JP2002096374A - Olefin resin foamed sheet, apparatus and method for manufacturing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for manufacturing an olefin resin foamed sheet which has a flat surface with no scoreline called corrugation and is thin and can be molded at a high speed. SOLUTION: A molten olefin resin containing a foaming agent is extruded from a die and is brought into contact with an intermediate roll in the neighborhood of starting of air bubbles appearance and foaming is finished on the intermediate roll or foaming is finished to the extent where corrugation can be prevented from being generated by a tension between the intermediate roll and a cooling roll and thickness of the sheet ia made thin by this tension. Thereafter, it is solidified by cooling by means of an air knife device and the cooling roll and is taken off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus, a method, and a foamed sheet for producing an olefin resin foamed sheet capable of forming a thin and high-speed foamed sheet with a smooth surface without vertical stripes called corrugation.

[0002]

2. Description of the Related Art When extruding and foaming an olefin resin to produce a foamed sheet, a phenomenon called vertical streak-like corrugation occurs immediately after the die exit due to volume expansion caused by foaming of the resin. The surface properties of the resulting material are impaired, resulting in defective products.

[0003] Corrugation has been prevented from occurring. For example, inflation molding method: A molten resin is extruded and foamed into a tube, expanded from the inside with compressed air, and then cooled to obtain a foamed sheet with good flatness. Sizing die method: Immediately after the flat sheet die, the product shape is formed. Install the combined cooling sizing die, pull the foamed resin sheet, use a flat die with a lip opening with an opening angle, and take the tip of the lip opening with a pair of forming rolls or a pair of forming belt conveyors The sheet-like foam obtained by extruding from a die is molded with a take-up machine roll at an angle of 30 to 60, which is molded close to the apparatus (Japanese Patent Publication No. 47-32585).
{Circle around (5)} A method in which the distance from the die exit to the contact point of the foam on the roll is 5 to 50 mm, and the roll is cooled and formed by a cooling roll into a sheet (Japanese Patent Application Laid-Open No. 9-763)
No. 31).

However, the above method has the following problems and is not the best method. The equipment cost is large, the thickness accuracy of the product sheet is inferior, it is difficult to use it as a non-foamed sheet or a multi-layer foamed sheet. The property is impaired, it is not suitable for application to thin foam sheet molding, the shape of the opening is too large, the viscosity at the time of melting can not hold the cell at the opening, and the foam breaks, from the die exit to the contact on the roll Since the distance is as long as 5 to 50 mm, foaming occurs during this time, corrugation occurs, and it is presumed that sheet smoothing is difficult, and for the treatment after corrugation occurs, when the wrinkles worsen during thermoforming after sheet molding. Guess, technically difficult.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus, a method and a sheet-like foam for producing an olefin resin foam sheet which is thin and can be molded at high speed with a smooth surface having no vertical stripes called corrugation.

[0006]

An extruder for plasticizing and melting an olefin resin containing a foaming agent and extruding the same from a die, a cooling roll for cooling the extruded olefin resin,
An apparatus for producing an olefin resin foam sheet, comprising a take-up machine, wherein an intermediate roll is provided between the die and the cooling roll. The intermediate roll is preferably arranged so as to start contacting the sheet at a position near the start of bubble appearance of the resin discharged from the die and at a position separated from the die by a gap of a die lip. Further, the olefin resin containing the foaming agent is plasticized and melted and extruded from the die, and is brought into contact with the intermediate roll near the start of bubble appearance, and to the extent that corrugation can be prevented by the end of foaming or the tension between the intermediate roll and the cooling roll. The present invention provides a method for producing an olefin resin foam sheet in which the sheet thickness is reduced by the action of tensile force in the flow direction between the intermediate roll and the cooling roll after foaming is completed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The olefin resin (also referred to as polyolefin) containing a blowing agent of the present invention includes polyethylene resin, polypropylene resin, polybutene resin.
Primary resins and the like are preferred, and polyethylene resins, polypropylene resins and mixtures thereof are preferred.
As the blowing agent, propane, butane, hydrocarbons such as pentane, monochlorodifluoromethane, volatile blowing agents such as halogenated hydrocarbons such as trichlorodifluoromethane,
Examples include gaseous foaming agents such as nitrogen, carbon dioxide, oxygen, and air, and pyrolytic foaming agents such as sodium bicarbonate, ammonium bicarbonate, monosodium citrate, dinitropentane, toluenesulfonylhydrazide, and azodicarbonamide.

[0008] The apparatus for producing an olefin resin foam sheet of the present invention has an extruder, an intermediate roll, a cooling roll, and a take-off machine. By providing an intermediate roll between the die and the cooling roll, the spread of the molten resin in the width direction (a phenomenon in which the spread is narrowed and becomes wavy is referred to as corrugation).
Suppressed by frictional resistance with the intermediate roll. The extruder is
There is no particular limitation, and ordinary extruders can be used, and examples include single-screw and twin-screw extruders. If it is a single screw, an HM extruder manufactured by Mitsubishi Heavy Industries, an ME extruder, etc. may be mentioned.
HM extruders capable of low resin temperature extrusion are preferred. Examples of the die include a normal T die.

The present invention is characterized in that an intermediate roll is used between the extruder and the cooling roll. The surface of the intermediate roll is hard chrome plating, Teflon (registered trademark) coating, ceramic coating, or the like, but Teflon coating is desirable for preventing adhesion to the foam sheet.
In addition, for example, the inside is jacketed and a refrigerant is passed through,
Those capable of controlling the temperature of the roll are preferred. The size (diameter and width) of the intermediate roll depends on the production speed of the foamed sheet and the foaming ratio.
(The amount of the foaming agent) and the width of the die.

The cooling roll is not particularly limited.
The inside of which is made of a jacket type and through which a refrigerant is passed so that the temperature of the roll can be adjusted can be used. The number of cooling rolls may be one or two or more, but is determined in consideration of conditions such as the thickness of the sheet-like foam and the speed of the cooling rolls. As a preferred embodiment of the present invention, an air knife for cooling the foamed sheet separated from the intermediate roll and closely adhering to the cooling roll can be used. These use air blown from an air knife. As the air knife, for example, a knife in which air is blown out from a slit-shaped mouth can be given. The take-off machine is not particularly limited, and a usual one can be used.

Hereinafter, the apparatus and method of the present invention will be described in detail with reference to specific examples shown in the drawings, but the present invention is not limited to these. The apparatus and method of the present invention are shown in FIG. The molten resin containing the foaming agent is extruded from the die outlet 2 at the tip of an extruder (not shown), and a sheet-like foam 7 is formed. This sheet-like foam 7 touches the intermediate roll 3, and then is cooled by an air knife 8 in which cooling air is blown out from a slit-shaped opening, and is closely adhered to the cooling roll 4. Machine 9 picks up. At this time, corrugation occurs when the spread in the width direction of the molten resin that occurs during foaming is reduced, but in the apparatus of the present invention,
Since the spread in the width direction is suppressed by the frictional resistance with the intermediate roll 3, a smooth sheet can be easily obtained. FIG. 4 shows a conventional molding apparatus and method using no intermediate roll. However, it is difficult to prevent corrugation using the conventional molding apparatus and method.

In the present invention, the position of the intermediate roll 3 with respect to the die 1 and the cooling roll 4 is important. This will be described with reference to FIG. When an appropriate foaming phenomenon occurs, a transparent region a (a die exit 2
Less than about 2 mm), and then the bubbles become apparent and white. When these bubbles become visible from the bubble appearance start position b and foam, corrugation occurs due to the spread of the molten resin in the width direction. Note that the vicinity of the start of the appearance of the bubble is where the bubble becomes visible and starts to turn white, and is determined based on visual observation. In FIG. 2, the horizontal axis represents the average bubble diameter,
The vertical axis also shows a conceptual graph in which the position from the die outlet 2 is taken, and also shows the average cell diameter c at the start of bubble appearance, the average cell diameter d at the end of foaming, and the foaming end position e. The vicinity of the beginning of the appearance of bubbles is the same as the length of the transparent region a and less than about 2 mm from the die exit, but varies depending on molding conditions such as resin properties, die lip gap, expansion ratio, and extrusion amount.

Since it is difficult to perform the corrugation prevention treatment after corrugation occurs, as described above, it is necessary to perform the prevention treatment at the same time as the foaming, that is, near the bubble appearance start b (near the die outlet 2). (Figure 3
reference). However, if the intermediate roll 3 is brought too close to the die outlet 2, the molten resin will be crushed by the die outlet 2 and the intermediate roll 3, resulting in a sheet having reduced surface properties. The distance h needs to be longer than the gap between the die lips. The die lip gap is the die exit gap. If the intermediate roll 3 is excessively disposed on the cooling roll side, the molten resin between the die outlet 2 and the intermediate roll 3 leaks to the anti-cooling roll side, resulting in a sheet having reduced surface properties. Therefore, it is preferable that the center m of the intermediate roll is disposed slightly closer to the cooling roll side than the die outlet 2. In the present invention, by setting the intermediate roll contact point near the start of bubble appearance, corrugation can be prevented almost simultaneously with foaming. In addition, by setting the distance between the die and the intermediate roll to be equal to or greater than the lip gap, a required sheet thickness can be secured without crushing the molten resin with the intermediate roll.

Since corrugation is caused by the spread of the molten resin in the width direction, the expansion in the width direction ends as the foaming ends. Accordingly, sheet-like foaming is performed until foaming is completed or foaming is completed to the extent that corrugation can be prevented by tension between the intermediate roll and the cooling roll (hereinafter, substantially referred to as foaming end including both). The body 7 needs to be in contact with the intermediate roll 3. That is, after the foaming is substantially completed, the sheet-like foam 7 is separated from the intermediate roll 3. In the present invention, by substantially terminating the foaming of the molten resin on the intermediate roll, it is possible to prevent corrugation from occurring between the air gaps up to the subsequent cooling roll. From this, the positional relationship among the die, the intermediate roll, the cooling roll, and the take-off machine is determined. The length of the molten resin from the die exit to the intermediate roll is preferably less than 5 mm, more preferably 2 mm or less. The time during which the intermediate roll is in contact with the molten resin is preferably at least 0.1 second, more preferably at least 0.2 second. The distance between the intermediate roll and the cooling roll is preferably 150 mm or less, more preferably 100 mm or less.

In the present invention, since the resin between the intermediate roll and the cooling roll is in a molten state, the sheet thickness can be reduced by the speed ratio between the intermediate roll and the cooling roll.
The speed ratio between the intermediate roll and the cooling roll, preferably,
It is possible to make it 1.6 or more, more preferably 2.0 or more. FIG. 3 is an enlarged view of one example of the apparatus of the present invention from the die 1 to the cooling roll 4.

The intermediate roll of the present invention preferably has a temperature controller capable of controlling the surface temperature of the intermediate roll to a predetermined temperature. By controlling the surface temperature of the intermediate roll to a predetermined temperature, it is possible to prevent winding of the molten resin around the intermediate roll. The predetermined temperature is determined in consideration of conditions such as the speed ratio between the intermediate roll and the cooling roll, the expansion ratio, and the prevention of uneven thickness and uneven foaming due to the tension between the intermediate roll and the cooling roll.
0 ° C, more preferably 160 to 190 ° C. For example, a coolant such as air is flowed into the intermediate roll to control the temperature of the surface of the intermediate roll, thereby preventing the molten resin from winding around the intermediate roll 3. However, in order to make the sheet thinner by the speed ratio between the intermediate roll 3 and the cooling roll 4, it is necessary to avoid cooling and solidification of the sheet-like foam 7 by cooling the intermediate roll. In addition, although a heat medium oil, air, etc. are used for a refrigerant | coolant, the point which can use air etc. is different from the cooling of the conventional cooling roll.

The sheet-like foam 7 is separated by an air knife 5 and a cooling roll 4 into an intermediate roll side f and a cooling roll side g.
Since both sides of the sheet-like foam 7 are rapidly cooled, gas dissipation from the sheet surface layer is suppressed.

In the present invention, the diameter of the intermediate roll is preferably smaller than the diameter of the cooling roll. In addition, in the present invention, preferably, an intermediate roll is housed between the die and the cooling roll, so that the existing sheet machine can be partially remodeled and used as a non-foamed sheet machine. That is, the intermediate roll is placed between the conventional die and the cooling roll, so that the existing roll can be used as a non-foamed sheet roll by partially remodeling the existing roll. In addition, if the diameter of the intermediate roll is too small, the intermediate roll may be deflected. Therefore, the diameter is preferably 20 mm or more.

The expansion ratio of the foam sheet using the apparatus and method of the present invention is not particularly limited, but is preferably 1.5 to 5.0 times, and more preferably 2.0 to 3.0 times.

[0020]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 3 and Comparative Examples 1 to 5 In Examples 1 to 3 and Comparative Examples 1 to 4, foamed polypropylene sheets were produced using the apparatus shown in FIG. Comparative Example 5
Then, foamed polypropylene was manufactured using the apparatus shown in FIG. The resin used is polypropylene FH34 manufactured by Chisso.
00, the foaming agent is a thermal decomposition type foaming agent EV40 manufactured by Eiwa Chemical Co., Ltd.
The extruder for 5D (a baking soda-based foaming agent master batch) was an HM extruder (φ90, L / D = 33) manufactured by Mitsubishi Heavy Industries. The T-die had a width of 1200 mm and a lip gap of 0.6 mm.
The temperature of the intermediate roll was adjusted to a predetermined temperature by using a jacket system inside and circulating a heating medium oil as a heating medium. The inside of the cooling roll was jacketed, and the temperature was adjusted to a predetermined temperature by a method of circulating water as a coolant. 100 parts by weight of FH3
400 and 2.99 parts by weight of EV405D were supplied to an extruder, melt-kneaded and extruded from a T-die 1 to obtain a foamed polypropylene sheet under the conditions shown in Table 1.

The foamed sheet thus formed was visually observed for corrugated marks and surface conditions, and evaluated according to the following criteria. ：: No corrugation or corrugation mark is observed. There is no surface roughness and it is smooth. ×: Corrugation and corrugation mark are recognized. Rough surface, not smooth.

[0022]

[Table 1]

[0023]

By providing an intermediate roll between the die and the cooling roll, the spread of the molten resin in the width direction is suppressed by frictional resistance with the intermediate roll. Preferably, by setting the intermediate roll contact point near the bubble appearance start, corrugation is prevented almost simultaneously with foaming. Preferably, by setting the distance between the die and the intermediate roll to be equal to or greater than the lip gap, a required sheet thickness can be secured without crushing the molten resin between the die outlet and the intermediate roll. The molten resin containing the foaming agent extruded from the die is brought into contact with the intermediate roll near the beginning of the appearance of bubbles, separated after the end of substantially foaming, and further pulled in the flow direction between the cooling roll to prevent corrugation and reduce the thickness of the sheet. Is possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of the device of the present invention.

FIG. 2 is an enlarged view showing a state in which a resin discharged from a die foams.

FIG. 3 is an enlarged view between a die and a cooling roll of FIG. 1;

FIG. 4 shows a conventional foam molding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die 2 Die exit 3 Intermediate roll 4 Cooling roll 5 Cooling roll 6 Cooling roll 7 Sheet foam 8 Air knife 9 Puller 10 Touch roll a Transparent area b Bubble manifestation start position c Average bubble diameter at the start of bubble manifestation d Average bubble diameter at the end of foaming e Foaming end position f Intermediate roll side g Cooling roll side h Intermediate roll contact point i Intermediate roll peeling point j Cooling roll contact point k Distance between die and intermediate roll m Intermediate roll center

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Tsuboi 1st place, Izuka-cho, Iwazuka-cho, Nakamura-ku, Nagoya-shi, Aichi Prefecture Inside the Industrial Equipment Division of Mitsubishi Heavy Industries, Ltd. (72) Inventor Yukio Tamura Iwasuka-cho, Nakamura-ku, Nagoya-shi, Aichi F-term (reference) inside Churyo Engineering Co., Ltd. 4F207 AA03 AA04 AA11 AB02 AG01 AG20 AJ03 AK01 AM32 AR06 KA01 KA11 KK56 KK63 KK65 KL84 KM16

Claims (9)

[Claims] 1. An apparatus for producing a foamed olefin resin sheet, comprising: an extruder for plasticizing and melting an olefin resin containing a foaming agent and extruding the olefin resin from a die; a cooling roll for cooling the extruded olefin resin; Providing an intermediate roll between the die and the cooling roll, the intermediate roll is near the beginning of the bubble appearance of the resin coming out of the die,
An apparatus for producing a foamed olefin resin sheet, wherein the apparatus is arranged so as to start contacting the sheet at a position separated from the die by a gap of a die lip or more. 2. The intermediate roll foams the resin discharged from the die on the intermediate roll, and ends foaming when leaving the intermediate roll, or prevents corrugation by tension between the intermediate roll and the cooling roll. The apparatus for producing an olefin resin foam sheet according to claim 1, wherein the apparatus is arranged so as to terminate foaming to the extent possible. 3. The apparatus for producing a foamed olefin resin sheet according to claim 2, wherein the diameter of the intermediate roll is smaller than the diameter of the cooling roll. 4. The apparatus for producing a foamed olefin resin sheet according to claim 2, wherein the intermediate roll has a temperature controller capable of controlling a surface temperature of the intermediate roll to a predetermined temperature. 5. The olefin resin foam sheet manufacturing apparatus according to claim 3, wherein the intermediate roll is accommodated between the die and the cooling roll. 6. The olefin resin foam sheet manufacturing apparatus according to claim 1, further comprising an olefin provided with an air knife for cooling the foam sheet separated from the intermediate roll and bringing the foam sheet into close contact with the cooling roll. 7. An olefin resin containing a foaming agent is plasticized and melted and extruded from a die, and is brought into contact with an intermediate roll near the beginning of the appearance of bubbles. Corrugation can be prevented after foaming is completed or by tension between the intermediate roll and the cooling roll. A method for producing a foamed olefin resin sheet in which the foamed sheet is separated from the intermediate roll after foaming is completed to the extent that the sheet thickness is reduced by the action of tensile force in the flow direction between the intermediate roll and the cooling roll. 8. The method for producing an olefin resin foam sheet according to claim 7, wherein the foam sheet separated from the intermediate roll is cooled using air from an air knife and closely adhered to the cooling roll. 9. An olefin resin foam sheet obtained by using the apparatus for producing an olefin resin foam sheet according to any one of claims 1 to 6.