JP5456421B2 - Extrusion foam board - Google Patents

Description

  The present invention relates to an extruded foam board made of polypropylene resin.

  Conventionally, polyethylene resin extruded foam is well known, but there are various problems in its physical properties. On the other hand, since the polypropylene-based resin has high rigidity, it can be made into an excellent foam product having high mechanical characteristics with a small amount of resin when it is made into an extruded foam and being lightweight. For this reason, development has been carried out in recent years.

  For example, Patent Document 1 discloses an extruded foam board containing a polypropylene resin, a polystyrene resin, and a styrene-ethylene / propylene block copolymer. Patent Document 2 discloses a method for producing a crystalline propylene-based resin-containing foam containing a crystalline propylene-based resin and a styrene-ethylene / butylene-styrene block copolymer. Patent Document 3 discloses foamed particles containing a polypropylene resin and a polystyrene resin.

JP 2000-281824 A Japanese Patent No. 2505543 JP 2001-302837 A

  However, conventional polypropylene resins have low viscosity and tension at the time of melting, so that the strength of the cell wall is not sufficiently maintained at the time of foaming, and it is not possible to produce a thick foam like a polyethylene resin foam It is extremely difficult.

  That is, in Patent Document 1, GPPS having a glass transition temperature (Tg) of about 100 ° C. is blended with polypropylene, and appropriate foaming occurs because the viscosity of GPPS is insufficient near the polypropylene foaming temperature. In addition, there is a problem that a foam board that sufficiently satisfies the requirements in terms of closed cell ratio and expansion ratio cannot be obtained. In addition, the obtained foam board is not sufficiently heat resistant, such as thermal deformation near the Tg of GPPS. Furthermore, since the viscosity is increased by cross-linking polypropylene, there is a problem in production such that it is necessary to plasticize with carbon dioxide during extrusion, and it is difficult to recycle the foam board.

  Even in the method of Patent Document 2, appropriate foaming did not occur in the vicinity of the foaming temperature of polypropylene, and the closed cell ratio was insufficient. Moreover, since polypropylene or a styrene-ethylene-butylene-styrene block copolymer is cross-linked, there is a problem that productivity is lowered and recycling is difficult due to an increase in viscosity.

  The foamed particles disclosed in Patent Document 3 is a production method in which the process of sequential foaming is increased, and production cost is an issue. Further, GPPS is mixed in order to lower the molding temperature of the expanded particles, and there is a problem that the heat resistance is not sufficient.

  In view of the above circumstances, an object of the present invention is to provide a polypropylene-based extruded board that has effects such as a high closed cell ratio, a high expansion ratio, and heat creep resistance (heat resistance).

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by alloying a high-Tg amorphous resin and a styrene-based thermoplastic elastomer into a polypropylene resin. As a result, the present invention has been made based on this finding.

  That is, the present invention includes (a) a polypropylene resin (also referred to as “component (a)” in the present specification), (b) an amorphous resin (in the present specification, “Tg” of 115 ° C. or higher). (B) component "), and (c) a styrenic thermoplastic elastomer (also referred to as" (c) component "in the present specification), and the component (a) and component (b) For a foam in which the mass ratio is 90:10 to 60:40 and the component (c) is 1 to 10 parts by mass with respect to a total of 100 parts by mass of the component (a) and the component (b). An extruded foam board obtained by foaming a resin composition is provided.

  The extruded foam board of the present invention adopts the above-described configuration, so that the foam resin composition has a sufficient viscosity at the proper foaming temperature of the polypropylene resin, so that the closed cell ratio, high foaming ratio, and heat resistance It can be set as a polypropylene resin extruded foam board having both creep characteristics.

  In the extruded foam board, the value obtained by subtracting the Tg of the component (b) from the melting point of the component (a) is preferably 0 to 45 ° C.

  By selecting (a) a polypropylene resin and (b) an amorphous resin having a Tg of 115 ° C. or higher in this manner, the elongation viscosity of the amorphous resin is appropriate in a temperature range suitable for foaming of the polypropylene resin. It is possible to obtain a good extruded foam board having a higher expansion ratio and higher closed cell ratio.

  The extruded foam board preferably has a foaming ratio of 2 to 100 cc / g and a thickness of 10 mm or more.

  The foam board of the present invention is a resin composition for foams at an appropriate foaming temperature by alloying an amorphous resin having a Tg of 115 ° C. or higher and a styrene thermoplastic elastomer to various polypropylene resins such as homo, block and random. The product has a sufficient viscosity and has effects such as a high closed cell ratio, a high expansion ratio, and heat creep resistance.

  Hereinafter, the present invention will be specifically described.

  The present invention relates to a polypropylene resin obtained by foaming a foam resin composition comprising (a) a polypropylene resin, (b) an amorphous resin having a Tg of 115 ° C. or higher, and (c) a styrene thermoplastic elastomer. Related to extruded foam board.

  (A) The polypropylene resin is not particularly limited as long as it is a polymer obtained by polymerizing a propylene monomer as a main component. Besides homopolypropylene, propylene and α such as ethylene, 1-butene or 4-methyl-1-pentene are used. -It may be a random or block copolymer with olefin, or a mixture of these copolymers.

  (A) As a polypropylene resin, what has a weight average molecular weight of 300,000-600,000 is preferable. In this specification, the weight average molecular weight is a calibration curve (standard polystyrene) obtained by measuring by gel permeation chromatography (GPC) and measuring the molecular weight of the peak of the chromatogram from measurement of commercially available standard polystyrene. The weight average molecular weight was determined using the following formula.

  Further, the melt flow rate (MFR) of the component (a) is preferably 0.01 to 10.0 g / 10 minutes, and more preferably 0.1 to 5.0 g / 10 minutes. When the MFR is within this range, melt-kneading of the foam resin composition is facilitated, and an extruded foam board having sufficient foamability is obtained. Here, in this specification, MFR means an opening (nozzle) when, for example, ASTM D1238 is used as an extrusion plastometer and a load of 2.16 kg is applied at 230 ° C. according to the method of JIS K7210. Means the weight of resin extruded per 10 minutes.

  The component (b) is an amorphous resin group consisting of polystyrene, methacrylic acid-styrene copolymer (SMAA), polyphenylene ether (PPE), acrylonitrile-styrene copolymer (AS), and polymethyl methacrylate (PMMA). Among those selected from one kind or a mixture of two kinds, Tg is 115 ° C. or higher. In the case of an amorphous resin in which two types are mixed, the mixed resin may have a Tg of 115 ° C. (B) When Tg of a component is 115 degreeC or more, the heat resistance of a foam improves, (a) Since the elongation viscosity in the foaming appropriate temperature range of a polypropylene-type resin is maintained, a favorable foam is obtained. It is done.

  In addition, in this specification, Tg of resin shows the value calculated | required based on JIS-K-7121 using the differential scanning calorimeter (for example, DSC-7 by Perkin-Elmer). Specifically, the temperature is raised from room temperature to 250 ° C. at 10 ° C./min in a nitrogen atmosphere, and then returned to room temperature at 10 ° C./min. The temperature is raised again to 250 ° C. at 10 ° C./min, and the glass transition temperature measured in the second temperature raising process is defined as Tg.

  Further, as the component (b), those having a weight average molecular weight of 10,000 to 400,000 are preferable.

  The component MFR (measurement conditions are as described above) is preferably 0.01 to 10.0 g / 10 minutes, and more preferably 0.1 to 5.0 g / 10 minutes. When the MFR is within this range, the foam resin composition can be easily melt-kneaded, and foamability is further improved.

  (A) The value obtained by subtracting the Tg of the component (b) from the melting point of the component (a) is 0 to 45 ° C. so that the viscosity of the component (b) is sufficiently satisfied at the proper foaming temperature of the polypropylene resin. It is preferable that the temperature is 10 to 45 ° C. If it is this range, in the foaming appropriate temperature range of (a) component, the elongation viscosity of (b) component is maintained more appropriately, and a more favorable foam with both a high foaming ratio and a closed cell ratio is obtained.

  Here, in this specification, (a) the appropriate foaming temperature range of the polypropylene resin is determined for each resin used as the (a) polypropylene resin. For example, (a) the melting point of the polypropylene resin is −20 to + 10 ° C. Temperature range.

  (C) In the styrene-based thermoplastic elastomer, the content of styrene with respect to the entire component (c) is preferably 40 to 85% by mass, more preferably 45 to 80% by mass, and 50 to 75% by mass. More preferably. If it is this range, (c) component will exist easily in the interface of (a) component phase and (b) component phase, and the compatibilizing effect by (c) component can fully be expected.

  (C) The styrene thermoplastic elastomer preferably contains a polybutadiene block. In this case, the 1,2-bonded polybutadiene content in the polybutadiene block in the component (c) is preferably 30 to 80% by mass and more preferably 40 to 75% by mass with respect to the total amount of polybutadiene. More preferably, it is 45-70 mass%. If it is this range, (c) component will exist more easily in the interface of (a) component phase and (b) component phase, and the compatibilizing effect by (c) component can fully be anticipated.

  In addition, the polybutadiene block in the component (c) has a polybutadiene double bond hydrogenation rate of preferably 40% or more, more preferably 70% or more. If it is this range, (c) component will exist more easily in the interface of (a) component phase and (b) component phase, and the compatibilizing effect by (c) component can fully be anticipated.

  Moreover, as (c) component, the thing whose weight average molecular weight is 30,000-100,000 is preferable.

  The component MFR (measurement conditions are as described above) is preferably 0.1 to 50 g / 10 min, more preferably 0.3 to 20 g / 10 min, and still more preferably 0.5 -10 g / 10 min. If it is this range, sufficient compatibilizing effect can be expected.

  As component (c), hydrogenated styrene-ethylene-butylene block copolymer (SEBS), styrene-butadiene block copolymer (SBS), solution polymerized styrene-butadiene rubber (SBR), modified solution polymerized styrene-butadiene. Examples thereof include rubber (modified SBR). Among these, SEBS is particularly preferable.

  The composition ratio of the component (a) and the component (b) contained in the foam resin composition is 90:10 to 60:40 in terms of mass ratio. When the mass ratio of the component (a) exceeds 90%, the foaming property is lowered. Conversely, when it is less than 60%, sufficient compression recovery property cannot be obtained. In the case of increasing the rigidity, the composition ratio of the component (b) is increased, and when the compression recovery property is emphasized, the ratio of the component (a) can be adjusted to be increased, but from the balance between the rigidity and the compression recovery property, The composition ratio of the component (a) and the component (b) is more preferably 85:15 to 65:25 in terms of mass ratio. Moreover, the resin composition for foams may contain resin other than (a) component and (b) component.

  Content of (c) component in the resin composition for foams is 1-10 mass parts with respect to 100 mass parts of total amounts of (a) component and (b) component, Preferably it is 2-8 masses. Part, more preferably 3 to 6 parts by mass. If it is less than 1 part by mass, the compatibilizing effect is insufficient. On the other hand, when the amount exceeds 10 parts by mass, the viscosity in the extruder is lowered to cause foaming in the die, and a good foam cannot be obtained. Even if a foam is obtained, sufficient rigidity cannot be obtained and it is not economical.

  The extruded foam board of the present invention can be obtained by adding a foaming agent to the above resin composition for foam and foaming. As the blowing agent, for example, carbon dioxide and hydrocarbons can be used. Specific examples of the hydrocarbons include propane, butane, pentane, pentene, hexene and the like. Two or more kinds of these foaming agents may be mixed and used.

  The types of foaming agents include physical foaming agents and chemical foaming agents, both of which can be preferably used. As a method for adding the foaming agent to the resin composition for foams, in the case of a physical foaming agent, a method in which the foaming agent is dissolved and kneaded with the resin in the extruder as a liquefied gas or supercritical fluid under high pressure, chemical foaming In the case of an agent, there may be mentioned a method in which a foaming agent and a resin are mixed and extruded, foamed by thermal decomposition in an extruder, and dissolved and kneaded in the resin.

  The addition amount of the foaming agent is preferably in the range of 5 to 50 parts by mass, more preferably in the range of 7 to 30 parts by mass per 100 parts by mass of the resin composition for foam. By setting the amount to 5 parts by mass or more, it becomes easy to obtain a high-magnification foam, and by setting it to 30 parts by mass or less, separation of the foam resin composition and the foaming agent hardly occurs and appropriate foaming is obtained. .

  You may add the gas-permeation modifier generally used to the said resin composition for foams as needed. Examples of the gas permeation modifier include fatty acid glycerides such as palmitic acid glyceride and stearic acid glyceride, fatty acid amides such as oleic acid amide and erucic acid amide, and alkyl fatty acid amides such as stearyl stearic acid amide. These gas permeation modifiers can be used alone or in combination as appropriate. By using these gas permeation modifiers, the outflow rate of the foaming agent and the inflow rate of air in the atmosphere can be adjusted, and the volume change of the foam can be suppressed and stabilized.

  If necessary, the above-mentioned foam resin composition can contain a cell nucleus forming agent that is usually used. Examples of the cell nucleating agent include inorganic fine powders such as talc and silicon oxide, organic fine powders such as zinc stearate and calcium stearate, and fine powders that can generate gas when heated such as citric acid and sodium bicarbonate. Powder or the like is used. In addition, inorganic fillers such as calcium carbonate, talc, glass fiber, glass beads, silica, whiskers, titanium oxide, aluminum hydroxide, ammonium hydroxide, and antimony oxide, and organic filling such as carbon black and carbon fiber as necessary. And additives such as antioxidants, pigments, flame retardants, antistatic agents, lubricants, ultraviolet absorbers and the like. The type of filler and additive is not particularly limited as long as it is generally used for blending plastics.

  The extruded foam board of the present invention is produced by an extrusion foaming method. In the extrusion foaming method, the foamable resin mixture and the foaming agent were melt-kneaded under pressure in an extruder and then cooled to an appropriate foaming temperature, and then the foamable molten mixture was attached to the tip of the extruder. This is due to extrusion and foaming through a die at atmospheric pressure.

  If necessary, the extruded foam board may be subjected to a perforating process in which a needle-like jig is pierced into the foam after being extruded and foamed under atmospheric pressure. By performing the perforation process, the replacement of the foaming agent with air in the atmosphere can be promoted.

  The thickness of the extruded foam board is preferably 10 mm or more, more preferably 25 mm or more, and further preferably 40 mm or more. Here, in the present specification, the thickness of the extruded foam board is the short of the plane perpendicular to the extrusion direction when the foam resin composition melt-kneaded under pressure is extruded through a rectangular die under atmospheric pressure. The side is the thickness. Alternatively, the long side may be a width, and the thickness and width may be adjusted by a forming apparatus such as a plate or a roll after extrusion from a die.

  The closed cell ratio of the extruded foam board is preferably 60 to 100%, more preferably 70 to 100%, and still more preferably 80 to 100%, excluding the hole portion due to perforation. When the closed cell ratio is 70% or more, sufficient buffer performance as a cushioning packaging material can be exhibited, and the water absorption rate can be lowered because water hardly enters the foamed body.

  The expansion ratio of the extruded foam board is preferably 2 to 100 cc / g, more preferably 25 to 100 cc / g. When the expansion ratio is 2 to 100 cc / g, it can be suitably used as a heat insulating material, a floating material, or a buffer packaging material. In the present specification, the expansion ratio means a value (cc / g) obtained by dividing the volume of the foam by the weight.

  The cell size of the extruded foam board is preferably 0.01 mm to 5.0 mm, more preferably 0.1 mm to 3.0 mm. In the heat insulating material application, the smaller the cell size, the better the heat insulation performance. When the cell size is large, water intrusion into the cell opening occurs when it comes into contact with water, leading to an increase in water absorption.

  Next, the present invention will be described with reference to examples and comparative examples.

In the examples and comparative examples, the following materials were used as raw material resins.
(1) Polypropylene resin PP-1: random polypropylene, density 0.90 g / cm ³ , melting point 150 ° C.
PP-2: Homopolypropylene, density 0.90 g / cm ³ , melting point 160 ° C.
(2) Amorphous resin SMAA: methacrylic acid-styrene copolymer, density 1.07 g / cm ³ , Tg 125 ° C.
GPPS: polystyrene, density 1.05 g / cm ³ , Tg 100 ° C.
PPE: polyphenylene ether, density 1.04 g / cm ³ , Tg 210 ° C.
(3) Styrenic thermoplastic elastomer SEBS-1: 67% styrene content, density 0.97 g / cm ³
SEBS-2: Styrene content 12%, density 0.89 g / cm ³

In the following Examples 1-4 and Comparative Examples 1-3, the above-mentioned each component was mixed with the mixing ratio shown in Table 1, and the foam was manufactured. The obtained foam was aged in an environment of 40 ° C., and after the foaming agent in the foam was dissipated and sufficiently substituted with air, the following evaluation was performed.
[1] Closed cell ratio Measured by the air pycnometer method (Tokyo Science Co., Ltd., using air comparison type hydrometer 1000 type) described in ASTM-D2856, and calculated with an average of n = 5.
[2] Foaming ratio After measuring the weight W (g) of the foam, the volume V (cc) was measured by the submerging method, and the value obtained by dividing the volume by the weight was defined as the foaming ratio (cc / g).
[3] Heat-resistant creep characteristics of foam (heat resistance)
Measurement was performed according to the compression creep method described in JIS K6767 except that the test temperature was changed to 130 ° C. The test load was 0.05 kgf / cm ² , the strain rate C (%) 24 hours after the start of the test was calculated by the following formula (1), and heat creep resistance was evaluated according to the following criteria based on the value.
C (%) = (t0−t1) / t0 × 100 (1)
[T0: initial thickness (mm) of test piece, t1: thickness after 24 hours of test piece (mm)]
Here, C is preferably less than 10%, and more preferably less than 5%. Within this range, good heat-resistant creep characteristics can be expected.
[4] Cross-sectional size of the foamed body The thickness of the obtained extruded foam board was measured with a caliper and the width was measured with a tape measure.
[5] Density of the foam After measuring the weight W (kg) of the foam, the volume V (m ³ ) was measured by the submerging method, and the value obtained by dividing the weight by the volume was the density of the foam (kg / m ³ ).

[Example 1]
Supplying a resin in which a polypropylene resin PP-1 and an amorphous resin SMAA are mixed at a mass ratio of 70/30 at a rate of 50 kg / hour to a supply region of a screw type extruder having a barrel inner diameter of 65 mm, At the same time, 5 parts by mass of styrene-based thermoplastic elastomer SEBS-1 and 0.2 parts by mass of talc as a bubble regulator and glycerin fatty acid ester (stearic acid monoglyceride and palmitic acid monoglyceride as gas permeation regulator) are added to 100 parts by mass of this mixed resin. A mixture of 1.0 part by mass was fed together. The barrel temperature of the extruder is adjusted to 180 ° C. to 230 ° C., and 13 parts by mass of normal butane as a foaming agent is injected into 100 parts by mass of the resin from a blowing agent injection port attached to the tip of the extruder, and the molten resin A foamable molten mixture was prepared by mixing with the composition.

  This foamable molten mixture is cooled to a foaming temperature of about 148 ° C. with a cooling device attached to the exit of the extruder, and then is cooled to an ordinary temperature from an orifice-shaped die having an average thickness of about 2.6 mm and an opening shape of about 50 mm width. , By continuously extruding and foaming in an atmosphere under atmospheric pressure, and immediately after sandwiching with a roll or plate from above and below, thickness 45mm, width 130mm, cell size 1.0mm, foaming ratio 48cc / g, closed cell A good plate-like resin foam having a rate of 85% and a heat creep of 5% was obtained.

[Example 2]
Except for changing PP-1 to PP-2 and changing the foaming temperature to about 155 ° C., the same method as in Example 1 was used, and the thickness was 40 mm, the width was 145 mm, the foaming ratio was 40 cc / g, and the closed cell ratio was 73%. An excellent plate-like resin foam having a heat creep of 4% was obtained.

[Example 3]
The SMAA was changed to a GPPS / PPE = 75/25 mixture (GPPS and PPE were completely compatible, Tg in this case was 127.5 ° C.), and the mass ratio of PP-1 to the above mixture was changed to 80 Except for the change to / 20, a good plate-like resin foam having a thickness of 40 mm, a width of 135 mm, an expansion ratio of 42 cc / g, a closed cell ratio of 75%, and a heating creep of 4% was obtained in the same manner as in Example 1. .

[Example 4]
Except for changing SEBS-1 to SEBS-2, a plate-like resin having a thickness of 35 mm, a width of 125 mm, an expansion ratio of 40 cc / g, a closed cell ratio of 64%, and a heating creep of 9% in the same manner as in Example 1. A foam was obtained.

[Comparative Example 1]
A plate-like resin foam having a thickness of 10 mm, a width of 88 mm, a foaming ratio of 12 cc / g, and a closed cell ratio of 5%, except that the addition amounts of SMAA and SEBS-1 were changed to 0 parts by mass. Got. The obtained foam did not foam normally, and heat creep could not be measured.

[Comparative Example 2]
The thickness is 25 mm, the width is 115 mm, and the expansion ratio is 18 cc, except that the mass ratio of PP-1 and SMAA is changed to 75/25 and the addition amount of SEBS-1 is changed to 0 parts by mass. / G, a plate-like resin foam having a closed cell ratio of 10% and a heat creep of 25% was obtained.

[Comparative Example 3]
The thickness was 25 mm, the width was 105 mm, the expansion ratio was 15 cc / g, and the closed cell ratio was 45%, except that SMAA was changed to GPPS and the mass ratio of PP-2 and GPPS was changed to 80/20. A plate-like resin foam with 13% heat creep was obtained.

  The extruded foam board of the present invention has a high closed cell ratio and a high expansion ratio, and has high heat-resistant creep characteristics, and is a high-performance cushioning material and heat insulating material, for example, buffer packaging material for industrial products, houses, etc. It can be used for heat insulation materials such as beet boards and body boats, and float materials such as floats.

Claims (3)

(A) a polypropylene resin, (b) an amorphous resin having a glass transition temperature of 115 ° C. or higher, and (c) a styrene-based thermoplastic elastomer, the mass ratio of the component (a) to the component (b) There 90: 10-60: a 40, and the (a) the component (c) Ri 1 to 10 parts by der per 100 parts by weight of said the component (b) component and the ( An extruded foam board obtained by foaming a resin composition for foams having a value obtained by subtracting the glass transition temperature of the component (b) from the melting point of the component a) . The extruded foam board according to claim 1, wherein the component (c) has a styrene content of 40 to 85 mass% with respect to the entire component (c).   The extruded foam board according to claim 1 or 2, wherein the expansion ratio is 2 to 100 cc / g, and the thickness is 10 mm or more.