JP6414435B2 - Foam blow molded product - Google Patents

Description

  The present invention relates to a foam blow molded article, and particularly relates to a foam blow molded article using polypropylene containing a polyethylene elastomer as a resin material.

  For example, various air-conditioning ducts that are mounted in an instrument panel of an automobile are known as foam blow molded products. For these air conditioning ducts, foam ducts formed by molding a foamed resin material are widely used. The foam duct is lightweight and can be easily manufactured by, for example, adding a foaming agent to a resin material such as polyolefin resin, melt-kneading, and blow-molding a foam parison extruded from a die of an extruder.

  Polyolefin resins are widely used as resin materials used for foam blow molded products, and among them, polypropylene resins are common. In recent years, replacement with a polyethylene-based resin has been studied for the purpose of making the material structure cheaper (see Patent Document 1 and the like).

  Patent Document 1 discloses a high-density polyethylene having a long-chain branched structure, a specific gravity of 0.95 to 0.96, a melt flow rate (MFR) of 3 to 7 g / 10 minutes, and a melt tension of 100 to 250 mN, and a melt flow rate. (MFR) An automotive duct is disclosed in which a chemical foaming agent is added to a mixed resin obtained by mixing high density polyethylene of 0.3 to 1.0 g / 10 min and blow-molded.

JP 2011-194700 A

  However, with regard to foam blow molded products using polyethylene resins, optimization regarding resin composition and physical properties is insufficient compared to polypropylene resins, and foam blow molded products using polypropylene are more practical. The fact is that it has an advantage.

  By the way, although it is a polypropylene foam blow molded product having excellent physical properties, it has a problem of insufficient impact resistance. For example, when the foam blow molded product is a rear arcura duct, the roof side duct installed adjacent to the curtain shield airbag may be scattered and cracked when the curtain shield airbag is deployed.

  In addition, the resin material used for the foamed blow molded product is desired to be recyclable from the viewpoint of resource saving, but deterioration due to heat history is unavoidable, and there is a limit to repeated use.

  The present invention has been proposed in view of such a conventional situation, and aims to provide a foam blow molded product capable of achieving both foam moldability and impact resistance. An object of the present invention is to provide a foamed blow molded product that can reuse a used resin material.

In order to achieve the above-mentioned object, the foam blow molded product of the present invention is a foam blow molded product formed by blow molding a foam resin containing a polypropylene resin and a polyethylene elastomer, and the foam resin is Further, it contains an antioxidant, and the content of the antioxidant is 2000 ppm or more with respect to the polyethylene-based elastomer and less than 1000 ppm with respect to the entire resin material .

  The foamed blow molded product of the present invention is mainly composed of a polypropylene resin, and can be easily optimized with respect to the resin composition and physical properties. Moreover, since the foamed blow molded article of the present invention uses a polyethylene-based elastomer in combination, the impact resistance is improved, and both foam moldability and impact resistance are achieved. Furthermore, the combined use of polyethylene-based elastomers may cause deterioration due to thermal history, but the foamed blow molded product of the present invention contains an antioxidant in a predetermined addition amount with respect to the polyethylene-based elastomer. This problem is avoided.

  ADVANTAGE OF THE INVENTION According to this invention, it is possible to provide the foam blow molding goods which are excellent in foam moldability, and are excellent in impact resistance, and there is no fear of a scattering crack. Further, according to the present invention, it is possible to reuse the used resin material by suppressing the deterioration due to the heat history, and it is possible to greatly improve the utilization efficiency of the resin material.

It is a schematic perspective view which shows an example of a foam duct. It is a schematic sectional drawing which shows typically the aspect at the time of blow-molding a duct.

  Hereinafter, an embodiment of a foam blow molded product to which the present invention is applied will be described in detail with reference to the drawings, taking a foam duct as an example.

  The foam duct 10 that is a foam blow-molded product is configured such that air-conditioning air supplied from an air conditioner unit (not shown) is circulated through an internal flow path and is ventilated to a desired portion. In addition, as a shape of the foam duct 10, it is not limited to what is shown in FIG. 1, It can be set as arbitrary shapes according to a use, an installation place, etc.

  The foam duct 10 of the present embodiment is obtained by blow molding by sandwiching a foam parison formed by extruding a foam resin from a die of an extruder with a mold. In addition, the duct immediately after blow molding is in a state where both ends are closed, and both ends are cut into an open shape by trimming after blow molding.

  The foam duct 10 of the present embodiment is formed of a hollow foamed resin molded product whose tube wall is constituted by a foam layer. By adopting a configuration in which the foamed layer has a closed cell structure, it is possible to obtain a duct that is lightweight and excellent in heat insulation. The closed cell structure is a structure having a plurality of independent cell cells, and means a cell having at least a closed cell ratio of 70% or more. With such a configuration, even when cooling air is circulated in the foam duct 10, the possibility of dew condensation can be almost eliminated.

  The foam duct 10 of this embodiment basically uses a polypropylene resin as the foam resin material. Polypropylene-based resins are characterized by being easily optimized in terms of physical properties and the like and having good foam moldability.

  Examples of the polypropylene resin to be used include a propylene homopolymer, a random or block copolymer of propylene and another α-olefin, and the like. Other α-olefins copolymerized with propylene include ethylene, butene, pentene, hexene, octene, methylpentene, and the like. The amount of α-olefin copolymerized with propylene is arbitrary, but is preferably about 0.1 to 20% by mass, for example, in order to maintain the excellent physical properties of polypropylene.

  The polypropylene resin preferably has a long chain branched structure. Polypropylene resin has the disadvantage that the melt tension at the time of melting is low and the molding processability is inferior in foam molding, but by introducing a long-chain branched structure, the melting characteristics can be improved. Can be eliminated.

  As described above, in the foam duct 10 of the present embodiment, since the polypropylene resin is used as the foam resin material, the foam ratio is, for example, 2.5 times or more, and the foam moldability is excellent. However, if only a polypropylene resin is used, impact resistance may be insufficient. Polypropylene resin is a material excellent in foam moldability, but has insufficient impact resistance, and for example, a phenomenon called scattering cracking may occur when an airbag is deployed. For example, in a so-called 1-box car rear cooler duct (ceiling duct), one roof side duct is adjacent to the curtain shield airbag. If the curtain shield airbag is deployed in such a state, the roof side duct made of polypropylene may be scattered and cracked.

  Therefore, in the foam duct 10 of the present embodiment, in addition to the polypropylene resin, a polyethylene elastomer is used in combination to improve the impact resistance and achieve both foam moldability and impact resistance.

  Polyethylene elastomer is a fine dispersion of olefin rubber in a matrix of polyethylene resin. It has excellent compatibility with polypropylene resin, and gives rubber elasticity to resin material to improve impact resistance. It has the feature of being able to.

  The proportion of the polyethylene elastomer in the resin material is preferably 5% by mass or more for the purpose of improving impact resistance. If the ratio of the polyethylene-based elastomer is less than 5% by mass, the impact resistance of the foam duct 10 may be insufficient. The greater the proportion of polyethylene-based elastomer, the more advantageous for impact resistance improvement, but when the proportion of polyethylene-based elastomer is too large, the proportion of polypropylene-based resin is relatively reduced, such as foam moldability, It becomes difficult to maintain the excellent physical properties of the polypropylene resin. From such a viewpoint, the proportion of the polyethylene-based elastomer is preferably 35% by mass or less. That is, the proportion of the polyethylene elastomer is preferably 5 to 35% by mass.

  Furthermore, in addition to the polyethylene-based elastomer, it is also a preferred form to add 3 to 5% by mass of a hydrogenated styrene-based thermoplastic elastomer (SEBS). A hydrogenated styrene-based thermoplastic elastomer is a polymer obtained by hydrogenating a double bond of a block copolymer of styrene and butadiene, and is characterized by excellent weather resistance and heat resistance, and excellent elastomer characteristics. As a specific example, Asahi Kasei Co., Ltd. product name Tough Tech H1062 etc. can be mentioned.

  As described above, when a polyethylene elastomer is used in combination, the resin material may be deteriorated due to the heat history, which may cause a decrease in continuous productivity when the resin material is reused. Therefore, in the foam duct 10 of this embodiment, a predetermined amount of antioxidant is added according to the amount of the polyethylene-based elastomer to avoid this problem.

  As for the antioxidant, it is preferable to add a phosphorus-based antioxidant and a phenol-based antioxidant. However, the present invention is not limited to this, and even if a single antioxidant such as phosphorus-based or phenol-based is added, it is effective There is. Note that the phosphorus-based antioxidant is excellent in hydrolysis resistance and volatilization resistance, and has a function of reacting with a resin bonded to oxygen and preventing oxidative deterioration by a chain reaction. Phenol-based antioxidants are antioxidants that are effective in improving the heat resistance of various resins and elastomers, and have a high molecular weight, and thus are characterized by low extractability and low volatility.

  In the present invention, it is preferable to add both a phosphorus-based antioxidant and a phenol-based antioxidant. By using these in combination, the synergistic effect is exhibited, and the crosslinking degradation of the polyethylene-based elastomer is effective. To be suppressed.

  Here, as the phosphorus-based antioxidant and the phenol-based antioxidant to be used, any known one can be used. For example, phosphorus antioxidants include high molecular weight phosphorus antioxidants and low molecular weight phosphorus antioxidants, either one of which may be used, or a mixture thereof.

  Specific examples of the high molecular weight phosphorus antioxidant include tris (2,4-branched C3-8 alkyl-butylphenyl) phosphite [tris (2,4-di-t-butylphenyl) phosphite]. Etc.] and tetrakis (2,4-di-branched C3-8 alkylphenyl) -4,4'-C2 such as tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphite -4 alkylene phosphite. Examples of commercially available products include “Irgafos 168” manufactured by Ciba Japan.

  Examples of low molecular weight phosphorus antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite; tri-2,4-dimethylphenylphosphine, tri-2,4, List phosphine compounds such as 6-trimethylphenylphosphine, tri-o-tolylphosphine, tri-m-tolylphosphine, tri-p-tolylphosphine, tri-o-anisylphosphine, tri-p-anisylphosphine, etc. Can do.

  As for the phenolic antioxidant, there are a high molecular weight phenolic antioxidant and a low molecular weight phenolic antioxidant, either of which may be used, or a mixture thereof may be used.

  Examples of the high molecular weight phenolic antioxidant include hindered phenolic compounds. Examples of the hindered phenol compound include tris (2-alkyl-4-hydroxy-5-branched C3) such as 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane. Tris (3,5-di-branched) such as -8 alkylphenyl) butane and 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene 1,3 such as C3-8 alkyl-4-hydroxybenzyl) benzene, 1,3,5-trimethyl-2,4,6, -tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene , 5-trialkyl-2,4,6-tris (3,5-di-branched C3-8alkyl-4-hydroxybenzyl) benzene, tetrakis [methylene-3- (3,5-di-t-butyl- 4-hi Roxyphenyl) propionate] tetrakis [alkylene-3- (3,5-di-branched C3-8 alkyl-4-hydroxyphenyl) propionate] C1-4 alkane, pentaerythrityltetrakis [3- (3,5 Pentaerythrityltetrakis [3- (3,5-di-branched C3-8 alkyl-4-hydroxyphenyl) propionate] such as -di-t-butyl-4-hydroxyphenyl) propionate]. Examples of commercially available products include “Irganox 1010” manufactured by Ciba Japan.

  Low molecular weight phenolic antioxidants include dibutylhydroxytoluene (BHT), butylated hydroxyanisole (BHA), 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4 -Ethylphenol, 2,6-di-t-butylphenol, 2,4-dimethyl-6-t-butylphenol, 2-methyl-4,6-di-nonylphenol, butylhydroxyanisole, styrenated phenol, 2,4, Monophenol compounds such as 6-tri-t-butylphenol and 4,4'-dihydroxydiphenyl, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl) -6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol) 4,4′-butylidenebis (2,6-di-t-butylphenol), 1,1′-bis (4-hydroxyphenyl) cyclohexane, 2,2′-dihydroxy-3,3′-di (α-methylcyclohexyl) ) Bisphenol compounds such as 5,5′-dimethyldiphenylmethane, hydroquinone compounds such as 2,5-di-t-butylhydroquinone, hydroquinone monomethyl ether, 2,5-di- (tertiary amyl) hydroquinone, n- Examples include hindered phenol compounds such as octadecyl-3- (4′-hydroxy-3 ′, 5′-di-t-butylphenol) propionate. Moreover, the low molecular weight phenolic antioxidant includes a hydrazine compound having a hindered phenol structure {N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine } And the like are also included.

  The addition amount of the antioxidant is preferably adjusted according to the amount of the polyethylene elastomer contained in the resin material, and is preferably added so as to be 2000 ppm or more with respect to the polyethylene elastomer. When the addition amount of the antioxidant is less than 2000 ppm with respect to the polyethylene elastomer, the effect may be insufficient, and it is difficult to suppress the crosslinking deterioration for a long period of time.

  Although there is no particular upper limit to the amount of the antioxidant added, if the content of the antioxidant with respect to the entire resin material is 1000 ppm or more, the content of the antioxidant is excessive, and the molded product (foaming duct 10) Since there is a possibility of bleeding out and there is a possibility of lowering the physical properties of the molded product, the content is preferably less than 1000 ppm with respect to the entire resin material.

  In order to manufacture the foamed duct 10, oxidation prevention is added to the above-described polypropylene resin or polyethylene elastomer, which is subjected to blow molding. In blow molding, foaming is performed using a foaming agent. As the foaming agent, inorganic foaming agents such as air, carbon dioxide gas, nitrogen gas and water, and organic foaming agents such as butane, pentane, hexane, dichloromethane and dichloroethane can be used. Among these, it is preferable to use air, carbon dioxide gas, or nitrogen gas as the foaming agent. By using these, mixing of organic substances can be prevented, and deterioration of durability and the like can be suppressed.

  Moreover, it is preferable to use a supercritical fluid as the foaming method. That is, it is preferable to make carbon dioxide gas or nitrogen gas into a supercritical state and foam the resin material. By using a supercritical fluid, foaming can be performed uniformly and reliably. The conditions when the supercritical fluid is nitrogen gas may be a critical temperature of 149.1 ° C. and a critical pressure of 3.4 MPa. The conditions when the supercritical fluid is carbon dioxide gas are as follows: critical temperature 31 ° C. The critical pressure may be 7.4 MPa.

  The foamed duct 10 is formed by blow molding the foamed resin material by a known method. FIG. 2 is a view showing an aspect when the foam duct 10 is blow-molded.

  In blow molding, first, a resin material used for molding is kneaded in an extruder to produce a base resin. In the case of molding using only the virgin resin, a modifier is added to the virgin resin of the above-described resin material as necessary and kneaded to prepare a base resin. When the recovered resin material is used, a predetermined ratio of virgin resin is added to the pulverized recovered resin material and kneaded to prepare a base resin.

  After adding a foaming agent to such a base resin and mixing in an extruder, it is stored in an in-die accumulator (not shown), and then a ring-shaped piston (not shown) is stored after a predetermined amount of resin is stored. Press down in the direction perpendicular to the horizontal direction (vertical direction). 2 is extruded between the divided molds 31 and 32 constituting the mold clamping device 30 as a cylindrical parison P, for example, at an extrusion speed of 700 kg / hour or more from the die slit of the annular die 21 shown in FIG. Thereafter, the divided molds 31 and 32 are clamped to sandwich the parison P, and air is blown into the parison P in a pressure range of 0.05 to 0.15 MPa to form the foam duct 10.

  After molding, a portion other than the finished product in the resin material that has been cooled and solidified is pulverized into a recovered resin material, and the same blow molding is performed again using a mixed resin obtained by adding a predetermined amount of virgin resin to the recovered resin material. By repeating such a manufacturing cycle, the foam duct 10 can be mass-produced.

  When molding a resin molded product by general blow molding, mold the molten resin material into the shape of the mold surface, release it from the mold in a cooled and solidified state, and remove burrs around the molded product. The finished product is obtained by cutting out the opening with a cutter or the like. In the production cycle for mass production by blow molding, from the viewpoint of resource saving and cost reduction, the recovered resin obtained by pulverizing the parts other than the finished product in the resin material solidified after being once melted in this way Material. Then, the recovered resin material is mixed with a virgin resin to which no heat history is added to form a mixed resin, and a blowing agent is added to perform blow molding again.

  In such a production cycle in mass production, the ratio of the recovered resin material in the resin material used for molding is about 70 to 90% depending on the case. For example, after performing blow molding, add about 10 to 30% of virgin resin to the recovered resin material obtained by blow molding, taking out the foamed molded product that is the finished product, and mix resin When the blow molding is performed again, the ratio of the recovered resin material is 70 to 90%.

  If you repeat the production cycle of performing blow molding in this way, adding virgin resin to the recovered resin material by blow molding to make a mixed resin, and then performing blow molding again, continuous molding tends to be difficult. In the molding of the foam duct 10 of the present embodiment, an antioxidant is added according to the content of the polyethylene elastomer contained in the resin material, so that continuous molding becomes possible and continuous moldability is maintained. Is possible.

  As described above, the foam duct of the present invention can achieve both foam moldability and impact resistance. For example, the foaming magnification is 2.5 times (2 to 3 times) and the average wall thickness is 2 mm (1.5 to 2.5 mm) foam ducts can be molded. Further, the foamed duct to be molded has sufficient impact resistance and does not cause scattering cracks. Furthermore, even when a used resin material is used, the problem of deterioration can be solved, and a recycling system having continuous productivity can be established.

  As mentioned above, although embodiment which applied this invention has been described, it cannot be overemphasized that this invention is not what is limited to the above-mentioned embodiment, In the range which does not deviate from the summary of this invention, a various change can be added. Is possible.

  Hereinafter, specific examples of the present invention will be described based on experimental results.

The composition shown in Table 1, using polypropylene resin, polyethylene elastomer, hydrogenated styrene thermoplastic elastomer (SEBS), and antioxidants (phosphorus antioxidant and phenolic antioxidant) as raw materials for producing the foam duct. The foam duct was blow-molded with (mass% for polypropylene resin, polyethylene elastomer, hydrogenated styrene thermoplastic elastomer, ppm for antioxidant). The raw materials used are as follows.
-Polypropylene resin A: manufactured by Boreales, trade name WB140 (polypropylene having a long chain branched structure)
Polypropylene resin B: manufactured by Sumitomo Chemical Co., Ltd., trade name: AH561
Hydrogenated styrene thermoplastic elastomer (SEBS): manufactured by Asahi Kasei Co., Ltd., trade name H1062
-Polyethylene elastomer: Product name DF605, manufactured by Mitsui Chemicals, Inc.
Phosphorous antioxidant: Ciba Japan, trade name Irgafos 168
-Phenol-based antioxidant: Ciba Japan, trade name Irganox 1010

Evaluation The produced foamed duct was evaluated for impact resistance, expansion ratio, and continuous productivity. The evaluation criteria are as follows.
-Impact resistance: A case where a 1 kg ball is dropped at -10 ° C and the drop crack height is 80 to 120 cm, △, a case where it is 130 to 160 cm, a case where there is no crack even at 170 to 200 cm did. In addition, the case where a crack arises at 80 cm or less is x.
-Foaming ratio: A case where the maximum foaming ratio was 2.5 times or more was rated as ◯, and a case where it was less than 2.5 times was rated as x.
・ Continuous productivity: 90% of the pulverized material was blended and crushed material was returned 5 times.

  As is clear from Table 1, by blending 5 to 35% by mass of a polyethylene-based elastomer, both foam moldability (foaming ratio) and impact resistance are compatible. However, if the antioxidant is not added, the continuous productivity does not satisfy the standard, and the continuous productivity is improved by adding 2000 ppm or more of the antioxidant to the polyethylene-based elastomer. Moreover, impact resistance is further improved by adding hydrogenated styrene-based thermoplastic elastomer (SEBS).

10 Foam duct 21 Annular die 30 Clamping device 31, 32 Split mold P Parison

Claims (6)

A foam blow molded product formed by blow molding a foam resin including a polypropylene resin and a polyethylene elastomer,
The foamed resin contains an antioxidant,
The foamed blow-molded product, wherein the content of the antioxidant is 2000 ppm or more with respect to the polyethylene elastomer and less than 1000 ppm with respect to the entire resin material .   The foamed blow molded product according to claim 1, wherein the content of the polyethylene elastomer is 5 to 35% by mass.   The foamed blow molded article according to claim 1 or 2, wherein the polypropylene resin has a long chain branched structure.   The foamed blow-molded article according to any one of claims 1 to 3, comprising 3 to 5% by mass of a hydrogenated styrene-based thermoplastic elastomer.   The foamed blow-molded product according to any one of claims 1 to 4, wherein the antioxidant contains a phosphorus-based antioxidant and a phenol-based antioxidant.   The foamed blow molded article according to any one of claims 1 to 5, wherein the foam blow molded article is an air conditioning duct for a vehicle.

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