JP4834602B2 - Resin composition for pier and pier - Google Patents

Description

  The present invention relates to a resin composition for piers, which is a kind of building exterior base material, and a pier obtained by extrusion foam molding using the resin composition.

  Wood has been used for a long time as a pedestal used as a building base material for trunk edges, tile piers, formwork, etc., but nowadays it is made of so-called plastic from the viewpoint of depletion of resources and environmental protection. Synthetic woods, especially those made of expanded polystyrene, are widely used (see Patent Document 1).

  Now, in order to prevent the exhaustion of petroleum resources, the reuse of various plastic products is being studied. Further, since polystyrene is an expensive plastic that is difficult to obtain, it is desired to reuse it. In fact, Patent Document 2 proposes a roof tile using recycled expanded polystyrene.

Moreover, as a synthetic resin composition for woodwork using polystyrene, Patent Document 3 proposes a combination of a polyolefin resin having a melt flow rate (MFR) of 0.3 to 30 and polystyrene having an MFR of 0 to 30. Has been.
Japanese Utility Model Publication No. 63-9682 JP 2004-218307 A Japanese Patent Laid-Open No. 10-101812

  However, piers such as trunk edges have rigidity (bending strength), impact resistance that does not cause cracking when nails and screws are driven in, and strength decreases even when the driven nails and screws are pulled out. Not only is it necessary to maintain strength (pullability of nails or screws), but it is also required to have no burrs (grindability) and lightness when cut with a saw, Conventionally known plastic piers do not satisfy all of the above characteristics, and improvements are desired. In particular, those using recycled polystyrene, such as the roof tile of Patent Document 2, are unsatisfactory in their strength characteristics. Moreover, when a crosspiece is molded using the synthetic resin composition for woodworking of Patent Document 3, the rigidity, impact resistance, or nail or screw retaining properties are unsatisfactory.

  Accordingly, the object of the present invention is to exhibit excellent properties in terms of rigidity, impact resistance, nail or screw retention, grinding workability, and light weight, and also when molded using recycled products. It is in providing the resin composition for piers which has the characteristics of the following, and the pier formed from the composition.

According to the present invention,
(A) 100 parts by weight of polystyrene having a melt flow rate (MFR) of 0.1 to 20 g / 10 min,
(B) 2.5 to 25 parts by weight of a polyethylene-based resin having an MFR in the range of 0.1 to 20 g / 10 min and in the range of 0.1 to 10 times the MFR of the polystyrene.
(C) 2.5-25 parts by weight of a polypropylene resin having an MFR in the range of 0.1 to 20 g / 10 min and 0.1 to 10 times the MFR of the polystyrene resin.
(D) Styrenic rubber 10 to 30 parts by weight (E) 0.1 to 3 parts by weight of a foaming agent,
The resin composition for piers comprising the polypropylene resin (PP) and the polyethylene resin (PE) in a weight ratio of PE / PP = 0.1 to 2.0. Is provided.

According to the present invention, there is also provided a crosspiece obtained by extrusion foam molding of the above resin composition.
It is preferable that the pier is foam-molded in a range where the expansion ratio is 1.8 to 3.0 times.

  The crosspiece obtained by extrusion foam molding of the crosspiece resin composition of the present invention is not only excellent in light weight, but also has excellent rigidity and impact resistance, as will be apparent from the examples described later. For example, the bending strength is 18 MPa or more, and when a nail or a screw is driven, cracks such as cracks do not occur, the nail and the screw are excellently retained, and a good strength is obtained even when the nail is pulled out. Show. Furthermore, the occurrence of burrs when cut with a saw is small, and the grindability is also good. In addition to polystyrene, polyethylene resin and polypropylene resin are blended, which is advantageous in terms of cost.

  Furthermore, the resin composition of the present invention is excellent in moldability and recyclability, and even when recycled products are used as polystyrene, polyethylene resin and polypropylene resin, a pier having the above characteristics is molded. be able to.

  The resin composition for piers of the present invention comprises (A) polystyrene, (B) polyethylene resin, (C) polypropylene resin, (D) styrene rubber, and (E) a foaming agent. Various additives are blended.

(A) Polystyrene:
Polystyrene is a base material for the resin composition of the present invention. By using polystyrene as a base material, it is possible to form a crosspiece having excellent mechanical properties. In the present invention, the post-styrene melt flow rate (MFR: ASTM D1236, 230 ° C.) needs to be in the range of 0.1 to 20 g / 10 min, particularly 1.0 to 10 g / 10 min. When the MFR is larger than the above range, molding becomes difficult, and when the MFR is smaller than the above range, properties such as strength are deteriorated and foaming becomes difficult.

(B) Polyethylene resin:
The polyethylene-based resin is a component for imparting impact resistance, and is used in an amount of 2.5 to 25 parts by weight, particularly 8 to 20 parts by weight, per 100 parts by weight of the polystyrene (A). When this amount is less than the above range, the impact resistance is lowered, and for example, cracking or the like occurs when nails or screws are driven. Moreover, if it is used in a large amount, the rigidity becomes unsatisfactory.

  Further, the MFR (ASTM D1236, 190 ° C.) of this polyethylene resin needs to be in the range of 0.1 to 20 g / 10 min, particularly 1.0 to 10 g / 10 min, similar to the above polystyrene. It is important that it is in the range of 0.1 to 10 times the MFR of the polystyrene. That is, if both MFRs are separated from each other, molding processability is deteriorated.

  Polyethylene resins include high density polyethylene (HDPE), medium density polyethylene (MDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), etc., but the MFR is within the above-mentioned range. As long as any of them can be used, each can be used alone or in combination of two or more.

(C) Polypropylene resin:
Polypropylene resin is a component for reinforcing rigidity, and is used in an amount of 2.5 to 25 parts by weight, particularly 10 to 20 parts by weight per 100 parts by weight of polystyrene. If this amount is less than the above range, the rigidity will be lowered, for example, the machinability will be lowered, and when the resulting pier is cut with a saw, the amount of burrs will be increased. Moreover, when it uses it in large quantities, it will become difficult to perform sufficient foaming.

  Furthermore, this polypropylene resin (PP) should be blended in such a ratio that the weight ratio (PE / PP) to the polyethylene resin (PE) is 0.1 to 2.0. That is, if a polypropylene resin is used in a larger amount than the above range compared to polyethylene, foaming becomes difficult, and if the amount of the polypropylene resin is less than the above range, the bending strength decreases, for example, The bending strength of the obtained pier is less than 18 MPa.

  Furthermore, in order to ensure moldability, the MFR (ASTM D1236, 230 ° C.) of this polypropylene resin is also in the range of 0.1 to 20 g / 10 min, particularly 1.0 to 10 g / 10 min, like the above polystyrene. It is necessary.

  As the polypropylene-based resin, any one having the above-mentioned MFR can be used in an isotactic structure or a syndiotactic structure. Polymerized polypropylene or block copolymerized polypropylene can also be used. Examples of the comonomer in these copolymers include olefins other than propylene, such as ethylene and 1-butene, or a combination of two or more. In the present invention, homopolypropylene is most preferable particularly from the viewpoint of rigidity.

(C) Styrene rubber:
The component (C) styrene rubber, like the polyethylene resin, is a component for improving the impact resistance, but the compatibility of the polyethylene resin or polypropylene resin with the base polystyrene (A) is improved. It is also a component for improving. That is, when other rubber components (for example, acrylic rubber) other than styrene rubber are used, the compatibility with polystyrene, polyethylene resin, or polypropylene resin is extremely low, resulting in poor dispersion and the like. The characteristics will deteriorate.

  Such a styrene rubber is a block copolymer having polystyrene phases at both terminal phases, and has an intermediate layer with polybutadiene and polyisoprene phases, respectively. It can be easily processed with a general plastic molding machine. These are called butadiene-styrene copolymer rubber (SBS) and isoprene-styrene copolymer rubber (SIS), but have a large impact resistance improving effect, from the viewpoint of resin modification, SBS rubber is optimal. Those having a polybutadiene content generally in the range of 5 to 80% by weight, particularly 50 to 70% by weight, are readily available.

  Such styrene rubber is used in an amount of 10 to 30 parts by weight, particularly 10 to 20 parts by weight, per 100 parts by weight of polystyrene. If this amount is less than the above range, poor dispersion of polyethylene resin or polypropylene resin will occur, not only the overall characteristics of the molded pier will be lowered, but also the moldability of the resin composition will be lowered. Resulting in. Further, use in a larger amount than the above range results in a decrease in rigidity.

(E) Foaming agent:
There are various types of foaming agents, but in the present invention, chemical foaming agents are used in particular. That is, physical foaming using gas impregnation and expansion requires a special facility for foaming, which is disadvantageous in terms of economy and productivity.

  Examples of the foaming agent used in the present invention include, but are not limited to, inorganic foaming agents such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, and ammonium nitrite; N, N′-dimethyl- Nitroso compounds such as N, N'-dinitroso / terephthalamide, N, N'-dinitroso / pentamethylene / tetramine; azodicarbonamide, azodicarboxamide, azobisisobutyronitrile, azocyclohexylnitrile, azodiaminobenzene, barium Azo compounds such as azodicarboxylate; sulfonyl hydrazide compounds such as benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, P, P′-oxybis (benzenesulfonyl hydrazide), diphenylsulfone-3,3′-disulfonyl hydrazide; calcium Azide compounds such as zido, 4,4′-diphenyldisulfonyl azide, p-toluenesulfonyl azide, etc. can be mentioned, and these can be used alone or in combination of two or more. It can also be used.

  Such a foaming agent is used in such an amount that the expansion ratio is 1.8 to 3.0 times, depending on the types, physical properties and blending amounts of the components (A) to (D) used. Is used in an amount of 0.1 to 3 parts by weight per 100 parts by weight of polystyrene (A). When the amount is smaller than this, foaming is insufficient, and the pier to be molded is unsatisfactory in terms of light weight and the like. Further, if it is used in a larger amount than the above range, foaming becomes excessive, and the rigidity of the molded pier is unsatisfactory, and particularly, a large amount of burrs are generated when it is cut with a saw.

(Various additives):
In the resin composition for piers of the present invention, various additives known per se can be blended in amounts as long as the properties such as the rigidity and impact resistance of the pier are not impaired.

  For example, a foaming aid can be blended in order to lower the decomposition temperature of the foaming agent, accelerate the decomposition, and make the bubbles uniform. Examples of such foaming aids include organic acids such as salicylic acid, phthalic acid and stearic acid; urea and derivatives thereof. Moreover, inorganic fine powders such as talc, various clays, calcium silicate, magnesium silicate and the like can be blended for the purpose of adjusting bubbles. In addition, for the purpose of improving processability and moldability, a lubricant such as a fatty acid metal soap such as barium stearate or magnesium stearate, a fatty acid amide, a polyethylene wax, or a microcrystalline wax may be blended. Furthermore, wood powder can be blended as appropriate for weight reduction. As such wood powder, those having a particle size of 100 mesh size or less (150 μm or less) are used. For example, any wood powder such as conifer, hardwood, lauan, etc. is used, and sawdust produced as a by-product during sawing. Sawdust and the like can also be powdered by ball milling or the like. In addition to these additives, fillers, colorants, heat stabilizers, weathering stabilizers, antioxidants, anti-aging agents, light stabilizers, UV absorbers, antistatic agents, etc., as necessary. As needed, it can mix | blend suitably.

<Manufacture of piers>
In the present invention, a pier having a desired shape is manufactured by preparing a resin composition containing each of the above-described components and then foam-molding the resin composition.

  The resin composition can be prepared by means known per se, for example, dry blending or melt blending. For example, each component can be mixed by dry blending using a blender, a Henschel mixer or the like, or can be performed by melt blending using a single or twin screw extruder, a Banbury mixer, a kneader or the like.

  There is no restriction | limiting in particular in the order of a mixing | blending, All the components may be blended simultaneously, and a component can also be blended in multiple steps. For example, the components excluding the blowing agent can be premixed in advance, and the blowing agent can be added to the premix to continue the blending. Alternatively, the foaming agent or other auxiliary agent can be premixed, and the premix can be added to the premix. Blending can also be continued by adding the resin or rubber component of (A) to (D).

  In general, foaming may be performed inside the extruder or outside the extruder, but in general, foaming is preferably performed inside the extruder because the operation is simple. In extrusion molding, each component is dry blended and supplied to the hopper of the extruder. As the extruder, a known extruder having a single-screw or a twin-screw is used. Each component and the foaming agent are mechanically melted and kneaded in an extruder, and extruded into the air through a die to form a foamed molded product. This extrusion foam molding has the advantage that the kneading, extrusion and foaming of each component are carried out by a single extruder, and the operation is simple and the productivity is high. In this case, the temperature at the time of melt kneading (cylinder temperature) is naturally set to a temperature not lower than the melting point of each component and not lower than the decomposition temperature of the foaming agent.

  If necessary, the foamed molded product extruded from the molding die can be passed through a sizing die to stabilize the dimensions and shape, thereby obtaining a target pier.

  Thus, the foaming magnification is 1.8 to 3.0 times, which is rich in lightness, and an inexpensive pier can be obtained. Such a pier has a bending strength of 18 MPa or more, is stiff, has excellent machinability, has very few burrs when cut with a saw, and has excellent impact resistance. For example, the nailing property is good, there is almost no cracking when the nail is driven, the pulling property of the nail is good, and the strength reduction when the nail is pulled is small.

  Furthermore, in the present invention, even when a recycled product is used as the resin components (A) to (C) described above, a crosspiece having the above-described excellent characteristics can be obtained.

  The pier according to the present invention is useful as a tile pier, an architectural formwork, a trunk edge, and the like.

  The invention is further illustrated in the following examples. The following examples are illustrative and the invention is not limited in any way.

Various components used in the following examples and comparative examples are as follows.
(A) Polystyrene Polystyrene (A-1): Recycled product
Specific gravity: 1.05
MFR: 1.5g / 10min
Polystyrene (A-2)
Specific gravity: 1.05
MFR: 8.0g / 10min
(B) Polyethylene resin Polyethylene (B-1): Recycled product
Specific gravity: 0.95
MFR: 2.5g / 10min
Polyethylene (B-2)
Specific gravity: 0.95
MFR: 10.0g / 10min
(C) Polypropylene resin Polypropylene (C-1): Recycled product
Specific gravity: 0.90
MFR: 2.5g / 10min
Polypropylene (C-2)
Specific gravity: 0.90
MFR: 10.0g / 10min
(D) Styrene rubber SBS (specific gravity: 0.96)
(E) Blowing agent Sodium bicarbonate Azodicarboxamide (ADCA)

(Examples 1-3, Comparative Examples 1-4)
Various components were charged into the extruder at the weight ratios shown in Table 1, melt-kneaded at a cylinder temperature of 130 to 190 ° C., foamed and extruded to form a 15 mm × 30 mm prismatic shape.
The obtained pier was measured for the specific gravity, density, expansion ratio, nail punching property, nail punching property, machinability and bending strength by the following methods, and the results are shown in Table 1.

(1) Specific gravity It calculated | required by calculation from specific gravity of each material used.
(2) Density (g / cm ³ )
It calculated | required based on the underwater substitution method of JISK-7112.
(3) Foaming ratio It calculated from the specific gravity and density which were calculated | required above.
(4) Nail driving characteristics A ring nail (made of stainless steel; φ = 2.5 mm, L = 50 mm) was driven at −10 ° C. with the 30 mm side up and down into the portion 10 mm inside from the small edge of the pier and evaluated by the number of cracks did. The evaluation criteria are as follows.
○: Number of cracks 0/20 ×: Number of cracks 0/20 or more (5) Nail extraction characteristics When the same ring nail as above is used, the ring nail that has been pierced with 30 mm sides up and down and pulled out at a speed of 10 mm / min Was measured and evaluated with an average value of N = 10.
(6) Cutting property The amount of burrs generated when cutting with an electric saw for woodworking was visually determined.
○: Almost no burrs are generated.
X: A lot of burrs were generated.
(7) Bending strength Based on JIS K7222-1, it measured on conditions of fulcrum distance: 100mm and speed 10mm / min.

Claims (3)

(A) 100 parts by weight of polystyrene having a melt flow rate (MFR) of 0.1 to 20 g / 10 min,
(B) 2.5 to 25 parts by weight of a polyethylene-based resin having an MFR in the range of 0.1 to 20 g / 10 min and in the range of 0.1 to 10 times the MFR of the polystyrene.
(C) 2.5-25 parts by weight of a polypropylene resin having an MFR in the range of 0.1 to 20 g / 10 min and 0.1 to 10 times the MFR of the polystyrene resin.
(D) Styrenic rubber 10 to 30 parts by weight (E) 0.1 to 3 parts by weight of a foaming agent,
The resin composition for piers comprising the polypropylene resin (PP) and the polyethylene resin (PE) in a weight ratio of PE / PP = 0.1 to 2.0. .   A crosspiece formed by extrusion foam molding of the resin composition according to claim 1.   The crosspiece according to claim 2, wherein the foaming ratio is foam-molded in a range of 1.8 to 3.0 times.