JPH1199593A - Sealing material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material containing a polyolefin as a main component which is excellent in sealability, transparency, mechanical strength, and others, is capable of a high frequency seal, and can be used as a substitute for a polyvinyl chloride material. SOLUTION: A high frequency sealing material is prepared by a method in which (A) on one side or both sides of a layer which is prepared from an ethylene-carbon monoxide copolymer and/or an ethylene-vinyl acetate copolymer and has the product of a dielectric constant of 13.56 MHz frequency and a dielectric loss tangent of at least 0.1, (B) an ethylene-α-olefin copolymer sealing layer which is prepared by a single site catalyst and has a density of 860-905 kg/m<3> is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency sealing material having excellent sealing properties, transparency, mechanical strength and the like.
More specifically, the present invention relates to a high-frequency sealing material mainly composed of an olefin polymer, which is suitable as a substitute material for polyvinyl chloride.

[0002]

2. Description of the Related Art Polyvinyl chloride is used in various fields as a resin having excellent transparency and flexibility. It also has the advantage of being capable of high-frequency sealing, and is therefore widely used for applications utilizing its characteristics. However, polyvinyl chloride has a drawback in that the liquid plasticizer leaches out over time on the surface of the molded article and contaminates the surface, impairing transparency and hardening. In addition, there is a problem in that when the waste is incinerated, there is a risk of generating corrosive gas or generating harmful substances. Therefore, a flexible alternative material containing no halogen is widely demanded.

As one of such polyvinyl chloride substitute materials, thermoplastic elastomers based on copolymers of olefins have attracted attention, but this material is inactive to high-frequency heating. is there. On the other hand, a copolymer of an olefin and a polar vinyl compound obtained by copolymerizing a polar vinyl monomer in a considerable amount is capable of high-frequency sealing and has sufficient flexibility. However, because of its low mechanical strength and poor solvent resistance, it cannot be said to be satisfactory as a substitute for polyvinyl chloride.

[0004]

In view of the above circumstances, the present inventors have sought a material based on an olefin polymer which is excellent in transparency, flexibility and mechanical strength, and which can be sealed with high frequency. went. As a result, they have found that a specific olefin polymer laminate as described below satisfies these requirements, and have reached the present invention. Accordingly, an object of the present invention is to provide an olefin polymer material which can be replaced with polyvinyl chloride and which can be sealed by high frequency.

[0005]

SUMMARY OF THE INVENTION The present invention comprises an ethylene / carbon monoxide copolymer and / or an ethylene / vinyl acetate copolymer and has a product of a dielectric constant and a dielectric loss tangent at a frequency of 13.56 MHz of 0.1. On one or both sides of the above layer (A), the density produced by the single-site catalyst is 860.
The present invention relates to a high-frequency seal material provided with an ethylene / α-olefin copolymer seal layer (B) of up to 905 kg / m ³ .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, when a layer (B) is provided on one surface of a layer (A), the layer (B) becomes a sealing layer, and the other surface of the layer (A) is adjacent to the other surface. To provide another layer (X). In this case, a layer (B) may be provided adjacent to the layer (X). When the (B) layer is provided on both sides of the (A) layer, at least one of the (B) layers may be used as a sealing layer, and another layer (X) is adjacent to one of the (B) layers. May be provided.

For the layer (A), an ethylene / carbon monoxide copolymer and / or an ethylene / vinyl acetate copolymer is used. These ethylene copolymers have a frequency of 13.56.
The product of the dielectric constant and the dielectric loss tangent measured in MHz is 0.1 or more,
Preferably, those having 0.1 to 0.5 are used. If the product of the two is smaller than the above range, sufficient high frequency sealing performance cannot be exhibited.

[0008] Of the ethylene copolymers used as the (A) layer, the ethylene / carbon monoxide copolymer includes not only a copolymer of ethylene and carbon monoxide but also a polar vinyl monomer. It may be a multi-component copolymer. As such a copolymer, ethylene is 50 to 9%.
5% by weight, preferably 55-90% by weight, carbon monoxide 3-30% by weight, preferably 5-20% by weight, polar vinyl monomer 0-40% by weight, preferably 5-30% by weight. Those copolymerized in a ratio are preferred. That is, if the ethylene content is less than the above range,
In some cases, the mechanical strength is low, and the interlayer adhesion with the layer (B) cannot be sufficiently increased. If the carbon monoxide content is less than the above range, the high-frequency sealing performance is reduced, while if the carbon monoxide content is too large, the mechanical strength and the interlayer adhesion to the (B) layer are adversely affected. So you should avoid it.

Further, in order to improve the high-frequency sealing property and the interlayer adhesion to the layer (B), it is desirable that a polar vinyl monomer is contained as a third component in an appropriate amount within the above range. As such a polar vinyl monomer,
Unsaturated carboxylic acids or anhydrides such as vinyl acetate, vinyl esters such as vinyl propionate, acrylic acid, methacrylic acid, maleic acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, and itaconic anhydride Salts of these unsaturated carboxylic acids, for example, salts of lithium, sodium, potassium, magnesium, zinc, etc., methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, Examples thereof include unsaturated carboxylic esters such as isobutyl methacrylate and diethyl maleate. These polar vinyl monomers may contain two or more kinds.

As the layer (A), an ethylene / vinyl acetate copolymer having a product of a dielectric constant and a dielectric loss tangent within the above range can be used. Such a copolymer has a vinyl acetate content of 21 to 40% by weight, preferably 2 to 40% by weight.
2 to 35% by weight. If the vinyl acetate content is smaller than the above range, the product of the dielectric constant and the dielectric loss tangent is generally small, and does not exhibit sufficient high-frequency sealing performance. On the other hand, if the vinyl acetate content is larger than the above range, the mechanical strength is small and the interlayer adhesion to the layer (B) is adversely affected. Of course, when two or more ethylene-vinyl acetate copolymers are used, one having a vinyl acetate content of less than 21% by weight may be used as one component as long as the above product is satisfied.

The above ethylene / carbon monoxide copolymer and / or
Or ethylene-vinyl acetate copolymer, moldability,
Considering the mechanical strength and the like, the melt flow rate at 190 ° C. and a load of 2160 g is 0.01 to 1000 g /
It is desirable to use one for 10 minutes, preferably about 0.1 to 200 g / 10 minutes.

Such an ethylene copolymer can be produced by a method similar to the method for producing high-pressure polyethylene.

As the (A) layer, an ethylene / carbon monoxide copolymer, an ethylene / vinyl acetate copolymer or a mixture thereof is used, and the product of the dielectric constant and the dielectric loss tangent satisfies 0.1 or more. As long as the object of the present invention is not impaired, other polymers can be blended in small amounts.

In the present invention, the density obtained by copolymerizing ethylene and an α-olefin in the presence of a single-site catalyst is preferably 860 to 905 kg / m ³ , as a seal layer on at least one surface of the layer (A). Is 8
A layer (B) of an ethylene / α-olefin copolymer of 70 to 900 kg / m ³ is provided, and this is used as a high-frequency sealing material as a sealing layer. Such an ethylene / α-olefin copolymer does not itself have high-frequency sealing properties, but the presence of the layer (A) enables high-frequency sealing.

When an ethylene / α-olefin copolymer having a density higher than the above range is used,
It is difficult to obtain a sealing material having excellent high-frequency sealing properties while sacrificing flexibility, and if a sealing material smaller than the above range is used, heat resistance is inferior, stickiness appears and solvent resistance is sufficient. Therefore, application to food and beverage packaging becomes difficult.

As the α-olefin in the above copolymer, in order to impart sufficient mechanical strength to the laminate,
It is desirable to select one having 4 to 18 carbon atoms, preferably 5 to 10 carbon atoms, and more preferably 6 to 8 carbon atoms. More specifically,
It is preferably selected from 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene and the like.

The composition of these copolymers is preferably such that the content of α-olefin is 2 to 45% by weight, especially 4 to 30% by weight.

In consideration of moldability, mechanical strength and the like, the copolymer has a melt flow rate at 190 ° C. and a load of 2160 g of preferably 0.1 to 200.
g / 10 minutes, particularly preferably 1 to 100/10 minutes.

The single-site catalyst is a polymerization catalyst having a single active site. As a single-site catalyst for olefin polymerization, for example, a catalyst comprising a cyclopentadienyl coordination transition metal compound and an aluminoxane (Macr.
omol. Chem. Macromol. Symp., 4, 103 (1986)) or a catalyst using a cyclopentadienyl-coordinated rare earth metal compound or an organometallic compound (J. Chem. Soc., Ch.
em. Comuni., 994 (1978)).

The ethylene / α-olefin copolymer obtained by such a single-site catalyst has a feature that the molecular weight distribution and the composition distribution are narrow, and for example, the MWD (weight average molecular weight / number average molecular weight) is 3 2.0, preferably 2.5 or less, and the composition distribution width index (C
DBI) of 50% or more, preferably 70% or more. One example of such a copolymer is disclosed in, for example, Japanese Patent Publication No. 6-509528. Ethylene obtained with a single-site catalyst
As another example of the α-olefin copolymer, the melt flow ratio (I ₁₀ / I ₂ ) is 5.63 or more, preferably 7 to 20 and the MWD is (I ₁₀ / I ₂ -4.63). ) The following can be exemplified. One example of such a copolymer is disclosed in the specification of WO 95/00857.

Such an ethylene / α-olefin copolymer has a lower melting point than ordinary ethylene / α-olefin copolymers having the same comonomer content, so that high-frequency sealing is easy and the molecular weight distribution is narrow. Because there are few low molecular weight components, there is little stickiness, there is no bleed out to the product surface, and there is no surface contamination,
An excellent high-frequency sealing material can be obtained by laminating with an ethylene copolymer which is suitable as a sealing layer material and has high-frequency sealing properties.

Additives can be arbitrarily added to the layers (A) and (B). Representative examples of such additives include tackifying resins, antioxidants, weather stabilizers, light stabilizers, ultraviolet absorbers, pigments, dyes, lubricants, antistatic agents, and the like.

In the present invention, the thickness of the layer (A) is preferably at least 100 μm, for example, 50 μm.
0 to 3000 μm, preferably 1000 to 2000 μm
Range. On the other hand, if the thickness of the layer (B) is too large, the high-frequency sealing property deteriorates. Therefore, the thickness is preferably 300 μm or less, for example, 2 to 300 μm, and more preferably 5 to 200 μm. As for the thickness ratio of the (A) and (B) layers, A / B is 20/1 to 1/2, particularly 1
The range of 5/1 to 1/1 is preferred.

In the present invention, as the other layer (X) which can be provided adjacent to the layer (A), one layer or two or more layers made of various thermoplastic resins, paper, woven fabric, non-woven fabric, etc. It is.

In order to obtain the sealing material of the present invention, a known laminating method, for example, a coextrusion method, an extrusion laminating method, a dry knee ram method, a press molding method, an injection molding method and the like can be adopted.

[0026]

The laminated sealing material of the present invention has sufficient flexibility derived from the materials of the layers (A) and (B) and has a feeling similar to that of soft polyvinyl chloride. While it is possible to obtain excellent interlayer adhesion between both layers,
Since the layer (B) has a high mechanical strength based on the layer (B) and has a good optical property as the surface layer, it has an excellent appearance and sufficient chemical resistance. Further, since the material constituting the layer (B) has a small amount of low molecular weight components, it does not bleed out to the product surface, and therefore does not generate surface contamination as seen in polyvinyl chloride. In addition, the combination of (A) and (B) allows the layer (B) to be used as a seal layer by high frequency. Having such excellent properties, it can be used in applications where polyvinyl chloride has been used conventionally, especially in fields where high-frequency sealing has been performed. For example, it can be used for cases such as stationery cases and cosmetic cases, and for applications such as tarpaulins.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

1. The following resin was used as the resin of each layer constituting the raw material laminate.

[Table 1] (1) Manufactured by Mitsui Dupont Polychemicals Co., Ltd. (2) Mitsui Petrochemical Industry Co., Ltd.

The composition, physical properties, and the like of the raw material resin are as follows. (1) E-VA-CO copolymer composition (% by weight): ethylene 66% vinyl acetate 24% carbon monoxide 10% MFR: 35 g / 10 minutes ε × tan δ: 0.40

(2) EVA vinyl acetate content: 25% MFR: 6 g / 10 min ε × tan δ: 0.17

(3) EVA vinyl acetate content: 19% MFR: 2.5 g / 10 min ε × tan δ: 0.09

(4) E · αO density: 895 kg / m ³ MFR: 4 g / 10 min) ε × tan δ ≦ 0.001

2. High frequency welder seal characteristic test method (1) Equipment used: High frequency welder KV-30 manufactured by Seidensha Electronics Industry Co., Ltd.
00TA

(2) Operating conditions Oscillation intensity 90%, 95%, 100% Oscillation time 3 seconds Cooling time 4 seconds Pressure 0.15 MPa

(3) Criteria for Adhesion Strength The high-frequency welder sealing properties of the films were evaluated by the following two steps. ：: Sufficiently adhered, and destruction of the material occurs when peeling is attempted. ×: The interface peels off at the seal portion.

[Embodiments 1 to 3] As a resin for layer A, EV was used.
Press sheets (layer A) having a thickness of 0.6 mm, 1 mm, and 2 mm, respectively, were prepared by using a hot press sheet molding machine using A.CO. On the other hand, as the B layer, an ethylene / 1-octene copolymer "Evolue P SC9540" (Mitsui Petrochemical Co., Ltd.) using a single site catalyst
) Was used to produce a 50 μm thick film using a 30 mmφ inflation molding machine. Next, using a press molding machine, a sample having a configuration in which the B layer was provided on both outer layers with the A layer as a core was prepared, and the film sealability between the AB layers was evaluated using a high frequency welder (oscillation strength: 90%). . Table 2 shows the results.

[Examples 4 to 6] In Examples 1 to 3,
EVA instead of E-VA-CO as resin for layer A
Examples 1 to 3 using (Evaflex P2805)
In the same manner as in Example 1, press sheets (layer A) having a thickness of 0.6 mm, 1 mm and 2 mm were prepared, the same layer B film as in Example 1 was laminated, and the high frequency welder sealing property between the layers AB was evaluated (oscillation strength 90%). Table 2 shows the results.

[Examples 7 to 9] In Examples 1 to 3,
A laminate having a B / A / B configuration was prepared in the same manner as in Examples 1 to 3, except that a film having a thickness of 100 μm was used as the B layer, and the sealing property was evaluated (oscillation strength: 95%). Table 3 shows the results.

[Examples 10 to 12] Laminates having a B / A / B configuration in the same manner as in Examples 4 to 6, except that a film having a thickness of 100 μm was used as the (B) layer in Examples 4 to 6. Was prepared and the sealing property was evaluated (oscillation intensity 95
%). Table 3 shows the results. In each of the above Examples 1 to 12, a laminated body which was firmly bonded was obtained.

Comparative Example 1 Using only the ethylene / 1-octene copolymer and E · αO films used as the layer B in the examples, the high-frequency welder sealing properties of the films were measured (oscillation strength). 100%). Table 4 shows the results. Since the high-frequency sealing ethylene copolymer was not laminated, the sealing property was poor and the interface was easily peeled off.

Comparative Examples 2 to 4 In Examples 4 to 6,
Using EVA (Evaflex P1905) instead of EVA as the resin for the A layer, in the same manner as in Examples 4 to 6, 0.6 mm, 1 mm, and 2 mm thick A layer press sheets were prepared and applied to both outer layers. The same layer B films as in Examples 4 to 6 were laminated, and their sealing properties were evaluated (oscillation intensity 10
0%). Table 5 shows the results. Ε of EVA used for layer A
Since × tan δ was small, the high-frequency sealing property was poor.

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

[0045]

[Table 5]

Claims (2)

[Claims] 1. A method comprising an ethylene / carbon monoxide copolymer and / or an ethylene / vinyl acetate copolymer,
The product of the dielectric constant and the dielectric loss tangent at 3.56 MHz is 0.1
A high-frequency seal material comprising the above-mentioned layer (A) provided on one or both sides thereof with an ethylene / α-olefin copolymer seal layer (B) having a density of 860 to 905 kg / m ³ produced by a single-site catalyst. 2. The high-frequency sealing material according to claim 1, wherein the ethylene / carbon monoxide copolymer is an ethylene / carbon monoxide / polar vinyl monomer copolymer.