JP2001269960A - Method for manufacturing in-mold foam molding made from aromatic polyester-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-mold foam molding manufactured from aromatic polyester-based resin, satisfying both internal fusing and appearance. SOLUTION: In the method in which prefoaming particles of the aromatic polyester-based resin are filled into a mold, heated, cooled and so on for an in-mold foam molding having a specified shape to be manufactured. Substantial heating is performed by the steam with 0.03 to 0.1 MPa in pressure after the preheating by a heating medium with temperatures of 90 to 105 deg.C. The temperature of the heating medium is adjusted to the range from 90 to 105 deg.C according to the mixing ratio of air to the steam. In this case, the temperature adjustment by the heating medium of 90-105 deg.C is carried out at first by either unidirectional or reverse-unidirectional heating or carried out by both of them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an in-mold foam molded article made of an aromatic polyester resin, and more particularly, to a low-density and strength physical property which can be used for industrial parts and cushioning materials. The present invention relates to a method for producing an in-mold foam molded article having excellent characteristics, and more particularly to a production method suitable for molding a molded article having a relatively large thickness.

[0002]

2. Description of the Related Art Aromatic polyester resins represented by polyethylene terephthalate resin are relatively inexpensive and have chemical properties such as chemical resistance, solvent resistance and weather resistance, heat resistance and rigidity. It has been evaluated for its excellent physical properties such as gas barrier properties, and is widely used in the field of packaging of electric / electronic parts, automotive parts, industrial parts, films, bottle containers and the like. As such a foamed molded article, the present applicant controls the crystallinity of the pre-expanded particles of the polyester resin to 25% or less, and when the pre-expanded particles are subjected to in-mold foam molding, the particles are fused to each other. It has been found that a desired in-mold foam molded product can be obtained (Japanese Patent Application Laid-Open No. 8-174590).

[0003] Further, this molded article has no voids between particles and is excellent in heat resistance. However, when an in-mold foam molded article of an aromatic polyester resin having a bulk density of 0.07 to 0.04 g / cm ³ or less is molded by a molding machine and a molding method for performing in-mold foam molding, the wall thickness is about 25 mm. The degree was limited, and a molded product having a larger thickness caused either poor internal fusion or poor appearance, and a phenomenon occurred in which a molded product satisfactory in both internal fusion and appearance was not obtained.

[0004] The main reason is that the above-mentioned foamed particles of the aromatic polyester resin are sensitive to temperature, and under the conventional molding conditions, only the surface of the molded article is foamed and fused at the moment when steam is emitted. It was found that steam could not enter into the molded product, resulting in poor fusion. By the way, it is one heating step before performing the main heating that largely controls the internal fusion of the molded article. In the conventional foam molding method, the steam produced by the boiler is reduced to a certain pressure and one side of the molded article is reduced. From the opposite side to promote internal fusion, but the above-mentioned aromatic polyester resin is sensitive to temperature, so it was necessary to lower the temperature of steam and heat it on the other hand, but the temperature of steam depends on pressure. However, if the temperature is lowered to 105 ° C. or lower, the pressure becomes too low, so that steam cannot be obtained, and as a result, poor fusion occurs.

In view of the above, the present invention has been intensively researched to provide an in-mold foamed molded article made of an aromatic polyester resin, which is satisfactory in terms of both internal fusion and appearance. is there.

[0006]

According to the method of the present invention for producing an in-mold foam molded article using an aromatic polyester resin, the pre-expanded particles of the aromatic polyester resin are molded into a mold as described in claim 1. In the method of filling, heating, cooling and the like to produce an in-mold foam molded article having a predetermined shape, first, before main heating, first heating with a heating medium at 90 to 105 ° C., and then 0.03 to 0.1 MPa The main heating is carried out by using steam.
Heating with a heating medium at 0 to 105 ° C., and then main heating, satisfying the temperature conditions sufficient for the pre-expanded particles of the resin to expand and fuse to the inside of the molded article, It is possible to provide a foam molded article having a compatible appearance.

The method for adjusting the temperature to 90 to 105 ° C. is characterized in that air is mixed with steam and the temperature is adjusted according to the ratio. By using this air-mixed steam, 90
There is a great advantage that the temperature can be easily adjusted within the range of -105 ° C. Further, as described in claim 3, the temperature adjustment of 90 to 105 ° C. is performed by performing one of the one-side heating and the one-side reverse heating, or by performing both the one-side heating and the reverse one-side heating. As a molded product, internal fusion is good and a fusion degree of 80% or more can be secured.
A molded article having good appearance can be provided.

[0008]

Next, embodiments of the present invention will be sequentially described. Using a pre-expanded particles of an aromatic polyester-based resin, a filling step into a molding die, a one-side heating step, a reverse one-sided heating step and a double-sided heating step of main heating are performed, preferably at 90 to 105 ° C., preferably 95-
The heating by the heating medium at 100 ° C. is performed by one heating performed first in the one-side heating step and the reverse one-side heating, or is performed in both the one-side heating and the reverse one-side heating, and is a mixed air (aeration). The air is mixed and used so that the above-mentioned steam temperature can be realized within a set steam pressure of 0.02 to 0.1 MPa, preferably 0.04 to 0.06 MPa.

Next, main heating is performed by heating both sides with steam of 0.03 to 0.1 MPa, and thereafter, cooling is performed and the mold is released to obtain a molded product. The details of the embodiment of the present invention will be apparent from the following time charts in which the reference numerals 101 to 118 in the molding apparatus using the male mold 10 and the female mold 20 in FIG. Note that reference numerals 119 and 120 in FIG. 1 indicate a temperature measuring means using a temperature measuring sensor or the like.

When heating with a heating medium at 95 to 100 ° C. is performed only in one heating step, one heating may be performed from either the female side or the male side.

[0011]

[Table 1]

[0012] The molding apparatus used for carrying out the present invention includes:
The difference from the conventional foam molding equipment is that low pressure (0.01 to
A steam valve 115 that can be adjusted to 0.02 MPa) and an aeration air valve 116 are installed on the female mold 20 side,
The steam valve 117 and the air valve 118 for aeration are installed on the male mold 10 side, and 90 to 105 ° C., preferably 95 to 105 ° C.
100 ° C air mixed steam from female side 20 or male side 10
In the above timing chart, the steam valve 115 and the aeration air valve 1 are used in the heating step performed from the female mold 20 side.
16, the heating step may be performed by supplying the air-mixed steam by the steam valve 117 and the aeration air valve 118 on the male mold 10 side. Further, the air-mixed steam may be supplied in both the one-side heating step and the reverse-side heating step to be performed.

[0013] In some cases, the heat retention step in the above time chart is omitted. As is clear from the above time chart, the one-side heating step and the reverse one-side heating step are indispensable for the present invention, for example, the following cases A (for example, Example 1) and B (for example, Example 2) using aeration. There is.

[0014]

[Table 2]

As for the aeration between the one heating step and the reverse one heating step, it is preferable that a small temperature difference is not obtained for stability. It is better to take a long time when the temperature is low. If you increase the supply rate of aeration by increasing the heating time, the heating time can be shortened,
It leads to cycle up. Next, the pre-expanded particles to be used in the practice of the present invention will be described. <Pre-expanded Particles> As the pre-expanded particles of the aromatic polyester resin used in the production method of the present invention, not only general-purpose PET resins conventionally used but also particularly those having a crystallization peak temperature of 120 to 180 ° C. More preferably, the temperature is 130 to 160 ° C.

Since the crystallization peak temperature indicates the temperature at which the crystallization rate is maximized by heating, it can be said that the higher the crystallization peak temperature, the lower the crystallization rate. The pre-expanded particles made of a general-purpose PET resin have a crystallization peak temperature lower than 120 ° C., and the crystallization speed is very fast. On the other hand, since the pre-expanded particles having a crystallization peak temperature of 120 ° C. or higher have a low crystallization speed, the degree of crystallization can be limited to a lower range than before. This is preferable because it is possible to suppress the progress of crystallization in the inner foam molding step.

The crystallization peak temperature is determined by a differential scanning calorimeter (DSC).
g Calorimetry) according to the measurement method described in Japanese Industrial Standards JIS K7121. Specifically, first, a predetermined amount of pre-expanded particles as a measurement sample is set in a DSC measurement container, and the temperature is raised to 280 ° C. at a rate of 10 ° C./min.
℃) for 10 minutes, then allowed to cool to room temperature (23 ℃),
Then, the crystallization peak temperature is measured while raising the temperature again at a rate of 10 ° C./min.

In order to keep the crystallization peak temperature of the pre-expanded particles within the above range, a dicarboxylic acid component constituting the aromatic polyester resin forming the pre-expanded particles,
The molecular structure of the resin may be modified by changing the composition of the diol component. Specifically, for example, a dicarboxylic acid represented by the formula (1):

[0019]

Embedded image

Either using isophthalic acid represented by the following formula or as a diol of the formula (2):

[0021]

Embedded image

The 1,4-dichlorohexanedimethanol represented by the formula (1) or a combination of the two, and a unit derived from the above-mentioned isophthalic acid (hereinafter, referred to as
The content ratio of a unit derived from 1,4-cyclohexanedimethanol (hereinafter referred to as a CHDM unit) and / or a unit derived from 1,4-cyclohexanedimethanol in an aromatic polyester-based resin (when either one is used alone) Is used alone, or when both are used together, the total content is adjusted to a range of 0.5 to 10% by weight.

The IPA unit and / or CH
In order to remarkably improve the fusion ratio between particles, the content ratio of the DM unit is particularly preferably 0.6 to 9.
It is preferably about 0% by weight, and more preferably about 0.7 to 8.0% by weight. Among the other components constituting the aromatic polyester resin together with isophthalic acid and 1,4-cyclohexanedimethanol, examples of the dicarboxylic acid include terephthalic acid and phthalic acid.

Examples of the diol component include ethylene glycol, α-butylene glycol (1,2-butanediol), β-butylene glycol (1,3-butanediol), and tetramethylene glycol (1,4-butanediol).
Butanediol), 2,3-butylene glycol (2,
3-butanediol), neopentyl glycol and the like. In addition, the raw material of the aromatic polyester resin may include, in addition to the above components, for example, as an acid component, a trivalent or higher polyvalent carboxylic acid such as a tricarboxylic acid such as trimellitic acid or a tetracarboxylic acid such as pyromellitic acid. A small amount of a trihydric or higher polyhydric alcohol such as a triol such as glycerin and a tetraol such as pentaerythritol may be contained as an acid, an anhydride thereof, or an alcohol component.

In the present invention, the following additives can be added to the aromatic polyester resin. Examples of the additives include a flame retardant, an antistatic agent, a coloring agent, a foam regulator, a melt tension modifier, an antioxidant, and the like, in addition to the foaming agent. As the foaming agent, any of a chemical foaming agent and a physical foaming agent can be used. Examples of the chemical blowing agent include azodicarbonamide, dinitrosopentamethylenetetramine, hydrazoldicarbonamide, and sodium bicarbonate.

Examples of the physical blowing agent include saturated hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, cyclopentane and hexane, and halogenated compounds such as methyl chloride and Freon (registered trademark). Hydrocarbon, dimethyl ether, methyl-tert-
Examples include ether compounds such as butyl ether. Further, an inert gas such as carbon dioxide and nitrogen can be used as a blowing agent.

[0027] Polytetrafluoroethylene resin is preferred as the foam control agent. In the present invention, the aromatic polyester-based resin includes, for example, a polyolefin-based resin such as a polypropylene-based resin, a thermoplastic elastomer resin such as a polyester-based resin, and a polycarbonate resin within a range that does not significantly affect the crystallinity and the rate of crystallization. Nate resin,
An ionomer resin or the like may be added. As the melt tension modifier, an epoxy compound such as glycidyl phthalate, an acid anhydride such as pyromellitic dianhydride, an Ia or IIa group metal compound such as sodium carbonate alone, or two or more kinds It can be mixed and used.

The pre-expanded particles can be produced by cutting an extruded foam obtained by extruding an aromatic polyester resin into particles. According to the above, the step of impregnating the aromatic polyester-based resin with a blowing agent is omitted to save time, cost and labor, and to further reduce the crystallinity of the pre-expanded particles, thereby reducing the particle size during in-mold foam molding. It is possible to improve the fusibility of each other. The size of the pre-expanded particles thus produced is preferably about 0.5 to 5 mm as an average particle diameter.

The degree of crystallinity (%) is measured by a differential scanning calorimeter (DSC) in the same manner as in the measurement of the crystallization peak temperature described above.
And the heat of cold crystallization and the heat of fusion measured according to the measurement method described in Japanese Industrial Standards JIS K7121 using the following equation.

[0030]

(Equation 1)

In the formula, the heat of fusion per mole of the perfectly crystalline PET was 26.9 kJ from the description in the Polymer Data Handbook [published by Baifukan]. Specifically, a predetermined amount of pre-expanded particles as a measurement sample is set 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 pre-expanded particles was determined based on the above equation. The bulk density of the pre-expanded particles is, in the present invention, 0.01 to less weight, in order to obtain a light-weight, mechanical strength, heat resistance, heat insulation, buffering properties, excellent in chemical resistance and the like in the mold. 1.0g
/ Cm ³ is preferred.

The bulk density of [0032] Note that pre-expanded particles are usually is preferably in particular 0.03 to 0.8 g / cm ³ approximately even within the above range, on the order 0.04~0.6g / cm ³ Is more preferred. However, in order to produce a lighter in-mold foam molded product, the bulk density of the pre-expanded particles is preferably 0.1 g even in the range of 0.01 to 1.0 g / cm ^3.
/ Cm ³ or less.

When pre-expanded particles having a relatively small bulk density of 0.1 g / cm ³ or less are to be produced, the pre-expanded particles produced by the above-described method are gas-phase impregnated under pressure and then heated. And then re-foaming to reduce the bulk density. The re-foaming step may be repeated twice or more. As the gas to be impregnated in the pre-expanded particles in the re-expanding step, nitrogen, air, carbon dioxide, helium, methane, ethane, propane,
Butane and the like.

[0034]

<Example 1> After filling the pre-expanded particles into a mold cavity formed by closing the male mold 10 and the female mold 20, first, the steam valve 115 on the female mold side and air for aeration are provided. The valve 116 is opened, and the male side drain valve 107 is opened. From the female side, steam having a gauge pressure of 0.04 MPa and regulated aeration air (so that the temperature in the chamber on the steam inlet side is 100 ° C.) 40)
For 2 seconds (one-side heating), and then steam with a gauge pressure of 0.04 MPa was introduced from the male side for 15 seconds (one-side heating) to introduce air into the mold cavities to remove air, and pre-expanded particles. Was fused.

Next, both male and female steam valves 104, 10
5 was opened and the drain valve was closed, and steam at a gauge pressure of 0.04 MPa was introduced into the mold cavity for 30 seconds (main heating) to perform in-mold foam molding (foaming and fusion). At this time, the temperature in the chamber was 110 ° C. Then a steam valve,
The drain valves were all closed, and the in-mold foam molded product in the mold cavity was left for 120 seconds.

Finally, water was injected from both the male and female cooling water nozzles to cool the in-mold foam molded product.
When it was confirmed that the temperature had dropped to, the mold was opened, and the in-mold foam molded product was taken out. The obtained in-mold foam molded article (vertical 400 × width 300 × wall thickness 100 mm) shows a high fusibility of a fusion rate of 90% (visual judgment), and has an external appearance (visuality by surface extension and appearance of the mold). It was good. <Example 2> After filling the pre-expanded particles into a mold cavity formed by closing the male mold 10 and the female mold 20, first, the steam valve 115 on the female mold side and the air valve 1 for aeration are provided.
16 and the drain valve 107 on the male side is opened, and steam with a gauge pressure of 0.04 MPa and regulated aeration air (adjusted to 100 ° C. in the steam inlet side chamber) from the female side. ) For 40 seconds (while heating), then open the male side steam valve 117 and the aeration air valve 118 and open the female side drain valve 106 to open a gauge pressure of 0.04 MPa from the male side. And the adjusted aeration air (adjusted so that the temperature in the chamber on the steam input side becomes 100 ° C.) for 40 seconds (reverse one-side heating), and then introduced into the mold cavity to release the air. It was removed and the pre-expanded particles were fused.

Next, both male and female steam valves 104, 10
5 was opened and the drain valve was closed, and steam at a gauge pressure of 0.04 MPa was introduced into the mold cavity for 30 seconds (main heating) to perform in-mold foam molding (foaming and fusion). At this time, the temperature in the chamber was 110 ° C. Then a steam valve,
The drain valves were all closed, and the in-mold foam molded product in the mold cavity was left for 120 seconds.

Finally, water was injected from both male and female cooling water nozzles to cool the in-mold foam molded product.
When it was confirmed that the temperature had dropped to, the mold was opened, and the in-mold foam molded product was taken out. The obtained in-mold foam molded article (vertical 400 × width 300 × wall thickness 100 mm) shows a high fusibility of a fusion rate of 90% (visual judgment), and has an external appearance (visuality by surface extension and appearance of the mold). It was good. <Comparative Example 1> (No aeration = ordinary EPS-expanded polystyrene molding method) After filling the pre-expanded particles into the mold cavity formed by closing the male mold 10 and the female mold 20, first, The female side steam valve 104 is opened, and the male side drain valve 107 is opened.
Steam of Pa was introduced for 15 seconds (one-side heating), and then steam of 0.04 MPa gauge pressure was introduced from the male mold side for 15 seconds (one-side heating), and introduced into the mold cavity to remove air. And the pre-expanded particles were fused.

Next, both male and female steam valves 104, 10
5 was opened and the drain valve was closed, and steam at a gauge pressure of 0.07 MPa was introduced into the mold cavity for 15 seconds (main heating) to perform in-mold foam molding (foaming and fusion). Next, the steam valve and the drain valve were all closed, and the in-mold foam molded product in the mold cavity was left for 120 seconds. Finally, water was injected from both the male and female cooling water nozzles to cool the in-mold foam molded product. When it was confirmed that the mold surface temperature had dropped to 50 ° C., the mold was opened and the in-mold foaming was performed. The molded body was taken out.

The obtained in-mold foam molded article (vertical 400.times.horizontal 300.times.thickness 30 mm) also had a very poor fusion ratio of 20%, and the surface condition was shrunk, so that a good product could not be obtained. <Comparative Example 2> (When the temperature in the chamber is low by aeration molding) After filling the pre-expanded particles into a mold cavity formed by closing the male mold 10 and the female mold 20, first, the female mold The steam valve (valve 115 in the drawing) and the aeration valve (valve 116 in the drawing) are opened, and the drain valve 107 on the male side is opened, and steam with a gauge pressure of 0.04 MPa and pressure regulation are performed from the female side. Aeration air (pressure adjusted to 80 ° C. in the chamber on the steam input side) is introduced for 40 seconds (while heating), and steam with a gauge pressure of 0.04 MPa is introduced from the male side for 15 seconds ( (Reverse heating)), each was introduced into a mold cavity to remove air, and fused with the pre-expanded particles.

Next, both the male and female steam valves 104, 10
5 was opened, the drain valve was closed, and steam at a gauge pressure of 0.04 MPa was introduced into the mold cavity for 30 seconds (main heating) to perform in-mold foam molding (foaming and fusion). At this time, the temperature in the chamber was 110 ° C. Then a steam valve,
The drain valves were all closed, and the in-mold foam molded product in the mold cavity was left for 120 seconds.

Finally, water was injected from both the male and female cooling water nozzles to cool the in-mold foam molded product.
When it was confirmed that the temperature had dropped to, the mold was opened, and the in-mold foam molded product was taken out. The obtained in-mold foam molded article (vertical 400 × horizontal 300 × wall thickness 100 mm) had a very low fusion rate of 20%, and a good molded product could not be obtained. <Comparative Example 3> (When the temperature in the chamber is high by aeration molding) After filling the pre-expanded particles into a mold cavity formed by closing the male mold 10 and the female mold 20, first, the female mold Side steam valve 115 and aeration air valve 116
And the drain valve 107 on the male side is opened, and steam with a gauge pressure of 0.04 MPa and regulated aeration air (regulated so that the temperature in the chamber on the steam input side becomes 110 ° C.) from the female side. ) Was introduced for 40 seconds (one-side heating), then steam with a gauge pressure of 0.04 MPa was introduced from the male mold side for 15 seconds (one-side heating), and introduced into each mold cavity to remove air, and The pre-expanded particles were fused.

Next, both male and female steam valves 104, 10
5 was opened, the drain valve was closed, and steam at a gauge pressure of 0.04 MPa was introduced into the mold cavity for 30 seconds (main heating) to perform in-mold foam molding (foaming and fusion). At this time, the temperature in the chamber was 110 ° C. Then a steam valve,
The drain valves were all closed, and the in-mold foam molded product in the mold cavity was left for 120 seconds.

Finally, water was injected from the cooling water nozzles of both the male and female molds to cool the foamed molded article in the mold.
When it was confirmed that the temperature had dropped to, the mold was opened, and the in-mold foam molded product was taken out. The obtained in-mold foam molded product (vertical 400 × width 300 × wall thickness 100 mm) had a very low fusion rate of 20%, and a good molded product was not obtained. As the pre-expanded particles used in the above Examples and Comparative Examples 1 to 3, the following FPET was used.

An aromatic polyester resin (T) synthesized by polycondensation reaction of ethylene glycol and terephthalic acid
g: 68 ° C.) 100 parts by weight, 0.03 parts by weight of pyromellitic dianhydride as a modifier, and 0.03 parts by weight of sodium carbonate as a modifying aid were extruded (caliber: 6).
5 mm, L / D ratio: 35), melted and kneaded under the conditions of a screw rotation speed of 50 rpm and a barrel temperature of 270 to 290 ° C., butane butane (n-butane / isobutane) as a foaming agent was fed from the middle of the barrel. = 7/3) was injected at a rate of 1% by weight with respect to the mixture.

Next, the mixture was extruded and foamed through each nozzle of a multi-nozzle mold (15 nozzles having a diameter of 0.8 mm arranged on a straight line) connected to the tip of the barrel of the extruder, and then cooled. Cooled in a water bath. Then, after the cooled strand-shaped extruded foam was sufficiently drained, it was cut into a substantially columnar shape using a pelletizer to obtain pre-expanded particles.
The bulk density of the pre-expanded particles was 0.13 g / cm ³ , the particle size was 1.4 to 2.5 mm, the crystallinity was 9.0%, and the crystallization peak temperature was 126.0 ° C.

The raw materials used and the range of the moldable wall thickness according to the production method of the present invention were confirmed as follows. <Raw materials><Moldable wall thickness> FPET pre-expanded particles (bulk density 0.045 g / cm ³ ) 100 mm FPET pre-expanded particles (bulk density 0.068 g / cm ³ ) 100 mm FPET pre-expanded particles (bulk density 0.135 g) / Cm ³ ) 50mm

[0048]

As described above, by adopting the above-mentioned method for producing an in-mold foam molded article using an aromatic polyester resin according to the present invention, a molded article which is satisfactory from both the internal fusion and the appearance can be provided. .

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a foam molding apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 10 Male type 20 Female type 115 Steam valve 116 Air valve for aeration

Claims (3)

[Claims] 1. A method of filling pre-expanded particles of an aromatic polyester resin into a mold, heating, cooling, etc., to produce an in-mold foam molded article having a predetermined shape, first of all, before heating. A method for producing an in-mold foam molded article made of an aromatic polyester resin, comprising heating with a heating medium at a temperature of about 105 ° C. and subsequently performing main heating with a steam of 0.03 to 0.1 MPa. 2. The method according to claim 1, wherein the temperature of the heating medium is adjusted to 90 to 105 ° C. by mixing air with steam and adjusting the temperature by the ratio. A method for producing a foam molded article. 3. The method of controlling the temperature of the heating medium at 90 to 105 ° C.
The in-mold foam molded article made of an aromatic polyester resin according to claim 1 or 2, wherein the one-side heating and the one-side heating are performed first by one-side heating or by both one-side heating and one-side reverse heating. Manufacturing method.