JPH0985807A - Production of polyolefinic resin foamed sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the lowering of the rigidity of a non-foamed layer to prevent the lowering of the rigidity of the whole of a sheet by bunging a cooling roll into contact with one surface of an extrusion sheet at the position spaced apart from the leading end of a T-die lip by a specific distance in an extrusion direction and spraying a cooling medium on the other surface thereof. SOLUTION: A first cooling roll 2 and a cooling medium jet device 3 are arranged at a desired position spaced apart from the leading end 1a of the lip of a T-die 1 extruding a foaming agent and a polyolefinic resin after kneading in a molten state by 1-150mm in an extrusion direction. Further, the second cooling rolls 4 used by a usual method are arranged so as to guide the obtained foamed sheet 5. The polyolefin resin containing a foaming agent is extruded from the T-die 1 in a molten sheet form and the first cooling roll is brought into contact with one surface of the molten extruded sheet and a cooling medium is sprayed on the other surface thereof from the cooling medium jet device 3 to cool the sheet and this sheet is passed through the gaps of the second cooling rolls 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a foam sheet which is easy to operate, lightweight, highly rigid and has a smooth surface.

[0002]

2. Description of the Related Art Conventionally, when a foaming sheet having a foaming ratio of 1.8 times or more is produced by extrusion-foaming a polyolefin resin, the surface appearance is poor and the expansion ratio is difficult to increase.
In general, in the case of extrusion foaming, various types of foaming agents are mixed with molten resin under pressure and then extruded under atmospheric pressure through a die to foam, but when foaming agents are used in large amounts to increase the expansion ratio. The partial pressure of the gas generated by the foaming agent is high, and it becomes very difficult to hold the gas as cells in the molten resin. Therefore, various methods have been proposed in which the melt tension of the resin is increased to increase the gas holding power. Part 1
One example is a method of lowering the resin temperature near the die exit by using a cooling means such as a roll or a metal belt.

[0003]

However, the roll 2
In the method of producing a foamed sheet by using a book as a cooling means and installing it near the exit of a die (see Japanese Patent Laid-Open No. 63-288731), when the thickness of the foamed sheet produced is small and molding is performed at a relatively high speed. It is difficult to adjust the roll gap,
In some cases, the foamed sheet may be crushed or contact with the roll may be insufficient, resulting in insufficient cooling.

Further, a method for producing a foamed sheet by sandwiching it in a metal endless belt and cooling it (see, for example, JP-A-47-47).
In Japanese Patent Laid-Open No. 22969), it is necessary to replace the metal belt due to wear of the metal belt, etc. Generally, considering the durability of the metal belt when continuously used, it is necessary to increase the diameter of the roll for driving the belt. Therefore, it is difficult to install the belt in the vicinity of the die exit, and there is a problem that the cooling cannot be performed at the position to be cooled.

First, the applicant of the present invention prevented a fold-like vertical line (so-called corrugate) caused by volume expansion at the time of foaming when a foamed sheet was manufactured by extrusion using a T-die, and was lightweight. In order to produce a highly rigid foamed sheet, a method has been proposed in which a layer containing a filler and containing no foaming agent (non-foaming layer) is laminated on at least one surface of the foamed sheet (Japanese Patent Laid-Open No. 63-252715). Issue).

However, it is difficult to produce a foamed sheet having a sufficiently smooth surface by only providing a non-foamed layer, and the productivity is high, and the foaming ratio is relatively high, and particularly foaming of 1.8 times or more. When trying to obtain a sheet, it is difficult to maintain the expansion ratio immediately after extrusion, so it is difficult to raise it to the desired expansion ratio, and the foam cells are deformed or the cells are united to make them non-uniform and huge, and The smoothness tended to be impaired. Further, a part of the gas generated from the foaming agent present in the foam layer, the higher the gas partial pressure,
The phenomenon that the non-foaming layer containing the filler diffuses and the non-foaming layer foams, and the original rigidity of the non-foaming layer is lowered, and the rigidity of the entire sheet is significantly lowered. .

[0007]

Means for Solving the Problems As a result of intensive investigations by the present inventors in order to solve such problems, as a result, after extruding a resin into a sheet shape, the resin is extruded on one surface of the extruded sheet at a predetermined position. The present invention has been completed by bringing a cooling roll into contact and blowing a cooling medium to the other surface to cool it.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, in producing a foamed sheet by melt-extruding a foaming agent-containing polyolefin resin into a sheet form from a T die, a 1 to 150 mm from the tip of the T die lip in the extrusion direction. A polyolefin resin foam sheet characterized in that the extruded sheet is cooled by bringing a cooling roll into contact with one surface of the melt extruded sheet and spraying a cooling medium on the other surface at any of the separated positions. Is a manufacturing method.

The second aspect of the present invention is to provide a layer comprising a foaming agent-containing polyolefin resin, and a filler which contains 5 to 400 parts by weight of a filler per 100 parts by weight of the resin and essentially does not contain a blowing agent. When a non-foamed layer is laminated by melt-extruding a layer made of an agent-containing polyolefin resin into a sheet form from a T-die, which is separated from the tip of the T-die lip by 1 to 150 mm in the extrusion direction. At the position of, the co-extruded sheet is cooled by bringing a cooling roll into contact with one surface of the melted co-extruded sheet and spraying a cooling medium on the other surface of the molten co-extruded sheet. Is the way.

The manufacturing method of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of an example of an apparatus used in the method for producing a foamed sheet of the present invention, which is a T-die 1 for extruding a foaming agent and a polyolefin resin after melt-kneading.
And 1 to 150 mm in the extrusion direction from the T-die lip tip 1a
The first cooling roll 2 and the cooling medium injection device 3 are installed at desired positions separated from each other. Further, three second cooling rolls 4 used in a usual method are installed at the tip of the obtained foamed sheet 5 being guided.

A polyolefin resin containing a foaming agent is melt-extruded into a sheet form from the T-die 1, a first cooling roll 2 is brought into contact with one surface of the melt-extruded sheet, and the other surface is cooled. Cooling is performed by blowing a cooling medium from the medium ejecting device 3, and then the second cooling rolls 4 are passed through to perform main cooling to obtain the foamed sheet 5. The material of the first cooling roll 2 used in the manufacturing method of the present invention is not particularly limited, and examples thereof include metal rolls, ceramic rolls, rubber rolls, etc., and particularly metal rolls are preferable, and water or the like inside the rolls is preferable. The temperature is adjusted by flowing a refrigerant. The temperature is not generally determined depending on the extrusion temperature, the extrusion amount, the sheet thickness, and the expansion ratio, but is 10 to 100 ° C.
Is preferred. The size of the cooling roll is also not particularly limited, but those having a diameter of about 20 to 200 mm are preferable.

This roll is installed at a desired position separated from the tip of the T die lip in the extrusion direction by 1 to 150 mm, preferably 10 to 80 mm. This distance is the distance from the die exit and the center where the molten sheet is in contact with the roll surface. If the roll position is 1 mm or less, there is a risk that the roll and the die may come into contact with each other, which is not practical. If the roll position is 150 mm or more, most of the foaming is completed before the molten sheet comes into contact with the roll. Is not obtained and the smoothness of the surface deteriorates.

The cooling medium used in the production method of the present invention is not particularly limited, but one which has a high cooling effect and is free from dangers such as flammability and explosiveness is preferable. For example, air, carbon dioxide gas, Included are nitrogen, water and mixtures thereof. As a method of spraying these cooling media,
A known general method may be used. For example, an apparatus (air knife or the like) having a slit matching the width of the molten sheet, a method of arranging a plurality of nozzles in the width direction and spraying the nozzles, and the like can be mentioned. The spraying position of the cooling medium is not particularly limited, but preferably ± 0 from the center of the molten sheet in contact with the roll.
A position of ± roll radius × 0.9 is preferable. Roll radius ×
If it is 0.9 or more, the support of the sheet by the roll becomes weak, so that the molten sheet is pressed by the jetting pressure of the fluid, deformation or flapping occurs, and stable cooling cannot be obtained.

After that, it is further cooled by passing between the second cooling rolls 4 and 4. The material of the second cooling roll 4 is not particularly limited, but examples thereof include metal rolls, ceramic rolls, rubber rolls, and the like. Particularly, metal rolls are preferable, and the temperature is adjusted by flowing a coolant such as water inside the rolls. To do. The temperature is not generally determined depending on the extrusion temperature, the extrusion rate, the sheet thickness, the expansion ratio, and the amount of warp, but is preferably 30 to 120 ° C. The size of the cooling roll is also not particularly limited, but a diameter of about 200 to 500 mm is preferable.

The cooling from the tip of the T-die lip to a specific position in the present invention may be carried out a plurality of times, if necessary, and is particularly effective when the production rate is high and the expansion ratio is high. Further, the manufacturing method of the present invention has been described with reference to an example using the second cooling roll for further cooling the foamed sheet, but the second cooling roll is used as needed, and particularly When a plurality of one cooling rolls are used, the second cooling roll may not be used. Furthermore, the surface of the sheet may be decorated with a texture by a second cooling roll. A heating / cooling roll for warping correction may be provided after the second cooling roll.

The polyolefin resin used in the production method of the present invention includes low density, medium density, high density polyethylene, cotton-like low density polyethylene, polypropylene, and ethylene or propylene and other α-olefin. Examples thereof include a polymer, a copolymer of ethylene and vinyl acetate, (meth) acrylic acid, (meth) acrylic acid ester, vinyl alcohol and the like, and a mixture thereof.

As the foaming agent used in the production method of the present invention, azodicarbonamide, azobisisobutyronitrile, diazoaminobenzene, N, N'-dinitrosopentamethylenetetramine, N, N'- Dimethyl
N, N'-dinitroterephthalamide, benzenesulfonyl hydrazide, p-toluenesulfonyl hydrazide,
p, p'-oxybisbenzenesulfonyl hydrazide,
Chemical blowing agents such as carbonates and organic acid salts, propane, butane,
Physical foaming agents such as pentane, dichlorodifluoromethane, dichloromonofluoromethane, trichloromonofluoromethane, methanol, ethanol, water and the like can be mentioned.
If necessary, these foaming agents and foaming aids usually used,
A crosslinking agent, a nucleating agent, etc. may be used in combination, and the foam may be crosslinked. The kneading method of the polyolefin resin and the foaming agent is not particularly limited, but they are appropriately kneaded and then extruded into a sheet form from the T die.

Next, the second aspect of the present invention comprises a layer made of a foaming agent-containing polyolefin resin, and 5 to 400 parts by weight of a filler per 100 parts by weight of the resin, and essentially no foaming agent. This is a method for producing a foamed sheet in which a non-foamed layer is laminated by melt-coextruding a filler-containing polyolefin resin layer into a sheet shape from a T die.

Also in this method, as described in the first aspect of the invention, 1 to 150 from the tip of the T die lip in the extrusion direction.
It is possible to cool the coextruded sheet by bringing a cooling roll into contact with one surface of the melted coextruded sheet and spraying a cooling medium on the other surface at any position separated by mm so that the surface is smooth and beautiful. It is necessary to obtain a fine foam sheet.

The cooling roll, the cooling medium, the cooling position, etc. used are the same as in the first aspect of the invention, and will be omitted. The layer composed of the foaming agent-containing polyolefin resin used in the present invention is as described above, but the layer composed of the filler-containing polyolefin resin essentially containing no foaming agent is the resin 10
The filler is contained in an amount of 5 to 400 parts by weight, preferably 10 to 100 parts by weight, based on 0 parts by weight.

If the amount of the filler is less than 5 parts by weight, the rigidity of the non-foamed layer formed from the resin containing the filler is low and the rigidity of the sheet as a whole is not improved. On the contrary, if it exceeds 400 parts by weight. Extrusion molding becomes difficult. Incidentally, this resin is selected from the same polyolefin-based resin as described above, even if the same resin as the foaming agent-containing polyolefin-based resin,
It may be different.

As the filler, in the case of an inorganic powder system, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, aluminum phosphate, talc, mica, clay, carbon black, white carbon, Graphite, zeolite, barium sulfate, hydrous calcium silicate, etc., organic powders include phenol resin powders, ebonite powders, etc., and fiber types include glass, pulp, asbestos, polyethylene terephthalate, polyamide, etc. To be

In addition to these, antioxidants, colorants, ultraviolet absorbers, antistatic agents, plasticizers, and slip agents such as fatty acid metal salts and fatty acid amides may be added as required. The resin containing the filler is extruded such that the non-foamed layer formed therefrom is laminated on at least one or both sides of the foamed layer. In order to efficiently increase the rigidity of the entire sheet, it is preferable that the sheets are laminated on both sides.

If desired, a non-foamed layer made of a polyolefin resin may be laminated as a skin layer on one or both outer sides of the non-foamed layer. The polyolefin resin used is basically the above-mentioned one. The same as that used for the foamed layer and the non-foamed layer containing a filler, and can be selected according to the required quality (for example, gloss, surface decoration, antifouling, heat sealability, etc.). .

The laminating method may be a method of laminating the above resin in a molten state before extruding from the T die. Generally, a multi-manifold system in which both resins are melt-kneaded in respective extruders and then laminated in a T die, or a feed block system (combining adapter system) in which they are laminated before flowing into the T die are used. Good. In addition,
When a skin layer is further laminated on the laminated body of both resins, a generally-used laminating method such as dry laminating, wet laminating, extrusion laminating, coextrusion, or pressing may be used. Hereinafter, the present invention will be described in more detail with reference to Examples.

[0026]

【Example】

Example 1 A propylene-ethylene block copolymer (trade name, manufactured by Mitsubishi Chemical Co., Ltd.) as a filler-containing polyolefin resin (the layer obtained from this is referred to as layer 2 in the table).
Mitsubishi Polypro BC8, melt index 1.8g / 1
0 minutes) 100 parts by weight of 11 parts by weight of talc as a filler, and a propylene-ethylene block copolymer (trade name: Mitsubishi Polypro EC manufactured by Mitsubishi Chemical Corporation)
(9, melt index 0.5 g / 10 min) 100 parts by weight of a blowing agent-containing polyolefin resin (obtained from this), which is a mixture of 1.5 parts by weight of a 1: 1 mixture of monosodium citrate and sodium hydrogen carbonate as a blowing agent. (The layer is referred to as layer 3 in the table) are melt-kneaded with extruders having a diameter of 90φ and a diameter of 65φ, respectively, and then these kneaded materials are used as a middle layer in the latter just before the T die by a feed block method. 750mm width
When extruding from the T-die, set so that the center of a metal roll with a diameter of 50 mmφ, whose temperature is adjusted to 20 ° C, will come to a position 30 mm from the T-die exit, cool from below the extruded sheet, and slit at the same position. Air cooled to 10 ° C. was blown at an air velocity of 40 m / sec from an air knife having a gap of 1 mm and a width of 800 mm to cool from the upper side of the sheet. Thereafter, at a position of 350 mm from the die exit, it was further cooled while being narrowed by three metal polishing rolls having a normal diameter of 300 mm to obtain a foamed sheet having a non-foamed layer laminated thereon. The foamed cell state and the three-point bending elastic modulus of the obtained sheet were evaluated according to the following procedures. The results are shown in Table 1.

Foamed cell state: A sheet cross section (direction perpendicular to the flow direction) was sliced into about 10 to 20 μm with a microtome, observed with an optical microscope and photographed, and the minor axis and major axis of the cell were randomly measured and averaged. The cell diameter was defined as the cell diameter, and if 20% or more of the cells were coalesced at the same time, it was determined to be coalesced. Three-point flexural modulus; measured according to JIS-K7203.

[0028]

[Table 1] In the table, PEC represents a propylene-ethylene block copolymer. In the table, PP represents polypropylene. H in the table
DPE stands for high density polyethylene.

Example 2 Filler-containing polyolefin resin talc was made into resin 100
A sheet was obtained in the same manner as in Example 1 except that 67 parts by weight was used with respect to parts by weight. Example 3 80 parts by weight of the same propylene-ethylene block copolymer as in Example 1 was used as the foaming agent-containing polyolefin resin, and high-density polyethylene (trade name: Mitsubishi Polyethylene-HD HY540, manufactured by Mitsubishi Chemical Corporation, melt index 1.0 g). / 10 minutes) A mixture of 20 parts by weight and 67 parts by weight of talc, and further homopolypropylene (trade name: Mitsubishi Polypro FY6C, manufactured by Mitsubishi Chemical Corporation, melt index 2.4 g / 10 minutes) (the layers obtained from this are shown. (Indicated as layer 1) is extruded with an extruder having a caliber of 40 mmφ to form 5 layers of 3 types having skin layers on both surfaces of the 3-layer laminate of Example 1, and then T having a width of 750 mm. Extruded through a die. For cooling, the position from the die outlet is 50 mm, and the air velocity is 60 m.
A foamed sheet was obtained in the same manner as in Example 1 except that the time was set to / sec.

Example 4 2.0 parts by weight of azodicarbonamide was used as a foaming agent, and a mist (air pressure of 2 kg / cm ² , water pressure of 1.2 kg / cm ² ) produced by mixing air and water was used for cooling from the upper surface of the sheet. Install the nozzles (3 places) at a position of 30 mm,
It carried out like Example 3 except spraying and carrying out.

Example 5 The same procedure as in Example 4 was carried out except that the cooling from the upper surface of the sheet was carried out by flowing out water at 10 ° C. at a flow rate of 80 l / min into the air knife used in Example 1. Example 6 The procedure of Example 1 was repeated except that only the blowing agent-containing polyolefin resin was extruded.

Comparative Example 1 The procedure of Example 2 was repeated, except that cooling was not performed near the die exit. Comparative Example 2 The procedure of Example 2 was repeated, except that cooling was performed at a position 200 mm from the die outlet. Comparative Example 3 Example 1 was repeated except that cooling near the die outlet was changed to air blowing, and the same metal roll arranged so as to come to the lower side of the foam sheet was also used to the upper side of the foam sheet. I went the same way. The foamed sheet has a non-foamed part partially due to crushing, and if you look only at the foamed part,
Since the cooling state was not constant, variations as shown in the table were recognized.

[0033]

According to the method for producing a foamed sheet of the present invention, cooling is performed at an appropriate position in the vicinity of the extrusion die. On the other hand, the expansion ratio of the foam layer is improved, the cell state of the foam is also fine, and the coalescence of the cells is extremely small and a good foam state is obtained. Further, the obtained foamed sheet has a high three-point bending elastic modulus, and in particular, the foamed sheets formed by laminating the non-foamed layers are compared with each other in the same material and the same layer constitution (Example 2 and Comparative Example 1). The foamed sheet obtained by the above does not cause foaming due to the diffusion of the foaming agent from the foaming layer in the filler-containing polyolefin-based resin, so that the elastic modulus of the original non-foaming layer is expressed and the weight is further reduced.
It is a highly rigid foam. Further, according to the method for producing a foamed sheet according to the present invention, the cooling is performed by spraying the cooling roll and the cooling medium, so that it is not necessary to adjust the roll gap as compared with the conventional technique of cooling between the two cooling rolls. As shown in the results of Table 1, the obtained foamed sheet has an improved expansion ratio, its foamed state is uniform and good, and its thickness is uniform. (Example 1 and Comparative Example 3).

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a manufacturing method of the present invention.

[Explanation of symbols]

 1: T-die 1a: T-die lip tip 2: first cooling roll 3: cooling medium injection device 4: second cooling roll 5: foamed sheet

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location B29L 9:00 (72) Inventor Takumi Matsuno 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Co., Ltd. Yokkaichi (72) Inventor Osamu Akaike 1 Toho-cho, Yokkaichi-shi, Mie Mitsubishi Chemical Co., Ltd. Yokkaichi Research Institute

Claims (2)

[Claims] 1. In producing a foamed sheet by melt-extruding a foaming agent-containing polyolefin resin into a sheet form from a T-die, in the extrusion direction from the tip of the T-die lip to 1 to 150.
A polyolefin resin foam, characterized in that the extruded sheet is cooled by bringing a cooling roll into contact with one surface of the melt extruded sheet and spraying a cooling medium on the other surface at any position separated by mm. Sheet manufacturing method. 2. A layer comprising a foaming agent-containing polyolefin resin, and a filler-containing polyolefin resin which contains 5 to 400 parts by weight of a filler per 100 parts by weight of the resin and essentially does not contain a foaming agent. In a foamed sheet in which a non-foamed layer is laminated by melt-extruding a layer with a layer from a T-die in a sheet shape, the melt-blended layer is melted at any position 1 to 150 mm away from the tip of the T-die lip in the extrusion direction. A method for producing a polyolefin resin foamed sheet, comprising cooling a coextruded sheet by bringing a cooling roll into contact with one surface of the extruded sheet and spraying a cooling medium on the other surface.