JPS6111216A - Manufacture of expanded polyethylene resin body - Google Patents

Abstract

PURPOSE:To prevent the formation of cavities in an expanded polyethylene resin having a high expansion ratio and a high closed cell ratio by a method in which a resin composition consisting primarily of polyethylene resin and polybutene resin is melted and mixed with a blowing agent, the mixture is extruded through the plural nozzles of an extruder while being expanded, and the fine lines of the expanded resin are mutually bonded. CONSTITUTION:A resin composition consisting primarily of polyethylene resin and polybutene resin is charged into an extruder 1 and plasticized by melting. The resin composition is well mixed by turning a screw 10 and mixed with a volatile blowing agent, and the mixture is extruded through the plural nozzles 120 of the extruding port 13 to form plural fine lines of expanded resin. The fine lines are properly cooled while being passed through a sizing mold 2 and integrally bonded to each other to form an expanded resin molding of a given thickness. In this case, 85-65pts.wt. polyethylene resin is mixed with 15-30pts. wt. polybutene resin, and a volatile blowing agent or a blowing agent to be decomposed when heated is used in an amount of 20-30pts.wt. on the basis of 100pts.wt. resin composition.

Description

[Detailed description of the invention] (Technical field) Reihatsumyo is a method of manufacturing polyethylene resin foam.

In particular, the present invention relates to a method for producing a polyethylene resin foam with a smooth surface and a high expansion ratio and a high closed cell ratio.

(Conventional technology) For a method of manufacturing a resin foam with a high expansion ratio.

For example, nine foamable thermoplastic resins are placed close together.

A method in which several hollow bodies are extruded in the same direction and then fused and integrated (Japanese Patent Application Laid-open No. 49-59170); resin foam strips are obtained from an extrusion port consisting of a plurality of holes, and these A method of obtaining a thick foamed molded product with no internal cavities by integrating the foamed resin (Makikai 52-137469); A method of obtaining a resin foam having a high-density surface layer without internal cavities by passing it through the body (Japanese Patent Laid-Open No. 58
-3837).

In any of the above conventional methods, the extruded foam can be easily fused during sizing because the foaming is carried out at a temperature considerably higher than the melting point of the resin used. But power 1
Since the first foaming temperature is so high and sizing is performed after the second foaming, the second foaming is suppressed and the foaming ratio is 1.
It is as low as 0 times or less. Although there is no description regarding the closed cell ratio, it is expected that this will also be low. On the other hand, if the foaming temperature is lowered below the melting point of the resin used in an attempt to obtain a foam with a high expansion ratio and a high closed cell ratio, the foam strips extruded from the extrusion port will not fuse together even during sizing. .

(Objective of the Invention) The object of the present invention is to produce a polyethylene resin foam having a high expansion ratio (10 times or more) and a high closed cell ratio (50% or more), and having a smooth surface and no internal cavities. The purpose is to provide a manufacturing method.

(Structure of the Invention) The present invention is based on the inventor's idea that the resin composition used is mainly composed of polyethylene resin and polybutene resin, and that the molding temperature range can be effectively expanded by foaming this with a foaming agent. It was completed based on new knowledge. Therefore, the method for producing a polyethylene resin foam of the present invention is (
1) Melting and plasticizing a resin composition mainly consisting of a polyethylene resin and a polybutene resin, (2) Adding a blowing agent to the melt-plasticized composition, (3) Melting a plurality of blowing agent-containing compositions. (4) fusing each extruded foam strip from the extrusion port to each other;
This achieves the above objective.

There are no particular restrictions on the degree of polymerization or density of the polyethylene resin constituting the resin composition, and any one type or a mixture of multiple types may be used. Its melt index ranges from 0.1 to 20.0, preferably from 0.3 to 5.0. As the polybutene resin, a copolymer of polybutene-1 and a small amount of olefin and/or a copolymer of butene-1 and a small amount of olefin is used. The melt index of the polybutene resin is in the range of 0.1 to 10.0, preferably in the range of 0.3 to 5.0. The polybutene resin is used in an amount of 15 to 30 parts by weight based on 85 to 65 parts by weight of the polyethylene resin. If the mixing ratio of the polybutene resin is less than 15 parts by weight, the polybutene resin will no longer be able to perform its original function of effectively expanding the molding temperature range of the extruded foam. As a result, the foam strips from the extrusion port are not sufficiently fused together. When the temperature at the extrusion port of multiple holes is raised to improve the adhesion between the foam strips, the adhesion improves, but the expansion ratio and closed cell ratio decrease.The mixing ratio of polybutene resin is 30 parts by weight. If it exceeds , the bubbles tend to collapse during the sizing process, resulting in a decrease in the closed cell ratio.

As the blowing agent, a volatile blowing agent or a blowing agent that decomposes when heated is used. Examples include low-boiling aliphatic hydrocarbons such as propane, butane, pentane, and hexane; low-boiling organic compounds such as alcohols, ketones, and esters; monochlorodifluoromethane, dichlorodifluoromethane, and dichloromethane. Volatile blowing agents such as halogenated hydrocarbons such as tetrafluoroethane; azo compounds, sulfohydrazide compounds, azide compounds.

There are pyrolytic blowing agents such as ammonium carbonate and soda bicarbonate. Particularly preferred are volatile blowing agents.

The blowing agent mixed into the thermoplastic resin can be mixed into the resin in advance, but in the case of a volatile blowing agent, the blowing agent is directly pressurized into the extruder cylinder and kneaded into the heated and melted resin. I can do it. The content of this foam in the resin composition is appropriately set depending on the type of resin composition, the desired expansion ratio, molding temperature, and the like. Usually, the amount is 20 to 30 parts by weight per 100 parts by weight of the resin composition.

Examples of resin foams obtained by the present invention include thick-walled foams (solid or hollow) and foams covering a core material.

The present invention will be explained below with reference to Examples.

(Example) FIGS. 1 and 2 show an example of an extrusion molding apparatus for obtaining a thick-walled foam by the method of the present invention.

This molding device includes an extruder 1 equipped with a resin extrusion port 13 at its tip, and a sizing mold 2 disposed near the extrusion port 13. A perforated plate 12 is disposed at the extruder tip 11, and a plurality of holes 120 in the perforated plate 12 constitute an extrusion port 13. There are no particular restrictions on the shape and dimensions of the hole 120, but as shown in FIG.

It is preferable that they be arranged in such a manner that The sizing mold 2 is placed in front of the perforated plate 12 and close to the perforated plate 12 . The inner surface of the sizing mold 2 is coated with a fluororesin such as Tef or Ron in order to improve the sliding contact with the outer surface of the foam passing through it. Also,
A refrigerant such as water or oil is circulated inside the sizing mold 2 so that the temperature can be controlled. Temperature control by air cooling is also possible.

Using the above apparatus, the resin foam of the present invention is manufactured as follows. The resin composition of the present invention, which is mainly composed of polyethylene resin and polybutene resin, is put into this extruder 1, where it is melted and plasticized.Next, the screw 10 is rotated to knead it, and at the same time, a volatile blowing agent is press-injected into it. Then, it is extruded from the extrusion port 13 while foaming. Extrusion port 1
3, the extruded foam forms a plurality of strips. These extruded foam strips are further cooled appropriately while passing through the forward sizing mold 2, and are fused together and integrated to form the desired thick-walled foam.

FIGS. 3 and 4 show an example of a covering mold apparatus for obtaining a covering foam for a core material by the method of the present invention. This device includes a coating mold 3 equipped with a resin extrusion port 32 at the tip,
Sizing mold 2 placed near the extrusion port 32
and has.

- The covering mold 3 is composed of, for example, an outer mold 21 and an inner mold 22. The inner mold 22 is fixed to the outer mold 21 at a rear portion 111 of the outer mold 21 by screw means 112 or the like across a resin passage 30. One end of this resin passage 30 is connected to a supply port 31 for the resin composition, and the other end is connected to an extrusion port 32 at the tip of the coating mold. The resin passage 30 is composed of a plurality of grooves 320 in the axial direction at the extrusion port 32 and its vicinity, as shown in FIG. These plurality of grooves 320 are formed around the core material transfer through hole 100 in the center of the inner mold 22 at equal intervals on a circumference concentric with the through hole.

The core material 101 to be coated is moved through the through hole 100 from the rear of the coating mold to the front by a core material transfer means such as a roll 5.

When forming a thick coating layer, in addition to the grooves 320, it is also possible to provide a plurality of concentric holes located on a concentric circle having a smaller diameter than the concentric circle in which the grooves are located. . If these conditions are selected appropriately, sizing mold 2
This facilitates molding and suppresses a decrease in expansion ratio and closed cell ratio due to excessive extrusion. The sizing mold 2 is the same as that of the extrusion molding apparatus.

The resin foam of the present invention can also be produced using such a covering mold device in the same manner as in the case of the extrusion molding device.

Specific examples of producing resin foam using each of the above-mentioned apparatuses will be described below.

80 parts by weight of pellets of polyethylene resin (trade name Yucalon NF90; manufactured by Mitsubishi Yuka Corporation, density 0.930 g/cm', melt index 1.5, melting point 116°C), polybutene resin (trade name A, A, polybutene #
8640, manufactured by Adeka Argus Co., Ltd., density 0.90
B. Melt index 1. O1 melting point 102.2℃ ~
20 parts by weight of pellets (112.5°C) and 0.8 parts by weight of fine talc powder were mixed. This is extruder 1 in Figure 1.
(diameter: 40 m, length/diameter -30).

The temperature of each part of the barrel of the extruder L is sequentially in the direction of the extrusion port 13: supply part 120 °C, compression part 150 °C, metering part 160
℃ and the torpedo portion was 140°C, and the temperature of the perforated plate 12 was 114°C. The resin extrusion rate was set to 8 kg/hr by rotating the screw 100 times. Freon 114 (trade name) as a volatile foaming agent is injected into the resin composition from the middle of the barrel at a ratio of 26 parts by weight per 100 parts by weight of the composition using a high-pressure pump, and then from the extrusion port 13 of the perforated plate 12. It was extruded while foaming. The perforated plate 12 is provided with nine equally pinched holes 120 each having a diameter of 1.5 square meters (a = 10 m). The sizing mold 2 has an inner cross section of 3 sides.
It is a square of 0m.

The shaft length (coaxially with extruder 1) was 100 mm. Its inner surface is coated with Teflon.

Its temperature was maintained at a constant level by circulating room temperature water inside.

The obtained foam had a smooth surface, good adhesion between the extruded foam strips, and no cavities were observed. The foaming ratio was as high as 27 (density was 0.034 g/cm'').The closed cell ratio was also as high as 78%.The results are shown in the table below along with other examples.

Experimental Examples 2 to 7 were carried out below by changing the mixing ratio of the polyethylene resin and polybutene resin in Experimental Example 1 and setting the temperature of the perforated plate 12 during extrusion foaming to a condition considered to be optimal for the resin composition. went.

Remarks 1111: 100% polyethylene resin was used and polybutene resin was not used, and the temperature of the perforated plate 12 was
Everything was the same as in Experimental Example 1 except that the temperature was set at 10°C. The resulting foam had poor adhesion between the foam strips. The foaming ratio is 25. The closed cell ratio was 92%.

Everything was the same as in Experimental Example 1 except that 10 parts by weight of the polybutene resin was used for 90 parts by weight of the polyethylene resin and the temperature of the perforated plate 12 was set at 113°C. The resulting foam had poor adhesion between the foam strips, and the foaming ratio was 25. The closed cell ratio was 82%.

Loss of armpit■↓ 15 parts by weight of polybutene resin was used for 85 parts by weight of polyethylene resin, and the temperature of the perforated plate 12 was adjusted to 1.
Everything was the same as in Experimental Example 1 except that the temperature was set at 13°C. The resulting foam had good adhesion between the foam strips. The foaming ratio is 25 times and the closed cell ratio is 78%.
Met.

叉幹■] Everything was the same as in Experimental Example 1 except that 30 parts by weight of polybutene resin was used for 70 parts by weight of polyethylene resin. The resulting foam had good adhesion between the foam strips. The foaming ratio is 30 times, and the closed cell ratio is 63.
It was %.

Everything was the same as in Experimental Example 1 except that 35 parts by weight of polybutene resin was used for 65 parts by weight of polyethylene resin for the armpit area. The resulting foam had good adhesion between the foam strips, the expansion ratio was 30 times, and the closed cell ratio was 57.
%Met.

Bold ■1 Everything was the same as in Experimental Example 1 except that 40 parts by weight of polybutene resin was used for 60 parts by weight of polyethylene resin. The resulting foam had good adhesion between the foam strips. The foaming ratio is 34 times, and the closed cell ratio is 35.
%Met.

Large U5■ Same as Experimental Example 1 except that Yucalon NH30 (density 0.925, melt index 2.8, melting point 112.5°C) manufactured by Mitsubishi Yuka Co., Ltd. was used as the polyethylene resin in Experimental Example 1. It is. The temperature of the perforated plate 12 was set at 113°C, which is considered to be optimal for this composition. The resulting foam had good adhesion between the foam strips. Its foaming ratio is 30. The closed cell ratio was 75%.

The procedure was the same as in Experimental Example 1 except that the temperature of the perforated plate 12 was 117°C instead of 114°C in Main Experimental Example 1. The resulting foam had good adhesion between each foam strip, but the expansion ratio was 18 and the closed cell ratio was 25%.
It was low.

(Margins below) 80 parts by weight of pellets of polyethylene resin (trade name: Yucalon NF90), polybutene resin (trade name: Meijin).

20 parts by weight of pellets of A polybutene 18640) and 0.8 parts by weight of fine talc powder were mixed. This was put into the coating mold apparatus shown in FIG. 3 through the resin supply port 31. The extrusion port 32 has 12 grooves 32 with a semicircular cross section of 0.75R.
Consists of 0. These grooves 320 are arranged at equal intervals on a circumference with a radius of 7.5 mm centered on the axial center of the core material transfer through hole 100 passing through the center of the inner mold 22. In this coating mold apparatus, the diameter of the extrusion mechanism section consisting of the outer mold 21 and the inner mold 22 was 40 mm, and the length and diameter were 30 mm. The temperature of each part of the barrel of the extrusion mechanism section was, in order toward the extrusion port 32, 120° C. in the feeding section, 150° C. in the compression section, 160.degree. C. in the metering section, and 140.degree. C. in the torpedo section.

The temperature near the groove 320 of the extrusion port 32 was 114°C.

From the middle of the barrel, add Freon 114 (trade name) as a volatile foaming agent to 100 parts by weight of the resin composition.

26 parts by weight were forced into the composition using a high pressure pump.

It was extruded through the groove 320 of the extrusion port 32 while foaming at an extrusion rate of 8 kg/hr. This was further passed through the sizing mold 2 in the front. The sizing mold 2 has an inner cross section with a diameter of 3
It is a circle of 0m and 2. The length in the axial direction (coaxial with the core material 101) is Loomm. The inner surface is coated with Teflon. Room-temperature water circulates inside to keep the sizing mold at a constant temperature.

The resulting foam had a smooth surface and a perfect circle.

It was in close contact with the core material 101. The expansion ratio was 29 (density 0.032 g/ctt+'') and the closed cell ratio was 78%.

(Effects of the Invention) According to the present invention, the molding temperature range can be effectively expanded by using polybutene resin in addition to polyethylene resin as the resin used. For this purpose, each foam strip extruded through a multi-hole extrusion port can be formed by properly selecting the molding temperature.

While passing through the sizing mold, they can fuse together to form an integrated foam without voids. The expansion ratio and closed cell ratio are both extremely high. The foam thus obtained can therefore be used very effectively as a heat insulating material or as an insulating material for covering a core material of an electric wire or the like.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an example of an apparatus for producing foam by the method of the present invention, FIG. 2 is a front view of the perforated plate 12 of the apparatus shown in FIG. 1, and FIG. 3 is a view of the foam producing apparatus. A side sectional view showing another example, and FIG. 4 is a front sectional view of the extrusion port 32 taken along line XX of the apparatus of FIG. 3. DESCRIPTION OF SYMBOLS 1... Extruder, 2... Sizing mold, 3... Coating mold, 4... Nozzle, 5... Roll, 10...
·screw. 12... Porous plate, 13.32... Extrusion 0.30.
...Resin passage, 31...Resin supply port, 100...
Through hole, 101... Core material, 120... Hole, 320.
...Mizojo. that's all

Claims (1)

[Claims] 1. (1) A step of melt-plasticizing a resin composition mainly consisting of a polyethylene resin and a polybutene resin, (2) A step of containing a blowing agent in the melt-plasticized composition, (3) (4) extruding the foaming agent-containing composition from an extrusion port of an extrusion molding machine having a plurality of holes; and (4) fusing each extruded foam strip from the extrusion port to each other. A method for producing a polyethylene resin foam. 2. The method according to claim 1, wherein the resin composition comprises 85 to 65 parts by weight of polyethylene resin and 15 to 30 parts by weight of polybutene resin. 3. Claim 2, wherein the polybutene resin is at least one of a copolymer of polybutene-1 and olefin and a copolymer of butene-1 and olefin.
The method described in section. 4. The method according to claim 1, wherein the fusion is performed using a sizing mold placed near the extrusion port.