JPH11147969A - Polyester resin foam and its production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester resin foam which has fine and uniform cells and a high expansion ratio and is excellent not only in heat insulation, shock absorption, gas barrier properties, and recyclabilty but also in heat resistance and mechanical strengths. SOLUTION: This foam is based on a copolyester contg. dicarboxylic acid units mainly comprising terephthalic acid units and 2,6-naphthalenedicarboxylic acid units and diol units mainly comprising ethylene glycol units, and the half crystallization time of the copolyester at a temp. equal to 1.25 times the absolute glass transition temp. is at least 20 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin foam excellent in various physical properties and a method for producing the same.

[0002]

2. Description of the Related Art Polyester resins, for example, polyethylene terephthalate, are excellent in mechanical properties, heat resistance, chemical resistance, dimensional stability, etc., and are used in injection molded products, blow molded products, press molded products, films and the like. It is widely used, and its foam has been recently developed for food containers and packaging materials. However, in general, polyethylene terephthalate is a resin having high crystallinity, and at a high temperature, the viscosity is too low, so that a good foam molded product cannot be obtained. On the other hand, the melt viscosity is increased by cooling,
When trying to obtain a melt viscosity of a resin suitable for foaming, a sharp increase in viscosity occurs due to crystallization, and it is extremely difficult to adjust the viscosity to a stable suitable viscosity, and a disadvantage that a good foam cannot be obtained is obtained. Have.

[0003] In order to improve such resin properties, a method of increasing the melt viscosity other than the cooling method has been studied.
For example, a method of mixing a diepoxy compound with calcium stearate and sodium carbonate by extrusion foaming (Japanese Patent Application Laid-Open No. 53-24364), a method of mixing a diepoxy compound with a montan wax salt or a montan wax ester salt (Japanese Patent Application Laid-open No. 54-50568) and the like have been proposed. These methods comprise a diepoxy compound and a metal or a metal compound of the periodic table Ia, IIa as essential components. Although the thickening reaction is remarkably promoted, the viscosity changes rapidly and the viscosity increases rapidly. However, since it rapidly decreases thereafter, it is difficult to obtain an optimum viscosity.

In order to solve the above-mentioned drawbacks, Japanese Patent Laid-Open No. 2-490
No. 39 discloses that diglycidyl phthalate and periodic table I
It has been proposed to mix the metal or metal compound of a and IIa, but the viscosity change was still abrupt and the foam could not be obtained stably.

As a method for improving these disadvantages, Japanese Patent Publication No. 3-16977 proposes mixing a polyfunctional glycidyl ester compound and a polyfunctional carboxylic anhydride with a thermoplastic polyester resin. According to this method, the melt viscosity can be adjusted to a value suitable for foaming without sufficient cooling, and a good foam can be obtained. However, since this foam mixes a polyfunctional glycidyl ester compound and a polyfunctional carboxylic anhydride as the third component, there is a problem of contamination during recycling.

Japanese Unexamined Patent Publication (Kokai) No. 8-231751 proposes an aromatic polyester resin foam using a mixture of cyclohexane dimethylol and ethylene glycol as a glycol component of the aromatic polyester resin. In the present invention, since an aromatic polyester resin using two kinds of diol components is used as a foam material, the crystallization rate can be delayed at the time of foaming, uniform and fine bubbles are provided, and at a high magnification, Moreover, a foam having good heat insulating properties, cushioning properties and recyclability has been obtained. However, this foam is not necessarily sufficient in terms of heat resistance and mechanical strength.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides uniform, fine bubbles, high magnification, excellent heat insulating properties, cushioning properties, gas barrier properties, recyclability, heat resistance and mechanical strength. It is another object of the present invention to provide a polyester resin foam excellent in quality and a method for producing the same.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, a polyester copolymer containing a terephthalic acid component unit and a 2,6-naphthalenedicarboxylic acid component unit as main dicarboxylic acid component units, and an ethylene glycol component unit as a main diol component unit, A polyester resin foam is provided, wherein the base resin is a polyester resin having a half-crystallization time of not less than 20 minutes at a temperature 1.25 times the glass transition temperature based on absolute temperature of the polyester copolymer. You. Further, according to the present invention, a terephthalic acid component unit and a 2,6-naphthalenedicarboxylic acid component unit are contained as main dicarboxylic acid component units, an ethylene glycol component unit is contained as a main diol component unit, and an absolute temperature-based glass transition temperature. A polyester copolymer having a half-crystallization time of not less than 20 minutes at a temperature of 1.25 times of the above and a foaming agent are kneaded with an extruder under high-temperature and high-pressure conditions to form a foamable melt. Extruded from a tip of an extruder into a low-pressure region and foamed, and a method for producing a polyester resin foam is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A polyester copolymer (hereinafter referred to as a polyester copolymer) containing a terephthalic acid component unit and a 2,6-naphthalenedicarboxylic acid component unit as dicarboxylic acid component units and an ethylene glycol component unit as a diol component unit is used in the present invention. , Also simply referred to as polyester copolymer))
The half-crystallization time at a temperature 1.25 times the glass transition temperature based on the absolute temperature is 20 minutes or more. As used herein, the glass transition temperature is defined as the temperature at which a dried sample is placed in an inert gas stream at 20 ° C.
From the DSC curve obtained by heating at a heating rate of
Extrapolated glass transition onset temperature determined according to IS K 7121. The half-crystallization time referred to in this specification is obtained by using a crystallization rate measuring device (MK-801 type manufactured by Kotaki Shoji Co., Ltd.) to measure a resin sample previously heated and melted at 300 ° C. based on the absolute temperature of the resin sample. 1.2 glass transition temperature
Put into a crystallization bath set to 5 times the temperature (absolute temperature),
Can be measured. The measurement sample is prepared in the form of a film. The thickness of the film is 0.1 ± 0.02
mm, and cut into 15 × 15 mm squares, which are inserted into a cover glass for a microscope.
The instruction value is set to 3 V for the brightness setting of the light source lamp. The crystallization rate measuring device manufactured by Kotaki Shoji Co., Ltd. is a device for determining the degree of crystallinity from the relationship between the crystallization of a sample and the birefringence of light, and the half-crystallization time referred to in the present invention is obtained by the above-mentioned measuring method. From the curve on the graph shown in FIG. 1, a value A in which the amount of light due to birefringence is constant is read from the vertical axis on the graph,
This value is obtained as a value C on the horizontal axis on the graph corresponding to the value B on the vertical axis on the graph obtained by multiplying the value by 0.5.

When the half-crystallization time is less than 20 minutes, such a polyester resin is extruded and foamed.
During cooling down to a temperature suitable for the extrusion temperature, a sharp increase in viscosity due to crystallization tends to occur, making it extremely difficult to adjust the resin to a viscosity suitable for foaming. As a result, the resulting foam is independent The bubble rate is significantly reduced. Such a foam having a reduced closed cell ratio is inferior in heat insulation, and may not be able to sufficiently exhibit the basic physical properties of the base resin. In addition, when the foam is in the form of a sheet and it is heated and vacuum formed into a container, etc., the sheet cannot be brought into close contact with the mold due to the low closed cell rate, and the shape matches the mold. There is a possibility that a problem that a molded article cannot be obtained may occur. On the other hand, a polyester copolymer having a half-crystallization time of 20 minutes or more does not substantially crystallize during normal extrusion foaming, and therefore, has a sharp viscosity during the process of cooling to a temperature suitable for the extrusion temperature. No change occurs, and it becomes easy to adjust the viscosity of the resin to a level suitable for foaming. As a result, the obtained foam has a high closed cell ratio, and has excellent heat insulating properties and mechanical strength. Further, such a sheet-like foam is suitable for differential pressure molding such as vacuum molding. In order to further enhance the reliability of preventing crystallization during extrusion, the half-crystallization time is more preferably 60 minutes or more. The polyester copolymer used in the present invention is preferably non-crystalline, and the upper limit of the half-crystallization time cannot be determined.
That is, the polyester copolymer having a half-crystallization time of 20 minutes or more in the present invention naturally includes not only those having crystals but also those having no crystals.

The polyester copolymer used in the present invention comprises:
It is produced by a method of polycondensing a dicarboxylic acid component and a diol component, a transesterification reaction of a polyester homopolymer and / or a polyester copolymer, or the like. The dicarboxylic acid component and the diol component of the polyester copolymer used in the present invention will be described in detail. As the dicarboxylic acid component, dicarboxylic acid or an ester-forming derivative thereof can be used. Examples of the ester-forming derivatives include ester derivatives such as dimethyl ester and diethyl ester, salts such as diammonium salts, and acid halides such as dichloride. The dicarboxylic acid component unit is mainly a terephthalic acid component unit and a 2,6-naphthalenedicarboxylic acid component unit, and the molar ratio thereof is preferably from 2: 8 to 8: 2. 3: 7 to 7: 3 is more preferable from the viewpoint of obtaining The dicarboxylic acid component unit includes terephthalic acid component unit and 2,6.
-In addition to the naphthalenedicarboxylic acid component unit, other dicarboxylic acid component unit is not more than 20 mol%, preferably 10 m
ol% or less. On the other hand, the diol component unit is an ethylene glycol component unit, and the other diol component unit is 20 mol% or less, preferably 10 m
ol% or less. Other dicarboxylic acid component units and diol component units include phthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid,
4'-diphenyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,5
Component units derived from an aromatic dicarboxylic acid such as -naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid or an ester-forming derivative thereof, or an aliphatic unit such as succinic acid, adipic acid, sebacic acid, dodecandioic acid, etc. Component units derived from a dicarboxylic acid or an ester-forming derivative thereof, or an alicyclic dicarboxylic acid such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, decalin dicarboxylic acid, tetralin dicarboxylic acid, or an ester thereof A component unit derived from a forming derivative, a component unit derived from an aliphatic diol such as propylene glycol, trimethylene glycol, diethylene glycol, 1,4-butanediol, or 1,4-cyclohexanedimethanol 1,3-cyclohexanedimethanol, may be mentioned 1,6-cyclohexane alicyclic diol is the component unit derived from such a diol or component units derived from such aromatic diol such as bisphenol A,. In addition, the above-mentioned polyester copolymer may have a molecular terminal sealed with a component unit derived from a monofunctional compound such as a small amount of benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, methoxypolyethylene glycol, or the like. Good. Further, a small amount of a component unit derived from a polyfunctional compound such as trimellitic acid, viromellitic acid, trimesic acid, glycerin, and pentaerythritol may be contained. Further, as the polyester copolymer used in the present invention, a recovered polyester resin such as a recovered polyethylene terephthalate may be mixed with the above-mentioned polyester copolymer. The half-crystallization time of the polyester copolymer can be adjusted by, for example, changing the molar ratio of the terephthalic acid component unit of the dicarboxylic acid component unit to the 2,6-naphthalenedicarboxylic acid component unit.

The polyester resin foam of the present invention is obtained by melting the polyester copolymer, preferably under high temperature and high pressure, mixing the melt with a foaming agent, and extruding and foaming in a low pressure zone. As the foaming agent, an inert gas,
Saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, ethers, ketones, and the like can be used alone or in combination of two or more. Specifically, carbon dioxide, nitrogen, methane, ethane, normal butane, isobutane, normal pentane, isopentane,
Neopentane, normal hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane,
2,3-dimethylbutane, methylcyclopropane, cyclopentane, 1,1-dimethylcyclopropane, cyclohexane, methylcyclopentane, ethylcyclobutane, 1,1,2-trimethylcyclopropane, benzene, 1,1,1,2 -Tetrafluoroethane, 1,1-
Examples thereof include zirfluoroethane, 1,1,1,2,2-pentafluoroethane, trichlorotrifluoroethylene, dichlorotetrafluoroethylene, dimethyl ether, 2-ethoxyethanol, acetone, ethyl methyl ketone, and acetylacetone. The foaming agent is used in an amount of 0.05 to 3 mol per 1 kg of the polyester resin. If the amount of the foaming agent is less than 0.05 mol, there is no cost advantage due to low foaming, and only a foam having poor heat insulating properties can be obtained. If the amount exceeds 3 mol, gas sealing with a die becomes unstable and good. A good foam cannot be obtained.

When the polyester copolymer is melted, and the melt is mixed with a foaming agent and extruded into a low pressure zone to obtain a foam, melt mixing and cooling are each performed by one or more extruders. Is desirable. That is, extrusion foaming is generally performed by melting a resin, adding a foaming agent, and then cooling until the resin reaches a viscosity suitable for foaming. For this reason, in the melt mixing of the resin and the foaming agent, it is desirable to knead sufficiently at a high rotation, and in cooling, extrude at a low rotation while suppressing shear heat as much as possible in order to increase the cooling efficiency. Is desired. Therefore, if a method in which the melt mixing and cooling for foaming are performed by a single extruder is adopted, it is necessary to extrude the resin and the foaming agent at a low rotation speed in order to perform sufficient cooling. There is a problem that the foaming state is easily deteriorated, and the discharge amount of the extruder is reduced, and the productivity is reduced. Therefore, in the present invention, it is preferable that each of the melt mixing and the cooling is performed by one or more extruders. The shape and type of the extruder are not particularly limited.

Further, in the production of the foam of the present invention, a nucleating agent such as talc is mixed, a crosslinking agent such as an ionomer, an inorganic filler containing fibers, a flame retardant, an antistatic agent, an antioxidant. , A colorant and the like may be appropriately mixed. The foam of the present invention obtained by the above method has a density of 0.03 to 0.03.
Those having a thickness of 0.6 g / cm ³ and a thickness of 0.5 to 5 mm are preferred. When the density is less than 0.03 g / cm ³ , the mechanical strength may be insufficient, and when the density exceeds 0.6 g / cm ³ , the heat insulating property and the cushioning property may be inferior. When the thickness is less than 0.5 mm, the heat insulating property, cushioning property, and mechanical strength may be insufficient. When the thickness exceeds 5 mm, the secondary workability such as thermoforming and bag making may be poor. There is.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to embodiments.

Examples 1 to 3 and Comparative Examples 1 to 3 A mixture of dimethyl terephthalate (DMT) and dimethyl 2,6-naphthalenedicarboxylate (NDC) having a molar ratio shown in Table 1 as a dicarboxylic acid component was used as a diol component. Polycondensation was performed using ethylene glycol (EG) to obtain a polyester copolymer. Next, the resin 100
0.05 parts by weight of talc was added as a nucleating agent per part by weight, and this was used as a raw material resin in a first extruder (φ6 for melt kneading).
5 mm), heated, melted and kneaded. Then, pentane as a foaming agent was pressed into a 0.2-mol extruder per 1 kg of the resin, and the melt-kneaded product was then extruded into a second extruder (φ90 m for cooling).
m), extruded from the annular die at the extruder tip at the temperature shown in Table 1, cooled as a tubular foam while taking it on a mandrel, and cut open along the extrusion direction to obtain a foamed sheet. . Table 1 shows the properties and physical properties of the obtained foamed sheet. Each of the foamed sheets of Examples 1 to 3 had uniform and fine bubbles, was a high-magnification foam, and was excellent in heat insulation, cushioning, gas barrier properties, and recyclability. (In Comparative Example 3 in Table 1, cyclohexane dimethylol was used as the diol component:
The one having a molar ratio of ethylene glycol of 35:65 was used. )

The methods for measuring and evaluating the physical properties in Table 1 are as follows. [Tensile strength] A dumbbell-shaped No. 1 test piece described in JIS K 6767 for extrusion direction was prepared, and the test speed was 500 mm / min and the distance between chucks was 50 mm using a universal testing machine in accordance with JIS K 6767A method. The test piece was subjected to a tensile rupture test, and the strength at the time of rupture of the test piece was used as the tensile strength. The number of samples was five, and the measured values of all samples were averaged. [Heat resistance] From the foam sheet, a square test piece of 100 mm in length and width was cut out with the extrusion direction being vertical and the width direction being horizontal, and this test piece was heated in an 85 ° C. oven for 30 minutes.
Sheets having a shrinkage ratio of 10% or less in the vertical and horizontal directions after heating were evaluated as having good heat resistance, and sheets having shrinkage ratios exceeding 10% were evaluated as having poor heat resistance. [Semi-crystallization time at a temperature (° K) of 1.25 times Tg (° K)] Using a heat press, a thickness of 0.1 mm from the base resin.
A 09 mm film was prepared and 15 × 1
A 5 mm square film was cut out and used as a measurement sample. The half-crystallization time of the measurement sample was determined by the above-mentioned method using a crystallization measuring device manufactured by Kotaki Shoji Co., Ltd. [Glass transition temperature (Tg)] Using a differential scanning calorimeter, DSC200 model, Seiko Denshi Kogyo Co., Ltd., about 10 mg of a dried and precisely weighed sample is placed in a non-sealed aluminum container, and
SC measurements were made. 20 ° C in a nitrogen stream (30ml / min)
/ Min to 300 ° C. and then cool at a rate of 10 ° C./min. Repeat this operation twice.
The extrapolated glass transition onset temperature was determined from the second DSC curve according to JIS K7121.

[0018]

[Table 1] * Foaming but uneven sheeting makes sheeting difficult

[0019]

The polyester resin foam of the present invention is
It has uniform, fine bubbles, high magnification, and has excellent heat insulation, buffering properties, gas barrier properties and recyclability, and also has remarkably excellent heat resistance and mechanical strength. It is extremely useful as another material.

[Brief description of the drawings]

FIG. 1 shows a crystallization time measurement graph.

[Explanation of symbols]

 (I) Light intensity curve correlated with crystallization (II) Crystallization bath temperature a Time during which the amount of light due to birefringence is constant A Amount of light due to birefringence at a B B A × 0.5 C semi-crystal Crystallization time D crystallization bath set temperature

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Muroi, Inventor Takashi Muroi 1-73, Yonishi-cho, Utsunomiya-shi, Tochigi Prefecture (72) Koji Yamamoto 5-6-1 Higashi-Hachiman, Hiratsuka-shi, Kanagawa Sanritsu Gas Chemical Co., Ltd. Hiratsuka Laboratory (72) Inventor Takeo Hayashi 5-6-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Inside the Hiratsuka Research Laboratory, Mitsui Gas Chemical Co., Ltd. (72) Inventor Masahiko Takashima 5-6-1, Higashi-Yawata, Hiratsuka-shi, Kanagawa Sanritsu Gas Chemical Co., Ltd. Hiratsuka Laboratory

Claims (3)

[Claims] 1. A polyester copolymer comprising a terephthalic acid component unit and a 2,6-naphthalenedicarboxylic acid component unit as main dicarboxylic acid component units, and an ethylene glycol component unit as a main diol component unit. A polyester-based resin foam characterized in that a resin having a half-crystallization time of 20 minutes or more at a temperature 1.25 times the glass transition temperature based on absolute temperature of the polymer is used as a base resin. 2. The molar ratio of a terephthalic acid component unit to a 2,6-naphthalenedicarboxylic acid component unit is 2: 8 to 8: 2.
The polyester resin foam according to claim 1, wherein 3. A terephthalic acid component unit and a 2,6-naphthalenedicarboxylic acid component unit as main dicarboxylic acid component units, an ethylene glycol component unit as a main diol component unit, and a glass transition temperature based on absolute temperature of 1. The half-crystallization time at 25 times the temperature is 20
Minutes or more and a foaming agent is kneaded with an extruder under high-temperature and high-pressure conditions to form a foamable melt, and the foamable melt is extruded from the extruder tip to a low-pressure region and foamed. A method for producing a polyester resin foam.