JP2002293977A - Method for producing preliminarily foamed particle of thermoplastic polyester-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide preliminarily foamed particles with controlled crystallinity and excellent foaming moldability. SOLUTION: This method for producing the preliminarily foamed particles of a thermoplastic polyester resin, comprising keeping the primarily foamed particles of the thermoplastic polyester resin in a pressured gas to impregnate the foamed particles with the gas in a gas phase, and then heating the particles to refoam the particles, is characterized in that the temperature of the primarily foamed particles before impregnated with the gas is lower by >=5 deg.C than the temperature of the primarily foamed particles when impregnated with the gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing pre-expanded particles of a thermoplastic polyester resin. More specifically, the present invention relates to a method for producing low-density thermoplastic polyester resin pre-expanded particles that can be suitably used for in-mold foam molding.

[0002]

2. Description of the Related Art Thermoplastic polyester resins have excellent properties not found in polystyrene and polyethylene, such as high rigidity, good shape stability, and excellent chemical resistance. Therefore, it has been proposed to foam a thermoplastic polyester-based resin to produce a foamed molded article which is lightweight and excellent in heat resistance, heat insulating properties, cushioning properties and the like. In particular, lower density foamed particles, for example 0.037
Pre-expanded particles having a particle size of less than g / cm ³ have been demanded because they can be used for lightweight heat insulating materials, core materials for structural members, and the like.

In-mold foaming of thermoplastic polyester resin
As a method for producing the shape, for example, thermoplastic polyester
Crystallization peak temperature of pre-expanded particles
In-mold foamed product excellent in fusion bonding property at 180 ° C
Is known. In particular, the density is 0.1 g /
cm^ThreeObtain a low-density in-mold foam molded article as follows
In this case, for example, after the primary expanded particles are formed by extrusion foaming or the like,
Heat re-foaming after impregnating while holding in pressurized inorganic gas
0.1g / cm by repeating the process several times ^Threebelow
It is known that low density pre-expanded particles can be made
ing. Such a method involves pre-expanded particles of any density
Is useful as a convenient way to obtain
There is a limit to reducing the density of pre-expanded particles in the expansion process.
Therefore, it was necessary to repeat this step.

[0004]

The method of repeating the step of re-expanding a plurality of times as described above also increases the cost, and the crystallinity of the pre-expanded particles increases each time re-expansion is repeated. There is a problem that the fusion-bonding property in the foam molding tends to be adversely affected, and it becomes difficult to obtain a molded article having good properties each time re-foaming is repeated. The present invention solves such problems and requires less re-foaming steps, preferably one re-foaming step, resulting in lower densities, for example 0.037.
An object of the present invention is to provide a method for producing pre-expanded particles that can easily produce pre-expanded particles of less than g / cm ³ .

[0005]

Means for Solving the Problems As a result of the inventors of the present invention diligently examining the above-mentioned problems, in order to solve the above-mentioned problems, the primary foamed particles before impregnation were more satisfactorily devised than under such conditions. Controlling the temperature was found to be very important, and led to the present invention. Thus, according to the present invention, when the primary expanded particles of the thermoplastic polyester resin are held in a pressurized gas and the gas is impregnated in the gas phase, and then heated and re-expanded, the primary expanded particles before the gas is impregnated. Is lower than the temperature at the time of impregnation by 5 ° C. or more, and a method for producing thermoplastic polyester-based resin pre-expanded particles is provided. According to the above method, low-density pre-expanded particles can be obtained using a general-purpose impregnating equipment.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The thermoplastic polyester resin used in the present invention is a high-molecular-weight chain polyester made from an aromatic dicarboxylic acid and a dihydric alcohol. Examples of the aromatic dicarboxylic acid include, in addition to terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenylether dicarboxylic acid, diphenoxydicarboxylic acid, and the like. As the dihydric alcohol, in addition to ethylene glycol, cyclohexane dimethanol, α-
Butylene glycol (1,2-butanediol), β-
Butylene glycol (1,3-butanediol), tetramethylene glycol (1,4-butanediol),
Examples thereof include 2,3-butylene glycol (2,3-butanediol) and neopentyl glycol. Also,
Using a tri- or tetracarboxylic acid such as trimellitic acid or pyromellitic acid as a part of the aromatic dicarboxylic acid, or using a trihydric or tetrahydric alcohol such as glycerin or pentaerythritol as a part of the dihydric alcohol Is also good.

[0007] High-molecular-weight linear polyesters made from these aromatic dicarboxylic acids and dihydric alcohols are commercially available, for example, as polyethylene terephthalate resins. However, in order to obtain pre-expanded particles of a thermoplastic polyester resin having excellent fusibility, use isophthalic acid as a dicarboxylic acid, or use cyclohexane dimethanol as a diol, or a combination of both. When either one is used alone, the content of the single component is used alone, and when both are used in combination, the total content is limited to a range of 0.5 to 10% by weight of all components. It is preferable to use a polyester resin. At that time, a raw material containing the above-mentioned components in a predetermined ratio, that is, isophthalic acid and / or cyclohexanedimethanol in a total amount of 0.5 to 10% by weight as described above, is subjected to a polycondensation reaction as in the past. It is possible to use a thermoplastic polyester resin produced by the above-mentioned method, or to use isophthalic acid and / or two or more thermoplastic polyester resins having different content ratios of cyclohexanedimethanol in all the components. It is manufactured by blending so that the content ratio of acid and / or cyclohexane dimethanol is in the range of 0.5 to 10% by weight in total, and melting and mixing under heating using, for example, an extruder. It does not matter.

According to this method, the pre-expanded particles can be produced only by changing the mixing ratio of two or more thermoplastic polyester resins having different contents of isophthalic acid and / or cyclohexane dimethanol. The content ratio of both components in the pre-expanded particles can be adjusted.
For this reason, there is an advantage that the adjustment operation can be simplified as compared with the case where the content ratio of both components is adjusted at the resin synthesis stage, and the specification can be flexibly changed. Also,
For example, by using materials recovered and reclaimed from used PET bottles and the like as one type of thermoplastic polyester resin to be blended, effective reuse of resources and reduction of dust, and reduction of pre-expanded particles There is also an advantage that cost can be reduced. In the above method, the two resins are melted and mixed sufficiently under heating so that each resin is alloyed by a transesterification reaction between two or more kinds of thermoplastic polyester resins to form a uniform thermoplastic polyester resin. Is preferred.

Here, the thermoplastic polyester-based resin is mixed with a foaming agent under high-pressure melting using an extruder or the like, then primary-foamed, then cut and re-foamed to produce the pre-expanded particles of the present invention. In this case, the production of a uniform thermoplastic polyester-based resin by melting and mixing two or more resins as described above is performed in an extruder at least prior to mixing of a blowing agent at the time of production of primary expanded particles, and then continuously. It is efficient and preferable to produce primary expanded particles. However, a uniform thermoplastic polyester-based resin prepared by melting and mixing two or more resins in advance using another apparatus is put into an extruder to produce pre-expanded particles of the present invention. No problem.

[0010] The primary expanded particles of the thermoplastic polyester resin are obtained by heating the thermoplastic polyester resin and a foaming agent at a high temperature.
It can be obtained by melt-mixing under high pressure and foaming. For example, an extrusion foaming method using an extruder is efficient and preferably employed. The extruder that can be used is not particularly limited, and an extruder having a sufficient melting and mixing ability is suitable, and a single-screw extruder, a twin-screw extruder, or the like usually used for this type of extrusion foaming method, And a tandem-type extruder in which are connected. Various extruders can be used. For example, an annular base, a flat base, a nozzle base, and a multi-nozzle base provided with a plurality of nozzles may be used. Using these bases, foams of various shapes such as sheet, plate, rod, etc. can be produced. Various methods are employed for forming the foam into the above-mentioned predetermined shape.

For example, in order to obtain a sheet-like foam, a cylindrical foam extruded from an annular base is formed into a sheet by advancing on a mandrel, or a thick plate extruded from a flat base. The foam may be formed into a sheet by a chill roll. In addition, in order to obtain a thick plate-like foam, a method in which the foam is advanced while being brought into close contact with a pair of metal plates to obtain a predetermined thickness is employed.
As a method for cooling the foam, various methods such as air cooling and water cooling, and contact with a temperature-controlled cooling device can be used. It is important to cool the foam as quickly as possible and to suppress excessive crystallization of the primary foam particles. Primary foam particles are completed by appropriately cutting the foams of various shapes manufactured as described above into a columnar shape, a square shape, a chip shape, or the like.

The cooling and cutting of the foam can be performed at various timings. For example, the foam extruded from the die may be cooled by passing it through water at any time during or after foaming, and then cut into a predetermined shape and size using a pelletizer or the like. Alternatively, the foam that has been extruded from the die, immediately before the completion of foaming or immediately after the completion of foaming, and immediately before cooling may be cut and then cooled. Further, the foam extruded in a sheet shape may be once wound up in a roll shape by a winder or the like, stored, and then cut by a crusher or a cutting machine. The size of the primary foamed particles of the present invention is preferably about 0.5 to 5 mm as an average particle size. The crystallinity of the primary expanded particles of the present invention is preferably about 1 to 8%.

If the degree of crystallinity of the primary expanded particles exceeds 8%, the secondary expansion force will be weakened in the subsequent step of expanding by heating and foaming, and the fusion of the pre-expanded particles obtained from the primary expanded particles will be reduced. Since the adhesiveness is not sufficient, there is a possibility that a foamed molded article having low mechanical strength may be obtained. On the other hand, if the crystallinity is lower than 1%, the primary foamed particles still having residual heat tend to coalesce when forming the primary foamed particles, which is not preferable. In addition, the crystallinity of the primary expanded particles is particularly preferably about 1 to 7%, and more preferably about 1 to 6%, within the above range. The crystallinity (%) was measured using a differential scanning calorimeter (DSC) in the same manner as in the measurement of the crystallization peak temperature described above, according to the measurement method described in Japanese Industrial Standards JIS K7121. It is determined from the heat of crystallization and the heat of fusion by the following equation.

[0014]

(Equation 1)

The heat of fusion per mole of the perfectly crystalline PET in the formula is 26.9 kJ from the description in the Polymer Data Handbook [published by Baifukan]. Specifically, a predetermined amount of primary expanded particles as a measurement sample is filled in a DSC measurement container, and the heat of cold crystallization and the heat of fusion are measured while heating at a heating rate of 10 ° C./min, From the measurement results,
The crystallinity of the primary expanded particles is determined based on the above equation. The open cell ratio of the primary expanded particles is preferably adjusted to 5 to 35%. 35% open cell ratio of primary expanded particles
Exceeding the range is not preferred because the re-foaming property may be low and it may be difficult to reduce the density. On the other hand, if it is less than 5%, the shrinkage of the foam molded article during in-mold foam molding is undesirably increased.

The density (bulk density) of the primary expanded particles is preferably adjusted in the range of 0.11 to 0.15 g / cm ³ . If it is larger than 0.15 g / cm ^3, it is not preferable because the cell membrane strength is high and it is difficult to re-foam. If it is less than 0.11 g / cm ³ , the cells are broken, so that the ratio of open cells becomes high. Various additives may be added to the primary expanded particles. Examples of the additive include, in addition to the foaming agent, for example, a foam regulator, a flame retardant, a colorant, and the like. Further, in order to improve the melting properties of the thermoplastic polyester resin, epoxy compounds such as glycidyl phthalate, acid anhydrides such as pyromellitic dianhydride, Group I and II metal compounds such as sodium carbonate, A metal sulfonate compound or the like can be added as a modifier alone or as a mixture of two or more. In particular, these modifiers are effective because they not only improve the re-foamability of the primary expanded particles, but also increase the expansion force of the primary expanded particles in order to increase the closed cell ratio of the primary expanded particles.

The blowing agent which can be used in the present invention is roughly classified into a solid compound which decomposes at a temperature higher than the softening point of the thermoplastic polyester resin to generate gas, and which is vaporized in the thermoplastic polyester resin when heated. Examples thereof include a liquid and an inert gas that can be mixed with the thermoplastic polyester resin under pressure. Examples of the solid compound include azodicarbonamide, dinitrosopentamethylenetetramine, hydrazoldicarbonamide, sodium bicarbonate and the like. Examples of the liquid to be vaporized include saturated aliphatic hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane and hexane; aromatic hydrocarbons such as benzene, xylene and toluene; Examples thereof include halogenated hydrocarbons such as methyl and Freon (registered trademark), and ether compounds such as dimethyl ether and methyl-tert-butyl ether.

Further, examples of the inert gas include carbon dioxide, nitrogen and the like. When the thermoplastic polyester resin is mixed with a foaming agent under high pressure melting using an extruder, extruded and primarily foamed, and then cut to produce primary foamed particles, from the die of the extruder, It is preferable to use a foaming agent that vaporizes the molten resin at the moment of being extruded and foams the molten resin, and also removes the heat of the molten resin.
Such foaming agents include, for example, saturated aliphatic hydrocarbons, halogenated hydrocarbons, and the like. These foaming agents are preferable because they act to cool the molten thermoplastic polyester resin and have an effect of suppressing the crystallinity of the primary foamed particles to a low level.

The thermoplastic polyester resin may be, for example, a polyolefin resin such as a polypropylene resin, a thermoplastic elastomer such as a polyester resin, a polycarbonate or an ionomer as long as the crystallinity and the rate of crystallization are not significantly affected. Etc. may be added. The thus obtained primary expanded particles are preferably aged for 48 hours or more after extrusion foaming. By the cooling after the foaming, the inside of the formed bubble is reduced in pressure. However, when air enters thereafter, the reduced pressure is eliminated and the strength of the bubble film increases. This is aging, but if the aging time is short, the degree of decompression is not yet high and sufficient foam film strength has not been obtained, so it is difficult to obtain low-density pre-expanded particles due to low foamability during refoaming. is there.

In the present invention, it is necessary to maintain the primary expanded particles under such a condition that the temperature of the primary expanded particles before the gas impregnation becomes lower than the temperature at the time of the impregnation by 5 ° C. or more.
By making the density lower, the density of the pre-expanded particles can be reduced to about 1/4 or less of the density of the primary expanded particles in one re-expansion step. Here, the temperature before the impregnation is preferably about 10 ° C. or lower than the temperature at the time of the impregnation.
A temperature range lower by 5 to 100C is more preferable. Refoamability is greatly affected by the amount of gas injected, but primary expanded particles made of a thermoplastic polyester resin have a property of becoming softer as the temperature rises. It is considered that the foamed particles are crushed and reduced in volume, and the amount of gas entering the particles is reduced. Therefore, in order to reduce the collapse of the primary expanded particles and obtain very low-density pre-expanded particles, the temperature of the primary expanded particles before gas impregnation is set to -50 to
It is preferable to adjust the temperature to 20 ° C.,
A temperature range of 15 ° C is more preferred, and a temperature range of -40 to 10 ° C is particularly preferred.

When the temperature of the pre-expanded particles exceeds 20 ° C.,
Since the resin is relatively soft and the particles are crushed by the pressure at the time of gas impregnation as described above, there is a possibility that the space into which the gas enters is small, the amount of the impregnated gas is reduced, and the re-foaming property is reduced. In the range of −50 to 20 ° C., since the resin is relatively hard, the particles are hardly crushed during the impregnation, and a large amount of gas can be injected into the particles, so that low-density pre-expanded particles can be obtained. Conceivable. -50 ° C
If the temperature is less than this, the particles will not be crushed, but since many commercially available refrigeration equipment cannot be lowered to a temperature lower than this, lowering the temperature below this increases the cost. In order to obtain stable low-density pre-expanded particles, it is desirable to store the primary expanded particles before gas impregnation in a place where the temperature is controlled. In order to make the temperature of the primary expanded particles uniform, for example, if the particles are stored in a cool box, they can be stabilized at a low temperature. The temperature of the primary expanded particles referred to herein is the temperature of the surface of the particles.

The type of gas used for gas impregnation is not particularly limited, but inorganic gases such as carbon dioxide, nitrogen and air are preferred.
The gas impregnation is preferably performed at a gauge pressure of 0.1 to 10 MPa, more preferably about 0.1 to 1 MPa. 0.1MP
If it is less than a, the effect is small, and in order to perform impregnation at a pressure exceeding 10 MPa, equipment that can be used at a higher pressure is required, which increases the cost and is dangerous because the operation involves danger. About impregnation time, 1-24
Time is desirable. If the time is less than 1 hour, the impregnation is not sufficient and the density of the pre-expanded particles increases, which is not preferable.
The heating temperature at the time of refoaming is preferably about 55 to 90 ° C. If the temperature is lower than 55 ° C., the re-foaming speed is too slow and the impregnated gas escapes before the target density is reached. If the temperature exceeds 90 ° C., the particles are likely to be bonded to each other, and the crystallinity is significantly increased.

According to the present invention, a single refoaming step
0.023-0.037 g / cm ^ThreeLow density
Pre-expanded particles can be obtained. Obtained low-density heat
The pre-expanded particles of plastic polyester resin are described above.
In-mold foam molding method, that is, can be closed but can be closed
Fill the pre-expanded particles into a mold that does not
Air is introduced to cause secondary foaming, and the foamed particles are thermally fused to each other.
By doing so, an in-mold foam molded article can be obtained. Obtained
If shrinkage is observed in the molded body,
Soaking air into the air bubbles
It is possible to make a good molded body with
Maintaining body in pressurized gas forcibly accelerates ripening
It is also possible to obtain a good molded product. In addition,
Pre-expanded particles were pressurized before filling with expanded particles
By holding in the gas, the gas is impregnated (internal pressure is applied).
And give the foaming particles sufficient foaming power
It is possible to obtain a molded article having a beautiful appearance and excellent fusion property.
At this time, suction of pre-expanded particles, filling into the mold, and molding are performed automatically.
By using an automatic molding machine that performs motion,
A low-density in-mold foam molded article can be obtained.

[0024]

EXAMPLES The advantages of the present invention will be specifically described below with reference to examples and comparative examples. In addition, the crystallization peak temperature of the thermoplastic polyester resin used and the crystallinity of the produced pre-expanded particles were both determined according to the measurement method described in Japanese Industrial Standard JIS K7121 as described above. The content ratio and bulk density of isophthalic acid and / or cyclohexanedimethanol were measured by the following methods, respectively.

(Measurement of Isophthalic Acid Content Ratio) Approximately 100 mg of a sample was weighed into a pressure-resistant Teflon (registered trademark) container, and then 10 ml of dimethyl sulfoxide for absorption analysis manufactured by Wako Pure Chemical Industries, Ltd. and a 5N sodium hydroxide-methanol solution were used. After adding 6 ml, the pressure-resistant Teflon container is put into a pressure-resistant heating container made of SUS and securely sealed.
Heated for hours. Next, the pressure-resistant heating container after heating was cooled to room temperature, and in a state of being completely cooled, the pressure-resistant Teflon container was taken out, the content was transferred to a 200 ml beaker, and distilled water was added to about 150 ml. Next, after confirming that the contents were completely dissolved, the solution was neutralized to pH 6.5 to 7.5 with hydrochloric acid.
After neutralization, the volume of the sample was increased to 200 ml and further diluted 10 times with distilled water to obtain a sample solution.

Next, using this sample solution and an isophthalic acid standard solution, high performance liquid chromatography (HPLC)
The measurement was performed by the apparatus under the following conditions. As the isophthalic acid standard solution, a solution obtained by dissolving an isophthalic acid reagent manufactured by Tokyo Chemical Industry Co., Ltd. in distilled water was used. Apparatus: Waters HPLC LC-module1 Column: Inertsil ODS-25μ manufactured by GL
m (4.6 × 250) Column temperature: 23 ° C. Room temperature mobile phase: 0.1% phosphoric acid / acetonitrile = 80 /
20 Flow rate: 0.5 ml / min Analysis time: 50 min Injection volume: 50 μl Detection wavelength: 210 nm

Next, a calibration curve was prepared using the peak area of isophthalic acid obtained from the standard solution on the X axis and the concentration on the Y axis, and using the obtained calibration curve, the concentration of isophthalic acid in the sample solution was determined. (Μg / ml) was calculated. Then, the content ratio (% by weight) of isophthalic acid (IPA) in the thermoplastic polyester resin was calculated from the above concentration using the following equation.

[0028]

(Equation 2)

(Measurement of content ratio of cyclohexane dimethanol) About 100 mg of a sample was weighed in a pressure-resistant Teflon container, and 10 ml of dimethyl sulfoxide for absorption analysis manufactured by Wako Pure Chemical Industries, Ltd. and 6 ml of a 5N sodium hydroxide-methanol solution were added. After the addition, place the above pressure-resistant Teflon container in a SUS pressure-resistant heating container and securely seal it.
Heated for hours. Next, the pressure-resistant heating container after heating was cooled to room temperature, and in a state of being completely cooled, the pressure-resistant Teflon container was taken out, the content was transferred to a 100 ml beaker, and a special-grade reagent methanol was added to about 70 ml. Next, after confirming that the contents were completely dissolved, the pH was adjusted to 6.5 to 7.5 with hydrochloric acid.
The sample was further diluted to 10 ml with a special-grade reagent acetone to obtain a sample solution. Next, the sample solution and the cyclohexanedimethanol standard solution were separately collected in 10 ml centrifuge tubes, and the solvent was evaporated to dryness while centrifuging. Add 2 ml and add 1 at 60 ° C.
Heated for hours.

The heated liquid was measured using a gas chromatograph (GC) under the following conditions. Equipment: Perkin Elmer GC Autosy
stem column: DB-5 (0.2 mmφ × 30 m × 0.25 μ)
m) Oven temperature: 100 ° C (for 2 minutes)-R1-200 ° C-
R2-320 ° C. (5 minutes) Heating rate: R1 = 10 ° C./min, R2 = 40 ° C./min Analysis time: 20 minutes Injection temperature: 300 ° C. Detector: FID (300 ° C.) Gas pressure: 18 psi A calibration curve is created using the peak area of the TMS compound of cyclohexanedimethanol obtained from the standard solution on the X axis and the concentration on the Y axis, and using the obtained calibration curve, the concentration of cyclohexanedimethanol in the sample solution ( μg / ml)
Was calculated. From the above concentration, the content (% by weight) of cyclohexanedimethanol (CHDM) in the thermoplastic polyester resin was calculated using the following equation.

[0031]

(Equation 3)

(Measurement of Bulk Density) Japanese Industrial Standard JIS K
According to the method described in No. 8767, the pre-expanded particles as a foam and the bulk density (g /
cm ³ ).

[0033]

(Equation 4)

(Measurement of fusion rate) After the foam molded article produced from the pre-expanded particles of each of Examples and Comparative Examples was bent and broken in the thickness direction, the number of all expanded particles present in the fractured surface was determined. Among them, the number of expanded particles in which the material itself was broken was counted. Then, a fusion rate (%), which is a reference of the fusion property between the particles, was determined by the following equation.

[0035]

(Equation 5)

(Continuous Bubble Ratio) A predetermined amount of water is put into a measuring cylinder, and then the rise in water level when a predetermined amount of pre-expanded particles are completely submerged in this water, that is, the volume increase of water is measured. It was determined as the apparent density V ₁ of the pre-expanded particles. In addition, the volume V of the closed cell portion of the same pre-expanded particles
₂ was measured using an air comparison hydrometer (manufactured by Tokyo Science Co., Ltd., air comparison hydrometer 1000 type). Then, the open cell ratio of the pre-expanded particles was determined by the following equation. Open cell ratio (%) = (V ₁ −V ₂ ) / V ₁ × 100

(Measurement of Temperature of Pre-expanded Particles) The temperature of the surface of the pre-expanded particles was measured by using a micro surface temperature sensor (manufactured by Rika Kogyo Co., Ltd.).

Example 1 100 parts by weight of a thermoplastic polyester resin synthesized by polycondensation reaction of ethylene glycol, cyclohexane dimethanol and terephthalic acid, and 0.15 parts by weight of pyromellitic dianhydride as a modifier Parts and 0.03 parts by weight of sodium carbonate as a reforming aid were extruded (caliber: 6
5 mm, L / D: 35). Next, while the input material was melted and mixed under the condition of a barrel temperature of 270 to 280 ° C., butane as a blowing agent was injected at a ratio of 1.1% by weight to the mixture from a press-fitting tube connected in the middle of the barrel. . Next, after the mixture in the molten state is extruded from the multi-nozzle mold connected to the tip of the barrel to cause primary foaming,
It was immediately cooled in a cooling water bath. After the cooled strand-shaped foam was sufficiently drained, it was cut into small particles using a pelletizer to produce primary expanded particles.

The bulk density of the obtained primary expanded particles is 0.14.
g / cm ³ , crystallinity 2.7%, open cell rate 17.
The content of CHDM was 0%, the content of CHDM was 0.9% by weight, and the crystallization peak temperature was 136.7 ° C. After the production of primary expanded particles, J
According to IS Z8703, one room temperature is controlled at 23 ° C.
It was stored for 20 hours to complete aging. The aged primary expanded particles were placed in a freezer adjusted to a temperature of -42 ° C for 3 hours.
Stored for 6 hours. At this time, the temperature of the surface of the primary expanded particles is-
40 ° C. Then, the container was immediately placed in a closed container, and air was injected at a pressure of 0.95 MPa and held for 10 hours.
The internal pressure application temperature at this time was 23 ° C. Thereafter, the mixture was taken out of the closed container, heated in a re-foaming device equipped with a stirring blade with a steam / air mixed heating medium at a heating temperature of 68 ° C. for a heating time of 3 minutes, and re-foamed to obtain pre-foamed particles. . The density of the obtained pre-expanded particles is 0.0240 g /
The density was as low as cm ³ .

Before filling the pre-expanded particles into a mold, the pre-expanded particles are kept in carbon dioxide gas pressurized to 0.2 MPa for 2 hours to impregnate the gas (apply the internal pressure). After giving sufficient foaming power to the pre-expanded particles, the pre-expanded particles are filled into the mold of the molding machine by automatic suction,
After heating at 0.06 MPa for 15 seconds, it was cooled and taken out to obtain a foamed molded product. The density of the obtained molded article was as low as 0.0245 g / cm ^3, and it was a molded article having a beautiful appearance with a fusion rate of 90%.

Example 2 Primary expanded particles were prepared in the same manner as in Example 1 except that 100 parts by weight of a thermoplastic polyester resin synthesized by polycondensation reaction of ethylene glycol with isophthalic acid and terephthalic acid was used. Created. The bulk density of the obtained primary expanded particles is 0.14 g / cm ³ , the degree of crystallinity is 4.5%, the open cell ratio is 16.0%, the IPA content is 1.5% by weight, and the crystallization peak temperature is 135.1 ° C. After the production of the primary expanded particles, the particles were stored in a room maintained at 23 ° C. for 120 hours to complete aging. The matured primary expanded particles were stored for 36 hours in a freezer adjusted to a temperature of -17 ° C. At this time, the temperature of the surface of the primary expanded particles was −15 ° C. Then, immediately put in a closed container, air was 0.95
It was press-fitted at a pressure of MPa and maintained for 10 hours. The internal pressure application temperature at this time was 23 ° C. Then, it was taken out of the closed container, heated in a refoaming device equipped with stirring blades with a steam / air mixed heating medium at a heating temperature of 68 ° C. for a heating time of 3 minutes, and refoamed to obtain pre-foamed particles. . The density of the obtained pre-expanded particles was as low as 0.0245 g / cm ³ . Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. The density of the foam is 0.0
The molded product was as low as 250 g / cm ³ , had a fusion rate of 90%, and had a beautiful appearance.

Example 3 Refoaming was carried out in the same manner as in Example 2 except that the storage temperature was 3 ° C. The temperature of the surface of the primary expanded particles stored at 3 ° C. was 5 ° C. The density of the obtained pre-expanded particles was as low as 0.0275 g / cm ³ . Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. The foam had a low density of 0.0280 g / cm ³ , a fusion rate of 90%, and a beautiful appearance.

Example 4 Example 3 was carried out except that the aging temperature was 5 ° C.
It was refoamed in the same manner as described above. The density of the obtained pre-expanded particles was as low as 0.0270 g / cm ^3, and there was no effect on the re-expanded density due to the difference in aging temperature. Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. The density of the foam is 0.0275 g / cm ³
It was a molded article having a low fusion rate of 90% and a beautiful appearance.

Example 5 Refoaming was carried out in the same manner as in Example 3 except that the aging temperature was 40 ° C. The density of the obtained pre-expanded particles was as low as 0.0285 g / cm ^3, and there was no effect on the re-expanded density due to the difference in aging temperature.
Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. The density of the foam is 0.0290 g / cm
^The molded product was as low as ³ and had a fusion rate of 90% and a beautiful appearance.

Example 6 Except that the pressure of the air to be injected was set to 0.6 MPa,
Refoaming was carried out in the same manner as in Example 2. The density of the obtained pre-expanded particles was as low as 0.0325 g / cm ³ . Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. The density of the foam is 0.0330 g /
The molded article was as low as ³ cm ^3, and had a fusion rate of 80% and a beautiful appearance.

Comparative Example 1 Refoaming was carried out in the same manner as in Example 2 except that the storage temperature was 23 ° C. The temperature of the surface of the primary expanded particles stored at 23 ° C. was 23 ° C. The density of the obtained pre-expanded particles was as high as 0.0380 g / cm ^3, and low-density pre-expanded particles could not be obtained. Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. Although the molded article had a beautiful fusion appearance with a fusion rate of 80%, the density of the foam was as high as 0.0385 g / cm ³ .

Comparative Example 2 Refoaming was carried out in the same manner as in Example 2 except that the storage temperature was 37 ° C. The temperature of the surface of the primary expanded particles stored at 37 ° C. was 35 ° C. The density of the obtained pre-expanded particles was as high as 0.0455 g / cm ^3, and low-density pre-expanded particles could not be obtained. Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. Although the molded article had a beautiful fusion appearance with a fusion rate of 70%, the density of the foam was as high as 0.0462 g / cm ³ .

Comparative Example 3 Refoaming was carried out in the same manner as in Comparative Example 1 except that the aging temperature was 40 ° C. The density of the obtained pre-expanded particles was as high as 0.0390 g / cm ^3, and low-density pre-expanded particles could not be obtained. Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. The molded article had a fusion rate of 80% and a beautiful appearance, but the density of the foam was as high as 0.0395 g / cm ³ .

Comparative Example 4 Refoaming was carried out in the same manner as in Comparative Example 2 except that the temperature during application of the internal pressure was 5 ° C. The density of the obtained pre-expanded particles was as high as 0.0430 g / cm ^3, and low-density pre-expanded particles could not be obtained. Using the pre-expanded particles, a foam molded article was obtained in the same manner as in Example 1. Fusion rate 8
At 0%, the molded article had a beautiful appearance, but the density of the foam was as high as 0.0435 g / cm ³ .

[0050]

[Table 1]

As can be seen from the examples, the density of the pre-expanded particles was reduced by lowering the temperature of the primary expanded particles before the gas impregnation by 5 ° C. or more than the temperature at the time of the impregnation. An expanded molded article obtained using the low-density pre-expanded particles is:
The appearance was good, the fusion rate was 80% or more, and the fusion property was excellent. The density of the obtained molded article was as low as the density of the pre-expanded particles. As seen from the comparative example, when the temperature of the primary expanded particles before the gas impregnation was equal to or higher than the temperature at the time of the impregnation, the re-expansion ratio of the pre-expanded particles tended to decrease.

[0052]

As described in detail above, according to the present invention,
By lowering the temperature of the primary expanded particles before the gas impregnation by 5 ° C. or more from the temperature at the time of the impregnation, it is possible to re-expand at a higher magnification.
Since the density can be reduced to the density of the pre-expanded particles, it is possible to reduce the number of times of the re-expansion step, and to suppress the crystallinity of the pre-expanded particles more, in other words, to be more excellent in foam moldability. Pre-expanded particles can be produced.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Tarumoto 81 Faku-term, Hakushoji-cho, Nara City, Nara Prefecture 4F074 AA65 BA32 BA33 CA23 CB53 CC04X CC04Y CC32X CC32Y CC34X CC34Y CC45 CC46 DA02

Claims (3)

[Claims] When the gas is impregnated with a gas by holding the primary expanded particles of a thermoplastic polyester resin in a pressurized gas and then re-expanded by heating, the temperature of the primary expanded particles before the gas is impregnated. Is 5 ° C. or more lower than the temperature at the time of impregnation. 2. The temperature of the primary expanded particles before gas impregnation is-
The production method according to claim 1, wherein the temperature is 50 to 20C. 3. The pressure during gas impregnation is 0.1 to 10 MPa.
The production method according to claim 1 or 2, which is a.