JPS58108234A - Foamed sheet - Google Patents

Abstract

PURPOSE:To manufacture a foamed sheet having improved physical properties such as elongation, light transmittance, strength, heat insulation, etc., by compounding an ethylene polymer prepared by high-pressure radical polymerization with a specific ethylene-alpha-olefin copolymer, and subjecting the mixture to extrusion foaming. CONSTITUTION:About 80-50(wt)% homopolymer or copolymer of ethylene prepared by the high-pressure radical polymerization is compounded with about 20-50%, preferably about 25-40% copolymer of ethylene and a 3-8C alpha-olefin having a density of 0.91-0.95g/cm<3>, and foamed by extruding in the presence of a foaming agent. The ethylene-alpha-olefin copolymer is preferably the one containing about 0.2-8mol% alpha-olefin (propylene, butene-1, etc.) and having a melt index of about 0.5-30g/10-min.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foam sheet. More specifically, it relates to non-crosslinked ethylene polymer foam sheet) K.

Foamed sheets of ethylene homopolymers or comonomers obtained by pressure radical polymerization have been used as heat-insulating materials for agriculture, but improvements in the physical properties of these foamed sheets are still desired. The inventors have
K
As a result, it was possible to obtain a non-crosslinked foamed sheet with further improved physical properties such as elongation and light transmittance.

Accordingly, the present invention relates to a non-crosslinked foamed sheet, which is made of about 80.50% by weight of an ethylene homopolymer or copolymer obtained by a high-pressure radical polymerization method and an ethylene having a density α91 to α96g and carbon number 3-8
It is obtained by foaming and extruding an ethylene polymer comprising about 20 to 50% by weight of a copolymer with α-olefin in the presence of a blowing agent.

Homopolymers or copolymers of ethylene obtained by high-pressure radical polymerization are generally produced at a reaction pressure of about 1,000 to 3,000 using oxygen, various organic peroxides, azo compounds, acetoximes, aminic acid compounds, etc. as polymerization initiators.
Obtained by radical polymerization carried out under high atmospheric pressure. Ethylene copolymers used in the same way as polyethylene include ethylene and vinyl esters such as vinyl acetate, vinyl formate, vinyl glycolate, vinyl propionate, vinyl benzoate, acrylic acid, methacrylic acid, ethacrylic acid, or these. Includes salts, copolymers with acrylic monomers such as alkyl esters, etc.

Copolymers of ethylene and α-olefins having 3 to 8 carbon atoms (densities α9 to α9577/cm ) include ethylenetopropylene, butene-11 pentene-1, hexene-1,
It is a copolymer with octene-1,3-methylbutene-1, Q3-dimethylbutene-1, etc., and these copolymers are copolymers with chromium oxide, molybdenum oxide, titanium trichloride or titanium tetrachloride-alkyl aluminum, tetrachloride, etc. Using various catalysts such as titanium compounds such as titanium chloride, magnesium compounds such as magnesium chloride, and alkylaluminum (chloride), gas phase polymerization is carried out under low to medium pressure of about 1 to 100 kg/l, slurry 1, Manufactured by Solution Togane and others. And these copolymers have approximately 0
2-8 mol% α-olefin containing racket and about α6-3
Preferably it has a melt index of 0 g/l 0 min.

The high-pressure radical polymerized ethylene homopolymer i or copolymer and the ethylene-α-olefin copolymer are used in a mixture of about 80 to 501% by weight and about 20 to 50% by weight, respectively. If the mixing ratio of the ethylene-α-olefin copolymer is less than about 20% by weight, the resulting foamed sheet will not have the effect of improving the physical properties. On the contrary, about 501% by volume
When mixed at the above ratio, this copolymer has a linear structure and a narrow range of molecular weight distribution, resulting in a high melt viscosity at high shear rates, which makes it difficult to perform foam extrusion. The load on the motors of the extruder, bread parry mixer, etc. increases, and extrusion performance deteriorates. Furthermore, this copolymer has a lower melt tension than high-pressure radically polymerized ethylene polymer, and when its mixing ratio is increased, the foam tends to break and the cell size increases. Problems also arise. Considering these extrudability, foamability, physical properties of the sheet, etc., the most preferable mixing ratio of the copolymer is within the range of about 25 to 401E%.

As blowing agents, decomposition type chemical blowing agents that generate the gas necessary to foam the resin by heating, such as inorganic blowing agents such as sodium carbonate, sodium bicarbonate, and ammonium nitrate, or diazoaminobenzene, azodicarbonamide, dicarbonate, etc. Organic blowing agents such as nitrosopentamethylenetetramine, p+1''-oxybisbenzene, sulfonyl hydrazide, azobisisobutyronitrile, p-)luenesulfonyl hydrazide are generally ethylene-based organic compounds such as propane, butane, petroleum ether, etc. , monochlorotrifluoromethane, dichlorodifluoromethane, monochlorodifluoromethane, dichlorotetrafluoroethane, trichloroethylene, etc. may be used as a blowing agent by impregnating or directly injecting gas into the extruder. They can also be used together.

The foam sheet is formed using high-pressure radical polymerization of ethylene 11.
1 combination, ethylene-α-olefin copolymer blowing agent and optionally blowing 1'I! l Auxiliary agents, coloring agents, etc. 4!
Is it an extruder or a mixing roll for R-tank compounding agent? After uniformly mixing at a temperature that does not decompose the blowing agent using
This is done by extruding the foam from an extruder at a temperature above the decomposition temperature of the foaming agent (approximately 150 to 250°C).

When using the obtained foam sheet for agricultural and thermal materials, etc., the thickness should be about 0.15 to 2.0 mm and the foaming ratio should be about 1.
It is desirable that it is about 3 to 40 times larger. This foam sheet Vi is particularly excellent in terms of elongation and light transmittance, and Hikiyao has good elongation even if it does not change much, so even if you pull this foam sheet, it is difficult to tear, which is probably due to its high tensile strength. For this reason, it is used as a heat-retaining material for dual purposes, and has excellent workability when it is stretched, and its good light transmittance makes it suitable for this type of use to promote plant growth. d) yields favorable results.

Therefore, the foam sheet according to the present invention can be effectively used as a low-cost agricultural heat-retaining material that is superior in terms of light transmittance and physical strength compared to conventional sheets.

To explain these points in more detail, foamed sheets of ethylene monomer or copolymer obtained by conventional high-pressure radical polymerization have a light transmittance of about 40 to 60%, which is suitable for use as agricultural heat-insulating materials. When trying to get the rate,
One of the following methods will be used: (1) It is possible to increase the expansion ratio to approximately 2 times or more, but on the other hand, this will significantly reduce the physical properties, making it impossible to use it for such purposes (2) By increasing the thickness and basis weight of the foam sheet, it is possible to obtain appropriate heat retention, light transmittance, physical strength, etc., but this is not desirable from an economic standpoint. Then, a pigment such as titanium oxide may be added, but although this maintains the physical strength, the foaming ratio is low, resulting in poor heat retention, and both methods are unsatisfactory. See you in the future.

However, the foamed sheet of the present invention obtained by blending the 1-ethylene-α-olefin copolymer has a basis weight of 1259
It is lightweight at about /a2, has a high foaming ratio of about 21 times, and has excellent heat retention.

What's more, a suitable light transmittance can be obtained without the use of additives such as pigments, and the physical properties are improved by 9.1 points (all improved) compared to conventional foam sheets. Therefore, it can be effectively used as an economical heat-insulating material for the rice cake industry.

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

EXAMPLE According to the formulation shown in Table 1, an ethylene-vinyl acetate co-monomer obtained by high-pressure radical oxidation method was produced.Mitsui Polychemical Product B-332-1, vinyl acetate content 631% by weight, melt index a Og/ l O minutes)
and an ethylene copolymer consisting of ethylene-α-olefin copolymer Mitsui Petrochemical Products Tsuruto Zexu 2020L; density α920 and plane-melt index 2.2 II/l 0 min), 1 azodicarbonate as a blowing agent, Add midi, sodium bicarbonate and blowing aid;
Dry pre-greased using a ribbon blender.

The formed mixture was passed through a 115 diameter extruder (with a 280I 11 diameter offset die (slit width α5).
Ll/D -22) is supplied to the hopper with a maximum temperature of 1
All foam molding was carried out under processing conditions adjusted to 90° C. to form a foam sheet having a thickness α28W1 density α4577/♂ and a basis weight 1251) 7 m.

Table 1 Regarding the obtained 6 foam sheets, JIS K-76'
Tensile strength, elongation and tear strength were measured by the method specified in 767. As shown in the results in Table 2, it can be seen that the physical strength and light transmittance of the foamed sheet are improved by combining the ethylene-α-olefin co-metallic material.

Table 2

Claims (1)

[Claims] The homopolymer of ethylene obtained by Li41 + pressure radial polymerization method is a copolymer of about 80 to 60% by weight and ethylene with a density of α91 to α96 #6 IP and a carbon number of 3 to 8
A non-crosslinked foam sheet obtained by foaming and extruding an ethylene polymer comprising about 20 to 60% by weight of a copolymer with α-olefin in the presence of a blowing agent.