JP3333241B2 - High molecular weight polycarbonate resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-molecular-weight polycarbonate resin foam having fine cells and a method for producing the same.
Highly heat-resistant, containing no harmful substances, high molecular weight polycarbonate resin foam, which can be suitably used for microwave oven containers, retort food containers, etc., which are particularly required to have heat resistance, such as composite core materials and packaging materials. It is about.

[0002]

2. Description of the Related Art Hitherto, with respect to a polycarbonate resin foam, various foaming agents, foaming conditions and the like have been studied in extrusion foaming and impregnation foaming. For example, JP-B-59-23336, JP-B-63-4502, JP-B1-41485, JP-A-2-2618.
No. 36, and the like. However, in each case, the average cell diameter of the foam was relatively large at 0.2 mm or more, or the cell diameter was not strictly studied.

[0003] V.I. Kumar et al. (ANTEC '
91. P1401 to 1405, P1406 to P141
0, and Am. Soc. Mech. Eng. Mate
r. Div. Vol 19, pp. 197 to 212) report that a commercially available polycarbonate resin sheet having a weight average molecular weight of at most about 35,000 was impregnated with carbon dioxide gas to obtain a microcell (cell diameter of 10 μm or less) foam. Only a foam with a magnification of at least 10 times was obtained.

[0004] As described above, a microcellular foam of a polycarbonate resin, in which the expansion ratio can be changed in a wide range and its uniform control is easy, has not been obtained by the prior art. Furthermore, the polycarbonate resin foams obtained by these conventional methods have, of course, insufficient heat resistance, solvent resistance and hot water resistance.

[0005]

SUMMARY OF THE INVENTION The present invention is to improve
A wide range of foaming ratio ( density 0.6 to 0.02)
g / cm ³ ) , and the objective is to obtain a polycarbonate resin foam which can easily and uniformly control the expansion ratio, and particularly a microcell foam which is particularly excellent in heat resistance. Is what you do.

[0006]

Means for Solving the Problems In order to solve this problem, the effect of the resin on the solution of the weight average molecular weight, particularly the effect of the resin having a weight average molecular weight of 40,000 or more, which is not commercially available and has not been studied at all, has been studied. As a result of various studies focusing on high molecular weight polycarbonate resin, it is possible to uniformly control the expansion ratio over a wide temperature range, and to obtain a polycarbonate resin foam having improved heat resistance, solvent resistance, hot water resistance, etc. I found something.

That is, the present invention is as follows. (1) A high molecular weight polycarbonate resin foam having a weight average molecular weight of 40,000 to 300,000. (2) The high molecular weight polycarbonate resin foam according to the above (1), wherein the foam has an average cell diameter of 100 μm or less. (3) Carbon dioxide is used as a foaming agent and the weight average molecular weight is 4
A method for producing a high molecular weight polycarbonate resin foam, comprising foaming a high molecular weight polycarbonate resin having a molecular weight of 0000 to 300,000.

[0008] Compared with resins having a weight average molecular weight of less than 40,000, resins having a weight average molecular weight of 40,000 to 300,000 do not cause shrinkage or surface roughness even when foamed at a high temperature. Since the expansion ratio can be changed, and since the relationship between the expansion ratio and the expansion temperature is gentle as shown in FIG. 1, even if the heating temperature varies somewhat, the expansion ratio is small and uniform foaming is achieved. It is easy to control foaming conditions. In addition, the foam has improved heat resistance of the resin, and has excellent heat resistance in practical use because finer cells are formed more uniformly than conventional products with large cells. Was. The practical heat resistance referred to here is not the heat resistance during continuous use for a long time but the short-time heat resistance of a microwave oven container or the like.

In the present invention, the average molecular weight of the polycarbonate resin (the average molecular weight described below means the weight average molecular weight) needs to be 40,000 to 300,000. If the molecular weight is less than 40,000, when the foaming heating temperature is increased, the foam shrinks, the surface is roughened, and the like, so that the foaming temperature range cannot be widened. Further, since the relationship between the expansion ratio and the expansion temperature is steep, if the heating temperature varies somewhat, the expansion ratio greatly changes, and it is difficult to control the expansion conditions. On the other hand, if the molecular weight exceeds 300,000, the viscoelasticity at the time of foaming is too large, so that the expansion ratio cannot be increased, so that the object of the present invention is not achieved.

The average molecular weight is preferably 42500-2.
00000, more preferably 45,000 to 10,000
0, particularly preferably in the range of 50,000 to 80,000. The measurement of the average molecular weight of the polycarbonate resin in the present invention was performed using GPC, and the measurement conditions were as follows. Using a tetrahydrofuran solvent and a polystyrene resin gel, the average molecular weight was calculated from the converted molecular weight calibration curve by the following equation based on the calibration curve of the standard monodisperse polystyrene resin.

M _pc = 0.359M _ps ^1.0389 (where M _pc is the average molecular weight of the polycarbonate resin and M _ps is the average molecular weight of the polystyrene resin.) The polycarbonate resin used in the present invention is as follows: 1) A polycarbonate resin having a main chain composed of a repeating unit represented by the formula.

[0012]

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(Where Ar is a divalent aromatic residue, for example, phenylene, naphthylene, biphenylene,
Examples include pyridylene and those represented by the following formula (2). ) -Ar ¹ -Y-Ar ^2- (2) (wherein, Ar ¹ and Ar ² are each an arylene group and represent, for example, a group such as phenylene, naphthylene, biphenylene, and pyridylene; Or an alkylene group or a substituted alkylene group represented by

[0014]

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Further, a divalent aromatic residue represented by the following formula (3) may be contained as a copolymer component. -Ar ¹ -Z-Ar ^2- (3) [wherein, Ar ¹ and Ar ² are the same as above, and Z is a mere bond or -O-, -CO-, -S-, -SO _{2
-, - CO 2 -, -} CON (R 1) (R 2) -,
(R ¹ and R ² are the same as described above). Examples of these divalent aromatic residues include those represented by the following chemical formulas 3, 4 and 5.

[0016]

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[0017]

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[0018]

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Wherein R ⁵ and R ⁶ are each hydrogen, halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkoxy, C ₁ -C ₁₀ cycloalkyl or phenyl, , M and n are integers of 1 to 4, and when m is 2 to 4, each R ⁵ may be the same or different, and when n is 2 to 4, each R ⁶ They may be the same or different.) Among them, the following (4)
What is represented by a formula is a preferable example.

[0020]

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In particular, those containing 85 mol% or more of a repeating unit in which the above formula (4) is Ar are preferable. The polycarbonate resin of the present invention may contain a trivalent or higher aromatic residue as a copolymer component. Although the molecular structure of the polymer terminal is not particularly limited, one or more terminal groups selected from a hydroxyl group, an aryl carbonate group, and an alkyl carbonate group can be bonded.

The aryl carbonate terminal group is represented by the following formula (5)

[0023]

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(Wherein, Ar ³ is a monovalent aromatic residue, and the aromatic ring may be substituted).

[0025]

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And the like. The alkyl carbonate terminal group is represented by the following formula (6)

[0027]

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(Wherein R ⁷ is a linear or branched alkyl group having 1 to 20 carbon atoms). Specific examples include, for example,

[0029]

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And the like. Among these, a phenyl carbonate group, a pt-butylphenyl carbonate group, a p-cumylphenyl carbonate group, and the like are preferably used. The hydroxyl group terminal is preferably as small as possible to reduce heat resistance, hot water resistance and the like. These polycarbonate resins can be produced by a known method. For example, by a method described in JP-A-61-238823, a method of polymerizing using 2,2-bis (4-hydroxyphenyl) propane, pt-butylphenol and phosgene, or a method described in JP-A-3-238823. According to the method described in Japanese Patent No. 68627, a method of polymerizing using 2,2-bis (4-hydroxyphenyl) propane and diphenyl carbonate is used as appropriate. The polycarbonate resin produced by the latter method has excellent safety without harmful halogen components remaining.

Further, if necessary, known additives such as a lubricant, a heat stabilizer, and an ultraviolet absorber may be added to the extent that the foamability is not significantly changed. As the chemical foaming agent used in the present invention, a known thermal decomposition type foaming agent is used, and azodicarbonamide, trihydrazinotriazine, benzenesulfonyl semicarbazide, p, p'-oxybisbenzenesulfonylhydrazide and the like are appropriately selected and used. Can be

The physical foaming agent used in the present invention includes generally known aliphatic hydrocarbons such as butane, pentane and hexane.
Aromatic hydrocarbons such as benzene, toluene and xylene; alcoholic hydrocarbons such as methanol and ethanol; ketone-based hydrocarbons such as acetone and methyl ethyl ketone;
Halogenated hydrocarbons such as 1,1,2-tetrafluoroethane and 1,1-difluoroethane, and inorganic gases such as carbon dioxide and nitrogen gas are preferably used. Among them, an inorganic gas, particularly a carbon dioxide gas, is preferable because it gives fine cells having a small average cell diameter of the foam.

Further, the polycarbonate resin obtained by the solid phase polymerization method described in JP-A-3-68627 is characterized in that it contains almost no harmful halogen as compared with the solution polymerization method. When carbon dioxide is used as the agent, a polycarbonate resin foam having excellent heat resistance and containing almost no harmful substances that cannot be obtained by the conventional technique can be obtained.

The physical foaming agent is introduced into a known method, for example, into a high-pressure container such as an autoclave containing a sheet or a molded product, and if necessary, impregnated under high-temperature and high-pressure conditions.
The impregnation conditions and the impregnation amount can be appropriately selected in consideration of the required expansion ratio and expansion temperature. For example, when carbon dioxide is used as the foaming agent, the temperature is not particularly limited, but the temperature is 0 to 30 ° C., the pressure is 10 to 75 kg / cm ² , and the time is 5 to 5.
48 hours are preferably used. Further, if necessary, known additional foaming means may be used.

As a heating means at the time of foaming, known methods such as hot air heating, heating oil heating, far infrared heating, steam heating and the like are appropriately selected. In particular, by using the relatively high water vapor permeability of the polycarbonate resin effectively, a high-magnification foam can be obtained by the steam heating method. Also,
The average cell diameter of the foam of the present invention is preferably as small as possible, and preferably 100 μm or less, because the higher the heat insulating property, the higher the practical heat resistance. It is more preferably at most 50 μm, further preferably at most 30 μm, particularly preferably at most 20 μm. Here,
The average cell diameter of the foam was measured by observing a cross section of the foam with an electron microscope photograph (scanning electron microscope, JSM-T300-FCS manufactured by JEOL Ltd.) at a magnification of about 100 to 1000 times, and 50 or more cells were observed. Is the value obtained by measuring and averaging the diameters of the cells.

Further, the density of the foam of the present invention can be appropriately selected depending on its use, but is usually 0.60 to 0.02.
g / cm ³ are preferred. Preferably, 0.40
0.025 g / cm ³ , more preferably 0.30 to
0.03 g / cm ³ , particularly preferably 0.24 to 0.1 g / cm ³ .
04 g / cm ³ . The magnification of the foam is a value obtained by dividing the density of the resin by the density of the foam.

The method for producing the foam of the present invention employs a generally known method for producing a foam in consideration of its use as appropriate. For example, expandable beads, bead pellets of the target resin in advance in a physical foaming agent solution, or in a physical foaming agent gas phase,
Alternatively, in an aqueous suspension solution containing a physical foaming agent, the foaming agent is absorbed into pellets while stirring, if necessary, or the physical foaming agent or After press-fitting a chemical foaming agent, melt-kneading it, extrude it from a die small hole nozzle, quench in order to suppress foaming in a water tank, and obtain beads containing a foaming agent, using either method Is also good. Beads containing a foaming agent can be molded into an arbitrary molded body by heat molding in a molding die, similarly to known bead foams represented by bead expanded polystyrene.

A flat or sheet foam can be obtained by extrusion foaming. Alternatively, a physical foaming agent or a chemical foaming agent is press-fitted during the extrusion of resin pellets by an extruder, and the mixture is melt-kneaded and mixed. After passing through a cooler or the like, the extrusion pressure is released from the die, and a flat or sheet-like foam can be obtained. These can be processed into an arbitrary formed body by a method such as vacuum forming.

[0039]

The present invention will be described below in detail with reference to examples.

[0040]

Example 1 A pellet of a polycarbonate resin (weight average molecular weight 56,000) produced from diphenyl carbonate and 2,2-bis (4-hydroxyphenyl) propane by the method described in JP-A-3-68627 was used. Melt extrusion was performed at a cylinder temperature of 320 ° C. using an extruder to prepare a sheet having a thickness of 1.3 mm.

A 100 × 100 mm sample was cut out from the sheet, placed in a small autoclave, pressurized with carbon dioxide gas to 40 kg / cm ^2, and left at room temperature for 48 hours. The pressure was released and the weight of the sample was measured. As a result, 9.5 parts by weight of the sample was impregnated with carbon dioxide. The impregnated sample was foamed by changing the foaming temperature in an oil bath from 150 to 180 ° C. and heating for 30 seconds. The foaming ratio was 2.5 times at 150 ° C. in proportion to the temperature rise in this temperature range. increased to 18 times at 180 ° C. from (density of 0.48 g / cm ³⁾ (density of 0.07g / cm ^3), it was confirmed possible to control the uniform expansion ratio. Each of the obtained foams had a cell diameter of 10 μm or less.

The foam did not shrink even when heated in an oil bath at 175 ° C. for 60 seconds, and was superior in heat resistance to the comparative example. The impregnated sample was heated at a heating temperature of 147 ° C., 151 ° C., and 155 ° C. for 1 minute by a steam-type heating device to obtain a foam. The densities of these foams were 0.24, 0.11, and 0.06 g / cm ³ , respectively, and were uniform microcell foams having an average cell diameter of about 10 μm or less. Tensile strengths measured according to JIS-K6767 are 168, 56, and 20 kg / cm ² , respectively.
The tensile elongation was 61, 59, and 44%, respectively.

[0043]

Example 2 After solid phase polymerization was carried out in the same manner as in Example 1, the weight average molecular weight was 42,000 (A) and 95,000.
A polycarbonate resin (B) was obtained. In the same manner as in Example 1, an extruded sheet was prepared and impregnated with carbon dioxide gas.
After obtaining 9.5 parts by weight of the impregnated sample, the impregnated sample was immersed in an oil bath and heated and foamed. The impregnated samples (A) and (B) were heated in an oil bath at a foaming temperature of 1
When foaming was performed by heating for 30 seconds while changing the temperature from 50 to 180 ° C., it was confirmed that the foaming ratio increased in proportion to the temperature rise in this temperature range, and that the foaming ratio was controlled uniformly. After heating from (A) at 170 ° C. for 1 minute, the density of the foam obtained was 0.07 g / cm ³ , and (B)
To 180 ° C. for 1 minute, the density of the foam obtained was 0.06 g / cm ³ , and the average cell diameter was about 10
It was a uniform microcell foam having a size of not more than μm.

In addition, even when any of the impregnated samples was heated and foamed in an oil bath at 175 ° C. for 1 minute, the foam did not shrink and was superior in heat resistance to the comparative example.

[0045]

Comparative Example 1 Weight average molecular weight 22500 [Panlite L
-1225, manufactured by Teijin Chemicals Ltd.) (C) and a weight average molecular weight of 30,000 [Panlite K-1300, manufactured by Teijin Chemicals Ltd.] (D) in the same manner as in Example 1. A 1.3 mm extruded sheet was obtained.

This sheet was sampled in a size of 50 × 50 mm, and impregnated with carbon dioxide gas in the same manner as in Example 1. Each impregnation amount was 9.5 parts by weight. When these impregnated sheets were immersed in an oil bath at 155 ° C., 165 ° C., and 175 ° C. for 30 seconds and foamed, the obtained foam had a small cell diameter, but had a density of (C), 0.
17, 0.18, 0.30 g / cm ³ , (D), 0.
24, 0.09 and 0.08 g / cm ³ . In all cases, at 175 ° C., shrinkage started during foaming after 30 seconds or more, and the heat resistance was insufficient and the foaming temperature range was narrow as compared with those of Examples. This indicates that it is difficult to control the foaming temperature conditions for obtaining a uniform foam as compared with the examples.

[0047]

Comparative Example 2 After solid-phase polymerization was performed in the same manner as in Example 1, a polycarbonate resin having a weight average molecular weight of 325,000 was obtained. In the same manner as in Example 1, an extruded sheet was prepared and impregnated with carbon dioxide gas to obtain 8.2 parts by weight of an impregnated sample. The impregnated sample was immersed in an oil bath and heated and foamed. . Raise the heating temperature to 180 ° C,
When foaming was performed by heating for 0 seconds, the obtained foam was a microcell foam, but the foam density was 0.13 g /
cm ³ (expansion ratio 9 times) was obtained, and under the heating condition more than that, the foam surface was roughened. this is,
It is considered that the expansion ratio could not be increased because the molecular weight was too high.

[0048]

Example 3 Using the resin of Example 1, bead-shaped pellets having an average of about 1 mmφ were obtained with an extruder. The beaded pellet was placed in a small autoclave, carbon dioxide gas was injected under pressure to 45 kg / cm ^2, and the mixture was left at room temperature for 48 hours. The pressure was released and the weight of the sample was measured. As a result, 8.9 parts by weight of the sample was impregnated with carbon dioxide. The impregnated beads were placed in a wire mesh basket, and heated at a heating temperature of 150 ° C. for 1 minute with a steam heating device to obtain pre-expanded beads having a density of 0.13 g / cm ³ . The pre-expanded beads were impregnated again with carbon dioxide to obtain foamed beads impregnated to about 15 parts by weight. The beads were filled in a molding die, and the entire mold was placed in a steam-type heating device and heated and foamed to obtain a plate-shaped foamed foam of 100 × 150 × 20 mm.

[0049]

Example 4 50 × from the extruded sheet obtained in Example 1
Sampling into a 50 mm square, containing n-pentane in the liquid phase
It was soaked to obtain 4 parts by weight of an impregnated sample. This impregnated sump
Immersion in a 170 ° C oil bath for 1 minute
Let density 0.20g / cm ^ThreeAnd an average cell diameter of about 100
A uniform microcell foam having a size of not more than μm was obtained. Also,
Samples impregnated by heating at 175 ° C oil bath for 1 minute
Even when foamed, the foam does not shrink and is more resistant than the comparative example.
Excellent heat resistance.

[0050]

Example 5 A microcell foam having a density of 0.15 g / cm ³ was obtained by heating in an oil bath at 165 ° C for 30 seconds in the same manner as in Example 1. The foam was again impregnated with carbon dioxide to obtain a sample impregnated with 12 parts of carbon dioxide. The sample was heated in an oil bath at 175 ° C. for 30 seconds to obtain a uniform microcell foam having a density of 0.03 g / cm ³ (expansion ratio of 40) and a cell diameter of about 30 μm or less. Even when the impregnated sample was foamed by heating in an oil bath at 175 ° C. for 1 minute, the foam did not shrink, and was superior in heat resistance to the comparative example.

[0051]

The foam of the polycarbonate resin of the present invention can be foamed in a wide temperature range, and becomes a uniform foam even if the foaming temperature varies to some extent. In addition, compared to the conventional polycarbonate resin foam, not only the heat resistance of the resin itself has been improved, but also the foam of the present invention is characterized in that fine cells are uniformly formed. Insulation is further improved than that of the product, and the heat resistance in practical use is excellent.

Further, in the method for producing a foam of the present invention using carbon dioxide as a foaming agent, a foam having a cell diameter of 10 μm or less is obtained. A foam having more excellent properties can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the expansion ratio and the heating temperature of the polycarbonate resin used in Example 1 and Comparative Example 1.

[Explanation of symbols]

Reference Signs List 1 Polycarbonate resin with weight average molecular weight of 64000 in Example 1 2 Polycarbonate resin with weight average molecular weight of 30,000 in Comparative Example 1 3 Polycarbonate resin with weight average molecular weight of 22500 in Comparative Example 1

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Nobunori Fukuoka 3-13-1 Utsudori, Kurashiki-shi, Okayama Examiner, Asahi Kasei Kogyo Co., Ltd. Examiner Satoshi Morikawa (56) References (58) Fields surveyed (Int. Cl. ⁷ , DB name) C08J 9/04-9/14

Claims (2)

(57) [Claims] 1. A high molecular weight polycarbonate resin foam having a density of 0.6 to 0.02 g / cm ³ and an average cell diameter of 100 μm or less and a weight average molecular weight of 40,000 to 300,000. 2. The resin is foamed using carbon dioxide as a foaming agent.
High molecular weight polycarbonate resin foam of claim 1, wherein Rukoto allowed.