JPS60188430A - Crosslinked polyethylene foam for folded plate - Google Patents

Abstract

PURPOSE:The titled foam improved in mechanical properties such as roll moldability and suited as a heat-insulating material for folded plates, prepared by mixing low-density PE with low-density linear PE, a blowing agent, other additives, etc., and crosslinking and expanding the mixture. CONSTITUTION:A crosslinked PE foam for folded plates, prepared by mixing 20-80pts.wt. low-density PE with 80-20pts.wt. low-density linear PE formed by copolymerizing ethylene with a 4-8C alpha-olefin (e.g., a copolymer formed by copolymerizing ethylene with 1-10pts.mol butene-1 and having a density of 0.915- 0.94g/cm<3> and MI of 0.05-50g/10min), a blowing agent, and other additives, and crosslinking and expanding the mixture. This crosslinked foam is good in heat insulation, lightweightness, cushion, sound insulation, etc., and excellent also in mechanical strength, especially roll moldability, so that it is suitable as a heat-insulating material for folded plates used as roofing materials or external wall materials of a house.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a polyethylene crosslinked foam for folded plates with improved roll formability.

[Prior Art of the Invention] Conventionally, crosslinked foam made of low-density polyethylene has been used as a heat insulating material for folded plates used for roofs and outer walls of buildings.

However, low-density polyethylene crosslinked foams do not have sufficient mechanical strength, particularly roll formability, and therefore have a problem in that depending on the shape of the folded plates, they tend to break during molding.

In order to solve these problems, attempts have been made to improve the roll formability of low-density polyethylene crosslinked foams by lowering their expansion ratio, adjusting their degree of crosslinking, or by combining them with other materials.

However, with these methods, a number of new problems have arisen, such as variations in roll formability, increased manufacturing costs, and inability to obtain products of stable quality. The current situation was that the law had not yet been discovered.

[Object of the Invention] The present invention has been made in view of the above points, and it has all the various favorable properties of conventional low-density polyethylene crosslinked foams, and also has mechanical properties such as roll formability. The object of the present invention is to provide a polyethylene crosslinked foam that has improved mechanical strength and is suitable as a heat insulating material for folded plates.

[Summary of the Invention] The first invention of the present invention provides low density polyethylene 20 to 80
Linear low-density polyethylene made by copolymerizing ethylene with an α-olefin having 4 to 8 carbon atoms, 20 to 8 parts by weight.
The second invention is a cross-linked polyethylene foam for folded plates, characterized in that it is formed by cross-linking and foaming 0 parts by weight of low density polyethylene, a foaming agent and other additives, etc. part and highly charged polyethylene 10 to 30
A linear low-density polyethylene made by copolymerizing ethylene with an α-olefin having 4 to 8 carbon atoms is 20 to 7
This polyethylene crosslinked foam for folded plates is characterized by being crosslinked and foamed by blending 0 parts by weight with a foaming agent and other additives.

[Structure of the invention] Low density polyethylene (hereinafter referred to as)-DPF used in the present invention
It shows. ), the density is 0.910 to 0.930!
II lc! , more preferably 0.918 to 0.925
(1/cffl, the value of the melt index (hereinafter referred to as M■) is 1.0 to 20(]/10 minutes, more preferably 2
．． It is preferable to use one in the range of 0 to 10 o/10 minutes.

In addition, linear low-density polyethylene (hereinafter referred to as L-LDPE), which is mainly composed of ethylene and copolymerized with α-olefin having 4 to 8 carbon atoms, is as follows:
For example, by ionic polymerization reaction under medium and low pressure, ethylene is converted into butene-1, pentene-1, hexene-1, octene-1,
By copolymerizing a small amount (approximately 1 to 10 mole parts) of α-olefin such as 1,4-methylpentene-1, an appropriate number of short chain branches are introduced into the linear backbone polymer, thereby increasing the density. It is a polymer reduced to the range of ordinary high pressure method I DPE, with a density of 0.915 to 0.91/cnr,
MIO, 05-50 (1/10 minute is preferable,
More preferably, the MI is 1.0 to 10.0(]/10 minutes.

Commercial products of such L-LDPE include, for example, Ultzex 2020-L, 208CIC (both trade names of Mitsui Petrochemicals), Sumikisen-L, and FA-201.
(all are product names of Sumitomo Chemical), etc.

Furthermore, the high density polyethylene (hereinafter referred to as HOPE) used in the second invention of the present invention has a density of 0.940.
~0.965 (1/c/, more preferably 0.945~
0.960 (MI is 1°0 to 20tJ/10 at 1/c/
minutes, more preferably in the range of 2.0 to 10.0(]/10 minutes).

In the first invention, 1--L is added to the L D P E.
The ratio of DPE to be blended is L-LDPE to 20
It is suitable to blend in a proportion of 80 parts by weight, more preferably 20 to 50 parts by weight. In addition, an appropriate amount of a blowing agent such as azodicarbonamide (hereinafter referred to as ADCA) and a foaming agent may be added as necessary to obtain a desired expansion ratio, for example, an average cell diameter of 0.4 mm or more. Additives and the like are added and mixed to obtain a resin composition.

The reason why the blending ratio of L-LDPE was limited to the range of 20 to 80 parts by weight is that if the blending ratio of L-LDPE is less than 20 parts by weight, a product with sufficient mechanical strength, especially good roll formability, cannot be obtained. On the other hand, if it exceeds 80 folds, other properties deteriorate and it cannot be put to practical use.

Further, the L D P E in the second invention of the present invention
.

As shown in FIG. 1, the blending ratio of L-LDPE and HDPE is preferably within the range shown by diagonal lines in the triangular coordinates between the three components.

That is, 20 to 70 parts by weight of LDPE and ~
A resin composition is made mainly of a mixture of 30 parts by weight and 1 part by 20 to 70 parts by weight of L-LDPE, and a blowing agent and other additives as necessary are added and mixed as in the first invention. get.

The reason why the blending ratios among the three components were limited to the range shown by diagonal lines in the triangular coordinates in Figure 1 is because a product with sufficient mechanical strength, especially good roll formability, cannot be obtained outside this range.
This is also because other properties deteriorate, making it impossible to put it into practical use.

Next, in both inventions-C, this resin composition is kneaded using an extruder or the like at a temperature at which the blowing agent does not decompose, extruded into a predetermined shape, and then crosslinked by a method such as irradiation with ionizing radiation. Thereafter, the foam is heated to a temperature higher than the decomposition temperature of the blowing agent to produce a crosslinked foam.

The crosslinked foam thus obtained has an apparent density of 0.
025 (] /d or less, the average bubble diameter is 0.4 forceps φ or more,
Preferably, it has closed cells of 0.4 to 1.0iiφ.

[Embodiments of the invention] Examples of the present invention will be described below.

Example 1 Density 0.921(+/C11?, MI4.O(+/
LDPE for 10 minutes 70 parts by weight (hereinafter referred to as parts) and density 0
゜920 (1/cffl, MI2.O (+/1/10
30 parts of l-DPE (Urtozex) and ADCA21
1 part and 0.5 part of carbon black were mixed, cross-melted using an extruder, and formed into a sheet having a thickness of 2.0 mm.

Next, both sides of this sheet were crosslinked by irradiating an electron beam of 5.5 Mrad, and then passed continuously through a hot air oven kept at 250°C to foam, resulting in a smooth surface with a thickness of about 8.0°C. A crosslinked foam sheet was obtained.

Example 2 50 parts of LDPE with density 0.921(]/ci, MT4.0(]/10 minutes and density 0.920a/Li, MI2,
Oo/10 minutes of Urtozex 30 parts and density 0.95
7(+/cut, M16.5(+/10min Hl)
Mix 20 parts of PE, AD CA 22811 and 0.5 part of carbon black, and use an extruder to make the mixture to a thickness of 2°0.
It was formed into a rabbit sheet.

Next, both sides of this sheet were irradiated with a 5 M rad electron beam to crosslink it, and then passed through a hot air oven at 250°C continuously to foam, resulting in a crosslinked foam with a smooth surface and a thickness of 8.0 mm. Got a sheet.

Comparative Example 7 - Density 0.920! + /c+/XMI4. Of+ /1
22 parts of ADCA and 5 parts of carbon black were added to 100 parts of 0.0% LDPE, mixed, and formed into a sheet with a thickness of 2.0 cm using an extruder.

Next, 5. on both sides of this sheet. After crosslinking by irradiation with an OMrad electron beam, the foam was continuously passed through a hot air oven at 250° C. to form a crosslinked foam sheet having a smooth surface and a thickness of 8.0 inches.

Next, the properties of the crosslinked foam sheets obtained in Examples 1 and 2 and Comparative Example were measured according to the JIS-6767 method. The measurement results are shown in Table 1.

In addition, as shown in Fig. 3, these cross-linked foamed 8-integrated sheets were sliced into 1/2 thickness 1 and placed on a steel plate 2.
This adhesive plate was then roll-formed into a folded plate shape. Table 2 shows the surface condition of the crosslinked foam sheet in the obtained heat insulating folded plate.

[Effects of the Invention] As is clear from the above examples, the crosslinked foam of the present invention has good heat insulation properties, light weight, cushioning properties, sound insulation properties, etc., and has excellent mechanical strength, especially roll formability. Therefore, it is suitable as a heat insulating material for folded plates used as roofing materials and exterior wall materials of houses.

[Brief explanation of the drawing]

Figure 1 shows LDPE and 1-LDPE in the second invention.
Fig. 2 is a perspective view of a heat-insulating folded plate formed to examine the roll formability of the crosslinked foam sheets obtained in Examples and Comparative Examples. It is. 1...Crosslinked foam sheet 2...
...... Steel plate Applicant: Sekisui Chemical Co., Ltd. Representative: Mototoshi Fujinuma 11- Figure 1 Figure 2

Claims (2)

[Claims] (1) 20 to 80 parts by weight of low density polyethylene, 20 to 80 parts by weight of linear low density polyethylene made by copolymerizing ethylene with an α-olefin having 4 to 8 carbon atoms, and a blowing agent and other additives. 1. A crosslinked polyethylene foam for folded plates, which is formed by crosslinking and foaming with a compounding agent, etc. (2) 20 to 70 parts by weight of low density polyethylene, 10 to 30 parts by weight of high density polyethylene, and 4 carbon atoms in ethylene.
A folded plate characterized by being crosslinked and foamed by blending 20 to 70 parts by weight of linear low density polyethylene obtained by copolymerizing α-olefins of 8 to 8 with a foaming agent and other additives. A method for producing a polyethylene crosslinked foam for use.