JP2015151471A - Polyphenylene sulfide resin foam sheet, and method for producing polyphenylene sulfide resin foam sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyphenylene sulfide resin foam sheet which is excellent in heat resistance, flame retardancy, electrical insulation properties and chemical resistance, and has excellent followability on the surface thereof when adhering to an adhesion body.SOLUTION: A polyphenylene sulfide resin foam sheet has an Asker C hardness of 10 or more and 90 or less on the surface thereof, and preferably has a density of 10 kg/mor more and 150 kg/mor less.

Description

  The present invention relates to a heat insulating material, a heat insulating material, an electric insulating material, a sealing material, a polyphenylene sulfide resin foam sheet for a protective material, and a polyphenylene sulfide resin, which are used as members of automobile parts, precision equipment parts, or electric / electronic parts. The present invention relates to a method for producing a foam sheet.

  A polyphenylene sulfide (PPS) resin is a resin excellent in heat resistance, flame retardancy, chemical resistance, moldability, recyclability, and the like. By foaming the polyphenylene sulfide resin, in addition to the excellent characteristics of the polyphenylene sulfide resin, it is possible to impart heat insulation, light weight, and electrical insulation.

Among them, the polyphenylene sulfide resin foam sheet produced by a so-called batch method, in which a polyphenylene sulfide resin sheet is impregnated with an inert gas and then heated and foamed, has a fine cell with a few micrometer and a closed cell shape, Since a non-foamed layer is formed on the surface layer, it has characteristics such as excellent mechanical strength, heat insulation, and surface properties.
Polyphenylene sulfide resin foam sheets with the above characteristics are lightweight in fields such as automotive parts, precision equipment parts, and electrical / electronic parts that require heat resistance, flame resistance, chemical resistance, light weight, and moldability. It has been widely used as a material, a heat insulating material, and an electric insulating material.

By the way, when foam sheets are used as lightweight materials, heat insulation materials, electrical insulation materials, etc. for parts of automobile parts, precision equipment parts, and electrical / electronic parts, the foam sheets are secondarily molded according to the shape of those parts. There is a case.
For example, in the case of a thermoplastic resin foam sheet typified by the polyphenylene sulfide resin foam sheet described in Patent Documents 1 and 2, the desired shape can be obtained by performing thermoforming such as vacuum forming, pressure forming, or press forming. Can be obtained.
In addition, a thermosetting resin foam sheet with excellent heat resistance can be formed by simple molding, and even if it has a slightly complicated shape, the foam sheet is crushed or polished. It can be processed into the desired shape.

Japanese Patent No. 3459454 JP 2013-60508 A

  By the way, in recent years, automobile parts and precision equipment parts have been made smaller and more complicated in shape than ever for the purpose of optimizing the performance. For this reason, the foamed sheet used together with such components is often required to be fine and complicated. In addition, when using the foam sheet as a heat insulating material, a heat insulating material, an electric insulating material, a sealing material, or a protective material, for reasons such as improving thermal efficiency, preventing deterioration of electric circuits, and saving space, There is an increasing demand to consciously adhere an adherend having a fine and complicated structure and a foam sheet.

  That is, in recent years, in addition to conventional requirements such as heat resistance and thermoformability, so-called surface followability has been demanded in which a foamed sheet adheres closely to a fine complex shape. However, thermosetting resin foam sheets typified by polyimide foam sheets and crosslinked / vulcanized resin foam sheets typified by silicone rubber foam sheets have high heat resistance, but secondary molding can be difficult. In particular, it is difficult to perform fine processing by thermoforming.

On the other hand, when focusing on good moldability, thermoplastic resin foam sheets represented by polystyrene foam sheet and polyethylene terephthalate foam sheet are mentioned, but heat resistance is not enough, and it is applied to recent automobile parts and precision equipment parts When doing so, the problem that the use will be limited has arisen.
On the other hand, there is a thermoplastic resin having high heat resistance. For example, there are a polyetherimide resin foam sheet having heat resistance of 180 ° C. or higher, and a polyphenylene sulfide resin foam sheet described in Patent Documents 1 and 2. However, the polyetherimide resin foam sheet is basically classified as a hard foam sheet, and its surface is extremely hard and cannot follow the fine shape.

  In addition, as for the conventional polyphenylene sulfide resin foam sheet having high heat resistance, in particular, Patent Document 2 attempts to improve moldability by limiting the crystallinity to 20% or less, but the followability is insufficient. there were. Actually, even if trying to adhere the conventional polyphenylene sulfide resin foam sheet to the adherend having a fine shape, a void is formed, or it is formed on the adherend by applying excessively high adhesion pressure. There has been a problem that the fine structure formed is destroyed or becomes one of them.

  Therefore, for the purpose of improving the followability of the surface, it has been considered to add a flexible elastomer to the surface of the polyphenylene sulfide resin foam sheet, but in general, the elastomer has a heat resistance compared to the polyphenylene sulfide resin. Such a method cannot take advantage of the characteristics of the polyphenylene sulfide resin because it is low, has poor chemical resistance, and deteriorates flame retardancy.

For example, in the case of heat insulation, air convection may cause a decrease in heat insulation and heat retention if there is a gap due to insufficient adhesion between foam parts, such as automotive parts, precision equipment parts, electrical / electronic parts, and foam sheets. In the case of electrical insulation, deterioration due to corona discharge may be caused. Further, when the adherend is made of a metal, it is a problem deeply related to the long-term reliability of the product in order to promote deterioration due to oxidation. For the reasons described above, improvement of the followability of the foam sheet surface has been an urgent task.
Recently, improvement in follow-up is also expected from the viewpoint of space saving accompanying downsizing of equipment.

  The present invention has been made in view of the above, and is excellent in heat resistance, flame retardancy, electrical insulation, and chemical resistance, and has good surface followability when adhered to an adherend. It aims at providing a resin foam sheet.

  In order to solve the above-described problems and achieve the object, the polyphenylene sulfide resin foam sheet of the present invention is characterized in that the surface Asker C hardness is 10 or more and 90 or less.

One embodiment of the polyphenylene sulfide resin foam sheet of the present invention is characterized in that the density is 10 kg / m ³ or more and 150 kg / m ³ or less.

  Also, one aspect of the polyphenylene sulfide resin foam sheet of the present invention has a melt index measured in accordance with ASTM D1238-70 at a temperature of 315 ° C. and a load of 5 kg within a range of 10 g / 10 min to 150 g / 10 min. It is characterized by being formed of polyphenylene sulfide resin.

  The method for producing a polyphenylene sulfide resin foam sheet of the present invention is a method for producing a polyphenylene sulfide resin foam sheet for producing the above-described polyphenylene sulfide resin foam sheet, wherein the polyphenylene sulfide resin body is impregnated with an inert gas, and And a foaming step for performing heat foaming under normal pressure.

Moreover, one aspect of the method for producing a polyphenylene sulfide resin foam sheet of the present invention is characterized in that, in the impregnation step, a polyphenylene sulfide resin foam sheet having a density of 220 kg / m ³ or more is further impregnated with an inert gas. .

  According to the present invention, it is possible to provide a polyphenylene sulfide resin foam sheet that is excellent in heat resistance, flame retardancy, electrical insulation, and chemical resistance, and has good surface followability when adhered to an adherend. it can.

FIG. 1 is a schematic explanatory view of a jig used for evaluating the followability of the surface of a polyphenylene sulfide resin foam sheet. (A) is a top view of a jig | tool, (b) is a perspective view of a jig | tool. FIG. 2 is a schematic explanatory diagram of a method for evaluating the followability of the surface of a polyphenylene sulfide resin foam sheet.

  Below, the embodiment of the manufacturing method of the polyphenylene sulfide resin foam sheet which concerns on this invention, and a polyphenylene sulfide resin foam sheet is demonstrated. In addition, this invention is not limited by this embodiment.

  The polyphenylene sulfide resin foam sheet according to the embodiment of the present invention is obtained by foaming a polyphenylene sulfide resin sheet, which is a polyphenylene sulfide resin body formed into a sheet, and has a surface hardness (asker) measured by an Asker rubber hardness meter C type. C hardness) is in the range of 10 to 90.

When the surface hardness of the polyphenylene sulfide resin foamed sheet is less than 10, the handling property may be remarkably deteriorated because the foamed sheet is easily crushed by a finger or the like.
Also, if the surface hardness of the polyphenylene sulfide resin foam sheet is greater than 90, even if it is in close contact with the adherend having a fine shape, it will not follow and a void will be formed, or an excessively high contact pressure will be applied. This may cause a problem that the fine structure formed on the adherend is destroyed.

  In the polyphenylene sulfide resin foam sheet according to the embodiment of the present invention, a total of 100% by mass of all the components constituting the foam sheet (excluding gas components such as inert gas (B)) is polyphenylene sulfide resin (A ) Is preferably contained in an amount of 50% by mass to 99.99% by mass. As a component other than the polyphenylene sulfide resin (A) in the polyphenylene sulfide resin foamed sheet, various additives such as a resin other than the polyphenylene sulfide resin and an inorganic filler can be contained as necessary.

  In addition, the polyphenylene sulfide resin foam sheet according to the embodiment of the present invention is a polyphenylene sulfide resin in a total of 100% by mass of all components (excluding gas components such as inert gas (B)) constituting the foam sheet. It is more preferable to contain 80% by mass or more of (A).

  The polyphenylene sulfide resin (A) constituting the polyphenylene sulfide resin foam sheet according to the embodiment of the present invention is a polymer having a repeating unit represented by the following structural formula (I). When all the units constituting the polyphenylene sulfide resin (A) are 100 mol%, the polyphenylene sulfide resin (A) contains 70 to 100 mol% of repeating units represented by the following structural formula (I). It is preferable.

  Further, the polyphenylene sulfide resin (A) has a repeating formula having the following structural formula (II) in which less than 30 mol% of the repeating units are 100 mol% when all the units constituting the polyphenylene sulfide resin (A) are 100 mol%. It can be configured in units.

  The polyphenylene sulfide resin (A) constituting the polyphenylene sulfide resin foam sheet according to the embodiment of the present invention has an MI (melt index) of 10 g / 10 min to 150 g / 10 min (temperature 315 ° C., load 5 kg, ASTM D1238- 70), more preferably in the range of 15 g / 10 min to 100 g / 10 min.

When MI is 10 g / 10 min or more, foamability becomes good and the density of the polyphenylene sulfide resin foam sheet can be reduced.
Moreover, when MI is 150 g / 10min or less, it can suppress drawing down at the time of preparation of the original fabric sheet (polyphenylene sulfide resin sheet) before foaming, and a sheet having more stable characteristics can be manufactured. Furthermore, when MI is 150 g / 10 min or less, the resin sheet itself is suppressed from becoming brittle and the followability is improved, so that the foamed sheet surface is cracked when closely adhered to the adherend having a fine structure. Can be suppressed.

About polyphenylene sulfide resin (A) which comprises the polyphenylene sulfide resin foam sheet which concerns on embodiment of this invention, what was superposed | polymerized and collect | recovered by the well-known technique etc. can be used.
For example, a mixture containing at least a polyhalogenated aromatic compound typified by p-dichlorobenzene, an alkali metal sulfide typified by sodium sulfide, and an organic polar solvent typified by N-methyl-2-pyrrolidone, Stepwise temperature rise to 200-290 ° C., usually after heat polymerization for about 0.5-50 hours, and then cooled to 220 ° C. or less, polyphenylene sulfide resin, by-products other than polyphenylene sulfide resin, water The polyphenylene sulfide resin can be recovered from the mixture after the polymerization reaction of an alkali metal halide salt and an organic polar solvent using an eye such as a sieve. At that time, a technique of polymerizing in a branched manner using a crosslinking aid or the like may be carried out.

  In the polyphenylene sulfide resin (A) constituting the polyphenylene sulfide resin foamed sheet, the polymerized and recovered polyphenylene sulfide resin may be post-treated. As described above, the polymerized / recovered PPS resin may contain low-molecular-weight polyphenylene sulfide resin, by-products, and impurities, and therefore, when subjected to hot water treatment or washing with an organic solvent. It is known that there is.

  Although there is no restriction | limiting in particular in the hot water used for the hot-water process of the polyphenylene sulfide resin which comprises a polyphenylene sulfide resin foam sheet, From the point of a washing | cleaning effect, it is preferable to use the water to use distilled water or deionized water. Moreover, it is preferable that a hot water temperature is also 90 degreeC or more.

  The organic solvent used for the organic solvent treatment of the polyphenylene sulfide resin is not particularly limited as long as it does not have an action of decomposing the polyphenylene sulfide resin, and N-methyl-2-pyrrolidone, dimethylacetamide, 1, 3 -Dimethylimidazolidinone, piperazinone-containing polar solvents containing nitrogen atoms, polar solvents containing halogen atoms such as methylene chloride, trichloroethylene, perchloroethylene, monochloroethane, dichloroethane, chloroform, chlorobenzene, acetone, methyl ethyl ketone, diethyl ketone, acetophenone And ketone solvents such as Among these, use of N-methyl-2-pyrrolidone, acetone or chloroform is particularly preferable. These organic solvents may be used alone or in combination of two or more. Moreover, it is preferable that the washing | cleaning temperature is the range of normal temperature-200 degreeC from the point of the washing | cleaning effect. Further, after washing with an organic solvent, washing with distilled water or deionized water may be performed, or the hot water washing may be performed.

  In the present embodiment, a cleaning additive may be used at the time of washing with water, and examples of the cleaning additive include acids, alkali metal salts, and alkaline earth metal salts. In particular, in order to obtain an extrusion-molded product having high whiteness and high design, it is preferable to wash with an alkaline earth metal salt and include an alkaline earth metal in the polyphenylene sulfide resin. Examples of the alkaline earth metal salt include magnesium salt, calcium salt, strontium salt, barium salt and the like of organic acid or inorganic acid, and calcium acetate salt and magnesium acetate salt are preferably used from the viewpoint of cost and handleability.

  The amount of the alkaline earth metal salt is preferably in the range of 0.01% by mass to 5% by mass with respect to the mass of the polyphenylene sulfide resin, and in the range of 0.1% by mass to 0.7% by mass. It is further preferable to perform washing by adding to water so as to be inside. The amount of alkaline earth metal in the polyphenylene sulfide resin thus obtained (for example, when calcium acetate is used, the amount of calcium in the polyphenylene sulfide resin) is 50 ppm (mass basis) or more and 3000 ppm (mass basis) or less. More preferably, it is 100 ppm (mass basis) or more and 2000 ppm (mass basis) or less.

In addition, content of a calcium component can be measured according to the following.
First, after washing the platinum dish with pure water, it is fired at 700 ° C. for 1 hour and dried in a desiccator. Subsequently, let A (g) be the value obtained by precisely weighing the platinum dish to 0.1 mg. Next, about 5 (g) of the polymer sample is collected in a platinum dish, and the total amount of the platinum dish and the sample is precisely weighed to 0.1 (mg) with an analytical balance is defined as B (g).
Thereafter, a platinum dish containing a polymer sample is placed on a stainless steel vat and placed in a high-temperature oven set at 440 ° C. and baked for 5 hours. Thereafter, the oven is raised to 500 ° C. and further baked for 5 hours. After performing the baking treatment, it is cooled to 300 (° C.) or lower, and the platinum dish is further stored in a desiccator for 12 hours. Thereafter, the platinum dish is taken out of the desiccator and placed in a muffle furnace stable at 538 (° C.) and baked for 6 hours. After the treatment, the platinum dish is taken out from the muffle furnace, and it is confirmed that the black carbide is completely removed from the sample. In addition, baking is further implemented when presence of black carbide is recognized even a little. After the completion of firing, the platinum dish is taken out from the muffle furnace and cooled in a desiccator for 30 minutes.

Next, 2 ml of pure water: hydrochloric acid (special grade) = 1: 1 (mass ratio, hereinafter referred to as 1: 1 hydrochloric acid) is added to the platinum dish. Then, using a hot plate, a platinum dish containing 1: 1 hydrochloric acid is heated to such an extent that boiling of the solution is confirmed. Stop heating before the contents of the platinum dish evaporate to dryness and cool the platinum dish to room temperature. Thereafter, the contents of the platinum dish are divided into several times while being washed with ion-exchanged water, placed in a 50 ml volumetric flask, and aligned with the 50 ml mark of the volumetric flask. Using the sample solution thus adjusted, measurement is carried out using an atomic absorption measurement apparatus with ion-exchanged water as a blank. As a method for determining the concentration value, the calcium concentration is calculated by a calibration curve prepared using a standard solution containing calcium to be analyzed. If the measured value deviates from the calibration curve, collect the sample solution X (ml), dilute with ion-exchanged water to Y (ml), and adjust the concentration so that it falls within the calibration curve range. The value measured using the sample solution thus adjusted is defined as C (ppm (mass standard)). Using the above numerical values, the calcium concentration (ppm (mass standard)) is calculated by the following formula.
Concentration (ppm (mass basis)) = C (ppm (mass basis)) / (BA) × 50 × Y / X

For foam sheet has a follow-up property, the density of the polyphenylene sulfide resin foam sheet is preferably at 150 kg / ^{m 3} or less, more preferably 140 kg / ^{m 3} or less, further not less 130 kg / ^{m 3} or less preferable.
By lowering the density of the polyphenylene sulfide resin foam sheet as compared with the conventional polyphenylene sulfide resin foam sheet as described above, the hardness of the surface of the foam sheet can be greatly reduced, and good followability to the fine shape can be expressed.

The crystallinity of the polyphenylene sulfide resin foam sheet according to the present embodiment is not particularly limited because the preferred crystallinity varies depending on the application, but is used at a temperature higher than the crystallization temperature of polyphenylene sulfide resin (about 140 degrees). For the applications to be performed, the crystallinity is preferably 10% or more, more preferably 15% or more, from the viewpoint of suppressing heat shrinkage.
When the degree of crystallinity is 10% or more, since the polyphenylene sulfide resin foamed sheet is in a crystalline state, thermal shrinkage can be reduced.

  The cell structure of the polyphenylene sulfide resin foamed sheet is preferably a closed cell structure for applications that require heat insulating properties, heat retaining properties, sealing properties, cushioning properties, and the like. The closed cell ratio is preferably 80% or more, and more preferably 90% or more. Even when the closed cell ratio is high, the gas in the vicinity of the surface of the polyphenylene sulfide resin foamed sheet is more likely to escape than the inside, so that the followability of the surface does not deteriorate.

The cell diameter (average cell diameter) of the polyphenylene sulfide resin foamed sheet is not particularly limited, but is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.
When a polyphenylene sulfide resin foam sheet is applied to applications that require a reduction in thickness or size, a polyphenylene sulfide resin foam sheet having a thickness of several mm or less may be required. At this time, if the average cell diameter is approximately the same as the thickness of the foam sheet, the mechanical strength may be significantly reduced. However, if the cell diameter is 200 μm or less, the mechanical strength of the foam sheet is maintained and the handleability of the foam sheet is maintained. can do.

  In the polyphenylene sulfide resin foam sheet according to the embodiment of the present invention configured as described above, since it is made of polyphenylene sulfide resin (A), heat resistance, flame retardancy, electrical insulation, chemical resistance, etc. Excellent. And since the Asker C hardness of a surface is made into the range of 10-90, the followable | trackability of the surface at the time of making it adhere | attach to a to-be-adhered body is favorable.

  When extremely high adhesion is required for the contact surface between the adherend and the surface of the foam sheet, a skin layer is preferably provided on the surface of the foam sheet. Here, the skin layer is an unfoamed layer formed on the foamed sheet surface. When the skin layer is present on the surface of the foam sheet, the contact area with the adherend is increased as compared to the state without the skin layer. Therefore, when the polyphenylene sulfide resin foam sheet according to the embodiment of the present invention is used for the purpose of preventing oxidation of the adherend, it is preferable to use the one having a skin layer formed thereon.

If the skin layer becomes too thick, the surface of the foamed sheet may become hard and surface followability in surface molding may be reduced. For this reason, the thickness of the skin layer of the polyphenylene sulfide resin foam sheet according to the embodiment of the present invention is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less.
Depending on the application, the skin layer is not necessarily required, and the skin layer may be used in a state where the bubbles are exposed. For example, by subjecting the polyphenylene sulfide resin foam sheet according to the present embodiment to slicing, it is possible to consciously expose and use the bubbles. As a slicing method, a slicer of a canna type or a band saw type can be used.

In the embodiment of the present invention, the surface followability of the polyphenylene sulfide resin foamed sheet is improved, that is, the polyphenylene sulfide resin foamed sheet is pressed against the adherend under a certain pressure to follow the fine shape of the adherend. Is the purpose. Therefore, there is no restriction | limiting in particular about the density of the polyphenylene sulfide resin foam sheet after pressure bonding opening.
However, when the polyphenylene sulfide resin foam sheet is used for heat insulation applications, heat insulation applications, electrical insulation applications, and buffer applications, the compression recovery rate of the foam sheets is preferably 10% or more and 90% or less. When the compression recovery rate is 10% or more, the polyphenylene sulfide resin foam sheet can be prevented from being crushed in the pressure-bonding load direction when it is pressure-bonded to the adherend, and desired characteristics can be reliably obtained. In addition, when the compression recovery rate is 90% or less, the restoring force of the polyphenylene sulfide resin foam sheet can be sufficiently reduced, so that the portion following the shape of the adherend can be prevented from returning to the original, Followability is good.

In order to make the compression recovery rate in the above range, the polyphenylene sulfide resin foam sheet has a closed cell structure, and the density of the polyphenylene sulfide resin foam sheet is preferably 10 kg / m ³ or more, and 25 kg / more preferably m is ³ or more, and still more preferably 30kg / ^{m 3} or more.
When the density is 10 kg / m ³ or more, the compressive strength of the polyphenylene sulfide resin foam sheet is sufficiently ensured, the pressure required when contacting with the adherend is reduced, and the pressure applied to the adherend is released after the pressure is released. However, the effects of predetermined heat insulation, heat retention, electrical insulation and buffering can be obtained.

  Next, the manufacturing method of the polyphenylene sulfide resin foam sheet which concerns on embodiment of this invention is demonstrated. The production method of the polyphenylene sulfide resin foam sheet is not particularly limited, but in the case of applications requiring mechanical strength, cushioning properties, heat insulation properties, sheet surface properties, etc., micronization of bubbles or independent It is preferable to use a batch foaming method that can easily achieve cell structuring and skin layer formation.

Here, the batch foaming method is composed of an impregnation step of impregnating a raw sheet (polyphenylene sulfide resin sheet) with an inert gas under high pressure and a foaming step of performing heat foaming under normal pressure (atmospheric pressure). It is a resin foaming method. In order to obtain a polyphenylene sulfide resin foam sheet that has been reduced in density to such an extent that followability is expressed by the batch foaming method, the sheet once foamed by the batch foaming method is again impregnated with gas at room temperature. It is more preferable to repeat the heat foaming.
The batch foaming method may be performed a plurality of times, but is preferably performed twice from the viewpoint of productivity and the obtained effect.

  Examples of the inert gas used at the time of foaming include helium, nitrogen, carbon dioxide, argon, or a mixed gas of two or more of these. Carbon dioxide is used in consideration of the permeability to the resin (penetration time, solubility). It is preferable.

The thickness of the raw fabric sheet (polyphenylene sulfide resin sheet) before foaming is preferably 0.03 mm or more and 5 mm or less, and more preferably 0.1 mm or more and 1 mm or less.
When the thickness of the original fabric sheet is 0.03 mm or more, the inert gas impregnated in the original fabric sheet is difficult to escape, and the foamability is improved during heat foaming. Therefore, a low-density foam sheet is obtained, the hardness of the surface of the polyphenylene sulfide resin foam sheet is lowered, and the followability of the surface when being adhered to the adherend is improved.
Moreover, when the thickness of an original fabric sheet is 5 mm or less, the time required for impregnating an inert gas to an original fabric sheet can be shortened, and productivity improves.

The raw fabric sheet has a crystallization nucleating agent, a crystallization accelerator, a cell nucleating agent, an antioxidant, an antistatic agent, an anti-ultraviolet agent, a light stabilizer, a fluorescent substance, as long as it does not affect the properties. Various additives such as whitening agents, pigments, dyes, compatibilizers, lubricants, reinforcing agents, cross-linking agents, cross-linking aids, plasticizers, thickeners and thickeners may be blended.
In addition, a resin containing the above additives may be laminated on the polyphenylene sulfide resin foam sheet according to the embodiment of the present invention, or a paint containing the above additives may be applied.

The crystallinity of the raw sheet is preferably 25% or less, more preferably 20% or less, and further preferably 15% or less.
When the crystallinity of the raw sheet is 25% or less, the inert gas can be sufficiently impregnated, so that the foamability is good at the time of heat foaming. Therefore, a low-density polyphenylene sulfide resin foam sheet is obtained, and as a result, the hardness of the sheet surface is lowered, so that the followability of the surface during secondary molding is improved.
As a method for obtaining a raw sheet having a low degree of crystallinity, a method of quenching when a molten resin is formed into a sheet by an extruder, an injection molding machine or the like is generally used.

In addition, in order to obtain a low-density polyphenylene sulfide resin foam sheet, it has been explained that there is a method of performing batch foaming a plurality of times, but the crystallinity of the polyphenylene sulfide resin foam sheet used at the time of the second and subsequent batch foaming There is no particular limitation.
The reason is that bubbles are already formed inside the sheet and the inert gas is easily impregnated even if the degree of crystallinity is high.

The density of the polyphenylene sulfide resin sheet used for the second and subsequent foaming is preferably 220 kg / m ³ or more, more preferably 250 kg / m ³ or more, and 320 kg / m ³ or more. Is more preferable.
When the density of the polyphenylene sulfide resin sheet used for the second and subsequent foaming is in the above range, the cell wall of the sheet can be made sufficiently thick, and the inert gas is difficult to escape during foaming. Thereby, a low-density foam sheet is obtained, and as a result, the hardness of the surface of the polyphenylene sulfide resin foam sheet is lowered, and the followability in the surface molding process is improved.

  Further, the present invention is not limited to the above-described embodiment. What was comprised combining each component mentioned above suitably is also contained in this invention. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

  In addition, the polyphenylene sulfide resin foam sheet can be formed into a molded body by a molding method such as in-mold foaming, vacuum molding, stamping molding, or compression molding. These molded bodies can be processed into a shape as required by thermal welding, vibration welding, ultrasonic welding, laser welding, or the like.

Moreover, the molded object obtained from the polyphenylene sulfide resin foam sheet which concerns on this embodiment is applied to various uses. For example, electronic and electrical parts such as LED lamps, connectors, switches, capacitors, PC cases, speakers, exhaust gas pipes and pipe covers, intake gas pipes and pipe covers, intake manifolds, reflectors for lamp reflectors, motor insulation It can be exemplified by automobile parts such as plates.
In addition, the polyphenylene sulfide resin foam sheet according to the present embodiment is a capacitor, chip that takes advantage of the electrical insulation and light weight that are the advantages of the foam sheet even in film applications, and the flame retardancy that is the advantage of the polyphenylene sulfide resin. It can also be used for a dielectric foam sheet of a capacitor, a motor insulating foam sheet, a foam sheet for mold release, and a foam sheet tape provided with an adhesive material.

(Example)
Next, examples of the present invention will be described. In this example, specimens of Examples 1 to 9 and Comparative Examples 1 to 5 were produced and subjected to various evaluation tests. First, the preparation methods of Examples 1 to 9 and Comparative Examples 1 to 5 will be described.

(Examples 1-6)
First, with respect to 100% by mass of polyphenylene sulfide resin of MI (melt index, resin viscosity) 70 g / 10 min (temperature 315 ° C., load 5 kg, conforming to ASTM D1238-70), the calcium component is 70 ppm (mass basis) at the time of washing. Using the product obtained by substitution, melt extrusion at 310 ° C. from a T die attached to the tip of the extruder, quenching with a cooling roll set at 80 ° C., thickness 0.7 mm, density 1310 kg / m ³ , crystal A polyphenylene sulfide resin sheet (raw fabric sheet) having a degree of conversion of 10% was produced.
The production of the polyphenylene sulfide resin foam sheet was performed in two steps as follows. First, the polyphenylene sulfide resin sheet was placed in a high-pressure vessel, and the gas was permeated for 48 hours in a carbon dioxide atmosphere (temperature 17 ° C., pressure 5 MPa). Thereafter, the sheet was taken out of the container and immediately heated for 1 minute in a thermostat set to the temperature of temperature condition 1 shown in Table 1 to obtain a foam sheet having a density A shown in Table 1.
Next, the obtained foamed sheet was put again in the high-pressure vessel, and the gas was infiltrated for 48 hours in a carbon dioxide atmosphere (temperature 17 ° C., pressure 5 MPa). Thereafter, the foam sheet impregnated with the gas was taken out of the container and immediately heated in a thermostat set to the temperature of the temperature condition 2 shown in Table 1 for 1 minute to obtain specimens of Examples 1 to 6.

MI was measured at a measurement temperature of 315 ° C. and a load of 5000 g in accordance with ASTM D1238-70.
The crystallinity is measured on the test object (raw sheet) using a differential scanning calorimeter at a heating rate of 10 ° C./min, and based on the thermal analysis result, the following equation is used. Were determined.
χ _c = {(ΔH _m −ΔH _c ) / ΔH ₀ } × 100
Here, χ _c : crystallinity [%]
ΔH _m : calorific value of crystal melting peak [J / g]
ΔH _c : exothermic peak during crystal growth [J / g]
H ₀ : calorific value of melting endothermic peak of 100% crystal (= 146.2 *) [J / g]
(*) Maemura E. et al. , Polym. Eng. Sci. , 29 (2), 140 (1989)

(Examples 7 to 9)
Using products obtained by replacing 100% by mass of polyphenylene sulfide resin of 3 types with different MI (24 g / 10 min, 100 g / 10 min, 140 g / 10 min, respectively) so that the calcium component becomes 70 ppm (mass basis) at the time of washing Then, a polyphenylene sulfide resin sheet was produced by the same method as in Examples 1-6. Foaming was also performed in two steps in the same manner as in Examples 1 to 6, and specimens of Examples 7 to 9 were obtained. The temperature condition 1, density A, and temperature condition 2 are as shown in Table 1.

(Comparative Example 1)
A polyphenylene sulfide resin sheet (raw sheet) produced in the same manner as in Examples 1 to 6 from a polyphenylene sulfide resin pellet of MI70 was used as a specimen of Comparative Example 1.
(Comparative Examples 2 to 4)
A polyphenylene sulfide resin sheet was produced from MI70 polyphenylene sulfide resin pellets in the same manner as in Examples 1-6. Next, the polyphenylene sulfide resin sheet was placed in a high-pressure vessel, and the gas was permeated for 48 hours in a carbon dioxide atmosphere (temperature 17 ° C., pressure 5 MPa). Thereafter, the sheet impregnated with the gas was taken out from the container, and immediately heated in a thermostatic bath at a temperature of temperature condition 1 shown in Table 2 for 1 minute to obtain specimens of Comparative Examples 2 to 4.

(Comparative Example 5)
A polyphenylene sulfide resin sheet was produced from MI3 polyphenylene sulfide resin pellets in the same manner as in Examples 1 to 6, and this was used as a specimen of Comparative Example 5. The foaming was also performed in two steps in the same manner as in Examples 1 to 6, and the temperature condition 1, the density A, and the temperature condition 2 were as shown in Table 1.

  For the specimens of Examples 1 to 9 and Comparative Examples 1 to 5 produced as described above, various evaluations were performed as shown below, and the average cell diameter, density, sheet thickness (the thickness of the specimen), Skin layer thickness, surface hardness, followability, compression recovery rate, closed cell rate, and flame retardancy were evaluated. In addition, about the test body of the comparative example 1, the measurement of the average bubble diameter, the compression restoration rate, and the closed cell rate was abbreviate | omitted.

(Sheet thickness)
Using a micrometer, the thickness of the specimen was measured at 10 points, and the average value was taken as the sheet thickness.
(Average bubble diameter)
It calculated | required based on ASTMD3576-77.
(Skin layer thickness)
Ten arbitrary points were selected from the SEM photograph of the cross section of the specimen (foamed sheet), and the average value was used as the skin layer thickness.

(Specimen density)
The density of the specimen was determined according to JIS K6767 (1999).
(Surface hardness of specimen)
The surface hardness of the specimen was measured using an Asker rubber hardness meter C type. In addition, when the thickness of the specimen was less than 5 mm, the hardness measurement was carried out by putting a plurality of specimens into a thickness of 5 mm or more.

(Followability)
The deformation amount of the specimen P when the aluminum (A5052) jig 10 having the projections 12 shown in FIGS. 1A, 1B, and 2 is manufactured and pressed against the specimen P. Therefore, the following rate γ was determined by the following equation.
γ = (S ′ / S) × 100 (%)
Here, S: cross-sectional area (m ² ) of the convex portion 12 in the jig 10
S ′: sectional area (m ² ) of a recess formed on the specimen P after the jig 10 is pressed against the specimen P

As for the shape of the aluminum jig 10, as shown in FIGS. 1 (a) and 1 (b), an aluminum substrate having a width of 3.5 mm × 25 mm on an aluminum substrate 11 having a width of 3.5 μm × 25 mm and a thickness of 10 mm. A rectangular parallelepiped convex portion 12 having a size of 200 μm and a height of 100 μm is arranged at intervals of 1 mm. The total number of convex portions is 26.
This is pressed against the specimen P with a load of 5 kgf to form a concave portion in the specimen P, and the cross-sectional area S (200 μm × 100 μm) of the convex portion 12 of the jig 10 and the concave sectional area S ′ of the specimen P (the cross section is SEM). The followability was evaluated from the ratio of (observation). However, the direction of the cross-section to be measured is the direction along the length of the aluminum substrate 11, and the concave cross-sectional area S ′ of the specimen P was calculated based on cross-sectional observation by SEM.
Moreover, it was confirmed visually whether the convex part 12 of the jig | tool 10 had a deformation | transformation after followable | trackability evaluation. When the test piece P follows normally without any deformation in the jig 10, a symbol “◯” is given in the table to be described later, and the test piece P is hard and the convex portion 12 of the jig 10 is deformed. In this case, the symbol “x” is attached.

(Compression restoration rate)
The thickness (60 minutes after compression release) of the specimen before and after being compressed by 50% was measured by Shimadzu AUTOGRAPH (AGS-X), and the compression recovery rate was defined by the following equation.
(Compression recovery rate) = {(Thickness of specimen after compression) − (Thickness of specimen at 50% compression)} × 100 / {(Thickness of specimen before compression) − (50% compression) Specimen thickness of time)} [%]
A 2.5 cm square specimen was used for the evaluation, and the compression speed was set so that the compression rate was 50% after 300 seconds.

(Closed cell rate)
The continuous void ratio of the specimen was measured by AIR COMPARSION PYCNOMETER (MODEL1000) manufactured by Tokyo Science Co., and the closed cell ratio was calculated by the following formula.
(Closed cell ratio) = {100− (continuous porosity)} [%]
(Combustion test)
It carried out according to the method of UL94 flammability test.
The results of the above evaluation are shown in Tables 1 and 2.

As shown in Table 1, Examples 1 to 9 had good followability because of low surface hardness and low density. Moreover, the flame retardancy was also good.
On the other hand, as shown in Table 2, Comparative Example 1 was inferior in followability to Examples 1-9 because the surface hardness was too high.
In Comparative Examples 2 to 5, the surface hardness was high and the density was high, so that the followability was deteriorated as compared with Examples 1 to 9.

P Specimen 10 Jig 11 Aluminum substrate 12 Convex part

Claims (5)

  A polyphenylene sulfide resin foam sheet having a surface Asker C hardness of 10 or more and 90 or less. The polyphenylene sulfide resin foam sheet according to claim 1, wherein the density is 10 kg / m ³ or more and 150 kg / m ³ or less.   The melt index measured according to ASTM D1238-70 under the conditions of a temperature of 315 ° C. and a load of 5 kg is formed of a polyphenylene sulfide resin within a range of 10 g / 10 min to 150 g / 10 min. Item 3. The polyphenylene sulfide resin foam sheet according to item 1 or 2. A method for producing a polyphenylene sulfide resin foam sheet for producing the polyphenylene sulfide resin foam sheet according to any one of claims 1 to 3,
A method for producing a polyphenylene sulfide resin foam sheet, comprising: an impregnation step of impregnating a polyphenylene sulfide resin body with an inert gas; and a foaming step of foaming by heating under normal pressure. 5. The method for producing a polyphenylene sulfide resin foam sheet according to claim 4, wherein in the impregnation step, an inert gas is further impregnated into the polyphenylene sulfide resin foam sheet having a density of 220 kg / m ³ or more.

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