is preferably at least 0.3 mol. Further, in order to improve the processability into a foam, the amount of the branching component is preferably 5 mol or less, more preferably 3 mol or less, based on 100 mol of the aromatic dicarboxylic acid unit. The intrinsic viscosity of the branched polyester is 0.4 dl / g in order to impart sufficient melt viscoelasticity.
As described above, it is preferably 0.5 dl / g or more, and in order to be able to easily perform melt molding, it is 1.1 dl / g or less, particularly 1.0 d / g.
It is preferably at most 1 / g.

The melting property modifier used in the present invention modifies the melt viscosity, melt tension, etc. of the thermoplastic polyester resin through a reaction with the thermoplastic polyester resin to improve extrusion foaming moldability. . The melt property modifier used in the present invention acts on the thermoplastic polyester resin to have a melt viscosity sufficient to suppress foaming in the extruder, a melt tension sufficient to suppress foam breakage during extrusion foaming, and the like. Any compound can be provided as long as it can be imparted, for example, a compound having two or more acid anhydride groups in one molecule such as pyromellitic dianhydride and benzophenonetetracarboxylic dianhydride, or a compound such as diglycidyl phthalate. Examples include compounds having two or more epoxy groups in the molecule. These may be used alone or as a mixture of two or more.

The blending amount of the melting property modifier is required to sufficiently exhibit the effect of using the melting property modifier, for example, the effect of imparting melt viscoelasticity suitable for extrusion foam molding. , Thermoplastic polyester resin 1
0.05 parts or more for 00 parts (parts by weight, the same applies hereinafter),
In particular, it is preferably at least 0.1 part. Also,
In order to prevent unnecessary gelling of the thermoplastic polyester resin, the amount is preferably 5 parts or less, more preferably 3 parts or less based on 100 parts of the thermoplastic polyester resin.

Further, a nucleating agent such as talc can be added to the thermoplastic polyester resin as a cell regulator at the time of foaming, and a stabilizer, if necessary,
One or more of pigments, fillers, flame retardants, antistatic agents and the like can be blended by appropriately adjusting the blending amount. In the present invention, extrusion foaming is performed using a tandem extruder in which a twin-screw extruder is a first-stage (first-stage) extruder and a single-screw extruder is a second-stage (second-stage) extruder. In this method, a thermoplastic polyester-based resin, a melt property modifier and other necessary additives are melt-mixed in a first-stage extruder.

As a method of adding the melting property modifier,
A method in which a thermoplastic polyester resin and a melting property modifier are mixed in advance with a thermoplastic polyester resin before melting and supplied to a first-stage twin-screw extruder from a fixed-quantity feeder. A method of feeding to a twin screw extruder can be adopted. The latter method is preferred for reducing the fluctuation of the mixing ratio between the thermoplastic polyester resin and the melting property modifier.

The foaming agent can be injected from a first-stage extruder, a conveying pipe from the first-stage extruder to the second-stage extruder, or any place in the second-stage extruder. In order to improve the dispersion and mixing of the agent, a method of injecting the mixture into a first-stage extruder is preferable. As the foaming agent, any of a liquid volatile foaming agent which is vaporized by heating and a gaseous foaming agent which can be melted into a resin under pressure can be used.

Specific examples of the volatile foaming agent include, for example, saturated aliphatic hydrocarbons such as butane, pentane and hexane; saturated alicyclic hydrocarbons such as cyclohexane; aromatic hydrocarbons such as benzene and xylene; Examples thereof include halogenated hydrocarbons such as methylene chloride, and fluorochloro-substituted hydrocarbons such as Freon (trade name). Further, specific examples of the gas-type blowing agent include, for example, nitrogen and carbon dioxide. The foaming agents can be used alone or in combination of two or more. 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 is about 0.5 to 50 parts based on 100 parts of the thermoplastic polyester resin.

The foamable resin composition melt-kneaded by the first-stage twin-screw extruder is transferred to the second-stage single-screw extruder through a transport pipe, and melt-kneaded by the second-stage single-screw extruder. While continuing
The resin structure and temperature are homogenized and the pressure is maintained so as to be suitable for foam formation. A die is attached to the tip of the second-stage single screw 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 the low pressure region to form a foam.

The twin-screw extruder used in the present invention preferably has a screw configuration in which a kneading disk or a kneading element is arranged. The kneading disk or the kneading element can be arranged at a plurality of places, but it is preferable to arrange at least one place at a portion upstream of the foaming agent injection port. By kneading with a twin-screw extruder having such a screw configuration, sufficient kneading can be given to the thermoplastic polyester resin and the melting property modifier, and the reaction resin composition can be more homogenized. And the injection amount and dispersion of the foaming agent can be stabilized.

Further, even when particles such as talc are used as a cell regulator, they can be uniformly mixed and dispersed by using a twin-screw extruder, and the particles are present as fine particles without agglomeration. Therefore, the function as a bubble regulator can be efficiently exhibited. Also,
The first-stage twin-screw extruder used in the present invention is connected to a decompression device in order to suppress undesired deterioration of the properties of the molten polyester due to the influence of volatile components, for example, moisture contained in the molten resin composition. Preferably, at least one vent hole is provided, and the pressure in the vent portion is reduced to 1500 Pa or less, more preferably 150 Pa or less.

[0025]

Next, the method for producing a polyester resin foam of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples.

EXAMPLE 1 A twin-screw extruder having a co-rotating intermeshing type having a blowing agent inlet in the rear half of a cylinder and a kneading disk (paddle) upstream of the inlet as a screw component was provided. As a second-stage extruder, a single-screw extruder having a cylinder diameter of 50 mm was connected as a second-stage extruder to a tandem-type extruder connected by a conveying pipe. A composition prepared by mixing 0.5 part of pyromellitic anhydride as a melting property modifier and 0.5 part of talc as a foam regulator was supplied at a rate of 12 kg / hr from a vibrating quantitative feeder. Liquefied butane gas as a foaming agent was injected at a ratio of 2.0 with respect to 100 parts of the melt, and extrusion foaming was performed under the following conditions to obtain a rod-shaped foam having fine bubbles of 12 kg / hr
At a rate of First stage extruder cylinder temperature 265-290 ° C Conveyor tube temperature 280-285 ° C Second stage extruder cylinder temperature 270-280 ° C Second stage extruder head temperature 270-280 ° C Second stage extruder base temperature 270-280 C. The apparent density and the state of air bubbles were measured for the foam 30 minutes and 60 minutes after the production of the foam was started, and evaluated according to the criteria shown in Table 2. The results are as shown in Table 1. Regardless of the elapsed time, the apparent density and the state of the bubbles were stable, and a constant quality could be maintained.

Example 2 The procedure of Example 1 was repeated, except that 100 parts of dry polyethylene terephthalate having an intrinsic viscosity of 0.65 dl / g were replaced with glycerin units at a ratio of 1 mol to 100 mol of the total number of terephthalic acid units. Polymerized intrinsic viscosity 0.60 dl /
A rod-shaped foam was obtained in the same manner as in Example 1 except that 100 parts of the branched polyester g was used. For the foam 30 minutes and 60 minutes after the start of the production of the foam, the apparent density and the state of the bubbles were measured in the same manner as in Example 1. The results are as shown in Table 1. Regardless of the elapsed time, the apparent density and the state of the bubbles were stable, and a constant quality could be maintained.

Example 3 Example 2 was repeated except that the degree of pressure reduction of the vent hole provided in the first half of the cylinder of the first stage extruder was set to 150 Pa and the amount of pyromellitic anhydride was changed to 0.3 part. A rod-shaped foam was obtained in the same manner as in Example 2. For the foam 30 minutes and 60 minutes after the start of the production of the foam, the apparent density and the state of the bubbles were measured in the same manner as in Example 1. The results are as shown in Table 1. Regardless of the elapsed time, the apparent density and the state of the bubbles were stable, and a constant quality could be maintained.

Comparative Example 1 A single-screw extruder having a cylinder diameter of 40 mm was provided as a first-stage extruder having a foaming agent injection port in the latter half of the cylinder, and a single-screw extruder having a cylinder diameter of 50 mm was transferred as a second-stage extruder. A tandem extruder connected by a pipe has an intrinsic viscosity of 0.65 dl
/ G dry polyethylene terephthalate (100 parts), a composition prepared by mixing 0.5 parts of pyromellitic anhydride and 0.5 part of talc with 100 parts of dry polyethylene terephthalate, and 100 parts of a liquefied butane gas as a blowing agent through a blowing agent inlet. 2.0 parts with respect to each other, and a rod-shaped foam was
g / hr. First stage extruder cylinder temperature 265-290 ° C Conveyor tube temperature 280-285 ° C Second stage extruder cylinder temperature 270-280 ° C Second stage extruder head temperature 270-280 ° C Second stage extruder base temperature 270-280 C. For the foam 30 minutes and 60 minutes after the start of the production of the foam, the apparent density and the state of the bubbles were measured in the same manner as in Example 1. The results are as shown in Table 1. The apparent density and the state of the bubbles changed with the lapse of time, so that a constant quality could not be maintained.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

As described above, according to the present invention, the melting reaction between a thermoplastic polyester resin and a melting property modifier is performed.
The kneading can be homogenized, and the foaming agent and other additives can be uniformly dispersed and contained. As a result, a foam having uniform and fine cells can be continuously and stably produced. I can do it. 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.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29K 105: 04

Claims (4)

[Claims] 1. A thermoplastic polyester resin and a melting property modifier are melt-mixed in an extruder, a foaming agent is mixed into the melted resin, and extruded from a die attached to a tip of the extruder to a low pressure region. A method for producing a foam by foaming a resin, comprising using a tandem extruder in which a twin-screw extruder is provided as a first-stage extruder and a single-screw extruder is provided as a second-stage extruder. How to make the body. 2. The method according to claim 1, wherein the twin-screw extruder is a vented twin-screw extruder having at least one vent hole. 3. The method according to claim 1, wherein the thermoplastic polyester resin and the melting property modifier are supplied to the twin-screw extruder from separate quantitative feeders. 4. The method according to claim 1, wherein the blowing agent is injected into a twin-screw extruder.