JPS6148409B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing extruded polyester foam, and its purpose is to provide a method that can uniformly and finely foam polyester and stably produce extruded foam with a high expansion ratio. Conventionally, aromatic polyesters, particularly polyethylene terephthalate, polybutylene terephthalate, etc., have been used for injection molded products, fibers, films, etc. because of their excellent mechanical properties, heat resistance, chemical resistance, dimensional stability, etc. However, aromatic polyester has a low melt viscosity, and when trying to manufacture foam molded products using the extrusion foaming method, it is difficult to make the bubble size and distribution uniform, and sometimes gas separates from the molten resin and falls off, resulting in good bubble formation. It was difficult to obtain molded products. In order to improve these drawbacks, high-polymerization degree polyesters are produced by solid-phase polymerization of polyesters or addition of polymerization accelerators, and polyesters with increased melt viscosity are produced by copolymerizing branching agents. It has been proposed to use polyester as a raw material, but it is difficult to increase the melt viscosity enough to obtain a foamed product with uniform, fine cells, and it is completely different from polymers used for other purposes. It has the disadvantage that it must be specially manufactured to have a melt viscosity, resulting in complicated processes and high costs. In order to improve this drawback, during extrusion foam molding, a diepoxy compound is mixed with one or more substances selected from metals of Group A and Group A of the Periodic Table, or their compounds, to reduce the melt viscosity of polyester. A method of increasing the melt viscosity of polyester by mixing a diepoxy compound with a montan wax salt and/or a montan wax ester salt (Japanese Unexamined Patent Publication No. 54-24364)
50568) etc. have been proposed. However, these methods require the use of metals from groups a and a of the periodic table or their compounds, which have a reaction accelerating effect on the diepoxy compound, and do not increase the viscosity of the diepoxy compound by using the metals or these compounds. The reaction is significantly accelerated,
Although this has the favorable effect of increasing the melt viscosity in the foaming extruder until it can exert the desired effect, on the other hand, this viscosity increase is too rapid and the viscosity is not stable enough, rapidly reaching the maximum viscosity. It has the disadvantage that the optimum operating range is narrow because it rapidly decreases after reaching . As a result of intensive research into a method for producing extruded polyester foam that does not have these drawbacks, the present inventor found that during extrusion foam molding of aromatic polyester,
If a diglycidyl ester compound is used, it is possible to mold a foam having uniform fine cells without using a metal compound as proposed above, and if a diglycidyl ester compound is also used in combination with a metal compound, the above-mentioned disadvantages can be avoided. In addition, the diglycidyl ester compound can extremely quickly increase the viscosity of polyester to the optimum viscosity for extrusion foaming, and this viscosity is maintained for a long time, allowing a wide stable operation range. The present invention was achieved based on the discovery that this compound has advantages and exhibits an action significantly different from that of other diepoxy compounds. That is, in the present invention, when manufacturing a foam by melt-extruding and foaming an aromatic polyester containing a blowing agent with a boiling point of 200°C or less at normal pressure, the aromatic polyester is used as a reference at a stage before melt-extrusion. This is a method for producing an extruded polyester foam characterized by incorporating 0.1 to 3% by weight of a diglycidyl ester compound. The aromatic polyester used in the present invention mainly contains aromatic dicarboxylic acids (85% of the total dicarboxylic acids).
It is a linear polyester containing a dicarboxylic acid component (accounting for mol% or more). Representative examples of the aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, and diphenoxyethane dicarboxylic acid. . Preferably used diol components of the polyester include ethylene glycol, trimethylene glycol, tetramethylene glycol, neopentylene glycol, hexamethylene glycol, cyclohexane dimethylol, tricyclodecane dimethylol, 2,2-bis(4- β-hydroxyethoxyphenyl)propane, 4,4′-bis(β-
Examples include hydroxyethoxy) diphenyl sulfone and diethylene glycol. The polyester contains an oxy acid such as P-oxybenzoic acid (15 mol% based on the dicarboxylic acid component).
(below), aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, etc. may be copolymerized in a small proportion (15 mol% or less of the dicarboxylic acid component),
In addition, a small proportion of polyfunctional compounds such as pentaerythritol, trimethylolpropane, trimellitic acid, pyromellitic acid, etc. or monofunctional compounds such as benzoic acid may be copolymerized. The intrinsic viscosity of the aromatic polyester used in the present invention does not need to be particularly high, but the preferable intrinsic viscosity (value measured at 35°C using O-chlorophenol as a solvent) is 0.4 or more, and a particularly preferable value is 0.5 or more. . On the other hand, from the viewpoint of ease of melt molding, it is preferable that the intrinsic viscosity is 1 or less. Aromatic polyesters particularly preferably used in the present invention include polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, or more than 50% of the number of repeating units is ethylene terephthalate, tetramethylene terephthalate,
Or modified polyethylene terephthalate, modified polytetramethylene terephthalate, modified polyethylene-2,6, in which the remainder is other components than ethylene-2,6-naphthalene dicarboxylate.
- Examples include naphthalene dicarboxylate. These modified polyesters in which the third component accounts for 30% or less of the number of repeating units are more preferably used. The substance used as a blowing agent for aromatic polyester in the present invention has a boiling point of 200°C or less at normal pressure. It goes without saying that this substance should be selected from among those that do not have an adverse effect that changes the quality of the aromatic polyester during extrusion foam molding (i.e., one that is inert to the aromatic polyester). stomach. More preferably, the blowing agent has a boiling point of 150° C. or lower at normal pressure. Preferably used blowing agents include carbon dioxide, nitrogen,
Inert gases such as helium, xenon, and neon, and the following organic compounds with a boiling point of 200°C or less at normal pressure: saturated aliphatic hydrocarbons, saturated alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons , ether, ketone, etc. Particularly preferably used organic compounds include hydrocarbons having 8 or less carbon atoms (e.g., saturated aliphatic hydrocarbons such as methane, ethane, butane, hexane, etc.; saturated alicyclic hydrocarbons such as cyclohexane, ethylcyclopentane, etc.; benzene; , aromatic hydrocarbons such as xylene, etc.), chlorinated saturated hydrocarbons having 2 or less carbon atoms (e.g. methyl chloride, methylene chloride, chloroform, carbon tetrachloride, ethyl chloride, dichloroethane, dichloroethylene, etc.), 2 or less carbon atoms fluorinated saturated hydrocarbons (e.g. carbon tetrachloride, ethyl fluoride, ethane tetrafluoride, etc.), chlorinated saturated hydrocarbons having 2 or less carbon atoms (e.g. chlorodifluoromethane,
Dichlorofluoromethane, chlortrifluoromethane, dichlordifluoromethane, trichlorofluoromethane, dichlortetrafluoroethane,
trichlorotrifluoroethane, tetrachlorodifluoroethane, etc.), fluorobenzene, chlorobenzene, ethers having 6 or less carbon atoms (preferably diethers, such as methylal, acetal,
1,4-dioxane, etc.), ketones having 4 or less carbon atoms (eg, acetone, ethyl methyl ketone, acetylacetone, etc.). Such blowing agents may be used alone or in combination of two or more. The proportion of the foaming agent added is the amount that imparts foamability to the aromatic polyester, and is usually 1 to 50% by weight based on the aromatic polyester. If the amount of the blowing agent is less than 1% by weight, there will be almost no foaming, so a practical foamed molded product will not be obtained;
If the amount is more than 50% by weight, the blowing agent will not be able to enter the molten resin uniformly and sufficiently, gas will blow out, and it will be difficult to obtain a foam with a predetermined shape, which is not preferable. A more preferable addition ratio of the blowing agent is 2 to 40% by weight. Furthermore, the epoxy compound used in the present invention is a diglycidyl ester compound, which is a diglycidyl ester of a difunctional carboxylic acid. The difunctional carboxylic acid is preferably an aromatic dicarboxylic acid or an alicyclic dicarboxylic acid, such as terephthalic acid, isophthalic acid, phthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, hexahydrophthalic acid, tetrahydroterephthalic acid, Examples include tetrahydroisophthalic acid and tetrahydrophthalic acid. Typical specific examples of diglycidyl ester compounds include diglycidyl phthalate, diglycidyl terephthalate, diglycidyl hexahydrophthalate, dicrycidyl tetrahydrophthalate, and the like. These may be used alone or in combination of two or more. Such diclycidyl ester compounds exhibit unique properties compared to diglycidyl ether of bisphenol A, which is a typical diepoxy compound. For example, in FIG. 1, the thickening effect of aromatic polyester depending on the type of diepoxy compound is shown by torque (viscosity) change behavior using a Brabender plastograph. In Figure 1, is the torque (viscosity) change curve when diglycidyl ether of bisphenol A and sodium montanate as a reaction catalyst are used together, and is 1,2
- Torque (viscosity) change curve when diglycidyl hexahydrophthalate is used alone,
The curves from both have the advantage that the torque (viscosity) tends to increase earlier and the time required for the torque to reach 1100 to 1200 Kg/cm to obtain a stable discharge condition is longer than that of the curve. Recognize. Also the first
The figure shows a curve when 1,2-diglycidylhexahydrophthalate is used in combination with sodium montanate, and these show that the torque (viscosity) change is large and the torque is
It can be seen that the time at 1100 to 1200 kg/cm becomes shorter and the stable operation range becomes narrower, which is not desirable. The amount of diglycidyl ester compound used is 0.1 to 3% by weight based on the polyester. If the diglycidyl ester compound is less than 0.1% by weight, the melt viscosity of the mixture will not increase sufficiently and it will be difficult to form uniform fine foam in the molded product, which is not preferable. Moreover, if the amount is more than 3% by weight, gelation will occur violently, making it difficult to suppress the foaming pressure to obtain a foam, and even if a foam molded product is obtained, the mechanical strength will decrease and the coloration will become significant. This is not desirable because it causes A more preferable usage amount is
It is 0.3 to 2% by weight based on polyester. The amount of the diglycidyl ester compound to be added is preferably determined experimentally depending on the molecular weight of the aromatic polyester. When adding the diglycidyl ester compound, 1. After mixing the aromatic polyester and the diglycidyl ester compound at a low temperature (for example, below 150°C) (for example, by sprinkling both components on the surface of the polymer pellet), add the hopper of the extruder. and melt it. 2. A polymer pellet obtained by mixing a diglycidyl ester compound with a molten polymer is charged into the hopper of an extruder and melted. 3. A diglycidyl ester compound is fed into the polyester previously melted in the extruder through a supply port provided in advance in the cylinder of the extruder. Methods such as the following can be used. The temperature at which the aromatic polyester is melted in the extruder is higher than the melting point of the aromatic polyester, but should be kept at 330°C or less, and if the melting point of the polyester is less than 200°C, the temperature should be kept at 200°C or more and 330°C or less. It is preferable to keep it. Further, it is preferable that the blowing agent is added by a press injection method. This press-fitting method is as follows: a. Press-fitting from the vent section provided in the middle of the cylinder of the extruder.b. Press-fitting at two locations in total: the vent section and the die section.c. Press-fitting at two locations at the die section.d. Press-fitting at two locations at the vent section. For example, it may be press-fitted at three locations, including two locations on the die portion. In the addition of the diglycidyl ester compound and the blowing agent, the epoxy compound is added at a location where a residence time sufficient for the aromatic polyester to thicken sufficiently for foaming is maintained before it leaves the die outlet, and the epoxy compound is It is preferable to add the blowing agent at a position from a region where the foaming agent melts and does not escape to the hopper side to a region where it can sufficiently mix with the molten polymer up to the exit of the die. According to the present invention, even if aromatic polyester, which has a low melt viscosity and is not suitable for conventional extrusion foam molding, can be easily extruded and foam molded. can be manufactured. Furthermore, the resulting foam molded product has fine air bubbles evenly distributed, has a beautiful appearance, and has excellent mechanical strength, heat resistance, and chemical resistance compared to other general-purpose resin foams, especially polyethylene terephthalate. In the case of , the heat resistance is sufficient to withstand an atmosphere of 150°C. The foam molded product obtained by the method of the present invention includes:
Stabilizers, foam nucleating agents (eg talc), pigments, flame retardants, antistatic agents, fillers and other additives can be included. The present invention will be explained in more detail with reference to Examples below. Note that parts in the examples represent parts by weight. Example 1 100 parts of polyethylene terephthalate pellets with an intrinsic viscosity of 0.65 were dried with hot air at 130°C for 8 hours, and then 1,2-diglycidylhexahydrophthalate was prepared.
Using a V-type blender, mix 0.6 parts of talc and 0.5 parts of talc as a foaming nucleating agent, and add 1,2- to the pellets.
Diglycidyl hexahydrophthalate and talc as a crystal nucleating agent were uniformly deposited. The pellets obtained above were put into a cylinder with a diameter of 40 mm.
mm, L/D 32, and an extrusion foam molding machine equipped with a die having a nozzle with a hole diameter of 5 mm to obtain a foam. In extrusion foam molding, 15 parts of dichlorodifluoromethane (polymer
(per 100 parts) using a plunger pump, and set the cylinder temperature to 280 in the supply zone.
℃, plasticization zone 280℃, metaling zone 270℃
℃, die section set at 270℃, and screw rotation speed
The discharge pressure was 30 rpm and 120 Kg/cm ² . The discharge pressure remained stable during extrusion foam molding. The obtained extruded foam had a foaming ratio of 15 times, had bubbles uniformly dispersed, and had a good appearance. Examples 2 to 4 Extrusion foam molding was carried out in the same manner as in Example 1, except that the epoxy compounds shown in Table 1 were used instead of 1,2-diglycidylhexahydrophthalate. The results are shown in Table 1.

【table】

[Table] Comparative Examples 1 to 4 100 parts of polyethylene terephthalate pellets with an intrinsic viscosity of 0.65 were dried with hot air at 130°C for 8 hours, and then 1,2-diglycidylhexahydrophthalate in the amounts shown in Table 2 below and Table 2 below were added. montanic acid sodium salt (melting point: 180° C.; montanic acid is a mixed acid of higher fatty acids) in the amount shown above, and the epoxy compound and montanic acid sodium salt were uniformly adhered to the pellets. Using the obtained pellets, extrusion foam molding was carried out in the same manner as in Example 1, and the stability of the extrusion foam molding was observed. The results are shown in Table 2.

[Table] Reference example: Intrinsic viscosity after drying in a hot air dryer at 130℃ for 8 hours
0.65 polyethylene terephthalate pellets, the diepoxy compound shown in Table 3, sodium montanate, and talc are melted and kneaded in a small kneader with two built-in rotors. Set temperature using a conshift meter (Brabender Plastograph)
Determined at 270℃. The results are shown in Figure 1 as the relationship between mixing time (minutes) and torque (Kg.cm).

[Table] Note: The values in the table are parts by weight based on 100 parts by weight of polyethylene terephthalate.
In FIG. 1, , , , and are curves showing the results of experiment numbers, , , and in Table 3, respectively. In FIG. 1, the curves show that 1,2 diglycidyl hexahydrophthalate of the present invention has a faster thickening effect than diglycidyl ether of bisphenol A, which is a typical conventional compounding agent. It can be seen that both reactions are quick. Also,
Comparison of the curves reveals that talc acts as a foaming agent and does not contribute in any way to promoting the reaction of the diepoxy compound. Comparison of the two curves shows that although the torque increases rapidly with the addition of sodium montanate, the controllability of the torque significantly decreases. Based on the data obtained from the mixing type consistency meter and the extruder, it is known that a torque of 1100 to 1200 kg cm is the appropriate operating range for extrusion foaming, so the experiment number (corresponding to Example 1) ) has a wide operating range. Furthermore, the curve shows that even if 1,2 diglycidyl hexahydrophthalate is reduced while sodium montanate is increased, the torque reaches its peak time later and its value is also smaller. From these facts, it is clear that it is more preferable to reach an appropriate operating range only by using the amount of the epoxy compound of the present invention without using an alkali (earth) metal compound such as sodium montanate that exhibits a catalytic action. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between kneading time and torque using a Brabender plastograph.

Claims (1)

[Claims] 1. When producing a foam by melt extruding and foaming an aromatic polyester containing a blowing agent with a boiling point of 200°C or less at normal pressure, the aromatic polyester must be 0.1 to 3 at the stage before melt extrusion.
A method for producing an extruded polyester foam, which comprises incorporating a diglycidyl ester compound in an amount of % by weight.