JPH085108B2 - Method for producing polyolefin resin plate-like foam - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polyolefin resin plate-like foam.

[Conventional technology]

An extrusion foam of a thermoplastic resin is usually prepared by melt-kneading a thermoplastic resin and a foaming agent under pressure in an extruder, and then melting and kneading the melt-kneaded product from an die provided in the extruder under an atmosphere of a pressure lower than that in the extruder. It is manufactured by a method of extruding into a foam and foaming. However, in order to manufacture a thick foam, a die with a large opening area is required, so the method of directly extruding from an extruder and foaming requires a large extruder with a high discharge rate, and enormous equipment costs. In short, it has been extremely difficult to inexpensively produce a thick foam by the above-mentioned conventional method.

As a method of solving the above problems and easily producing a thick-walled extrusion foam without using an expensive large-sized extruder, after melting and kneading a thermoplastic resin and a foaming agent under pressure, this melting A method has been proposed in which a kneaded product is extruded into a holding region at a temperature and pressure at which a foaming action does not occur, a predetermined amount of the melt-kneaded product is stored in the holding region, and then extruded from the holding region to foam. 501317).

[Problems to be solved by the invention]

The present inventors have repeatedly conducted experiments for producing a thick-walled polyolefin resin plate-like foam based on the method described in Japanese Patent Publication No. 57-501317. However, the above special table Sho 57
According to the method described in No. 501317, although a thick-walled polyolefin-based resin plate-like foam is certainly obtained, a thick-walled polyolefin-based resin plate-shaped foam excellent in physical properties such as surface condition and compression hardness is necessarily obtained. There is a problem that the body is not always obtained, especially when trying to obtain a high foamed material, there will be tremendous surface roughness and corrugated, the closed cell ratio will decrease, and it will become an open celled foam with high water absorption. There was a big problem that it was easy.

As a result of intensive studies to solve the above problems, the present inventors set a discharge rate per 1 cm ² of the opening of the orifice of the die in a specific range and extruded from an accumulator to give excellent physical properties. It was found that the above-mentioned polyolefin resin plate-shaped foamed product was obtained, and the present invention was completed.

That is, according to the present invention, a polyolefin resin and a foaming agent are melt-kneaded under pressure to form an expandable melt-kneaded product, and the melt-kneaded product is extruded into an accumulator maintained at a temperature and pressure at which a foaming action does not occur. , Thereafter, the pressure of the movable ram through a die orifice provided in the accumulator tip, with respect to the area 1 cm ² per orifice opening at the discharge speed 600~1500kg / hr · cm ² from the accumulator The gist of the present invention is to provide a method for producing a polyolefin resin plate-like foam, which comprises extruding and foaming in a low-pressure atmosphere.

Examples of the polyolefin resin used in the present invention include high-density polyethylene, low-density polyethylene,
Linear low density polyethylene, linear ultra low density polyethylene,
Olefin homopolymers such as polypropylene and polybutylene, ethylene-propylene random copolymers, ethylene-propylene block copolymers, ethylene-propylene-butene random copolymers, or the above polyolefin resins and styrene resins and / or acryl. Examples of the olefin-based copolymer such as a graft polymer with a resin-based resin, polyethylene or ethylene-based copolymer is preferable among them, particularly melt flow rate (g / 10 minutes) (hereinafter,
Abbreviated as MFR. ) Is the x-axis and the crystallization temperature is the y-axis, P ₁ (0.1,100), P ₂ (2,100), P ₃ (1
0,95), P ₄ (10,90), P ₅ (2,90), P ₆ (0.1,95) The area enclosed by the hexagon formed by connecting straight lines in sequence (also on the straight line A polyethylene resin having an MFR represented by a point Pi (xi, yi) and a crystallization temperature is preferable.
In order to further improve the effect of the present invention that a thick plate-like foam having no surface roughness or corrugation is obtained, it is preferable to use a resin having an MFR and a crystallization temperature within the above ranges. In the case of a copolymer, it may be a block copolymer or a random copolymer, but a random copolymer is preferred. The above MFR is a value measured at 190 ° C. and a load of 2160 g, and the crystallization temperature is determined by differential scanning calorimetry (DSC).
Using 8 to 10 mg of resin, measure the temperature rise to 200 ° C at a temperature rise rate of 10 ° C / min, and then measure the temperature rise from 200 ° C to 40 ° C at a temperature decrease rate of 10 ° C / min.
The temperature was measured to be lowered to ℃, and the temperature was determined from the exothermic peak temperature of the DSC curve during this temperature measurement.

In the present invention, as shown in FIG. 1, first, a polyolefin resin is supplied from an hopper 1 to an extruder 2, and the resin is melted in the extruder 2 and pressurized with a foaming agent supplied from a foaming agent supply pipe 3. Knead. The temperature and pressure in the extruder 2 at this time are generally 110 to 250 ° C. and 100 to 200 kg / cm, although they vary depending on the melting temperature of the resin, the type of foaming agent, etc.
It is about ² (G). Examples of the foaming agent include volatile foaming agents such as propane, butane, pentane, dichlorodifluoromethane, dichlorotetrafluoroethane, methyl chloride and methylene chloride, azodicarbonamide, dinitrosopentamethylenetetramine and azobisisobutyronitrile. , A decomposition type foaming agent such as sodium hydrogen carbonate is used. Usually, an inorganic powder such as talc or silica, a mixture of polyvalent carboxylic acid and sodium hydrogencarbonate, or a foam control agent such as a reaction product is added to the melt-kneaded product.
Usually, the amount of the foaming agent and the amount of foam control agent added is preferably about 5 to 50 parts by weight and 0.01 to 0.1 parts by weight, respectively, per 100 parts by weight of the resin.

The melt-kneaded product melted in the extruder 2 and kneaded with the foaming agent is extruded into the accumulator 4 which is kept under pressure at a temperature at which a foaming action does not occur. The temperature and pressure conditions in the accumulator 4 may be any temperature and pressure as long as they do not cause foaming in the melt-kneaded product, but are usually 100 to 110 ° C. and 20 to 70 kg / cm ² (G). preferable.

When a predetermined amount of melt-kneaded material is stored in the accumulator 4, the hydraulic cylinder 6 connected to the rod 5 operates and the rod 5 slides in the direction of the arrow, and the pressure of the movable ram 7 connected to the rod 5 causes the hydraulic cylinder 6 to slide. The melted and kneaded product in the accumulator 4 is extruded from a die 8 provided at the tip of the accumulator 4 under a low-pressure atmosphere (usually under atmospheric pressure) to foam the accumulator 4. It is necessary to extrude the melt-kneaded product so that the discharge speed will be 600 to 1500 kg / hr · cm ² per 1 cm ² of the orifice opening area. If the discharge rate per 1 cm ² of orifice opening area is less than 600 kg / hr ・ cm ² , corrugates will be generated in the obtained plate-like foam, the closed cell ratio will decrease, and the specified thickness and width will be reduced. When it exceeds 1500 kg / hr · cm ² , corrugation is similarly generated and the surface is roughened, and in any case, a good plate-shaped foam cannot be obtained.

According to the method of the present invention, the expansion ratio is usually 5 to 50 times, and the thickness is 15 to
200mm, polyolefin resin plate-like foam with a weight of 1kg or more can be produced without causing corrugation, surface roughness, decrease in closed cell ratio, etc., but it is suitable as a method for producing thick-walled foam, and particularly It is suitable as a method for producing a polyolefin resin plate-shaped foam having a thickness of 30 to 150 mm, an expansion ratio of 20 to 35 times, a weight of 1.5 kg or more, and a large-sized, large-sized polyolefin resin plate-like foam having a high expansion ratio.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to examples.

Examples 1-6, Comparative Examples 1-2 Resin 100 shown in Table 1 in an extruder with a discharge capacity of 100 kg / hr.
Parts by weight per the blowing agent and talc shown in Table 120 kg / cm ²
Melt kneading under pressure of (G), 30 kg / cm ² (G), 103
After extruding into the accumulator maintained at 0 ° C., it was extruded and foamed from a die having an orifice opening area shown in Table 1 at a discharge speed shown in the same table. The properties of the resulting plate-like foam are also shown in Table 1.

Was determined.

[Effects of the Invention] As described above, the present invention, after melt-kneading a polyolefin resin with a foaming agent, extrudes the melt-kneaded product into an accumulator maintained at a temperature and pressure at which foaming action does not occur, and then accumulator Since a method of foaming by extruding in a low pressure atmosphere from inside the lator is adopted, it is possible to easily obtain a thick polyolefin resin plate-like foam without using a large extruder and to open the orifice of the die. 600 to 1500 kg / hr ・ cm ² per 1 cm ² of area
By adopting the method of extruding from the accumulator so that the discharge speed of the above is adopted, it is possible to obtain a plate-like foam having an excellent cell structure with high closed cell ratio without surface roughness or corrugation even if it is thick In particular, it has an effect that a foam having excellent properties can be obtained even when it is thick and large and has a high expansion ratio.

[Brief description of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic view showing the production method of the present invention. 2 ... Extruder, 4 ... Accumulator 7 ... Movable ram, 8 ... Dice

Claims (11)

[Claims] 1. A polyolefin resin and a foaming agent are melt-kneaded under pressure to form a foamable melt-kneaded product, and the melt-kneaded product is then placed in an accumulator maintained at a temperature and a pressure at which no foaming action occurs. Extruding, and then, due to the pressure of the movable ram through the orifice of the die provided at the tip of the accumulator, the discharge speed is 600 to 1500 kg / hrcm ^{2 in the} accumulator per 1 cm ² of the orifice opening area. A method for producing a polyolefin resin plate-shaped foam, which comprises extruding and foaming under a lower pressure atmosphere. 2. A polyolefin resin comprising high-density polyethylene, low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, polypropylene, polybutene, ethylene-propylene random copolymer, ethylene-propylene block copolymer, The production of a polyolefin resin plate-like foam according to claim 1, which is an ethylene-propylene-butene random copolymer or a graft copolymer of the above polyolefin resin and a styrene resin and / or an acrylic resin. Law. 3. The polyolefin resin has a crystallization temperature (provided that 8 to 10 mg of resin is increased by differential scanning calorimetry, with a melt flow rate (g / 10 min) (190 ° C., 2160 g load) as the x-axis. The temperature of the exothermic peak obtained from the DSC curve during temperature measurement when the temperature is raised to 200 ° C at a temperature rate of 10 ° C / min. P ₁ (0.1,100), P _{2 at the} axis coordinates
(2,100), P ₃ (10,95), P ₄ (10,90), P ₅ (2,90), P
_A point P _i (x _i , in the range surrounded by a hexagon (including straight lines) formed by connecting ₆ (0.1, 95) sequentially
The method for producing a polyolefin resin plate-like foam according to claim 1, which is polyethylene having a melt flow rate and a crystallization temperature represented by y _i ). 4. The method according to claim 1, wherein the polyolefin resin and the foaming agent are melt-kneaded in an extruder at 110 to 250 ° C. and a temperature and pressure of 100 to 200 kg / cm ² (G). The method for producing a polyolefin resin plate-shaped foam according to any one of claims. 5. The polyolefin resin plate-like foam according to any one of claims 1 to 4, wherein the amount of the foaming agent added is 5 to 50 parts by weight with respect to 100 parts by weight of the polyolefin resin. Manufacturing method. 6. The melt-kneaded product in the extruder is heated at 100 to 110 ° C. for 20
The method for producing a polyolefin-based resin plate-shaped foam according to any one of claims 1 to 5, which comprises extruding into an accumulator held at 70 kg / cm ² (G). 7. A foaming ratio of 5 to 50 times, a thickness of 15 to 200 mm, and a weight of 1.
The method for producing a polyolefin resin plate-like foam according to any one of claims 1 to 6, wherein a foam having a weight of at least kg is obtained. 8. The method for producing a polyolefin resin plate-shaped foam according to any one of claims 1 to 7, wherein the foaming agent is a volatile foaming agent. 9. The polyolefin resin plate-like foam according to claim 8, wherein the volatile foaming agent is propane, butane, pentane, dichlorodifluoromethane, dichlorotetrafluoroethane, methyl chloride or methylene chloride. Manufacturing method. 10. The method for producing a polyolefin resin plate-like foam according to any one of claims 1 to 7, wherein the foaming agent is a decomposable foaming agent. 11. The decomposition type foaming agent is azodicarbonamide,
11. The method for producing a polyolefin resin plate-like foam according to claim 10, which is dinitrosopentamethylenetetramine, azobisisobutyronitrile, or sodium hydrogen carbonate.