JP2007091974A - Thermoplastic foamed resin composition - Google Patents

Abstract

[Object] To provide a composition for a thermoplastic foam resin capable of obtaining a foam having an excellent molded appearance and flexibility.
[Structure] Hydrogenated block copolymer obtained by hydrogenating a block copolymer having at least one polymer block A mainly composed of an aromatic vinyl compound and at least one polymer block B mainly composed of a conjugated diene compound 50 to 200 parts by mass of a non-aromatic rubber softener (b) and 5 to 50 parts of a polyethylene resin (c) polymerized using a metallocene catalyst are mixed with 100 parts by mass of the blend (a). A thermoplastic foamed resin composition obtained by blending 0.5 to 5 parts by mass of a chemical foaming agent (e) having a decomposition temperature of 160 ° C. or less with respect to 100 parts by mass of the obtained resin composition.
[Selection figure] None

Description

The present invention relates to a thermoplastic foamed resin composition mainly composed of an aromatic vinyl compound-based thermoplastic elastomer, particularly a styrene-based thermoplastic elastomer.
The thermoplastic foamed resin composition obtained in the present invention is excellent in foamability, and the foam obtained by foam-molding the thermoplastic foamed resin composition has fine foam cells, and its uniformity and Dispersibility is better than before, and flexibility is improved.

  Thermoplastic foams can be used to provide features such as weight reduction, thermal insulation, softening, and shock absorption, so they are widely used as components for automobile interior materials, information equipment, home appliances, and shock absorbers for vibration and noise. Has attracted attention. Of these, styrene thermoplastic elastomers that are recyclable, flexible, and relatively inexpensive are drawing attention. However, since the foam of the composition containing a styrene-type thermoplastic elastomer until now can only be obtained with a low foaming ratio or is originally a foam of a composition with poor flexibility, the resulting foam There were problems such as poor flexibility.

  Examples of obtaining a foamed molded article by foaming a resin composition containing a styrenic thermoplastic elastomer include (1) a melt tension and melt ductility above a certain value under specific conditions, a specific hardness, and a specific range of MFR. Extruded foam molded product obtained by extrusion foam molding of a composition comprising a styrenic thermoplastic elastomer and a foaming agent (see Patent Document 1); (2) Uniaxial melting at each of two elongation deformation strains at any two points One or two selected from the group consisting of a polypropylene resin in which the ratio of elongational viscosity satisfies the specific formula and does not contain a gel component, and a polyethylene resin, olefin elastomer, and styrene elastomer having a specific range of flexural modulus Disclosed is a resin composition comprising more than one kind of flexibility-imparting component, which is excellent in foamability (see Patent Document 2); 3) A foamed resin composition obtained by blending a specific amount of a chemical foaming agent with a resin composition containing a styrene-based thermoplastic block copolymer, polyoctenamer, and, if necessary, a polyolefin-based elastomer in a specific ratio (see Patent Document 3) ) Etc. are known.

JP-A-7-18106 JP-A-8-81590 JP-A-6-73218

  The extruded foam molded body disclosed in Patent Document 1 has a high JIS-A hardness of 60 to 65 according to JIS K 6301 (the JIS-A hardness at the stage of the styrene thermoplastic elastomer composition before foaming is 81 to 89). And higher), there is room for improvement in flexibility. The evaluation of the flexibility of the foamed molded product obtained by foaming the resin composition disclosed in Patent Document 2 is merely a visual observation of the occurrence of folding when the foamed molded product is bent at an angle of 90 °. There is a problem with quantitativeness. The foamed resin composition disclosed in Patent Document 3 provides a foam having good foam cell uniformity and flexibility, but a suitable styrene-based thermoplastic block copolymer is an unhydrogenated product (SBS, SIS), and there is room for improvement in the weather resistance and heat resistance of the foam obtained.

In order to impart flexibility to a foamed molded article obtained by foaming a resin composition containing a styrenic thermoplastic elastomer, the content ratio of the styrenic thermoplastic elastomer in the resin composition is increased. Methods such as increasing the addition ratio are conceivable. However, as described above, the former has a tendency to lower the foamability, and the latter has a problem that the rubber softener bleeds out from the foamed molded product, resulting in surface stickiness.
Thus, an object of the present invention is to provide a thermoplastic foamed resin composition capable of obtaining a foamed molded article having uniform and fine foamed cells without impairing the flexibility of the styrenic thermoplastic elastomer. That is.

According to the present invention, the above object is
[1] Hydrogenated block copolymer obtained by hydrogenating a block copolymer having at least one polymer block A mainly composed of an aromatic vinyl compound and at least one polymer block B mainly composed of a conjugated diene compound. 50 to 200 parts by mass of the non-aromatic rubber softener (b) and 5 to 50 parts by mass of the polyethylene resin (c) polymerized using a metallocene catalyst are mixed with 100 parts by mass of the blend (a). A thermoplastic foamed resin composition obtained by blending 0.5 to 10 parts by mass of a chemical foaming agent (e) having a decomposition temperature of 160 ° C. or less with respect to 100 parts by mass of the resin composition obtained in this manner;
[2] Hydrogenated block copolymer obtained by hydrogenating a block copolymer having at least one polymer block A mainly composed of an aromatic vinyl compound and at least one polymer block B mainly composed of a conjugated diene compound. Non-aromatic rubber softening agent (b) 50-200 parts by mass, polyethylene-based resin (c) 5-50 parts by mass polymerized using a metallocene catalyst, and high Chemical foaming agent (e) 0.5 to 10 parts by mass with a decomposition temperature of 160 ° C. or less with respect to 100 parts by mass of a resin composition obtained by mixing 0.1 to 50 parts by mass of a melt tension polypropylene resin (d) A thermoplastic foamed resin composition comprising a part;
[3] A foam obtained by foam-molding the thermoplastic foamed resin composition of [1] or [2].

  ADVANTAGE OF THE INVENTION According to this invention, the thermoplastic foamed resin composition which is excellent in the softness | flexibility when foamed and can be used for a wide range of uses can be obtained. Moreover, since the foam obtained by foam-molding such a thermoplastic foamed resin composition has a high foaming ratio, the amount of the resin used is small and lightweight, which is advantageous from the viewpoint of energy saving and economics. Furthermore, when producing a foam, a general molding method such as injection molding or extrusion molding can be applied as a foam molding method. In particular, the extrusion molding method can be continuously produced, and is used for automobile interior and exterior. It is suitable for manufacturing mass-produced products such as products.

  In the hydrogenated block copolymer (a) used in the present invention, examples of the aromatic vinyl compound constituting the polymer block A include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, and p-methyl. Styrene, pt-butylstyrene, 2,4-dimethylstyrene, 2,4,6-trimethylstyrene, p-methoxystyrene, monofluorostyrene, monochlorostyrene, dichlorostyrene, vinylnaphthalene, vinylanthracene, indene, acetonaphthylene, etc. Is mentioned. Among these, styrene, p-methylstyrene, or α-methylstyrene is preferable. An aromatic vinyl compound may be used individually by 1 type, and may use 2 or more types together.

The content of the structural unit derived from the aromatic vinyl compound in the hydrogenated block copolymer (a) is preferably in the range of 10 to 45% by mass, and in the range of 10 to 35% by mass, It is more preferable from the viewpoint of flexibility and mechanical properties of the foam obtained from the plastic foamed resin composition. When the content is less than 10% by mass, the mechanical properties of the foam obtained from the thermoplastic foamed resin composition tend to be insufficient. On the other hand, when the content exceeds 45% by mass, the flexibility of the foam Tends to be damaged. The content of the polymer block A in the hydrogenated block copolymer (a), for example, can be determined by such ^{1 H-NMR} spectrum.

  On the other hand, as the conjugated diene compound constituting the polymer block B in the block copolymer before hydrogenation of the hydrogenated block copolymer (a), for example, butadiene, isoprene, 2,3-dimethyl-1, 3-butadiene 1,3-pentadiene, 1,3-hexadiene and the like. As the conjugated diene compound, one kind may be used alone, or two or more kinds may be used in combination, and in that case, the mixing ratio (mass ratio) of each compound is not particularly limited. Among these, butadiene, isoprene or a mixture of butadiene and isoprene is preferable, and a mixture of butadiene and isoprene is more preferable.

  In the polymer block B before hydrogenation, the microstructure of the structural unit derived from the conjugated diene compound is not particularly limited. For example, when the polymer block B is composed of butadiene, The ratio is preferably 5 to 90 mol%, more preferably 20 to 70 mol%. When the polymer block B is composed of isoprene or a mixture of butadiene and isoprene, the total of 1,2-bond units and 3,4-bond units is 4 to 80 mol%. It is preferable that it is 6-60 mol%.

  In the polymer block B in the hydrogenated block copolymer (a), 80% or more of carbon-carbon double bonds derived from the conjugated diene compound are preferably hydrogenated, and 90% or more are hydrogenated. More preferably. If it is less than 80%, the heat resistance and weather resistance of the foam obtained from the thermoplastic foamed resin composition tend to be impaired.

  The bonding mode of the polymer block A and the hydrogenated polymer block B in the hydrogenated block copolymer (a) may be linear, branched, star-shaped, or any combination thereof. A triblock structure represented by B-A is preferred in view of rubber elasticity, mechanical properties, and handleability.

  The hydrogenated block copolymer (a) preferably has a weight average molecular weight (hereinafter abbreviated as “Mw”) in the range of 30,000 to 300,000, and more preferably in the range of 50,000 to 150,000. If the Mw of the hydrogenated block copolymer (a) is less than 30000, the rubber elasticity and mechanical properties of the obtained thermoplastic foamed resin composition are liable to deteriorate, whereas if it exceeds 300000, the obtained thermoplastic foam is obtained. The fluidity of the resin composition becomes poor and the molding processability tends to be poor. In addition, Mw in this specification means Mw of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

  The hydrogenated block copolymer (a) can be produced, for example, by the following method. That is, a block copolymer is formed by sequentially anionic polymerization of an aromatic vinyl compound and a conjugated diene compound in an organic solvent inert to anionic polymerization such as n-hexane and cyclohexane using an alkyl lithium compound as a polymerization initiator. Then, the resulting block copolymer is supported on a carrier such as carbon, alumina, diatomaceous earth, or the like, in a saturated hydrocarbon solvent such as cyclohexane, Raney nickel; metal such as Pt, Pd, Ru, Rh, Ni, etc. Heterogeneous catalyst; Ziegler-type catalyst comprising a combination of an organometallic compound comprising a Group 8-10 metal such as cobalt or nickel and an organoaluminum compound or organolithium compound such as triethylaluminum or triisobutylaluminum; titanium Transition metals such as zirconium and hafnium In the presence of a hydrogenation catalyst such as a metallocene catalyst comprising a combination of a s (cyclopentadienyl) compound and an organometallic compound comprising lithium, sodium, potassium, aluminum, zinc or magnesium, the reaction temperature is usually 20 to 20 The reaction can be carried out at a temperature in the range of 100 ° C. and a hydrogen pressure in the range of 0.1 to 10 MPa, and a hydrogenated product of the block copolymer, that is, a hydrogenated block copolymer (a) can be obtained.

  In addition, the hydrogenation rate of the carbon-carbon double bond derived from the conjugated diene compound of the polymer block B in the hydrogenated block copolymer (a) is determined by iodine value measurement method, infrared spectrophotometer, nuclear magnetic resonance. The amount of the carbon-carbon double bond in the polymer block B before and after the hydrogenation reaction is measured by a measuring means such as and can be calculated from the measured value.

  As the non-aromatic rubber softener (b) used in the present invention, a non-aromatic rubber softener (b) having a ratio of carbon atoms constituting the aromatic component of less than 50% of the total carbon number is used. Non-aromatic rubber softeners are known per se, and in the present invention, these known ones can be used without particular limitation. Non-aromatic rubber softener (b), for example, paraffinic process oil, naphthenic process oil, white oil, mineral oil, ethylene and α-olefin oligomer, paraffin wax, liquid paraffin, polybutene, low molecular weight polybutadiene Etc. The non-aromatic rubber softener (b) may be used alone or in combination of two or more. Among these, paraffinic process oil is preferable. As paraffin-based process oils, Diana Process Oil Series (trade name) marketed by Idemitsu Kosan Co., Ltd. Syntac Series (trade name) marketed by Kobe Oil Chemical Co., Ltd., JOMO marketed by Japan Energy Co., Ltd. Process P series (trade name), Thumper series (trade name) marketed by Nippon Oil Corporation, and Fukkor Process P series (trade name) marketed by Fuji Kosan Co., Ltd.

  The amount of the non-aromatic rubber softener (b) used must be in the range of 50 to 200 parts by mass with respect to 100 parts by mass of the hydrogenated block copolymer (a). It is preferable that it is the range of a mass part. When the amount is less than 50 parts by mass, the molding processability of the obtained thermoplastic foamed resin composition tends to be impaired. When the amount exceeds 200 parts by mass, the mechanical properties of the foam obtained from the thermoplastic foamed resin composition Decreases and the problem arises that the non-aromatic rubber softener (b) bleeds out of the foam.

  The polyethylene-based resin (c) polymerized using a metallocene catalyst used in the present invention (hereinafter sometimes simply referred to as polyethylene-based resin (c)) is a transition metal bis (such as titanium, zirconium, hafnium). (Cyclopentadienyl) compound directly produced by copolymerizing ethylene and 1-butene, 1-hexene, 1-octene or the like preferably α-olefin having 4 to 12 carbon atoms in the presence of a so-called metallocene catalyst. It means chain low density polyethylene. These polyethylene resins (c) are industrially manufactured and marketed, for example, the Kernel Series (trade name) marketed by Nippon Polyethylene Co., Ltd., and the Evolue Series (trade name) marketed by Prime Polymer Co., Ltd. Engage series (trade name) marketed by Dow Chemical Company.

  The amount of the polyethylene resin (c) used must be 5 to 50 parts by mass with respect to 100 parts by mass of the hydrogenated block copolymer (a), and should be in the range of 10 to 40 parts by mass. Is more preferable. In the present invention, the polyethylene resin (c) has an effect of improving the dispersibility of the resin component to be used, and when the blending amount is less than 5 parts by mass, a sufficient dispersion effect cannot be obtained, while 50 masses. When exceeding a part, the softness | flexibility of a foam falls.

  The high melt tension polypropylene resin (d) further used as necessary in the present invention is a material having a unique rheological property improved by low melt tension, which was a drawback of the conventional polypropylene resin. It is commercially available as suitable for foam molding, extrusion thermoforming, extrusion coating, fiber and blow molding. For example, the HMS-PP series (trade name) marketed by Sun Allomer Co., Ltd. You can cite the newstrain series (product name).

  When the high melt tension polypropylene resin (d) is further blended, the amount used must be 0.1 to 50 parts by mass with respect to 100 parts by mass of the hydrogenated block copolymer (a). The range of 5 to 30 parts by mass is more preferable. When it exceeds 50 mass parts, the softness | flexibility of the foam obtained will fall.

  In the present invention, a chemical foaming agent (e) having a decomposition temperature of 160 ° C. or lower is used. When a chemical foaming agent having a decomposition temperature exceeding 160 ° C. is used, the foaming ratio is low and the foaming state is also deteriorated. The type of the chemical foaming agent (e) is not particularly limited as long as it decomposes at 160 ° C. or lower and generates an inert gas. An inorganic foaming agent can be mentioned, and a sodium hydrogencarbonate-based foaming agent is particularly preferable in view of the decomposition temperature. In addition, it is common practice to use a mixture of different types of chemical foaming agents. Furthermore, a foaming aid for adjusting the decomposition temperature, a dispersing agent or a nucleating agent for uniformly dispersing the foaming agent may be used.

  The amount of the chemical foaming agent (e) used is the hydrogenated block copolymer (a), the non-aromatic rubber softener (b), the polyethylene resin (c) and, if necessary, a high melt tension. It is used in the range of 0.5 to 10 parts by mass, preferably in the range of 1 to 5 parts by mass, per 100 parts by mass of the resin composition obtained by mixing the polypropylene resin (d) at a predetermined blending ratio. When the amount is less than 0.5 parts by mass, the foamability is not good, and when the amount exceeds 10 parts by weight, it is not preferable due to economic problems.

  If necessary, the thermoplastic foamed resin composition of the present invention may further contain various additives such as an antioxidant, an ultraviolet absorber, a colorant, an antistatic agent, and a lubricant depending on the purpose of use. May be.

  The thermoplastic foamed resin composition of the present invention comprises, for example, a hydrogenated block copolymer (a), a non-aromatic rubber softener (b), a polyethylene resin (c) and, if necessary, a high melt tension polypropylene system. Resin (d) is kneaded in advance with a single screw extruder, twin screw extruder, Brabender, Banbury mixer, kneader, etc. to obtain a resin composition, and then the chemical foaming agent (e) and further optional components are added and kneaded. Can be obtained. Preferably, the foam is obtained by subjecting the thermoplastic foamed resin composition obtained in the kneading step to a molding step such as injection molding or extrusion molding as it is.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention in detail, this invention is not limited at all by these Examples. In addition, the physical property evaluation of the foam obtained by each Example and the comparative example was performed as follows.

<1> Foaming ratio It calculated | required by the following formula | equation from the specific gravity of the resin composition before foaming evaluated by the underwater substitution method, and the specific gravity of the foam after foaming. In addition, about the specific gravity of the resin composition before foaming, each component (excluding the chemical foaming agent) of the ratio of each Example and Comparative Example was kneaded with a Brabender at 140 ° C. for 5 minutes to prepare a resin composition, The specific gravity of the resin composition was used.
Foaming ratio = (specific gravity of resin composition before foaming) / (specific gravity of foam after foaming)

<2> JIS-A Hardness In accordance with JIS K 6253, the hardness was measured using a JIS-A type hardness meter.

<3> Appearance The foams obtained in each of the examples and comparative examples were visually evaluated, and those that had a good appearance were evaluated as excellent, those that were poor in appearance were evaluated as poor, and the space between them was evaluated as good and acceptable. did.

Moreover, the detail of the component used by the Example and the comparative example is as follows.
Hydrogenated block copolymer (a)
A triblock copolymer was obtained by sequentially anionic polymerization of styrene, a mixture of isoprene / butadiene = 50/50 (mass ratio), and styrene in cyclohexane using s-butyllithium as a polymerization initiator. The triblock copolymer was subjected to a hydrogenation reaction at 75 ° C. for 5 hours under a hydrogen pressure atmosphere of 0.8 MPa using a Ziegler catalyst in cyclohexane, and then the catalyst was removed to obtain a styrene content of 30 mass. %, Mw = 100000, and a hydrogenated block copolymer (a) having a hydrogenation rate of 98% was obtained.

Non-aromatic rubber softener (b)
“Diana Process PW-380” (trade name, manufactured by Idemitsu Kosan Co., Ltd., paraffinic process oil, kinematic viscosity: 381.6 mm ² / s (40 ° C.), pour point: −15 ° C.)

Polyethylene resin polymerized with metallocene catalyst (c)
“Kernel KS560” (trade name, manufactured by Nippon Polyethylene, density 0.90 g / cm ³ , MFR = 16.5 g / 10 min (190 ° C., 21 N))
Normal polyethylene (f)
“NOVATEC LD LJ800” (trade name, manufactured by Nippon Polyethylene, density 0.92 g / cm ³ , MFR = 20 g / 10 min (190 ° C., 21 N))

High melt tension polypropylene resin (d)
“HMS-PP PF814” (trade name, manufactured by Sun Allomer, density 0.90 g / cm ³ , MFR = 2.8 g / 10 min (190 ° C., 21 N))
Normal polypropylene (g)
“J225T” (trade name, manufactured by Grand Polymer Co., Ltd., density 0.90 g / cm ³ , MFR = 9 g / 10 minutes (190 ° C., 21 N))

Chemical foaming agent (e) with a thermal decomposition temperature of 160 ° C or lower
“Selfon SC-P” (trade name, manufactured by Eiwa Kasei Co., Ltd., component: sodium bicarbonate, decomposition temperature: 150 ° C., amount of generated gas 140 ml / g (0 ° C., 1 atm))
Chemical foaming agent with a thermal decomposition temperature higher than 160 ° C (h)
“Polyslen EE207” (trade name, manufactured by Eiwa Kasei Co., Ltd., component: carbon dioxide gas, decomposition temperature: 205 ° C., amount of generated gas 120 ml / 5 g (0 ° C., 1 atm) PE master batch)

Antioxidant (i)
"Irganox 1010" (trade name, manufactured by Ciba Specialty Chemicals, pentaerythrityl tetrakis (3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate)

Examples 1-2 and Comparative Examples 1-4
The above hydrogenated block copolymer (a), softener for non-aromatic rubber (b), polyethylene resin (c) or ordinary polyethylene (f), high melt tension polypropylene resin (d) or ordinary In accordance with the composition shown in Table 1, polypropylene (g), chemical foaming agent (e) or chemical foaming agent (h), and antioxidant (i) were premixed in advance and then a twin-screw extruder having an inner diameter of 25 mm. Supplied to. After melt-kneading at each temperature shown in Table 1, it was extruded from a rectangular die provided at the outlet of the twin-screw extruder to obtain a foam (sheet) having a thickness of about 2 mm and a width of about 10 mm. Using the foam thus obtained, the physical properties were evaluated according to the above. The results are summarized in Table 1.

  As is clear from the results in Table 1, the foams obtained from the thermoplastic foamed resin compositions of Examples 1 and 2 are improved in comparison with the comparative example in the balance of foaming ratio, foam appearance, and flexibility. .

The thermoplastic foamed resin composition obtained in the present invention is a composite molding having a foam layer and a hard material layer by combining, for example, a foam having a soft feel or a hard material for obtaining a certain strength as a base material. Used as a body, automotive interior materials (seat skins, pillars, weather strips, etc.), exterior materials (malls, trims, etc.), industrial products (pipes, tubes, wire covering materials, etc.), furniture (chair seats and armrests) Etc.) and parts and products such as miscellaneous goods (shoes, slippers, etc.).

Claims (3)

Hydrogenated block copolymer obtained by hydrogenating a block copolymer having at least one polymer block A mainly composed of an aromatic vinyl compound and at least one polymer block B mainly composed of a conjugated diene compound (a ) It is obtained by mixing 50 to 200 parts by mass of a non-aromatic rubber softener (b) and 5 to 50 parts by mass of a polyethylene resin (c) polymerized using a metallocene catalyst with respect to 100 parts by mass. A thermoplastic foamed resin composition obtained by blending 0.5 to 10 parts by mass of a chemical foaming agent (e) having a decomposition temperature of 160 ° C. or less with respect to 100 parts by mass of the resin composition. The thermoplastic foam according to claim 1, wherein 0.1 to 50 parts by mass of a high melt tension polypropylene resin (d) is further added to 100 parts by mass of the hydrogenated block copolymer (a). Resin composition. A foam obtained by subjecting the thermoplastic foamed resin composition according to claim 1 or 2 to foam molding.