JPH09174665A - Manufacture of polyester resin foamed sheet of superior moldability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a polyester resin foamed sheet of superior moldability. SOLUTION: The crystallinity index of one surface of sheet and the crystallinity index of the other surface of the sheet are set 15% or less respectively and the difference between the crystallinity of one surface and the crystallinity of the other surface of the sheet are set 2% or less by heating the extrusion foamed sheet of thickness of 0.5-3.0mm composed of polyester resin as a base resin to the temperature more than the glass transitiorl temperature and lower than the crystallizing temperature by 20 deg.C.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention belongs to the technical field of producing a polyester-based resin foam sheet having excellent moldability.

[0002]

2. Description of the Related Art A foamed container formed by foaming a resin such as polystyrene resin into a container shape is widely used as a container having a light weight and a heat insulating property.

However, since a foam container made of polystyrene resin as a base resin has poor heat resistance, it cannot be directly stored in a cooking device such as a microwave oven or an oven to directly cook food.

Polyester-based resins have higher heat resistance than polystyrene-based resins, and are therefore expected as a new base resin for foaming. For example, JP-A-59-13523
No. 7 discloses a polyester resin foam, and further describes that a product obtained by molding a sheet of the foam into a food container can be heated in an oven.

On the other hand, as a method for industrially producing a foamed container, a method is used in which an extruded foamed sheet produced by an extrusion foaming method is used as a raw material, and this is formed into a desired container shape by a method such as vacuum forming or match mold forming. Is widely known.
For example, extruded foam sheets such as polystyrene resin,
A method in which a base resin and a foaming agent are mixed in an extruder, a cylindrical foam extruded from an annular die and foamed is brought into contact with a mandrel to cool, and then cut open to form a flat sheet. It is known that an extruded foam sheet having a polyester resin as a base resin can be produced by the same method.

However, since the polyester resin is a crystalline resin, the secondary moldability is different depending on the crystallinity of the extruded foam sheet, and if the crystallinity is high, the secondary molding can be performed successfully. If you can't do it, it will happen.

In view of the secondary moldability, it has been proposed to suppress the crystallinity of the polyester resin extruded foam sheet to a certain value or less. For example, Japanese Examined Patent Publication 5-8357
Japanese Patent Publication No. 3 describes that a high temperature thermoplastic polyester resin foam immediately after foaming is rapidly cooled to a temperature not higher than a glass transition point to have a crystallinity of 30% or less.

As described above, as a conventional technique, in order to improve the secondary moldability of the polyester resin foam sheet, it is effective to suppress the crystallinity of the polyester resin in the foam sheet to a certain value or less. It is known.

[0009]

DISCLOSURE OF THE INVENTION In order to improve the secondary moldability of a polyester-based resin foam sheet, the present inventors have to suppress the crystallinity of the polyester-based resin in the foam sheet to a certain value or less. A follow-up test was carried out based on the conventional knowledge that it was good, but a foamed sheet was produced in which the crystallinity of the polyester resin in the foamed sheet was kept below a certain value.
It has been found that it is not always possible to obtain a uniform molded product because wrinkles and distortions occur in the molded product and the size and shape of the bubbles in the molded product become uneven even after the subsequent molding.

[0010]

The inventors of the present invention have made extensive studies as to the reason why the secondary moldability is not always good, and as a result, in the polyester-based resin foamed sheet, the resin crystal of each part in the foamed sheet is formed. The difference in the degree of chemical composition has a great influence on the properties that influence the secondary moldability such as the glass transition temperature and the extensibility of each part in the foam sheet, and due to the large number of small bubbles contained in the foam sheet. Polyester with crystallinity suppressed below a certain value that the thermal conductivity at the time of subsequent molding becomes small and the difference in moldability due to partially different crystallinity becomes more remarkable than that of non-foamed one. The inventors have come to the conclusion that when the resin-based foamed sheet is softened by heating and subjected to secondary molding, uniform molding cannot be performed and molding failure occurs.

Based on the above idea, the present inventors have proposed a method for obtaining a foamed sheet having good secondary processability by producing a foamed sheet in which the deviation of the crystallinity in the polyester resin foamed sheet is controlled. As a result of repeated studies, the present invention has been completed.

That is, according to the present invention, an extruded foam sheet having a thickness of 0.5 to 3.0 mm and containing a polyester resin as a base resin is heated to a temperature not lower than the glass transition temperature and not higher than 20 ° C. lower than the crystallization temperature. As a result, the crystallinity of one surface portion and the crystallinity of the other surface portion of the sheet are 15% or less, respectively, and the crystallinity of one surface portion and the crystallinity of the other surface portion of the sheet are 2% difference from the degree
The present invention relates to a method for producing a polyester-based resin foam sheet having excellent moldability, which is characterized by:

[0013] The conventional knowledge has no description about the influence of the deviation of the crystallinity in a single polyester-based resin foam sheet on the secondary moldability, and therefore, naturally, the crystals in the foam sheet are not described. No attempt has been made so far to reduce the deviation of the crystallinity in order to reduce the adverse effect of the deviation of the crystallinity on the secondary formability and the like.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an extruded foam sheet having a thickness of 0.5 to 3.0 mm and containing a polyester resin as a base resin is used.

The polyester resin is 230 to 30.
It has thermoplasticity at 0 ° C. and has a melt viscosity of 100 to 10,000 Pa · s at a temperature selected from the temperature range of this range.
It is preferably 300 to 10,000 Pa · s,
For example, the main component is a polyester obtained by polymerizing a polyvalent carboxylic acid and a polyhydric alcohol.

The melt viscosity is measured according to JIS K 71
99 Viscosity at a shear rate of 60.8 s ^-1 measured in accordance with "Method for testing flow characteristics of thermoplastics by capillary rheometer". In addition, the polyester obtained by polycondensing the polyvalent carboxylic acid and the polyhydric alcohol as a main component means that the polyester-based resin contains 70% of the polyester constituent portion composed of the polyvalent carboxylic acid and the polyhydric alcohol. % By weight, the same shall apply hereinafter), and further 85% or more.

Examples of the polyester composed of the polyvalent carboxylic acid and the polyhydric alcohol include, for example, a linear polyester obtained by polycondensation of an aromatic dicarboxylic acid and a diol component and / or at least 3 of the linear polyester. And a branched polyester obtained by copolymerizing a branching component having 3 to 6 ester-forming groups.

As the aromatic dicarboxylic acid component, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid,
Diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid and the like can be mentioned. These may be used alone or in combination of two or more.

As the diol component, ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol, hexamethylene glycol, cyclohexane dimethylol,
Tricyclodecane dimethylol, 2,2-bis (4-β
-Hydroxyethoxyphenyl) propane, 4,4-bis (β-hydroxyethoxy) diphenylsulfone and the like. These may be used alone or in combination of two or more.

Specific examples of the linear polyester include:
Examples thereof include polyethylene terephthalate, polybutylene terephthalate, poly-1,4-cyclohexane dimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, etc. Among them, they have high industrial utility value and are easy to handle. Therefore, polyethylene terephthalate, polybutylene terephthalate, and poly-1,4-cyclohexanedimethylene terephthalate are preferably used.

The intrinsic viscosity of the linear polyester is 0.4 to 1.1 dl / g, more preferably 0.5 to 1.1 from the viewpoint of exhibiting melt viscoelasticity that allows easy production of a foamed sheet. It is preferably 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 branching component is a component used for facilitating the formation of a branched structure in the main chain of polyester, and the branching component has at least three hydroxyl groups and / or carboxyl groups. The above object is achieved by the above. By introducing a branch into the main chain of polyester, the melt viscosity and melt elasticity of the polyester resin can be increased, and a foamed sheet having fine cells can be easily manufactured.

Specific examples of the branching component include, for example, tri- or tetracarboxylic acids such as trimellitic acid and pyromellitic acid, and lower ones thereof (having 1 to 6 carbon atoms).
Examples thereof include alkyl esters, glycerin, trimethylolpropane, trimethylolethane, tri- or tetraols such as pentaerythritol, dihydroxycarboxylic acids, hydroxydicarboxylic acids and their derivatives. These may be used alone or in combination of two or more. Among the above branching components, glycerin is preferable from the viewpoint of easily adjusting the degree of polymerization of the branched polyester.

In the branched polyester,
In order to have the preferable melt viscoelastic properties imparted to the branched polyester by the branching component and to maintain the stability, the number of the branching component units is 0 relative to 100 mol of the total number of moles of the aromatic dicarboxylic acid unit. The amount is preferably 1 mol or more, more preferably 0.3 mol or more, and in order not to impair the moldability when molding a resin composition containing a branched polyester, an aromatic dicarboxylic acid is used. There are 5 branching component units per 100 moles of total units.
It is preferable that the amount is not more than 3 mol, more preferably not more than 3 mol.

Specific examples of the branched polyester include branched polyester composed of terephthalic acid, ethylene glycol and glycerin, branched polyester composed of terephthalic acid, ethylene glycol and trimethylolpropane, terephthalic acid, ethylene glycol and pentaerythritol. Branched polyesters, terephthalic acid, butanediol, glycerin branched polyesters, naphthalene dicarboxylic acid, ethylene glycol, glycerin branched polyesters, and the like. Among them, industrial utility value is high, easy to handle, etc. From the viewpoint of terephthalic acid, ethylene glycol, branched polyester composed of glycerin, terephthalic acid, butanediol, branched polyester composed of glycerin, naphthalene Dicarboxylic acid, ethylene glycol, branched polyesters consisting of glycerin is preferably used.

The branched polyester has an intrinsic viscosity of 0.4 to 1.1 dl from the viewpoint that it has melt-viscoelastic characteristics suitable for producing a foamed sheet and does not impair moldability.
/ G, more preferably 0.5 to 1.0 dl / g.

In the present invention, the term "polyester resin as a base resin" means that the polyester resin is used as a base resin, and in addition, a resin melting property adjusting agent, a bubble adjusting agent, a stabilizer,
A pigment, a filler, a flame retardant, an antistatic agent, etc. may be added in an amount of 30% or less, and further 15
It means that the one added by not more than% can be used.

The resin melt characteristic modifier is a component for increasing the melt viscoelasticity at the time of foaming and preventing breakage of the foam, and specific examples thereof include pyromellitic dianhydride,
Examples include compounds having two or more acid anhydride groups in one molecule such as benzophenone tetracarboxylic dianhydride, and compounds having two or more epoxy groups in one molecule such as diglycidyl phthalate. .

The blending amount of the resin melt property adjusting agent is sufficient to sufficiently bring out the effect of using the resin melt property adjusting agent, for example, the effect of imparting melt viscoelasticity suitable for extrusion foam molding. The amount is preferably 0.05 part or more, and more preferably 0.1 part or more, based on 100 parts of the polyester resin (parts by weight, the same below), and a resin composition obtained from the polyester resin or the resin melt property adjusting agent. In order to sufficiently prevent the progress of gelation, the amount is preferably 5 parts or less, especially 3 parts or less with respect to 100 parts of the polyester resin.

Specific examples of the bubble control agent include nucleating agents such as talc.

In the present invention, the melt viscosity at a temperature selected from the temperature range of 230 to 300 ° C. is 100 to 10000 Pa as a preferable range of the melt viscoelasticity of the resin which allows easier extrusion foam molding.・
s, more preferably 300 to 10,000 Pa · s, but from the viewpoint that such melt viscoelastic properties can be easily adjusted according to the purpose, a linear polyester is used as the polyester resin used in the production of the foamed sheet. It is preferable to use a branched polyester obtained by copolymerization with a branching component, and it is possible to stably maintain the imparted melt viscoelastic property and to easily produce a foamed sheet having more uniform fine bubbles. From the viewpoint, it is preferable to use the branched polyester with a resin melting property modifier added.

The thickness of the foamed sheet used in the present invention is 0.5 to 3.0 mm, more preferably 0.7 to 3.0 mm, as described above.
Although it is 2.0 mm, the thickness of 0.5 mm or more is a preferable thickness from the viewpoint that the strength, rigidity and heat insulating property of the molded body after the secondary molding are sufficiently exhibited, and the thickness is 3.0 m.
A thickness of m or less means that when a foamed sheet having poor thermal conductivity is heated from the surface, the temperature gradient between the surface and the inside does not increase, the difference in fluidity does not increase, and wrinkles are not formed during container molding. It is a preferable thickness because it is less likely to cause distortion or distortion.

The density of the foamed sheet is 0.7 g.
/ Cm ³ or less, more preferably 0.5 g / cm ³ or less is preferable from the viewpoint of taking advantage of the properties such as lightness of the foam, and 0.1 g / cm ³ or more, and further 0.15 g.
/ Cm ³ or more is preferable from the viewpoint that the molded product after secondary molding exhibits sufficient rigidity.

The closed cell rate of the cells present in the foamed sheet is preferably 80% or more, and more preferably 85% or more from the viewpoint of enhancing the heat insulating property.

As a method for producing the foamed sheet,
The extrusion foaming method is suitable because a foamed sheet can be continuously produced by a simple industrial production method.

When a foamed sheet is produced by the extrusion foaming method, for example, a resin (which may be a composition) having the above polyester resin as a base resin is supplied to an extruder and melted to contain a foaming agent. It is produced by extruding into a sheet form from a die provided with an extruding hole having a linear or annular cross-sectional shape attached to the tip of an extruder as an unexpandable resin composition and foaming.

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

When a solid decomposable foaming agent is used as the foaming agent, it is preferably supplied to the extruder as a resin composition having a polyester resin as a base resin. Further, when a volatile type foaming agent or a gas type foaming agent is used as the foaming agent, it is preferable to press it in the middle of the extruder.

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 obtained foam sheet. Usually, the amount of the foaming agent used is about 0.5 to 50 parts based on 100 parts of the polyester resin.

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, and aromatic compounds such as benzene and xylene. hydrocarbon,
Examples include halogenated hydrocarbons such as methylene chloride, and fluorochloro-substituted hydrocarbons such as Freon (trade name).

Further, specific examples of the gas type foaming agent include nitrogen and carbon dioxide.

A polyester resin composition containing a foaming agent is extruded in a sheet form from an extrusion hole, and the extruded sheet is foamed by being moved from the extruder in the high pressure region to the atmospheric pressure in the low pressure region. Becomes

As the extruder used in the extrusion foaming method, an extrusion molding machine such as a single-screw extruder, a multi-screw extruder or a tandem extruder can be used.

Since the polyester resin is a crystalline resin as described above, crystallization proceeds from the high temperature state immediately after extrusion until it is sufficiently cooled and solidified. In order to facilitate the processing of the extruded foamed sheet into a molded product having a desired shape in the subsequent thermal processing step, the progress of crystallization is fixed amount or less, specifically 20% or less, and further 15% or less.
It is necessary to keep it below%. In order to suppress the progress of crystallization, it is effective to cool the foamed sheet as soon as possible after extrusion, specifically, within 0.1 to 10 seconds, and further within 0.1 to 5 seconds after extrusion. However, since the foamed sheet contains a large number of small bubbles, it has a low thermal conductivity, and it is very difficult to quench the entire foamed sheet in the same manner. As a result, the crystallinity of the resulting foamed sheet tends to vary greatly from place to place. For example, the inner surface of a cylindrical foam sheet immediately after extrusion is cooled (usually cooled to 10 to 30 ° C.) using a circular die and a mandrel that are usually used in the production of conventional extruded foam sheets. In the method of contacting with and cooling rapidly, the crystallinity of the surface on the side that was in contact with the mandrel is relatively small (specifically 6 to 10%), but the surface on the side that is not in contact with the mandrel is Since the cooling is delayed, the crystallinity becomes large (specifically 9 to 15%), and the crystallinity greatly differs between one surface and the other surface of the same foamed sheet.

The foamed sheet produced in this way is
Depending on the thickness of the foamed sheet and the expansion ratio, for example, when the thickness is 0.8 mm and the expansion ratio is 5.4 times, the crystallinity of the surface on the cooled side is 6 to 8%, the non-cooled side. The surface of the sheet has a crystallinity of 9 to 12% and a thickness of 1.4.
In the case of mm, the expansion ratio of 5.9 times, the sheet has a crystallinity of 6 to 9% on the cooled side and a crystallinity of 9 to 14% on the non-cooled side.

In the present invention, a foamed sheet (hereinafter referred to as an original foamed sheet) having a deviation in crystallinity as described above is crystallized at a glass transition temperature (usually 30 to 90 ° C.) or higher (usually 100 to 160 ° C.). By heating at a temperature 20 ° C. lower than that, the crystallization of the relatively high crystallinity portion of the original foam sheet is suppressed, while the crystallization of the relatively low crystallinity portion is preferentially performed. By advancing it, the deviation of the crystallinity is reduced, and the crystallinity of one surface part of the sheet and the crystallinity of the other surface part are each 15%.
The difference between the crystallinity of one surface portion of the sheet and the crystallinity of the other surface portion of the sheet can be set to 2% or less.

Although the mechanism of action by which the deviation of the crystallinity is reduced by the heating as described above is not clear, the polyester resin used in the present invention has a higher glass transition temperature as the crystallinity increases. On the other hand, since crystallization does not easily proceed at a temperature below the glass transition temperature, it is considered that only a portion having a low crystallinity is preferentially crystallized by heating at a specific temperature.

The means for heating the foamed sheet is not particularly limited, and methods such as heating by conduction, heating by radiation, heating by convection, and heating by high frequency can be used. Among them, the method of heating by contacting with heated air is simple and preferable.

The heating time may be determined according to the heating temperature and the degree of deviation of the crystallinity of the original foam sheet, and is usually 3
It is preferably carried out for about 0 minutes to 24 hours. Generally, when the heating temperature is relatively high, the heating time can be shortened, and when the heating temperature is relatively low, the heating time can be lengthened. When the difference in crystallinity of the original foamed sheet is large, the heating time can be lengthened, and when the difference in crystallinity of the original foamed sheet is small, the heating time can be shortened.

The crystallization temperature in this specification means a differential scanning calorimeter (DSC2 manufactured by Seiko Denshi Kogyo KK).
00) in advance of about 50 from the glass transition temperature.
After holding the equipment at a low temperature of ℃ until the equipment became stable, it was 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 was drawn. From the obtained DSC curve, JIS K 7121 It means the crystallization peak temperature at the time of temperature rise, which is obtained according to "9.2 How to obtain crystallization temperature" in "Plastic transition temperature measurement method".

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 (DSC200 manufactured by Seiko Denshi Kogyo Co., Ltd.) at a temperature rising rate of 10 ° C./min, the heat quantity of cold crystallization of the thermoplastic polyester resin ΔH
c (J / g) and heat of fusion ΔHm (J / g) were measured, and the values are calculated according to the following formula.

Crystallinity (%) = {(ΔHm−ΔHc) / ΔHo} × 100 (In the formula, ΔHo represents the heat of fusion (J / g) per 1 g of the completely crystallized thermoplastic polyester resin. "Polymer Data Handbook First Edition" edited by Japan Society of Polymer Science (Showa 6)
According to Baifukan Co., Ltd., issued on January 30, 1st, the heat of complete crystallization per 1 mol of repeating unit of polyethylene terephthalate is 26.9 KJ, which can be converted into the heat of complete crystallization per 1 g. Since it is 140.1 J, 140.1 (J / g) is used as ΔHo in the present invention. Note that the surface portion in this specification means a portion from the surface of the foamed sheet to a certain thickness, and in the present invention, the thickness of the surface portion is 150 μm. The surface crystallinity is about 150μ
It is the crystallinity of a stripped film with a thickness of m.

In this way, the crystallinity of one surface portion of the sheet and the crystallinity of the other surface portion are each 15% or less, preferably 12% or less, and the crystallinity of one surface portion of the foamed sheet is A foamed sheet is produced in which the difference between the crystallinity and the crystallinity of the other surface portion is 2% or less, preferably 1% or less.

The reason why the crystallinity of one surface portion of the sheet and the crystallinity of the other surface portion of the foamed sheet obtained by the present invention are each 15% or less is as follows.

That is, when the crystallinity of the surface portion of the foamed sheet exceeds 15%, the glass transition temperature rises when the foamed sheet is softened by heating and then shaped by a mold having a predetermined shape. The softening temperature becomes high and the easiness of elongation decreases, resulting in poor shapeability and poor secondary formability. In particular, in the case of a foamed sheet, since the base resin is present as a very thin film, if the crystallinity becomes high and the softening temperature becomes high as described above, bubble breakage tends to occur during secondary molding. In addition, wrinkles due to irregular deformation of bubbles are more likely to occur, and other adverse effects are prominent. This phenomenon is a phenomenon found by the present inventors.

Further, in the foamed sheet obtained by the present invention, the difference between the crystallinity of one surface portion of the sheet and the crystallinity of the other surface portion is 2% or less for the following reason. .

That is, when the difference between the crystallinity of one surface portion and the crystallinity of the other surface portion exceeds 2%, the one having a lower crystallinity in the preheating stage at the time of secondary molding is used. The surface of No. 1 first softens and secondary foaming occurs, and the bubbles become large, and if shaping is performed as it is, a molded product having different bubble sizes in the thickness direction or a molded product having a wrinkled surface is likely to occur. In order to reduce such unevenness in secondary foamability and shapeability and impart good secondary moldability, it is preferable that the difference in crystallinity between the two surface layers of the foamed sheet is 2% or less. It is more preferably 1% or less.

In the heating and softening step, secondary foaming is likely to occur in a portion having low crystallinity. Therefore, if the crystallinity of the foamed sheet is partially different, the size and shape of the bubbles after heating will be uneven. The phenomenon that the moldability becomes poor is a phenomenon first discovered by the present inventors.

[0062]

EXAMPLES The method of the present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 dl / g and glycerin were copolymerized according to a conventional method, and the glycerin unit was contained in a ratio of 1 mol based on 100 mol of the total mols of the terephthalic acid unit. Intrinsic viscosity 0.70dl
A branched polyester of / g was obtained. The melt viscosity of this branched polyester at 280 ° C. 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 fed to the extruder. After melt-mixing with the obtained melted mixture, isopentane was injected at a ratio of 1.2 g / 100 g, and extruded from a circular die having a clearance of 0.4 mm under the following conditions to obtain a cylindrical foam sheet, Immediately (2 seconds after extrusion), the surface temperature was kept at 20 ° C. While adhering to a cylindrical cooling mandrel made of aluminum, the mixture was allowed to proceed for 10 seconds to cool from the inner surface side.
The cooled cylindrical foam sheet was cut open to obtain a flat extruded raw foam sheet. The obtained original foam sheet has a thickness of 1.
4 mm, apparent density 0.23 g / cm ³ (foaming ratio about 5.
It was a sheet having a closed cell ratio of 89%.

Extruder temperature: 270 to 300 ° C. Extruder head temperature: 275 to 285 ° C. Extrusion amount: 13 kg / hr The surface of the obtained original foam sheet that was in close contact with the cooling mandrel (hereinafter, referred to as the surface. , And the opposite surface (hereinafter referred to as the back surface) were examined for crystallinity by the following methods, and found to be 7.4% and 10.6, respectively.
%Met.

This original foamed sheet was placed in an oven having an internal temperature of 80 ° C. and held for 6 hours, then taken out of the oven and cooled to room temperature. When the crystallinity of the front surface and the back surface of the obtained foamed sheet was examined by the following method, they were 8.9% and 10.8%, respectively.

The original foamed sheet had a glass transition temperature of about 72 ° C. and a crystallization temperature of about 124 ° C.

The foamed sheet thus obtained was heated to 130 to 140 ° C. with an infrared heater using a single shot molding machine,
It is shaped with a mold whose temperature is adjusted to 0 ° C and promotes crystallization, and has a diameter of 70 mm, a depth of 20 mm and a bottom diameter of 55.
It was molded into a mm container. The secondary moldability of the obtained container was evaluated by the following method.

Table 1 shows the results.

(Crystallinity) A skin layer having a thickness of about 150 μm was peeled from the front and back surfaces of the foamed sheet, and a differential scanning calorimeter (DSC20 manufactured by Seiko Denshi Kogyo KK) was peeled off.
0) is used to measure the heat of cold crystallization and the heat of fusion,
Formula: Crystallinity (%) = (heat of fusion per gram−heat of cold crystallization per gram) ÷ 140.1 × 100.

(Secondary Moldability) With respect to the obtained container, the appearance of the surface and the bubble state of the cross section were observed, and the secondary moldability was evaluated based on the following evaluation criteria.

Evaluation Criteria A: The size of bubbles is uniform, and the surface is free from cracks, cracks and wrinkles. B: The size of bubbles is a little uneven, but the surface cracks.
No cracks and wrinkles. C: Part of the surface has cracks, cracks and wrinkles. D: There are cracks, cracks and wrinkles on the entire surface.

Example 2 Example 1 except that the oven time was 12 hours.
A foamed sheet was obtained in the same manner as in.

When the crystallinity of the front surface and the back surface of the obtained foamed sheet was examined in the same manner as in Example 1, they were 9.8% and 10.8%, respectively.

Secondary foamability of the obtained foamed sheet was evaluated in the same manner as in Example 1.

Table 1 shows the results.

Example 3 The thickness was 0.8 mm and the apparent density was 0.25 g / cm ³ (foaming ratio about 5.4 times) in the same manner as in Example 1 except that the clearance of the circular die was 0.3 mm. An extruded raw foam sheet having a closed cell rate of 87% was obtained.

When the crystallinities of the front and back surfaces of the obtained original foam sheet were examined in the same manner as in Example 1, they were 6.8% and 9.2%, respectively.

The original foamed sheet was placed in an oven having an internal temperature of 90 ° C. and held for 1 hour, then taken out of the oven and cooled to room temperature. When the crystallinity of the front surface and the back surface of the obtained foamed sheet was examined, they were 9.6% and 10.0%, respectively.

Secondary foamability of the obtained foamed sheet was evaluated in the same manner as in Example 1.

Table 1 shows the results.

Comparative Example 1 The extruded raw foamed sheet (thickness 1.
4 mm, apparent density 0.23 g / cm ³ (foaming ratio about 5.
9 times), front and back crystallinity 7.4% and 1
0.6%), the secondary formability was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 The extruded raw foam sheet obtained in Example 3 (thickness: 0.
8 mm, apparent density 0.25 g / cm ³ (foaming ratio about 5.
4.times.), Front and back crystallinity 6.8% and 9.
2%) was evaluated for secondary moldability in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 In Example 1, the extruded raw foam sheet was heated to an internal temperature of 80 ° C.
A foamed sheet was obtained in the same manner as in Example 1 except that it was placed in an oven with an internal temperature of 120 ° C. and held for 30 minutes instead of being placed in the oven and held for 6 hours.

The crystallinities of the front and back surfaces of the obtained foamed sheet were examined in the same manner as in Example 1 and found to be 15.4% and 15.8%, respectively.

Secondary foamability of the obtained foamed sheet was evaluated in the same manner as in Example 1.

Table 1 shows the results.

[0088]

[Table 1]

From the results shown in Table 1, the foamed sheet having a small degree of crystallinity and a small deviation thereof obtained by the method of the present invention has a small degree of crystallinity but a large deviation thereof, and a small deviation of the crystallinity degree. Is more crystalline than
It can be seen that the secondary formability is good, and there is a large difference in the secondary formability due to the degree and deviation of the crystallinity.

[0090]

According to the manufacturing method of the present invention, it is possible to manufacture a foamed sheet having a crystallinity of the foamed sheet and a small deviation thereof.

The foamed sheet obtained according to the present invention has a small degree of crystallinity and its deviation, and therefore has a large degree of deviation of the degree of crystallinity as seen in conventional thermoplastic polyester resin extruded foamed sheets. It is excellent in secondary moldability because it can reduce molding defects such as cracks and wrinkles during molding and unevenness of bubbles in the molded product.

Further, the foamed sheet according to the present invention is a foamed sheet which uses a thermoplastic polyester resin having excellent heat resistance as a base resin, and can be easily subjected to various printing and sticking of a decorative film. By molding as a container, it is possible to obtain a container which is excellent in designability, heat resistance, heat insulation, and the like and can be suitably used for various uses.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 7:00 C08L 67:02

Claims (1)

[Claims] 1. A sheet obtained by heating an extruded foam sheet having a thickness of 0.5 to 3.0 mm using a polyester resin as a base resin to a temperature not lower than the glass transition temperature and not higher than 20 ° C. lower than the crystallization temperature. The crystallinity of one surface portion of the sheet and the crystallinity of the other surface portion are each 15% or less, and the difference between the crystallinity of one surface portion of the sheet and the crystallinity of the other surface portion To 2% or less, a method for producing a polyester resin foam sheet having excellent moldability.