JPH10329206A - Thermoforming method for polycarbonate resin foam sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a molded product with a wide thermoforming temperature range, easy temperature control during thermoforming, and excellent in appearance, dimensional stability, mechanical properties and the like in a short molding cycle. The present invention provides a method for thermoforming a foamed polycarbonate resin sheet. SOLUTION: A polycarbonate resin foam sheet (preferably a resin mixture) based on a mixed resin of 100 parts by weight of an aromatic polycarbonate resin and 0.3 to 10 parts by weight of an acrylic resin having a viscosity average molecular weight of 200,000 to 1.3 million is preferably used. , Closed cell ratio of 70% or more, density of 0.05 g / cm ³ or more, and thickness of 0.
(3 to 5 mm) is softened by heating and molded by a mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for thermoforming a polycarbonate resin foam sheet, and more particularly to a method for forming a thermoformable polycarbonate resin foam sheet having a wide temperature range.

[0002]

2. Description of the Related Art Polycarbonate resin foam sheets are excellent in dimensional stability and mechanical properties from −70 ° C. to 140 ° C. brass, and are used in a wide variety of applications such as food packaging materials, packaging materials for machine parts, building materials, and automobile parts. Is expected,
As disclosed in Japanese Patent Application Laid-Open No. 8-66953, there has been proposed an extruded polycarbonate resin sheet having a specific cell diameter and cell shape and good dimensional stability during heat molding. However, although excellent effects in dimensional stability at the time of heat molding are obtained, the polycarbonate resin foam sheet is compared with the conventionally used polystyrene resin foam sheet at the time of heat molding. Heat molding temperature range (hereinafter, referred to as “the following”)
(It is simply called the thermoforming temperature range), and it is difficult to control the temperature at the time of thermoforming, and molding is difficult. Therefore, despite the high functionality of the polycarbonate resin foam sheet, a polystyrene resin foam sheet that still has good heat moldability can be obtained. It is currently the mainstream. The thermoforming temperature range is a range of heating temperature conditions at which a foamed sheet molded article free from cracks and partial thinning is obtained when the foamed sheet is heated to a temperature at which thermoforming can be performed and molded. It is.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a wide thermoforming temperature range.
It is an object of the present invention to provide a thermoforming method for a polycarbonate resin foam sheet, in which temperature control during thermoforming is easy and the thermoforming time can be shortened.

[0004]

Means for Solving the Problems In the thermoforming of a polycarbonate resin foam sheet, the present inventors have developed a polycarbonate resin foam sheet based on a mixture of an aromatic polycarbonate resin and a specific resin. By using and thermoforming, it has been found that the thermoforming temperature range can be widened without impairing the high functionality of the polycarbonate resin foam sheet, and the present invention has been completed.

That is, according to the present invention, 100 parts by weight of an aromatic polycarbonate resin and a viscosity average molecular weight of 20
Polycarbonate resin foaming, characterized in that a polycarbonate resin foam sheet based on a mixed resin of 0.3 to 10 parts by weight of an acrylic resin of 10,000 to 1.3 million is softened by heating and molded by a mold. A method for thermoforming a sheet is provided. According to the present invention, there is further provided a method for thermoforming the polycarbonate resin foam sheet, wherein the softened polycarbonate resin foam sheet has a surface temperature of 170 to 230 ° C. Furthermore, according to the present invention, the foamed sheet has a closed cell ratio of 70% or more and a density of 0.05 g / cm ^3.
As described above, there is provided a method for thermoforming a polycarbonate resin foam sheet, characterized by using a foam sheet having a thickness of 0.3 to 5 mm.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The aromatic polycarbonate resin used in the thermoforming method of the polycarbonate resin foam sheet of the present invention is a carbonic acid component and a polycarbonate formed from an aromatic diol component such as a bisphenol compound or a diol component mainly containing the same. Ester or a mixture thereof. Among them, an aromatic polycarbonate resin having diphenylalkane in the molecular chain is preferable because of its high crystallinity, high melting point, and excellent heat resistance, weather resistance and acid resistance. As such a polycarbonate resin,
2,2-bis (4-oxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-oxyphenyl) butane, 1,1-bis (4-oxyphenyl) cyclohexane, 1,1-bis ( Examples thereof include polycarbonate resins formed from bisphenol compounds such as 4-oxyphenyl) isobutane and 1,1-bis (4-oxyphenyl) ethane.

On the other hand, acrylic resins mixed with aromatic polycarbonate resins include methacrylic acid, acrylic acid, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, butyl acrylate and the like. Or a high-molecular-weight polymer having a viscosity average molecular weight of 200,000 to 1.3 million obtained by polymerizing an acrylic monomer or a monomer containing these as a main component. When the viscosity average molecular weight of the acrylic resin is less than 200,000, the effect of expanding the thermoforming temperature range of the polycarbonate resin foam is insufficient, and good thermoforming becomes difficult. On the other hand, when the viscosity average molecular weight exceeds 1.3 million, when mixed with a polycarbonate-based resin, the mixed resin has reduced heat fluidity, and a good foamed sheet suitable for thermoforming may not be obtained.
In particular, in order to further improve the effect of widening the thermoforming temperature range, the viscosity average molecular weight of the acrylic resin is preferably more than 400,000 and not more than 1,000,000.

In the present invention, the viscosity of the acrylic resin is
The average molecular weight (Mv) is the value of chloroform of the acrylic resin.
Let the viscosity of the solution be η and the viscosity of the chloroform solvent be η₀When
In this case, the intrinsic viscosity [η] given by the following equation (1)
(100 ml / g) and calculated by the following equation (2).
Value. (However, C is the concentration of the acrylic resin in chloroform solution.
g / 100 ml, and the measurement temperature is 25 ° C. ) [Η] = KMv^α... (2) (However, K = 0.34 × 10^Four, Α = 0.83)

In the present invention, the mixing ratio of the aromatic polycarbonate resin and the acrylic resin is 0.3 to 10 parts by weight of the acrylic resin with respect to 100 parts by weight of the aromatic polycarbonate resin. It is preferably from 7 to 7 parts by weight. When the amount of the acrylic resin to be mixed is small, the intended effect of the present invention is insufficient, and when the amount of the acrylic resin to be mixed is too large, the fluidity greatly changes and the thermoformability of the foamed sheet is increased. And the resulting moldability may be degraded in appearance and the thickness and thickness may be reduced. Further, other resins or rubber components can be added to the base resin composed of the aromatic polycarbonate resin and the acrylic resin as long as the effects of the present invention are not impaired.

The foaming agent used in the present invention can be any of an inorganic foaming agent, a volatile foaming agent and a decomposable foaming agent. Since it is difficult to obtain a foam having a high foaming ratio, it is preferable to use an inorganic foaming agent or a volatile foaming agent. As the inorganic foaming agent, carbon dioxide, air, nitrogen and the like are preferably used. As volatile foaming agents, propane, n-
Lower aliphatic hydrocarbons such as butane, i-butane, n-pentane, i-pentane and hexane; lower alicyclic hydrocarbons such as cyclobutane and cyclopentane; aromatic hydrocarbons such as benzene, toluene and xylene; Aliphatic lower monohydric alcohols such as ethanol; lower aliphatic ketones such as acetone and methyl ethyl ketone; 1-chloro-1,
1-difluoroethane, pentafluoroethane, 1,
Low boiling halogenated hydrocarbons such as 1,1,2-tetrafluoroethane and 1,1-difluoroethane; and the like.

The blowing agents described above can be used alone or in combination of two or more. For example, different types of blowing agents such as an inorganic blowing agent and a volatile blowing agent can be used in combination. The amount of the foaming agent used varies depending on the type of the foaming agent and the desired expansion ratio, and the density of the foamed sheet is determined by the expansion ratio. Therefore, it can be said that the amount of the foaming agent used is mainly determined by the desired density of the foamed sheet. The foam sheet has a density of 0.05 g / cm ³ or more, preferably 0.08 to 0.5.
g / cm ³ is desirable, and a foaming agent may be used so as to fall within this range. When the density of the foamed sheet of the present invention is less than 0.05 g / cm ^3, it is difficult to control the closed cell rate of the foamed sheet, and the closed cell rate of the thermoformed article is further reduced. Further, the upper limit of the density of the foamed sheet is determined in a desirable range from the viewpoint of practicality such as a decrease in heat insulation and an increase in weight.

In order to foam the base resin used in the present invention smoothly, a foam control agent can be added to the melt-kneaded product of the resin and the foaming agent, if necessary. In this case, as the cell regulator, inorganic powders such as talc and silica, acidic salts of polyvalent carboxylic acids, and mixtures of polyvalent carboxylic acids with sodium carbonate or sodium bicarbonate are preferable. The addition amount is 0.01 to 100 parts by weight of the resin.
1.0 parts by weight, preferably 0.05 to 0.5 parts by weight. Further, in the present invention, known additives such as a flame retardant, a heat stabilizer, a weather resistance improver, and a coloring agent, which are added to an ordinary foamed sheet, can be added.

The foamed polycarbonate resin sheet used in the present invention is obtained by melt-kneading the mixed resin of the aromatic polycarbonate resin and the acrylic resin with the foaming agent under high temperature and high pressure using an extruder. Body and
It can be manufactured by extruding the melt from a circular die portion at the tip of the extruder or a T-die into a low-pressure region and foaming.

The thickness of the foamed sheet is 0.3 to
5 mm is preferable from the viewpoint of thermoforming, especially 1 to 3 m
m is preferred. When the thickness of the foamed sheet is too large, the inside of the foam cannot be uniformly heated during heating during thermoforming, and the thermoforming becomes difficult. When the thickness is too small, the deep drawability becomes insufficient. There is.

Further, the closed cell rate of the foamed sheet is preferably 70% or more, and if it is less than 70%, since a good surface layer is not formed, the closed cell rate is greatly reduced by thermoforming, and The appearance, physical properties, oil penetration resistance and the like may be insufficient. The closed cell rate is
It is a value determined by the following equation (3) by the air pycnometer method according to ASTM D2856. Closed cell rate (%) = [Vx−Va (ρf / ρs)] / [Va−Va (ρf / ρs)] × 100 (3) [Vx: actual volume of foam sheet sample (c)
m ³ ), Va: Apparent volume of foam sheet sample (c)
m ³ ), ρf: Apparent density (g /
cm ³ ), ρs: density of resin (g / cm ³ ). ]

In the thermoforming method of the present invention, the foamed sheet is softened by heating to a temperature at which thermoforming is possible,
It is formed by a mold. As a heating method of the foamed sheet, usually, using a heating furnace, in a non-contact state by radiant heating and / or heat transfer heating by an infrared heater or the like,
The foamed sheet is heated and softened without insufficient heating or overheating.

In the thermoforming method of the present invention, the surface temperature of the foamed sheet heated to a temperature at which thermoforming is possible and in a softened state is preferably 170 to 230 ° C., and when the surface temperature is lower than 170 ° C. The elongation of the foamed sheet may be uneven in some places, while the surface temperature is 23
If the temperature exceeds 0 ° C., the cell structure of the foamed layer of the foamed sheet may be broken, and a good molded product may not be obtained. In particular, the foamed sheet is heated and softened for a heating time of 30 seconds or more, and the surface temperature of the foamed sheet is set to 175 to 200 ° C.
This is preferable because the foamed sheet can be softened to the inside more uniformly and the moldability becomes better. Incidentally, the surface temperature of the softened foam sheet referred to in the present invention, the surface temperature of each of the front and back of the foamed sheet immediately after the softened foam sheet came out of the heating furnace was measured with an infrared radiation thermometer, It is determined by the average value.

In the present invention, the foam sheet is male and / or
Or, using a female mold, vacuum forming, pressure forming, and applications such as free drawing forming, plug and ridge forming, ridge forming, matched mold forming, straight forming, drape forming, and reverse draw. Molding, air slip molding, plug assist molding, Prada assist reverse draw molding, or the like, or a combination of these methods can be used to form a desired molded product.

The molded article of the polycarbonate resin foam sheet obtained by the method of the present invention can be used without deteriorating the functions expected of the polycarbonate resin foam sheet, such as dimensional stability and mechanical properties, without deteriorating its appearance and sheet thickness. It is excellent in terms of thickness.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

Examples 1-3 As a polycarbonate resin, Iupilon MS-2000 viscosity average molecular weight 29000 manufactured by Mitsubishi Gas Chemical Company was used, and as an acrylic resin, Metablen P501A (methyl methacrylate-alkyl acrylate copolymer) manufactured by Mitsubishi Rayon Co., Ltd. was used as an acrylic resin. ) And dry blended at the ratios shown in Table 1 into an extruder, and heated, melted and kneaded so that n-pentane is in a ratio of 0.2 mol per 1 kg of the mixed resin. After being pressed into an extruder, it is further kneaded,
A molten resin containing a foaming agent was extruded and foamed into a cylindrical shape at a resin temperature of 210 to 220 ° C. from a circular die at the tip of the extruder. After cooling, the resin was cut open in the extrusion direction to obtain a foamed sheet. Table 1 also shows the thickness, density, and closed cell rate of the obtained foamed sheet. Next, the obtained foamed sheet was softened in a heating furnace atmosphere temperature of 245 ° C. in a far-infrared heater heating furnace under six heating conditions of heating time 25, 30, 35, 40, 45, and 50 seconds, The softened foam sheet was molded into a dough-shaped container having an opening area of 133 cm ² and a depth of 5 cm by plug assist molding using a vacuum molding die, and the foam sheet molded body obtained under each molding condition was subjected to the following criteria. The moldability was evaluated and the results are shown in Table 2.
It was shown to.

Evaluation of moldability ：: Good mold reproducibility, good condition with no cracks or partial thin parts in the molded article △: Mold reproducibility is slightly deteriorated, but molding is possible X: A state in which molding is impossible due to breakage, or a state in which cells of a molded article have been destroyed due to overheating. In addition, the surface temperature of the foamed sheet in Table 2 was obtained by measuring the temperature of the front and back surfaces of the foamed sheet immediately after coming out of the heating furnace with an infrared radiation thermometer, and calculating the average value of the temperatures of the front and back surfaces. Value.

Comparative Example 1 As shown in Table 1, a foamed sheet was produced in the same manner as in Example 1 except that the acrylic resin was changed to Sumipex (methyl methacrylate polymer) manufactured by Sumitomo Chemical Co., Ltd. Table 1 shows the physical properties and the like, and the moldability was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 2 As shown in Table 1, a foamed sheet was prepared in the same manner as in Example 1 except that the acrylic resin was changed to Metablen P551A (methyl methacrylate / alkyl acrylate copolymer) manufactured by Mitsubishi Rayon Co., Ltd. Are shown in Table 1 and the evaluation results of the moldability of the foamed sheet are shown in Table 2.

Comparative Example 3 As shown in Table 1, the same procedure as in Example 1 was carried out except that the acrylic resin was changed to Metablen P530A (methyl methacrylate / alkyl acrylate copolymer) manufactured by Mitsubishi Rayon Co., Ltd. Are shown in Table 1 and the evaluation results of the moldability of the foamed sheet are shown in Table 2.

Comparative Example 4 The same procedure as in Example 1 was carried out except that the acrylic resin was not used. Table 1 shows the physical properties of the foamed sheet and Table 2 shows the evaluation results of the moldability of the foamed sheet.

[0027]

[Table 1]

[0028]

[Table 2]

From the results of Examples and Comparative Examples shown in Tables 1 and 2, it can be seen that when a foamed sheet based on a mixture of an aromatic polycarbonate resin and a specific acrylic resin is thermoformed, good molding is obtained. It can be seen that the molding time range in which the body is obtained is 15 seconds or more, and the thermoforming temperature range is wider than in the case of thermoforming a foamed sheet whose base material is not mixed with an acrylic resin. It is also found that when an acrylic resin having a viscosity average molecular weight outside the range specified in the present invention is mixed, the range of the molding time for obtaining a good molded article is narrowed, and the thermoforming temperature range is narrowed.

[0030]

According to the present invention, there is provided a thermoforming of a foamed polycarbonate resin sheet which is obtained by softening a foamed sheet made of a mixed resin obtained by mixing a specified amount of an acrylic resin with an aromatic polycarbonate resin in a specified amount and molding the same with a mold. The thermoforming method of the present invention has a wide thermoforming temperature range, whereby the appearance is good, the sheet thickness is not thin, the dimensional stability, and the high functional properties such as mechanical properties are also reduced. It is possible to obtain a good molded body of the polycarbonate resin foam sheet in a short molding cycle without performing the molding.

Claims (3)

[Claims] 1. A foamed polycarbonate resin sheet based on a resin mixture of 100 parts by weight of an aromatic polycarbonate resin and 0.3 to 10 parts by weight of an acrylic resin having a viscosity average molecular weight of 200,000 to 1.3 million, A thermoforming method for a polycarbonate-based resin foam sheet, wherein the sheet is softened by heating and molded by a mold. 2. The thermoforming method for a polycarbonate resin foam sheet according to claim 1, wherein the softened polycarbonate resin foam sheet has a surface temperature of 170 to 230 ° C. 3. The foamed sheet has a closed cell ratio of 7
0% or more, density 0.05 g / cm ³ or more, thickness 0.3 to
The thermoforming method for a polycarbonate resin foam sheet according to claim 1 or 2, wherein a 5 mm foam sheet is used.