JPH10119078A - Manufacture of foam, resin composition, and foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothen a skin layer by a method in which the skin layer is formed simultaneously with the completion of the supply of a molten resin with a specified pressure applied, a cavity clearance is enlarged, and an expanded core layer is formed. SOLUTION: During the supply of poly(phenylene ether) type molten resin 8 mixed with a chemical foaming agent, a mold 3 selected from male and female molds is moved to that the pressure of the molten resin 8 supplied into a cavity 6 is 5-100kg/cm<2> , and a cavity clearance is enlarged. Next, while a pressure of 5-100kg/cm<2> being applied to the molten resin 8 simultaneously with the completion of the supply of the molten resin, a skin layer is formed. Moreover, the cavity clearance is enlarged, and after an expanded core layer being formed, a molding is cooled in 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 producing a foam, a resin composition, and a foam. More specifically, the present invention is a foam comprising a polyphenylene ether-based resin, the skin layer is smooth without foaming,
There is no flash or silver mark on the surface of the molded body, good gloss, no warpage, and the cell structure of the foam has a unique inclined structure that the center part is large and it becomes dense as it gets closer to the surface. TECHNICAL FIELD The present invention relates to a foam having excellent characteristics of having a surface strength and a mechanical strength, and thus a method for producing the foam and a resin composition used in the method.

[0002]

2. Description of the Related Art Polyphenylene ether resin is a material having excellent heat resistance, and is used for structures requiring various heat resistances. It is possible to impart functions such as performance and sound insulation.

Conventionally, injection molding and extrusion molding have been proposed as molding methods for polyphenylene ether-based resin foams.

With respect to injection molding, there is a method in which a foaming agent is mixed with a resin as a raw material for molding, or a bead molding method in which a foamed molded body is obtained from so-called foamed particles obtained by previously mixing a foaming agent with a resin. Are known. However, in the former method, it is difficult to obtain a molded product having a high expansion ratio, and in the latter method, a molded product having a high expansion ratio is obtained, but a fusion line between particles occurs in the appearance, and the appearance is impaired. There is a disadvantage that. In order to further improve these drawbacks, there has been proposed a method in which a counter pressure method in which the inside of a mold cavity is pressurized with a high-pressure fluid prior to injection of a molten resin is improved (Japanese Patent Application Laid-Open No. Hei 6-1994).
198668). However, although this method can produce a highly foamed molded body, it has a disadvantage that the mold structure is complicated, the operation of the molding machine during molding is complicated, and the pressure during molding is high. It also has disadvantages.

On the other hand, in the extrusion molding method, it is possible to obtain a molded article having a high cell expansion ratio having a fine cell shape, but it is difficult to mold a molded article having a complicated shape.

[0006]

Under such circumstances, an object to be solved by the present invention is to solve the above-mentioned problems of the prior art, and to provide a foam made of polyphenylene ether-based resin. There is no foaming, the molded product surface has no flash, no silver mark, good gloss, no warpage, and the foam cell structure is
The central part is large and has a peculiar inclined structure that becomes dense as it gets closer to the surface, so that the surface strength,
An object of the present invention is to provide a foam having excellent characteristics that are advantageous in exhibiting mechanical strength, a method for producing the foam, and a resin composition used in the method.

[0007]

That is, a first aspect of the present invention is a pair of male and female metal members slidable at an engagement portion (5) and having a cavity clearance (t) that can be arbitrarily set. A method for producing a foam, comprising the following first to fourth steps using a mold (3, 4),
The present invention relates to a method for producing a foam using a polyphenylene ether-based resin composition having an MFR at 280 ° C. and 5 kgf of 2.0 to 60 g / 10 minutes measured according to S7210. First step: Supplying a polyphenylene ether-based molten resin (8) mixed with a chemical foaming agent into the cavity from a molten resin passageway (7) provided in either the male or female mold with a cavity clearance of 1 mm or less. Second step: During the supply of the molten resin (8), the pressure of the molten resin supplied into the cavity is 5 to 100 kg / cm ^2.
Step of increasing the cavity clearance by moving either the male or female mold so that
Step of forming a skin layer while applying a pressure of 00 kg / cm ² Third step: A step of further increasing the cavity clearance (t) to form a foamed core layer, and then cooling the molded body in a mold.

[0008] The second invention of the present invention is characterized in that the MFR at 280 ° C and 5 kgf, measured in accordance with JIS7210, used in the production method of the first invention is 2.0 to 60.
The present invention relates to a polyphenylene ether-based resin composition having a g / 10 min.

Further, a third aspect of the present invention relates to a foam obtained by the production method of the first aspect.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 2 is a schematic vertical sectional view of a mold used in the present invention.

(1) is a platen, which is connected to a drive device (not shown) which operates up and down by hydraulic pressure.
(2) is a lower platen, which is fixed. (3) is a female mold, which is attached to the upper platen (1) and moves up and down. (4) is a male mold, which is attached and fixed to the lower platen (2). (5) is a mating portion of the male and female molds. The gap between the male and female molds of this part is small so that the resin does not leak out of the part and is slidable.
(6) is a cavity formed by the male and female molds, and the cavity clearance (t) is obtained by moving the female mold up and down.
Can be set arbitrarily. (7) is a molten resin passage provided in the male mold, one end (7 ') of which is connected to a molten resin supply device (not shown) for plasticizing the resin and supplying it to the cavity. (8) indicates the molten resin being supplied into the cavity (6).

FIG. 3 is a schematic longitudinal sectional view showing a state immediately after the molding is completed and the mold is opened.

FIG. 1 is an explanatory view schematically showing the process of the manufacturing method of the present invention. The vertical axis shows the cavity clearance (t), and the horizontal axis shows the time elapsed during molding.

According to the method for producing a foam of the present invention, a pair of male and female dies (3, 3) slidable at the engagement portion (5) and the cavity clearance (t) can be arbitrarily set.
4) is a method for producing a foam comprising the following first step to fourth step, wherein the MFR at 280 ° C. and 5 kgf measured according to JIS 7210 is 2.0 to 60 g /
This is a method for producing a foam using a polyphenylene ether-based resin composition for 10 minutes. First step: Supplying a polyphenylene ether-based molten resin (8) mixed with a chemical foaming agent into the cavity from a molten resin passageway (7) provided in either the male or female mold with a cavity clearance of 1 mm or less. Second step: During the supply of the molten resin (8), the pressure of the molten resin supplied into the cavity is 5 to 100 kg / cm ^2.
Step of increasing the cavity clearance by moving either the male or female mold so that
A step of forming a skin layer while applying a pressure of 00 kg / cm ² Fourth step: a step of further increasing the cavity clearance (t) to form a foamed core layer, and then cooling the molded body in a mold.

Hereinafter, a more detailed description will be given with reference to FIG.

First, the drive unit is operated from the state of point A in which the male and female molds are open, and the female mold is lowered to the position of point B where the cavity clearance (t) is 1 mm or less. Next, a polyphenylene ether-based resin (8) mixed with a chemical foaming agent is supplied to the cavity (6) through the resin passage (7) (first step).

When the supply of the molten resin is started, the female mold is set so that the pressure of the molten tree (8) supplied into the cavity falls within a range of 5 to 100 kg / cm ² while the molten resin is supplied. Then, the cavity clearance (t) is increased to supply the resin to the entire surface of the cavity (second step).

The reason why the first step and the second step are performed in this way is to suppress foaming of the molten resin at this stage.

From the point D at which the supply of the molten resin is completed, a pressure of 5 to 100 kg / cm ² is applied to the molten resin in the cavity, and the molten resin is held for a predetermined time to form a skin layer (third step). The pressure holding times D to E in this step are selected so that the molten resin in a portion in contact with the mold surface in the cavity is solidified by cooling, and the inside of the molten resin is not yet solidified and is in a foamable state. However, the conditions can be arbitrarily set depending on the desired thickness of the molded article and the expansion ratio.

After the skin layer is formed, the female mold is raised to increase the cavity clearance (E ~).
F) Foaming the central portion of the molten resin to form a foamed core layer. Thereafter, the molded article is cooled to form the desired foam molded article (fourth steps EG). In this cooling step, the cavity clearance may be kept constant, or may be pressurized when the cooling and solidification of the foam core layer has progressed to some extent. In particular, pressurizing at a stage where cooling and solidification has progressed to some extent is effective for preventing warpage of a molded product that is likely to warp. Next, the female mold (3) is raised, the cavity clearance (t) is increased to H, the mold is opened, and the molded body is taken out. In addition, the rising speed of the cavity clearance (t) in the fourth step is preferably 5 to 100 mm / sec in order to form the skin layer in the vertical direction and hold the decomposition gas of the foaming agent.

As described above, in the present invention, the molten resin (8) is supplied into the cavity while foaming is suppressed in the first and second steps, and the skin layer is formed in the third step. Because only the core layer is foamed, the skin layer is smooth without foaming, and the resin flows inside the cavity in a state where foaming is suppressed and is shaped to form the skin layer. A high-gloss foamed article without flashes and silver marks and no warpage can be obtained. Furthermore, the cell structure of this foam has a unique inclined structure in which the central portion is large and becomes dense as the surface becomes closer, which is advantageous in exhibiting surface strength and mechanical strength. I can say. In addition, it is preferable that the ratio of the cell diameter of the center part inside a foam body to the surface vicinity part is 2 or more.

In the example shown here, the upper platen is movable and the lower platen is fixed, but this may be reversed. In this example, the upper die is a female type and the lower die is a male type. The resin passage may be provided in the female mold.

The polyphenylene ether resin used in the present invention is a resin obtained by combining poly (2,6-dimethylphenylene ether) with another polymer such as polyamide such as polystyrene and nylon 6 and polyolefin such as polypropylene. In addition, components other than those described above, for example, an impact resistance improver, a weather resistance improver, an antioxidant, an inorganic or organic filler or reinforcing agent, a flame retardant, a colorant, and the like can be added.

In the present invention, in order to obtain a foam having a dense cell structure, it is important to control the flowability of the molten resin, and the measurement is carried out according to JIS7210.
MFR at 0 ° C. and 5 kgf is 2.0 to 60 g / 10
Min, preferably a polyphenylene ether-based resin composition of 5.0 to 50 g / 10 min. If the MFR is too low, the fluidity of the resin is low, so it is necessary to heat the resin to a high temperature in order to fill the mold. However, if the resin temperature is too high, the melt viscosity of the resin decreases, so the cell structure Becomes coarse, and a good foam cannot be obtained. On the other hand, when the MFR is too high, the retention of gas generated by the decomposition of the foaming agent is poor, and the foam cells become coarse and the foaming ratio does not increase.

As the foaming agent used in the present invention, those which are usually used for foaming thermoplastic resins can be used, and inorganic foaming agents such as baking soda and organic foaming agents such as azodicarbonamide can be used. Agents can be used.

In the present invention, after the skin material has been supplied between the molds in advance, a molten resin is supplied and subjected to foam molding to obtain a foam molded article in which the skin material is bonded. As the skin material that can be used, various materials can be used according to the purpose, and examples thereof include vinyl chloride leather having a textured or printed pattern.

[0028]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the invention thereto.

Example 1 Artrex HR8100 (manufactured by Sumitomo Chemical Co., Ltd.) was used as a polyphenylene ether resin, and 2.0 phr of a foaming agent CellMike 417 (an inorganic foaming agent manufactured by Sankyo Kasei) was added thereto. Was used. Since the foaming agent was a powder, liquid paraffin was used as the adhering agent. That is, the surface of the resin pellets was wetted with liquid paraffin in advance, and then a foaming agent was added and sufficiently stirred to obtain a uniform foaming composition. The mold was molded under the following conditions using a mold for a disk molded body (diameter 300 mm) in FIG. The cylinder temperature of the injection molding machine was set to 260 ° C., and the mold temperature was set to 40 ° C. for both the upper and lower dies.

(First Step) The cavity clearance was set to 0.5 mm, and the supply of the molten resin was started (FIG. 1C). (Second step) The cavity clearance was set to 3.0 mm so that the pressure of the molten resin in the cavity during the supply of the molten resin was 50 kg / cm ² (FIGS. 1C to 1D). (Third step) The pressure of the molten resin after supplying the molten resin is set to 20 k.
g / cm ² and held for 1 second to form a skin layer (FIGS. 1D to 1E). (Fourth Step) After the skin layer was formed, the cavity clearance was set to 6.0 mm (FIGS. 1E to 1F), and the foamed core layer was formed by holding for 60 seconds and cooled (FIGS. 1F to 1G).
At this time, the mold opening speed was 10 mm / sec.

The foam thus obtained was a molded article having excellent surface smoothness and dense cells as shown in Table 1.

Example 2 In Example 1, Artrex HR4400 (Sumitomo Chemical Co., Ltd.) was used as the polyphenylene ether resin.
Molding was performed in the same manner as in Example 1 except that MFR = 8.4) was used.

Example 3 In Example 1, 4 phr of a foaming agent was used, the cavity clearance in the second step was 5 mm, and
The molding was performed in the same manner as in Example 1 except that the cavity clearance after forming the skin was changed to 15 mm in the fourth step.

Example 4 Molding was carried out in the same manner as in Example 1, except that 0.8 phr of Cellmic C191 (ADCA foaming agent manufactured by Sankyo Kasei Co., Ltd.) was used as the foaming agent.

Comparative Example 1 In Example 1, the polyphenylene ether resin was changed to H
R4700 (manufactured by Sumitomo Chemical Co., Ltd., MI = 1.4)
Molding was performed in the same manner as in Example 1 except that the cylinder temperature of the injection molding machine was 280 ° C.

Comparative Example 2 Molding was performed in the same manner as in Example 1 except that the cavity clearance at the start of the supply of the molten resin in the first step of Example 1 was 4 mm. Flashes and silver marks were generated on the surface of the obtained molded body.

Example 5 A box-shaped molded body having a skin material bonded to the surface was formed. The same resin and foaming agent as in Example 1 were used, and a decorative sheet made of vinyl chloride was used as the skin material (having an adhesive layer on the back surface).
Was used. The thickness of the skin material was 0.5 mm. (First step) The skin material is supplied onto the male mold so that the leather surface faces up, and the cavity clearance (in this case, the value obtained by removing the thickness of the skin material 0.6 mm from the clearance between the upper and lower molds) Was set to 1.1 mm, and the supply of the molten resin was started. (Second Step) The cavity clearance was set to 4.0 mm so that the pressure of the molten resin in the cavity during the supply of the molten resin was 50 kg / cm ² (FIGS. 1C to 1D). (Third step) The molten resin pressure after supplying the molten resin is 5 kg /
cm ² for 4 seconds to form a skin layer (FIGS. 1D to 1E). (Fourth step) After forming the skin layer, the thickness was set to 7.0 mm (FIG. 1E).
To F) and held for 60 seconds to form a foamed core layer (FIGS. 1F to 1G).

The foam thus obtained was a molded article having excellent surface smoothness and dense cells as shown in Table 1.

Table 1 summarizes the conditions and results. The following can be seen from the results. All examples satisfying the conditions of the present invention show satisfactory results in all evaluation items. On the other hand, Comparative Example 1 in which the MFR of the used polyphenylene ether-based resin composition was too low was inferior in surface smoothness and appearance and large in cell diameter. Comparative Example 2, in which the cavity clearance in the first step is excessive, is inferior in appearance.

[0040]

Table 1------------------------------------------------------------------------------ 1 2 MFR g / 10min 42 8.4 42 42 42 1.4 42 CV clearance mm 0.5 0.5 0.5 0.5 0.5 0.5 4.0 Expansion ratio 1.9 2.0 3.0 1.9 1.9 1.9 1.9 Surface smoothness ○ ○ ○ ○ ○ △ ○ Appearance ○ ○ ○ ○ ○ × × Cell diameter mm Center part (1) 0.12 0.28 0.80 0.40 0.12 1.50 0.50 Near surface (2) 0.05 0.10 0.10 0.10 0.05 0.30 0.20 (1) / (2) 2.4 2.8 8.0 4.0 2.4 5.0 2.5 −−−−−−−− −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

MFR: 28 of the used polyphenylene ether-based resin composition measured according to JIS7210
MFR at 0 ° C., 5 kgf ・ CV clearance: cavity clearance in the first step ・ Surface smoothness: The surface smoothness of the foam was visually observed, and
(Good) and Δ (Somewhat bad) ・ Appearance: The appearance of the foam was visually observed, and ○ (good) and ×
Cell diameter: The cell diameter at the center and inside the foam was measured from the cross section of the foam.

[0042]

As described above, according to the present invention, a foam made of a polyphenylene ether-based resin is obtained, the skin layer is smooth without foaming, and the surface of the molded article has no gloss and no silver mark, and has a high gloss. In addition, the cell structure of the foam has no peculiar inclination structure that the central part is large and becomes dense as the surface becomes closer, thus exhibiting surface strength and mechanical strength. A foam having excellent characteristics that are advantageous in the above, a method for producing the foam, and a resin composition used in the production method can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a molding step, in which the vertical axis represents cavity clearance, and the horizontal axis represents elapsed time.

FIG. 2 is a longitudinal sectional view of a mold for performing foam molding.

FIG. 3 is a longitudinal sectional view of a mold for performing foam molding.

FIG. 4 is a perspective view of the obtained disk molded product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper platen 2 Lower platen 3 Upper die 4 Lower die 5 Engaging part 6 Cavity 7 Molten resin passage 7 'Connection port 8 Molten resin 8' molded object

Claims (5)

[Claims] 1. A pair of male and female molds (3, 4) slidable in a meshing portion (5) and having a cavity clearance (t) arbitrarily settable. A method for producing a foam, comprising the steps of:
A method for producing a foam using a polyphenylene ether-based resin composition having an MFR at 280 ° C. and 5 kgf of 2.0 to 60 g / 10 minutes measured according to S7210. First step: Supplying a polyphenylene ether-based molten resin (8) mixed with a chemical foaming agent into the cavity from a molten resin passageway (7) provided in either the male or female mold with a cavity clearance of 1 mm or less. Second step: During the supply of the molten resin (8), the pressure of the molten resin supplied into the cavity is 5 to 100 kg / cm ^2.
Step of increasing the cavity clearance by moving either the male or female mold so that
A step of forming a skin layer while applying a pressure of 00 kg / cm ² Fourth step: a step of further increasing the cavity clearance (t) to form a foamed core layer, and then cooling the molded body in a mold. 2. The method according to claim 1, wherein the increasing speed of the cavity clearance (t) in the fourth step is 5 to 100 mm / sec. 3. JI used in the manufacturing method according to claim 1.
A polyphenylene ether-based resin composition having an MFR at 280 ° C. and 5 kgf of 2.0 to 60 g / 10 minutes measured according to S7210. 4. A foam obtained by the production method according to claim 1. 5. The foam according to claim 4, wherein the ratio of the cell diameter between the central portion inside the foam and the portion near the surface is 2 or more.