JP2009298964A - Polypropylene-based resin foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene-based resin foam which is light in weight, excellent in mechanical strength and weatherability, and exhibits little deterioration in mechanical properties. <P>SOLUTION: The polypropylene-based resin foam has a density of not less than 10 and less than 300 kg/m<SP>3</SP>and a closed cell ratio of not less than 60%. Its base resin includes a benzotriazole-based ultraviolet absorbent in an amount of 0.05-0.5 pts.wt. to 100 pts.wt. of the polypropylene-based resin. This composition gives a foam which has an excellent mechanical strength and exhibits an extremely little lowering of the mechanical strength even after the foam is subjected to a weatherability test. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polypropylene resin foam that is lightweight and excellent in mechanical strength, and further excellent in weather resistance, and therefore has little deterioration in mechanical properties even when used for a long period of time.

  Polypropylene resins are used in various applications because they are excellent in heat resistance, chemical resistance and rigidity. However, polypropylene resin is generally inferior in weather resistance, and has a problem that, for example, it loses mechanical properties when exposed to sunlight or ultraviolet rays for a long time.

  For this problem, it is known that a hindered amine light stabilizer, an ultraviolet absorber, a mixture of a hindered amine light stabilizer and an ultraviolet absorber, and the like can be used as a weather resistance improver.

Polypropylene resin foam, on the other hand, has the characteristics of polypropylene resin, as well as the characteristics of lightweight and resource saving because it is a foam material, such as automobile parts, housing materials, packaging materials, curing materials, etc. It is considered that it is suitably used in applications.
For example, Patent Document 1 discloses an extruded foam sheet having a density of about 250 kg / m ³ and having no open cells, which is based on a specific non-crosslinked propylene resin.

  Since these foam sheets have a relatively low density and a high closed cell ratio, they can be suitably used for the above-mentioned applications. However, when this foam is used in these applications that are used for a relatively long period of time and often exposed to sunlight and ultraviolet rays, the weather resistance is not necessarily sufficient, and exposure to sunlight and ultraviolet rays is not sufficient. As a result, there is a problem that the mechanical characteristics are deteriorated.

Specifically, there was a problem that the polypropylene resin constituting the foamed sheet deteriorated and the tensile elongation of the foamed sheet was lowered. More practically, the exposed foam sheet loses the inherent flexibility, and there is a problem that bending due to rupture or buckling occurs with a slight bending stress. .
JP-A-4-363227

  In view of the above problems, the present inventors have attempted to improve the weather resistance of polypropylene resin foams by using various known weather resistance improving materials as part of the base material. Surprisingly, however, it has been found that it is extremely difficult to develop a weather resistance improving effect in the case of a foam.

  Therefore, as a result of further investigation, when a specific ultraviolet ray inhibitor was used, the effect of improving weather resistance was manifested with a specific small addition amount, and without losing growth even in relatively long-term outdoor exposure, The present inventors have found that the foam itself can be effectively prevented from being destroyed.

  That is, the present invention has the following configuration.

1). In a polypropylene resin foam having a density of 10 or more and less than 300 kg / m ³ and a closed cell ratio of 60% or more, the base resin is 0.05 to 0.5 parts by weight of benzo with respect to 100 parts by weight of the polypropylene resin. A polypropylene resin foam comprising a triazole ultraviolet absorber.

  2). 1) characterized in that the polypropylene resin is a modified polypropylene resin obtained by melt-kneading (a) polypropylene resin, (b) isoprene, and (c) radical polymerization initiator. The polypropylene resin foam described.

  3). The polypropylene resin foam according to 1) or 2), which is obtained by an extrusion foaming method.

4). The polypropylene resin foam according to any one of 1) to 3), which has a density of 90 or more and less than 250 kg / m ^{3 and} a sheet or plate shape having a thickness of 0.5 to 10 mm.

  According to the present invention, since the density is low and the closed cell ratio is high, it is excellent in lightness and mechanical properties, and also exhibits excellent weather resistance, and it is realized in a small amount of additive, so that it is excellent in manufacturing cost. Provided is a polypropylene resin foam that can be suitably used for applications such as automobile members, housing materials, packaging materials, and curing materials.

  The first feature of the present invention is that the base resin contains a benzotriazole-based ultraviolet absorber.

In the present invention, the benzotriazole ultraviolet absorber preferably contains a compound represented by the general formula (1) as a main component. Here, R _{1 to} R ₈ can be hydrogen, halogen, alkyl, aryl, alkoxyl, or an aromatic alkyl substituent, and any one of R _{1 to} R ₈ is an alkylene group via the alkylene group. In addition, it may be a compound having a structure in which two or more molecules of the compound represented by the general formula (1) are bonded.

  Preferred examples include 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4-6-bis (1-methyl-1-phenylethyl) ) Phenol, 2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl-6- (t-butyl) phenol, 2- [5-chloro (2H) -benzotriazol-2-yl ] -4,6-di- (t-butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di- (1,1-dimethylpropyl) phenol, 2- (2H-benzo Triazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1 , 3,3-Tetramethylbu Le) phenol] and the like.

  Moreover, as a preferable specific example marketed, Tinuvin P, Tinuvin 234, Tinuvin 326, Tinuvin 329, Tinuvin 360 (Ciba Japan Co., Ltd.), LA-32, LA-36, LA-31 (ADEKA Co., Ltd.) can be mentioned. .

  The content of the benzotriazole-based ultraviolet absorber is 0.05 to 0.5 parts by weight with respect to 100 parts by weight of the polypropylene resin, and preferably 0.07 to 0.48 parts by weight. Moreover, 0.15-0.45 weight part is preferable from the point of the retention rate of elongation, and 0.16-0.34 weight part is preferable at the point from which both the retention rate of elongation and a closed cell rate are high.

  When the content is small, the effect of improving the weather resistance, which is the effect of the present invention, tends to be insufficient. When the content is too large, the effect of improving the weather resistance tends to reach a peak, and in addition to being wasted. The closed cell ratio of the foam of the present invention tends to decrease, which is not preferable.

  The polypropylene resin in the base resin preferably exhibits a high melt tension from the viewpoint of increasing the closed cell ratio of the foam of the present invention and easily reducing the density.

  As a preferable method for showing the melt tension, there is a method in which a polypropylene resin showing a high melt tension is used as all or a part of the polypropylene resin in the base resin.

  Specific examples of such a polypropylene resin exhibiting high melt tension include PF-814 and SD-632 manufactured by Sun Allomer, and New Former FH3400 manufactured by Nippon Polypro.

  In addition, as a specific example of a polypropylene resin exhibiting high melt tension, a modified polypropylene resin obtained by melt-kneading a polypropylene resin, a radical polymerizable monomer, and a radical polymerization initiator can be exemplified. .

  Among them, it is particularly preferable that the modified polypropylene resin is obtained by melt-kneading (a) a polypropylene resin, (b) isoprene, and (c) a radical polymerization initiator.

  As a specific example preferably used in such a modified polypropylene resin, there is a modified polypropylene resin obtained by the method disclosed in JP-A-9-188729.

  The addition amount of the isoprene to be melt-kneaded is preferably 0.1 to 100 parts by weight, more preferably 0.2 to 20 parts by weight, and more preferably 0.3 to 100 parts by weight of the raw material polypropylene resin. It is preferable that it is -10 weight part. Moreover, even if it is 0.3-1 weight part, it is preferable.

  Examples of the radical polymerization initiator generally include peroxides and azo compounds. Examples of the radical polymerization initiator include ketone peroxides such as methyl ethyl ketone peroxide and methyl acetoacetate peroxide; 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis Peroxyketals such as (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane; permethane hydroper Hydroperoxides such as oxide, 1,1,3,3-tetramethylbutyl hydroperoxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide; dicumyl peroxide, 2,5-dimethyl-2,5-di ( t-Butylperoxy) hexane α, α′-bis (t-butylperoxy-m-isopropyl) benzene, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxide) Dialkyl peroxides such as oxy) hexyne-3; diacyl peroxides such as benzoyl peroxide; peroxys such as di (3-methyl-3-methoxybutyl) peroxydicarbonate and di-2-methoxybutylperoxydicarbonate Dicarbonate: t-butyl peroxyoctate, t-butyl peroxyisobutyrate, t-butyl peroxylaurate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxy Isopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylpa Oxy) hexane, t- butyl peroxy acetate, t- butyl peroxybenzoate, one or more organic peroxides such as peroxy esters such as di -t- butyl peroxy isophthalate and the like.

  Of these, those having a particularly high hydrogen abstraction ability are preferred. Examples of such radical polymerization initiators include 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1. Peroxyketals such as bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane; dicumyl Peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, t-butylcumyl peroxide, di Dialkyl peroxides such as t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3; Diacyl peroxides such as nzoyl peroxide; t-butyl peroxyoctate, t-butyl peroxyisobutyrate, t-butyl peroxylaurate, t-butylperoxy-3,5,5-trimethylhexano Ate, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxybenzoate, di-t-butylperoxyiso 1 type, or 2 or more types, such as peroxyesters, such as a phthalate, is mention | raise | lifted.

  The addition amount of the radical polymerization initiator is 0.1 to 10 weights with respect to 100 parts by weight of the raw material polypropylene resin because the modified polypropylene resin is easily elastically deformed when melted and is economical. It is preferably within the range of parts, more preferably 0.2 to 5 parts by weight, and particularly preferably 0.2 to 1 part by weight.

  The order and method of mixing and melt-kneading these modified polypropylene resins, isoprene, radical polymerization initiators and other added materials are not particularly limited. For example, starting polypropylene resins, isoprene, radical polymerization initiation It may be melt-kneaded after mixing the agent and other additive materials added as necessary, or after melt-kneading the raw material polypropylene resin, it is added to isoprene, a radical polymerization initiator, and if necessary. Other additive materials may be mixed at the same time or separately, collectively or divided, and melt-kneaded.

  Although the heating temperature at the time of melt kneading varies depending on the type of resin, etc., it is usually 130 to 400 ° C. that the raw material polypropylene resin is sufficiently melted and is not thermally decomposed to obtain sufficient elongation viscosity characteristics. This is preferable in that it can be performed. The time for melt kneading (the time after mixing the radical polymerization initiator and the aromatic vinyl monomer) is generally 30 seconds to 60 minutes.

  The melt kneading apparatus includes a roll, a kneader, a Banbury mixer, a brabender, a kneader such as a single screw extruder, a biaxial extruder, a horizontal type such as a biaxial surface renewal machine, and a biaxial multi-disc apparatus. Examples thereof include an apparatus capable of heating a polymer material such as a stirrer or a vertical stirrer such as a double helical ribbon stirrer to an appropriate temperature and kneading while applying an appropriate shear stress. Among these, a single-screw or twin-screw extruder is particularly preferable from the viewpoint of productivity. Moreover, in order to mix each material sufficiently uniformly, the melt kneading may be repeated a plurality of times.

  The modified polypropylene resin obtained by this method can be made relatively inexpensive and easily have a high melt tension, and is a case where the modified polypropylene resin and other resins are mixed and used. However, it is excellent in that a foam having a low density and a high closed cell ratio can be easily obtained.

  The polypropylene resin exhibiting a high melt tension is preferably 30 to 100% by weight, more preferably 55 to 100% by weight, further 80 to 100% by weight, particularly 95 to 100% by weight of the polypropylene resin in the base resin. It is preferable to set it as the range of weight%.

  Specific examples of other components of the polypropylene resin in the base resin include propylene homopolymers and copolymers of propylene and other monomers.

  Among them, the polypropylene homopolymer is preferable from the viewpoint of high rigidity and low cost, and a block copolymer of the propylene and other monomers is preferable from the viewpoint of high rigidity and impact resistance. From the viewpoint of being relatively flexible, a random copolymer of propylene and another monomer is preferable.

  When the other component is a block copolymer of propylene and another monomer or a random copolymer of propylene and another monomer, the high crystallinity and high rigidity that are characteristic of polypropylene resins From the viewpoint of maintaining good chemical resistance, the propylene monomer component contained is preferably 75% by weight or more, and more preferably 90% by weight or more.

  In the polypropylene resin, in the case of a block copolymer of propylene and another monomer, and a random copolymer of propylene and another monomer, specific examples of other monomers preferably used include , One or more monomers selected from the group consisting of ethylene, α-olefin, cyclic olefin, diene monomer and vinyl monomer. Further, as this monomer, ethylene, α-olefin or diene monomer is preferable because it is easily copolymerized with propylene and is inexpensive.

  Specific examples of the α-olefin copolymerizable with propylene include butene-1, isobutene, pentene-1, 3-methyl-butene-1, hexene-1, 3-methyl-pentene-1, 4-methyl-pentene. -1,3,4-dimethyl-butene-1, heptene-1, 3-methyl-hexene-1, octene-1, decene-1, etc., and an α-olefin having 4 to 12 carbon atoms.

  Examples of the cyclic olefin copolymerizable with propylene include cyclopentene, norbornene, 1,4,5,8-dimethano-1,2,3,4,4a, 8,8a-6-octahydronaphthalene. Etc.

  Examples of the diene monomer that can be copolymerized with propylene include 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 1,4-hexadiene, methyl-1,4-hexadiene, Examples thereof include 7-methyl-1,6-octadiene.

  Examples of the vinyl monomer copolymerizable with propylene include vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, and methyl methacrylate. And maleic anhydride.

  Of these monomers, ethylene or butene-1 is more preferable because of its low cost.

  Moreover, as other components of the polypropylene resin in the base resin, resins and rubbers other than the polypropylene resin can be used as long as the effects of the present invention are not impaired.

  Specific examples include, for example, polyethylene; poly α-olefins such as polybutene-1, polyisobutene, polypentene-1, and polymethylpentene-1; ethylene / propylene copolymers having a propylene content of less than 75% by weight, ethylene / butene- Ethylene or α-olefin / α- such as 1 copolymer, ethylene / hexene-1 copolymer, ethylene / octene-1 copolymer, propylene / butene-1 copolymer having a propylene content of less than 75% by weight Olefin copolymer; ethylene or α-olefin / α-olefin / diene monomer copolymer such as ethylene / propylene / 5-ethylidene-2-norbornene copolymer having a propylene content of less than 75% by weight; ethylene / Vinyl chloride copolymer, ethylene / vinylidene chloride copolymer, ethylene / acrylic Ronitrile copolymer, ethylene / methacrylonitrile copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylamide copolymer, ethylene / methacrylamide copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer Polymer, ethylene / maleic acid copolymer, ethylene / ethyl acrylate copolymer, ethylene / butyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / maleic anhydride copolymer, ethylene / acrylic Ethylene or α-olefin / vinyl monomer such as acid metal salt copolymer, ethylene / methacrylic acid metal salt copolymer, ethylene / styrene copolymer, ethylene / methylstyrene copolymer, ethylene / divinylbenzene copolymer Copolymer: polyisobutene, polybutadiene, polyisoprene Polydiene copolymers such as styrene / butadiene random copolymer vinyl monomers / diene monomer random copolymers; styrene / butadiene / styrene block copolymers, styrene / isoprene / styrene block copolymers Vinyl monomer such as coalescence / diene monomer / vinyl monomer block copolymer; Hydrogenation (vinyl monomer / diene monomer random) such as hydrogenation (styrene / butadiene random copolymer) Copolymer); Hydrogenation (Styrene / Butadiene / Styrene Block Copolymer), Hydrogenation (Styrene / Isoprene / Styrene Block Copolymer), etc. (Vinyl Monomer / Diene Monomer / Vinyl Monomer) Block copolymer); acrylonitrile / butadiene / styrene copolymer, methyl methacrylate / butadiene / styrene copolymer Vinyl monomers such as coalescence / diene monomers / vinyl monomer graft copolymers; polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyvinyl acetate, polyethyl acrylate, polybutyl acrylate, polymethacryl Vinyl polymers such as methyl acrylate; vinyl chloride / acrylonitrile copolymers, vinyl chloride / vinyl acetate copolymers, acrylonitrile / styrene copolymers, vinyl copolymers such as methyl methacrylate / styrene copolymers, etc. It is done.

  The amount of these other resins or rubber added to the polypropylene resin varies depending on the type of this resin or rubber, and may be within a range that does not impair the effects of the present invention. Usually, it is preferably about 25% by weight or less when it is 100% by weight.

  In addition, the polypropylene resin in the base resin may further include an antioxidant, a metal deactivator, a phosphorus processing stabilizer, a light stabilizer, a fluorescent brightener, a metal soap, an antacid adsorbent, if necessary. Stabilizers such as UV absorbers other than benzotriazoles, or additives such as crosslinking agents, chain transfer agents, nucleating agents, lubricants, plasticizers, fillers, reinforcing materials, pigments, dyes, flame retardants, antistatic agents May be added within a range not impairing the effects of the present invention.

  There is no restriction | limiting in particular in the method of manufacturing the foam of this invention, For example, well-known techniques, such as an extrusion foaming method, an injection foaming method, a blow foaming method, can be used.

  Of these, the extrusion foaming method is preferably used from the viewpoint of high productivity and easy density reduction.

  As a particularly preferred specific example used as a method for producing the foam of the present invention, (1) a foam obtained by melt-kneading a base resin containing a benzotriazole-based ultraviolet absorber and a foaming agent in an extruder and then extruding from a die. And (2) a method of adding a foaming agent to a base resin containing a benzotriazole-based ultraviolet absorber in a melted state or press-fitting it and then extruding it from a die.

  At this time, the base resin supplied to the extruder may be a blend of a powder or pellet-shaped polypropylene resin and a powder or liquid benzotriazole-based UV absorber, or a powder or pellet. It may be a blend of a polypropylene resin in the form of a benzotriazole ultraviolet absorber that has been masterbatched in advance.

  When the benzotriazole-based UV absorber is supplied as a master batch, the master batch uses one or more of polyethylene and polypropylene as a carrier resin, and the benzotriazole-based UV absorber is used with respect to 100 parts by weight of the carrier resin. It is preferable to use those prepared at a ratio of 1 to 10 parts by weight from the viewpoint that the dispersion of the ultraviolet absorber is good and the amount of the master batch used can be reduced. In this case, the content of the benzotriazole ultraviolet absorber relative to the polypropylene resin is calculated assuming that the carrier resin of the masterbatch constitutes a part of the polypropylene resin of the base resin.

  As the foaming method, when the above method (1) is employed, a preferable example of the foaming agent is a pyrolytic foaming agent. Specific examples of preferred pyrolytic foaming agents include nitroso foaming agents such as N, N′-dinitrosopentamethylenetetramine and N, N′-dimethyl-N, N′-dinitrosotephthalamide; azodicarbonamide Azo foaming agents such as barium azodicarboxylate; sulfohydrazide foaming agents such as p, p′-oxybisbenzenesulfonyl hydrazide and p-toluenesulfonyl semicarbazide; trihydrazinotriazine; bicarbonate soda-sodium bicarbonate organic such as citric acid 1 type, or 2 or more types, such as acid type blowing agents;

  At this time, the addition amount of the foaming agent may be selected depending on the type of foaming agent and the target foaming ratio, but is preferably in the range of 0.5 to 100 parts by weight with respect to 100 parts by weight of the base resin.

  In this case, the base resin and the thermally decomposable foaming agent are supplied to an extruder, a gas is generated by thermally decomposing the foaming agent while melt kneading at an appropriate temperature, and a molten state containing this gas is generated. A foam can be obtained by discharging the base resin from the die. The melt-kneading temperature and melt-kneading time at that time must be appropriately selected depending on the foaming agent to be used, and vary depending on the type, but generally the melt-kneading temperature is 130 to 300 ° C. and the melt-kneading time is 1 to 60 minutes. Is normal.

  When the method (2) is adopted as the foaming method, a volatile foaming agent is an example of a preferable foaming agent. Among these, preferable volatile foaming agents include, for example, aliphatic hydrocarbons such as propane, butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane, and cyclohexane; chlorodifluoromethane, difluoromethane, Trifluoromethane, trichlorofluoromethane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, trichlorofluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, tetrafluoroethane, difluoroethane, penta Fluoroethane, trifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane , Chloropentafluoroethane, halogenated hydrocarbons such as perfluorocyclobutane; carbon dioxide, nitrogen, inorganic gases such as air; one, such as water or two or more thereof.

  At this time, the addition amount of the foaming agent may be selected depending on the type of foaming agent and the target foaming ratio, but is preferably in the range of 0.5 to 30 parts by weight with respect to 100 parts by weight of the base resin.

  In this case, the base resin is melted in an extruder, the volatile foaming agent is press-fitted into the extruder, and is kneaded with the molten base resin while maintaining a high pressure. By discharging more, a foam can be obtained. The melt-kneading temperature and melt-kneading time at that time must be appropriately selected depending on the foaming agent used, and differ depending on the type, but generally the melt-kneading temperature is 130 to 300 ° C. and the melt-kneading time is 1 to 120 minutes. Is normal.

  In addition, in the step of obtaining the foam, a method of using a component used as a so-called foam nucleating agent in combination with the present invention is preferably used in the present invention for the purpose of controlling the bubble diameter of the obtained foam to an appropriate size. It is done. Preferable specific examples of such a foam nucleating agent include sodium bicarbonate-organic acid-based foaming agents such as sodium bicarbonate-citric acid, and inorganic powders such as talc, calcium carbonate, and mica. Added to the mixture. In this case, the foam nucleating agent may be a master batch.

  The addition amount of the foam nucleating agent is generally 0.01 parts by weight or more and 1 part by weight or less with respect to 100 parts by weight of the base resin. In addition, when using what was made into the masterbatch as a foam nucleating agent, carrier resin calculates the addition amount of a foam nucleating agent as what comprises a part of polypropylene resin of base resin.

  As the die used when the foam of the present invention is produced by the extrusion foaming method, an appropriate one may be used in consideration of the shape, productivity and the like of the foam to be obtained. As the types of dies that can be used, so-called circular dies; so-called T dies such as fishtail dies, coat hanger dies, and manifold dies; and slit dies can be preferably used.

  In addition, for the purpose of further shaping the foam discharged from the die, a method using various sizing devices in combination can also be preferably used.

  As a specific example of the shaping method using such a sizing device, the discharged foam is held by a pair of upper and lower rolls, and further, a roll in which a large number of rolls are arranged in the discharge direction. The shape of the foamed foam, and the shape of the discharged foam is shaped through the foam discharged to a sizing die that has an opening cross-sectional shape of a desired shape and is cooled with a coolant such as water as necessary. And a method of shaping the foam discharged in an annular shape by bringing it into contact with the outer surface of a mandrel that has a cylindrical shape and is cooled with a coolant such as water, if necessary, and stretched and cooled. can give.

  In addition, when using these shaping methods, for the purpose of improving the surface smoothness and appearance of the foam, a method of cooling the surface of the discharged foam by blowing air or the like may be used in combination.

  The foam of the present invention is shaped by the above-described method, and then subjected to processing such as winding and cutting according to the necessity associated with the shape to obtain a product.

The foam of the present invention preferably has a density of 10 or more and less than 300 kg / m ³ , more preferably 90 or more and less than 250 kg / m ³ , and even more preferably 120 or more and less than 240 kg / m ³ . The foam of the present invention is lightweight and excellent in mechanical properties.

  Since the foam of the present invention has different lightness and mechanical properties required depending on the application to be used, the density of the foam may be appropriately set accordingly. Since the body becomes too flexible, it tends to be difficult to use in these applications. On the other hand, when the density is higher than the density according to the present invention, the lightness which is one of the features of the foam of the present invention tends to be impaired, which is not preferable.

  The closed cell ratio of the foam of the present invention is preferably 60% or more, more preferably 70% or more, and particularly preferably 75% or more. A low closed cell ratio tends to impair the good mechanical properties that are characteristic of the foam of the present invention, and is not preferable. In this invention, the foam which has a closed cell ratio of 60% or more can be easily obtained by employ | adopting the structure of the base resin mentioned above and the manufacturing method of a foam.

  Furthermore, as one of the particularly preferred embodiments in applications such as automobile members, housing materials, packaging materials, and curing materials in which the foam of the present invention is used, the foam has a thickness of 0.5 to 10 mm, more preferably 1 It may be a sheet shape or plate shape of ˜8 mm.

  When the thickness is less than 0.5 mm, the mechanical properties of the foam tend to be insufficient, which is not preferable. On the other hand, when the thickness exceeds 10 mm, it tends to be difficult to sufficiently maintain the surface smoothness required for these applications.

  In order to obtain such a foam shape, in the foam manufacturing method described above, a method of appropriately setting the opening cross-sectional shape of the die from which the foam is discharged and the opening cross-sectional shape of the sizing device, For example, a method of adjusting the take-up speed of the discharged foam can be used.

  Moreover, when the foam of this invention is a sheet form or plate shape, a different layer may be formed in the foam at least on one side. Preferred examples include a method in which a film that may be printed on the surface is adhered using a technique such as a thermal lamination method or an extrusion lamination method, and a co-extrusion method or an extrusion lamination method on the surface of the foam. The method of forming a different resin layer by this method, etc. can be raised, and these can further improve the mechanical properties of the foam of the present invention, improve the scratch resistance of the surface, antistatic properties, conductivity, etc. These functions can be imparted or design properties can be imparted.

When the foam of the present invention having such properties is in the form of a sheet or plate, the preferred basis weight (weight per 1 m ² ) is in the range of 300 to 1500 g / m ² , more preferably 350 to 950 g / m ² . is there.

  If necessary, the foam of the present invention can be further subjected to secondary processing. Specific examples of such secondary processing include shaping processing by thermoforming, punching processing, cutting processing, thermal ruled line processing, bending processing, and the like.

  Since the foam of this invention obtained by the above is lightweight and shows a favorable mechanical characteristic, it is used suitably for uses, such as a motor vehicle member, a housing material, a packaging material, and a curing material.

  In addition, the foam of the present invention has a small decrease in elongation even when placed in an environment exposed to sunlight or ultraviolet rays, and it is difficult to cause breakage with a slight amount of deformation. Very useful.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to this Example.

Production Example 1 Production of Modified Polypropylene Resin PP1 Propylene homopolymer (manufactured by Prime Polymer Co., Ltd., F102W, 230 ° C., melt flow rate 2 g / 10 min at a load of 2.16 kg) 100 parts by weight t- A compound feeder prepared by stirring and mixing 0.3 parts by weight of butyl peroxy-isopropyl monocarbonate (manufactured by Nippon Oil & Fats Co., Ltd., Perbutyl I) with a ribbon blender is manufactured by Nippon Steel Works, Ltd., twin screw extruder (TEX44XCT-38) ) At a rate of 50 kg / h. Furthermore, by supplying isoprene at a ratio of 0.5 part by weight with respect to 100 parts by weight of the propylene homopolymer using a liquid pump in the middle of the extruder, melt-kneading in the twin-screw extruder, and melt-extruding. A pellet of modified polypropylene resin (PP1) was obtained.

The biaxial extruder was the same direction biaxial type, the screw diameter was 44 mmφ, and the maximum screw effective length (L / D) was 38. The set temperature of the cylinder part of this twin screw extruder was set to 180 ° C. up to the isoprene supply port, 200 ° C. thereafter, and the screw rotation speed was set to 140 rpm.
According to JIS K7210, the melt flow rate of (PP1) measured under the conditions of a temperature of 230 ° C. and a load of 2.16 kg was 0.4 g / 10 min.

(Example 1)
A master batch of a sodium bicarbonate-organic acid-based foaming agent as a foaming nucleating agent (0.2 parts by weight) and 100 parts by weight of (PP1) benzotriazole-based ultraviolet absorber (ADEKA Corporation, LA-36) 0.5 parts by weight of Nissei Kasei Co., Ltd., Dainichi Seika Co., Ltd., PO510K) were mixed with a ribbon blender.

  The obtained mixture was supplied to a tandem extruder having a first stage cylinder diameter of 65 mm and a second stage cylinder diameter of 90 mm, and melted at 220 ° C. in the first stage extruder. Further, isobutane as a blowing agent was injected at a ratio of 1.5 parts by weight with respect to 100 parts by weight of the mixture at the front end of the first stage extruder and kneaded, and then 160 ° C. in the second stage extruder. And then extruded from a circular die having a diameter of 68 mm and a lip gap of 0.3 mm.

  At this time, the discharge amount from the extruder was adjusted to 50 kg / h. Furthermore, while the extruded foam was taken up by a mandrel having an outer peripheral length of 635 mm, one portion of the cylindrical foam was cut with a cutter to form a sheet, and then wound into a roll to obtain a foam sheet.

  About the obtained foamed sheet, thickness, density, basis weight, and closed cell ratio were measured by the following methods. The results are shown in Table 2.

<Measurement of thickness of foam sheet>
Measurement points were provided at intervals of 30 mm in the width direction of the foamed sheet, and after measuring the thickness of each measurement point using a thickness gauge (teclock thickness gauge), the average of the measured values at each point was taken as the thickness of the foamed sheet. .

<Measurement of density of foam sheet>
It measured according to JIS-K6767.

<Measurement of basis weight of foam sheet>
A sample having a width of foam sheet × 100 mm was cut out and calculated from the weight w (g) according to the following formula (1).

  (Weight) = w / (0.1 × width of foam sheet (m)) (1).

<Measurement of closed cell ratio of foam sheet>
Measurement was performed with an air pycnometer according to the method described in ASTM D2856.

  In addition, the obtained foamed sheet was subjected to a tensile elongation test before and after outdoor exposure in the following manner to measure the elongation retention.

<Measurement of elongation retention>
From the obtained foamed sheet, the extrusion direction is taken as the longitudinal direction, a sample of 120 mm × 10 mm × thickness is cut out, and two marked lines are written with an oil pen at intervals of 40 mm in the longitudinal direction (hereinafter sometimes referred to as a pre-exposure sample). ).

  This sample was subjected to a tensile test in accordance with JIS K6767 at room temperature, a distance between chucks of 40 mm (the sample was set so that the portion between the marked lines was subjected to tensile stress), and a tensile speed of 500 mm / min. The distance between chucks at the time of measurement was measured, and the elongation defined by the following formula (2) was measured. The test was performed with n = 5, and the elongation was calculated by averaging the obtained five measurements.

  (Elongation) = {(Distance between chucks at break (mm)) − 40} / 40 (2).

  On the other hand, the sample cut out in the above was in a state where both ends 40 mm in the longitudinal direction were masked with tape (the portion between the marked lines was exposed), and the sample was exposed outdoors for 30 days (Osaka) Settsu City, south side, 45 degree slope). At this time, the samples obtained in the following examples and comparative examples were also exposed under the same conditions.

  After the exposure, the elongation rate was measured in the same manner as the pre-exposure sample for the sample in which the masked tape was peeled off (hereinafter sometimes referred to as an exposure sample). Furthermore, the elongation retention defined by the following formula (3) was calculated and used as an index of elongation decrease due to outdoor exposure, and evaluated according to the following criteria.

(Elongation retention rate (%)) = (Elongation rate of exposed sample) / (Elongation rate of sample before exposure) × 100 (3)
○: Elongation retention is 70% or more Δ: Elongation retention is 50% or more and less than 70% X: Elongation retention is less than 50% Table 2 shows the results.

  Further, the exposed sample obtained above was subjected to a bending test in the following manner.

<Bending test>
One end of the exposed portion of the exposed sample is chucked and fixed so that the thickness direction is vertical, and the sample is located at the center of the short side of the sample, 20 mm away from the chuck position in the direction of the sample length and toward the opposite end of the sample. The position was pushed down by 10 mm with a circular indenter having a diameter of 4 mm, and the behavior of the sample at that time was evaluated according to the following criteria.

○: No bending due to destruction or buckling.
X: Destruction occurs. Or it bends by buckling.

  The results are shown in Table 2.

(Examples 2 to 4)
A foamed sheet was prepared and evaluated in the same manner as in Example 1 except that the amount and type of the benzotriazole-based ultraviolet absorber in Example 1 were changed as shown in Table 1. The results are shown in Table 2.

(Example 5)
A benzotriazole ultraviolet absorber (manufactured by ADEKA Corporation, LA-36) with respect to 95 parts by weight of a propylene homopolymer (manufactured by Prime Polymer, J105G, 230 ° C., melt flow rate 9 g / 10 min at a load of 2.16 kg) ) A mixture obtained by stirring and mixing 5 parts by weight with a ribbon blender was fed at a rate of 50 kg / h to a twin screw extruder (TEX44XCT-38) manufactured by Nippon Steel Works, Ltd. with a measuring feeder. Was melt-kneaded and melt-extruded to obtain a benzotriazole-based ultraviolet absorber master batch.

  At this time, the set temperature of the cylinder part of the twin-screw extruder was 200 ° C., and the screw rotation speed was set to 150 rpm.

  In Example 1, instead of 100 parts by weight of (PP1), 96 parts by weight of (PP1) and 4 parts by weight of the benzotriazole-based UV absorber masterbatch obtained above instead of 0.2 parts by weight of the benzotriazole-based UV absorber A foamed sheet was prepared and evaluated in the same manner as in Example 1 except that the part was changed. The results are shown in Table 2.

(Comparative Examples 1-6)
The amount and type of the benzotriazole-based UV absorber in Example 1 or the amount and type of the weather resistance improver other than the benzotriazole-based UV absorber are changed as shown in Table 1 in the same manner as in Example 1. A foamed sheet was prepared and evaluated. The results are shown in Table 2.

  As is clear from Table 2, the foam of the present invention exhibits a high elongation retention even after outdoor exposure by including a specific amount of a benzotriazole-based ultraviolet absorber in the base resin, and also in a bending test. It can be seen that there is no problem due to bending due to destruction or buckling.

MB: Masterbatch BT1: Propylene homopolymer / BT1 = 95/5 (parts by weight): benzotriazole UV absorber (LA-36, manufactured by ADEKA Corporation)
BT2: Benzotriazole-based ultraviolet absorber (manufactured by Ciba Japan Co., Ltd., Tinuvin 234)
UVA: Benzophenone-based ultraviolet absorber (Ciba Japan Co., Ltd., CHIMASSORB 81)
HALS: hindered amine light stabilizer (Ciba Japan Co., Ltd., Tinuvin 770)

Claims (4)

In a polypropylene resin foam having a density of 10 or more and less than 300 kg / m ³ and a closed cell ratio of 60% or more, the base resin is 0.05 to 0.5 parts by weight of benzo with respect to 100 parts by weight of the polypropylene resin. A polypropylene resin foam comprising a triazole ultraviolet absorber. The polypropylene resin is a modified polypropylene resin obtained by melt-kneading (a) a polypropylene resin, (b) isoprene, and (c) a radical polymerization initiator. The polypropylene resin foam described in 1. The polypropylene resin foam according to claim 1 or 2, which is obtained by an extrusion foaming method. The polypropylene resin foam according to any one of claims 1 to 3, wherein the polypropylene resin foam has a density of 90 or more and less than 250 kg / m ^{3 and} a sheet or plate shape having a thickness of 0.5 to 10 mm.