JPH1161085A - Antistatic adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antistatic adhesive which is excellent in clarity and adhesion to polyethylene films, fluororesin films, etc., and can improve the antistatic properties of the surface of a laminate by compounding a polyester- urethane resin having a specified wt. average mol.wt. with polyethylene oxide and an alkali metal salt. SOLUTION: 100 pts.wt. polyester-urethane resin having a wt. average mol.wt. of 100,000-300,000, pref. 200,000-250,000, is compounded with 3-25 pts.wt., pref. 15-20 pts.wt., mixture prepd. by mixing 100 pts.wt. polyethylene oxide having a wt. average mol.wt. of 200-2,000, pref. 800-1,200, with 5-20 pts.wt., pref. 8-15 pts.wt., alkali metal salt to give an antistatic adhesive of which the total light transmission (JIS K 7165) is 85% or higher at a coating thickness of 5 μm and is 75% or higher at a coating thickness of 20 μm. This adhesive is applied in a dry thickness of 1-20 μm to an adherend to give a laminate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The surface resistivity is 10 ¹² Ω / □.
When the above-mentioned plastic sheets or films are laminated and used, the laminated films are easily charged with static electricity. The present invention relates to an adhesive suitable for imparting an antistatic property for neutralizing such static electricity.

[0002]

2. Description of the Related Art Conventionally, films such as polyolefins, polyesters, polyimides, polycarbonates and fluororesins represented by polyethylene, polypropylene, etc. are laminated with various materials by utilizing their excellent chemical resistance and gas barrier properties. It is used for coating materials and the like. In many cases, these films are transparent.For example, a laminate obtained by laminating a transparent fluororesin film and a printed vinyl chloride resin via an adhesive can easily remove dirt and has high designability. , Wallpapers, door materials,
It is used for electronic whiteboards and bulletin boards.

However, these laminated films have a high surface resistivity, and the laminate having the film as the outermost layer also has a surface resistivity as high as 10 ¹² Ω / □ or more. The dust and dirt inside are easily sucked and the dirt is easily removed, but there is a drawback that the dirt is easily stained.

In order to solve this problem, (1) a method in which a resin containing an antistatic agent is formed into a film and laminated using an adhesive, and (2) aluminum is formed on the surface of the molded film.
A method in which a conductive metal such as copper is vapor-deposited and laminated using an adhesive (JP-A-52-19503), and a method in which (3) an adhesive having antistatic properties is laminated (JP-A-1-253482). ), Are being considered.

In the method (1), the antistatic agent migrates to the surface, adsorbs moisture in the air, and has a surface specific resistance of 10 ¹⁰ Ω /.
□ It is characterized by the fact that the antistatic agent has poor thermal stability, so that the antistatic agent tends to be bleeding (stickiness on the surface) or blooming (dusting phenomenon). Adhesion is inhibited, and the adhesive strength is low even when an adhesive is used.

In the method (2), the surface resistivity of the outermost film does not decrease, but the static electricity generated on the film surface is electrically neutralized by the conductive metal layer formed under the film. The surface potential of the film surface is reduced, and dust and dirt in the air do not adhere. However, since it has a structure of a plastic film layer / conductive metal layer / adhesive layer / counter substrate having a high surface resistivity, for example, when aluminum is deposited, only an aluminum-colored laminate can be obtained. When a transparent conductive oxide such as antimony-doped tin oxide is deposited, there is a disadvantage that the material is expensive.

The method (3) essentially uses the principle of the method (2), and uses an acrylic resin having a quaternary ammonium group having conductivity as an adhesive, carbon black, A method has been proposed in which a so-called conductive filler such as tin oxide or metal powder is blended in an epoxy resin adhesive, and a method in which an antistatic agent is blended in an epoxy resin adhesive. The method (3) is the cheapest method in which the antistatic property of the surface of the laminate is exhibited without changing the surface characteristics of the film of the outermost layer, similarly to the method (2).

However, according to the method (3), when an acrylic resin having a quaternary ammonium group is used as the adhesive, the adhesive strength to polyethylene and fluororesin is low, so that practical adhesive strength is not reached and the conductivity is low. There is a disadvantage that it is easily dependent on humidity. When the conductive filler is compounded, the amount of the conductive filler for exhibiting the antistatic property is required to be about 15 parts by weight or more based on 100 parts by weight of the resin which is a component of the adhesive. Is less transparent. When the antistatic agent is contained in the epoxy resin adhesive, the initial adhesive strength is excellent, but the antistatic agent is dissolved in the boiling water only by immersion in boiling water for about 2 hours, and the antistatic property is lost.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a film which adheres well to, for example, a polyethylene film or a fluororesin film, has excellent transparency, and the surface of a laminate obtained by laminating these films has an antistatic property. The purpose is to provide an adhesive whose effect is permanent.

[0010]

SUMMARY OF THE INVENTION The present inventor has sought to reduce the surface resistivity of an adhesive without impairing its original adhesiveness, and to impart an antistatic property to a laminate using the adhesive. The inventor of the present invention has studied diligently how to control the dispersion state of the conductivity-imparting agent to be added to the toner to exhibit antistatic properties. As a result, polyethylene oxide, weight average molecular weight 100,000 ~
With a polyester-based urethane resin of 300,000 and an adhesive compounded with an alkali metal salt, more preferably,
It has been found that the above problem can be solved by an adhesive obtained by mixing a polyethylene urethane resin having a weight average molecular weight of 100,000 to 300,000 with polyethylene oxide in which an alkali metal salt is dissolved.

What is important in the present invention is that a mixture of polyethylene oxide and an alkali metal salt is blended in the polyester-based urethane resin to form a continuous streak or mesh structure in the adhesive. It is believed that this structure exhibits antistatic properties.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The resin which is a component of the adhesive of the present invention is a polyester urethane resin. Polyester urethane resin, adipic acid, azelaic acid, sebacic acid, dibasic acids such as isophthalic acid and ethylene glycol, 1,4-butanediol, polyester polyol obtained by the reaction of diols such as neopentyl glycol, It is synthesized by reacting polyisocyanates such as isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-diphenylmethane diisoanate and tolylene diisocyanate. When the adhesive is required to have weather resistance, it is preferable to use a polyester urethane resin synthesized from dibasic acid and aliphatic polyisocyanate (for example, hexamethylene diisocyanate) as raw materials.

Although the polyester-based urethane resin alone has a high adhesive strength to, for example, polyethylene or a fluororesin, it is preferable to further increase the adhesive strength by blending a curing agent with the adhesive. By adding a curing agent, higher adhesive strength can be obtained, and high adhesive strength can be maintained even after the boiling water test, which is preferable. The curing agent has an effect of increasing the cohesive force of the adhesive by reacting with the terminal hydroxyl group or terminal isocyanate group of the polyester-based urethane resin.

As the curing agent, when the polyester-based urethane resin has a hydroxyl group at the terminal, hexamethylene diisocyanate, isophorone diisocyanate,
Polyisocyanates such as 4'-diphenylmethane diisoanate and tolylene diisocyanate or urethane-modified products thereof (for example, trimethylolpropane adduct of polyisocyanate) are preferable. When the polyester urethane resin has an isocyanate group at the terminal, Polyols such as polyethylene glycol, polypropylene glycol and tetramethylene glycol are preferred.

As the polyester-based urethane resin, generally, those having a weight average molecular weight of about 20,000 to 40,000 are often used, but in the present invention, those having a high molecular weight of 100,000 to 300,000 are used. It is used, and those having about 200,000 to 250,000 are particularly preferable. When the molecular weight is within this range, the surface resistance of an adhesive in which an alkali metal salt described later and polyethylene oxide are blended can be reduced.

The polyethylene oxide used in the present invention is preferably one consisting essentially of a polyethylene oxide chain, but is not limited thereto. Those having a polyethylene oxide chain as a part of the main chain or having a polyethylene oxide chain as a side chain are preferred. It may be contained in a chain. For example, a block copolymer of ethylene oxide-epichlorohydrin, a (meth) acrylate homopolymer (or copolymer) having a polyethylene oxide chain in a partial side chain, or a polyethylene oxide chain at a terminal of polyamideimide And those having the following.

These polyethylene oxides may be liquid or solid, but must be soluble in an organic solvent such as toluene, ethyl acetate or methyl ethyl ketone which dissolves the polyester-based urethane resin, and have a certain degree of compatibility with the polyester-based urethane resin. Having a weight average molecular weight of about 200 to 2,000.

When the compatibility between the polyester-based urethane resin and polyethylene oxide is low and the phases are completely separated from each other, a streak-like or network-like continuous structure cannot be formed in the adhesive, so that no antistatic property is exhibited. Think. Even when the compatibility is good, the two are uniformly mixed and the above structure cannot be formed in the adhesive. A certain degree of compatibility refers to such a degree that the above-mentioned structure is formed after being mixed and applied as an adhesive.

Polyethylene oxide gradually crystallizes even at room temperature, but this crystallization not only causes a decrease in transparency but also inhibits the movement of dissolved alkali metal salts, and thus leads to a loss of antistatic properties. Therefore, it is preferable to use a polyethylene oxide having a weight average molecular weight of 800 to 1200 which has been crosslinked in advance.

It is necessary to add an alkali metal salt in order to express the antistatic property of the laminate using the adhesive and suppress the humidity dependence of its function. Preferably, the alkali metal salt is soluble in an organic solvent,
For example, ClO ₄ ⁻ , BF ₄ ⁻ or PF as anions
₆ ^- those having the preferred examples. Specifically, for example, LiClO ₄ , LiBF ₄ , LiPF ₆ , NaBF
₄ , NaClO ₄ , NaPF ₆ , KBF ₄ , KClO
₄ , KPF _{6 and the} like, especially LiClO ₄ , LiB
When a lithium salt such as F ₄ or LiPF ₆ is added, a higher conductivity of 10 to 1000 times as compared with the case of using polyethylene oxide alone is obtained, which is preferable in exhibiting the antistatic property of the laminate.

The mixing amount of the alkali metal salt is preferably about 5 to 20 parts by weight, particularly preferably about 8 to 15 parts by weight, based on 100 parts by weight of the polyethylene oxide. The amount of the mixture of the alkali metal salt and polyethylene oxide is preferably 3 to 25 parts by weight, particularly preferably 15 to 20 parts by weight, based on 100 parts by weight of the polyester-based urethane resin. If the amount of the mixture is too large, the adhesive strength is reduced, and if the amount is too small, the laminate does not exhibit antistatic properties.

The adhesive of the present invention has a thickness of 1 to 20 after drying in order to obtain a practical adhesive strength of the laminate.
It is used after being applied to a thickness of about μm. It is preferable that the adhesive has high transparency. Specifically, the total light transmittance by a method in accordance with JIS-K7105 is 8 at a coating thickness of 5 μm.
The transmittance is preferably 75% or more even when the coating thickness is 5% or more and 20 μm.

As the material of at least one of the adherends, particularly both, to be adhered using the adhesive of the present invention, polyolefins such as polyethylene and polypropylene, polyesters, polyimides, polycarbonates and fluororesins are preferred. It is generally preferable that the materials of both adherends be different, but both may be the same material. As an adhesive structure that adheres these adherends, a laminated film,
Examples include a laminated sheet or a laminated tube.

When the adherend is a fluororesin film, the surface of the fluororesin film coated with the adhesive is subjected to a discharge treatment such as a corona discharge treatment, a plasma treatment, a sputter treatment, a flame treatment, a metal sodium treatment or the like by a known method. JIS-K6
The wetting index measured according to 768 is 32 dynes / cm
By increasing the thickness as described above, the fluororesin film can be bonded very firmly.

Since the fluororesin has a surface resistivity of 10 ¹³ Ω / □ or more and a water absorption of 0.1% or less, it tends to be charged with static electricity. It does not carry static electricity, and it is difficult to electrically attract dust and dust.

As the fluororesin, for example, ethylene-tetrafluoroethylene copolymer (hereinafter referred to as ETFE)
Abbreviated), vinylidene fluoride-based polymer, (perfluoroalkoxy) ethylene-tetrafluoroethylene-based copolymer, vinyl fluoride-based polymer, hexafluoropropylene-tetrafluoroethylene-based copolymer, hexafluoropropylene-tetra A fluoroethylene-vinylidene fluoride copolymer or the like is preferred.

The adhesive of the present invention electrically neutralizes static electricity on a plastic surface generated by contact or friction,
The principle that the surface potential of the laminate is set to zero as much as possible is used.

[0028]

The present invention will be described with reference to Examples (Examples 1 and 2) and Comparative Examples (Examples 3 and 4). The effects of the present invention were confirmed by performing the following tests.

[Surface resistivity] 25 μm-thick ET with a corona discharge treatment to increase the wetting index to 40 dynes / cm
An adhesive is applied to the FE film, and the surface specific resistance after drying is measured by a resistivity meter (Hyresta manufactured by Mitsubishi Chemical Corporation).
The measurement was performed by applying a constant voltage of 0V.

[Electrostatic potential] The ETFE surface of a laminate obtained by laminating the above-mentioned ETFE film coated with an adhesive on a soft vinyl chloride resin having a thickness of 200 μm by pressing is 2
Rubbing with gauze for 30 seconds in an atmosphere of 3 ° C. and a relative humidity of 40%, an electrostatic potential measuring device (KSD-010 manufactured by Kasuga Electric Co., Ltd.)
Using 3), the surface potential after 5 seconds was measured.

[Ash test] The surface of the laminated body was rubbed with gauze for 30 seconds, brought close to 1 cm to the tobacco ash, and the presence or absence of tobacco ash was checked.

[Adhesive Strength of Laminate] The laminate was immersed in boiling water for 5 hours, the adhesive force before and after the immersion was measured, and the reliability of the adhesive force of the adhesive was confirmed. Subsequently, the antistatic property of the sample after the boiling water test was confirmed by the ash test.

[Transparency] An adhesive was applied to a 25 μm ETFE film having a corona discharge treatment and a wetting index increased to 40 dynes / cm so that the coating thickness after drying was 5 μm, and in accordance with JIS-K7105. The measured total light transmittance was measured.

Example 1 379.6 g of adipic acid, 1,4
A polyester polyol synthesized from 252.2 g of butanediol and 2.5 g of neopentyl glycol,
A polyester urethane resin (weight average molecular weight: 250,000) modified with hexamethylene diisocyanate was synthesized, and a 30% solution dissolved in methyl ethyl ketone was prepared.

On the other hand, 2 g of LiClO ₄ was added to 20 g of liquid polyethylene oxide having a weight average molecular weight of 1,000.
A dissolved mixture was prepared, and 5 g of the mixture was mixed with 100 g of the polyester-based urethane resin solution to prepare a main agent A. To 20 g of the main agent A, 1 g of a curing agent comprising a trimethylolpropane adduct of hexamethylene diisocyanate was added to prepare an adhesive 1.

E having a thickness of 25 μm and a total light transmittance of 95%
One surface of the TFE film is subjected to corona discharge treatment in air,
The adhesive 1 was applied so that the applied thickness after drying was 5 μm. The ETFE film coated with this adhesive has a total light transmittance of 89% and a surface resistivity of 2 × 10 ⁹ Ω /.
It was □.

A 200 μm thick soft vinyl chloride resin was pressed on the adhesive surface at 70 ° C. and cured at 40 ° C. for 3 days to obtain a laminate. The surface potential of the ETFE film surface of this laminate was -0.2 kV. In addition, no ash was observed in the ash test. The adhesive strength of this laminate was 450 g / cm, the adhesive strength was low at 420 g / cm even after 5 hours of the boiling water test, and no ash was observed in the ash test after the boiling water test.

The adhesive 1 containing the above mixture was mixed with 5
As a result of observation with SEM of 000 times, as shown in FIG.
A network-like continuous structure was formed.

Example 2 431.6 g of terephthalic acid, 1,
A polyester-based urethane resin (weight-average molecular weight: 200,000) was prepared by modifying a polyester polyol synthesized from 252.0 g of 4-butanediol and 2.5 g of neopentyl glycol with tolylene diisocyanate, and dissolved in methyl ethyl ketone. A solution was made.

On the other hand. A mixture was prepared by dissolving 1 g of LiClO ₄ in 20 g of a liquid polyethylene oxide having a weight average molecular weight of 600, and 5 g of the mixture was mixed with 100 g of the polyester-based urethane resin solution to prepare a base material B. 1 g of a curing agent composed of a trimethylolpropane adduct of tolylene diisocyanate in 20 g of the base material B
Was added to prepare an adhesive 2.

The same ETFE film as used in Example 1 was subjected to corona discharge treatment in the same manner as in Example 1, and the coating thickness after drying was 5 μm.
m was applied to the adhesive 2. The total light transmittance of the ETFE film coated with this adhesive is 88%,
The surface resistivity was 2 × 10 ¹⁰ Ω / □.

On this adhesive surface, a soft vinyl chloride resin having a thickness of 200 μm was pressed at 70 ° C. and cured at 40 ° C. for 3 days to obtain a laminate. The surface potential of the ETFE film surface of the laminate was -0.4 kV. In addition, no ash was observed in the ash test. The adhesive strength of this laminate was 500 g / cm, and 4
The decrease in adhesive strength was as small as 60 g / cm, and no ash was observed in the ash test after the boiling water test.

Example 3 To 20 g of the polyester-based urethane resin solution used in Example 1, only 1 g of the curing agent used in Example 1 was added, and an adhesive 3 containing neither polyethylene oxide nor an alkali metal salt was prepared.

The same ETFE film as used in Example 1 was subjected to corona discharge treatment in the same manner as in Example 1, and the coating thickness after drying was 5 μm.
m was applied to the adhesive 3. The total light transmittance of the ETFE film coated with this adhesive is 92%,
The surface resistivity was 10 ¹⁴ Ω / □ or more.

A 200 μm-thick soft vinyl chloride resin was pressed on the adhesive surface at 70 ° C. and cured at 40 ° C. for 3 days to obtain a laminate. The surface potential of the ETFE film surface of the laminate was -5.7 kV, and ash was observed in the ash test. The adhesive strength of this laminate was 480 g /
cm, and even after 5 hours of the boiling water test, there was little decrease in adhesive strength at 450 g / cm, but ashing was also observed in the ash test after the boiling water test.

Example 4 379.6 g of adipic acid, 1,4
A polyester-based urethane resin (weight average molecular weight: 50,000) obtained by modifying a polyester polyol synthesized from 90.0 g of butanediol and 208.0 g of neopentyl glycol with hexamethylene diisocyanate was synthesized and dissolved in methyl ethyl ketone. % Solution was made.

The above polyester urethane resin solution 10
0 g was mixed with 5 g of the same mixture of polyethylene oxide and LiClO ₄ as prepared in Example 1 to prepare a base material C. Curing agent 1 consisting of trimethylolpropane adduct of hexamethylene diisocyanate in 20 g of base material C
g was added to prepare an adhesive 4.

The same ETFE film as used in Example 1 was subjected to corona discharge treatment in the same manner as in Example 1, and the coating thickness after drying was 5 μm.
m was applied to the adhesive 4. The total light transmittance of the ETFE film coated with this adhesive is 90%,
The surface resistivity was 10 ¹⁴ Ω / □ or more.

On the surface of the adhesive layer, a 200 μm-thick soft PVC was pressed at 70 ° C. and cured at 40 ° C. for 3 days to obtain a laminate. The surface potential of the ETFE film surface of the laminate was -3.7 kV, and ash was observed in the ash test. The adhesive strength of this laminate is 560 g / cm,
Even after 5 hours of the boiling water test, the adhesive strength was small at 500 g / cm, but ash was observed in the ash test after the boiling water test.

As a result of observing the adhesive 4 with a SEM at a magnification of 5000, as shown in FIG. 2, the mesh-like structure was broken in the middle.

[0051]

According to the adhesive of the present invention, a film-like adherend which is easily charged with static electricity can be firmly adhered to another adherend of different or the same material, and the surface of the laminate can be rubbed. In addition, the surface potential is suppressed to a low level by the electrical neutralizing action, and a clean surface is maintained without electrically sucking dust and dirt in the air.

[Brief description of the drawings]

FIG. 1 is a 5000 × SEM photograph of adhesive 1 of Example 1.

FIG. 2 is a 5000 times SEM photograph of adhesive 4 of Example 4.

Continuation of the front page (72) Inventor Hideaki Miyazawa 3-474-2 Tsukakoshi, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Asahi Glass Co., Ltd. Tamagawa Branch Office (72) Inventor Masanori Kaya 3-474-2 Tsukakoshi 2-chome, Saiwai-ku, Kawasaki-shi, Kanagawa Asahi Glass Stock (72) Inventor Ryosuke Otomo, 25-26 Torikawa-cho, Hiki-gun, Hiki-gun, Saitama Pref. Inside

Claims (4)

[Claims] 1. Polyethylene oxide, weight average molecular weight 1
An antistatic adhesive containing a polyester-based urethane resin having an amount of from 10,000 to 300,000 and an alkali metal salt. 2. The adhesive according to claim 1, further comprising a curing agent. 3. An adhesive structure wherein an adherend is adhered using the adhesive according to claim 1 or 2, wherein the adhesive structure is a laminated film, a laminated sheet or a laminated tube. 4. The adhesive structure according to claim 3, wherein the material of at least one adherend is a fluororesin, polyolefin, polyester, polyamide, polyimide or polycarbonate.