JPH09183860A - Production of polyester-based resin foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyester-based resin foam without producing injurious crease or crack when a foaming sheet is molded into the form. SOLUTION: A polyester-based resin foaming sheet containing a polyester- based resin as a substrate resin, having 0.5-3mm thickness and <=13% average crystallinity and <=3% difference between crystallinity of either one surface layer of the sheet and crystallinity of the other surface layer and <=3% difference between the crystallinity of center layer of the sheet and crystallinity of the each surface layer is heated to carry out secondary foaming and then molded in heated mold to raise the average crystallinity of the resin foam to >=20%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polyester-based resin foam molded article. More specifically, the present invention relates to a method for producing a polyester-based resin foam molding which can be suitably used, for example, in a container that is lightweight and has heat insulating properties.

[0002]

2. Description of the Related Art Conventionally, a polystyrene resin has been mainly used as a material resin for a light-weight and heat-insulating foam container.

However, since the polystyrene resin is inferior in heat resistance, it is not possible to store the food in a foaming container having this as a base resin and directly heat it with a heating cooker such as a microwave oven or an oven.

Therefore, in recent years, as a base resin replacing polystyrene resin, a polyester resin having excellent heat resistance as compared with polystyrene resin has been attracting attention, and a food obtained by molding a polyester resin foam sheet. A container has been proposed (JP 59-135237 A).

Although the food container has heat resistance to the extent that it can be heated in an oven, there is a problem that wrinkles and cracks occur when the foam sheet is molded into a food container.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and is a polyester resin foam molded article which does not cause harmful wrinkles or cracks when a foamed sheet is molded into a molded article. It aims at providing the manufacturing method of.

[0007]

The present invention uses a polyester resin as a base resin, has a thickness of 0.5 to 3 mm and an average crystallinity of 13% or less, and crystallizes one surface layer of a sheet. And the crystallinity of the other surface layer are 3% or less, and the difference between the crystallinity of the central layer of the sheet and the crystallinity of each surface layer is 3% or less. The present invention relates to a method for producing a polyester resin foam-molded article, which comprises heating a foamed sheet for secondary foaming and then molding it with a heating die to increase the average crystallinity to 20% or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Conventionally, in order to facilitate secondary molding of a foam sheet of a polyester resin, it is known that the crystallinity of the polyester resin is suppressed to a certain value or less. Even if the crystallinity is suppressed, there is a problem that wrinkles and cracks are generated during the secondary molding.

As a result of intensive studies to solve the above problems, the present inventors have found that in a foamed sheet using a polyester resin as a base resin, the polyester resin has an uneven crystallinity (unevenness). Have a great influence on the properties that influence the secondary formability such as glass transition temperature and stretchability.

Further, since the foamed sheet contains a large number of small bubbles, the thermal conductivity at the time of secondary molding is low,
The crystallinity of the foamed sheet becomes partially different,
It has been found that since a secondary molded body cannot be obtained in a state having a uniform crystallinity, a remarkable molding defect occurs.

The present invention is based on the fact that the uneven crystallinity of the polyester resin foamed sheet has an effect on the moldability in molding into a molded body and the characteristics of the container after molding. An object of the present invention is to provide a method for producing a foamed molded article using a foamed sheet whose degree of deviation is controlled.

As described above, the polyester resin foam sheet used in the present invention has a polyester resin as a base resin, a thickness of 0.5 to 3 mm and an average crystallinity of 1.
3% or less, the difference between the crystallinity of one surface layer of the sheet and the crystallinity of the other surface layer is 3% or less, and the crystallinity of the central layer of the sheet and each of the above surface layers. The difference with the crystallinity of is less than 3%.

The polyester resin used in the present invention is preferably one which exhibits thermoplasticity in the range of 230 to 300 ° C. The melt viscosity at a temperature when the polyester resin exhibits thermoplasticity is 100 Pa · s or more, preferably 300 Pa · s, from the viewpoint of easily producing a foamed sheet having fine cells and having a high closed cell rate.
It is preferably s or more, and from the viewpoint that the moldability of the foamed sheet is not easily impaired, it is preferably 10,000 Pa · s or less, and more preferably 8000 Pa · s or less.

The melt viscosity is defined in JIS K 7199.
Viscosity at a shear rate of 60.8 s ^-1 , measured in accordance with "Method for testing flow characteristics of thermoplastics by capillary rheometer".

As the polyester resin, for example, a resin containing a polyester obtained by polycondensing a polyvalent carboxylic acid and a polyhydric alcohol as a main component is preferably used.

The main component of the polyester obtained by polycondensing the polyhydric carboxylic acid and the polyhydric alcohol is that the polyester resin is composed of a polyester component consisting of the polyhydric carboxylic acid and the polyhydric alcohol.
0% by weight or more, and more preferably 85% by weight or more.

As a typical example of the polyester, for example, a linear polyester obtained by polycondensing an aromatic dicarboxylic acid and a diol, the linear polyester, and at least 3, preferably 3 to 6 ester-forming groups. Examples thereof include branched polyesters obtained by polycondensation with a branch-forming component having The linear polyester and the branched polyester can be used alone or in combination of two or more.

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

Typical examples of the diol include 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.

Specific examples of preferable linear polyesters include polyethylene terephthalate, polybutylene terephthalate, poly-1,4-cyclohexanedimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, and the like. Among these, polyethylene terephthalate, polybutylene terephthalate, and poly-1,4-cyclohexanedimethylene terephthalate are more preferably used from the viewpoint of high industrial utility value and easy handling.

The intrinsic viscosity of the linear polyester is 0.4 to 1.1 dl / g in order to develop the melt viscoelasticity which facilitates the melt molding, and especially the value of 0.
It is preferably from 5 to 1.0 dl / g.

The intrinsic viscosity of the resin in the present specification means a value measured at 23 ° C. using a mixture of phenol and tetrachloroethane (weight ratio 1/1) as a solvent.

The branched polyester can be obtained by polycondensing the linear polyester with a branch-forming component.

When the branched polyester is used, there are advantages that the melt viscosity and melt viscoelasticity are increased, and a foamed sheet having fine cells is easily manufactured.

The branch-forming component is a component used to form a branched structure in the main chain of 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.

Typical examples of the branching component include tri- or tetracarboxylic acids such as trimellitic acid and pyromellitic acid, and their lower alkyl esters;
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 admixture of two or more. Among these branch-forming components, glycerin is preferable from the viewpoint of easy adjustment of the degree of polymerization of the branched polyester.

In preparing the branched polyester, in order to sufficiently improve the retention stability of the melt viscoelasticity of the branched polyester by the branch-forming component, the amount of the branch-forming component is set to the aromatic dicarboxylic acid. It is preferably 0.1 mol or more, particularly 0.3 mol or more, relative to 100 mol of the acid. Further, in order to improve the processability into a sheet, the amount of the branch forming component is preferably 5 mol or less, particularly 3 mol or less, relative to 100 mol of the aromatic dicarboxylic acid.

The intrinsic viscosity of the branched polyester is
To impart sufficient melt viscoelasticity, 0.4 dl /
It is preferably at least g, especially at least 0.5 dl / g, and in order to facilitate melt molding, 1.1 dl / g or less, especially 1.
It is preferably 0 dl / g or less.

The polyester resin may be, for example, pyromellitic acid dianhydride or benzophenonetetracarboxylic acid dianhydride as a resin melting property adjusting agent for increasing melt viscoelasticity during foaming and preventing breakage of the foam. Compounds having two or more acid anhydride groups in one molecule such as, and compounds having two or more epoxy groups in one molecule such as diglycidyl phthalate can be blended.

The blending amount of the resin melt characteristic modifier is sufficient to sufficiently bring out the effect of using the resin melt characteristic modifier, for example, the effect of imparting melt viscoelasticity suitable for extrusion foam molding. , 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 progress of gelation of the polyester resin, 5 parts or less relative to 100 parts of the polyester resin,
It is preferably 3 parts or less.

Further, in the present invention, when the polyester resin is used as the base resin, the polyester resin is
In addition to nucleating agents such as talc as a foam control agent at the time of foaming, other additives such as stabilizers, pigments, fillers, flame retardants, antistatic agents, etc. are blended by appropriately adjusting the blending amount. Means that you can do it. The content of these additives is preferably 30% by weight or less of the polyester resin, and more preferably 15% by weight or less.

In the present invention, it is preferable to use the branched polyester from the viewpoint that the melt viscoelasticity of the polyester resin used in the present invention can be easily adjusted, and the polyester resin is melted. From the viewpoint that the viscoelasticity can be stably maintained and a foamed sheet having more uniform and fine bubbles can be obtained, it is preferable to use the branched polyester to which a resin melting property modifier is added. .

As a method for producing the foamed sheet used in the present invention from the polyester resin, the extrusion foaming method is suitable from the viewpoint of a simple industrial production method capable of continuously producing the foamed sheet.

The production of the foamed sheet by the extrusion foaming method can be carried out, for example, as follows.

A polyester resin and, if necessary, a resin melting property adjusting agent and an additive are supplied to an extruder and melted,
A foaming resin composition containing a foaming agent is mixed with the foaming agent.

A die is attached to the tip of the extruder, and the die is provided with an extrusion hole having a linear or annular cross-sectional shape. From this extrusion hole, the foamable resin composition is pressed into a sheet. put out. In this way, by extruding from the inside of the extruder under high pressure to the atmospheric pressure in the low pressure region, foaming is performed to form a foamed sheet.

As the foaming agent, a solid decomposition type foaming agent which decomposes to generate gas by heating, a liquid volatile type foaming agent which is vaporized by heating, and a gas type gas type foaming agent which can be melted into a resin under pressure. Any of these can be used.

When a solid decomposition type foaming agent is used as the foaming agent, it is preferably supplied to the extruder as a mixture containing a polyester resin as a base resin. When a liquid volatile foaming agent or a gas gas foaming agent is used as the foaming agent, it is preferable to press-fit from the middle of the extruder.

Specific examples of the decomposition type foaming agent include azodicarbonamide, dinitrosopentamethylenetetramine, hydrazodicarbonamide, sodium bicarbonate and the like.

Specific examples of the volatile blowing agent include saturated aliphatic hydrocarbons such as butane, pentane and hexane, saturated alicyclic hydrocarbons such as cyclohexane, aromatic hydrocarbons such as benzene and xylene, and methylene chloride. Examples thereof include halogenated hydrocarbons and fluorochloro-substituted hydrocarbons such as Freon (trade name).

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

The above foaming agents can be used alone or in admixture 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 foamed sheet obtained. Usually, the amount of the foaming agent used is about 0.5 to 50 parts based on 100 parts of the polyester resin.

Examples of the extruder used in the extrusion foaming method include extrusion molding machines such as a single-screw extruder, a multi-screw extruder and a tandem extruder.

The polyester resin is, as described above,
Since it is a crystalline resin, crystallization proceeds from the high temperature state immediately after extrusion until it is sufficiently cooled and solidified.

In order to obtain a foamed sheet that can be used in the present invention, it is necessary to suppress the progress of crystallization to a certain amount or less.

In order to suppress the progress of crystallization, it is effective to cool the foamed sheet after extrusion foaming as early as possible. However, since the foamed sheet contains a large number of small bubbles, it has a low thermal conductivity, so that it is very difficult to uniformly quench the entire foamed sheet. For example, using a circular die and a mandrel as is usually performed when manufacturing a conventional extruded foam sheet, the inner surface of the cylindrical foam sheet immediately after extrusion,
When the method of contacting with the cooled mandrel and quenching is adopted, the crystallinity of the surface in contact with the mandrel becomes 9.7%, whereas the crystallinity of the surface on the opposite side is 9.7%. The degree of crystallinity is 14.0%, and although the same foamed sheet has the same degree of crystallinity on the front surface and the back surface (see the example described in JP-B-5-47570).

Therefore, the foamed sheet used in the present invention can be applied to both surfaces of the foamed sheet extruded from the die of the extruder as soon as possible, for example, a solid, a liquid or a liquid having a temperature lower than the crystallization temperature of the polyester resin. It can be produced by bringing a gas into contact with the polyester resin and cooling it to a temperature not higher than the crystallization temperature of the polyester resin.

For example, when the extrusion hole of the die attached to the tip of the extruder has a straight cross-sectional shape and the foamed sheet to be extruded is a flat plate, the temperature range is adjusted in front of the extruder. Multiple sets of cooling rolls were combined and arranged so that each central axis direction was at right angles to the traveling direction of the sheet, and were guided to the cooling roll while blowing cooling air on both sides of the foamed sheet immediately after extrusion. After that, the surface of the foamed sheet is advanced while being brought into contact with a cooling roll that rotates in accordance with the traveling speed of the foamed sheet, and a cooling medium such as water or air is brought into contact with the outer surface of the foamed sheet, and the temperature is not higher than the crystallization temperature. Cool it to.

When the extrusion hole has an annular cross section and the foam sheet to be extruded has a cylindrical shape, a temperature-controlled cylindrical cooling mandrel is provided in front of the extruder in the same manner as described above. Arranged so that the central axis direction is parallel to the traveling direction of the foamed sheet, while blowing air for cooling on both sides of the foamed sheet immediately after extrusion, after guiding to the mandrel,
The inner surface of the foamed sheet may be advanced while contacting the mandrel, and the outer surface of the foamed sheet may be contacted with a cooling medium such as cooling water or air to cool the foamed sheet to a crystallization temperature or lower.

A method for extruding a cylindrical foam sheet through an extrusion hole having an annular cross section is obtained by adjusting the ratio of the outer diameter of the cooling mandrel to the diameter of the extrusion hole to obtain the extruded cylindrical shape. Since it is possible to easily adjust the stretch ratio in the width direction of the foam sheet, it is preferable in that the stretch ratio in the length direction and the width direction of the foam sheet can be easily adjusted independently.

In the above cooling method, the temperature of the cooling medium needs to be equal to or lower than the crystallization temperature, but if the temperature of the cooling medium is too low, the portion of the foamed sheet that does not come into direct contact with the cooling medium. Compared with (for example, the central layer of the sheet), only the portion in contact with the cooling medium (for example, the surface layer of the sheet) rapidly cools and the crystallinity becomes small, so that the central layer The difference in crystallinity between the surface layer and the surface layer tends to increase.

Especially when a cooling solid having a high thermal conductivity is used as the cooling medium, such a tendency becomes strong. Therefore, the temperature of the cooling medium is preferably about the glass transition temperature or higher.

When the inner surface of the cylindrical foamed sheet is brought into contact with the mandrel for cooling, in order to avoid that only the inner surface of the foamed sheet is preferentially cooled, for example, the outer surface of the foamed sheet is Cooling water at room temperature or 0
It is preferable that cooling from the outer surface is promoted by contacting cooling air at about -20 ° C.

As the cooling solid, one having a high thermal conductivity, which does not physically or chemically change upon contact with the foamed sheet, is preferably used. Specific examples of the cooling solid include, but are not limited to, rolls, plugs, and plates made of metal such as stainless steel and aluminum.

The crystallization temperature referred to in this specification is obtained as follows.

That is, the crystallization temperature was measured by a differential scanning calorimeter (DSC20 manufactured by Seiko Instruments Inc.).
0) is used, the glass transition temperature is about 50% or more in advance.
After keeping the equipment at a low temperature of ℃ until it stabilizes, it is heated to a temperature of about 50 ℃ higher than the end of the crystallization peak at a heating rate of 10 ℃, and a DSC curve is drawn. It is a crystallization peak temperature at the time of temperature rise, which is obtained according to "9.2 How to obtain crystallization temperature" in "Method for measuring transition temperature of plastics" of K 7121.

Further, the crystallinity in the present specification means J
IS K 7122 "Method for measuring the transition heat of plastics"
In accordance with the above, using a differential scanning calorimeter (manufactured by Seiko Denshi Kogyo Co., Ltd., DSC200) under a temperature rising condition of 10 ° C./min, the heat quantity of cold crystallization H of the thermoplastic polyester resin is measured.
c (J / g) and heat of fusion Hm (J / g) were measured,
The value calculated according to the following formula.

[Crystallinity (%)] = {(Hm-Hc) /
Ho} × 100 Here, Ho in the formula represents the heat of fusion (J / g) per 1 g of the fully crystallized thermoplastic polyester resin. According to “Polymer Data Handbook (First Edition)” edited by The Society of Polymer Science, Ltd. (Sho 61-1-30, Baifukan Co., Ltd.), a repeating unit 1 of polyethylene terephthalate among thermoplastic polyester resins is used. The amount of heat of complete crystallization per mole is 26.9 kJ. Converting this to the amount of heat of complete crystallization per gram, it becomes 140.1 J.
Therefore, in the present invention, Ho is 140.1 J / g.
Is used.

The present inventors have found that the deviation of the crystallinity of the polyester resin foamed sheet can be reduced by the method of cooling the foamed sheet after extrusion as described above. Further, it has been found that the secondary formability of the foamed sheet can be improved by reducing the deviation of the crystallinity in this way.

The reason why the foamed sheet used in the present invention has an average crystallinity of 13% or less is that if the average crystallinity exceeds 13%, the secondary formability of the sheet becomes poor.

That is, in the present invention, in order to produce a molded article from a foamed sheet, the foamed sheet is heated and softened to 2
Next, it is foamed and then molded with a mold having a predetermined shape. When the crystallinity of the polyester resin increases, the softening temperature of the polyester resin increases due to the increase of the glass transition temperature, or the elongation of the polyester resin decreases. However, the secondary foamability during heating and the subsequent shapeability become poor. In particular, in the case of a foamed sheet, the base resin is present as a very thin film, so that an increase in crystallinity tends to cause bubble breakage during secondary molding, and wrinkles due to irregular deformation of bubbles. The adverse effects such as easy occurrence and easy occurrence of strain in the molded product are remarkable. In order to reduce such adverse effects and obtain good secondary moldability, the foamed sheet has an average crystallinity of 13% or less, preferably 10% or less.

The average crystallinity in this specification means a value calculated according to the following formula.

[Average crystallinity (%)] = (Crystallinity of one surface layer + Crystallinity of the other surface layer + Crystallinity of central layer × 2) / 4 Surface in the present specification The layer means a layer from the surface of the foamed sheet to a certain thickness, and in the present invention, the thickness of the surface layer is 150 μm. Further, the central layer in the present specification refers to a layer having a constant thickness in the substantially central portion in the thickness direction of the foam sheet, and in the present invention, the central layer is from the central portion in the thickness direction of the foam sheet. It was a layer with a thickness of up to 150 μm.

In the foamed sheet used in the present invention, the difference between the crystallinity of one surface layer and the crystallinity of the other surface layer is 3% or less, and the center layer of the foamed sheet is crystallized. And the crystallinity of each surface layer is 3% or less.

In the foamed sheet used in the present invention,
The reason why the difference in crystallinity is within 3% is as follows.

In the present invention, the foamed sheet is heated for secondary foaming. In this secondary foaming, the ease of secondary foaming varies depending on the degree of crystallization of the foamed sheet. Therefore, if the crystallinity of the foamed sheet is partially different, the size of the bubbles after secondary foaming and The shapes become uneven, which not only adversely affects the characteristics after molding, but also deteriorates the secondary moldability. For example, if the crystallinity of the front surface and the back surface of the foamed sheet are greatly different, the surface with the lower crystallinity is softened first in the preliminary stage of molding, secondary foaming occurs, and the bubbles become large, If the molding is carried out as it is, a molded body having different bubble sizes in the thickness direction or a molded body having a wrinkled surface is likely to be formed.

When the crystallinity of the central layer is higher than that of the surface layer, in addition to the difference in crystallinity, the heat insulation of the foamed sheet causes the surface layer and the central layer to be generated during heating. And the difference in the behavior of the secondary foaming between the surface layer and the central layer becomes more noticeable.

In order to reduce such unevenness in secondary foamability and moldability and to provide good secondary moldability, the foam sheet is provided between both surface layers (front surface and back surface) and between each surface layer and the center layer. The difference in crystallinity between the two is within 3%. The difference in crystallinity is preferably less than 1%.

In the present invention, the foamed sheet may have various thicknesses depending on its use.

In the present invention, the thickness of the foamed sheet is set to 0.5 mm or more in order to sufficiently develop the mechanical strength and rigidity of the molded article after the secondary molding. When a foamed sheet that does not have good heat conduction is heated from the surface, the temperature gradient between the surface and the inside of the sheet does not increase, so the difference in formability in the thickness direction does not increase, and the formed body wrinkles. It is set to 3 mm or less from the viewpoint that distortion is unlikely to occur.

The apparent density of the foamed sheet is preferably 0.7 g / cm ³ or less, more preferably 0.5 g.
By setting it to be / cm ³ or less, advantages such as lightness as a foam can be utilized. Furthermore, the closed cell ratio of the bubbles present in the foamed sheet is preferably 80%.
As described above, more preferably 85% or more, it is possible to further enhance the heat insulating property of the foam produced.

The polyester resin foamed sheet thus obtained is heated to be secondarily foamed and then molded with a heating die to increase the average crystallinity to 20% or more, whereby a polyester resin foamed molded product is obtained. .

In the present invention, the heat treatment for softening the sheet by heating to cause secondary foaming is carried out so that the temperature of the surface layer and the central layer of the sheet becomes equal to or higher than the glass transition temperature of the polyester resin before the heat treatment. Is more preferable, and more preferably the glass transition temperature is 40 ° C. or higher and the glass transition temperature is 100 ° C. or lower. If the treatment temperature is too low, secondary foaming becomes difficult, and if the treatment temperature is too high, the crystallization of the sheet proceeds too much and the formability deteriorates.

Here, the glass transition temperature means JIS K
7121 “Plastic transition temperature measurement method” refers to the value determined according to “How to determine glass transition temperature”.

Further, during the heat treatment for secondary foaming, the crystallization of the foamed sheet also proceeds at the same time. However, if the crystallinity becomes too high, the moldability of the heating die in the next step deteriorates. Therefore, the average crystallinity of the foamed sheet before molding by the heating mold is 1
It is preferably 8% or less, and more preferably 16% or less.

The temperature of the heating mold used for molding is preferably not less than the glass transition temperature of the polyester resin before molding and less than the melting start temperature, glass transition temperature plus 40 ° C. or more, melting start temperature minus 20 ° C. The following is more preferable. If it is lower than the glass transition temperature, molding becomes difficult, and if it is higher than the melting start temperature, the foam will be heat-shrinked.

In the present invention, it is preferable to form the secondary expanded foamed sheet by the matched molding method because it is easy to obtain a foamed molded article having a predetermined shape.

In the present invention, the secondary expanded foamed sheet is molded into a predetermined shape by a heating mold and the average crystallinity is 2
Perform processing to raise it to 0% or more. This treatment may be carried out by taking out the molded foamed sheet from the heating mold once and subjecting it to another heat treatment, and keeping the foamed sheet in the heating mold used in the molding step, the average crystal It may be performed by continuously performing heat treatment until the degree of conversion increases.

If the average crystallinity is less than 20%, thermal deformation is likely to occur at a high temperature. Therefore, in order to obtain a molded article having excellent heat resistance, the average crystallinity is 20% or more, preferably 22%. That is all.

According to the production method of the present invention, a foamed molded product free from harmful wrinkles and cracks can be obtained from a polyester resin foamed sheet, and the foamed molded product can be used as a lightweight and heat-insulating container or the like. It can be used preferably.

[0082]

EXAMPLES Next, the method for producing the polyester resin foam molded article of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 dl / g and glycerin were polycondensed, and the glycerin unit was contained at a ratio of 1 mol per 100 mol of the total mols of terephthalic acid units. A branched polyester of 0.70 dl / g was obtained. The glass transition temperature of this branched polyester is about 74 ° C, the melting start temperature is about 230 ° C, 280 ° C.
The melt viscosity at was 650 Pa · s.

The obtained branched polyester was dried in a dehumidifying dryer at 140 ° C. for 4 hours, and then a mixture of 100 parts of the branched polyester and 0.3 part of pyromellitic dianhydride was prepared with a clearance of 0.4 mm. It is supplied to an extruder equipped with a circular die of and melted under the following extrusion conditions,
Isopentane was added at a ratio of 1.2 parts to 100 parts of the melt from the middle of the extruder and further kneaded.
It was extruded from a circular die as a cylindrical foam sheet.

(Extrusion Conditions) Extruder temperature: 270 to 300 ° C. Extruder head temperature: 275 to 285 ° C. Extrusion amount: 13 kg / hr Continue to keep the surface temperature of the obtained cylindrical foamed sheet at 80 ° C. By advancing while adhering to a cylindrical cooling mandrel made of aluminum, cooling was performed from the inner surface side, and air was also blown from the periphery of the foam sheet at a temperature of about 10 ° C. to cool from the outer surface side. The cooled cylindrical foam sheet was cut open to obtain a flat foam sheet.

The obtained foamed sheet has a thickness of 1.4 mm,
Apparent density 0.24 g / cm ³ (expansion ratio about 5.6
It was a foamed sheet having a closed cell rate of 89%.

A skin layer on the side of the obtained foamed sheet that was in close contact with the cooling plug (hereinafter referred to as the front surface layer), a skin layer on the opposite side (hereinafter referred to as the back surface layer), and The crystallinity of the central layer was investigated by the following method. The results and the average crystallinity values are also shown in Table 1.

(Crystallinity) The crystallinity of the skin layer was measured by a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd.) by peeling off the skin layer having a thickness of about 150 μm from both surfaces of the foamed sheet.
Manufactured by DSC200), and the heat of cold crystallization and the heat of fusion were measured and calculated according to the following formulas. The crystallinity of the central layer is about 1 after tearing the foam sheet into half thickness.
The center layer having a thickness of 50 μm was stripped off, and the calculation was performed by the same method as described above.

[Crystallinity (%)] = (amount of heat of fusion per gram-amount of heat of cold crystallization per gram) ÷ 140.1 ×
100 In the above formula, 140.1 is the amount of heat of complete crystallization (J / g) per 1 g of polyethylene terephthalate.

The obtained foamed sheet is heated at 130 to 140 ° C. for 10 seconds by an infrared heater to secondary foam, and then sandwiched between male and female molds whose surface temperature is controlled at 180 ° C. and molded. It promotes crystallization while holding it in the mold and has a diameter of 70 mm, a depth of 20 mm and a bottom diameter of 55 mm.
To obtain a container-shaped molded body.

A part of the sheet after heating and secondary foaming was cut out before molding with a mold and examined for apparent density and average crystallinity. The apparent density was 0.18 g / cm 3. ³ (foaming ratio about 7.7 times), and the average crystallinity was 13.2%.

The average crystallinity of the obtained molded product is 2
It was 4.8%.

Next, the state of the obtained molded body was visually observed, and the secondary moldability was evaluated based on the following evaluation criteria. Table 1 shows the results.

(Evaluation Criteria) A: The molded product is free from cracks, cracks and molding wrinkles. B: Cracks, cracks and molding wrinkles are observed in part of the molded product. C: Cracks, cracks and molding wrinkles are remarkable on the entire molded body.

Further, as a heat resistance evaluation test of the molded product,
Place the molded body in an oven whose internal temperature is kept at 180 ℃.
After leaving for 0 minutes, the presence or absence of deformation was examined, and it was found that no change was observed in the shape of the container and the heat resistance was good.

Example 2 In Example 1, instead of the aluminum cylindrical cooling mandrel whose surface temperature was maintained at 80 ° C., an aluminum cylindrical cooling mandrel whose surface temperature was maintained at 40 ° C. was used. A thickness of 1.3 mm and an apparent density of 0.26 g / cm were obtained in the same manner as in Example 1 except that water having a temperature of about 20 ° C. was blown instead of blowing air having a temperature of about 10 ° C. around the cylindrical sheet. ³ (foaming ratio about 5.2 times),
A foam sheet having a closed cell ratio of 90% was obtained.

The crystallinity of the surface layer, back surface layer and center layer of the obtained foamed sheet was examined by the same method as in Example 1. The results and the average crystallinity values are shown in Table 1.
Shown in

Using the obtained foamed sheet, a container-shaped molded body was obtained in the same manner as in Example 1.

The apparent density and the average crystallinity of the sheet before heating and secondary foaming and before molding with a die were examined in the same manner as in Example 1. The apparent density was 0.19 g. / Cm ³ (foaming ratio of about 7.
4 times), and the average crystallinity was 12.2%.

The average crystallinity of the obtained molded product is 2
It was 4.4%.

Then, the obtained molded product was evaluated for secondary moldability in the same manner as in Example 1. Table 1 shows the results.

Further, the heat resistance evaluation test of the molded product was carried out in the same manner as in Example 1. As a result, it was found that no change was observed in the shape of the container and the heat resistance was good.

Comparative Example 1 In Example 1, instead of the aluminum-made cylindrical cooling mandrel whose surface temperature was kept at 80 ° C., an aluminum-made cylindrical cooling mandrel whose surface temperature was kept at 20 ° C. was used. A thickness of 1.5 mm and an apparent density of 0.25 g / c were obtained in the same manner as in Example 1 except that air having a temperature of about 10 ° C. was not blown from around the cylindrical sheet.
A foamed sheet of m ³ (foaming ratio of about 5.4 times) was obtained.

The crystallinity of the surface layer, back surface layer and center layer of the obtained foamed sheet was examined by the same method as in Example 1. The results and the average crystallinity values are shown in Table 1.
Shown in

Further, using the obtained foamed sheet, a container-shaped molded product was obtained in the same manner as in Example 1, and then the secondary moldability was evaluated. Table 1 shows the results.

Comparative Example 2 From the foamed sheet obtained in Comparative Example 1 60 cm × 60 cm
After cutting out a sheet of size 1 and heating it in an oven at 110 ° C for 1 hour, remove it from the oven and let it cool at room temperature to a thickness of 2.1 mm and an apparent density of 0.18 g / c.
A foamed sheet of m ³ (foaming ratio of about 7.4) was obtained.

The crystallinity of the surface layer, back surface layer and center layer of the obtained foamed sheet was examined by the same method as in Example 1. The results and the average crystallinity values are shown in Table 1.
Shown in

Further, using the obtained foamed sheet, Example 1
After obtaining a container-shaped molded product in the same manner as in (1), the secondary moldability was evaluated. Table 1 shows the results.

COMPARATIVE EXAMPLE 3 A thickness of 3.2 mm and an apparent density of 0.14 g were obtained in the same manner as in Example 1 except that isopentane was injected at a rate of 2.4 g per 100 g of the melt.
A foamed sheet having a / cm ³ (foaming ratio of about 9.6) was obtained.

The crystallinity of the surface layer, back surface layer and center layer of the obtained foamed sheet was examined by the same method as in Example 1. The results and the average crystallinity values are shown in Table 1.
Shown in

Further, using the obtained foamed sheet, a container-shaped molded product was obtained in the same manner as in Example 1, and then the secondary moldability was evaluated. Table 1 shows the results.

[0112]

[Table 1]

From the results shown in Table 1, when the crystallinity of each part of the foamed sheet and the mutual difference are large,
It can be seen that the secondary formability becomes poor and there is a large difference in the secondary formability due to the degree and deviation of the crystallinity.

Comparative Example 4 In Example 1, the foamed sheet was heated by an infrared heater to 13
Instead of heating at 0-140 ℃ for 10 seconds for secondary foaming, sandwich it between two heating plates with a space of 1.4 mm and
A container-shaped molded body was obtained in the same manner as in Example 1 except that the secondary foaming was not performed only by heating at 30 to 140 ° C. for 10 seconds.

The apparent density and average crystallinity of the sheet before heating after heating were 0.24 g / cm ³ respectively.
(Expansion ratio was about 5.6 times) and 13.5%, and the average crystallinity of the obtained molded product was 24.4%.

The obtained foam had wrinkles over the entire surface and had a markedly impaired appearance. Moreover, when the cross section of the molded body was visually observed, the sizes of the bubbles were extremely uneven.

From the results of Example 1 and Comparative Example 4, when the foamed sheet was not subjected to the secondary foaming during heating before molding, the secondary moldability of the molded article was deteriorated and the secondary foaming was observed depending on the presence or absence of the secondary foaming. It can be seen that there is a large difference in formability.

Comparative Example 5 In Example 1, after molding the foamed sheet with a mold,
A container-shaped molded body was obtained in the same manner as in Example 1 except that the molded body was immediately taken out.

The average crystallinity of the obtained molded body is 18.7.
%Met.

Next, a heat resistance evaluation test of the molded product was carried out in the same manner as in Example 1. As a result, the shape of the container was markedly changed, and it was judged that this molded product had extremely poor heat resistance.

From the results of Example 1 and Comparative Example 5, when the crystallinity after molding is small, the heat resistance of the molded article becomes poor, and the secondary moldability depends on the crystallinity after molding. It turns out that there is a big difference.

[0122]

EFFECT OF THE INVENTION The polyester resin foam molded article obtained by the production method of the present invention is formed by heating a foamed sheet having a uniform crystallinity to carry out secondary foaming, and then molding with a heating die to obtain average crystallization. Since the degree is increased to 20% or more, cracks and wrinkles at the time of secondary molding caused by unevenness of crystallinity as seen when using a conventional extruded foamed sheet of thermoplastic polyester resin. There are no molding defects such as, and non-uniformity of bubbles in the molded product.

Further, according to the production method of the present invention, since the thermoplastic polyester resin having excellent heat resistance is used as the base resin, when it is molded as a container, the design, heat resistance, It is possible to obtain a polyester resin foamed molded article that is excellent in heat insulation and can be suitably used for various purposes.

Claims (4)

[Claims] 1. A polyester resin as a base resin, having a thickness of 0.5 to 3 mm and an average crystallinity of 13% or less, wherein one surface layer of the sheet has a crystallinity and the other surface layer has a crystallinity. The polyester resin foamed sheet having a difference in crystallinity of 3% or less and a difference in crystallinity of the center layer of the sheet from the crystallinity of each surface layer is 3% or less Foam and then mold in a heating mold to obtain an average crystallinity of 20
% Or more, and a method for producing a polyester-based resin foam molding. 2. The difference between the crystallinity of one surface layer of the polyester resin foam sheet and the crystallinity of the other surface layer is 1
%, And the difference between the crystallinity of the center layer of the sheet and the crystallinity of each of the surface layers is less than 1%. 3. The method for producing a polyester resin foam molded article according to claim 1 or 2, wherein the average crystallinity of the polyester resin foam sheet before molding with a heating mold is 18% or less. 4. The method for producing a polyester resin foam molded article according to claim 1, 2 or 3, wherein the polyester resin foam sheet is secondarily foamed and then molded by a matched molding method.