JP3511689B2 - Polyolefin resin composition and method for forming polyolefin resin molded article having wood texture - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin composition containing wood powder, particularly a polyolefin resin having improved mechanical strength and capable of forming a thick molded product having a texture of wood. The present invention relates to a composition and a molding method capable of producing a thick-walled molded product having a texture of wood by using these polyolefin resin compositions.

[0002]

2. Description of the Related Art Conventionally, a building with a wooden texture by mixing wood powder into a thermoplastic resin such as polyethylene or polypropylene,
Various attempts have been made to obtain resin molding materials for furniture and daily necessities. For example, in Japanese Unexamined Patent Publication No. 58-204050, a thermosetting resin material is added to wood powder particles, followed by thermocompression hardening, cutting and crushing, and mixing with a thermoplastic resin such as styrene resin or vinyl chloride resin for extrusion molding. A method of doing so is disclosed. However, when wood flour treated and cured with a thermosetting resin is used, the original soft wood texture can no longer be expressed. JP-A-60-188445 and JP-A-60-19
2746 is a vinyl chloride resin having a small linear expansion coefficient and excellent impact resistance, which is obtained by blending vinyl chloride resin with wood powder, glass fiber or an inorganic filler, and a modifier such as ABS resin. System resin moldings have been proposed. However,
This vinyl chloride resin molded body stores heat during molding and generates hydrochloric acid gas due to thermal decomposition to generate bubbles.
It is difficult to mold a thick product of 1 cm or more. Japanese Patent Laid-Open No. 58-107314 discloses a method in which chips of a composite of a thermoplastic resin and a paper material are added to a polyolefin resin to form pellets, and the pellets are extruded together with the polyolefin resin to obtain a sheet. . According to this method, in the case of manufacturing a thick product having a wooden texture, at the melting temperature of polyolefin, wood powder is decomposed by internal heat storage, and therefore a thick building product cannot be obtained.

[0003]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a thermoplastic resin composition which can be blended with wood powder to increase mechanical strength and to give a thick molded article having a wood texture. To do.

[0004]

[Structure] The first aspect of the present invention is a polyolefin resin 100.
Parts by weight, 20 to 200 parts by weight of wood powder having an average particle size of 1 to 500 μm (based on 100 parts by weight of polyolefin resin),
And a polyolefin resin composition for extrusion molding containing 2 to 20 parts by weight of a lubricant having a melting point of 200 ° C. or higher (based on 100 parts by weight of the polyolefin resin).
The polyolefin resin used in the present invention includes high-density polyethylene, low-density polyethylene, polypropylene, polybutene, polyisoprene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer,
Examples thereof include ethylene-propylene copolymers, ethylene-propylene-diene terpolymers, and mixtures of at least two types of these resins. The wood powder is not particularly limited in type as long as it is a pulverized product of plant fibers, and examples thereof include wood and rice husk. The average particle size of this wood flour is 1 to 500 μm, preferably 1 to 2
The thickness is 00 μm. When the addition amount of wood powder is 20 to 200 parts by weight with respect to 100 parts by weight of the polyolefin-based resin composition, the linear expansion coefficient of the molded product is reduced without deteriorating the moldability and impact resistance, and Thermal deformation is less likely to occur due to the change, and a woody appearance can be imparted.
When wood flour is not added at all or a small amount of less than 20 parts by weight is added to 100 parts by weight of the polyolefin resin, no sufficient effect can be expected, and 200 parts by weight is added. If added in a large amount exceeding the above range, the moldability will be poor, the appearance of the molded product will not be smooth, and the impact resistance will be poor. If the particle size is less than 1 μm, it is too fine and difficult to handle.
If it is larger than 0 μm, the molded product lacks homogeneity and the mechanical strength decreases. The dry state of the wood powder has a water content of 0.8% by weight or less, preferably 0.5% by weight or less. If the water content exceeds 0.8% by weight, foaming occurs during molding. That is, when the wood powder whose moisture content is suppressed to 0.8% by weight or less is mixed and dispersed in the resin, the generation of gas is suppressed to be extremely small, and it is possible to prevent voids that are likely to occur around the wood powder. It is possible and the adhesion between wood powder and resin is good. Further, this composition has extremely good moldability, and the obtained molded product has a small linear expansion coefficient and is unlikely to undergo thermal deformation due to temperature change, and further has extremely excellent physical properties such as tensile strength and impact resistance. In addition, since the surface condition of the molded product is smooth and uniform, and there is no large void inside, the woody appearance can be exhibited.

One feature of the present invention is that, in addition to the polyolefin resin and the wood powder, a lubricant having a melting point of 200 ° C. or higher is used as a substance having a specific lubricating effect. If the melting point is less than 200 ° C, it will be absorbed by wood powder during kneading and will not function as a lubricant. Examples of such a lubricant include barium stearate (melting point 220 ° C.), lithium stearate (melting point 220 ° C.), dibasic lead stearate (melting point 280 ° C.), barium laurate (melting point 240 ° C.) and the like. Barium is preferred. The present invention prevents the storage of heat due to frictional heat during kneading by adding a lubricant having a melting point of 200 ° C. or more to a polyolefin resin composition containing wood powder, and does not cause decomposition of wood powder, but is thick. Molded articles can also be easily manufactured. The amount of the lubricant having a melting point of 200 ° C. or higher is 2 to 20 parts by weight with respect to 100 parts by weight of the polyolefin resin,
It is preferably 5 to 10 parts by weight. When the amount is less than 2 parts by weight, heat is accumulated by frictional heat during kneading, and wood powder is easily decomposed,
If it is more than 20 parts by weight, it will be too slippery to make uniformization difficult. The polyolefin resin composition for extrusion molding of the present invention includes, in addition to the polyolefin resin, wood powder and lubricant, a filler such as calcium carbonate, a pigment, a colorant, an antistatic agent, an ultraviolet absorber, etc., if necessary. You may add the additive of.

Before the extrusion molding, it is preferable that the above-mentioned components are melt-mixed with a mixer, preferably a high-speed mixer or the like so as to be sufficiently homogenized. Melting temperature is 180-200
C is preferred. The polyolefin resin composition obtained as described above is molded into a molded article by extrusion molding. As the extrusion molding machine, a commonly used extruder such as a uniaxial or biaxial extruder is used. However, it is preferable to use an extruder which is not equipped with a breaker plate which is usually provided at the end of the material melt-kneading zone. When an extruder equipped with a breaker plate is used, a pressure is generated between the tip of the screw and the cylinder, causing a local temperature rise, and burning is likely to occur as in the prior art.

Specific embodiments of the present invention will be described below. 1. 100 parts by weight of polyolefin resin, average particle size 1 to
Wood flour 20-2, 500 μm, preferably 1-200 μm
Lubricants 2 to 20 having 100 parts by weight and a melting point of 200 ° C. or higher
A polyolefin resin composition for extrusion molding having a part by weight. 2. The polyolefin resin composition for extrusion molding of the polyolefin resin composition of 1, wherein the lubricant is barium stearate. 3. The polyolefin resin composition for extrusion molding according to 1 or 2 above, wherein the wood powder has a water content of 0.8% by weight or less. 4. A method for producing a polyolefin-based resin molded article, which comprises subjecting the above-mentioned polyolefin-based resin composition of 1, 2 or 3 to extrusion molding using an extruder in which a breaker plate is not attached to a tip portion. 5. A polyolefin-based resin molded product having a wood texture, which is produced by extrusion-molding the above-mentioned 1, 2 or 3 polyolefin-based resin composition. 6. The wood-like polyolefin resin molded article produced by the above-mentioned production method 4, wherein the wood-like polyolefin resin molded article of 5 above is manufactured.

[0008]

EXAMPLES The present invention will be described in more detail based on the following examples.

Example 1 Wood powder pulverized with a turbo mill and having an average particle size of 100 μm was dried with a tray hot-air dryer to a water content of 0.5% by weight. 100 parts by weight of this wood flour, 30 parts by weight of high-density polyethylene [SS-6008FD from Showa Denko KK], 70 parts by weight of polypropylene [SK-711 from Showa Denko KK] and 20 parts by weight of calcium carbonate are used in Henschel. After mixing with a mixer, the temperature was raised to 180 ° C., and after cooling, 6 parts by weight of barium stearate was added and further mixed to obtain a granular compound. Granule compound was charged into a single-screw extruder without the breaker plate at the tip of the kneading section, and the barrel temperature was set to 1
Extrusion was performed at 80 ° C and a die temperature of 185 ° C. The temperature of the melt at the tip was 195 ° C. 30mm x 40mm x 1000mm with a die attached to the tip for extrusion molding
Got a square stick. A square bar with a smooth surface and no thermal discoloration was obtained. The physical properties of the square bar were as follows. Flexural modulus 35,400 kgf / cm ² Flexural strength 334 kgf / cm ² Linear expansion coefficient 3.90 × 10 ⁻⁵ cm / cm · ° C.

Comparative Example 1 The procedure of Example 1 was repeated except that the amount of barium stearate was 1.5 parts by weight. The resin temperature at the tip of the extruder is 21
The temperature became 0 ° C., and wood powder burned. Barrel temperature 160 ℃
Even if it was lowered to, the tip was over 200 ° C and burning did not stop.

Comparative Example 2 The procedure of Example 1 was repeated except that calcium stearate (melting point 180 ° C.) was used in the same weight in place of barium stearate. The resin temperature at the tip of the extruder reached 220 ° C., and burnt wood powder occurred.

Comparative Example 3 The same procedure as in Example 1 was carried out except that a breaker plate was attached to the tip of the kneading section of the extruder. The resin temperature at the tip of the extruder is 25
It became 0 ° C., and burning of wood flour occurred.

[0013]

[Effect] According to the present invention, the mixing of wood powder improves the mechanical properties such as bending elastic modulus and bending strength and the thermal properties such as linear expansion coefficient, and does not cause burning of wood powder or the like. It is possible to obtain a thick-walled molded product having the texture of.

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP 61-16965 (JP, A) JP 55-131032 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08J 5/00 C08L 23/00 C08L 97/02

Claims (3)

(57) [Claims] 1. A polyolefin resin composition having 100 parts by weight of a polyolefin resin, 20 to 200 parts by weight of wood powder having an average particle size of 1 μm to 500 μm, and 2 to 20 parts by weight of a lubricant having a melting point of 200 ° C. or higher is extruded. Will be done
Polyolefin resin molding with wall thickness of 30 mm or more
body. 2. The melting point according to claim 1, which is 200 ° C. or higher.
Characterized in that one lubricant is barium stearate
The polyolefin resin molded article according to claim 1, wherein 3. A polyolefin resin 100 parts by weight, flat
20 to 200 parts by weight of wood powder with a uniform particle size of 1 μm to 500 μm
And 2 to 20 parts by weight of a lubricant having a melting point of 200 ° C. or higher
The polyolefin resin composition for extrusion molding according to claim 1 or 2 , characterized in that the polyolefin resin composition for extrusion molding is extruded using an extruder having no breaker plate at its tip. Manufacturing method.