JP5992193B2 - Resin composition for extrusion foaming, method for producing resin foam, and resin foam - Google Patents

Description

  The present invention relates to a resin composition for extrusion foaming (also simply referred to as a resin composition in the present invention), a method for producing a resin foam, and a resin foam. More specifically, the present invention relates to a resin composition for extrusion foaming for producing a resin foam having a beautiful surface and high magnification, and a method for producing a resin foam and a resin using the resin composition for extrusion foaming Relates to foam.

  At present, resin foams containing polystyrene resins and polyolefin resins as resin components are widely used as cushioning materials for packaging, structural members for automobiles, and the like because of their various characteristics.

  Among them, a resin foam containing a polyolefin resin, ultra-low density polyethylene, thermoplastic elastomer, etc. as a resin component has attracted a great deal of attention because it is excellent in cushioning properties, dust resistance, moldability, etc. Resin foams have been proposed.

  Specifically, Patent Document 1 discloses an extruded foam containing ultra-low density polyethylene, excellent in heat resistance, and excellent in foamability, dimensional stability and appearance. Patent Document 2 proposes a resin foam that contains a polyolefin-based resin and rubber or a thermoplastic elastomer and does not cause significant shrinkage or deformation after foaming and has excellent softness and cushioning properties.

Japanese Patent Laid-Open No. 07-241898 Japanese Patent No. 4036601

  Here, when such a resin foam is used in various applications, the resin foam is required to have a beautiful surface and a high magnification. However, the polypropylene-based extruded foam of Patent Document 1 has a low blending amount of ultra-low density polyethylene and a narrow range of suitable foaming temperature, so that the width of a suitable shear rate is narrow and production is not easy. Moreover, it does not describe about the characteristic of the resin foam at the time of making into a sheet, and the characteristic of the resin foam obtained by using greenhouse gas as a foaming agent. Furthermore, the production of the foam of Patent Document 1 requires a gear pump.

  Further, from the description in Patent Document 2, it is not possible to specifically confirm the presence or absence of a corrugate that greatly affects the surface properties and surface aesthetics. A corrugate is a corrugated foam that can be generated by the foam from the annular die to absorb the linear expansion in the circumferential direction due to volume expansion. It does not match the resin characteristics used by the part, and it means a dot-like or streak-like thing that occurs due to the occurrence of bubble breakage inside the mold or failure to form in the foam molding part.

  Patent Document 2 describes the melt viscosity of the polypropylene resin and the hardness of the elastomer, but does not describe the characteristics of the entire composite resin required for extrusion foaming and the molten state inside the extruder. .

  On the other hand, even when individual resins have suitable characteristics, if a resin composition containing them is used as a raw material for extrusion foaming, desired physical properties may not be obtained due to the influence of resin components. Specifically, even when such a resin composition is used, it may be impossible to stably produce a resin foam having a beautiful surface and high magnification. For this reason, from such a viewpoint, the methods described in Patent Documents 1 and 2 are not always satisfactory.

  This invention is made | formed in view of the said problem, and makes it a subject to provide the resin composition for extrusion foaming for manufacturing the resin foam with the beautiful surface and high magnification.

  As a result of intensive studies, the present inventors have used a resin composition for extrusion foaming containing a polyolefin resin and a polyethylene plastomer and exhibiting a specific melt viscosity and die swell ratio. The inventors have found that a resin foam having a high magnification can be produced, and have come to carry out the present invention.

Thus, according to the present invention, the polyolefin resin and the polyethylene plastomer are included in a mass ratio of 20:80 to 80:20,
Die swell ratio under a shear rate of 3686.4s ^-1, the melt viscosity under a shear rate of melt viscosity and 57.6S ^-1 under a shear rate of 3686.4s ^-1, respectively, W _1, V When ₁ and V _2, W ₁ is 1.8 to 4.0, and extruded foaming resin composition V ₂ / V ₁ is characterized in that it is a 9-18 is provided.

  Moreover, according to this invention, the manufacturing method of a high quality resin foam is provided.

  Moreover, according to this invention, a high quality resin foam is provided.

  According to the present invention, it is possible to provide a resin composition for producing a resin foam having a beautiful surface and a high magnification. Moreover, the characteristic of the resin composition suitable for extrusion foaming can also be provided.

According to the present invention, if V ₂ is a 700~1800Pa · s, surface is beautiful, it is possible to manufacture a high-magnification resin foam more easily.

Further, according to the present invention, when the die swell ratio under the shear rate of 57.6 s ⁻¹ is W ₂ and V ₂ / W ₂ is 350 to 1000 Pa · s, the surface is also beautiful in this case, A high-magnification resin foam can be more easily produced.

According to the present invention, when V ₁ / W ₁ is 30~100Pa · s, even in this case, the surface is a beautiful, it is possible to manufacture a high-magnification resin foam more easily.

  According to the present invention, when the resin composition for extrusion foaming has a melt flow rate of 0.1 to 20 g / 10 min as measured under a load of 230 ° C. and 21.18 N, the surface However, it is possible to more easily produce a high-magnification resin foam.

Further, according to the present invention, when the polyethylene plastomer is an ethylene-α-olefin copolymer having a density of 0.85 to 0.91 g / cm ³ , the surface is beautiful and the magnification is high. A resin foam can be more easily produced.

  Further, according to the present invention, when the polyolefin resin is a polypropylene resin, a resin foam having a high surface and a high magnification can be more easily produced in this case as well.

  According to the present invention, a simple method for producing a resin foam having a beautiful surface and high magnification can be provided.

  Further, according to the present invention, when the melt-kneaded product has a temperature 1 to 10 ° C. higher than that of the mold at the time of extrusion foaming, in this case as well, a simpler method for producing a resin foam with a high surface and high magnification Can be provided.

  According to the present invention, when the foaming agent is carbon dioxide, it is possible to provide a simpler method for producing a resin foam having a beautiful surface and a high magnification.

  Further, according to the present invention, when the mold includes a bubble generation part and a foam molding part, it is possible to provide a simpler method for producing a resin foam having a beautiful surface and a high magnification. .

  According to the present invention, a resin foam having a beautiful surface and high magnification can be provided.

Further, according to the present invention, it is possible to provide a resin foam having a high surface and a beautiful surface having an apparent density of ³⁰ to 100 kg / m ³ .

  Further, according to the present invention, it is possible to provide a resin foam having a beautiful surface and a high magnification that has a thickness of 0.1 to 3.0 mm.

  Further, according to the present invention, it is possible to provide a resin foam having a beautiful surface and a high magnification that has an average cell diameter of 0.02 to 0.2 mm.

  Further, according to the present invention, it is possible to provide a resin foam having a beautiful surface and a high magnification that has an open cell ratio of 70 to 95%.

FIG. 1 is a schematic sectional view of a mold. FIG. 2 is a photograph showing a resin foam having no corrugated surface. FIG. 3 is a photograph showing a resin foam having a corrugated surface.

The feature of the resin composition for extrusion foaming according to the present invention includes a polyolefin resin and a polyethylene plastomer in a mass ratio of 20:80 to 80:20,
Die swell ratio under a shear rate of 3686.4s ^-1, the melt viscosity under a shear rate of melt viscosity and 57.6S ^-1 under a shear rate of 3686.4s ^-1, respectively, W _1, V ₁ and V ₂ , W ₁ is 1.8 to 4.0, and V ₂ / V ₁ is 9 to 18.

  Here, the die swell ratio means a value obtained by dividing the diameter of the discharged resin by the diameter of the mold or capillary when the molten resin is discharged from the mold or capillary. Represents the rate of expansion and deformation. Moreover, melt viscosity means the viscosity of resin measured in a molten state. Furthermore, the shear rate means a value indicating the magnitude of the rate of straining the resin (the rate of deformation due to flow), and the shear rate increases when the extrusion amount is large or the die gap is narrow. The present invention is described in detail below.

<Resin composition>
The resin composition of the present invention contains a polyolefin resin and a polyethylene plastomer as resin components. In addition, since the resin composition contains a polyethylene plastomer in a suitable ratio, a suitable viscosity is imparted to the polyolefin resin at any of a low shear rate or a high shear rate without impairing the properties of the polyolefin resin. be able to.

  The resin composition comprises a polyolefin resin and a polyethylene plastomer in a mass ratio of 20:80 to 80:20, preferably a mass ratio of 40:60 to 80:20, more preferably a mass of 50:50 to 70:30. Include in ratio.

  The total of the polyolefin resin and the polyethylene plastomer is 100% by mass. Moreover, when content of polyolefin resin in a resin composition is less than 20 mass%, the hardness of a resin foam falls too much and favorable foams, such as a mechanical physical property, cannot be obtained. When the content of the polyolefin resin in the resin composition is more than 80% by mass, the hardness of the resin foam is excessively increased, and a foam having good flexibility cannot be obtained.

<Polyolefin resin>
Examples of the polyolefin resin used in the present invention include resins containing an α-olefin such as ethylene, propylene, butylene and the like as monomer units. Moreover, since desired physical properties can be easily obtained, as the polyolefin resin, a polypropylene resin, a polyethylene resin, and a combination thereof are preferable, and a polypropylene resin is more preferable.

Examples of polyethylene resins include branched low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, and ethylene-propylene copolymer containing ethylene monomer as a main component, ethylene-α- Mention may be made of polymers such as olefin copolymers. In said example, it is preferred that the low density, which is 0.91~0.94g / cm ^3, more preferably 0.91~0.93g / cm ^3. Preferably high density and is 0.95~0.97g / cm ^3, more preferably 0.95~0.96g / cm ^3. The medium density is an intermediate density between the low density and the high density.

  As the polypropylene resin, a propylene homopolymer or a copolymer of propylene and another olefin is preferable, and a propylene homopolymer is more preferable. Examples of other olefins copolymerized with propylene include, in addition to ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, and the like. An α-olefin having 4 to 10 carbon atoms. As a copolymer of propylene and another olefin, a copolymer having a small ethylene component is preferable, and either a random copolymer or a block copolymer may be used. A copolymer is preferred.

  Moreover, as polyolefin resin used for this invention, since it is excellent in foamability, it is preferable to use a high melt tension polypropylene resin. High melt tension polypropylene resins include high melt tension polypropylene (HMS-PP) that has free-end long-chain branching in the molecular structure by electron beam cross-linking, etc., and increased melt tension by including high molecular weight components. There are things. A commercial item can be used as this high melt tension polypropylene.

  Polyolefin-based resins may be used alone or in combination of two or more.

<Polyethylene plastomer>
In the present invention, the polyethylene plastomer means a low density polyethylene polymer. By adding such a polyethylene plastomer to the polyolefin resin, a resin foam having a beautiful surface and a high magnification can be more easily produced. Specific examples include a polyethylene polymer containing a copolymer component such as an ethylene homopolymer or an α-olefin. In the present invention, since the desired flexibility and strength can be easily obtained, the polyethylene plastomer is preferably a copolymer of ethylene and an α-olefin. The α-olefin preferably has 4 to 8 carbon atoms, and examples thereof include 1-butene, 1-hexene, 1-octene and combinations thereof. Specifically, as the polyethylene-based copolymer, trade name kernel KS240T (ethylene-1-hexene copolymer) manufactured by Nippon Polychem Co., Ltd. and trade name kernel KS571 (ethylene-1-hexene copolymer manufactured by Nippon Polychem Co., Ltd.) are used. Coalesced).

The density of the polyethylene plastomer is preferably 0.85 to 0.91 g / cm ³ , more preferably 0.86 to 0.89 g / cm ³ . When the polyethylene plastomer has a density higher than 0.91 g / cm ³ , the hardness of the resin foam may be excessively increased and desired flexibility may not be obtained. On the other hand, when the polyethylene-based plastomer has a density lower than 0.85 g / cm ³ , the hardness of the resin foam may be too low, and a desired mechanical strength may not be obtained.

  The polyethylene plastomer preferably has a melt flow rate in the range of 0.2 to 20 g / 10 min when measured under a load of 190 ° C. and 21.18 N. When the melt flow rate is less than 0.2 g / 10 min, the load on the extruder increases, the productivity decreases, or the molten polyolefin resin containing the foaming agent can flow smoothly in the mold. In some cases, the surface of the resulting polyolefin resin foam may be uneven and the appearance may be lowered. If the melt flow rate is greater than 20 g / 10 min, the resin pressure in front of the mold ring die will decrease, and the resin pressure in the ring die bubble generation section will also decrease, so bubbles will be generated in front of the bubble generation section. Therefore, the foaming property is lowered due to abrupt bubble formation in the foam forming part, and the appearance of the obtained foam may be deteriorated or the foam may not be obtained. A more preferred melt flow rate is in the range of 0.3 to 15 g / 10 min, and a further preferred melt flow rate is in the range of 0.5 to 13 g / 10 min.

  As long as the desired physical properties are not affected, the polyolefin resin and the polyethylene plastomer may be used alone or in combination of two or more. Moreover, when using a copolymer as these resin components, a copolymer may be a random copolymer and a block copolymer may be sufficient as it.

<Bubble nucleating agent>
The cell nucleating agent promotes the generation of cell nuclei when the extruded foaming resin composition forms cells, and has an effect on the refinement and uniformity of the cells. Examples of the cell nucleating agent include talc, mica, silica, diatomaceous earth, alumina, titanium oxide, zinc oxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, potassium carbonate, calcium carbonate, magnesium carbonate, potassium sulfate, Inorganic compounds such as barium sulfate, sodium hydrogen carbonate, glass beads; organic compounds such as polytetrafluoroethylene, azodicarbonamide, a mixture of sodium hydrogen carbonate and citric acid, and inert gases such as nitrogen. Among them, talc is preferable for inorganic compounds, and polytetrafluoroethylene is preferable for organic compounds because it has a high effect on bubble miniaturization. Further, it is particularly preferable that the polytetrafluoroethylene becomes a fibril when dispersed to increase the melt tension of the resin.

  The cell nucleating agent may be mixed with the compounded resin composition in its own form and supplied as a thermoplastic resin composition or separately into the extruder, and further mixed with the compounded resin composition as a masterbatch to form a thermoplastic resin composition. It may be fed into the extruder as a product or separately. The base resin of the masterbatch is not particularly limited as long as it has excellent compatibility with the compounded resin composition. For example, homopolypropylene, block polypropylene, random polypropylene, low density polyethylene, high density polyethylene and the like are preferable. Can be used.

  The bubble nucleating agent and the additive described later should be used as a master batch for ease of handling and prevention of contamination of the production environment due to powder scattering and for improving dispersibility in the thermoplastic resin. You can also. The masterbatch can be usually obtained by kneading an additive or the like in a thermoplastic base resin at a high concentration to form a pellet. The base resin is not particularly limited as long as it has excellent compatibility with the blended resin composition, and for example, homopolypropylene, block polypropylene, random polypropylene, low density polyethylene, high density polyethylene and the like can be suitably used.

  The amount of the cell nucleating agent used is preferably 0.01 to 15% by mass with respect to the entire resin composition. When it is less than 0.01% by mass, it is difficult to increase the number of bubbles of the obtained foam, and the surface smoothness of the obtained foam may be lowered. If it exceeds 15% by mass, secondary agglomeration is likely to occur, and the surface smoothness of the foam due to poor extrusion foaming may be reduced. A more preferable usage amount is 0.1 to 12% by mass.

<Other ingredients>
The resin composition may contain other additives other than those described above as necessary. Examples include surfactants, dispersants, weathering stabilizers, light stabilizers, pigments, dyes, flame retardants, plasticizers, lubricants, ultraviolet absorbers, antioxidants, fillers, reinforcing agents, antistatic agents, and the like. It is done.

  The surfactant imparts slipperiness and antiblocking property. The dispersant improves the dispersibility of the cell nucleating agent. Examples of the dispersant include higher fatty acids, higher fatty acid esters, higher fatty acid amides, and the like. The content of the other additives can be appropriately selected within a range that does not impair the formation of bubbles and the physical properties of the foam, and the content contained in a normal foam can be employed.

  The mass and mass ratio of the raw material resin and other components and the mass and mass ratio of the resin composition, resin foam, etc. are substantially the same. Moreover, the qualitative and quantitative determination of the raw materials contained in the resin composition and the resin foam can be performed according to a known method using NMR, IR, GPC or the like.

Here, when the die swell ratio under a shear rate of 3686.4 s ⁻¹ is W ₁ , W ₁ is 1.8 to 4.0, preferably 1.9 to 3.5, and more preferably 1. 9-3.0. When W ₁ is smaller than 1.8, the die swell at the mold foaming portion becomes small, and a sufficient thickness cannot be maintained. On the other hand, when W ₁ is larger than 4.0, the surface smoothness cannot be maintained at the mold forming portion, and corrugation occurs.

When the die swell ratio under a shear rate of 57.6 s ⁻¹ is W ₂ , W ₂ is preferably 1.3 to 4.0, more preferably 1.4 to 3.9. When W ₂ is smaller than 1.3, the die swell at the mold forming portion becomes small and sufficient thickness and surface smoothness may not be obtained. On the other hand, when W ₂ is greater than 4.0, the surface smoothness cannot be maintained at the mold forming part, and corrugation may occur.

Here, the shear rate of 3686.4 s ^{−1 and} the shear rate of 57.6 s ⁻¹ indicate values close to the shear rate of the mold foam molding part and the mold bubble generation part, respectively. The die swell ratio and melt viscosity of the resin composition have an important influence on obtaining a foam having a high magnification and a beautiful surface.

When the melt viscosity at a shear rate of 3686.4 s ⁻¹ is V ₁ , V ₁ is preferably 50 to 140 Pa · s, more preferably 60 to 140 Pa · s. When V ₁ is smaller than 50 Pa · s, the viscosity under a high shear rate becomes too low, and a high-magnification resin foam may not be obtained. On the other hand, when V ₁ is larger than 140 Pa · s, the viscosity at a high shear rate becomes too high, and in this case as well, a high-magnification resin foam may not be obtained.

When the melt viscosity at a shear rate of 57.6 s ⁻¹ is V ₂ , V ₂ is preferably 700 to 1800 Pa · s, more preferably 700 to 1700 Pa · s, and still more preferably 700 to 1600 Pa · s. . If V ₂ is less than 700 Pa · s, the viscosity under a low shear rate becomes too low, and a high-magnification resin foam may not be obtained. On the other hand, when V ₂ is larger than 1800 Pa · s, the viscosity at a low shear rate becomes too high, and in this case as well, a high-magnification resin foam may not be obtained.

V ₂ / V ₁ is 9-18, preferably 9-17, more preferably 9-16. When V ₂ / V ₁ is smaller than 9, the melt viscosity under a high shear rate becomes too low with respect to the melt viscosity under a low shear rate, and a resin foam cannot be stably obtained. On the other hand, when V ₂ / V ₁ is larger than 18, the melt viscosity under a high shear rate becomes too high with respect to the melt viscosity under a low shear rate, and in this case, a resin foam can be obtained stably. Can not.

V ₁ / W ₁ is preferably 30~100Pa · s, more preferably 30~90Pa · s. When V ₁ / W ₁ is smaller than 30 Pa · s, the melt viscosity under a high shear rate is too low with respect to the die swell ratio under the high shear rate, and the resin foam cannot be stably obtained. is there. On the other hand, when V ₁ / W ₁ is greater than 100 Pa · s, the melt viscosity at a high shear rate is too high relative to the die swell ratio at a high shear rate, and in this case as well, the resin foam is stabilized. There are things you can't get.

V ₂ / W ₂ is preferably 350 to 1000 Pa · s, more preferably 350 to 900 Pa · s. When V ₂ / W ₂ is smaller than 350 Pa · s, the melt viscosity at a low shear rate is too low with respect to the die swell ratio at the low shear rate, and the resin foam cannot be stably obtained. is there. On the other hand, when V ₂ / W ₂ is larger than 1000 Pa · s, the melt viscosity at a low shear rate becomes too high with respect to the die swell ratio at the low shear rate, and also in this case, the resin foam is stabilized. There are things you can't get.

W ₁ , W ₂ , V ₁ and V _{2 as described above} indicate that the resin composition of the present invention has a low shear rate close to the shear rate of the mold foam molding part and the shear rate of the mold bubble generation part. It shows a suitable viscosity both under near high shear rates. That is, according to the present invention, it is shown that a resin foam having a beautiful surface and a high magnification can be produced easily and stably. These measurement methods and measurement conditions will be described in detail in Examples.

  When the resin composition of the present invention is measured under a load of 230 ° C. and 21.18 N, the resin composition preferably has a melt of 0.1 to 20 g / 10 minutes, more preferably 0.2 to 15 g / 10 minutes. It has a flow rate. When the melt flow rate is lower than 0.1 g / 10 min, the load on the extruder increases and the productivity decreases, or the molten polyolefin resin containing the foaming agent flows smoothly in the mold. When it becomes impossible, a corrugate is generated on the surface of the resulting polyolefin resin foam and the appearance is deteriorated. On the other hand, when the melt flow rate is higher than 20 g / 10 minutes, particularly when an annular die is used as the mold, the resin pressure in front of the annular die is reduced, and the resin pressure in the annular die bubble generating portion is also reduced. As a result, bubbles are generated in front of the bubble generation part, and foaming is abruptly generated in the foam formation part, resulting in a decrease in foaming property, and the appearance of the resulting foam is deteriorated or a foam cannot be obtained. there is a possibility.

<Method for producing resin foam>
The resin foam of the present invention can be produced, for example, by a known extrusion foam molding method. For example, the resin foam of the present invention can be obtained by a production method including a step of producing a resin foam by extrusion-foaming a melt-kneaded product obtained from the composition and the foaming agent as described above from a mold. .

  The melt-kneaded product has a temperature that is preferably 1 to 10 ° C, more preferably 1 to 7 ° C higher than that of the mold during extrusion foaming. In such a temperature range, the smoothness between the melt-kneaded product and the mold is not lost, and the resin foam having a high surface and a high magnification can be more easily produced.

  The production method of the present invention will be described with an example. Examples of the extruder that can be used in this method include a single-screw extruder, a twin-screw extruder, and a tandem extruder. Of these, a tandem type extruder is preferred because the extrusion conditions can be easily adjusted. The foam raw material is kneaded in an extruder, and becomes a foam by extrusion foaming from a die (die) provided at the tip of the extruder. Usually, a T die, an annular die or the like is used as the mold. A preferable example of such a die is a mold (annular die) shown in the schematic cross-sectional view of FIG.

  An annular die D shown in FIG. 1 is connected to a bubble generation unit 2 formed at the throttle of the foaming agent-containing melt-kneaded flow path unit 3 and the bubble generation unit 2, and the growth of the generated bubbles and the foam surface It has the foam molding part 1 which performs smoothing. In FIG. 1, 4 is an annular die-in side mold, and 5 is an annular die-out side mold. The resin pressure in front of the annular die is a pressure measured by a measuring instrument such as a strain gauge in the flow path from the tip of the extruder to the annular die. Specifically, it can be measured with a strain gauge attached to the end flange of the extruder, a straight pipe mold having flanges on both sides, and a straight pipe mold part connected in order to the ring die.

By forming a foam using an annular die as described above, even if the bubbles constituting the foam are finer than conventional ones, generation on the surface of a large number of corrugates that reduces surface smoothness Can be suppressed. The inventors consider that this is because the annular die can suppress the generation of corrugation in the bubble generation part by an appropriate slip resistance in the foam molding part. Here, extrusion foaming is performed under conditions where the resin discharge speed V in the bubble generating portion 2 of the annular die D is 50 to 300 kg / cm ² · hour and the resin pressure before the annular die D is 7 MPa or more. It is preferable.

When the discharge speed V is smaller than about 50 kg / cm ² · hour, it is difficult to obtain finer bubbles and a foam with a high expansion ratio. On the other hand, when it is larger than about 300 kg / cm ² · hour, the resin generates heat at the mold bubble generation part and the bubbles are broken, and the expansion ratio is likely to be lowered. In addition, a corrugated corrugate is likely to occur, and the bubble diameter may be non-uniform and the surface smoothness of the foam may be reduced. The discharge speed V can be appropriately adjusted according to the cross-sectional area of the annular die bubble generating part and the extrusion discharge amount.

Here, the resin discharge speed V (kg / cm ² · hr) is a value defined by the following equation.
V = extruded resin weight / mould bubble generating section cross-sectional area / time Extruded resin weight refers to the total weight extruded from the mold. Therefore, the weight of the extruded resin is the total amount of the thermoplastic resin composition and the foaming agent. Further, the weight of the extruded resin can be expressed as a discharge amount per hour (kg / hour).

More preferably ejection velocity V is approximately at 70~250kg / cm ² ·, and more preferably about at 100~200kg / cm ² ·. The resin pressure before the ring die is preferably 7 to 20 MPa. By extrusion foaming under the above conditions, the foamability of the resin can be improved, the bubbles can be refined, and the strength of the cell membrane can be increased. Under these conditions, the obtained foam has improved processability in the case of secondary processing. For example, a sheet-like foam obtained by slicing can have excellent surface smoothness. The method of adjusting the cross-sectional area of the bubble generating part includes changing the length of the bubble generating part of the mold (in the case of a flat mold) and the diameter (in the case of an annular die) and the interval between the bubble generating parts of the mold. There are two methods including a method of changing (in the case of a flat die or an annular die).

  If the resin pressure in front of the annular die is lower than 7 MPa, bubbles may be generated before the annular die bubble generating part, and a good foam may not be obtained. Moreover, when it becomes higher than 20 MPa, the load on the extruder may become too high. In addition, the injection pressure may be too high to allow the foaming agent to be injected. The resin pressure in front of the annular die can be appropriately adjusted according to the molten resin viscosity, the extrusion discharge amount, and the sectional area of the annular die bubble generating portion. Further, the molten resin viscosity can be appropriately adjusted depending on the viscosity of the blended resin composition, the amount of foaming agent added, and the molten resin temperature. Note that the molten resin temperature means a temperature measured by a thermocouple attached so as to be in direct contact with the molten resin in a straight pipe mold for measuring the resin pressure before the annular die.

  The resin temperature is preferably in the range of about 10 ° C. to 20 ° C. higher than the melting point of the resin in order to improve foamability. When the resin temperature approaches the melting point, crystallization of the resin starts, the viscosity suddenly increases, the extrusion conditions may become unstable, and the load on the extruder may increase. On the other hand, if it is too high, the solidification of the resin after foaming may not catch up with the foaming speed, and the foaming ratio may not increase.

  The raw material of the foam includes a foaming agent. That is, a resin foam is produced by extruding and foaming a melt-kneaded product obtained by adding a foaming agent to the above-described resin composition from a mold. The foaming agent is not particularly limited, and various known foaming agents can be used. For example, hydrocarbons such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, cyclopentane, cyclopentadiene, n-hexane, petroleum ether, ketones such as acetone and methyl ethyl ketone, methanol, ethanol, isopropyl alcohol, etc. Alcohols, low boiling point ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, halogen-containing hydrocarbons such as trichloromonofluoromethane, dichlorodifluoromethane, inorganic gases such as carbon dioxide, nitrogen, ammonia, etc. Is mentioned. These foaming agents may be used alone or in combination of two or more.

  Of the foaming agents, inorganic gas is preferable, and carbon dioxide is more preferable. Carbon dioxide is a foam having finer bubbles than conventional foams obtained by using carbon dioxide in other forms by using supercritical, subcritical, or liquefied carbon dioxide. You can get a body. It is particularly preferable to use supercritical carbon dioxide. The foam having fine bubbles can improve the surface smoothness and flexibility.

  The amount of the foaming agent that is press-fitted into the extruder can be appropriately adjusted according to the apparent density of the resin foam. However, when the amount is small, the apparent density of the resin foam is lowered, and the lightness and flexibility may be lowered. On the other hand, if it is large, foaming may occur in the mold, and large voids may be generated in the resin foam. Therefore, the amount of the foaming agent is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and further preferably 3 to 6 parts by mass with respect to 100 parts by mass of the resin foam. preferable.

  Other manufacturing conditions such as process temperature, process pressure, process time, and manufacturing equipment are appropriately set according to the raw materials used. Moreover, as long as desired physical properties can be obtained, the raw materials used may be used alone or in combination of a plurality of raw materials.

<Resin foam>
Since the resin foam of the present invention uses the resin composition as described above as a raw material, the resin foam is a foam molded article having a beautiful surface and high magnification.

Specifically, the apparent density of the resin foam is preferably 30 to 100 kg / m ³ , and preferably 35 to 80 kg / m ³ . If the apparent density of the resin foam is less than 30 kg / m ³ , the strength of the resin foam may be reduced. On the other hand, if the apparent density of the resin foam is greater than 100 kg / m ³ , a flexible resin foam may not be obtained.

  The thickness of the resin foam is preferably 0.1 to 3.0 mm, and preferably 0.2 to 2.8 mm. If the thickness of the resin foam is smaller than 0.1 mm, the strength of the resin foam may be reduced. On the other hand, if the thickness of the resin foam is larger than 3.0 mm, moldability may become a problem.

  Furthermore, the average cell diameter of the resin foam is preferably 0.02 to 0.2 mm, and preferably 0.05 to 0.18 mm. If the average cell diameter of the resin foam is smaller than 0.02 mm, a high-magnification resin foam may not be obtained. On the other hand, when the average cell diameter of the resin foam is larger than 0.2 mm, the surface property may be lowered.

  Furthermore, the open cell ratio of the resin foam is preferably 70 to 95%, and preferably 70 to 93%. If the open cell ratio of the resin foam is less than 70%, a high-magnification resin foam may not be obtained. On the other hand, when the open cell ratio of the resin foam is larger than 95%, the strength may be lowered.

  The shape of the resin foam can be a desired shape by the above-described extrusion foaming, but is preferably a sheet-like resin foam, that is, a resin foam sheet. In the case of such a shape, the above physical properties can be obtained more easily.

  The resin foam of the present invention has a beautiful surface and a high magnification. For this reason, a resin foam can be used conveniently as a base material of an adhesive tape or a sealing material.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these description.

(Preparation of resin composition for measuring die swell ratio, melt viscosity and melt flow rate)
A state in which 100 parts by mass of a composition in which a polyolefin resin and a polyethylene plastomer are mixed at a mass ratio shown in Table 1 is melt-kneaded at 200 ° C. in an extruder and maintained at 200 ° C. (extruder, mold temperature) 200 ° C.), and then cooled in water to obtain a polyolefin-based resin mixed composition (extruded foaming resin composition) molded into a cylindrical pellet. The obtained resin composition is measured for the die swell ratio, melt viscosity, and melt flow rate by the measurement methods described later.

(Die swell ratio)
The die swell ratio of the resin composition is measured by a method based on the method described in JIS K 7199: 1999 “Plastic-capillary rheometer and plastic flow characteristic test method using slit direometer”. Specifically, the sample resin was heated and melted at 230 ° C. in a cylinder (preheating time was 5 minutes) in a cylinder using a twin-bore capillary rheometer Rheological 5000T (manufactured by Chiast, Italy). While the piston descending speed is kept constant from 10 mm and the inflow angle is 90 degrees), the diameter of the extruded strand is measured at the test temperature to measure the die swell. The extrusion rate is 0.032 to 4.096 mm / s and the shear rate is 57.6 to 7372.8 s ⁻¹ (the shear rate when the extrusion rate is 0.032 mm / s is 57.6 s ⁻¹ , the extrusion rate The shear rate is 3686.4 s ^-1 ) when the thickness is 2.048 mm / s.
Die swell ratio = extruded strand diameter (mm) / capillary diameter (mm)

(Melt viscosity)
The melt viscosity of the resin composition is measured by a method based on the method described in JIS K 7199: 1999 “Plastic-capillary rheometer and plastic flow characteristic test method using slit direometer”. Specifically, using a twin-bore capillary rheometer Rheological 5000T (made by Chiast, Italy), the sample resin was heated and melted at 230 ° C. in a cylinder (preheating time was 5 minutes) and the orifice (caliber 1.. From 0 mm, length 10 mm, inflow angle 90 degrees), while keeping the piston descending speed constant and extruding into a string shape, the apparent viscosity is measured to obtain the melt viscosity. The extrusion rate is ¹ to 500 mm / min and the shear rate is 12.16 to 6080 s ⁻¹ (when the extrusion rate is 0.032 mm / s, the shear rate is 57.6 s ⁻¹ and the extrusion rate is 2.048 mm / s. The shear rate at this time is 3686.4 s ⁻¹ ).
Melt viscosity (Pa · s) = shear stress (Pa) / shear rate (s ⁻¹ )

(Melt flow rate (MFR))
The melt flow rate of the resin composition, the polypropylene resin, and the thermoplastic elastomer is a value measured as follows in accordance with the MFR and MVR test methods of the thermoplastic resin of Method B of JIS K 7210: 1999. Say. Specifically, the measurement is performed at a test temperature of 230 ° C., a test load of 21.18 N, and a preheating time of 5 minutes. A semi-auto melt indexer manufactured by Toyo Seiki Seisakusho is used for the measuring device. The melt flow rate of the polyethylene plastomer is measured at a test temperature of 190 ° C., a test load of 21.18 N, and a preheating time of 5 minutes in accordance with the method B of JIS K 7210: 1999. As a measuring device, a semi-auto melt indexer manufactured by Toyo Seiki Co., Ltd. can be used.

(Apparent density)
The apparent density of the resin foam is measured by a method based on the method described in JIS K 7222-1999. Specifically, a test piece of 10 cm ³ or more (100 cm ³ or more in the case of semi-rigid and soft materials) is cut from the sample without changing the original cell structure of the sample, its mass is measured, and calculate.
Apparent density (kg / m ³ ) = Test piece mass (g) / Test piece volume (cm ³ ) × 10 ³

(Thickness)
The thickness of the resin foam is measured with a thickness gauge manufactured by Mitutoyo Corporation.

(Average bubble diameter)
The average cell diameter of the resin foam refers to that measured as follows based on the test method of ASTM D2842-69. Specifically, the foamed sheet is cut along an arbitrary surface including a straight line parallel to the thickness direction, and the center of the cut surface (W ₁ ) is enlarged with a scanning electron microscope (S-3000N manufactured by Hitachi, Ltd.). To shoot.

Next, the photographed image is printed on A4 paper, and a straight line having a length of 60 mm is drawn on the image. A straight line is drawn in the horizontal direction (horizontal with respect to the sheet) and the vertical direction (perpendicular to the sheet) of each image. At this time, the magnification in the electron microscope is adjusted so that about 10 to 20 bubbles are formed on a straight line of 60 mm. The average chord length (t) of the bubbles is calculated from the number of bubbles present on the straight line by the following formula, and this average chord length is defined as the average bubble diameter of the cross section.
Average string length t = 60 / (number of bubbles × photo magnification)

When drawing a straight line, the straight line should be penetrated as much as possible without making point contact with the bubbles. Also, if some of the bubbles are in point contact with a straight line, this bubble is included in the number of bubbles, and if both ends of the straight line are located in the bubble without penetrating the bubbles Includes the bubbles in which both ends of the straight line are located in the number of bubbles. Based on the average chord length t calculated by the above formula, the bubble diameter is calculated by the following formula.
Bubble diameter (mm) D = t / 0.616

Similarly, a cut surface (D ₂ ) cut by a plane perpendicular to the cross section (D ₁ ) and a cut surface (D D) cut by a plane including a straight line orthogonal to a straight line parallel to the thickness direction of the foam sheet (D ₂ ) Calculate the bubble diameter in the same way. And each arithmetic mean value is made into the average bubble diameter of an olefin resin foam.
Average bubble diameter (mm) = (D ₁ + D ₂ + D ₃ ) / 3

(Open cell ratio)
The open cell ratio is measured according to ASTM D-2856-87. Specifically, the volume A of the test piece is measured using a cyclic automatic densimeter manufactured by Shimadzu Corporation. Further, the apparent volume A0 of the test piece is calculated from the outer shape of the test piece. The open cell ratio is calculated by substituting the volumes A and A0 into the following equation.
Open cell ratio (%) = (A0−A) / A0 × 100

(Surface condition)
The surface state of the resin foam is visually observed. Specifically, the presence or absence of corrugation on the sheet surface is confirmed.

Example 1
A tandem extruder was prepared by connecting a second extruder having a diameter of 75 mm to the tip of a first extruder having a diameter of 65 mm. In the first extruder of this tandem type extruder, polypropylene resin (Newstrain SH9000, Nippon Polypro SH9000, MFR: 0.3 g / 10 min), 40 parts by mass, polyethylene plastomer (Japan Polyethylene Kernel KS240T, MFR) : Master batch (Talpet 70P manufactured by Nitto Flour Chemical Co., Ltd.) containing 70% by weight of talc having an average particle size of 13 μm as a cell nucleating agent in 100 parts by mass of a resin composition obtained by adding 60 parts by mass of 2.2 g / 10 min) A polyolefin resin foaming composition in which 10 parts by mass and 10 parts by mass of a pigment (PPM OYA164 BLK-FD manufactured by Toyochem Co., Ltd.) were mixed was supplied to the first extruder and melt-kneaded. 4.2 parts by mass of carbon dioxide in a supercritical state as a blowing agent is injected from the middle of the first extruder, and the foamed polyolefin resin foaming composition and carbon dioxide are mixed and kneaded uniformly. The molten resin composition containing the agent was continuously supplied to the second extruder and melted and kneaded while cooling to a resin temperature suitable for foaming.

Thereafter, the temperature of the mold attached to the tip of the second extruder was set to 175 ° C., the discharge amount from the annular die was 30 kg / hour (discharge speed V = 109 kg / cm ² · hour), the melt kneaded material temperature was 176 ° C., A cylindrical foam was obtained by extrusion foaming under the condition of a melt pressure of 11.4 MPa before the annular die. The annular die has a bubble generating part diameter of 36 mm, a mold bubble generating part interval of 0.25 mm (cross-sectional area of the bubble generating part: 0.275 cm ² ), a foam forming part interval of 3.4 mm, and a foam forming part of It has an outlet diameter of 70 mm. The cylindrical foam molded in the foam molding part of the annular die was put on a cooled mandrel, and the outer surface was cooled by blowing air from the air ring. The cooled cylindrical foam was cut with a cutter at one point on the mandrel to obtain a sheet-like polyolefin resin foam. The foam obtained by the above method was free from corrugation and excellent in surface smoothness.

(Example 2)
Polypropylene resin (New Train SH9000, manufactured by Nippon Polypro, MFR: 0.3 g / 10 min) as a polyolefin resin is added to 60 parts by mass, and polyethylene plastomer (kernel KS240T, MFR: 2.2 g / 10 min manufactured by Nippon Polyethylene Co., Ltd.). ) Was changed to 40 parts by mass, and a sheet-like polyolefin resin foam was obtained in the same manner as in Example 1. The foam obtained by the above method was free from corrugation and excellent in surface smoothness.

(Example 3)
Polypropylene resin (New Train SH9000, manufactured by Nippon Polypro, MFR: 0.3 g / 10 min) as a polyolefin resin is added to 40 parts by mass, polyethylene plastomer (kernel KS571, MFR: 1.2 g / 10 min manufactured by Nippon Polyethylene Co., Ltd.) ) Was changed to 60 parts by mass, and a sheet-like polyolefin resin foam was obtained in the same manner as in Example 1. The foam obtained by the above method was free from corrugation and excellent in surface smoothness.

Example 4
Polypropylene resin (Nippon Polypro's NEWSTRA SH9000, MFR: 0.3 g / 10 min) as a polyolefin resin is added to 60 parts by mass, polyethylene plastomer (Nippon Polyethylene Kernel KS571, MFR: 1.2 g / 10 min) ) Was changed to 40 parts by mass, and a sheet-like polyolefin resin foam was obtained in the same manner as in Example 1. The foam obtained by the above method was free from corrugation and excellent in surface smoothness.

(Example 5)
A resin composition was prepared in the same manner as in Example 1 except that it was changed to a polypropylene resin (E110G manufactured by Prime Polymer Co., Ltd., MFR: 0.3 g / 10 min) as a polyolefin resin. A sheet-like polyolefin-based resin foam was obtained in the same manner as in Example 1 except that the mold temperature attached to the tip was set to 175 ° C and the melt temperature was 178 ° C. The foam obtained by the above method was free from corrugation and excellent in surface smoothness.

(Example 6)
A resin composition was prepared in the same manner as in Example 2 except that the resin was changed to a polypropylene resin (E110G manufactured by Prime Polymer Co., Ltd., MFR: 0.3 g / 10 min) as a polyolefin resin. In the same manner as above, a sheet-like polyolefin resin foam was obtained. The foam obtained by the above method was free from corrugation and excellent in surface smoothness.

(Example 7)
A resin composition was prepared in the same manner as in Example 3 except that the polyolefin resin was changed to polypropylene resin (E110G manufactured by Prime Polymer, MFR: 0.3 g / 10 min). A sheet-like polyolefin resin foam was obtained in the same manner as in Example 1 except that the temperature of the attached mold was set to 174 ° C. and the melt temperature was set to 175 ° C. The foam obtained by the above method was free from corrugation and excellent in surface smoothness.

(Example 8)
A resin composition was prepared in the same manner as in Example 4 except that the polyolefin resin was changed to polypropylene resin (E110G manufactured by Prime Polymer Co., Ltd., MFR: 0.3 g / 10 min). In the same manner as above, a sheet-like polyolefin resin foam was obtained. The foam obtained by the above method was free from corrugation and excellent in surface smoothness.

(Comparative Example 1)
Polypropylene resin as a polyolefin-based resin (Newstrain SH9000 made by Nippon Polypro, MFR: 0.3 g / 10 min) is added to 20 parts by mass of a thermoplastic elastomer (Mitsubishi Chemical Corporation) which is a non-crosslinked ethylene-propylene-diene copolymer elastomer. Thermoran Z101N, MFR: 11 g / 10 min, density 0.88 g / cm ³ ) was added to 80 parts by mass to obtain 100 parts by mass of the resin composition, and the mold temperature attached to the tip of the second extruder was set to 174 ° C. Then, a sheet-like polyolefin resin foam was obtained in the same manner as in Example 1 except that the melt temperature was 176 ° C. Although the foam obtained by the above method can be made into a sheet, it is a sheet having a lot of corrugation and inferior surface smoothness. In addition, there is a problem that corrugation is often generated and secondary workability such as slicing cannot be performed due to poor smoothness.

(Comparative Example 2)
A thermoplastic elastomer (Esporex 820 manufactured by Sumitomo Chemical Co., Ltd.) which is a non-crosslinked ethylene-propylene-diene copolymer elastomer is added to 60 parts by mass of a polypropylene resin (VP103W manufactured by Prime Polymer Co., Ltd., MFR: 3 g / 10 min) as a polyolefin resin. MFR: 0.5 g / 10 min, density 0.88 g / cm ³ ) was added to 40 parts by mass to prepare 100 parts by mass of the resin composition, and the mold temperature attached to the tip of the second extruder was 175 ° C. A sheet-like polyolefin resin foam was obtained in the same manner as in Example 1 except that the melt temperature was set to 179 ° C. Although the foam obtained by the above method can be made into a sheet, it is a sheet having a lot of corrugation and inferior surface smoothness. In addition, there is a problem that corrugation is often generated and secondary workability such as slicing cannot be performed due to poor smoothness.

(Comparative Example 3)
A resin composition was prepared in the same manner as in Example 2 except that it was changed to polypropylene resin (WB135 manufactured by Borealis, MFR: 2.4 g / 10 min) as a polyolefin resin, and then the same as in Example 2. Attempts were made to make a sheet, but it was impossible to make a sheet.

(Comparative Example 4)
A resin composition was prepared in the same manner as in Comparative Example 2, except that it was changed to a polypropylene resin (Nippon Polypro FTS3000, MFR: 10 g / 10 min) as a polyolefin resin. Attempted to make a sheet, but could not be made into a sheet.

  From the above evaluation results, it is shown that the resin foam obtained in the example is a resin foam having a beautiful surface and a high magnification compared with that obtained in the comparative example.

  For this reason, the resin foam of this invention can be used conveniently as a base material of an adhesive tape and a sealing material.

1: foam forming part 2: bubble generating part 3: foaming agent-containing melt-kneaded flow path part 4: annular die-in side mold 5: annular die-out side mold D: annular die

Claims (15)

A polypropylene resin and a polyethylene-based plastomer 20: 80 to 80: wherein in 20 weight ratio, a extrusion foaming resin composition containing no antistatic agent,
Die swell ratio under a shear rate of 3686.4s ^-1, the melt viscosity under a shear rate of melt viscosity and 57.6S ^-1 under a shear rate of 3686.4s ^-1, respectively, W _1, V ₁ and V ₂ , W ₁ is 1.8 to 4.0, and V ₂ / V ₁ is 9 to 18; The resin composition for extrusion foaming according to claim 1, wherein the V ₂ is 700 to 1800 Pa · s. If the die swell ratio under a shear rate of 57.6s ^-1 and W _2, extrusion foaming resin composition according to claim 1 or ₂ V 2 / W 2 is 350~1000Pa · s. V ₁ / W ₁ is extruded foaming resin composition according to any one of claims 1 to 3 is 30~100Pa · s.   The extrusion foaming resin composition according to any one of claims 1 to 4, having a melt flow rate of 0.1 to 20 g / 10 min as measured under a load of 230 ° C and 21.18 N. A resin composition for extrusion foaming. The resin composition for extrusion foaming according to any one of claims 1 to 5, wherein the polyethylene plastomer is an ethylene-α-olefin copolymer having a density of 0.85 to 0.91 g / cm ³ . . A resin foam comprising a step of producing a resin foam by extruding and foaming a melt-kneaded product obtained from the resin composition for extrusion foaming according to any one of claims 1 to 6 and a foaming agent from a mold. Production method. The method for producing a resin foam according to claim 7 , wherein the melt-kneaded product has a temperature that is 1 to 10 ° C. higher than the temperature of the mold during the extrusion foaming. The method for producing a resin foam according to claim 7 or 8 , wherein the foaming agent is carbon dioxide. The mold manufacturing method of the resin foam according to any one of claims 7-9 and a and foam molding portion bubble generator. The resin foam comprised from the extruded foam of the resin composition as described in any one of Claims 1-6 . The resin foam according to claim 11 , wherein the resin foam has an apparent density of ^{30 to} 100 kg / m ³ . The resin foam according to claim 11 or 12 , wherein the resin foam has a thickness of 0.1 to 3.0 mm. The resin foam according to any one of claims 11 to 13 , wherein the resin foam has an average cell diameter of 0.02 to 0.2 mm. The resin foam according to any one of claims 11 to 14 , wherein the resin foam has an open cell ratio of 70 to 95%.