JP2012020444A - Method of manufacturing polyester based resin foamed molding, and polyester based resin foamed molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a polyester based resin foamed molding by which the polyester based resin foamed molding prevented from thermal strain is produced and to prevent the polyester based resin foamed molding prevented from thermal strain.SOLUTION: In the method of manufacturing the polyester based resin foamed molding, the polyester based resin foamed molding is produced through a preheating step of preheating a polyester based resin foamed sheet and a molding step of press-molding the preheated polyester based resin foamed sheet to form into a product shape. After the preheating step is carried out so that the surface temperature: Ts (°C) of the polyester based resin formed sheet may become Tc≤Ts≤(Tm-50) when the crystallization temperature determined by the differential scanning calorimetric analysis of the polyester based resin foamed sheet is defined by Tc (°C) and the melting point is defined by Tm (°C) and the molding step of carrying out the press-molding at a temperature equal to or below the surface temperature (Ts) using a mold, a heat insulating step of keeping the product shape under a temperature condition equal to or above Tc and equal to or below (Tm-50) is carried out.

Description

  The present invention relates to a method for producing a polyester resin foam molded article and a polyester resin foam molded article. More specifically, the present invention relates to a polyester resin for producing a polyester resin foam molded article by press molding a polyester resin foam sheet. The present invention relates to a method for producing a foam molded article, and a polyester resin foam molded article produced by such a production method.

Conventionally, a polyester resin sheet is formed into a product shape such as a container by performing a forming process by a sheet forming method such as vacuum forming or press forming.
Polylactic acid resins and polyethylene terephthalate resins are known as polyester resins that serve as materials for this polyester resin sheet. In particular, polyethylene terephthalate resins are widely used because of their excellent strength and heat resistance.

Although this polyethylene terephthalate resin usually has a high melting point exceeding 200 ° C., it has a crystallization temperature in the temperature range of about 140 ° C. Therefore, for example, a polyethylene terephthalate resin sheet is molded into a molded product formed by sheet molding. When the strain remains, when heat exceeding 100 ° C. is applied to the molded product, molecular rearrangement may occur, causing shrinkage or strain.
For this reason, studies have been made to prevent thermal distortion of molded products. For example, in Patent Document 1 below, heat is generated by using a biaxially oriented polyester resin film in vacuum molding or the like. It is described that a molded article with suppressed strain can be formed.

By the way, in applications such as food trays that require light weight and heat insulation, foam molded products such as foam trays are used as molded products using polyester resins.
And such a polyester resin foam molded article is also produced by sheet-molding a polyester resin foam sheet. In that case, a polyester resin as described in Patent Document 1 is used. Measures different from those for forming a film are required.

  However, until now, no sufficient study has been made on countermeasures against thermal distortion related to a polyester resin foam molded article obtained by sheet molding a polyester resin foam sheet, and no solution has been established.

JP 2004-122767 A

  The present invention aims to solve the above problems, and provides a method for producing a polyester resin foam molded product capable of producing a polyester resin foam molded product in which thermal distortion is suppressed, As a result, it aims at provision of the polyester-type resin foaming molded article by which the thermal distortion was suppressed.

  The present invention relating to a method for producing a polyester resin foam molded article for solving the above problems includes a preheating step of preheating the polyester resin foam sheet, and press molding the preheated polyester resin foam sheet. A method for producing a polyester resin foam molded article, wherein a molding step for forming a product shape is performed to produce a polyester resin foam molded article, the crystal obtained by differential scanning calorimetric analysis of the polyester resin foam sheet The preheating is performed so that the surface temperature of the polyester resin foam sheet: Ts (° C.) satisfies Tc ≦ Ts ≦ (Tm-50), when the temperature is Tc (° C.) and the melting point is Tm (° C.). After performing the step and performing the molding step of press molding with a mold having a temperature equal to or lower than the surface temperature (Ts), Tc or more (Tm It is characterized by performing the heat insulating step of holding the product shape at a temperature of 50) below.

According to the method for producing a polyester resin foam molded article of the present invention, after the product shape is formed on the polyester resin foam sheet by press molding, a heat retaining step for holding the product shape at a predetermined temperature is performed. Therefore, the distortion generated during the press molding is alleviated by the heat retaining step.
That is, since the residual strain is suppressed, it is possible to suppress the occurrence of distortion in the molded product even when the obtained molded product is heated.

Explanatory drawing which shows the measuring method of calorie | heat amount of fusion and crystallization calorie | heat amount.

Embodiments of the present invention will be described below.
First, the polyester resin foam sheet used will be described.

A polyester resin foam sheet (hereinafter also simply referred to as “foamed sheet”) used in the method for producing a polyester resin foam molded article (hereinafter also simply referred to as “foam molded product”) of the present embodiment is a foam molded product. It is possible to widely adopt what is used as a raw material of the material, and the thickness and the foamed state are not particularly limited, but the thickness of the foamed sheet is 0.15 mm or more and 2 mm or less The average bubble diameter is preferably 50 nm or more and 200 μm or less.
In addition, about the thickness of this foam sheet, it can measure easily, for example using the Mitsutoyo Corporation thickness gauge.
Moreover, about an average bubble diameter, it can measure based on the test method of ASTM D2842-69.
More specifically, first, the foamed sheet is cut along the MD direction (extrusion direction) and the TD direction (direction orthogonal to the extrusion direction), and the central part of each cut surface is scanned with an electron microscope (for example, ( Magnified photograph with model name “S-3000N” manufactured by Hitachi, Ltd.
Next, the photographed image is printed on A4 paper, and in the cut surface image cut along the MD direction, a straight line having a length of 60 mm parallel to the extrusion direction is drawn, and bubbles existing on the straight line are drawn. The number is counted, and the average chord length (t) in the extrusion direction is calculated based on the following formula (1).

Average chord length (t) = 60 / (number of bubbles × photo magnification) (1)

Similarly, in the image of the cut surface cut along the TD direction, one straight line having a length of 60 mm parallel to the direction orthogonal to the extrusion direction is drawn, the number of bubbles existing on this straight line is counted, and the above formula Based on (1), the average chord length (t) in the direction orthogonal to the extrusion direction is calculated.
In each of the MD direction and the TD direction, the magnification in photographing with the electron microscope is adjusted so that about 10 to 20 bubbles are arranged on the straight line of 60 mm.

  Also, when drawing a straight line, try to make the straight line penetrate as much as possible without making point contact with the bubble, and if some of the bubbles make point contact with the straight line, include this bubble in the number of bubbles, Further, when the both ends of the straight line are located in the bubbles without penetrating the bubbles, the bubbles in which both ends of the straight line are positioned are included in the number of bubbles.

Then, the calculated average chord length (t) in each direction is defined as the bubble diameter (D _MD ) in the _MD direction and the bubble diameter (D _TD ) in the TD direction, respectively, and the average bubble is calculated by arithmetic mean shown in the following formula (2). Calculate the diameter.

Average bubble diameter: D (mm) = (D _MD + D _TD ) / 2 (2)

Moreover, it is preferable that some degree of crystallization is caused in the foamed sheet constituting the foamed molded product so that the foamed molded product exhibits excellent strength.
Furthermore, in the point which can suppress the thermal distortion of a foam-molded product, it is preferable that the foam sheet itself used for formation of this foam-molded product is in a state in which thermal strain is unlikely to occur.
That is, it is preferable to approximate the crystallization state between the foamed sheet before being molded and the foamed molded product after being molded, and the foamed sheet before being molded is in a state in which crystallization is less likely to occur. It is preferable that
Whether or not the foamed sheet is in a state in which crystallization hardly occurs can be determined by differential scanning calorimetry.

For example, when polyethylene terephthalate resin, which is generally crystallized to some extent, is subjected to a differential scanning calorimeter (DSC) and heated from room temperature to about 300 ° C. (first run), an exothermic peak is observed around 140 ° C. An absorption peak is observed around 260 ° C.
And when it cools rapidly from 300 degreeC to normal temperature and it heats to about 300 degreeC again (second run), the peak of around 140 degreeC usually increases compared with the time of a first run.
The peak temperature of the exothermic peak that appears in the vicinity of 140 ° C. is the crystallization temperature (Tc), and the exothermic energy per unit mass is the crystallization heat (ΔH _Tc ).
Moreover, the peak temperature of the absorption peak that appears in the vicinity of 250 ° C. is the melting point (Tm), and the endothermic energy per unit mass is the heat of fusion (ΔH _Tm ).
Therefore, it can be determined that the smaller the crystallization heat amount (ΔH _Tc ) in the first run, the more difficult it is for the foamed sheet to crystallize.
Further, regarding the degree of crystallinity of the foam sheet, 100% is obtained by subtracting the heat of crystallization by heating in this DSC, that is, the heat of crystallization (ΔH _Tc ), from the heat of fusion in the first run (ΔH _Tm ). It can be determined by calculating the percentage with respect to the theoretical heat of fusion in the case of crystallization (ΔH ₀ : 140.1 mJ / mg for polyethylene terephthalate, 93.0 mJ / mg for polylactic acid).
That is, the crystallinity of the foam sheet can be determined by calculating the following formula.

Crystallinity (%) = [ΔH _Tm −ΔH _Tc ] / ΔH ₀ × 100 (%)

Note that detailed measurement conditions by differential scanning calorimetry will be described in detail in Examples later.

As described above, it is preferable that the foam sheet used for molding the foam-molded product has a degree of crystallinity of a certain level or more and is more difficult to crystallize.
Specifically, the foamed sheet has a difference (ΔH _Tm −ΔH _Tc ) between a heat of fusion (ΔH _Tm ) and a heat of crystallization (ΔH _Tc ) determined by differential scanning calorimetry of 0.03 J / mg or more, The crystallinity is preferably 20% or more and 50% or less.
Note that the above difference (ΔH _Tm −ΔH _Tc ) is small, which means that crystallization is likely to occur more easily than the current state, and thermal distortion is likely to occur, or excellent foam molded products even when sufficiently crystallized. Therefore, the foamed sheet not only has a predetermined crystallinity but also the difference (ΔH _Tm −ΔH). _Tc ) is preferably 0.03 J / mg or more.
In general, the upper limit of crystallinity (%) is 60%. Therefore, the upper limit of this difference (ΔH _Tm −ΔH _Tc ) is 0.08 J / mg in the case of polyethylene terephthalate resin. In the case of resin, it is 0.06 J / mg.

In this specification, when expressing the numerical value about crystallization calorie | heat amount and the heat of fusion, and the comparison of numerical values, unless there is particular notice, the absolute value and the comparison of absolute value are represented.
Therefore, normally, the heat of fusion is observed as a negative value in DSC, and the heat of crystallization is observed as a positive value. For example, the heat of fusion (ΔH _Tm ) is “−X (J / mg) ”, and when the crystallization heat (ΔH _Tc ) is observed as“ Y (J / mg) ”, the difference between the heat of fusion (ΔH _Tm ) and the crystallization heat (ΔH _Tc ) (ΔH _Tm −ΔH " _Tc )" does not mean "-(X + Y) (J / mg)" but "(XY) (J / mg)".

The material constituting such a foamed sheet will be described. The foamed sheet used in the present embodiment uses a polyester resin as a main component.
The polyester resin is a general term for polymer compounds in which the main bond in the main chain is an ester bond, and is usually obtained by condensation polymerization of a dicarboxylic acid component and a glycol component.

  Examples of the dicarboxylic acid component constituting the polyester resin include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodiumsulfonedicarboxylic acid. Aromatic dicarboxylic acids such as acid and phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids, paraoxy And oxycarboxylic acids such as benzoic acid.

Examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, and polypropylene glycol, and cyclohexanedimethanol. And aromatic glycols such as bisphenol A and bisphenol S.
Further, a hydroxy acid that has a carboxylic acid component and an alcohol component in the molecular structure and forms a polyester by self-condensation polymerization, for example, an aliphatic hydroxy acid such as glycolic acid or lactic acid can also be employed.

  As the polyester resin constituting the foamed sheet in the present embodiment, a polyethylene terephthalate resin using terephthalic acid and ethylene glycol among the dicarboxylic acid component and glycol component described above is excellent in versatility and is preferably used.

  Also, poly D-lactic acid resin, poly L-lactic acid resin, poly DL-lactic acid resin that is a copolymer of poly D-lactic acid and poly L-lactic acid, and a mixture of poly D-lactic acid resin and poly L-lactic acid resin (Stereo complex), copolymer of poly D-lactic acid and hydroxycarboxylic acid, copolymer of poly L-lactic acid and hydroxycarboxylic acid, poly D-lactic acid or poly L-lactic acid and aliphatic dicarboxylic acid and aliphatic A polylactic acid resin such as a copolymer with a diol is also preferably used because of its excellent versatility like the polyethylene terephthalate resin.

For the polyethylene terephthalate resin and polylactic acid resin, other dicarboxylic acid components or glycol components may be introduced (copolymerized) into the molecule as long as the heat resistance and moldability are not impaired.
Two or more polyester resins may be used in combination in the foam sheet.

If it mentions about the method of producing a foam sheet with such a material, the said polyester-type resin foam sheet may be manufactured by a well-known method.
That is, a method of foaming by adding a liquefied gas or a chemical foaming agent to the molten resin when forming a sheet in an extruder, or adding incompatible organic / inorganic fine particles that become cell nuclei in an extruder. , A method of forming a void at the interface between the polyester resin as a matrix and the fine particles by a process such as uniaxial stretching, sequential biaxial, and simultaneous biaxial stretching performed after the sheet is formed, and under high temperature and high pressure after the sheet is formed. After impregnating the gas, it can be produced by a method of foaming a sheet by releasing pressure.

The incompatible organic / inorganic fine particles described above can be added within a range that does not impair the heat resistance and moldability of the polyester resin as the matrix.
The incompatible organic fine particles are not particularly limited as long as they are not compatible with the matrix at the time of extrusion molding and are finely dispersed and do not melt at the time of sheet molding. For example, polyolefin such as polypropylene, polymethylpentene, and cyclic olefin , Polycarbonate, fine particles made of polystyrene, acrylic acids, methallylic acids, polyesters, etc., crosslinked fine particles of an amorphous resin such as a divinyl compound and a divinylbenzene crosslinking agent, silicone polymer particles, and the like can be used.

Further, as incompatible inorganic fine particles, wet silica, dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, aluminum oxide, mica, kaolin, clay and the like can be used. .
Among the above-described organic fine particles, polymethylpentene, cyclic olefin, fine particles made of acrylic acid and crosslinked fine particles of divinyl compound are preferable because they are transparent and excellent in non-coloring properties.
In the inorganic system, particles made of wet silica, dry silica, aluminum silicate, titanium oxide, calcium carbonate, and barium sulfate are preferable because they are transparent or white and excellent in non-coloring properties.
These organic / inorganic fine particles may be used in combination of two or more.

  The foam sheet is not limited to a single layer, and a foam sheet having a laminated structure having a non-foamed skin layer on one or both sides can also be used in the method for producing a foam molded product of the present embodiment. is there.

Also, the foam sheets produced, prior to use in the production of foam moldings, heat of fusion difference between ([Delta] H _Tm) and the crystallization heat _{(ΔH Tc) (ΔH Tm -ΔH} Tc) is 0.03 J / It is preferable to make adjustments such as heat treatment so that the crystallinity is 20% to 50%.

As a production method for producing a foam molded product using such a foam sheet,
(A) a preheating step of preheating so that the surface of the polyester resin foam sheet has a predetermined temperature condition;
(B) releasing from the preheating state;
(C) a molding step of forming a product shape by press molding with a pair of male and female molds prepared on both sides of the sheet;
(D) a heat retaining step in which the mold is closed after the press molding, and the product shape is maintained at a predetermined temperature for a predetermined time; and (e) the foam is opened by opening the mold after the heat retaining step. And a punching process in which the product is removed by punching the outer periphery of the formed product shape.

Alternatively, after performing the steps (a) to (c) above,
(E) After performing the punching process of punching the outer periphery of the formed product shape and taking out the product in advance,
(D ′) A method of performing a heat retaining step of setting the punched product on a jig for retaining the shape and retaining the punched product at a predetermined temperature for a predetermined time is performed instead of the above method. You can also.

(A) Preheating step The preheating step is preferably performed in a state in which the end of the foamed sheet is constrained to prevent thermal distortion of the foamed sheet. For example, press forming is performed in a progressive manner using a belt-like foamed sheet. If this is the case, clamp the foam sheet at least at two locations apart in the length direction, and preferably clamp and fix the four ends when single-molding using one rectangular foam sheet, It is preferable to carry out by heating for a certain time in a heating furnace in which heaters are installed above and below.

  In this preheating step, the surface temperature (both sides) of the polyester resin foam sheet when the crystallization temperature obtained by differential scanning calorimetry of the polyester resin foam sheet is Tc (° C.) and the melting point is Tm (° C.). It is important to preheat so that Ts (° C.) satisfies Tc ≦ Ts ≦ (Tm−50).

  At this time, the surface temperature of the foam sheet can be confirmed by pasting a temperature indicating seal commercially available from NOF Corporation under the trade name “Thermo Label” on both sides of the foam sheet.

  Moreover, about the crystallization temperature Tc (degreeC) and melting | fusing point Tm (degreeC) of a polyester-type resin foam sheet, although the test piece cut out from the polyester-type resin foam sheet can be directly measured with a DSC measuring apparatus, it can measure. With respect to the crystallization temperature Tc (° C.), it may be difficult to observe a clear peak temperature in the first run measurement. Therefore, the peak temperature observed in the second run performed after the rapid cooling is expressed as the crystallization temperature Tc ( C.) and the above preheating conditions can be set.

  The preheating is preferably carried out so that the surface temperature is within the above condition by 30 seconds, more preferably 15 seconds after the polyester resin foam sheet is introduced into the heating furnace. After reaching, it is preferable to proceed to the molding step promptly (for example, within 5 seconds).

It is important that the surface temperature of the polyester resin foam sheet in the preheating step is within the above range. If the preheat is a temperature condition exceeding “melting temperature −50 ° C.”, This is because there is a possibility that the cell shape may change remarkably or disappear and the desired properties cannot be imparted to the foamed molded product.
Also, if the preheating is performed at a temperature lower than the “crystallization temperature” and then the molding process is carried out, residual distortion is likely to occur in the foam molded product, and it may take a long time for the heat retention process to alleviate the distortion. This is because there is a risk that wrinkles and cracks may occur due to insufficient formability of the foam sheet in the molding process.

(B) Step of releasing from the preheating state After the preheating step, it is preferable to quickly shift to the molding step, so that the surface temperature does not fall below the “crystallization temperature” before shifting to the molding step. It is preferable to make it.

(C) Molding process In the molding process, press molding is usually performed with a pair of male and female molds, and the surface temperature of the mold surface at that time must be equal to or lower than the surface temperature of the foam sheet in the preheating process. is there.
It is necessary to carry out the molding process at such a temperature, even if the temperature is not higher than “melting point−50 (° C.)”, it is heated to a temperature exceeding the surface temperature of the foamed sheet in the preheating process. This is because, when press molding is performed with a mold, an appearance defect is caused in the molded product.
Note that the mold surface temperature is preferably set to a lower temperature in the case of producing a transparent, white, or light-colored product whose appearance is easily affected by yellowing or change in bubble shape.
As the mold, it is possible to adopt a mold that has been subjected to a surface treatment for improving releasability or that has a vacuum suction mechanism for molding assist.
The press molding timing conditions can be set conveniently depending on the heating conditions (surface temperature) of the foam sheet and the product shape.

(D, d ′) Insulation step After the above molding step, the product shape is maintained as it is with the molding die, or separately removed from the foam sheet by punching out from the molding die, and this is cured. The product is set on a tool and the product shape is held by the jig, and a predetermined heat treatment is performed as the heat retaining step.
In order to hold the product shape with the mold, if the mold is held in a closed state, or if a vacuum suction mechanism is provided, the male mold or female mold can be opened while the mold is open. A method of holding the product shape by adsorbing to one of the two by the vacuum suction mechanism can be employed.

The heat treatment conditions at this time are the “crystallization temperature” or more in order to alleviate the distortion that has occurred in the molding process or that is still inherent from the time of the foam sheet, and to suppress the thermal distortion of the foam molded product. It is important that the melting point is −50 (° C.) or less.
It is important to carry out the heat retaining step under such a temperature condition. If the temperature condition exceeds “melting temperature−50 ° C.”, the foam shape of the foamed molded product may change or disappear. This is because if the temperature is lower than the “crystallization temperature”, the foamed molded product may be left with strain, which may result in a product that is susceptible to thermal strain.

In addition, the time for keeping the temperature is usually 3 seconds or more, preferably 5 seconds or more.
However, even if heat treatment is performed for an excessively long period of time, it is difficult to further improve the effect of suppressing thermal distortion, which may reduce the production efficiency of the foam molded product. May cause deterioration.
From this, the time for keeping the temperature is usually 1 minute or less, preferably 30 seconds or less.

(E) Punching process The punching process which punches the product shape formed in the foam sheet can be implemented using, for example, a Thomson blade mold.
Moreover, not only the punching method by such a blade type but the method of isolate | separating a product from a foam sheet by methods, such as a wire cut, can also be implemented as the said punching process.

The foam-molded article obtained by such a production method is preferably formed so that the dimensional change rate when the heat treatment at 100 ° C. × 24 hours is performed is within ± 5%.
“Dimensional change rate is within ± 5%” means, for example, if the product shape is a rectangular parallelepiped shape, the dimensional change rate is within ± 5% in any of the vertical, horizontal and thickness directions. It means that.
Further, for example, if the product shape is circular, it means that the dimensional change rate is within ± 5% in any of the diameter, length, and thickness.
Furthermore, when twisting occurs due to thermal strain, the dimensions are not measured in a natural state, but are pressed with a flat plate or the like, and the shape is corrected to the original state, and the dimensions are measured. .

In addition, the foamed molded product obtained by such a production method has a product thickness of 0.15 mm or more and 2 mm or less and an average bubble diameter of 50 nm or more and 200 μm or less, and the heat of fusion determined by differential scanning calorimetry ( The difference (ΔH _Tm −ΔH _Tc ) between ΔH _Tm ) and the crystallization heat quantity (ΔH _Tc ) is 0.03 J / mg or more, and the crystallinity is 20% or more and 60% or less. Is preferred.
By being formed in such a state, it is difficult to be deformed even when receiving heat, and it can be easily applied to high temperature applications.

  As described above, according to the method for producing a polyester resin foam molded article according to the present embodiment, a polyester resin foam molded article in which thermal strain is suppressed can be produced. The present invention is not limited to the above exemplary embodiment, and various improvements can be added.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Differential scanning calorimetry)
The foam sheet used for the production of the foam molded product, and values of the obtained foam molded product, such as crystallization temperature (Tc), melting point (Tm), heat of crystallization (ΔH _Tc ), Δ heat of fusion (ΔH _Tm ) Was obtained under the following conditions.
・ Differential scanning calorimeter: Model name “DSC6220” manufactured by SII Nano Technology
·conditions:
Based on JIS K7121, the measurement conditions were a sample mass of 6.5 ± 0.5 mg, a heating rate of 5 ° C./min, and a scanning temperature range of 30 to 300 ° C.

1) Calculation of crystallinity The heat of fusion (ΔH _Tm ) of the polyester resin composition constituting the foamed sheet or foamed molded product is calculated based on the DSC chart, and the crystallinity (Xc) is calculated from the following formula: Asked.

Crystallinity: Xc (%) = [ΔH _Tm −ΔH _Tc ] / ΔH ₀ × 100 (%)

(Where Xc: crystallinity (%), ΔH _Tm : heat of fusion at melting point (Tm) (J / mg), ΔH _Tc : heat of crystallization at crystallization temperature (Tc) (J / mg), ΔH ₀ : heat of fusion at a crystallinity of 100% (140.1 mJ / mg for polyethylene terephthalate, 93.0 mJ / mg for polylactic acid))
The heat of fusion and the heat of crystallization can be obtained by integrating the heat (J / mg) in the region between the straight line connecting the baseline before and after each peak and the peak curve between them. It can be obtained by analysis software provided in “DSC 6220”.
A typical DSC chart is shown in FIGS.
Thus, basically, as shown in (a), the integration of the part corresponding to the area between the peak seen on the low temperature side and the straight line connecting the baselines before and after this peak (broken line in the figure) The amount of heat of crystallization (ΔH _Tc ) is observed as a value, and the integral corresponding to the area between the peak seen on the high temperature side and the straight line connecting the baseline before and after this peak (broken line in the figure) As a value, Δ heat of fusion (ΔH _Tm ) is obtained.
Also, as shown in (b), even when the baseline is distorted, the region between the straight line connecting the peak start point and the end point and the peak curve is expressed as the amount of crystallization heat (ΔH _Tc ) And Δ heat of fusion (ΔH _Tm ).
Furthermore, as shown in (c), when the peak is observed as a plurality of peaks (valleys), the area between the straight line connecting the start point and the end point and the peak curve is determined for each peak. By obtaining and summing them, the amount of crystallization heat (ΔH _Tc ) and Δ heat of fusion (ΔH _Tm ) can be obtained.
As shown in (c), when the peak is observed as a plurality of peaks (valleys), it is determined whether or not the condition of “Tc ≦ Ts ≦ (Tm−50)” is satisfied. The crystallization temperature (Tc) and the melting point (Tm) are the peak temperatures observed on the lowest temperature side.

2) Melting point (Tm)
Regarding the melting point of the foam sheet, the endothermic peak temperature observed in the first run was observed as the melting point.

3) Crystallization temperature (Tc)
Regarding the crystallization temperature of the foam sheet, in principle, the sample was rapidly cooled after the first run (for example, −20 ° C./min), and the peak temperature associated with crystallization when the second scan was performed was obtained as the crystallization temperature. .

<Evaluation case 1>
(Manufacturing method of foam molded product)
(Foam sheet)
The details of the used foam sheet are as follows.
Furukawa Electric Co., Ltd., Polyethylene terephthalate resin foam sheet, trade name “MCPET”
・ Thickness: 1mm
-Average bubble diameter: 10 μm
-Apparent specific gravity: 0.325
Crystallization temperature: 143.1 ° C
Melting point: 252.1 ° C

Example 1
First, a thermolabel 5E manufactured by NOF Giken Kogyo Co., Ltd. was attached to both surfaces of the foamed sheet, and four ends (both ends of MD / TD) were clamped and introduced into a preheating heating furnace.
The foam sheet was introduced into a heating furnace in which the upper and lower heater temperatures were set to 330 ° C., and the preheating process was completed when it was confirmed by “thermo label” that the surface temperature of the foam sheet exceeded 150 ° C.
When the surface temperature of the foamed sheet at this time was measured using a radiation thermometer, the upper surface side was 150 ° C. and the lower surface side was 155 ° C.
Next, this foamed sheet was introduced into a press molding machine to perform a molding process.
At this time, the mold is an aluminum mold that has been subjected to a surface treatment by Teflon coating, the mold temperature is 150 ° C. for the upper mold, and 150 ° C. for the lower mold (reading value of the temperature control display panel). The overall size is 33.9mm x 24.7mm, the bottom is 33.4mm x 14.2mm, and the depth is 12.3mm. A reflector shape of 287.4 mm × 323.4 mm was formed.
Then, while maintaining the shape of the product with the mold closed, a temperature maintaining step was performed while maintaining a temperature of 150 ° C. for 20 seconds.
And the outer periphery was punched out using the Thomson blade type | mold, and the product was isolate | separated from the foam sheet.
The obtained product was good although it was slightly rounded at the place where it should be squared.

Result of the differential scanning calorimetry on a sample taken from the product, the difference between the heat of fusion ([Delta] H _Tm) and the crystallization heat _{(ΔH Tc) (ΔH Tm -ΔH} Tc) is located at 0.04 J / mg It was confirmed that the crystallinity was 33%.

And this product is heated at 100 ° C. for 24 hours, and the dimensional change in the extrusion direction (MD direction) of the foam sheet, the direction orthogonal to the extrusion direction (TD direction), and the thickness direction (H direction) is measured with calipers. It was measured.
As a result, it was confirmed that the deformation in the MD direction was -0.8% (shrinkage), the deformation in the TD direction was -1.0% (shrinkage), and the deformation in the H direction was -0.5%. did it.

(Examples 2 to 11 and Comparative Examples 1 to 9)
A molded product was produced and evaluated in the same manner as in Example 1 except that the conditions of the preheating step, the molding step, and the heat retention step were as shown in Table 1 below.

<Evaluation case 2>
(Manufacturing method of foam molded product)
(Foam sheet)
A tandem type extruder in which a second-stage single-screw extruder (caliber: 115 mm) was connected to the tip of a first-stage single-screw extruder (caliber: 90 mm) via a connecting tube was prepared.
A polylactic acid resin (trade name “HV6250H” manufactured by Unitika Co., Ltd.) and 1 part by mass of polytetrafluoroethylene particles as a cell nucleating agent with respect to 100 parts by mass of the polylactic acid resin are supplied to the first stage extruder 200. After melt-kneading at 100 ° C., 2 parts by weight of butane (isobutane / normal butane (mass%) = 35:65) is press-fitted into the first-stage extruder with respect to 100 parts by weight of the polylactic acid resin, and further melt-kneaded. Then, a foamable polylactic acid resin composition was prepared in an extruder.
Subsequently, the foamable polylactic acid resin composition is continuously supplied from the first-stage single-screw extruder through the connecting pipe to the second-stage single-screw extruder, and the foamable polylactic acid resin composition is cooled to 165 ° C. Then, it was continuously supplied to an annular die attached to the tip of the second stage single screw extruder and extruded and foamed into a cylindrical shape to continuously produce a cylindrical foam.
In the opening of the annular die, the outer diameter of the inner die was 107 mm and the slit interval was 0.7 mm.
Thereafter, the cylindrical foam is taken up while gradually expanding the diameter, and the cooling water at 25 ° C. is circulated inside the cylindrical cooling mandrel having a diameter of 353 mm and a length of 500 mm. While cooling, air is blown to the entire outer peripheral surface of the cylindrical foam from the air ring outlet arranged in a state surrounding the cooling mandrel, and then the cylindrical foam is expanded in the diameter direction. A polylactic acid resin foamed sheet was obtained by cutting between the inner and outer peripheral surfaces at two points facing each other, and opening and developing (polycrystallization degree 18%).
After sufficiently aging, the polylactic acid resin foam sheet was annealed at 100 ° C. for 50 seconds to obtain a single-layer foam sheet having a crystallinity of 30%.

The details of the foam sheet thus produced are as follows.
・ Thickness: 1.6mm
・ Average bubble diameter: 0.15mm
-Apparent specific gravity: 0.22
Crystallization temperature: 79.2 ° C
Melting point: 163.3 ° C

(Examples 12-16, Comparative Examples 10-16)
Evaluation was performed in the same manner as in Evaluation Example 1 except that the polylactic acid resin foam sheet was used and the molding conditions were as shown in Table 2.
The results are also shown in Table 2.

  From the above results, it can be seen that according to the present invention, it is possible to produce a polyester-based resin foam molded article in which thermal distortion is suppressed.

Claims (7)

A polyester for producing a polyester resin foam molded article by performing a preheating process for preheating the polyester resin foam sheet and a molding process for forming a product shape by press molding on the preheated polyester resin foam sheet. A method for producing a resin-based resin foam molded article,
When the crystallization temperature obtained by differential scanning calorimetric analysis of the polyester resin foam sheet is Tc (° C.) and the melting point is Tm (° C.), the surface temperature of the polyester resin foam sheet: Ts (° C.) is , Tc ≦ Ts ≦ (Tm−50), the preheating step is performed and the molding step of press molding with a molding die having a temperature equal to or lower than the surface temperature (Ts) is performed. 50) A method for producing a polyester-based resin foam molded article, which comprises carrying out a heat retaining step for maintaining the product shape under the following temperature conditions. The polyester-based resin foam sheet has a thickness of 0.15 mm or more and 2 mm or less and an average bubble diameter of 50 nm or more and 200 μm or less, and heat of fusion (ΔH _Tm ) and crystallization when differential scanning calorimetry is performed. heat ([Delta] H _Tc) the difference between (ΔH _Tm -ΔH _Tc) is not less 0.03 J / mg or more, the production of the polyester type resin foamed molded article according to claim 1 crystallinity of 20% to 50% Method.   The method for producing a polyester resin foam molded article according to claim 1 or 2, wherein a main component of the polyester resin foam sheet is a polyethylene terephthalate resin.   The method for producing a polyester resin foam molded article according to claim 1 or 2, wherein a main component of the polyester resin foam sheet is a polylactic acid resin.   A polyester resin foam-molded product obtained by the method for producing a polyester resin foam-molded product according to any one of claims 1 to 4.   The polyester resin foam-molded article according to claim 5, wherein a rate of dimensional change upon heat treatment at 100 ° C for 24 hours is within ± 5%. The thickness is 0.15 mm or more and 2 mm or less and the average bubble diameter is 50 nm or more and 200 μm or less, and the difference between the heat of fusion (ΔH _Tm ) and the heat of crystallization (ΔH _Tc ) when differential scanning calorimetry is performed ( The polyester-based resin foam-molded product according to claim 5 or 6, wherein ΔH _Tm -ΔH _Tc ) is 0.03 J / mg or more and the crystallinity is 20% or more and 60% or less.

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