JP3419512B2 - Molding method of polyolefin resin composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method for extruding a polyolefin-based resin composition into a sheet and vacuum- and / or pressure-molding the same, and more particularly to a molded article having excellent soundproofing performance. A molding method suitable for obtaining 2. Description of the Related Art Conventionally, as one method of molding a polyolefin resin composition, a resin composition which has been heated and melted is extruded into a sheet of a fixed width by a sheet extruder, or
In addition, there is a molding method in which the extruded sheet is gripped at the end thereof, taken off, and shaped by vacuum, air pressure molding or the like before the sheet is cooled. The advantage of this molding method is that since the sheet is extruded and molded immediately after, the sheet is extruded, a cooling step is provided, the sheet is taken out, and then the sheet is sent to the molding step again, reheated, and molded. The number of processes is smaller than that of, and energy efficiency can be improved. In this molding method, the resin composition is extruded into a sheet and then molded before being cooled and solidified. Therefore, the following conditions are required as sheet extrusion conditions (or physical properties of the extruded sheet). (1) Stretching conditions The extruded resin sheet has sufficient stretchability. Preferably, the elongation of the resin at the time of melting is 200% or more. (2) Elastic condition The extruded resin sheet has sufficient elasticity. Preferably, immediately after being discharged from the discharge hole, the thickness of the resin sheet is increased to about 1.3 to 1.5 times by the elastic after-effect. (3) Tension conditions The extruded resin sheet generates a certain tension or more with respect to stretching. (4) Rate of change in tension The change in tension should be as small as possible with respect to the change in the sheet take-up speed when the extruded resin sheet is taken out. If the conditions (1) to (3) are not satisfied among these conditions, the stretching of the resin sheet does not proceed smoothly, the sheet is likely to be uneven in thickness or torn, and is not suitable for forming a complicated shape. If the condition (2) is not satisfied, it is difficult to adjust the thickness of the resin sheet, and the thickness of the resin sheet tends to be uneven. If (4) is not satisfied, the neck-in amount of the resin sheet (the amount of shrinkage in the width direction of the sheet from being extruded through the discharge hole 6a to entering the split mold portion) changes during the sheet taking-in process. This is not preferable for vacuum forming or pressure forming. On the other hand, in the actual application of polyolefin resin compositions, for example, to automotive parts, molding materials having a relatively long size and a large area are often used after processing sheet-like moldings, especially liner materials for automobiles. Is a product whose shape is complicated and sound insulation performance is required.
In some cases, polyethylene or the like is used as a base material and an elastomer or various inorganic fillers are mixed to improve the soundproofing properties (vibration damping properties). When such a resin-based composite material is extruded into a sheet by a conventional method, a decrease in stretchability of the sheet and a tension with respect to the stretching occur, so-called drawdown is remarkable, and a molded article having a large size and a large area is obtained. I couldn't. Techniques for improving the drawdown during the thermoforming include, for example, extruding a sheet using a resin composition comprising a crystalline polypropylene having a specific fluidity and a partially crosslinked ethylene-propylene copolymer, and before cooling and solidifying. Molding method (Japanese Unexamined Patent Publication No. Sho 58)
No. -21409) is disclosed, but the draw-down property, such as the uniformity of the thickness of the molded product, has not yet reached a sufficiently satisfactory level, and the more complicated the shape of the molded product, the more difficult it is.
This tendency is remarkable. [0003] Conventionally, the above-mentioned (1)-
There has been no suitable molding method for a resin that satisfies the condition (4) and has excellent soundproofing properties. The present invention solves the above-mentioned problems, and extrudes a polyolefin-based resin composition into a sheet shape, and cools, in a method of molding before solidifying, mixing the inorganic filler into the resin, and suitably molding. The present invention provides a method for molding a polyolefin-based resin composition that can be used. [0004] Means for solving the problems of the present invention is that the melt flow rate at a temperature of 230 ° C and a load of 2.16 kg as component (A) is 0.1 to 1.0.
A crystalline polypropylene resin having a melt flow rate of 0.1 to 2.0 under a temperature of 230 ° C. and a load of 2.16 kg as a component (B); The melt flow rate at a temperature of 190 ° C. and a load of 2.16 kg is 0.01 as a component (C).
０．３0.3 and weight average molecular weight Mw of 5 × 10 ⁴ -30
× 10 ⁴ , a high-density polyethylene resin having a weight average molecular weight Mw and a number average molecular weight Mn (Mw / Mn) of 10 to 50, and talc, calcium carbonate, silicates, or glass fiber as the component (D). Inorganic filler,
(A) component is 5 to 20% by weight, (B) component is 25 to 70% by weight, out of a total of 100% by weight of (A) to (D),
Component (C) is 5 to 45% by weight, component (D) is 10 to 50% by weight.
The polyolefin-based resin composition mixed so as to have a ratio of weight% is heated and melted and extruded into a sheet,
A molding method for a polyolefin-based resin composition, wherein the sheet is molded by vacuum and / or pressure molding before the sheet is cooled and solidified. Hereinafter, the present invention will be described in detail with reference to examples. The polyolefin-based resin composition according to the present invention comprises (A) a crystalline polypropylene resin, (B) an ethylene-propylene copolymer resin, (C) a high-density polyethylene resin, and (D) an inorganic filler. As the component (A), a so-called homopolypropylene and an ethylene-propylene block copolymer are used alone or as a mixture thereof. These crystalline polypropylenes have a fluidity of 230 ° C. when melted and a melt flow rate (AS) of 2.16 kgf.
(Hereinafter referred to as MI based on TM D-1238)
The index is preferably in the range of 0.1 to 2.0. In this embodiment, the one having MI of 0.5 is used.
The component (B) is a so-called ethylene-propylene random copolymer different from crystalline polypropylene,
It is preferable that MI of 2.16 kgf at 0.1 degreeC is 0.1-2.0. In the present example, a material having an MI of 0.7 was used. As the component (C), so-called high-density polyethylene is preferably used, and the MI of 190 ° C. and 2.16 kgf has a MI of 0.01 to 0.3 and a weight average molecular weight of 5 × 10 ^{4 to} 3.
It is preferably 0 × 10 ⁴ . In this embodiment, MI
Of 0.3, a weight average molecular weight Mw of 17 × 10 ⁴ and a molecular weight distribution Mw / Mn of 30 were used. The component (C)
It plays a role of generating a constant tension on the sheet when the sheet is taken up, and has an effect of preventing drawdown. It has been found that when the molecular weight distribution exceeds 50, the fluidity at the time of melting greatly fluctuates, and the thickness deviation and neck-in amount increase. The component (D) is mainly composed of talc, calcium carbonate, silicates, and glass fibers. The shape and particle size (aspect ratio) of these inorganic fillers are not particularly limited as long as they do not adversely affect the formability, appearance and physical properties of the molded body. In this embodiment, the apparent specific gravity is 0.85 and the specific surface area is 12,000.
cm ² / g of heavy calcium carbonate was used. The molding device is shown in FIG. A plunger 2 is provided in the cylinder 1 so as to be movable in the axial direction, and the cylinder 1 and the plunger 2 constitute an accumulator head 3. An extruder 5 having a screw 4 is attached to the head of the cylinder 1, and a guide hole 5 </ b> A formed in the extruder 5 communicates with a storage hole 3 </ b> B formed in the cylinder 1. An operating cylinder (not shown) is provided at the upper end of the plunger 2 via a shaft portion 2a. By operating the operating cylinder, the plunger 2 can be forcibly moved in the axial direction. It is configured. At the lower end of the cylinder 1, a molten resin discharge port 6 is provided.
A T-die 6 having an a is attached. Below the T-die 6, a sheet thickness adjusting section 8 for pulling down and stretching the resin sheet 7 discharged from the melt discharge port 6a is provided. . The sheet thickness adjusting unit 8 is configured so that the chuck unit 11 can be moved up and down by the up and down movement of the rod 10 of the sheet thickness cylinder 9 to perform the stretching operation. A split mold portion 22 including a first mold 20 and a second mold 21 is disposed below the T-die 6 while holding the sheet thickness adjusting portion 8 therebetween. A female die 20a is formed on the male die 20 and a male die 21a and an air discharge port 21b are formed on the second die 21. A compressed air source 23 such as a compressor is connected to the air discharge port 21b. The compressed air source 23 is connected to the control unit 24, and the sheet thickness cylinder 9 is also connected to the control unit 24. , The operation of which is controlled. In this state, when the molten resin is stored in the storage hole 3B of the accumulator head 3 by the screw 4 of the extruder 5, the plunger 2 rises upward from the state shown in FIG. When the required amount of molten resin as a raw material is stored in the storage hole 3B, the plunger 2 is pushed down through an operating cylinder (not shown), and the molten resin discharge sheet 6 forms a molten resin sheet 7 from the molten resin discharge port 6a. Injected into. The resin sheet 7 by the above-mentioned injection is melted and discharged 6a.
Simultaneously, the rod 10 of the cylinder 9 for sheet thickness of the sheet thickness adjusting section 8 rises upward, and the chuck section 11 closes to chuck the lower end of the resin sheet 7. At the same time as this chuck operation is completed,
Since the rod 10 is lowered, the resin sheet 7 is extended downward to have a desired thickness, and is in a state corresponding to the female mold 20 a of the first mold 20. In the above-described state, the second mold 21 is joined to the first mold 20 via a cylinder (not shown), and the female mold 20a and the male mold 21a are tightly fitted with the resin sheet 7 held therebetween, and at the same time, the compressed air source is The compressed air from 23 is discharged to the resin sheet 7 and the skin 25a through the air discharge holes 21b, and the resin sheet 7 is formed by compression molding. In the forming apparatus shown in FIG. 1, it was extruded into a sheet, and was compressed and formed before being cooled and solidified. in this case,
The resin temperature is set to 200 to 220 ° C. inside the sheet, the discharge hole thickness of the molten resin is set to 1.5 mm, and the take-up speed of the resin sheet is set to 0.
The thickness of the sheet was adjusted by changing the thickness at a rate of ~ 300 m / s, and the drawn sheet was pressure-formed at a pressure of 4 kg / cm ² . The resin compositions of the examples were evaluated from the viewpoint of moldability and soundproofing, and good results were obtained. Regarding the moldability, the effects were confirmed in the following four points. The drawdown indicating the ease of dripping of the extruded sheet was evaluated as small and good, and the uneven thickness indicating the thickness variation of the extruded and stretched resin sheet was evaluated as small and good. No tear was observed during stretching or molding of the resin sheet. The resin sheet extruded from the discharge hole 6a is
The neck-in, which shows the contraction rate of the sheet width before entering 2,
The evaluation was small and good. The evaluation of soundproofing was performed by the device 30 shown in FIG. FIG. 3 shows a pendulum 34 composed of a steel ball 35 having a mass of 250 g and connected to the tip of a thin string having a length of 200 mm with respect to a test piece 31 (molded product) mounted on a support 32 with a locking member 33. From the horizontal position, and hit the test piece end. At this time, the noise generated by the impact of the pendulum is simultaneously detected by the sound collector 36, and the vibration of the test piece is simultaneously detected by the acceleration detector 37, and recorded on a recorder (not shown). The small absolute value of the initial noise and the rapid vibration damping were evaluated as having excellent soundproofing. FIG. 3 shows a measurement example of vibration damping. The effect was confirmed by comparing the example (a) of the present invention having good soundproofing properties with the example (b) having poor soundproofing properties.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a molding method (molding machine) to which the present invention is applied. FIG. 2 shows a soundproofing evaluation device. FIG. 3 shows a measurement example of a vibration damping state. [Description of Signs] 1 ... Cylinder 2 ... Plunger 2a ... Shaft 3 ... Accumulator head 3B ... Reservoir 4 ... Screw 5 ... Extruder 5A ... Guide hole 6 ... ··· T die 6a ··· molten resin discharge hole 7 ··· resin sheet 8 ··· wall thickness adjusting unit 9 ··· cylinder 10 ··· rod 11 ··· chuck unit 20 ··· first die 20a ··· Female mold 21 ··· Second mold 21b ··· Female mold 23 ··· Compressed air source 24 ··· Control unit 30 ··· Soundproof evaluation device 31 ··· Test piece 32 ··· Support 33 ... Locking device 34 ... Pendulum 35 ... Steel ball 36 ... Sound collecting device 37 ... Acceleration detector

Continuation of the front page (51) Int.Cl. ⁷ identification code FI B29K 23:00 B29K 23:00 105: 16 105: 16 (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 69/00- 69/02 B29C 47/00-47/96 B29C 51/00-51/46 B29C 55/00-55/30 C08L 23/00-23/36

Claims (1)

(57) [Claim 1] The component (A) has a melt flow rate of 0.1 to under a temperature of 230 ° C. under a load of 2.16 kg.
A crystalline polypropylene resin having a melt flow rate of 0.1 to 2.0 under a temperature of 230 ° C. and a load of 2.16 kg as a component (B); The melt flow rate at a temperature of 190 ° C. and a load of 2.16 kg is 0.01 as a component (C).
０．３0.3 and weight average molecular weight Mw of 5 × 10 ⁴ -30
× 10 ⁴ , a high-density polyethylene resin having a weight average molecular weight Mw and a number average molecular weight Mn (Mw / Mn) of 10 to 50, and talc, calcium carbonate, silicates, or glass fiber as the component (D). Inorganic filler,
(A) component is 5 to 20% by weight, (B) component is 25 to 70% by weight, out of a total of 100% by weight of (A) to (D),
Component (C) is 5 to 45% by weight, component (D) is 10 to 50% by weight.
The polyolefin-based resin composition mixed so as to have a ratio of weight% is heated and melted and extruded into a sheet,
A method for molding a polyolefin-based resin composition, characterized in that the extruded sheet is gripped at an end portion to perform variable speed take-off in the vertical direction, and is formed by vacuum and / or pressure forming before the sheet is cooled and solidified.